Preface
Research Center for Electron Photon Science (ELPH) is an accelerator laboratory operating a 1.3
GeV electron synchrotron and three linear accelerators (LINAC) in Tohoku University. ELPH has been
providing electron and photon beams not only to users inside the university but outside as well. This
stance of our laboratory policy has been unchanged since it was founded in 1966 as a laboratory attachedto Faculty of Science. Recently ELPH was approved to be a Joint Usage/Research Center by the Ministryof Education and Science as the center of research for electron photon science over the framework of auniversity. This organization started on April 1, 2011, unfortunately with enormous pain due to theGreat East-Japan Earthquake Disaster that started to happen on March 11, 2011.
Indeed it was a hard departure of the new organization in rough seas with seriously damaged
accelerators. Our 300 MeV LINAC was fatally injured by the earthquake and forced to shut down
forever after more than 40 years of operation. It was consoling, however, that about 1/4 of the LINAC
was rescued and restored but with some difficulty to be a low energy LINAC dedicated to conspicuously
high current experiments. The remaining part of the LINAC was unfortunately scrapped. We foundscratches on the surface of a synchrotron magnet (the paint peeling off) indicating that a nearby shieldblock hit the magnet several times. Thus realignment of all the elements was made to restore thesynchrotron. A 90 MeV LINAC was newly installed as the injector of the synchrotron instead of the
300 MeV LINAC. We restarted operation of all accelerators for users on December 20, 2013 at long last.
Thus we spent almost three years to reconstruct our accelerator facilities.

This is the combined issue of ELPH Annual Reports for FY2011, 2012, and 2013, including a special
report on the disaster. During this period some researches were continued at other laboratories such as
SPring-8, RIKEN Nishina Center and J-PARC.
An agreement was signed on September 1, 2011 by Research Center for Nuclear Physics (RCNP)
Osaka University and ELPH to undertake a joint research project focusing on quark nuclear physics
with photon beams. It is essential in this project to combine a high-resolution 4π electromagnetic (EM)calorimeter, BGOegg/ELPH, and a polarized photon beam, LEPS2/RCNP. The project has been conducted mainly at SPring-8 under the collaborative partnership between the two Joint Usage/ResearchCenters. BGOegg, a brand new EM calorimeter, consists of 1320 BGO crystals, each of which has adepth of 220 mm corresponding to 20 radiation lengths. The BGOegg group started assembling crystals
in October 2011 and ended the task just one year later. Then BGOegg was transported to SPring-8
in December 2012, installed on the LEPS2 beamline, and partially tested during the initial beamline
commissioning that took place in January 2013. The first beam test started in December 2013 for fully
equipped BGOegg.
The SCRIT (Self-Confining RI Ion Target) joint project has been going on to realize never-yetperformed electron-RI scattering. The collaboration team has been constructing the world’s first facility providing electron-RI scattering at RIKEN Nishina Center. During the period of FY2011-2012, the
ELPH SCRIT group designed and constructed an electron spectrometer consisting of a large dipole mag-net and detectors including a large drift chamber. They have been successfully installed at the SCRIT
facility in FY2013, and the commissioning is currently underway. The first electron-RI scattering will be
performed during FY2014.
The development of a coherent terahertz source is one of the main subjects of the accelerator physicists in our laboratory. They have been making every effort to continue their researches in parallel tothe post-disaster reconstruction work and promoting the t-ACTS (test accelerator as a coherent terahertz source) project, which aims at creating very short electron bunches less than 100 fs to generate
coherent synchrotron radiation from an isochronous ring. The injector for t-ACTS has been constructed
and magnet fabrication for a half of the ring is in progress in Light Source House at ELPH.
Planning work is well underway on the project to construct a new high brilliance third-generationsynchrotron radiation facility. The project was proposed by a council consisting of the presidents of seven
universities in the Tohoku region. The ELPH accelerator group has been working on the design of the
facility including a 3 GeV synchrotron radiation source, naming it SLiT-J (Synchrotron Light in Tohoku,
Japan). We set up the promotion office for the SLiT-J project in our laboratory.
On a final note, I am pleased to announce that the renovation and extension work was finallycompleted for the main building of our laboratory at the end of July 2014. We now have a conference
room, Mikamine Hall, to accommodate an audience of about 100.

SHIMIZU Hajime
Director of Research Center for Electron Photon ScienceELPH annual report, 2011-2013
Contents
I. Recovery from Great East Japan Earthquake
The Great East Japan Earthquake Disaster

1

Report of recovery works of accelerator facilities in FY2011, FY2012, and FY2013
Accelerator and beam physics division

3

Recovery of the NKS2 from the Tohoku earthquake
21
H. Kanda, T. Fujii, Y. Fujii, H. Homma, K. Honda, T. Ishikawa, M. Kaneta, Y. Kasai,
C. Kimura, J. Kusaka, K. Maeda, S. Nagao, S. N. Nakamura, T. Nishizawa, K. Nochi,
K. Ozeki, T. Sasaki, H. Shimizu, K. Tsukada, R. Yagi, F. Yamamoto, H. Yamazaki
Damage to GeV-γ beam line caused by the Tohoku-Pacific Ocean Earthquake
H. Yamazaki

26

Commissioning of the photon beamline II after the recovery of the earthquake in FY2013
T. Ishikawa, Y. Honda, M. Miyabe, T. Muto, I. Nagasawa, K. Nanbu, H. Shimizu,
S. Takahashi, Y. Tsuchikawa, H. Yamazaki, R. Yamazaki

28

Commissioning of the positron beamline for testing detectors after the recovery of theearthquake in FY2013
33
T. Ishikawa, Y. Honda, Y. Matsumura, M. Miyabe, M. Muto, H. Shimizu, K. Shiraishi,
Y. Tsuchikawa, H. Yamazaki, R. Yamazaki, S. Yoneyama
Reconstruction of 1st Experimental Hall damaged by the 2011 earthquake off the
Pacific coast of Tohoku and storage of radioactivated materials
H. Kikunaga for reconstruction team of 1st Experimental Hall

37

Restoration of 3rd Experimental Room and response to the accident at the Fukushima
Daiich Nuclear Power Plant
Nuclear and Radiochemistry Group40

II. Papers
Current status of meson photoproduction experiments with FOREST
T. Ishikawa, S. Masumoto, Q. He, R. Hashimoto, Y. Honda, H. Fujimura, J. Kasagi,
K. Maeda, M. Miyabe, N. Muramatsu, A. Nakamura, K. Ozawa, H. Shimizu,
K. Suzuki, Y. Taniguchi, Y. Tajima, Y. Tsuchikawa, H. Yamazaki, R. Yamazaki
Bose-Einstein correlations between two neutral pions from photoproduction at energies
below 1.2 GeV
Q. He, H. Fujimura, H. Fukasawa, R. Hashimoto, Y. Honda, T. Ishikawa, T. Iwata,
S. Kaida, J. Kasagi, A. Kawano, S. Kuwasaki, K. Maeda, S. Masumoto, M. Miyabe,
F. Miyahara, K. Mochizuki, N. Muramatsu, A. Nakamura, K. Nawa, S. Ogushi,
Y. Okada, Y. Onodera, K. Ozawa, Y. Sakamoto, M. Sato, H. Shimizu, H. Sugai,
K. Suzuki, Y. Tajima, S. Takahashi, Y. Taniguchi, Y. Tsuchikawa, H. Yamazaki,

4373

R. Yamazaki, H.Y. Yoshida
Kinematical fit for the analysis of the FOREST experiments
119
T. Ishikawa, Q. He, Y. Honda, S. Masumoto, M. Miyabe, H. Shimizu, Y. Taniguchi,
Y. Tsuchikawa, H. Yamazaki, R. Yamazaki
Estimation of a Gaussian width for a partly measured variable
T. Ishikawa, Q. He, Y. Honda, S. Masumoto, M. Miyabe, N. Muramatsu,
H. Shimizu, Y. Tsuchikawa, H. Yamazaki, R. Yamazaki

123

Measurement of target thickness of liquid H2, D2 with the laser displacement meter
H. Yamazaki, H. Fujimura, T. Ishikawa, M. Miyabe, A. Nakamura, Y. Tsuchikawa

126

Positron beams for testing detectors at SPring-8/LEPS
T. Ishikawa, M. Miyabe, H. Fujimura, H. Shimizu, H. Yamazaki

135

Construction of the new large acceptance electro-magnetic spectrometer BGOegg
M. Miyabe, Y. Honda, T. Ishikawa, K. Matsuda, Y. Matsumura, N. Muramatsu,
A. Nakamura, Q. H. He, H. Shimizu, K. Shiraishi, Y. Taniguchi, Y. Tsuchikawa,
H. Yamazaki, R. Yamazaki

144

First beam observation and near future plans at SPring-8 LEPS2 experiments
151
N. Muramatsu, T. Ishikawa, Y. Matsumura, M. Miyabe, H. Shimizu, K. Shiraishi,
Y. Tsuchikawa, H. Yamazaki, R. Yamazaki, J.K. Ahn, S. Ajimura, W.C. Chang,
J.Y. Chen, M.L. Chu, S. Date, J. Goetz, H. Hamano, T. Hashimoto, K. Hicks,
T. Hiraiwa, T. Hotta, C.Y. Hsieh, Y. Kasamatsu, H. Kohri, S. Masumoto, K. Mizutani,
T. Nakano, T. Nam, M. Niiyama, Y. Nozawa, Y. Ohashi, H. Ohkuma, H. Ohnishi,
T. Ohta, K. Ozawa, T. Shibukawa, Y. Sugaya, M. Sumihama, S. Suzuki, A. Tokiyasu,
N. Tomida, T. Yorita, M. Yosoi
Conceptual design of a data acquisition system for LEPS2 experiments with a BGO
calorimeter
T. Ishikawa, Y. Honda, S. Masumoto, M. Miyabe, N. Muramatsu, K. Ozawa,
H. Shimizu, Y. Taniguchi, Y. Tsuchikawa, H. Yamazaki, R. Yamazaki
The first observation of the neutral pions at SPring/LEPS2 and developing modules
for the upgrade of the data acquisition
T. Ishikawa, S. Masumoto, Y. Tsuchikawa, H. Hamano, H. Hotta, Y. Honda,
Y. Kasamatsu, M. Miyabe, N. Muramatsu, Y. Nozawa, K. Ozawa, H. Shimizu,
Y. Sugaya, Y. Taniguchi, N. Tomida, H. Yamazaki, R. Yamazaki, M. Yosoi

161

175

Pseudoscalar mesons detected with a BGO calorimeter at LEPS2
183
T. Ishikawa, Q. He, Y. Honda, S. Masumoto, M. Miyabe, N. Muramatsu, K. Ozawa,
H. Shimizu, Y. Tsuchikawa, H. Yamazaki, R. Yamazaki
Development of a new multi-purpose logic module MPLM4
I. Nagasawa, T. Ishikawa, H. Hamano, T. Hotta, K. Mizutani, K. Nanbu,
K. Takahashi, Y. Tsuchikawa

194

Feasibility studies at the SCRIT electron scattering facility

201

T. Suda, T. Adachi, T. Amagai, A. Enokizono, M. Hara, T. Hori, S. Ichikawa,
R. Kitazawa, K. Koizumi, K. Kurita, N. Lundkvist, T. Miyamoto, R. Ogawara,
T. Ohnishi, Y. Shimakura, H. Takehara, T. Tamae, S. Tamaki, M. Togasaki,
T. Tsuru, S. Wang, K. Yanagi, S. Yoneyama, M. Wakasugi
A large-acceptance magnetic spectrometer for electron scattering off unstable nuclei
T. Tamae, T. Adachi, T. Miyamoto, T. Suda

213

Radiochemical measurement of photonuclear reaction yields for photon
activation analysis
Y. Ohura, H. Ikeda, Y. Miura

226

Production of 57Co radioactive source for Mössbauer measurements by photon
activation method
K. Akiyama, T. Tadai, Y. Takahashi, S. Kubuki

229

Atmospheric activity concentration of radiocesium at Mikamine, Sendai and radioactivity
distribution on the collection filters used in the measurement234
H. Kikunaga, T. Ohtsuki, H. Fujimura, M. Hiraga, T. Ishikawa, S. Kashiwagi,
K. Matsuda, M. Miyabe, F. Miyahara, T. Muto, I. Nagasawa, K. Nanbu, Y. Shibasaki,
Y. Sugawara, K. Suzuki, K. Takahashi, S. Takahashi, H. Yamazaki
A test accelerator as a coherent terahertz source (t-ACTS)
237
S. Kashiwagi, F. Hinode, M. Kawai, T. Muto, I. Nagasawa, K. Nanbu, Y. Shibasaki,
K. Takahashi, H. Hama
Lattice design of a sub-nm emittance storage ring for the synchrotron lightin Tohoku, Japan (SLiT-J)
H. Hama for SLiT-J Design Team

242

III. Status Report for 2011, 2012, and 2013
Operation status of accelerator complex in 2013
Accelerator group

247

User Support Office Report
T. Ishikawa

248

放射線安全管理室報告（平成 23 年 4 月～平成 26 年 3 月）
Radiation Safety Report 2011, 2012, and 2013
Radiation Control Office256

IV. List of Publication (2011, 2012, and 2013)

261

V. Members of Committees (2011, 2012, and 2013)

285

VI. Approved Experiments (2013)

295

ELPH Annual Report, Tohoku University (2011-2013)

1

The Great East Japan Earthquake Disaster
Triple disaster (earthquake-tsunami-nuclear accident)
We experienced an unprecedented triple disaster. The Tohoku-Pacific Ocean Earthquake occurredat 14:46 on March 11, 2011 at an epicenter of approximately 130 km east of Sendai with a depth of 24 km.
It was the most powerful earthquake ever recorded in Japan with a magnitude of 9.0 (M9.0) and led to a
massive tsunami up to 40.1 m in height, devastating the wide coastal area of East Japan. The number ofvictims (dead or missing) has sadly exceeded 18 thousands, with most of the victims being caused by thetsunami. Within 1 hour, the initial shock was followed by 3 strong aftershocks greater than M7.0. Since
then we have been suffering from the aftershock sequence even after 3 years have passed. As a matter offact, more than 800 aftershocks occurred in the M5 range in these 3 years. The third disaster happened
at Fukushima No.1 Nuclear Power Plant. The major earthquake cut down the external electric power
and the ensuing tsunami stopped the backup diesel generators that had powered the cooling systems in
the reactors, resulting in hydrogen explosions, the subsequent release of radioactivity into the air, andmeltdowns of three of six nuclear reactors. The accident was rated 7 on the International Nuclear Event
Scale (INES), the highest level. The triple disaster represents one of the greatest disasters to strikethe nation of Japan in modern history, being named the Great East Japan Earthquake Disaster (3.11
Disaster).

Atmospheric radioactivity measurements
We started measuring environmental radiation on March 14 at a fixed place in our laboratory. A
generator was employed to get radiation detectors in operation in the blackout for the first three days.
On March 15, additional aerosol particle samples became ready to be collected on a filter paper madeof cellulose-glass fibers. And the radioactivity of radio-cesium on the filter paper was measured by agamma-ray spectrometer. This series of tasks was performed 1-3 times per day by all the staff members,
even though they needed to secure the urgent lifelines of themselves.

Damage to our accelerator facilities
Our laboratory, located away from the coast, had no direct damage caused by the tsunami. But our
accelerator facilities could not escape unharmed from the M9.0 devastating earthquake. The 300 MeV
LINAC constructed in 1967 was in operation when the first blow came on and seriously damaged. We
found no cooling water at all in the cooling water system of the LINAC. The amount of pure cooling water
estimated to be lost was about 5t. Many cracks were found on the waveguides and accelerator tubes. It
turned out afterward that part A (the first 1/4 of the LINAC) was serious but might be repaired and thatpart B (the remaining 3/4 of the LINAC) was very serious and beyond hope of recovery. Thus the whole
300 MeV LINAC would not be restored anymore. Compared to the LINAC, the 1.2 GeV synchrotron was

2found to be repairable. But several power suppliers for the synchrotron were broken. And we had tostart by realigning all the accelerator elements including the bending magnets of the synchrotron in therestoration work.

Post-disaster restoration
The first thing to do for restoration of our accelerator facilities was to clean up the area in thebasement where the accelerators were located. We had to wait, however, about a half year before themassive restoration work started because of the budget approval for reconstruction. The total floor
space of the accelerator facilities is 3526 m2 . It took us about three months to take away disorderedradiation-shield blocks, which were placed everywhere around the accelerators. We removed 500 blocks,
corresponding to about 1000t in weight, out of the underground accelerator facilities so as to be able toalign accelerator elements later. After the cleaning-up job was over, part B of the 300 MeV LINAC was
disassembled. A large amount of radioactive wreckage out of the broken LINAC was disassembled into
pieces, which were classified, labeled, and kept properly in a radiation control area in the basement.
This series of works was performed for all scrap materials down to small activated-parts including bolts
and nuts. Counting some amounts of such small pieces in a bag as one item, we registered more than2000 radioactive wrecks. And we built many shelves in a long line to fit them in the storage place thatused to be a neutron TOF tunnel. A united work by all the laboratory staff made it possible to complete
this psychologically exhausting job.

Accelerator rearrangement
The late 300 MeV LINAC had two functions. It provided a high intensity beam of the energy lessthan 60 MeV in a low energy high repetition mode and worked as a pre-accelerator for the 1.2 GeV
synchrotron in a high energy low repetition mode. Separating these functions, we reconstructed a low
energy high intensity LINAC corresponding to part A, making use of the remains of the wrecked LINAC
at first. Then we constructed a low-repetition-rate 90 MeV LINAC independently as a new injector
for the synchrotron, which therefore had to be improved so as to be able to accept much lower energy
electrons than before. Taking this opportunity, we upgraded our synchrotron to 1.3 GeV.

ELPH Annual Report, Tohoku University (2011-2013)

3

Report of Recovery Works of Accelerator Facilities in
FY2011, FY2012, and FY2013
Accelerator and Beam Physics Division

Research Center for Electron Photon Science, Tohoku University, Sendai, 982-0826

The electron accelerator facilities (300 MeV linac and 1.2 GeV booster synchrotron) had serious
damages by the Great East Japan Earthquake on March 11, 2011. As part of the recovery work, the highenergy part of the damaged linac was replaced with a new 90 MeV linac, which is used as a dedicatedinjector for the booster synchrotron. Instead, the low energy part of the old linac was renovated as a
facility for the RI production. At the same time, some magnets and power supplies were also replaced
for the booster synchrotron (BST ring). The synchrotron, which was previously called STB (STretcher
Booster) ring, had been also utilized as a pulse stretcher to generate the CW electron beam [1]. However
the stretcher operation had not been proposed any longer in recent years, therefore it was also decided
to omit the stretcher function in this recovery work. In this report, the recovery works of the accelerator
facilities between FY2011 and 2013 are described.

§ 1. Low Energy Linac for RI Production
1.1 Overview of the low energy linac for RI production
By the East Japan Earthquake, the 300 MeV linac of 46 years was seriously dameged. Becauseof oldness and specifications (high repetition rate and high charge), it is difficult to get repair parts
today and to recover without any change. One of purposes of our linac is radioisotope (RI) production forradiochemistry, which requires high repetition rate and high charge but moderate energy (∼50 MeV).
Therefore we decided to reconstruct it as “low energy linac” with available parts of the 300 MeV linac.
1.2 Modulators and klystrons
The 300 MeV linac had five sets of modulators and klystrons, and the low energy linac needs two
sets of them. We selected two modulators #1 and #5 in good condition, and then modulator #5 was
replaced modulator #2. Some parts of modulator #2, #3, #4 and those waveguides have also stocked as
repair parts. After #2 replacement, diode test was performed and two modulators were confirmed toreach the rated voltage.
Fig.1 shows snapshot of removal work of old #2 modulator.

4

Fig.1.

Snapshot of removal work of modulator #2.

1.3 Electron gun
The high voltage pulser for electron gun was also old and dameged. Therefore, the pulser was
replaced. It is shown in Fig.2. The specifications of high voltage pulser are the maximum voltage 80 kV,
maximum pulse current of 1 A, and pulse width of 6 µs (FWHM) with maximum repetition rate of 300
Hz. The grid pulser have maximum voltage of 1 kV, maximum pulse current 2 A, pulse width 1∼5 µs,
and the gun bias of 500 V DC negative, 2 mA. The electron gun has been used with no change. Prior tobeam acceleration, we confirmed electron extraction from the cathode after the upgrading of the pulser.

Fig.2.

The electron gun and the high voltage gun pulser.

5

1.4 Acceratiing tube
Eight 1m accerating tubes(A1 - A8) in A-part of 300 MeV linac are still used.
1.5 Beam tranport
Some modification for beam transport was done. The layout of the low energy linac is shown in
Fig.3.

STC6

STC5
F
Q3
D

BM
AQ
AQ
BM
STC4

Fig.3.

D F D

STC3

STC2

Q2
D F

Q1
D F

STC1

Layout of the low energy linac for RI production.

The quadrupole doublet (Q2), located between accelerating tubes A4 and A5, was replaced with new
doublet and screen monitor (Fig.4). The quadrupole has bore radius of φ34 mm, number of turns of 28
turns/pole, and maximum gradient of 1.9 T/m at the maximum current of 8 A.
Two dipole magnets (BM), two quadrupole magnets (AQ), and vacuum chamber were newly manifactured and installed in dispersive section as beam energy analyzer (See Fig.5). Specifications of BMs
are bending radius 680 mm, bending angle 45 degree, pole gap 40 mm, and maximum magnetic field 0.37
T at the maximum current of 30 A. Analyzing Quadrupoles (AQs) have bore radius φ110 mm, numberof turns of 346 turns/pole, and maximum gradient of 2.29 T/m at the maximum current of 8 A.
Some quadrupoles (Q3, Q5) downstream of the energy analyzer were also rearranged.
1.6 Beam status
After reconstruction, beam tuning was done with beam energy 20, 30, 50 MeV. Typical beam pulse
are shown in Fig.6. In this case, beam was extracted to experimental hall #1 with energy 30 MeV, peakcurrent 100 mA, pulse length of 4 µs with repetition rate of 300 Hz.

6

Fig.4.

Fig.5.

Fig.6.

New doublet Q2

Energy analyzer is consisted of two dipoles (BM) and two quadrupoles (AQ).

Typical beam pulse with energy 30MeV. channel 1 (yellow):beam current at gun out,channel 2(cian):beam current at exp hall #1,channel 3(magenta):RF pulse, channel4(green):A8 out.

7

§ 2. New 90 MeV Injector Linac for the 1.3 GeV Booster Synchrotron
New linac is constructed as the injector for the booster synchrotron. The injector consists of athermionic rf-gun, an alpha magnet, two 3m-long accelerating structures, and transport line to thesynchrotron. The maximum energy of injector is 90 MeV with beam loading. The beam commissioningof the injector linac had been started in January 2013, and the first beam acceleration up to 95 MeV
with 3mA was succeeded in January 29th, 2013. The detail of the new injector linac is described in thissection.
2.1 90 MeV Injector for Synchrotron
As a result of examining the some configurations of the injector, we decided to build a new injector
linac which is that a thermionic rf gun is employed as electron source and only one klystron modulator
unit is used to accelerate a beam up to 90 MeV. Since injection energy is lower than the previous linac,
the beam instability due to the low energy injection is concerned. However we believe that the beam
instability does not occur, because it has been renewed to a sophisticated synchrotron power supply
for the magnets in this recovery. A beam line of the injector consists of a thermionic rf gun, an alphamagnet, two 3m-long S-band accelerating structures and two transport lines, one is injection beam line
to the synchrotron and another is test beam line for beam tuning (Fig. 7 ). In the following subsection,
the details of each system are presented.
0+]
ᵡᵵRF
switchMasterOscillator

Pre-Amp

Pulse
Modulator

Directional coupler

LLRF system

Hybrid coupler
Driver Amp.

Variable Attenuator

50MW
klystron

Phase shifter

Alpha magnet
4XDGV

RF monitor system

0:

12dB
Hybrid 0:

3dB Hybrid

0:Beam dump

Steering magnet(for 2MeV)
Steering magnet(for Transport line)

0:

6WHHULQJ
4XDGV

$&&

Beam slit

Bending magnet

0:

&7

Current monitor

Quad(for disp. section)

6WHHULQJ

10dB Hybrid

Alpha
MagnetBeam profile monitor%HQG

RF window

&7
4XDGV

&7

Dublet Quads

Dummy load

ITC
RF gunDoublet Quads(for 2MeV)

350

%0

$&&

350

4XDGV
6WHHULQJ

350

350

&7

4XDG

%0

%0

4XDGV

%HDP
6OLW

%HDP GXPS

350
4XDG

%0

4XDGV

%HDP
GXPS

&7
350
4XDGV

TO
Synchrotro n

Fig.7.

90 MeV injector linac for the booster synchrotron.

8

2.1.1 Electron source
In new injector linac, a thermionic rf gun in combination with an alpha magnet system is used aselectron souse. We have developed a thermionic rf gun consists of two independent cavities so as to manipulate the longitudinal phase space distribution of electron beam, named the Independently-Tuneable
Cells (ITC) rf gun [2]. There are two waveguides connected to the two cells separately for controlling therf field strength and the relative phase between cells. This makes it possible to manipulate the energytime correlation of electrons by varying the rf field strengths and phase difference between the two cells.
The generated beam by the ITC rf gun has strong energy-time correlation because the electrons arecontinuously extracted from the cathode in the duration of half rf cycle and the electrons are densely
populated at the bunch head. Using the beam slit installed in vacuum chamber of the alpha magnet,
it is possible to cut a desired part of the bunch head. (Fig. 8) The quality factors Q0 for the cathodecell and the accelerating cell are estimated to be 9500 and 12500, respectively. The coupling constant βfrom the waveguide to each cell is designed to be relatively large so as to get a shorter cavity filling timearound 200 ns for both cells. The macro-pulse duration has to be shorter to avoid excrescent heating of
the cathode due to the back-bombardment. A LaB6 single crystal cathode with a diameter of 1.78 mm
has been chosen to obtain low emittance and high current density.

Fig.8.

Drawing of the ITC rf gun and alpha magnet

2.1.2 RF system
High power rf unit consists of a 50 MW klystron, a klystron modulator, rf vacuum waveguide system, ITC rf gun, two accelerating structures as shown in Fig. 7. The high power S-band klystron, model
E3730A, produce rf pulses with peak power of 50 MW and pulse durations of 3.0 µs. The klystron needs
a 317 kV pulsed voltage with a 3.0 µs flat-top to operate the 50 MW. A conventional line type modulator
consists of 9 sections of pulse-forming network (PFN), and is resonantly charged and discharged by athyratron switch. This klystron pulse modulator has good stability and flatness of the output pulsed

9

voltage. The amplitude jitter of output voltage was about 0.22 % (p-p) and the pulse flatness was 0.30 %(within ¿ 3.0 µs pulse flat-top). The klystron output power is distributed using the vacuum waveguidesystem, including the hybrid couplers, high power attenuator, phase shifter and rf windows to the ITC rf
gun and S-band accelerating structures as shown in Fig. 7 . The amplitude and the phase of rf fed to thetwo rf gun cells can be independently controlled using the high power attenuators and phase shifters,
respectively.
2.1.3 Accelerator section
The 3 m-long accelerating structure is a constant gradient and high shunt impedance type. It consists of input and output couplers and 84 normal cells. The input and output of accelerating structure
are quasi-symmetric coupler to minimize the beam deflection and emittance growth. The main parameter of accelerating structure; the shunt impedance (r), attenuation parameter (α) and filling time (τt ),are 59 MV/m, 0.57 and 0.83 µs, respectively. With 20 MW input rf power for each structure, it can accelerate electron beam to about 98 MeV without beam loading and the energy loss due to beam loading
is estimated about 4 MeV with 50 mA electron beam. The energy gain with different klystron output
power listed in Tabel 1 .
Table 1. Klystron output power and energy gain.
Kly. Output [MW]Acc. Input [MW]Eg [MeV/m]
Eg/str. [MeV]
Eg/linac [MeV]
Eg/linac with BL [MeV](Vb [MeV, Ib = 50mA])

50
19.6
16.19
48.58
97.15
93.05
(-4.1)

48
18.8
15.86
47.58
95.15
91.05
(-4.1)

46
18.1
15.56
46.68
93.36
89.26
(-4.1)

2.1.4 Transport line
The beam transport consists of quadrupole doublets and beam monitors as shown in Fig. 7 A
dispersion section is located at downstream of the accelerator section, and maximum dispersion function(η) is 0.6 m at the center of quadrupole magnet. A beam current along the injector beam line wasmeasured using the fast current transformer (CT) at four points. The button type beam position monitors(BPMs) and the beam profile monitors (PRMs) with 200 µm thickness YAG crystal screen installed forbeam instrumentation.
2.2 Beam commissioning
The beam commissioning of the injector linac was started in January 2013, and the first beam acceleration up to 95 MeV with 3mA was succeeded in January 29th, 2013. Figure 9 shows the photographof new injector linac taken from upstream of the linac and the profile of accelerated beam first observed
at dispersion section. The characteristics of the electron beam strongly depend on the operating parameters of ITC rf gun such as input rf power and phase. Figure 10 shows the result of phase scan which

10

Fig.9.

Photograph of new injector linac and the beam profile of first accelerated beam at dispersion section.

was measured by changing the ITC gun phase. Keeping the field strength of two cells, field gradientof 1st and 2nd cells were 27MV/m and 70 MV/m respectively, the relative phase between two cells waschanged by every 10o steps. Comparing the measured beam current at gun exit with the simulation, we
can know the approximate operating phase of the rf gun. The measured beam current at downstreamof alpha magnet is lower than at gun exit, since a low-energy part of the beam is cut by the slit in thealpha magnet. Since there is a correlation between the momentum and trajectories of electron in thealpha magnet, we can measure an energy spectrum of the beam using a movable slit in alpha magnet.
Figure 10 shows the measured beam current and its variation at downstream of the alpha magnet withdifferent slit position. The current variation corresponds to the energy spectrum of beam. Beam withsmall energy spread can be achieved by measuring the energy spectrum and adjusting the field strengthand phase of the ITC gun.
The transverse emittance measurement was performed by means of a quadrupole scan downstream
from the second accelerating structure. The transverse beam size was measured using PRM with digital CCD camera for different quadrupole focusing. Figure 11 shows the measurement result of thequadrupole scan. Columns left and right represent the measurement results of the horizontal and vertical directions, respectively. Upper of Fig.11 shows the measured beam size (solid dots) as function of thequadrupole strength and the solid line retrieved from the χ2 minimization. For the beam of 25 mA and
92 MeV (γ=180), the projected transverse emittance were nx =6.7 πmm mrad and ny =8.9 πmm mrad.
This large measured emittance could be due to an inhomogeneities emission from the cathode surface
and edge. It is expected that the cathode surface has been damaged in the past operation, therefore
we will replace with new cathode. The lower of Fig. 11 shows beam parameters (α, β, γ) as ellipse in11

Beam current @ CT2 [mA]

Beam current [mA]

80

60

40

20

0

50

100

150

200

250

300

350

40
30

0.02
20
0.01

10
0
2.05

400

Phase [deg]Fig.10.

0.03

2.1

2.15 2.2 2.25 2.3
Momentum [MeV/c]

2.35

Differential beam current [a.u.]

Att1=2.3dB,
ATT2=1.16dB
slit posi.=50mm

CT1 [mA]
CT2 [mA]

0

0.04

50

100

0
2.4

(Left) Measured beam current at the gun exit (solid circles) and downstream of alphamagnet (open circles), respectively. (Right) Measured beam current (solid circles) andits variation (open circles) at downstream of alpha magnet with different slit position.

the phase space derived from the quadrupole scan. These parameters and emittance were used to theoptics matching from the injector to the synchrotron. The current setting of quadrupoles in transportline calculated from the optics matching. [3]0.4

0.4
Vertical
0.35

0.35

Beam size (s) [mm]Beam size (s) [mm]Horizontal

0.3

0.3

0.25

0.25
0.2
0.15

0.2

0.15

0.4

0.6
0.8
1
K- value (QF3L)

0.1
0.2

1.2

-0.5
0
0.5
Beam size [mm]10.1
dx/ds [mrad]

0.1
dy/ds [mrad]

1.2

VerticalHorizontal

0

0

-0.1

-0.1

Fig.11.

0.6
0.8
1K- value (QD3L)

0.2

0.2

-0.2
-1

0.4

-0.5
0
0.5
Beam size [mm]

1

-0.2
-1

Quadrupole scan using single magnet in horizontal (left) and vertical (right) directions.
The graphs of bottom row are beam ellipses in transverse phase space.

The optics matching by a quadrupole scan down stream of accelerating section is performed to
inject the beam to the booster synchrotron. Figure 12 shows the layout of beam transport line from theexit of second accelerating structure to injection point of the ring. Accelerator room located the new
injector linac and second experimental room of the booster synchrotron are separated with the wall of
4-m-thick concrete. The transport line for injection and the beamline of the synchrotron cross in the
2nd experimental room. In this cross section, the electron beam pass through the synchrotron magnet,
therefore the beam is influenced by the leakage magnetic field of the bending magnet (BM7). Correction
for dipole field components is carried out by changing the trajectory of beam by steering magnets placed

12around the intersection. And to minimize the effects of the higher order components of leakage magnetic
field, the beam is focused in the cross point. Consequently, the matching condition of the transport line
are to adjust Twiss parameters at the injection point and to focusing the beam in horizontal and verticaldirections at the cross point (Figure 13). After optics matching, even when the bending magnet of thering is turned on, it could be confirmed a screen monitor (SCM3) of the intersection downstream havenever beam profile such distorted.

Fig.12.

The layout of beam transport line from the exit of second accelerating structure to injection point of the booster synchrotron.

Fig.13.

Twiss parameter along the beam transport line.

13§ 3. Upgrade of Booster Synchrotron (BST ring)
In the recovery work of the booster synchrotron, some quadrupole magnets in the straight sections
were replaced to the combined function magnets which include the sextupole component. Modifying thering optics to introduce the horizontal dispersion on the combined magnet position, this replacement
work makes it possible to correct the chromaticity. By the replacement of power supplies of synchrotron
magnets, the maximum beam energy was also increased from 1.2 to 1.3 GeV. Those power supplies for
dipole and three quadrupole families capable of pattern operation with ramping time of about 1 second
had been installed, which have excellent performance of good stability and small tracking error overwide energy range from 90 to 1300 MeV. Damaged power supplies of pulsed magnets for beam injection
were also replaced as well as the control system of those devices, and thus more reliable and stable beam
operation can be expected. Fig. 14 shows the BST ring after the recovery work.

Fig.14.

BST ring after the recovery work (August, 2013).

3.1 Lattice modification and chromaticity correction by adopting the combined function magnets
Main parameters and lattice functions of the BST ring are shown in Table 2 and Figure 15, respectively. Although the synchrotron was originally designed to be consisted with the double-bend
achromatic cells, finite dispersion function is introduced into the straight section so as to correct thechromaticity by employing the combined function magnets. In a circular accelerator, the control of the

14chromaticity is important to avoid loss of particles due to tune shift and also to prevent beam loss dueto head tail instability. Since the natural chromaticities ξx0 , ξy0 for horizontal and vertical plane havealways negative values and cause the head tail instability, thus the chromaticities should be corrected
to positive values, which can be realized by sextupole components introduced in the dispersive section
as shown in equation,


1 H


ξx = ξx0 +βx m(s)ηx ds,
4π


1 H

ξ = ξ −βy m(s)ηx ds,
y
y0
4π

(1)

where βx/y and ηx are beta functions and horizontal dispersion function, m(s) show the sextupole
components, respectively.
Table 2. Main parameters of the BST ring
Lattice
Circumference
Maximum energy
Injection energy
Betatron tune
Corrected chromaticity
RF frequency
Harmonic number
Natural emittance
Momentum compaction
Dispersion at straight section
Beam current

Fig.15.

CEmax
Ei(νx , νy )(ξx , ξy )
fRF
h

α
ηx
Ib

Double Bend, 4 cells
49.75 m> 1.3 GeV
90 MeV(3.24, 1.18)(1.4, 1.2)
500.14 MHz
83
160 nmrad (@1.2 GeV)
0.04580.6 m
200 mA (@1.2 GeV)

Lattice functions of the BST ring for one cell.

Focus (QSF) and defocus (QSD) combined function magnets placed in the straight section have essentially the same dimensions as the replaced magnets except the pole face shapes. Those pole face

15

shapes can be basically deduced from an equipotential surface for a given field strengths and a bore
radius, however, a 3D field calculation shows that the sextupole field has shorter effective length ( 7 %)than that of the quadrupole. Therefore the actual pole face was determined by taking this shorter effective length into account. The ratio, mS /kQ , of the field strength for sextupole component to quadrupole
was designed to be 1.2 (1.9) for QSF (QSD) magnet, where the both components mS and kQ are expressed as By (x) = kQ × x + mS × x2 with the vertical field in the median plane. Fig. 16 shows
combined function magnets installed into the straight section of the ring, which manufacturing and fieldmeasurement were carried out by SIGMAPHI. According to the result of the field measurement employing the rotating coil, it was found that the integrated quadrupole components were in good agreementwith the field calculation by TOSCA but sextupole components were smaller than the calculation for theboth of QSF and QSD magnets. As a result, the ratio of the field strength for sextupole component toquadrupole became smaller than designed one. However, this discrepancy would be still acceptable byadjusting the dispersion function at the straight section for the chromaticity correction. Since the sextupole component has much stronger saturation than the quadrupole, the field ratios for the maximum
excitation current are getting smaller comparing with the nominal current, which must be also taken
into account for the actual beam operation.

Fig.16.

Combined function magnets installed in the ring.

3.2 Replacement of magnet power supplies
Damaged power supplies for pulsed magnets were also replaced by the newly fabricated ones. The
basic parameters of the power supplies for pulsed magnets (one septum magnet and three bump magnets) for the beam injection are shown in Table 3.
The power supply for the septum magnet, which is driven by half sinusoidal pulse, consists of
200µF/800V main capacitor, 600V/1.3A charging power supply, thyristor stack FTS1000HJ and control

16

Table 3. Main parameters of pulsed power supplies

Max. current
Pulse width
Current stability
Fall time
Timing jitter
Rep. rate

Bump magnet
220 A> 1µs @flat part
< 1 % (p-p)<∼ 0.5 µs< 10 ns> 10 pps

Septum magnet
1210 A
200 ± 10 µs< 2 % (p-p)< 10 ns> 10 pps

units, etc. The power supply for the bump magnet is composed of a charging power supply HDV-15K10ST
to drive PFN, thyratron CX1191D and other control units. Measured waveform of the output current forthe bump magnet shows good stability with well suppressed ringing tail. The maximum output currentof bump magnet was set to 220 A taking some margin for future upgrade of injection energy up to ∼150
MeV.
Power supplies for the dipole and three quadrupole families (QSF, QSD and QC) were also manufactured. These are high-precision IGBT chopper type power supplies that have very excellent performanceof a current ripple less than ±1 × 10−5 and also a tracking error less than ±1 × 10−4 . Main parametersof the power supplies are listed in Table 4. A PXI system communicates with a built-in memory modulein the each power supply via Ethernet to send 16 bit pattern data, while timing signals such as clock
and trigger are transferred via RS422.
Table 4. Main parameters of power supplies for synchrotron magnets

Max. current
Min. current
Output voltage
Ramping rate

Dipole1400 A80 A
645 V
980 A/sec

QC
800 A
40 A
55 V
665 A/sec

QSF , QSD
700 A
35 A
77 V
565 A/sec

3.3 Status of beam commissioning
After the beam commissioning of the injector linac, the beam injection to the BST ring was started
in May, 2013. The brief history of the commissioning is shown in Table 5. In the early stage of the beamcommissioning, pick-up signals from two strip-line monitors were observed to handle the beam orbit aswell as some beam loss monitors instead of the beam position monitors (BPMs). After the success ofbeam storage in the ring, nine buttom-type BPMs were utilized to correct the closed orbit distortion.
With a great deal of elaboration in the tuning work, finally sufficient beam current was obtained so as
to perform a pre-service inspection, which is required based on the Law concerning the Prevention ofRadiation Hazards.
One of the serious issues caused by the combined function magnets, especially for the injected beam,would be a problem in the reduction of dynamic aperture due to the nonlinear field by the sextupole

17

Table 5. Brief history of the beam commissioning
Date
April
end of May
7th, June
13th, June
10th, July
19th, December
end of December

issuesCommissioning start in injection line
Commissioning start for ring
multi-turn circulation in the ring
RF capture of the injected beam
Success for beam acceleration up to max.
energy ( 1.3 GeV)
Passed pre-service inspection basedon Radiation Hazards Prevention Law
Start of user machine timecomment

Ib ∼2 mA
Ib =15 mA@Eb =1.3 GeV

component. Because the bump orbit would exist over the long region including some combined magnets
for the small synchrotron such as BST, so that the injected beam must pass through the combined
magnets with large offset for several turns even the ideal bump orbit. As the result, the electrons having
the larger amplitude than the dynamic aperture would be lost. Furthermore longer radiation damping
time for the lower energy beam is also a troublesome problem. The damping time in the order of 10
seconds is comparable to the beam life time for the injected beam with 90 MeV at the present vacuum
level, thus it is hard to perform the study with the beam keeping its energy. For this reason, to begin
with, we measured some parameters with the accelerated beam to the higher energy. Figure 17 presents
an example of the measured horizontal dispersion function for the accelerated beam to 900 MeV, whichshows good agreement with the model calculation. Figure 18 also shows the measured variation of thechromaticity depending on the dispersion function in the straight section. Expected values by SAD code
are also shown in the Figure, which shows somewhat different slope with the measurement, however, it
is successfully confirmed that the chromaticity can be corrected as expected.
3.4 Reconstruction of control system and other infrastructure
In this recovery work, it was also required to reconstruct the whole control system of the injector
linac and synchrotron. Taking into account of the limited resources for the development, we decided
to construct a control system based on the PC-based network with LabVIEW and Visual-Basic as theGUI, while EPICS (Experimental Physics and Industrial Control System) was employed in building
distributed control systems. In order to handle the several operation modes depending on the beamuser, the control system of the power sources for synchrotron magnets, which is required to have precise
timing control and capability of a flexible pattern generation for the ramping-up, was developed withField Programmable Gate Arrays (FPGAs) on the PXI system. Figure 19 shows the new control room
for the accelerator complex after the renovation. Although the user machine time has been alreadyrestarted, the development of the control software is still continued toward the easier and also morereliable operation at the moment.
The great earthquake caused serious damage not only the accelerator components but also theutilities of the facility such as air conditioning system of buildings, water cooling system for accelerator

dispersion [m]

18

s [m]
Example of dispersion measurement for the stored beam at 900 MeV.

chromaticity

Fig.17.

dispersion [m]Fig.18.

Measured chromaticity dependence on dispersion. Plots show the horizontal and vertical chromaticities, while solid lines show the expectation given by SAD codes.

components and drainage system for contaminated water by radioisotopes. Damaged air handling unit
in the air conditioning system had been operated for long time more than 40 years, and then asbestos
insulation was provided in the old air ducts, which is prohibited to use nowadays. Although the removal
work of old components in the system had to be carried out cautiously and thus it took much time tocomplete the work, these all reconstruction works for the infrastructure were successfully completed

19

Fig.19.

New control room for the accelerator complex after the renovation.

by the end of FY2012 to meet the requirement that the pre-service inspection should be performed in
FY2013 as mentioned before.

§ 4. Summary and prospect
So far we had conducted the recovery work from the great earthquake almost over three years. In
this FY2013, then we have started the beam commissioning for the accelerator complex in the facility,and finally user machine time has been successfully restarted. Newly constructed injector linac is pretty
stable and reliable comparing with the original one, on the other hand the low energy part of the oldlinac had been replaced in some damaged components and then operated for the user application again.
Concerning the BST ring, this recovery work made it possible to increase the maximum energy to 1.3
GeV and also to correct the chromaticity. Although the user machine time had been already carried out
with the similar beam current as before, the considerable effort will be conducted to fully realize theexpected performance towards the utilization as a light source for an educational purpose in the future.

Acknowledgment
The authors would like to thank Dr. S. Miura, Messrs. D. Suzuki and M. Nakagaki of Mitsubishi
Heavy Industries Ltd., and also the companies, SIGMAPHI, Toshiba Corp. and Nissin Pulse Electronics
Co. Ltd., for their considerable cooperation in the construction of the new injector linac and the reconstruction work of synchrotron. We also like to express our gratitude to Prof. K. Kanazawa and thevacuum group in KEK for their kind support and help in transfer of many NEG pumps.

20

References[1]

F. Hinode et al.: Proc. 2nd Asian Particle Accelerator Conf., (2001) 106-108.

[2]

H. Hama et al.: New J. Phys.8 (2006) 292.

[3]

S. Kashiwagi et al.: Proc. The 4th Int. Particle Accelerator Conf., (2013) 1607-1609.

ELPH Annual Report, Tohoku University (2011-2013)

21

Recovery of the NKS2 from the Tohoku earthquake
Hiroki Kanda1 , Takao Fujii1 , Yu Fujii1 , Hiroki Homma1 , Kazuhisa Honda1 ,Takatsugu Ishikawa2 , Masashi Kaneta1 , Yuma Kasai1 , Chigusa Kimura1 ,Junichiro Kusaka1 , Kazushige Maeda1 , Sho Nagao1 , Satoshi N. Nakamura1 ,Takashi Nishizawa1 , Kazuki Nochi1 , Keiichi Ozeki1 , Takayuki Sasaki1 ,Hajime Shimizu2 , Kyo Tsukada1 , Ryouun Yagi1 , Fumiya Yamamoto1 ,and Hirohito Yamazaki2
1
2

Department of Physics, Tohoku University, Sendai, 980-8578

Research Center for Electron Photon Science, Tohoku University, Sendai, 982-0826

We carry out the recovery works of the NKS2 and devices along the photon beam line after thedamage by the Tohoku earthquake on 11 March 2011. No serious trouble was found in the Pair Magnet,
the 680 Magnet, hodoscopes and drift chambers of the NKS2. On the other hand, a neutron detector,a beam profile monitor, the STB Tagger, and the power supplies for the magnets were damaged. The
neutron detector, the beam profile monitor and the power supply for the Pair Magnet were renewed. The
power supply for the 680 Magnet was repaired. A new tagger is currently being developed to replace the
STB Tagger. The commissioning of the beam line and the test detector of the new tagger started in thelate 2013. Completion of the whole tagger system is planned in FY 2014. The recovery of the detectorsof the NKS2 is planned in early FY 2014. It is also completed in FY 2014.

§ 1. Introduction
We study the meson photoproduction on the deuteron with tagged photon beams and the Neutral
Kaon Spectrometer 2 (NKS2) at the Research Center for Electron Photon Science (ELPH), Tohoku University. The NKS2 is a magnetic spectrometer for the charged particle detection and we have provided
unique data in the neutral kaon photoproduction [1, 2] and charged pion photoproduction [3] on the
deuteron. After data production runs were successfully performed in September and October 2010, theTohoku earthquake struck the ELPH and the NKS2 on 11 March 2011.

§ 2. Status after the Tohoku earthquake
We checked the status of magnets, detectors, and electronic devices for the NKS2 soon after the
Tohoku earthquake. The magnets had not been much affected by the ground motion. The 680 Magnet
did not move from its original position. Its horizontality was kept after the Tohoku earthquake. The
Pair Magnet (PM) jumping on the pedestal had been witnessed during the Tohoku earthquake. But, wefound that it was in its original position, judging from scratches on the side of the PM. No trouble was22found in their cooling water system and their coils. The NKS2 detectors, hodoscopes and MWDC’s had
not been severely damaged. We confirmed signals of all the counters in hodoscopes with supplying highvoltage. We successfully applied high voltage to the MWDC’s and thus no broken wire was expected.
A neutron detector stored in GeV-γ preparation room had fallen down and severely broken (Fig.
1(a)). The electronic devices for the STB-Tagger had been hit by concrete shielding blocks and someof them slipped off from the rack and hang from other modules (Fig. 1(b)). Detector case of the highspeed beam profile monitor (HSBPM) [4] had been deformed. Its pedestal and linear motion table weredamaged. Some of the 19” racks for the electronics devices in the NKS2 counting room had fallen down.
Modules held on them and cables connected between the modules were damaged.

Fig.1. Photographs of damaged devices taken after the earthquake: (a) the neutron detectorand (b) the electronics devices of the STB-Tagger.

§ 3. Recovery of the damaged devices
The power supply for the 680 Magnet suffered some troubles in its control electronics, power transistors and cooling water system. These troubles were found and repaired by its manufacturer, Kudo
Electric Co. Ltd. After the repair and conditioning, it successfully supplied 1000 A current to the 680
Magnet with a stability less than 1 × 10−4 for 8 hours of the test operation. The power supply for the PM
was dismantled after the Tohoku earthquake due its damage. It was replaced by a new power supply
with the maximum current of 266 A. Power lines from the power supply to the PM was replaced.
A neutron detector was made by K. K. CI Kogyo. A new frame made of aluminum pipes were
designed with adjustable height. Five plastic scintillator bars with size of 100 × 100 × 1000mm3 madeof Eljen Technology EJ-200 were read out with photomultiplier tubes from both ends. It was deliveredin the end of FY2012. It is stored in the GeV-γ preparation room fixed to a pillar of a built-in racks withsafety wires in order to avoid stumbling.

23

A new detector case for the HSBPM was made by K. K. G-Tech. It was designed with similar
structure of the beam profile monitor developed for the GeV-γ beam line [5]. It was coupled to a newlinear motion table with an adaptor place and a precision lab jack. The linear motion table was fixed on apedestal made of aluminum frames. The adaptor plate and the pedestal were designed and constructedby the technical staff in the faculty of science, Tohoku University. We assembled the detector and placed
it on the photon beam line (Fig. 2(a)). The commissioning of the HSBPM was performed in the machinetime in March 2014. The obtained profile of the gamma beam is shown in Fig. 2(b).

Fig.2. (a) a photograph of the HSBPM placed in the photon beam line and (b) the profile of thephoton beam measured with it.

We have been developing a new photon tagger with MPPC based scintillation counters. The MPPC
is an abbreviation of Multi-Pixel Photon Counter, a kind of semiconductor photon sensor developed byHamamatsu Photonics K. K. Its compactness, magnetic field tolerance and good timing resolution aresuitable for the scintillation counter used for the tagger. We developed several variations of prototype
counters and they were tested at NewSUBARU, Laboratory of Advanced Science and Technology for
Industry, University of Hyogo by courtesy of its special support for the Tohoku Earthquake [6] and at
the electron beam line at MAMI-B in University Mainz. A prototype counter using an MPPC with anactive area of 3 × 3mm2 and another prototype counter using an 4 × 4 MPPC array exhibited the time
resolutions of ∼ 100ps(σ) and < 80ps(σ), respectively [7, 8]. The latter one was tested in the hit rate up
to ∼ 200 kHz, an expected hit rate for a nominal operation condition of the tagger, and no degradation oftiming resolution was found. The geometry of the counter units were optimized with a Geant4 simulation
which simulated realistic position of the bending magnet (BM4) and its magnetic field map. The setup
is shown in Fig. 3(a). The tagged photon energy range of 0.80 ≤ Eγ ≤ 1.28 GeV at the electron energy of
1.32 GeV was obtained in the simulation (Fig. 3(b)). We proceed with a mechanical design of the detector
case based on these positions for counter units. The MPPC printed board and electronic modules were
manufactured by Fuji Diamond International Co. Ltd. They were delivered by the end of March 2014.
The construction of the tagger system is currently in progress and will be completed in 2014.
We started the recovery of the detectors, namely scintillation counters and multiwire drift cham-

24

(a)

(b)
Count

x (mm)

100

photon
0

-100

700
600
500

Unit1
400

n
tro
ec
l
EUnit39

-200

-300

Unit2
300
200

Unit40

-400

100
-500

0

1200

1000

800

600

400

200

0

-200

800

y (mm)

900

1000

1100

1200

1300

Energy (MeV)

Fig.3. (a) Geometries of the tagging counters and simulated electron orbits and (b) an energy
distribution of the tagged photons. Photons tagged by even numbered counter units areshown in hatched regions.

bers of the NKS2. The routing of signal and high voltage cables were refined. A machine time for thecommissioning of the NKS2 detector is scheduled in early FY 2014. It will be completed in FY 2014.

§ 4. Summary
We carried out the recovery works of the NKS2 and its beam line after the Tohoku earthquakeon 11 Mar. 2011. Some of the damaged devices were renewed, some of them were repaired. For therecovery of the STB-Tagger, we have developed a new scintillation counter with readout with the MPPC.
Its development and construction is currently underway. The recovery of the detectors in the NKS2 isalso underway. They will be completed in FY2014.

Acknowledgment
We would like to thank the administration and technical staff in ELPH and the faculty of science
for their support in our recovery works. We would like to thank Prof. S. Miyamoto and Drs. S. Amanoand K. Horikawa in Laboratory of Advanced Science and Technology for Industry, University of Hyogo
for their support in the experiment at New SUBARU. We would like to thank Dr. P. Achenbach andother staff in University Mainz for their support in the experiment at MAMI. We would like to thankMr. Y. Shoji for his great assistance and efforts in the development of the amplifier circuits for thereadout of the MPPC. This program was partly supported by Core-to-core program (21002), strategic
young researcher overseas visits program for accelerating brain circulation (R2201), and KAKENHI
Grant Number 23540334 by JSPS.

References[1]

K. Futatsukawa et al.: EPJ Web of Conferences 20 (2012) 2005.

[2]

B. Beckford et al.: submitted to Phys. Rev. C.

[3]

Y. C. Han et al.: Nucl. Phys. A834 (2010).

25

[4]

M. Nanao et al.: Research Report of Laboratory of Nuclear Science 36 (2003) 56.

[5]

S. Ogushi: Master’s thesis, Tohoku University (2010).

[6]

http://www.lasti.u-hyogo.ac.jp/NS/result2/earthquake support/support121019/, (2012).

[7]

H. Kanda et al.: Proceedings of Science (PhotoDet 2012) (2013) 031.

[8]

T. Nishizawa et al.: IEEE trans. Nucl. Sci. 61 (2014) 1278.

26

ELPH Annual Report, Tohoku University (2011-2013)

Damage to GeV-γ beam line caused by the Tohoku-Pacific
Ocean Earthquake
H. Yamazaki
Research Center for Electron Photon Science, Tohoku University, Sendai, 982-0826§ 1. STB-Tagger II
The energies of tagged photons at the GeV-γ beam line are determined by the momentum measurements of recoil electrons with STB-Tagger II. It was installed between the pole-piece and the return yokeof BM5 which is one of the bending magnets of STB-ring at the second experimental hall. The tagger
and the bending magnet swayed and hit each other many times during the earthquake.

§ 2. GeV-γ experimental room
The RTAGX magnet (Fig. 1) was installed in the GeV-γ experimental room at the most upstreamof the beam line to sweep out charged particles. The weight of the RTAGX magnet is approximately
25 tons. It shook violently and moved to the east about 30 mm (Fig. 2).

Fig.1.

The RTAGX magnet. Its weight isabout 25 tons.

Fig.2.

The support base (yellow steel
frame) of RTAGX with a scale.

The electro-magnetic calorimeter complex FOREST is placed in the GeV-γ experimental room.
FOREST is mainly composed of SCISSORS III (pure CsI crystals), SPIDER (plastic scintillating countersin front of SCISSORS III), LEPS BG (lead-scintillating fibre modules), IVY (plastic scintillating counters in front of BG), Rafflesia II (lead glass Cherenkov counters), LOTUS (plastic scintillating countersin front of Rafflesia II) and a cryogenic target system. They were deeply damaged by the Tohoku-Pacific
Ocean Earthquake.
As shown in Fig. 3, SCISSORS III hit the support frame and some crystals cracked in the aluminumcases. The surface film of SPIDER was ripped and some photo multiplier tubes were broken on impact(Fig. 4). Some modules of Rafflasia II slipped a few centimeters and hit LOTUS as shown in Fig. 5.

27

Fig.3.

SCISSORS III hit the support
frame and some pure CsI crystals
cracked in the aluminum cases.

Fig.5.

Some modules of Rafflesia
slipped and hit LOTUS.

II

Fig.4.

The surface film was ripped andsome photo multiplier tubes werebroken.

Fig.6.

Smashed flexible metal hose.

A flexible metal hose which connects a compressor and a refrigerator of a cryogenic target system wassmashed under a concrete shield (Fig. 6).

Fig.7.

Many spare modules of Rafflesia II
crashed on the floor.

Fig.8.

Many signal cables were broken.

Spare modules of Rafflesia II were stored in the detector assemble room on the ground floor. Many
spare modules crashed on the floor (Fig. 7).
The electronic circuit system was also damaged because the electricity was off and on repeatedly ina short period. And many signal cables were broken physically by the tilted rack (Fig. 8).

28

ELPH Annual Report, Tohoku University (2011-2013)(ELPH Experiment : #2761)

Commissioning of the photon beamline II after the recoveryof the earthquake in FY2013
T. Ishikawa1 , Y. Honda1 , M. Miyabe1 , T. Muto1 , I. Nagasawa1 , K. Nanbu1 ,H. Shimizu1 , S. Takahashi1 , Y. Tsuchikawa1 , H. Yamazaki1 ,and R. Yamazaki1
1Research Center for Electron Photon Science (ELPH), Tohoku University, Sendai 982-0826,
Japan

No photon beam was available for 2.5 years after the 2011 earthquake off the Pacific coast of Tohoku
known as 2011 Earthquake because the accelerator complex at ELPH became out of order. The primarycirculating electron beam of the electron synchrotron came back in the end of 2013 thanks to the great
effort of the accelerator staff at ELPH. The synchrotron has been able to provide the bremsstrahlung
photons. The commissioning status of the photon beamline II is described in this report.

§ 1. Photon beam course
The commisioning of the accelerator complex of the injector linac and synchrotron was made continuously in 2013. The circulating current in the synchrotron was low even if the accelerator staffs madeefforts on tuning of its operation. They suspected that the STB-Tagger II and iron fence for it [1] madethe operation of the synchrotron unstable. Therefore, these items were removed on October 15 in 2013.
After that, the main reason why high current was not available was found to come from the lack of theB` integration in BM4 and BM5 having special vacuum chambers for providing bremsstrahlung photons and detecting recoil electrons. These magnets were moved by shifting 20–30 mm toward the innerdirection of the ring. The high current primary beam of the electron synchrotron became available in
December, and the commssioning of the photon beamline II started for the planned experiments.
The first photon beam did not come onto the center of the target position in the GeV-γ experimental
hall. We tried to find the solution by adjusting the operation of the synchrotron with a help of accelerator staffs. The beamline at that time was the same as that before the 2011 Earthquake, and it wasdetermined by the actual bremsstrahlung photon beam before the earthquake. We failed, however, andwe selected the photon beam course that the photons came in the center of RTAGX and had the slope
dx/dz = +0.6 mrad horizontally and dy/dz = −1.2 mrad vertically, as an optimum one. Figure 1 shows
the optimum photon beam course in the end of December in 2013. Two experiments for testing detectors
were carried out in this condition. One tested GEM trackers and a hadron blind electron/positron detector for the J-PARC E15 experiment at the 23◦ positron beamline, which was conducted by K. Ozawa
in Institute of Particle and Nuclear Studies, KEK (#2759). The other tested a ring imaging Čerenkov
counter for the J-PARC P50 experiment at the 23◦ positron beamline, which was conducted by K. Shiro-

29

tori in Research Center for Nuclear Physics, Osaka University (#2771). Since both the experiment did
not require high energy (momentum) resolution of the positron (electron) beam, the vaccum chamberWallinside RTAGX and the vacuum pipes for these beamlines were not placed.

Cable Pit

12.2 mShield Blockso30 Beamline

19.5 m2755

30 deg2771 (白鳥)Shield Blocks

2759 (小沢)
23 degFig.1.

Optimum photon beam course in the end of December 2013. The distances from thecarbon radiator which produces the bremsstrahlung photons are 12.2 m and 19.5 m to
the front face of RTAGX and the beam profile monitor placed in front of the beam dump.
The detectors for the 2759 experiment (K. Ozawa, IPNS, KEK) were placed at the 23◦
positron beamline, and those for the 2771 experiment (K. Shirotori, RCNP, Osaka Univ.)
were placed at the +30◦ elecron beamline. The thick green lines show the photon beamcourse.

The STB-Tagger II and iron fence for it were replaced inside the BM5 bending magnet again on
January 8 in 2014 because they were found not to affect the magnetic field of BM4 and BM5. The
commisioning of the photon beamline was made in the end of January but the situation did not change
from that in December. From February 10 in 2014, we made the new beamline markers according to
the previous line between BM4 and BM5. It should be noted that the previous beamline had been madefrom the actual photon beam course in the special mode at the photon beamline II. The RTAGX magent
and the beam dump were moved by approximately 2 and 3 cm toward the north with respect to the newbeamline. We obtained the photon beam course on March 7 in 2014 which came in both the centers of
RTAGX and beam dump and had the slope dx/dz = +0.14 mrad horizontally and dy/dz = +0.01 mrad
vertically. Figure 2 shows the measured position of the photon beam. The beam profiles were measured
with Polaroid films at the lead apertures in the second experimental hall and in front of RTAGX, andthat was measured with a BPM detector consisting of scintillating fiber hodoscopes [2] in front of the

30

beam dump. It should be mentioned that the BM4 and BM5 magnets were still shifted by 20–30 mm
from the nominal position.

z (m)

20

20

BPM

17.5

17.5

15

15

12.5

12.5

ポラロイド

10

7.5

5

5

ポラロイド

0
-10

-5

0

2.5

5

x (mm)
Fig.2.

ポラロイド

10

7.5

2.5

BPM

10

0

ポラロイド

-4

-2

0

2

4

y (mm)

Measured position of the photon beam. The z position stands for the distance from thecarbon fiber. The beam profiles were measured with Polaroid films at the lead aperturesin the 2nd experimental hall and in front of RTAGX. That was measured with a BPM
detector consisting of scintillating fiber hodoscopes [2] in front of the beam dump.

§ 2. Transmittance of the photon beam
The tagged photons do not always reach the target because of the conversion of the photons into
positron and electron pairs, the detection of the electrons which do not emit the bremsstrahlung photons (Moller scattering) due to the instability of the synchrotron, and so on. We define the photontransmittance (so called tagging efficiency) as a fraction of photon coming events to the target position
among electron detected events with each tagging counter. The transmittance was measured by detecting tagged photon with an SF5 lead glass Čerenkov counter with a size of 150 × 150 × ×300 mm3 [3] fora faint primary electron beam. The transmittance was measured with a data acquisition system basedon CAMAC for the first sixteen channels of the STB-Tagger II. Figure 3 shows the measured transmittance of the photon beam for the first sixteen channels of the STB-Tagger II. No significant drop of thetransmittance was observed.

31

0.8
0.7
Transmittance

0.6
0.5
0.4
0.3
0.2
0.1
0

Fig.3.

0

20

40
60
80
Tagging Channel

100

120

Transmittance of the photon beam for the first sixteen channels of the STB-Tagger II.
The red filled circles show the data for the current measurement, and the energy of thecirculating electron beam is 1.3 GeV, and the diameters of 20 and 25 mm for the lead
apertures in the second experimental hall and in the GeV-γ experimental hall, respectively. The data are compared with previous measurement before the 2011 Earthquake.
The black filled circles and boxes show the data for the circulating energy of 1.2 GeV withthe diameters of 10, and 25 mm for the lead apertures. The black open circles show thefor the circulating energy of 0.9 GeV with the diameter of 10, and 20 mm for the lead
apertures. The previous data are quoted from the reference [1].

§ 3. Summary and future prospects
The bremsstrahlung photon beams coming to the center of the target are available now after theshift of the beamline. The photon beam has the slope dx/dz = +0.14 mrad, and dy/dz = +0.01 mrad
horizontally, and vertically, respectively. The photon beam intensity as a function of the elapsed timein a spil is different spill by spill. This instability is thought to come from that in the operation of thesynchrotron. More dedicated adjustment of the radiator (carbon fiber) operation should be made after
the synchrotron operation becomes stable.

Acknowledgment
The authors express their sincere thanks to the ELPH accelerator staff for the reconstruction of theaccelerator complex after the great earthquake. This work was supported in part by Grant-in-Aid for
Scientific Research (A) (24244022).

32

References[1]

T. Ishikawa et al.: The second GeV tagged photon beamline at ELPH, Nucl. Instr. and Meth. A 622,
1 (2010).

[2]

H. Fujimura et al., Development of a Beam Profile Monitor for GeV-γ Beamline, Research Reportof LNS 42&43, Tohoku University, 144 (2011).

[3]

A. Ando et al., Electron Beam Test of the Active Converter Device, KEK-79-21 (1979).

ELPH Annual Report, Tohoku University (2011-2013)

33(ELPH Experiment : #2762)

Commissioning of the positron beamline for testing
detectors after the recovery of the earthquake in FY2013
T. Ishikawa1 , Y. Honda1 , Y. Matsumura1 , M. Miyabe1 , M. Muto1 , H. Shimizu1 ,K. Shiraishi1 , Y. Tsuchikawa1 , H. Yamazaki1 , R. Yamazaki1 ,and S. Yoneyama1
1

Research Center for Electron Photon Science (ELPH), Tohoku University, Sendai 982-0826,
Japan

No positron (electron) beam for testing detectors was available for 2.5 years after the 2011 earthquake off the Pacific coast of Tohoku known as 2011 Earthquake because the accelerator complex at
ELPH became out of order. The primary circulating electron beam of the electron synchrotron cameback in the end of 2013 thanks to the great effort of the accelerator staff at ELPH. The synchrotron has
been able to provide the bremsstrahlung photons, and the positron (electron) beams for testing detectors.
The commissioning status of the positron beamline for testing detectors is described in this report.

§ 1. Photon beam course
The optimum photon beam course in the end of December in 2013 was that the photon beam camein the center of RTAGX and had the slope of dx/dz = +0.6 mrad and dy/dz = −1.2 mrad. The positron
beamline was designed assuming that the photon beam came to the center of RTAGX in the parallel direction to the photon beamline. The photon beam which was not parallel to the beamline gave the shiftof the energy centroid and the larger edge scattering effects on the lead aperture. The first two experiments did not require high energy (momentum) resolution of the positron (electron) beam. One tested
GEM trackers and a hadron blind electron/positron detector for the J-PARC E15 experiment at the 23◦
positron beamline, which was conducted by K. Ozawa in Institute of Particle and Nuclear Studies, KEK(#2759). The other tested a ring imaging Čerenkov counter for the J-PARC P50 experiment at the 23◦
positron beamline, which was conducted by K. Shirotori in Research Center for Nuclear Physics, Osaka
University (#2771). The vaccum chamber inside RTAGX and the vacuum pipes for these beamlines were
not placed.
We made the new beamline markers in Ferbruary 2014 according to the previous line between BM4
and BM5 before the 2011 Earthquake. We obtained the photon beam coming in March 2014 both on thecenters of RTAGX and beam dump with the slope of dx/dz = +0.14 mrad and dy/dz = +0.01 mrad bymoving the RTAGX magent and the beam dump with respect to the new beamline. The details of thecommissioning of the photon beamline is discussed elsewhere [1].

34

§ 2. Installation of the vacuum pipe
Since the positron beams traveled in the air, the intensities of them were lowered due to the multiple
scattering. The intensities became very low for the low momentum positron beams with momenta lessthan 200 MeV/c. Focusing of the positron beams with a tripple quadrupole megnets (RFQ) were not so
effective in this low energy region also due to the multiple scattering in the air. An experiment for testing
an electro-magenetic calorimeter desired 100 MeV/c positron beams, which was conducted by J. Tojo in
Kyushu University (#2768). The calorimeter will be used for the J-PARC E21 COMET experiment, whichaims to detect the muon-electron conversion events (to search for lepton flavor violation). To increase
the intensity of positrons (electrons) in this momentum region, we decided to install the vacuum pipe on
the positron beamline. The lead aperture was placed inside the pipe, and its diameter was changed from
20 to 16 mm because the inner diameter of the vacuum pipe between the aperture and the RFQ was
23.9 mm. The lead blocks were also placed outside the pipe. Figure 1 shows the photos of the vacuum
pipe installed on the positron beamline in February 2014.

Fig.1.

Photos of the vacuum pipe installed on the positron beamline in February 2014. The lead
aperture with a diameter of 16 mm is placed inside the pipe. The lead blocks were also
placed outside the pipe.

The positron beam profiles were measured for the RTAGX current of 25, 50, and 75 A corresponding to approximately 50, 100, and 150 MeV/c with a BPM detector consisting of scintillating fiber hodoscopes [3]. In this measurement, all the trigger plastic scintillators and the Al converter were removed.
Figure 2 shows the measured positron beam profiles for the RTAGX current of 25, 50, and 75 A. The
x and y widths (σx , σy ) became (15, 16), (11, 7), and (10,6) mm for 25, 50, and 75 A, respectively. The(σx , σy ) widths before the installation of the vacuum pipe were (25, 27), and (18, 19) for 50, and 75 A,
respectively. The (σx , σy ) for 25 A could not be determined since the x and y distribution showed almost
flat. An excellent improvement was obtained on the beam profiles for these low energy positron beams.

35

RTAGX: 25A

RFQ: OFF x 10-6
1.4

20

1.2
1

0

RTAGX: 25A

RFQ: ON

20
0

0.8
-20

0.6

-20

0.4
-40

-20

0

RTAGX: 50A

20

40

RFQ: OFF x 10-6
8
7
6
5
4
3
2
1

20
0

y (mm)

-40

-20
-40

-20

0

RTAGX: 75A

20

0
-20
-40

-20

0

20

20

40

RFQ: ON

0
-20
-40

-20

0

RTAGX: 75A20

x 10-6

RFQ: ONx 10-6

0
-20
-20

0

20

40

RFQ: ON

20
15
10
5
0
-5
-10
-15
-20
-20 -15 -10 -5

0

5

RTAGX: 50A

10 15 20

RFQ: ON

20
15
10
5
0
-5
-10
-15
-20
-20 -15 -10 -5

35
30
25
20
15
10
5
-40

RTAGX: 25A

40

20

40

2.5
2.25
2
1.75
1.5
1.25
1
0.75
0.5

14
12
10
8
6
4
2

20

RFQ: OFF x 10-6

200

RTAGX: 50A

40

18
16
14
12
10
8
6
4
2

-20

x 10-60

5

RTAGX: 75A

10 15 20

RFQ: ON

20
15
10
5
0
-5
-10
-15
-20
-20 -15 -10 -5

05

10 15 20x (mm)
Fig.2.

Measured positron beam profiles for the RTAGX current of 25, 50, and 75 A corresponding to approximately 50, 100, and 150 MeV/c. The left, central columns show the results
without and with applying RFQ magnet, and the right shows the results with the optimum RFQ operation after the installation of the vacuum pipe. The left two columns were
the results before the 2011 Earthquake reported in the reference [2].

§ 3. Summary and future prospects
After introducing the vacuum pipe for the positron beamline, more intense positron beams havebecome available especially in the low momentum region. The intensities and beam profiles for the
positron beams for testing detectors should be measured for several RTAGX currents. The intensities ofthe photon beam and positron beam for testing detectors as a function of the elapsed time in a spill isdifferent spill by spill. This instability is thought to come from that in the operation of the synchrotron.
More dedicated adjustment of the radiator (carbon fiber) operation should be made after the operationof the synchrotron becomes stable.

Acknowledgment
The authors express their sincere thanks to the ELPH accelerator staff for the reconstruction of theaccelerator complex after the great earthquake. They also appreciate K. Matsuda for preparing the lead
aperture blocks inside and outside the beam pipe. This work was supported in part by Grant-in-Aid for
Scientific Research (A) (24244022).

36

References[1]

T. Ishikawa et al.: Commissioning of the photon beamline II after the recovery of the earthquake
in FY2013, in this annual report.

[2]

Y. Tsuchikawa and T. Ishikawa et al.: Focusing the positron beam for testing detectors by triple
quadrupole magnets RFQ, ELPH Annual Report 2010 Vol. 1, Tohoku University, 107 (2012).

[3]

T. Ishikawa et al.: The second GeV tagged photon beamline at ELPH, Nucl. Instr. and Meth. A 622,
1 (2010).

ELPH Annual Report, Tohoku University (2011-2013)

37

Reconstruction of 1st Experimental Hall damaged by the2011 earthquake off the Pacific coast of Tohoku and storageof radioactivated materials
H. Kikunaga for reconstruction team of 1st Experimental Hall

Research Center for Electron Photon Science, Tohoku University, Sendai, 982-0826

The Research Center for Electron Photon Science, Tohoku University was taken on a lot of damage
by the 2011 earthquake off the Pacific coast of Tohoku. Here the reconstruction of 1st Experimental Halland storage of radioactivated materials arising as a result thereof are described.

§ 1. Reconstruction of 1st Experimental Hall and storage of radioactivated materials
The 1st Experimental Hall at the Research Center for Electron Photon Science has been mainly
used for production of the radioisotopes and photon activation analyses. The irradiation beam line
including the irradiation apparatus for electron and bremsstrahlung was taken on a lot of damage by
the 2011 earthquake off the Pacific coast of Tohoku (Fig. 1). Thus, reconstruction works had to be carriedout hard for a few years after the earthquake.

Fig.1.

The irradiation apparatus broken by the 2011 earthquake off the Pacific coast of Tohoku.

First of all, unnecessary materials such as a broken apparatus and unneeded beam lines were
removed from the reconstruction area such as 1st and 2nd Experimental Hall, klystron room, and LINAC
room to secure a work space. These unnecessary materials were divided into radioactivated materials

38

and other materials. The registered radioactivated materials are over 2000 items and have been stored
in the storage room which is newly designated waste site in the radiation controlled area (Fig. 2). Almost
all staff worked on this clearance for more than a year.

Fig.2.

A part of radioactivated materials in the storage room.

After the clearance works, a new irradiation site for electron and bremsstrahlung was set up. A
water-cooled irradiation apparatus and a sweeping magnet for a bremsstrahlung irradiation without
electrons are located on the beam axis (Fig. 3) and a water-cooled beam dump is behind those. These
components were surrounded with the concrete block wall of 1 meter or more to block scattered radiations and neutrons produced by photonuclear reactions (Fig. 4).

Fig.3.

A water-cooled irradiation apparatus and a sweeping magnet.

39

Fig.4.

Shielding concrete blocks around the irradiation site.

The operation as a ”Joint Usage / Research Center” using this irradiation site was restarted fromFebruary, 2014. An average current of 120 µA at 50 MeV has been obtained, which is substantially sameas that before the earthquake. Improvement of the irradiation system, such as adding a current monitor
system, is carried out gradually.

40

ELPH Annual Report, Tohoku University (2011-2013)

Restoration of 3rd Experimental Room and response to theaccident at the Fukushima Daiich Nuclear Power Plant
Nuclear and Radiochemistry Group

Research Center for Electron Photon Science, Tohoku University, Sendai, 982-0826

Fortunately, the 3rd Experimental Room did not have such a large damage except for some detectors, so that radioactivity measurement using high-purity Ge semiconductor detectors is immediately
resumed after power recovery. Here the measurements of radioactivity released from the accident of the
Fukushima 1 Nuclear Power Plant at the 3rd Experimental Room are described briefly.

§ 1. Summary of measurement of radioactivity released from the Fukushima 1 Nuclear PowerPlant
The Fukushima 1 Nuclear Power Plant accident released various radionuclides into the environment. Because the Research Center for Electron Photon Science, Tohoku University is located near
Fukushima prefecture and has several high-purity Ge semiconductor detectors, we have worked actively on the measurement of radioactivity of these radionuclides. Fortunately, the 3rd Experimental
Room did not have such a large damage except for some detectors, so that radioactivity measurement
using the Ge detectors is immediately resumed after power recovery.

Radioactive concentration in soil kBq/m3

Fig.1.

Radioactivity concentration in soil of southern Miyagi prefecture and sampling points

41

Fig.2.

Example of measurement samples

The atmospheric activity of released radionuclides on the aerosol particles has been measured fromMarch 15, 2011 to present [1]. Soil samples at the Center and southern Miyagi prefecture (Fig. 1),
rainwater samples at the Center were also collected and subjected to γ-spectrometry. Besides, the soil
samples from the ”Creating Radioactive Contamination Map Project” by Environment Monitoring Teamof Emergency Operation Center (EOC) of MEXT [2], plant samples from Fruit Tree Research Center,
Fukushima Agricultural Technology Center [3], and biological samples from the Livestock ResearchCenter, Fukushima Agricultural Technology Center, IAEA-PT samples and so on were measured at therequests from outside of the Center. An example of measurement samples is shown in Fig. 2. Almost
all samples were enclosed in a 100 mL container (U-8 type). To efficiently analyze a large number ofsamples, an automatic measuring apparatus for successive measurement of U-8 samples was developed(Fig. 3). Measurement of radioactivity released from the Fukushima 1 Nuclear Power Plant accident isstill continues.

References[1]

H. Kikunaga et al.: ”Atmospheric activity concentration of radiocesium at Mikamine, Sendai andradioactivity distribution on the collection filters used in the measurement”, in this annual report.

[2]”Survey of Fukushima Soil Radioactivities” hhttps://www.rcnp.osaka-u.ac.jp/dojo/index_en.
phpi

[3]

for example hhttp://www.pref.fukushima.lg.jp/w4/nougyou-centre/kenkyu_houkoku/radio_sp_
2014/2014_02_22.pdfi

42

Fig.3.

Automatic measuring apparatus for successive measurement of U-8 samples

ELPH Annual Report, Tohoku University (2011-2013)43(ELPH Experiment : #2623, #2640, #2655, #2694)

Current status of meson photoproduction experiments with
FOREST
T. Ishikawa1 , S. Masumoto2,3 , Q. He1 , R. Hashimoto1,4 , Y. Honda1 ,H. Fujimura1 , J. Kasagi1 , K. Maeda5 , M. Miyabe1 , N. Muramatsu1 ,A. Nakamura1 , K. Ozawa6 , H. Shimizu1 , K. Suzuki1 , Y. Taniguchi1 ,Y. Tajima7 , Y. Tsuchikawa1 , H. Yamazaki1 , and R. Yamazaki1
1Research Center for Electron Photon Science (ELPH), Tohoku University, Sendai 982-0826,
Japan
2

Department of Physics, University of Tokyo, Tokyo 113-0033, Japan
3

4

Department of Physics, Yamagata University, Yamagata 990-8560, Japan
5

6
7

Nishina Center, RIKEN, Wako 351-0198, Japan

Department of Physics, Tohoku University, Sendai 980-8578, Japan

Institute of Particle and Nuclear Studies, KEK, Tsukuba 305-0801, Japan

Networking and Computing Service Center, Yamagata University, Yamagata 990-8560, Japan

Meson photoproduction experiments with an electro-magnetic calorimeter FOREST were carriedout from May 2008 to May 2010. The main purpose of the FOREST experiments was to study a nucleon
resonance N ∗ (1670), which is a candidate of anti-decuplet pentaquark baryons, via η photoproduction
on the neutron. Ten series of long term FOREST experiments were made before the 2011 Earthquake,and measured the differential and total cross sections for the γp → ηp, γd → ηpn, and other reactions.
The photoproduction data were acquired with two STB circulating currents of 1200 and 920 MeV.
The numbers of events collected were 2.13 G, 2.26 G, and 0.24 G events for hydrogen, deuterium, andempty targets in the high energy mode, and those were 211 M, 200 M, and 24 M events in the low energy
one. In this report, the statuses of the analysis on the performance of FOREST from the fiscal year (FY)2011 to 2013 are presented.

§ 1. Introduction
Quark nuclear physics is a research field where we study the strong interacting matter to understand its properties and interactions coming from underlying fundamental theory Quantum Chromodynamics (QCD). It is a challenge to give an answer to the internal structure of the nucleon and its
excited states in terms of effective degrees of freedom. The baryon resonance spectroscopy is an important testing ground for non-perturbative QCD calculations in the low energy scale. In this scale, theeffective theories are often used because the coupling constant becomes very large and because perturbative calculations are not applicable. Among the effective models and theories, the constituent quark
model, which describes baryons with three valence quarks, has succeeded to reproduce the ground statebaryons. Yet, the phenomena that cannot be explained by it come out. Some excited baryons — single

44

excited positive parity and double excited negative parity baryons — are still missing in spite of various
experimental efforts [1]. S01 (1405)Λ is proposed as a superposition of two state having different properties — which couple to πΣ and K̄N , respectively [2]. A mass-order-reverse problem is claimed between
S11 (1535)N with the orbital angular momentum L = 1 and P11 (1440) with a principal quantum number
n = 1, and between S11 (1535) and S01 (1405)Λ having s quark with L = 1 [3]. Evidences for Θ+ pentaquark baryon are reported although we have controversial results of its existence [4]. These suggeststhat a new effective degree of freedom emerges such as diquark correlation in a hadron, quark-gluon
hybrid, meson-baryon molecule, and so on [5].
Meson photoproduction is utilized for baryon spectroscopy complementary to π-N elastic scattering.
It should be noted that excited baryon resonances highly depend on the production processes, and highly
excited baryons have a small branching ratio to the πN final states. At the first stage, the proton
channels are intensively investigated such as the γp → π + n and γp → π 0 p reactions. The γp → ηpreaction is also investigated by means of an isospin filtering. While the π channels are associated withboth a half and three half isospin resonances, the η channel is associated only with a half isospin one,
namely not the delta resonances but the nucleon resonances. In the second stage, multi-meson photoproduction selecting some resonances comes within a range by a large solid angle detector. Single meson
photoproduction on the neutron has been also undertaken. Recently, a narrow resonance has been
observed in η photoproduction on the neutron.
It was observed at Laboratory of Nuclear Science (the former name of ELPH) [6], GRAAL [7], and
CB-ELSA [8]. The resonance would be attributed to a member of anti-decuplet pentaquark baryons
with hidden strangeness since no signature corresponding to this bump has been observed so far in the
proton channel. Fig. 1 shows the baryon octet and anti-decuplet penta-quark baryons. Although the N50
member can be photoproduced from the neutron, photoproduction of the N5+ member having a U-spinof 3/2 is forbidden due to the U -spin conservation because the U -spin of the proton is 1/2 and that ofthe photon is 0. The baryon resonances including this bump has been studied with an EM calorimeter
FOREST at ELPH, Tohoku University by using various photoproduction reactions.

§ 2. Electromagnetic calorimeter FOREST
Meson photoproduction experiments with an electromagnetic calorimeter complex FOREST werecarried out from May 2008 to May 2010 at ELPH, Tohoku University. Bremsstrahlung photons wereused as a beam, being generated with a carbon fiber inserting into circulating 1200 or 920 MeV electrons
in the STretcher booster (STB) ring. Each photon was tagged by detecting the corresponding postbremsstrahlung electron inside a bending magnet of the ring. The details of the photon tagging counter
STB-Tagger II are described elsewhere [9]. The energies of the tagged photon beam ranged from 740 to1150 MeV for circulating 1200 MeV electrons and from 580 to 880 MeV for 920 MeV ones.
Two γ rays from π 0 → γγ or η → γγ were detected with FOREST. The details of the design
are described elsewhere [10] and the status report of FOREST achieved in 2006–2010 can be found in
Ref. [11–16]. Fig. 2 shows the schematic view of FOREST.

45

Y=B+S
Θ+
n
Σ−

Σ+
1/2

0

ΛΣ

Ξ0
1

Ξ−
1/2
Octet
Fig.1.

U3

p

0

+

Ν5

Ν5

Σ−

Σ0

Q
Σ+
I3

Ξ−− Ξ−
Ξ0
Ξ+
1
1/2
3/2
0
Anti-decuplet

Octet baryons and anti-decuplet penta-quark baryons. The N50 member can be photoproduced from the neutron, but photoproduction of the N5+ member is forbidden due to the
U -spin conservation.

FOREST consists of different three EM calorimeters: the forward one ‘SCISSORS III,’ the central
one ‘LEPS Backward Gamma detector,’ and the backward one ‘Rafflesia II.’ SCISSORS III is comprisedof 192 pure CsI crystals, LEPS Backward Gamma detector is made up of 252 lead scintillating fiber
modules, and Rafflesia II is composed of 62 lead glass Čerenkov counters. Plastic scintillator (PS) hodoscopes are placed in front of each calorimeter. The forward hodoscopes called ‘SPIDER’ consist of left
and right-handed spiral-shaped PS’s, and can determine the incident position of the detected particle.
The central and backward hodoscopes called ‘IVY ’ and ‘LOTUS’ consist of 18 and 12 PS’s, respectively.
Ten series of long term FOREST experiments were made before the 2011 Earthquake, and we callthe periods 2008A–2008C, 2009A–2009E, 2010A, and 2010B. The developed FOREST cryogenic target
system [17] enables us to change targets within 6 hours. The high speed data acquisition system (DAQ)
FOREST-DAQ dedicated to the FOREST experiments [18] was used. The DAQ efficiency was 76% at thetrigger rate of 2 kHz. The details of the FOREST experiments are described elsewhere [15]. The collected
data in the FOREST experiments are summarized in Table 1 in Ref. [16]. Construction of Rafflesia II
finished after the 2008A term ended, and the readout of signals from all the counters in Rafflesia II was
ready from the 2008C. LOTUS was constructed just before the 2009D started. The data taking with thedeuterium target started in the 2008C, and the data for both the hydrogen and deuterium targets wereacquired in a term except for a short term 2009C. The circulating electron energy of the STB ring was
920 MeV for the 2009E and 2010A periods, and 1200 MeV for the other ones.

46

LEPS Backward Gamma
SCISSORS III

SPIDER

LOTUS
IVY

Rafflesia II

FORESTFig.2.

Schematic view of FOREST. It consists of three EM calorimeters: the forward one with
192 pure CsI crystals ‘SCISSORS III,’ the central one with 252 lead scintillating fiber
modules ‘LEPS Backward Gamma detector,’ and the backward one with 62 lead glassČerenkov counters ‘Rafflesia II.’ Plastic scintillator hodoscopes are placed in front of thesecalorimeters: SPIDER, IVY, and LOTUS.

§ 3. Progress of the analysis in FY2011
The progress of the analysis in FY2011 is described in this section. The proton momentum reconstruction was given for Backward Gamma clusters [19]. The photon beam position measured witha beam profile monitor [20] during the FOREST experiments were summarized [21], and the reaction
point of a Monte-Calro simulation had become to be determined by using these profiles. The position
reconstruction for the SCISSORS III and Backward Gamma clusters was updated [22, 23]. The effective number of counts for the photon tagging system, which includes the trigger formation and DAQ
efficiencies, was investigated [24]. The trigger formation efficiency was updated [25]. The timing reconstruction of the SPIDER and IVY scintillators was updated [26, 27]. by taking into account themeasured energy and the polar angles or radius (distance from z axis). The center of the cryogenic target was discussed [28, 29], and shortening of the aluminum pipe for the target holder was suggested at
approximately 20 K. The energy resolutions for the SCISSORS III and Backward Gamma clusters were
investigated [30] for the preparation of using a kinematic fit technique [31]. The efficiency for the proton
detection with Backward Gamma was discussed [32].

47

3.1 Proton momentum reconstruction for Backward Gamma clusters
The proton momentum reconstruction was investigated for Backward Gamma clusters by using theγp → π 0 p reaction events for the hydrogen target. Since the γp → π 0 p is a two body reaction, thedetecting angle of the proton gives its energy or momentum. The π 0 generated events were selectedby gating the invariant of two photons from 100 to 170 MeV, and the missing mass mX is required
from 850 to 1050 MeV assuming the reaction γp → π 0 X. Figure 3 shows the correlation between themeasured time between the proton and the photons and the calculated time difference from the proton
emitted angle between the proton and the particle travelling with the speed of light. The slope for thecorrelation is not unity probably due to the energy loss in the material on the way. The correlation iswell reproduced with tBe − tγγ = 1.2241 (tp − tc ) + 0.27785 ns, which gives the proton momentum fromthe measured time when the proton is detected with the Backward Gamma detector. The details of theanalysis is described elsewhere [19].
2.5
2.25
2

tBe-tγγ (nsec)

1.75
1.5
1.25
1
0.75
0.5
0.25
0

Fig.3.

0

0.25

0.5

0.75

1 1.25 1.5
δt=tp-tc (nsec)

1.75

2

2.25

2.5

Correlation between the measured time between the proton and the photons and thecalculated time difference from the proton emitted angle between the proton and theparticle travelling with the speed of light. The data are compared with tBe − tγγ =1.2241 (tp − tc ) + 0.27785 ns.

3.2 Photon beam position measured with a beam profile monitor
The photon beam position measured with a beam profile monitor [20] during the FOREST experiments were summarized in Ref. [21], and the reaction point of a Monte-Calro simulation had become tobe determined by using these profiles. Figure 4 shows the mean and width of the photon beam x and yprofiles. The mean of the x profile gradually increased and that of y decreased in the same period. By
selecting tagged photons, both the widths σx and σy becomes smaller.
No correlation of µx , µy , σx , and σy to the circulating current in STB ring (intensity of the photon

480µy (mm)µx (mm)

2
0
-2

-4
12000

13000 14000
Run Number

15000

14

14

12

12
σy (mm)σx (mm)

-2

10
8
6

Fig.4.

15000

12000

13000 14000
Run Number

15000

8
12000

13000 14000
Run Number

6

15000

Mean and width of the photon beam x and y profiles. The µx (µy ) stands for the meanof the x (y) profile, and σx (σy ) is the width of the x (y). The blue markers show themean and width of the profiles for all the photons, and the red show those for the tagged
photons.

2.5

2.5µy (mm)

5µx (mm)

13000 14000
Run Number

10

5

0

0

-2.5

-2.5

-5

-5
2

12

4
6
Time in a spill

8

10

10

8

6

2

4
6
Time in a spill

2

4
6Time in a spill

8

10

2

4
6
Time in a spill

8

10

12

σy (mm)σx (mm)

12000

8

10

10

8

6

Fig.5. µx , µy , σx , and σy as a function of the elapsed time in a spill (run13364). The elapsed
time is divided into ten groups.

49beam) and tagged photon energy. Approximately 3 mm decrease of mux is observed in a spill in the 1200
MeV mode. Figure 5 shows µx , µy , σx , and σy as a function of the elapsed time in a spill. The details of
the analysis for the photon beam profiles are described in Ref. [21].
3.3 Update of the position reconstruction for the SCISSORS III clusters
The photons emitted from the target does not inject onto the SCISSORS III in perpendicular direction to the front faces of CsI crystals. The position of a cluster determined from the center of thefront faces of CsI crystals in the cluster is slightly shifted according to the shift of the injection angle.
Figure 6 shows the schematic view of the shift of the reconstructed position. The correction of this shift
was determined by considering the depth with the maximum energy deposit. Figure 7 shows the depthwith the maximum energy deposit as a function of the initial photon energy injecting to crystals. The
details of the correction are described elsewhere [22].

Pr
Pi

lmax
Pi

lmax

Normal Vector

PPrr

Fig.6.

Schematic view of the shift of the reconstructed position. When the photon does not cometo a CsI crystal perpendicularly to its front face, the reconstructed position is shifted
according to the depth with the maximum energy deposit.

3.4 Update of the position reconstruction for the Backward Gamma clusters
The position reconstruction was updated for the Backward Gamma clusters similarly to that developed for the prototype BGO calorimeter [33]. Figure 8 shows the position resolutions as a functionof the incident positron energy obtained in the previous analysis [34], and Figures 9 and 10 show theposition resolutions with a new method for the central and peripheral modules, respectively. The x andy are defined for the prototype calorimeter comprised of 3 × 3 Lead/SciFi modules, and correspond to
azimuthal and polar angle directions, respectively. The resolution for the central modules is well reproduced by the equation σ/mm = 7.41(Ee /GeV)−0.2279 , and that for the peripheral ones is expressedby σ/mm = 9.09(Ee /GeV)−0.1717 . The position resolution obtained with a new method becomes muchbetter than that obtained with a previous method. The details of the position reconstruction for the
Backward Gamma clusters are described elsewhere [23].
3.5 Effective number of counts for the photon tagging system
The correction validity for the counting loss of the tagging signals was investigated [24], and theratio between the corrected numbers of tagging signals was found to be constant independently of the

50

140
120

Depth (mm)

100
80
60
40
20
0
Fig.7.

0

200

400
600
800 1000
Incident Energy (MeV)

1200

Depth with the maximum energy deposit as a function of the incident photon energy. The
data are compared with a function µ` (Eγ )/mm = 17.19 log(1 + 0.0916Eγ /MeV) + 39.87.

tagging rate. The trigger formation efficiency was updated by taking account the next leading order ofthe correction [25], and the validity of the correction was checked by means of the γp → π 0 p yield foreach tagging channel and for each intensity.
3.6 Update of the timing reconstruction of the SPIDER scintillators
The timing calibration of the SPIDER scintillators was made by considering the dependence of themeasured energy and the radius (distance from z axis) [26]. To avoid the effect of the time of flight,
the charged clusters coming from electrons and positrons were selected by using the energy leakage
information. The measured time as a function of radius was investigated for the measured energy
ranging from 1.3 to 1.7. The radial behavior of the measured time was assumed to be the same. Figure 11
shows the measured time as a function of the radius. The measured time was well reproduced by thefunction((1)µ(r) = t0 − α1(r/1000.)β1 +

α2r/1000.

 β2 )+q
r 2 + L20 − L0
c

(1)

(1)

where L0 = 972.3 mm. The parameters t0 ∼ 0.7, α1 ∼ 13, α2 ∼ 0.3, β1 ∼ 1.5, β2 ∼ 5 were determinedfor each period. Figure 12 shows the measured time as a function of the measured energy after theradial correction was applied. The measure time was well reproduced by the function
nπ
o
(2)
µe (ESp ) = t0 + α3
− tan−1 α4 ESp .
2(2)

The parameter α3 ∼ 2 was determined for each period, and α4 ∼ 0.5 was determined for each half a day.
These parameters were given crystal by crystal. After these corrections, the width of the time difference

51

Position Resolution (mm)

20
17.5
15
12.5
10
7.5
5
2.5
0

0

100

200

300

400

500

600

700

800

900

Incident Energy (MeV)

Position resolutions as a function of the incident positron energy obtained in the previous
analysis [34]. The blue and red makers show the resolutions for x and y, respectively.
The data are compared with σ/mm = 9.2183(Ee /GeV)−0.38387 . The cyan and magentalines denote a twelfth of the x and y length of the front face, respectively.

Position Resolution (mm)Fig.8.

Fig.10.

0

100

200

300
400
500
600
Incident Energy (MeV)

700

800

900

Position resolutions as a function of the incident positron energy for the central modules
with a new method. The blue and red makers show the resolutions for x and y, respectively. The data are compared with σ/mm = 7.41(Ee /GeV)−0.2279 . The green horizontal
lines denote a twelfth of the x and y length of the front face.

Position Resolution (mm)Fig.9.

22
20
18
16
14
12
10
8
6
4
2
0

26
24
22
20
18
16
14
12
10
8
6
4
2
0

0

100

200

300
400
500
600
Incident Energy (MeV)

700

800

900

Position resolutions as a function of the incident positron energy for the peripheral modules with a new method. The blue and red makers show the resolutions for x and y,
respectively. The data are compared with σ/mm = 9.09(Ee /GeV)−0.1717 . The green
horizontal lines denote a twelfth of the x and y length of the front face.

52

between the SPIDER plastic scintillator and the average of the two photon clusters became 0.35 ns. The
details of the timing reconstruction of the SPIDER scintillators are described elsewhere [27].
3.7 Update of the timing reconstruction of the IVY scintillators
The timing calibration of the IVY scintillators was made by considering the dependence of themeasured energy and the polar angle [27]. To avoid the effect of the time of flight, the charged clusters
coming from electrons and positrons were selected by using the energy leakage information similarly to
the SPIDER case. The data were well reproduced with the functionµt = t0 − CV (E) − Cθ (`) = t0 + αV E −βV − αθ (` − 3)βθ ,(3)and the parameters αθ , βθ , αV , and βV were determined period by period for each IVY plastic scintillator. The width of the time difference between the IVY plastic scintillator and the average of thetwo photon clusters became 0.45 ns after the correction according to the measured energy and polar
angle was applied. The details of the timing reconstruction of the IVY scintillators are described elsewhere [27].
3.8 Center of the cryogenic target
The differential cross section for the γp → ηp reaction near the threshold is flat due to the large
contribution of the S11 nucleon resonance as an intermediate state. To make the differential cross section
flat, the acceptances for the Backward Gamma detector should be changed artificially to be lower at
small polar angles and higher at large angles. This suggests that the actual target center is upstreamof the designed one. The events were selected that three final state particles were detected with the
Backward Gamma detector for the γp → π 0 p reaction. The polar angle number distributions of photon
clusters are estimated for the proton detected polar angle numbers B3, B4, and B4. The optimum shiftof the target center was determined so that the distributions estimated by a Monte-Carlo simulation
fitted to the data for each proton detected angle. The shifts of −12 and −8 mm were obtained for 1200
and 920 MeV circulating electron modes, respectively. Shortening of the aluminum pipe for the target
holder was suggested at the pipe temperature of approximately 20 K. The details of the analysis are
discussed [28, 29].
3.9 Energy and angular resolutions for the SCISSORS III and Backward Gamma clusters
The energy and angular resolutions were investigated [30] for the preparation of using a kinematic
fit technique [31].
3.10 Efficiency for the proton detection with Backward Gamma
The efficiency for the proton detection with Backward Gamma was discussed [32], and is alreadyreported in the previous annual report [35].

53

0.5

Mean of tSp-tave (nsec)

0
-0.5
-1
-1.5
-2
-2.5
50

Fig.11.

100

150

200
250
Radius rSp (mm)

300

350

400

Measured time as a function of the radius (2010B) for the measured energy ranging
from 1.3 to 1.7. The data are well reproduced with the equation (1) show in the green
curve.

Mean of tSp-tave (nsec)

1.5
1
0.5
0
-0.5
-1
-1.5
-2
1.5
1
0.5
0
-0.5
-1
-1.5
-2
1.5
1
0.5
0
-0.5
-1
-1.5
-2
1.5
1
0.5
0
-0.5
-1
-1.5
-2
1.5
1
0.5
0
-0.5
-1
-1.5
-2
1.5
1
0.5
0
-0.5
-1
-1.5
-2

Sp37

Sp38

Sp39

Sp40

Sp41

Sp42

Sp43

Sp44

Sp45

Sp46

Sp47

Sp48

Sp49

Sp50

Sp51

Sp52

Sp53

Sp54

Sp55

Sp56

Sp57

Sp58

Sp59

Sp60

Sp61

Sp62

Sp63

Sp64

Sp65

Sp66

Sp67

Sp68

Sp69

Sp70

Sp71

Sp72

0 1 2 3 4 50 1 2 3 4 50 1 2 3 4 50 1 2 3 4 50 1 2 3 4 50 1 2 3 4 5Energy (Emip)

Fig.12.

Measured time as a function of the measured energy (2010B) after the radial correction
is applied. The data are well reproduced with the equation (2) show in the red curves.

Mean of Timing Difference Distribution (nsec)

54

1
0
-1
-2
-3

Bp01

Bp02

Bp03

Bp04

Bp05

Bp06

1
0
-1
-2
-3

Bp07

Bp08

Bp09

Bp10

Bp11

Bp12

1
0
-1
-2
-3

Bp13

Bp14

Bp15

Bp16

Bp17

Bp18

0 1 2 3 4 50 1 2 3 4 50 1 2 3 4 50 1 2 3 4 50 1 2 3 4 50 1 2 3 4 5Energy (EMIP)

Fig.13.

Measured time as a function of the measured energy (2009D) for each polar angle number of the maximum energy module of the corresponding Lead/SciFi module in a cluster.
The data are well reproduced with the equation (3) show in the red curves.

§ 4. Progress of the analysis in FY2012
The progress of the analysis in FY2012 is described in this section. The further discussion wasmade for the center of the cryogenic target [36]. The library for the kinematical fit was introduced tothe analysis code for the FOREST experiments [37, 38]. The position reconstruction for the Rafflesia
II clusters was updated [39], and the energy calibration was made according to this change [40]. The
further investigation of the energy and angular resolutions was made with comparison between theexperimental data and the simulation data [41–49]. The improvement of the momentum reconstruction
for the proton, neutron, charged pion was discussed by using time of flight information [50–55]. The
detection efficiency of the proton, and charged pions with SCISSORS III and Backward Gamma wasdiscussed [56–58]. The shapes of the H2 and D2 targets were measured with a laser displacement
meter, and the number of target protons and deuterons were determined precisely [59]. The tagging
energy and its resolution was investigated [60–62]. The placement of the Backward Gamma detector,
and the geometry of the SCISSORS III frame and Rafflesia II was studied by using the experimental
reaction data [63–65]. The timing resolution implemented to the simulation was discussed [66, 67].
The correlation between the IVY scintillator and Lead/SciFi module was updated [68, 69]. The timedifference between a plastic scintillator and an electromagnetic calorimeter module is investigated [70].
4.1 Further study of the center of the cryogenic target
The further discussion was made for the center of the cryogenic target [36]. The angular distribution
for the γp → π 0 p reaction was uniform in the simulation of the previous analyses [28, 29]. Since
the tagging counters cover the threshold of the γp → ηp reaction, the tagging energies near the η
photoproduction threshold are reliable. The similar analysis to the previous analyses [28, 29] was made

55
in the 920 MeV circulating electron mode with a realistic angular distribution for the γp → π 0 p reaction.
The optimum shift of the target center was again −8.0 mm. The details of the further study of the centerof the cryogenic target are described elsewhere [36].
4.2 Library for the kinematical fit
The library for the kinematical fit was introduced to the analysis code for the FOREST experiments [37, 38]. The kinematical fit introduced is also discussed in Ref. [31].
4.3 Update of the position reconstruction for the Rafflesia II clusters
The position reconstruction was updated for the Rafflesia II clusters [39] similarly to that developed
for the prototype BGO calorimeter [33]. Rafflesia II consists of two different modules with front faces of
75 × 75 (SF6) and 150 × 150 mm2 (SF5). Additionally, the photons do not come in perpendicular direction
to the front faces of lead glass Čerenkov counters. The parameters for the position reconstruction were
determined module by module. The energy calibration was made according to this change [40].
4.4 Energy and angular resolutions for the electromagnetic calorimeters
The energy and angular resolutions were investigated [30], and the obtained resolutions for theexperimental and simulation data were compared with each other for the γp → ηp [41] and γp → π 0 preactions [42]. Here, these reactions were selected by a kinematical fit with four constraints:
1. the invariant mass of two photons should be the meson rest mass,
2. the missing mass mX for γp → η(π 0 )X should be the proton mass,
3. the correlation of polar angles between the meson and the proton, and4. the correlation of azimuthal angles between the meson and the proton.
The momentum and angular resolutions were obtained for the proton by using the simulation [44]. Theenergy and angular resolutions were estimated again [43, 45, 47] according to the following changes:
1. the iron frame for SCISSORS III was implemented [65],2. the energy calibration was updated for SCISSORS III [52],3. the position reconstruction for the Backward Gamma clusters was updated [23],4. the target thickness was precisely determined [59],5. the target center was updated [36],6. the placement of Backward Gamma was modified [63],7. the position reconstruction was updated for Rafflesia II clusters [39], and8. the energy calibration was made with the new position reconstruction for Rafflesia II clusters [40].
The obtained resolutions for the experimental and simulation data were compared with each other forthe γp → ηp [48] and γp → π 0 p reactions [49]. Here, these reactions were selected by a kinematical fit
with four constraints:
1. the invariant mass of two photons should be the meson rest mass, and2. three equations obtained by eliminating the proton momentum from four energy and momentum
conservation ones.

56

Figures 14, 15 and 16 show the widths of the ratio distribution between the measured and fitted energies
Emeas /Efit for Backward Gamma, SCISSORS III, and Rafflesia II clusters, respectively. The width of
the Emeas /Efit distribution given for the experimental data agrees with that given for the simulation
except for the R7 crystals (peripheral INS-type crystals) in SCISSORS III. The details of the comparison
between the experimental and simulation data are described elsewhere [48, 49].
4.5 Momentum reconstruction for the proton, the neutron and charged pions
The momentum reconstruction for the neutron was given by the correlation between the measured
time and the fitted momentum by analyzing the γp → π 0 π + n reaction events, which were selected by akinematical fit with four constraints:
1. the invariant mass of two photons should be the pion mass, and2. three equations obtained by eliminating the pion momentum from four energy and momentum
conservation ones.
Figure 17 shows the correlation between the measured timing and the neutron momentum detected withSCISSORS III and Backward Gamma. The mean of the measured timing distribution is well reproducedby the equation

βm
αm
µm =
.
pn + δm(4)

The parameters α, β, and δ were given for SCISSORS III and Backward Gamma separately. The momentum resolution for the neutron was also determined as a function of the momentum. The details of
the analysis are given elsewhere [50, 53].
The momentum reconstruction for the proton detected with SCISSORS III was investigated by
the correlation between the measured time and the time corresponding to the fitted momentum for the
γp → ηp reaction events, which were selected by a kinematical fit with four constraints:
1. the invariant mass of two photons should be the η mass,
2. the missing mass mX for γp → ηX should be the proton mass,
3. the correlation of polar angles between the meson and the proton, and4. the correlation of azimuthal angles between the meson and the proton.
As for the proton detected with Backward Gamma, the γp → π 0 p events were selected instead in thesimilar way. Figure 18 shows the measured time and the time corresponding to the fitted momentum.
The details of the analysis for the γp → ηp reaction for reconstructing the proton momentum detectedwith SCISSORS III are given elsewhere [51, 54]. The details of the analysis for the γp → π 0 p reaction
for reconstructing the proton momentum detected with Backward Gamma are given elsewhere [52, 55].
4.6 Detection efficiency of the proton and charged pion
The detection efficiency of the proton with Backward Gamma was estimated by analyzing the γp →π 0 p events, which were selected by a kinematical fit with two constraints:
1. the invariant mass of two photons should be the π 0 mass, and2. the missing mass mX for γp → π 0 X should be the proton mass.

57
0.3 B3

DATA
MC
KF

B4

DATA
MC
KF

B5

DATA
MC
KF

DATA
MC
KF

B8

DATA
MC
KF

B9

DATA 0
MC
KF

B6

DATA
MC
KF

0.25
0.2
0.15

Energy Resolution

0.1
0.05
0
0.3 B7

200

400

600

800

0.25
0.2
0.15
0.1
0.05
0
0

Fig.14.

200

400

600

800
0

200

400

600

800
0

200

Efit (MeV)

400

600

800

Width of the ratio distribution between the measured and fitted energies Emeas /Efit for
Backward Gamma clusters.The black and red points show the results from the experimental and simulation data, respectively. The green show the width of the ratio between
the fitted and generated energies Efit /Egen , indicating the bias of the kinematical fit.
Ring1

DATA
MC
KF

Ring2

DATA
MC
KF

Ring3

DATA
MC
KF

Ring5

DATA
MC
KF

Ring6

DATA
MC
KF

Ring7

DATA 0
MC
KF

0.25

Ring4

DATA
MC
KF

0.2
0.15

Energy Resolution

0.1
0.05
0
0.25

200

400

600

800

0.2
0.15
0.1
0.05
0
0

Fig.16.

400

600

800
0

200

400

600

800
0

200

Efit (MeV)

400

600

800

Width of the ratio distribution between the measured and fitted energies Emeas /Efit for
SCISSORS III clusters. The black and red points show the results from the experimental
and simulation data, respectively. The green show the width of the ratio between thefitted and generated energies Efit /Egen , indicating the bias of the kinematical fit.

Energy Resolution

Fig.15.

200

0.45 R1
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
0.45 R5
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
0
200

DATA
MC
KF

R2

DATA 0
MC
KF

400

600

800

DATA
MC
KF

200

400

600

R3

800
0

DATA
MC
KF

200

400

600

R4

800
0

DATA
MC
KF

200

400

600

800

Efit (MeV)

Width of the ratio distribution between the measured and fitted energies Emeas /Efit for
Rafflesia II clusters. The black and red points show the results from the experimental
and simulation data, respectively. The green show the width of the ratio between thefitted and generated energies Efit /Egen , indicating the bias of the kinematical fit.

58

10

3.5

SCISSORS III

Backward Gamma

8

Measured timing (ns)Measured timing (ns)

3

6
4
2
0
0

2
1.5
1
0.5
0

200

400

600

800

1000 1200

Neutron momentum (MeV/c)
Fig.17.

2.5

0

200

400

600

800

1000 1200

Neutron momentum (MeV/c)

Correlation between the measured timing and the neutron momentum detected withSCISSORS III (left) and Backward Gamma (right). The blue markers show the mean of
the measured timing distribution, and the red show the width of it. The mean is well
reproduced by the equation (4).

Figure 19 shows the detection efficiencies of the proton with IVY and with Backward Gamma. The
sizable difference between the experimental and the simulation data can be observed. This difference
comes from the different energy response at low energies between the experimental data and the simulation later. The details of the analysis on the proton detection efficiency with Backward Gamma aredescribed elsewhere [56].
The proton detection efficiency with SCISSORS III was also estimated by analyzing the γp → ηpevents. They were selected in the similar way to the γp → π 0 p events. Figure 20 shows the detection
efficiencies of the proton with SPIDER and with SCISSORS III. The experimental data and the simulation agree very well. The details of the analysis on the proton detection efficiency with SCISSORS III
are described elsewhere [57].
The detection efficiency of the charged pion was also investigated. The details of the analysis are
given elsewhere [58].
4.7 Shapes of the H2 and D2 targets measured with a laser displacement meter
The shapes of the H2 and D2 targets were measured with a laser displacement meter. The thicknesses of the H2 and D2 targets were found to be 45.1 and 45.9 mm in the central region, respectively.
The details of the measurement are described elsewhere [59, 71].
4.8 Tagging energy
The change of the tagging energy in a spill was investigated for each tagging channel [60], and it was
found to be large in the end of spills in many periods. The change of the tagging energy was implemented
to the simulation, and its resolution was estimated by taking it into account. The deterioration of it is10

tBe-tγγtSc-tγγ

59

9

6

5

8
7

4

6
5

3

4
2

3
2

1

1
0
0

1

2

3

4

5

6

7

8

9

10

0
0

1

tp-tc (nsec)
Fig.18.

2

3

4

5

6

tp-tc (nsec)

Measured time and the time corresponding to the fitted momentum. The left panel
shows the correlation of SCISSORS III for the γp → ηp reaction. The right panel shows
the correlation of Backward Gamma for the γp → π 0 p reaction.

several MeV.
The validity of the tagging energy was checked for the behaviors of the yields near the production
threshold for the γp → ηp and γp → ωp reactions. The γp → ηp events were selected by a kinematical
fit with two constraints:
1. the invariant mass of two photons should be the η mass, and2. the missing mass mX for γp → ηX should be the proton mass.
Figure 21 shows the yield as a function of the tagging energy. The yield was determined by the numberof η produced events and that of photons. The current tagging energy well reproduced the threshold of
the γp → ηp reaction. The details of the analysis are given elsewhere [62]. The γp → ωp events wereselected by a kinematical fit with five constraints
1. the invariant mass of two photons should be the π 0 mass, and2. the energy and momentum conservations
and two unmeasured variables (two charged pion momenta). The current tagging energy also well reproduced the threshold of the γp → ωp reaction [61].
4.9 Geometry of Backward Gamma, SCISSORS III, and Rafflesia II
The azimuthal angle distribution for the events that the proton for the γp → π 0 p reaction was
detected with B3 Lead/SciFi modules in Backward Gamma shows a sine curve. The events were selectedby a kinematical fit with four constraints:
1. the invariant mass of two photons should be the pion mass, and2. three equations obtained by eliminating the proton momentum from four energy and momentum

Efficiency

Efficiency

60

1

1

0.8

0.8

0.6

0.6

0.4

0.4

0.2

Bp(920MeV)
Bp(1200MeV)
RFSBp(920MeV)
RFSBp(1200MeV)

0.2

Be(920MeV)
Be(1200MeV)
RFSBe(920MeV)
RFSBe(1200MeV)

00

100 200 300 400 500 600 700 800 900 1000

00

100 200 300 400 500 600 700 800 900 1000

proton momentum (MeV)
Fig.19.

proton momentum (MeV)

Detection efficiencies of the proton with IVY and with Backward Gamma. The left panel
shows the efficiency for IVY, and the right shows that for Backward Gamma. The sizable
difference between the experimental and the simulation data can be observed.

conservation ones.
The amplitude of the sine curve corresponds to the −6.0 mm shift of the y direction according to thesimulation. The details of the analysis can be found in Ref. [63]. After the analysis was finished, themeasurement of the Backward Gamma placement was made. And the −6 mm shift was found as sameas the result of the analysis.
The placement of Rafflesia II was adjusted so that the fitted direction of photons coming to Rafflesia
II agreed between the experimental data and the simulation for the γp → ηp reaction. The γp → ηpevents were selected by a kinematical fit with five constraints:
1. the invariant mass of two photons should be the pion mass, and
2. four energy and momentum conservation ones,
and the energy, polar, and azimuthal angles are treated as unmeasured for the photon coming to Rafflesia
II. The details of the analysis are described in Ref. [64].
The iron frame of the SCISSORS III was implemented to the simulation, and the shape of it wasslightly adjusted so that the upper limit of the polar angle of the proton detected with SCISSORS III
agreed between the experimental data and the simulation. The details of the implementation of the
SCISSORS III iron frame are described elsewhere [65].
4.10 Update of IVY scintillators in front of a Lead/SciFi module
IVY plastic scintillators placed in front of a certain Lead/SciFi module was investigated. Charged
pions from the γp → π 0 π + n reaction and protons form the γp → π 0 π + n reaction were selected with ahelp of kinematical fits, and simultaneous response of the IVY scintillator and Lead/SciFi module wasscanned corresponding to these charged particles. The details of the determination of IVY scintillators

Efficiency

Efficiency

61

1

1

0.8

0.8

0.6

0.6

0.4

0.4

0.2

Sp(920MeV)
Sp(1200MeV)
RFSSp(920MeV)
RFSSp(1200MeV)

0.2

Se(920MeV)
Se(1200MeV)
RFSSe(920MeV)
RFSSe(1200MeV)

00

100 200 300 400 500 600 700 800 900 1000

00

100 200 300 400 500 600 700 800 900 1000

proton momentum (MeV)
Fig.20.

proton momentum (MeV)

Detection efficiencies of the proton with SPIDER and with SCISSORS III. The left panel
shows the efficiency for SPIDER, and the right shows that for SCISSORS III.

in front of a Lead/SciFi module are described elsewhere [68, 69].
4.11 Time difference between a plastic scintillator and an electromagnetic calorimeter module
All the charged particles penetrating a plastic scintillator (PS) and coming into an electromagnetic
calorimeter (EMC) module do not travel with the speed of light. In addition, the time resolution is poor
for low energy particles. Therefore, the spread of the time difference between PS and EMC is large at
low energies, and becomes constant at high energies. The upper and lower limits of the time difference
was determined [70].

§ 5. Progress of the analysis in FY2013
The progress of the analysis in FY2013 is described in this section. The detection efficiency is related
to the energy response at low energy, and the momentum reconstruction is related to the time responsein the simulation. Much progress on the improvement of the simulation was made to reproduce the experimental data. The detection efficiency together with the energy response was discussed [72–80], andthe momentum reconstruction together with the times response was discussed [81–90]. The geometry of
the SPIDER and IVY plastic scintillator hodoscopes were adjusted to reproduce the acceptance.
5.1 Detection efficiency for the proton, the neutron and charged pions
The detection efficiency of the neutron with Backward Gamma as a function of the momentum wasestimated by analyzing the γN ∗ → π 0 N events [72], which were selected with two constraints:
1. the invariant mass of two photons should be the π 0 mass, and2. the missing mass mX for γN ∗ → π 0 X should be the nucleon mass.

62

500

500

FOREST2009E
707.37±0.02 MeV

708.16±0.04 MeV
400
Yield (a.u.)

Yield (a.u.)

400
300
200
100

300
200
100

0

0
660

Fig.21.

FOREST2010A

680

700
720
Eγ (MeV)

740

660

680

700
720
Eγ (MeV)

740

Yield as a function of the tagging energy (2009E and 2010B). The current tagging energy
well reproduces the threshold of the γp → ηp reaction.

The detection efficiency of the neutron with SCISSORS III was estimated by analyzing the gammaN ∗ →ηN events in the similar way [73]. Figure 22 shows the neutron detection efficiency as a function of the
momentum. The difference between the experimental data and the simulation was found.
The measured energy for the proton with SCISSORS III in the experimental data was higher thanthat in the simulation. To reproduce the measured energy in the experimental data, the light output was
adjusted as a function of the stopping power of the proton [74]. The sum of the γp∗ → π 0 p and γn∗ →π 0 n events can be smaller than that of the γd → π 0 X events. Therefore, the detection efficiency of theneutron was estimated by using the γp → π 0 π + n events, and also the physics list for the simulation
was changed to QGSP_BERT_HP from LHEP. Figure 23 shows the neutron detection efficiency as a functionof the momentum estimated by using the γp → π 0 π + n events. The difference between the experimental
data and the simulation became much smaller. The details of the detection efficiency of the neutron are
discussed in Ref. [75, 76, 79]
The proton detection efficiencies were updated for Backward Gamma and SCISSORS III by using
the γp → π 0 p and γp → ηp reactions [77, 78]. The rising edge of the efficiency curve for SCISSORS
III is different between the experimental data and the simulation for some polar angles. An in-efficientregion was set in the surface of a CsI crystal to remove these differences. Figure 24 shows the proton
detection efficiency as a function of momentum. with the optimum in-efficient region in the surface ofa CsI crystal. The efficiency of the experimental data for each polar angle was well reproduced by thesimulation. The details of setting the in-efficient region are described in Ref. [80].

0.5

0.4

Efficiency

Efficiency

63

DATA(09E)
DATA(09D)
RFS(09E)
RFS(09D)

0.5

0.4

0.3

0.3

0.2

0.2

0.1

0.1

0
0

100

200

300

400

500

600

700

800

Neutron momentum (MeV)
Fig.22.

00DATA(09E)
DATA(09D)
RFS(09E)
RFS(09D)

200

400

600

800

1000

1200

Neutron momentum (MeV)

Neutron detection efficiency as a function of the momentum. The left panel shows theefficiency for the detection with Backward Gamma, and the right shows that for thedetection with SCISSORS III.

5.2 Momentum reconstruction for the proton, the neutron and charged pions
The measured timing was determined by considering the travelling time of the scintillation lightto the photomultiplier tube. Since the waveform depends on the incident particle, the measured timing was adjusted for the proton, the neutron, and charged pions to reproduce the small difference ofthe measured timings of them in the experimental data [81, 83]. The difference between the measured
timings between the experimental data and the simulation became small, and the equations for reconstructing the momentum for these particles between them became similar [82] The momentum reconstruction of the neutron is discussed in Ref. [84], that of the proton with SCISSORS III is described inRef. [85, 88, 90], that of the proton with Backward Gamma is in Ref. [86, 89], and that of the charged
pions with SCISSORS III is written in Ref. [87].
5.3 Geometry of the detectors
The peripheral materials for detectors, the POM core of SCISSORS III, light guides for SPIDER
plastic scintillators, iron core of Rafflesia II were added [91, 92]. The position reconstruction was updated
again for the Rafflesia II clusters [93] according to the change of the placement of lead glass Čerenkov
counters [64], and the energy calibration was made according to this change [94]. The placement oflead glass Čerenkov counters in Rafflesia II was further updated [95, 96], which was determined by theγp → ηp events to reproduce the residual for the polar and azimuthal angles in this reaction finally.
The z position of the IVY hodoscope was determined the fraction of the events coming to the overlapped
region between SPIDER and IVY [97], The x and y shifts of it was given from the behavior of theazimuthal angle distribution [98]. The z position, tilting angle α, and the axis of the tilt Φ of the

0.5
0.45
0.4

Efficiency

Efficiency

64

DATA(09E)
DATA(09D)
RFS(09E)
RFS(09D)

0.5
0.45
0.4

0.35

0.35

0.3

0.3

0.25

0.25

0.2

0.2

0.15

0.15

0.1

0.1

0.05

0.05

0
0

100

200

300

400

500

600

700

800

0
0

Neutron momentum (MeV)
Fig.23.

DATA(08C-09E)
DATA(10A-10B)
RFS(08C-09E)
RFS(10A-10B)

100

200

300

400

500

600

700

800

Neutron momentum (MeV)

Neutron detection efficiency as a function of the momentum estimated by using theγp → π 0 π + n events. The physics list of the simulation was changed to QGSP BERT HP.
The left panel shows the efficiency for the detection with Backward Gamma, and theright shows that for the detection with SCISSORS III.

SPIDER hodoscope was adjusted to give the same polar angle for each combination of the left and righthanded scintillators for the γp → ηp reaction [99, 100]. Figure 25 shows the mean and width of thepolar angle distribution as a functino of the azimuthal angle for n12 =1 and for n13 =1. The n12 =1 andn13 =1 denote the overlapped region of the first and second layers and of the first and third layers at
most outside. The difference between the experimental data and simulation becomes small after themodification was made for the SPIDER geometry in the simulation. The placement of CsI crystals were
updated [92, 101] to make SCISSORS III compact, and the optimum z position of SCISSORS III wasdetermined [102] fitting the polar angle distribution of the simulation to that in the experimental data
by using the γp → ηp events. The optimum shift of the target center was estimated again after themodification of the simulation code, and the value of −6.6 mm was obtained [103].
5.4 Momentum and angular resolutions for the kinematical fit
The momentum and angular resolutions are used for a kinematic fit which selects the events corresponding to the reaction. The mean value and resolution of the polar and azimuthal angles measured
with a CsI crystal were determined for the proton, the neutron, and charged pion [104]. The residuals
for the polar and azimuthal angles given by a SCISSORS III cluster were compared between the experimental data and the simulation for the proton, the neutron, and the charged pion from the γp → ηpand γp → π 0 π + n reactions [105, 106]. Those given by a combination of a SCISSORS III cluster and a
SPIDER knot were compared [107]. The momentum and angular resolutions were estimated again after
the POM core, iron frame were added, and the determination of the measured energy with SCISSORS
III was modified [108]. The momentum and angular resolutions for the proton were determined by theEfficiency / 20 MeV

65

1
0.8
0.6
0.4
0.2
0
1
0.8
0.6
0.4
0.2
0
1
0.8
0.6
0.4
0.2
0
1
0.8
0.6
0.4
0.2
0
1
0.8
0.6
0.4
0.2
0
1
0.8
0.6
0.4
0.2
0
1
0.8
0.6
0.4
0.2
0

0

Fig.24.

250

500

4,5 deg

5,6 deg

6,7 deg

7,8 deg

8,9 deg

9,10 deg

10,11 deg

11,12 deg

12,13 deg

13,14 deg

14,15 deg

15,16 deg

16,17 deg

17,18 deg

18,19 deg

19,20 deg

20,21 deg

21,22 deg

22,23 deg

23,24 deg

24,25 deg

750

1000 0250 500 750 1000 0
Proton Momentum (MeV/c)

250

500

750

1000

Proton detection efficiency as a function of momentum. with the optimum in-efficientregion in the surface of a CsI crystal. The blue show the experimental data and the redshow the simulation data.

Fig.25.

θ (deg) for n13=1

Before the modification
24
23.5
23
22.5
22
21.5
21
20.5
20
19.5
19
0
100
200
300
Azimuth φ (deg)After the modification
24
23.5
23
22.5
22
21.5
21
20.5
20
19.5
19
0
100
200
300
Azimuth φ (deg)θ (deg) for n13=1

θ (deg) for n12=1

θ (deg) for n12=1

66

24
23.5
23
22.5
22
21.5
21
20.5
20
19.5
19

24
23.5
23
22.5
22
21.5
21
20.5
20
19.5
19

0

100
200
300
Azimuth φ (deg)

0

100
200
300
Azimuth φ (deg)Mean and width of the polar angle distribution as a functino of the azimuthal angle for
n12 =1 (left) and for n13 =1 (right). The upper panel show those before the modification for
the SPIDER geometry in the simulation and the lower show those after the modification.

simulation, and the validity of them were carefully checked by comparing the experimental data to thesimulation [109–115]. Those for the photon were also determined by the simulation, and the validity ofthem were checked by comparing the experimental data to the simulation [116–120].

§ 6. Preliminary results on the cross section
The total cross sections as a function of the incident photon energy are obtained for η photoproduction on the proton by using the hydrogen target events taken in the FOREST2009D and 2009E period.
Fig. 26 shows the preliminary results of the total cross section as a function of the incident photon energy
for η photoproduction on the proton.
The total cross sections as a function of the incident photon energy are obtained for π 0 photoproduction on the proton by using the same events for η photoproduction. Fig. 27 shows the preliminary

67

18

γp→ηp

16

ETA-MAID2003
SAID GW2009
BoGa 2011-2

Cross Section (µb)

14
12
10
8
6
4
2
0

P

e
r

700

900
1000
γ Energy (MeV)

1100

1200

The preliminary results of the total cross section as a function of the incident photon energy for η photoproduction on the proton. The data are compared with the ηMAID2003 [121], SAID [122], and BoGa [123] calculations.

Cross Section (µb)

Fig.26.

800

m
i
l

in

y
r
a

50

π0p

40

MAID2007SAID 2012
BoGa 2011-2

30

20

10

P

e
r

m
i
l

a
in

y
r

0
600
Fig.27.

700

800
900 1000γ Energy (MeV)

1100

1200

The preliminary results of the total cross section as a function of the incident photon energy for π 0 photoproduction on the proton. The data are compared with the
MAID2007 [124], SAID [122], and BoGa [123] calculations.

68
results of the total cross section as a function of the incident photon energy for π 0 photoproduction on
the proton.
The slight difference between the experimental and simulation data still exists at this moment. We
are now working on this problem to finalize the FOREST data.

§ 7. Summary
Ten series of meson photoproduction experiments with FOREST has been carried out in 2008–2010. The main purpose of the FOREST experiments is to study a nucleon resonance N ∗ (1670), which
is a candidate of antidecuplet pentaquark baryons via η photoproduction on the neutron. The energy
and timing calibrations of all the detectors have been finished. The software alignment of SPIDER,SCISSORS III, and Rafflesia II has been made. The estimation of the nucleon detection efficiency has
been completed. The precise determination of the time of flight for the nucleon has also been developed.
The preliminary results of the total and differential cross sections for the γp → π 0 p and γp → ηpreactions are obtained. Now, we are working on the slight difference between the experimental andsimulation data to finalize the FOREST data.

Acknowledgment
This work was supported in part by Grant-in-Aids for Scientific Research (B) (17340063), for Specially promoted Research (19002003), and for Scientific Research (A) (24244022).

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ELPH Annual Report, Tohoku University (2011-2013)73(ELPH Experiment : #2623, #2640, #2655, #2694)

Bose-Einstein correlations between two neutral pions fromphotoproduction at energies below 1.2 GeV
Q. He1 , H. Fujimura1 , H. Fukasawa1 , R. Hashimoto1 , Y. Honda1 ,T. Ishikawa1 , T. Iwata2 , S. Kaida1 , J. Kasagi1 , A. Kawano3 , S. Kuwasaki1 ,K. Maeda4 , S. Masumoto5 , M. Miyabe1 , F. Miyahara1 , K. Mochizuki1 ,N. Muramatsu1 , A. Nakamura1 , K. Nawa1 , S. Ogushi1 , Y. Okada1 ,Y. Onodera1 , K. Ozawa6 , Y. Sakamoto3 , M. Sato1 , H. Shimizu1 , H. Sugai1 ,K. Suzuki1 , Y. Tajima2 , S. Takahashi1 , Y. Taniguchi1 , Y. Tsuchikawa1 ,H. Yamazaki1 , R. Yamazaki1 , and H.Y. Yoshida2
1

Research Center for Electron Photon Science, Tohoku University, Sendai 982-0826, Japan2

3

Department of Physics, Yamagata University, Yamagata 990-8560, Japan

Department of Information Science, Tohoku Gakuin University, Sendai 981-3193, Japan
4

Department of Physics, Tohoku University, Sendai 980-8578, Japan

5
6

Department of Physics, University of Tokyo, Tokyo 113-0033, Japan

Institute of Particle and Nuclear Studies, KEK, Tsukuba 305-0801, Japan

Double neutral pion photoproduction was measured at the Research Center for Electron Photon Science (ELPH) at Tohoku University in the years 2008, 2009 and 2010 just before the Great East-Japan
Earthquake. A 4π electro-magnetic calorimeter complex, named FOREST, was employed to detect neutral mesons decaying into photons as well as some charged particles in the final state. The authors
present the total cross section of the γp → 2π 0 p reaction at incident photon energies ranging from
0.5 to 1.2 GeV. In addition, we for the firt time study the space-time properties of the two–pion emitter via Bose-Einstein correlations (BEC) between two neutral pions emitted from double neutral pion
photo-productions in the incident photon energy region from 1.0 to 1.15 GeV. FOREST datasets for the
exclusive reaction γp → 2π 0 p and the inclusive reactions γp → 2π 0 X and γd → 2π 0 X, taken in 2009,
are used in the BEC analysis. To do this analysis, an event mixing technique is developed and proves tobe effective. Two BEC parameters r0 and λ2 , which characterize the size of the emission region and thedegree of being chaotic of emission, are obtained. In this work, we present these BEC analysis results.

§ 1. Introduction
The Bose-Einstein (BE) effect was used for the first time in the 1950s by Hanbury-Brown andTwiss [1–3] in astronomy to measure the the sizes of astronomical objects. Accordingly, BE effect is also
referred to as the Hanbury-Brown-Twiss (HBT) effect. This BE-effect-based method, commonly called
two-particle intensity interferometry (intensity correlation) method, is based on the fact that photons arebosons and obey the Bose-Einstein statistics. Fig.1 gives a schematic illustration of the Bose-Einsteineffects of two identical particles. Two-boson wave-function should be symmetric with respect to the74exchange of two bosons, leading to an enhanced probability of emission when two bosons have very
similar energy-momenta. The enhancement can be measured in term of the two particle correlation
function:C2 (1, 2) =P (1, 2),
P (1)P (2)(1)

where P (1, 2) is the two particle probability and P(i) (i=1,2) is the single particle probability. If a sphereof reaction volume with a Gaussian density distribution is assumed and a chaoticity parameter λ2 isintroduced [6], the equation (1) gets the form
2 2

C2 (Q) = N (1 + λ2 e−Q r0 ),(2)

where N is the normalized factor, Q is the relative momentum invariant mass Q2 = −(p1 − p2 )2 =M 2 − 4µ2 (p1 , p2 and M are the four-momentum vectors and the invariant mass of the two identicalbosons of mass µ ) and r0 is the emitting source dimension parameter with the assumption of a Gaussian
density distribution22

ρ(x) = ρ(0)e−x /2r0 .

(3)The parameter λ2 was introduced in order to accommodate possible situations in which the reaction
source is not completely chaotic. λ2 can vary between 0, corresponding to a completely coherent case, to1, corresponding to a totally chaotic situation.
In the hadron physics sector, Bose-Einstein correlation is also used as a tool to study the space-time
properties of hadron reaction region. In this work, we study the spatial extension of the two neutral pions
emitting source for double neutral pion photo-productions off the proton/deuteron at incident photon
energies ranging from 1.0 to 1.15 GeV, by using FOREST dataset taken in 2009.

x1

π 0 ( p1 )π 0 ( p1 )x2sourceπ 0 ( p2 )π 0 ( p2 )Detector 1

d1
Detector 2

d2

Fig.1. Schematic illustration of Bose-Einstein Correlations between two identical particles.
These two particles are emitted from points x1 and x2 in a source. They are detected
at two separate positions d1 and d2 with momenta p1 and p2 , respectively. Two possible
trajectories (full and dashed lines) cannot be distinguished. In the hadron physics sector,
the distance between the emission points is of the order of a femtometer. The distance
between the detector and the particles emission source is of the order of a meter.

§ 2. Total cross section of γp → 2π 0 p
The reaction γp → 2π 0 p is reconstructed by its decay channel γp → 2π 0 p → 4γp, which has 5 final
particles in total. Therefore, candidate events should have four neutral clusters (4 photon candidates)

75
and one charged cluster (proton candidate) detected by FOREST detector. The process 2π 0 → 4γ isreconstructed by an invariant mass analysis. No matter the proton is detected or not, a missing mass
analysis is required for the judgment of the hypothesis that the reconstructed two pions and one charged
particle are decayed from a γp → 2π 0 p reaction. The missing mass analysis is very useful for rejecting
background channels like γp → 2ηp → 6π 0 p.
The event selection is performed in two steps. First, candidate events are picked up with several cut
conditions. Then, these survived events are subjected to a 7 constraints (7C) kinematic fitting. Eventswith confidence level higher than a certain CL cut value are accepted for further physical analysis.
The following cut conditions are used in the first step of event selection:• Two pairs of neutral clusters are detected. In each pair, the time difference between two nuetralclusters should be within the time window −1.5 ns ≤ ∆t ≤ 1.5 ns.
• There is no other neutral cluster detected in the time region from -3.0 to 15.0 nanosecond withrespect to the average time of the four selected neutral cl nusters t4γ .
• There is no knot signal in LOTUS because proton cannot go backward according to the kinematicsof the γp → π 0 π 0 p reaction.
• The sum of the number of knot signals in SPIDER and IVY should not be larger than 1.
The events that passed through the above cut conditions are subjected to a kinematic fitting analysis, in which the four-momentum conservation law and the invariant masses of pion’s and proton’s areused as constraints.
Fig. 2 shows the total cross section of the γp → π 0 π 0 p reaction as a function of the incident photon
energy, which is the averaged value over all cross sections from different datasets in periods of 2009A,
2009B, 2009C, 2009D and 2009E. Our result is compared with previous data. Within error bars, our data
is fairly consistent with all previous results in the region 0.85 GeV ≤ Eγ ≤ 1.1 GeV . These previous
data used in the comparison are from GRAAL [15], CB-ELSA [16, 17], DAPHNE [18], TAPS [17], andCrystal Ball/TAPS [19]. However, in the second resonance region (corresponding the first peak in thiscase) our data is roughly 5% higher than previous data.

§ 3. Event mixing method
In order to observe the Bose-Einstein effects experimentally, one needs to compare the spectra of
Q for the original events to that in a reference sample, which serves as a yardstick. Then, the ratio of
the original Q distribution to the reference one is fitted by the correlation function (2). A valid reference
sample should be identical to the real data (signal sample) in all aspects but free of BE effects. A big
challenge of the BEC study is that it depends rather strongly on the choice of reference sample, whichis thus the main source for the overall systematic errors associated with the fitted parameters. One of
the methods to make a reference sample is event mixing, which construct a mixed event by taking two
particles from different real events. In the case of BEC analysis for two neutral pions, we employ event
mixing technique to make reference sample.
In the studies to extract resonance signals and observe Bose-Einstein effects for inclusive reactions

76

Cross Section (µb)

12
10
8
6
GRAAL-2003.dat
MAMI-Crystal Ball/TAPS-2012

4

CB-ELSA-2008
MAMI-DAPHNE-2005
MAMI-TAPS-2008

2

This work; 1200 MeV Mode
This work; 920 MeV Mode

0

0.5

1

1.5

Eγ (GeV)Fig.2. Total cross section for the reaction γp → π 0 π 0 p. The averaged value is taken over thosein period of 2009A, 2009B, 2009C, 2009D and 2009E. Our results are compared to the previous data from GRAAL [15], CB-ELSA [16, 17], DAPHNE [18], TAPS [17], and Crystal
Ball/TAPS [19].

with large multiplicity, this method proves to be an effective method. In 1984, D. Drijard, H.G. Fischer
and T. Nakada [8] studied in detail the application of event mixing in extraction of resonance signals ininclusive reactions. The features of the invariant mass distribution obtained from combinations of particles from different events, i.e. event mixing, was investigated. They concluded that special kinematicconstraints are needed to reproduce the shape of the uncorrelated invariant mass distribution. Event
mixing is also used as a tool to observe Bose-Einstein correlations in identical boson pairs produced ininclusive reactions with large multiplicities [9–14]. This technique works because it can eliminate all
correlations between particles.
However, the application of event mixing in exclusive reactions encounters a big challenge due tothe fact that energy-momentum conservation is violated. In this section, we study the features of event
mixing for exclusive reactions and attempt to find an effective event mixing technique which can be used
to observe BE effects for 2 π 0 from exclusive/semi-exclusive photo-induced reactions.
3.1 Event mixing technique for the exclusive reaction γp → π 0 π 0 p
Suppose we have a sample containing exclusive reactions with three final-state particles, 2 π 0 s andone proton, produced in accordance with pure phase space kinematics. The total four-momentum of⃗S ), as shown in Fig. 3 (a) and (b). Mixed event is constructed by taking
every reaction is fixed as (ES ,P
two neutral pions from different events. If there is no requirement on the mixing, any two pions fromdifferent events could be paired to form a mixed event as shown in Fig. 3 (c). But such a simple process

77

0
⇡2a

0
⇡1a

p1

S

0
⇡2a
0
⇡2a

S
p2

S : (ES , P~S )0⇡1a : (E1a , P~1a )S : (ES , P~S )0⇡2a : (E2a , P~2a )0⇡1b: (E1b , P~1b )p1 : (E1 , P~1 )0⇡2b: (E2b , P~2b )p2 : (E2 , P~2 )(a) Event 1

miss particle

0
⇡2b

0
⇡1b

(b) Event 2

0
⇡1a

0
⇡1a

miss : (Emiss , P~miss )No Constraint

Constraints:
Emiss = ESP~miss = P~S2Emiss(c) Mixed Event

E1a
P~1a

E2a
P~2a

2
P~miss= m2p(d) Mixed Event

Fig.3. (color online) Mixed event (c) and (d) are buil6t by taking two pions from event 1 (a) andevent 2 (b). In (d), missing mass cut is used.
fails to guarantee the four-momentum conservation and doesn’t take into account the third particle
proton.
3.1.1 Missing mass cut
As the original event is a three final states reaction with 2 π 0 s and one proton, the mixed event
should also obey such a three final states kinematics. Therefore, the missing particle in the mixed event
must satisfy the four momentum conservation and its invariant mass should be proton’s mass (see Fig.
3 d).
Monte Carlo simulation is used to evaluate the performance of the missing mass cut. Pure phasespace events for the γp → π 0 π 0 p reaction are generated with a ROOT∗ utility class ”TGenPhaseSpace”†. Fig. 4 (left) shows the Dalitz plot for the generated phase-space events. Mixed event is constructedby taking two pions from different events. Fig.4 (right) shows the Q (two pions relative momentum
invariant mass) distributions for the phase-space events, the mixed events without missing mass cut
and that with missing mass cut. It is found that the reference sample constructed without any constraint
have some events exceeding the allowed region of Q, while that with missing mass cut restricts all events
within the allowed region.
3.1.2 Pion energy cut
As discussed previously, a valid event mixing method should construct a mixed event identical tothe original events in all aspects but free of Bose-Einstein effects. It means that for the pure phasespace γp → π 0 π 0 p events, a valid event mixing method should reproduce the shape of the phase space
Q distribution for 2 π 0 . However, the ratio of the Q distribution for the phase-space sample to that
constructed with event mixing with missing mass cut is not flat (see Fig. 5 a), indicating that this event
mixing with missing mass cut fails to preserve the phase space effects. Then additional kinematic cuts
∗ http://root.cern.ch† http://root.cern.ch/root/html/TGenPhaseSpace.html

78

30000

m2 (p, π0 )

2.5

350

RMS x
RMS y

300

0.13480.3322

250

2
200
150

1.5

hQ2

Phase Space
Entries 187018
Mean
0.4586
Mixed (no cut)
RMS
0.153
Mixed (missing mass cut)

20000

CountsdalitzEntries 374040
Mean x 0.3066
Mean y
1.777

10000

100
50

1
0

0.1

0.2

0.3

0.4

m2 (π ,π )
0

0.5

0.6

0

0.7 0

00

0.2

0.4

0.6

0.8

1

Q (GeV)

Fig.4. (color online) Left: Dalitz plot (invariant mass squared of pion and proton versus that oftwo pions). Right: Distributions of the invariant mass of the relative four momentum of
two pions for mixed events. Blue line indicates phase space events, red line represents
mixed event with missing mass cut and the green line shows the mixed events without
missing mass cut.

are needed. Our strategy is to try various cut conditions and see the shape of the ratio between thephase-space Q distribution and the mixed Q distribution. In the mixing, missing mass cut is always
kept.
Fig. 5 b shows the ratio of the Q distribution of the original events to that obtained by event
mixing with additional kinematic constraint on two pions energy both for the original and mixed events:
Eπ0 < 0.6Eγ (Eγ is the incident photon energy) . Fig.5 c, d and e show the same but with the cuts of
Eπ0 < 0.5Eγ , Eπ0 < 0.4Eγ and Eπ0 < 0.3Eγ respectively. Eventually, it is found that the kinematic cut
condition Eπ0 < 0.5Eγ makes a ratio which is close to a flat distribution.
In order to find the optimum pion energy cut condition Eπ0 < Eπmax , different values of Eπmax
ranging from 0.55Eγ to 0.65Eγ with step size 0.01Eγ are tried. As shown in Fig. 6, each result of thecorrelation function is fitted by a linear function y = a + bx. The best cut condition should make thecorrelation function have a slope of 0. The fitted slope parameter b is plotted as a function of Eγ andfitted by a forth order polynomial (see Fig. 7). The optimum pion energy cut condition is determined by
the cross point between the fitted polynomial and y = 0 line. Also, the error of the optimum cut value isdetermined by the cross point between the y = 0 line and the boundary of the fitting uncertainty with
95% confidence interval. For the exclusive reaction γp → π 0 π 0 p, the optimum pion energy cut value isfound to be Eπmax /Eγ = 0.499 ± 0.006.

79

(a)
1.2
1
0.8
0

0.1
(b)

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0

0.1
(c)

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0

0.1
(d)

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0

0.1
(e)

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

1.2
1

Ratio

0.8

1.2
1
0.8

1.2
1
0.8

1.2
1
0.8
0

Q (GeV)

Fig.5. The ratio between the phase-space Q distribution and the mixed Q distribution. Mixed
events are build with missing mass cut and additional kinematic cuts: (a) no additional
cut, (b) Eπ0 < 0.6Eγ , (c) Eπ0 < 0.5Eγ , (d) Eπ0 < 0.4Eγ and (e) Eπ0 < 0.3Eγ , where Eπ0
is pion energy, and Eγ is the incident photon energy. Pion energy cut is applied both forthe signal and reference sample.

Ndata(Q)/Nmixing(Q) (a.u.)χ 2 / ndf

1.2

p1

0

0.8

0.2 χ 2 / ndf
0.4

1.2

0.6
0
16.31 / 130.8

0

0.8

0.2 χ 2 / ndf
0.4

0.6
0
18.67 / 130.8Eπ≤0.47Eγ

p0

p1-0.04574 ± 0.04423

p1-0.01683 ± 0.043

p1

0.8

0.8

0.2 χ 2 / ndf
0.4

1.006 ± 0.02046

1.2

1.2

0.8
0
0.6
20.99 / 130.8
0.8793 ± 0.01784
1.2
0.2676 ± 0.03846

Eπ≤0.51Eγ

0.2 χ2 / ndf
0.4

0.2 χ 2 / ndf
0.4

p0
p1

p0

1
0.8

0.2

0.4

0.6

0.8
0

0.8

0.8

0.2

0.4

0.6

0.8
0

-0.08666 ± 0.04619

0.2

χ 2 / 0.4
ndf

0.6
18.79 / 130.8

p0

0.9453 ± 0.01892

p1

0.1194 ± 0.04015

0.6
017.5 / 13 0.8

Eπ≤0.52Eγ
0.2

0.4

0.6

0.8

0.2

0.4

0.6

0.8

0.8857 ± 0.01773

1.2
0.2529 ± 0.03809

p1

1
Eπ ≤0.54Eγ

p1

1

p0
p1

Eπ ≤0.53Eγ

0.6
017.18 / 130.8

1.20.07074 ± 0.04151

0.2 χ2 / ndf
0.4

0.6 / 130.8
0
16.05
0.9355 ± 0.01856
1.2
0.1415 ± 0.03943

1.037 ± 0.02195

Eπ≤0.48Eγ

0.9671 ± 0.01961

1Eπ≤0.50Eγ

19.82 / 13

p0

1

p0

1

0

Eπ≤0.46Eγ

1

1.2

0.8

1

1.019 ± 0.02104

Eπ≤0.49Eγ

1.2-0.1107 ± 0.04742

p1

p0

1
0.8

p1

χ2 / ndf

18.27 / 13
1.047 ± 0.02249

p0

1.2-0.1066 ± 0.048451Eπ≤0.45Eγ

χ 2 / ndf

24.31 / 13
1.044 ± 0.02284

p0

1.2-0.1601± 0.05107

10.8

χ 2 / ndf

22.21 / 13
1.068 ± 0.02401

p0

1
0.8

Eπ ≤0.55Eγ
0.2

0.4

0.6

0.8
0

Q (GeV)Fig.6. The ratio between the phase-space Q distribution and that from mixed events. Mixed
events are constructed with missing mass cut and different pion energy cuts. The pionenergy cut condition is indicated by the text like ‘Eπ ≤ xEγ ’ in each panel. Each ratio isfitted by function y = p0 + p1 · x with fitting parameters shown in the same panel.

80

Slope

0.2

0.505
0.499
0.493

0

-0.2
0.45

0.5

Pion Energy Cut (× Eγ )0.55

Fig.7. The slope parameter p0 (see Fig. 6) as a function of pion energy cut for the γp → π 0 π 0 preaction.

81

3.1.3 Monte Carlo study of the event mixing method with missing mass cut and pion energy cut
Monte Carlo simulation is used to evaluate the performance of this event mixing method which employs missing mass cut and the pion energy cut Eπmax /Eγ = 0.499 ± 0.006. One containing pure phasespace events and eight samples consisting of events with Bose-Einstein (BE) effects for the γp → π 0 π 0 preaction are generated. The phase space events are generated using a ROOT utility class ”TGenPhaseSpace” ‡ . The BE samples are based upon the pure phase events. The Bose-Einstein effects are imposedby rejecting some phase-space events according to the GGLP parameterization of the two-particle correlation function [5]C2 (Q) =2 2
ρBE (Q)= N (1 + λ2 er0 Q ),
ρnoBE (Q)(4)

where ρBE (Q) and ρnoBE (Q) stand for the Q dependence of event density with BE effects and thatwithout BE effects. N is normalization factor. From the point of view of statistics, equation (4) is therelative density function of BE events with respect to the phase-space events. Because equation (4) has
a maximum value C2max = N (1 + λ2 ) when Q = 0, we employ the following procedure to construct a
new sample with BE effects:• Calculate the Q value of a phase-space event.
• Generate a uniform random number R ranging from 0.0 to 1.0.
• Compare R with the ratio C2 (Q)/C2max ; if C2 (Q)/C2max > R, then accept this event.
The probability of C2 (Q)/C2max > R is proportional to C2 (Q), so this method allows one to get correct
density distribution subject to equation (4). In this work, we generate one event sample without BE
effects and eight BE samples with different combinations of BE parameters. For simplicity, we takeN = 1 for all BE samples. Incident photon energy Eγ and BE parameters λ2 and r0 are listed in Table
1.
Table 1. Incident photon energy Eγ and combinations of BE parameters λ2 and r0 for Monte
Carlo BE/noBE samples of the γp → π 0 π 0 p reaction.
Event Sample
noBE
BE,1
BE,2
BE,3
BE,4
BE,5
BE,6
BE,7
BE,8

Eγ (GeV)
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1

r0 (fm)
−−
0.4
0.7
1.0
1.3
0.4
0.7
1.0
1.3

λ2
−−
1.0
1.0
1.0
1.0
0.5
0.5
0.5
0.5

Event mixing with missing mass cut and the pion energy cut Eπmax /Eγ = 0.499 ± 0.006 together
is used to build mixed events for every generated BE/noBE sample. The corresponding correlation functions (the ratio of the original Q distribution to that obtained by event mixing) are shown in Fig. 8.

‡ http://root.cern.ch/root/html/TGenPhaseSpace.html

82

Within error bars, it is shown that fitted BE parameters are consistent with the input parameters. This
indicates that this event mixing method can be used to observe the BEC signals and extract reasonable
BE parameters. The masses of the missing particles both in the mixed events and the original events
are shown in Fig. 9. In this case, the missing particle’s mass for the original events is the proton’s mass.
2

NBE(Q)/N (Q) 2

BE,1

Mix

NBE(Q)/NMix

NBE(Q)/N (Q)2

BE,3

PS

(Q)

NBE(Q)/NMix

NBE(Q)/NMix

1.5

N = 0.94
λ 2 = 0.93 ± 0.031.5
r 0 = 1.11 ± 0.02 fm

1

1

1

1

0.2

0.4

0.6
0.820
NBE
(Q)/N (Q)

0.2

Mix

0.4

BE,6

PS

NBE(Q)/N

N0.6(Q)/N 0.8
(Q)20
BE

0.2

NBE(Q)/N

Mix

0.4

BE,7

PS

(Q)

N0.6
(Q)/N 0.8
(Q)20
BE
PS

(Q)

NBE(Q)/N

Mix

1.5

1

1

1

1

0.2

0.4 NPS0.6(Q)/N 0.8
(Q)20
PS

0.2

0.4

0.6

0.820

0.2

0.4

0.6

0.4

BE,8

N0.6
(Q)/N 0.8
(Q)
BE
PS

Mix

N = 0.97
λ 2 = 0.52 ± 0.031.5
r 0 = 1.14 ± 0.04 fm

noBE

0.2

NBE(Q)/N

N = 0.94
λ 2 = 0.44 ± 0.021.5
r 0 = 0.78 ± 0.03 fm

0.820

(Q)

N = 0.97
λ 2 = 0.96 ± 0.04
r 0 = 1.45 ± 0.03 fm(Q)

N = 0.66
λ 2 = 0.73 ± 0.31 1.5
r 0 = 0.27 ± 0.05 fm

20

PS

(Q)

N = 0.88
λ 2 = 0.84 ± 0.021.5
r 0 = 0.78 ± 0.01 fm

BE,5

NBE(Q)/N (Q)

BE,4

PS

(Q)

N = 0.69
λ 2 = 0.86 ± 0.08 1.5
r 0 = 0.37 ± 0.02 fm

20

Ratio

NBE(Q)/N (Q)2

BE,2

PS

NBE(Q)/N(Q)

N = 0.98
λ 2 = 0.45 ± 0.03
r 0 = 1.42 ± 0.06 fm

0.2

0.4

0.6

0.8

0.2

0.4

0.6

0.8

NPS(Q)/NMix (Q)1.5

N = 0.56
1.5
λ2 = 0.81 ± 0.36
r 0 = 0.05 ± 0.02 fm

1.5

1.5

1

1

1

1

0

0.2

0.4

0.6

0.8 0

0.2

0.4

0.6

0.8 0
0.2
Q (GeV)

0.4

0.6

0.8 0

Fig.8. The ratios (NBE (Q)/NM ix (Q)) between the Q distribution of the generated BE/noBEsample to that from the mixed events. For comparison, the ratio NBE (Q)/NP S (Q) between the Q distribution of BE/noBE sample and the pure phase-space (noBE) Q distribution is also shown in each panel. Red lines show the fitting results for the ratio
NBE Q/NM ix (Q) and the fitted BE parameters are shown in each pad by red text.

× 10

3

400 BE,1×10

BE
Mix300

3

×10

BE300

BE,2

3

×10

BE300

BE,3

Mix

×10

BE

Mix

300
200

3

BE,4

3

BE,5

Mix
300

200

200

100

100

×10

BE300

3

×10

BE300

BE,6

Mix

3

×10

BE300

BE,7

Mix

3

×10

3

600

BE

BE,8

Mix

noBE

noBE

Mix

Mix

200

200

200

400

100

100

100

200

200

200
100

100
0

0

0.8 0.9

1 1.1 0.8 0.9

01

1.1 0.8 0.9

100

0

1

0

1.1 0.8 0.91

1.1 0.8 0.9

01

1.1 0.8 0.9

01

1.1 0.8 0.9

01

1.1 0.8 0.9

01

1.1 0.8 0.91

1.1

The Third Particle Mass (GeV)

Fig.9. Missing particle (or the third particle) mass for the mixed events 2π 0 X. For comparison,
the mass of the missing particle of the original event, the proton’s mass, is shown as well.

83
3.2 Event mixing technique for the inclusive γp → π 0 π 0 X reaction
For the BEC analysis, using data sample of the inclusive γp → π 0 π 0 X reaction has the advantage
of better statistics compared to the exclusive case. But the corresponding event mixing method is a little
bit different because the mass of the missing particle X varies widely. Fig. 10 gives a typical distributionof the missing mass for the γp → π 0 π 0 X reaction at incident photon energies from 1.1 to 1.15 GeV. The
first peak corresponds to the proton, while the second wide peak represents other contributions.
hmmdt
Entries
14032
Mean
1.057
RMS
0.1591

400
300
200
100
0 0.4

0.6

0.8

1
1.2
mX (GeV)

1.4

1.6

Fig.10. The missing mass distribution of the inclusive reaction γp → π 0 π 0 X at incident photon
energies ranging from 1.1 to 1.15 GeV.
Our treatment of the event mixing for the inclusive case is dividing the whole sample into subsamples in terms of the mass of the missing particle in every events and performing the event mixing
with missing mass cut and appropriate pion energy cut. It is demanded that the mass of the missing
particle in a mixed event be the same as that in the original events. The optimum pion energy cut fordifferent missing mass is found in the same way as the exclusive case. It is found that the best pion

χ2 / ndf

0.6

0.5

3.78 / 7

p01.231 ± 0.02299

p1-0.0007752 ± 2.284e-05

fit=p0+p1•x

0.4

0.3

Eγ =900MeV
800

900

1000

1100

1200

Third Particle Mass (MeV)Best Pion Energy Cut (× Eγ )Best Pion Energy Cut (× Eγ )energy cut is sensitive to the missing mass.
χ2 / ndf

0.5

4.273 / 7

p0

1.095 ± 0.02012

p1-0.0006369 ± 1.997e-05

fit=p0+p1•x
0.4

0.3

E γ =1100MeV

800

900

1000

1100

1200

Third Particle Mass (MeV)

Fig.11. The optimum pion energy cut as a function of the third particle mass mX of inclusive
reaction γp → π 0 π 0 X at incident photon energies of 900 MeV (left) and 1100 MeV(right).
In order to find the optimum pion energy cut, nine data samples of inclusive reaction γp → π 0 π 0 X

84

are generated and mixed using this event mixing method. The masses of the missing particle X in these9 samples are assigned the values mp − 100M eV , mp − 50M eV , mp , mp + 50M eV , mp + 100M eV ,mp + 150M eV , mp + 200M eV , mp + 250M eV and mp + 300M eV , respectively, where mp is the massof the proton. Different pion energy cut conditions are tried in the event mixing. Each ratio between the
Q distribution of the original sample and that of the mixed events is fitted by the function y = a + bx
and the slope parameter b is plotted as a function of pion energy cut value. Fig. 12 shows b as a functionof pion energy cut at different missing particle masses when the incident photon energy Eγ = 0.9 GeV .
Fig. 13 shows the same but Eγ = 1.1 GeV .
The optimum pion energy cut should make a flat correlation function, which means the fitted slope
parameter b should be equal to 0. The best pion energy cut is determined by the cross point between they = 0 line and the plot of b versus pion energy cut which is fitted by a 4 order of polynomial. Fig. 11
shows the optimum pion energy cut as a function of the missing particle mass mX of inclusive reaction
γp → π 0 π 0 X at incident photon energies of 900 MeV and 1100 MeV.
m3=mp-100MeV

0.4

m3=mp-50MeV

0.5

m3=mp

0.588

0.2

0.514

Slope

0.539

Slope

Slope

0.576
0.564

0

0.530
0.521

0

0.504
0.494

0
-0.2

-0.5
0.45

0.5

0.55

0.6

Pion Energy Cut (× Eγ )

-0.5

0.65

0.45

m3=mp+50MeV

0.5

0.5

0.55

0.6

-0.4

0.65

Pion Energy Cut (× Eγ )m3=mp+100MeV

0.55

m3=mp+150MeV
0.402

0.438
0.429
0.420

0

Slope

Slope

Slope

0.468
0.466
0.464

0.5

Pion Energy Cut (× Eγ )

0.5

0.5

0

0.45

0.392
0.382

0

-0.5
-0.5

-0.5
0.35

0.4

0.45

0.5

Pion Energy Cut (× Eγ )

0.55

0.3

m3=mp+200MeV

1

0.370
0.350
0.330

0

0.35

-1
0.25

0.5

0.3

0.35

0.4

0.45

0.3

0.35

Pion Energy Cut (× Eγ )m3=mp+300MeV

0.318
0.311
0.304

1

Slope

Slope

Slope

0.45

m3=mp+250MeV

0
-1

0.4

Pion Energy Cut (× Eγ )

-1

0.265
0.254
0.236

0
-1

-2

-2
0.2

0.25

0.3

0.35

Pion Energy Cut (× Eγ )

0.4

0.2

0.25

0.3

0.35

Pion Energy Cut (× Eγ )

0.4

-2
0.15

0.2

0.25

Pion Energy Cut (× Eγ )Fig.12. The slope parameter b as a function of pion energy cut at different third particle masses(or missing particle mass) for γp → π 0 π 0 X reaction. The missing particle mass m3 isindicated by the text in each pad. The incident photon energy is 900 MeV.

85

0.4

0

0.545
0.538
0.531

0

0.55

0.6

0.65

0.45

0.5

0

Slope

0.471
0.456
0.441

0.5

0.55

0.6

0.45

0.65

Pion Energy Cut (× Eγ )m3=mp+100MeV

0.5

0.435
0.428
0.421

Slope

0.5

Pion Energy Cut (× Eγ )m3=mp+50MeV

0.5

0

0.4

0.45

0.5

0.55

Pion Energy Cut (× Eγ )

0.3

0.5

m3=mp+200MeV
0.393
0.382
0.371

-0.5

0.4

0.45

Pion Energy Cut (× Eγ )

0.5

0.25

0.3

0.35

Pion Energy Cut (× Eγ )0.4m3=mp+150MeV

0

0.25

0.3

0.35

0.4

0.45

Pion Energy Cut (× Eγ )1m3=mp+300MeV 0.320

0.342
0.334
0.326

0.310
0.300

0

-0.5

-1
0.2

0.55

0.412
0.400
0.388

m3=mp+250MeV

0

Slope

0

0.35

Slope

0.35

0.5

Pion Energy Cut (× Eγ )

-0.5

-0.5

Slope

0

-0.2

0.45

-0.5

0.505
0.499
0.493

-0.2

-0.2

Slope

m3=mp
0.2

0.2

0.563
0.557
0.551

Slope

Slope

0.2

m3=mp-50MeV

Slope

m3=mp-100MeV

-1

-2
0.2

0.25

0.3

0.35

Pion Energy Cut (× Eγ )

0.4

0.15

0.2

0.25

0.3

0.35

Pion Energy Cut (× Eγ )Fig.13. The slope parameter b as a function of pion energy cut at different third particle masses.
The missing particle mass is indicated by the text in each pad. The incident photon
energy is 1100 MeV.

86
3.2.1 Monte Carlo study of the event mixing technique for the inclusive reaction γp → π 0 π 0 X
Monte Carlo simulation is used to test the event mixing method for the inclusive reaction γp →π 0 π 0 X. The procedure is very similar to the case of the exclusive reaction γp → π 0 π 0 p. The only difference is that we generate γp → π 0 π 0 X events with the missing particle mass mX having a distribution
similar to that in Fig. 10. This is done by combining two Gaussian distributions together with certain
weight for each one. Here we assign the first one µ = 938 MeV, σ = 70 MeV and weight of 0.7, and thesecond one µ = 1200 MeV, σ = 80 MeV and weight of 0.3. Fig. 14 shows the missing mass distribution
produced in this way. We generate one event sample which is free of BE effects and eight BE samples
with different combinations of BE parameters r0 and λ2 . Incident photon energy Eγ and BE parameters
λ2 and r0 are listed in Table 2.
hmmdt
Entries
558514
Mean
0.998
RMS
0.1331

25000
20000
15000
10000
5000
0

0.6

0.8

1

1.2

1.4

1.6

mX (GeV)Fig.14. The missing particle mass distribution for the inclusive reaction γp → π 0 π 0 X produced
by Monte Carlo simulation.

Table 2. Combinations of BE parameters λ2 and r0 for Monte Carlo samples of the inclusive
reaction γp → π 0 π 0 X.
Event Sample
noBE
BE,1
BE,2
BE,3
BE,4
BE,5
BE,6
BE,7
BE,8

Eγ (GeV)
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1

r0 (fm)
−−
0.4
0.7
1.0
1.3
0.4
0.7
1.0
1.3

λ2
−−
1.0
1.0
1.0
1.0
0.5
0.5
0.5
0.5

The developed event mixing method for the inclusive reation γp → π 0 π 0 X is used to construct themixed events for all of the Monte Carlo BE/noBE samples. Missing mass cut and the optimum pionenergy cut Eπmax /Eγ = 1.1 − 0.64Eγ (Eγ in the unit of GeV ) are required in the mixing. It is also
demanded that two events can only be mixed when their missing particles masses are close enough :|mX1 − mX2 | < 20M eV .

87

The corresponding correlation functions (the ratio of the Q distribution of BE sample to that obtained by event mixing) are shown in fig.15. For comparison, the ratio between the Q distribution ofeach BE sample and that of noBE sample is also shown. For the noBE sample, this event mixing method
make a flat distribution of the correlation function. For the BE samples, we observe the BE effects as we
input in the simulation, which indicates this method can be used to observe BE effects for the inclusive
reaction γp → π 0 π 0 X. In extracting the BE parameters r0 and λ2 , however, this method does not perform as good as that in the exclusive case. As long as the λ2 is concerned, this method underestimate
its value. And the r0 parameters are overestimated in most cases. This will introduce a big systematic
error in the BEC analysis. The masses of the missing particles both in the mixed events and the original
events are shown in Fig. 16. Good agreements are found between them.
2

NBE(Q)/N (Q) 2

BE,1

PS

NBE(Q)/NMix

PS

NBE(Q)/NMix

NBE(Q)/N (Q)2

BE,3

PS

(Q)

NBE(Q)/NMix

1.5

N = 0.88
λ 2 = 0.58 ± 0.011.5
r 0 = 0.79 ± 0.02 fm

N = 0.93
λ 2 = 0.72 ± 0.021.5
r 0 = 1.22 ± 0.03 fm

1

1

1

1

0.2

BE,5

0.4

0.6
0.820
NBE
(Q)/N (Q)PS

NBE(Q)/N

Mix

0.2

BE,6

0.4

N0.6
(Q)/N 0.8
(Q)20
BE
PS

(Q)

NBE(Q)/N

Mix

0.2

BE,7

0.4

N0.6
(Q)/N 0.8
(Q)20
BE
PS

(Q)

NBE(Q)/NMix

1.5

N = 0.94
λ 2 = 0.29 ± 0.011.5
r 0 = 0.76 ± 0.04 fm

N = 0.97
λ 2 = 0.40 ± 0.021.5
r 0 = 1.29 ± 0.05 fm

1

1

1

1

0.2

noBE

0.4 NPS0.6(Q)/N 0.8
(Q)20
PS

0.2

0.4

0.6

0.820

0.2

0.4

0.6

PS

NBE(Q)/N

Mix

0.820

(Q)

N = 0.96
λ 2 = 0.77 ± 0.03
r 0 = 1.57 ± 0.04 fm

0.2

BE,8

0.4

N0.6
(Q)/N 0.8
(Q)
BE
PS

(Q)

N = 0.61
λ 2 = 0.78 ± 0.06 1.5
r 0 = 0.22 ± 0.01 fm

20

NBE(Q)/N (Q)

BE,4

(Q)

N = 0.65
λ 2 = 0.78 ± 0.16 1.5
r 0 = 0.31 ± 0.03 fm

20

Ratio

NBE(Q)/N (Q)2

BE,2

(Q)

NBE(Q)/NMix(Q)

N = 0.98
λ 2 = 0.41 ± 0.03
r 0 = 1.60 ± 0.07 fm

0.2

0.4

0.6

0.8

0.2

0.4

0.6

0.8

NPS(Q)/NMix (Q)1.5

N = 0.65
1.5
λ2 = 0.56 ± 0.54
r 0 = 0.06 ± 0.02 fm

1.5

1.5

1

1

1

1

0

0.2

0.4

0.6

0.8 0

0.2

0.4

0.6

0.8 0
0.2
Q (GeV)

0.4

0.6

0.8 0

Fig.15. The ratios (NBE (Q)/NM ix (Q)) between the Q distributions of the generated BE/noBEsamples to those from the mixed events. The ratio NBE (Q)/NP S (Q) of NBE (Q) to thatof pure phase space sample is also shown in each panel for comparison. Red lines show
the fit results for the ratio NBE Q/NM ix (Q) and the fitted BE parameters are shown ineach pad by red text.

88

BE,1
20000

20000
BE
Mix

BE,2

BE

BE,3

Mix
15000

BE

BE,4

15000
Mix

BE
20000

BE,5

Mix

15000

BE

BE,6

BE

BE,7

BE

BE,8

BE
30000

Mix
15000

15000
Mix

15000
Mix

Mix

10000

10000

10000

20000

5000

5000

5000

10000

noBE

noBE
Mix

15000
10000

10000

10000

10000

10000

0

0

0.8 1 1.2 1.4

5000

5000

5000

0

0.8

1 1.2 1.4

5000

0

0.8

1 1.2 1.4

0

0.8

1

1.2 1.4

0

0.8

1

1.2 1.4

00.8

1 1.2 1.4

00.8

1 1.2 1.4

00.8

1 1.2 1.4

0.8

1

1.2 1.4

The Third Particle Mass (GeV)

Fig.16. Missing particle (or the third particle) mass for mixed events 2π 0 X. For comparison,
the mass of the missing particle of the original event, the proton’s mass, is shown as
well.

89

3.3 Treatment of photon cluster overlapping
Photon cluster overlapping is a fatal problem in the event mixing for two neutral pions. For the
FOREST data, a neutral pion is reconstructed by its decayed two photons. When taking two pionsfrom different events, we actually take two photons from one event and other two photons from anotherevent. As for FOREST detector, a photon is identified by corresponding electromagnetic shower, which
commonly extends to several adjacent detector modules. All corresponded detector modules are grouped
into a cluster. This means FOREST cannot distinguish two photons if their clusters are too close. To
coincide with this situation for the real data, mixed event with overlapping photon clusters should be
rejected as well. To make things clear, it is demanded that there be no two photon clusters with any
overlapping detector modules both for the real data and mixed events.
To study the effect of the cluster overlapping treatment on the BEC analysis for real data, we perform event mixing for a Monte Carlo simulated sample (named RFS simulation). In the simulation,phase space γp → π 0 π 0 p events are generated and send to the detector simulation. The smeared eventsby the detector simulation are mixed. Fig. 17 shows the correlation functions for 2π 0 obtained with cluster overlapping treatment (left) and without the treatment (right). A flat distribution of the correlation
function is obtained with the overlapping treatment, while a skewed distribution is shown without thistreatment. This study shows that the treatment of the cluster overlapping has a big effect on the event
mixing and must be applied in the mixing.
hQ2

RFS Simulation
Event Mixing

hQ2
16309
0.50160.1475

1000

Ratio

1.5

RFS Simulation
Event Mixing

16356
0.50150.1475

1000

0.2

0.4

0.6

Q (GeV)

0.8

00

1

with cluster overlapping treatment

1.5
Ratio

00

Entries
Mean
RMS

Counts

2000

Counts2000

Entries
Mean
RMS

1

0.2

0.4

0.6

Q (GeV)

0.8

1

without cluster overlapping treatment

1
0.5

0.5
0

0.2

0.4

0.6

Q (GeV)

0.8

1

00

0.2

0.4

0.6

Q (GeV)

0.8

1

Fig.17. Upper: Q distributions for RFS data (NRF S (Q)) and mixed events (Nmix (Q)). Lower:
The ratio NRF S (Q)/Nmix (Q). The left is the results obtained with cluster overlapping
treatment while the right without the treatment. In this example, the RFS data is
obtained by generating pure phase space data and sending it to the detector simulationand surviving the same event selection as for the real data. The incident photon energy
is from 1.11 to 1.13 GeV.

90

3.4 Summary of the event mixing technique
All factors essential for the event mixing method used in BEC analysis are discussed in the previous
sections. A short summary of this method is given here. Events in real data will be mixed in threesteps. Fig. 18 illustrates these three steps schematically. First, original events which fail to satisfy the
optimum pion energy cut condition Eπmax /Eγ = 1.1 − 0.64Eγ (Eγ in the unit of GeV ) are rejected. In
the second step, the original event sample is divided into sub-samples in terms of the third particle mass
mX of each event. Finally, in each sub-sample, events will be mixed only if missing mass cut is satisfied
and any photon cluster does not overlap with any other photon cluster. It should be pointed out that theexclusive case is just a special case for the inclusive case. This event mixing method is capable both forthe inclusive the exclusive cases.

…
satisfy pion !
energy cut

Event mixing

×
Step 1mX…
Step 2

mixed events

Step 3

Fig.18. Schematic illustration of event mixing for real data.

In order to judge the performance of this method, A Monte Carlo sample, which is produced bygenerating pure phase-space γp → π 0 π 0 p events and sending it to the detector simulation and making
it pass through the same event selection criterion as that for the real FOREST data, is mixed by thesame event mixing procedure. Fig. 19 shows the correlation functions for π 0 π 0 . Flat distributions ofcorrelation functions at various incident photon energy bins are obtained, indicating this event mixing
technique works well and it can be used for the real data. The missing mass distributions for theoriginal events and mixed events are shown in Fig. 20. The shapes of the missing mass distributions forthe original data are reproduced by the event mixing method.

91

1.5

1.5
N= 0.84
λ 2 = 0.20 ± 0.17
r0= 0.04 ± 0.22 fm

1

1

0.2

λ 2 = -0.02 ± 0.06
r0= 0.78 ± 1.00 fm

Nsig(Q) / N

mix

(Q)

1

1090-1110 MeV

0.5
0.4 N=
0.60.330.81.5 0

0.2

λ 2 = 1.39 ± 2.10
r0= 0.06 ± 0.04 fm

10.2

λ 2 = -0.15 ± 0.10
r0= 1.30 ± 0.44 fm

1

1.5 0

0.4 N=
0.61.030.8

λ 2 = -0.05 ± 0.05
r0= 0.43 ± 0.50 fm

1

0.2

850- 870 MeV
830- 850 MeV
0.5
0.5
0.4 N=
0.60.200.81.5 0
0.2 0.4 N=
0.60.170.81.5 0
0.2 0.4 N=
0.60.210.8
λ2 = 4.33 ± 2.85
λ2 = 5.17 ± 2.85
λ2 = 4.09 ± 1.39
r0 = 0.13 ± 0.02 fm
r0 = 0.12 ± 0.01 fm
r0 = 0.13 ± 0.02 fm

1

1

1

1

0.5

810- 830 MeV
0.5
0.2 0.4 0.6 0.8 0790- 810 MeV
0.5
0.2 0.4 0.6 0.8 0770- 790 MeV
0.5
0.2 0.4 0.6 0.8 000.2

λ 2 = 2.96 ± 1.70
r0= 0.10 ± 0.02 fm

870- 890 MeV

0.5
0.4 N=0.6
0.35 0.81.5 0
λ2 = 1.93 ± 3.92
r0 = 0.11 ± 0.06 fm

0.2

0.2

λ 2 = 1.14 ± 1.96
r0= 0.06 ± 0.05 fm

910- 930 MeV

0.5
0.4 N=
0.60.260.81.5 0

1890- 910 MeV

0.4 N=
0.61.010.8

λ 2 = -0.11 ± 0.11
r0= 1.53 ± 0.84 fm

930- 950 MeV

0.5
0.4 N=
0.60.470.81.5 0

1

0.5

0.2

λ 2 = 1.46 ± 2.10
r0= 0.08 ± 0.05 fm

1

950- 970 MeV

0.5
0.4 N=0.6
1.01 0.81.5 0

0.2

0.2

λ 2 = 2.53 ± 2.18
r0= 0.08 ± 0.02 fm

990-1010 MeV

0.5
0.4 N=
0.60.410.81.5 0

1970- 990 MeV

0.4 N=
0.61.200.8

λ 2 = -0.16 ± 0.08
r0= 0.05 ± 0.12 fm

1010-1030 MeV

0.5
0.4 N=
0.60.290.81.5 0

1

0.5
1.5 0

0.2

λ 2 = 3.00 ± 2.40
r0= 0.09 ± 0.02 fm

1

1030-1050 MeV

0.5
0.4 N=0.6
0.42 0.81.5 0

0.2

1070-1090 MeV

0.5
0.4 N=
0.60.260.81.5 0

11050-1070 MeV
0.5
1.5 0

0.2

λ 2 = 2.12 ± 1.88
r0= 0.06 ± 0.03 fm

1

N= 1.01
λ 2 = -0.20 ± 0.11
r0= 1.10 ± 0.28 fm

1

1110-1130 MeV

0.5
0.4 N=0.6
1.01 0.81.5 0

0.2

N= 1.01 1.5
λ 2 = -0.10 ± 0.09
r0= 0.86 ± 0.39 fm

1

1130-1150 MeV
0.5
1.5 0

N= 0.29 1.5
λ 2 = 2.61 ± 2.47
r0= 0.07 ± 0.02 fm

750- 770 MeV
0.2 0.4 0.6 0.8

Q (GeV)
Fig.19. Distributions of C2 (Q) for 2π 0 from the simulated γp → π 0 π 0 p events and the result of
the fit by equation (2). The solid circles represent data points and the solid line indicatesthe fit results.
800
600

Data 1000
Mix

1130-1150 MeV

400

1500

Data
1000
Mix

1110-1130 MeV

500

500

0
1500
0.7

0

Data
Mix 1000

1090-1110 MeV

Data
Mix

1070-1090 MeV

500

200
0
0.7
0.8
0.9
1500 1050-1070 MeV

1

1.1

1000

1.2

Data
Mix 1000

0
2000
0.7

1500

970- 990 MeV

0.9

1

1.1

1.2

Data
Mix 1500

1000

1000

500

500

0

0

1

1.1

1.2

Data
Mix 1000

0.7

0.8

0.9

1010-1030 MeV

1

1.1

1.2

0.8

0.9

950- 970 MeV

1

1.1

1.2

0

0.7

0.8

890- 910 MeV

0.9

1

1.1

1.2

Data
2000
Mix

Data
Mix 10000.8

0.9930- 950 MeV

1

1.1

0.7

0.8

0.9

870- 890 MeV

1

1.1

1.2

0

Data
Mix 2000

1000

1.2

0

Data
Mix 2000

0.7

0.8

0.9

850- 870 MeV

1

1.1

1.2

0

Data 2000
Mix 1500

0.9

1

1.1

0.8

0.9

1

1.1

0.8

0.9

1

1.1

0.8

0.9

1

1.1

0.8

0.9

1

1.1

1.2

Data
Mix

0.7

910- 930 MeV

1.2

Data
Mix

0.7

830- 850 MeV

1.2

Data
Mix

1000

1000

500

500

0 0.7

0.8

0.9

1

1.1

1.2

0 0.7

600

Data 2000
Mix 1500

400

1000

200

500

0

0.8

990-1010 MeV

1000

1000

800

0.7

500

0.7

500

1500

0

Data 1500
Mix

500

500

0

0.8

0.9

1000

500

0.7

0.8

1030-1050 MeV

810- 830 MeV

0.7

0.8

0.9

1

1.1

1.2

0

0.8

0.9

790- 810 MeV

1

1.1

1.2

0 0.7

Data
2000
Mix

0.8

0.9

770- 790 MeV

1

1.1

0 0.7
1.2 2000

Data
Mix 1500

750- 770 MeV

1.2

Data
Mix

1000
1000
500

0.7

0.8

0.9

1

1.1

1.2

0

0.7

0.8

0.9

1

1.1

1.2

0

0.7

1.2

Missing Mass (GeV)

Fig.20. Distributions of missing mass for both the simulation data of γp → π 0 π 0 p reaction andthe mixed events.

92§ 4. BEC results from real data
4.1 Raw BEC results
Employing the event mixing method developed in the last sections, we obtained the the results of
the Bose-Einstein correlations in 2 π 0 emitted from the exclusive reaction γp → π 0 π 0 p and inclusive
reactions γp → π 0 π 0 X and γd → π 0 π 0 X. We here present these results.
The BEC results for the exclusive reaction γp → π 0 π 0 p are shown in Fig. 21, 22 and 23. Fig. 21
shows the correlation functions at different incident photon energy bins. Fig. 22 shows the Q distributions both for the original and mixed events. Fig. 23 shows the missing mass distributions both for theoriginal events and the mixed events.
The BEC results for the inclusive reaction γp → π 0 π 0 X are given in Fig. 24, 25 and 26. Fig. 24
shows the correlation functions at different energy bins. Fig. 25 shows the Q distributions both for theoriginal and mixed events. Fig. 26 shows the missing mass distributions both for the original events andmixed events.
In Fig. 27, 28 and 29, are shown the BEC results for the inclusive reaction γd → π 0 π 0 X. Fig.
27 shows the correlation functions. Fig. 28 shows the Q distributions both for the original and mixed
events. Fig. 29 shows the missing mass distributions both for the original events and the mixed events.
As can be seen in the experimental correlation functions, BEC-like enhancements at low Q regions
can be easily observed at higher energy bins, while at low energy bins some bump structures are observed. A reasonable explanation of such bump structures is still missing. More detailed studies are
required to investigate this phenomenon. The dimension parameter r0 and chaoticity parameter λ2 are
extracted by fitting the equation (2) to the correlation function.
We do not intend to discuss the BEC results without a discussion about the effects of special kinematics (like ∆ sequential decay) of the 2π 0 channel, because the event mixing method, developed basedon pure phase space kinematics, might be affected by the special kinematics.
The Dalitz plots for γp → π 0 π 0 p indicates the ∆ sequential decay is the dominant contribution
to this channel both in the second and third resonance regions. There might also be a minor contribution from the P11 (1440) → p(π 0 π 0 )I=0
S−wave decay. Thus, we mainly investigate the effects of these twoprocesses on the BEC analysis. This will be described later in sections 4.2 and 4.3.

93

1.5

1.5
N= 0.90λ 2 = 0.36 ± 0.06
r0= 0.44 ± 0.08 fm

N= 0.85 1.5
λ 2 = 0.35 ± 0.18
r0= 0.32 ± 0.14 fm

N= 1.00 1.5
λ 2 = 0.01 ± 0.05
r0= 0.47 ± 0.89 fm

1

1

1

1

1130-1150 MeV

Nsig(Q) / N

mix

(Q)

0.5
1.5 0

0.2

0.4

0.6

1

1110-1130 MeV
0.5
0.81.5 0

0.2

0.4

0.6

1

0.2

0.4

0.6

1.5 0

0.2

0.4

0.6

0.2

0.4

0.6

0.2

0.4

0.6

0.2

0.4

0.6

0.2

0.4

0.6

0.6

0.8

990-1010 MeV
0.5
0.81.5 0

0.2

0.4

0.6

0.8

0.2

0.4

0.6

910- 930 MeV
0.5
0.81.5 0

0.2

0.4

0.6

0.8

1
850- 870 MeV
0.2

0.4

0.6

830- 850 MeV
0.5
0.81.5 0

1

1

1

1

0.5

810- 830 MeV
0.5
0.2 0.4 0.6 0.8 0790- 810 MeV
0.5
0.2 0.4 0.6 0.8 0770- 790 MeV
0.5
0.2 0.4 0.6 0.8 0

0

0.4

1

1

0.5
0.81.5 00.2

1930- 950 MeV
0.5
0.81.5 0870- 890 MeV
0.5
0.81.5 0

0.6

1

1890- 910 MeV

0.4

1070-1090 MeV
0.5
0.81.5 01010-1030 MeV
0.5
0.81.5 0950- 970 MeV
0.5
0.81.5 0

0.2

1

1

1

0.5

0.6

1030-1050 MeV
0.5
0.81.5 0970- 990 MeV
0.5
1.5 0

0.4

1
1050-1070 MeV

0.5
1.5 0

0.2

1090-1110 MeV
0.5
0.81.5 0

N= 1.00
λ 2 = 0.02 ± 0.04
r0= 0.45 ± 0.49 fm

0.2

0.4

0.6

0.8

750- 770 MeV
0.2 0.4 0.6 0.8

Q (GeV)
Fig.21. Distributions of C2 (Q) for 2π 0 in γp → π 0 π 0 p and the result of fitting by equation (2).
The solid circles represent data points and the solid lines indicate the fitting results.
FOREST dataset 2009D is used.

94

2000

original

1130-1150 MeV

original

1110-1130 MeV

2000

mixed2000

1500

1090-1110 MeV

mixed

original
3000

1500
1000

original

1070-1090 MeV

mixed

mixed

2000

1000

1000

1000

500

500

0
0

0.2

0.4

1050-1070 MeV

0.6

3000

0

0.8
01
original
3000

0.2

0.4

0.6

0

0.8

original 01

1030-1050 MeV

mixed

0.2

0.4

0.6

1010-1030 MeV

mixed
2000

01
original
3000

00

0.2

0.4

970- 990 MeV

0.6

1000

0.8

original

001

0.2

0.4

950- 970 MeV

3000

3000

0.6

original

2000

1000

1000

00
3000

001
0.8
original
4000

0.6

0.2

0.4

870- 890 MeV

0.6

0.4

930- 950 MeV

0.6

001

0.8

original
4000

1000
0.2

0.4

850- 870 MeV

0.6

001

0.8

original

mixed
4000

mixed
4000

2000

2000

2000

0.4

910- 930 MeV

0.6

original 1

0.8

original

0.2

0.4

830- 850 MeV

0.6

0.8

original

00

0.2

0.4

810- 830 MeV

0.6

001

0.8

0.2

6000
original

0.4

0.6

001

0.8

original

790- 810 MeV

0.2

0.4

0.6

770- 790 MeV

6000

mixed
2000

4000

1000

2000

mixed

0.8

001
6000

original

0.2

0.4

0.6

750- 770 MeV

mixed
4000

0.8

original

0.2

0.4

0.6

001

0.8

2000

2000
0.2

0.4

0.6

001

0.8

0.2

0.4

0.6

0.8

001

0.2

0.4

0.6

0.8

1

Q (GeV)

Fig.22. Q Distributions both for the real events and the mixed events for the γp → π 0 π 0 preaction.

Data
Mix

1130-1150 MeV

600

Data 800
Mix 600

400

400

1110-1130 MeV

800

Data
1000
Mix

1090-1110 MeV

Data
Mix

1070-1090 MeV

400
200

200

200

0

0

1000
0

0.8

1050-1070 MeV

1

1.2

1000

1.4

0.6

Data 1000
Mix

0.8

1

1030-1050 MeV

1.2

1.4

Data
Mix

500

0.6

0.8

1

1010-1030 MeV

1.2

1.4

0

0.6

Data 1000
Mix

0.8

1

1.2

1.4

0.8

1

1.2

1.4

0.8

1

1.2

1.4

0.8

1

1.2

1.4

0.8

1

1.2

1.4

990-1010 MeV

Data
Mix

500
500

500

0
1000

0.6

0.8

970- 990 MeV

1

1.2

1.4

0

500

0.6

Data 1000
Mix

500

500

0
1000 0.6

0

0.8

1

950- 970 MeV

1.2

1.4

0

Data 800
Mix 600

0.6

0.8

1

930- 950 MeV

1.2

1.4

0
1500
0.6

Data
Mix 1000

910- 930 MeV

Data
Mix

400
500
200

0.8

890- 910 MeV

1

1.2

1.4

0.6

Data
Mix 10000.8

1870- 890 MeV

1.2

0
1.4
0.6
Data 1500

Mix

0.8

1

850- 870 MeV

1.2

1000

1.4

0

0.6

Data 1500
Mix

830- 850 MeV

Data
Mix

1000

500
500

0 0.6

1000

0.8

810- 830 MeV

1

1.2

1.4

0 0.6

Data 1500
Mix

500

0.8

1

790- 810 MeV

1.2

1000

500

0

0.6

1

mixed

4000

00

0.6

1

mixed

1000

3000

600

1

mixed

3000

500
001

0.2

mixed

2000

original

3000

1000

0.8

mixed

1000

0.8

mixed
2000

0.2

1500

2000

0.4

0.6

1000

mixed

2000

0.2

001

0.8

mixed

890- 910 MeV

0.4

990-1010 MeV

2000

1000

1000

0.2

mixed

2000

2000

0

0.8

0.8

1

1.2

1.4

1.4

500

0 0.6

Data2000
Mix 15000.8

1770- 790 MeV

1.2

1.4

0 0.6

Data1500
Mix 1000

750- 770 MeV

Data
Mix

1000

500

500

0

0

0.6

0.8

1

1.2

1.4

500

0.6

0.8

1

1.2

1.4

0

0.6

Missing Mass (GeV)
Fig.23. Distributions of the missing mass mX for the hypothesis γp → π 0 π 0 X. The results
both for the real events and the mixed events for the γp → π 0 π 0 p reaction are shown.

95

1.5

N= 0.92
1.5
λ 2 = 0.34 ± 0.05
r 0 = 0.63 ± 0.12 fm

N= 0.94
1.5
λ 2 = 0.31 ± 0.05
r 0 = 0.72 ± 0.12 fm

N= 0.95
1.5
λ 2 = 0.38 ± 0.07
r 0 = 0.91 ± 0.12 fm

1

1

1

1

1130-1150 MeV

0.5
0

0.4

0.6

0.8

0

1.5

N= 0.91
1.5
λ 2 = 0.35 ± 0.05
r 0 = 0.75 ± 0.12 fm

1

1

(Q)
mix

Nsig(Q) / N

0.2

1110-1130 MeV

0.5

1050-1070 MeV

0.5
0

0.2

0.4

0.6

0.2

0.4

0.6

0.8

0

N= 0.94
1.5
λ 2 = 0.30 ± 0.06
r 0 = 0.85 ± 0.12 fm

0.2

0.4

0.6

1030-1050 MeV
0

0.2

0.4

0.6

0.8

0

N= 0.94
1.5
λ 2 = 0.28 ± 0.06
r 0 = 0.87 ± 0.15 fm

1010-1030 MeV
0

0.2

0.4

0.6

0.8

0

1.5

1.5

1.5

1

1

1

1

970- 990 MeV
0

0.2

0.4

950- 970 MeV

0.5
0.6

0.8

0

0.2

0.4

0.6

930- 950 MeV

0.5
0.8

0

0.2

0.4

0.6

0.8

0

1.5

1.5

1.5

1

1

1

1

890- 910 MeV
0

0.2

0.4

870- 890 MeV

0.5
0.6

0.8

0

0.2

0.4

0.6

850- 870 MeV

0.5
0.8

0

0.2

0.4

0.6

0.8

0

1.5

1.5

1.5

1

1

1

1

810- 830 MeV
0

0.2

0.4

0.6

0.5
0.8

790- 810 MeV
0

0.2

0.4

0.6

0.5
0.8

0.8

770- 790 MeV
0

0.2

0.4

0.6

0.5
0.8

0.2

0.4

0.6

0.8

0.2

0.4

0.6

0.8

830- 850 MeV

0.5

1.5

0.5

0.6

N= 0.92
λ 2 = 0.39 ± 0.06
r 0 = 0.94 ± 0.11 fm

910- 930 MeV

0.5

1.5

0.5

0.4

990-1010 MeV

0.5

1.5

0.5

0.2

1

0.5
0.8

1070-1090 MeV

0.5

1

0.5
0.8

1090-1110 MeV

0.5

N= 0.95
λ 2 = 0.29 ± 0.05
r 0 = 0.82 ± 0.11 fm

0.2

0.4

0.6

0.8

750- 770 MeV
0

0.2

0.4

0.6

0.8

Q (GeV)
Fig.24. Distributions of C2 (Q) for 2π 0 in γp → π 0 π 0 X and the results of fitting by equation (2).
The solid circles represent data points and the solid lines indicate the fitting results.
FOREST dataset 2009D is used.

96

original
3000

1130-1150 MeV

3000
original

1110-1130 MeV

mixed

2000

1090-1110 MeV

mixed

original
4000

1070-1090 MeV

mixed

2000

2000

1000

1000

0
4000
01

0
0.8
original 01
3000

original
mixed

3000
2000

1000

0
0
4000

0.2

0.4

1050-1070 MeV

0.6

1000

0.8
original

0.2

0.4

0.6

1030-1050 MeV

mixed3000

0.2

0.4

0.6

1010-1030 MeV

mixed

3000

400001
original

4000

0.4

970- 990 MeV

001
original
4000

0.6

0.8

0.4

950- 970 MeV

001
original
3000

0.6

0.8

2000

2000

1000

1000
0.2

0.4

890- 910 MeV

0.6

001

0.8

0.2

original
6000

0.4

870- 890 MeV

0.6

0.8

original 1
mixed

930- 950 MeV

0.6

001

0.8

6000
original

0.2

0.4

910- 930 MeV

0.6

mixed

1000

2000

001

0.2

0.4

850- 870 MeV

0.6

0.8

0.8

original

001
8000

original

mixed
6000

mixed
6000

4000

4000

2000

2000

0.2

0.4

830- 850 MeV

0.6

0.8

original

2000

0.2

0.4

810- 830 MeV

0.6

001

0.8

0.2

original
8000

4000

0.4

0.6

001

0.8

original
10000

790- 810 MeV

mixed

0.4

0.6

770- 790 MeV

8000
original

0.2

0.4

0.6

0.4

0.6

750- 770 MeV

0.8

original
mixed

4000

0.2

0.4

0.6

001

0.8

0.2

0.4

0.6

001

0.8

0.2

0.4

0.6

0.8

Q (GeV)

Fig.25. Q Distributions both for the real events and the mixed events for the γp → π 0 π 0 X
reaction.

Data
Mix

1130-1150 MeV

600

Data 800
Mix 600

400

400

200

200

1110-1130 MeV

800

400
200

0.6

0.8

1050-1070 MeV

1

1.2

1000

1.4

0.6

0.8

1

1030-1050 MeV

1.2

1.4

Data
Mix

0.6

0.8

970- 990 MeV

1

1.2

1000

1.4

0

0.8

1

950- 970 MeV

1.2

1.4

500

0
1000
0.6

0

Data 800
Mix 600

0.8

11010-1030 MeV

1.2

1.4

0

0.6

Data 1000
Mix

0.8

1

1.2

1.4

0.8

1

1.2

1.4

0.8

1

1.2

1.4

0.8

1

1.2

1.4

0.8

1

1.2

1.4

990-1010 MeV

Data
Mix

0.6

0.8

1

930- 950 MeV

1.2

1.4

0

0.6

Data 1500
Mix

910- 930 MeV

1000

Data
Mix

400

500

500

Data
Mix

1070-1090 MeV

500

0.6

Data
1000
Mix

Data
1000
Mix

1090-1110 MeV

500

500

500

0

0

Data 1000
Mix

500
200

0
0.6
0.8
1000 890- 910 MeV

1

1.2

1.4

0
1500
0.6

Data
Mix 10000.8

1870- 890 MeV

1.2

1.4

0

Data 1500
Mix

0.6

0.8

1

850- 870 MeV

1.2

1.4

0

0.6

Data
1500
Mix

1000

830- 850 MeV

Data
Mix

1000

500
500

0 0.6

1000

0.8

810- 830 MeV

1

1.2

1.4

0 0.6
2000

Data
1500
Mix

500

0.8

1

790- 810 MeV

1.2

1.4

0.6

0.8

1

1.2

1.4

0

0.8

1

770- 790 MeV

1.2

1.4

0 0.6

Data1500Mix

750- 770 MeV

1000

Data
Mix

1000

500
0

500

0 0.6

Data2000
Mix 1500

1000

500

500

500

0.6

1

2000

001

0.8

0.2

6000
mixed

2000
00

001

0.8

5000

4000

2000

0.2

mixed

6000

0

1

mixed

4000

1000

600

1

mixed

4000

8000
original

2000

00

0.4

2000

0.8

mixed
3000

0.6

1000
0.2

mixed

3000

00

0.2

mixed

3000

4000

1000

1000
0.2

0.4

990-1010 MeV

2000

2000

00

0.2

mixed
3000

2000

2000
1000

0

0.8

0.8

1

1.2

1.4

0

0.6

0.8

1

1.2

1.4

0

0.6

Missing Mass (GeV)
Fig.26. Distributions of the missing mass both for the real events and the mixed events for the
γp → π 0 π 0 X reaction.

1

97

1.5

N= 0.98
1.5
λ 2 = 0.32 ± 0.05
r 0 = 0.84 ± 0.13 fm

N= 0.98
1.5
λ 2 = 0.30 ± 0.05
r 0 = 0.86 ± 0.15 fm

N= 0.98
1.5
λ 2 = 0.30 ± 0.05
r 0 = 0.85 ± 0.12 fm

1

1

1

1

1130-1150 MeV

0.5
0

0.4

0.6

0.8

0

1.5

N= 0.991.5
λ 2 = 0.29 ± 0.04
r 0 = 0.99 ± 0.10 fm

1

1

(Q)
mix

Nsig(Q) / N

0.2

1110-1130 MeV

0.5

1050-1070 MeV

0.5
0

0.2

0.4

0.6

0.2

0.4

0.6

0.8

0

N= 0.98
1.5
λ 2 = 0.28 ± 0.04
r 0 = 0.86 ± 0.10 fm

0.2

0.4

0.6

1030-1050 MeV
0

0.2

0.4

0.6

0.8

0

N= 0.98
1.5
λ 2 = 0.27 ± 0.04
r 0 = 0.90 ± 0.11 fm

1010-1030 MeV
0

0.2

0.4

0.6

0.8

0

1.5

1.5

1.5

1

1

1

1

970- 990 MeV
0

0.2

0.4

950- 970 MeV

0.5
0.6

0.8

0

0.2

0.4

0.6

930- 950 MeV

0.5
0.8

0

0.2

0.4

0.6

0.8

0

1.5

1.5

1.5

1

1

1

1

890- 910 MeV
0

0.2

0.4

870- 890 MeV

0.5
0.6

0.8

0

0.2

0.4

0.6

850- 870 MeV

0.5
0.8

0

0.2

0.4

0.6

0.8

0

1.5

1.5

1.5

1

1

1

1

810- 830 MeV
0

0.2

0.4

0.6

0.5
0.8

790- 810 MeV
0

0.2

0.4

0.6

0.5
0.8

0.8

770- 790 MeV
0

0.2

0.4

0.6

0.5
0.8

0.2

0.4

0.6

0.8

0.2

0.4

0.6

0.8

830- 850 MeV

0.5

1.5

0.5

0.6

N= 0.98
λ 2 = 0.25 ± 0.04
r 0 = 0.89 ± 0.11 fm

910- 930 MeV

0.5

1.5

0.5

0.4

990-1010 MeV

0.5

1.5

0.5

0.2

1

0.5
0.8

1070-1090 MeV

0.5

1

0.5
0.8

1090-1110 MeV

0.5

N= 1.00
λ 2 = 0.34 ± 0.05
r 0 = 1.10 ± 0.12 fm

0.2

0.4

0.6

0.8

750- 770 MeV
0

0.2

0.4

0.6

0.8

Q (GeV)
Fig.27. Distributions of C2 (Q) for 2π 0 in γd → π 0 π 0 X and the results of fitting by equation (2).
The solid circles represent data points and the solid lines indicate the fitting results.
FOREST dataset 2009D is used.

98

6000

original

1130-1150 MeV

original
6000

1110-1130 MeV

6000

mixed

1090-1110 MeV

mixed

4000

original
8000

1070-1090 MeV

mixed

4000

4000

2000

2000

0
0.8
01
original
8000

8000
0
01

original
mixed

6000
4000

2000

0
0
10000

0.2

0.4

1050-1070 MeV

0.6

2000
0.2

0.4

0.6

0.8

original

1030-1050 MeV

6000

0.4

970- 990 MeV

8000

0.2

0.4

0.6

990-1010 MeV

mixed

0.8

original 1
mixed

4000

0.8

0.2

0.4

950- 970 MeV

0.6

001

0.8

original

2000
0.2

0.4

930- 950 MeV

0.6

6000
mixed

mixed
5000

original 01

2000

001
original
10000

0.6

0

0.8

6000

4000

0.2

0.6

4000

2000
00
10000

0.4

6000
mixed

mixed
5000

0.2

1010-1030 MeV001
0.8 15000

original

0.2

0.4

910- 930 MeV

0.6

mixed

0.8

original

1

mixed

10000

4000

5000

5000
2000
0
1000000.2

0.4

890- 910 MeV001
0.8 15000

0.6

0.2

original

0.4870- 890 MeV

0.6

001

0.8

original

15000

mixed

10000

5000

00

0.2

0.4

810- 830 MeV

0.6

0.8

original

001

0.2

0.4

0.6

0.4

0.6

0.4

830- 850 MeV

0.6

5000

0.2

0.4

0.6

770- 790 MeV

0.8

original001
0.8 15000

original

0.2

0.4

0.6

750- 770 MeV

mixed

0.8

original

10000
5000

5000
0.2

0.4

0.6

001

0.8

0.2

0.4

0.6

001

0.8

0.2

0.4

0.6

0.8

Fig.28. Q Distributions both for the real events and the mixed events for the γd → π 0 π 0 X
reaction.

Data
Mix 1000

Data
1000
Mix

500

500

Data
1500
Mix

Data
Mix

1000
500

500
0
2000 0.6

0.8

1

1.2

1500

1.4

0

0.6

Data 1500
Mix

0.8

1

1.2

1.4

0
1500 0.6

Data
Mix 1000

0.8

1

1.2

1.4

500

500

0
2000 0.6

02000 0.6

1

1.2

1.4

1500

Data
Mix 1500

1000

1000

500

500

0.8

1

1.2

1.4

0

0.8

1

1.2

1500

1.4

0

Data
Mix 1000

0.6

0.8

1

1.2

1.4

0 0.6

0.8

1

1.2

1.4

Data
2000
Mix

0.8

1

1.2

1.4

0.6

0.8

1

1.2

1.4

0
3000
0.6

0.8

1

1.2

1.4

0.8

1

1.2

1.4

0.8

1

1.2

1.4

Data
Mix

500

0.6

0.8

1

1.2

1.4

0

Data
Mix 2000

Data
Mix

1000

500

0
2000
0.6

0.6

1000

1000

0.8

0

Data
1500
Mix

1000

500

0
3000 0.6

Data
Mix 2000

0.8

1

1.2

1.4

0.8

1

1.2

1.4

Data
Mix 2000

Data
Mix

1000
1000

0.8

1

1.2

1.4

0 0.6

1000

Data 3000
Mix 2000

500

1000

1000

0

0

0

1500

0.6

0.8

1

1.2

1.4

1000

1000

500
0 0.6

Data3000
Mix
2000

0.6

1

mixed

Q (GeV)

1000

1

10000

001

0.8

0.2

mixed

5000

mixed
15000

5000
0.2

001
15000

original

10000

001

10000

0.8

10000

original
20000

mixed

00

0.6

mixed

0.8

790- 810 MeV

15000

5000

0.4

850- 870 MeV

mixed

5000

10000

0.2

0.8

1

1.2

1.4

0 0.6

Data
2000
Mix

Data
Mix

1000

0.6

0.8

1

1.2

1.4

0

0.6

Missing Mass (GeV)
Fig.29. Distributions of the missing mass both for the real events and the mixed events for the
γd → π 0 π 0 X reaction.

1

99

4.2 Effects of ∆ sequential decay on BEC analysis
We here investigate the effects of the ∆ sequential decay on the BEC analysis with a Monte Carlosimulation. In the simulation, a sample of γp → ∆π 0 → p2π 0 events are generated, where the mass ofthe ∆ has a Breit-Wigner distribution with mass of 1232 M eV and width Γ = 117 M eV . Fig. 30 shows
the mass distribution of the generated ∆. Fig. 31 shows the spectra of the pπ 0 invariant mass and theenergy of π 0 for the Monte Carlo sample. Fig. 32 and 33 show the Dalitz plots.

hmdelta_free
Entries 23861
Mean
1.236
RMS
0.15113000

2000
p π0 mass limit
Syst. energy limit

1000

0
0.6

0.8

1

1.2

1.4

1.6

1.8

∆ mass (GeV)
Fig.30. The mass distribution of ∆ and the kinematic limits due to the ∆ sequential decay. The
incoming photon energy is 1100 MeV.
As can be seen in Fig. 31, the kinematical behavior of the ∆ decayed π 0 is different from another π 0 ,especially when the incidental photon energies are greater than 1.0 GeV . It shows that the ∆ decayed
π 0 s tend to share a relatively smaller momentum compared to the other one. Such properties should
be taken into account when performing the event mixing, which will be discussed later. The m(p, π 0 )spectra also show that the ∆ resonance results in a shoulder structure in the higher side when Eγ
greater than 1.0 GeV , which can also be easily found in the Dalitz plot as shown in Fig. 32. In theexperimental results of the Dalitz plots, the shoulder structures are obviously observed, indicating that∆ sequential decay is dominant for the γp → p2π 0 channel.
The event mixing method which is developed based on the γp → p2π 0 reaction (see section 3.4),
is applied for this Monte Carlo sample to get the correlation function of 2π 0 . In Fig. 34 are shown
the correlation functions. As can be seen in the plots, the correlation functions exhibit an increasing
tendency with Q going up when the incident photon energies greater than 1.0 GeV. In addition, the plotsshow a bump structure in the tail of the correlation functions. When the incoming photon energies below
1.0 GeV, a roughly flat distribution is observed in conjunction with some minor bump structure in the
tail.

100

m(π01,p)m(π02,p)both1150 MeV
1000m(π01,p)m(π02,p)both

1100 MeV
1000

1500

m(π01,p)m(π02,p)both1050 MeV

1000m(π01,p)m(π02,p)both1000 MeV
1500

1000
500

0

500

1

1.2

1.4

1.6

0

500

1

1.2

m(π ,p) (GeV)

1500

1500

500

1

1.2

1

1.2

1.4

1.6

1500

500

500
1

1.2

m(π ,p) (GeV)

0

1

1.2

1.4

1.6

0

1.4

1.6

m(π0,p) (GeV)m(π01,p)m(π02,p)both

850 MeV

2000

1000

0

1.6

m(π ,p) (GeV)

1000m(π01,p)m(π02,p)both

800 MeV
2000

1000

1

1.2

m(π ,p) (GeV)

0

1.4
0

m(π01,p)m(π02,p)both

900 MeV

2000

1000

0

0

0

m(π01,p)m(π02,p)both

950 MeV

1.6m(π ,p) (GeV)

0

2000

1.4

500

1.4

1.6

0

1

1.2

m(π ,p) (GeV)

0

1.4

1.6

m(π0,p) (GeV)

0m(π01,p)m(π02,p)both

750 MeV
2000
1500
1000
500
0 1

1.2

1.4

1.6

m(π0,p) (GeV)
From ∆
Another

1150 MeV

800

800

From ∆
Another

1100 MeV

400

400

400

200

200

200

0

0.2

0.4

0.6
0

0.8

1

0

Energy of π (GeV)
800
600

0.2

0.4

0.6
0

0.8

0

Energy of π (GeV)
800

From ∆
Another

950 MeV

900 MeV

600

From ∆
Another

200

200

0.4

0.6

0.8

0.2

0.4

0.6

Energy of π0 (GeV)

0

From ∆
Another

0.6

0.8

400
200
0

0.2

0.6

From ∆
Another

0.4600From ∆
Another

800 MeV

400

200

0.2

0.4

0.6

Energy of π0 (GeV)

0

0.2

0.4

Energy of π0 (GeV)

400

200

00.1

0.2

0.3

0.4

0.8

Energy of π0 (GeV)

From ∆
Another

750 MeV

600

0

0.4

850 MeV

200

Energy of π0 (GeV)

0.2

600

400

1000 MeV

600

Energy of π (GeV)

400

0.2

800

0

400

0

From ∆
Another

1050 MeV

600

600

600

800

0.5

Energy of π0 (GeV)

Fig.31. The spectra of pπ 0 invariant mass (upper) and π 0 energy (lower) as a function of theincident photon energy for the Monte Carlo events γp → ∆π20 → pπ10 π20 .

0.6

101

80

60

2

40

1.5
20

0.2

0.4

0.6

100
80

2
60
40

1.5

1
0

m2(π0,π0) (GeV 2)

2.5

100
80

2

60

1.5

40

0.2

0.4

0.6

1
0

0

0.8

2.5

160
140
120

2

100
80

1.5

60
40

m2(π0,p) (GeV 2)

180

120
100

2

80
60

1.5

40

0.2

0.4

0.6

20

1
0

0

0.8

200

2.5

150

2
100

1.5
50

0.2

0.4

0.6

0

0.8

m2(π0,π0) (GeV 2)

3250

900 MeV200140m2(π0,π0) (GeV 2)

3220

950 MeV

160

2.5

20

m2(π0,π0) (GeV 2)3m2(π0,p) (GeV 2)

120

180

1000 MeV

140

20

0

0.8

2.5

3

1050 MeV

m2(π0,p) (GeV 2)

1
0

120

3

300

850 MeV

250

2.5
200

2

150

100

1.5

m2(π0,p) (GeV 2)

2.5

3

140

1100 MeV
m2(π0,p) (GeV 2)m2(π0,p) (GeV 2)

100m2(π0,p) (GeV 2)

31150 MeV

m2(π0,p) (GeV 2)

3

800 MeV

350

2.5

300
250
200

2

150

1.5

100

50
50

20

1
0

0.2

0.4

0.6

1
0

0

0.8

m2(π0,π0) (GeV 2)

0.2

0.4

0.6

1
0

0

0.8

m2(π0,π0) (GeV 2)

0.2

0.4

0.6

1
0

0

0.8

m2(π0,π0) (GeV 2)

0.2

0.4

0.6

0

0.8

m2(π0,π0) (GeV 2)3m2(π0,p) (GeV 2)

750 MeV

400
350

2.5

300
250

2

200
150

1.5

100
50

1
0

0.2

0.4

0.6

0

0.8

m2(π0,π0) (GeV 2)

Fig.32. Two dimensional plots of m2π0 π0 versus m2π0 p as a function of the incident photon energy
Eγ for the Monte Carlo generated events γp → ∆π 0 → pπ 0 π 0 .

80

2

60

40

1.5

3

1100 MeV
2.5

100
80

2
60
40

1.5

20

1.5

2

2.5
2

3

1
1

0

m2(π0,p) (GeV )

120
100

2

80
60

1.5

40

1.5

2

2.5
2

3

200
180

2.5

160
140
120

2

100
80

1.5

60
40

1000 MeV

160
140
120

2

100
80
60

1.5

1
1

0

40

1.5

2

2.5
2

3

20

1
1

0

m2(π0,p) (GeV )

2.5

200

150

2

100

1.5
50

2

2.5
2

3

3
300

850 MeV

250

1.5

250

2.5

200

2

150

100

1.5

400

800 MeV

350

2.5

300
250

2

200
150

1.5

100

50

50

20

1
1

1.5

2

2.5
2

3

0

m2(π0,p) (GeV )

1.5

2

2.5
2

m2(π0,p) (GeV )

3

3

0

1
1

1.5

2

2.5
2

m2(π0,p) (GeV )

3

0

1
1

1.5

2

2.5
2

3

0

m2(π0,p) (GeV )450

750 MeVm2(π0,p) (GeV 2)110m2(π0,p) (GeV )3900 MeV

180

2.5

20

3

220

950 MeVm2(π0,p) (GeV 2)m2(π0,p) (GeV 2)

2.5m2(π0,p) (GeV )

3

140

20

m2(π0,p) (GeV 2)

1
1

3

160

1050 MeV

120

m2(π0,p) (GeV 2)

2.53m2(π0,p) (GeV 2)

100m2(π0,p) (GeV 2)m2(π0,p) (GeV 2)1150 MeV

m2(π0,p) (GeV 2)

120

3

400
350

2.5

300
250

2

200
150

1.5

100
50

1
1

1.5

2

2.5

3

0

m2(π0,p) (GeV2)

Fig.33. Two dimensional plots of m2π0 p versus m2π0 p as a function of the incident photon energy
Eγ for the Monte Carlo generated events γp → ∆π 0 → pπ 0 π 0 .

102

1.5

NBE(Q)/N (Q)1.5

1150 MeVPS

NBE(Q)/N

Mix

(Q)

1

0.5
1.50

PS

NBE(Q)/N

Mix

0.4

0.6
0.8
NBE
(Q)/N (Q)
1.50
PS

NBE(Q)/N

1

(Q)

0.2

750 MeV

0.4

N0.6(Q)/N 0.8
(Q)
1.50
BE
PS

NBE(Q)/N

Mix

0.5
0.4 NPS0.6(Q)/N 0.8
(Q)
1.50
PS

1050 MeVNBE(Q)/N (Q)
1.5PS

NBE(Q)/N

Mix

(Q)

0.4

0.6

0.5
0.8
1.50

1000 MeVNBE(Q)/N (Q)PS

NBE(Q)/N

Mix

(Q)

0.5
0.2

850 MeV

0.4

N0.6(Q)/N 0.8
(Q)
1.50
BE
PS

NBE(Q)/N

Mix

1

0.2

(Q)

1

0.5
0.2

900 MeV

1

0.5

(Q)

1

0.5
0.2

Mix

Ratio

NBE(Q)/N (Q)1.5

1950 MeV

1.50

1100 MeV(Q)

0.2

800 MeV

0.4

N0.6(Q)/N 0.8
(Q)
BE
PS

NBE(Q)/N

(Q)

Mix

1

0.2

0.4

0.6

0.5
0.8
1.50

0.2

0.4

0.6

0.8

0.2

0.4

0.6

0.8

NPS(Q)/NMix (Q)

1

0.5
0

1

0.2

0.4

0.6

0.5
0.8 0

1

0.2

0.4

0.6

0.5
0.8 0
0.2
Q (GeV)

1

0.4

0.6

0.5
0.8 0

Fig.34. Correlation functions of 2 π 0 for the Monte Carlo sample γp → ∆π 0 → p2π 0 at different
incident photon energies, indicated by the text in each pad. These results are obtainedwith the event mixing method that is developed based on the pure phase space events
γp → 2π 0 p (see section 3.4).

103

4.3 Effects of σ decay on BEC analysis
Here we study the effects of the P11 (1440) → p(π 0 π 0 )I=0
S−wave decay on the BEC analysis with aMonte Carlo simulation. Generally, the correlated two pions in a S-wave is sometimes seen as a verybroad particle, the σ meson with mass about 500 M eV and width ∼ 500 M eV . We produced a Monte
Carlo sample of γp → P11 (1440) → pσ → p2π 0 events. Fig. 35 shows the mass distribution of thegenerated σ and a typical Q distribution of the 2π 0 .

hmsig_free

500
π π mass limit
0 0

400

Entries
Mean
RMS

20090
0.56530.2978hQ

800

Entries
Mean
RMS

10000
0.43020.1676

0.8

1

600

300
200

Syst. energy limit

100
00 0.2 0.4 0.6 0.8 1 1.2 1.4
σ mass (GeV)

400
200
00

0.2

0.4

0.6

Q of 2π (GeV)0

Fig.35. Left: The mass distribution of σ and the corresponding kinematic limits due to theprocess σ → 2π 0 and energy-momentum conservation. Right: A typical distribution of
the invariant mass of the relative four-momentum of 2π 0 . The incoming photon energy
is 1100 MeV.
The same event mixing process (see section 3.4) is employed for this Monte Carlo sample to get
the correlation functions of 2π 0 . In Fig. 36 are shown the correlation functions at different incoming
photon energies. As can be seen in the plots, the correlation functions exhibit a roughly flat distribution.
However, some abnormal structures of the correlation functions are observed. In the very beginning andthe very end of the correlation functions, sharp enhancements are observed. The sharp enhancement at
low Q region may lead to a misidentification of the BEC enhancement. But this misidentification can be
negligible because the σ contribution is minor compared to the ∆ contribution, which will be discussed
later. Fig. 37 shows the Q distributions of 2π 0 both for the original events and the mixed events.

104

3

NBE(Q)/N (Q) 31150 MeV

Mix

(Q)

PS

NBE(Q)/NMix(Q)

NBE(Q)/N (Q)31050 MeV

Mix

(Q)

2

2

2

1

1

1

1

0.2

0.6
0.830
NBE
(Q)/N (Q)0.4

950 MeVPS

NBE(Q)/N

Mix

(Q)

0.2

900 MeV

0.4

N0.6(Q)/N 0.8
(Q)30
BE
PS

NBE(Q)/N

Mix

(Q)

0.2

850 MeVPS

NBE(Q)/N

Mix

(Q)

2

2

2

2

1

1

1

1

30

0.4 NPS0.6(Q)/N 0.8
(Q)30
PS

0.2

750 MeV

0.2

0.4

0.830

0.6

0.2

0.4

0.2

800 MeV

0.4

(Q)

N0.6
(Q)/N 0.8
(Q)
BE
PS

NBE(Q)/N

(Q)

Mix

0.830

0.6

PS

NBE(Q)/N

Mix

N0.6(Q)/N 0.8
(Q)30
BE

0.4

NBE(Q)/N (Q)1000 MeVPS

NBE(Q)/N

2

30

Ratio

NBE(Q)/N (Q)3

1100 MeVPS

NBE(Q)/N

0.2

0.4

0.6

0.8

0.2

0.4

0.6

0.8

NPS(Q)/NMix (Q)

2

2

2

2

1

1

1

1

0

0.2

0.4

0.6

0.8 0

0.2

0.4

0.6

0.8 0
0.2
Q (GeV)

0.4

0.6

0.8 0

Fig.36. Correlation functions of 2 π 0 for the Monte Carlo events γp → P11 (1440) → pσ → p2π 0
at different incident photon energies, indicated by the text in each pad. These results
are obtained with the event mixing method that is developed based on the pure phasespace events γp → 2π 0 p (see section 3.4).
1000

1000

original

1150 MeV

1000
original

1100 MeV800

mixed800

mixed800

600

600

600

600

400

400

400

400

200

200

200

200

00
1000

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

00
1

0.1

original
1000

950 MeV

0.2

0.3

0.4

0.5

0.6

0.7

0.8

00
0.9 12001

0.1

original

900 MeV

0.2

0.3

0.4

0.5

0.6

0.7

mixed

0.8

0.9

00
1

original

1000 MeV

mixed

0.1

1200
original

850 MeV

1000

mixed
800

Counts1000

original

1050 MeV

mixed 800

0.2

0.3

0.4

0.5

0.6

0.7

mixed1000

0.8

0.9

1

original

800 MeV

mixed

800
800
800

600

600
600

400

400

200

0
14000

1200

200

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

00
1

600

400

400

200

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

00
1

200

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

00
1

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

original

750 MeV

mixed
1000

800

600

400

200

0

0

0.2

0.4

0.6

0.8

1

Q (GeV)

Fig.37. Q distributions for the Monte Carlo sample γp → P11 (1440) → pσ → p2π 0 at different
incident photon energies.

105

4.4 Effects of combined sample of ∆ sequential decay and σ decay
Although the Dalitz plots show that the ∆ sequential decay is the dominant contribution to the
double pion channel, we don’t know the exact contribution of this process and how much the σ processcontribution accounts for. We here study the combing effects of these two processes by using a toy
simulation, where some events are from the ∆ process and the remaining events are from the σ decay.
Because the ∆ contribution is dominant, there is no reason for one to include more than half eventsfrom σ process. I here perform two simulations. In the first one, the ∆ contribution accounts for 50%,
while in the second one it accounts for 80%. Fig. 38 shows the correlation functions obtained in the firstsimulation. In Fig. 39 are given the correlations functions from the second simulation.
These toy simulations show that even though the contribution of σ process accounts for up to 50%,
the whole effects can not leads to an BEC-like enhancement when Q close to 0. This means that the
special kinematical effects of σ decay can not explain the enhancement at low Q in the correlation
function obtained from the real experimental data. The experimental observed enhancement is more
likely due to the BEC effects of two pions.
3

NBE(Q)/N (Q) 31150 MeVPS

NBE(Q)/N

Mix

1100 MeVNBE(Q)/N (Q)3PS

NBE(Q)/N

Mix(Q)1050 MeVNBE(Q)/N (Q)3PS

NBE(Q)/N

Mix

(Q)

2

2

2

2

1

1

1

1

30

0.2

950 MeV

0.4

0.6
0.830
NBE
(Q)/N (Q)PS

NBE(Q)/N

Mix

Ratio

(Q)

(Q)

0.2

900 MeV

0.4

N0.6(Q)/N 0.8
(Q)30
BE
PS

NBE(Q)/N

Mix

(Q)

0.2

850 MeV

0.4

N0.6(Q)/N 0.8
(Q)30
BE
PS

NBE(Q)/N

Mix

(Q)

2

2

2

2

1

1

1

1

30

0.2

750 MeV

0.4 NPS0.6(Q)/N 0.8
(Q)30
PS

0.2

0.4

0.6

0.830

0.2

0.4

0.6

0.830

1000 MeVNBE(Q)/N (Q)PS

NBE(Q)/N

Mix

0.2

800 MeV

0.4

(Q)

N0.6
(Q)/N 0.8
(Q)
BE
PS

NBE(Q)/N

(Q)

Mix

0.2

0.4

0.6

0.8

0.2

0.4

0.6

0.8

NPS(Q)/NMix (Q)

2

2

2

2

1

1

1

1

0

0.2

0.4

0.6

0.8 0

0.2

0.4

0.6

0.8 0
0.2
Q (GeV)

0.4

0.6

0.8 0

Fig.38. Correlation functions for the combined sample that consists of ∆ sequential decay eventsand σ decay events. In this sample, the ∆ contribution accounts for 50% and the σcontribution accounts for 50%. These results are obtained with the event mixing methodthat is developed based on the pure phase space events γp → 2π 0 p (see section 3.4).

106

2 1150 MeV

NBE(Q)/N (Q) 2
PS

NBE(Q)/N

Mix

1100 MeVNBE(Q)/N (Q)2
PS

NBE(Q)/N

Mix(Q)1050 MeVNBE(Q)/N (Q)2
PS

NBE(Q)/N

Mix

(Q)

1.5

1.5

1.5

1.5

1

1

1

1

0.50
0.2
2 950 MeV

0.4

0.5

0.6
0.820
NBE
(Q)/N (Q)PS

NBE(Q)/N

Mix

Ratio

(Q)

(Q)

0.2

900 MeV

0.4

0.5

N0.6
(Q)/N 0.8
(Q)20
BE
PS

NBE(Q)/N

Mix

(Q)

0.2

850 MeV

0.4

0.5

N0.6
(Q)/N 0.8
(Q)20
BE
PS

NBE(Q)/N

Mix

(Q)

1.5

1.5

1.5

1.5

1

1

1

1

0.50
2

0.2

750 MeV

0.5
0.4 NPS0.6(Q)/N 0.8
(Q)20
PS

0.2

0.4

0.6

0.50
0.8
2

0.2

0.4

0.6

0.50
0.8
2

1000 MeVNBE(Q)/N (Q)PS

NBE(Q)/N

Mix

0.2

800 MeV

0.4

(Q)

N0.6
(Q)/N 0.8
(Q)
BE
PS

NBE(Q)/N

(Q)

Mix

0.2

0.4

0.6

0.8

0.2

0.4

0.6

0.8

NPS(Q)/NMix (Q)

1.5

1.5

1.5

1.5

1

1

1

1

0.50

0.2

0.4

0.6

0.50
0.8

0.2

0.4

0.6

0.50
0.8
0.2
Q (GeV)

0.4

0.6

0.50
0.8

Fig.39. Correlation functions for the combined sample which consists of ∆ sequential decay
events and σ decay events, where the ∆ contribution accounts for 80% and the σ contribution accounts for 20%. These results are obtained with the event mixing method thatis developed based on the pure phase space events γp → 2π 0 p (see section 3.4).

107

4.5 Improved event mixing method
Since the Dalitz plots indicate that the dominant contribution to the double π 0 channel is from the∆ sequential decay, corresponding improvements should be made for the event mixing method. Monte
Carlo simulations for the γp → ∆π 0 → pπ 0 π 0 events are performed to tune the mixing method.
As for the γp → ∆π20 → pπ10 π20 process at incident photon energies above 900 MeV, at most times
the π10 shares a relative small momentum compared to the π20 . Thus, it is better to exchange two pions
both with lower/higher energies from two different events when performing the event mixing. Fig. 40
demonstrates this special mixing process.
Because the event mixing method is also sensitive to the pion energy cut condition, we repeat thesame procedure as in the case of pure phase space events γp → pπ 0 π 0 to find the new optimum pionenergy cut. The new pion energy cut condition is found to be Eπ /Eγ < (2.5 − 1.6Eγ ) ∗ (1.1 − 0.64 ∗ mX ),where both the Eγ and mX are in the units of GeV .
With this special treatment and the new pion energy cut, we obtain the new results of the correlation functions for the Monte Carlo sample with pure ∆ contribution as shown in Fig. 41. The simulation
results show that the new special treatment in the mixing method can give a flat distribution for thecorrelation function. Thus, we can use this special treatment to extract BE parameters r0 and λ2 if allcontributions to the double pion channel are from ∆ sequential decays.
We test this improved method with the Monte Carlo events of γp → ∆π 0 → pπ 0 π 0 with BoseEinstein effects. Fig. 42 shows the correlation functions from the Monte Carlo events with input BE
parameters r0 = 0.8 f m and λ2 = 0.5. Fig. 43 shows the correlation functions from the Monte Carloevents with input BE parameters r0 = 0.8 f m and λ2 = 1.0.

π0π0higher energy

π0lower energy

event 1higher energy

π0lower energy

event 2

π0
π0

π0
π0

mixed event 1 mixed event 2

Fig.40. Illustration of swapping two pions in two different events in the improved event mixing
method.

108

1.5

NBE(Q)/N (Q)1.5

1150 MeVPS

NBE(Q)/N

Mix

(Q)

1

0.5
1.50

Mix

0.4

0.6
0.8
NBE
(Q)/N (Q)
1.50
PS

NBE(Q)/N

1

(Q)

0.4

N0.6
(Q)/N 0.8
(Q)
1.50
BE
PS

NBE(Q)/N

Mix

0.5
0.4 NPS0.6(Q)/N 0.8
(Q)
1.50
PS

0.2

750 MeVNBE(Q)/N (Q)1.5

1050 MeVPS

NBE(Q)/N

Mix

(Q)

0.4

0.6

0.5
0.8
1.50

NBE(Q)/N (Q)1000 MeVPS

NBE(Q)/N

Mix

(Q)

0.5
0.2

850 MeV

0.4

N0.6(Q)/N 0.8
(Q)
1.50
BE
PS

NBE(Q)/N

Mix

1

0.2

(Q)

1

0.5
0.2

900 MeV

1

0.5

(Q)

1

0.5
0.2

Mix

Ratio

PS

NBE(Q)/N

1

950 MeV

1.50

NBE(Q)/N (Q)1.51100 MeV(Q)

0.2

800 MeV

0.4

N0.6(Q)/N 0.8
(Q)
BE
PS

NBE(Q)/N

(Q)

Mix

1

0.2

0.4

0.6

0.5
0.8
1.50

0.2

0.4

0.6

0.8

0.2

0.4

0.6

0.8

NPS(Q)/NMix (Q)

1

0.5
0

1

0.2

0.4

0.6

0.5
0.8 0

1

0.2

0.4

0.6

1

0.5
0.8 0
0.2
Q (GeV)

0.4

0.6

0.5
0.8 0

Fig.41. Correlation functions for the Monte Carlo events of γp → ∆π 0 → pπ 0 π 0 . These results
are obtained with the improved event mixing method.

1100 MeV

1150 MeV
1.5

N = 0.89
λ 2 = 0.32 ± 0.051.5
r 0 = 0.64 ± 0.10 fm

N = 0.93
λ 2 = 0.31 ± 0.041.5
r 0 = 0.84 ± 0.09 fm

1

1

1

C2 (Q)

0.2

0.4

950 MeV

1.5

0.6

0.2

0.8 0

0.2

0.4

900 MeV

0.6

0.8 0

0.2

0.4

850 MeV

0.6

0.8 0

N = 0.94
λ 2 = 0.38 ± 0.04 1.5
r 0 = 0.97 ± 0.06 fm

N = 0.93
λ 2 = 0.44 ± 0.031.5
r 0 = 0.92 ± 0.05 fm

N = 0.94
λ 2 = 0.46 ± 0.031.5
r 0 = 0.98 ± 0.04 fm

1

1

1

1

0

1000 MeV

N = 0.91
λ 2 = 0.40 ± 0.08 1.5
r 0 = 1.00 ± 0.08 fm

1

01050 MeV

750 MeV

0.4

0.6

0.8 0

0.2

0.4

0.6

0.8 0

0.2

0.4

0.6

0.8 0

1.5

N = 0.91
1.5
λ2 = 0.50 ± 0.03
r 0 = 1.00 ± 0.36 fm

1.5

1.5

1

1

1

1

0

0.2

0.4

0.6

0.8 0

0.2

0.4

0.6

0.8 0
0.2
Q (GeV)

0.4

0.6

0.8 0

N = 0.92
λ 2 = 0.37 ± 0.04
r 0 = 0.88 ± 0.07 fm

0.2

0.4

800 MeV0.6

0.8

N = 0.92
λ 2 = 0.52 ± 0.03
r 0 = 1.00 ± 0.03 fm

0.2

0.4

0.6

0.8

0.2

0.4

0.6

0.8

Fig.42. Correlation functions for the Monte Carlo events of γp → ∆π 0 → pπ 0 π 0 with BoseEinstein effects (r0 = 0.8 f m and λ2 = 0.5). These results are obtained with the
improved event mixing method..

109

1100 MeV

1150 MeV
1.5

0.2

C2 (Q)

950 MeV1.5

N = 0.87
λ 2 = 0.64 ± 0.061.5
r 0 = 0.89 ± 0.08 fm

N = 0.88
λ 2 = 0.59 ± 0.051.5
r 0 = 0.85 ± 0.08 fm

1

1

1

0.4

0.6

0.2

750 MeV

0.8 0

0.2

0.4

900 MeV

0.6

0.8 0

0.2

0.4

850 MeV

0.6

0.8 0

N = 0.86
λ 2 = 0.80 ± 0.04 1.5
r 0 = 0.87 ± 0.04 fm

N = 0.85
λ 2 = 0.84 ± 0.041.5
r 0 = 0.85 ± 0.04 fm

N = 0.83
λ 2 = 0.86 ± 0.031.5
r 0 = 0.83 ± 0.03 fm

1

1

1

1

0

1000 MeV

N = 0.89
λ 2 = 0.63 ± 0.09 1.5
r 0 = 0.97 ± 0.12 fm

1

01050 MeV

0.4

0.6

0.8 0

0.2

0.4

0.6

0.8 0

0.2

0.4

0.6

0.8 0

1.5

N = 0.85
1.5
λ2 = 0.83 ± 0.03
r 0 = 0.95 ± 0.03 fm

1.5

1.5

1

1

1

1

0

0.2

0.4

0.6

0.8 0

0.2

0.4

0.6

0.8 0
0.2
Q (GeV)

0.4

0.6

0.8 0

N = 0.86
λ 2 = 0.71 ± 0.05
r 0 = 0.87 ± 0.05 fm

0.2

800 MeV

0.4

0.6

0.8

N = 0.86
λ 2 = 0.84 ± 0.03
r 0 = 0.94 ± 0.03 fm

0.2

0.4

0.6

0.8

0.2

0.4

0.6

0.8

Fig.43. Correlation functions for the Monte Carlo events of γp → ∆π 0 → pπ 0 π 0 with BoseEinstein effects (r0 = 0.8 f m and λ2 = 1.0). The results are obtained with the improved
event mixing method..

110

4.6 Extraction of BE parameters with the improved event mixing method
With the improved event mixing method, we extract the BE parameters r0 and λ2 for the exclusive
reaction γp → π 0 π 0 p and inclusive reactions γp → π 0 π 0 X and γd → π 0 π 0 X, and present these results.
Fig. 44 shows the correlation functions for 2π 0 in the exclusive reaction γp → π 0 π 0 p at different
energy bins. Fig. 45 shows the correlation functions for 2π 0 from the inclusive reaction γp → π 0 π 0 X
at different energy bins. Fig. 46 shows the correlation functions for 2π 0 from the inclusive reaction
γd → π 0 π 0 X. The dimension parameter r0 and chaoticity parameter λ2 are extracted by fitting theC2 (Q)

equation (2) to the correlation function.

1.5

N= 0.96λ 2 = 0.48 ± 0.23
r 0= 1.10 ± 0.24 fm1.5

N= 0.93
λ 2 = 0.41 ± 0.14
1.5
r 0= 0.89 ± 0.18 fm

N= 0.92
λ 2 = 0.59 ± 0.18
1.5
r 0= 1.10 ± 0.17 fm

1

1

1

1

0.5

1130-1150 MeV

0

0.2

1.5

0.5
0.4
0.6 0.8 0
N= 0.93
λ 2 = 0.44 ± 0.13
1.5
r0 = 1.18 ± 0.15 fm

1
0.5

1110-1130 MeV

0.2

1
0.2

0.4

0.6

0.5
0.8 0

1090-1110 MeV

0.2

0.5
0.4N= 0.94
0.6 0.8 0
λ 2 = 0.35 ± 0.11
r0 = 0.96 ± 0.151.5
fm

1

1050-1070 MeV

00.5
0.4N= 0.93
0.6 0.8 0
λ 2 = 0.38 ± 0.11
r0 = 1.10 ± 0.121.5
fm

0.2

1070-1090 MeV

0.2

0.4N= 0.94
0.6 0.8
λ 2 = 0.61 ± 0.14
r0 = 1.18 ± 0.12 fm

0.2

0.4

1

1030-1050 MeV

1010-1030 MeV

0.4

0.4

0.6

N= 0.93
λ 2 = 0.39 ± 0.11
r 0= 1.02 ± 0.12 fm

0.5
0.8 0 0.2
Q (GeV)

0.6

0.5
0.8 0

990-1010 MeV

0.6

0.8

C2 (Q)

Fig.44. Correlation functions C2 (Q) for γp → 2π 0 p, obtained with the improved event mixing
method, in which one event is mixed with up to 20 other events. The FOREST dataset
2009A, 2009B, 2009C and 2009D are used. In the plots, only statistic errors are shown.

1.5

N= 0.93
λ 2 = 0.47 ± 0.10
r 0= 1.19 ± 0.16 fm1.5

N= 0.94
λ 2 = 0.44 ± 0.09
1.5
r 0= 1.18 ± 0.18 fm

N= 0.89
λ 2 = 0.51 ± 0.07
1.5
r 0= 1.02 ± 0.09 fm

1

1

1

1

0.5

1130-1150 MeV

0

0.2

1.5

0.5
0.4
0.6 0.8 0
N= 0.90λ 2 = 0.62 ± 0.06
1.5
r0 = 1.17 ± 0.08 fm

1
0.5

1110-1130 MeV

0.2

1
0.2

0.4

0.6

0.5
0.8 0

1090-1110 MeV

0.2

0.5
0.4N= 0.89
0.6 0.8 0
λ 2 = 0.61 ± 0.05
r0 = 1.00 ± 0.071.5
fm

1

1050-1070 MeV

00.5
0.4N= 0.88
0.6 0.8 0
λ 2 = 0.69 ± 0.05
r0 = 1.06 ± 0.061.5
fm

0.2

1030-1050 MeV

1010-1030 MeV

0.4

0.5
0.8 0 0.2
Q (GeV)

1070-1090 MeV

0.2

0.4N= 0.90
0.6 0.8
λ 2 = 0.72 ± 0.05
r0 = 1.09 ± 0.05 fm

0.2

0.4

1

0.4

0.6

N= 0.90λ 2 = 0.55 ± 0.06
r 0= 1.08 ± 0.08 fm

0.6

0.5
0.8 0

990-1010 MeV

0.6

0.8

Fig.45. Correlation functions C2 (Q) for the inclusive reaction γp → 2π 0 X at different incident
photon energy bins, obtained with the improved event mixing method, in which one
event is mixed with up to 20 other events. The FOREST dataset 2009A, 2009B, 2009C
and 2009D are used. In the plots, only statistic errors are shown.
We summarize the results of the BEC analysis for 2 π 0 from the exclusive reaction γp → π 0 π 0 p andthe inclusive reactions γp → π 0 π 0 X and γd → π 0 π 0 X in Fig. 47.
The dimension parameter r0 and the chaoticity parameter λ2 for the emitting source are shown as

C2 (Q)111

1.5

N= 0.95
λ 2 = 0.52 ± 0.08
r 0= 1.09 ± 0.13 fm1.5

N= 0.95
λ 2 = 0.57 ± 0.07
1.5
r 0= 1.14 ± 0.10 fm

N= 0.94
λ 2 = 0.54 ± 0.06
1.5
r 0= 1.03 ± 0.08 fm

1

1

1

1

0.5

1130-1150 MeV

0

0.2

1.5

0.5
0.4
0.6 0.8 0
N= 0.93
λ 2 = 0.51 ± 0.03
1.5
r0 = 0.92 ± 0.05 fm

1
0.5

1110-1130 MeV

0.2

1
0.2

0.4

0.6

0.5
0.8 0

1090-1110 MeV

0.2

0.5
0.4N= 0.94
0.6 0.8 0
λ 2 = 0.62 ± 0.04
r0 = 1.03 ± 0.051.5
fm

1

1050-1070 MeV

00.5
0.4N= 0.94
0.6 0.8 0
λ 2 = 0.55 ± 0.03
r0 = 0.97 ± 0.041.5
fm

0.2

1030-1050 MeV

1010-1030 MeV

0.4

0.5
0.8 0 0.2
Q (GeV)

1070-1090 MeV

0.2

0.4N= 0.93
0.6 0.8
λ 2 = 0.60 ± 0.03
r0 = 0.97 ± 0.03 fm

0.2

0.4

1

0.4

0.6

N= 0.94
λ 2 = 0.50 ± 0.04
r 0= 0.99 ± 0.06 fm

0.6

0.5
0.8 0

990-1010 MeV

0.6

0.8

Fig.46. Correlation functions C2 (Q) for γd → 2π 0 X at different incident photon energy bins,
obtained with the improved event mixing method, in which one event is mixed with up
to 20 other events. The FOREST dataset 2009A, 2009C and 2009D are used. In theplots, only statistic errors are shown.

a function of the incident photon energy Eγ . Within error bars, the radii r0 obtained from the three different reaction channels are in good agreement. And the r0 values demonstrate a constant distribution
over the incident photon energy within error bars. This result indicates that the size of the 2 π 0 emitting
source is independent of the incident photon energy.
The λ2 parameter is also extracted in the fitting to the correlation functions. The results demonstrate a constant values ∼ 0.5 at all energy bins and good consistency between different data samples isfound.
Finally, weighted average values for the r0 and λ2 over Eγ are obtained:(1) For γp → π 0 π 0 p,
r0 = 1.07 ± 0.05, λ2 = 0.43 ± 0.05.
(2) For γp → π 0 π 0 X,
r0 = 1.08 ± 0.03, λ2 = 0.61 ± 0.02.
(3) For γd → π 0 π 0 X,
r0 = 0.99 ± 0.02, λ2 = 0.56 ± 0.01.
(4) For the combined three samples together,r0 = 1.02 ± 0.01, λ2 = 0.57 ± 0.01.
4.7 Systematic uncertainties
The systematic uncertainties on the BEC parameters, r0 and λ2 , are estimated by varying theanalysis procedure and comparing the corresponding results. These two parameters in the fitting are
obviously correlated. But here we estimate their systematic errors separately.
A big source of the systematic uncertainties is the event mixing technique. Although the missing
mass and pion energy cuts work well to eliminate the correlation of two pions arising from energymomentum conservation and to get a quite flat correlation function, this event mixing method still

112

0

0

γ p → 2π p0
γ p → 2π X
0
γ d → 2π X

1

1.5

λ2

r 0 (fm)2

γ p → 2π p0
γ p → 2π X
0
γ d → 2π X

0.5

1
0.5
0

1

1.05

1.1

1.15

0

1

Eγ (GeV)

1.05

1.1

1.15

Eγ (GeV)Fig.47. (color online) The dimension parameter r0 (left) and the chaoticity parameter λ2 (right)
for the emitter source as a function of the incident photon energy Eγ obtained by the
BEC analysis for 2 π 0 from the exclusive reaction γp → π 0 π 0 p and the inclusive reactions γp → π 0 π 0 X and γd → π 0 π 0 X.
introduces a big systematic error when extracting the r0 and λ2 .
To discuss the systematic error due to the event mixing method itself, we rely mainly on the Monte
Carlo simulation. As shown in Fig. 42 and Fig. 43, where the correlation functions are obtained for
the Monte Carlo γp → 2π 0 p events with BE effects, the improved event mixing method underestimate
the λ2 values—the fitted λ2 value averagely accounts for ∼70% of the input one in the energy region
1.0 GeV ≤ Eγ ≤ 1.15 GeV . Therefore, the fitted value of λ2 must be corrected. Similar systematic
bias also happens to r0 , and corresponding corrections are required. In Table 3 is listed the correction
coefficients by which the experimental BE parameters are multiplied to get the corrected values.
Remember that the improved method is based upon the assumption that all the γp → 2π 0 p eventsare from ∆ sequential decay. Although this assumption is quite reasonable—Dalitz plots confirmed
the dominant contribution from ∆—100% contribution is not the exact process for the two π 0 channel.
Unfortunately, there is no conclusion of the exact contribution from ∆ sequential decay. Our strategy is
to estimate two BEC results based two limits, 100% ∆ contribution and 100% three body phase spacecontribution, and then to calculate the average value between these two results. The true value should be
between these two limits. And we treat the difference between these two extreme results as a systematic
error. In each extreme assumption, the correction for r0 and λ2 are needed. The corresponding correction
coefficients are listed in Table 3.
The variations of the pion identification criteria (different CL cuts and photon energy thresholdcuts) are also studied. The uncertainties introduced by this effect can be negligible.
The variations in BEC results caused by changing the fitting region in Q are investigated. Thesevariations introduce a systematic error for r0 up to 0.04 fm. And the λ2 uncertainties can be negligible.
The systematic errors due to the binning in Q is also investigated. It is found that this effect can be
negligible.
The total systematic uncertainties caused by above mentioned sources are obtained by making a

113

quadratic adding for all the contributions. The overall systematic uncertainty for r0 is 0.04 fm. The λ2
uncertainty is introduced by the two extreme contribution assumption, and it’s value is just the half ofthe difference between these two extreme BEC results. Finally the systematic error of λ2 is found tobe 0.23. Because the difference of r0 between these two limitation is accidentally 0, the corresponding
systematic error is 0.

Table 3: BEC results from the simulation with different assumptions of dominant process for the γp → 2π 0 p reaction. In
the end of each assumption, the correction coefficients (Cor.) for
r0 and λ2 are given.
Eγ (GeV)r0 (fm)λ2

χ2 /ndf

Combination (1): 100% ∆, 0% phase space
BEC input: r0 = 0.8 f m, λ2 = 0.51.15

1.00±0.08

0.40±0.08

6.71/61.10

0.64±0.10

0.32±0.05

12.15/9

1.05

0.84±0.09

0.31±0.04

16.61/9

1.00

0.88±0.07

0.37±0.04

9.11/9

Cor.

0.93

1.47

BEC input: r0 = 0.8 f m, λ2 = 1.0
1.15

1.07±0.11

0.62±0.09

12.18/91.10

0.97±0.07

0.60±0.06

19.11/91.05

0.90±0.06

0.57±0.05

8.42/91.00

0.94±0.04

0.68±0.05

18.64/9

Cor.

0.85

1.61

Ave. Cor.

0.89

1.54

Combination (2): 0% ∆, 100% phase space
BEC input: r0 = 0.8 f m, λ2 = 0.51.15

1.05±0.09

0.77±0.09

9.81/91.10

0.85±0.05

0.80±0.06

13.06/9

1.05

0.91±0.05

0.82±0.06

14.76/9

1.00

0.83±0.04

0.74±0.04

8.56/9

Cor.

0.92

0.65

BEC input: r0 = 0.8 f m, λ2 = 1.0
1.15

1.06±0.06

1.19±0.10

15.46/9

Continued on next page114

Table 3 – continued from previous pageEγ (GeV)r0 (fm)λ2

χ2 /ndf

1.10

0.88±0.04

1.13±0.07

7.77/91.05

0.96±0.04

1.23±0.07

18.70/91.00

0.90±0.03

1.15±0.05

7.95/9

Cor.

0.86

0.85

Ave. Cor.

0.89

0.75

§ 5. Discussion
We here discuss the BEC results from the exclusive reaction γp → π 0 π 0 p and the inclusive reactions
γp → π 0 π 0 X and γd → π 0 π 0 X. Within error bars, these three reaction channels give consistent dimension parameter r0 and correlation strength λ2 (or chaoticity parameter). Because the Bose-Einsteincorrelations between two π 0 only depend on the space-time extension of the source, it is not surprisingthat the inclusive and the exclusive channels give the similar results. That the 2π 0 channels off the
proton and the deuteron have consistent BEC results indicates that an incident photon mainly interacts
with one nucleon in the deuteron, the size of two π 0 emitting source for the proton is the same as thatfor the neutron, and the correlation strength of the two π 0 emitted from the proton is also similar to thatfrom the neutron.
The r0 and λ2 seem to be independent of the incident photon energy Eγ in the energy region
1.0 GeV ≤ Eγ ≤ 1.15 GeV . In principle, the λ2 is a measure of the degree of being chaotic of the
2 π 0 emission. But in the experimental side, many factors affect the extracted value of λ2 , such as theresolution of observables and analysis method. In this work, the event mixing method may introduce a
big uncertainty in the λ2 observation. We address this issue by using different event mixing methods
and treat the difference in λ2 from the different methods as a systematic error.
Because we observe consistent BEC results from the three channels and constant values of themover Eγ , weighted average values for r0 and λ2 over Eγ are obtained from all these three channels
together. It is determined to be r0 = 1.02 ± 0.01(stat.) f m and λ2 = 0.57 ± 0.01(stat.). As discussed
before, the experimental results need to be corrected, because the improved event mixing method, developed based on the assumption that the 2 π 0 channel is completely dominated by the ∆ sequential decay,
introduces a systematic bias. As we do not know the exact contribution of the ∆ sequential decay, thecorrection should be done based on two extreme assumptions: (1) 100% ∆ contribution; (2) 100% threebody phase space contribution. The true value should be between these two corrected BEC results. We
take the averaged value of these two extreme results as the true value and treat the difference between
them as a systematic error. Below are shown the corrected r0 and λ2 values based on the two extreme
assumptions:(1) 100% ∆ contribution

115
r0 = 0.91 ± 0.01(stat.) f m, λ2 = 0.88 ± 0.01(stat.),(2) 100% three body phase space contribution
r0 = 0.91 ± 0.01(stat.) f m, λ2 = 0.43 ± 0.01(stat.).
The averaged values between these two extreme results and the corresponding systematic errors are:r0 = 0.91 ± 0.01(stat.) ± 0.04(syst.) f m,
λ2 = 0.66 ± 0.01(stat.) ± 0.23(syst.).
This r0 gives information about the spatial extension of baryon resonances, because the 2 π 0 emitted
in photoproduction are decayed from excited baryon states. For the two neutral pion photoproduction on
the nucleons (the proton or neutron), one can easily expect that the size of the two pion emitting sourcein the baryon resonance energy region is comparable to the nucleon size ∼ 1.0 f m. Our study based on
the BEC analysis confirms this expectation.
It is difficult to make a quantitative comparison with BEC results from other experiments, because
the situations for other measurements are much different than our case. In the work [?], they measured
the source size for hadronic events at the Z resonance and found the radius to be about 0.5 f m. In thecase of heavy-ion collisions, the source size is found to be larger, of the order of several femtometre [?].
This is nature because of the large size of the colliding particles.
As we have seen in the Dalitz plots for the reaction γp → π 0 π 0 p, the dominant process in this′′channel is the resonance sequential decay γp → R → R π 0 → p2π 0 , where R and R stand for baryon
resonances. Fig. 48 shows a schematic illustration of this resonance sequential decay. Our method,developed for the BEC analysis, for the first time provides an useful tool to measure the space-time
properties of the excited baryon states and might shed more light on the resonance-resonance transitions. In the double π 0 channel, the sequential decay of γp → ∆π 0 → pπ 0 π 0 is dominant. This meansthat the two π 0 are not generated simultaneously. Thus the r0 is not only a measure of the source size, italso contains the delayed time information (∼ 10−23 s) on the later generated π 0 due to the ∆ decay. The
r0 and λ2 values obtained in the BEC analysis may provide crucial information about this sequential
decay.

π0

R

π0

R'

Fig.48. An example of resonance sequential decay.
Without the information about the exact contributing processes for the double π 0 channel, we would
say that the r0 is a measure of the size of the reaction region. However, as we already know, the dominant
contribution to this channel is ∆ sequential decay. Let’s discuss this issue based on the assumption that

116

the ∆ sequential decay is completely dominant, i.e., all events are from the ∆ process. In this case, the∆ appears when one π 0 is emitted and the ∆ disappears when another π 0 is produced. Thus, during theemission of the two π 0 , the reaction region undergoes a propagation process especially along the beam
direction. This means that what we measure on the r0 also contains the information on the propagating
particle that produces the second pion. This motivates the attempt to link the r0 to the time informationof the propagating particle. Since the spherical shape of the emitter is assumed, the r0 should be related
to the propagation length of the ∆ within its lifetime τ : r0 ≈ γβτ , where γ and β are the Lorentz factor
and the velocity of the ∆, respectively. For the photoproduction on the proton with the incident photon
energy of ∼ 1.1 GeV , the momentum and the invariant mass of the whole system are ps = 1.1 GeV√
and s ≈ 1.71 GeV , respectively. If we assume that the ∆ has a similar momentum as the whole√system, its velocity should be γβ = ps / s ≈ 0.64. Then the lifetime of the propagating particle isgiven by τ = r0 /(γβ) = 0.91 f m/0.64 ≈ 1.4 f m. This lifetime corresponds to a width of the mass,∼ 141 M eV , which is comparable with the Breit-Wigner full width of the ∆ ∼ 117 M eV . This simple
discussion shows that the propagation time of the ∆ during the two pions emission would provide an
accepted explanation of the experimental r0 value from the BEC analysis. But such an explanation is
not completed if we do not have the size information in the transverse direction with respect to the beam
direction. To do this, we need to perform the two-dimensional BEC analysis by using the correlation
function expressed in terms of the longitudinal component Qz of Q and the transverse component QT :
2

2

2

2

C2 (Qz , QT ) = 1 + λ2 e−(rz Qz +rT QT ) . Present study is limited from this point of view. Experimental datain the future with more statistics will be very helpful for such more precise analysis.

§ 6. Summary
We study the space-time extension of the two-pion emitting source using Bose-Einstein (BE) correlations between the two neutral pions. This is the first time attempt to observe the BE effects of two π 0from photoproduction in the baryon resonance energy region in the world. Bose-Einstein correlations ofidentical bosons were discovered more than 50 years ago and it was immediately realized that it provides an approach to the spatial extension of the bosons emission source. Actually, BEC analysis is the
only method to measure the size of unstable hadrons. Extensive theoretical and experimental studies
about BEC have been carried out in the hadronic reaction field and heavy-ion collisions at high energies
over 50 years. However, in the non-perturbative QCD energy region, BEC analysis has not yet been
performed because the observation of the BE effects is strongly obscured by many factors such as strict
kinematical limits and resonance effects. And there was no reliable method previously to address thisproblem. In this work, we study the space-time properties of the excited nucleon in the non-perturbative
QCD region a BE correlations in two neutral pions from photoproduction off a proton/neutron target
both in the exclusive and the inclusive cases.
The BE correlations of 2π 0 are measured in terms of the correlation function, the ratio of the Q
distribution of the real data to that from a reference sample free of BE effects. Here Q stands for theinvariant mass of the two neutral pions’ relative four-momentum. The correlation function is parame-

117

terized by two parameters: r0 , a measure of the size of the pion emitting source, and λ2 , a measure of thestrength of the correlation (or degree of being chaotic for the emission). To construct a valid reference
sample, we developed an event mixing method, which constructs an event in the reference sample bycombining two pions from different events with appropriate kinematic cut conditions. The BE parameters r0 and λ2 are extracted by fitting the theoretical correction function to the measured one. With thisevent mixing method, the dimension parameter r0 and the chaoticity parameter λ2 for the two pions
emitting source are obtained via the BEC analysis of the two neutral pions from the exclusive reaction
γp → π 0 π 0 p and the inclusive reactions γp → π 0 π 0 X and γd → π 0 π 0 X. Within error bars, thesethree reaction channels show consistent results for the r0 and the λ2 . And the BE parameters from theproton and the deuteron show consistent values. These results indicate that an incident photon mainlyinteracts with one nucleon in the deuteron, the sizes of two π 0 emitting source for the proton and theneutron are the same as each other, and the correlation strength of the two π 0 emitted from the proton
is also similar to that from the neutron.
As shown in the BEC results, both the r0 and λ2 values do not depend on the incident photon
energy in the region 1.0 GeV ≤ Eγ ≤ 1.15 GeV . Weighted average values for the r0 and the λ2 overEγ are obtained from all these three channels together. It is determined to be r0 = 0.91 ± 0.01 (stat.) ±0.04 (syst.) f m and λ2 = 0.66±0.01 (stat.)±0.23 (syst.). Because the 2π 0 in photoproduction are frombaryon resonances, this r0 value provides information about the spatial extension of the excited baryon
states. For the double neutral pion photoproduction on the nucleon (the proton or neutron), it is natural
to expect that the size of the two pion emitting source is comparable to the nucleon size ∼ 1.0 f m. Our
study confirmed this expectation in the baryon resonance region. And the method we developed for the
first time in this study also provides another approach to measure the size of baryon resonances.

Acknowledgment
This research was supported in part by the Ministry of Education and Science of Japan (Grant No.
19002003), and JSPS KAKENHI (No. 24244022).

References[1]

Hanbury-Brown R and Twiss R Q: Phil. Mag. 45 (1954) 663.

[2]

Hanbury-Brown R and Twiss R Q: Nature 177 (1956) 27.

[3]

Hanbury-Brown R and Twiss R Q: Nature 178 (1956) 1046.

[4]

Goldhaber G et al.: Phys. Rev. Lett. 3 (1959) 181.

[5]

Goldhaber G et al.: Phys. Rev. Lett. 120 (1960) 300.

[6]

M. Deutschmann et al.: Nucl. Phys. B 204 (1982) 333.

[7]

B. Andersson, G. Gustafson and C. Sjogren, Nucl. Phys. B 380 (1992) 391.

[8]

Drijard D et al.: Nucl. Instrum. Meth. A 225 (1984) 367[9]

TPC collaboration, Aihara H et al.: Phys. Rev. D 31 (1985) 996

118[10] TASSO collaboration, Althoff M et al.: Z. Phys. C 30 (1986) 355[11] AMY collaboration, Choi S K et al.: Phys. Lett. D 355 (1995) 406[12] ALEPH collaboration, Decamp D et al.: Z. Phys. C 54 (1992) 75[13] DELPHI collaboration, Abreu P et al.: Phys. Lett. B 286 (1992) 201[14] L3 collaboration, Achard P et al.: Phys. Lett. B 524 (2002) 55[15] Assafiri Y et al 2003 Phys. Rev. Lett. 90 222001[16] U. Thoma et al., Phys. Lett. B 659, 87 (2008).
[17] A. V. Sarantsev et al., Phys. Lett. B 659, 94 (2008).
[18] J. Ahrens et al., Phys. Lett. B 624, 173 (2005).
[19] V. L. Kashevarov et al. Phys. Rev. C 85, 064610 (2012).

ELPH Annual Report, Tohoku University (2011-2013)

119

Kinematical fit for the analysis of the FOREST experiments
T. Ishikawa1 , Q. He1 , Y. Honda1 , S. Masumoto2,3 , M. Miyabe1 , H. Shimizu1 ,Y. Taniguchi1 , Y. Tsuchikawa1 , H. Yamazaki1 , and R. Yamazaki1
1Research Center for Electron Photon Science (ELPH), Tohoku University, Sendai 982-0826,
Japan
2

Department of Physics, University of Tokyo, Tokyo 113-0033, Japan
3

Nishina Center, RIKEN, Wako 351-0198, JapanThe kinematical fit (KF) is a kind of methods to improve the measured quantities and/or determine
the unmeasured ones by applying the constraints. The KF library implemented to an analysis code for
the FOREST experiments is described in this report.

§ 1. Formulation
The kinematical fit (KF) is a procedure of fitting in which one uses the external knowledge on
the physical laws for the reaction and/or decay of the particles to improve the measured quantities
and/or determine the unmeasured ones. The formulations of kinematical fits are described in many
textbooks [1, 2]. Here, the fitting with constraints used in an analysis code for the FOREST experiments
is described. The fitting technique is based on the well-known Lagrange multiplier method, and it isassumed that the constraint equations can be linearized. Let X represent the kinematical variables(measured and unmeasured quantities) and Lagrange multipliers by a vectortX ≡ (x1 , x2 , . . . , xnv , λ1 , λ2 , . . . , λnc ) .

(1)

The nv and nc denote the number of variables and that of constraints, respectively. Here, one does nothave to know whether a variable is measured or not. The subscript of X gives the number of iterationsin the successive approximation, a subscript of 0 shows the initial value of X. The initial values forthe measured, unmeasured variables, and Lagrange multiplies are given by the measured values, theestimated values, and 0, respectively. The Xf stands for the final (fitted) values of them. Let V represent
the (nv + nc ) × (nv + nc ) covariant matrix which describes the resolutions of the measured variables


σ12




σ22




..


.






2
V ≡
(2)
.
σnv






0




.
..




0

120
The diagonal elements (i, i) have the values of σi2 where σi is the resolution for the i-th kinematicalvariables, and other elements have the value of 0. The resolutions for the unmeasured variables are also
given by 0. The quality of the fit can be calculated astχ2 = (Xf − X0 ) G (Xf − X0 )by using the (nv + nc ) × (nv + nc ) covariant matrix


σ1−2




σ2−2




..


.






−2
G≡

σnv






0




.
..




0

(3)

(4)

where the non-zero elements in V are replaced with their inverse numbers. The constraint equations
fi = 0 (i = 1, 2, . . . , nc ) are also expanded to the nv + nc vector
F = (0, 0, . . . , 0, f1 , f2 , . . . , fnc )(5)where the first nv elements have the value of 0. The KF procedure is a problem to search for a vector
Xf which minimizestχ2 = (Xf − X0 ) G (Xf − X0 ) + 2F Xf .

(6)

§ 2. KF procedureIf χ2 is a continuous and differentiable everywhere, the derivative of χ2 with respect to Xf becomes∂χ2t= (Xf − X0 ) G + G (Xf − X0 ) + 2D t Xf + 2F = 2G (Xf − X0 ) + 2D t Xf + 2F = 0,(7)∂Xf
where D ≡ ∂F/∂Xf is the (nv + nc ) × (nv + nc ) matrix described as


0
0
···
0
0 0 ··· 0



..
..
..
..
.. ..
..
.. 

.
.
.
.
. .
.
. 





0
0
···
0
0 0 ··· 0 


 ∂f1

∂f1
∂f1

···
0 0 ··· 0 


nv
1
2
∂xf
∂xf
∂xf
.
D=


 ∂f2

∂f2
∂f2


·
·
·
0
0
·
·
·
0
nv
 ∂x1

2
∂xf
∂xf


f

..
..
..
.. ..
..
.. 
..


.
.
.
.
. .
.
. 



∂fnc
∂fnc
 ∂fnc

·
·
·
0
0
·
·
·
0
n
v
1
2
∂x
∂xf
∂xf
f

(8)

The condition to minimize χ2 in the equation (6) is
G (Xf − X0 ) + D t Xf + F = 0,

(9)

121

and the (n + 1)-th successive approximation is given byt
G (Xn+1 − X0 ) + Dn
Xn+1 = 0(10)

with a requirement of F = 0.
The Taylor expansion of the constraint matrix Fn+1 at Xn+1 = Xn isFn+1 = Fn + Dn (Xn+1 − Xn ) + · · · .

(11)

Assuming Fn+1 = 0, one getsFn + Dn (Xn+1 − Xn ) = 0(12)

by ignoring the higher order than (Xn+1 − Xn ). The equation
t∆Xn+1 = −Fn + Dn H (Xn − X0 )G + D n + Dn

(13)

is given from the equations (10) and (12). Here, ∆Xn+1 is a vector whose elements are (xi )n+1 − (xi )0
for the measured variables, (xi )n+1 − (xi )n for the unmeasured variables, and (λi )n+1 for the Lagrange
multipliers, respectively. The H is a (nv + nc ) × (nv + nc ) matrix to select the measured variables whose
diagonal elements corresponding to the measured variables are 1 and the other elements are 0. The
matrix ∆Xn+1 is calculated ast∆Xn+1 = G + Dn + Dn

−1{−Fn + Dn H (Xn − X0 )} .

(14)

The (n + 1)-th fitted values for the kinematical variables can be calculated easily by using ∆Xn+1 .
One can separate a vector X describing the measured, unmeasured variables, and the Lagrange
multipliers to three vectors, and a successive approximation to three steps for them to reduce the degreesof the matrices. Yet, this kind of method is not recommended in a textbook [2] Therefore, we do not adopt
a separated method. The details of the implementation of the KF library including the C language codeare described elsewhere [3, 4].

§ 3. Quality of the fit
The most important value giving the quality of the fit is χ2 . The χ2 can be obtained by the equation (6), and the χ2 probability is also calculated by using χ2 and the degree of freedom nc − nu where
nu stands for the number of unmeasured variables. The error of the kinematical fit for the variables arealso important. The second derivative of χ2 with respect to Xf is∂ 2 χ2= 2 G + Dt + D ,∂Xf2
where it should be noted that ∂D t /∂Xf = 0. The variance VX for Xf is!−1
−1∂ 2 χ2
VX = 2= G + Dt + D
,
2
∂Xf

(15)

(16)

and the diagonal elements of VX are the error of kinematical fit for the variables, namelyδXf (i) = VX (i, i).

(17)

122

The pull distribution is useful to check whether the kinematical variables and the resolution for them
are correctly determined or not, The pull is defined by the residual Xf − X0 divided by the resolution of
the measurement. The resolution of the measurement is not a resolution for the measured variable but
σ 2 = σi2 − σf2(18)

where σi and σf denote the resolution for the measured variable (the fluctuation of the initial value) andthe error of it (the fluctuation of the final value). If everything is correctly estimated, the pull distribution
becomes a Gaussian with a mean of 0 and with a width of 1. The details of the implementation of
deducing the quality of the fit are described elsewhere [5].

Acknowledgment
This work was supported in part by Grants-in-Aid for Scientific Research (B) (17340063). for Specially promoted Research (19002003), and for Scientific Research (A) (24244022).

References[1]

A.G. Frodesen, O. SkjeggestadAH. Tofte, Probability and statistics in particle Physics, Universitetsforlaget (1979).

[2]

L. Lyons, Statistics for nuclear and particle physicists, Cambridge University Press, 152 (1986).

[3]

T. Ishikawa: Internal GeV-γ Analysis Note No. 254P (2012).

[4]

T. Ishikawa: Internal GeV-γ Analysis Note No. 263P (2012).

[5]

T. Ishikawa: Internal GeV-γ Analysis Note No. 337F (2013).

ELPH Annual Report, Tohoku University (2011-2013)

123

Estimation of a Gaussian width for a partly measured
variable
T. Ishikawa1 , Q. He1 , Y. Honda1 , S. Masumoto2 , M. Miyabe1 , N. Muramatsu1 ,H. Shimizu1 , Y. Tsuchikawa1 , H. Yamazaki1 , and R. Yamazaki1
1Research Center for Electron Photon Science (ELPH), Tohoku University, Sendai 982-0826,
Japan
2

Department of Physics, University of Tokyo, Tokyo 113-0033, JapanThe residual and pull distributions given by the kinematical fitting sometimes show asymmetricbehavior due to the cut condition or threshold effect. Therefore, it is difficult to determine the resolution
for a variable from these distributions.w In this report, the estimation of a Gaussian width (standard
deviation) for a partly measured variable is discussed assuming the mean of the distribution is correctly
determined.

§ 1. Partly measured Gaussian distribution
At first, the mean µ, the root mean square (rms) r, and standard deviation σ are obtained fora partly measured Gaussian distribution. Here, the given µ and given σ is assumed to be 0 and 1,
respectively. The values µ, r, and σ are obtained as

n
X



µ
=
xi ,




i=1

v

u

n

u1 X

r=t
x2i ,
n



v i=1
v


u
u
n
n


u1 X
u1 X



2
t
σ=
(xi − µ) = t
x2i − µ2 , and



n
n
i=1

(1)

i=1

for n elements xi (i = 1, 2, . . . , n). The relationr 2 = µ2 + σ 2(2)is valid by the definition.
The obtained µ, r, and σ values are investigated for a partly measured Gaussian distribution witha given µ is 0 and a given σ is 1. The 100,000,000 elements are generated giving the Gaussian distribution [1] with µ = 0, σ = 1, and being higher than the lower limit xmin . The µ, r, and σ values arecalculated for the obtained distribution. The lower limit xmin is given from −3.0 to +3.0 by a step of 0.1.
Fig. 1 shows the obtained µ, r, and σ values as a function of the lower limit xmin .
When the lower limit xmin is low enough, the obtained µ is almost the same as the given mu = 0.
The obtained µ gradually increases as xmin goes higher. The obtained r is almost the same as the given

3

3

2

2
r

µ

124

1
0

1

-2

0

0

2

xmin

-2

0
xmin

2

1.5

σ

1

0.5

0

Fig.1.

-2

0
xmin

2

Obtained µ, r, and σ values as a function of the lower limit xmin . The left-upper, rightupper, and left-lower panels show the obtained µ, r, and sigma values, respectively.

r = 1 for the lower limit xmin less than 0. The obtained r monotonically increases for the lower limit
xmin more than 0. The obtained σ is almost the same as the given σ = 1 for low xmin , and it decreases
gradually as xmin goes higher.

§ 2. Estimation of the given width
The obtained µ, r, and σ values are investigated for a partly measured Gaussian distribution in §1.
Here, a function is discussed which reproduces the given σ = 1 by using the obtained µ, r, and σ values.
The function is assumed to be expressed by a linear sum of the µ, r, and σ values:(3)

σ0 (µ, r, σ) = αµ µ + αr r + ασ σ.

Three parameters αµ , αr , and ασ are determined so that the function σ0 gives 1 independently of xmin .
The parameters are changed by a step of 0.001, and the optimum parameters are searched for. The
minimum χ2 expressed by the equation
χ2 =

X

2

{σ0 (µ, r, σ) − 1}

(4)

xmin

is required for the optimum parameters. Here,P

xmin stands for summing up the values for all the lower

limit xmin . The obtained optimum parameters are
α = +0.836, µαr = −0.650, and ασ = +1.656,

(5)

125
and χ2 is 0.014. Since the number of the sets for the lower limit xmin is 61, the σ0 has a 1.5% deviation
form 1 in average. Fig. 2 shows the optimum σ0 as a function of the lower limit xmin . The value σ0 shows
almost 1 for all the xmin regions.
1.5

w

1

0.5

0

Fig.2.

-2

0
xmin

2

Optimum σ0 as a function of the lower limit xmin . The horizontal lines corresponding to
the values of 0.95 and 1.05 are drawn to guide the eyes.

The µ, r, and σ values have the same order as the elements xi , and the linear response is obtained
between the given σ and the obtained µ, r, and σ. Therefore, the σ0 given by the equation (3) is expected
to be the given σ. The σ0 in case of changing the lower limit xmin has been discussed above. Only doeschange the sign of the obtained µ for the case that the xi larger than the upper limit xmax are notmeasured. Thus, the given σ can be estimated by the equation
σ0 (µ, r, σ) = αµ |µ| + αr r + ασ σ

(6)in general.

§ 3. Summary
The given σ can be estimated by the equation
σ0 (µ, r, σ) = 0.836 |µ| − 0.650r + 1.656σ(7)

for a partly measured Gaussian distribution with a symmetry around 0, where µ, r, and σ denote theobtained mean, rms, and standard deviation, respectively. The details of the analysis are described
elsewhere [2].

Acknowledgment
This work was supported in part by Grants-in-Aid for Scientific Research (B) (17340063), for Specially promoted Research (19002003), and for Scientific Research (A) (24244022).

References[1]

T. Ishikawa: Internal GeV-γ Analysis Note No. 01 (2004).

[2]

T. Ishikawa: Internal GeV-γ Analysis Note No. 350P (2014).

126

ELPH Annual Report, Tohoku University (2011-2013)

Measurement of target thickness of liquid H2, D2 with thelaser displacement meter
H. Yamazaki1∗ , H. Fujimura1 , T. Ishikawa1 , M. Miyabe1 , A. Nakamura1 ,and Y. Tsuchikawa1
1

Research Center for Electron Photon Science, Tohoku University, Sendai, 982-0826

The thickness of the cryogenic hydrogen and deuterium target have been measured with a laser displacement meter. The target thickness at the central region are 45.1 mm and 45.9 mm for the hydrogenand the deuterium, respectively. The uncertainty of the thickness was estimated less than 1%.

§ 1. Cryogenic target for FOREST
A series of research programs of hadron physics have been carried out at Research center for ELectron PHoton science (ELPH), Tohoku University. The electro-magnetic calorimeter complex FOREST is
one of the main detector systems. It covers a large solid angle and has an azimuthal symmetry. In orderto study the properties of nuclear resonances, a liquid hydrogen or deuterium cryogenic target system [2]has been applied.
The cryogenic target system mainly comprises four parts: a 2-stage Gifford-McMahon (GM) refrigerator (Sumitomo Heavy Industries, Ltd. RKD-415D), a heat transfer tube, a target cell, and a heatshield. The refrigerating capacity of the RKD-415 is 35 W at 50 K for the first stage and 1.5 W at 4 K
for the second stage. Because the free space is limited around the beam line, the refrigerator should beplaced at least 900 mm upstream from the target cell. Heat is transfered from the target cell via theheat transfer tube made of pure aluminium. The size of the heat transfer tube is 920 mm in length,
65 mm in outer diameter, and 2 mm in thickness.
The shape of the target cell is a circular cylinder whose inner diameter is 61 mm with a length of
40 mm. It is made of aluminium alloy with a thickness of 2 mm. The target cell has two beam windows
at the top and the bottom faces of it. The window is made of an aramid film with its thickness of 12.5 µm.
Windows are glued onto the aluminium rings with an adhesive (Emerson&Cuming Co., STYCAST 1266).
Each ring has the circular opening of 54 mm in diameter. Two rings are glued onto the bottom and the
top faces of the target cell. The target cell is glued onto the end of the heat transfer tube.
The heat shield protects the heat transfer tube and the target cell from heat radiation. The copper
shield whose thickness is 4 mm is mounted on the 1st stage of the refrigerator surrounding the 2ndstage. The cylindrical aluminum shield is connected to the copper shield. It covers the heat transfer∗

Present address: Radiation Science Center, High Energy Accelerator Research Organization, 2-4
Shirane Shirakata, Tokai-mura, Naka-gun, Ibaraki, 319-1195

127

tube and the target cell. Its thickness around the target cell is 0.1 mm and its length is 1775 mm. The
temperature around the target cell is about 100 K.
The operation temperatures of the cryogenic target are 15.4 K for a hydrogen and 19.4 K for a
deuteron. The fluctuation of the temperature were +1 K and +2 K for a hydrogen and a deuterium,
respectively. Because the operation pressures of a liquid hydrogen and deuterium are about 70 torr
and 140 torr respectively, the target windows become to blister. In order to reduce the systematic error
caused by the uncertainty of the target thickness, the shapes of the windows should be measured.

§ 2. Shape of a pressurized blister of a membrane
A shape of a circular isotropic plate with a linear elasticity should obey the von Karman equations [4]. Wan et al. calculate the shape of the pressurized blister of the membrane without an initialstress under a uniform hydrostatic pressure analytically [3]. The displacement w(ξ) are expressed as,ρ0 1 − ξ 2
2 I0 (x0 ξ) − I0 (x0 )w(ξ) = T,+2
I1 (x0 )x20
x30
where T is the thickness of the membrane, ξ is the distance from a center of the membrane with an unitof a half radius (a). In (x) is the i-th modified Bessel function and is defined by
In (x) =∞X
m=0 x n+2m
1.
m! Γ(n + m + 1) 2

ρ0 and x0 are the dimensionless quantities calculated with the applied pressure and the physical properties of the membrane. A dimensionless pressure (ρ0 ) is defined by
ρ0 =

pa4
,
2DT

where D = ET 3 /12(1 − ν 2 ), E and ν are the Young’s modulus and the Poisson coefficient. A dimensionless tensile strength at the center of the membrane (x0 ) is defined by the root of

1/2
x
ρ0 =
,
6f (x)
where f (x) is
f (x) =

3xI1 (x)2 − 2xI0 (x)I2 (x) − 8I1 (x)I2 (x).
4x5 I1 (x)2

When the displacement of the membrane is large, Wan’s result has the considerable uncertainty.
We calculated the standard shape with the low pressure of 0.2 torr and multiplied the normalization
factor to reproduce the actual shape measured with a laser displacement meter. The properties of themembrane are supposed to be the general values at the normal temperature because there are no data
at low temperature. 13 GPa and 0.36 are applied for the Young’s modulus and the Poisson coefficient.
The calculated values of the ρ0 and the x0 are 233171.14 and 65.38, respectively.

§ 3. Measurement with a laser displacement meter
The displacement of the pressured membrane was measured with the laser displacement meter LKH155 (KEYENCE Co.). It measures the distance between the the laser head and the measured object

128

using the laser triangulation method. Fig. 1 shows the measurement principle of the laser displacement
meter. A red laser beam (650 nm of the wave length) emitted from the semiconductor laser is transported

Photo sensor (CCD)
Semiconductor
laser

Drivercircuit

Incident laser
To receiver lens

Amp
Diﬀuse Reﬂection

Transmitter
lensReceiver lensStandard position

Displacement

Measured object

Fig.1.

Measurement principal of the laser displacement meterto the measured object. The reflected light from the measured object is collected by the receiver lens andfocused on the position sensitive photo sensor. When the distance between the transmitter lens andthe measured object changes, the incident angle of the reflected light at the receiver lens changes. The
focused light is detected at the different position on the photo sensor. The measurable displacementof the LK-H155 is 150 ± 40 mm. The incident angle at the receiver lens is 17◦ for the distance to themeasured object of 150 mm. The size of the laser beam on the measured object is 120 µm×4200 µm.
Although transparent objects such as glass, liquid and films reflect the lights with a small fraction, thelaser displacement meter can measure the path length of lights. But the refractive correction should beapplied when transparent materials exist on the light path.

§ 4. Setup and measurements
The measurements of the shapes of the blistered films were carried out on 3rd Aug. and 12th Aug.
2011 for a hydrogen and a deuterium target, respectively. Fig. 2 shows the setup and coordinate axes.
The target cell filled with hydrogen or deuterium liquid was placed in the vacuum chamber. The laser
head of the displacement meter was fixed on the XY-axis stage in the air. The origin of the XY-stage
was settled at the center of the films by eye. The exact position of the film center can be fixed with themeasured data. The laser beam emitted from the transmitter lens travels to the inverse direction of
the z-axis and passes through a view port (optical glass BK7 with a thickness of 12 mm). It is reflectedby the measured object and collected by the receiver lens. After the refractive correction, the distance
between the transmitter lens and the object can be calculated. The laser head was moved to x and y
direction with the 8 mm pitch. The measured points were mapped on a films like a mesh structure.

129yView port（Optical glass BK7）
Laser head

Laser range

JIS185 ﬂangezx

Laser head shift

Laser displacement meter(Keyence LK-H155)

Fig.2.

Vacuum chamber

Schematic drawing of setup and coordinate axes

§ 5. Crossing point search
The read value of the displacement meter zm can be converted to the laser incident angle θ with
45.9 mm−1
θ = tan,
150 mm − zm
where 45.9 mm is the distance between the centers of the transmitter and the receiver lenses. The
position vector of the emission points (~p0 ) is expressed as,p~0 = (xm , ym , 150 mm),where (xm , ym ) are the read values of the XY-stage. The direction vector of the laser beam (~s) is~s = (0, 0, − 1),by definition. The position and direction vectors of the reflected light at the receiver lens (~q0 , −~t) areexpressed as,q~0 = (xm + 45.9 mm, ym , 150 mm),−~
t = (sin θ, 0, cos θ).
The incident and reflected light are extrapolated from p~0 and q~0 along the direction vectors ~s and ~
t stepby step. The size of the calculation step was 20 µm. If light enters the different medium, the direction
vector is re-calculated with the Snell’s law. The crossing point of 2 extrapolated lines from (p~0 , ~s) and(q~0 , ~t) should exist on the film surface.
5.1 Snell’s law
When light travels different media which have the different refractive indices, an incident and arefracted directions should obey the following equation as,n̂ × x̂ =n1n2

ˆn̂ × d,130ˆ x̂ are the direction vectors of incident and refracted light. n̂ is a normal vector of a boundary
where d,of media, n1 and n2 are refractive indices of first and second media. The norms of all vectors should benormalized to 1. Solving it, the refractive direction can be written as,
"
#

2 n
o 1/2
o
n1 n ˆn1
2
1 − (dˆ · n̂)−x̂ = −n̂ 1 −d − (dˆ · n̂)n̂ .
n2
n2
The normal vector (n̂) was calculated as the gradient of two points (±0.5 mm) on the standard shapefunction.
5.2 Refractive index
As for the refractive index of the BK7 for the red laser (wave length of 650 nm), 1.514 is used, whichis measured with the red emission line (656.3 nm) of a hydrogen lamp.
As for the liquid hydrogen and deuterium, the refractive index can approximate,−0.062 


ρL
λ
−6
,
n − 1 = (4.73 × 10 )nm
mol/m3where λ and ρL are the wave length of light and liquid density [5]. This equation can be applied whenthe λ ranges from 320 to 694 nm. The density of the liquid (ρL ) can be written as
 2
ρL
T
=A−B
.
mol/m3K
For the ortho-hydrogen and the ortho-deuterium, the A and B are,
 40860 (for LiqH2)
 14.04 (for LiqH2)
A=B=.
 47500 (for LiqD2)
 12.32 (for LiqD2)
Considering the operational temperatures of the hydrogen and the deuterium target, the refractive indices for the red light are,
n(H2)

=

1.120 (for LiqH2)

n(D2)

=

1.136 (for LiqD2).

The expected uncertainties of refractive indices are about 0.3%, which can be ignored below.
5.3 Crossing point of 2 lines
A 3-dimensional straight line can be written with a starting point vector, a direction vector and ascaler parameter. The incident (~p) and the reflected (~q ) light path can be expressed as,

p
~ = p
~0 + u~
s
,
q
~ = q
~ + v~
t0~ is expressed
where u and v are scaler parameters. The minimum approach distance of two lines (|∆l|)
as,
~ =
|∆l|

(~
s ×~
t ) · (~
q0 − p~0 ).
~|~s × t|

131~ < 0.2 mm), two lines are judged to have a crossing point.
If the closest distance is less than 0.2 mm (|∆l|
Its position (~p(u0 )) can be written as,p~(u0 ) = p~0 +where δ = ~
s ·~
t

2

~
s  ~2−|t | (~
q0 − p~0 ) · ~s + (~s ·~t ) (~
q0 − p~0 ) · ~
t ,
δ

− |~
s |2 |~
t |2 . p~(u0 ) should exist on the surface of the blistered film.

§ 6. Determination of the shape functions of films
Depending on the apertures of the light path, about 50 and 30 position vectors were measured forthe downstream and the upstream membranes, respectively. The shapes of them were determined byfitting the normal shape functions (w(ξ)) to the measured points, whose weights were set to 1. Center
positions, z-positions of edges and amplitudes were treated as free parameters.
Fig 3 and Fig 5 show the results of fitting for the downstream and the upstream films. Fig 4 andFig 6 show the fitting residuals. The left columns correspond to the hydrogen, and the right to thedeuterium for all figures. The widths of the fitting residuals for the downstream films are 60 and 50 µm
for liquid hydrogen and liquid deuterium, respectively. They for the upstream films are slight larger(120 and 90 µm), but they are still small enough.
23.0
31.0
22.5
22.0

30.0

z [mm]z [mm]

30.5

29.5

21.5
21.0
20.5

29.0

∆ z = 2.66 mm∆ z = 3.10 mm
20.0

Center = ( 0.12, 0.89)

28.5

Center = ( 3.61, 0.53)
19.5

0Fig.3.

510

15
r [mm]

20

25

5

10

15
r [mm]

20

25

Shape functions of the downstream films for the hydrogen target (left) and the deuterium
target (right).

Table 1 shows the determined free parameters. Because the measurement setups for the hydrogentarget and the deuterium target were changed, the absolute values of the z-component are slight different. The z-component differences of the film edges between upstream and downstream are 40.4 mm andTable 1. Determined free parameters of shape functions

H Downstream
H Upstream
D Downstream
D Upstream

Amplitudes
8.06 ± 0.09
6.19 ± 0.30
9.38 ± 0.07
6.89 ± 0.34

x Center (mm)0.12 ± 0.08
2.01 ± 0.63
3.61 ± 0.06
4.58 ± 0.29

y Center (mm)0.89 ± 0.09
2.43 ± 0.30
0.35 ± 0.06
−1.36 ± 0.56

film edge z (mm)28.30 ± 0.02
−12.06 ± 0.08
19.68 ± 0.01
−20.88 ± 0.09

40.5 mm for the liquid hydrogen target and the liquid deuterium target, respectively. They are consistent

132

22
25
20
18
20
Counts / 60 µ m

Counts / 60 µ m

16
14
12
10
8

15

10

6
5

4
2
0
-0.3

Fig.4.

-0.2

-0.1

0.0
∆ x [mm]

0.1

0.2

0
-0.3

0.3

-21.0

∆ z = -2.04 mm
Center = ( 2.01, 2.43)

z [mm]z [mm]

0.0∆ x [mm]

0.1

0.2

0.3

∆ z = -2.28 mm
Center = ( 4.58, -1.36)

-21.5

-12.5

-13.0

-13.5

-22.0

-22.5

-14.0

Fig.5.

-0.1

Residual distributions of the fitting for the downstream films. Left one is for the hydrogentarget, and right one is for the deuterium target.

-12.0

0

-0.2

-23.0
5

10

15
r [mm]

20

25

5

10

15
r [mm]

20

25

Shape functions of the upstream films for the hydrogen target (left) and for the deuterium
target (right).

with the design value of the target cell. Subtracting the downstream shape function from the upstream
one, the thickness of the target as a function of a radial position can be derived. The thickness at thecenter of the films are 45.1 mm and 45.9 mm for the hydrogen and the deuterium target, respectively.

§ 7. Uncertainties
The errors of the measurement with the laser displacement meter are naively expressed as thewidths of the fitting residuals; 0.09 mm and 0.12 mm for the liquid hydrogen target and the liquid
deuterium target. But the reproducibility of the measurements, the effect of the misalignment of thelaser beam and the effect of the temperature fluctuation should be considered independently.
The reproducibility of the laser displacement meter was estimated by measuring the same point
many times. The measured values changed about 200 µm at the normal distance. The error caused by
the reproducibility is estimated as 200 µm for each point.
The accuracy of the alignment of the laser beam was estimated less than 6 mrad from the measured results of the fixed film edges. When the misalignment of the laser beam was induced by hand,
the results of the calculated thickness changed from -80 µm to +250 µm. So the error caused by the

133

6

9
8

5
Counts / 60 µ m

Counts / 60 µ m

7
4
3
2

6
5
4
3
2

1
1
0
-0.3

Fig.6.

-0.2

-0.1

0.0
∆ x [mm]

0.1

0.2

0.3

0
-0.3

-0.2

-0.1

0.0
∆ x [mm]

0.1

0.2

0.3

Residual distributions of the fitting for the upstream films. Left one is for the hydrogentarget, and right one is for the deuterium target.

misalignment is estimated as 250 µm.
The operation temperatures changed 15.4 K + 1 K for the liquid hydrogen target and 19.5 K + 2 K
for the liquid deuterium target. The density of the liquid is the function of the temperature as describedin the §5.2. But the product of the density and the thickness changes less than 0.4% which can beignored.
The total uncertainties of the target thickness are 400 µm and 390 µm for the liquid hydrogentarget and the liquid deuterium target, respectively.

§ 8. Summary
The thickness of the cryogenic target has been measured with the laser displacement meter. The
thickness (FT ) as a function of non-dimensional radial position (ξ) is written,ρ01 − ξ2
2 I0 (x0 ξ) − I0 (x0 )FT (ξ) = α T
+ 3
+ β,
2
I1 (x0 )x20
x0
where T , ρ0 , x0 are the thickness of the film (12.5 µm) and the dimensionless scale parameters ofpressure (233171.14) and tensile strength (65.38). α and β are determined by fitting as, 14.2 (for LiqH2)
 40.36 mm (for LiqH2)
α=β=.
 16.3 (for LiqD2)
 40.55 mm (for LiqD2)
The errors of the thickness are estimated 390 µm and 400 µm for the hydrogen and the deuterium
targets, respectively, which correspond to less than 1% of the target thickness.

Acknowledgment
The authors would like to appreciate KEYENCE corporation for allowing the trial use of a laser
displacement meter. This work was partly supported by JSPS Grant-in-Aid for Scientific Research(C)(1754027) and MEXT Grant-in-Aid for Specially promoted Research (19002003).

134

References[1]

T. Ishikawa: Internal GeV-γ Analysis Note No. 130A (2009).

[2]

R. Hashimoto et al.: Research Report of LNS 41, Tohoku University, (2008) 31.

[3]

K.-T. Wan et al., Thin Solid Films 425 (2003) 150.

[4]

S.P. Timoshenko and S. Woinowsky-Krieger, Theory of Plates and Shells, second ed., McGraw-Hill,
Inc, New York, 1959.

[5]

P.C. Souers, Hydrogen Properties for Fusion Energy, University of California Press, (1986) 70.

ELPH Annual Report, Tohoku University (2011-2013)135

Positron beams for testing detectors at SPring-8/LEPS
T. Ishikawa1 , M. Miyabe1 , H. Fujimura1 , H. Shimizu1 , and H. Yamazaki1
1Research Center for Electron Photon Science (ELPH), Tohoku University, Sendai 982-0826,
Japan

Experiments for testing various kinds of detectors were performed at the positron beamline in the
GeV-γ experimental hall at Research Center for Electron Photon Science (ELPH). The positron beam
was generated by converting bremsstrahlung photons with a metal converter. The Great East-Japan
Earthquake taking place on March 11 in 2011 broke the electron synchrotron which had been used forgenerating bremsstrahlung photons, and the positron beams are not available until the synchrotron isrecovered (at least for two years). The positron beams generated by converting laser induced electron
photons at SPring-8 can be used for testing detectors instead of those in the GeV-γ experimental hall.
The positrons with the intensity of 110 Hz and the energy of 600 MeV are expected to be available within
10 mm square at (z, x) = (1500, 500) mm by utilizing a 0.5 mm thick lead converter. The positron beam
has the energy resolution of 2.8%. Tracking devices can be tested by irradiating positrons as minimum
ionizing particles.

§ 1. Experimental setup
The positron beamline for testing detectors in the GeV-γ experimental hall at ELPH provided theelectrons and positrons with a maximum energy of 850 MeV [2]. The positron beam was generated byconverting bremsstrahlung photons with a metal converter, a gold plate with a thickness of 20 µm forexample, and was momentum-analyzed by utilizing a bending magnet RTAGX [1]. The gap between thepole pieces of RTAGX is only 220 mm, and the y component of the magnetic field in this region is uniform
and other components are very small. The energy resolution of electron/positron beams delivered to the−30◦ line is 0.6% for higher than 500 MeV. The intensity is approximately 3 kHz in normal operation(with an extraction time of 8 s in a 14-s cycle and a 20-mA circulating current of the primary electron
beam in a synchrotron), and it is suitable for testing detectors. Performance tests were conducted forvarious types of electro-magnetic calorimeters, using high momentum resolution of the positron beam.
For example, the details of a BSO calorimeter are reported in a referece [3]. Many tracking devices havealso been tested using positrons as minimum ionizing particles.
Both the 300 MeV linear accelerator and the 1.2 GeV electron synchrotron were damaged by theGreat East-Japan Earthquake taking place on March 11 in 2011. They were used for injecting electrons
onto the synchrotron, and producing bremsstrahlung photons. Therefore, the positron beams are notavailable at least for two years until the accelerator complex recovers.
The Laser Electron Photon at SPring-8 (LEPS) facility provides linearly polarized photons which is

136

produced by backward Compton scattering, and promotes hadron physics experiments. An ultra violet
laser is injected onto the 8 GeV electrons in the storage ring of SPring-8. The photons are irradiatedto the liquid hydrogen or deuterium targets mainly, and the momentum and the time of flight of eachemitted final state charged particle is measured. The momentum is determined from the trajectory
inside the large acceptance dipole magnet with a maximum magnetic flux of 0.7 T, a width of 1350 mm,
and the height of 550 mm. The positrons and electrons can be generated by converting photons with ametal converter placed in front of this magnet. Roughly speaking, those delivered to the specified angle
have the monochromatic energy. Figure 1 shows the experimental setup for producing positron beams at
SPring-8/LEPS. The converter is assumed to be placed in front of the start counter of the LEPS standard

D

ha
m
be
ft
rD
C
ha
C
m
2
be
rD
C
3
ri

ft
ri

ri
D

D

ft

C

C

ha
m
be

rD

C

1

&

SS

D

detector system to minimize the deterioration of the energy resolution due to the multiple scattering.

Li

qu

id

Ta
rg
et

x

z

St
Siart
lic C
a Aou
ernte
og r
el

Photon Beam
Converter

Detector Test Area
~ 1.5 m x ~ 1 m

Dipole Magnet

z=1395.5 mm
z=3178.5 mm

Fig.1.

Time of Flight
Stop Counters

Experimental setup for producing positron beams at SPring-8/LEPS. The converter isplaced in front of the start counter of the LEPS standard detector system, and thepositrons and electrons are delivered to the downstream of the drift chamber DC3. The
cryogenic target system can be placed to the off-center position Roughly 1.5 × 1.0 m2 area
can be used for the detector to be tested.

§ 2. Monte-Carlo simulation
The energy distribution and the intensity for the positrons delivered to the specified area are calculated by using a Geant4 based Monte-Carlo simulation. The physics list used in the simulation is LHEP,

137

which is a combination of the standard electromagnetic physics processes and low energy parameterized
and high energy parameterized hadronic models. The magnetic field used in the simulation is given by
the TOSCA Ver. 6.6 program in the Opera 3D package (Vector Fields) [4]. Lead plates are placed atz = −880 mm with a width of 100 mm and a height of 100 mm. Thickness of them are 0.25, 0.5, 1.0, and
2.0 mm, which correspond to 0.05, 0.1, 0.2, and 0.4 in a radiation length unit.
The photons are generated by taking into account the parameters of the injecting laser and theelectron beams in the storage ring:
1. the circulating electron energy E = 7.970 GeV,
2. the laser energy k1 = 3.53 eV,
3. the x spread of the circulating electrons σx = 105, 15, 105 µm,
4. the y spread of the circulating electrons σy = 18, 8, 30 µm,
5. the x shift of the circulating electrons µx = 0, 0, 50 µm, and6. the flight length from the interaction point to the target fp = 70 m.
The three components of the spread and shift are selected randomly in the same probability. The crosssection for the backward Compton scattering is summarized in ref. [5]. The maximum energy of thegenerated photons is approximately 2.4 GeV, which is determined by the laser energy of 3.53 eV.
The materials on the beamline constituting the standard detector system at SPring-8/LEPS [4, 6, 7]
are placed. The virtual counter is placed at z = +1500 mm (behind DC3), which measures 5 mm inthickness, 5000 mm in width, and 100 mm in height. The energy resolution is estimated by using hit
information of this virtual detector. Table 1 lists the materials placed. Figure 2 shows the correlation
between the energy and the x position, and the x and y profile at z = 1500 mm for the positrons andelectrons coming to the virtual detector. To suppress the effect of the secondary particles, the incident
particles to the virtual detector are selected with an energy higher than 0.6 MeV. The energy of thepositron and electrons goes lower as the distance from the photon beamline becomes larger. The locusx ∼ 0 mm corresponds to the pair creation inside the virtual detector. The intensity in a unit width ishigher near the photon beamline. The positrons and electrons are concentrated at y ∼ 0 mm.
Table 1. The materials placed on the beamline. The center of the dipole magnet is defined asz = 0 mm. The e+ e− blockers are placed at x = −120, and +130 mm.
detector
SSD
DC1
DC2
DC3
e+ e− blocker

material
Si
Ar+C4 H10
Ar+C4 H10
Ar+C4 H10
Pb

width (mm)63.1
1060.02560.02560.050.0height (mm)
61.3
580.0
1120.01120.049.0

thickness (mm)
0.30
286.0
286.0
286.0
50.0

z position−909.9−466.0+860.5+1260.5−203.0

number20
1
1
1
2

2.1 Energy resolution
The energy spread was estimated for the incident charged particles on the virtual detector. Figure 3
shows the energy distribution for the positrons injecting to the x position 200–210, 500–510, and 800–

138

810 mm (a lead converter with a thickness of 0.5mm).
200
1400
150
1200
100
50

y (mm)Ee (MeV)

1000
800
600

0
-50

400

-100

200

-150

0
-1500

-1000

-500

0

500

1000

-200
-1000 -750

1500

-500

x (mm)
Fig.2.

-250

0

250

500

750

1000

x (mm)

Correlation between the energy and the x position (left), and the x and y profile at z =1500 mm (right) for the positrons coming to the virtual detector. The converter is a leadplate with a thickness of 0.5 mm.
350

200-210mm

Counts/8.0 MeV

300
250

500-510mm200
150

800-810mm

100
50
0
200

400

600

800

1000

1200

1400

1600

1800

Ee (MeV)Fig.3.

Energy distribution for the positrons injecting to the x position 200–210, 500–510, and
800–810 mm (a lead converter with a thickness of 0.5mm). The x region is described in
the figure.

The centroid µe and width σe of the energy distribution were estimated by fitting a Gaussianfunction to the distribution in each x region. The fitting was repeated several times in the region[µe − 2σe , µe + 2σe ). The energy resolution σE /E is given by the equation:
σe
σE
=
.
E
µe

(1)

Figure 4 shows the centroid of the energy distribution and the energy resolution as a function of the x
position.

139
0.07
1400
0.06
1200
0.05

0.04

σe/µe

µe (MeV)

1000

800

0.03

0.02

600

0.01

400

200

400

600

800

1000

1200

0

200

400

x (mm)
Fig.4.

600

800

1000

1200

x (mm)

Centroid µe of the energy distribution (left) and energy resolution σE /E (right) as afunction of the x position. The black, read, green, and blue points indicate the results forthe lead converter thicknesses of 0.25, 0.5, 1.0, and 2.0 mm.

2.2 Intensity
The fraction of the positrons injected in the specified x position was estimated. Figure 5 shows theintensity of the positrons injected in the 10 mm square as a function of the x position. The intensity isgiven by the fraction between the number of the positrons injected in the 10 mm square of the virtual
detector and the number of the incident photons to the lead plate including untagged ones. The intensityof positrons is 1.5 × 10−4 at x = 500 mm with a 0.5 mm thick converter. Assuming that the total rate of
the tagging counters is 1 MHz and that the transmittance of the photon is 50%, the rate of the positron
injection to the virtual counter is expected to be approximately 110 Hz. It should be noted that all the
positrons and electrons are not generated from the tagged photons.
2.3 dx/dz
The positrons and electrons do not inject on the virtual detector perpendicularly. The dx/dz distribution was estimated for different x positions. Figure 6 shows the typical dx/dz distribution for the x
position 200–210, 500–510, and 800–810 mm. The dx/dz becomes larger as the absolute value of x goeslarger.
The centroid µs and width σs of the dx/dz distribution were estimated by fitting a Gaussianfunction to the distribution in each x region. The fitting was repeated several times in the region[µs − 2σs , µs + 2σs ). Figure 7 shows the centroid µs and width σs for the dx/dz distribution. The
centroid µs is almost proportional to the absolute value of the x coordinate of the position. The µs is
almost the same independently of the converter thickness. The width σs behaves a first-order polynomial function of the absolute value of the x coordinate of the position. The σs is a little bit larger for the
thicker converter. The intensity at z = 1500 mm (corrected intensity) was estimated for the positrons

140

x 10

-2

0.1

Intensity #Positrons/#Photons

0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0

200

400

600

800

1000

1200

x (mm)
Fig.5.

Intensity of the positrons injected in the 10 mm square as a function of the x position.
The intensity is given by the fraction between the number of the positrons injected in the
10 mm square of the virtual detector and the number of the incident photons including
untagged ones. The black, read, green, and blue points indicate the intensities for thelead converter thicknesses of 0.25, 0.5, 1.0, and 2.0 mm.

200-210mm

3000

Counts/0.004

2500

2000

1500

1000

500-510mm500

800-810mm
0

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

dx/dz
Fig.6. dx/dz distribution for the x position 200–210, 500–510, and 800–810 mm (a lead converter with a thickness of 0.5mm). The x region is described in the figure.

141
0.9

0.025
0.0225

0.8

0.02
0.7
0.0175
0.015

σs

µs

0.6
0.5

0.01250.01

0.4

0.0075
0.3
0.005
0.2
0.1

0.0025
200

400

600

800

1000

1200

0

200

400

x (mm)
Fig.7.

600

800

1000

1200

x (mm)

Centroid µs (left) and width σs (right) for the dx/dz distribution. The black, read, green,
and blue points indicate the centroids and widths for the lead converter thicknesses of
0.25, 0.5, 1.0, and 2.0 mm.

injected onto 10 mm square perpendicular to their orbit by using the centroid µs of the dx/dz distribution. Figure 8 shows the corrected intensity at z = 1500 mm for the positrons injected onto 10 mm
square perpendicular to their orbit.

§ 3. Positron beams for testing detectors
The following properties are desired for the positron beams for testing detectors:
1. high energy,
2. high intensity, and3. high energy resolution.
These properties are correlated, and the higher energy and higher intensity positron beam is obtained
for small x region. But small x region deteriorates the energy resolution. The thicker converter makes
the intensity higher without the change of the centroid energy, but makes the energy resolution poorer.
By considering the energy resolution shown in Figure 4 and intensity shown in Figure 8, The z = 1500
and x = 500 mm condition is thought to be effective, and the properties
1. energy centroid 604 MeV,
2. intensity 109.6 Hz, and
3. energy resolution 2.8%
are expected. In this condition, the positron orbit gives dx/dz = 0.349, and passes x = 849 mm at
z = 2500 mm. Table 2 summarizes the centroid energy, energy resolution, and intensity of positrons at
z = 1500 mm for x = 200–1160 mm (a 0.5 mm thick lead converter). The details of the simulation are
described elsewhere [8].

142

x 10

-2

0.1

Intensity #Positrons/#Photons

0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0

200

400

600

800

1000

1200

x (mm)
Fig.8.

Corrected intensity at z = 1500 mm for the positrons injected onto 10 mm square perpendicular to their orbit as a function of the x position. The black, red, green, and blue points
indicate the intensities for the lead converter thicknesses of 0.25, 0.5, 1.0, and 2.0 mm.

Three experiments, which were proposed to ELPH, were carried at SPring-8/LEPS. The first one
was a performance test of a thick GEM TPC for J-PARC E15 by M. Tokuda (Tokyo Institute of Technology) and F. Sakuma (RIKEN) et al.@ (ELPH Experiment #2742). The second one was a development of ahodoscope with wavelength shifting fibers for a new electromagnetic calorimeter by Y. Tajima (Yamagata
University) and T. Ishikawa (ELPH, Tohoku University) et al.@ (ELPH Experiment #2745). The last one
was a performance test of a readout system for a GEM tracker by K. Ozawa (University of Tokyo) etal.@ (ELPH Experiment #2749). These experiments aimed to test some tracking devices, and were successfully carried out. The fringing magnetic field is strong in the area where a detector is placed, and aµ-metal sheet is needed to make a photomultiplier tube work well. All the performance test experiments
proposed to ELPH for electromagnetic calorimeters had been canceled since the energy resolution of thepositron beam for testing detectors was poor at SPring-8/LEPS.

Acknowledgment
We are gratefully acknowledge the LEPS collaboration for its cooperation of providing positron
beams for testing detectors. We also thank the SPring-8 staff for their efforts.

143

Table 2. Centroid energy, energy resolution, and intensity of positrons at z = 1500 mm for x =200–1160 mm (a 0.5 mm thick lead converter). Two intensities are described for the
expected number of positrons for an incident photon, and for the expected rate for the 1
MHz tagging rate.
x(mm)
200–210250–260
300–310
350–360
400–410450–460
500–510550–560
600–610650–660
700–710
750–760
800–810850–860
900–910
950–960
1000–1010
1050–1060
1100–1110
1150–1160

energy(MeV)
1437.0 ± 0.9
1158.0 ± 0.8
972.9 ± 0.7
840.9 ± 0.6
740.7 ± 0.5
664.5 ± 0.4
604.1 ± 0.5
554.5 ± 0.5
513.4 ± 0.5
478.5 ± 0.5
449.0 ± 0.5424.2 ± 0.5
402.6 ± 0.5
383.9 ± 0.5
368.1 ± 0.5
352.7 ± 0.3
339.4 ± 0.5
328.3 ± 0.6
318.1 ± 0.5
306.7 ± 0.6

energyresolution (%)
4.5 ± 0.1
3.9 ± 0.1
3.4 ± 0.1
3.2 ± 0.1
3.0 ± 0.1
2.8 ± 0.1
2.8 ± 0.1
2.6 ± 0.1
2.6 ± 0.1
2.5 ± 0.1
2.7 ± 0.1
2.5 ± 0.1
2.2 ± 0.1
2.4 ± 0.1
2.4 ± 0.1
2.2 ± 0.1
2.3 ± 0.1
2.3 ± 0.1
2.2 ± 0.2
2.3 ± 0.2

dx/dz
0.14
0.18
0.21
0.25
0.28
0.32
0.35
0.39
0.42
0.46
0.50
0.53
0.57
0.61
0.65
0.68
0.72
0.76
0.80
0.84

intensity (10−5 )@1γ
109.1 ± 2.3
76.7 ± 2.0
55.3 ± 1.6
43.3 ± 1.5
35.1 ± 1.3
27.6 ± 1.1
21.9 ± 1.0
18.4 ± 1.0
16.8 ± 0.9
13.2 ± 0.8
11.2 ± 0.7
9.3 ± 0.7
8.5 ± 0.6
7.7 ± 0.6
6.3 ± 0.5
5.9 ± 0.5
4.8 ± 0.5
4.3 ± 0.5
4.7 ± 0.5
4.2 ± 0.6

intensity (Hz)@ 1 MHz
545.4
383.3
276.6
216.6
175.7
138.1
109.6
92.2
83.9
65.9
56.1
46.4
42.6
38.5
31.5
29.4
23.9
21.3
23.3
20.8

References[1]

T. Ishikawa et al., Installation of a Dipole Electromagnet RTAGX, Research Report of LNS 39,
Tohoku University, 39 (2007).

[2]

T. Ishikawa et al., Electron/Positron Test Beamline, Research Report of LNS 40, Tohoku University,
6 (2008).

[3]

T. Ishikawa, et al., A detailed test of a BSO calorimeter with 100-800 MeV positrons, Nuclear
Instruments and Methods in Physics Research Section A 694 (2012) 348.

[4]

T. Ishikawa, φ photo-production from Li, C, Al, and Cu nuclei at Eγ = 1.6–2.4 GeV, PhD thesis,
Kyoto University (2005).

[5]

A. D’Angelo et al., Generation of Compton backscattering γ-ray beams, Nucl. Instr. and Meth. in
Phys. Res. A 455, 6 (2011).

[6]

M. Sumihama, Photon beam asymmetries for the p(~
γ , K + )Λ and p(~
γ , K + )Σ0 reactions at SPring8/LEPS, PhD thesis, Osaka University (2003).

[7]

T. Mibe, Measurement of φ-meson photoproduction near production threshold with linearly polarized photons, PhD thesis, Osaka University (2004).

[8]

M. Miyabe and T. Ishikawa: Internal GeV-γ Analysis Note No. 229E (2011).

144

ELPH Annual Report, Tohoku University (2011-2013)

Construction of the new large acceptance electro-magnetic
spectrometer BGOegg
M. Miyabe1 , Y. Honda1 , T. Ishikawa1 , K. Matsuda1 , Y. Matsumura1 ,N. Muramatsu1 , A. Nakamura1 , Q. H. He1 , H. Shimizu1 , K. Shiraishi1 ,Y. Taniguchi1 , Y. Tsuchikawa1 , H. Yamazaki1 , and R. Yamazaki1
1Research Center for Electron Photon Science, Tohoku University, Sendai, 982-0826

A new large acceptance electro-magnetic spectrometer BGOegg has been constructed. BGOegg
consists of 1320 isosceles trapezoid shape BGO crystals and 2 type photo-multiplier-tubes (PMT). The
construction started from July 2011 at Research Center for Electron Photon Science (ELPH), Tohoku
University. In December 2012, BGOegg has been transported from ELPH to SPring-8 LEPS2 experimental building. From December 2012 to December 2013, All channels of BGOegg has been equippedand plastic scintillator hodoscope is placed inside of BGOegg. The beam test for BGOegg and peripheral
detectors has been performed, and the clear π 0 and η peak structure at γγ invariant mass distributions
are observed.

§ 1. BGOegg overview
BGOegg is a large solid angle electromagnetic calorimeter which covers about 87% of all the solid
angles aiming at detection of the gamma ray which decayed and came out from the generation target.
It is an egg-shaped gamma ray detector which consists of 1320 BGO inorganic crystal scintillators of
220 mm in length (equal to 20 radiation length). As energy resolution to the gamma ray of 1GeV, 1.3%,
position resolution amounts to 3 mm and has the world highest performance [1, 2]. BGOegg has 22
layers and covers from 24 degrees to 144 degrees at polar angle. Each layer has 60 crystals and covers
360 degrees at azimuthal angle. In the forward side less than 90 degrees at polar angle, the front centerof BGO crystal is located on a rotating ellipsoid. On the other hand, in the backward side more than 90
degrees at polar angle, BGOegg has spherical shape for saving the amount of crystals. By combining theboth the forward and the backward side, BGOegg shows the egg-like shape(Fig.1).
Each BGO crystals has isosceles trapezoid shape in the front and back side. It has the shape withthe taper from the front face to back face. By focusing effect, when all surface of crystal with the taper
are polished, the amount of light output measured by the photomultiplier tube is not uniform for theemission position. In order to suppress this non-uniformity, we polished only the front face and backface where photomultiplier tube is connected, and the other surface of BGO crystal is etched.
We adopted the 65µm thickness VikuitiTM Enhanced Specular Reflector (ESR) as a reflective material
for BGOegg. ESR has succeeded in suppressing the non-uniformity of the light output with its high

145

420

BGOegg

200

319

24 o

200f

36 o

460

charge detector
165

295

1320 BGO blocks
Elphs Lab
1.9t
Fig.1. Cross Section view of BGOegg crystals

reflectance.

Fig.2. BGO crystal(Left) and ESR film reflector(Right)

BGOegg is maintaining the shape by the crystals support each other. Since it is necessary to connect
the photomultiplier in the back face, there is a significant restriction on the structure that supports the
BGO crystals. Crystals are supported from outside by eight pieces of 5mm thickness quarter circle
stainless steel plates around 90 degrees at polar angle, six stainless plates in down side, total of 400
steel rod (20 in each layer) and cone disks of the upstream and the downstream (See Fig.3). Fig.4 shows
the support structure with dummy crystal made from wood.

146

BGOegg support structures
Quarter circle plate

Pole

Rod

H11334MOD

BGO crystals
H6524MODSUS plateCone Disks

36 o

24 o

Backward

100

Rubber plate
PMT support jig

ForwardFig.3. Schematic cross section view of BGOegg
support structure.

Fig.4. dummy crystals and support structure (without the cone disk).

§ 2. Construction of BGOegg
BGOegg was constructed approximately two years from 2011 through 2013. Research Center forElectron Photon science (ELPH), Tohoku University had to suffer great damage and spend much timeon the restoration by the Great East Japan Earthquake in March 11th, 2011. However BGO crystals
and photomultiplier tubes more than 1300 and support frame of BGOegg in the preparation stage of
construction fortunately were almost safely without the damage of the earthquake. So we were able tocontinue the construction of BGOegg simultaneously with the restoration of accelerator and the experimental facility FOREST in ELPH.
2.1 Construction in 2011FY
The basic design of BGOegg was almost finished before the earthquake occurred in March, and examined the support structure by making wooden dummy crystals. Since a rough structure was designed,
we disassembled these prototype support frame around July 2011 after earthquake and the construction work using actual BGO crystals was begun. Placement of the crystals had to be performed in thecondition rotated 90 degrees from the actual experimental situation in consideration of the workability. First of all, the assembling work was started from B-part corresponding to the backward section of
BGOegg After the main platform was rotated 90 degrees to the B-part upward, we started to arrange 60
crystals per layer from B00-layer corresponds to the polar angle 90 degree to 96 at B-part. Each BGO
crystal was placed in a circle on the base platform after the wrap with ESR reflector and attached rubber
plate and stainless steel plate to the back face of crystal. These plates have the hole for photomultiplierinstallation. After the placement and alignment of 60 crystals was completed, the layer was tied up
from the outside of the stainless plates by using 2 stainless steel wires of 1mm in diameter. When thearrangement of a layer with a large polar angle, the slope of crystals increased and the crystal would
fall during the installation by gravity. Therefore, the acrylic disk was installed in the support frame
center to prevent the falling and make the precise alignment possible. In these way, arrangement of thecrystals in the B-part has been completed in about 10 months while repeating some of the modification.

147

In Fig.5, The construction situation of BGOegg at the end of 2011 fiscal year is shown. We had completed
the placement of 7 layers (420 crystals) in total 9 layers of B-part.

Fig.5. BGOegg construction at the end of 2011 Japanese fiscal year.

2.2 Construction in 2012FY
From fiscal year 2012, installation of the crystals in B-part was continuously performed. Since
arrangement of 540 crystals in B-part(9-layers) was completed in May 2012, fixation work for crystals
by support frame structure was carried out. Crystals are fixed so that crystals may be kept down insideby 20 stainless rods per layers and the corn disk as a top board of BGOegg. After all the crystals in Bpart were confirmed that all the components were completely fixed, BGOegg was rotated 180 degrees for
installing the forward side crystals(F-part). When rotating, in order to support the weight of a crystal
with a margin, we used an additional reinforcement structure. Fig.6 shows the situation of rotation
work. Using a Chain Hoist which supports the weight of BGOegg, it was carefully rotated by Worm
Drive which is located in the pivot point of BGOegg. After the rotation was successfully finished, crystal
arrangement of the F-part was started. Crystals were mounted concentrically by the acrylic disk as wellas the case of the B-part, and installation of all crystals was completed in October 2012 approximately
two months later.
2.2.1 Transportation from ELPH to SPring-8/LEPS2
After installing the top corn disk and completing the fixation by the support stainless steel rods,
we rotated BGOegg again in preparation for transportation. The F-part(13 layers) is heavier than the
B-part(9-layers), therefore, In order to lower the center of gravity of BGOegg, the F-part was moved tothe bottom side again. Additionally, we placed 30 αGELTM SF-50 [5] at the base of BGOegg body to148

Fig.6. turning process of BGOegg at July 25, 2012absorb a shock during transport. The transportation took two days from December 13, 2012 to 14th by
the land route at distance of approximately 1,000km from Research Center for Electron Photon Science,
Tohoku University at Miyagi-prefecture to SPring-8/LEPS2 building at Hyogo-prefecture. Fig.7-8 shows
the situation of this transport. The transportation was greatly succeeded, and none of the crystals andstructure was broken.

Fig.7. carry out work of BGOegg from
ELPH GeV-γ building

Fig.8. carry in work of BGOegg at SPring8/LEPS2 building

2.3 First beam test at SPring-8/LEPS2
After installing BGOegg in the upstream side of LEPS2 experimental building, we attached thephotomultiplier tubes for F-part as the top again. We mounted Hamamatsu Photonics Head-on typephotomultiplier tube H6524MOD for the most forward 4 layers and metal package type H11334 forthe 5-th layer [6]. At the beginning of BGOegg experiment, for the absence of High Voltage supplierand readout system, beam test was performed with only the forward 5 layers(300ch). After mounting
photomultiplier tube and fixing by the support structure, BGOegg was set to correct position by the 90
degree rotation. At the end of 2012 fiscal year, with the LEPS2 Backward Compton scattering gamma
beam and Carbon target (2cm thickness), we took the first hadron photo-production experiment data in149

LEPS2 project. Fig.9 shows the invariant mass distributions of two γ detected by BGOegg. The peakstructure from π 0 is clearly observed.

26.92

1800

Constant
Mean
Sigma

/ 8
1598.
131.9
15.46

20.60
0.17450.1997

1600

π

1400

0

Counts / 5MeV

1200
1000
800
600
400
200
0

0

100

200

300

400

500

Invariant Mass γγ

600

700

800

(MeV)

Fig.9. Invariant mass distribution of γγ with 300 crystals in February 2012

2.4 Construction and experiment in 2013FY
After the beam test using the forward 300ch, we removed all photomultiplier tubes again to improvethe method of fixing photomultiplier. Until August 2013 the new fixing support jig of photomultiplier was
installed and connected each stainless plates of the crystal back face in each layer. We attached all 1,320
photomultiplier tubes and shaded the light leak for photomultiplier tubes after reinforcement work inapproximately one month at November 2013. After having turned again at the original position(Fig. 10),
we connected the signal and high voltage cables and installed the plastic scintillation counters (Inner
Plastic Scintillators, IPS) for charged particle identification in the inside of BGOegg. IPS is consists of
30 plastic scintillators of 5mm-thickness, 26mm-width and 413mm-length and read out signals by Multi
Pixel Photon Counter(MPPC) [7]. On the other hand, in order to detect the charged particle which was
generated simultaneous with the target at forward angle, Drift Chamber (DC), Resistive Plate Chamber(RPC) were installed as the forward detectors. DC is located at the downstream about 1.6m from thetarget and can detect the charged π ± meson or proton with a few hundred µm position resolution. DC
covers in the front area that cannot be covered with BGOegg, and RPC which was installed in the 14m
downstream can measure the flight time of the proton emitted most forward angle by the time resolutionof 50 ps. In BL31LEP beam line, by the incident 351-nm ultra violet laser into the SPring-8 electron
storage ring, we generate a backward Compton scattering gamma which led to the LEPS2 experimentbuilding. Moreover, energy of a gamma ray is tagged by measuring the position of the scattered electrons
with Tagging Counter. It succeeded in generating a maximum of 1.8-MHz tagged gamma ray by carrying

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out a total of 3 simultaneous incidence of the laser of 16W and 24W in December 2013.
2.4.1 Experimental result
We performed data taking using these Backward Compton gamma beam and BGOegg detector
systems in December 2013. We succeeded to collect the data of about 2 × 107 events by using the carbon
and polyethylene target. After the data taking, the performance evaluation of each detection device isbeing carried out and all detectors show the expected performance. Fig.11 shows the invariant mass
distribution of 2 γ detected with the BGOegg. We can successfully observe not only the π 0 but also
the η meson. Experimental resolution is good enough by comparison with the simulation results. As
we continue analysis the detailed research of nuclear resonance using meson photo-production and thesearch for the η′ mesic nuclei [8], we will provide important knowledge to understand QCD.

Counts / 2 MeV

10 4

π0
10 3

η
10

2

0

200

Fig.10. Current status of BGOegg

400

600

Invariant Mass of γγ

800

1000

[MeV]

Fig.11. Invariant mass distribution of γγ
in December 2013

References[1]

T. Ishikawa: Internal GeV-γ Analysis Note No. 231B (2011)[2]

T. Ishikawa: Internal GeV-γ Analysis Note No. 238B (2012)[3]

T. Ishikawa: Internal GeV-γ Analysis Note No. 133B (2009)[4]

R. Yamazaki: JPS meeting 2012 autumn 12aSB-6 (2012)[5]

http://www.taica.co.jp/gel/search/product/insulator.html[6]

http://www.hamamatsu.com/jp/en/index.html[7]

http://www.hamamatsu.com/jp/ja/4004.html[8]

H. Nagahiro, S Hirenzaki: Phys. Rev. Lett. 94, 232503

ELPH Annual Report, Tohoku University (2011-2013)

151

First Beam Observation and Near Future Plans at SPring-8
LEPS2 Experiments ∗N. Muramatsu1 , T. Ishikawa1 , Y. Matsumura1 , M. Miyabe1 , H. Shimizu1 ,K. Shiraishi1 , Y. Tsuchikawa1 , H. Yamazaki1 , R. Yamazaki1 , J.K. Ahn2 ,S. Ajimura3 , W.C. Chang4 , J.Y. Chen3 , M.L. Chu4 , S. Daté5 , J. Goetz6 ,H. Hamano3 , T. Hashimoto7 , K. Hicks6 , T. Hiraiwa3 , T. Hotta3 , C.Y. Hsieh4 ,Y. Kasamatsu3 , H. Kohri3 , S. Masumoto8 , K. Mizutani7 , T. Nakano3 , T. Nam3 ,M. Niiyama7 , Y. Nozawa7 , Y. Ohashi5 , H. Ohkuma5 , H. Ohnishi9 , T. Ohta3 ,K. Ozawa10 , T. Shibukawa8 , Y. Sugaya3 , M. Sumihama11 , S. Suzuki5 ,A. Tokiyasu3 , N. Tomida7 , T. Yorita3 , and M. Yosoi3
1

Research Center for Electron Photon Science, Tohoku University, Sendai, Miyagi 982-0826
2
3

Department of Physics, Korea University, Seoul 136-713, Korea

Research Center for Nuclear Physics, Osaka University, Ibaraki, Osaka, 567-0047
4
5

6

Institute of Physics, Academia Sinica, Taipei 11529, Taiwan

Japan Synchrotron Radiation Research Institute, Sayo, Hyogo 679-5143

Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701, USA
7
8

Department of Physics, Kyoto University, Kyoto 606-8502

Department of Physics, University of Tokyo, Tokyo 113-0033
9

10

RIKEN Nishina Center, Wako, Saitama 351-0198

High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801
11

Faculty of Education, Gifu University, Gifu 501-1193

The first photon beam was successfully produced by laser Compton backscattering at the LEPS2
beamline, which was newly constructed at SPring-8 for the purpose to increase the beam intensity one
order of magnitude more than that of the LEPS experiments and to achieve the large acceptance coverage with high resolution detectors. The BGOegg electromagnetic calorimeter with associated detectors
are being set up at the LEPS2 experimental building for the physics programs, including the searchesfor η’-bound nuclei and highly excited baryon resonances. In parallel to the BGOegg experiments, theLEPS2 charged particle spectrometer will be prepared inside the 1 Tesla solenoidal magnet, transported
from the BNL-E949 experiment.

§ 1. From LEPS to LEPS2
At the LEPS experiments, which started from 1999, the ultraviolet (UV) laser light with the wavelength of 355 nm has been injected into the 8 GeV electron storage ring in order to produce the laser∗

Presented at BARYONS 2013 on 27 June, 2013. Available as ELPH Report 2044-13 (2013) and arXiv:
1307.6411.

152

Fig.1.

(a) Photon beam spread at the 135 m downstream from the Compton scattering point.
The solid line comes from the purely kinematical calculation of backward Compton scattering. Actually, it is smeared by the electron beam divergences at the LEPS and LEPS2
beamlines, as shown in the shaded areas (corresponding to RMS). (b) The schematic viewof the LEPS2 facility around the newly installed vacuum chambers and the laser sideinjection system.

Compton backscattering (LCS) photon beam [1]. The beam intensity has exceeded ∼ 106 Hz in thetagged photon energy range of 1.5–2.4 GeV. High polarization is transferred from the laser light to thephoton beam, so that the t-channel exchange reaction with a forward meson photoproduction is usable
as a parity filter. Such reactions have been extensively investigated by the LEPS forward spectrometer, which covers the polar angle region within ±20◦ and ±10◦ in the horizontal and vertical directions,
respectively. For example, we have analyzed the forward K∗0 → K+ π − production from a proton target
with the identification of the associated Σ+ in the missing mass distribution [2]. In this study, the LCS
photon beam energy was upgraded up to 2.9 GeV by using a deep UV laser. The dominance of natural parity exchange in the t-channel was observed based on the parity spin asymmetry measurement,
indicating the evidence of the controversial scalar meson κ(800).
On the other hand, the further systematic studies of hadron photoproduction generally requirelarger acceptance coverage and higher photon beam intensity. Recently, we measured the differential
cross sections of backward η’ photoproduction with the forward proton detection at the LEPS forward
spectrometer [3]. It was suggested that the bump structure at W∼2.3 GeV may be enhanced in themost backward angles, which are not covered by the CLAS experiments [4]. There may be a resonancecontribution with a high angular momentum, but it is needed to increase the statistics possibly with awide angular acceptance. Because of the demands represented by this measurement, we are motivatedto start the LEPS2 project at another beamline of SPring-8 [5].

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Fig.2.

(a) Photon beam energy spectra with and without laser injection at the LEPS2 beamline.
(b) and (c) Photon beam profiles at the LEPS2 experimental site without and with laser
injection, respectively.

§ 2. LEPS2 Facility
The LEPS2 beamline utilizes a 30 m-long straight section, the number of which is limited to only
4 of the 62 beamlines at SPring-8. The horizontal divergence of the electron beam at this straightsection is reduced to 14 µrad in σ, while the usual 7.8 m-long straight section including the LEPS
beamline provides the divergence of 58 µrad. As shown in Fig. 1(a), the LCS photon beam spread at the
LEPS2 beamline is determined not largely by the electron beam divergence but mostly by the Compton
scattering angle, which is calculated by the kinematics depending on the photon energy. This achieves
a well collimated photon beam with the radius below 10 mm even at the 135 m downstream from theCompton scattering point, enabling us to construct a large experimental site outside the storage ringbuilding.
We also aim to increase the tagged photon beam intensity nearly up to 107 Hz for the photon energy
range below 2.4 GeV by using the UV lasers with the wavelength of 355 nm. We plan the simultaneous
injection of four lasers, whose output power have increased from 8 W to 16 W or 24 W. The multiple laser
operation has become possible thanks to the reduced electric power consumption of those new lasers. For
the simultaneous injection, we have installed new beamline chambers with large apertures [6]. As shownin Fig. 1(b), the laser injection from the side concrete shield wall into the SPring-8 ring tunnel is adopted
in order to reduce the total length and apertures of the newly installed chambers. The radiation level at
the laser injection room is also lowered with the minimized shield materials, so that we can easily accessthe laser optics for adjustments. The large mirror to guide the four laser beams from the side direction
toward the straight section inside a vacuum chamber has been modified to possess a horizontal slit anda small center hole for avoiding the heat input from x-rays and the e+ e− conversions of the LCS photon
beam, respectively. In addition to the LCS beam with the UV lasers, we plan to improve the intensityof a high energy photon beam using the deep UV lasers with the wavelength of 266 nm. We expect thetagged photon intensity approaching to 106 Hz with the techniques similar to the UV case.
The construction of the LEPS2 beamline was approved in 2010. The LEPS2 experimental site,whose size is 12 m × 18m in area with the height of 10 m, was built in 2011. The constructed experimental building has the volume 15 times larger than the experimental hutch of the LEPS experiments. In

154

2011, we also transported the BNL-E949 magnet, which is a 1 Tesla solenoidal magnet with the weightof 400 tons, and successfully installed it into the LEPS2 experimental building. This magnet has thebore diameter of 2.96 m and the inner length of 2.22 m, where the charged particle spectrometer described later will be placed. The beamline vacuum chambers and the laser injection system were finallyinstalled and aligned in late 2012.

§ 3. First Beam Observation
After adjusting the electron beam orbit at the straight section and degassing the absorbers and themask with synchrotron radiation, the first LCS photon beam at the LEPS2 beamline was produced with
the injection of a single UV laser beam during the machine study on 27 Jan. 2013. The simultaneous
injection of three UV laser beams was then tested on 2 Apr. for the further investigation of beam properties as described below. Figure 2(a) shows the photon energy spectra, which have been measured by alarge Bi4 Ge3 O12 (BGO) crystal with the diameter of 8 cm and the length of 30 cm. The blue histogram
represents the spectrum for a bremsstrahlung photon beam without laser injection at the electron beam
current of 10 mA, while the black histogram shows that for a LCS photon beam with the contaminationof a bremsstrahlung beam at the current of 0.1 mA. The two spectra are normalized by the electron beam
current, the data taking time, and the DAQ live time. The lowest photon energy part of the LCS beam
spectrum is cut off at ∼0.65 GeV because of a φ7 mm lead collimator inside the storage ring tunnel. The
intensity of a LCS photon beam, corresponding to the spectrum height, is nearly two orders of magnitude
higher than that of a bremsstrahlung beam, although the straight section is long.
The photon beam profile was measured by the 16 ch. × 16 ch. two-dimensional array of 3 mm-squarescintillating fibers with a 0.5 mm-thick aluminum converter, which was placed between the plastic scintillators for the charge veto and the trigger. We refer to this detector as a beam profile monitor (BPM).
As shown in Fig. 2(b), the profile of a bremsstrahlung photon beam is a bit spread with the RMS radius of ∼9 mm because of the electron beam orbit structure at the 30 m-long straight section. On theother hand, the profile with laser injection is well collimated with the dominance of a LCS photon beam
(Fig. 2(c)), resulting in the RMS radius of ∼6 mm as expected from Fig. 1(a).
The photon beam intensity was measured with the simultaneous three laser injection. The intensity
is usually measured by counting the recoil electron rate at the tagger, but its optimization is still underway. Therefore, we adopted the following two alternative methods for the intensity measurement: Oneof them is the estimation from the change of electron beam life before and after the laser injection. The
electron beam life corresponding to the Compton scattering loss was measured to be ∼120 hours. Thismeasurement was performed with the electron beam current of 100 mA, so the backward Compton scattering rate corresponding to the photon beam intensity was calculated to be ∼7 MHz for 0<Eγ <2.4 GeV.
Another estimation was done by the measurement of the e+ e− conversion rate at the BPM. The BPM
trigger rates were 29.0 kHz and 3.7 kHz for the cases with laser on and off, respectively. By taking
into account the pair production cross sections at the converter and the trigger scintillator, the photon
beam transmission through the beamline materials (∼76%), and the cutoff of low energy photons by the155

Fig.3.

(a) Side views of the BGOegg electromagnetic calorimeters. (b) A schmatic top view of theforward detector setup for charged particles.

collimator, the intensity of a LCS photon beam is calculated to be ∼7 MHz, which is consistent with theestimation from the electron beam life. The obtained beam intensity is nearly half of our expectation, sothat we are trying to fix the problems of laser injection optics.

§ 4. Experimental ProgramsTwo different detector setups are being prepared for the experimental programs at the LEPS2
facility. The first experiments will be carried out with the electromagnetic calorimeter called ’BGOegg’
from the latter half of FY2013. The calorimeter system has been installed in the upstream part of
the LEPS2 experimental building, and covered by a thermostatic booth to avoid the calorimeter gainchange which is expected at the level of −1.5%/◦ C. In the center part of the LEPS2 building, the BNLE949 solenoidal magnet has been set up with a pit hole. We will keep constructing the LEPS2 charged
particle spectrometer inside the solenoid during the BGOegg experiments in parallel. The experimentswith this spectrometer will follow the BGOegg experiments in a few years.
4.1 BGOegg Experiments
The BGOegg electromagnetic calorimeter is an ’egg’-shaped assembly of 1320 BGO crystals, as
shown in Fig. 3(a). Each crystal with the shape of a truncated square pyramid has the longitudinallength of ∼220 mm, corresponding to 20 radiation length. The BGO crystals are separately stacked in
the forward 13 layers and the backward 9 layers of the 60 crystal ring without partition supports. The
BGOegg covers the large geometrical acceptance from 24◦ to 144◦ in polar angles. We will install acylindrical drift chamber (CDC) and plastic scintillators inside the BGOegg for the detection of charged
particles. The BGOegg calorimeter was constructed at Research Center for Electron Photon Science(ELPH), Tohoku University, and was successfully transported to SPring-8 in December 2012.
The performance of the BGOegg calorimeter has been examined at ELPH by injecting a positron

156

Fig.4.

(a) Energy resolutions and (b) position resolutions as a function of the incident energy at
the positron beam test of the prototype BGOegg calorimeter. The data points indicated as‘central’ in (b) were measured by the energy weights in 3×3 BGO crystals with the beam
injection into the central crystal. (c) The distribution of 2γ invariant mass measured at
the partial operation (only forward 300 channels) of the BGOegg calorimeter. The two
histograms, which must be scaled by the indicated magnification factors, are plotted forthe different threshold values of an individual γ energy.

beam into a 5×5 crystal array with the front coverage by scintillating fiber hodoscopes [7]. As shownin Fig. 4(a), the measured energy resolution varies as a function of the incident energy, resulting in∆E/E=1.3% at 1 GeV. The positron beam position was also measured from the shower distribution in
3×3 crystals, and was compared with the hodoscope information. The position resolution was estimatedto be 3.1 mm at the center part of the crystal array for the incident energy of 1 GeV. (See Fig. 4(b).)
In January 2013, the BGOegg was partially operated at the LEPS2 beamline for a commissioning
purpose. Photomultipliers, high voltage suppliers, and a related DAQ system were prepared only forthe most forward 5 layers or 300 BGO crystals. A test beam of the LCS photons was irradiated onto a
20 mm-thick carbon target at the BGOegg center. Shower activities which coincide with the tagger signal
timing were clustered after the rough gain calibrations of 300 crystals. In Fig. 4(c), two of such clusters
were combined to calculate the invariant mass with the different conditions of energy thresholds. A clear
peak of the π 0 → γγ decays is observed with the mass resolution of ∼15 MeV, which is slightly worse
than the expected resolution because the precise energy calibrations has not been done. The η → γγ
decays require larger opening angles, so the corresponding signal peak is not clear in this plot due to thelimited geometrical acceptance.
4.2 Physics Programs expected at the BGOegg Experiments
We are considering to search for the η’-bound nuclei as one of main physics programs at the BGOegg
experiments. By the partial restoration of the chiral symmetry, the η’ mass is theoretically expected todecrease by ∼150 MeV at a normal nuclear density [8]. This produces a potential for the η’ meson to bebound inside a nucleus. Such a state may be accessible by injecting a high energy photon into a nucleus
and by striking a proton to the extremely forward direction.
At the BGOegg experiments, the forward acceptance hole of the calorimeter is covered by TOF

157

Fig.5.

(a) The simulated η’ recoil momenta as a function of the photon beam energy in the casethat the final state proton in the γp → η’p reaction is detected at the RPC, covering theextremely forward angles less than 8.5◦ . The photon energy ranges accessible with the
UV and deep UV lasers at the LEPS2 experiments are also indicated. (b) The expected
momentum resolutions as a function of the proton momentum, measured from the TOF
at the RPC. The maximum proton momenta at the various photon energies are also indicated.

detectors to measure the momenta of charged particles, as shown in Fig. 3(b). For the extremely forward region at θ<8.5◦ , a 2 m×4 m wall of resistive plate chambers (RPC), whose individual size is
20 cm×100 cm, will be placed at the 12 m downstream of the target. The time resolution of the RPC wasmeasured by a beam test at the LEPS beamline, and was estimated to be 50 psec [9]. We are planningto cover the forward angles between the RPC wall and the calorimeter (8.5◦ <θ<24◦ ) by the TOF wallof plastic scintillators at the just upstream of the E949 solenoid. The positions and angles of forwardly
produced charged particles will be measured by a drift chamber (DC), which has an effective diameter of1280 mm. The DC consists of 6 planes with three different wire angles, possessing 16 mm-square drift
cells. The position resolution of 130 µm has been confirmed at a beam test [10].
The setup of the BGOegg calorimeter with the forward charge detection is suitable for the η’-boundnuclei search. In the case that the forward proton is detected at the RPC, the recoiled η’ has a low
momentum (∼400 MeV/c) to be bound at a proton hole. (See Fig. 5(a).) The higher photon beam energy with the injection of deep UV laser reduces the lower limit of the recoil momentum further. The
momentum resolution for the forward proton detected at the RPC is estimated to be less than 1% asshown in Fig. 5(b). This results in the missing mass resolution of 15 MeV at Eγ =2.4 GeV. The BGOegg
calorimeter will be used to improve the S/N ratio, and it may be possibly used to detect η’ decays for aline shape analysis. The η’ mass resolution by two gamma invariant mass is estimated to be 30 MeV at
Eγ =2.4 GeV without a kinematical fitting.
The η’-related physics will be also explored extensively by preparing a liquid hydrogen or deuterium
target with a long nose. For example, it may be possible to measure the η’p scattering length. This

158

Fig.6.

A schematic view of the LEPS2 charged particle spectrometer.

measurement has become possible by extending the lower limit of the tagged photon energy range to1.35 GeV with the modification of a LEPS2 beamline chamber and by covering the kinematical region
well below the η’ production threshold of Eγ ∼1.45 GeV. Our detector setup has the feasibility for thisstudy because, at low photon energies, a proton is directed to the extremely forward angles and theη’ angle dependence of BGOegg acceptance gets small. At Eγ <2.4 GeV, the η’ yield of the elementary
photoproduction process is estimated to be ∼60,000 events × Branching Fraction × Acceptance per day
by assuming the total cross section of 0.8 µb, the beam intensity of 107 Hz, and the liquid hydrogentarget length of 4 cm.
Highly excited baryon resonances, which are not well explained by the constituent quark model,
strongly couple to the final state of multi-mesons and a nucleon. We therefore plan to investigate thedouble meson photoproduction in the ππN, πηN, and ηηN channels. Especially, the ηηN channel works
as an isospin filter, which only allows a resonance with I=1/2. Similar studies with partial wave analyses
can be done at the CBELSA/TAPS experiments through the various combinations of beam and target
polarizations. The BGOegg experiments would be able to contribute to this field with the high linear
polarization beam at high energies, while the linear polarization of the CBELSA/TAPS experiments isachievable up to Eγ ∼1.7 GeV.
4.3 LEPS2 Charged Particle Spectrometer
After a few years run with the BGOegg detector, the next experiments with the LEPS2 charged
particle spectrometer are planned by covering large solid angles, as shown in Fig. 6. The BNL-E949
magnet provides the solenoidal field of 1 Tesla, where we are going to place a time projection chamber(TPC) and DCs as a tracking system. The momentum resolution of about 1% is expected for the polar

159
angle region greater than 10◦ . Particle identification will be done by a cylindrical side wall of RPCs anda forward wall of TOP counters. A part of the DCs and the RPCs will be recycled from the BGOegg
experiments. The most outer part of the barrel region is occupied by the sampling electromagnetic
calorimeter, which has been originally used at the E949 experiment, although the energy resolution is
expected to be around 10%.
As one of the physics programs with the LEPS2 charged particle spectrometer, we will perform thesystematic study of the pentaquark candidate Θ+ , which has not been established yet. The reaction of
γn → K− Θ+ ; Θ+ → K0S p; K0S → π + π − will be examined because the final state of this mode includes only
charged particles. The mass resolution for the Θ+ , which will be reconstructed by the π + π − p invariant
mass, is expected to be 6 MeV. On the other hand, we are finalizing the exclusive analysis of the reaction
γn → K− Θ+ ; Θ+ → K+ n in the LEPS data by taking into account the importance of the final state
nucleon identification [11]. The new data to confirm the observed structure in the K+ n mass spectrum
is being accumulated with the LEPS forward spectrometer, whose trigger counter has been enlarged formore efficient detection of a proton.

§ 5. Summary
We have constructed a new laser Compton backscattering beamline (LEPS2) at SPring-8, aiming
one order of magnitude higher intensity and larger acceptance coverage compared with the LEPS experiments. We have successfully obtained the first photon beam at the LEPS2 beamline, resulting in the
beam size of σ ∼6 mm and the intensity of ∼7 MHz for 0<Eγ <2.4 GeV. The photon energy spectrum
has been also measured using a large BGO crystal.
We will start the BGOegg calorimeter experiments from the latter half of FY2013 with the forward
coverage by TOF detectors and a DC. We will carry out η’-related physics programs, double meson photoproduction studies, etc. The momentum resolution less than 1% is expected for the proton which isdetected by the RPC, and the η’ mass resolution in the 2γ decay mode is estimated to be ∼3% without akinematical fitting. Experiments with the LEPS2 charged particle spectrometer will follow the BGOegg
experiments in a few years. Physics results at the LEPS experiments will be upgraded.

Acknowledgement
We greatly thank to the support of the staff at SPring-8 for the beamline construction and commissioning. This research was supported in part by the Ministry of Education, Science, Sports and Cultureof Japan, JSPS KAKENHI Grant No. 24244022, and Scientific Research on Innovative Areas Grant
No. 21105003.

References[1]

N. Muramatsu, arXiv:1201.4094 (2012).

[2]

S.H. Hwang et al., Phys. Rev. Lett. 108, 092001 (2012).

160

[3]

Y. Morino et al., Submitted Phys. Lett. B; Also Talked in BARYONS 2013, Hadron Spectroscopy
Session 1-2.

[4]

M. Williams et al., Phys. Rev. C 80, 045213 (2009).

[5]

M. Yosoi, AIP Conf. Proc. 1388 (2011) 163; M. Yosoi, SPring-8 Reasearch Frontiers 2011, 138.

[6]

T. Yorita, IPAC 2013 Proc. (in press), WEPWA016.

[7]

T. Ishikawa et al., ELPH Annual Report Vol.1, 61 (2012).

[8]

H. Nagahiro et al., Phys. Rev. C 74, 045203 (2006).

[9]

N. Tomida, Master Thesis, Kyoto University (2012).

[10] T. Hashimoto, Master Thesis, Kyoto University (2013).
[11] Y. Kato, Few-Body Syst. (2013), DOI:10.1007/s00601-013-0681-6; N. Muramatsu, Few-Body Syst.
(2013), DOI:10.1007/s00601-013-0614-4.

ELPH Annual Report, Tohoku University (2011-2013)

161(ELPH Experiment : #2717)

Conceptual design of a data acquisition system for LEPS2
experiments with a BGO calorimeter
T. Ishikawa1 , Y. Honda1 , S. Masumoto2,3 , M. Miyabe1 , N. Muramatsu1 ,K. Ozawa4 , H. Shimizu1 , Y. Taniguchi1 , Y. Tsuchikawa1 , H. Yamazaki1 ,and R. Yamazaki1
1Research Center for Electron Photon Science (ELPH), Tohoku University, Sendai 982-0826,
Japan
2

Department of Physics, University of Tokyo, Tokyo 113-0033, Japan
3

4

Nishina Center, RIKEN, Wako 351-0198, Japan

Institute of Particle and Nuclear Studies, KEK, Tsukuba 305-0801, Japan

We plan to search for the possible η 0 -mesic nucleus with a BGO calorimeter at SPring-8/LEPS2
to investigate the properties of the η 0 meson at finite density coming from partial restoration of chiralsymmetry in connection with the axial anomaly problem. We also measure the single heavy meson anddouble meson photoproduction processes to study highly excited baryons. In this report, the conceptual
design of a data acquisition system for these experiments is discussed.

§ 1. Introduction
The η 0 (958) meson has an exceptionally large mass although it would be a Nambu-Goldstone bosoncoming from the spontaneous breakdown of chiral symmetry. The mass generation of it is considered to
be a result of the interplay of quark symmetry and gluon dynamics in connection with the axial anomaly
problem. Recently, the possibility of the η 0 -mesic nucleus formation is theoretically investigated [1]. The
η 0 -mesic nucleus is a good probe to figure out the properties of the η 0 meson at finite density and thenon-trivial vacuum structure of QCD.
We have developed a homogeneous calorimeter consisting of 1,320 BGO crystals [2] to search for theη 0 -mesic nucleus by using a missing mass technique of the (γ, p) reaction. The experiment will be carriedout at SPring-8/LEPS2. The LEPS2 facility is one of the Laser Electron Photon beamlines at SPring-8(LEPS). High energy photon beam is generated by the backward Compton scattering of ultraviolet laser
photons from 8 GeV electrons circulating in the SPring-8 synchrotron radiation ring. The energy of thebeam is tagged by photon tagging counters. The protons emitted at forward angles are planned to be
detected to minimize the recoil momentum of the produced η 0 mesons. The momentum-analysis andtime of flight measurement for the forward scattered protons will be made by using a bending magnet
placed downstream of the calorimeter. To reduce the large amount of background events, we plan todetect the η mesons from the η 0 N → ηN conversion in a nucleus.
Baryon spectroscopy is a testing ground for non-perturbative QCD calculations in the low energy
scale, and sheds a light on the internal structure of the nucleon and its excited states in terms of effective

162

degrees of freedom. Good data on π scattering and π photoproduction are available, and the baryon
resonances have been investigated by analyzing intermediate states of these reactions. Highly excited
baryons do not have a large decay branching ratio to the πN final state. Therefore, other final state
reactions are desired for investigating highly excited baryons. For this purpose, single heavy mesonand double meson photoproduction processes will be measured at SPring-8/LEPS2 such as γN → ηN ,γN → ωN , γN → η 0 N , γN → π 0 ηN , γN → π ± ηN , γN → ηηN , and so on. Neutral mesons decay
into several photons, π 0 , η, and η 0 decay into γγ for example, and these photons will be detected withthe calorimeter.

§ 2. Cirucuitry
The data acquisition system for LEPS2 experiments with the calorimeter is designed to reuse many
modules used in the BNL-E949 detector system, which were transported from BNL. The main modules
to be reused are CAMAC ones:
1. LeCroy 4300B fast encoding readout ADC modules (FERA),
2. LeCroy 4413 16 channel programmable discriminator modules (4413), and3. Kinetic Systems 3952 enhanced type L-2 serial crate controller modules (3952).
The FERA’s are used for measuring the energies of BGO crystals. The 4413’s generate logic signalsof BGO crystals for measuring timings and forming a trigger of the data acquisition. These CAMAC
modules in each crate are controlled by a 3952 module. It sets the virtual station number and readout
mode in each FERA, and the discriminator threshold in each 4413.
The main trigger of the data acquisition is assumed to be the coincidence signal between the triggers from BGO crystals and tagging counters. To minimize the length of the delay cables for analog
signals of BGO crystals delivered to ADC modules, a fast clear method is applied. The gate signal isgenerated according to the BGO trigger. The digitized data of ADC and TDC modules are readout when
the corresponding tagging counter signal exists, and the ADC modules are cleared when it does not exist.
The conceptual design of the circuitry for the data acquisition is discussed step by step.
2.1 Overview of the circuitry
The energy of each BGO crystal is measured with an ADC module FERA, and the timing of it ismeasured with a multi-hit TDC module CAEN V1190A. Figure 1 shows the basic scheme of the circuitry
for the energy and time measurement of BGO crystals. Two kinds of photo-multiplier tubes (PMT) havebeen adopted [2] to readout the scintillation light in BGO crystals. A nominal head-on type PMT’s called
H6542 are used in six layers 12F, 11F, 10F, 09F, 07B, and 08B of which the rear faces are very small, anda metal-packaged PMT’s called H11334 are used in the other sixteen layers. The cable for each H11334
is 2.1 m longer than that for each H6542 by considering the difference of the rising times of these PMT’s.
The difference of the rising times of these PMT’s is discussed in §2.2.
The analog signal from each BGO crystal is divided into two. One is delivered to a FERA througha 30 m delay cable and a 30 dB attenuator. The optimization of the length of the delay cable and the163

attenuation factor is discussied in §2.3. The other is sent to a discriminator (4413) to generate a logic
signal, and it is delivered to a TDC module. The burst guard mode is selected in the discriminators, inwhich the output is extended until the trailing edge of an input pulse. The discriminator generates ananalog signal (current sum output) which is proportional to the number of channels which exceed thethreshold (50 mV/hit with a 50 Ω load). It can be used to give the multiplicity of the input signals, and isdelivered to a linear fanin-fanout (FI/FO) module for forming a trigger of the data acquisition system.
H11334
1~2 nsα delay

47 ns
Divider
45 ns
9.0 m

47 ns
DividerH6542~2 ns
α+10.5 ns delay 34.5 ns
6.9 m

Fig.1.

5m

72 ns
Delay

247 ns5m
Attenuator
ADC
30 m~30 dB
TDC

64 ns
Discriminator
95 ns
LeCroy 4413
3m
1 us Attenuator
A Trigger
Burst Guard
3m
1 m 100 ns
15 channel OR
16 ns delay
247 ns5m
72 ns
5m
Attenuator
ADC
Delay
30 m
~30 dB
62 ns
TDC
Discriminator
93 ns
LeCroy 4413
3m
1 us Attenuator
A Trigger
Burst Guard
1 m 100 ns
15 channel OR 3 m
16 ns delay

Basic scheme of the circuitry for the energy and time measurement of BGO crystals. The
analog signal from each BGO crystal is divided into two. One is delivered to an ADC
module (FERA) through a 30 m delay cable and a 30 dB attenuator, and the other isinput to a discriminator (4413). A logic signal generated with the discriminator is sent toa TDC module, and a multiplicity signal (50 mV/hit) of the discriminator is delivered to alinear fanin-fanout (FI/FO) module for forming a trigger of the data acquisition system.
The burst guard mode is selected in the discriminators, which makes the output width∼ µs. Another attenuator is placed between the discriminator and the linear FI/FO
module. The cable length between a photo-multiplier tube (PMT) and the splitter isdifferent because the rising time is different between H11334 and H6542 PMT’s.

The first level trigger is used for generating the ADC gate signal with respect to the BGO trigger.
When a corresponding signal of the tagging counters is not found, the conversion of ADC modules is
stopped and the digitized data of them is cleared. Figure 2 shows the circuitry for generating the firstlevel trigger. The first level trigger request is generated with a discriminator when the analog sum of themultiplicity signals of all the discriminators exceeds the threshold corresponding to the specified numberof hits. Since the multiplicity signal has a pulse height of 50 mV/hit with a 50 Ω load, the discriminator
thresholds of 25 mV and 75 mV correspond to 1 and 2 hits among all the crystals, respectively. The firstlevel trigger accept is only generated when the previous trigger accept has been processed or cleared(fast clear). A gate signal for ADC modules is generated with a gate generator module according to thefirst level trigger accept. Approximately 2 µs width is appropriate for the gate signal because the decay
time of BGO scintillator is very long (∼ 300 ns).
Although the conversion of ADC modules starts according to the first level trigger accept, the digitized data of them are cleared when a corresponding signal of the tagging counters is not found. The
second level trigger is used to start the readout process of the digitized data from all the ADC and TDC
modules. Figure 3 shows circuitry for generating the second level trigger. The second level trigger is164

108 nsSum Amp

118 nsDiscriminator

143 ns168 nsGate Generator

1st level
128 nstrigger

…

Busy

ADC GATE

2m

151 nsTrigger B
Gate Generator ADC Busy
Start Latch Mode
FI/FO

Sum Amp
Trigger Circuit for Scaler

198 ns2 us

Majority
Logic Unit…

Trigger A…

98 ns
Sum AmpStop
CPU Busy

Fast Clear

Fig.2.

Circuitry for generating the first level trigger. The first level trigger request is generated
with a discriminator when the analog sum of the multiplicity signals (50 mV/hit) of all
the discriminators exceeds the threshold corresponding to the specified number of hits.
The first level trigger accept is only generated when the previous trigger accept has beenprocessed or cleared (fast clear). A gate signal for ADC modules is generated with a gate
generator module according to the first level trigger accept. Approximately 2 µs widthis appropriate for the gate signal because the decay time of BGO scintillator is very long(∼ 300 ns).

generated with a multiplicity logic unit module with respect to coincidence between the first level trigger accept and the logic sum of the tagging signals. When the first level trigger accept is generated andthe second level trigger is not generated, all the ADC modules are cleared and they are not readout (fastclear). To estimate the DAQ efficiency, the number of coincidence signals are also counted with a scaler
module between the first level trigger request and the logic sum of the tagging signals.
Discriminator~20 nsMajority
151 ns
Logic Unit
Trigger B
209 ns delay

Delay

Fast Clear
ADC CLEAR

Busy
Tagger

FI/FO

Coincidence
370 nsTrigger

Majority
Logic Unit…

Start Gate Generator

50 ns + 150 m (3D-FB)−100m (photon)=350 ns

360 nsBusy

Stop from
CPU
…

FI/FO

Latch Mode

CPU Busy

Tagger Analog
150 m (3D-FB)−100m (photon)=300 ns(automatically delayed)

Fig.3.

Circuitry for generating the second level trigger. The second level trigger is generated
with a multiplicity logic unit module with respect to coincidence between the first level
trigger accept and the logic sum of the tagging signals. When the first level trigger accept is generated and the second level trigger is not generated, all the ADC modules arecleared and they are not readout (fast clear). To estimate the DAQ efficiency, the number of coincidence signals are also counted between the first level trigger request and thelogic sum of the tagging signals.

165

2.2 Time responses of H6542 and H11334
Two types of PMT’s have been adopted [2] to be connected to BGO crystals. A metal-packaged PMT’s
Hamamatsu H11334 are used in central sixteen layers from 10F to 06B. It is difficult to connect H1134
with a BGO crystal in the other six layers 12F, 11F, 10F, 09F, 07B, and 08B since the rear face of thecrystal is very small. Thus, nominal head-on type PMT’s Hamamatsu H6542 are used in these layers.
The difference of rising times was investigated between H6542 and H11334. The waveforms ofsignals from H6542 and H11334 connected to both sides of a plastic scintillator (PS) were acquired by
employing a digital phosphor oscilloscope, Tektronix DPO-4104, with a sampling frequency of 5 GHz [3].
The PS measures 30×30×30 mm3 . It was connected to H6542 and H1134 with optical grease OKEN6262A,
and wrapped with Tyvek 1073D paper. The output signals from H6542 and H11334 were directly input
to DPO-4104. Fig. 4 shows the experimental setup for the waveform acquisition. To define the incident
position, a 3 mm thick PS with an area of 10 × 10 mm2 was placed in front of the BSO crystal. Two sidesof PS were connected to PMT’s R4125GMOD through acrylic light guides. The signals from PS (PS1 andPS2) were also directly input to DPO-4104. Five thousand events of the waveforms for cosmic rays wereacquired.

Fig.4.

Experimental setup for measuring time responses of two PMT’s H6542 and H11334.
H11334 and H11334 connected to a PS with a size of 30 × 30 × 30 mm3 are locatedbehind the trigger PS. A PMT R4125GMOD is connected to each side of the trigger PS.

The correlation of the maximum pulse heights between H6524 and H11334 were investigated for
H6524
H11334each event. Figure 5 shows the correlation between −Vminand −Vmin. Vmin stands for the minimum

value of the voltage. It should be noted that the voltage is negative for outputs from these PMT’s. Events
H6524
H11334are concentrated near (Vmin, Vmin∼ (0, 0) V. The events were selected with the minimum values

from −4.5 to −1.0 V of the voltage are both for H6524 and H11334.
The voltages of signals can be reproduced very well with a function of timing t,t − t0t − t0exp −,V (t) = −V0 freq
τR
τD

(1)

where freq stands for a Gaussian convoluted step function [4]. The fits were made in the time region

166
4.5
4
3.5
H6542
-Vmin
(V)

3
2.5
2

1.5
1
0.5
0

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

H11334-Vmin(V)

Fig.5.

H11334
H6524
H6524
and Vmin. The −Vmin
Correlation between the minimum value of the voltage Vmin
H11334and −Vmin
are plotted. The area of the events to be used is indicated by the red box.

[t0 − 10τD , t0 + 20τD ). The parameters V0 , t0 , τR , and τD correspond to the amplitude, the response
timing, the rising time, and the effective decay time, respectively. Figure 6 shows the typical waveformsof H6524 and H11334 signals with fitted functions (1). The response of the H11334 is approximately−10 ns earlier than that of H6542. Figure 7 shows the obtained parameters V0 , τR , and τD . The similar
distributions are obtained for V0 and τR parameters between H6524 and H11334. The τD parameter for

Pulse Height (V)H11334 is larger than that for H6542.

Fig.6.

0
-0.5
-1
-1.5
-2
-2.5
-3
-3.5
-4
-40

H11334

-30

-20

H6542

-10
0
Time (ns)

10

20

30

Typical waveforms of H6524 and H11334 signals with fitted functions (1). The responseof the H11334 is approximately −10 ns earlier than that of H6542.

The difference of the time responses between H6524 and H11334 are estimated as
δt = tH6524− tH11334
.
0
0

(2)

Figure 8 shows the difference of t0 parameters between H6524 and H11334. The mean and standard

167

Counts / 0.05 ns

Counts / 0.1 V

10
5
0
0

2 4 6 8 10
-V0H11334 (V)Counts / 0.05 ns

80

15

60
40
20
0
0

2
4
6
τRH11334 (ns)00Fig.7.

2 4 6 8 10
-V0H6542 (V)Counts / 0.05 ns

Counts / 0.05 ns

Counts / 0.1 V

5

30
20
10
0
0

2
4
6
τRH6542 (ns)

8

100
50
0
0

8

40
10

150

1

2 3 4
τDH11334 (ns)

5

1

2 3 4
τDH6542 (ns)

5

80
60
40
20
0
0

Distributions of the obtained parameters V0 , τR , and τD for H6524 and H11334. The
upper panels show those for H11334, and the lower show those for H6524. The left,
central, and right panels show V0 , τR , and τD distributions, respectively.

deviation are 10.50 ± 0.01 and 0.29 ± 0.01 ns for δt distribution, suggesting the response of the H11334
is approximately −10.5 ns earlier than that of H6542. The −10.5 ns difference of time responses correspond to the 2.1 m difference of the RG-174/U cable lengths. The details of the waveform analysis aredescribed elsewhere [5].
2.3 Energy measurement
The decay time of BGO scintillator is very long (∼ 300 ns). The charge integration for the typicalfull-scale of ADC modules is 400–1000 pC, and the corresponding pulse height is roughly 64–160 mV
with a 50 Ω termination. Assuming that the full scale of an ADC module corresponds to the energy of 2
GeV, the pulse height for the energy of 20 MeV is as small as 0.6–1.6 mV. It is difficult to generate a logic
signal correctly by using a nominal discriminator. Therefore, the input signals to ADC modules should
be attenuated.
To discuss the ratio of the pulse height of input signals to an ADC module and a discriminator,
the waveform of a BGO crystal was acquired with a digital phosphor oscilloscope Tektronix DPO-4104
with a sampling frequency of 5 GHz. The analog signal from the BGO crystal was directly input to theoscilloscope. The trigger was generated by coincidence of the logic signals for central x8 and y8 BPM
fibers [6]. The data set is the same as that reported in §4.4 in ref. [2] The voltage of a BGO signal can be

168

70

Counts / 0.1 ns

60
50
40
30
20
10
0

Fig.8.

6

8

10∆t (ns)1214

Difference of t0 parameters between H6524 and H11334. The mean and standard deviation are 10.50 ± 0.01 and 0.29 ± 0.01 ns.

reproduced very well with a function of timing t [7],






t − t0 −V0 1 − exp − t − t0
exp −for t ≥ t0
τR
τD
V (t) =
 0
for t < t0(3)

Table 1 summarizes the mean and width of the distributions for the parameters V0 , τR , and τD of a
fitted function (3) for each RTAGX current.
Table 1. Mean, width, and asymmetry of the distributions for the parameters V0 , τR , and τD ofa fitted function (3) for each RTAGX current I (A). Ee (MeV) stands for the positronenergy corresponding to I. The µ (ns) and σ (ns) denote the mean and width, and η isthe asymmetry. The V0 distribution is fitted with a logarithmic Gaussian [8], and τR andτD distributions are fitted with nominal Gaussian functions.
I
50
100
150
230
300
400

Ee
99.80
200.23300.10457.75588.62743.55µcV0.392(3)0.806(3)1.207(4)1.856(5)2.382(5)3.016(6)σVc
0.054(2)0.080(2)0.101(2)0.121(2)0.135(2)0.159(3)ηVc
0.444(42)0.334(26)0.225(24)0.214(26)0.206(24)0.148(25)µcR
6.827(18)
6.927(11)
6.967(09)6.994(07)7.015(06)7.044(06)c
σR
0.606(17)0.413(10)0.353(08)0.274(06)0.245(05)0.225(05)µcD
251.21(19)250.15(10)250.30(05)249.32(03)248.59(03)247.24(03)cσD
6.39(18)
3.96(10)
3.26(08)2.52(06)
2.24(05)
1.96(04)

The µV , µR , and µD are well fitted with one dimensional polynomial functions of the incident
energy Ee :µV (Ee ) = (−0.013 ± 0.003 MeV/nsec) + (4.072 ± 0.008 MeV/nsec) Ee /GeV,µR (Ee ) = (6.88 ± 0.01 nsec) + (0.23 ± 0.02 nsec) Ee /GeV, andµD (Ee ) = (252.22 ± 0.06 nsec) − (6.50 ± 0.10 nsec) Ee /GeV.
Figure 9 shows the µV , µR , and µD as a function of the incident energy.

(4)

6
4
2
0
0

1000
Energy (MeV)
Fig.9.

2000

7.4
7.2
7
6.8
6.6
0

255
250

µD (ns)8µR (ns)µV (MeV/ns)

169

245
240

1000
Energy (MeV)

2000

235
0

1000
Energy (MeV)2000µV , µR , and µD as a function of the incident energy with fitted functions (3).

E
The maximum pulse height Vmax
and charge integration QE
int in the energy unit are given as
E
Vmax(2000 MeV) = 7.083 MeV/nsec,

QE
int (2000 MeV) = 1886.7 MeV(5)for the incident energy of 2 GeV from the obtained parameters. The full scale of an ADC module QADC =1000 pC is assumed to correspond to the energy of 2 GeV, giving the maximum pulse height as
Vmax = ZC

E
QADC
ZC QADC Vmax
=
,
E
tW /2
Qint

(6)

where ZC stands for 50 Ω of the termination. The maximum pulse height Vmax is 187.7 mV for 2 GeV.
E
and QEFor the incident energy of 20 MeV, Vmax
int areE(20 MeV) = 0.060 MeV/nsec,
Vmax

QE
int (20 MeV) = 16.8 MeV,

(7)

corresponding to the maximum pulse height
Vmax =EZC QADC QE
int (20 MeV)/Qint (2000 MeV)
= 1.59 mV.
tW (20 MeV)/2(8)

The attenuation factor of 1/6.3 is obtained to satisfy the energy of 20 MeV corresponding to the discrimE
inator threshold of 10 mV. For the incident energy of 10 MeV, Vmax
and QE
int areE(10 MeV) = 0.024 MeV/nsec,
Vmax

QE
int (10 MeV) = 6.8 MeV,

(9)giving Vmax (10 MeV) =0.64 mV. The attenuation factor of 1/15.6 is obtained to satisfy the energy of 20
MeV corresponding to the discriminator threshold of 10 mV.
The minimum energy to generate a logic pulse can be adjusted by a high voltage supplied to PMT,
an attenuation factor, and a discriminator threshold. Realistic thresholds of discriminator 10, 20 mV
give the attenuation factor of 1/15.6, 1/6.3 for 1000 pC full scale of an ADC module, respectively. The fullscale of FERA modules is 500 pC which gives the attenuation factor of 1/31.2 (30 dB) for the minimum
discriminator threshold of 10 mV. The details of the discussion on the attenuation factor are described
elsewhere [9].
A fast clear method has been applied to minimize the length of the delay cable, and the gate signals
for ADC modules are delivered at approximately 150 ns from the signal divider. The analog signal should

170

be delayed by 200 ns, the appropriate length of the RG-58 delay cable (5 ns/m) is 30 m assuming thatthe connection cables in the both sides of the delay cable have a length of 5 m (RG-174/U).
To measure the energies of 1,320 BGO crystals, 88 FERA modules are needed assuming that fifteen
channels are used in each module. The digitized data are collected by UIO modules [10] by utilizing the
FERAbus transfer. To keep the dead time coming from the FERAbus data transfer less than 100 µs, The
FERA modules should be divided into six subsystems.
2.4 Timing measurement
The timing measurement is made by using a multihit TDC module CAEN V1190A. The ECL outputs
from the 4413 discriminators are sent to V1190A, The BGO trigger signal is also input to each V1190A
module to obtain a correct time difference between the BGO crystal and trigger signals. To measure
the timing of 1,320 BGO crystals, 88 of 4413 discriminator modules are needed assuming that fifteen
channels are used in each module, and eleven V1190A modules are required. Since a V1190A module
needs 5.5 A for +6 V, V1190A’s are divided into two subsystems to keep the total +6V current small in a
VME crate.
2.5 CAMAC initialization
The threshold value of each LeCroy 4413 discriminator module can be adjusted by a CAMAC function. And also the virtual station number for the FERAbus transfer and readout mode should be specifiedin each LeCroy 4300B fast encoding readout ADC module by a CAMAC function. Kinetic Systems 3952
enhanced type L-2 serial crate controller modules (3952) are used for generating CAMAC functions. The
3952 module is a slave of the CAMAC serial highway, and is controlled by a master. The candidate of themaster module is Kinetic Systems 3992 serial highway driver (3992). The 3992 transmits and receiveson the CAMAC serial highway, and can control many 3952 CAMAC crate controller modules. Figure 10
shows the schematic view of the CAMAC serial highway.

K3952

K3952

K3952

K3952

K3952

master

K3992
K3952

Fig.10.

Schematic view of the CAMAC serial highway. The master 3992 module controls many
3952 CAMAC crate controller modules. Each 3952 set the threshold value of LeCroy
4413 discriminator modules or specify the virtual station number and readout mode of
LeCroy 4300 FERA modules in the same crate.

171

2.6 High voltage supplier
It is necessary to supply high voltages (HV) to 1,320 BGO crystals. The maximum voltage for 960
H11334 PMT’s is 1000 V (negative), and that for 360 H6524 PMT’s is 1500 V (negative). The independent
HV control of each channel is preferred. But this kind of HV supplier is very expensive, and it takes
40,000 yen/channel including a HV cable. Therefore, an HV distributor is planned to be developed for
960 H11334 PMT’s. The distributor gives HV’s to 64 output channels from the primary DC current
source with the maximum voltage of −1 kV. The primary to output drop is expected to be 80%–100%
or 90%–100%, and the drop of each output channel is controlled with a potentiometer. The interlock
system is planned to be implemented so that the primary input is blocked when the over current is
detected (trip) in some channel. The trip channel is also displayed in an LED.

§ 3. DAQ framework
The data acquisition (DAQ) will be constructed based on the framework developed at ELPH for the
FOREST experiments [11]. It consists of collectors, an event builder, and a recorder processes. The
collector subsystem reads out the digitized data from the front-end electronics, and converts the data toa single data fragment. The event-builder subsystem gathers the data fragments from all the collector
subsystems, and construct a physics event from the fragments. The physics event is transferred to
the recorder subsystem, and stored on hard disk. The communication between different subsystems
are made by using the Transmission Control Protocol/Internet Protocol (TCP/IP). Three independent
networks will be constructed:
1. between the collector and event-builder subsystems for the data transfer,
2. between the event-builder and recorder subsystems for the data transfer, and3. between all the subsystems for the command transfer.
We have decided to use LeCroy 4300B fast encoding readout ADC (FERA) modules, which wereoriginally used for the BNL-E949 experiments, for the energy measurements of BGO crystals due toa limited budget. The digitized data of FERA modules in each collector subsystem are collected byusing a LeCroy 4301 FERA driver and a universal I/O (UIO) module. Both the LEPS experiments at
SPring-8 and FOREST experiments at ELPH have adopted the similar readout system for the energy
measurement. The response timings of BGO crystals and tagging detectors are measured with CAEN
V1190A 128 channel multihit TDC modules. The FOREST experiments uses the similar readout system
for the timing measurement. The front-end electronics for the other peripheral detectors have not been
decided yet. The number of readout words is expected to be approximately 2 k words for each event.
To reduce the dead time for processing an event, the parallel readout of the digitized data is made byseveral collector subsystems. To acquire two thousand events in a second, the processing rate of 32 Mbit/s
is required for data recording on hard disks and data transfer in the networks. The rate can be achieved
easily by using ordinal hard disks and Gigabit Ethernet. Figure 11 shows the configuration of front-end
electronics in the DAQ system, and Figure 12 shows the schematic view of the networks used in the
DAQ system.

172

1 VME TDC
ADC system
VME

VME

VME

VME

Tagger &Inner Plastic
Scintillator

3 VME TDC systems
TDC

TDC + Scaler

TaggerADC V792

TDC + Scaler@ a different station
Event Builder
Recorder
VME
UIO

VME
UIO

VME
UIO

VME
UIO

VME
UIO

VME
UIO

6 FERA-UIO systems
CAMAC

CAMAC

FERA
Driver

FERA
DriverFERA x 16

Fig.11.

CAMAC

FERA
DriverFERA x 16

CAMAC

FERA
DriverFERA x 16

CAMAC

FERA
DriverFERA x 16

CAMAC

FERA
DriverFERA x 16

FERA x 16

Configuration of front-end electronics in the DAQ system. The framework consists ofcollectors, an event builder, and a recorder subsystems. Ten collector subsystems areprepared for the main detectors, to read out the digitized data from the front-end electronics, four VME subsystems and six FERA-UIO subsystems.

BGO
15 FERA/CPU

15 FERA/CPUPS
TaggerBGO & PS

2 V792/CPU

6 V1190A/CPU 6 V1190A/CPU

TaggerTagger
3 V1190A/CPU

eggc01 eggc02 … eggc07 eggc08 eggc09 eggc10
data transfer network C

eggeb
data transfer network R

eggr01

command transfer network
Fig.12.

Schematic view of the networks used in the DAQ system. Three independent networks(two data transfer networks, and a command transfer network) are used.

173

Two types of collector subsystems are prepared. One is a FERA-UIO collector, and the other is a
VME collector:
1. FERA-UIO collector
The energy of a BGO crystal is digitized with a FERA module in a CAMAC crate. The digitizeddata are collected by a LeCroy 4301 FERA driver in the crate through the FERAbus, and are stored
in a universal I/O (UIO) module in a VME crate. The UIO has two buffers, one is used to store thedigitized data coming from the FERA driver, and the other is used to send them to a collector
process on a VME computer Sanritz SVA041 which has an interface to the VMEbus. These buffers
are switched according to the buffer change signal which is generated once for several events. The
ADC values are readout without a pedestal suppression, and the dead time processing an event
is expected to be less than 100 µs coming from the bus communication speed between UIO andFERA.
2. VME collector
The timing of a BGO crystal is digitized with a CAEN V1190A TDC module in a VME crate, Thedigitized data are transferred to a VME computer Sanritz SVA041 when an I/O register REPIC
RPV-130 in the VME crate receives the trigger signal. The data buffer of V1190A is a first-in firstout (FIFO) structure, and the dead time processing an event is expected to be less than 50 µs. Theenergy of a peripheral detector is digitized with a CAEN V792 ADC module, and the digitized dataof V792 can be treated similarly to those of V1190A.

§ 4. Summary
We plan to use the same data acquisition (DAQ) software framework as the FOREST experiments
at ELPH. The framework consists of collectors, an event builder, and a recorder subsystems. The communication between different subsystems are made by using the Transmission Control Protocol/Internet
Protocol (TCP/IP). We have decided to use LeCroy 4300B Fast Encoding Readout ADC (FERA) modules,
which were originally used for the BNL-E949 experiments, for the energy measurements of BGO crystals due to a limited budget. The response timings of BGO crystals and tagging detectors are measured
with CAEN V1190A 128 Channel Multihit TDC modules. The number of readout words is expected tobe approximately 2 k words for each event. To reduce the dead time for processing an event, the parallel
readout of the digitized data is made by several collector subsystems. To acquire two thousand eventsin a second, the processing rate of 32 Mbit/s is required for recording on hard disks and data transfer in
the networks. The rate can be achieved easily by using ordinal hard disks and Gigabit Ethernet.

Acknowledgment
This work was supported in part by Grant-in-Aid for Specially promoted Research (19002003).

174

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H. Nagahiro and S. Hirenzaki: Formation of η 0 (958)-Mesic Nuclei and Axial UA (1) Anomaly at
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Y. Tsuchikawa: Internal GeV-γ Analysis Note No. 259B (2012).

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[7]

T. Ishikawa: Internal GeV-γ Analysis Note No. 222B (2011).

[8]

H. Ikeda et al.: A detailed test of the CsI(T`) calorimeter for BELLE with photon beams of energy
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SPring-8, Nucl. Inst. Meth. in Phys. Res. A 437, 68 (1999).
[11] H. Fujimura et al.: A New Data Acquisition System for 4π EM calorimeter FOREST, Research
Report of Laboratory of Nuclear Science 2008 Vol. 1, ToTohokuniversity, 26 (2009).
¯

ELPH Annual Report, Tohoku University (2011-2013)

175

The first observation of the neutral pions at
SPring-8/LEPS2 and developing modules for the upgrade ofthe data acquisition
T. Ishikawa1 , S. Masumoto2 , Y. Tsuchikawa1 , H. Hamano3 , H. Hotta3 ,Y. Honda1 , Y. Kasamatsu3 , M. Miyabe1 , N. Muramatsu1 , Y. Nozawa4 ,K. Ozawa5 , H. Shimizu1 , Y. Sugaya3 , Y. Taniguchi1 , N. Tomida4 ,H. Yamazaki1 , R. Yamazaki1 , and M. Yosoi3
1

Research Center for Electron Photon Science (ELPH), Tohoku University, Sendai 982-0826,
Japan
2

3

Department of Physics, University of Tokyo, Tokyo 113-0033, Japan

Research Center for Nuclear Physics (RCNP), Osaka University, Ibaraki 567-0047, Japan
4
5

Department of Physics, Kyoto University, Kyoto 606-8502, Japan

Institute of Particle and Nuclear Studies, KEK, Tsukuba 305-0801, JapanA peak corresponding to the neutral pions was observed with a newly constructed BGO calorimeterat SPring-8/LEPS2 in the beginning of February 2013 for the first time. The high voltages were supplied
only for the forward 300 crystals, and the digitized data of them were acquired. The commissioning of
the BGO calorimeter with a partly developed data acquisition system and the modules planned to be
developed for the future are discussed.

§ 1. Introduction
Baryon spectroscopy is an important testing ground for non-perturbative quantum chromo-dynamics(QCD) calculations in the low energy scale. The data of double meson photoproduction processes such asγN → π 0 ηN , γN → π ± ηN , and γN → ηηN are desired to investigate highly excited baryons having
a small decay branching ratio to the πN final state. We have developed a high resolution calorimeterconsisting of 1,320 BGO crystals [1] to study these reactions.
The properties in the nuclear medium is one of the hot topics in nuclear physics. The possible η 0 mesic nucleus [2] is a good probe to figure out the properties of the η 0 meson at finite density. The massof the η 0 meson is considered to be a result of the interplay of quark symmetry and gluon dynamics inconnection with the axial anomaly probe, and the sizable shift of the mass is expected in a nucleus. We
search for the η 0 -mesic nucleus by using a missing mass technique of the (γ, p) reaction. The protons
emitted at forward angles are planned to be detected to minimize the recoil momentum of the produced
η 0 mesons. To reduce the large amount of background events, we plan to detect the η mesons from theη 0 N → ηN conversion in a nucleus.

176§ 2. First observation of the neutral pions at SPring-8/LEPS2
The data acquisition (DAQ) system for the experiments with the BGO calorimeter at SPring-8/LEPS2
was designed by taking into account the limited budget and the available modules transported from BNL
E949. We had a chance for the commissioning of the BGO calorimeter in the end of the fiscal year 2012.
Only the forward 300 crystals were connected with the photomultiplier tubes (PMT’s) because of several
reasons:
1. 320 cables with a length of 30 m were available for the delay of analog signals,
2. 20 LEMO00-flat conversion cables with an attenuator and a length of 5 m were available for the
inputs of FERA, each of which had 16 channels,
3. four crate controllers of the CAMAC system were available for controlling LeCroy FERA fast readout ADC and LeCroy 4413 discriminator modules,
4. 328 channels were available in the high voltage supplies, and
5. 300 PMT’s could be connected to crystals with light shielding due to the limited time from thetransportation to the commissioning run.
The serial high way driver module, Kinetic Systems 3992 for example, was not available, and many
CAMAC crate controllers Kinetic Systems 3952 could not be operated. Instead, four CAMAC crates wereused at that time by using CAMAC-PCI interfaces Toyo CC-7700, two of them controlled FERA modules,
and the others controlled the 4413 discriminators. Figure 1 shows the photo and cross-sectional view of
the BGO calorimeter in February 2013. The target used were the carbon with a thickness of 20 mm.
x/y
H11334 (R11265)

B
07 B
06 B
05
B
04
03B
02B
01B
00B
00F
01F
02F
03F
04
05 F
06 F
07 F
F

420

B

08

200

H6524 (R4125)

F
08 9F F
0 0
1 1F
1
12F

BGO calorimeterphoton beam

photon beam

Fig.1.

−200+400
targetz

Photo and cross-sectional view of the BGO calorimeter in February 2013. The BGO crystals are depicted in red which high voltages were supplied. The target used were thecarbon with a thickness of 20 mm.

The circuitry for the DAQ system was constructed according to the designed one including the fast
clear system. The details of the designed DAQ system are described elsewhere [3]. Since the trigger
rate was not so high even if the tagging signal was not required, the trigger was generated by using only
signals from BGO crystals during almost all the beamtime. There was no serious problem in the DAQ
system during the beamtime, and we could concentrate to the adjustment of the high voltages supplied
to the crystals.

177

The adjustment of the high voltage values were made step by step. At the first step, we set the highvoltage values to the crystals so that the slope of the energy distribution for each crystal in the samelayer. The slope stands for the parameter b when we fit the function
N (A) ∝ exp (−bA)(1)

to the distribution by utilizing an exponential shape of it. In the second step, the channel-to-energy
factor was further adjusted so that the peak position corresponding to the neutral pions became the rest
mass of them for each crystal. Here, the invariant mass was calculated by using the measured energies
E1m and E2m of two crystals in the same layer and opening angle θ m of them asqmγγ = 2E1m E2m (1 − cos θ m ).

(2)

Finally, the channel-to-energy factor was adjusted for each crystal similarly to the second step. Here, theinvariant mass was calculated by using the measured energies E1c and E2c of two clusters and opening
angle θ c of them asqmγγ = 2E1c E2c (1 − cos θ c ).

(3)

We have observed a peak corresponding to the neutral pions for almost all the crystals after these stepsof the procedure to determine the channel-to-energy factors. Figure 2 shows the invariant mass of two
photons. The clear peak corresponding to the neutral pions was observed. A bump at the high masscame from the mis-combination of two photons because of the small coverage of the BGO calorimeter atthat time and because no detector was placed to distinguish the incident particle whether it was charged
or neutral.

x 1000 (100 MeV)
x 2000 (200 MeV)Counts / 10 MeV

9
8
7
6
5
4
3
2
1
0

Fig.2.

0

250
500
750
1000
γγ invariant mass (MeV)

Invariant mass of two photons. Two histograms are plotted with an energy thresholdof 100 (blue) and 200 (red) MeV for clusters. A bump at the high mass comes from themis-combination of two photons because of the small coverage of 300 BGO crystals andbecause no charge identification detector is placed.

178

The data from a temporal photon tagging system consisting of eleven telescopes of two plastic scintillators were also obtained. Unfortunately, the system did not work well due to a large amount of X rays,
which were replaced with a new one in the end of September 2013. Figure 3 shows the time difference
between the BGO crystals and the tagging counters. The filling pattern of the storage ring in SPring8 at that times is A-mode (203 bunches), and the peaks corresponding to the accidental coincidence
were observed with an interval of 23.6 ns. The missing mass mX was obtained assuming the reaction
γp → π 0 X. Figure 4 shows the correlation between the missing mass mX and the invariant mass mγγ .
The event concentration can not be observed near (mγγ , mX ) = (mπ0 , mp ) bacause the target used was
the carbon at that time and because single neutral pion production scarcely takes place in this energy√
region. The given s makes a locus having a negative slope in the high mass region [4], and six loci areobserved because the energy of the laser Compton scattering photon was measured only with six sets ofplastic scintillators (the other five sets covered the higher energy than 2.4 GeV which was the maximum
photon energy corresponding to the wavelength of the laser used at that time).

203 bunches (interval 23.6 ns)
Counts / 2 ns

10 4

10 3

10 2
-100

Fig.3.

-50
0
50
ttagger-tbgo (ns)100Time difference between the BGO crystals and the tagging counters. The filling patternis A-mode (203 bunches), and the peaks are observed with an interval of 23.6 ns.

§ 3. Developing modules for the upgrade of the data acquisition
Four kind of modules started to be developed after the commissioning of the BGO calorimeter. An
FPGA logic module MPLM4 was developed by a technical staff at ELPH. An HV distributor GeVγ-131
and multiplicity logic discriminator GeVγ-139 were developed by Fuji Diamond International Co.@ Ltd.@(FDI). A discriminator with a charge to time converter was under development in cooperation with FDI.
The purposes and specifications of these modules were described in this section.

179

γγ missing mass (MeV)

2500

1500
10

1000
500
0

Fig.4.

10 2

2000

0

250
500
750
1000
γγ invariant mass (MeV)

1

Correlation between the missing mass mX and the invariant mass mγγ . Six loci are observed because the photon energy was measured only with six sets of plastic scintillators
at that time.

3.1 FPGA logic module MPLM4
The photon tagging counters at LEPS2 comprises two layers of plastic scintillator (PS) hodoscopes
and two layers of scintillating fiber (SciFi) hodoscopes. The PS signals are used to generate the trigger
for DAQ and to count up the number of photons, and the SciFi signals are used to determine the energyof the photon. The trigger is generated by the logic sum of coincidence signals of the corresponding
upstream and downstream PS’s. Since an upstream PS corresponds to one or two downstream PS,
the logic for the trigger generator is somehow complicated. We developed a multi-purpose logic module
MPLM4 with an FPGA chip of Spartan-6 having 36 input and 18 output channels. The details of MPLM4
are described elsewhere [5].
3.2 HV distributor GeVγ-131
It is necessary to supply high voltages (HV) to 1,320 BGO crystals. The maximum voltage for 960
H11334 PMT’s is 1000 V (negative), and that for 360 H6524 PMT’s is 1500 V (negative). The independent
HV control of each channel is preferred. But this kind of HV supplier is very expensive, and it takes
40,000 yen/channel including a HV cable. Therefore, an HV distributor is planned to be developed for
960 H11334 PMT’s. The distributor gives HV’s to 64 output channels from the primary DC current sourcewith the maximum voltage of −1 kV. The primary to output drop is designed to be 90%–100%, and thedrop of each output channel is controlled with a potentiometer. The channel is selected by using tworotary switches each of them having eight clicks, and the selected channel is indicated with a green LED
near the corresponding HV connector. The supplied high voltage for the selected is displayed in an LED
panel. The interlock system is implemented so that the primary input is blocked when the over current
is detected (trip) in some channel. The trip channel is indicated in an LED near the corresponding

180

connector. This HV distributor is called GeVγ-131 and developed by FDI. Figure 5 shows the photo of
the manufactured HV distributors GeVγ-131.

Fig.5.

Photo of the manufactured HV distributors GeVγ-131. The front panel has an LED panel
to display the high voltage value for the selected channel, two rotary switches for selecting the channel of which the supplied high voltage to be displayed in its panel, 64 HVconnectors each of which has a green LED indicating selected and an red LED as a trip
indicator. The rear panel has an SHV connector for the primary high voltage input.

3.3 Multiplicity logic discriminator GeVγ-139
The BGO trigger (the first level trigger request) is generated with a discriminator when the analog
sum of the multiplicity signals of all the LeCroy 4413 discriminators exceeds the threshold corresponding
to the specified number of hits. To make the analog sum of 88 multiplicity signals, two stage cascade oflinear fanin fanout (FIFO) modules is required (the input channel of available modules is less than 20).
Since the multiplicity signal has a pulse height of 50 mV/hit with a 50 Ω load, additional discriminators
are needed with thresholds of 25 (75) mV corresponding to 1 (2) hits among all the crystals. To minimize
the latency of these processes, we plan to develop a new module called multiplicity logic discriminator
GeVγ-139 with a help of FDI, which includes the linear FIFO with 96 input channels and three independent discriminators whose input is connected to the output of the linear FIFO. Figure 6 shows thecircuit diagram which the multiplicity logic discriminator GeVγ-139 includes, and Figure 7 shows thephoto of manufactured GeVγ-139. The latency of the first level trigger generation can be reduced thanks
to GeVγ-139.
3.4 Discriminator with a charge to time converter
A charge integration type ADC (QDC) like FERA requires a long delay cables for analog signals.
An option to remove the long cable is introducing flash ADC (FADC) which converts the pulse height tothe digital data at intervals corresponding to the sampling rate. A high sampling rate FADC (∼GHz) ora filter circuit to stretch the analog signal is needed for obtaining the charge integration of the narrow

181

…

Sum Amp
Sum Amp

Discriminator…

…

Sum AmpFig.6.

Circuit diagram which the multiplicity logic discriminator GeVγ-139 includes. It includes
the linear FIFO with 96 input channels and three independent discriminators whose
input is connected to the output of the linear FIFO.

Fig.7.

Photo of the manufactured multiplicity logic discriminator GeVγ-139 having 96 input
channels, two linear output channels, and three independent discriminators with threelogic output channels for each.

waveform correctly like an output of a plastic scintillator. Another option is a charge-to-time converter(QTC). A discriminator which gives a logic pulse with a width corresponding to the charge integration
is useful. Many multihit TDC module can digitize both the leading and trailing edges. The charge integration can be reduced from the time difference between the leading and trailing edges. A discriminatorwith a QTC function is planned to be developed with a help of FDI, and this kind of discriminator isfitted to the SciFi hodoscopes in the photon tagging system.

Acknowledgment
This work was supported in part by Grant-in-Aids for Specially promoted Research (19002003), andfor Scientific Research (A) (24244022).

182

References[1]

T. Ishikawa et al.: New electro-magnetic calorimeter BGO EGG, ELPH Annual Report 2010 Vol. 1,
Tohoku University, 61 (2012).

[2]

H. Nagahiro and S. Hirenzaki: Formation of η 0 (958)-Mesic Nuclei and Axial UA (1) Anomaly at
Finite Density, Phys. Rev. Lett. 94, 232503 (2005).

[3]

T. Ishikawa et al.: Conceptual design of a data acquisition system for LEPS2 experiments with a
BGO calorimeter, in this ELPH Annual Report.

[4]

T. Ishikawa: Internal GeV-γ Analysis Note No. 118S (2008).

[5]

I. Nagasawa and T. Ishikawa, et al.: Development of a new multi-purpose logic module MPLM4,
in this annual report.

ELPH Annual Report, Tohoku University (2011-2013)

183

Pseudoscalar mesons detected with a BGO calorimeter at
LEPS2
T. Ishikawa1 , Q. He1 , Y. Honda1 , S. Masumoto2,3 , M. Miyabe1 ,N. Muramatsu1 , K. Ozawa4 , H. Shimizu1 , Y. Tsuchikawa1 , H. Yamazaki1 ,and R. Yamazaki1
1Research Center for Electron Photon Science (ELPH), Tohoku University, Sendai 982-0826,
Japan
2

Department of Physics, University of Tokyo, Tokyo 113-0033, Japan
3

4

Nishina Center, RIKEN, Wako 351-0198, Japan

Institute of Particle and Nuclear Studies, KEK, Tsukuba 305-0801, JapanA BGO calorimeter consisting of 1,320 BGO crystals has been constructed at SPring-8/LEPS2. Basic
information on the calorimeter for the experiments conducted at LEPS2 is described in this report, which
includes the mass resolution and acceptance of pseudoscalar mesons detected.

§ 1. Introduction
Baryon spectroscopy is a testing ground for non-perturbative quantum chromo-dynamics (QCD)
calculations in the low energy scale, and sheds a light on the internal structure of the nucleon and its
excited states in terms of effective degrees of freedom. The highly excited baryons having a small decaybranching ratio to the πN final state can be studied by a double meson photoproduction processes suchas γN → π 0 ηN , γN → π ± ηN , and γN → ηηN . We have developed a homogeneous calorimeterconsisting of 1,320 BGO crystals [2] to study these reactions.
The properties in the nuclear medium is one of the hot topics in nuclear physics. The possible η 0 mesic nucleus [1] is a good probe to figure out the properties of the η 0 meson, whose mass is considered to
be a result of the interplay of quark symmetry and gluon dynamics in connection with the axial anomaly
problem, at finite density and the non-trivial vacuum structure of QCD. We search for the η 0 -mesic
nucleus by using a missing mass technique of the (γ, p) reaction. The protons emitted at forward angles
are planned to be detected to minimize the recoil momentum of the produced η 0 mesons. To reduce thelarge amount of background events, we plan to detect the η mesons from the η 0 N → ηN conversion in a
nucleus.

§ 2. BGO calorimeter
The properties of BGO scintillator, the geometry, the energy response to the photon, and the energy
deposit of the proton are described in this section.

184

2.1 BGO scintillator
Bismuth germanate Bi4 Ge3 O12 is a good candidate for the detector element of an electromagnetic
calorimeter to be employed in nuclear and particle physics. Table 1 summarizes the characteristics of thetypical inorganic scintillators. The shorter decay time is better for EM calorimeters since it is desiredin high counting rate experiments. BGO scintillator has a little bit long decay time of approximately
300 ns. The other properties are welcome for the EM calorimeters in the energy region from 10 MeV toa few GeV.
Table 1. Properties of the typical inorganic scintillator. The superscripts f and s stand for fastand slow components, respectively.

density (g/cm3 )radiation length (cm)Molière radius (cm)peak emission λ (nm)relative light output
decay time (ns)hygroscopic

BGO
7.13
1.12
2.23
480
21
300
no

BSO
6.80
1.15
2.63
480
4.4
100
no

PWO
8.3
0.89
2.00
420f , 425s
0.077f , 0.3s
10f , 30s
no

CsI
4.51
1.86
3.53
310f , 420s
1.1f , 3.6s
6f , 30s
somewhat

NaI(Tl)
3.67
2.59
4.13
410
100
245
very

2.2 Geometry of the BGO calorimeter
The BGO calorimeter covers the polar angle from 24◦ to 144◦ . It takes a shape like an egg. The
center of the front face is placed on a prolate spheroid for the forward crystals with the polar angle
smaller than 90◦ . As for the backward crystals with the polar angle larger than 90◦ , the center of thefront face is placed on the sphere like LEPS Backward Gamma detector used in FOREST [3]. The detailsof the geometry for the crystals are described elsewhere [2]. Figure 1 shows the cross sectional view of
the BGO calorimeter. Only the forward 300 crystals (08F–12F) were used at the test experiment carriedout in February 2013.
2.3 Response to the photon
The response to the positrons was measured at the positron beamline for testing detectors at ELPH.
The energy and position resolutions are discussed in ref. [2]. The energy resolution σE /E obtained is!2 2 σ 2
1.058%
0.445%
E2= 0.6316% + p
+
(1)
E
E/GeV
E/GeV
, and the position resolution σx obtained is
σx /mm = 3.07 ± 0.03 (E/GeV)−0.202±0.008, σx /mm = 3.70 ± 0.02 (E/GeV)−0.154±0.005(2)

for the central and peripheral crystals, respectively. Here, the central crystal stands for the crystal
having eight adjacent ones ,and the peripheral stands for the one having only five adjacent ones. Theenergy resolution is shown in Figure 11 of the reference [2] and also in Figure 4. The position resolution
is plotted in Figure 18 of the reference [2].

185

x/y
H11334 (R11265)

B
07 B
06 B
05
B
04
03B
02B
01B
00B
00F
01F
02F
03F
04
05 F
06 F
07 F
F

420

H6524 (R4125)

w2 h

L

B

08

200

w1
F
08 9F F
0 0
1 1F
1
12F

R
photon beam

Fig.1.

z

+400

−200

targetCross sectional view of the BGO calorimeter.

2.4 Energy deposit of the protons
To estimate the minimum energy (momentum) of the protons which penetrate the BGO crystals andthe stopping power (the energy deposit as a function of the travel length, the range was made by using
SRIM2008 [4]. The proton with an energy of 434 MeV (corresponding to the momentum of approximately
1 GeV/c) has a range of 220 mm, which is the length of the BGO crystals. Figure 2 shows the stopping
power dE/dx of BGO scintillator to the proton as a function of the proton velocity.
20

Stopping Power (MeV/mm)

18
16
14
12
10
8
6
4
2
0

Fig.2.

0

0.1

0.2

0.3

0.4 0.5 0.6
Velocity β

0.7

0.8

0.9

1

Stopping power dE/dx (MeV/mm) of BGO scintillator as a function of the proton velocity
β. The data are compared to the equation (3). The velocity ranges from that for theenergy of 0.01 GeV to that for 3.00 GeV.

186

The stopping power of BGO scintillator can be reproduced with an equation:dE= (0.814 ± 0.001 MeV/mm) β −1.550±0.001 ,dx(3)and the similar equation can be found for a plastic scintillator EJ-212:dE= (0.179 ± 0.001 MeV/mm) β −1.704±0.004 .
dx(4)Assuming the stopping power dE/dx to the charged pions is expressed with eq. (3), the minimum energy(momentum) of the protons penetrating the BGO crystals is 253 MeV (290 MeV/c).

§ 3. Expected performance
The kinematics for the single pseudoscalar-meson photon-production processes is summarized,
and the mass resolution and the acceptance with the BGO calorimeter determined by using a MonteCalro (MC) simulation based on Geant4 are discussed.
3.1 Two-body kinematics
The two-body kinematics for the single pseudoscalar-meson photon-production processes γp → π 0 p,
γp → ηp, and γp → η 0 p reactions are calculated for the incident photon energies Eγ = 1.6,2.0AC2.4 GeV.
Figure 3 shows the momentum and emitted angle of the meson, and the momentum and emitted angleof the proton in the laboratory frame as a function of the meson emitted angle in the γp center of massframe for the incident energies of 1.6, 2.0, and 2.4 GeV.
The maximum emitted angle of the proton is approximately 70◦ , which is obtained for the reaction
γp → π 0 p which produces the lightest meson. The maximum emitted angle of the proton for the γp →
η 0 p reaction is approximately 43◦ .
3.2 Reproduction of the energy resolution
To estimate the energy resolution of the BGO calorimeter, an MC simulation based on Geant4
has been develoed. The geometry for the BGO crystals are implemented to fit the designed one which
includes the gap between crystals corresponding to 0.02◦ . The measured energy of a BGO crystal in MC
is determined by smearing the energy deposit in the crystal. The unit energy E 1 corresponding to one
photoelectron is determined from the Gaussian mean µ1 and width σ1 for each crystal and each event.
And the expected number of photoelectrons n is determined by the equation
n=

E
,
E1

(5)

and the actual number of photoelectrons detected n is determined by the random generator for the Poisson distribution [5]. The measured energy in MC is determined from E 1 and n giving the fluctuation
corresponding to the electric noise expressed by the b2 parameter. The µ1 , σ1 , and b2 parameters are
determined so that the MC simulation reproduces the measured energy resolution. The optimum parameters are found to be (µ1 , σ1 , b2 ) = (0.002 MeV, 0.001 MeV, 1.38 MeV). Figure. 4 shows the energy
resolution obtained for the prototype BGO calorimeter with the optimum parameters together with themeasured energy resolution.

Fig.3.

Meson emiited angle (deg)Eγ=2.0 GeV
2

1

-1

-0.5

0
cosθcm

0.5

1
Proton emitted angle (deg)0Eγ=2.0 GeV
2

1

-1

-0.5

0
cosθcm0.5

1
Meson emiited angle (deg)0Eγ=2.0 GeV
2

1

-1

-0.5

0
cosθcm

0.5

1
Proton emitted angle (deg)0Eγ=2.0 GeV
2

1

-1

-0.5

0
cosθcm0.5

1
Meson emiited angle (deg)0Eγ=2.0 GeV
2

1

0

-1

-0.5

0
cosθcm

0.5

1
Proton emitted angle (deg)Proton momentum (GeV/c)

Meson momentum (GeV/c)

Proton momentum (GeV/c)

Meson momentum (GeV/c)

Proton momentum (GeV/c)

Meson momentum (GeV/c)

187

Eγ=2.0 GeV
2

1

0

-1

-0.5

0
cosθcm0.5

1Eγ=2.0 GeV
100

50

0

-1

-0.5

0
cosθcm0.5

10cosθcm0.5

1Eγ=2.0 GeV
100

50

0

-1

-0.5

Eγ=2.0 GeV
100

50

0

-1

-0.5

0
cosθcm0.5

10cosθcm0.5

1Eγ=2.0 GeV
100

50

0

-1

-0.5

Eγ=2.0 GeV
100

50

0

-1

-0.5

0
cosθcm0.5

10cosθcm0.5

1Eγ=2.0 GeV
100

50

0

-1

-0.5

Two-body kinematics for the single pseudoscalar-meson photon-production processes
γp → π 0 p (black), γp → ηp (blue), and γp → η 0 p (red). The upper, central, lower four
panels show the correlations for the incident energies of 1.6, 2.0, and 2.4 GeV, respectively. The momentum and emitted angle of the meson, and the momentum and emitted
angle of the proton in the laboratory frame as a function of the meson emitted angle inthe γp center of mass frame are plotted in each incident energy.

188
0.1
0.09
0.08
Energy Resolution σE/E

0.07
0.06
0.05
0.04
0.03
0.02
0.01
0

Fig.4.

0100

200 300 400 500 600 700
Incident Momentum (MeV)

800

900

Energy resolution obtained for the prototype BGO calorimeter with the optimum
parameters (µ1 , σ1 , b2 ) = (0.002 MeV, 0.001 MeV, 1.38 MeV). The data are comparedwith the red curve corresponding to the measured energy resolution σE /E =q20.6316%2 + 1.058%2 / (E/GeV) + 0.445%2 / (E/GeV) .

3.3 Resolutions for the detected pseudoscalar mesons
The mass, momentum, and angular resolutions of mesons depend on the energies of the photons
from the mesons decay. These resolutions are estimated by the MC simulation for the emitted π 0 , η,and η 0 pseudoscalar mesons. All these pseudoscalar mesons are assumed to decay into two photons witha branching ratio of 100%. The x and y coordinates of the reaction point is determined so that x andy distributions behave Gaussian shape at (x, y) = (0, 0) with widths of σx = 9.0 and σy = 9.6 mm,
respectively. The z coordinate is given uniformly from −20 to +20 mm. The pseudoscalar mesons
are emitted isotropically with the polar angles 84◦ –90◦ , and azimuthal angles −180◦ –+180◦ . Since
the several BGO crystals near the incident position have a certain energy due to the electro-magnetic
shower, these crystals are made into a group called cluster. A cluster has a connected crystals having
a larger than 20 MeV and adjacent crystals to them. The energy of the cluster is given by the sum of
the measured energies of the crystals, and the position is determined by the center of gravity. Figure 5
shows the distributions for the γγ invariant mass, the ratio between measured and generated momenta,
the residual of the polar angles, and the residual of the azimuthal angles. The residual is given by
subtracting the generated value from the measured one.
To estimate the mass resolution, the mean µm and width σm are determined by fitting Gaussianfunctions to the γγ invariant mass distributions. Fitting process is repeated five times in the region[µm − 2σm , µm + 2σm ). The mean µ and width σ are also determined by calculating the averageand standard deviation for the distributions of the ratio between measured and generated momenta,
the residual of the polar angles, and the residual of the azimuthal angles. The calculating process isrepeated five times in the region [µ − 2σ, µ + 2σ). Since a fraction of the photon energy leaks from BGO

0.5
1
pm / p0

1.5

0

400

2000

200

1000

0

0

0

0.5
1
pm / p0-20020δθ (deg)

0

0

0.5
1
pm / p0

0

-20

0
20
δθ (deg)020
δφ (deg)-20020
δφ (deg)-20020
δφ (deg)-20020
δφ (deg)-20020
δφ (deg)

25
0

0

0

0

0

200
100

0

-20

0
20
δθ (deg)

1000
500

250

0.5
1
pm / p0

-20

50

500

500

0

0
20
δφ (deg)

1000

100

100

Counts / 0.01

0

-20

200

250

0

Fig.5.

020δθ (deg)

500

200

500
1000
γγ invariant mass (MeV)

-20

100

0

Counts / 0.5 deg

1.5

0

200

2000

500
1000
γγ invariant mass (MeV)20Counts / 0.5 deg

1.5

40

0

Counts / 0.5 deg

0020δθ (deg)

Counts / 0.5 deg

0.5
1
pm / p0-20Counts / 0.5 deg

0

0

250

Counts / 0.5 deg

Counts / 0.5 deg

0.5
1
pm / p0200

200 400 600
γγ invariant mass (MeV)500Counts / 5 MeVCounts / 0.5 deg

0Counts / 0.01

Counts / 5 MeV

0

0

400

200 400 600
γγ invariant mass (MeV)

500

1.5

Counts / 0.5 deg

0Counts / 0.5 deg

Counts / 5 MeV

500

0

500

200

100

50 100 150 200
γγ invariant mass (MeV)

1000

1.5

Counts / 0.5 deg

0Counts / 0.01

50 100 150 200
γγ invariant mass (MeV)

50

1.5

Counts / 0.5 deg

0

400

500

Counts / 0.01

Counts / 5 MeVCounts / 5 MeV

1000

Counts / 0.01

2000Counts / 0.01

Counts / 5 MeV

189

0

-20

0
20
δθ (deg)

Distributions for the γγ invariant mass (left column), the ratio between measured andgenerated momenta (second column), the residual of the polar angles (third column),
and the residual of the azimuthal angles (right column). The distributions for 200,
2400 MeV/c π 0 mesons, 200, 2400 MeV/c η mesons, and 200, 2400 MeV/c η 0 meson. The
red curves in the invariant mass distributions are fitted Gaussian functions.

190

0.1

15

0.075

10

σP/P

σM (MeV)

20

5

0.025

0

0.05

0

0.5

1
1.5
P0 (GeV/c)

2

0

2.5

7.5
5
2.5
0

0

0.5

2

0

0.5

1
1.5
P0 (GeV/c)

2

2.5

0

0.5

1
1.5
P0 (GeV/c)

2

2.5

0

0.5

1
1.5
P0 (GeV/c)

2

2.5

0

0.5

1
1.5
P0 (GeV/c)

2

2.5

0

0.5

1
1.5
P0 (GeV/c)

2

2.5

0.1
0.075

20
10

0.025

0.05

0

0.5

1
1.5
P0 (GeV/c)

2

0

2.5

10
σφ (deg)σθ (deg)

2.5

5
0

2.5

10
7.5
5
2.5
0

7.5
5
2.5

0

0.5

60

1
1.5
P0 (GeV/c)

2

0

2.5

0.1
40

0.075

σP/P

σM (MeV)

2

7.5

σP/P

σM (MeV)1
1.5
P0 (GeV/c)

30

0

0.05

20

0.025
0

0

0.5

1
1.5
P0 (GeV/c)

2

2.5

7.5
5
2.5
0

0

10
σφ (deg)10σθ (deg)1
1.5
P0 (GeV/c)

2.5

40

Fig.6.

0.5

10
σφ (deg)σθ (deg)

10

0

7.5
5
2.5

0

0.5

1
1.5
P0 (GeV/c)

2

2.5

0

Resolutions for the mass, momentum, polar angle, and azimuthal angle σM , σP /P , σθ ,and σφ . The upper four panels show the resolutions for π 0 mesons, the central show
those for η mesons, and the lower show those for η 0 mesons, The red curves show fitted
functions (8).

191
crystals, the peaks corresponding to π 0 mesons are a little bit lower than the rest masses. The mass
resolution σM is determined by the equation
σM = σm

m0
,
µm

(6)

where m0 stands for the rest mass of the π 0 meson. The ratio between measured and generated momenta
is also lower than 1 due to the shower leakage. The momentum resolution σP /P is given by the equation
σp
σP
=
.
P
µp

(7)

Figure 6 shows the resolutions as a function of the incident photon energy for the mass, momentum,
polar angle, and azimuthal angle σM , σP /P , σθ , and σφ .
The mass, momentum, and angular resolutions σ = σM , σP /P , σθ and σφ are well reproduced by
the equationσ(P0 ) = α

P0
GeV/c

β
+C

(8)

with appropriate parameters α, β, and C. Table 2 summarizes the optimum parameters for describing
the mass, momentum, and angular resolutions σ = σM , σP /P , σθ and σφ .
Table 2. Optimum parameters α, β, and C in equation (8) for describing the mass, momentum,
and angular resolutions σ = σM , σP /P , σθ and σφ . The units of α and C are MeV forσM , those are deg for σθ and σφ . The other parameters are deimensionless.

σM
σP /P
σθ
σφ

π0
η
η0
α
β
C
α
β
C
α
β
C
−193.7(5) 0.0115(3) 204.8(5)−486.5(11) 0.0116(1) 509.7(11) 19.9(15) −0.50(4) 9.3(14)0.0166(6) 0.44(1) −0.0028(6) 0.0099(1)1.17(1) 0.0063(1) 0.0182(2) 1.05(1) 0.0038(2)0.28(9)0.53(12)2.26(9)0.25(1)1.71(4)2.39(1)0.84(2)1.40(2)2.17(2)0.04(2)
1.51(28)
1.66(2)0.11(1)1.91(6)
1.62(0)0.42(1)1.50(2)
1.51(1)

3.4 Acceptances for the pseudoscalar mesons
The acceptances for detecting the pseudoscalar mesons, namely the identifying these mesons with
the BGO calorimeter, are estimated. The pseudoscalar mesons are generated with polar angles ranging
from 0◦ to 80◦ with a 10◦ step. Here, the azimuthal angles of the generated mesons are given uniformly.
The mesons are treated to be detected when the γγ invariant mass is higher than 0.7m0 , where m0
shows the rest mass of the π 0 meson. Figure 7 shows the acceptances as a function of the generated
momentum for π 0 , η, and η 0 mesons.
Since the BGO calorimeter covers the polar angles from 24◦ , only low momentum mesons can bedetected when they are emitted in the forward angles. The opening angle of two photons from the highmomentum π 0 mesons is too small to identify two clusters. The acceptance is lower for the π 0 mesons
having the momentum higher than 1 GeV/c even they are emitted in the backward angles.

192

π

0.75

0

0.25

0

1
Acceptance01
2
P0 (GeV/c)
10 20
η′

30

1

0.75
0.25

0
30

1

1
2
P0 (GeV/c)

1
P0 (GeV/c)
40 50

60

η
1
2
P0 (GeV/c)
70 80

0.5
0

0

1
0.75

0.5
0

60

1
2
P0 (GeV/c)
70 80

0.25

0.25

0

0

1

η
2

0.75

0.5

0

0.75

0.5
0

π

0.5
0

1
2
P0 (GeV/c)
40 50

0.25

0

80

0.25

0.75

0.5

70

0.75

0.5
0

60

1

0

AcceptanceAcceptance1
2
P0 (GeV/c)
10 20
η

0.75

Fig.7.

π

Acceptance

0

1

0

50

0.25

Acceptance

0.25

0

40

0.75

0.5
0

30

1

0

Acceptance20

AcceptanceAcceptance10

Acceptance

0

1

0.5

0.25

0

1
P0 (GeV/c)

η′
2

0

0

η′
1
2
P0 (GeV/c)

Acceptances as a function of the generated momentum for π 0 , η, and η 0 mesons. The
upper, central, lower panels show the acceptances for π 0 , η, and η 0 mesons, respectively.
The left columns show those for the emitted angles of 0◦ (red), 10◦ (green), and 20◦ (blue).
The central show those for the emitted angles of 30◦ (red), 40◦ (green), and 50◦ (blue). The
right show those for the emitted angles of 60◦ (red), 70◦ (green), and 80◦ (blue).

§ 4. Summary
Since the BGO calorimeter has high energy and position resolutions for the photons, it gives ushigh mass, momentum, and angular resolutions for pseudoscalar mesons detected. The acceptance isalso high for the pseudoscalar mesons thanks to its large solid angle covering when they are emitted
in the central and backward angles. The acceptance is lower for the π 0 mesons having the momentum
higher than 1 GeV/c because the opening angle of two photons from the high momentum π 0 mesons
is too small to identify two clusters. The special treatment is required for the analysis of the eventswith high momentum π 0 mesons producing only one cluster. The details of the discussion are described
elsewhere [6].

Acknowledgment
This work was supported in part by Grant-in-Aids for Specially promoted Research (19002003), andfor Scientific Research (A) (24244022).

193

References[1]

H. Nagahiro and S. Hirenzaki: Formation of η 0 (958)-Mesic Nuclei and Axial UA (1) Anomaly at
Finite Density, Phys. Rev. Lett. 94, 232503 (2005).

[2]

T. Ishikawa et al.: New electro-magnetic calorimeter BGO EGG, ELPH Annual Report 2010 Vol. 1,
Tohoku University, 61 (2012).

[3]

T. Ishikawa: Internal GeV-γ Analysis Note HD No. 132B (2009); T. Ishikawa et al.: Research
Report of LNS 42&43, Tohoku University, 1 (2011).

[4]

J.P. Biersack and J.F. Ziegler, SRIM2008, Web site: hhttp://www.srim.org/i.

[5]

T. Ishikawa: Internal GeV-γ Analysis Note No. 01 (2004);[6]

T. Ishikawa: Internal GeV-γ Analysis Note HD No. 322B (2014).

194

ELPH Annual Report, Tohoku University (2011-2013)

Development of a new multi-purpose logic module MPLM4
I. Nagasawa1 , T. Ishikawa1 , H. Hamano2 , T. Hotta2 , K. Mizutani3 , K. Nanbu1 ,K. Takahashi1 , and Y. Tsuchikawa1
1

Research Center for Electron Photon Science (ELPH), Tohoku University, Sendai 982-0826,
Japan

2

Research Center for Nuclear Physics (RCNP), Osaka University, Ibaraki 567-0047, Japan3

Department of Physics, Kyoto University, Kyoto 606-8502, Japan

We have developed a new multi-purpose logic module MPLM4 with an FPGA chip of which theoperating frequency is 200 MHz. The behavior of this module can be described easily by a hardware
description language. The MPLM4 is used as a trigger generator for the photon tagging counters at
SPring-8/LEPS2.

§ 1. Introduction
Meson photoproduction experiments are conducted at super photon ring 8 GeV (SPring-8) by thequark nuclear physics laboratory at ELPH in cooperation with other laboratories. High energy photon
beam is generated by the backward Compton scattering of ultraviolet laser photons from 8 GeV electrons circulating in the SPring-8 synchrotron radiation ring. The energy of the beam is tagged by photon
tagging counters. The photon tagging counters at LEPS2 comprises two layers of plastic scintillator (PS)hodoscopes and two layers of scintillating fiber (SciFi) hodoscopes. Fig. 1 shows the schematic view ofthe photon tagging counters at SPring-8/LEPS2. The PS signals are used to generate the trigger for thedata acquisition and to count up the number of photons, and the SciFi signals are used to determine
the energy of the photon. The trigger is generated by the logic sum of coincidence signals of the corresponding upstream and downstream PS’s. Since an upstream PS corresponds to one or two downstream
PS, the trigger generator is complicated and a set of logic modules for it is thought to be expensive. A
logic module with a field programmable gate array (FPGA) is useful for this kind of purpose because its
behavior is programmable. We had developed a multi-purpose logic module (MPLM) with an FPGA chipof SPARTAN3 with a frequency of 33.3 MHz and with 16 input and 16 output channels. But the numberof input channels larger than 24 and the operating frequency higher than 200 MHz are required for thetrigger generator for the photon tagging counters. Therefore, a newly designed MPLM with an FPGA
chip of Spartan-6, having 36 input and 18 output channels, has been developed.

§ 2. Feature of FPGAAn FPGA is a semiconductor device which is programmable for any logic function by a designer
similarly to an application-specified integrated circuit (ASIC). Since the function of the ASIC cannot

195

PS

SciFi

2.4 GeV

3.0 GeV

3.3 GeVFig.1.

Schematic view of the photon tagging counters at SPring-8/LEPS2. Three arrows indicate
the trajectory of the recoil electrons of the backward Compton scattering corresponding
to the generated photon energy of 2.4, 3.0, and 3.3 GeV.

be changed once it is manufactured, it is difficult to handle an ASIC to implement a specified design
without bugs. On the other hand, the FPGA can be configured like a software on a personal computer
after it is manufactured. It is easy to shorten designing time to obtain the specified logic function bya trial-and-error method. The FPGA contains programmable logic components called logic blocks, andprogrammable interconnects. Logic blocks can be programmed to operate any combination of basic logic
gates (AND, OR, XOR, flip-flops, and so on). The FPGA manufactured by Xilinx contains configurable
logic blocks (CLB), input/output blocks (IOB), block random access memories (RAM), multipliers, anddigital clock managers (DCM). The internal circuit of FPGA is constructed by connecting these elements.
The behavior of FPGA is usually designed with a hardware description language (HDL). Configuration
data of logic blocks and interconnects which are fitted to the actual FPGA architecture are generated by
a FPGA design software. The data are typically downloaded via a Joint Test Action Group (JTAG) link
cable. Since recent FPGA chips have large resources of logic gates and RAM blocks together with a DCM
function, one can implement a fast complicated digital circuit in FPGA.

§ 3. Developed MPLM4
We have developed a new logic module called multi-purpose logic module MPLM4 with an FPGA
chip. It is upgraded from MPLM [1, 2] with large number of modifications. The number of input andoutput channels, the FPGA chip used, the programmable ROM chip used have been changed from MPLM
to MPLM4. The MPLM4 is packaged in a double-width nuclear Instrumentation module (NIM) module.
Fig. 2 shows the design of front panel and the photo of the circuit board of MPLM4. The FPGA used is a
Xilinx Spartan-6, and contains 9,152 logic cells, 11,440 flip-flops (FF), and 576 kbit RAM in total.
This newly developed module accepts NIM standard signals through 36 input and 18 output channels. Since the FPGA itself does not accept the NIM signal, additional level converters between the NIM

196

RESET

01

19

01

02

20

02

03

21

03

04

22

04

05

23

05

06

24

06

07

25

07

08

26

08

09

27

09

10

28

10

11

29

11

12

30

12

13

31

13

14

32

14

15

33

15

16

34

16

17

35

17

18

36

18

JTAG

LED

MPLM4

IN

Fig.2.

IN

LEMO00 connectors
for inputs/outputs

FPGA (Spartan-6)
Power supply
from an NIM cratelevel convertors
OUT

Front panel and photo of the circuit board of MPLM4. The left panel shows the front
panel of the MPLM4, in which 36 and 18 LEMO00 connectors are placed for input andoutput NIM signals, and a JTAG, three LED, and RESET button is placed at the upper
part. The right panel shows the photo of the circuit board of MPLM4.

standard and the Low Voltage Transistor-Transistor Logic Level (LVTTL) signals are employed. The
propagation delay from the input to the output is less than 10 ns, in which the conversion time from the
NIM to LVTTL signals is dominant. Fig. 3 shows the block diagram of the MPLM4. The MPLM4 contains
36 inputs with NIM to LVTTL converters, 18 outputs with LVTTL to NIM converters, a peripheral circuit for the configuration of the FPGA, a clock signal, and three status light emitting diodes (LED). The
clock signal is generated by a crystal oscillator with a frequency of 10 MHz, and the frequency stability
is better than 100 ppm. The FPGA receives a clock signal through a built-in global buffer (GBUF). The
power source for many devices in the MPLM is provided through regulated power supplies as shownin Fig. 3. The MPLM supports the In-System Programming (ISP) through the JTAG interface, and a
FPGA configuration system in a Platform Flash Memory (PROM). This module detects failures of theclock signal and those of power system. An operational amplifier (OPAMP) is operated with a higher
frequency to shorten the leading time of the NIM standard signal (∼3 ns). The input impedance of the
OPAMP is rather low for the FPGA. Nevertheless, the generated signal with the OPAMP meets the NIM
standard although some reflection is observed in a pulse of the signal due to the impedance mismatch.
Since this module is constructed on a four layer printed-circuit board (PCB), the impedance of the powersystem is reduced, which results in the noise level suppressed, in addition the high frequency operation
allows the use of surface-mount components.
The digital clock manager (DCM) in Spartan-6 is a function to implement delay locked loop, digitalfrequency synthesizer, digital phase shifter, or a digital spread spectrum. It enables us to generate 200

197Power Supply
Input±6, ±12 V
Output+3.3, +1.2.
±5.0 V
Level Converter
NIM to LVTTL

Clock
10 MHzDvicesPower Status

PROM for Configuration
XCF04SJTAG Connector

FPGA
Spartan-6
XC6SLX9-3TQ144

×36

Clock Driver
LVT244×18

Level Converter
LVTTL to NIM

DA converter
DAC0800LCN

Analog output

Buffer

LED
LVT125Clock Alarm
Detector

Fig.3.

Block diagram of MPLM4. MPLM4 contains 36 inputs with NIM to LVTTL converters,
18 outputs with LVTTL to NIM converters, a peripheral circuit for the configuration of
the FPGA (Spartan-6), a clock signal, and three status light emitting diodes (LED), andpower supplies. The power supply of ±12 V is required only for MPLM4, and the analog
output is prepared only for MPLM4S.

MHz clock from the incoming 10 MHz clock. The time jitter of the logic is less than 5 ns by using edgealigned signals with the 200 MHz clock. Three MPLM4 modules were produced, and one minor updated
MPLM4S one was manufactured as the second version. The input channels have been changed fromthe negative logic (MPLM4) to the positive logic (MPLM4S), and the analog output has been added in
MPLM4S. The MPLM4S does not use ±12V power supplies any longer.

§ 4. Applications of MPLM4
The first application of MPLM4 is the trigger generator for the photon tagging counters (TAGGER)
at SPring-8/LEPS2. The trigger of TAGGER is generated when corresponding upstream and downstream PS’s respond in coincidence. The trigger generator has the following four functions:
1. twelve coincidence signals between corresponding upstream and downstream PS’s,
2. logic sum of the twelve coincidence signals (trigger),
3. 1/1000 prescaled signal with a width of 50 ns among the twelve coincidence signals, and
4. logic sum of all the input channels.
The input channels from 1 to 12 receive the upstream PS signals, and those from 19 to 30 receive thedownstream PS ones. The output channel i gives the logic sum of two coincidence signals between input
channels i and i + 18 and between input channels i and i + 19 for i = 1, 2, . . . , 11. The output channel
12 gives the coincidence signal between input channels i and i + 18. The output channels 13 and 14 givethe logic sum of these twelve coincidence signals, and those 15 and 16 give 1/1000 prescaled signal witha width of 50 ns among the twelve coincidence signals. The output channel 17 gives the logic sum of all
the input channels from 1 to 12 and from 19 to 30. The latency (time interval between the stimulation
and response) of the output channels from 1 to 14 is 40 ns, and that for the output channels 15 and 16 is198

55 ns.
The second application is a trigger handler of the LEPS2 experiments with a BGO calorimeter. The
trigger handler has the following four functions:
1. 0.5 and 0.1 Hz clock signals with a width of 200 ns for the scaler trigger,
2. fanin-fanout logic to generate and distribute the DAQ busy signal,
3. event tag generator, and
4. scaler trigger handler.
The 0.5 and 0.1 Hz clock signals are used as request signals for the scaler triggers. The accept signals of
the scaler triggers clear the waiting time of these clock signals. The output channels 13 and 14 provide
the 0.5 and 0.1 Hz clock signals, respectively. The fanin-fanout logic for the DAQ busy signal is used tosynchronize the several collector subsystems. The input channels from 1 to 16 and the output channels
15 and 16 are used. The event tag generator is a four-bit binary counter of the accept signals of thedata acquisition, and is used to check event consistency between the digitized data fragments acquiredwith different collector subsystems. The input channel 17 receives the request signal for the counterincrement, and the input channel 18 receives the clear signal of the counter. The output signals from
1 to 4 and from 5 to 8 give the level outputs of the event tag, and the output signals from 9 to 12 givethe pulse outputs of the event tag. The scaler trigger handler controls the scaler trigger so that all
the collector subsystems collect the data fragments corresponding to the same event in the same order.
The input channels from 19 to 32 receive the clear signal (Clr) from each collector subsystem which is
generated when all the readout process for the scaler trigger finishes. The input channel 35 and 36
receive the request signals (Req) for the scaler trigger, and the busy signal (Bin) for the standard trigger,
respectively. The output channels 17 and 18 send the accept signal (Acc) and busy signal (Bout) for the
scaler trigger. Fig 4 shows the state machine of the scaler trigger handler.
The third application is a beam profile monitor (BPM) for the GeV-γ beamline [3]. The BPM consistsof two PS’s, an Al convertor placed between them, and two layers of the SciFi hodoscopes. The upstream
PS vetoed online charged particles which are generated in the materials on the beamline. The convertor
creates a positron and electron pair from a photon. The downstream PS is used to form the trigger of thedata acquisition. The trigger condition is described as
Gv ⊗ Gt1 ⊗ Gt2(1)

where Gv stands for the signal from the upstream PS, and Gt1 and Gt2 denote the signals from two
photomultiplier tubes connected with the downstream PS. The responding upstream and downstream
SciFi’s determine the y and x positions of the penetration of the pair. Each SciFi measures a crosssection of 3 mm2 , and determines x or y position in a 3 mm step. Fig. 5 shows the schematic view of thecurrent BPM.
The data acquisition system was originally implemented to MPLM2 which is a special modified version of MPLM and has 36 input channels and 4 output channels. The system can make two dimensional
histogram for the photon beam position with a dead time of 45 ns (3 clocks) for an event. Since we have
only one MPLM2 and we cannot manufacture it anymore, the data acquisition system has been imple-

199

any staterequest wating statewhen
DAQ busy = 1

when
Req = 1

initial statewhen
DAQ busy = 0

ready state
Acc = 1
wait 60 ns
Acc=0
wait 0.5 Hz clock
Bout=0when
Bin = 1

wait 60 ns
Acc=1
wait 60 ns
Acc=0clear wating state
when
all Clr=1

Fig.4.

Bout = 1
wait 300 ns

wait 60 ns
Bout=0State machine of the scaler trigger handler. The condition which makes the state transition is described in the left of an arrow, and the behavior in the transition state is
described in the right. The details are described in the text.

mented to MPLM4. The concept of the implementation to MPLM4 is the same as that to MPLM2, but
the architecture has been newly constructed and is completely different from the original one. The system is designed as a stand alone one, and is composed of a communication and a data acquisition parts.
To control the system, the communication between MPLM4 and a personal computer (PC) are made by
the RS-232C serial interface. The TxD and RxD signals of the RS-232C for the data transmission are
generated and received by converting to a NIM standard ones, respectively. MPLM4 receives Gv, Gt1,
Gt2, and 32 SciFi logic signals which are generated by discriminator modules from the analog signalsof them. The position is determined from the responding x and y SciFi’s when the trigger condition issatisfied, the number of responding x SciFi’s (Nx ) is 1, and that of responding y SciFi’s (Ny ) is 1. The
number of counts in each position is stored in a block read access memory (BRAM). The number of clock
signals, that of trigger request signals, that of trigger accept signals, that of Nx Ny = 0 events, that ofNx Ny = 1 events, that of Nx Ny = 2 events, and that of Nx Ny > 2 events are stored in a distributed
read access memory. To clear, transmit the number of these counts, start, stop counting up are controlled
by PC through the RS-232C interface. The 8-N-1 (eight data bits, no parity bit, and one stop bit) and
115.2 kbps are adopted for the serial data transmission. It takes approximately 91 ms to send the histograms from MPLM4 to PC. The dead time processing an event is 20 ns (4 clocks) in the new version of
BPM, where one more clock is used to confirm the trigger condition in a safe manner. The typical beamprofile obtained can be found in elsewhere [3].

200

Scintillating Fiber
Hodoscopes
Trigger Counter
Al Converter
Veto CounterFig.5.

Schematic view of the current BPM. It consists of two plastic scintillators (PS) with athickness of 1 mm. A 0.5 mm thick Al plate is used as an e+ e− converter. Scintillatingfiber (SciFi) hodoscopes are placed at downstream of the PS’s. Each hodoscope has 16
SciFi’s with a square of 3 mm, two layers of SciFi hodoscopes cover the active area of48 × 48 mm2 .

§ 5. Summary
A new Multi-purpose Logic Module MPLM4 has been developed. This kind of module is necessary
to handle digitized data efficiently. The MPLM4S module is used for the trigger generator of the photon
tagging counter at LEPS2, and MPLM4 modules are used for the trigger handler at LEPS2 and the highspeed beam profile monitor at ELPH [3].

References[1]

K. Nanbu and T. Ishikawa: Internal GeV-γ Analysis Note No. 223A (2011).

[2]

K. Nanbu, T. Ishikawa and H. Shimizu, Development of a Multi-Purpose Logic Module with the
FPGA, Research Report of LNS 40, Tohoku University, 27 (2008).

[3]

H. Fujimura et al., Development of a Beam Profile Monitor for GeV-γ Beamline, Research Reportof LNS 42&43, Tohoku University, 144 (2011).

ELPH Annual Report, Tohoku University (2011-2013)

201

Feasibility studies at the SCRIT Electron Scattering
FacilityToshimi Suda1 , Tatsuya Adachi2 , Tatsuya Amagai1 , Akitomo Enokizono3 ,Masahiro Hara2 , Toshitada Hori2 , Shin’ici Ichikawa2 , Ryoya Kitazawa1 ,Kouji Koizumi3 , Kazuyoshi Kurita3 , Niklas Lundkvist1† , Takaya Miyamoto1 ,Ryo Ogawara3 , Tetsuya Ohnishi2 , Yuto Shimakura3 , Hiroki Takehara4 ,Tadaaki Tamae1 , Seiichi Tamaki3 , Mamoru Togasaki3 , Teruaki Tsuru1 ,Shuo Wang14 , Kayoko Yanagi1 , Shunpei Yoneyama1 ,and Masanori Wakasugi2
1

Research Center for Electron Photon Science, Tohoku University, Sendai, 982-0826
2
3

4

Nishina Center, RIKEN, Wako, Saitama,351-0198

Department of Physics, Rikkyo University, Tokyo, 171-8501

Department of Electrical Engineering, Nagaoka University of Technology, Nagaoka, Niigata,940-2137

During the years of 2011 to 2012, a series of experiments at the SCRIT electron scattering facility
to study facility performances, such as achievable luminosities, has been carried out immediately after
completion of its construction. Using stable nuclei as the trapped targets, 133 Cs and 132 Xe, the minimum
required luminosity for elastic electron scattering, ∼ 1027 /cm2 /s, has been proved to be achievable atthis facility. The world’s first researches of the internal structure of exotic nuclei by electron scattering
will soon start when an electron spectrometer system and an ISOL based on photo-fission of uranium
are ready.

§ 1. Introduction
A brand-new electron scattering facility, SCRIT Electron Scattering Facility, was being constructed
at RIKEN RI Beam Factory, Japan, and it has partly started its operation since the year 2010. Thisis the world’s first electron scattering facility dedicated to the structure studies of short-lived nuclei.
The goal of this facility is to determine the charge density distributions of short-lived nuclei by elastic
electron scattering.
Electron scattering is one of the most powerful tools of the structure studies of atomic nuclei. Indeed, it has consistently played a key role in our understanding of the nuclear structures. A well-known
textbook-style example is the charge density distributions of stable nuclei precisely determined by elastic scattering [1]. They are the one of the fundamental ground state properties of atomic nuclei, and have∗

Present address: School of Space Science and Physics, Shandong University, Weihai, China†

Present address: School of Physics, Uppsala Universitet, Uppsala, Sweden

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been essential testing ground of nuclear structure theories. Ever since the Nobel-prize experiments by
R. Hofstadter and his colleagues about a half-century ago [2], elastic scattering has remained the one
and only way to determine the charge density distributions.
So far, electron scattering experiments have been limited to stable nuclei, with some exceptions suchas 3 H having rather long lifetimes. No experiment has been ever attempted for highly unstable nuclei,
in some of which peculiar structures such as halo, skin, magicity loss and appearing new magic numbers
were observed or identified. Due to the obvious advantages of electron scattering for the structurestudies [3], application of electron scattering to the structure studies of exotic nuclei has been longawaited.
The difficulty of applying electron scattering to highly unstable nuclei is a target preparation due totheir short lifetimes and difficulty of their production. One way to overcome this difficulty, and believed
to be the only way, is to employ a collider between an electron beam and a beam of exotic nucleus. The
invention of an alternative way discussed in this paper, however, changed this situation completely.
About 10 years ago, we proposed a novel target-forming technique for the electron scattering experiments of short-lived nuclei [4]. The technique, named SCRIT (Self-Confining RI Target), uses theion trapping phenomena to keep target exotic nucleus on the electron beam. The ion trapping is generally a problematic phenomenon at electron storage rings. Residual gases ionized by circulating electron
beam at electron storage rings are trapped by the electron beam itself. Electrons are scattered off by
the trapped ions resulting shorter beam life. When the ion trapping becomes severe, beam instability iseven invoked.
Our idea is to trap short-lived target nucleus on a high-energy electron beam by using this ion
trapping in a positive way. A proof-of-principle experiment of the SCRIT scheme has proved that thisscheme works and provides the luminosity required for the elastic electron scattering experiments [5, 6].
Based on the success, we have started the construction of the world’s first electron scattering facility,
the SCRIT Electron Scattering Facility, dedicated to the structure studies of short-lived nuclei in 2009.

§ 2. The SCRIT Electron Scattering Facility
2.1 Facility overview
Figure 1 shows a floor plan of the SCRIT electron scattering facility. It consists of an electron
accelerator, an ISOL system for neutron-rich isotope production and an electron spectrometer. The
electron accelerator consists of a 150-MeV injector racetrack microtron and a 700-MeV electron storage
ring equipped with the SCRIT system. The stored electron beam energy is variable from 150 MeV to 700
MeV. The stored beam current as of today is 300 mA with a beam lifetime over 200 min..
2.2 The SCRIT system
Figure 2 shows the SCRIT system installed in the straight section of the storage ring. The system
consists of a set of deflectors for ion injection and ejection, three electrodes and a trapped-ion analyzer.
Two sets of beam scrapers and two sets of button-type beam position monitors (BMPs) are installed

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Fig.1.

The SCRIT electron scattering facility

along the electron (and ion) beam line. The electrodes at both ends form a mirror potential to keep theions longitudinally inside the SCRIT device, and the central electrode with a length of 500 mm is to trap
the ions with the kinetic energy of an order of a few eV.
The pulsed ion beam from the ISOL is transported through the deflector and merged with the stored
electron beam. The ions are introduced inside the mirror potential by controlling the voltage of theentrance electrode, and they are trapped on the electron beam. After a certain trapping time for electron
scattering experiments, they are ejected from the potential to refresh the (short-lived) target ions. The
trapped-ion analyzer is used to measure their charge state of the ejected ions . By controlling the voltage
applied to the electrodes for the mirror potential, one easily controls ion injection and ejection, andthereby the ion-trapping period being essential for targeting short-lived nuclei.

Fig.2.

The SCRIT device.

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2.3 ISOL (ERIS)An ISOL system, ERIS (Electron-beam-driven RI Separator for SCRIT) [7] to produce neutron-richnuclei via the photo-fission process of uranium is being under construction. The long beam lifetime ofthe stored electron beam, typically two hours, enables us to use the microtron as a driver for the ISOL.
This ISOL system makes it possible to operate this facility completely independent to the other facilitiesof the RI Beam Factory.
Production of short-lived nuclei is carried out by bombarding a uranium carbide target, , 238 UCx ,with the150-MeV electron beam. Photo-fission (and electro-fission) of uranium is known to be an efficient
way to produce medium-heavy neutron-rich nuclei, such as Sn isotopes including 132 Sn [8].
Photo-fission of uranium is mainly induced by the excitation of the giant dipole resonance of 238 U
at Eγ ∼ 15 MeV. The GEANT simulations show that the photo-fission rate per unit beam power for the
optimized target geometry does not strongly depend on the incident electron energy; ∼108 fission/watt.
After the beam-power upgrade to 1 kW, fission rate of ∼ 1011 /s is expected to result in the production
rate of 132 Sn is about 109 /s.
2.4 SCRIT electron spectrometer
During the period of 2011 to 2012, the design and construction efforts of a new electron spectrometer
were made. Their detailed will be described in a report by Tamae to be submitted in this volume of the
ELPH report. For self-containment of this report, however, a brief description on the spectrometer will
be given.
The electron spectrometer, as shown in Fig. 3, consists of a dipole magnet and a set of drift chambers
at both the entrance and the exit of the magnet to measure the trajectories of scattered electrons.
n electron spectrometer has been constructed and its commissioning will soon start. It consists ofa dipole magnet and a set of drift chambers at both the entrance and exit of the magnet to measure thetrajectories of the scattered electrons. In order to measure the elastic scattering cross section, the spectrometer must have the momentum resolution better than ∆p/p ∼1 x 10−3 . This resolution is needed
to identify the elastic scattering events from those of inelastic scattering. In addition, the spectrometershould cover a wide range of scattering angle 30-60 degrees enabling one to measure an accurate angular distribution, and have enough acceptance of scattered electrons from the spatially extended target,∼500 mm, along the electron beam. This angular coverage corresponds to the momentum transfer range
from 80 MeV/c to 300 MeV/c for the electron beam energies of 150 MeV and 300 MeV. The effect of the
field leakage to the circulating electron beam must be minimized.
In order to fulfill these requirements, detailed calculations were carried out using The OPERA3D calculations [9]. Finally, a window-frame type dipole magnet is employed with a gap of 170 cm(width) × 29 cm (height) ×140 cm (length). The window-frame type magnet is known to provide theuniform magnetic field distribution over the whole gap region. It is found by the calculations that two
field-clamps at each side are needed to minimize the field leakage, a few Gauss, at the position of thecirculating electron beam.

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Fig.3.

SCRIT Electron Spectrometer§ 3. Performance studies of the facility
In the years of 2011 to 2012, the electron accelerators equipped with the SCRIT device have been
completed and their commissioning has started. The design studies of ISOL and the electron spectrometer were under ways. Immediately after the commissioning of the electron accelerators, a series of
performance studies of the whole facility has been conducted immediately. One of the most importantstudies was to study the luminosities achievable at the new facility. The electron beam energy has been
fixed to 150 MeV during the studies.
Since the ERIS device was under construction, stable ions were used instead of unstable nucleus.
One was 133 Cs from the ion source used in the proof-of-principle study [5, 6]. When the ion-beam transport line from the ERIS was completed, a natural Xe gas was used as a target. Stable 132 Xe ion was
mass-separated and was used.
The electron magnetic spectrometer was not also available, thus the electron detection system usedin the previous study [5, 6] was employed. It consists of pureCsI calorimeters and a drift chambers.
This electron detection system does not show the energy energy resolution required to resolve elastic
scattering events unambiguously.
3.1 Study using stable Cs and Xe ions
The first study immediately after the accelerator commissioning was conducted using stable 133 Csions. The ion source of the surface-ionization type used in the KSR study was attached to a temporarilybuild ion-beam transport line.
After completion of the ion transport line from the ISOL, named ERIS (Electron-beam-Driven RI
Separator for SCRIT), we started to use the ERIS instead of the ion source used at the Cs study. Natural
Xe gas ionized at ERIS were pulsed, accelerated to 6.05 kV, mass-separated and then they were transported in a long transport line to the SCRIT system. Here it is interesting to note that no elastic electron
scattering data is available for even stable Xe isotopes, probably due to difficulties of preparation of

206

isotopically-separated Xe target. It is now easy to perform such measurement for even stable nucleus at
the SCRIT facility.
A pulsed 133 Cs1+ or 132 Xe1+ ion beam with the pulse width of 300 µs and kinetic energy of 6.05 kV
was transported to the SCRIT system. Optimization of the spatial overlap between the electron beamand the injected Cs ions was done by detecting events by a pair of plastic scintillators placed closed to thebeam line. It detected events originated from elastically scattered electrons at an ultra-forward angle,
where the elastic cross section is huge.
Electron Detectors
calorimeter
drift chamber

Luminosity
MonitorFig.4.

Set up for luminosity determination using elastic scattering events.

Ion-trapping cycles were repeated at a frequency of 20 Hz at the storage beam current of about 200
mA. In order to mimic the target with short-lived nuclei, the trapping time was set to 45 ms. The ionswere injected every two cycles by controlling the grid of the ion source for repetitive measurements ofthe scattered electrons under conditions with and without the trapped Cs ions.
For precise luminosity determination, we measured the elastically scattered electrons from thetrapped ions. The scattered electrons were detected by a drift chamber and a pure CsI calorimeteras in the KSR study [6], as shown in Fig. 4. The precise scattering angle and reaction vertices were
determined from the electron trajectories measured by the drift chamber. Knowing the electron energy
measured by the calorimeter, elastic events from the trapped ions could be identified. Since the elastic
cross section is known, one can determine the achieved luminosity.
Figure 5 shows the vertex distribution and the energy spectra of the detected electrons with andwithout the trapped ions. Here, electrons whose energies are over 100 MeV were used for this plot. A
clear enhancement due to the trapped ions was seen in the vertex distribution, Fig.5 a) and c) , whichis consistent with the ion-trap region set by the electrodes. The sharp peaks observed at -350 mm, -150mm and 400 mm were attributed to beam halos hitting the thick terminal electrodes. The upper panels
in Fig.5 a) and c) show the vertex distribution where the contribution from the trapped ions, where
ion-off distributions were subtracted. Electrons from only the trap region are seen, and the beam-halocontribution disappears. The vertex dependence is found to be consistent with the angular dependenceof the elastic cross section.
Figure 5 b) and d) show the energy spectra of the detected electrons with and without the trapped
ions. Note that their vertices are limited in the trapping region. The spectrum shape of the subtracted
events, shown in the upper panel in Figure 5 b) and d) , is consistent with the detector response simulated

207

Fig.5.

Electron vertex distribution and energy distributions for 133 Cs ( a) and b)) and 132 Xe ( c)and d)). Solid (dashed) lines show the distributions measured with (without) trapped Cs
or Xe ions. The scattered electrons, whose energies are larger than 100 MeV, are selected.
The upper panel in figure a) and c) show the subtract vertex distributions. Figure b) andd) are the scattered electron energy spectra, whose vertices are in the trapped region. The
upper panel in figure b) and d) show the subtracted energy spectrum with the detector
response for Ee =150 MeV simulated by Geant3.

by GEANT for 150 MeV electrons. Thus, they are concluded to be those from elastic scattering. It should
be noted here that a contribution from inelastic scattering is safely neglected under the momentum
transfer discussed here.
Figure 5 shows the accpentace-corrected angular distribution of the observed elastic events for132

Xe, as an example, where the vertical axis denotes Ldσ/dΩ. Note that the measurements were only

a few hours. The solid line shows the results of a fit of the data with an elastic cross section calculatedby the distorted wave calculation, DREPHA code [10], where the fitting parameter is the luminosity L.
Detailed analysis including a DWBA calculation using figured out that the absolute luminosity achieved
were 9× 1026 /cm2 /s and 4× 1026 /cm2 /s for Cs and Xe, respectively. The number of injected Cs ions was
2 × 109 /s on average, and about 17 % of them were found to contribute to the collision luminosity.
This is closed to the luminosity required for elastic scattering for short-lived nuclei. We, thus,
concluded that elastic electron-scattering experiments for short-lived nuclei are feasible at the SCRIT
electron scattering facility.

§ 4. Luminosity Monitoring
In the studies for Cs and Xe discussed above, the luminosities were determined by the measurements of the elastic scattering cross section from the stable nuclear targets. This was possible since theircharge density distributions were well known or one can estimate it reasonably from the systematics,
thus one can calculate the elastic cross section. Nevertheless to say, however, one needs to measure, for208

Fig.6.

Xe angular distribution. The line denotes the result of DWBA calculation.

exotic nuclei, the elastic scattering cross section for determination of their charge density distributions.
One needs, therefore, to measure luminosity independently from the elastic cross section measurements,
and importantly within a reasonably short time.
Among possible reactions for the luminosity determination where any detailed internal structureof the target exotic nuclei are not important, we take the bremsstrahlung process. The bremsstrahlung
process is pure electromagnetic process between electron and atomic nuclei, and its cross section is wellunderstood. The bremsstrahlung photons are strongly forward peaking, typically θ = me /Ee = 1.7 mrad(σ) for Ee = 300 MeV, which enables us to detect the most of bremmstrahlung photons produced at thetrapped ions at the downstream of the SCRIT region.

Pb
Cer glassenk
ov

Fig.7.

Bremsstrahlung luminosity monitor currently used.

A luminosity monitor system consisting of a position detector and a calorimeter, shown in Fig. 7,
was placed at 670 cm downstream from the center of the SCRIT device. The position detector consistsof two identical fiber-scintillator detectors that cross each other and is placed in front of the calorimeter.
Each detector has 16 optically isolated fiber scintillators (BFC-10) of 2 × 2 mm2 cross-section areas with
1 mm spacing, and they are coupled to a 4 × 4 multi-anode PMT (Hamamatsu H6568). The calorimeteris a Pb-glass Cerenkov detector. The size of the Pb glass is 100 × 100 × 300 mm3 , and the glass is coupled

209

to a 5” phototube (Hamamatsu R1250). In front of the position detector, a Pb collimator of 50-mmφ isplaced to limit the angular acceptance and and a thin plastic scintillator follows to remove any charged
particles produced upstream of the luminosity monitor, whose effect is shown to be not significant.
800
VerticalHorizontal

Events

600

400

200

0
-40

-20

0

20

40

Position (mm)Fig.8.

Spatial distribution of the bremsstrahlung (Eγ ≥ 100 MeV)

Figure 8 shows a typical example of the spatial distribution of the bremsstrahlung. The stored
electron energy is 300 MeV. The solid (open) circles show the distributions in the vertical (horizontal)
direction. Since background bremsstrahlung due to collisions with residual gases in the storage ring isinevitable, bremsstrahlung measurements with and without the target Cs ions are alternately repeatedfor background subtraction.
A Geant4 simulator of the luminosity monitor is prepared, and the simulator estimate the acceptance of the monitor system with a 50-φ Pb collimator and correct for the effect of the detection thresholdof the calorimeter having a rather poor energy resolution.
Figure 9 shows the comparison between the two luminosities, independently determined by thebremsstrahlung luminosity monitor and by the measurement of elastic scattered electron from thetrapped stable Xe ions. This result shows that two luminosities determined independently are consistent, though the agreement is not perfect. Possible reason for this is considered to be a difficulty tocontrol or account for the effect of the energy threshold of the Pb-glass Cerenkov calorimeter, whoseenergy resolution is quite poor, to estimate the bremsstrahlung cross section.
In order to improve this, a new calorimeter consisting of pure CsI crystals is under discussion. Much
improved energy resolution of the new calorimeter will ensure the accurate treatment of the threshold
effects in the integration of the bremsstrahlung cross section. Figure 10 shows a proposed new luminosity monitoring system.

210

Fig.9.

Luminosities determined by bremsstrahlung luminosity monitor and elastic scatteredelectron measurement.

pureC

Fig.10.

sI

A new bremsstrahlung luminosity monitor

4.1 possible new research opportunity at the SCRIT facility
Recently, a new research possibility at the SCRIT electron scattering facility was pointed out: themeasurement of the total photoabsorption cross section of short-lived nuclei [11].
It is well known that the inelastic electron scattering cross section at the forward angle, θ ∼ 0, offers
the same information as nuclear excitation by real photons [12]. We intend to measure the inelastic crosssection at the forward angle to determine the photonuclear response of short-lived nuclei in the photon
energy range from a few MeV to 40 MeV to cover the giant dipole resonance. Assuming a luminosityof 1027 /cm2 s, the estimated counting rate of photonuclear reaction for Sn isotopes in the giant dipole
resonance region is shown in Fig. 11. The measured photo absorption cross section for 124 Sn [13] isused for the estimation, and the virtual photon theory by Onley [14] is employed to calculate the virtualphoton spectrum.
Inelastically scattered electrons at extremely forward angles will be momentum-analyzed and detected in the bending magnet of the storage ring in coincidence with nuclear reaction products such as

211

neutrons. A feasibility study for detecting lower-energy electrons inside the dipole magnet has alreadybeen initiated.

Fig.11.

The expected photo absorption rate in the giant dipole resonance region of Sn isotope(solid line) at the luminosity of 1×1027 /cm2 /s and the virtual photon spectrum. The virtual photon spectrum calculated is shown in the dashed line. The total photo absorption
cross section for 124 Sn [13] is used.

§ 5. Conclusions
The SCRIT electron scattering facility will open a completely new research field in nuclear physics:
the structure studies of short-lived nuclei by electron scattering. The primary goal of this facility is todetermine their charge density distributions for the first time by elastic electron scattering.
During the years of 2011 to 2012, a series of experiments at the SCRIT electron scattering facility
has been attempted to study facility performances, such as achievable luminosities. Using stable nuclei
as the trapped targets, 133 Cs and 132 Xe, the minimum required luminosity for elastic electron scattering,∼ 1027 /cm2 /s, has been proved to be achievable at this facility.
In parallel to the feasibility studies, the design of a high-resolution and large-acceptance spectrometer has been carefully undertaken, and its construction of a window-frame dipole magnet has been
completed in the year 2012. After the precise field measurement of the spectrometer being essential
to realize the high momentum resolution of 10−3 , the dipole magnet has been installed at the SCRIT
electron scattering facility in the end of the FY 2013 (March 2014).
The world’s first researches of the internal structure of exotic nuclei by electron scattering will soon
start when an electron spectrometer system and an ISOL based on photo-fission of uranium are ready.

Acknowledgment
This work is supported by Grants-in-Aid for Scientific Research (S) (Grants No. 22224004) from
JSPS.

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References[1]

H. deVries, C.W. deJager and C. deVries, At. Data Nucl. Data Tables 36(1987) 495.

[2]

B. Hahn, D.G. Ravenhall and R. Hofstadter, Phys. Rev. 101 (1956) 1131.

[3]

T. deForest Jr., and J. D. Walecka, Adv. in Phys. 5 (1966) 1.

[4]

M. Wakasugi, T. Suda and Y. Yano, Nucl. Instrum. Methods A532 (2004) 216.

[5]

M. Wakasugi et al., Phys. Rev. Lett. 100 (2008) 164801.

[6]

T. Suda et al., Phys. Rev. Lett. 102 (2009) 102501.

[7]

T. Ohnishi et al., Nucl. Instrum. Methods, B317, (2013) 357.

[8]

D. De Frenne et al., Phys. Rev. C29 (1984) 1908.

[9]TOSCA, Vector Fields Ltd, Oxford, England.

[10] B. Dreher, DREPHA : a phase-shift calculation code for elastic electron scattering, communicatedby J. Friedrich.
[11] T. Suda et al., Prog. Theor. Exp. Phys. 03C008(2012).
[12] C. A. Bertulani, Phys. Rev. C75, 024606 (2007).
[13] B. L. Berman and S. C. Fultz, Rev. Mod. Physics 47, 713 (1975).
[14] P. Durgapal and D. S. Onley, Comp. Phys. Communication 32, 291 (1984).

ELPH Annual Report, Tohoku University (2011-2013)

213

A large-acceptance Magnetic Spectrometer for Electron
Scattering off Unstable Nuclei
T. Tamae1 , T. Adachi1 , T. Miyamoto1 , and T. Suda1
1

Research Center for Electron Photon Science, Tohoku University, Sendai, 982-0826

A large acceptance magnetic spectrometer has been constructed, which is used for electron scattering off unstable nuclei at RIKEN RI Beam Factory. The spectrometer consists of a large window-frame
rectangular dipole magnet and has no focal plane. The momentum of electrons up to 300 MeV is determined with a momentum resolution of ∆p/p ∼ 10−3 through the tacking of electrons in the magnetic
field. The design and construction of the spectrometer is briefly introduced in this report.

§ 1. Introduction
Electron scattering is a useful tool for investigation of the nuclear structure; a lot of experiments
were performed on stable nuclei, but no experiments on short-lived nuclei due to difficulty of target
preparation. A unique technique named SCRIT (Self-Confining Radioactive isotope Ion Target) [1–3]
has opened the opportunity of the experiment, where target ions are trapped using the electric field
induced by electrodes and the electron beam in a storage ring. The feasibility of the SCRIT system has
been proved using stable nuclei, 133 Cs and 132 Xe [4, 5]. (See also a report written by Suda et al. in this
ELPH Report.)
A magnetic spectrometer is necessary to distinguish elastic events from inelastic ones; the firsttarget of our experiments is to measure the charge distribution of short-lived nuclei such as 132 Sn. The
spectrometer requires several essential conditions:(1) maximum field flux density: 8,000 G; the orbit radius is 1.25 m for electrons with 300 MeV,
(2) momentum resolution: ∆p/p ∼ 10−3 ,(3) large solid-angle: ∆Ω ∼ 100 msr ,(4) wide angular range: 30◦ ∼ 60◦ ; it is important to measure the angular distribution out of theerror of the luminosity monitor.

§ 2. Design Study
Conceptual design studies using a transfer matrix and Monte Carlo simulations chose a rectangular dipole magnet of window-frame type as a spectrometer that satisfies the above conditions. The
spectrometer has no focal plane, therefore the momentum and vertex point are fixed by trajectory tracking using position information obtained by drift chambers. Uncertainties caused by multiple scatteringand position errors of the detectors give the limit on a momentum resolution of ∆p/p ∼ 10−3 . As shown214

in Fig.1 the spectrometer is set parallel to the electron beam, and a strong edge-focusing in the verticaldirection works to enlarge the vertical acceptance.

Fig.1. Layout of the spectrometer system.

2.1 Magnet yoke design
Final parameters of the spectrometer are shown in Table 1. The aperture size of the magnet wasdetermined to satisfy the conditions listed in Introduction. Magnetic field distributions for low-carbon
steel (AISI-1010) and carbon steel (SS400) calculated using OPERA-3D code [6] were compared, andthe low-carbon steel was selected for the pole and return yoke in order to satisfy uniform magnetic fieldin the aperture. In addition, the permeability of the low-carbon steel is more reliable than that of the
carbon steel. Pole edges were cut by 10 cm with 45◦ to ease the field saturation at the corner. The magnet
yoke was separated in 6 solid blocks: two for each of upper and bottom yokes and two side yokes.
Other subjects shown bellow were considered:(a) optimum steel volume as to the field saturation and cost,(b) inference of hollow of the coil and spaces between every turn of the coil,(c) inference to the magnetic field from the spectrometer supporting stage,(d) inference to the magnetic field from the hole for an NMR cable.
2.2 Field clamps
As shown in Fig. 1, the magnet is very close to the circulating electron beam in the storage ring. The
closed- orbit distortion (COD) calculation required less than 10 G for the magnetic field on the electron

215

Table 1. Parameters of a window frame type magnet.
Apertureheightwidth
lengthMagnetic flux density
Bending radius
Angular range
Solid angle
Weight

29 cm
171 cm140 cm
0.8 T (max)
1.25 m30◦ ∼ 60◦
77 msr
46.6 tonbeam. Several types of field clamps were compared using OPRA-3D code, and the field clamp composedof two plates of carbon steel (SS400) were adopted; the inner plate has a return path to the yoke ateach of upper and lower ends, and the outer plate has no return (Fig.2). The final result shows that hemagnetic field calculated using OPERA-3D is 6.5 G along the electron beam in the storage ring. The
value is within acceptable levels for the stray field at the beam position.
3.6
3.2

C

FC

10

A

29

10

A
C

FC

17

Fig.2. Structure of magnet front. A: magnet yoke, C: coil, FC: field clamp.

2.3 Coils
Bedstead coils of copper were constructed for the window-frame magnet (Fig.3); coil heads are bent
to fill the entire side with conductor and to leave the whole space of entrances for measured electrons.

216
The coil consists of upper and lower ones. Each coil has 112 turns (8 layers × 14 rolls). The cross sectionof hollow conductor is 16 mm square with 10 mm hole in diameter for water-cooling. Each turn of coils
is insulated with epoxy impregnated glass fiber tapes. An entire length of coils is electrically connected,
and every two layers are separated for water-cooling.

Fig.3. Bedstead-type coil.

2.4 Supporting stage
As shown in Fig.1, the space between the spectrometer and the vacuum chamber of SCRIT is narrow, and access to front detectors and the SCRIT chamber is hard. The problem is removed by a movablestage; the magnet set on the upper stage can be moved along linear rails by 1.5 m on the base stage. It
is convenient also for the setting of rear detectors.

§ 3. Field Simulations using OPERA-3D CodeResults of field simulations using the OPERA-3D code are briefly introduced. The coordinate system
is shown in Fig.8; it is the right-handed system with the origin at the center of the magnet, the xcoordinate is sideways and the y-coordinate is vertical.
The field was calculated in the region of the aperture and its extension. A contour plot of the fieldstrength in the medium plane is shown in Fig.4; numbers attached to lines show the ratio of the fieldstrength to the central field strength. The figure shows the field is almost uniform all the way to coils,
which is a unique merit of the window-frame magnet.
Figure 5 shows the magnetic flux densities along the central line at different heights. The fieldstrength in the medium plane is flat in the aperture, and smoothly drops around the magnet boundary.
But the field distribution close to the pole face reflects the structure of the magnets; it increases at the
cut-edge and oscillates at the field clamps shown in Fig.2.

217

Fig.4. Contour plot of the magnetic field in the medium plane. Numbers attached to lines sow
the ratio to the central field.

Fig.5. Magnetic flux density distribution at different heights: larger points y = 0 cm, smaller
points y = 13 cm.

§ 4. Spline Fitting
The calculation step described in the previous section is too coarse for the trajectory tracking ofelectrons; Runge-Kutta calculations are made at about 10 µm step, whereas the calculation step madeby OPERA-3D is 1 cm. In order to interpolate the magnetic field, a spline fitting program was developed;
a successive division method adapted is described in Appendix. Parameters calculated to the z-direction
at every (x, y) mesh are stored in data files, and needed values in the Runge-Kutta calculation arerecalculated using those parameters. The interpolation in the (x, y) plane is performed linearly; the218

spline fitting is not good when the number of data is small, and the spline fitting in the (x, y, z) space istime-consuming. The calculation time of the field at every point using the spline fitting in one-direction isin a few µs, whereas a few ms is needed for the cubic spline fitting, that is too much for the Runge-Kutta
calculation.

Fig.6. Comparison between OPERA-3D calculations and spline functions:
OPERA-3D, smaller points spline functions.

larger points

Results of the spline fitting are shown in Fig.6 for (x = 0 cm, y = 0 cm) and (x = 0 cm, y = 13 cm). As
shown in the figure, the fitting by the spline function is quite well for y = 0 cm. However there are small
but undeniable differences around peaks for y = 13 cm. In order to obtain better fitting, the calculation
was modified using a method described in Appendix; the result for y = 13 cm is shown in Fig.7. In this219

method, the fitting function corresponds with every value obtained by OPERA-3D. This modified spline
functions will be used in the tracking calculation.

Fig.7. Comparison between OPERA-3D calculations and modified spline functions for (x = 0 cm,
y = 13 cm). Larger points: OPERA-3D, smaller points: modified spline functions.

§ 5. Field Measurement
The magnetic field distribution was measured using Hall probes (Panasonic OH10008) at NEC
TOKIN Co.. The detail of the field measurement is referred in Master thesis by T. Miyamoto [7]. The
probe for measurement of the vertical field is well calibrated, but the calibration of probes for other two
directions is out of the acceptable levels for our requirement. Therefore, only the field of the verticaldirection (By ) is discussed below. The field of 1/8 of the aperture and its extension to the z-direction
was measured, as shown in Fig.8. Step sizes of the measurement is ∆y = ∆z = 2 cm in the fringe fieldregion, and ∆y = ∆z = 4 cm in other regions. The step size to the x-direction is ∆x = 5 cm in all regions.
The field strengths needed for analysis considering the symmetry of the field distribution were alsomeasured. The field strength at (x = -65 cm, y = z = 0 cm) was monitored using an NMR (EFM-3000AX,
Echo Co.), and the current was controlled to keep the value of the NMR in ∆B ≤ 0.5 G. Measurements
were made at BNMR = 4097, 7628, and 8017 G. The orientation of the Hall probe was determined byusing the values at z = ± 6.5 cm, where the field distribution was assumed to be symmetric in the up
and down regions.
The difference of the measured By and the OPERA-3D calculation is shown in Fig.9. As shown in
the figure, there is a substantial difference in the fringe field region; in OPERA-3D calculation, the B-H
curve of the low-carbon steel was used instead of that of SS400 for the field clamps, in order to obtainbetter agreement. The difference becomes larger out of the medium plane. Electron momenta estimatedfrom the tracking using the measured and calculated field distributions have differences of 0.1 ∼ 0.3%. It

220Y

y=13 cmy=-4 cmNMR

z= -4 cmX

x=80 cmx= -5 cmYZ
z=148 cmz=155 cmFig.8. Region of field measurement. Measured region is represented by a color of grey. An upper
figure shows a cross-sectional view of the magnet, and a lower one shows a plan view.

shows the use of the reliable field distribution in the analysis is essential to reach the aimed resolution.
The stray magnetic field along the line of z = 155cm, where corresponds to the position of the electron
beam in SR2 ring, is about -3 G. A COD calculation shows the value is within acceptable levels for ring
operation.

Fig.9. Difference between measured By and the OPERA-3D calculation for x = y = 0 (graypoints). Measured By is also shown by dark points.

221§ 6. Commissioning of Spectrometer
The spectrometer was installed at Riken RI Beam Factory in the spring of 2013. A complete view of
the SCRIT experiment after installation of the spectrometer is shown in Fig.10. The installation errorof the spectrometer was smaller than 0.1 mm, and the position did not change after sliding to and fro on
the supporting stage. Safety tests after installation was made without any problems. After that, effectsof the stray field from the spectrometer on the circulating electron beam in SR2 ring were measured.
Values of the COD in the horizontal plane were about 3.2 mm at maximum, which is about twice of thevalue estimated using the measured magnetic field distribution. In addition, an unexpected COD of 1.2
mm in the vertical plane was observed. So far the source of the differences is not clear; the stray fieldtransferred through supporting stages of the spectrometer and other devices may be responsible to theeffects. In any case, the COD in both direction is within acceptable levels, and it can be corrected using
steerers in the operation for experiments.

Fig.10. SCRIT Electron Scattering Facility after installation of the spectrometer. White magnets: dipole magnets of SR2 ring, grey magnet: window-frame type dipole magnet of thespectrometer.

§ 7. Conclusion
A large-acceptance magnetic spectrometer has been constructed and installed at RIKEN RI Beam
Factory. This window-frame type spectrometer has a large aperture, where the strength of the magnetic
field is almost constant, and its momentum resolution is reasonable (∆p/p ∼ 10−3 ). The field distribution was measured using Hall probes and an NMR device, and compared with OPERA-3D calculations.
A spline function code was developed for interpolation of the magnetic field, which will be used for tracking calculation of electrons. The commissioning of the spectrometer at RIKEN has proved the operationof the spectrometer does not give severe effects on the operation of the electron storage ring (SR2) for
SCRIT experiments.

222

Appendix
A. Spline Fitting [8]A.1 Successive division method
A spline function is composed of piecewise polynomials which connected each other with given continuity conditions at knots; the knot is the junction point of polynomials. In the successive division
method, the number of knots is increased one by one, so that the fitting function gives better agreement.
We use a combination of 3rd-order polynomials as a fitting function; both of values and gradients of thepolynomials smoothly continue to those of neighboring regions at knots.
The 3rd-order polynomials have 4 independent parameters. If the polynomials are defined withvalues and gradients at knots of the both ends, the effect by change of parameters for any region does
not spread beyond neighboring regions. We represent a 3rd-order function in the region of [ξi , ξi+1 ] as,2

Si (x) = mi(x − ξi+1 ) (x − ξi )hi 2

2(x − ξi ) (x − ξi+1 )+ mi+1

hi 2

+ yi

hi 3

(1)

2

2

(x − ξi+1 ) {2 (x − ξi ) + hi }+ yi+1(x − ξi ) {2 (ξi+1 − x) + hi }
hi 3

.

Here,
yi ≡ Si (ξi ),
mi ≡

(2)

dSi (ξi )
,
dx
x=ξi

and hi is the length of the region. Using expression:
2

ai (x) ≡(x − ξi+1 ) (x − ξi )
hi 2

,

2

bi (x) ≡(x − ξi ) (x − ξi+1 )
hi 2

,
(3)

2

ci (x) ≡(x − ξi+1 ) {2 (x − ξi ) + hi }
hi 3

,

2

di (x) ≡(x − ξi ) {2 (ξi+1 − x) + hi }hi 3,eq.(1) is rewritten as:
Si (x) = mi ai (x) + mi+1 bi (x) + yi ci (x) + yi+1 di (x).

(4)

We consider the case where one region is divided into two regions. Parameters which determinefunctions in the two regions are (yi−1 , mi−1 , yi , mi , yi+1 , mi+1 ). If those parameters are changed,
functions in 4 regions between [ξi−2 , ξi+2 ] are affected. Let us consider a value which evaluates thefitting goodness of the function to data Fk in the region of [ξi−2 , ξi+2 ] :
Qi ≡

∑

2

(S(xk ) − Fk ) .

(5)kThe parameters which give the best-fit are obtained by resolving 6 simultaneous equations:∂Q∂Q== 0 (j = i − 1, i, i + 1),
∂yj
∂mj

(6)

223

where
Q≡

i+1
∑

(7)

Qj .

j=i−2

Calculating eqs.(6), we finally obtain the following normal equation:

 


g1A + g1B
yi−1
A11 + B11 A12 + B12 B13 B14
0
0

 



 


  mi−1   g2A + g2B  A21 + B21 A22 + B22 B23 B24
0
0

 



 



  yi  

g3B
B31
B32
B33 B34
B35
B36
 ,(8)
=



 



  mi  

g4B
B41
B42
B43 B44
B45
B46

 



 



0
0
B53 B54 B55 + C55 B56 + C56   yi+1   g5B + g5C 

 


g6B + g6C
mi+1
00
B63 B64 B65 + C65 B66 + C66
Explicit expressions of the individual terms are given in subsection 6.3. Only if ξi−1 is the end ofknots,
Am,n = gjA = 0,

(9)and if ξi+1 is the end of knots,
Cm,n = gjC = 0.

(10)

The normal equation is easily solved, but positions of the knots have not been optimized yet. Therefore, the positions of all knots are rearranged to obtain smaller Q whenever the number of knots isincreased.
A.2 Modification of spline function
As shown in Fig.6, there is small but undeniable differences between the data and the spline function around positions where data values rapidly change. In order to fit the function to all data, theinterpolation at x between xk and xk+1 is made such as:[]x − xk+1x − xk′S(x) = S(x) − {S(xk ) − Fk }+ {S(xk+1 ) − Fk+1 }xk − xk+1
xk+1 − xk(11)

An example of the modified function is shown in Fig.7. The curvature of the modified function isalmost same as the original one between the data points, but the continuity of its gradient is broken at
the data points. This fault does not damage the tracking calculation, and the modification is useful forinterpolation of the magnetic field in the Runge-Kutta calculation.
7.1 Explicit expressions of matrix
The followings are explicit expressions of the individual terms in eq.(8). Here, the minimum andmaximum data-numbers in the region [ξj , ξj+1 ] are represented as pj and qj , individually.
∑

qi−2

A11 =

di−2 (xk ) ,A12 =k=pi−2

∑

∑

qi−2
2

bi−2 (xk )di−2 (xk ),k=pi−2

qi−2

A21 =

k=pi−2

∑

(12)

qi−2

bi−2 (xk )di−2 (xk ),A22 =k=pi−22

bi−2 (xk ) ,

224
∑

∑

qi−1

B11 =

qi−1
2

ci−1 (xk ) ,B12 =k=pi−1∑ai−1 (xk )ci−1 (xk ),k=pi−1B13 =ci−1 (xk )di−1 (xk ),B14 =k=pi−1

∑

∑

B22 =

B24 =

B32 =

qi
∑

2

di−1 (xk ) +k=pi−1
qi
∑

B34 =

qi
∑

B36 =

∑

bi−1 (xk )ci−1 (xk ),bi (xk )ci (xk ),

B42 =

B53 =

B55 =

B63 =

B65 =

k=pi
qi
∑
k=pi
qi
∑
k=pi
qi
∑
k=pi
qi
∑

qi
∑

bi−1 (xk )di−1 (xk )+ai (xk )di (xk ),ci (xk )di (xk ),

B46 =

B54 =

∑

qi−1

ai (xk )ci (xk ),

B44 =

qi
∑
k=pi
qi
∑

k=pi−12bi−1 (xk ) +

qi
∑

2

ai (xk ) ,k=pi

ai (xk )bi (xk ),ai (xk )di (xk ),k=pi
2

di (xk ) ,

B56 =

qi
∑

bi (xk )di (xk ),k=pi

bi (xk )ci (xk ),bi (xk )di (xk ),

B64 =

B66 =

∑

k=pi
qi
∑

ai (xk )bi (xk ),2bi (xk ) ,

∑

qi+1
2

ci+1 (xk ) ,C56 =k=pi+1

∑

qi
∑

k=pi

qi+1

ai+1 (xk )ci+1 (xk ),k=pi+1

qi+1

C65 =

ai−1 (xk )bi−1 (xk ),

k=pi

k=pi

C55 =

(13)

∑

k=pi−1k=pi−1B45 =bi (xk )ci (xk ),

k=pi

qi−1

qi−1

qi
∑

qi
∑

k=pi

k=pi−1B43 =bi−1 (xk )di−1 (xk ) +k=pi−1

k=pi
qi−1

B41 =

∑

qi−1
2

ci (xk ) ,k=pi

ci (xk )di (xk ),∑ai−1 (xk )di−1 (xk ),k=pi−1

qi−1

B35 =

∑

qi−1

ci−1 (xk )di−1 (xk ),k=pi−1∑ai−1 (xk )bi−1 (xk ),k=pi−1

qi−1

B33 =

∑

qi−1

ai−1 (xk )di−1 (xk ),k=pi−1∑2

ai−1 (xk ) ,k=pi−1

qi−1

B31 =

∑

qi−1

ai−1 (xk )ci−1 (xk ),k=pi−1B23 =bi−1 (xk )ci−1 (xk ),k=pi−1

qi−1

B21 =

∑

qi−1

qi−1

k=pi+1

∑

∑

(14)

qi+1

ai+1 (xk )ci+1 (xk ),

C66 =

2

ai+1 (xk ) ,k=pi+1

qi−2

g1A =

di−2 (xk ) {Fk − ci−2 (xk )yi−2 − ai−2 (xk )mi−2 },k=pi−2

∑

(15)

qi−2

g2A =

k=pi−2bi−2 (xk ) {Fk − ci−2 (xk )yi−2 − ai−2 (xk )mi−2 },

225
∑

∑

qi−1

g1B =

qi−1

ci−1 (xk )Fk ,g2B =k=pi−1

∑

qi−1

g3B =

di−1 (xk )Fk +ci (xk )Fk ,

k=pi

∑

qi
∑

bi−1 (xk )Fk +k=pi−1

g5B =

qi
∑

k=pi−1
qi−1

g4B =

qi
∑

(16)
ai (xk )Fk ,k=pi

di (xk )Fk ,

k=pi

∑

ai−1 (xk )Fk ,k=pi−1

g6B =

qi
∑

bi (xk )Fk ,

k=pi

qi+1

g5C =

ci+1 (xk ) {Fk − di+1 (xk )yi+2 − bi+1 (xk )mi+2 },k=pi+1

∑

(17)

qi+1

g6C =

ai+1 (xk ) {Fk − di+1 (xk )yi+2 − bi+1 (xk )mi+2 }.

k=pi+1

Acknowledgment
We wish to thank SCRIT group members in RIKEN and Rikkyo University for their support to
the installation of the spectrometer and its commissioning. The spectrometer was manufactured by
NEC TOKIN Co., and its magnetic field distribution was measured using a automated system with Hall
probes there.
This work is supported by Grants-in-Aid for Scientific Research (S) (Grants No. 22224004) from JSPS.

References[1]

M. Wakasugi, T. Suda, and Y. Yano : Nucl. Instr. and Meth. A 532 (2004) 216.

[2]

M. Wakasugi et al.: Phys. Rev. Lett. 100 (2008) 164801.

[3]

M. Wakasugi et al. : Nucl. Instr. and Meth. B 317 (2013) 668.

[4]

T. Suda et al.: Phys. Rev. Lett. 102 (2009) 102501.

[5]

M. Wakasugi et al.: Eur. Phys. J. A 42 (2009) 453.

[6]

TOSCA, Vector Field Ltd, Oxford, England.

[7]

T. Miyamoto: Master thesis (in Japanese) (2014).

[8]

K. Ichida and F. Yoshimoto: Spline function and its application (in Japanese), Education Press.

226

ELPH Annual Report, Tohoku University (2011-2013)(ELPH Experiment : #2757)

Radiochemical Measurement of Photonuclear Reaction
Yields for Photon Activation Analysis.
Yasuji Oura1 , Hitomi Ikeda1 , and Yoshitaka Miura1
1

Department of Chemistry, Tokyo Metropolitan University, Hachioji, 192-0397

Relative reaction yields of (γ, n) reaction induced by bremsstrahlung of maximum end-point energyof 30 MeV were reported for the target nuclides with mass number from 69 to 197. Relative yields weresystematically increased with a increase of target mass number. With this correlation any yield ratio
are able to be estimated.

§ 1. Introduction
Instrumental activation analysis using induced radionuclides is one of simultaneous multi-elemental
and non-destructive analytical method. Usually (n, γ) reaction by reactor neutrons are commonly used
for activation and it’s method is called instrumental neutron activation analysis (INAA), because it iscomparatively easy to prepare samples and use reactor neutrons. Instrumental neutron activation analysis is widely applied to a lot of research fields. Instrumental photon activation analysis (IPAA) using
mainly (γ, n) reaction by bremsstrahlung from an electron accelerator is also high sensitive multielemental nondestructive analytical method and a complementary method to INAA. Since IPAA use a different
nuclear reaction with INAA, IPAA can determine some elements which INAA can not determine. At
the present, however, IPAA is not used well like INAA. One of reasons of a little use is guessed that
it is not easy for IPAA users to refer reaction yield values of (γ, n) reactions for estimation of induced
radioactivity. As far as authors know, a useful compilation table of reaction yields (γ, n), (γ, p), and so
on for IPAA users is almost nothing.
Segebade et al. published a textbook on photon activation analysis in 1988 [1], in which a kindof (γ, n) reaction yields is listed. This table is probably most useful for IPAA user to estimate induced
radioactivity at the present, though given values are activity ratios to activity of 57 Ni produced by 58 Ni(γ,n) reaction on the assumption of a irradiation for 1 hour. Thus we have been determining reaction yieldsof photon nuclear reactions that is valuable for IPAA users since 2012 using LINAC at Kyoto University
Reactor Research Institute (KURRI) [2]. Unfortunately, yields of reaction producing radionuclide withshort half life (< about a few hours) could not be determined due to the allocation of facilities. In
this work using the facility of ELPH, Tohoku University, remeasurement of reaction yield observed at
KURRI and new measurement of reaction yield for reactions producing radionuclide with short half life
are primary objectives.

227§ 2. Experimental
About 50 to 100 mg of high purity powder reagents, MgO, KCl, Sc2 O3 , Ga2 O3 , SrCl2 , KBr, CdO,
Na2 H4 TeO6 , KI, and Yb2 O3 were wrapped in aluminum foil to be formed a disk (10 mmφ). For Au target
and Ni monitor, 10 mmφ of Au foil (0.01 mm thick) and 10 mmφ of Ni foil (0.04 mm thick) were used.
The targets together with Ni monitors in a quartz tube were irradiated for 5 min with bremsstrahlung
beam of maximum end-point energy (E0 ) of 30 and/or 20 MeV. After irradiation, target disks were subjected to gamma-spectrometry by a Ge detector. To reduce true coincidence effect a sample was placedat about 20 cm far from a detector.

§ 3. Results and discussion
Since the bremsstrahlung beam flux was not determined, relative yields to one of 58 Ni(γ, n)57 Ni
were calculated as well as radioactivity ratios to induced radioactivity of 57 Ni. Target mass yields of(γ, n) reactions at E0 = 30 MeV are shown together with yield ratios obtained by irradiation at E0 =28, 31, and /or 32 MeV at KURRI in Fig.1 1. Relative yields increase smoothly with increasing target
mass number except for 120 Te. Yield values obtained at KURRI and ELPH were almost consistent inthis systematic relation. Most of activity ratios determined in this study were about 0.7 to 2 time higher
than those by Segabade et al. Our values were fairy consistent with those by them. Activity ratio for120

Te in this study were about 3 time higher than one by Segabade et al. Although reexamination for120

Te should be required, it seems to be evident that 120 Te deviates from the systematic relation between

relative yield and target mass number.

Fig.1.

Target mass yield for (γ, n) reactions at E0 = 30 MeV. Relative yield values normalizedwith a yield of 58 Ni(γ, n)57 Ni are shown.

Nickel-58, which is a nuclide used for normalize to calculate relative yields, shows also a deviationfrom the systematic relation between relative yield and target mass number. According to the relation,

228
a relative yield for 58 Ni is predicted to be about 3, that is 3 time higher the definition. The fact that58

Ni has a smaller (γ, n) reaction yield is also observed in an excitation function of (γ, n) reaction crosssection using mono-energetic photon. Maximum cross section of (γ, n) reaction is about 25 mb at 18 MeVof photon in the excitation function, whereas surrounding nuclides, such as 55 Mn, 56 Fe, 59 Co, 60 Ni, 63 Cu,
and 65 Cu, have about 60 - 90 mb at about 17 MeV of photon. One of a possible reason of this smaller
value than a prediction based on the relation is that 58 Ni has a magic number (Z = 28) of protons and aclose magic number (N = 30) of neutrons. But a relative yield of 48 Ca that has double magic number ofnucleon does not show a deviation.
Although observed values at less than 50 of a target mass number are not sufficient, the systematic correlation between relative reaction yield and mass number observed in this study can help an
estimation of (γ, n) reaction yields for various elements.

Acknowledgment
The authors are indebted to Dr. H. Kikunaga and the accelerator operating crew members of Tohoku
University for their invaluable cooperation in irradiation of samples and/or accelerator operation.

References[1]

C. Segebade et al.: Photon Activation Analysis, Walter de Gruyter (1988).

[2]

Y. Oura et al.: CO2-1 in KURRI Progress Report 2012 (2013).

ELPH Annual Report, Tohoku University (2011-2013)

229(ELPH Experiment : #2770, #2774)

Production of 57Co radioactive source for Mössbauer
measurements by photon activation method
K. Akiyama, T. Tadai, Y. Takahashi, and S. Kubuki
Graduate School of Science, Tokyo Metropolitan University, 1-1 Minami-Ohsawa, Hachioji,
Tokyo 192-0397
The radioactivity and production rate of 57 Ni and 57 Co by photon activation method were estimatedintended to produce 57 Co Mössbauer source without both chemical separation and homogeneous diffusion process. Based on this data, simulated Mössbauer source was also produced. The production rate
for 57 Co are evaluated from the γ-ray measurement of 1 mm thickness Ni plate and found to be 1.8
Bq/mg·min for the irradiation with 20 MeV bremsstrahlung and to be 30 Bq/mg·min for the irradiation with 30 MeV bremsstrahlung. Simulated source was produced with 30 MeV bremsstrahlung
irradiation and their radioactivity was found to be about 20 kBq from 122 keV γ-ray peak analysis.
Compare to the old Mössbauer source with 84 kBq radioactivity, the intensity of 14.4 keV γ-ray peak
was found to be about one-seventh from the low energy γ-ray measurement by a proportional counter.

§ 1. Introduction
Mössbauer spectroscopy is powerful tool to determine the local structure and electronic state of
the targeted elements, such as iron and tin, from the spectrum shape and intensity of low-energy γrays concerning to first excited state. Iron-57 is well known as widely used Mössbauer nuclei. In the57

Fe Mössbauer spectroscopy, the γ-ray absorption of 57 Fe in the samples is studied by using the 14.4

keV γ-ray emitted from 57 Fe subsequent to the electron capture (EC) decay of 57 Co. The cobalt-57 ina radioactive source used for 57 Fe Mössbauer spectroscopy is homogeneously dispersed in a thin metal
matrices with around 5 to 10 µm thickness. Currently, various nuclear reaction, such as 56 Fe(d,n)57 Co
and 58 Ni(p,2p)57 Co, is employed for the production of 57 Co [1], however it is very troublesome in orderto prepare for a Mössbauer source because the chemical separation of 57 Co from targeted metal and thehomogeneous diffusion of 57 Co into the thin matrices are required so the produced 57 Co is located on apart of the target. On the other hand, it is expected to produce a good radioactive source without bothchemical separation and homogeneous diffusion process, so the photon activation method is possible toirradiate a target homogeneously by using the photons with high transmittance for the nuclear reaction.
So the γ-ray source for the Mössbauer measurement has not been supplied by domestic production and
it relies on imports, it is an important issue to consider the possibility of the source production in Japan
from the view point of the RI production .
In this study, it is intended to produce 57 Co radioactive source for the 57 Fe Mössbauer spectroscopy
in terms of using 57 Co (272 days half-life) produced by the photon activation of a nickel. Here, we230report the estimation of the produced radioactivity and the production rate of 57 Ni and 57 Co and also
preparation of the simulated Mössbauer source.

§ 2. Experimental
2.1 Preparation of irradiation samples for the production rate determination.
Ni plates of 99.9% purity, 10 mm diameter, and 1 mm thickness (about 700 mg, The Nilaco corp.)
were used for irradiation samples. These plates were sealed in a quartz tube under the vacuum for theirradiation with bremsstrahlung of 20 and 30 MeV for 1 minute. Averaged beam currents during these
irradiation were 62 µA and 87 µA, respectively. After irradiation, the samples were removed from thequartz tube to measure the γ-ray by a Ge semiconductor detector.
2.2 Preparation of simulated Mössbauer radioactive source.
Based on the above mentioned irradiation conditions, a simulated Mössbauer radioactive source
was produced. A Ni foil of 99.9% purity, 10 mm diameter, 5 µm thickness (about 3.5 mg, The Nilaco
corp.) was sandwiched between Al plates of 0.1 mm thick, and then wrapped in Al foil with 0.05 mm
thickness. This sample was sealed in a quartz tube with 10 mm diameter under the vacuum for theirradiation with bremsstrahlung of 30 MeV for 6 hours with the averaged beam current of 90 µA. After
irradiation, this Ni foil was fixed by the adhesive on the backing material of Ni plate with 5 mm thickness and was placed in the source holder. The γ-ray spectrum of this simulated source was measured
by Ge detector. After that, the simulated source was installed to the driving unit for the Mössbauer
measurement and then low energy γ-ray emitted from this source were measured by a proportionalcounter.

§ 3. Results and Discussion
3.1 Produced radioactivity and production rate.
Figure 2 shows the γ-ray spectra of the samples irradiated by bremsstrahlung of (a) 20 MeV and(b) 30 MeV. The γ-ray peaks derived from 57 Ni and its progeny nuclide of 57 Co, produced by the reaction (γ,n) of 58 Ni at 20 MeV bremsstrahlung, are dominantly observed. Also, the peak at 810 keV
is considered to be derived from 58 Co produced by the (γ, n) reaction of 59 Co exist as an impurity in
the Ni plate. On the other hand, γ-ray peaks from 56 Ni produced by the (γ, 2n) reaction of 57 Ni at
30 MeV bremsstrahlung were observed in addition to those from 57 Co and 57 Ni. The radioactivity of57

Co listed in table 1 was evaluated from the results obtained after 20 days passed when it is consid-

ered that almost all of 57 Ni was decayed out. The determined radioactivity and production rate for eachradionuclides were listed in the Table 1.
3.2 As a Mössbauer radioactive source.
It is considered that the ideal thickness of 57 Co employed for the Mössbauer spectroscopy on a backing metal plate is about 5 to 10 µm so as to prevent the line broadening and the self-absorption of γ-ray

231

Co

a)
5

L.T. 20567.9 sec

Ni

3

Ni
57

Ni

2

10

10

1

6

b)

Co

10

10

Co
56

Co

57

Ni

Co
58

Co

Ni

56

56

Ni
56

56

2

56

Ni

Ni,

56

10

56

3

Ni

10

4

57

10

L.T. 110 sec

5

Co

10

57

Counts

57

10

58

Co

10

4

57

10

57

Co

10

6

57

10

1

0

0

500

1000

1500

2000

Energy / keV

Fig.1.

The γ-ray spectra of the samples irradiated by bremsstrahlung of (a) 20 MeV and (b) 30
MeV.

Table 1. Determined radioactivity at the end of bombardment and production rate for each produced radionuclide.
Irrad. Energy
20 MeV

Nuclide
57
Ni
57

Co

56

30 MeV

57
57

Ni
Ni

Co

Energy / keV
1377.63122.06136.47158.38749.951377.63122.06136.47Iγ
0.81700.85600.10680.98800.49500.81700.85600.1068

Activiy / Bq
3.7 x104

Production rate / Bq/mg·min
53

1.2 x1031.8

2.2 x1033.2

6

1.3 x101800

2.1 x10430[2]. Figure 3a shows the observed low energy γ-ray spectrum of irradiated Ni foil with 5 µm thickness
for the simulated source by a proportional counter. Low energy γ-ray spectrum of old Mössbauer source(925 MBq at 2004/9/15) is also shown in figure 3b for comparison. The radioactivity of this old sourceat the measurement date (2014/9/29) is estimated to be 84 kBq. Despite the averaged beam currents
at these two experiments were almost same as each other, expected radioactivity of 57 Co in Ni foil iscalculated from the production rate of 57 Co at 30 MeV irradiation listed in table 1 and found to be about

232

38 kBq, but the actual radioactivity determined from the 122 keV γ-ray peak of this sample is foundto be 20 kBq. This (20 kBq) is about one-half of estimated radioactivity (38 kBq) and is also about
one-fourth of that for old source (84 kBq). On the other hand, estimated radioactivity of this 57 Co fromthe comparison of the peak intensity at 14.4 keV shown in figure 3a and 3b is found to be about oneseventh of that for old source. Considering about the half value layer of 14.4 keV γ-ray within Ni [3],the attenuation of peak intensity in the low energy spectrum seems to be reasonable. Although about
85 Bq of 57 Co derived from recoil nuclei by (γ, n) and (γ, p) reaction, was observed from Al used for the
packaging of the irradiated sample, this is only about 0.4% of that observed in Ni foil. Since there is afairly large difference between the expected radioactivity and the actual radioactivity, production rate is
likely to be overestimated.

15.0

(a)

x10

14.4 keV

10.0

Count Rate / cps

5.0

0.0
15.0

(b)

x10

10.0

5.0

0.0
0

500

1000

1500

2000

ChannelFig.2.

Low energy γ-ray spectra of (a) simulated Mössbauer source and (b) old source. Bothsources were measured at 2.5 cm distant from the detector surface.

§ 4. Conclusion
We attempt to produce 57 Co Mössbauer source from commercially supplied Ni foil using photon
activation method. Production rate of 57 Co at 20 MeV and 30 MeV are estimated to be 1.8 Bq/mg·min
and 30 Bq/mg·min, respectively. Simulated Mössbauer source was prepared by the irradiation of Ni
foil with bremsstrahlung of 30 MeV for 6 hours according to the optimal irradiation condition obtained

233

from these experiments. Produced radioactivity of simulated source was found to be 20 kBq from 122
keV γ-ray peak analysis and this is about one-seventh compare to that of old Mössbauer source. In thenear future, we will try to improve the production rate of 57 Co with bremsstrahlung of higher energy,
such as 40 MeV and 50 MeV, and also we will carry out the development of the Mössbauer source withhigher radioactivity which is applicable for the Mössbauer measurement.

Acknowledgment
We deeply thank to the facility staffs of research center for electron photon science at Tohoku University for supplying the high-quality electron beam. And also we thank to Professor Hidetoshi Kikunaga
and Doctor Kyo Tsukada for helping us in the sample irradiation.

References[1]

E. Huenges, J. Loock, H. Morinaga, and F. Parak, Nucl. Instr. Meth. Phys. Res. 203 527-531 (1982).

[2]

G. Longworth, B. Window, J. Phys. D: Appl. Phys. 4 835-839 (1971).

[3]

J. H. Hubbell and S. M. Seltzer, in Tables of X-Ray Mass Attenuation Coefficients and Mass EnergyAbsorption Coefficients from 1 keV to 20 MeV for Elements Z = 1 to 92 and 48 Additional Substances of Dosimetric Interest. Physical Reference Data (NISTIR 5632),NIST,(1996).

234

ELPH Annual Report, Tohoku University (2011-2013)

Atmospheric activity concentration of radiocesium at
Mikamine, Sendai and radioactivity distribution on thecollection filters used in the measurement
Kikunaga, H.1 , Ohtsuki, T.1 , Fujimura, H.1 , Hiraga, M.1 , Ishikawa, T.1 ,Kashiwagi, S.1 , Matsuda, K.1 , Miyabe, M.1 , Miyahara, F.1 , Muto, T.1 ,Nagasawa, I.1 , Nanbu, K.1 , Shibasaki, Y.1 , Sugawara, Y.1 , Suzuki, K.1 ,Takahashi, K.1 , Takahashi, S.1 , and Yamazaki, H.1
1

Research Center for Electron Photon Science, Tohoku University, Sendai, 982-0826

The Fukushima 1 Nuclear Power Plant accident released various radionuclides. Monitoring of environmental radioactivity should provide important information on the behavior of the radionuclides. To
investigate the time variation of atmospheric activity concentration of radiocesium, we have regularlycollected aerosol particle samples at Mikamine, Sendai from March 15, 2011 to present. As a measurement result, it was found that the maximum activity concentrations of radiocesium were recorded in
March 20-21, 2011 and then the atmospheric activity concentrations of radiocesium decreased with anapparent half-life of 10 - 30 d. In addition, radioactivity distribution on the collection filters used in themeasurement was measured by using imaging plate technique.

§ 1. Introduction
The Fukushima 1 Nuclear Power Plant suffered major damage from the 2011 off the Pacific coast of
Tohoku Earthquake and subsequent tsunami on March 11, 2011 and released various radionuclides. To
date, the radionuclides with short half-lives has disintegrated and then cesium isotopes become major
sources of radioactivity contamination. To investigate the time variation of atmospheric activity concentration of radiocesium, we have regularly collected aerosol particle samples at Mikamine, Sendai fromMarch 15, 2011 to present.
In this work, we present these results. Additionally, distribution of radiocesium on the collection
filters have been investigated to obtain information on the state of radiocesium in the early stage, whichshould be in good preservation on the filter.

§ 2. Experimental
Air sampling was carried out at Research Center for Electron Photon Science, Tohoku University,
Sendai, Miyagi, Japan (38◦ 13’33”N, 140◦ 51’19”E) with air samplers, SP-30 (M&F Enterprose, Sampling
rate: 30 L/min) and Self-made sampler (100 L/min, Figure 1). An inlet port of the air samplers was located 1 m above the ground surface. Aerosol particles were collected on a cellulose-glass filter (Advanted,
HE-40T) with a diameter of 48 mm for 1 - 120 h.

235

Fig.1.

Self-made aerosol collection apparatus

The radioactivity in the aerosols collected was determined by gamma-ray spectrometry using highpurity germanium detectors. The atmospheric activity concentrations of radioactivity were calculated
as the ratio between the radioactivity in the aerosol particle sample and the total volume of sampling
air. Profile of the radioactivity on the cellulose-glass filters was measured by using an imaging-platetechnique (Scanner: Fujifilm BAS-5000, Plate: Fujifilm BAS-2025SR) after June 2012.

§ 3. Results
γ-ray spectra of the aerosol sample collected at March 21, 2011 are shown in Figure 2. The upperand lower spectra were measured at March 21, 2011 and September 7, 2012, respectively. The γ peaksof 99 Mo (99m Tc), 131 I, 132g Te (132 I), 134 Cs, 136 Cs, and 137 Cs are observed in the former spectrum, while only134

Cs and 137 Cs in the latter spectrum. At that time of measuring profile of the radioactivity, a primaryradioactivity is due to radiocesium isotopes.
Time variation of 137 Cs atmospheric activity are shown in Figure 3. It is found that the apparent
half-life of 137 Cs atmospheric activity was 13±1 d, which was on the same level with a mean residence
time of aerosol. Superimposed images in the Figure 3 shows distributions of radioactivity on the filters236

which are collected at from March 21, 2011 to March 13, 2012. ”Hot points” on the filters were observed
through the whole period. These results indicate that radiocesium is attached to aerosol particles. This
aerosol collection and measurement of radioactivity is still going on.

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resuspension?
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Backgroung level before F1NPP accident

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Fig.3.

Time variation of 137 Cs atmospheric activity and radioactivity on the filters

ELPH Annual Report, Tohoku University (2011-2013)237

A test Accelerator as a Coherent Terahertz Source (t-ACTS)
Shigeru Kashiwagi, Fujio Hinode, Masayuki Kawai, Toshiya Muto,
Ikuro Nagasawa, Ken-ichi Nanbu, Yoshinobu Shibasaki,
Ken Takahashi, and Hiroyuki Hama
Research Center for Electron Photon Science, Tohoku University, Sendai, 982-0826, Japan§ 1. Overview of the t-ACTS
A test accelerator as a coherent terahertz source (t-ACTS) project has been under development
at Tohoku University, in which the generation of intense coherent terahertz (THz) radiation from subpicosecond electron bunch is demonstrated. A wide-band coherent THz radiation is emitted from circulated electron beam in the isochronous ring [1, 2] and a narrow-band coherent THz radiation using
an undulator has been considered [3, 4]. We have numerically studied a production of the very shortelectron bunch to generate intense coherent THz radiation. The bunch length of electron beam must
be shorter than a wavelength of coherent radiation. In the case of coherent THz radiation, the electron
bunch should be compressed to the order of a few hundred femtosecond in bunch length. The electron
bunch is compressed employing a velocity bunching in accelerating structure. To generate an electron
beam suitable for the velocity bunching, we have developed a thermionic cathode RF gun which canmanipulate a longitudinal phase space distribution of electron beam. The construction of a linear accelerator part was completed on 2013 and beam experiment of extremely short bunch generation has been
conducted.

§ 2. Accelerator
Accelerator-based light source house was built at Research Center for Electron Photon Science,
Tohoku University. The accelerator system was installed inside of the accelerator-based light source
house as shown in Fig. 1. Basic beam parameters of t-ACTS is described in Table 1. The injector
system of t-ACTS was designed to generate the sub-picosecond electron bunch for the coherent THz radiation. The injector part of t-ACTS is composed of a thermionic cathode RF gun, an alpha magnet,
and a 3 m-long accelerating structure (Fig. 2, Fig. 3). The thermionic RF-gun consists of two independent cavities so as to manipulate the longitudinal phase space distribution of electron beam, named theIndependently-Tuneable Cells (ITC) RF-gun [5]. The two cavities of the ITC RF gun have no electricalcoupling, therefore two RF cavities can be independently controlled. It was designed to manipulate theelectron distribution in the longitudinal phase space for the velocity bunching [6]. The high energy partof the electron beam is selected using a movable slit mounted in the alpha-magnet vacuum chamber. We
can measure an energy spectrum of the beam using the movable slit in alpha magnet, because trajec-

238

Fig.1.

Accelerator-based light source house.

tories of electron in the alpha magnet correlate with the beam momentum. Accelerated beam energy
and current are measured downstream of 45 degrees bending magnet using a screen monitor and a fastcurrent transformer (FCT).
Table 1. Beam parameters of t-ACTS.
Maximum beam energy [MeV]50

Peak current in macro-pulse [mA]

60

Beam pulse width (macro-pulse) [ µs]3.0

Beam repetition (maximum) [Hz]5

Figure 4 shows a schematic drawing of high power RF system. A klystron produces an RF pulse of
50 MW at peak power with pulse duration of 3 µs, and the RF power is divided by a 9 dB hybrid coupler
into two RF waveguides for the ITC RF-gun and an S-band accelerating structure. The waveguidesystem for the two cavities of the ITC RF-gun includes a 6.5 dB hybrid power divider, two high power
phase shifters and attenuators, two circulators, and RF windows. The waveguides for RF-gun are filledwith pressurized SF6. The amplitude and phase of RF powers supplied to the two RF-gun cavities are
independently controlled using the high power attenuators and phase shifters.

§ 3. Extremely short bunch generation
In the velocity bunching, the non-relativistic electron bunch is injected into zero-cross phase (ψ =0) of an accelerating structure. In case of t-ACTS, maximum momentum of the beam at RF-gun exit isless than 2.5 MeV/c. Since the phase velocity of the accelerating structure is equal to the speed of light,
the non-relativistic electron bunch slips backward to the direction of crest phase and starts to accelerate

239

Fig.2.

Photograph of t-ACTS injector beam line. The beam line is composed of the ITC RFgun, the alpha-magnet with a movable slit, four quadrupole magnets and beam monitors(beam current monitor, screen monitor ).

Fig.3.

Photograph of the beam line of t-ACTS with a 3 m-long accelerating structure and undulator.

as rotating its longitudinal phase space as shown in Fig. 5. Injected electron bunch moves along theequi-potential line in the longitudinal phase space. Ideally, the compression factor becomes maximum
when the injected electron distribution is exactly on the same equi-potential line. Since nonlinearity

240

Fig.4.

Schematic diagram of the high power RF system for the t-ACTS injector.

of the equi-potential line at higher injection energy is stronger, a lower energy beam with mono-energy
electron distribution in the longitudinal phase space is helpful to relieve the nonlinear effect (Fig. 5).
The bunch length after acceleration strongly depends on the longitudinal phase space distribution of
injection bunch into accelerating structure.

Fig.5.

Equi-potential lines for the peak accelerating field E0 = 20 MV/m. Evolutions of electron
distributions injected at 0 degree are plotted with colored lines.

§ 4. Operation of t-ACTS
The t-ACTS is not user machine but R&D machine for beam physics and accelerator science. The
beam commissioning of the t-ACTS linac was started in October 2013, and the facility was approved for241

the regulation of radiation safety on December 19th 2013. We, the accelerator physics group, conduct
the study of an extremely short bunch generation with using t-ACTS.

References[1]

H. Hama et al.: New J. Phys.8 (2006) 292.

[2]

H. Hama et al., Nucl Instr. and Meth., A637 (2006) 292.

[3]

H. Hama and M. Yasuda: Proc. of FEL2009, (2009) 394.

[4]

F. Hinode et al., Nucl Instr. and Meth., A637 (2011) S72-S75.

[5]

F. Hinode et al., Proc. of IPACf10, (2010) 1731.

[6]F. Miyahara et al., Proc. of IPACf10, (2010) 4509.

242

ELPH Annual Report, Tohoku University (2011-2013)

Lattice Design of a Sub-nm Emittance Storage Ring for the
Synchrotron Light in Tohoku, Japan (SLiT-J)
Hiroyuki Hama for SLiT-J Design Team∗Electron Light Science Centre, Tohoku University, Sendai 982-0826, JapanA new project of high brilliant synchrotron light source facility, SLiT-J (Synchrotron Light in Tohoku, Japan), has been proposed by 7 national universities in Tohoku area of Japan since 2011. The
accelerator complex consisted with a 3 GeV low emittance storage ring and a C-band full-energy injector
linac has been designed. The circumference of the storage ring is less than 400 m to secure compactness
for saving construction cost and power consumption in operation. The target horizontal emittance of thestorage ring is 1 nmrad or below to provide synchrotron radiation in soft x-ray region (0.1 ∼ 5 keV) witha brilliance of 1021 photons/mm2 /mrad2 /s/0.1%bandwidth. Design strategy of storage ring lattice andtentative one are reported.
Key words: synchrotron radiation, storage ring, low emittance, brilliance.

§ 1. Introduction
After the disaster of the Great East Japan Earthquake and Tsunami on March 11, 2011, we areaware that the role of Tohoku area for basic science, technology and industry is very much significant.
However we are still in recovering stage and have been struggling for the future of the Tohoku area
along with a wretched incident of nuclear power plants. In this significant situation, a new project of a
3 GeV light source has been proposed by 7 national universities in Tohoku area for future development
and reconstruction of Tohoku area, and then for those of Japan.

§ 2. SLiT-j storage ring
2.1 Double double-bend lattice with finite dispersion
At the moment a light source storage ring and an injector are under preliminary design stage. Since
huge budget cannotbe anticipated, the accelerator-complex has to be compact without any deteriorationin performance. The performance of the SLiT-J has to be really competitive with newly constructing
3rd generation light sources, such as NSLS-II, MAX-IV and TPS. In order to provide highest level ofbrilliance, the horizontal emittance of the ring should be 1 nmrad or below. Taking a look at the ringsize, the circumference of the NSLS-II ring is ∼ 800 m and those of MAX-IV and TPS are above 500 m.
Since the natural horizontal emittance is inversely proportional to n3B in general, where nB is numberof bending magnets in a ring, large size circumference is required for low emittance ring. However the∗email: hama@lns.tohoku.ac.jp

243

Figure1.

A double double-bend lattice for SLiT-J. Horizontal and vertical beta functions areindicated by red and blue line. Green line denotes the dispersion function.

construction and running cost would be limited, so that a large size ring cannot be considered for the
SLiT-J project to achieve lower emittance.
In Figure 1, a tentative lattice of SLiT-J is shown. We have employed 4-bend structure for unit
cell. In order to reduce effective emittance, small momentum dispersion (˜ 7cm) is introduced in the longstraight section. Number of cell is 14 and the circumference is 340 m. Although the natural emittance is
1.1 nmrad, introducing a short multi-pole wiggler (MPW) in the short straight section at the cell center
to enhance the radiation damping effect, the effective emittance reaches to be 0.85 nmrad.
Dynamic aperture is evaluated by using a genetic algorism for optimizing interleaved 6-family sextupoles. The thickness of sextupoles is 20 cm and proper strength is found to be reasonably small (lessthan 700 T/m2 ). Derived dynamic aperture using a tracking function in SAD code is shown in Figure 2.
2.2 16-cell option
Since the length of unit cell is less than 25 m, a circumference of 16-cell ring is still shorter than
400 m, which is sufficiently smaller than other advanced rings.
In the case of 16-cell option, the natural emittance is 0.78 nmrad and MPWs give an effective oneof 0.55 nmrad that is almost comparable to that of NSLS-II with damping wigglers. In Table 1, main
parameters of the SLiT-J storage ring are listed together with those of the 16-cell option.

§ 3. Future prospect
Owing to success of XFEL at SACLA, SPring-8/RIKEN, we will employ C-band accelerating structures for a full-energy injector linac. Seeding technology for high quality FEL is now studied worldwide

244

Figure2.

Dynamic aperture of 14-cell SLiT-J. Strengths of 6-family sextupoles are optimized bya genetic algorism.

Table 1. Basic Parameters of SLiT-J Storage Ring
Beam energy
Lattice structure
Circumference
Number of cells (bends)
Long straight section
Short straight section
Betatron tune
Natural chromaticity
Natural horizontal emittance
Momentum compaction factor
Natural energy spread
Lattice functions at LSS
Damping partition number
Damping time
Energy loss in bends
RF frequency
RF voltage
Harmonic number
Natural bunch lengthEC
N cell(ν x , ν y )(ξ x , ξ y )εxα
σ E /E(β x , β y , η x )(D, J x , J s )(τ x , τ y , τ s )
U0
f RF
V RF
h
σb

14-cell lattice2.998 GeV
4-bend cell339.92 m
14 (56)
5.33 m × 14
1.43 m × 14
(25.85, 6.75)(-64.8, -44.7)
1.13 nmrad (0.85 nmrad)0.000470.0858 %(13.2, 2.96, 0.07) m(-0.341, 1.341, 1.659)(7.7, 10.3, 6.2) ms
0.662 MeV/turn
508 MHz
3 MV
576
3.43 mm (11.1 ps)

16-cell option
2.998 GeV
4-bend cell388.480m
16 (64)5.33 m × 14
1.43 m × 14
(29.15, 7.25)(-65.2, -47.5)
0.78 nmrad (0.55 nmrad)0.000370.0805 %(11.9, 3.73, 0.06) m(-0.349, 1.349, 1.651)(9.9, 13.4, 8.1) ms
0.579MeV/turn
508 MHz
3 MV
658
2.95 mm (9.85 ps)

245

as next light sources following SASE FEL, so Soft-XFEL option of the injector linac will be considered
as a next stage.
Although the project budget is not predictable at present, we anticipate that construction will bestarted in FY2016 by means of gathering Japanese mature technology of accelerators, and the facility
will be opened in 2019 for users.

Acknowledgement
We would like to thank Prof. Y. Waseda of Tohoku University and Dr. N. Kumagai of JASRI for
their leadership for the project.

References[1]

SLiT-J Conceptual Design Report v1.0 (in Japanese), 2014.7, SLiT-J Progress Office, Tohoku University.

ELPH Annual Report, Tohoku University (2011-2013)

247

Operation status of accelerator complex in 2013
Accelerator group§ 1. Statistics of 2013
After the recovery works of the accelerator facilities, the test operation was carried out from early
2013. The electron accelerator complex, are the low energy linac for a radioisotope (RI) production, thebooster synchrotron (BST ring) with new injector linac, the t-ACTS, was approved for the regulation ofradiation safety at Dec. 19th 2013. Monthly operating time after the inspection of radiation safety issummarized in Fig. ??. In this four month, approximately 550 hours were devoted to user machine time.
In the present accelerator configuration, we can operate the low energy linac and the booster synchrotron
simultaneously, therefore both experiment of the RI production for radiation chemistry and the nuclear
physics experiments using the booster synchrotron can be conducted in parallel.

Fig.1.

Monthly statistics of the operation time in FY 2013.

248

ELPH Annual Report, Tohoku University (2011-2013)

User Support Office Report in FY2011
T. Ishikawa on behalf of the user support office
Research Center for Electron Photon Science (ELPH), Tohoku University, Sendai 982-0826,
Japan
Research Center for Electron Photon Science (ELPH) became a joint usage/research center from
April 1 in 2011. The User Support Office coordinates communication between the users and scientists
at ELPH and management of the beamtime. In this fiscal year, no electron and photon beams (including
electron/positron beam for testing detectors) were provided due to the 2011 earthquake off the Pacificcoast of Tohoku (2011 Earthquake).

§ 1. Introduction
Our facility has a 300 MeV electron linear accelerator (linac) and 1.2 GeV electron scynchrotron
called STretcher Booster (STB) ring. The two accelerators providing electron and photon beams areopen to all the users in Physics and Chemistry. The beams often utilized by the experimentalists before
2011 Earthquake can be classified into three:
1. high intensity low energy electrons (∼ 100µ A and 30 MeV at maximum) for producing radio active
sources (Radiochemistry),
2. high energy tagged photons for meson photoproduction experiments (Nuclear Physics), and3. positrons (electrons) with the variable energy for testing detectors (Particle Physics, Nuclear Physics,
and so on).
There was basically no difference between the latter two in the operation of the accelerator complex.

§ 2. 2011 Earthquake
The 2011 Earthquake took place at 14:46 on March 11th in 2011. The damage of the 2011 Earthquake to the two accelerators were serious. Many cracks on the waveguides and the accelerator columns
were found in 300 MeV linac. The elements of the STB ring slipped out of place, some magnets were hit
by shield blocks, and several power suppliers were broken. The damage to the beamline apparatuses
were also serious. The bending magnet for the RI beamline was broken. The dipole magnet RTAGX
slipped in a few cm for sweeping out undesired charged particles in the photon beam and for providing
electron and positron beams. An electromagnetic calorimeter FOREST in the GeV-γ experimental hallbecame out of order. Some photomultiplier tubes (PMT’s) were rifted. Many detector elements shiftedout of place. The reserved detectors in GeV-γ preparation room suffered the extensive damages. Some
plastic scintillators and their PMT’s for the neutron detection were cracked. Many lead glass Čerenkov
counters were smashed. The details of the damages in this facility are summarized elsewhere [1].

249

§ 3. Experiments at SPring-8/LEPS
Experiments for testing various kinds of detectors had been performed at the positron beamline in
the GeV-γ experimental hall at ELPH. The positron beam was generated by converting bremsstrahlung
photons with a metal converter. The positron beams generated by converting laser induced electron
photons at SPring-8 can be used for testing detectors instead of those in the GeV-γ experimental hall.
The positrons with the intensity of 110 Hz and the energy of 600 MeV are expected to be available within
10 mm square at (z, x) = (1500, 500) mm by utilizing a 0.5 mm thick lead converter. The positron
beam has the energy resolution of 2.8%. Tracking devices can be tested by irradiating positrons as
minimum ionizing particles. The details of the positron beams obtained at SPring-8/LEPS are described
elsewhere [2].
Three experiments, which were proposed to ELPH, were carried at SPring-8/LEPS. The first one
was a performance test of a thick GEM TPC for J-PARC E15 by M. Tokuda (Tokyo Institute of Technology) and F. Sakuma (RIKEN) et al.@ (ELPH Experiment #2742). The second one was a development ofa hodoscope with wavelength shifting fibers for a new electromagnetic calorimeter by Y. Tajima (Yamagata University) and T. Ishikawa (ELPH, Tohoku University) et al.@ (ELPH Experiment #2745). The
last one was a performance test of a readout system for a GEM tracker by K. Ozawa (University of Tokyo)
et al.@ (ELPH Experiment #2749). These experiments aimed to test some tracking devices, and weresuccessfully carried out.

§ 4. Recovery works
The design works on the accelerator started to provide the electron and photon beams including
electron/positron beam for testing detectors as well before 2011 Earthquake. The late 300 MeV linac
had two functions, providing the high intense beam with energies less than 60 MeV for producing radio
isotopes, and injecting the beam onto the 1.2 GeV synchrotron for investigating the structure of thenucleon and its excited states. We plan to rebuild a linac from the broken 300 MeV one for providing thehigh intense beam and to construct a 90 MeV linac newly for injecting the beam onto the synchrotron.
The power supplies of the synchrotron will be also replaced to accept the lower energy electron beam(∼ 90 MeV) from the injector linac.
The design works on the tagging counters for the photon beamlines I and II also started for replacing
the broken ones. The tagging counter for the beamline I was planned to consist of plastic scintillator
hodoscopes connected with multi-pixel photon counters (MPPC). That for the beamline II was planned
to consist of plastic scintillator hodoscopes and a drift chamber.

§ 5. ELPH workshops and ELPH seminars
From this fiscal year, ELPH started to put out a call for workshop plans as a part of its joint
usage/research center project, supported an workshop on beam dynamics held at ELPH and partly the
first international school for strangeness nuclear physics [3]. It was great sorrow that Professor Osamu
Hashimoto, the chair of the school, passed away on February 3 in 2012 before the school started. Five

250

seminars were held at ELPH in this fiscal year.

References[1]

H. Yamazaki: Damage to GeV-γ beam line caused by the Tohoku Pacific Ocean Earthquake, in thisannual report.

[2]

T. Ishikawa and M. Miyabe et al.: Positron beams for testing detectors at SPring-8/LEPS, in thisannual report.

[3]

O. Hashimoto and K. Imai: Web site hhttp://lambda.phys.tohoku.ac.jp/snpsc2012/i.

ELPH Annual Report, Tohoku University (2011-2013)

251

User Support Office Report in FY2012
T. Ishikawa on behalf of the user support office
Research Center for Electron Photon Science (ELPH), Tohoku University, Sendai 982-0826,
Japan
The User Support Office coordinates communication between the users and scientists at ELPH
and management of the beamtime. In this fiscal year, no electron and photon beams (including electron/positron beam for testing detectors) were provided due to the 2011 earthquake off the Pacific coastof Tohoku (2011 Earthquake).

§ 1. Introduction
Our facility has a 300 MeV electron linear accelerator (linac) and 1.2 GeV electron scynchrotron
called STretcher Booster (STB) ring. The two accelerators providing electron and photon beams areopen to all the users in Physics and Chemistry. The beams often utilized by the experimentalists before
2011 Earthquake can be classified into three:
1. high intensity low energy electrons (∼ 100µ A and 30 MeV at maximum) for producing radio active
sources (Radiochemistry),
2. high energy tagged photons for meson photoproduction experiments (Hadron Physics), and3. positrons (electrons) with the variable energy for testing detectors (Particle Physics, Nuclear Physics,
and so on).
There was basically no difference between the latter two in the operation of the accelerator complex.
Two accelerators were out of order due the damage of the 2011 Earthquake.

§ 2. Recovery works
The late 300 MeV linac had two functions, providing the high intense beam with energies less than
60 MeV for radio chemistry, and injecting the beam onto the 1.2 GeV synchrotron for hadron physics.
Two functions were separated into two linacs: rebuilding of a new linac from the broken 300 MeV one
for providing the high intense beam, and construction of a new 90 MeV linac for injecting the beam onto
the synchrotron were started. The production of new power supplies of the synchrotron started because
the old ones cannot accept the lower energy electron beam (∼ 90 MeV) from the injector linac. A bending
magnet for the RI beam course to sweep out the high intense electron beam was constructed. The R&D
works were made for the new tagging counters. The design work of an RI drainage equipment started,which was used for measuring the RI concentration in waste water from the radiation controlled areaand decreasing the concentration to a prescribed reference value or lower.

252§ 3. ELPH workshops and ELPH seminars
In this fiscal year, ELPH supported a workshop on beam dynamics and that on hadron physics, andboth of them were held at ELPH. It also supported in part the second international school for strangenessnuclear physics [1]. Four seminars were held at ELPH.

References[1]

H. Tamura and K. Imai: Web site hhttp://lambda.phys.tohoku.ac.jp/snpsc2013/i.

ELPH Annual Report, Tohoku University (2011-2013)

253

User Support Office Report in FY2013
T. Ishikawa on behalf of the user support office
Research Center for Electron Photon Science (ELPH), Tohoku University, Sendai 982-0826,
Japan
The User Support Office coordinates communication between the users and scientists at ELPH andmanagement of the beamtime. The bremsstrahlung photon beam came back in the end of December 2013
after the recovery of the 2011 Earthquake, and the experiments using electron/positron beams for testing
detectors started. The high intense low energy electron beam also came back, and the experiments using
it started in the end of February 2014.

§ 1. Introduction
Our facility has a 300 MeV electron linear accelerator (linac) and 1.2 GeV electron scynchrotron
called STretcher Booster (STB) ring. The two accelerators providing electron and photon beams areopen to all the users in Physics and Chemistry. The beams often utilized by the experimentalists before
2011 Earthquake can be classified into three:
1. high intensity low energy electrons (∼ 100µ A and 30 MeV at maximum) for producing radio active
sources (Radiochemistry),
2. high energy tagged photons for meson photoproduction experiments (Hadron Physics), and3. positrons (electrons) with the variable energy for testing detectors (Particle Physics, Nuclear Physics,
and so on).
There was basically no difference between the latter two in the operation of the accelerator complex.
Two accelerators were out of order due the damage of the 2011 Earthquake.

§ 2. Recovery works
The late 300 MeV linac had two functions, providing the high intense beam with energies less than
60 MeV for radiochemistry, and injecting the beam onto the 1.2 GeV synchrotron for hadron physics.
Two functions were separated into two linacs: a new linac was rebuilt from the broken 300 MeV one
for providing the high intense beam, and a new 90 MeV linac was constructed for injecting the beam
onto the synchrotron. The power supplies of the synchrotron was introduced to accept the lower energy
electron beam (∼ 90 MeV) from the injector linac. Since 1.2 GeV synchrotron called STretcher Booster(STB) ring had lost its stretcher function (slow extraction), it was renamed as BooSTer (BST) ring. The
R&D works were still on-going for the new tagging counters. Construction of an RI drainage equipment,
which is used to measure the RI concentration in waste water from the radiation controlled area and to
decrease the concentration to a prescribed reference value or lower, was finished in the end of June 2013.

254§ 3. Beamtime operated
The inspection of our facility having accelerators for the radiation safety was made on December
12–13 in 2013. Since the operation of the accelerators were permitted, and the experiments of the users
outside started from December 20 in 2013. It should be noted that the maximum energy of 1.3 GeV wasachieved in the synchrotron. Unfortunately, the optimum photon beam course in the end of December in2013 was not parallel to the designed photon beamline (dx/dz = +0.6 mrad and dy/dz = −1.2 mrad).
The FOREST collaboration made the new beamline markers in Februar 2014 according to the previous
line between BM4 and BM5 before the 2011 Earthquake. At the beginning of March 2014, we obtained
the photon beam in the parallel direction with respect to the new beamline (dx/dz = +0.14 mradand dy/dz = +0.01 mrad) by moving the RTAGX magnet and the beam dump. The details of thecommissioning of the photon beamline are discussed elsewhere [1]. To increase the intensity of the low
energy positron beam for testing detectors, the vacuum pipe on the positron beamline was installed. An
excellent improvement was obtained on the beam profiles for the low energy positron beams. The detailsof the positron beams for testing detectors are discussed elsewhere [2]. The control system of the booster
ring was modified in February 2014. The RI experiments of the users outside started from February
25 in 2014. It should be noted that both RI and BST experiments were carried out simultaneously on
March 6 in 2014 for the first time.
The radiation time was 50.7 hours for the RI linac operation and 356.5 hours for the BST operation,and it was 407.2 hours in total. The beam provided time (user beamtime) was 32.1 and 476.1 hours for
the RI linac and BST operations, and it was 508.2 hours in total. When the several experimental groups
use the beamtime, the user beamtime is doubly counted. Table 1 summarizes the radiation times, anduser beamtimes in FY2013.
Table 1. Radiation times, and user beamtimes in FY2013. They are given by the sum of the times
that the beam is coming to the beamline, and that the beam is provided to the users. The
beamtimes are classified to RI linac and BST used ones.
month
DecemberJanuary
February
Marchsum

RI linacradiation (h) user (h)
0.7
0.0
0.0
0.0
26.9
20.4
23.1
11.7
50.7
32.1

BST
radiation (h) user (h)
124.3
198.5
54.5
115.8
0.0
0.0
177.6
161.8
356.5
476.1

The beams can be utilized by the experimentalists after the recovery of 2011 Earthquake can beclassified into three:
1. high intensity low energy electrons (∼ 100µ A and 30 MeV, ∼ 120µ A and 50 MeV at maximum)for producing radio active sources (Radiochemistry),
2. high energy tagged photons for meson photoproduction experiments (Hadron Physics), and3. positrons (electrons) with the variable energy for testing detectors (Particle Physics, Nuclear Physics,
and so on).

255

There was basically no difference between the latter two in the operation of the accelerator complex.

§ 4. ELPH workshops and ELPH seminars
In this fiscal year, ELPH supported a workshop on hadron physics, that on radiochemistry. The
research building of ELPH were not available from the end of December 2013 to be reformed. Therefore,
the former was held at Graduate School of Agriculture in Amamiya campus, and the latter was held
at Sakura hall in Katahira campus. ELPH also supported in part the third international school for
strangeness nuclear physics [3]. A seminar was held at ELPH.

References[1]

T. Ishikawa et al.: Commissioning of the photon beamline II after the recovery of the earthquake
in FY2013, in this annual report.

[2]

T. Ishikawa et al.: Commissioning of the positron beamline for testing detectors after the recoveryof the earthquake in FY2013, in this annual report.

[3]

H. Tamura and K. Imai: Web site hhttp://lambda.phys.tohoku.ac.jp/snpsc2014/i.

ELPH Annual Report, Tohoku University (2011-2013)

256

放射線安全管理室報告（平成 23 年 4 月〜平成 26 年 3 月）
放射線安全管理室

Radiation Safety Report 2011, 2012, and 2013
Radiation Control Office2011 年度（平成 23 年 4 月〜平成 24 年 3 月）
§ 1 . 変更申請
2011 年度の変更承認申請はない。

§ 2 . 個人管理
2.1 放射線業務従事者登録100 人（東北大 41 人、研究者以外 59 人）
2.2 個人被ばく管理
1 年間の個人被ばく線量 5 mSv 以下 100 人
2.3 教育訓練
定期講習
平成 23 年 7 月 25 日 再教育 85 人 （新人教育は実施せず）
特別講演の内容：日本原子力研究開発機構

J-PARC センター 柴田 徳思 先生「放射線防護 ICRP2007 の考え方を中心に」不定期の講習6回

14 人§ 3 . 管理区域内作業34 件。 すべての作業において、被ばく無し。

257§ 4 . 自主点検
1 回目 平成 23 年 9 月 21、22 日
2 回目 平成 24 年 3 月 15 日

§ 5 . 製造核種と数量
2011 年度は加速器の運転がないため製造された核種はない。

258

2012 年度（平成 24 年 4 月〜平成 25 年 3 月）
§ 1 . 変更申請
2012 年度の変更承認申請はない。

§ 2 . 個人管理
2.1 放射線業務従事者登録194 人（東北大 47 人、研究者以外 132 人）
2.2 個人被ばく管理
1 年間の個人被ばく線量 5 mSv 以下 194 人
2.3 教育訓練
定期講習
平成 24 年 6 月 26 日 新規教育 13 人 再教育 53 人
特別講演の内容：日本原子力研究開発機構 永井 泰樹 先生「加速器中性子による 99Mo 等医療用 RI 生成研究」
不定期の講習19 回 131 人§ 3 . 管理区域内作業71 件。 すべての作業において、被ばく無し。

§ 4 . 自主点検
1 回目 平成 24 年 9 月 18 日
2 回目 平成 25 年 3 月 14 日

§ 5 . 製造核種と数量
2012 年度は加速器の運転がないため製造された核種はない。

§ 6 . 検査関係
平成 24 年 9 月 27 日 定期検査・定期確認
定期検査 合格保留（貯留槽 使用不可のため）定期確認 適合（定期確認証番号 放確発 24 確第 114 号）

259

2013 年度（平成 25 年 4 月〜平成 26 年 3 月）
§ 1 . 変更申請等
1.1 放射性同位元素等の承認使用に係る変更承認申請
平成 25 年 9 月 4 日申請，平成 25 年 10 月 30 日承認
変更の内容

1. 加速装置の新設・変更とそれに伴うビームラインの変更(ア) 電子直線加速装置を 70 MeV 電子直線加速装置に再構成(イ) 100 MeV 電子直線加速装置の新設(ウ) 電子シンクロトロンの最大エネルギーを 1.2 GeV から 1.3 GeV に変更(エ) 加速装置の変更に伴うビームラインの変更(オ) 50 MeV 直線加速装置の新設
2. 排水浄化槽の更新とそれに伴う管理区域の変更
3. 光源加速器棟の新設
4. 保管廃棄設備の新設
5. 使用核種の見直し
1.2 放射線障害予防規程の変更
平成 25 年 12 月 20 日付§ 2 . 個人管理
2.1 放射線業務従事者登録155 人（ 東北大 50 人 学外 55 人 研究者以外 50 人）
2.2 個人被ばく管理
1 年間の個人被ばく線量 5 mSv 以下 155 人
2.3 教育訓練
定期講習
平成 25 年 6 月 18 日 新規教育 22 人 再教育 68 人
特別講演の内容：福島県農業総合センター果樹研究所 主任研究員 佐藤守 氏「福島における原発事故の果樹への影響」
不定期の講習18 回 73 人§ 3 . 管理区域内作業50 件。 すべての作業において、被ばく無し。

260§ 4 . 自主点検
1 回目 平成 25 年 9 月 18 日
2 回目 平成 26 年 3 月 13 日

§ 5 . 製造核種と数量
2010 年度に本加速器施設で製造され、共同研究に使用された放射性同位元素は次のとおり。
核種

数量 (kBq)

Au-196

1,500

Br-77

15

Ca-47

200

Cl-34m

550

Co-57

320

K-42

50

K-43

50

Na-24

200

Ni-57

3,000

Sc-44

2,000

Sc-44m

100

Sc-47

100

Sr-85

50

Yb-175500

全 14 核種

計 8,635 kBq§ 6 . 検査関係
平成 25 年 12 月 12 日〜13 日 施設検査
平成 25 年 12 月 19 日付 合格（施設検査合格証番号 放検発 25 合第 256 号）
定期検査（平成 24 年 9 月 27 日 実施）
平成 25 年 12 月 19 日付 合格（定期検査合格証番号 放検発 24 合第 154 号）§ 7 . 放射線取扱主任者の選任・解任
選任：平成 25 年 6 月 1 日 菊永英寿、武藤俊哉
解任：平成 26 年 3 月 31 日 大槻 勤

§8 . そ の 他
1. ) 原子力規制委員会 平成 25 年 5 月 30 日付「Ｊ−ＰＡＲＣにおける放射性物質の漏えいを踏まえた対応について（要請）」（原規放発第 1305301 号）に対する回答を平成 25 年 6 月 4 日付 提出した。

2. ) 文部科学省 平成 25 年 5 月 31 日付 「加速器施設に係る安全管理体制等の再確認について」（25 文科振大 355 号）に対する報告を平成 25 年 9 月 4 日付 提出した。

ELPH Annual Report, Tohoku University (2011-2013)

261

List of Publication (論文リスト) (2011)
Papers Published in Refereed Journals
Test-Accelerator as Coherent Terahertz Source Program (t-ACTS) at Tohoku University
H. Hama, M. Kawai, S. Kashiwagi, F. Hinode, F. Miyahara, K. Nanbu, T. Muto, Y. Tanaka,
X. Li, N.Y. Huang
Energy Procedia, Vol. 9, 391-397 (2011).
Interaction cross sections for Ne isotopes towards the island of inversion and halo structures of 29 Ne and
31

Ne
M. Takechi, T. Ohtsubo, M. Fukuda, D. Nishimura, T. Kuboki, T. Suzuki, T. Yamaguchi,
A. Ozawa,T. Moriguchi, H. Ooishi, D. Nagae, H. Suzuki, S. Suzuki, T. Izumikawa, T. Sumikama,
M. Ishihara,H. Geissel, N. Aoi, Rui-Jiu Chen, De-Qing Fang, N. Fukuda, I. Hachiuma, N. Inabe, Y. Ishibashi, Y. Ito, D. Kameda, T. Kubo, K. Kusaka, M. Lantz, Yu-Gang Ma, K. Matsuta,
M. Mihara, Y. Miyashita, S. Momota, K. Namihira, M. Nagashima, Y. Ohkuma, T. Ohnishi,
M. Ohtake, K. Ogawa, H. Sakurai, Y. Shimbara, T. Suda, H. Takeda, S. Takeuchi, K. Tanaka,
R. Watanabe, M. Winkler, Y. Yanagisawa, Y. Yasuda, K. Yoshinaga, A. Yoshida, K. Yoshida
Physics Letters B 707 (2012) 357-361.

The ’Study on Nuclear Data by Using a High Intensity Pulsed Neutron Source for Advanced Nuclear
System’ Nuclear Data Project and the Characteristics of the Neutron Beam Line for the Capture Cross
Section Experiments at J-PARC
Y. Kiyanagi, K. Kino, M. Furusaka, F. Hiraga, T. Kamiyama, K. Kato, M. Igashira, T. Katabuchi,
M. Mizumoto, M. Oshima, H. Harada, J. Katakura, K. Furutaka, S. Goko, A. Kimura, T. Kin,
F. Kitatani, M. Koizumi, S. Nakamura, M. Ohta, Y. Toh, T. Ohtsuki, K. Hirose, T. Fujii, J. Hori,
K. Takamiya, S. Fukutani, M. Shibata, K. Yamada, H. Utsunomiya
Journal of Korean Physical Society 59 (2011) 1781-1784.
Cross section measurements for neutron-induced fission of minor actinides with lead slowing-down spectrometer at KURRI
K. Hirose, T. Ohtsuki, Y. Shibasaki, N. Iwasa, J. Hori, S. Sekimoto, K. Takamiya, H. Yashima,
K. Nishio, and Y. Kiyanagi
Journal of Korean Physical Society 59 (2011) 1733-1736.
Precision measurement of the half-life of 90m Nb and 99m Tc
H. Kikunaga, H. Fujisawa. K. Ooe, R. Takayama, A. Shinohara, K. Takamiya, Y. Kasamatsu,
Y. Ezaki, H. Haba, T. Nakanishi, T. Mitsugashira, K. Hirose, T. Ohtsuki
Proc. Radiochim. Acta 1, (2011) 113-116.
Precision measurements of the half-life of 196 Au and 202 Tl
K. Hirose, H. Kikunaga, T. Ohtsuki

262

Proc. Radiochim. Acta 1, (2011) 109-111.
Half-life measurement of 7 Be in beryllium metals
T. Ohtsuki, K. Hirose, K. Ohno, T. Morisato
Proc. Radiochim. Acta 1, (2011) 101-104.
Production of 265 Sg in the 248 Cm(22 Ne, 5n) 265 Sg reaction and decay properties of two isomeric states in
265

Sg
H. Haba, D. Kaji, Y. Kudou, K. Morimoto, K. Morita, K. Ozeki, R. Sakai, T. Sumita, A. Yoneda,
Y. Kasamatsu, Y. Komori, A. Shinohara, H. Kikunaga, H. Kudo, K. Nishio, K. Ooe, N. Sato,
K. Tsukada
Physical Review C 85 (2012) 024611/1-11.

Determination of the half-life of the ground state of 229 Th by using 232 U and 233 U decay series
H. Kikunaga, T. Suzuki, M. Nomura, T. Mitsugashira, A. Shinohara
Physical Review C 84 (2011), 014316/1-5.
Production and decay properties of the 1.9-s isomeric state in 261 Rf
H. Haba, D. Kaji, H. Kikunaga, Y. Kudou, K. Morimoto, K. Morita, K. Ozeki, T. Sumita,
A. Yoneda
Physical Review C 83 (2011), 034602/1-7.
Separation of Am(III), Cm(III), and Cf(III) using capillary electrophoresis
H. Kikunaga, T. Yoshimura, T. Kuribayashi, Y. Kitamoto, N. Takahashi, H. Haba, Y. Ezaki,
S. Enomoto, T. Mitsugashira, A. Shinohara
Proceeding in Radiochemistry 1 (2011), 167-171.
Extraction behavior of carrier-free and macro amounts of molybdenum and tungsten from HCl solution
K. Ooe, W. Yahagi, Y. Komori, H. Fujisawa, R. Takayama, H. Kikunaga, T. Yoshimura, N. Takahashi, H. Haba, Y. Kudou, Y. Ezaki, A. Shinohara
Proceeding in Radiochemistry 1 (2011), 127-129.
Solvent extraction of trivalent actinides with di(2-ethylhexyl) phosphoric acid
R. Takayama, K. Ooe, W. Yahagi, H. Fujisawa, Y. Komori, H. Kikunaga, T. Yoshimura, N. Takahashi, K. Takahisa, H. Haba, Y. Kudou, Y. Ezaki, A. Toyoshima, M. Asai, Y. Nagame, T. Saito,
T. Mitsugashira, A. Shinohara
Proceeding in Radiochemistry 1 (2011), 157-160.
The Electron-Ion Scattering experiment ELISe at the International Facility for Antiproton and Ion Research (FAIR) - a conceptual design study
A.N. Antonov, M.K. Gaidarov, M.V. Ivanov, D.N. Kadrev, M. Aiche, G. Barreau, S. Czajkowski,
B. Jurado, G. Belier, A. Chatillon, T. Granier, J. Taieb, D. Dore, A. Letourneaux, D. Ridikas,
E. Dupont, E. Berthoumieux, S. Panebianco, F. Reymund, C. Schmitt, L. Audoin, E. Khan,
L. Tassan-Got, T. Aumann, P. Beller, K. Boretzky, C. Scheidenberger, A. Dolinskii, P. Egelhof,
H. Emling, B. Franzke, H. Geissel, A. Kelic-Heil, O. Kester, N. Kurz, Y. Litvinov, G. Muenzenberg, F. Nolden, K.-H. Schmidt, H. Simon, M. Stech, H. Weick, J. Enders, N. Pietralla,

263

A. Richter, G. Schrieder, A. Zilgers, M.O. Distler, H. Merkel, U. Muller, A. Junghans, H. Lenske,
M. Fujiwara, T. Suda, S. Kato, T. Adachi , S. Hamieh, M.N. Harakeh, N. Kalantar-Nayestanaki,
H. Wortche, G.P.A. Berg, I.A. Koop, P.V. Logatchov, A.V. Otboev, V.V. Parkhomchuk, D.N. Shatilov,
Y.M. Shatunov, S.V. Shiyankov, D.I. Shvartz, A.N. Skrinsky, L.V. Chulkov, B.V. Danilin, A.A. Korsheninnikov, E.A. Kuzmin, A.A. Ogloblin, V.A. Volkov, Y. Grishkin, V.P. Lisin A.N. Mushkarenkov,
V. Nedorezov, A.L. Polonski, N.V. Rudnev, A.A. Turinge, A. Artukh, S.N. Ershov, A. Fomichev,
M. Golovkov, A.V. Gorshkov, L. Grigorenko, S. Klygin, S. Krupko, I.N. Meshkov, A. Rodin,
Y. Sereda, I. Seleznev, S. Sidorchuk, E. Syresin, S. Stepantsov, G. Ter-Akopian, Y. Teterev,
A.N. Vorontsov, S.P. Kamerdzhiev, E.V. Litvinova, S. Karataglidis, R. Alvarez Rodriguez,
M.J.G. Borge, C. Fernandez Ramirez, E. Garrido, P. Sarriguren, J.R. Vignote, L.M. Fraile
Prieto, J. Lopez Herraiz, E. Moya de Guerra, J. Udias-Moinelo, J.E. Amaro Soriano, A.M. Lallena Rojo, J.A. Caballero, H. Johansson, B. Jonson, T. Nilsson, G. Nyman, M. Zhukov, V. Avdeichikov, P. Golubev, D. Rudolph, K. Hencken, J. Jourdan, B. Krusche, T. Rauscher, D. Kiselev,
D. Trautmann, J. Al-Khalili, W. Catford, R. Johnson, P. Stevenson, C. Barton, D. Jenkins,
R. Lemmon, M. Chartier, D. Cullen, C.A. Bertulani, A. Heinz
Nucl. Instr. and Meth. Phys. Res. A, 637, 60, 2011.
A novel spectrometer for studying exotic nuclei with the electron/ion collider ELISe
G.P.A. Berg, T. Adachi, M.N. Harakeh, N. Kalantar-Nayestanaki, H.J. Wörtche, H. Simon,
I.A. Koop, M. Couder, M. Fujiwara
Nucl. Instr. Meth. Phys. Res. A, 640, 123, (2011).
The 150 Nd( 3 He, t) and 150 Sm(t, 3 He) reactions with applications to ββ decay of 150 Nd
C. J. Guess, T. Adachi, H. Akimune, A. Algora, Sam M. Austin, D. Bazin, B. A. Brown, C. Caesar, J. M. Deaven, H. Ejiri, E. Estevez, D. Fang, A. Faessler, D. Frekers, H. Fujita, Y. Fujita,
M. Fujiwara, G. F. Grinyer, M. N. Harakeh, K. Hatanaka, C. Herlitzius, K. Hirota, G. W. Hitt,
D. Ishikawa, H. Matsubara, R. Meharchand, F. Molina, H. Okamura, H. J. Ong, G. Perdikakis,
V. Rodin, B. Rubio, Y. Shimbara, G. Süsoy, T. Suzuki, A. Tamii, J. H. Thies, C. Tur, N. Verhanovitz, M. Yosoi, J. Yurkon, R. G. T. Zegers, and J. Zenihiro
Phys. Rev. C 83, 064318 (2011).
High-resolution study of the 9 Be(3 He, t) 9 B reaction up to the 9 B triton threshold
C. Scholl, Y. Fujita, T. Adachi, P. von Brentano, H. Fujita, M. Górska, H. Hashimoto, K. Hatanaka,
H. Matsubara, K. Nakanishi, T. Ohta, Y. Sakemi, Y. Shimbara, Y. Shimizu, Y. Tameshige,
A. Tamii, M. Yosoi, and R. G. T. Zegers
Phys. Rev. C 84, 014308 (2011).
Complete Electric Dipole Response and the Neutron Skin in 208 Pb
A. Tamii, I. Poltoratska, P. von Neumann-Cosel, Y. Fujita, T. Adachi, C. A. Bertulani, J.Carter,
M. Dozono, H. Fujita, K. Fujita, K. Hatanaka, D. Ishikawa, M. Itoh, T. Kawabata, Y. Kalmykov,
A. M. Krumbholz, E. Litvinova, H. Matsubara, K. Nakanishi, R. Neveling, H. Okamura,
H. J. Ong, B. Özel-Tashenov, V. Yu. Ponomarev, A. Richter, B. Rubio, H. Sakaguchi, Y. Sakemi,

264

Y. Sasamoto, Y. Shimbara, Y. Shimizu, F. D. Smit, T. Suzuki, Y. Tameshige, J. Wambach,R. Yamada, M. Yosoi, and J. Zenihiro
Phys. Rev. Lett. 107, 062502 (2011).
High-precision 28 Si(p, t)26 Si reaction to determine 22 Mg(α, p) 25 Al reaction rates
A. Matic, A. M. van den Berg, M. N. Harakeh, H. J. Wörtche, M. Beard, G. P. A. Berg,
J. Görres, P. LeBlanc, S. O’Brien, M. Wiescher, K. Fujita, K. Hatanaka, Y. Sakemi, Y. Shimizu,
Y. Tameshige, A. Tamii, M. Yosoi, T. Adachi, Y. Fujita, Y. Shimbara, H. Fujita, T. Wakasa,
J. P. Greene, R. Crowter, and H. Schatz
Phys. Rev. C 84, 025801 (2011).
High energy-resolution zero-degree facility for light-ion scattering and reactions at iThemba LABS
R. Neveling, , H. Fujita, F.D. Smit, T. Adachi, G.P.A. Berg, E.Z. Buthelezi, J. Carter, J.L. Conradie, M. Couder, R.W. Fearick, S.V. Förtsch, D.T. Fourie, Y. Fujita, J. Görres, K. Hatanaka,
M. Jingo, A.M. Krumbholz, C.O. Kureba, J.P. Mira, S.H.T. Murray, P. von Neumann-Cosel,
S. O’Brien, P. Papka, I. Poltoratska, A. Richter, E. Sideras-Haddad, J.A. Swartz, A. Tamii,
I.T. Usman, J.J. van Zyl
Nucl. Instrum. and Meth. in Phys. Res. A, 654, 29 (2011).
High-resolution (3 He, t) reaction on the double-β decaying nucleus 136 Xe
P. Puppe, D. Frekers, T. Adachi, H. Akimune, N. Aoi, B. Bilgier, H. Ejiri, H. Fujita, Y. Fujita, M. Fujiwara, E. Ganioǧlu, M. N. Harakeh, K. Hatanaka, M. Holl, H. C. Kozer, J. Lee,
A. Lennarz, H. Matsubara, K. Miki, S. E. A. Orrigo, T. Suzuki, A. Tamii, and J. H. Thies
Phys. Rev. C 84, 051305 (2011).
The

71

Ga(3 He, t) reaction and the low-energy neutrino response

D. Frekers, H. Ejiri, H. Akimune, T. Adachi, B. Bilgier, B.A. Brown, B.T. Cleveland, H. Fujita,
Y. Fujita, M. Fujiwara, E. Ganioglu, V.N. Gavrinh, E.-W. Grewea, C.J. Guesse, M.N. Harakeh,
K. Hatanaka, R. Hodak, M. Holl, C. Iwamoto, N.T. Khai, H.C. Kozer, A. Lennarz, A. Okamoto,
H. Okamura, P.P. Povinec, P. Puppe, F. Simkovic, G. Susoy, T. Suzuki, A. Tamii, J.H. Thies,
J. Van de Walle, R.G.T. Zegers
Phys. Lett. B 706, 134, (2011).
Constant-gap spectrometer design for the electron/ion collider ELISeT. Adachi, M.N. Harakeh, N. Kalantar-Nayestanaki, H.J. Wörtche, G.P.A. Berg, H. Simon,
I.A. Koop, M. Couder, M. Fujiwara
Nucl. Instrum. and Meth. in Phys. Res. A 659, 198, (2011).
High-resolution study of Gamow-Teller transitions via the 54 Fe(3 He, t) 54 Co reaction
T. Adachi, Y. Fujita, A. D. Bacher, G. P. A. Berg, T. Black, D. De Frenne, C. C. Foster, H. Fujita,
K. Fujita, K. Hatanaka, M. Honma, E. Jacobs, J. Jänecke, K. Kanzaki, K. Katori, K. Nakanishi, A. Negret, T. Otsuka, L. Popescu, D. A. Roberts, Y. Sakemi, Y. Shimbara, Y. Shimizu,
E. J. Stephenson, Y. Tameshige, A. Tamii, M. Uchida, H. Ueno, T. Yamanaka, M. Yosoi, andK. O. Zell

265

Phys. Rev. C 85, 024308 (2012) .
Spin-Density Matrix Elements for γ p → K∗0 Σ+ at Eγ =1.85-3.0 GeV with Evidence for the K(800) Meson
Exchange
S. H. Hwang, K. Hicks, J. K. Ahn, T. Nakano, D. S. Ahn, W. C. Chang, J. Y. Chen, S. Date,
H. Ejiri, H. Fujimura, M. Fujiwara, S. Fukui, W. Gohn, T. Hotta, K. Imai, T. Ishikawa, K. Joo,
Y. Kato, H. Kohri, Y. Kon, H. S. Lee, Y. Maeda, M. Miyabe, T. Mibe, Y. Morino, N. Muramatsu, Y. Nakatsugawa, M. Niiyama, H. Noumi, Y. Oh, Y. Ohashi, T. Ohta, M. Oka, J. Parker,
C. Rangacharyulu, S. Y. Ryu,, T. Sawada, Y. Sugaya, M. Sumihama, T. Tsunemi, M. Uchida,
M. Ungaro, and M. Yosoi (LEPS Collaboration)
Phys. Rev. Lett. 108, 092001 (2012).
Absorption Capacity and Heat Evolution with Loading of Hydrogen Isotope Gases for Pd Nanopowder
and Pd/Ceramics Nanocomposite
T. Hioki, H. Azuma, T. Nishi, A. Itoh, S. Hibi, J. Gao, T. Motohiro and J. Kasagi
J. Condensed Matter Nucl. Sci. 4 (2011) 69-80.
Observation of Low Energy Nuclear Transmutation Reactions Induced by Deuterium Permeation throughMultilayer Pd and CaO thin Film
Y. Iwamura, T. Itoh, N.Yamazaki, J. Kasagi,Y. Terada, T. Ishikawa, D. Sekiba, H. Yonemura
and K. Fukutani
J. Condensed Matter Nucl. Sci. 4 (2011) 132-145.
Screening Potential of 6 Li(d, α) 4 He and 7 Li(p, α) 4 He Reactions in Liquid Lithium
K. H. Fang, T. S. Wang, H. Yonemura, A. Nakagawa, T. Sugawara and J. Kasagi
J. Phys. Soc. Jpn., 80 (2011) 084201-1-6.
Measurement of the partial cross sections σT T , σLT , and (σT + ϵσL ) of the 1 H(e, e′ π + ) n reaction in the∆(1232) resonance
J. M. Kirkpatrick, N. F. Sparveris, I. Nakagawa, A. M. Bernstein, R. Alarcon, Bertozzi, T. Botto,
P. Bourgeois, J. Calarco, F. Casagrande, M. O. Distler, K. Dow, M. Farkondeh, S. Georgakopoulos, S. Gilad, R. Hicks, M. Holtrop, A. Hotta, X. Jiang, A. Karabarbounis, S. Kowaski, R. Milner, R. Miskimen, C. N. Papanicolas, A.J. Sarty, Y. Sato, S. Sirca, J. Shaw, E. Six, S. Stave,
E. Stiliaris, T. Tamae, G. Tsentalovich, C. Tschalaer, W. Turchinetz, Z.-L. Zhou, and T. Zwart
Physical Review C 84 (2011) 28201(1-4).
Measurements of the generalized electric and magnetic polarizabilities of the proton at low Q2 using thevirtual Compton scattering reaction
P. Bourgeois, Y. Sato, J. Shaw, R. Alarcon, A. M. Bernstein, W. Bertozzi, T. Botto, J. Calarco,
F. Casagrande, M. O. Distler, K. Dow, M. Farkondeh, S. Georgakopoulos, S. Gilad, R. Hicks,
M. Holtrop, A. Hotta, X. Jiang, A. Karabarbounis, J. Kirkpatrick, S. Kowaski, R. Milner,
R. Miskimen, I. Nakagawa, C. N. Papanicolas, A. J. Sarty, S. Sirca, E. Six, N.F. Sparveris,
S. Stave, E. Stiliaris, T. Tamae, G. Tsentalovich, C. Tschalaer, W. Turchinetz, Z.-L. Zhou, andT. Zwart

266

Physical Review C 84 (2011) 35206(1-8).
Measurement of interaction cross-sections for neutron-rich Na isotopes
T. Kuboki, T. Ohtsubo, M. Takechi, I. Hachiuma, K. Namihira, T. Suzuki, T. Yamaguchi, Y.
Ohkuma, Y. Shimbara, S. Suzuki, R. Watanabe, M. Fukuda, M. Mihara, D. Nishimura, Y.
Ishibashi, Y. Ito, T. Moriguchi, D. Nagae, H. Ooishi, K. Ogawa, A. Ozawa, Y. Yasuda, H.
Suzuki, T. Sumikama, K. Yoshinaga, H. Geissel, M. Winkler, T. Izumikawa, S. Momota, N.
Aoi, N. Fukuda, N. Inabe, D. Kameda, K. Kusaka, T. Kubo, M. Lantz, T. Ohnishi, M. Ohtake,T. Suda, H. Takeda, K. Tanaka, Y. Yanagisawa, A. Yoshida, K. Yoshida
Acta Physica Polonica B, 42 (2011) 765-768.

Papers Published in International Conference Proceedings
Coherent synchrotron radiation source based on an isochronous accumulator ring with femtosecond
N.Y. Huang, H. Hama, M. Kawai, S. Kashiwagi, F. Hinode, K. Nanbu, T. Muto, F. Miyahara,
Y. Tanaka, X. Li
Proc. of IPAC2011, 2085-2087, Spain, (2011).
Expected performance characteristic of accelerator-based THz source at Tohoku University
H. Hama, M. Kawai, S. Kashiwagi, F. Hinode, K. Nanbu, T. Muto, Y. Tanaka, X. Li, N.Y. Huang
Proc. of IPAC2011, 2990-2992, Spain, (2011).
Injector system of test Accelerator as Coherent Terahertz Source
S. Kashiwagi, F. Hinode, M. Kawai, T. Muto, K. Nanbu, Y. Tanaka, X. Li, H. Hama, N.Y. Huang
Proc. of IPAC2011, 2993-2995, Spain, (2011).
Commissioning of ITC-RF Gun for t-ACTS project at Tohoku University
F. Hinode, H. Hama, S. Kashiwagi, M. Kawai, X. Li, T. Muto, K. Nanbu, Y. Tanaka, F. Miyahara
Proc. of FEL2011, THPA31, China, (2011).
Study of the backbombardment effect in the ITC-RF Gun for t-ACTS project at Tohoku University
X. Li, H. Hama, F. Hinode, S. Kashiwagi, M. Kawai, T. Muto, K. Nanbu, Y. Tanaka, N.Y. Huang
Proc. of FEL2011, THPA17, China, (2011).
Study of reflective optics for LFC-camera
K. Nanbu, S. Kashiwagi, M. Kawai, F. Hinode, X. Li, T. Muto, Y. Tanaka, H. Hama
Proc. of FEL2011, THPB08, China, (2011).
Study of charged pion photoproduction on deuteron
Y.C. Han, B. Backford, N. Chiga, T. Fujii, T .Fujibayashi, T. Gogami, K. Futatsukawa, O. Hashimoto,
K. Hirose, K. Hosomi, A. Iguchi, T. Ishikawa, H. Kanda, M. Kaneta, D. Kawama, T. Kawasaki,
C. Kimura, S. Kiyokawa, T. Koike, Y. Ma, K. Maeda, N. Maruyama, A. Matsumura, Y. Miyagi,
K. Miwa, S.N. Nakamura, A. Okuyama, T. Otani, M. Sato, A. Shichijo, K. Shirotori, H. Shimizu,
K. Suzuki, H. Tamura, N. Taniya, N. Terada, T. Yamamoto, T. Yamamoto, K. Yokota, T. Tamae,
T.S. Wang and H. Yamazaki

267

Nucl. Phys. A 834, 596c (2010) 596c.
Neutral kaon photo-production in the threshold energy region
B. Beckford, P. Bydžovský, J. Fujibayashi, T. Fujii, Y. Fujii, K. Futatsukawa, T. Gogami,
O. Hashimoto, Y. C. Han, K. Hirose, K. Hosomi, A. Iguchi, T. Ishikawa, H. Kanda, M. Kaneta,
D. Kawama, T. Kawasaki, S. Kiyokawa, T. Koike, K. Maeda, N. Maruyama, K. Miwa, Y. Miyagi,
S. N. Nakamura, A. Sasaki, H. Shimizu, K. Shirotori, K. Suzuki, T. Tamae, H. Tamura, N. Terada, K. Tsukada, and H. Yamazaki
AIP Conf. Proc. (BARYONS’ 10), 1388 (2011),280-283.
Li+D and D+D rusion assisted with acoustic cavitation
Y. Toriyabe, E. Yoshida and J. Kasagi
Proceedings of 15th International Conference on Condensed Matter Nuclear Science ICCF15,(2011), 257-262.
Hydrogen/Deuterium absorption property of Pd fine particle systems and heat evolution associated with
Hydrogen/Deuterium loading
T. Hioki, H. Azuma, T. Nishi, A. Itoh, J. Gao, S. Hibi, T. Motohiro, J. Kasagi
ibid. 88-93.
Electron scattering
Toshimi Suda
French-Japanese Symposium on Nuclear Structure Problems, ed. H. Otsu, T. Motobayashi,
P. Chomaz and T. Otsuka: World Scientific 230-235, 2011.
Present status of the RIKEN RI Beam Factory
Toshimi Suda
10th International Spring Seminar on Nuclear jh,6Physics: New Quests in Nuclear Structure,
ed. A. Covello and A. Garagano (Journal of Physics): Conference Series 267, 012008, 2011.

Invited Talk and Oral Presentations at International Conferencest-ACTS project employing isochronous ring and undulator together with femtosecond electron pulse at
Tohoku University
H. Hama
Chiang Mai University, Chiang Mai, Thailand, May 30, 2011.
Status and prospect of t-ACTS at Tohoku University, Sendai
H. Hama
Quantum beam based Radiation research Center, Korea Atomic Energy Research Institute,Daejeon, Korea, September 22, 2011.
Low-energy nuclear reactions in liquid metal
J. Kasagi
FUSION11, International Conference on Reaction Mechanisms and Nuclear structure around
Coulomb Barrier, Saint-Malo, France, May 2 - 6, 2011.

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Electron scattering for exotic nuclei
T. SudaThe International Symposium on Physics of Unstable Nuclei 2011 Hanoi, Vietnam, November, 2011.
Strangeness photoproduction in the threshold energy region
Kazushige Maeda
ECT* Workshop on Strange Hadronic Matter, Trento, Italy, 2011/9/26 - 30.
Baryon resonances studied via η and π 0 photoproduction
T. Ishikawa
ECT* Workshop on Strange Hadronic Matter, Trento, Italy, 2011/9/26 - 30.
Narrow baryon resonance studied via η photoproduction at ELPH and SPring-8/LEPS
T. Ishikawa
RCNP Workshop on Hadron Structure and Interactions in 2011, Osaka, Japan, 2011/11/25.

学位論文 (電子光理学研究センター所属)
博士論文「光生成閾値近傍での ω − N 相互作用の研究」
橋本 亮，平成 23 年，東北大学
博士論文「閾値近傍の πη 光生成反応によるハドロン相互作用の研究」
鈴木 耕拓，平成 23 年，東北大学
修士論文 「不安定核用自己閉じ込め型標的 (SCRIT) を用いた電子散乱実験のルミノシティ測定」
北沢 僚也, 平成 23 年, 東北大学
修士論文 「電磁カロリメータによる Λ 光生成反応の研究」
土川 雄介, 平成 23 年, 東北大学
修士論文 「電磁カロリメータ FOREST による γp → π 0 π + n 反応の研究」
中村 聡彦, 平成 23 年, 東北大学
修士論文「Study on the Back-bombardment Effect in a Thermionic RF gun Equipped with Single Crystal

Cathode of LaB6 」
Xiangkun Li (李 相坤), 平成 23 年, 東北大学
修士論文 「Vibrating wire 法を用いる THz アンジュレータの磁場測定の研究」
田中 佑, 平成 23 年, 東北大学

学位論文 (他機関所属)
博士論文「Study of Low Energy 6 Li + d Nuclear reaction in Lithium Target」

Fang Kai-Hong，2011 年，蘭州大学
修士論文「π 中間子光生成反応を利用した標識化光子エネルギー決定方法の研究」
金子 勇介,

平成 23 年度，東北大学

修士論文「ω 中間子光生成を利用した光子標識化装置の較正方法の研究」
松原 正夫，平成 23 年，東北大学

269

修士論文「積分型 SOI pixel 検出器による高エネルギー粒子ビーム飛跡再構成実験」
葛山 浩教，平成 23 年，東北大学
修士論文「GEM を用いた軌跡検出器のための読み出し電極の開発」
高木 敦子，平成 23 年，東京大学

270

List of Publication (論文リスト) (2012)
Papers Published in Refereed Journals
Nuclear physics at the SCRIT electron scattering facility
T. Suda, T. Adachi, T. Amagai, A. Enokizono, M. Hara, T. Hori, S. Ichikawa, K. Kurita,
T. Miyamoto, R. Ogawara, T. Ohnishi, Y. Shimakura, T. Tamae, M. Togasaki, M. Wakasugi,
S. Wang and K. Yanagi
Prog. Theor. Exp. Phys. 03C008, 2012
Interaction cross sections for Ne isotopes towards the island of inversion and halo structures of Ne-29
and Ne-31
M. Takechi, T. Ohtsubo, M. Fukuda, D. Nishimura, T. Kuboki, T. Suzuki, T. Yamaguchi,
A. Ozawa, T. Moriguchi, H. Ooishi, D. Nagae, H. Suzuki, S. Suzuki, T. Izumikawa, T. Sumikama,
M. Ishihara, H. Geissel, N. Aoi, Rui-Jiu Chen, De-Qing Fang, N. Fukuda, HI. achiuma, N. Inabe, Y. Ishibashi, Y. Ito, D. Kameda, T. Kubo, K. Kusaka, M. Lantz, Yu-Gang Ma, K. Matsuta,
M. Mihara, Y. Miyashita, S. Momota, K. Namihira, M. Nagashima, Y. Ohkuma, T. Ohnishi,
M. Ohtake, K. Ogawa, H. Sakurai, Y. Shimbara, T. Suda, H. Takeda, S. Takeuchi, K. Tanaka,
R. Watanabe, M. Winkler, Y. Yanagisawa, Y. Yasuda, K. Yoshinaga, YA. oshida, K.Yoshida,Phys. Lett. B 707 (2012) 357-361.
Progress in the R&D experiments about a novel method of electron scattering off short-lived nuclei
Wang Shuo, T. Suda, M. Wakasugi, T. Tamae, K. Kurita, A. Noda, T. Shirai, H. Tongu, Y. Yano
Plasma Science & Technology 14 (2012) 419-420.
Feed-forward control of the amplitude and the phase of a high-power RF pulse based on the overdrive
techniqueK. Kawase, Y. Morio, Y. Kon, M. Fujimoto, S. Hirata, J. Shen, R. Kato, A. Irizawa, G. Isoyama,
S. Kashiwagi
Nucl. Instr. Meth. A, 679 (2012) 44-53.
Determination of trace amount of nickel in cosmic spherules by photon activation analysis
S. Sekimoto, K. Hirose, M. Takimoto, T. Ohtsuki, S. Shibata
Journal of Radioanalytical and Nuclear Chemistry 291, 457-459(2012).
Fusion probabilities in the reactions 40;48 Ca + 238 U at energies around the Coulomb barrier
K. Nishio, S. Mitsuoka, I. Nishinaka, H. Makii, Y. Wakabayashi, H. Ikezoe, K. Hirose, T.
Ohtsuki, Y. Aritomo, S. Hofmann
Physical Review C 86, 034608 (1-6) (2012).
Fission cross-section measurements of 237 Np, 242m Am, and 245 Cm with lead slowing-down neutronspectrometer
K. Hirose, T. Ohtsuki, Y. Shibasaki, N. Iwasa, J. Hori, S. Sekimoto, K. Takamiya, H. Yashima,
K. Nishio, Y. Kiyanagi
Journal of Nuclear Science and Technology, 49,1057-1066 (2012).

271

Evidence for hindrance in fusion between sulfur and lead nuclei
J. Khuyagbaatar, K. Nishio, S. Hofmann, D. Ackermann, M. Block, S. Heinz, F. P. Heßberger,
K. Hirose, H. Ikezoe, B. Kinlder, B. Lommel, H. Makii, S. Mitsuoka, I. Nishinaka, T. Ohtsuki,
Y. Wakabayashi, S. Yan
Physical Review C 86, 064602(1-6) (2012).
Production of 265 Sg in the 248 Cm(22 Ne, 5n) 265 Sg reaction and decay properties of two isomericstates in
265

Sg
H. Haba, D. Kaji, Y. Kudou, K. Morimoto, K. Morita, K. Ozeki, R. Sakai, T. Sumita, A. Yoneda,
Y. Kasamatsu, Y. Komori, A. Shinohara, H. Kikunaga, H.Kudo, K. Nishio, K. Ooe, N. Sato and
K. Tsukada
Physical Review C: Nuclear Physics, 85 (2012), 024611/1-024611/11

New result in the production and decay of an isotope, 278 113, of the 113th element
K. Morita, K. Morimoto, D. Kaji, H. Haba, K. Ozeki, Y. Kudou, T. Sumita, Y.Wakabayashi,
A. Yoneda, K. Tanaka, S. Yamaki, R. Sakai, T. Akiyama, S. Goto, H. Hasebe, M. Huang, T.
Huang, E. Ideguchi, Y. Kasamatsu, K. Katori, Y. Kariya, H. Kikunaga, H. Koura, H. Kudo,
A. Mashiko, K. Mayama, S. Mitsuoka, T. Moriya, M. Murakami, H. Murayama, S. Namai, A.
Ozawa, N. Sato, K. Sueki, M. Takeyama, F. Tokanai, T. Yamaguchi, A. Yoshida
Journal of the Physical Society of Japan, 81 (2012), 103201/1-103201/4
A detailed test of a BSO calorimeter with 100-800 MeV positrons
T. Ishikawa, H. Fujimura, R. Hashimoto, J. Kasagi, R. Kitazawa, S. Kuwasaki, A. Nakamura,
K. Nawa, Y. Okada, M. Sato, H. Shimizu, K. Suzuki, Y. Tajima, S. Takahashi, Y. Tsuchikawa,
H. Yamazaki, H.Y. YoshidaNucl. Instr. & Meth. A694 (2012) 348-360.
Spin-density matrix elements for γp → K ∗0 Σ+ at Egamma = 1.85-3.0 GeV with evidence for κ(800)meson exchange
S.H. Hwang et al. (LEPS Collaboration)
Phys. Rev. Lett. 108 (2012) 092001.
Search for the decay B 0 → DK ∗0 followed by D → K − π +K. Negishi et al. (Belle Collaboration)
Phys. Rev. D 86 (2012), 011101(R).
Acceleration of nuclear fusion in metal lithium acoustic cavitation
Y. Toriyabe, E. Yoshida, J. Kasagi, and M. Fukuhara
Phys. Rev. C85 (2012) 054620-1-20.
TOF-SIMS investigation on nuclear transmutation from Sr to Mo with deuterium permeationthroughmulti-layered Pd/CaO
A. Murase, N. Takahashi, S. Hibi, T. Hioki, T. Motohiro and J. Kasagi
J. Condensed Matter Nucl. Sci. 6 (2012) 34-39.

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Papers Published in International Conference Proceedings
Development of THz sources based on femtosecond electron pulse train
H. Hama
Proc. of Workshop on Terahertz Sources for Time Resolved Studies of Matter, (2012), website.
Present status of thermionic RF-gun for terahertz source project at Tohoku University
F. Hinode, H. Hama, N.Y. Huang, S. Kashiwagi, M. Kawai, T. Muto, I. Nagasawa, K. Nanbu,
Y. Shibasaki, K. Takahashi, X. Li
Proceedings of FEL2012, (2012), MOPD45, 1-3.
Investigation of CSR effect for femtosecond electron bunches in an isochronous accumulator ring
N.Y. Huang, H. Hama, M. Kawai, S. Kashiwagi, F. Hinode, K. Nanbu, T. Muto, Y. Shibasaki,
I. Nagasawa, K. Takahashi
Proceedings of IPAC2012, (2012), 589-591.
Progress in reducing the back-bombardment effect in the ITC-RF Gun for t-ACTS project at Tohoku
University
X. Li, S. Kashiwagi, M. Kawai, F. Hinode, K. Nanbu, T. Muto, F. Miyahara, Y. Tanaka,
H. Hama
Proceedings of IPAC2012, (2012), 643-645.
Magnetic field measurement for a THz undulator using the vibrating wire method
S. Kashiwagi, Y. Tanaka, F. Hinode, M. Kawai, X. Li, T. Muto, K. Nanbu, H. Hama
Proceedings of IPAC2012, (2012), 732-734.
FEL gain measurement with a novel method
M. Fujimoto, R. Kato, K. Kawase, A. Irizawa, F. Kamitsukasa, H. Ohsumi, M. Yaguchi,
G. Isoyama, S. Kashiwagi, S. Yamamoto
Proc. of FEL2012, (Nara, Japan, 2012), pp.515-518.
1ms multi-bunch electron beam acceleration by a normal conducting RF gun and superconducting accelerator
M. Kuriki , H. Iijima, S. Hosoda, K. Kawase, G. Isoyama, R. Kato, K. Watanabe, H. Hayano,J. Urakawa, A. Kuramoto, S. Kashiwagi, K. Sakaue
Proc. of LINAC2012, (Tel-Aviv, Israel, 2012), pp.228-230.
Multi-bunch beam generation by photo-cathode RF gun for KEK-STF
M. Kuriki, H. Iijima, S. Hosoda, K. Kawase, G. Isoyama, R. Kato, ISIR, K.Watanabe, H.Hayano,
H. Sugiyama, J. Urakawa, A. Kuramoto, Y. Takahashi, S. Kashiwagi, K. Sakaue
Proc. of IPAC2012, New Orleans, USA, (2012), 1479-1481.
Λ photoproduction studied with an electromagnetic calorimeter FOREST
Y. Tsuchikawa, H. Fujimura, H. Fukasawa, R. Hashimoto, T. Ishikawa, T. Iwata, S. Kaida,
J. Kasagi, A. Kawano, S. Kuwasaki, K. Maeda, S. Masumoto, M. Miyabe, F. Miyahara, K.
Mochizuki, A. Nakamura, K. Nawa, S. Ogushi, Y. Okada, Y. Onodera, K. Ozawa, Y. Sakamoto,
M. Sato, H. Shimizu, H. Sugai, K. Suzuki, Y. Tajima, S. Takahashi, H. Yamazaki, and H.Y.

273

YoshidaQNP2012 proceedings PoS(QNP2012)100 (1-5).
Test of lepton flavor universality by precise Γ(Ke2 )/Γ(Kµ2 ) measurement, using stopped positive kaonsat J-PARC
S. Shimizu and TREK Collaboration
Proc. of 19th International Conference on Particles and Nuclei(PANIC11), AIP Conf. Proc.
1441 (2012) 338-340.
Search for non-standard model physics using the transverse muon polarization in stopped K + decay
S. Bianchin and TREK Collaboration
Proc. of 19th International Conference on Particles and Nuclei(PANIC11), AIP Conf.Proc.
1441 (2012) 567-569.
Search for T-violating transverse muon polarization in K + → π 0 µ+ ν decay at J-PARC
S. Shimizu for the J-PARC E06/E36 collaboration
Proc. of 20th International SPIN Physics (SPIN2012), to be published in Phys. of Elem.Part.
and Atom. Nucl.
The TREK program at J-PARC
Chaden Djalali (and TREK Collaboration)
IX Latin American Symposium on Nuclear Physics and Applications, AIP Conf. Proc. 1423
(2012) 297-302.
GeV photon beams for nuclear/particle physics
N. Muramatsu
arXiv:1201.4094 (2012); Prepared for a monograph paper

Laser Compton Scatter Photon

Beam Facilities - Techniques and Applications in Basic and Applied Science’, (Edited by
C. Rangacharyulu and S. Daté, World Scientific).

Invited Talk and Oral Presentations at International Conferences
Development of THz sources based on femtosecond electron pulse train
H. Hama
Workshop on Terahertz Sources for Time Resolved Studies of Matter, July 30-31, 2012, Argonne, USA.
Project of a 3 GeV synchrotron radiation facility in Tohoku, Japan (STIR/SLiT-J)
H. Hama
The 17th Hiroshima International Symposium on Synchrotron Radiation, February 27-March
1, 2013, Higashi-Hiroshima, Japan.
A THz source based on cavity configuration with femtosecond pulse train
H. Hama
JSPS Asian Core Workshop 2013, March 7-8, 2013, Daejeong, Korea.
Physics programs at ELPH-Tohoku

274

H. Shimizu
2nd International School for Strangeness Nuclear Physics, Feb.14-20, 2013, Sendai.
Recent progress and results of LEPS, LEPS2, and ELPH
N. Muramatsu
The 20th International IUPAP Conference on Few-Body Problems in Physics, 20-25 Aug2012,
Fukuoka.
Anomalous behavior of the d+d reaction in liquid indium bombarded by low-energy deuterons
J. Kasagi
CLUSTER12 10th International Conference on Clustering Aspects of Nuclear Structure andDynamics, Debrecen, Hungary, Sept. 24-28, 2012.
Astrophysical Sbare (E) factor of the 6 Li(d, α) 4 He and 7 Li(p, α) 4 He reactions
J. Kasagi
ND2013 International Conference on Nuclear Data for Science and Technology, New York,USA, March 4-8, 2013.
Electron scattering off short-lived nuclei
T. SudaMiniWorkshop : Systematic study of nuclear radii -Theory and Experiment-, Wako, Japan,
December, 2012.
SCRIT electron scattering facility at RIKEN
S. Wang, T. Adachi, M. Hara, T. Hori, S. Ichikawa, R. Kitazawa, K. Koizumi, K. Kurita, Y.
Miyashita, R. Ogawara, T. Ohnishi, T. Suda, H. Takehara, T. Tamae, S. Tamaki, M. Togasaki
and M. Wakasugi
EXON 2012 Vladivostok, Russia 2012/10/1 10/6.
SCRIT electron scattering facility - Hofstadter’s experiments for exotic nuclei
T. Sudamini-workshop on Exotic Nuclei, Hanoi, Vietnum, October, 2012.
SCRIT electron scattering facility at RIKEN
S. Wang, T. Adachi, M. Hara, T. Hori, S. Ichikawa, R. Kitazawa, K. Koizumi, K. Kurita, Y.
Miyashita, R. Ogawara, T. Ohnishi, T. Suda, H. Takehara, T. Tamae, S. Tamaki, M. Togasaki
and M. Wakasugi
mini workshop about SCRIT method, Beijing, China 2012/09
SCRIT electron scattering facility - Hofstadter’s experiments for exotic nuclei T. Suda
Direct Reaction with Exotic Beams, Pisa, Italy, March, 2012.
Two nucleon correlation in 6 He and 6 Li
T. SudaMini-workshop on nucleon correlation, Hanoi, Vietnam, Vietnam Atomic Energy Institute,
October, 2012.

275

Development of a scintillation counter with MPPC readout for the internal tagging system
N. Kanda
International Workshop on New Photon-detectors 2012(PhotoDet 2012), Orsay, France, 2012/6/13- 15.
Study of γd → π + π − d reaction in an energy region of 0.67 ≤ Eγ ≤ 1.08 GeV
C. KimuraThe 20th International IUPAP Conference on Few Body Physics, Fukuoka, Japan 2012/8/19 25.
Study of strangeness photoproduction on the neutron in the threshold region
N. Kanda
The 20th International IUPAP Conference on Few Body Physics, Fukuoka, Japan 2012/8/19 25.
The investigation of strangeness photoproduction in the threshold region at ELPH-Tohoku
M. Kaneta
XI International Conference on Hypernuclear and Strange Particle Physics (HYP2012), Barcelona,
Spain, 2012/10/1 - 5.

学位論文 (電子光理学研究センター所属)
修士論文「GeV 光子ビームプロファイルモニターの開発」
谷口 雄亮，平成 23 年，東北大学
修士論文「多重光子検出によるηメソン崩壊の研究」
山崎 竜司，平成 23 年，東北大学
修士論文「SCRIT 法による不安定核の電子散乱実験用 Luminosity monitor 系の開発」
天谷 達哉，平成 23 年，東北大学
修士論文「D3+ イオン入射による液体 In 中での DD 反応の研究」
本多 佑記，平成 23 年，東北大学

学位論文 (他機関所属)
博士論文「Study of the strangeness photoproduction process in the γd → ΛX reaction at photon energies

up to 1.08 GeV」
Brian Beckford Doctor thesis，平成 23 年度，東北大学
修士論文「MPPC を用いた内部標的型光子標識化装置の開発」
葛西 裕磨，平成 23 年，東北大学

276

List of Publication (論文リスト) (2013)
Papers Published in Refereed Journals
Ground design of a 3 GeV accelerator-complex for the synchrotron light in Tohoku, Japan (SLiT-J)
H. Hama, T. Muto, F. HinodeJ. Phys., Conf. Ser., 425 (2013), 072010, 1-4
Upgrade of the 1.2 GeV STB ring for the SR utilization in Tohoku University
F. Hinode, T. Muto, M. Kawai, S. Kashiwagi, Y. Shibasaki, K. Nanbu, I. Nagasawa, K. Takahashi and H. Hama
J. Phys., Conf. Ser., 425 (2013), 072011, 1-4
1 ms pulse beam generation and acceleration by photocathode radio frequency gun and superconducting
accelerator
M. Kuriki, H. Iijima, S. Hosoda, K. Watanabe, H. Hayano, J. Urakawa, G. Isoyama, R. Kato,
K. Kawase, A. Kuramoto, S. Kashiwagi and K. Sakaue
Jpn. J. Appl. Phys. Vol. 52, 2013, 056401-1- 056401-7.
Construction of nanosecond and picosecond pulse radiolysis system with supercontinuum probe
Y. Hosaka, R. Betto, K. Sakaue, R. Kuroda, S. Kashiwagi, K. Ushida, M. Washio
Radiat. Phys. Chem. 84 (2013) 10-13.
Construction of the SCRIT electron scattering facility at the RIKEN RI Beam Factory
M. Wakasugi, T. Ohnishi, S. Wang, Y. Miyashita, T. Adachi, T. Amagai, A. Enokizono, A.
Enomoto, Y. Haraguchi, M. Hara, T. Hori, S. Ichikawa, T. Kikuchi, R. Kitazawa, K. Koizumi,
K. Kurita, T. Miyamoto, R. Ogawara, Y. Shimakura, H. Takehara, T. Tamae, S. Tamaki, TM.
ogasaki, T. Yamaguchi, K. Yanagi, T. Suda
Nucl. Instrum. And Method B 317, (2013), 668-673.
Density distributions of Li-11 deduced from reaction cross-section measurements
T. Moriguchi, A. Ozawa, S. Ishimoto, Y. Abe, M. Fukuda, I. Hachiuma, Y. Ishibashi, Y. Ito, T.
Kuboki, M. Lantz, D. Nagae, K. Namihira, D. Nishimura, T. Ohtsubo, H. Ooishi, T. Suda, H.
Suzuki, T. Suzuki, M. Takechi, K. Tanaka, T. Yamaguchi.
Phys. Rev. C 88(2013)024610.
Elastic scattering of protons from C-9 with a 290 MeV/nucleon C-9 beam
Y. Matsuda, H. Sakaguchi, H. Takeda, S. Terashima, J. Zenihiro, T. Kobayashi, T. Murakami,
Y. Iwao, T. Ichihara, T. Suda, T. Ohnishi, Y. Watanabe, H. Otsu, K. Yoneda, Y. Satou, K. Ozeki,
M. Kanazawa.
Phys. Rev. C 87 (2013)034614.
不安定核構造を映す電子顕微鏡をつくる
若杉昌徳、大西哲也、須田利美、栗田和好
日本物理学会 BUTSURI 68, (2013), 810 - 817.

Electron scattering for exotic nuclei

277

T. SudaPramana Journal of Physics (Indian Academy of Scineces) : in press.
ウシの体内での放射性セシウムの分布-コンパートメントモデルによる解析高瀬つぎ子、内田守譜、大槻勤、高貝慶隆、難波謙二、村松康行

RADIOISOTOPES, 62, 281-290, (2013).
Comparison of the decay constants of 51 Cr with metal, oxide, and chromate chemical states
H. Kikunaga, K. Takamiya, H. Hirose, and T. Ohtsuki
Journal of Radioanalytical and Nuclear Chemistry (in press)
Excitation functions for production of Rf isotopes in the 248 Cm + 18 O reaction
M. Murakami, S. Goto, H., Murayama, T. Kojima, H. Kudo, D. Kaji, K. Morimoto, H. Haba, Y.
Kudou, T. Sumita, R. Sakai, A. Yoneda, K. Morita, Y. Kasamatsu, H. Kikunaga, T.N. Sato.
Physical Review C: Nuclear Physics, 88 (2013), 024618/1-024618/8.
Suppression of β-particle events using a capillary tube in liquid scintillation α spectrometry
K. Komori, H. Kikunaga, T. Yoshimura, A. Shinohara.
Applied Radiation and Isotopes, 72 (2013), 195-199.
New result in the production of 277 Cn by the 208 Pb + 70 Zn reaction
T. Sumita, K. Morimoto, D. Kaji, H. Haba, K. Ozeki, R. Sakai, A. Yoneda, A. Yoshida, H.
Hasebe, K. Katori, N. Sato, Y. Wakabayashi, S. Mitsuoka, S. Goto, M. Murakami, Y. Kariya,
F. Tokanai, K. Mayama, M. Takeyama, T. Moriya, E. Ideguchi, T. Yamaguchi, H. Kikunaga, J.
Chiba, K. Morita.
Journal of the Physical Society of Japan, 82 (2013), 024202/1-024202/5.
Search for K − pp bound state via γd → K + π − X reaction at Eγ = 1.5-2.4 GeV
A.O. Tokiyasu, M. Niiyama, J.D. Parker, D.S. Ahn, J.K. Ahn, S. Ajimura, H. Akimune, Y.
Asano, W.C. Chang, J.Y. Chen, S. Date, H. Ejiri, H. Fujimura, M. Fujiwara, S. Fukui, S.
Hasegawa, K. Hicks, K. Horie, T. Hotta, S.H. Hwang, K. Imai, T. Ishikawa, T. Iwata, Y. Kato,
H. Kawai, K. Kino, H. Kohri, Y. Kon, N. Kumagai, D.L. Lin, Y. Maeda, S. Makino, T. Matsuda, T. Matsumura, N. Matsuoka, T. Mibe, M. Miyabe, M. Miyachi, N. Muramatsu, R. Murayama, T. Nakano, Y. Nakatsugawa, M. Nomachi, Y. Ohashi, H. Ohkuma, T. Ohta, T. Ooba,
D.S. Oshuev, C. Rangacharyulu, S.Y. Ryu, A. Sakaguchi, T. Sawada, P.M. Shagin, Y. Shiino,
H. Shimizu, E.A. Strokovsky, Y. Sugaya, M. Sumihama, J.L. Tang, Y. Toi, H. Toyokawa, T.
Tsunemi, M. Uchida, M. Ungaro, A. Wakai, C.W. Wang, S.C. Wang, K. Yonehara, T. Yorita, M.
Yoshimura, M. Yosoi, R.G.T. Zegers, (LEPS Collaboration)
Phys. Lett. B 728, (2014), 616-621.
Development of high intensity laser-electron photon beam up to 2.9 GeV at the SPring-8 LEPS beamline
N. Muramatsu et al. (LEPS Collaboration)
Nucl. Instr. Meth. A 737 (2014) 184-194; arXiv:1308.6453 (2013).
Evidence for the suppressed decay B − → DK − , D → K + π − π 0
M. Nayak et al. (Belle Collaboration)

278

Phys. Rev. D 88 (2013), 091104(R).
SPring-8 新レーザー電子光ビームライン LEPS2:建設とコミッショニング
村松憲仁, 與曽井優, 依田哲彦, 鈴木伸介
学会誌「加速器」, Vol.10, No.3, (2013), 171-180.

Effect of multiple scattering on proton spectrum from D(d,p)T reaction in low energy region
J.T. Zhao, T.S. Wang, Q. Wang, X.X. Xu, S. Zhang, Y.S. Zhou, K.H. Fang and J. Kasagi
Nucl. Instr. Meth. B299 (2013) 54-60
Effects of high-energy proton and electron irradiation on GaN Schottky diodeS. Narita, T. Hitora, E. Yamaguchi, Y. Sakemi, M. Itoh, H. Yoshida, J. Kasagi and K. Neichi
Nucl. Instr. Meth. A 717 (2013) 1- 4.
Dynamical saturated concentration of deuterium in a beryllium foil studied by low energy D(d,p)T reaction
J.T. Zhao, T.S. Wang, Q. Wang, X.X. Xu, S. Zhang, Y.S. Zhou, K.H. Fang and J. Kasagi
Nucl. Instr. Meth. B. 316 (2013) 13-16.

Papers Published in International Conference Proceedings
Status of upgrade project of the 1.2 GeV booster synchrotron at Tohoku University
F. Hinode, H. Hama, S. Kashiwagi, T. Muto, I. Nagasawa, K. Nanbu, Y. Shibasaki, K. Takahashi
Proc. of IPAC2013, (2013), 151-153.
Construction of new 90 MeV injector linac for the 1.2 GeV booster synchrotron at Tohoku University
S. Kashiwagi, H. Hama, F. Hinode, M. Kawai, T. Muto, I. Nagasawa, K. Nanbu, Y. Shibasaki,
K. Takahashi, N.Y. Huang
Proc. of IPAC2013, (2013), 1607-1609.
東北放射光計画 -光源加速器システムの概要濱広幸

日本放射光学会、放射光, (2013), Vol.26, No.4, 233-237.

In-beam fission study at JAEA for heavy element synthesis
K. Nishio, H. Ikezoe, S. Hofmann, D. Ackermann, Y. Aritomo, V. F. Comas, Ch. E. D´’u llmann,
S. Heinz, J. A. Heredia, F. P. Heßberger, K. Hirose, J. Khuyagbaatar, B. Kindler, I. Kojouharov,
B. Lommel, M. Makii, R. Mann, S. Mitsuoka, I. Nishinaka, T. Ohtsuki, S. Saro, M. Schädel,A. G. Popeko, A. Tü rler, Y. Wakabayashi, Y. Watanabe, A. Yakushev, A. Yeremin
AIP Conf. Proc. 1524, 68-72, (2013).
π 0 and η photoproduction on the deuteron at ELPH, Tohoku University
T. Ishikawa, H. Fujimura, H. Fukasawa, R. Hashimoto, Q. He, Y. Honda, T. Iwata, S. Kaida,
J. Kasagi, A. Kawano, S. Kuwasaki, K. Maeda, S. Masumoto, M. Miyabe, F. Miyahara, K.
Mochizuki, N. Muramatsu, A. Nakamura, K. Nawa, S. Ogushi, Y. Okada, Y. Onodera, K.
Ozawa, Y. Sakamoto, M. Sato, H. Shimizu, H. Sugai, K. Suzuki, Y. Tajima, S. Takahashi, Y.

279

Taniguchi, Y. Tsuchikawa, H. Yamazaki, R. Yamazaki, H.Y. Yoshida
Few Body Systems DOI:10.1007/s00601-013-0676-3(2013).
Study for the ω − N interaction through ω photoproduction near the threshold
R. Hashimoto, H. Fujimura, H. Fukasawa, Q. H. He, Y. Honda, T. Ishikawa, T. Iwata, S.
Kaida, J. Kasagi, A. Kawano, S. Kuwasaki, K. Maeda, S. Masumoto, M. Miyabe, F. Miyahara,
K. Mochizuki, N. Muramatsu, A. Nakamura, K. Nawa, S. Ogushi, Y. Okada, Y. Onodera, K.
Ozawa, Y. Sakamoto, M. Sato, H. Shimizu, H. Sugai, K. Suzuki, Y. Tajima, S. Takahashi, Y.
Taniguchi, Y. Tsuchikawa, H. Yamazaki, R. Yamazaki, H. Y. Yoshida
Few Body Systems DOI:10.1007/s00601-013-0658-5(2013).
π 0 and η photoproduction on the deuteron at Eγ < 1.2 GeV
T. Ishikawa, H. Fujimura, H. Fukasawa, R. Hashimoto, Q. He, Y. Honda, S. Kaida, J. Kasagi,
S. Kuwasaki, M. Miyabe, F. Miyahara, K. Mohizuki, N. Muramatsu, A. Nakamura, K. Nawa,
S. Ogushi, Y. Okada, Y. Onodera, M. Sato, H. Shimizu, H. Sugai, K. Suzuki, S. Takahashi, Y.
Taniguchi, Y. Tsuchikawa, H. Yamazaki, R. Yamazaki
PoS(Hadron 2013) 095.
Production of intense high energy gamma beam for LEPS2 project at SPring-8
T. Yorita et al.
Proceedings of IPAC2013, (2013), 2162-2164.
Search for new physics using a precision measurement of the Ke2 /Kµ2 branching ratio
M. Hasinoff, on behalf of the J-PARC TREK-E36 collaboration
Proc. of 11th conference on the Intersection of Particle and Nuclear physics (CIPANP2012),
AIP Conference Proceedings, 1560 (2013) 251-253
Search for new physics with the TREK detector
S. Strauch for the TREK collaboration
Proceedings of KAON2013, http://pos.sissa.it/cgi-bin/reader/conf.cgi?confid=181 014.pdf
The TREK/E36 experiment at J-PARC
M. Kohl for the TREK collaboration
Workshop to Explore Physics Opportunities with Intense, Polarized Electron Beams at 50-300
MeV, AIP Conf. Proc., 1563, (2013), 147-150.
The investigation of strangeness photoproduction in the threshold region at ELPH-Tohoku
M. Kaneta, B. Beckford, P. Bydžovský, T. Fujibayashi, T. Fujii, Y. Fujii, K. Futatsukawa, T.
Gogami, Y.C. Han, O. Hashimoto, K. Hirose, K. Hosomi, R. Honda,A. Iguchi, T. Ishikawa,H. Kanda, Y. Kaneko, Y. Kasai, T. Kawasaki, C. Kimura, S. Kiyokawa, T. Koike, K. Maeda,
N. Maruyama, M. Matsubara, K. Miwa, Y. Miyagi, S. Nagao, S.N. Nakamura, A. Okuyama,
M. Sotona, T. Tamae, H. Tamura, K. Tsukada, N. Terada, T.S. Wang, F. Yamamoto, T.O. Yamamoto, H. Yamazaki
Nucl. Phys. A914 (2013) 69-73.
SCRIT electron scattering facility at RIKEN

280

S. Wang, M. Hara, T. Hori, S. Ichikawa, R. Kitazawa, K. Koizumi, K. Kurita, Y. Miyashita,
R. Ogawara, T. Ohnishi, T. Suda, H. Takehara, T. Tamae, S. Tamaki, M. Togasaki and M.
Wakasugi
The Proceedings of Exotic Nuclei Proceedings of the International Symposium on Exotic Nuclei (EXON-2012), 383 (2013).
Development of a scintillation counter with MPPC readout for the internal tagging system
H. Kanda, Y. Kasai, K. Maeda, T. Nishizawa and F. Yamamoto
Proceedings of Science (PhotoDet 2012) (2013), 18.
Study of strangeness photoproduction on the neutron in the threshold region
Hiroki Kanda, Brian Beckford, Takeji Fujibayashi, Takao Fujii, Yu Fujii, Kenta Futatsukawa,Toshiyuki Gogami, Yun-Cheng Han, Osamu Hashimoto, Kentaro Hirose, Ryotaro Honda,
Kenji Hosomi, Alan Iguchi, Takatsugu Ishikawa, Yusuke Kaneko, Masashi Kaneta, Yuma
Kasai, Daisuke Kawama, Taito Kawasaki, Chigusa Kimura, Shogo Kiyokawa, Takeshi Koike,
Kazushige Maeda, Tomofumi Maruta, Nayuta Maruyama, Masao Matsubara, Koji Miwa,
Yohei Miyagi, Sho Nagao, Satoshi N. Nakamura, Akira Okuyama, Kotaku Suzuki, Tadaaki
Tamae, Hirokazu Tamura, Nobuhiro Terada, Kyo Tsukada, Tie-Shang Wang, Fumiya Yamamoto, Takeshi O. Yamamoto, and Hirohito Yamazaki
Few Body Systems, 54, (2013), 1175.
Study of γd → π + π − d reaction in an energy region of 0.67 ≤ Eγ ≤ 1.08 GeV
C. Kimura, B. Beckford, T. Fujibayashi, T. Fujii, Y. Fujii, K. Futatsukawa, T. Gogami, O.
Hashimoto, Y. C. Han, K. Hirose, R. Honda, K. Hosomi, A. Iguchi, T. Ishikawa, H. Kanda, Y.
Kaneko, M. Kaneta, Y. Kasai, T. Kawasaki, S. Kiyokawa, T. Koike, K. Maeda, N. Matsubara,
K. Miwa, Y. Miyagi, S. Nagao, S. N. Nakamura, A. Okuyama, H. Shimizu, T. Tamae, H.
Tamura, N. Terada, K. Tsukada, F. Yamamoto, T. O. Yamamoto, and H. Yamazaki
Few Body Systems, 54, (2013), 1319.
Investigation of strangeness photoproduction near the threshold at ELPH, Tohoku University
Masashi Kaneta, Brian Beckford, Petr Byd?ovsky, Takeshi Fujibayashi, Takao Fujii, Yu Fujii,
Kenta Futatsukawa, Toshiyuki Gogami, Yuncheng Han, Osamu Hashimoto, Kentaro Hirose,
Kenji Hosomi, Ryotarou Honda, Aran Iguchi, Takatsugu Ishikawa, Hiroki Kanda, Yusuke
Kaneko, Yuma Kasai, Taito Kawasaki, Chigusa Kimura, Shogo Kiyokawa, Takeshi Koike,
Kazushige Maeda, Nayuta Maruyama, Masao Matsubara, Koji Miwa, Yohei Miyagi, Sho Nagao, Satoshi N. Nakamura, Takashi Nishizawa, Akira Okuyama, Miloslav Sotona, Tadaaki
Tamae, Hirokazu Tamura, Kyo Tsukada, Nobu Terada, Tieshan Wang, Fumiya Yamamoto,Takeshi O. Yamamoto, and Hirohito Yamazaki
Proceedings of the 12th Asia Pacific Physics Conference, JPS Conf. Proc. 1, (2014) 013071.
DOI:013071, 10.7566/JPSCP.1.013071
Study of double delta photoproduction on the deuteron in the energy region of Eγ = 0.65 − 1.1 GeVFumiya Yamamoto, Brian Beckford, Takeji Fujibayashi, Takao Fujii, Yu Fujii, Kenta Fu-

281

tatsukawa, Toshiyuki Gogami, Yun-Cheng Han, Osamu Hashimoto, Kentaro Hirose, Kenji
Hosomi, Ryotaro Honda, Alan Iguchi, Takatsugu Ishikawa,Hiroki Kanda, Masashi Kaneta,
Yusuke Kaneko, Taito Kawasaki, Chigusa Kimura, Shogo Kiyokawa, Takeshi Koike, Kazushige
Maeda, Nayuta Maruyama, Masao Matsubara, Koji Miwa, Yohei Miyagi, Sho Nagao, Satoshi
N. Nakamura, Akira Okuyama, Hajime Shimizu, Kotaku Suzuki, Tadaaki Tamae, Hirokazu
Tamura, Kyo Tsukada, Nobu Terada, Mifuyu Ukai, Tie-Shan Wang, and Hirohito Yamazaki
Proceedings of the 12th Asia Pacific Physics Conference, JPS Conf. Proc. 1, (2014) 013072.
013072, 10.7566/JPSCP.1.013072
Measurement of charged pion photoproduction at ELPH
Hiroki Kanda, Brian Beckford, Takeji Fujibayashi, Takao Fujii, Yu Fujii, Kenta Futatsukawa,Toshiyuki Gogami, Yun-Cheng Han, Osamu Hashimoto, Kentaro Hirose, Kenji Hosomi, Ryotaro Honda, Alan Iguchi, Takatsugu Ishikawa, Masashi Kaneta, Yusuke Kaneko, Yuma Kasai, Taito Kawasaki, Chigusa Kimura, Shogo Kiyokawa, Takeshi Koike, Kazushige Maeda,
Nayuta Maruyama, Masao Matsubara, Koji Miwa, Yohei Miyagi, Sho Nagao, Satoshi N.
Nakamura, Takashi Nishizawa, Akira Okuyama, Hajime Shimizu, Kotaku Suzuki, Tadaaki
Tamae, Hirokazu Tamura, Kyo Tsukada, Nobu Terada, Mifuyu Ukai, Tie-Shan Wang, Fumiya Yamamoto, and Hirohito Yamazaki
Proceedings of the 12th Asia Pacific Physics Conference, JPS Conf. Proc. 1, (2014) 013075.
013075, 10.7566/JPSCP.1.013075

Invited Talk and Oral Presentations at International Conferences
Injector linac reliability employing thermionic RF gun for a booster synchrotron
H. Hama
Accelerator Reliability Workshop 2013, April 14-19, 2013, Melbourne, Australia.
SLiT-J: 3 GeV synchrotron radiation facility project
H. Hama
The 18th Hiroshima International Symposium on Diffraction Limited Light Source Accelerators and Insertion Devices, March 8, 2013, Higashi-Hiroshima, Japan.
Electron scattering and photonuclear reaction for short-lived nuclei
T. SudaJUSTIPEN-JUSEIPEN International Workshop, Dec. 9-12, 2013, Wako, Japan.
Electron scattering for exotic nuclei - the SCRIT electron scattering facility T. Suda
International DAE Symposium on Nuclear Physics, Dec. 2-6, 2013, Munbai, India.
Electon scattering for exotic nuclei
T. SudaInternational School for Strangeness Nuclear Physics, Jan. 13-19, Sendai, Japan.
Experiments at ELPH/Sendai before and after the disaster282

H. Shimizu
International WS on Physics of Exited Nucleons (NSTAR2013), May 27-30, 2013, Peniscola,
Spain.
First beam observation and near future plans at SPring-8 LEPS2 experimentN. Muramatsu
BARYONS2013-International Conference on the Structure of Baryons, 24-28 June 2013, Glasgow.
”Cooperative colliding” d+d reaction caused in liquid Indium bombarded by low-energy D3+molecularbeam
J. KasagiInternational Nuclear Physics Conference INPC2013, Firenze, Italy, June 2-7, 2013.
New measurement of screening potential by cooperative colliding process for the d+d reaction in metallic
electron environment
J. Kasagi
The 18th International Conference on Condensed Matter Nuclear Science ICCF18, Columbia,
USA, July 21-26, 2013.
MPPC based scintillation counters for the internal photon tagger
Hiroki Kanda on behalf of the NKS2 collaboration2013 IEEE Nuclear Science Symposium, Seoul, Republic of Korea, 2013/10/27 - 11/2.
0±π π photoprodution on the deuteron at ELPH
S. Masumoto
YITP workshop on Hadron in Nucleus, Kyoto, Japan, 2013/10/31.
Recent status and plans at SPring-8 LEPS2 facility
M. Miyabe
YITP workshop on Hadron in Nucleus, Kyoto, Japan, 2013/11/1.

学位論文 (電子光理学研究センター所属)
修士論文「SCRIT 電子スペクトロメータの磁場解析と性能評価」
宮本 嵩也，平成 24 年，東北大学

学位論文 (他機関所属)
修士論文「Spring-8 における BGOEGG 実験のための荷電粒子検出器の開発」
渋川 卓也,

平成 23 年度，東京大学

学位論文 (他機関所属)

2011 年度

修士論文「Development of the large GEM tracker and the trigger system for the J-PARC E16 experiment」
小原 裕貴,

平成 23 年度，東京大学

283

学位論文 (他機関所属)

2011 年度

修士論文「チャームバリオン分光実験用粒子識別検出器の設計」
山我 拓巳,

平成 23 年度，大阪大学

285

Steering Committee
2011

Hajime SHIMIZU*

ELPH

Hiroyuki HAMA

ELPH

Toshimi SUDA

ELPH

Tsutomu OHTSUKI

ELPH

Masayuki KAWAI

ELPHShigeru KASHIWAGI

ELPH

Hirokazu TAMURA

Graduate School of Science

Teruya ISHIHARA

Graduate School of Science

Kazushige MAEDA

Graduate School of Science

Kouichi HAGINO

Graduate School of Science

Norio TERAMAE

Graduate School of Science

Yasushi KINO

Graduate School of Science

Asuka FUJII

Graduate School of Science

Keizo ISHII

Graduate School of of Engineering

Kenji OHOYAMA

Institute for Materials Research

Mihiro YANAGIHARA

Institute of Multidisciplinary Research for Advanced Materials

Michio NIWANO

Research Institute of Electrical Communication

Yasuhiro SAKEMI

Cyclotron and Radioisotope Center

Tetsuo TANIUCHI

Center for Interdisciplinary Research* Chairperson

286

2012

Hajime SHIMIZU*

ELPH

Hiroyuki HAMA

ELPH

Toshimi SUDA

ELPH

Tsutomu OHTSUKI

ELPH

Masayuki KAWAI

ELPHShigeru KASHIWAGI

ELPH

Hirokazu TAMURA

Graduate School of Science

Teruya ISHIHARA

Graduate School of Science

Kazushige MAEDA

Graduate School of Science

Kouichi HAGINO

Graduate School of Science

Fujinori MISAIZU

Graduate School of Science

Yasushi KINO

Graduate School of Science

Asuka FUJII

Graduate School of Science

Hitoshi MIMURA

Graduate School of of Engineering

Kenji OHOYAMA

Institute for Materials Research

Mihiro YANAGIHARA

Institute of Multidisciplinary Research for Advanced Materials

Michio NIWANO

Research Institute of Electrical Communication

Yasuhiro SAKEMI

Cyclotron and Radioisotope Center

Tetsuo TANIUCHI

Center for Interdisciplinary Research* Chairperson

287

2013

Hajime SHIMIZU*

ELPH

Hiroyuki HAMA

ELPH

Toshimi SUDA

ELPH

Tsutomu OHTSUKI

ELPH

Hidetoshi KIKUNAGA

ELPH

Fujio HINODE

ELPH

Shigeru KASHIWAGI

ELPHNorihito MURAMATSU

ELPH

Hirokazu TAMURA

Graduate School of Science

Teruya ISHIHARA

Graduate School of Science

Kazushige MAEDA

Graduate School of Science

Kouichi HAGINO

Graduate School of Science

Fujinori MISAIZU

Graduate School of Science

Yasushi KINO

Graduate School of Science

Asuka FUJII

Graduate School of Science

Atsuki TERAKAWA

Graduate School of of Engineering

Kenji OHOYAMA

Institute for Materials Research

Mihiro YANAGIHARA

Institute of Multidisciplinary Research for Advanced Materials

Keiichi EDAMATSU

Research Institute of Electrical Communication

Yasuhiro SAKEMI

Cyclotron and Radioisotope Center

Tetsuo TANIUCHI

Center for Interdisciplinary Research* Chairperson

288

General Advisory Committee
2011

Hajime SHIMIZU*

ELPH

Hiroyuki HAMA

ELPH

Toshimi SUDA

ELPH

Tsutomu OHTSUKI

ELPH

Hirokazu TAMURA

Tohoku University

Yasushi KINO

Tohoku University

Yasuhiro SAKEMICYRIC

Tetsuo TANIUCHI

CIR

Takahiro IWATA

Yamagata University

Shin’ya SAWADA

IPNS, KEK

Takashi NAKANORCNP, Osaka University

Atsushi HOSAKARCNP, Osaka University

Hideaki OHGAKI

IAE, Kyoto University

Shigemi SASAKIHSRC, Hiroshima University

Atsushi SHINOHARA

Osaka University

Keisuke SUEKI

University of Tsukuba* Chairperson

289

2012

Hajime SHIMIZU*

ELPH

Hiroyuki HAMA

ELPH

Toshimi SUDA

ELPH

Tsutomu OHTSUKI

ELPH

Hirokazu TAMURA

Tohoku University

Yasushi KINO

Tohoku University

Yasuhiro SAKEMICYRIC

Tetsuo TANIUCHI

CIR

Takahiro IWATA

Yamagata University

Shin’ya SAWADA

IPNS, KEK

Takashi NAKANORCNP, Osaka University

Atsushi HOSAKARCNP, Osaka University

Hideaki OHGAKI

IAE, Kyoto University

Shigemi SASAKIHSRC, Hiroshima University

Atsushi SHINOHARA

Osaka University

Keisuke SUEKI

University of Tsukuba* Chairperson

290

2013

Hajime SHIMIZU*

ELPH

Hiroyuki HAMA

ELPH

Toshimi SUDA

ELPH

Tsutomu OHTSUKI

ELPH

Hidetoshi KIKUNAGA

ELPH

Hirokazu TAMURA

Tohoku University

Yasushi KINO

Tohoku University

Yasuhiro SAKEMICYRIC

Tetsuo TANIUCHI

CIR

Hiroaki OHONISHI

RIKEN

Shin’ya SAWADA

IPNS, KEK

Takashi NAKANORCNP, Osaka University

Atsushi HOSAKARCNP, Osaka University

Hideaki OHGAKI

IAE, Kyoto University

Shigemi SASAKIHSRC, Hiroshima University

Atsushi SHINOHARA

Osaka University

Keisuke SUEKI

University of Tsukuba* Chairperson

291

Program Advisory Committee
2011

Hiroyuki HAMA

ELPH

Toshimi SUDA

ELPH

Tsutomu OHTSUKI

ELPH

Kazushige MAEDA

Tohoku University

Satoshi N. Nakamura

Tohoku University

Hitoshi MIMURA

Tohoku University

Yasuhisa TAJIMA *Yamagata University

Kyoichiro OZAWA

IPNS, KEK

Tomoaki HOTTA

RCNP, Osaka University

Yoshihiko SHOJILASTI, University of Hyogo

Keisuke SUEKI

University of Tsukuba

Yasuji OURATokyo Metropolitan University* Chairperson

292

2012

Hiroyuki HAMA

ELPH

Toshimi SUDA

ELPH

Tsutomu OHTSUKI

ELPH

Kazushige MAEDA

Tohoku University

Satoshi N. Nakamura

Tohoku University

Hitoshi MIMURA

Tohoku University

Yasuhisa TAJIMA *Yamagata University

Kyoichiro OZAWA

IPNS, KEK

Tomoaki HOTTA

RCNP, Osaka University

Yoshihiko SHOJILASTI, University of Hyogo

Keisuke SUEKI

University of Tsukuba

Yasuji OURATokyo Metropolitan University* Chairperson

293

2013

Hiroyuki HAMA

ELPH

Toshimi SUDA

ELPH

Tsutomu OHTSUKI

ELPH

Hidetoshi KIKUNAGA

ELPH

Kazushige MAEDA

Tohoku University

Satoshi N. Nakamura

Tohoku University

Asao YAMAURA

Tohoku University

Yasuhisa TAJIMA

Yamagata University

Toshiyuki TAKAHASHI *IPNS, KEK

Tomoaki HOTTA

RCNP, Osaka University

Yoshihiko SHOJILASTI, University of Hyogo

Keisuke SUEKI

University of Tsukuba

Yasuji OURATokyo Metropolitan University* Chairperson

295

平成 25 年度後期採択課題一覧
課題番号

課

題

名

申込責任者

採択シフト数小沢 恭一郎5

原子核関連分野

2759

J-PARK E16 実験用大型 GEM tracker と電子同定検出器のテスト
実験

2761

光子ビームライン II の再整備

石川 貴嗣

施設

2762

検出器テスト用陽電子ビームラインの再整備

石川 貴嗣

施設

2763

電磁カロリーメータモジュールの読み出し方向の違いに対する測定

石川 貴嗣

3

エネルギーの変化

2765

リアルタイムストロンチウム 90 カウンターの絶対感度の測定

河合 秀幸

留保

2766

ビームを用いた NKS2 実験スペクトロメータの動作確認及び調整

金田 雅司

4

2767

NKS2 実験のための光子ビーム調整

神田 浩樹

施設

2768

J-PARK E21 実験 (COMET 実験) のための電磁カロリーメータの

東城 順治

6

南條 創

6

開発

2769

KOTO 実験中性ビーム中で稼働する荷電粒子、ガンマ線検出器の性能評価

放射化学関連分野

2757

光量子放射化分析のための光核反応収率の測定

大浦 泰嗣

1

2758

シロイヌナズナのカリウム輸送挙動解明のためのトレーサー製造

魚住 信之

2

2760

電子ライナックを用いた有用放射性トレーサー製造法の開発

菊永 英寿

2

2764

第 1 実験室照射装置整備のためのテスト実験

菊永 英寿

施設

2770

光量子放射化法による 57 Co メスバウアー線源の作成

秋山 和彦

2

J-PARK チャームバリオン実験用粒子識別チェレンコフ検出器のテ

白鳥 昴太郎

5

石川 貴嗣

5

随時申込

2771

スト実験

2772

BGO EGG 電磁カロリメータのタイミング分解能