Preface
Research Center for Electron Photon Science (ELPH) is a university-based laboratory that operates
an electron linear accelerator (LINAC) and a synchrotron capable of accelerating electrons up to 1.2 GeV.
ELPH, originally named Laboratory of Nuclear Science (LNS), was founded in 1966 as a laboratory
afﬁliated to Faculty of Science, Tohoku University. Since then ELPH has been providing electron andphoton beams not only to researchers and students inside the university but also to users outside. It
aims to promote fundamental study and applied research of the various classes of materials in electron
photon science as well as to educate students and young researchers. Reorganized from LNS, ELPH
started functioning now as a laboratory directly operated by Tohoku University on December 1, 2009 to
get a better situation for all of the users in joint researches. The present ELPH Annual Report is theinaugural issue reporting on research activities at ELPH for its ﬁrst academic year 2010.
Two tagged photon beam lines, GeV-γ BL1 and BL2, have been used for strangeness nuclear physics
and quark nuclear physics. The upgraded Neutral Kaon Spectrometer (NKS2) is symmetrically placedat the center on GeV-γ BL1 to detect neutral kaons (K 0 ) and lambdas (Λ) by measuring their decayedcharged particles. A series of strangeness photoproduction experiments was performed in a long periodof time in this academic year at BL1, using the NKS2 system equipped with a liquid deuterium target.
Another project aiming to study baryon resonances and exotic hadrons has been promoted by employing
FOREST, a 4π electro-magnetic calorimeter installed on GeV-γ BL2, which is capable of detecting neutral mesons decaying into photons. The ﬁrst stage of the FOREST experiment was over before the fall of2010. These major projects, with NKS2 and FOREST, having been conducted at ELPH are both now insort of analysis phase.
Test experiments for many kinds of detector were performed at the positron beam line (PBL) in GeVγ Experimental Hall. The positron beam with an intensity of typically 3 kHz is produced by converting
GeV Bremsstrahlung photons coming through GeV-γ BL2 with a removable convertor of 20 μm thickAu foil. The converter is placed in front of RTAGX, a charge-sweeping magnet utilized for the FOREST
experiment. PBL starts from the center of RTAGX and is located 30◦ away from GeV-γ BL2. This
conﬁguration enables us to have the maximum positron energy of 850 MeV. A set of triple Q-magnets
was brought in from KEK and installed on PBL so as to handle the beam better. This was made under
the agreement of cooperation between KEK and Tohoku University.
A high-intensity electron/photon beam has been used for radio-chemistry in Experimental Hall 1.
The high intensity beam makes it possible to realize distinctive works such as precise life-time measurements of various nuclei in a certain environment as well as to produce radioactive isotopes effectively.
During the time covered by this annual report, the maximum energy was limited to 30 MeV.
I have to touch upon the Great East-Japan Earthquake that occurred at 14:46 on March 11, 2011,
the very end of academic year 2010. It was the biggest earthquake ever recorded in Japan. Since thenwe are still suffering from the on-going aftershock sequence. The death toll from the earthquake andthe ensuing tsunami has sadly reached 15,854 as of March 11, 2012, just one year after the disaster,while 3,155 people are still missing. ELPH is located far from the coast and had no damage caused by

the tsunami. But our accelerator facility could not be evacuated from the 9.0-magnitude devastating
earthquake. The 300 MeV LINAC constructed in 1967 was in operation when the ﬁrst blow came on andseriously damaged. Many cracks were found on the wave guides and the accelerator tubes. Comparedto the LINAC, the 1.2 GeV synchrotron was not beyond hope of recovery. But several power suppliers
for the synchrotron were broken. And we have to start with realigning all the elements including thebending magnets of the synchrotron in the restoration work. It turned out afterward that the 300 MeV
LINAC would not be restored anymore. The late 300 MeV LINAC had two functions. It provided a highintensity beam of the energy less than 60 MeV (low energy high repetition mode) and worked as a preaccelerator for the 1.2 GeV synchrotron (high energy low repetition mode). Separating these functions,
we are planning to rebuild a low energy high intensity LINAC out of the remains of the wrecked LINAC
at ﬁrst. And we will construct a low-repetition-rate 90 MeV LINAC independently as a new injector
for the 1.2 GeV synchrotron, which therefore has to be improved so as to be able to accept low energy
electrons from the 90 MeV LINAC. We are doing our best to recover our accelerator facility as soon as
possible.

SHIMIZU Hajime
Director of Research Center for Electron Photon ScienceELPH annual report 2010
Volume 1 (2011)
Contents
I. Nuclear Physics
Current status of meson photoproduction experiments with FOREST
1
T. Ishikawa, H. Fujimura, R. Hashimoto, S. Kaida, J. Kasagi, K. Maeda, A. Nakamura,
H. Shimizu, K. Suzuki, S. Takahashi, Y. Tsuchikawa, and H. Yamazaki
13
Detection efficiency of the proton with Backward Gamma detector
A. Nakamura, T. Ishikawa, H. Fujimura, R. Hashimoto, S. Kaida, J. Kasagi, K. Maeda,
K. Nawa, S. Ogushi, M. Sato, H. Shimizu, H. Sugai, K. Suzuki, S. Takahashi,
Y. Tsuchikawa, and H. Yamazaki
Report on strangeness photoproduction experimentsperformed with the Neutral Kaon
Spectrometer 2
B. Beckford, A. Chiba, D. Doi, T. Fujibayashi, T. Fujii, Y. Fujii,K. Futatsukawa,
T. Gogami, O. Hashimoto, Y.C. Han, K. Hirose, S. Hirose, R. Honda, K. Hosomi,
A. Iguchi, T. Ishikawa, H. Kanda, M. Kaneta, Y. Kaneko, S. Kato, D. Kawama,
T. Kawasaki, S. Kiyokawa, T. Koike, K. Maeda, K. Makabe, N. Maruyama,
M. Matsubara, K. Miwa, Y. Miyagi, S. Nagao, S. N. Nakamura, A. Okuyama,
K. Shirotori, K.Sugihara, K.Suzuki, T. Tamae, H. Tamura, N. Terada, K. Tsukada,K. Yagi, F. Yamamoto, T. O. Yamamoto, H. Yamazaki, and Y. Yonemoto

19

高レートビームトラッキング用シリコン検出器のテスト
Test of a silicon microstrip detector for high-rate beam tracking
27
Kiyoshi Tanida, Choonjae Yoon, Hyoungchan Bhang, Mijung Kim, Sunji Kim, Hiroyuki
Fujioka, Hidemitsu Asano, Yuta Sada, Koji Miwa, Ryotaro Honda, Keisuke Makabe,Tomoaki Hotta, and Mizuki Sumihama
Waveform of the light output for BSO scintillator in response to the positron beam
T. Ishikawa, H. Fujimura, R. Hashimoto, S. Kaida, R. Kitazawa, A. Nakamura,
H. Shimizu, K. Suzuki, S. Takahashi, Y. Tsuchikawa, and H. Yamazaki

37

47
Test of APD readout system of CsI(Tl) calorimeter forJ-PARC TREK experiment
S. Masumoto, Y. Igarashi, J. Imazato, A. Ivashkin, K. Ozawa, D. P. Nguyen, S. Shimizu,
S. Strauch, A. Takagi, Y. Tanizaki, H. Yamazaki, and K. Yoshihara
New electro-magnetic calorimeter BGO EGG
T. Ishikawa, H. Fujimura, R. Hashimoto, S. Kaida, R. Kitazawa, A. Nakamura,
H. Shimizu, K. Suzuki, S. Takahashi, Y. Tsuchikawa, and H. Yamazaki

61

87
Test of GEM tracker and HBD for J-PARC E16 experiment
Y. Komatsu, K. Aoki, Y. Hori, J. Kanaya, K. Kanno, S. Masumoto, R. Muto, W. Nakai,
K. Ozawa, M. Sekimoto, A. Takagi, Y. S. Watanabe, and S. Yokkaichi

Developments of Time Projection Tracking Chamber with Gating Functionality
97
Susumu SATO, Hiroyuki SAKO, Hitoshi SUGIMURA, Ryuta KIUCHI, Satoshi
ADACHI, Kyoichiro OZAWA, Kiyoshi TANIDA, Joo CHANG-WOO, Koji MIWA, and
KenIchi IMAI
Development of aerogel cherenkov counter for J-PARC P36 experiment
Akihisa Toyoda, Yoichi Igarashi, Jun Imazato, Aine Kobayashi, Suguru Shimizu,
Keito Horie, Hirohito Yamazaki, and Keisuke Yoshihara

101

Focusing the positron beam for testing detectors by triple quadrupole magnets RFQ
Y. Tsuchikawa, T. Ishikawa, H. Fujimura, R. Hashimoto, T. Muto, A. Nakamura,Y. Shibasaki, H. Shimizu, K. Suzuki, and H. Yamazaki

107

Comparison of the light outputs between BSO and BGO crystals
T. Ishikawa, H. Fujimura, S. Kaida, A. Nakamura, H. Shimizu, S. Takahashi,
Y. Tsuchikawa, and H. Yamazaki

117

Temperature dependence of the light output for BSO scintillator
S. Takahashi, T. Ishikawa, H. Fujimura, R. Hashimoto, S. Kaida, A. Nakamura,
H. Shimizu, K. Suzuki, and H. Yamazaki

123

II. Radiochemistry

Precision measurement of the half-life of 99mTc
K. Takamiya, H. Kikunaga, K. Hirose, and T. Ohtsuki

129

Photon Flux correction for Photon Activation Analysis
Yasuji Oura, Hirofumi Hamanaka, Yutaka Sasaki, Ayaka Wada, Yuka Arai, andMitsuru Ebihara

135

III. 2010 Status Report
Operation status of accelerator complex in 2010
Accelerator group

139

User Support Office Report
T. Ishikawa

143

放射線安全管理室報告（平成 22 年 4 月〜平成 23 年 3 月）
Radiation Protection Report 2010
Radiation Control Office147

IV. List of Publication (2010)

149

V. Members of Committees (2010)

155

VI. Approved Experiments (2010)

159

ELPH Annual Report 2010, Tohoku University Vol. 1

1(ELPH Experiment : #2623, #2640, #2655, #2694)

Current status of meson photoproduction experiments with
FOREST
T. Ishikawa1 , H. Fujimura1 , R. Hashimoto1 , S. Kaida1 , J. Kasagi1 , K. Maeda2 ,A. Nakamura1 , H. Shimizu1 , K. Suzuki1 , S. Takahashi1 , Y. Tsuchikawa1 ,and H. Yamazaki1
1Research Center for Electron Photon Science (ELPH), Tohoku University, Sendai 982-0826,
Japan
2

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

Meson photoproduction experiments with FOREST started in May 2008. The main purpose of the
FOREST experiments is to study a nucleon resonance N ∗ (1670), which is a candidate of anti-decuplet
pentaquark baryons, via η photoproduction on the neutron. The 10 series of long term FOREST experiments were carried out from May 2008 to May 2010 to measure the differential and total cross sections
for the γp → ηp and γd → ηpn 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 current status of the analysis on the performance of FOREST is 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). The baryon resonance spectroscopy is an important testing ground for understanding
low energy QCD. The coupling constant becomes very large and perturbative calculations are not applicable at low energies. Thus, the effective theories are often used in this energy scale. Among them,the constituent quark model, which describes baryons with three valence quarks, has succeeded, andwell reproduces the ground state baryons. Yet, the phenomena that cannot be explained by it comeout. At first, some excited baryons — single 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 havings quark with L = 1 [3]. Evidences for Θ+ pentaquark baryon are reported although its existence isstill controversial [4]. These suggests that a new effective degree of freedom emerges such as diquark
correlation in a hadron, quark-gluon hybrid, meson-baryon molecule, and so on [5].

2Meson photoproduction is utilized for baryon resonance spectroscopy complementary to π-N elastic
scattering. It should be noted that excited baryon resonances highly depend on the production processes.
At the first stage, the proton channels are intensively investigated such as the γp → π + n and γp → π 0 preactions. The γp → ηp reaction is also investigated by means of an isospin filtering. While the π channels are associated with both a half and three halves isospin resonances, the η channel is associated onlywith a half isospin one. In the second stage, multi-meson photo-production 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 theneutron.
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.

Y=B+S
Θ+
n
Σ−

U3

p
Σ+
1/2

Λ Σ0
Ξ0
1

Ξ−
1/2
Octet

0

+

Ν5

Ν5

Σ−

Σ0

Q
Σ+
I3

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

Fig.1. Octet baryons and anti-decuplet penta-quark baryons.

§ 2. Electromagnetic calorimeter FOREST
Meson photoproduction experiments were carried out at ELPH, Tohoku University. Bremsstrahlung
photons were used 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 post-bremsstrahlung 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

3

740 to 1150 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 an EM calorimeter complex FOREST.
The details of the design are described elsewhere [10] and the status report of FOREST achieved in
2006–2009 can be found in Ref. [11–14]. Fig. 2 shows the schematic view of FOREST.

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.

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.
No newly constructed elements in FOREST exist during this fiscal year.

4§ 3. Collected data
As for this fiscal year, two series of long period FOREST experiments were carried out in January2010 and in May 2010. Ten series of FOREST experiments were carried out in total from May 2008
to May 2010 to measure the differential and total cross sections for meson photoproduction reactions
in which neutral mesons decaying into photons. The targets used were liquid hydrogen, deuterium,and empty. The developed FOREST cryogenic target system [16] enables us to change targets within
6 hours. The high speed data acquisition system (DAQ) FOREST-DAQ dedicated to the FOREST experiments [17] was used. The DAQ efficiency was 76% at the trigger rate of 2 kHz. The details of the
FOREST experiments are described elsewhere [15]. Table 1 summarizes the number of spills and eventsin the FOREST experiments.
Table 1. Numbers of spills and events collected in the FOREST experiments. The circulating electron energy of the STB ring was 1200 MeV for the periods 2008A–2009D and 2010B, andwas 920 MeV for the 2009E and 2010A periods. The targets used were liquid hydrogen,deuterium, and empty.
period
2008A
2008B
2008C
2009A
2009B
2009C
2009D
2009E
2010A
2010B
total (1200 MeV)
total (920 MeV)

hydrogen#spills#events
10.83 k76.49 M
29.17 k234.48 M
25.52 k388.15 M
23.16 k225.14 M
23.98 k211.34 M
27.45 k254.13 M
56.38 k492.71 M
34.84 k100.37 M
60.84 k111.52 M
34.89 k245.19 M
231.37 k 2127.63 M
95.68 k211.89 M

deuterium#spills#events————
11.43 k282.93 M
20.28 k297.43 M
35.47 k548.43 M——
45.28 k891.66 M
22.89 k85.89 M
37.06 k114.35 M
22.28 k235.78 M
134.79 k 2253.28 M
59.95 k200.24 M

empty#spills#events
3.50 k
30.43 M
7.96 k
27.48 M
19.93 k73.20 M
6.00 k
13.58 M
5.99 k
13.31 M
4.93 k
13.84 M
7.31 k
23.40 M
16.48 k12.76 M
9.85 k10.83 M
13.17 k40.77 M
68.80 k 235.99 M
26.33 k23.59 M

Construction of Rafflesia II finished after the 2008A term ended, and the readout of signals fromall the counters in Rafflesia II was ready from the 2008C. LOTUS was constructed just before the 2009D
started. The data taking with the deuterium target started in the 2008C, and the data for both thehydrogen and deuterium targets were acquired 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 theother ones.

§ 4. Current status of analysis
The calibration of the energy and timing of EM calorimeter modules and plastic scintillators is
discussed in Ref. [15]. The software alignment of the SPIDER plastic scintillators is described, and thedetection of the nucleons — the detection efficiency and the time of flight — are also discussed in thesame reference. In this section, precise determinations of the z position for Rafflesia II, SPIDER, and
SCISSORS III are described. The preliminary results of the total cross sections are presented for the

5
γp → π 0 p and γp → ηp reactions. Here, S3, BG, and R2 denote SCISSORS III, LEPS Backward Gamma
detector, and Rafflesia II, respectively.
4.1 Precise determination of z position
Since η mesons are photoproduced from the proton via the nucleon resonance S11 (1535) at theincident energy less than 850 MeV, the emitted angle distribution of them should be isotropic in thecenter of mass system for the incident photon and the target proton. The z position for Rafflesia II isprecisely determined by using the events for η photonproduction on the proton.
At first, the η photoproduced events are selected by using the proton missing mass MX for thereaction γp → pX. The events satisfied the conditions:
1. incident energy ranges from 720 to 850 MeV,
2. the number of clusters is 2 or 3 in total,
3. the number of S3 clusters is 1,
4. the number of BG clusters is 1,
5. BG cluster is neutral,
6. the energy of SPIDER PS is larger than 2.5,
7. SPIDER responds at the delayed timing from BG, and8. no IVY and LOTUS PS’s responds
are selected for the candidate of the γp → ηp reaction. Fig. 3 shows the proton missing mass MX
distribution for the reaction γp → pX under the conditions that one of two photons from η decays
are detected with BG. Here, the accidental coincidence events are subtracted by means of a side-bandbackground subtraction between the tagging counter and the FOREST detector.

1400

Counts / 10 MeV

1200
1000
800
600
400
200
0

0

200

400
600
γγ Invariant Mass (MeV)

800

1000

Fig.3. Proton missing mass MX distribution for the reaction γp → pX under the conditions
that one of two photons from η decays are detected with BG. The lower histogram shows
the MX distribution estimated under the condition that the invariant mass of two photons are larger than 400 MeV. Two vertical lines show the boundaries 520 and 580 MeV
for the selection of η produced events.

6

To select the η produced events, the conditions:
9. MX is in [520, 580) MeV and
10. γγ invariant mass is larger than 400 MeV
are required. Since only one photon of two is required to be detected with BG from η decay, the four
momentum of another photon is calculated from the momenta of the detected proton wit S3 and detected
photon with BG.
The emitted polar angle distributions for another photon are compared between the experimental
and simulation data. Fig. 4 shows the typical emitted polar angle distributions for another photon andthe typical probability distributions for the detection of it with R2.
The probability distributions for the detection of another photon with R2 is fitted with a Gaussianconvoluted step function to determine the starting polar angle of the detection with R2. The starting
polar angles of the detection with R2 are given in the same way for the experimental and simulation
data. Fig. 5 shows the difference of the starting polar angle of the detection with R2 as a function of theazimuthal angle for different periods.
The differences of the starting angles between the experimental and simulation data are fitted withδµθ (ϕ) = A cos(ϕ − ϕ0 ) + B(1)for different assemblies of the lead glass counters for R2. The obtained parameters are ϕ0 = 49.9 ± 20.1, A = 2.67 ± 0.87, B = +0.16 ± 0.64 for 2008C–2009A,

ϕ0 = 74.8 ± 15.3, ϕ0 = 69.5 ± 28.6,

A = 3.10 ± 0.83, B = −0.68 ± 0.60 for 2009B–2009C, and(2)

A = 1.34 ± 0.64, B = +2.23 ± 0.47 for 2009D–2010B.

The mean of the difference of the starting angle δµθ comes from the difference of the z positions of lead
glass counters between the experimental and simulation data. The difference of the z positions δz canbe obtained byδµθ = tan−1rr− tan−1z + δzz(3)

with a radius r given byr = z tan µsθ .
Thus δz is expressed by()−z tan δµθ 1 + tan2 µsθ
.
δz =tan µsθ + tan δµθ

(4)

(5)

Actual z positions of lead glass counters for R2 ranges from −205 to −160 mm, from −200 to−155 mm, and from −205 to −185 mm for the FOREST2008C–2009A, 2009B–2009C, and 2009D–2010B
periods. The position of R2 became upstream by the placement of LOTUS, and the difference of z positions for different azimuthal angles are very small after the FOREST2009D period. The details of the
precise determination of z position for Rafflesia II are described elsewhere [18].
In the similar way, the z position and tilting angle for SPIDER is precisely determined. The detailsof the precise determination of z position for Rafflesia II are described elsewhere [19]. The (x, y, z)7-180:-157.5

1 -180:-157.5-157.5:-135

1 -157.5:-135-112.5:-90

0
1 -112.5:-90-67.5:-45

0
1 -67.5:-45-22.5:00
1 -22.5:0

100

100

0

-135:-112.5

0
1 -135:-112.5

0

100

100

0

-90:-67.5

0
1 -90:-67.5

0
100

100

0

-45:-22.5

0
1 -45:-22.5

0100Counts / 5 deg, Faction

100

0
100

0:22.50
1 0:22.5

0100

22.5:450
1 22.5:45

0100

45:67.5

0
1 45:67.5

0100

67.5:900
1 67.5:90

0100

90:112.50
1 90:112.5

0

112.5:135

0
1 112.5:135

157.5:1800
1 157.5:180

100

0

135:157.5

0
1 135:157.5

0
100

100

0

100

150

0

100

150

0

100

150

0

100

150

Emitted Angle (deg)Fig.4. Emitted polar angle distributions for another photon and probability distributions for thedetection of it with R2 (FOREST2009D–2010B). The azimuthal angle region of anotherphoton is described in each panel in degree, The first and third columns show the polar angle distributions, and the lower histogram shows that for the events that anotherphoton is detected with R2 in each panel of these columns, and the second and fourthcolumns show the probability ones. The solid curves in the probability distributions show
the fitted Gaussian convoluted step functions.

8

10

FOREST2008C-2009A

50

Difference of Boundaries (deg)

-5
-10
10

FOREST2009B-2009C
5
0
-5
-10
10

FOREST2009D-2010B
5
0
-5
-10

-150

-100

-50
0
50
Emitted Angle (deg)

100

150

Fig.5. Difference of the starting polar angle of the detection with R2 as a function of the azimuthal angle for different periods. The upper, middle and lower panels show those for
the FOREST2008C–2009A, 2009B–2009C, and 2009D–2010B periods. The lead glass
counters for R2 were reassembled just before the 2009B and 2009D periods. The solid
curves show the fitted function with eq. (1).
position is found to be shifted by (−1.6, −2.4, −27.7) mm from the designed one. The SPIDER plane isalso found to be rotated by 5.6◦ around the vector in the xy plane corresponding to the azimuthal angleof −19.0◦ . The z position for S3 is also precisely determined in the similar way, and is found to be shiftedby −1.5 mm from the measured one with pScan3D [20, 21]. The details of the precise determination ofz position for Rafflesia II are described elsewhere [22]. Fig. 6 shows the geometry for SPIDER andS3, which is implemented in our Geant4 [23] based Monte-Carlo simulation code Reference FOREST
simulator (RFS).
4.2 Preliminary results
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. 7 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 photopro-

9

Fig.6. Geometry for SPIDER and S3, which is implemented in our simulation code FS.

duction on the proton by using the same events for η photoproduction. Fig. 8 shows the preliminary
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.

§ 5. Summary
Ten series of meson photoproduction experiments with FOREST has been carried out in 2008 and2010. The main purpose of the FOREST experiments is to study a nucleon resonance N ∗ (1670), which isa candidate of antidecuplet pentaquark baryons via η photoproduction on the neutron. A huge amountof the events have been collected at the STB circulating energy of 1200 MeV: 2.13 G for the hydrogenand 2.25 G for the deuterium targets. The energy and timing calibrations of all the detectors havebeen 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 timeof 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 → ηp reactions are obtained. Now, we are working on the slightdifference between the experimental and simulation data to finalize the FOREST data.

Acknowledgment
This work was supported in part by Grant-in-Aid for Scientific Research (B) (17340063) and forSpecially promoted Research (19002003).

10

18

920 MeV

in
ar
y

16
14

1200 MeV
10
8
6
4

Pr
el
im

Cross Section (mb)12

η-MAID2003

2
0

700

800

900
1000
γ Energy (MeV)

1100

1200

Fig.7. 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 η-MAID2003
calculation [24].

50

Cross Section (mb)

401200 MeV
30

20

MAID2003
MAID2000
MAID2007

920 MeV

10

0

600

700

800
900
γ Energy (MeV)

1000

1100

1200

Fig.8. 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 MAID2000,
MAID2003, and MAID2007 calculations [25].

11References[1]

S. Capstick and N. Isgur: Phys. Rev. D 34, 2809 (1986);
S. Capstick and W. Roberts: Phys. Rev. D 47, 1994 (1993);
S. Capstick and W. Roberts: Phys. Rev. D 58, 074011 (1998);
S. Capstick and W. Roberts: Prog. Part. Phys. 45, S241 (2000);
K. Nakamura et al. (Particle Data Group): J. Phys. G 37, 075021 (2010).

[2]

D. Jido, E. Oset, A. Ramos, and U.G. Meißner, Nucl. Phys. A 725, 181 (2003).

[3]

B.S. Zou, Nucl. Phys. A 790, 110c (2007).

[4]

T. Nakano et al., Phys. Rev. C 79, 025210 (2009), and references therein.

[5]

M. Kaliner and H.J. Lipkin, Phys. Lett. B 575, 249 (2003);
R.L. Jaffe and F. Wilczek, Phys. Rev. Lett. 91, 232003 (2003).

[6]

F. Miyahara et al.: Prog. Theor. Phys. Suppl. 168, 90-96 (2007); H. Shimizu: talk at NSTAR2007.

[7]

V. Kuznetsov et al.: Phys. Lett. B 647, 23 (2007).

[8]

I. Jaegle et al.: Phys. Rev. Lett. 100, 252002 (2008).

[9]

T. Ishikawa et al.: Nucl. Instr. and Meth. A 622, 1 (2010).

[10] T. Ishikawa: Internal GeV-γ Analysis Note No. 130A (2009).
[11] T. Ishikawa et al., Research Report of LNS 39, Tohoku University, 35 (2007).
[12] T. Ishikawa et al., Research Report of LNS 40, Tohoku University, 23 (2008).
[13] T. Ishikawa et al., Research Report of LNS 40, Tohoku University, 19 (2008).
[14] T. Ishikawa et al., Research Report of LNS 41, Tohoku University, 7 (2009).
[15] T. Ishikawa et al.: Research Report of LNS 42&43, Tohoku University, 1 (2011).
[16] R. Hashimoto et al.: Research Report of LNS 41, Tohoku University, 31 (2009).
[17] H. Fujimura et al.: Research Report of LNS 41, Tohoku University, 26 (2009).
[18] T. Ishikawa: Internal GeV-γ Analysis Note No. 209F (2011).
[19] T. Ishikawa: Internal GeV-γ Analysis Note No. 224F (2011).
[20] K. Suzuki: Internal GeV-γ Analysis Note No. 69 (2007).
[21] T. Ishikawa: Internal GeV-γ Analysis Note No. 154F (2009).
[22] T. Ishikawa: Internal GeV-γ Analysis Note No. 225F (2011).
[23] S. Agostinelli et al. (Geant4 Collaboration): Nucl. Instr. and Meth. A 506, 250 (2003);
J. Allison et al.: IEEE Trans. on Nucl. Sci. 53, 270 (2006).
[24] W.-T. Chiang, S. N. Yang, L. Tiator, M. Vanderhaeghen and D. Drechsel, Phys. Rev. C 68, 045202(2003);
web site for η-MAID2003: http://wwwkph.kph.uni-mainz.de/MAID//eta2003/.
[25] D. Drechsel, S.S. Kamalov and L. Tiator: Nucl. Phys. A 645, 145-174 (1999);
D. Drechsel, S.S. Kamalov and L. Tiator: Eur. Phys. J. A 34, 69 (2007);
web site for MAID2000: http://wwwkph.kph.uni-mainz.de/MAID//maidnew/maidnew.html;
web site for MAID2003: http://wwwkph.kph.uni-mainz.de/MAID//maid2003/maid2003.html;

12

web site for MAID2007: http://wwwkph.kph.uni-mainz.de/MAID//maid2007/maid2007.html.

ELPH Annual Report 2010, Tohoku University Vol. 1

13(ELPH Experiment : #2623, #2640, #2655, #2694)

Detection efficiency of the proton with Backward Gamma
detector
A. Nakamura1 , T. Ishikawa1 , H. Fujimura1 , R. Hashimoto1 , S. Kaida1 ,J. Kasagi1 , K. Maeda2 , K. Nawa1 , S. Ogushi1 , M. Sato1 , H. Shimizu1 ,H. Sugai1 , K. Suzuki1 , S. Takahashi1 , Y. Tsuchikawa1 , and H. Yamazaki1
1Research Center for Electron Photon Science (ELPH), Tohoku University, Sendai 982-0826,
Japan
2

Department of Physics, Tohoku University, Sendai 980-8578, JapanThe central calorimeter in FOREST is LEPS Backward Gamma detector which consists of 252
lead scintillating fiber (Lead/SciFi) modules. Lead/SciFi module is a sampling-type device for the photon
detection, and a matrix of scintillating fibers is embedded in lead alloy. The electromagnetic (EM) shower
is generated mainly in lead alloy, and the energy of the incident particle is measured by the scintillatingfibers. Since only the scintillating fibers are active for the energy response, the detection efficiency ofthe charged hadrons with Lead/SciFi is not thought to be unity. Therefore, the detection efficiency ofthe proton with Lead/SciFi is estimated by using the γp → π 0 p reaction. In this report, we abbreviate
SCISSORS III, LEPS Backward Gamma detector and Rafflesia II to S3, BG, and R2, respectively. The
details of FOREST is described in Ref. [1].

§ 1. Event selection for the γp → π 0 p reaction
The FOREST data taken with the liquid hydrogen target in the 2010B period were used in theanalysis. The events satisfied the conditions
1. the number of clusters is 2 or 3
2. S3 has one neutral cluster,
3. BG has one neutral cluster,
4. BG has less than two charged clusters,
5. R2 does not have a cluster,
6. both the S3 and BG neutral clusters have the energy higher than 50 MeV,7. the maximum energy module in the S3 and BG neutral clusters have timing information,
8. the timing difference between the S3 and BG neutral clusters is [−1, +1) ns, and
9. No module in BG is shared with different clusters
are selected for the candidates for the γp → π 0 p reaction. Here, the average timing of the S3 and BG
neutral clusters is defined as tγγ , and the timing of FOREST is given by tγγ .
To estimate the accidental coincidence between FOREST and the photon tagging counter STBTagger II [2], side-band background subtraction is made. The prompt timing region is [−1.5tRF , +1.5tRF )14and the background one is [−4.5tRF , −2.5tRF ) and [+2.5tRF , +12.5tRF ) where tRF = 1.99928 ns stands
for the radio frequency period for the STretcher Booster ring. Fig. 1 shows the timing difference between
the FOREST and STB-Tagger II.

40000
35000
Counts/0.1 nsec

30000
25000
20000
15000
10000
5000
0
-40

-30

-20 -100
1020Timing Difference tγγ-tTc (nsec)

30

40

Fig.1. Timing difference between the FOREST and STB-Tagger II. The periodic bumps areclearly observed in every tRF = 1.99928 ns. The vertical lines show the boundaries ofthe prompt and background timing regions for the side-band background subtraction.
Modules that have the energy higher than a certain threshold or have timing information weretreated as a central part of the cluster for the responding calorimeter ones. The particle which has theenergy less than the threshold does not form a cluster. To suppress the background process which has
low energy particles, the condition
10. No module having the energy higher than 10 MeV is found that does not belong to clusters
is required for the events of interest. Some particles are only detected with plastic scintillators (PS’s) inhodoscopes, thus the following conditions are also required:
11. IVY PS’s are not found or found in response to one particle within the time [tγγ − 4 ns, tγγ + 12 ns),
12. No SPIDER PS’s are found in response to one particle within the time [tγγ − 2 ns, tγγ + 10 ns), and
13. No LOTUS PS’s are found in response to one particle within the time [tγγ − 2 ns, tγγ + 10 ns).
Fig. 2 show the correlation for the selected events between the γγ invariant mass and the π 0 missing
mass MX for the γp → π 0 X reaction.
The concentration of the events at (Mγγ , MX ) = (mπ0 , mp ) is observed corresponding to the γp →π 0 p reaction where m0π and mp stand for the π 0 and proton masses at rest. Another bump is also found

15

1150
10 2

1100

MX (MeV)

1050
1000
10

950
900
850

1
800
750
0

50

100

150 200 250
Mγγ (Mev)

300

350

400

Fig.2. Correlation for the selected events with conditions 1–13 between the γγ invariant massand the π 0 missing mass MX for the γp → π 0 X reaction. The events in the white box isselected for the γp → π 0 p reaction to estimate the proton detection efficiency with BG.
at MX higher than 1150 MeV with Mγγ = mπ0 which corresponds to the γp → π 0 π + n reaction∗ . The
events with the conditions:14. the γγ invariant mass is [100, 170) MeV, and
15. the π 0 missing mass MX is [840, 1040) MeV
are selected for the γp → π 0 p reaction.

§ 2. Proton detection efficiency with IVY and BG
The event selection for the γp → π 0 p reaction is discussed in section 1. To estimate the detection
efficiency with IVY and BG, The events must be selected that the proton in the final state injects onto
IVY and BG. Whether the proton injects onto IVY and BG or not is determined by using the polar angle⃗X for the γp → π 0 X reaction.
given by the π 0 missing momentum vector P⃗X is investigated. Here, θX stands for the polar angle ofAt first, the precision of the polar angle of P
⃗X , and θBe denotes that given by the BG cluster position which is given by the energy-weighted averagePof the centers of the front faces of the Lead/SciFi modules. Fig/ 3 shows the correlation between θBe andθX for the IVY responding events. The IVY PS is assumed to be responding that have the energy higher
than 0.5 and timing information.
A Lead/SciFi module in BG covers the polar angle of 10◦ and the azimuthal angle of 10◦ . Since its
lateral coverage of the solid angle in a Molière radius is large, little energy leakage is found in a event∗ A π 0 meson and a charged particle are detected in such a event, and the π 0 missing mass M
X is approximately thesum of the mp and the pion rest mass mπ . The final state particles in the lowest number configuration are π 0 , π + ,and n.

16

110
10 3

100
90

10 2

θBe (deg)

80
70
60

10

50
40
1

30
20
20

30

40

50

60 70
θX (deg)8090

100 110

Fig.3. Correlation between θBe and θX . The final state proton must inject onto IVY and BG forthe events with θX ≥ 60◦ depicted in the solid vertical line.
that which kind of particles are incident on it. The cluster position for the charged hadrons which do not
generate the EM shower is approximately same as the center of the front face of the Lead/SciFi module.
Therefore, θBG shown in Fig. 3 has the discrete values. To select the events that the final state proton
must inject onto IVY and BG, the additional condition:
16. θX equals or is larger than 60◦
is required. The maximum polar angle of the final state proton for the γp → π 0 p reaction is about 80◦
at the incident energy less than 1.2 GeV [3]. The requirement of the upper limit for θX is not necessary.
Almost all the final state protons must inject onto IVY and BG for the selected events.
The events are classified into four categories by means of IVY and BG responses, and the numberof the classified events are defined as
NBp×Be : the number of events that IVY and BG respond,
NBp×Be : the number of events that IVY responds and BG does not,NBp×Be : the number of events that IVY does not respond and BG does, and
NBp×Be :the number of events that neither IVY nor BG respond.
The NBp×Be , NBp×Be , NBp×Be and NBp×Be are determined for different absolute value of the π 0 missing
momenta PX . The number of all the selected events Nall is given by
NBp×Be + NBp×Be + NBp×Be + NBp×Be ,(1)

and that of IVY responding events NBp is
NBp = NBp×Be + NBp×Be .

(2)

17

In terms of these variables, the proton detection efficiency with IVY becomesηpIVY =

NBp×Be + NBp×Be
NBp
=
,
Nall
NBp×Be + NBp×Be + NBp×Be + NBp×Be(3)

and that with BG becomes′ηBG=

NBp×BeNBp×Be.
=Nall
NBp×Be + NBp×Be + NBp×Be + NBp×Be(4)

Fig. 4 shows the proton detection efficiencies with IVY and BG as a function of the π 0 missing momentum
PX . Both ηpIVY and ηpBG are unity for the high momentum, and they decrease as the momentum becomes
lower. The ηpIVY is almost 1 for PX ≥ 350 MeV/c, and ηpBG is almost 1 for PX ≥ 550 MeV/c. The
drop of ηpIVY at low energies comes from the stopping due to the energy loss in the material between thereaction point and the surface of the IVY, namely the aluminum pipe for holding the hydrogen target,
the radiation shield for the cryogenic system, and the vacuum chamber with CFRP, the air, and so on.

Efficiency ηpIVY and ηpBG

1

IVY

0.8

BG

0.6
0.4
0.2
0
200

400

Proton Momentum (MeV)600

Fig.4. Proton detection efficiencies with IVY and BG as a function of the π 0 missing momentum(proton momentum) PX .
The ηpBG also drops at low energies, and the IVY PS including wrapping materials and inactive leadalloy affect the efficiency in addition to the materials between the target and the IVY surface. To exclude
the effects of the materials on the way from the target to IVY,
ηp′ =

ηpBG
NBp×Be=ηpIVY
NBp×Be + NBp×Be(5)

is calculated. The ηp′ is approximately the same as the proton detection efficiency with BG in the ideal
condition that there is no material on the way from the target to BG. Fig. 5 shows the ratio ηp′ = ηpBG /ηpIVY
as a function of the π 0 missing momentum PX .

18

Ratio of Efficiencies ηpBG/ηpIVY

1
0.8
0.6
0.4
0.2
0
200

400

Proton Momentum (MeV)600

Fig.5. Ratio ηp′ = ηpBG /ηpIVY as a function of the π 0 missing momentum (proton momentum) PX .

§ 3. Summary
The proton detection efficiencies ηpIVY and ηpBG with IVY and BG are estimated by using the FOREST
events acquired in the 2010B period. Both ηpIVY and ηpBG are unity for the high momentum, and they
decrease as the momentum becomes lower. The details of the analysis for the proton detection efficiency
with BG are described elsewhere [4].

Acknowledgment
This work was supported in part by Grant-in-Aid for Scientific Research (B) (17340063) and forSpecially promoted Research (19002003).

References[1]

T. Ishikawa et al..: Research Report of LNS 42&43, Tohoku University, 1 (2011).

[2]

T. Ishikawa et al.: Nucl. Instr. and Meth. A 622, 1 (2010).

[3]

F. Miyahara: Internal GeV-γ Analysis Note No. 103P (2008).

[4]

A. Nakamura: Internal GeV-γ Analysis Note No. 243F (2012).

ELPH Annual Report 2010, Tohoku University Vol. 1

19(ELPH Experiment : #2633, #2638, #2658)

Report on strangeness photoproduction experiments
performed with the Neutral Kaon Spectrometer 2.
B. Beckford1 , A. Chiba1 , D. Doi1 , T. Fujibayashi1 , T. Fujii1 , Y. Fujii1 ,K. Futatsukawa1 , T. Gogami1 , O. Hashimoto1 , Y.C. Han3 , K. Hirose2 ,S. Hirose1 , R. Honda1 , K. Hosomi1 , A. Iguchi1 , T. Ishikawa2 , H. Kanda1 ,M. Kaneta1 , Y. Kaneko1 , S. Kato1 , D. Kawama1 , T. Kawasaki1 , S. Kiyokawa1 ,T. Koike1 , K. Maeda1 , K. Makabe1 , N. Maruyama1 , M. Matsubara1 , K. Miwa1 ,Y. Miyagi1 , S. Nagao1 , S. N. Nakamura1 , A. Okuyama1 , K. Shirotori1 ,K.Sugihara1 , K.Suzuki2 , T. Tamae2 , H. Tamura1 , N. Terada1 , K. Tsukada1 ,K. Yagi1 , F. Yamamoto1 , T. O. Yamamoto1 , H. Yamazaki2 , and Y. Yonemoto1
1
2

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

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

School f Nuclear Science and Technology, Lanzhou University, Lanzhou, 730000

An experiment designed to investigate the strangeness photoproduction process using a tagged photon beam in the energy range of 0.90 -1.08 GeV incident on a liquid deuterium target was successfully
performed. The purpose of the experiment was to measure the production of neutral kaons and thelambda particles on a deuteron. The generation of photo produced particles was verified by the measurement of their decayed charged particles in the Neutral Kaon Spectrometer 2. The reconstructedinvariant mass distributions were achieved by selecting events where two or more particles tracks wereidentified. Preliminary results are presented here.

§ 1. Introduction
The reaction of interest discussed in this report is the photoproduction of neutrally charged strange
particles, Λ and K 0 , from a deuteron target. The strangeness production processes by the electromagnetic interaction can be used as a probe to bestow indispensable information on the strengths of mesonbaryon coupling and internal structure of hadrons with the strangeness as a degree of freedom [1] . The
exploration into the strangeness production mechanism in the threshold region allows for the frontier ofphysics to be explored particularly concerning the experimental measurement of the photo-produced Λparticle’s momentum and angular distribution.
As a result of the series of the NKS experiments [2] [3], the re-envisioned Neutral Kaon Spectrometer, NKS2, was newly designed and constructed at the Laboratory of Nuclear Science of Tohoku
University (LNS) in 2004, replacing an original version, NKS. Its main purpose is to investigate thephoto-production process, particularly the production of neutral strange particles via single K 0 and Λ∗

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

20

measurement with acceptance less biased at the forward region compared with that of the NKS spectrometer. It was further renovated in 2008 with the addition of a new inner detectors and hence forth isreferred to as the upgradedNKS2.

§ 2. The Upgraded NKS2 Spectrometer System
The upgraded NKS2 is composed of a cryogenic target system located in the center of various detector systems that works in tandem with a photon tagging array. It is positioned along the bending
magnet (BM4) in the second experimental hall at the ELPH facility. Using a carbon wire as a target, photon beams are produced via the electromagnetic interaction with the electrons orbiting in theStretcher Booster Ring (STB) in the form of the bremsstrahlung radiation. The STB ring is capable ofaccelerating electrons injected from a 0.15 GeV Linac injector up to 1.2 GeV. The photon beam is guided
through a collimator in order to reduce the beam halo, a sweep magnet, and into the NKS2+ and isbombarded on the target located in the spectrometer. Moving from the inner most position outwards,
is the target which is surrounded by a Vertex Drift Chamber (VDC) and a Inner Hodoscope comprisedof twenty plastic scintillator segments (IH), which acts as the initiation time trigger for time of flightmeasurements. These pair of detectors are then surrounded and fully enclosed in a Cylindrical Drift
Chamber (CDC). All detectors are themselves located in between the poles of a dipole magnet with 680
mm aperture.

OHγ beam
Fig.1. The figures shows a schematic perspective the recently improved NKS2 spectrometer.
Here is a view along the beam plane,where the ẑ direction = 0. Inner detector package
have been redesigned and installed and is visible in the zoomed image on the bottom
right.

21

Table 1. Summary of data for physics production runs.
Experiment Period
2010
September

Flat Top[s]
21

Number of
Accepted Events
0.64 x 109

Number of
Photons [γ]0.89 x 1012

Beam Rate[MHz]
1.5 - 2.5 MHz§ 3. Data summary and analysis procedure
3.1 Trigger
Our data acquisition utilized the UNIDAQ on Linux as a core system . The main trigger utilized
for physics production experiments was defined as equation 1. In the equation, nTagSum is used todenote a photon being generated and tagged with an over a range of 0.8≤Eγ ≤1.1 GeV, the energy ofthe photon is known by tagging the the recoil electron. The trigger required that a minimum of a twoparticle event be detected in by the inner hodoscope(nIH) and the outer hodoscope(nOH). For the OH, a
mixture of hitsbetween the horizontal and vertical groups would be valid. Lastly, the EV is included into
the trigger logic as a veto. A summary of the data analyzed for the results discussed in this report arelisted in table 1.
Trigger = (nTagSum ≥ 1 ⊗ nIH ≥ 2) ⊗ nOH ≥ 2 ⊗ EV

(1)

3.2 Time of flight
Time of flight measurements (TOF) allow for a particles mass to be determined by knowledge offlight time, the momentum, and the path length L [4]. The time of flight for a particle exiting theinner hodoscopes and passing through the outer is found by the difference of the mean time of the outerwith that of the inner. The time-of-flight (TOF) particle identification method in combination with amomentum measurement was used for determination of the particle species. The technique was to notselect the particles only by their mass but instead by two dimensional histograms of the momentum
versus inverse velocity (β) was considered. From the energy-momentum relation the velocity can becalculated as,

m2 = (1p 2) = p2 ( 2
)
β
β −1

(2)

Figure. 2 displays the two dimensional plot of the charge of the particle multiplied by momentum
versus inverse beta. The colored locus plot was produced with an additional limitation on the opening
angle between particles; The requirement of -0.9 ≤cosθ ≤ 0.9 was applied for the purpose of rejecting
the abundant amount of electron positron pairs. The bands around 1/β = 1 are the distributions that
correspond to charged pions, indicated in the red lined regions, and the band is for protons which lie
within the blue lined region. The time of flight resolution between the vertical segments of the OH and
IH was found to be 326 (σ)± 2 ps. For the the left and right second segments of the inner hodoscopes

/22(IH2), which are used in the trigger logic for data acquisition, the relative time resolution was 170 (σ) ±Momentum*Charge [GeV/c]

1 ps.

1
D
p

0.5
/+

0

/+

-0.5

-1
-1

0

1

2

3

4

5
6
7
8
9
Inverse Velocity [`-1]

Fig.2. The particle momentum multiplied with the particle charge plotted as a function of theinverse velocity is shown in figure. 2. The proton and pion selection regions are shown by
the red and blue regions respectively. The charged pions are identified by the sign of the
momentum.

A study into the separation power of time of flight measurements between πand protons was conducted to quantitatively ascertain the performance of the upgraded NKS2 spectrometer with the inclusion of the new inner hodoscope (IH). The separation power of the particle species is evident when aprojection of the inverse velocity distribution is produced for a specified momentum region as presented
in figure. 3, where the pion and proton inverse beta distributions are seen left to right respectively. The
regions of momenta selection are 0.02-0.25, 0.3-0.35, 0.4-0.4.5,0.5-0.55 ,0.60-0.65, and 0.7-0.75 GeV/c.
This plot includes an additional requirement for the opening angle such that −0.9 ≤ cos θ ≤ 0.9. The
opening angle for electron positron pairs is much smaller than that of charged pions from the kaon decay
in the energy region of this experiment. The results of the study of the separation power between pions
and protons with respect to momentum was performed and the extracted results are shown in figure 4.
The separation power nσi was defined by the following equations 3, 4 , 5, where the distributions infigure 3 were fitted to a Gaussian function. µ1 , µ2 , σ1 and σ2 are the mean values and the standard
deviations of the gaussian fits of the pion and proton distributions. The calculation of the separation
power nσi is,nσ1 =|µ1 + µ2 |(σ1 + σ2 )/2(3)|µ1 + µ2 |nσ2 = √
2
(σ1 2 + σ2 )(4)|µ1 + µ2 |(σ1 + σ2 )

(5)

nσ3 =

Counts

Counts

23

30

20

10

10

1 1.5 2

2.5 3 3.5

4 4.5

0
0 0.5

5

Inverse velocity `-1

Counts0
0 0.5Counts30

2030

1 1.5 2 2.5 3 3.5

4 4.5

5

1 1.5 2 2.5 3 3.5

4 4.5

5

1 1.5 2 2.5 3 3.5

4 4.5

5

1 1.5 2 2.5 3 3.5

4 4.5

5

Inverse velocity `-1

40
30

20
20
10

10
2.5 3 3.5

4 4.5

0
0 0.5

5

Inverse velocity `-1

30

20

10

10

2.5 3 3.5

4 4.5

0
0 0.5

5

Inverse velocity `-1

Counts

1 1.5 2

30

20

10

10

1 1.5 2

2.5 3 3.5

4 4.5

5

Inverse velocity `-1

Inverse velocity `-1

30

20

0
0 0.5

Inverse velocity `-1

30

20

0
0 0.5

Counts

1 1.5 2

CountsCounts

0
0 0.5

0
0 0.5

Inverse velocity `-1

Separation [m]Fig.3. 1/β distributions, where β = (v/c). The figures are for a momentum selection region of
0.02-0.22, 0.3-0.32, 0.4-0.4.2,0.5-0.52 ,0.60-0.62, and 0.7-0.72 GeV/c

12
10
8
//p

6
4
2
0
0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7
Momentum [GeV/c]

Fig.4. Separation power between pions and protons with respect to momentum for momentum
selected regions of 0.02-0.25, 0.3-0.35, 0.4-0.4.5,0.5-0.55 ,0.60-0.65, and 0.7-0.75 GeV/c.
The results of equations 3, 4 , 5 are shown as the black , blue and red data points respectively.

Counts

Rigidity * Charge [GeV/c]

24

1

103

0.5

102
0

10

-0.5
-1

1

-0.5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

01

Mass squared [GeV2/c4]

2

3

4

5

6

Mass squared [GeV/c2]

Fig.5. Rigiidity multiplied by particle charge plotted verses mass squared event distribution(left); Mass squared event distribution (right).

As can be understood from the equations the particles species separation power was defined as
being proportional to the mean of the sigmas, equation 3, the square root of the sum of the squares ofthe sigmas, equation 4, and the sum of the sigmas, equation5. Therefore, we define the potential upperbound and lower bound separation between protons and pions as equations 3 and 5.
From equation 2 the region selection of the identification of charged pions is specified as,−0.5 ≤ m2 ≤ 0.25(GeV2 /c4 )(6)and for the protons,
0.5 ≤ m2 ≤ 1.8(GeV2 /c4 )(7)

The mass squared distributions of the detected particles versus the momentum that has been multiplied by the charge is shown in figure 5.

§ 4. Invariant Mass
For the identification of the lambda particle it was necessary to reconstruct its invariant mass fromtwo particle combinations of a negatively charged pion and a proton. The invariant mass is calculatedby the following equation,√√Mpπ− 2 = ( m2p + |⃗pp |2 + m2π− + |⃗pπ− |2 )2 − |⃗pp + p⃗π− |2(8)

The pπ − invariant mass distribution in the inclusive γN →pπ − X measurement is shown figure 6
for the energy bin of 0.9 -1.08 GeV. The distributions associated with the energy bins of 0.9-1.0 and
1.0 - 1.08 GeV are can be seen in figure 6. However, there lies the chance of a fallaciously identified
decay vertex point such that the combination of a pion from the kaon decay and a proton from a lambda
decay. The background present in the invariant mass spectrum after the application of kinematicaland various cuts is attributed mainly to this mis-combination. The photon induced production of a ∆0particle and it’s subsequent decay can also contribute to the background. The distributions were fitted by
the combination of a gaussian and third degree polynomial function. The resolution of the distribution
generated for the energy bin of 0.9 -1.08 GeV was determined to be 2.87 ± 0.19 MeV/c2 in RMS. In theCounts/ 2[Mev/c2]

25

140
120
100 m =2.87 ! 0.19[MeV/c2]
80
60
40
20
0
1 1.021.04 1.06 1.08 1.1 1.121.141.16 1.18 1.2

p/- Invariant Mass [GeV/c2]

120
100 m =2.87 ! 0.19[MeV/c2]
80

Counts/ 2[Mev/c2]

140Counts/ 2[Mev/c2]

Counts/ 2[Mev/c2]

Fig.6. Invariant mass resolution for the energy bin of 0.9 -1.1 GeV was found by fitting as 2.87
50100
± 0.19 MeV/c
40
0.9 < Ea < 1.0 GeV
30m =2.56 ! 0.29[MeV/c2]
20p0

118.3 ! 9.0

p1

1.114 ! 0.000

10p2

0.002872 ! 0.000190

p3-3761 ! 5.5

6464 ! 5.9
0p4
1 1.021.04-2762
1.06! 4.3
1.08 1.1 1.121.141.16 1.18 1.2
p5

-

2

p/ Invariant Mass [GeV/c ]

80
60
40

1.0 < Ea < 1.08 GeVm =3.26 ! 0.30[MeV/c2]

200
1 1.021.04 1.06 1.08 1.1 1.121.141.16 1.18 1.2

p/- Invariant Mass [GeV/c2]

60
40
20

50
40
0.9 < Ea < 1.0 GeV
30m =2.56 ! 0.29[MeV/c2]
20
100
1 1.021.04 1.06 1.08 1.1 1.121.141.16 1.18 1.2
p/- Invariant Mass [GeV/c2]

Counts/ 2[Mev/c2]

Counts/ 2[Mev/c2]0
1 1.021.04 1.06 1.08 1.1 1.121.141.16 1.18 1.2
p/- Invariant Mass [GeV/c2]

100
80
60
40

1.0 < Ea < 1.08 GeVm =3.26 ! 0.30[MeV/c2]

200
1 1.021.04 1.06 1.08 1.1 1.121.141.16 1.18 1.2
p/- Invariant Mass [GeV/c2]

Fig.7. Invariant mass resolution for the energy bins of 0.9-1.0 and 1.0 -1.1 GeV are seen in the
figures left to right respectively., where the fitted resolution were found to be 2.56 ± 0.29
MeV/c and 3.26 ± 0.30 MeV/c

26

Table 2. pπ − invariant mass resolution

Selection
Eall
γ
E1γ
E2γ

Region [ GeV]
0.90 ≤ Eγ ≤1.1
0.90 ≤ Eγ ≤1.0
1.0 ≤ Eγ ≤1.1

Inclusive Λ measurement
Resolution [MeV/c2 ]2.87 ± 0.19
2.56 ± 0.20
3.26 ± 0.30

Yield (S)349 ± 25.49
102 ± 14.42
247 ± 20.59

Noise(N)166±12.88
49±7.00
72±10.24

S/N
2.1
2.1
3.4

two smaller energy bins, 0.9-1.0 and 1.0-1.1 GeV, the resolutions were 2.56 ± 0.2 and 3.26 ± 0.30 GeV
respectively. Full details are listed in table 2.

§ 5. Summary
The experiment in the photoproduction of strangeness on a deuteron target was accomplished using
a tagged photon beam at the ELPH research facility. The time of flight particle identification (PID)
capability of the upgraded NKS2+ spectrometer was evaluated. The separation power between protons
and pions was examined and reported. The invariant mass spectrum of pπ − was obtained and theresolution of the spectrums have been detailed. We are placing immense effort in the proper calibrationof the data and in furthering the status of data analysis, which is still underway.

Acknowledgment
This research endeavor was partially supported by the Creative Research Program funded by theJapan Promotion of Science and also by the JSPS Core to Core program.

References[1]

T. Mart et al.: Nucl. Phys. A684 (2001) 502.

[2]

K. Tsukada et al.: Phys. Rev. C78 (2008) 14001.

[3]

T. Watanabe et al.: Phys.. Rev. Lett. B651 (2007) 269.

[4]

E.Nappi et al.: Instrumentation in elementary particle physics 674 (2003) 18-35.

ELPH Annual Report 2010, Tohoku University Vol. 1

27(ELPH Experiment : #2699)

高レートビームトラッキング用シリコン検出器のテスト
谷田 聖 1 , Yoon Choonjae 1∗ , Bhang Hyoungchan1 , Kim Mijung 1 , Kim Sunji 1 ,藤岡 宏之 2 , 浅野 秀光 2 , 佐田 優太 2 , 三輪 浩司 3 , 本多 良太郎 3 , 真壁 佳佑 3 ,堀田 智明 4 , 住浜 水季 5
1 Department of Physics and Astronomy, Seoul National University, Seoul 151-747
2 京都大学大学院理学研究科（606-8502 京都市左京区北白川追分町）
3 東北大学大学院理学研究科（980-8578 仙台市青葉区荒巻字青葉）
4 大阪大学核物理研究センター（567-0047 大阪府茨木市美穂ヶ丘）
5 岐阜大学教育学部（501-1193 岐阜市柳戸）

Test of a silicon microstrip detector for high-rate beam
tracking
Kiyoshi Tanida1 , Choonjae Yoon1∗ , Hyoungchan Bhang1 , Mijung Kim1 ,Sunji Kim1 , Hiroyuki Fujioka2 , Hidemitsu Asano2 , Yuta Sada2 , Koji Miwa3 ,Ryotaro Honda3 , Keisuke Makabe3 , Tomoaki Hotta4 , and Mizuki Sumihama5
1

Department of Physics and Astronomy, Seoul National University, Seoul 151-747
2
3
4

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

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

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

Graduate School of Education, Gifu University, Gifu, 501-1193

We performed a test experiment to measure the performance of our silicon microstrip detector (SSD)
under high beam-rate up to 100 MHz. The detector worked well in such high-rate conditions. We
measured detection efficiency, noise level, and timing resolution as a function of beam rate. We also
performed a test on glass cherenkov counter to be used in J-PARC E15 experiment as a parasite.

§ 1 . 高レートビームトラッキング用シリコン検出器（SSD）
1.1 SSD の開発動機とテストの目的
近年、特に 2 次ビームを使う実験において、ビーム強度が増加し、実験に使用できるビーム強度が加速器側ではなく、検出器側で制限される例が増えてきた。たとえば、J-PARC の K1.8 ビームラインでは、毎秒108 個程度以上の π を供給可能であると見積もられているが、今のところ実際の実験で使えているのは、毎秒 106 個ないし 107 個程度がせいぜいである。
この制限には主にトラッキングディテクターが効いている。つまり、より高いビーム強度で使えるトラッ
キングディテクターを開発すれば、全体として使用できるビーム強度が上がり、より高い統計を得ることが∗Present address: Research Center for Nuclear Physics, Osaka University, Osaka, 567-0047

28

第1図

我々が開発した SSD 試作機の写真。

可能になる。そこで、我々は、SSD に目をつけた。SSD は細かいピッチ（50 ∼ 100 µm）を持つのが特徴
で、ビームを多数のストリップで分散して受けることにより、高いビーム強度下でも動作することが期待できる。また、電荷収集時間もガスチェンバーよりやや早く（30 ns 程度）、残留イオンによる空間電荷効果もないため、この点でも高レート検出器に向いている。
我々の開発した SSD 試作機の写真を図 1 に、その仕様を表 1 に示す。センサーは ATLAS 実験によって開発されたもの [1]（浜松ホトニクス社製）を使用した。これは高い放射線耐性を持ち、高強度ビームを長時間当て続けることが可能なようになっている。読み出しチップには、CMS 実験によって開発された APV25
チップ [2]を用いた。このチップは 1 枚で 128 チャンネル分の信号を処理することができ、信号を増幅・整形した後、マルチプレクサ―を通してシリアル信号として出力する。この点は長らく SSD 読み出しによく使われていた VA チップ（IDEAS 社）と同様であるが、シェイピングタイムが 50 ns 程度と短いこと、動作周波数が 40 MHz と高く、早い読み出しが可能であること、マルチサンプルが可能である、といった違いがある。中でも、マルチサンプルが可能なことは APV25 の最大の特徴で、これによって波形データを読み出すことができ、数 ns といった高い時間分解能を達成することができる。これにより、高レート下で問題になるアクシデンタルヒットの問題に対処することができる。
第 1表

SSD センサーの仕様

面積
有感領域
厚さ
結晶方位
ストリップ間隔
ストリップ数

64.0 mm × 63.6 mm
62.0 mm × 61.6 mm
290 µm⟨111⟩
80 µm
768+2(ダミー)

本実験の目的は、この試作機を実際に高強度ビームのもとでテストし、その性能を実証することにある。

29

第2図

実験セットアップの概念図。

具体的には、検出効率、時間分解能、信号の大きさ、ノイズのそれぞれをビーム強度（105 ∼ 108 Hz）の関数として測定した。

1.2 実験セットアップ
実験は、2009 年 12 月 22 日から 24 日の三日間（昼間のみ）、GeV-γ ビームラインにおいて行われた。テ
スト実験用の電子／陽電子ビームラインではビーム強度が不足するので、メインの γ 線ビームラインに銅のコンバーターを置き、対生成によって出てくる電子および陽電子を使った。そのセットアップの概略を図2 に示す。SSD を 2 cm 間隔で 2 台（X 方向と Y 方向）並べ、その前後にさらにプラスチックシンチレー
ター（2 mm × 2 mm × 2 mm）をおいて、トリガーカウンターとした。シンチレーターの信号の読み出
しには MPPC(Multi-Pixel Photon Counter) を用いている。なお、タガーの情報は（下に述べるビーム
強度モニター用を除き）使っていない。

SSD に荷電粒子がいくら当たっているかについては、ビーム強度が弱い際に SSD とほぼ同じサイズのシンチレーターを置いて直接測定したものを GeV-γ ビームラインのタガー、およびトリガーカウンターのレートを用いてスケールしたものを目安とし、最終的にはオフラインで SSD 自身のアクシデンタルヒット（クロックトリガーによる）を数えて算出した。ビーム強度の変更については、弱い（< 3 × 106 Hz）強度
では加速器の周回電流を変えることで行い、それ以上の強度については、コンバーターの厚さを 2 mm から 6 mm に変え、さらにスピル長を 6 秒から 2 秒に変えることで行った。

1.3 結

果

まずはクロックトリガーを用いて、アクシデンタルヒットからビームプロファイルを導出したものを図 3に示す。ビームは X,Y 方向ともに RMS で 170 ストリップ、すなわち 1.4 cm ほどの拡がりであることが分かる。図中、線で囲まれた領域（サンプル領域）はトリガーカウンターが存在している場所に対応してお

30

第3図

第4図

クロックトリガーにて取得したビームプロファイル。左が X 方向（SSD2）で、右が Y 方向（SSD1）。線で囲まれた領域（サンプル領域）はトリガーカウンターに対応し、トリガーによって選ばれる領域に相当する。SSD2 にはデッドストリップが見られるが、この領域は解析には使用していない。

SSD1 のピーク波高分布。70 チャンネル付近に minimum ionizing particle に対応するピークがはっきり確認できる。実線はランダウ分布をガウス分布でたたみこんだものによるフィットの結果。

第5図S/N 比の計数率依存性。ストリップ一本あたりの計数率が上がるにつれ、S/N 比は悪化していく。

31

第6図

時間分解能の計数率依存性。ストリッ
プ一本あたりの計数率が上がるにつれ、時間分解能は悪化していくが、一番高い計数率でも 4 ns (RMS) より良い値が得られた。

第7図

検出効率の計数率依存性。ストリップ一本あたりの計数率が上がるにつれ、パイルアップ
により検出効率はわずかに落ちる。

り、この領域のヒットについて解析を行った。この領域内の 1 ストリップあたりのヒットレートは全体のヒットレートに対し、SSD1（Y 方向）で約 1/400、SSD2（X 方向）で約 1/1400 であった。なお、X 方
向の SSD（SSD2）については、340 チャンネルから 520 チャンネルにかけて極端にヒット数の少ないス
トリップが存在した。この原因は不明であるが、以降の解析において、この領域は使用していない。
次に、SSD のピーク波高分布を図 4 に示す。まずはきれいな minimum ionizing particle によるピーク
が見える（なお、γ 線が上流でコンバートする際には対生成で 2 つの荷電粒子ができるが、その両方が同じ
ストリップに飛び込む確率は無視していいほど低い）。このピーク波高については、レート依存性はほとん
ど見られなかったが、ノイズレベルについては、レートが高くなるにしたがって大きくなり、結果として

S/N 比が悪化する傾向が見られた（図 5 参照）。これは、前の信号のテールが存在することによる影響として解釈できる。ただし、最もレートが高い場合（SSD 全体で 108 Hz、ストリップあたりで 3 × 105 Hz）でも、S/N 比は 10 を超えており、信号をノイズから分離するには十分であることがわかった。
時間分解能については、ビームが弱い際には RMS で 3.3 ns (SSD1) と 3.1 ns (SSD2) という結果が得られた。この値はビーム強度が増えるに連れ、図 6 に見られるように少しずつ悪化している。これは、ノイズレベルが増えたせいと思われる。この分解能は、例えば 107 Hz のビームを受けた際でも、アクシデンタル
ヒットが平均 0.2 個以下というレベルであり、真のヒットを高い確率で選択可能であることを示している。
最後に、検出効率であるが、トリガーの質も考慮に入れた結果、片方の SSD のサンプル領域中の 1 スト
リップのみにヒットがある、という条件の下、もう片方の SSD のサンプル領域中にヒットがある割合、という定義で算出した。まず、ビーム強度が低い場合の検出効率は SSD1,2 ともに 99.0 ± 0.5%という値が得られた。1%程度の不感率がある理由はわかっていないが、大きな問題ではないと考えている。続いて、検出効率のレート依存性を図 7 に示す。レートが高くなるにしたがって、検出効率が落ちているのがわかる
が、これはパイルアップにより 1 ヒットあたり 100 ns 程度の不感時間があるとして解釈でき、SSD 全体の動作に特に問題は見られない。
以上、SSD は期待通り高強度ビームのもとでも動作することが実証された。

32§ 2 . ガラスチェレンコフカウンター
2.1 開発動機とテストの目的
J-PARC E15 実験はヘリウム 3 標的に K − ビームを照射することで K 中間子原子核を探索する実験である。E15 実験において、(K − , p) 反応により散乱された陽子を検出するためには、K − ビームが標的を通過した事象を除く必要がある。そのため標的下流で K − と陽子を識別する検出器が必要となる。ただし標的下流にはそれほど多くの空間的余裕はない。そこでその要求に応える検出器として我々は全反射型ガラス
チェレンコフ検出器の開発を行うこととした。この検出器はガラスの全反射条件とチェレンコフの輻射角の条件を組み合わせることで速度閾値を設定する検出器である。つまり閾値以下の速度の荷電粒子が出すチェ
レンコフ光は全反射条件を満たさず輻射体の外に抜け、閾値以上の速度をもつ粒子のチェレンコフ光は全反射しガラス内を通過し光電子増倍管に入り信号となる。
測定する K 中間子原子核の missing-mass を 2.20〜2.55 GeV/c2 の範囲にとると、散乱陽子の運動量は1.0 ∼ 1.4 GeV/c (β = 0.729 ∼ 0.831) になる。一方、K − ビームの運動量は 1.0 GeV/c (β = 0.891)であるので全反射型チェレンコフの閾値をこの間に設けると両粒子の識別が可能となる。その際、屈折率n ∼ 1.53 程度で透明度の高い輻射体が必要である。この条件を満たすものとしてホウケイ酸ガラスの一種(BK7) と紫外線透過ガラス (Super Clear 日本板硝子製、以下 SC) が挙げられる。そのため、これらの輻射体で試作機を製作し、電子光理学研究センターの陽電子ビームを使用し実験を行った。実験の目的としては、試作機の測定結果をシミュレーションと比較し検出器が想定通りの振る舞いをするかをテストすることである。具体的には輻射体の違いや PMT の依存性、また入射角度・入射位置による依存性の測定しシミュ
レーションと比較した。
ガラスチェレンコフカウンターの実験は、GeV-γ ビームラインのテスト実験用の陽電子ビームラインにて行った。この実験では以下の 2 つのテスト機• テスト機 1
輻射体は BK7(200mm × 200mm × 5mm）、PMT は H6522 を各側 2 本計 4 本使用。
輻射体をアルミの小さなフレームで支え、なるべく面を空気以外のものと接触させない構造にした。

PMT と輻射体の接着は optical grease([BC-630] Saint-Gobain 製) を使用した。
• テスト機 2
輻射体は 50mm × 50mm × 5mm のサイズの BK7, SC1(6 面を 1λ ∼ 633nm 以内の面精度で加工した SC), SC2(側面をパフ研磨精度で加工した SC) を入れ替え可能な設計。PMT も H6522、R7600、

R8900 を付け替え可能で各側 1 本計 2 本使用。その他の設計はテスト機１と基本的に同じである。SC1と SC2 を比較することで側面の研磨の面精度による影響も考察する。
について行った (写真:図 8)。テスト機 1 では角度・位置依存性の測定、テスト機 2 では輻射体・PMT の差異についての測定を目的とし、シミュレーションと比較し検出器が想定通りの振る舞いをするかを調べた。
実験のセットアップはテスト機 1, 2 を図 9 のように配置し、エネルギー 450MeV の陽電子を照射しテス
ト機 1 で角度・位置依存性を、テスト機 2 では輻射体と PMT の差異について測定した。trigger には 50 ×

10 × 5mm のプラスティックシンチレーター (図 9) を十字に組み合わせたものをテスト機 1, 2 の前後に配
置した。

33

(a) テスト機 1

第8図(b) テスト機 2

テスト機 1、テスト機 2 の写真

テスト機1
TR1

テスト機２

TR2

TR4

e+ beam
TR3

800mm
第9図

2.2 結

実験のセットアップ

果

テスト機 1 についての結果をまず、図 10 に示す。それぞれテスト機 1 の角度依存性（左）と x 軸における位置依存性（右）である。実線が実 data、点線がシミュレーション結果である。結果とシミュレーショ
ンはその振る舞いにおいてよく一致している。ただし、光電子数の絶対値はシミュレーションのおよそ 2/3程度になっている。これはシミュレーションで考慮しきれない影響によるもの（ガラスと PMT の接合面の気泡等）と考えられる。しかし光電子数の総数としては十分な数があるので十分な性能が得られたと考えている。
次にテスト機 2 による、PMT（R7600,R8900,H6522）とガラス（BK7,SC1,SC2）による依存性の結果を図 11 に示す。結果は PMT の組み合わせごとになっており、それぞれ
図 11(a) R7600, R8900 の組の結果
図 11(b) R7600, H6522 の組の結果
図 11(c) R8900, H6522 の組の結果である。
輻射体ごとの違いとしては、接着面での不定性のため誤差が大きくなってしまったため、SC1(全面で面
精度 < λ 以下) と SC2(側面、パフ研磨精度) に有意な差を見ることはできなかった。ただ、BK7 と SC との差についてはある程度確認でき、ふらつきは大きいが SC の方が光電子数において 2, 3 割の増加が見ら34

Sum of all PMT
Num of p.e

Num of p.e

Sum of all PMT
24
22

Sim

20

Sum of all PMT

24
23
22
21
Sim

20

18

19

16

Sum of all PMT

18
14

17
12

16

10

15

8
-30

-20

-10

0

10

14

20
30
angle[deg](a) テスト機 1 からの全信号 (PMT1, 2, 3, 4 の合計)の位置 (0, 0) における角度依存性

第 10 図

-4

-2

0

2

4

6

8
x[cm]

(b) テスト機 1 からの全信号 (PMT1, 2, 3, 4 の合計) のy = 0 での x 位置依存性

R7600 H6522

45

Num of p.e

Num of p.e-6

テスト機 1 の角度依存性と位置依存性。点線がシミュレーションの値で実線が実験デー
タである。

R7600 R8900
BK7 Sim
BK7

40

SC Sim
SC1
SC2

35

45

SC Sim
SC1
SC2

35
30

25

25

20

20

15

15

10

10

5

BK7 Sim
BK7

40

30

0

-8

5

R7600

R8900

(a) PMT が R7600 と R8900 の組での輻射体の差
異による光電子数の変化

0

R7600

H6522

(b) PMT が R7600 と H6522 の組での輻射体の差異による光電子数の変化

Num of p.e

R8900 H6522
45
BK7 Sim
BK7

40

SC Sim
SC1
SC2

35
30
25
20
15
10
5
0

R8900

H6522

(c) PMT が R8900 と H6522 の組での輻射体の差
異による光電子数の変化

第 11 図PMT と輻射体の差異による光電子数の変化。左にある 2 本の棒グラフがそれぞれ BK7でのシミュレーションと実験データ、右側の 3 本が左から SC でのシミュレーション、
SC1(面精度 < λ 以下) の実験データ、SC2(側面、パフ研磨精度) の実験データである。

35

れ、誤差の範囲内でシミュレーションともおおよそ一致している。しかし、H6522 は輻射体が SC の場合にシュミレーションの見積もりより光電子数が少なくおよそ 80% 程度しかなかった (図 11(b), 11(c))。この原因は接着面の悪さが最も疑わしいが確かなことはこれらのデータからはいえない。
以上、テスト機 1，2 の結果より位置、角度の依存性においてシミュレーションにより傾向がよく知れることを確認でき、また BK7 より SC のほうが光量の増加が見られることが確認できた。これにより試作機として十分な性能であることが確認できた。

§3 . ま と め
SSD の試験では、期待通り 108 Hz という高レートのもとでも、十分な S/N 比、検出効率、時間分解能が得られることがわかった。また、パラサイトにて行ったガラスチェレンコフカウンターの試験においても、試作機として十分な性能であることが確認できた。位置、角度の依存性の傾向については、絶対値こそノーマライゼーションが必要なものの、シミュレーションにより再現できることがわかった。また、ガラスによる違いとしては、BK7 より SC のほうが光量の増加が見られることがわかった。

謝辞

ケーブル等を貸して下さったり、ビームの調整をして実験を手伝って下さった電子光理学研究センターの皆様、特に石川助教に感謝致します。

参
[1]

考

文

献

Y. Unno: ATLAS silicon microstrip Semiconductor Tracker (SCT), Nucl. Instr. and Meth. bf
A453 (2000) 109.

[2]

M. Raymond et al.: The CMS Tracker APV25 0.25 µm CMOS Readout Chip, Paper presented
at the 6th workshop on electronics for LHC experiments (Krakow, Poland, September 2000).

ELPH Annual Report 2010, Tohoku University Vol. 1

37(ELPH Experiment : #2711)

Waveform of the light output for BSO scintillator in
response to the positron beam
T. Ishikawa1 , H. Fujimura1 , R. Hashimoto1 , S. Kaida1 , R. Kitazawa1 ,A. Nakamura1 , H. Shimizu1 , K. Suzuki1 , S. Takahashi1 , Y. Tsuchikawa1 ,and H. Yamazaki1
1Research Center for Electron Photon Science (ELPH), Tohoku University, Sendai 982-0826,
Japan

We have paid attention to BSO scintillator for a new electromagnetic (EM) calorimeter for coming
high precision photoproduction experiments at ELPH. We investigate the basic scintillation characteristics of BSO crystals with and without the beam. In this report, the waveform of the light output ispresented for BSO scintillator in response to the positron beam§ 1. Introduction
The nucleon resonance spectroscopy is an important testing ground for understanding low energy
QCD. Meson photoproduction is utilized for it complementary to π-N scattering. It should be noted that
excited baryon resonances highly depend on the production processes. At ELPH, the excited baryons areintensively studied via η photoproduction on the neutron by using an EM calorimeter FOREST [1]. We
plan to construct a new EM calorimeter for the next generation photoproduction experiments. Bismuth
silicate (Bi4 Si3 O12 : BSO) [2–6] is a candidate of the detector element for EM calorimeters in the photon
energy region from 100 MeV to a few GeV.
We investigate the properties of the BSO crystals [7] which were produced at Futek Furnace Co.,
Yokohama, Japan [8]. Four rectangular parallelepiped crystals with a size of 40 × 40 × 210 mm3 were
cut and polished from the ingots.

§ 2. Experimental setup
The waveform of BSO light outputs was acquired by employing a digital phosphor oscilloscope,
Tektronix DPO-4104, with a sampling frequency of 5 GHz [9]. One of the 40×40×210 mm3 BSO crystals
was looked into. It was connected to PMT H6410 with optical grease OKEN6262A, and wrapped with
Tyvek 1082D paper. The output signal was directly input to DPO-4104. Fig. 1 shows the experimental
setup for the waveform acquisition. To deﬁne the incident position and timing of positrons, a 3 mm thickplastic scintillator (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.
The trigger signal for the waveform acquisition was generated when the pulse height of the PS138

PS1 (DPO-4104 CH 1)

R4125GMOD

H6410

Light Guidee+
Plastic
Scintillator

BSO crystal
Light Guide
BSO (DPO-4104 CH 3)
R4125GMOD

PS2 (DPO-4104 CH 2)
Fig.1. Experimental setup for the waveform acquisition. The 3 mm thick plastic scintillator
with an area of 10 × 10 mm2 is placed in front of the BSO crystal to deﬁne the position
and timing of incident positrons.

signal reached a threshold voltage of −300 mV. The waveforms of PS1, PS2, and BSO signals wereacquired on an event by event basis for the time from the trigger signal from −0.2 to 1.8 μs. The
RTAGX current was set to be 50, 100, 150, 230, 300, and 400 A, which approximately corresponded tothe energy of 100, 200, 300, 458, 589, and 744 MeV, respectively. About two thousand waveforms wereobtained for each RTAGX current. The typical waveform acquisition rate was about 0.9 Hz which was
limited by the acquisition speed with DPO-4104. The ground level was measured with DPO-4104 eventby event for the time interval from −70 to −10 ns. It was subtracted to give the pulse height. The typical
waveforms for PS and BSO are shown in ﬁgs. 2 and 3, respectively.

§ 3. Shape parameters of the waveform
The pulse height of PS 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 [10]. The parameters V0 , t0 , τR , and τDcorrespond to the amplitude, the response timing , the rising time, and the effective decay time, respectively. The ﬁts were made in the time region [−10, +140) ns for PS1. Fig. 4 shows V0 , t0 , τR , and τD
distributions for PS1 waveforms. Since the V0 parameter is proportional to the energy loss of positrons

39

Pulse Height (mV)

0
-200
-400
-600
PS1

-800

0

50
100
Timing (ns)Fig.2. Typical PS waveform at a positron energy of 589 MeV (PS1). The solid curve is a ﬁtted
function with eq. (1).

Pulse Height (mV)

0
-200
-400
-600
-800
0

200
Timing (ns)400

Fig.3. Typical BSO waveform at a positron energy of 744 MeV. The solid curve is a ﬁt to thedata with function (3).

in 3 mm thick plastic scintillator, the V0 distribution is well reproduced with an approximate expressionof the Landau distribution (the Moyal function) [11]:




CV
x − μV
1 x − μV,
+ exp −exp −fV (V0 ) = √
2
σV
σV
2π

(2)

where μV and σV correspond to the mean and width of the distribution, respectively. Each of the τR andτD distributions can be well ﬁtted with a Gaussian function. Fig. 5 shows the obtained mean and width
for each of the parameters, V0 , τR , and τD , as a function of the incident positron energy. The mean andwidth of all the distributions are almost constant with respect to the incident positron energy.

40
201000 2000 3000

V0 (mV)PS1 150
Counts / 0.05 nsec

100

60

0
0

PS1

Counts / 0.05 nsec

Counts / 20 mV

PS1

80

Counts / 0.05 nsec

40

400
300

100

200

50

100

0
-2

0

t 0 (ns)

2

0
0

PS1

1

2

τR (ns)

50
0

0

2

τD (ns)4

Fig.4. Distributions for amplitude V0 , response timing t0 , rising time τR , and effective decay
time τD for the PS1 waveform at a positron energy of 458 MeV. The V0 distribution iscompared with the ﬁtted function (2), and the τR and τD distributions are comapredwith the ﬁtted Gaussian functions.

400
200

3.4
Mean (ns) of τD

600

0.94
Mean (ns) of τR

Mean (mV) of V0

800

0.92
0.90

0.88

3.2
3.0
2.8

0.86

2.6
0.35
0.12
0.30
200
0.10
0.25
150
0.08
0.20
0.06
0.15
100
0.04
0.10
50
0.02
0.05
0
0
0
0 200 400 600 800
0 200 400 600 800
0 200 400 600 800
Incident Energy (MeV)
Incident Energy (MeV)
Incident Energy (MeV)
Width (ns) of τD

Width (ns) of τR

Width (mV) of V00

Fig.5. Mean (upper panel) and width (lower panel) of the V0 , τR , and τD distributions for PS1.
A Moyal function (2) is ﬁtted to the V0 distribution to give the result. A Gaussian function
is employed for the ﬁt to the data of the τR and τD distributions.

We can reproduce the waveform of BSO signals with
⎧





t − t0⎪⎨ −V0 1 − exp − t − t0
exp −
τR
τD
V (t) =⎪
⎩ 0

for t ≥ t0
for

(3)

t < t0taking into account a longer decay time of BSO signals. Here parameters V0 , t0 , τR , and τD havethe same meaning as before. Fitting was repeated several times in the time region [−10 ns, t0 + 6τD ).
Fig. 6 shows V0 , t0 , τR , and τD distributions for the BSO waveform. Every one of the V0 , τR , andτD distributions follows a Gaussian shape at each incident positron energy. Fig. 7 shows the mean
and width of the V0 , τR , and τD distributions as a function of the incident positron energy. The mean
and width of the V0 distribution are proportional to the incident positron energy since V0 corresponds

BSO 300

BSO 150

150

200

100

100

20
00

Counts / 0.1 nsec

40

500

1000

V0 (mV)Counts / 0.02 nsec

BSO 200
Counts / 0.1 nsec

Counts / 2 mV

41

100

50
0
20

22

24

t 0 (ns)

26

0
2

4

6

τR (ns)

BSO

50
0
90

100

τD (ns)110

Fig.6. Distributions for amplitude V0 , response timing t0 , rising time τR , and effective decay
time τD for the BSO waveform at a positron energy of 589 MeV.

to the energy deposit of positrons in the BSO crystal. The means of the τR and τD distributions are
independent of the positron energy, and almost constant. And the widths of them become narrower as
the positron energy goes up. The decay time measured by the conventional single photon method [12] isreported in ref. [13] giving the fast component of 30 ± 13 ns with an intensity of 43% ± 4%, and the slow
component of 106 ± 6 ns with 57% ± 4%. We obtained the mean of τD consistent with the decay time ofthe slow component in the present way of ﬁtting with one decay parameter.

0
60
50
40
30
20
10
0
0 200 400 600 800
Incident Energy (MeV)

Width (ns) of τR

Width (mV) of V0

200

4.0
3.5

101.5

Mean (ns) of τD

400

4.5

3.0
1.0
0.8
0.6
0.4
0.2
0
0 200 400 600 800
Incident Energy (MeV)

101.0
100.5

100.0
99.5
99.0
4

Width (ns) of τD

600

Mean (ns) of τR

Mean (mV) of V0

800

102.0

5.0

1000

3
2
1
0
0 200 400 600 800
Incident Energy (MeV)

Fig.7. Mean (upper panel) and width (lower panel) of the V0 , τR , and τD distributions for BSO.
Those are obtained with a Gaussian ﬁtting.

§ 4. Timing response
The response timing t0 was determined by ﬁtting the PS waveform with eq. (1) and the BSO waveform with eq. (3). The time resolutions for the PS and BSO signals were estimated from them. Two time42
PS
− tPS2and tBSO− tPS
difference distributions tPS10000 were obtained, where t0 was given by the average ofand tPS2
tPS1
00 . Fig. 8 shows the time difference distributions at a positron energy of 458 MeV.

400

PS1-PS2Counts / 0.1 nsec

Counts / 0.1 nsec

300
200
100
0

-2

-1
0
1
tPS1-tPS2 (nsec)

2

BSO-PS

300
200
100
0
21

22
23
24
tBSO-tPS (nsec)

25

Fig.8. Time difference distributions at a positron energy of 458 MeV. The left panel shows thePS1-PS2 distribution. The right shows the time difference between BSO and PS, wheretPS means the average timing of PS1 and PS2. The solid curves show the ﬁtted Gaussianfunctions.

In general, the time difference ti − tj should have the resolution of σi2 + σj2

1/2, where σi and σj

are resolutions of measured timings ti and tj , respectively. The obtained time resolution of the BSO
signal σt can be well reproduced with
20.103 ± 0.003
2√
σt2 = (0.022 ± 0.041) +(4)
E
as a function of the incident positron energy E as shown in ﬁg. 9, where σt and E are given in ns andin GeV, respectively. Here σPS1 and σPS2 are assumed to be the same. The obtained time resolutionof the BSO signal is 0.11 ± 0.09 ns for 1 GeV positrons, while that of the PS signal is 0.19 ± 0.02 ns,
independent of the positron energy.

§ 5. Energy response
The energy deposit of an incident positron in the BSO crystal is proportional to the charge of PMT
outputs measured with DPO-4104. The charge Q was obtained by integrating the PMT output signal in
the region [−10, +1800) ns,
 +1800 nsec
−V (t)dt,
Q=
ZI−10 nsec(5)

where ZI is a 50 Ω input impedance of DPO-4104. Fig. 10 shows the Q distributions corresponding to
the energy deposits of positrons in the BSO crystal for the positron energies of 200 and 744 MeV. Everycharge distribution has a tail in the lower part due to EM shower leakage since only one BSO crystal was
employed in the measurement. The charge distribution can be ﬁtted with a logarithmic Gaussian [14]:


 
2
σ02
x−μ
1
,
(6)
log 1 −−
ηGL (x) = N exp −
σ
2
2σ02

Timing Resolution (nsec)

43

0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0

0

100

200

300 400 500 600
Energy (MeV)

700

800

Fig.9. Time resolution√ of the BSO signal as a function of the incident positron energy. The solid
curve shows E dependence corresponding to eq. (4).

where η is called an asymmetry parameter giving a tail of the Gaussian and σ0 is described asηξ2sinh−1,(7)ξ
2√with a constant ξ = 2 log 4. Thus the logarithmic Gaussian becomes a normal Gaussian when η goes to
σ0 =0. The obtained asymmetry parameter η was 0.25 ± 0.02 for 200 MeV positrons and 0.15 ± 0.03 at 744
MeV for the single BSO crystal with a size of 40 × 40 × 210 mm3 .

100 A

400 A

100
Counts / 10 pC

Counts / 10 pC

225
200
175
150
125
100
75
50
25
0

80
60
40
20

0

0

500 1000 1500 2000 2500
Charge (pC)0500 1000 1500 2000 2500
Charge (pC)

Fig.10. Charge distributions of the BSO crystal. The left and right panels show those at thepositron energies of 200 and 744 MeV, respectively. The solid curves show the ﬁtted
logarithmic Gaussian.

Fig. 11 shows the energy resolution of the one BSO crystal σE /E = σ/μ as a function of the incident
positron energy. The energy resolution of the one BSO crystal as a function of the positron energy E iswell ﬁtted with
σE
E

2


2

= (1.49% ± 0.30%) +3.54% ± 0.06%
√
E

2
.

The energy resolution of the one BSO crystal corresponds to 3.84% ± 0.13% at 1 GeV.

(8)

44

Energy Resolution (%)

12
10
8
6
4
2
0

0

100

200

300 400 500 600
Energy (MeV)

700

800

Fig.11. Energy resolution of the one BSO crystal as a function of the incident positron energy.
The solid curve shows the ﬁtted function (8).

§ 6. Summary
BSO is one of the candidates for a new EM calorimeter for the next generation photoproduction
experiments at ELPH. The waveform of BSO light outputs was acquired with a digital phosphor oscilloscope Tektronix DPO-4104. The results of the parameters for the waveform shapes, and the timing
and energy responses are discussed. The time resolution of the BSO signal is 0.11 ± 0.09 ns for 1 GeV
positrons. The energy resolution of a single BSO crystal corresponds to 3.84% ± 0.13% at 1 GeV. The
details of the waveform analysis are described elsewhere [15].

Acknowledgment
This work was supported in part by Grant-in-Aid for Scientiﬁc Research (B) (17340063) and forSpecially promoted Research (19002003).

References[1]

T. Ishikawa et al..: Research Report of LNS 42&43, Tohoku University, 1 (2011).

[2]

M. Kobayashi et al..: Nucl. Instr. and Meth. 205 (1983) 133.

[3]

M. Kobayashi et al..: Nucl. Instr. and Meth. A 372 (1996) 45.

[4]

M. Kobayashi et al..: Nucl. Instr. and Meth. A 400 (1997) 392.

[5]

M. Ishii et al..: J. Crystal Growth 205 (1999) 191.

[6]

M. Ishii et al..: Opt. Mater. 19 (2002) 201.

[7]

T. Ishikawa et al..: Research Report of LNS 42&43, Tohoku University, 176 (2011).

[8]

Futek Furnace website: http://www.futekfurnace.com/.

[9]

T. Ishikawa: Internal GeV-γ Analysis Note No. 151A (2009);
T. Ishikawa: Internal GeV-γ Analysis Note No. 177A (2010).

45[10] Computing and Networks Division, CERN Program Library Ofﬁce: CERNLIB — CERN Program
Library Short Writeups C301, 1996.
[11] J.E. Moyal, Phil. Mag. 46 (1955) 263; M.D. Marucho, C.A. Garcia Canal, H. Fanchiotti, Int. J. Mod.
Phys. C 17 (2006) 1461.
[12] M. Moszyǹski, B. Bengtson, Nucl. Instr. and Meth. 142 (1977) 417.
[13] H. Shimizu, et al., Nucl. Instr. and Meth. A 550 (2005) 258.
[14] H. Ikeda, et al., Nucl. Instr. and Meth. A 441 (2000) 401.
[15] T. Ishikawa: Internal GeV-γ Analysis Note No. 216D (2011).

ELPH Annual Report 2010, Tohoku University Vol. 1

47(ELPH Experiment : #2715)

Test of APD readout system of CsI(Tl) calorimeter for
J-PARC TREK experiment
S. Masumoto1 , Y. Igarashi2 , J. Imazato2 , A. Ivashkin3 , K. Ozawa2 ,D. P. Nguyen4 , S. Shimizu5 , S. Strauch6 , A. Takagi1 , Y. Tanizaki1 ,H. Yamazaki7 , and K. Yoshihara1
1

Department of Physics, University of Tokyo, Tokyo, 113-0033
2

3

Institute for Nuclear Research, Russian Academy of Sciences, Russia
4
5

6
7

KEK, Tsukuba, 305-0801

University of Natural Sciences, Vietnum

Department of Physics, Osaka University, Osaka, 560-0043

Department of Physics and Astronomy, University of South Carolina, USA

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

A new readout system of the CsI(Tl) calorimeter using Avalanche-photo diode and Flash ADC isdeveloped. The system is tested using a positron beam to evaluate energy resolution, timing resolution
and rate capability for the energy range from 50 MeV to 460 MeV. The test is performed at the ResearchCenter for Electron Photon Science (ELPH) of Tohoku University. Energy deposit of a 3×3 crystal matrix
is measured using the new readout and energy resolution is evaluated refer to positron momentum.
Archived energy resolutions are 9.0±1.0, 6.76±0.35 and 4.92±0.16% (σE /E) at energies of 50, 100 and
200 MeV, respectively.

§ 1. Introduction
The main goal of the experiment TREK at J-PARC is a search for T-violating transverse muonpolarization in the K+ → π 0 µ+ ν (Kµ3 ) decays of stopped K + mesons. The TREK experiment is upgrade
experiment of the prior KEK-PS experiment, KEK-E246.
The E246 experiment used the stopped K+ beam and a super conducting toroidal spectrometer.
The K+ beam intensity is 105 /s. The spectrometer system is shown in Fig.1. It consists of a largeacceptance CsI(Tl) barrel, racking chambers, an active target and muon polarimeters. The final resultof E246 is PT = −0.0017 ± 0.0023(stat) ± 0.0011(syst) corresponding to the upper limits of |PT | <0.0050(90%C.L.) [1].
The E246 result is essentially statistics-limited. The TREK experiment propose to improve theE246 result by at least a factor of 20 by improving both statistical and systematics uncertainties. The
detector system of the TREK experiment is an upgraded version of the KEK-E246 experiment. Majorchanges in the hardware are: i) improved changed particle tracking by incorporating the state-of-theart
GEM detectors, ii) new readout system of the CsI(Tl) calorimeter, iii) introducing active polarimeters forthe muon decay positions, and iv) a new magnet for the uniform muon field. The upgrade, with increased

48
beam intensity of 106 /s and a run time, will improve the E246 result by the factor of 20 and the discovery
potential to δPT < 2 × 10−4 [1].

Fig.1. E246 setup; (a) side view, (b) front view. [3].

§ 2. Photon calorimeter
The photon calorimeter, which is used to detect the π 0 decay, is required to be upgraded. In the
TREK experiment, the Kµ3 decay is identified by detecting the π 0 from the decay. High resolution π 0measurement is needed for clear separation of the Kµ3 decay from other K+ decay modes and for ameasurement of the in-plane normal muon polarization. In addition, high counting rate capability of thecalorimeter is required at the TREK experiment to cope with the K+ beam intensity of 106 /s at J-PARC.
Figure 2 shows the photon calorimeter of the KEK-E246 experiment. The counter has a barrel of
768 CsI(Tl) crystals surrounding the target region. The geometries of each crystals are listed in Table
1. An individual crystal covers 7.5 degrees in both polar and azimuthal angles. The length of crystal
is 250 mm, which corresponds to 13.5 radiation length (X0 ). The average transverse dimensions of thesegments are close to 3 × 3 cm2 at front end and 6 × 6 cm2 at rear end of the crystal. There are 12
so-called muon holes to let the charged particle enter the spectrometer. The performance of the E246
Calorimeter is reported in [2] [3]. Figure 3 shows the schematic view of the calorimeter readout which
consists of PIN photodiode of 18 × 18 mm2 , charge sensitive preamplifier, shaping amplifier and peakhold ADC. A shaping time of the shaping amplifier is 1 µs. Photodiode is necessary because the toroidal
magnet is placed near the calorimeter and there is a huge magnetic field.
Requirements for the photon detector are: (a)The detector parameters must be optimized to detectphotons of the Kµ3 decay over an energy range from about 10 MeV to 250 MeV with high energy resolution and good position resolution in order to reconstruct the π 0 kinematics, and (b)Good timing is neededfor efficient background rejection and neutral pion identification. In addition, high counting rate capability is required at the TREK experiment. Although the maximum counting rate per crystal in the E246

49

experiment is a few ten kHz, in the TREK experiment, the maximum counting rate is 300 kHz, since
the beam intensity of the TREK is 10 times higher than the E246. Counting rate capability of the E246
calorimeter readout is limited by the readout shaping time of the shaping amplifier. The shaping timeis determined by 1 µs of a light decay time constant of CsI(Tl) scintillation light. To achieve 300 kHz
counting rate with the readout system, the shaping time should be less than 0.1 µs. However, Pin photodiode does not have amplification mechanism, thus, if the shaping time sets less than 0.1 µs, S/Nratio of the shaping amplifier output is not enough and an energy resolution of the calorimeter becomesworse [1]. Required energy resolutions is less than 8 and 6% (σE /E) at energies of 100 and 200 MeV.
Thus, whole readout system including photo device needs to be upgraded. Basing on the counting raterequirement, the 5 × 5 mm2 Hamamatsu S8664-55 avalanche photo-diodes (APD) [4] are considered
to be photo-detecors. The APD has a gain of 50 and relatively small integration time can be chosen inorder to increase a maximum counting rate capability. Table 2 shows readout scheme of APDs comparedto E246-PIN readout. Furthermore, the output from the amplifier system is read by FADCs to resolve
pulse pileup.

Fig.2. KEK E246 photon calorimeter view [2].

Fig.3. Pin photodiode readout system of CsI(Tl) calorimeter at KEK E246 [2]. The readout consists of Pin photodiode of 18 × 18 mm2 , charge sensitive preamplifier, shaping amplifierand peak-hold ADC.

50

Table 1. Dimension of CsI(Tl) crystals in mm. See Fig. 2 for numbering [2].
Type number
1
2
3
4
5
6
7
8
9
10

A
61.14
59.76
57.42
53.30
50.92
48.10
42.26
35.77
28.52
42.15

B
61.98
62.31
61.71
56.87
55.61
54.01
49.16
43.69
37.51
62.21

H
57.76
58.46
59.69
61.58
64.35
68.37
70.75
72.64
76.42
82.42

a
5.63
5.64
5.66
24.86
24.87
24.88
22.27
19.35
15.96
25.08

b
6.00
6.77
7.60
26.53
27.17
27.95
25.94
23.70
21.09
37.12

h
24.99
25.68
26.92
28.81
31.58
35.60
37.28
39.87
43.65
49.46

§ 3. Experimental setup
To test CsI(Tl) calorimeter with APD+FADC readout system, we used positron beams of an energy
range from 50 to 460 MeV. The test is performed at the Research Center for Electron Photon Science(ELPH) of Tohoku university. Figure 4 shows the experimental setup and data acquisition system forthe beam test. Nine CsI(Tl) crystals with APDs are organized into a 3 × 3 matrix in the same mannerused in the TREK detector. The type numbers of the nine crystals are #4, #5 and #6 in Table 1. The
entire matrix is placed on a movable stage that enabled changes in the position and angle of the matrix.
The signals from the APDs are fed to the current amplifier which is developed by the INR (MOSCOW)
group [5]. The current amplifier is shown in Fig. 5. The amplifier signals are recorded by FADCs (60MHz sampling with 12 bits dynamic range), which is an FINESSE board on the COPPER system [6].
A fiber hodoscope is installed in front of the crystal to determine the incident position of a positron.
The fiber hodoscope consisted of two layers, which comprise sixteen fibers with a 3-mm pitch. Two layers
are used to measure vertical and horizontal beam position. The raw signals from the fibers are fed tothe discriminator. The outputs of the discriminator are recorded by a MWPC encoder, which is also an
FINESSE board on the copper system. The event trigger is made by the coincidence of the signals fromthe both layers of the fiber hodoscope.
Test are performed with following steps: (a) Calibration of each module, (b) Energy resolution measurements at 50, 100, 200, 300 and 460 MeV positron beams, and (c) Rate capability properties andpileup event analysis. In addition, we evaluate time resolution of the single module by the measurements. For (a) and (b) low intensity beam of about a few kHz is used and for (c) high intensity beam

51

Table 2. Readout scheme of APDs compared to E246-PIN readout.
Parameter
Diode
Sensitive region
Quantum efficiency
Photoelectron/MeV
Diode gain
Preamplifier

E246
S3204-03
18 × 18 mm2
∼ 70%
11000
1
Charge sensitive

APD readout
S8664-55
5 × 5 mm2
∼ 80%
∼ 100050
Current amplifierof about 10 kHz ∼ 1 MHz is used. It should be noted that the gain characteristics of APDs depend on
both stability of the bias voltage and temperature of APD [7]. Therefore, for (a) and (b) measurements
start after 10 hours from starting supplying bias voltage. In addition, to evaluate the stability of APD
gain, energy spectra of two crystals are measured before and after energy resolution test using 200 MeV
positron beam injected into the center of each crystal and there are no significant differences between the
spectra of the first and second measurements. Thus, the influence of APD gain fluctuation is neglectedin the energy resolution test.
Each CsI(Tl) crystal is hereinafter referred to as shown in Fig. 6 for convenience of explanation.

Fig.4. The experimental set up and data aquisition system for the beam test.

§ 4. FADC wave form fitting of the calorimeter
Pulse amplitude and timing information of the calorimeter signals are obtained from the wave form
measured by FADC. The wave form is fitted by a function
V (t) = B − A0)exp[ −(t−t
]
τD
S

0)
1 + exp[ −(t−t
]
τR
S

exp[
+ AR

−(t−(t0 +t0L ))]τDL

1 + exp[−(t−(t0 +t0L ))
]
τRL

,

(1)

where B is a baseline of FADC wave, A is a pulse amplitude, R is a ratio of fast and slow scintillation
light amounts, t0 is a time zero, t0 is a timing difference of fast and slow scintillation light, τRS and τDS

52

Fig.5. Current amplifier of APD. [5]Fig.6. End view of the matrix of CsI(Tl) module with name of each module.

are a rise time and a decay time of fast scintillation light and τRL and τDL are a rise time and a decay
time of slow scintillation light. Since CsI(Tl) scintillation light has fast and slow components, the fitting
function has two components. The second term indicates the fast components of scintillation light andthe third term indicates the slow component. Figure 7 shows the fitting result of the wave form of thecalorimeter signal. In evaluation of the energy and timing resolution, the parameters of τRS , τRL , τDS ,τDL , t0L and R are fixed as constant values crystal-by-crystal such as about 4.4 ns, 45 ns, 0.9 µs, 4.9µs, 19 ns, 0.15, respectively. The fixed values of these parameters are determined by using the data forcalibration of each module. The parameters A, t0 and B are fitting parameters and correspond to energy
deposit, timing of the signal and baseline respectively.

§ 5. Gain calibration
For each event, the energy deposit ECsI in the CsI(Tl) matrix by the incident positrons is determinedfrom summed output from the 3×3 crystals according to the relation
ECsI =

9∑
C#5−center
i=1

Ci

Ai

(2)

where Ci is a gain calibration factor of the ith module, C#5−center is the gain calibration factor of the#5-center module and Ai is the pulse amplitude of ith module in Eq.1.

FADC amplitude [ch]

53

2000
1800
1600
1400
1200
1000
0

2

4

6

8

10

time [µs]Fig.7. Fitting result of a typical FADC wave form of the calorimeter signal. The dash-dottedline is fast component, the dotted line is slow component of scintillation, and the solidline is fitting result of Eq. 1.
Gain calibration of each crystal is done using 100, 200, 300, and 460 MeV positron beams injected
into the center of each crystal. Here, the positron beams are injected at the 9 mm × 12 mm area of thecenter of each crystal which is determined by using the fiber hodoscope hits. Energy deposit is obtained
as described in sec. 5 and energy spectra for each incident momentum are made for each crystal. Theenergy spectra are fitted by a logarithmic Gaussian function
F (x) = N exp[−σ02
1x − xp
2
ln
(1
−
η)
−
]
σE
2
2σ02

(3)

where xp is the peak value, η is the asymmetry parameter, N is the normalization factor and σ0 is
√
−1 ηξ
2
ξ sinh2 (ξ = 2 ln 4 = 2.36). The resolution, σE , is defined as the ratio of the full-width at halfmaximum (FWHM) of the resolution function to ξ [8]. Figure 8 shows the peak values of each crystal
energy spectrum as a function of positron beam energy. Gain calibration factors are determined by fitting

Fitting parameter A [ch]with a linear function. The gradient values of the fitting are used as the gain calibration factors Ci .

1400
1200
1000
800
600
400
200
0
0

[0]#6-left[1]#6-center[2]#6-right[3]#5-left[4]#5-center[5]#5-right[6]#4-left[7]#4-center[8]#4-right

100

200

300

400

500

Positron beam energy [MeV]Fig.8. Peak values of each single-module’s energy spectrum as functions of positron beam energy. They have good proportionality in the range from 100 to 460MeV. The gradientvalues are used as gain calibration factors.

54§ 6. Energy resolution
Energy resolution is evaluated for momenta of 50, 100, 200, 300 and 460 MeV positron beams
injected into the center of the CsI(Tl) matrix. Energy deposits of 3×3 crystals are summed by Eq.2 andtotal energy deposit spectrum is obtained. The spectrum is fitted by the logarithmic Gaussian function.
Then, energy resolution is obtained as a fitting result. The the obtained energy resolutions are shown in
Table 3 and Fig. 9(a). Here, the positron beams are injected at the 3 mm × 6 mm area of the center ofthe matrix which is determined by using the fiber hodoscope hits. An energy fluctuation of the positron
beam [9] is already subtracted. The obtained resolutions are fitted by the following function
√
(
)2
σE
63.6
√
=
+ 1.912 ,(4)
EE
E in MeV. The first term indicates statistics-related fluctuations, such as photoelectron statistics andEM shower fluctuation. The second term is systematic effects, such as the module-to-module calibration
uncertainties. An electric noise contribution of the energy resolution is small enough and not includedin the function.
Figure 9(b) shows the peak position of the energy spectrum of total sum of the 3 × 3 crystal matrix
as a function of positron beam energy. The linearity of the energy response is uniform for the energy
range from 50 MeV to 460 MeV. The gradient value is used to convert the calorimeter output channel[ch] to Energy [MeV].
Table 3. Energy resolution result. The energy fluctuation of the positron beam is already subtracted [9].
Beam energy
E[MeV]
50
100
200
300
460

Beam energy
fluctuation [MeV]
1.84±0.23
1.77±0.06
2.18±0.04
2.68±0.03
3.39±0.03

Energy resolution of the calorimeter
σE /E [%]
9.0±1.0
6.76±0.35
4.92±0.16
3.99±0.16
3.57±0.11§ 7. Timing resolution
The timing resolution is evaluated by calculating a timing difference between signals of neighborhood two crystals from EM shower produced by the same single positron. In the analysis, positron beamenergy of 460 MeV is used. However, energy deposit vary due to difference of initial injected position of
the positron. Thus, energy dependence of timing resolution can be evaluated.
It should be noted that the timing resolution depends on the energy deposit. As a result, it isconstant for the energy range of greater than 200 MeV [2] [3]. Figure 10 shows the timing difference
between #5-center and #5-right modules. Here, both energy outputs of modules are 200∼220 MeV. The
timing resolution of single-module is 1.63 ± 0.06 ns for the energy range of 200∼220 MeV.
Figure. 10 shows the timing resolution as a function of deposit energy. The timing resolution as afunction of the deposit energy is evaluated by the timing difference between the #5-center and #5-right

14
12
10
8
6
4
2
0
0

100

200

300

400

500

Positron bem energy [MeV]Peak of energy spectrum [ch]Energy resolution σE /E [%]

55

1400
1200
1000
800
600
400
200
0
0

100

200

300

400

500

Positron beam energy [MeV]Fig.9. (a) The result of the energy resolution as a function of the positron beam energy. The
points are result of the energy resolution after iteration and the solid line is a fitting
result of Eq. 4. (b) The peak position [ch] of the energy spectrum of total sum of the 3 ×
3 crystal matrix as a function of positron beam energy [MeV]. The linearity of the energy
response is uniform for the energy range from 50 MeV to 460 MeV. The gradient value isused to convert the calorimeter output channel [ch] to Energy [MeV].
modules. Here, it is required that the energy output of #5-center module is 200∼220 MeV and the energy
deposit of #5-right module is varied. Then, total timing resolution of timing difference is varied due to#5-right. Timing resolution of #5-center module is assumed as a constant, 1.63 ns and it is already

80
70
60
50
40
30
20
10
0

Timing resolution σ [ns]Countssubtracted.

-20

-10

0

10

20

14
12
10
8
6
4
2
0
0 20 40 60 80 100 120 140 160 180 200

Timing difference [ns]Energy [MeV]Fig.10. (a)Timing difference between the #5-center and #5-right modules. Here, both energy
outputs of modules are 200-220 MeV. σ of the spectrum is 2.31 ns. (b)Timing resolutionof the #5-right module per an energy window, ∆E = 10 MeV, as a function of the energy
output of the module.

§ 8. Pileup event analysis
To evaluate rate capability, pileup events are collected using the highest instantaneous beam rate.
The intensity of beam is about 10 kHz ∼ 1 MHz and the momentum of the beam is 200 MeV. In theanalysis, only one pileup events are selected. Events which have more than 3 peaks are rejected. The
fitting function of wave form in the pileup events is following
V (t) = B − Wp (t) − W0 (t) − W1 (t)(5)

where B is baseline of FADC wave, Wp is a prior pulse of the first peak, since the first peak is alreadyon the previous pulse in the high intensity, and W0 and W1 are the first and second peaks, i.e,
Wp (t) = ASp exp[−t−t
] + ALp exp[],
τDSp
τD L p(6)

56

Wi (t) = Aii)exp[ −(t−t
]
τD

exp[

S

i)
1 + exp[ −(t−t]τR+ Ai RS−(t−(ti +t0L ))]τDL

1 + exp[−(t−(ti +t0L ))]τRL, (i = 0.1),(7)

where ASp are DSp are an amount and a decay time of the fast scintillation light of the prior pulse, ALp
are DLp are an amount and a decay time of the slow scintillation light of the prior pulse, Ai is a pulse
amplitude of the ith peak and ti is a time zero of the ith peak. In the analysis, the parameters of τRS ,τRL , τDS , τDL , t0L and R are fixed as constant values crystal-by-crystal and the parameters B, ASp ,ALp , τDSp , τDLp , Ai and ti are fitting parameters. Figure 12 shows energy spectrum of the first peak
and the energy resolution of the first peak is 5.65±0.08%. An energy fluctuation of the positron beam is
3.50 MeV [9] and already subtracted. Here, the first positron beam is injected at the 3 mm × 6 mm areaof the center of the CsI(Tl) matrix which are measured by using the fiber hodoscope. Whereas, in cace ofthe second peak, an incident position of the second positron could not be identified, since a time range of
BPM is too narrow. In the analysis, we require that the #5-center crystal have the largest energy output
to select the second positron injected at the center. Figure 13 shows the energy resolution of the second
peak as a function of the timing difference between the first and second peaks. An energy fluctuationof the positron beam is already subtracted. The timing of the first and second peaks are defined as the

FADC amplitude [ch]value t1 − t0 .
2100
2000
1900
1800
1700
1600
1500
1400
1300
1200
0

2

4

6

8

10

time[µs]

CountsFig.11. Fitting result of a typical pileup event.

220
200
180
160
140
120
100
80
60
40
20
0
0

100 200 300 400 500 600 700 800

Energy output [ch]Fig.12. Energy spectrum of first pulse of only two pulse in FADC range event at 200 MeV
positron beam.

Energy resolution σ/E [%]

57

8
7
6
5
4
3
2
1
0
0

1

2

3

4

5

6

7

Timing difference [µs]Fig.13. The energy resolution of the second peak, per an timing difference window, ∆(t1 − t0 ) =1µs, as a function of the timing difference between the first and second peaks.

§ 9. Discussion
We compare the result of the CsI(Tl) calorimeter with APD+FADC readout with a test of a prototypeof the CsI(Tl) calorimeter with Pin photodiode. The prototype consists of 30 CsI(Tl) crystals assembled
in a matrix of 5×6. Each individual crystal has a length of 25 cm and the shape of a truncated pyramidwith bases of 3×3 and 6 ×6 cm2 , that represented typical dimensions of crystals to be used for thecalorimeter. Pin photodiode of sensitive region 28×28 mm2 (S3584-05) are glued on the rare faces. The
results of the prototype beam test are presented in Ref. [10], where the energy resolution is obtained tobe σE /E=2.8% for a 200 MeV electron beam. For photons, the energy resolution is 4.3 and 2.8% (σE /E)
at energies of about 100 and 200 MeV, respectively. The energy resolution of the APD+FADC readout isworse compared to the Pin photodiode readout. The reason of the energy resolution difference between
the Pin photodiode and the APD+FADC readout are following.
1. The geometry of CsI(Tl) crystal is difference. The prototype of the E246 calorimeter is a symmetricmatrix, however the E246 calorimeter consists of the crystals of various geometries.
2. The Pin photodiode of the prototype has a broad sensitive region compared to the Pin photodiode of
the E246 and Hamamatsu S8664-55 APD. Obtained numbers of photoelectrons are listed in Table 4.

Table 4. Numbers of photoelectrons.

Diodesensitive region
Photoelectron/MeV

prototype of E246
Pin photodiode28×28 mm2
∼26000

E246 readout
Pin photodiode18×18 mm2
∼11000APD+FADC readout
APD
5×5 mm2∼1000§ 10. Conclusion
The performance of a new readout system of the CsI(Tl) calorimeter is evaluated at ELPH of Tohoku
University. The measured energy resolutions are 9.0±1.0% at 50 MeV, 6.76±0.35% at 100 MeV, and58
4.92±0.16% at 200 MeV, are archived using the sum of energy deposits in a 3 × 3 crystal matrix. We
evaluate counting rate capability properties and the obtained energy resolution is 5.7% at 200 MeV near
1 MHz counting rate.

Acknowledgment
The authors would like to appreciate Prof. H. Shimizu, Dr. T. Ishikawa, and other LNS staffs fortheir great support and providing excellent experimental condition.

59

References[1]

J. Imazato et al., Measurement of T-violation Transverse Muon Polarization in K + → π 0 µ+ ν
Decays, J-PARC 50-GeV PS Experimental Proposal(2006).

[2]

D.V. Dementyev et al., Nucl. Instrum. Meth. A440 (2000) 151.

[3]

Yu.G. Kudenko, Nucl. Instrum. Meth. A494 (2002) 318.

[4]

http://jp.hamamatsu.com/resources/products/ssd/pdf/s8664 series kapd1012e04.pdf[5]

A. Ivashkin, private communication.

[6]

http://kekps.kek.jp/tauchi/finesse/index.html[7]

J. Kataoka et al., Nucl. Instrum. Meth. A564 (2006) 300.

[8]

H. Ikeda et al.., A detailed test of CsI(Tl) calorimeter for BELLE with photon beams of energy
between 20 MeV and 5.4 GeV, Nucl. Instr. and Meth. A441, (2000) 401.

[9]

T. Ishikawa, GeV-γ Analysis report No.78, Electron & Positron Beamline II (2008).

[10] J. Imazato et al., Proceedings of PANIC XIII, Perugia, Italy, June 28-July 2, 1993, p. 791

ELPH Annual Report 2010, Tohoku University Vol. 1

61(ELPH Experiment : #2717)

New electro-magnetic calorimeter BGO EGG
T. Ishikawa1 , H. Fujimura1 , R. Hashimoto1 , S. Kaida1 , R. Kitazawa1 ,A. Nakamura1 , H. Shimizu1 , K. Suzuki1 , S. Takahashi1 , Y. Tsuchikawa1 ,and H. Yamazaki1
1Research Center for Electron Photon Science (ELPH), Tohoku University, Sendai 982-0826,
Japan

Construction of a 4π electro-magnetic (EM) calorimeter with 1,320 BGO crystal is planned to study
the structure of hadrons in detail. In this report, the design of the new EM calorimeter, manufactured
BGO crystals, and the energy and position resolutions obtained with a 5 × 5 prototype BGO calorimeterin response to the positron beams at the energy ranging from 100 to 800 MeV are described.

§ 1. Introduction
Various types of electromagnetic (EM) calorimeters have been used in nuclear and particle physics.
A calorimeter should consist of heavy materials (short radiation length) since the EM shower generated
in it is utilized for the energy measurement of several hundred MeV photons. Although a sandwich
calorimeter made up of a heavy material and sensitive detector is the cheapest, the energy resolution atenergies less than 1 GeV is not so high (for example, 7.2% is obtained for a lead and scintillating fiber
calorimeter [1]) and the detection efficiency for the charged hadrons depends on the incident position.
A lead glass Čerenkov counter has the higher energy resolution for electrons, positrons, and photons(for example, 4.9% is obtained for an SF5 lead glass calorimeter at 1 GeV positrons [2]). It is however
insensitive to the low energy charged particles that do not generate the EM shower since Čerenkov
photons are not emitted from them. Among the EM calorimeter modules, inorganic scintillators havethe better energy resolutions at high energies.
We are especially interested in the energy region of several hundred MeV for meson photoproduction
experiments conducted at Research Center for Electron Photon Science (ELPH) and SPring-8/LEPS tostudy the properties of mesons and baryon resonances. The following characteristics are desired for an
EM calorimeter module:
1. good energy resolution,
2. fast response for high counting rate experiments,
3. short radiation length for constructing a compact EM calorimeter, and
4. absence of hygroscopicity for easy treatments.
Since techniques of growing Bi4 Ge3 O12 (BGO) single crystals have been established, we have decided toconstruct an EM calorimeter with 1,320 BGO ones. Table 1 summarizes the characteristics of BGO.

62

Table 1. Characteristics of BGO. Approximate ratios of light yields to that of NaI(Tl) are listed in
the light output row. Properties of BGO are given in ref. [3].
Property
Density
Radiation length X0
Decay time
Peak emission
Light output ratio to NaI(Tl)
Hygroscopicity

BGO
3
7.13 g/cm
11.2 mm∼ 300 ns
480 nm0.1
No§ 2. Design of the new EM calorimeter BGO EGG
The new EM calorimeter covers the polar angle from 24◦ to 144◦ . The shape of each crystal is afrustum of isosceles trapezoid. The front and rear faces of each crystal have circumscribed spheres witha center (0, 0, 0). Not to make the area of the front face too small, the center of the front face is placed ona 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 the front face is placed on the sphere like
LEPS Backward Gamma detector used in FOREST [4]. Since it takes a shape like an egg, we call it
EGG.
2.1 Forward BGO crystals
The front faces of the crystals takes a prolate spheroid as
x2 + y 2

z2
+
=1
2
2
(200 mm)(400 mm)(1)in the forward section. The 360◦ azimuthal angles are divided into 60, and each crystal covers 6.0◦ . The
polar angles from 24◦ to 90◦ are divided into 13 so that the heights of the isosceles trapezoids for thefront and rear faces of each crystal becomes roughly 20 and 40 mm. The crystal covers the polar angle of
6.0◦ near z = 0. Since the cluster size in response to the incident particle is different between neutron
and photon, we prefer the large number of divisions. Fig. 1 shows the cross sectional view of the forward
section of EGG and the definition of the variables for the crystal shape and placement.
A crystal covers the polar angle from θ1 to θ2 . Its front and rear face has a circumscribed sphere witha center of (0,0,0) and a radius of r and r + L, respectively. It covers the azimuthal angle of ∆ϕ = 6.0◦ .
Since we required the rotation symmetry around z-axis, the covered azimuthal angle is assumed to befrom −∆ϕ/2 to +∆ϕ/2 without loss of generality. The superscript f and b stand for the front and rearfaces, respectively. The height of the isosceles trapezoid for the face, namely the distance from θ1 to θ2on the face, is h, and the lengths of the parallel sides are w1 and w2 which correspond to the polar angleof θ1 and θ2 , respectively. Once r, L, θ1 , θ2 , and ∆ϕ are given, the shape of the isosceles trapezoid bothfor the front and rear surfaces are determined.

63

x/y
w2

h
w1

L

200

R
θ2
θ1

z
400
Fig.1. Cross sectional view of the forward section of EGG and the definition of the variables forthe crystal shape and placement.
The vertices of the isosceles trapezoid with a given radius R for the circumscribed sphere are
 


 
∆ϕ
∆ϕ
R
sin
θ
cos
R
sin
θ
cos
x
2
1
 


 
2
2
 


 
∆ϕ
∆ϕ




,  ±R sin θ2 sin(2) y  =  ±R sin θ1 sin



 
2  
2 
z
R cos θ1
R cos θ2
where R = r and R = r + L for the front and rear faces. Therefore, The height h and lengths of theparallel sides w1 and w2 become

}1/2
{


2
2
f
2 ∆ϕ

+ (cos θ2 − cos θ1 )
 h = r (sin θ2 − sin θ1 ) cos


2



∆ϕ
w1f = 2r sin θ1 sin
2





∆ϕ

f


 w2 = 2r sin θ2 sin 2
for the front face, and become

}1/2
{


2
2
b
2 ∆ϕ

+
(cos
θ
−
cos
θ
)
h
=
(r
+
L)
(sin
θ
−
sin
θ
)
cos

2
1
2
1


2



∆ϕ
w1b = 2(r + L) sin θ1 sin
2





∆ϕ

b


 w2 = 2(r + L) sin θ2 sin 2
for the rear surface. The area of the front and rear faces are given by

1

f
f
f
f


 S = 2 (w1 + w2 )h
1

b
b
b
b


 S = 2 (w1 + w2 )h

(3)

(4)

(5)

64

and the volume of the crystal areV =1 b ′b1
f
S z − Sf z′ .
3
3

(6)

Here, z ′ and z ′ show the distance to the front and rear faces from the origin, and are expressed by
f

b









∆ϕ
sin (θ2 − θ1 ) cos
2

=

√
.
′b
z
r+L
2 ∆ϕ
2 θ1 + θ2(sin θ2 − sin θ1 ) cos
+ tan
2
2
z

′f

r

(7)

The polar angles from 24◦ to 90◦ are divided into 13. The parameters θ1 , θ2 , and r is determined
for the crystal type i as{}
(i + 1)∆ϕ
π

−1

−
tan
b
tan
θ
=
 1

2
b


{
}



π
i∆ϕ

 θ2 =− tan−1 b tan
2
b


200
mm


r = √(


)2 (
)2


1
θ1 + θ2
θ1 + θ2


cos
+ sin

2
2
2

(8)

with b = 1.3 so that the heights of the isosceles trapezoids for the front and rear faces of each crystal
becomes roughly 20 and 40 mm. The length of the crystal is fixed at L = 220 mm. The crystal typei ranges from 0 to 12, and starts from the polar angle of 90◦ . Table 2 summarizes the parameters fordescribing each crystal shape.
Table 2. Parameters for describing each crystal shape in the forward section. The unit of theangle, length, area, and volume are degree, mm, mm2 , cc=cm3 , respectively. The wholevolume is 152.6 ℓ in total.
i
00F
01F
02F
03F
04F
05F
06F
07F
08F
09F
10F
11F
12F

θ1
θ2
84.01 90.00
78.07 84.01
72.23 78.07
66.54 72.23
61.02 66.54
55.69 61.02
50.58 55.69
45.67 50.58
40.97 45.67
36.46 40.97
32.13 36.46
27.97 32.13
23.95 27.97

∆θ
5.99
5.94
5.84
5.69
5.52
5.32
5.12
4.91
4.70
4.51
4.33
4.16
4.02

r
200.21201.84205.11210.00216.47224.51234.07245.11257.56271.32286.27302.18318.76hf
w1f
w2f
20.92 20.84 20.96
20.91 20.67 21.01
20.89 20.45 21.01
20.86 20.16 20.93
20.84 19.82 20.79
20.85 19.41 20.56
20.89 18.93 20.24
20.97 18.35 19.82
21.12 17.67 19.28
21.32 16.88 18.62
21.60 15.94 17.81
21.94 14.83 16.82
22.33 13.54 15.65

Sf
437.3
435.8
432.9
428.6
423.2
416.6
409.0
400.3
390.3
378.5
364.4
347.2
326.0

hb
w1b
w2b
43.92 43.74 43.98
43.70 43.20 43.91
43.29 42.38 43.54
42.71 41.29 42.86
42.02 39.97 41.91
41.28 38.43 40.70
40.52 36.71 39.26
39.80 34.82 37.61
39.16 32.77 35.76
38.62 30.56 33.72
38.20 28.18 31.49
37.91 25.63 29.07
37.75 22.89 26.45

Sb
1926.41903.5
1859.41797.11720.41633.2
1539.31441.41341.71241.11139.71036.8
931.2

V
240.0
237.7
233.3
227.0
219.3
210.4
200.7
190.4
179.8
168.8
157.4
145.3
132.5

2.2 Backward BGO crystals
To reduce the number of crystals, the front faces of the crystals takes a sphere as
x2 + y 2 + z 2
2(200 mm)

=1

(9)

65
in the backward section. The polar angles from 90◦ to 144◦ are divided into 9. Every crystal covers thepolar angle of 6.0◦ and the azimuthal angle of 6.0◦ . The parameters θ1 , θ2 , and r is determined for the
crystal type i asπ θ1 = 2 + i∆ϕ, andπ θ2 = 2 + (i + 1)∆ϕ.

(10)

The crystal type i ranges from 0 to 8, and starts from the polar angle of 90◦ . Table 3 summarizes theparameters for describing each crystal shape.
Table 3. Parameters for describing each crystal shape in the backward section. The unit of theangle, length, area, and volume are degree, mm, mm2 , and cc=cm3 , respectively The
whole volume is 111.5 ℓ in total.
i
00B
01B
02B
03B
04B
05B
06B
07B
08B

θ1
θ2
84.00 90.00
78.00 84.00
72.00 78.00
66.00 72.00
60.00 66.00
54.00 60.00
48.00 54.00
42.00 48.00
36.00 42.00

∆θ
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00

r
200.00200.00200.00200.00200.00200.00200.00200.00200.00w2f
hf
w1f
20.93 20.82 20.93
20.93 20.48 20.82
20.93 19.91 20.48
20.93 19.12 19.91
20.93 18.13 19.12
20.93 16.94 18.13
20.92 15.56 16.94
20.92 14.01 15.56
20.92 12.30 14.01

Sf
437.0
432.2
422.7
408.5
389.8
366.9
339.9
309.3
275.2

w2b
hb
w1b
43.96 43.72 43.96
43.96 43.00 43.72
43.96 41.81 43.00
43.95 40.16 41.81
43.95 38.07 40.16
43.94 35.57 38.07
43.94 32.67 35.57
43.93 29.42 32.67
43.93 25.84 29.42

Sb
1927.4
1906.2
1864.11801.51719.21618.01499.1
1363.81213.6

V
240.0
237.4
232.2
224.4
214.2
201.6
186.8
170.0
151.3

2.3 EM calorimeter EGG
The central 1,020 crystals are directly connected to a metal-packaged photo-multiplier tube (PMT)H11334, and the peripheral 300 are directly connected to a 3/4 inch PMT H6524. Fig. 2 shows theschematic view of the new EM calorimeter EGG.

Fig.2. Schematic view of the new EM calorimeter EGG. Two types of photo-multiplier tubes areused: a metal-packaged H11334 for the central 1,020 crystals and a head-on 3/4 inch
H6524 for the peripheral 300. The arrow indicates the incident photon beam.

66§ 3. Manufactured prototype BGO crystals
Since the crystal for EGG takes a tapered shape, the significant longitudinal non-uniformity oflight output is observed due to the focusing effect when all the surfaces are polished. To uniform thelight output as a function of the distance from the PMT window, the front and rear faces are polished,
and the other surfaces are etched [5]. To check the etching effect, Prototype 00F and 12F BGO crystals
were manufactured with two different surface condition at Nikolaev Institute of Inorganic Chemistry [6]in Novosibirsk, Russia. Fig. 3 shows the manufactured 00F and 12F crystals, and Table 4 summarizes
the properties of them. The polished crystals have a good gloss, and the etched ones seem like a frosted
glass. The weights of 00F and 12F ones are about 1.7 and 0.9 kg, respectively.

Polished

Polished

Polished

Polished

EtchedEtchedEtchedEtchedFig.3. Manufactured 00F and 12F crystals. The upper panel shows 00F one, and the lower
shows 12F one. Two crystals of different surface conditions were prepared for each type:
all the surfaces were published, and the contact face was polished and the other surfaces
were etched.

Table 4. Manufactured 00F and 12F crystals. Two crystals with the same type was cut from thesame ingot. All the crystals are wrapped with about 300 µm thick Teflon sheet.
ID
00F-p.09.1
00F-e.09.2
12F-p.09.1
12F-e.09.2

type
00F
00F
12F
12F

ingot
B12-235
B12-235
A8-109A8-109surface condition
all the surfaces were polishedthe contact face was polished and the other surfaces were etched
all the surfaces were polishedthe contact face was polished and the other surfaces were etched67

3.1 Experimental setup
The longitudinal uniformity of the light output of the manufactured prototype BGO crystals wasmeasured by using 661.7 keV γ rays from a radioactive source 137 Cs. The crystal was wrapped with
about 300 µm thick Teflon sheet, and was connected to R8900U with a breeder E5996MOD2 throughan optical grease OKEN6262A. The supplied high voltages are −1000, −1050, −980, −1050 V for thepolished 00F, etched 00F, polished 12F, etched 12F crystals, respectively. The lead aperture with adiameter of 3 mm was placed in front of 137 Cs. The 137 Cs and the aperture are fixed, and the crystal was
moved along its length. Fig. 4 shows the experimental setup for the measurement of the longitudinal
uniformity.

Side View
R8900U
3φ
E5996MOD2

100 mm
100 mmMovableTop View~50 mm

16 mm

R8900UPb Aperture

E5996MOD2

50 mm
Pb Block

Pb Block137

Cs

Fig.4. Experimental setup for the measurement of the longitudinal uniformity. The upper andlower panels show the side and top views. The diameter of the lead aperture is 3 mm.
We measured the energy spectra of the output signals from the BGO crystals in response to γ rays
with a CAMAC based data taking system. The anode signal from each PMT was split into two equalparts. One part was sent into a LeCroy 2249W ADC module, and its charge was integrated over a 1.5 µs
ADC gate. The other split signal was used to make a trigger for the data acquisition system and to
generate the gate for the ADC module. The decay times of these crystals are rather long and the output
signal does not form a single pulse in response to a single γ ray. Therefore, the width of the signal forthe trigger was set 2 µs.
The background events were measured without the 137 Cs source to be subtracted. The pedestal
in each energy spectrum was measured with a 1 kHz clock trigger. Fig. 5 shows the typical energy
spectra for the BGO crystals. The decrease of the light output is apparently observed for the polished
00F crystals for the short distances from the PMT window.
The centroid µ of the photoelectric peak was obtained by fitting a Gaussian to the peak. Fitting was

1000

185 mm from PMT
S

S

135 mm from PMT
S

B

110 mm from PMTS

Pedestal

B
PedestalPedestalCounts / 10 channel

2000

160 mm from PMT

S
B

0

PedestalPedestal

2000

210 mm from PMT

Pedestal

68

85 mm from PMT
S

1000
60 mm from PMT

S

B

35 mm from PMT

Pedestal

S

B
Pedestal

2000

Pedestal

B

0S

10 mm from PMT

1000

1000

0

210 mm from PMT

S

500
1000
ADC (channel)

S

S

60 mm from PMT

S

1000

0

500

S
B

35 mm from PMTS
B

085 mm from PMT

B
PedestalPedestal

2000

160 mm from PMT

B

110 mm from PMT

B

0

0

10 mm from PMT

S
B

1000

1000

S

Pedestal

135 mm from PMT

S

1000

500

B
PedestalPedestalCounts / 10 channel

2000

0

185 mm from PMT

B

0

B

Pedestal

1000

500

PedestalPedestal

2000

0

B

Pedestal

B

0

500
1000
ADC (channel)

B

0

500

1000

Fig.5. Typical ADC distributions for the 00F BGO crystals for different source distances fromthe PMT window. The upper panel shows the ADC distribution for the polished crystals,
and the lower shows that for the etched crystals. The ADC distribution in response to
the γ rays from 137 Cs is deduced by subtracting that measured without 137 Cs (B) fromthat with 137 Cs (S). The pedestal ADC distributions taken with a clock trigger is also
displayed. The solid curves show the fitted Gaussian for the peak component.

69
repeated several times in the region [µ − 0.8σ, µ + 2σ), where σ denotes the width of the peak. Fig. 6
shows the light output as a function of the source distance from the PMT window. The light output
strongly depends on the distance for the polished ones, and larger light output is obtained for the longer
distance. As for the etched ones, the light output is almost constant for both the 00F and 12F ones. Sincea plastic and BGO phoswich detector was considered as a module for the charge identification [7], we
decided that the front and rear faces were polished and the other surfaces were etched for EGG crystals.

900

900
800
00F-e.09.2

700
600
500
400

00F-p.09.1

300
200
100
0

Light Output (channel)

Light Output (channel)

80012F-e.09.2

700
600
500
400

12F-p.09.1

300
200
100

0

50
100
150
200
Distance from PMT (mm)

0

0

50
100
150
200
Distance from PMT (mm)Fig.6. Light output as a function of the source distance from the PMT window. The left and rightpanel shows the light output for the 00F and 12F crystals. The light output strongly
depends on the distance for the polished ones, and it is almost constant for the etchedones.

§ 4. Beam test of prototype BGO calorimeter
The performance study of a prototype calorimeter was made at the positron beamline for testing
detectors at ELPH. The prototype calorimeter was made up with 25 BGO crystals, and the crystals werealigned in a 5 × 5 matrix. The 01B, 00B, 00F, 01F, and 02F type crystals were used in the calorimeter.
Fig. 7 shows the experimental setup for the performance study of the prototype BGO calorimeter.
Momentum-analyzed positrons were used as an incident beam with the energy ranging from 100
to 800 MeV/c. A beam profile monitor (BPM) was used to specify the position of the incident positrons
and make a trigger for the data acquisition. BPM consists of two layers of scintillating fiber (SciFi)
hodoscopes. Each hodoscope consists of 16 SciFi’s with a cross section of 3 × 3 mm2 . The upstream anddownstream layers determine the y and x positions of the incident positron, respectively.
The energy response of 25 BGO crystals and 32 BPM fibers were measured with a CAMAC based
data taking system. The output analog signal of each BGO crystal was input to a LeCroy 2249W ADC
module through a RG-58C/U coaxial cable with a delay of 200 ns and about 20 dB attenuator. The trigger
condition for the data acquisition was described as[x fiber OR] ⊗ [y fiber OR],

(11)

70

+y

x1

+x

x16

+z
01 02 03 04 05

y16

e-BPM

11 12 13 14
16 17 18 19

y1

02F
01F
15
00F
20
00B
25
01B

06 07 08 09 10

21 22 23 24

Fig.7. Experimental setup for the performance study of the prototype BGO calorimeter. The
16 × 16 scintillating fiber hodoscopes are placed in front of the calorimeter to determine
the position of incident positions.

where ⊗ means coincidence of signals. The energy calibration for the BGO crystals was made by using
200, 300, 399, 458, 589, and 744 MeV/c positrons injected onto the central region (9 × 9 mm2 ) of eachcrystal one by one. The BGO crystal has the shape of a frustum of isosceles trapezoid. Therefore theposition and the tilted angle of the calorimeter were set so that the beam axis was perpendicular to thefront face of the module of interest. Then, the gain of each detector module was roughly adjusted.
The experiments were performed from 5th to 10th in July 2010 as follows:
1. a series of measurements for the energy calibration and the rough adjustment of the gain for eachcrystal,
2. two series of measurements for the energy and position resolutions,
3. a series of measurements for the energy calibration, and
4. acquisition of waveforms for the central nine crystals.
4.1 Energy Calibration
The energy calibration for 25 crystals was made by using 200, 300, 399, 458, 589, and 744 MeV/cpositrons injected onto the central region (9×9 mm2 ) of each crystal one by one. The charge integration(ADC) distribution in each measurement was fitted with a logarithmic Gaussian [8], and the mean µc

71and width σc were determined. Fig. 8 shows the ADC distributions that the positrons are incident on

Counts / 10 channel

500 1000 1500 2000
ADC (channel)

13-230

1000

500
0
0

500 1000 1500 2000
ADC (channel)

500
0
0

500 1000 1500 2000
ADC (channel)

Counts / 10 channel

1000

Counts / 10 channel

1500 13-150
1000

2000

0
0

Counts / 10 channel

3000 13-100

Counts / 10 channel

Counts / 10 channel

the central region of No. 1 crystal.

1000
1000 13-400
13-4501000 13-300
750
750
750
500
500
500
250
250
250
0
0
0
0
500 1000 1500 2000
0500 1000 1500 2000
0500 1000 1500 2000
ADC (channel)
ADC (channel)
ADC (channel)

Fig.8. ADC distributions that the positrons are incident on the central region of 00F-3 (13)crystal. The incident positron momentum is described in each panel. The solid line
shows the fitted logarithmic Gaussian. The ADC distribution measured with a 1 kHz
clock trigger is also plotted in each panel.

The pedestal distribution was measured with a 1 kHz clock signal trigger in each measurement,
and the mean µp and width σp of which were determined by fitting with a nominal Gaussian. Since
the energy leakage in the lateral direction exists, the ratios µ/Ee are different for different incident
energies Ee where µ = µc − µp . Fig. 9 shows the ratio µ/Ee as a function of the incident energy EE .
The ratio µ/Ee as a function of the incident energy Ee is different between 25 crystals, and theslope is negative for all the crystals. This behavior cannot be explained only with the energy leakage inthe lateral direction. The µ/Ee was well fitted with a linear function for all the crystals. The gain ofeach crystal was adjusted so that the limit of µ/Ee at E = 0 should be the same. The energy of eachcrystal Ei was given by
Ei = αi (A − µp ) ,where A is a measured ADC value and αi is the limit of (µ/Ee )

(12)
−1

at Ee = 0. Two series of the mea-

surements for the energy calibration were made before and after a series of the measurement for the
performance study. The obtained factor αi was different between the first and second series of the measurements for the energy calibration for some BGO crystals. Thus, the obtained αi ’s from two series
were averaged to give the energy.
4.2 Energy resolution
The energy resolution of the calorimeter was measured by injecting positrons with momenta from100 to 800 MeV/c onto the central 00F crystal ‘13 (00F-03).’ The energy of the calorimeter E was recon-Ratio of Mean to Incident Energy µc/Ee (channel/MeV)

72

1.9 011.8
1.7
1.6
1.9 06

02

03

04

05

07

08

09

10

12

13

14

15

17

18

19

20

22

23

24

25

1.8
1.7
1.6
1.9 111.8
1.7
1.6
1.9 161.8
1.7
1.6
1.9 211.8
1.7
1.6

0 250 500 7500 250 500 7500 250 500 7500 250 500 7500 250 500 750
Incident Energy (MeV)
Fig.9. Ratio µ/Ee as a function of the incident energy Ee . The µ/Ee is not constant due tothe energy leakage mainly in the lateral direction. The solid line shows the fitted linear
function.

structed by the sum of 25 crystal energies Ei as
E=

25
∑

Ei .

(13)

i=1

Fig. 10 shows the typical energy distributions of the calorimeter for all the incident positron energies.
The energy distributions were also fitted with a logarithmic Gaussian and the mean µ, width σ, andasymmetry parameter η were obtained for each incident positron energy for each incident position.
The energy resolution σE /E was estimated as( σ )2 ( σ ) 2 ( σ ) 2 ( σ ) 2
E
b
p
=
−
−
E
µ
µb
µ

(14)

from the mean µ and width σ of the reconstructed energy distribution, the beam energy spread σb /µb
given in Ref. [9], and the width σp of the energy distribution for the clock trigger (pedestal distribution).
Fig. 11 shows the energy resolution as a function of the incident energy.

73Counts / 5 MeV

350 50 A-1
300
250
200
150
100
50
0
0 100 200 300
300 150 A-1
250
200
150
100
50
0
0
200 400

75 A-1

0

100 A-1

100 200 300

0175 A-1

600 0

200

125 A-1

100 200 300

0200 A-1

400

600 0

200

100 200 300
230 A-1

400

600 0

200

400

600

300 A-1
350 A-1
400 A-1
250 250 A-1
200
150
100
50
0
0 250 500 750 1000 0 250 500 750 1000 0 250 500 750 1000 0 250 500 750 1000
200 450 A-1
150
100
50
0

0 250 500 750 1000
Energy (MeV)

Fig.10. Typical energy distributions of the prototype BGO calorimeter for all the incident
positron energies together with the fitted logarithmic Gaussians. The positrons are
incident on the central 3 × 3 mm2 region determined by the x8 and y8 BPM fibers. The
incident energy is described in each panel.

When the energy resolution is fitted withσE
c1
(Ee ) = √,E
Ee /GeV(15)

c1 ranges from 1.29%–1.48% for different incident positions determined from the combinations of x andy BPM fibers. The value of c1 directly corresponds to the energy resolution for 1 GeV/c positrons. Whenthe energy resolution is fitted with
v
)2 (
(
u
)2
u
σE
c2
c1
2
t
(Ee ) = (c0 ) + √+,E
Ee /GeV
Ee /GeV(16)

the energy resolution for 1 GeV/c positrons ranges from 1.21% to 1.37%. Although the obtained c2
parameter is stable independently of the incident position, the values of c0 and c1 differ very much fordifferent incident positions. It seems that two parameters c0 and c1 do not behave independent free
ones in fitting with eq. (16). Therefore, the energy resolution is again fitted with eq. (16) by fixing theEnergy Resolution σE/Ε74

0.06 (05,05) (06,05) (07,05) (08,05) (09,05) (10,05) (11,05)
0.04
0.02
0
0.06 (05,06) (06,06) (07,06) (08,06) (09,06) (10,06) (11,06)
0.04
0.02
0
0.06 (05,07) (06,07) (07,07) (08,07) (09,07) (10,07) (11,07)
0.04
0.02
0
0.06 (05,08) (06,08) (07,08) (08,08) (09,08) (10,08) (11,08)
0.04
0.02
0
0.06 (05,09) (06,09) (07,09) (08,09) (09,09) (10,09) (11,09)
0.04
0.02
0
0.06 (05,10) (06,10) (07,10) (08,10) (09,10) (10,10) (11,10)
0.04
0.02
0
0.06 (05,11) (06,11) (07,11) (08,11) (09,11) (10,11) (11,11)
0.04
0.02
0
0 500 0 500 0 500 0 500 0 500 0 500 0 500
Incident Energy (MeV)

Fig.11. The energy resolutions of the prototype BGO calorimeter as a function of the incident
positron energy for different combinations of x and y BPM fibers. The energy resolutions
obtained by two series of energy resolution measurements are plotted where the central
00F crystal ‘13 (00F-03)’ is aligned on the positron beamline. The combination of x andy fibers is described in each panel. The solid curves show the fitted functions (16).

coefficient for the constant term c0 = 0.63% which is obtained from a Geant4 [10] based simulation. The
averages of the obtained c1 and c2 parameters between all the incident positions become c = 1.058% ± 0.043%1.
 c = 0.445% ± 0.027%

(17)

2

The average energy resolution is 1.31% ± 0.04% for 1 GeV/c positrons. The details of the analysis forthe energy resolution are described elsewhere [11].
4.3 Position resolution
The incident position can be determined from the energy responses of the crystals. The position
resolution of the calorimeter is estimated by comparing the position determined with the calorimeter tothat given by BPM fibers.
The width and height are given by ax = 20.87 and ay = 20.91 mm for the front face of the centercrystal ‘13 (00F-03),’ respectively. Here, ay is given by the average of y coordinate for 07 (01F-02), 08

75(01F-03), and 09 (01F-04) and that for 17 (00B-02), 18 (00B-03), and 19 (00B-04), Fig. 12 shows the front
face of the prototype BGO calorimeter and the definition of the variables used in this subsection.

e-BPM
x1
y

y16

x16

01

02

03

04

05

06

07

08

09

10

02F

x

Ey+

y+

ax

z

11

12

x+
16

ay
y1

BGO 13 (00F-03)

17 y−

13

14

01F
15

Ey0

x−
19

21 Ex+
22 Ex023 Ex−
24

00F
20

Ey−

00B +y

25

01B

+x
+z

Fig.12. Front face of the prototype BGO calorimeter and definition of the variables. The widthand height are denoted by ax and ay for the front face of the center crystal ‘13 (00F-03).’
The vectors y⃗+ = ⃗
r08 − ⃗
r13 , y⃗− = ⃗
r18 − ⃗
r13 , ⃗
x+ = ⃗
r12 − ⃗
r13 , and ⃗x− = ⃗
r14 − ⃗
r13 standfor ones from the center of the front face of the center crystal to that of the upper, lower,
left, and right ones, respectively. The sum of energies for three crystals aligned in a line
are defined as Ex+ = E07 + E12 + E17 , Ex0 = E08 + E13 + E18 , Ex− = E09 + E14 + E19 ,Ey+ = E07 + E08 + E09 , Ey0 = E12 + E13 + E14 , and Ey− = E17 + E18 + E19 for the central
nine crystals.
The vectors from the center of the front face of the center crystal to that of the upper, lower, left,
and right ones are denoted by
⃗x+ = ⃗
r12 − ⃗
r13 ,




 ⃗
x =⃗
r −⃗
r ,
−

14

13



y
⃗+ = ⃗
r08 − ⃗
r13 , and




 y
⃗− = ⃗
r18 − ⃗
r13 .

(18)

Here, ⃗
ri stands for the position vector to the center of the front face for the i-th crystal. The approximations ⃗x+ ≃ +ax x̂, ⃗x− ≃ −ax x̂, y⃗+ ≃ +ay ŷ, and y⃗− ≃ −ay ŷ are valid for the prototype calorimeter
where x̂ and ŷ are unit vectors giving the +x and +y direction. In addition, the sums of energies forthree crystals aligned in a line are defined as Ex+ = E17 + E12 + E07 ,






Ex0 = E18 + E13 + E08 , E =E +E +E ,
x−
19
14
09


Ey+ = E07 + E08 + E09 ,






Ey0 = E12 + E13 + E14 , and Ey− = E17 + E18 + E19

(19)

76

for the central nine crystals. The ratios are also defined between the energy sums between the central
and outer lines as
Wx+ = Ex+ /Ex0 , W = E /E ,
x−

x−

x0

(20)



Wy+ = Ey+ /Ey0 , and Wy− = Ey− /Ey0 .
Here, the position reconstructed with these ratios is discussed.

At first, the incident position is investigated for different energy ratios Wx± and Wy± . Fig. 13
shows the typical incident x position determined by the x BPM fiber for different energy ratios Wx− .
The mean of the incident position xb distribution becomes smaller as Wx− becomes higher as shown in
Fig. 13, and that of yb also becomes smaller as Wy− becomes higher. On the other hand, xb (yb ) becomes
higher as Wx+ (Wy+ ) becomes higher.
-0.04,-0.02-0.02,0.00

0.00,0.02

0.02,0.04

0.04,0.06

10 3 0.06,0.08

0.08,0.10

0.10,0.12

0.12,0.14

0.14,0.16

0.18,0.20

0.20,0.22

0.22,0.24

0.24,0.26

0.26,0.28

0.28,0.30

0.30,0.32

0.32,0.34

0.34,0.36

1 0.36,0.38
10 2

0.38,0.40

0.40,0.42

0.42,0.44

0.44,0.46

0.48,0.50

0.50,0.52

0.52,0.54

0.54,0.56

0.58,0.60

0.60,0.62

0.62,0.64

0.64,0.66

10 3
10 2

10 2
10 3
10 0.16,0.18
10 2Counts

10
10 2
10

10
1 0.46,0.48
10 2
10
1 0.56,0.58
10 2
10
1

-10

0

10
-10

0

10
-10

0
xb (mm)

10
-10

0

10
-10

0

10

Fig.13. Typical incident x position xb determined by the x BPM fiber for different energy ratio
Wx− . The RTAGX current is 450 A, and are plotted for the first series of measurements
for the energy resolution. The energy ratio Wx− is described in each panel.
The mean µb and width σb of the distribution is determined by the average and standard deviationfor each energy ratio. Fig. 14 shows the typical means of the incident position distributions µx±
b /ax andµy±b /ay as a function of Wx± and Wy± .
y±
The means of the incident position distributions µx±
b /ax and µb /ay as a function of Wx± and

0.5
0.4
0.3
0.2
0.1
0
-0.1
-0.2
-0.3
-0.4
-0.5

Position x/ax

0.5
0.4
0.3
0.2
0.1
0
-0.1
-0.2
-0.3
-0.4
-0.5

0

0.2
0.4
Wx-=Ex-/Ex0

0.6

Position y/ay

Position y/ay

Position x/ax

77

0

0.2
0.4
Wy-=Ey-/Ey0

0.6

0.5
0.4
0.3
0.2
0.1
0
-0.1
-0.2
-0.3
-0.4
-0.5

0.5
0.4
0.3
0.2
0.1
0
-0.1
-0.2
-0.3
-0.4
-0.5

0

0.2
0.4
Wx+=Ex+/Ex0

0

0.2
0.4
Wy+=Ey+/Ey0

0.6

0.6

y±
Fig.14. Typical means of the incident position distributions µx±
b /ax and µb /ay as a functionof Wx± and Wy± . The RTAGX current is 450 A. The solid lines show the fitted function
eq. (21) to the data.

Wy± are fitted with the function
 x±
(
)
µb
2 x
Wx±
1

−1


(W
)
=
±
β
tan
± δbx ∓
and
x±
b

x
 ax
π
αb
2
(
)


µy±
2 y
Wy±
1

−1
b

(Wy± ) = ± βb tan± δby ∓

ay
π
αyb
2
x/y

for every RTAGX current, and the parameters αb

x/y

, βb

(21)

x/y

, and δb

are determined. Fig. 15 shows the

x/y
x/y
x/y
parameters αb , βb , and δb as a function of the incident energy.
yThe differences between x and y are very small for all the parameters. The parameters αx
b and αbdecrease monotonically as the incident energy becomes higher, and they are well fitted with{}α2
αb (Ee /GeV) = α0b − α1b tan−1 (Ee /GeV) b ,
where




α0 = 0.8688 ± 0.0007, b
α1b = 1.0123 ± 0.0009, and α2 = 0.0464 ± 0.0003.

(22)

(23)

b

The parameters δbx and δby also decrease monotonically, and they are fitted with{}δ2
δb (Ee /GeV) = δb0 − δb1 tan−1 (Ee /GeV) b

(24)

78

1

0.12

0.4
0.8

0.1
0.3

0.06
0.04

0.2

0.4

0.1

0.02
0

0.6
βb

δb

αb

0.08

0

200 400 600 800
Incident Energy (MeV)
x/y

x/y

0

0.2
0

200 400 600 800
Incident Energy (MeV)00

200 400 600 800
Incident Energy (MeV)x/yFig.15. Parameters αb , βb , and δb for eq. (21) as a function of the incident energy. The
solid curves are fitted function to the data (see text).
where




δ 0 = 0.6279 ± 0.0009, bδb1 = 0.5233 ± 0.0012, and δ 2 = 0.3202 ± 0.0008.

(25)

b

The parameters βbx and βby increase monotonically, and are fitted with}{βb (Ee /GeV) = βb1 tan−1 βb2 (Ee /GeV)where
 β 1 = 0.5560 ± 0.0003, andb β 2 = 7.1064 ± 0.0175.

(26)

(27)

b

Since all the parameters are given by the incident energy dependent functions, the position is reconstructed by the equations:

(
)
x
2 x
Wx±
1

−1

(W
)
=
±
β
tan
± δbx ∓ , and

x±

 ax
π b
αx
2
b
(
)


2
Wy±
1
y


(Wy± ) = ± βby tan−1± δby ∓ .

y
ay
π
αb
2
The conditions Wx± < 0 and/or Wy± < 0 are not included in the domain of eq. (28), and


1
x


(Wx± ) = ±δb ∓
and

ax
2


y
1


(Wy± ) = ±δb ∓
ay
2

(28)

(29)

are used in these conditions. The reconstructed positions concentrate the negative and positive regions
when Wx− (Wy− ) and Wx+ (Wy+ ) are used, respectively. Fig. 16 shows the typical correlation betweenyx/ax (y/ay ) and the mean µx
r /ax (µr /ay ) of the residual x − xb (y − yb ) distribution.
y
The mean µx
r /ax (µr /ay ) of the residual x − xb (y − yb ) distribution is fitted with

(
)

x
1
µx

r

(x)
=
s
+

x−
ax
a
2
( x
)
y

y
1
µ

 r (x) = sy−
+

ay
ay
2

(30)

79

0.4

0.4
Wx-

0.2
x/ax-xb/ax

x/ax-xb/ax

0.2
0
-0.2

0
-0.2

-0.4

-0.4

-0.2

0
x/ax

0.2

-0.4

0.4

0.4

-0.4

-0.2

0
x/ax

0.2

0.4

-0.2

0
y/ay

0.2

0.4

0.4
Wy-

0.2
y/ay-yb/ay

0.2
y/ay-yb/ay

Wx+

0
-0.2

Wy+

0
-0.2

-0.4

-0.4

-0.2

0
y/ay

0.2

0.4

-0.4

-0.4

y
Fig.16. Typical correlation between x/ax (y/ay ) and the mean µx
r /ax (µr /ay ) of the residualx − xb (y − yb ) distribution. The RTAGX current is 450 A. The solid lines show the fitted
functions (30) and (31). The horizontal lines at x − xb = 0 (y − yb = 0) indicate thecorrect position reconstruction.

for the position reconstruction with Wx− and Wy− , and is fitted with

(
)

µx
x
1

r

(x) = sx+
−

ax
ax
2
(
)

y
1
µyr


(x) = sy+
−

ay
ay
2

(31)

for the position reconstruction with Wx+ and Wy+ . The obtained sx and sy are well fitted with s (E /GeV) = s + s E /GeV
x
e
0
1 e
(32)
 s (E /GeV) = s + s E /GeV
y

e

0

1

e

by using the same parameters given by s = −0.068, and0 s = −0.180.

(33)

1

The realistic position can be obtained by the correction as

(
)
x
1
x


←
−s x+

ax
ax
2)
(
y
1
y


←
−s y+

ay
ay
2
for the position reconstruction with Wx− and Wy− , and is obtained as

(
)
x
1
x


←
−s x−

ax
ax
2)
(
y
1
y


←
−s y−

ay
ay
2

(34)

(35)

80

for the position reconstruction with Wx+ and Wy+ . Here, s is given by(36)

s = s0 + s1 E/GeV

with already determined parameters s0 and s1 . Fig. 17 shows the typical residual x − xb (y − yb )distribution. By averaging the position given by Wx− and that by Wx+ or by averaging Wy− andWy+ ones, the measured position is also reconstructed for each event. The errors of the reconstructed
positions only with Wx− (Wy− ) or only with Wx+ (Wy+ ) are assumed to be given by the differentiates
of eq. (28) as{)2 }−1
(

W

x±

, and

 σx (Wx± ) = 1 +
αx
b
{
}
(
)2 −1


Wy±


,
 σy (Wy± ) = 1 +
αyb

(37)

and the weights for the average is determined by the inverse square of the error. When Wx± − Cbx < 0
and/or Wy± − Cby < 0, the errors are assumed to be σ (W ) = 1, and/orxx± σ (W ) = 1.
y

(38)

y±

15000

x(W )

x-

x(W )

x+

x(W ,W )

x-

x+

y-

y(W )

y+

y(W ,W )

y-

y+

10000

Counts / 1 mm

5000

0
15000

y(W )

10000

5000

0

-20

-10

0

10

20
-20
-10
0
10
20
-20
Residual x-xb and y-yb (mm)

-10

0

10

20

Fig.17. Typical residual x − xb (y − yb ) distribution. The RTAGX current is 450 A. The upperand lower panels show the x − xb and y − yb distributions, respectively. The left andmiddle panels show the residual distributions estimated by the reconstructed positions
with Wx− (Wy− ) and Wx+ (Wy+ ). The right panels show the residual distributions
where the positions are reconstructed by using both Wx− and Wx+ or by using bothWy− and Wy+ .
The position resolutions is estimated from the width (σ) of the residual x − xb (y − yb ) distribution
and the width 3 mm of the BPM fibers. The position resolution√2
σr = σ 2 − σBPM

(39)

81
√
where σBPM = 3 mm/ 12 assuming that the positron beam comes uniformly in the square determinedby the combination of x and y BPM fibers. Fig. 18 shows the x and y position resolutions as a function

Position Resolution (mm)of the incident positron energy.
7
6.5
6
5.5
5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0

0

100

200

300
400
500
600
Incident Energy (MeV)

700

800

900

Fig.18. x and y position resolutions as a function of the incident positron energy. The upper
data points are the position resolutions estimated by the reconstructed positions onlywith Wx− (Wy− ) and only with Wx+ (Wy+ ). The lower are the resolutions estimated byusing both Wx− and Wx+ or by using both Wy− and Wy+ . The data are compared withσr /mm = 3.70(Ee /GeV)−0.1538 and σr /mm = 3.07(Ee /GeV)−0.2024. The horizontalline√√shows the position resolution of 6.0 mm corresponding to ax / 12 and ay / 12.
The position resolutions estimated by the reconstructed positions only with Wx− (Wy− ) and onlywith Wx+ (Wy+ ) are well fitted with a function−βp

σp = αp Ee

with parameters α = 3.70 mm ± 0.02 mm, andp β = 0.1538 ± 0.0051.

(40)

(41)

p

The resolutions estimated by using both Wx− and Wx+ or by using both Wy− and Wy+ are expressedby eq. (40) with parameters α = 3.07 mm ± 0.03 mm, andp β = 0.2024 ± 0.0080.

(42)

p

The position resolution is 3.07 mm ± 0.03 mm for 1 GeV/c positrons when the cluster has all the adjacent members. It is 3.70 mm ± 0.02 mm for 1 GeV/c when the cluster does not have adjacent members
corresponding to a side line. The details of the analysis for the position resolution are described elsewhere [12].
4.4 Development of the EM shower
After the measurements for the energy calibration and the energy resolution was finished, thewaveforms of the central nine crystals were acquired with three digital phosphor oscilloscope Tektronix

82

DPO-4104, MSO-4104, and DPO-4054 The sampling frequencies are 5, 5, and 2.5 GHz, respectively. The
analog signal from each BGO crystal was directly input to them. To synchronize the measured timings
for all of them, the trigger signal was input to the first channel of each oscilloscope. The trigger was
generated by coincidence of the logic signals for x8 and y8 BPM fibers. Table 5 summarizes the inputs
for all the oscilloscopes.
Table 5. Inputs for all the oscilloscopes.
oscilloscope
DPO-4104
MSO-4104
DPO-4054

channel 1
triggertriggertriggerchannel 2
07 (01F-02)
12 (00F-02)
09 (01F-04)

channel 3
08 (01F-03)
13 (00F-03)
17 (00B-02)

channel 4
18 (00B-03)
14 (00F-04)
19 (00B-04)

The charge integration measured with a oscilloscope is proportional to the energy deposit in a BGO
crystal. The ratio of the charge integration to the deposit energy is explained mainly by the gain of the
PMT used. Fig. 19 shows the diagram for the circuitry for the energy measurement with oscilloscopes.
The coefficient αpmt for each PMT gain is required to compare the measured charge integration withdifferent channels.
BGO

E

DPO / MSO

αpmtE

Fig.19. Diagram of the circuitry for the energy measurement with oscilloscopes.
The energy calibration was made during the performance study of the prototype BGO calorimeterby using ADC modules. In this case, the calibration factor αi depends on the attenuation factor αatt , thechannel to charge ratio αadc , and αpmt . Since αi has been already determined in subsection §4.1, αpmt
iwill be obtained by
αpmt
=
i

1

(43)

att
αi αadci αiwith αadc
and αatt
i
i . Fig. 20 shows the diagram of the circuitry for the energy measurement by using ADC
modules.
BGO

E

Delay

αpmtE

AttenuatorαattαpmtE

ADC
2249W α α α E
adc att pmt

Fig.20. Diagram of the circuitry for the energy measurement by using ADC modules.
To obtain αadc
and αatt
i
i , the charges of the logic signal were measured with and without attenuator by using ADC modules. Fig. 21 shows the diagram of the circuitry for the measurement of theattenuation factor.
The attenuation factor αatt
i is determined by the ratio of the pedestal subtracted ADC values withand without attenuator. The charge of the un-attenuated logic signal obtained was 316 pC by integrating

83

Logic Signal

Delay

Attenuator

ADC
2249W α α Q
adc att

αattQ

Q

Fig.21. Diagram of the circuitry for the measurement of the attenuation factor.
the pulse heights for the acquired waveform with a oscilloscope. Therefore, the ADC value and obtained
pmt
adc
adc
att
is
αatt
i give αi . Since all the coefficients αi , αi , and αi are determined, the absolute value of αiestimated. Table 6 summarizes the coefficient αpmt
for all the BGO crystals.
iTable 6. Coefficient αpmt
(pC/MeV) for all the BGO crystals. Those for the central nine crystalsi
are used in the analysis.
BGO
01
02
03
04
05

αpmt
i
7.376(20)
4.578(07)3.253(05)4.110(07)4.056(08)αpmt
i4.777(07)5.763(07)4.887(05)8.256(14)3.257(05)

BGO
06
07
08
09
10

BGO
11
12
13
14
15

αpmt
i
3.766(06)4.025(04)6.612(34)9.080(10)5.916(10)

BGO
16
17
18
19
20

αpmt
i
5.027(09)4.554(07)7.361(08)5.464(10)9.104(16)

BGO
21
22
23
24
25

αpmt
i
7.627(12)6.738(11)5.162(08)5.460(09)7.956(14)Since the coefficients αpmt
are obtained for all the BGO crystals, the measured pulse height can beiconverted into the energy unit MeV/ns. Fig. 22 shows all the acquired waveforms with a RTAGX currentof 400 A for the central nine BGO crystals, for example.
0
-0.2
-0.4
-0.6

Pulse Height (MeV/ns)-0.8

BGO 07

BGO 08BGO 09BGO 12

BGO 13
x 1/5

BGO 14BGO 17BGO 18BGO 19

0

-0.2
-0.4
-0.6
-0.8
0
-0.2
-0.4
-0.6
-0.8
0

200

400

600

0

200 400
Timing (ns)

600

0

200

400

600

Fig.22. All the acquired waveforms with a RTAGX current of 400 A for the central nine BGO
crystals. The pulse height for the center crystal 13 (00F-03) is scaled by 1/5. The verticallines indicate the timing of −82 ns.
At first, the measured energy resolution as a function of the integration gate width is investigated.
The charge (energy) distributions are fitted with a logarithmic Gaussian, and the mean µ and width σ

84

are obtained. Fig. 23 shows the mean µ and width-mean ratio σ/µ as a function of the integration gate.
Although µ goes larger as the gate width broader, σ/µ is almost constant in a wide gate width range.
Assuming the gate signal is correctly distributed at the same timing, the obtained energy resolution isalmost independent of the width of the gate signal.

Mean of Energy Distribution (MeV)

125

µ

100

σ/µ

75
50
25
0

50 A (x8-y8)5001000 1500 2000

µ

600

350
300
0.08 250
0.06 200
150
0.04
100
0.02 50
0
0
0.1

0.04

800

µ
σ/µ
100 A (x8-y8)5001000 1500 2000µ

0.04 1000

300 A (x8-y8)

0.03 800
600
0.02
400
0.01 200

0.03 600σ/µ4000.01 200

230 A (x8-y8)
0

500

σ/µ

0.02 400

200
1000 1500 2000

0

0

0.07
0.06 400
0.05 300
0.04
0.03 200
0.02
100
0.01
0
0

500

1000 1500 2000

0

0

0.04

σ/µ

µ

0.03
0.02

150 A (x8-y8)5001000 1500 2000

µ

0.01
0

0.04
0.03

σ/µ
400 A (x8-y8)5001000 1500 2000

0.02
0.01
0

Ratio of Width to Mean

150

Gate Width (nsec)
Fig.23. Mean µ and width-mean ratio σ/µ as a function of the integration gate. Although µ
goes larger as the gate width broader, σ/µ is almost constant in a wide gate width
range. The values of µ and σ/µ are referred by the left and right axes, respectively. The
RTAGX current is described in each panel.
Next, the measured time from the adjacent to the center crystals. Fig. 24 shows the measured
time distributions from the upper, lower, left, and right to the center crystals. All the time distributions
take a symmetric shape, and are well fitted with nominal Gaussians. Table 7 summarizes the fitted
mean µt and width σt for the time distributions. The σt goes smaller as the RTAGX current becomes
higher, corresponding that the timing resolution is good for the high current, namely the high positron
momentum. The µt is almost constant independently of the current, and the timings are approximately
0.2 ns delayed in the adjacent crystals.
Table 7. Fitted mean µt and width σt for the time distributions. The unit for µt and σt is ns.
RTAGX
50 A
100 A
150 A

µt
0.16(4)0.18(2)0.20(2)σt1.15(4)0.83(2)0.67(2)

RTAGX
230 A
300 A
400 A

µt
0.19(1)0.23(1)0.23(1)σt0.54(1)0.48(1)0.41(1)

Here, the two results obtained from the acquired waveforms are presented. The details of theanalysis and other results are described elsewhere [13].

100

40
20
0

75
50
25
0

-5
0
5
Timing Difference (nsec)

100 A (x8-y8)Counts / 0.1 nsec

60 50 A (x8-y8)Counts / 0.1 nsec

Counts / 0.1 nsec

85

150 A (x8-y8)
100

50

0

-5
0
5
Timing Difference (nsec)-505Timing Difference (nsec)

100
50
0

-5
0
5
Timing Difference (nsec)

300 A (x8-y8)Counts / 0.1 nsec

230 A (x8-y8)Counts / 0.1 nsec

Counts / 0.1 nsec

200
150

150
100
50
0

-5
0
5
Timing Difference (nsec)

200 400 A (x8-y8)
150
100
50
0

-5
0
5
Timing Difference (nsec)

Fig.24. Measured time from the upper, lower, left, and right to the center crystals. The RTAGX
current is described in each panel, and the solid curves show the fitted Gaussians.

§ 5. Summary
Construction of a new EM calorimeter with 1,320 BGO crystals is planned at ELPH. The shapes of
all the crystals have been designed, and the new EM calorimeter covers the polar angle from 24◦ to 144◦ .
It takes a shape like an egg, and we call it EGG. The performance study of a prototype calorimeter has
been made at the positron beamline for testing detectors at ELPH. The prototype calorimeter is madeup with 25 BGO crystals in a 5 × 5 matrix. The energy resolution obtained as a function of the incident
energy is
{σ

E

E

}2
2
(Ee ) = (0.63%) +(1.06% ± 0.04%√
Ee /GeV)2(+0.45% ± 0.03%
Ee /GeV

)2
,

(44)

and that is 1.31% ± 0.04% for 1 GeV/c positrons. The position resolution obtained is 3.07 mm ± 0.03 mm
for 1 GeV/c positrons when the cluster has all the adjacent members. It is 3.70 mm±0.02 mm for 1 GeV/cwhen the cluster does not have adjacent members corresponding to a side line.

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

References[1]

K. Mochizuki, T. Ishikawa et al.: Research Report of LNS, Tohoku Univ. 40, 15 (2008).

[2]

M. Sato, T. Ishikawa et al.: Research Report of LNS, Tohoku Univ. 41, 22 (2009).

[3]

M.J. Weber and R.R. Monchamp, J. Appl. Phys. 44 (1973) 5495.

[4]

T. Ishikawa et al.: Research Report of LNS 42&43, Tohoku University, 1 (2011).

86
[5]

E. Auffray, F. Cavallari, M. Lebeau, P. Lecoq, M. Schneegans: Nucl. Instr. and Meth. A 486, 22(2002).

[6]

Web site: ⟨http://www.che.nsk.su/⟩.

[7]

S. Kaida, T. Ishikawa et al.: Research Report of LNS 42&43, Tohoku University, 150 (2011).

[8]

H. Ikeda et al.: Nucl. Instr. and Meth. A 441, 401 (2000).

[9]T. Ishikawa et al.: Research Report of LNS 40, Tohoku University, 6 (2008);
T. Ishikawa: Internal GeV-γ Analysis Note No. 78 (2008).

[10] S. Agostinelli et al. (Geant4 Collaboration): Nucl. Instr. and Meth. A 506, 250 (2003);
J. Allison et al.: IEEE Trans. on Nucl. Sci. 53: 270 (2006).
[11] T. Ishikawa and H. Fujimura: Internal GeV-γ Analysis Note No. 218B (2011);
T. Ishikawa: Internal GeV-γ Analysis Note No. 231B (2011).
[12] T. Ishikawa: Internal GeV-γ Analysis Note No. 238B (2011).
[13] T. Ishikawa: Internal GeV-γ Analysis Note No. 222B (2011).

ELPH Annual Report 2010, Tohoku University Vol. 1

87(ELPH Experiment : #2723, #2749)

Test of GEM tracker and HBD for J-PARC E16 experiment
Y. Komatsu1,2 , K. Aoki2 , Y. Hori4 , J. Kanaya2 , K. Kanno1 , S. Masumoto1,2 ,R. Muto3 , W. Nakai1 , K. Ozawa3 , M. Sekimoto3 , A. Takagi1 , Y. S. Watanabe1 ,and S. Yokkaichi2
1

Department of Physics, University of Tokyo, Hongo, 113-0024
2

RIKEN Nishina Center, RIKEN, Wako, 351-0198
3
4

KEK, Tsukuba, 305-0801

CNS, University of Tokyo, Wako, 351-0198

J-PARC E16 experiment measures mass modification of ϕ meson in nuclear matter at J-PARC 50
GeV proton synchrotron. The particle tracker of E16 experiment applies Gas Electron Multiplier (GEM)
for the amplification of electrons. GEM tracker gives two-dimensional hit positions by x and y strips on
the readout board. The position resolution and efficiency of the tracker are investigated with new GEM
foils and a new readout board. GEM tracker is also tested in a high rate environment of e+ e− beam
converted from photon beam. A performance of a Cherenkov detector called Hadron Blind Detector(HBD) is evaluated at the same time.

§ 1. Introduction
The mass spectrum of hadrons is predicted to be modified in hot and/or dense matter due to thechiral symmetry restoration [1]. J-PARC E16 experiment investigates the mass modification of ϕ mesonin nuclear matter with high statistics and high mass resolution [2]. The particle tracker for E16 experiment is designed to measure the momentum of e+(−) from the decay of ϕ meson. The tracker consistsof three layers which measures three points of a track in a magnetic field. Each layer has Gas Electron
Multiplier (GEM) and a two-dimensional readout plane. GEM is a foil with many small holes whose
diameter is ∼70 µm. Polyimide of 50 µm thickness is sandwiched by copper electrodes of 4 µm thickness
on each side [3]. Voltage of ∼400 V is added between the copper electrodes and electron avalanche isinduced in the holes. GEM amplifies ionized electrons by tens of thousands and can be operated in ahigh rate environment [4].
GEM Tracker needs three different sizes of GEM, 10×10 cm2 , 20×20 cm2 and 30×30 cm2 . Position
resolution of 100 µm for 0◦ and 15◦ beam is achieved with 10×10 cm2 GEM [5]. Position resolution
is expected to degrade according to the incident angle of the beam, but that is solved by using timing
information of the charge cluster. GEM foils of 20×20 cm2 and 30×30 cm2 are newly developed andtested at GeV-γ beam line of ELPH, Tohoku University in November, 2010.
A new type of readout is manufactured and tested in March, 2011. The readout board is coatedwith carbon for the bottom side (Y strips) to collect more charge. The carbon coated on the surface is88

expected to prevent charge-up phenomena. A performance of GEM tracker in a high rate environmentis also evaluated by converting photon beam into e+ e− .
Cherenkov detector is called Hadron Blind Detector (HBD). HBD is a mirrorless windowless Cherenkov
detector [6] and is used for electron identification from pion. CF4 is used as the radiator and amplification gas. CsI evaporated GEM serves as a photocathode. LCP-GEM which has thickness of 100µm isused for the prototype. The purpose of the test experiment is to evaluate the performance of a prototype
of Hadron Blind Detector (HBD) for the J-PARC E16 experiment.
A schematic drawing of the photocathode is shown in Figure 1. A photon is converted into a photoelectron by the CsI which is evaporated on top of the GEM. Then the photoelectron is amplified by thestack of GEMs and the signals are readout with the pads. A mesh is placed over the top GEM and isused to manipulate the field between the mesh and the top GEM. The field is called the bias field. Whenreverse bias field is applied, electrons between the mesh and the top GEM are swept into the mesh.
Since photoelectrons are produced near the GEM surface, most of them drift to the GEM holes and arereadout even in the reverse bias field. In this way, the HBD is sensitive to photons while is insensitive
to ionization electrons from energy loss. For the configuration of the prototype with the radiator lengthof 50 cm, about 20 photoelectrons are expected.The required rejection power for the experiment is 100

Ch
ph erenoto kon v

incidelect entron

and it can be achieved with a threshold at about 16 photoelectrons.

mesh

4 mm photo-

electron

1.5 mm
2 mm

n
tio
CsI

za
oni

i

GEM
GEM

readout pad
Fig.1. Schematic drawing of the photocathode§ 2. Test experiment of GEM tracker: test of 20×20 cm2 and 30×30 cm2 GEM
2.1 Set up
Set up at GeV-γ beam line is shown in the left of Figure 2. The momentum of e+ beam is 750
MeV/c. Trigger is made by a coincidence of 4 scintillators. GEM tracker is set between the Silicon Strip
Detectors (SSDs) and can be rotated 15◦ and 30◦ so that incident angle of the beam can be changed. The
strip of SSDs is one-dimensional and the pitch is 80 µm, so they have better position resolution than
GEM tracker. SSDs give a reference position to evaluate the position resolution of tracker.

89

Signals from GEM tracker are sampled at 100M Hz by FADC (RPV-160) modules. The number ofchannels is 32.

Fig.2. Set up at GeV-γ beam line. left) Set up for large GEM test. right) Set up for a carbon
coated readout board and high rate runs.

2.2 Analysis methods
Analysis method to calculate the hit position on GEM tracker changes according to the incident
angle.
2.2.1 0◦ beam
Center of Gravity (COG) of charge distribution or middle point of hit strips is calculated.
• COG method : Hit position is calculated as the weighted mean of the charge distribution.
N∑
Qn
xGEM =
p × ni ∑N i
(1)
Q
n
j
j=1
i=1
p is the strip pitch. ni is the strip number in which ADC value is over the threshold. N is thenumber of hit strips. Qni is the maximum value of the waveform of the strip ni between 0 and 100
clocks.
• Middle point method : Hit position is calculated as the middle point of the hit strips.
n1 + nN
xGEM = p ×2(2)

2.2.2 15◦ /30◦ beam
• Timing fit method : The position where primary and secondary electrons appear is reconstructedby the timing of the signals. The arrival timing of a signal is defined as the clock at which the
waveform exceeds the threshold. The distance between ionization position and readout plane iscalculated as the product of arrival timing and drift velocity.
zni = vd × tni(3)

zni is the distance between ionization position and readout plane. vd is the drift velocity of electron.
vd is simulated by simulation software Magboltz [7] and tuned so that position resolution gets

90

better. tni is the arrival timing in hit strip ni .
The equation of a track is obtained by fitting (p×ni , zni )i=1...N with a linear function. Hit position
xGEM is calculated from this equation for a fixed z.
• Timing fix method : The slope of the equation of a track is fixed as the known value (tan 75◦ ortan 60◦ ) in fitting when timing fix method is used.
2.3 Results
2.4 Gain
The gain and electric field in each gap are shown in Table 1 for 10×10 cm2 , 20×20 cm2 and 30×30
cm2 . The electric field in each gap is determined by the ratio of the resistor value for the gap and wholevalue of the resistor chain to distribute the high voltage. The voltage added to the transfer gap is twiceas the voltage between the GEM electrodes for 10×10 cm2 GEM, but it is same for 20×20 cm2 and30×30 cm2 GEM. Thus the electric field of the transfer gap is lower in the configuration of large GEM
than 10×10 cm2 . Gain is calculated from the gain of preamplifier (3.2 V/pC) and FADC (1 V/256 ch).
The gain of 20×20 cm2 and 30×30 cm2 GEM are lower than 10×10 cm2 . The difference of the gain is
not considered to be explained only by the electric field of the transfer gap according to the electric fielddependence of gain [8]. The difference of inner pressure of the chamber is suspected as a reason, butneeds to be investigated. The position resolution is better than 100 µm for 0◦ in three types of GEM.
Gap nameED [kV/cm]
ET 1 [kV/cm]
ET 2 [kV/cm]
EI [kV/cm]
VGEM [V]gain

10×10 cm2
0.6
4.1
4.1
4.1
410
16000

20×20 cm2
0.6
2.1
2.1
4.2
420
4800

30×30 cm2
0.6
2.1
2.1
4.2
420
5200

Table 1. Configuration of the electric field of each gap. ED denotes the electric field in drift gap,
ET 1 is the transfer gap near top, ET 2 is the transfer gap near the readout plane and EI
is the induction gap.

2.5 Position resolution and efficiency
The position resolution with 350 µm pitch and 700 µm pitch readout are shown in Figure 3. The
strip pitch of all the readout board is 350 µm, but two strips are collected up and 700 µm pitch ineffective for 20×20 cm2 and 30×30 cm2 readout boards. The position resolution of ∼100 µm is achievedin the top side (X strips) for 15◦ with 350 µm pitch readout in use of timing information. But it is difficult
with 700 µm pitch.
The efficiency vs incident angle is shown in Figure 4. The efficiency is kept more than 95% up to 15◦
in the top side for both 350 µm and 700 µm pitch readout. But the efficiency of the bottom side is only
less than 80% for 0◦ . The low efficiency is due to the low pulse height in the bottom side. The charge
sum distribution of the top side and the bottom of the 350 µm pitch readout are shown in Figure 5. The

91charge sum of the bottom side is much lower than the top side and signal to noise ratio is worse. The
polyimide between the top side and the bottom side is considered to prevent the detection of charge inthe bottom side. The improvement of the readout board is underway.

600
500
400

700µm top:resolution vs angle
resolution[µm]resolution[µm]350µm top:resolution vs angle

COG
MiddleTiming fit
Timing fix

COG
MiddleTiming fit
Timing fix

900
800
700
600
500

300

400
300

200

200
100

0

100
5

10

15

20

25

30

deg[°]

00resolution[µm]350µm bottom:resolution vs angle
600

400

300

300

200

200

100

100

10

15

15

20

25

30

deg[°]

20

25

30

COG
MiddleTiming fit
Timing fix

500

400

5

10

600

COG
MiddleTiming fit
Timing fix

500

0
0

5

700µm bottom:resolution vs angle

deg[°]

0
0

5

10

15

20

25

30

Fig.3. Position resolution vs incident angle. top left) 350 µm pitch, top side, top right) 700 µm
pitch, top side, bottom left) 350 µm pitch, bottom side, bottom right) 700 µm pitch, bottomside§ 3. Test experiment of GEM tracker: test of a new readout and a performance in a high rateenvironment
3.1 Set up
The set up at GeV-γ beam line is shown in the right of Figure 2. γ beam from STB ring is converted+ −to e eby a converter. Al foil and Cu (2mm or 4mm thickness) are used as the converters. Trigger ismade by a coincidence of two scintillators (3cm×3cm) or four scintillators ((3cm×3cm) ×2+ (2mm×2mm)
×2). The signals from 2mm×2mm scintillators are read out by Multi-Pixel Photon Counters (MPPCs)
whose active area is 1mm×1mm. MPPCs are used to evaluate the rate in case the rate is so high thatphototomultipliers can not count the beam rate correctly.
GEM tracker is sandwiched by three Silicon Strip Detectors (SSDs). Hit position at the GEM
tracker is obtained by interpolating the hit positions at the SSDs. Position resolution of the GEM tracker
is evaluated by a residual distribution between the hit positions determined by the GEM tracker and
SSDs. The signals from GEM tracker are amplified and the waveforms are recorded by FADC modules(RPV-160) for all the 32 ch.
3.2 Analysis
There are multiple hits on SSDs in most events. Valid tracks are found from SSD hits by thefollowing algorithms.
SSDs are called SSD1, SSD2 and SSD3 from upstream. GEM tracker is set between SSD1 and
SSD2. First, the hit positions on SSD1 and SSD2 are connected in all combinations and extrapolated to

92

100

efficiency [%]700µm top: efficiency vs angle

100
90
80
70

COG
MiddleTiming fit
Timing fix

60
50
40

80
70

50

30

20

20

10

10
5

10

15

20

100

80
70

10

15

20

25
30
incident angle [°]

100

COG
MiddleTiming fit
Timing fix

90
80
70

60

60

50

50

40

40

30

30

20

20
10

10
0
0

5

700µm bottom: efficiency vs angle

COG
MiddleTiming fit
Timing fix

90

0
0

25
30
incident angle [°]350µm bottom: efficiency vs angle

COG
MiddleTiming fit
Timing fix

40

30

0
0

efficiency [%]90

60

efficiency [%]efficiency [%]350µm top: efficiency vs angle

5

10

15

20

25
30
incident angle [°]

0
0

5

10

15

20

25
30
incident angle [°]Fig.4. Efficiency vs incident angle.

SSD3.
Second, extrapolated tracks are numbered according to the distance to the nearest hit position on
SSD3. Independent combinations of three hit positions (HitSSD1 , HitSSD2 , HitSSD3 ) are selected as
the track candidates.
Finally, hit positions on the GEM tracker is searched within ±1 mm around the track candidates
in horizontal direction on the readout plane. If there is a hit position of the tracker within ±1 mm,
the residual between the hit position of the tracker and the one determined by SSDs is calculated. The
position resolution is obtained as σ by fitting the residual distribution with Gauss function.
3.3 Results
3.3.1 Charge sum of the bottom side with a new readout board
The amount of charge detected by the bottom side (Y strips) of the readout board is evaluated using
a carbon coated readout board. The strip pitch of the carbon coated readout is 350 µm in both of the
top side and the bottom. The charge sum of the charge cluster is shown in Figure 6. Charge cluster isdefined as a group of strips which are next to next and whose ADC values are over the threshold. Charge
sum is calculated as the sum of ADC values in the charge cluster which contains the strip of the highest
ADC value.
Charge sum concentrates in much lower values in the bottom side than the top side. The amount ofcharge detected by Y strips is not improved by the carbon coated readout.

93

charge sum: Vgem=410V, top side

60
50

charge sum: Vgem=410V, bottom side

h14

h14
Entries
Mean
RMS

9498
201.3
134.5

2500

Entries
Mean
RMS

14992
25.86
50.83

2000
40
1500

30

1000

20

500

10
0
0 100 200 300 400 500 600 700 800

00 100 200 300 400 500 600 700 800
ADC [ch]

ADC [ch]Fig.5. left) Charge sum of the top side. The pitch of the readout board is 350 µm. right) The
bottom side.

charge sum: top side, Vgem=400V

charge sum: bottom side, Vgem=400V
h14

70
60
50

EntriesMean
RMS
χ2 / ndf
Constant
MPV
Sigma

8688
217
150.7
510.9 / 383
383.4 ± 6.4
121 ± 1.1
43.74 ± 0.60

40

1800
1600
1400

h14
Entries
Mean
RMS

6771
47.89
79.6

1200
1000
800

30
20

600
400

10

200

0
0 100 200 300 400 500 600 700 800

00 100200300400500600700800

ADC [ch]

ADC [ch]Fig.6. left) Charge sum of a cluster in the top side (x strips). right) In the bottom side (y strips)
using the carbon coated R/O board.

3.3.2 Gain
The charge sum is compared between a lower rate run (∼ 1.2 × 103 Hz/3 × 3cm2 ) and a higher one(∼ 4.3 × 105 Hz/3 × 3cm2 ) to see the rate dependence of gain. Histograms of the charge sum are shownin Figure 7 and fitted with Landau function. The peak value of the higher rate run is larger than thelower one by 6%.
The charge cluster with the strip of max ADC value may not always be made by converted e+(−)
beam when rate is so high that there are multiple clusters on GEM tracker. A valid method to select acharge cluster generated by beam should be developed as a future plan.
3.3.3 Residual
The residual is obtained as the difference of the hit positions determined by GEM and SSDs following the algorithms described in 3.2. The residual distributions of a lower rate run and a higher one areshown in Figure 8. Tail component is larger in the higher rate run than the lower one. This is considered
to be due to the miss of the track finding because of the multiple hits on SSDs..

94

charge sum: 1.2×103 Hz/3×3 cm2charge sum: 4.3×105 Hz/3×3 cm2
h14__145

EntriesMean
RMS
χ2 / ndf
Constant
MPV
Sigma

40
35
30

8688
217
150.7
693.8 / 726
186.6 ± 3.2
121 ± 1.1
44.4 ± 0.625h14
Entries
11575
Mean
253.3
RMS
184.5
2
χ / ndf
950.1 / 782
Constant
175.7 ± 3.0
MPV128.8 ± 1.4
Sigma
59.86 ± 0.98

50
40
30

20
20

15
10

10

5
0
0 100 200 300 400 500 600 700 800

00 100 200 300 400 500 600 700 800

ADC [ch]

ADC [ch]Fig.7. left) Charge sum of the run in which the counting rate is 1.2×103 Hz/3×3 cm2 . right) The
counting rate is 4.3×105 Hz/3×3 cm2 .

residual: 1.2×10 Hz/3×3 cm2
3residual: 4.3×105 Hz/3×3 cm2

h_single_good
140

EntriesMean

120-0.006452

RMS

0.4078

χ2 / ndf

15.65 / 16

Constant

100

3555

127 ± 4.2

Mean

0.0193 ± 0.0060

Sigma

0.176 ± 0.009

h_single_good

420

Entries

400

24591

Mean

-0.019780.5466

RMS

380
360
340

χ2 / ndf

43.17 / 35

Constant

368.5 ± 4.7

Mean-0.03967 ± 0.01637

Sigma

0.7069 ± 0.0473

320

80

300
60
280
260

40

240
20
220
-1 -0.8 -0.6 -0.4 -0.20

0.2 0.4 0.6 0.8 1
GEM-Si [mm]-1 -0.8 -0.6 -0.4 -0.20

0.2 0.4 0.6 0.8 1
GEM-Si [mm]Fig.8. left) Residual distribution of the run in which the counting rate is 1.2×103 Hz/3×3 cm2 .
right) The counting rate is 4.3×105 Hz/3×3 cm2 .

§ 4. Test experiment of HBD
4.1 The Experimental setup

light baffle

Scintillators

Scintillators

CsI-GEM
HBD prototype
chamber

1x1 cm1x1 cm3x3 cm1x1 cmCherenkov radiation

e+

50 cm

Fig.9. Experimental setup

The Figure 9 displays the experimental setup. The prototype chamber is made of stainless steel
and has a radiator (CF4 gas) with the length of 50 cm. CsI-GEM is placed on the bottom of the chamber.

95
The size of the GEM is 10 cm × 10 cm. The readout pad has the size of 5 cm × 5 cm and consists of
5 × 5 pads. The diameter of the Cherenkov blob is about 3.4 cm. The prototype was sandwiched byfour trigger scintillators. The positron beams were restricted by the scintillators so that the cherenkov
blob was within the readout area. A light baffle was prepared as in the figure. Therefore, the differenceof the charge distributions with and without the baffle indicates successful observation of Cherenkov
radiation. The momentum of the positron beam was 670 MeV.
The oxygen and water contamination should be kept at ppm level since they absorb ultraviolet lightof interest. The chamber was operated with CF4 at the flow rate of about 1.5 L/min. The oxygen was
about 0.4 ppm and the water contamination was about 3 ppm. The contamination is expected to absorb
less than 5% of the Cherenkov radiation.
4.2 Results
Figure 10 displays the charge distributions obtained with and without the baffle. The difference
clearly indicates that we successfully observed Cherenkov radiation from the positron beam. The number of photoelectrons was about 10 and was less than what we expected. A study is going on to under-a.u.

stand the results.
0.12

Baffle ON

0.1(residual dE/dx only)
0.08
0.06

Baffle OFF
0.04(Cherenkov+ residual dE/dx)

0.02

-10

0

10

20

30

40

50

PhotoelectronsFig.10. Charge distribution§ 5. Conclusions
Large size GEM foils of 20×20 and 30×30 cm2 are newly developed and tested. The gain is relatively
lower than 10×10 cm2 GEM, but the position resolution of 100 µm is achieved for 0◦ beam with 700 µm
pitch readout. 10×10 cm2 GEM is tested with 350 µm pitch readout. The obtained results are summed
up in Table 2. The pitch of the readout strips should be 350 µm to achieve the position resolution of 100µm for 15◦ inclined particles.
The carbon coated readout board is tested for the charge balance between the top side and thebottom, but the charge amount detected by the bottom side is still much lower than the top. New typesof the readout boards are to be developed. There are two ideas. One has thinner polyimide between the
top side and the bottom, 12.5 µm thickness. The other type electrically connects the top side and thebottom by through holes.

96

strip pitch and direction
350 µm-X
700 µm-X
350 µm-Y
700 µm-Y

COG
77
79
134
175

0◦
Middle
122
184
159
257

15◦ 30◦timing fix
105 127
166 235
182
341

Table 2. Position resolution with 350 µm and 700 µm pitch readout. The unit is µm. The firstrow shows the incident angle and analysis method.

Gain and residual are evaluated in a high rate run, but there are difficulties in finding tracks ofbeam because of the multiplicity of SSD hits. Some solution is needed to find correct tracks, for example,
taking the timing information of the SSD signals or increasing the number of SSD layers.
As for HBD, Cherenkov radiation is successfully observed. The analysis about quantum efficiencyof the photocathode is on-going.

Acknowledgment
The authors would like to appreciate Prof. H. Shimizu, Dr. T. Ishikawa, Dr. H. Yamazaki and other
LNS staff for their great support. Fortunately, we could escape from the affected area safely and quickly
by the help of the ELPH staff. We sincerely hope Tohoku University and ELPH recover from the damageof the earthquake.

References[1]

T. Hatsuda and T. Kunihiro: Phys. Rep. 247 (1994) 221.

[2]

http://j-parc.jp/NuclPart/pac_0606/pdf/p16-Yokkaichi_2.pdf[3]

F. Sauli, Nucl. Instr. and Meth. A386 (1997) 531.

[4]

B. Ketzer et al.: Nucl. Instrum. Meth A 535 (2004) 314.

[5]

Y. S. Watanabe et al.: Research Report of Laboratory of Nuclear Science, Tohoku Univeristy Vol.
43(2010), LNS experiment: #2657[6]

A. Kozolov et al.: Nucl. Instr. and Meth. A523 (2004) 345.

[7]

S.F. Biagi: Nucl. Instrum. Meth A 421 (1999) 234.

[8]

S. Bachmann et al.: Nucl. Instrum. Meth A 438 (1999) 376-408.

ELPH Annual Report 2010, Tohoku University Vol. 1

97(ELPH Experiment : #2725)

Developments of Time Projection Tracking Chamber with
Gating Functionality
Susumu SATO1 , Hiroyuki SAKO1 , Hitoshi SUGIMURA2,1 , Ryuta KIUCHI3,1 ,Satoshi ADACHI2,1 , Kyoichiro OZAWA4,1∗ , Kiyoshi TANIDA3,1 ,Joo CHANG-WOO3 , Koji MIWA5 , and KenIchi IMAI1
1

Advanced Science Research Center, JAEA, Tokai Ibaraki, 319-1195
2
3Seoul National University, Seoul, 151-747 Korea
45

Kyoto University, Kyoto, 606-8502

University of Tokyo, Tokyo, 113-0033

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

A time projection tracking chamber with gating functionality has been developed for higher beam
intensity to study exotic hadrons or rare resonances. Some basic studies are performed with electron(and positron) tracks from 105 to 107 [cps] at the ELPH facility.

§ 1. Introduction
It is required for search of exotic particles or hadronic rare resonances with strangeness, for example
H-dibaryon [1] or K-pp resonance, to use as high intensity meson beam (kaon or pion beam) as tracking
detectors can handle. And it is also required to track all the engaged particles (incoming, outgoing
scattering, and outgoing decayed particles) in three dimensional coordinates. The three dimensional
tracking chamber (Time Projection Chamber, known as TPC) which has good tracking capability in highbeam rate condition (aiming up to 107 particles per second) is therefore being developed. To achieve
such capability, we adopt gating functionality with gating wires at the bottom of tracking chamber.
Then ionization electrons are coming drifted, and then only during the gate-opened period the electrons
are amplified at GEM (gas electron multiplier) sheets located after the gating wires. In the future, it isplaned to test such gating functionality at the GEM itself without the gating wires.

§ 2. Time Projection Tracking Chamber, TPC
We have made the time projection chamber with three layers of GEM sheets for amplification ofionized electrons. Figure 1 shows the photo of the chamber. Forty layers of field wire are implemented
with HV breeding resistance (1M ohm) in each gap. And at the bottom of the field wires and just above
the top layer of GEM sheet, there is a plane of gating wires. Unless a trigger signal opens the gate,
the gating wires provide positively and negatively deviated voltage (nominally ± 150 V) from the fieldpotential so that drifting electrons can be absorbed before amplification. Those electrons which pass∗

Present address: KEK, Tsukuba Ibaraki, 305-0801

98ଢǒƔƳ્ᩓྵᝋƸƳƘŴǛМဇƠŴƷᩓ‫ן‬ǛኖᲭᲰᲪ ǇưɥƛǔƜƱƕưƖƨŵ
ǲǤȳƸ10 ឬƑǛᢋ঺ŵ

Fig.2. Amplification gains in GEM [2].
Fig.1. Photo of the TPC detector with GEM
amplifier at the bottom. (Outer gas
chamber is taken off in this picture.)through the gate plane are traveling through tree GEM planes (50 µm thickness, separated in 2 mmwith each other, and made by SHiMTEK corp.). The GEM gives electron amplification with respect tothe applied high voltage between its top and bottom face. Figure 2 shows the amplification gains when
P10 gas (Ar : CH4 = 90:10) is used. Over 104 times of amplification is provided by some 360 V for eachlayer.

§ 3. Experimental Test
We have performed experimental test of the TPC chambers at the ELPH facility from January 24th
to 28th , 2011. Electron (and positron) beam with intensity of 105 to 107 [cps] are irradiated on thechamber. Scintillation trigger counters (2 mm square in cross section) are located both just upstream
and downstream of the TPC chambers so that only a certain configuration of electron tracks can beselected. Figure 3 shows track hit pattern for accumulated tracks. We have four kinds of readout pad
widths (2, 3, 4, and 6 mm) with length of 10 mm, and the figure is for the case of 4 mm pads.
We have evaluated residual distribution of hit positions with respect to the reconstructed track.
Figure 4 shows the distribution for relatively lower beam intensity of some 105 [cps]. Note that any
magnetic field (to minimize drifting electrons diverged) had not been applied. Nominal measured residuals are some 600 µm for 105 [cps], and some 1400 µm for 107 [cps] [2] where we thought the effect ofelectric fields made by a massive amount of charged particles came in [3]. Tracking efficiency is someȈȩȃǭȳǰƴǑǔസࠀЎࠋ
99

Fig.3. Track hit pattern (for accumulated
tracks) [2].

Fig.4. Residual distribution from tracks [2].

99 % and some 92 %, respectively. We have tested also Silicon Strip Detector (SSD) and it has time
resolution of 3.4 [ns] for higher beam intensity (107 [cps]).

᳧§ 4. Outlook
We planed to improve high voltage input of the TPC chamber for heightening the maximum voltageof the drift field, and to improve gating field for minimizing radiative noises from pulsing gates. And
then another performance test with hadron beam is planned in the end of this year, in cooperate with
the SSD detectors and with scintillation fiber tracking detectors.

Acknowledgment
This experiment is performed with excellent quality of beam provided by great supports from theaccelerator group of ELPH, Tohoku university.

References[1]

J.K.Ahn, K.Imai et al.: Letter of Intent at J-PARC PAC in 2011 Jul. ”Search for H-Dibaryon
with a Large Acceptance Hyperon Spectrometer”, KEK J-PARC-PAC2011-03 (archived at http://j-parc.jp/jhf-np/pac 1107/pdf/KEK J-PARC-PAC2011-03.pdf )[2]

H.Sugimura: presented at JPS meeting, Hirosaki, 2011 Sep.

[3]

H.J.Hilke, Rep. Prog. Phys. 73 (2010) 116201.

ELPH Annual Report 2010, Tohoku University Vol. 1

101(ELPH Experiment : #2727)

Development of aerogel cherenkov counter for J-PARC P36
experiment
Akihisa Toyoda1 , Yoichi Igarashi1 , Jun Imazato1 , Aine Kobayashi4 ,Suguru Shimizu3 , Keito Horie3 , Hirohito Yamazaki2 , and Keisuke Yoshihara4
1
2

KEK IPNS, Tsukuba, 305-0801

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

Osaka University, Toyonaka, 560-0043
4

University of Tokyo, Tokyo, 113-0033

In this experiment, we measured detection efficiency of an aerogel cherenkov (AC) counter dedicatedto J-PARC P36 experiment which is now accepted as J-PARC E36 experiment. This experiment requests
efficiency of the AC counter to detect decay electrons as high as 99.9 %. Due to lack of photon number,we cannot achieve this efficiency, but we successfully reproduced the efficiency by using Monte Carlosimulation within uncertainty of 5 % or less.

§ 1. Introduction
The J-PARC E36 experiment aims to determine the decay ratio of Γe /Γµ (Γe is the decay rate of
K + → e+ ν, Γµ is the decay rate of K + → µ+ ν) with uncertainty as low as 0.1 %. One of the mostimportant challenge of this experiment is separation of decay positron whose momentum is 247 MeV/cand decay muon whose momentum is 236 MeV/c. For this purpose, we plan to use conbination of the
TOF technique and an aerogel cherenkov (AC) counter. The following points are important for the AC
counter.
• Number of decay muons is about 10000 times larger than that of decay positrons, thus it should
be ensured that the AC counter do not respond to muons at the level of 100 ppb or less. For thispurpose, refractive index (n) of the aerogel should be less than 1.095.
• For the uncertainty less than 0.1 %, decay positron efficiency of the AC counter should be larger
than 99.9 % and uniform for incident position and angle.
We produced a prototype AC counter and measured detection efficiency of the counter with several
combinations of the position and angle.

§ 2. Experimental setup
Figure 1 shows layout of the E36 experiment. The AC counters are located between TOF1 counters
and CsI(Tl) counters, and divided into 6 pieces. K+ beam stops in target and decay positron hits the
AC counter. Generated cherenkov photons inside the aerogel are reflected by the sawtooth mirror andinner flat mirror, and go into the winstone cone. The winstone cone gathers the cherenkov photons and102

Layout of E36 experiment

1 piece of Aerogel Cherenkov counter
winstonecone

Z

Sawtooth mirror

Y

X

air

Ä beamAerogelAecherenkov

PMT

Decay electron
Dec
ectronnAlminized Mylar0

K+ BeamBeam stopping distribution

5 cm

TargetFig.1. Left figure shows J-PARC E36 setup at around the target from beam direction view. Right
figure is for one piece of the Aerogel Cherenkov counter. X direction is kaon beam direction, and Z direction is radial direction.

transports them to a photomultiplier (PMT). Due to space limitation and CsI(Tl) γ detection, cherenkov
photons should be gathered far from the central region, thus position dependence of the efficiency would
be the most important issue. To recover the low efficiency at around central region, we have a plan touse sawtooth mirror as shown in Figure 1. Parameters of the AC counter such as a counter thickness,
an aerogel thickness, a counter length, winstone cone shape, sawtooth mirror shape are optimized byusing Monte Carlo simulation to maximize the detection efficiency. This simulation includes all effects
expected in this counter such as Rayleigh scattering, reflection, refraction, absorption, and so on. The
prototype AC counter used standard aerogel material with n of 1.05, and transmission length (TL) of 20mm. We used the Hamamatsu R2256-02 PMT which has quartz window to maximize detection efficiency.
The winstone cone and sawtooth mirror were Al coated, and other surface was covered by the Al mylar.

Fig.2. ELPH 2727 experiment setup.

Table 1. Data number assignment
Data #
Angle
Position

1
0.0
0.0

2
0.0
−50.0

3
0.0
−100.0

4
−44.4
−71.4

5
44.4
0.0

6
44.4
35.7

7
63.0
0.0

8
63.0
22.7

9
63.0
45.4

To estimate dependence of the detection efficiency on incident angle and position, we prepared test

103

experiment setup as shown in Figure 2. We can change incident position by using X stage and incident
angle by using rotation stage. Vertical angle can be changed by using Z stage and Y angle stage. One data
set is composed of nine data points as shown in Table 1 and Figure 3. ELPH positron beam momentumis chosen to be 458 MeV/c (TAGX = 230 A) to increase beam intensity. Effect of momentum difference
between real 247 MeV/c and the 458 MeV/c is estimated to be negligible due to small β difference. The
positron beam is almost parallel, and its size is restricted to be 12 mm x 12 mm by coincidence of a fiber
scintillator detector. These conditions are included in the simulation program.

Fig.3. Data set for combination of angle and position of positron beam track. Number indicateddata number listed in Table 1§ 3. Experimental data
In this test experiment, we take data set on the following conditions.
• Use a flat mirror instead of the sawtooth mirror as a main reflector to check the sawtooth mirror
performance.
• Use the sawtooth mirror.
• Use the sawtooth mirror with slant y injection. This data set is to check dependence of the detection
efficiency on the Y angle indicated in right figure of Figure 3.
• Use the sawtooth mirror with left-right inverse injection. In this case, positron beam is injectedwith inversed angle and position. This data set is to check systematic uncertainty of the detection
efficiency possibly coming from the PMT performance difference and other things.
3.1 Flat mirror case
Figure 4 shows comparison between result of the test exeperiment and simulation result in the flat
mirror case. The experimental data agree well with the calculation except for the data number 9. For
the data number 9, positron beam directly hits the PMT. The direct hit will create cherenkov photons in
the PMT window, which is not included in the simulation. This is one of the possibilities to explain theabove difference. This figure clearly shows existence of position and angle dependence of the detection
efficiency. This figure also indicates that it is the most difficult to get high efficiency for perpendicularand central incidence corresponding to data number 1 as expected.

104

Fig.4. Dependence of detection efficiency on data number in the case of the flat mirror. Blue line
is for experimental data, and green line is for simulation result.

3.2 Sawtooth mirror case

Fig.5. Dependence of detection efficiency on data number in the case of the sawtooth mirror.
Blue line is for experimental data, and green line is for simulation result.

Figure 5 shows comparison between result of the test exeperiment and simulation result in thesawtooth mirror case. The experimental data agree well with the calculation except for the data number
9. Data number 9 difference probably comes from the same reason described in subsection 3.1. Performance for perpendicular and central incidence (data number 1) is increased by 5 % or so, but it is notenough to achieve the 99.9 % goal. To achieve the goal, more efficient mirror configuration and aerogelmaterial are necessary.
3.3 Sawtooth mirror and slant y injection case
Figure 6 shows comparison between result of the test exeperiment and simulation result in thesawtooth mirror and slant y (25.2 degree) injection case. The experimental data agree well with thecalculation except for the data number 1. One of the important points is that the simulation reproduces

105

Fig.6. Dependence of detection efficiency on data number in the case of the sawtooth mirror
and slant y injection. Blue line is for experimental data, and green line is for simulation
resultdata number 9 well. In this case, positron does not hit the PMT directly, thus it indicated that thedata number 9 difference in subsection 3.1, 3.2 comes from the beam direct hit effect. Relatively large
difference (about 20 %) of the data number 1 is still under investigation.
3.4 Sawtooth mirror and left-right inverse caseFig.7. Dependence of detection efficiency on data number in the case of the sawtooth mirror
and left-right inverse injection. Blue line is for experimental data with left-right inverse
injection, green line is for experimental data with normal injection, and green line is for
simulation result with left-right inverse injection.

Figure 7 shows comparison between result of the test exeperiment and simulation result in thesawtooth mirror and left-right inverse injection case. The left-right inversion data agree well with thenormal data except for data number 4. The data number 4 difference is now under investigation, probably comes from some defects of aerogel material or mirror coating.

106§ 4. Summary
We could not achieve the goal detection efficiency of 99.9 % with first prototype AC counter. However
we successfully reproduced dependence of the efficiency on incident angle and position by using Monte
Carlo simulation within uncertainty of 5 % or less except for small data points.

Acknowledgment
We acknowledge all the ELPH staffs who arranged our beam time, supported us to perform thisexperiment, and delivered stable positron beam.

ELPH Annual Report 2010, Tohoku University Vol. 1

107(ELPH Experiment : #2740)

Focusing the positron beam for testing detectors by triple
quadrupole magnets RFQ
Y. Tsuchikawa1 , T. Ishikawa1 , H. Fujimura1 , R. Hashimoto1 , T. Muto1 ,A. Nakamura1 , Y. Shibasaki1 , H. Shimizu1 , K. Suzuki1 , and H. Yamazaki1
1Research Center for Electron Photon Science (ELPH), Tohoku University, Sendai 982-0826,
Japan

Triple quadrupole magnet system RFQ was installed in the positron beamline for testing detectors
in GeV-γ experimental hall to focus the positron beams. The commissioning of RFQ was carried out in
December 2010. In this report, we discuss the experimentally determined optimum magnetic field gradients and the positron beam profiles with and without RFQ operation for different positron momenta.

§ 1. Introduction
The positron beamline for testing detectors [1] in GeV-γ experimental hall uses the momentumanalyzed pair-created positrons with a bending magnet RTAGX [2]. The bremsstrahlung photons are
generated by inserting a carbon thread into the primary circulating electron beam in the STretcher
Booster (STB) ring [3]. The photons irradiates a thin metal plate so that the pair creation takes place.
Since the gap of RTAGX is short and its magnetic field is uniform and strong, a positron beam with asmall momentum spread is provided at fixed angle (−30◦ ), for example, the momentum spread is about
0.5% for 800 MeV positrons [4]. The intensity of the positron beam is about 3 kHz in the normal operation
where a gold plate with a thickness of 20 µm is used for the pair creation and bremsstrahlung photons
are generated during 7 s in every 14 s cycle. The positron beam is very useful for testing detectors,
and many groups coming from Particle Physics, Nuclear Physics, and so on, uses the beam for testing
calorimeters and tracking devices.
More intense beam is preferred by some experimental groups, namely the larger number of positronsa second in a unit area is desired. Utilizing the thicker metal plate and/or the shorter period for the generation of the bremsstrahlung photons make the higher intensity. The 1 MHz intensity was achieved at
maximum in May 2008 for testing MWPC’s and MWDC’s for the J-PARC beamline [5] under the condition that about 0.5 radiation length copper plate was used and the photon generation period was 20 ms.
The number of circulating electrons in STB ring is limited, higher intensity makes the duty factor small.
To obtain the higher intensity in a unit area without shortening the photon generation period, triple
quadrupole magnets (QF-QD-QF) has been introduced to focus the positron beam for testing detectors.

108§ 2. Triple quadrupole magnets RFQ
The triple quadrupole magnets were given by High Energy Accelerator Research Organization(KEK), and which was originally used for the injector linac of the photon factory (PF) at KEK. The
pole lengths of the magnets are 100, 200, and 100 mm from the upstream, and both the pole gaps are
110 mm. The magnetic field gradient of 20 T/m is obtained for the maximum coil current of 30 A. To
focus the positron beam, we placed the triple quadrupole magnet at 340 mm downstream of the exit
Pb aperture in the end of October 2010. We also laid two power suppliers below the magnets with aconstant voltage of 5 V and the maximum current of 35 A. We call the triple quadrupole magnets RFQ
which stands for recycled focusing quadrupole magnet. Fig. 1 shows the RFQ placed at the positron
beamline for testing detectors. Among three magnets in RFQ, outside two magnets are operated with apower supplier, and central one is operate with the other one, and RFQ have a QF-QD-QF cell.

Fig.1. Triple quadrupole magnet RFQ placed at the positron beamline for testing detectors.
At first, we calculated the intensity of the positron beam [6] in the central area with given magnetic
field gradient
)
(

∂By
′


, and
 BQF =( ∂x )QF
∂By

′

=
.
 BQD
∂x QD

(1)

The initial positrons were generated at the entrance of RFQ with a GEANT3 based Monte Carlo simulation where the profile of the bremsstrahlung photon and the magnetic field map of RTAGX were taken
into account. The final positron profiles were obtained by using the transfer matrices


1 L

M0 (L) = 
0 1
for a drift space with a length of L,


√
√
1
√ sin KL 
cos KLK √MF (L) =  √
√cos KL− K sin KL

(2)

(3)

109

for focusing by a magnetic field gradient with a length of L, and


√
√
1
√ sinh KL 
 cosh KL
K √MD (L) =  √√K sinh KL
cosh KL(4)for defocusing. Here, K is express by
K=

q ∂By
p ∂x

(5)

with the magnetic field gradient ∂By /∂x = ∂Bx /∂y and the positron momentum p. No fringing mag√netic field was simply assumed in this calculation. As a barometer for focusing, we adopted 1/ σx σywhere σx and σy denote the widths of the x and y distributions at 2.8 m downstream of the exit of RFQ√′′
and BQD
atwhere tested detectors are thought to be placed. Fig. 2 shows 1/ σx σy as a function of BQF
2.8 m downstream of the exit of RFQ.
20

TAGX: 25 A

20

18

18

16

16
14

12

10

-2

10

B'QF (T/m)

B'QF (T/m)

14

12

6

4

4

5

10
15
B'QD (T/m)

20

10

5

TAGX: 150 A
10

18

2

-3

-1

-2

8

6
2

20

10
15
B'QD (T/m)

20

10

-3

TAGX: 230 A

18
16

14

14

12

B'QF (T/m)

16
B'QF (T/m)

10

10

8

20

TAGX: 50 A

10

-1

12

10

10

8

-2

10
8

6

6

4

4

2
5

10
15
B'QD (T/m)

20

10

-3

2
5

10
15
B'QD (T/m)

20

√
′
′
Fig.2. 1/ σx σy as a function of BQF
and BQD
at 2.8 m downstream of the exit of RFQ.
′′′′
The optimum condition is obtained BQF≃ BQD, and the higher BQF
and BQD
is required for thehigher positron momentous. The positron momentum in MeV is roughly twice of RTAGX current in A.
When the RTAGX current is higher than 230 A (the positron momentum is higher than 460 MeV/c),focusing positron beam requires to exceed the maximum coil currents for three magnets.
′′§ 3. Search for the optimum BQF
and BQD′′
To search for the optimum BQF
and BQD, the positron beam profiles were measured at 2.76 m′′
downstream of the exit of RFQ with given BQF
and BQD
from 15th to 17th December in 2010 [7]. A110beam profile monitor (BPM) was used to determine the position of the incident positrons. BPM consistsof two layers of scintillating fiber (SciFi) hodoscopes. Each hodoscope consists of 16 SciFi’s with a crosssection of 3 × 3 mm2 . The upstream and downstream layers determine the y and x positions of theincident positron, respectively. The widths σx and σy were obtained by fitting Gaussian to the x and y′′distributions. Fig. 3 shows the typical obtained x and y distributions with given BQF
and BQD
togetherwith the fitted Gaussians.

RTAGX 25 A (run15898)
100

2000

RTAGX 50 A (run15812)
2000

50

1000

1000

50
0

-20

0

20

0

-20

0

20

0

-20

RTAGX 75 A (run15890)

Counts / 3 mm

1000
0

0

20

0

20

1000
-20

0

2000

RTAGX 150 A (run15757)
2000

1000

1000
-20

0

20

0

-20

0

2000
1000

2000
-20

0

20

0

20

0

20

0

-20

0

20

0

20

x (mm)

0

0

-20

0

20

2000

0

-20

0

20

1000
-20

0

-20

0

0

-20

0

20

RTAGX 350 A (run15873)
4000

20

0

2000
-20

0

20

0

-20

0

20

RTAGX 450 A (run15851)

2000
-20

20

RTAGX 230 A (run15820)

RTAGX 400 A (run15863)
4000
1000

0

1000

RTAGX 300 A (run15841)
4000

0

-20

1000

2000
0

0

RTAGX 100 A (run15784)

1000
-20

0

20

y (mm)

2000

5000

1000

2500

0

-20

0

20

x (mm)

0

-20

0

20

y (mm)′′
Fig.3. Typical obtained x and y distributions with given BQF
and BQD. The solid curves show
the fitted Gaussians to obtained the widths of the distributions.

′′
We search for the combination of BQF
and BQD
as an optimum, giving the minimum beam size
′
′
′
′
′
′
′
σx σy . Fig. 4 shows the σx σy as a function of BQF
, BQD
, BQF
+ BQD
, and BQF
− BQD
. To determine BQF′
and BQD
for the minimum beam size, The σx σy as a function of the magnetic field gradient is fitted with

2 dimensional polynomial function. The axis of the function gives the optimum magnetic field gradient.
When the optimum gradient apparently exceeds 20 T/m, the optimum gradient is fixed at 20 T/m. As for
the RTAGX current of 25 A, the beam sizes for given gradients do not differ so much. Thus the maximum
counting rate of BPM is assumed to give the optimum magnetic field gradients. Table. 1 summarizes the

111
′
′
optimum magnetic field gradient BQF
and BQD
for different RTAGX current.

50 A, QD=6.1

1000
800
600

4

5 6 7
QF (T/m)

8

600

4

100 A, QD=10.9 240

5 6 7
QD (T/m)

8200

σx σy (mm )

200

10 11
QF (T/m)

12

9

230 A, QD=20.0

10 11 12 13
QD (T/m)

100

500
10 15 20 25
Q+ (T/m)

0

100
10

15
20
QF (T/m)

100

110

100

100

90

16 18 20
QF (T/m)

16 18 20
QD (T/m)

120

350 A, QD=20.0 120

350 A, QF=17.3 140

110

110

120

100
16 18 20
QD (T/m)

450 A, QD=20.0

450 A, QF=15.9

100
10150 A, QF=15.6

200

110

16 18 20
QF (T/m)-5 -2.5 0 2.5 5
Q- (T/m)

150 A, QD=15.6 300

300 A, QD=20.0 120

100

100

5

230 A, QF=20.0 120
200

150

350

200

200
9

1000

300

75 A, Q+=17.0

1500

400

100 A, QF=10.9

220

210

75 A, Q-=0.0

450

800

220

2

50 A, QF=6.1

1000

16 18 20
QF (T/m)

90

400 A, QD=20.0

1520QD (T/m)
300 A, QF=18.0

16 18 20
QD (T/m)
400 A, QF=15.9

120

15
20
QF (T/m)

100
10

15
20
QD (T/m)

150

150

125
100
10

15
20
QF (T/m)

100
10

15
20
QD (T/m)

′
′
′
′
′
′
Fig.4. Beam size σx σy as a function of BQF
, BQD
, BQF
+ BQD
, and BQF
− BQD
. The RTAGX′′′′
current and given magnetic field gradients QF: BQF and QD: BQD , or Q+: BQF
+ BQD
, and
′
′
Q−: BQF − BQD are written in each panel. The solid curves show the fitted 2 dimensional
polynomial functions.

§ 4. Positron beam profile
The optimum magnetic field gradients for RFQ were obtained for RTAGX currents of 25, 50, 75,
100, 150, 230, 300, 350, 400, and 450 A. Therefore, we measured the positron beam profile for these
RTAGX currents at 2.76 m downstream of the exit of RFQ for the comparison with and without the
RFQ operation. Since BPM does not cover the whole of the positron beam spot, the beam profiles forthe same RTAGX current and the same RFQ conditions were measured three or five times by shifting
BPM in x and y directions. The measured intensity of the positron beam in each square determined byx and y BPM fibers is normalized by using the counts of the 81st tagging channel in STB-Tagger II [3]and that of the plastic scintillator placed at the opposite electron beamline (+30◦ ). Fig. 5–7 show thepositron beam profile for the different RTAGX currents. The positron beams were well focused for the112

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

-20
-40

-20

0

20

40

RFQ: ON20
0-20

RFQ: OFF x 10-6

0

20

-20

0

RTAGX: 75A

20

RFQ: ON

-20
-40

-20

0

20

40

RTAGX: 100A RFQ: ON

25
20

0

15
10

-20

20
0
-20

5
-40

-20

0

20

40

x 10-6
70
60
50
40
30
20
10

30
20

x 10-6
35
30
25
20
15
10
5

0

RTAGX: 100A RFQ: OFF x 10-6

x 10-6

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
-40

18
16
14
12
10
8
6
4
2

0

RTAGX: 50A

40

20

-20

-6

x 10

-40

-20

0

20

40

x (mm)
Fig.5. Positron beam profile for the RTAGX currents of 25, 50, 75 and 100 A. The left panels
show the profile obtained when RFQ is turned off, and the right shows the profile for the
optimum RFQ coil currents.

113

RTAGX: 150A RFQ: OFF x 10

-6

RTAGX: 150A RFQ: ON

50
20

40
30

0

20
0

20
-20

10
-40

-20

0

20

40

-40

RTAGX: 230A RFQ: OFF x 100y (mm)

-6

80
70
60
50
40
30
20
10

20

-20
-40

-20

0

20

-20

0
-20
-40

-20

0

20

150

0

100
-20

50
-20

0

20

40

RTAGX: 300A RFQ: ON
20
0
-20
-40

RTAGX: 350A RFQ: OFF x 10-6

-20

0

20

40

RTAGX: 350A RFQ: ON

100

20

60
0

0
40

-20

20
-40

-20

0

20

40

x 10-6
200

-40

80

40

160
140
120
100
80
60
40
20
0

250

40

20

20

20

RTAGX: 300A RFQ: OFF x 10-6
200

RTAGX: 230A RFQ: ON

40

90
80
70
60
50
40
30
20
10

-20

-6

x 10

-20

0

-40

-20

0

20

40

0

x 10-6
225
200
175
150
125
100
75
50
25
0

x 10-6
200
175
150
125
100
75
50
25
0

x (mm)
Fig.6. Positron beam profile for the RTAGX currents of 150, 230, 300 and 350 A. The left panels
show the profile obtained when RFQ is turned off, and the right shows the profile for the
optimum RFQ coil currents. The white boxes in the right panels indicate the measured
profile area.

114

′
′
Table 1. Optimum magnetic field gradient BQF
and BQD(T/m) for different RTAGX current. As
for the RTAGX current of 25 A, the maximum counting rate of BPM is assumed to givethe optimum magnetic field gradients.

′
BQF
′
BQD

25 A 50 A 75 A
100 A
150 A 230 A 300 A
350 A
400 A
450 A
4.4 6.41(7) 8.10 10.94(165) 15.73(2) 21.36 19.08(29) 18.92(28) 17.61(16) 17.38(17)3.7 5.83(0) 7.92 10.71(5) 15.62(2) 20.35
20.0
20.0
20.0
20.0

RTAGX: 400A RFQ: OFF x 10
200

y (mm)

-20
-40

-20

0

20

40

90
80
70
60
50
40
30
20
10
0

RTAGX: 450A RFQ: OFF x 10
20
0
-20
-40

-20

0

20

40

-6

RTAGX: 400A RFQ: ON
20
0
-20
-40

-6

90
80
70
60
50
40
30
20
10
0

-20

0

20

40

RTAGX: 450A RFQ: ON
20
0
-20
-40

-20

0

20

40

-6

x 10

180
160
140
120
100
80
60
40
20
0

x 10-6
160
140
120
100
80
60
40
20
0

x (mm)
Fig.7. Positron beam profile for the RTAGX currents of 400 and 450 A. The left panels show the
profile obtained when RFQ is turned off, and the right shows the profile for the optimum
RFQ coil currents. The white boxes in the right panels indicate the measured profile
area.
optimum RFQ coil currents for every current. When the RTAGX current is higher than 230 A, focusing
in x direction is worse as compared with that in y direction.
The 6 × 6 mm2 area giving the maximum intensity were searched for with and without the RFQ
operation. Table. 2 lists the maximum intensities in a square 6 × 6 mm2 for different RTAGX currents.

§ 5. Summary
RFQ has been installed in the positron beamline for testing detectors in GeV-γ experimental hall
to focus the positron beams. By operating RFQ, three times intense beams can be provided in a central
6 × 6 mm2 area at maximum for the RTAGX current of 230 A, which corresponds roughly to the positron
momentum of 460 MeV/c.

115

Table 2. Maximum intensity in a square 6 × 6 mm2 with and without the RFQ operation. The
IRFQ and I0 stand for the maximum intensity with and without the RFQ operation, andwhich are given by dividing the number of positron counts in a square 6 × 6 mm2 by thatof 81st tagging channel counts.
RTAGX
25 A
50 A
75 A
100 A
150 A

IRFQ (10−6 )
10.03
56.16
149.75298.11653.68I0 (10−6 )
5.89
33.15
76.54
131.96228.11

IRFQ /I0
1.70
1.69
1.96
2.26
2.87

RTAGX
230 A
300 A
350 A
400 A
450 A

IRFQ (10−6 )1062.97
883.01780.22725.45681.85I0 (10−6 )342.00382.82394.80379.60365.00

IRFQ /I0
3.11
2.31
1.98
1.91
1.87

Acknowledgment
This research was supported in part by High Energy Accelerator Research Organization (KEK)for the corporations between Tohoku University and KEK. The authors thank Prof. J. Haba (Detector
Technology Project, KEK) for giving us the opportunity to introduce focusing elements to our positron
beamline for testing detectors.

References[1]

T. Ishikawa et al.: Research Report of LNS 40, Tohoku University, 6 (2008).

[2]

T. Ishikawa et al.: Research Report of LNS 39, Tohoku University, 39 (2007).

[3]

T. Ishikawa: Nucl. Instr. and Meth. A 622, 1 (2010).

[4]

T. Ishikawa: Internal GeV-γ Analysis Note No. 43 (2007);
T. Ishikawa: Internal GeV-γ Analysis Note No. 78 (2008).

[5]

T. Takahashi: Nucl. Phys. A 835, 88 (2010).

[6]

T. Ishikawa: Internal GeV-γ Analysis Note No. 194E (2010).

[7]

Y. Tsuchikawa: Internal GeV-γ Analysis Note No. 219E (2011).

ELPH Annual Report 2010, Tohoku University Vol. 1

117

Comparison of the light outputs between BSO and BGO
crystals
T. Ishikawa1 , H. Fujimura1 , S. Kaida1 , A. Nakamura1 , H. Shimizu1 ,S. Takahashi1 , Y. Tsuchikawa1 , and H. Yamazaki1
1Research Center for Electron Photon Science (ELPH), Tohoku University, Sendai 982-0826,
Japan

BSO is one of the candidates for the detector element of a new electromagnetic (EM) calorimeter
which we plan to construct at ELPH for meson photoproduction experiments. We have continued toinvestigate the basic scintillation characteristics of BSO crystals with and without the beam. In thisreport, the comparison of the light outputs between BSO and BGO crystals is made.

§ 1. Introduction
Study of exotic hadrons has been a subject of great interest in nuclear phyiscs. A nucleon resonanceN ∗ (1670) is a candidate of an adjacent member to Θ+ among the anti-decuplet pentaquark baryons [1].
The excited resonances including the relevant resonance are studied via η photoproduction on the neutron by using an electromagnetic (EM) calorimeter complex FOREST [2] in the GeV-γ experimental hallat ELPH. The energy of photons to be detected ranges from several ten MeV to a few GeV in the experiments conducted at ELPH. We plan to construct a new EM calorimeter appropriate for photon detectionin that energy range for the next generation experiments.
The energy resolution is generally the most important property for EM calorimeters. The detector
element of the calorimeters is usually required to be a high density substance having a short radiation
length for compactness. In addition, it is required to have no hygroscopicity for easy treatment. Bismuth
silicate (Bi4 Si3 O12 : BSO) is one of the candidates for the detector element of an EM calorimeter. BSO is
produced by replacing Ge in Bi4 Ge3 O12 (BGO) [3] with Si, and it has been developed as an alternative
to BGO. The characteristics of BSO and BGO are summarized in Table 1. The decay time of BSO(∼ 100 ns) is much shorter than that of BGO (∼ 300 ns), while BSO resembles BGO in physical andoptical properties. The shorter decay time is the better for EM calorimeters since it is desired in highcounting rate experiments. Light output of BSO is about one fifth of that of BGO but is good enough forhigh resolution measurements of photons/electrons in the intermediate energy region from 100 MeV toa few GeV. BSO would be the detector element of choice for EM calorimeters in this energy region.
We have investigated the properties of the BSO crystals which were produced at Futek Furnace Co.,
Yokohama, Japan [9]. For this purpose, five BSO ingots of 70 mm in diameter were grown by the vertical
Bridgman method up to the length of 300 mm. Five crystals were originally out of the ingots: four
rectangular-parallelepiped crystals with a size of 40 × 40 × 210 mm3 and an additional 40 mm cube. A

118

Table 1. Some physical properties of BSO and of BGO in comparison. Light output is given relative to the light yield of NaI(Tl). The numbers listed here are taken from refs. [4–8] for
BSO and ref. [3] for BGO.
()
3
Density g/cm
Radiation length X0 (mm)Decay time (ns)Peak emission (nm)
Refractive index nLight output
Hygroscopicity

BSO

BGO

6.80
11.5
∼ 100
480
2.06
0.02–0.04
No

7.13
11.2
∼ 300
480
2.15
0.1
No

small crystal is advantageous in some measurements of crystal properties since light attenuation effects
are relatively ignored, compared to a large crystal. We employed for this end a small 17.3 mm cube of
BSO which was cut out of the 40 mm cube after the excitation-emission spectrum measurement [10]. A
16.8 mm BGO cube was also employed for comparison.

§ 2. Experimental setup
The relative light output of BSO to BGO scintillators was measured by comparing the positionsof the photoelectric peak in the energy spectrum of γ rays from a 137 Cs radioactive source. In thismeasurement we used small BSO and BGO cubes, the size of which was normalized to be 1.5X0 . Eachcube was wrapped with Tyvek 1073D paper and optically coupled to a 2-inch photo-multiplier tube (PMT)
Hamamatsu H6410. The optical contact was made with optical grease OKEN6262A (refractive index
n=1.42 at λ ≈ 450 nm). The room temperature was well-controlled to be 19◦ C during the measurement.
It is rather difficult to conduct a precise measurement for the relative light outputs of different
scintillators. Actually it is almost impossible to make absolutely the same experimental conditions for
optical contact, high voltage stability, geomagnetic effects, room temperature and so on, in the light
output measurement. In addition to those, the position of the photoelectric peak in the energy spectrum
slightly changes as time goes on after the high voltage to PMT is turned on. We need to suppress such
fluctuations as come from the small difference of the conditions in the measurement as much as we can.
Two PMT’s of the same type, A and B, are used. At first, the light output of BSO with A and thatof BGO with B are measured simultaneously in the same place with the same data acquisition system.
Then the same measurement is made again but with PMT’s swapped. We assume that the observed
light output signal Y from a PMT is described with a factorized form:
Y (i, j, k) = Li Gj Fk ,(1)

where Li denotes the light output of the crystal, Gj stands for the gain in the PMT, and Fk is a factor
depending on the environment when each measurement is carried out. The observed light output signals

119

for BSO and BGO are given as Y (BSO, A, 1st) = L
BSO GA F1st , Y (BGO, B, 1st) = L
G F ,
BGO

B

(2)

1st

in the first measurement and those for the second become Y (BSO, B, 2nd) = L
BSO GB F2nd , Y (BGO, A, 2nd) = L
G F .
BGO

A

(3)

2nd

A bunch of measurements should be carried out to have the data as a function of the elapsed time after
the high voltage to the PMT’s is turned on. The relative output LBSO /LBGO can be obtained as√
LBSO
Y (BSO, A, 1st) Y (BSO, B, 2nd)=.
LBGO
Y (BGO, B, 1st) Y (BGO, A, 2nd)

(4)

Fig. 1 shows the experimental setup for the comparison of light outputs between BSO and BGO.

1st measurement
BGO FENV 1
BSO

L BGO

L BSO

2nd measurement
BSO FENV 2
BGO

L BSO

L BGO

(PMT1)(PMT2)(PMT1)(PMT2)

Hamamatsu H6410

Hamamatsu H6410

Hamamatsu H6410

Hamamatsu H6410

GPMT 1GPMT 2GPMT 1GPMT 2

Fig.1. Experimental setup for the comparison of light outputs between BSO and BGO. The left
panel shows the first measurement in a bunch, and the right shows the second one.

We measured the charge distribution (energy spectra) of the output signals from the BSO and BGO
crystals in response to γ rays from 137 Cs with a CAMAC based data taking system. The anode signal
from each PMT was split into two equal parts. One part was sent into a LeCroy 2249W ADC module,
and its charge was integrated over a 2.4 µs ADC gate. The other split signal was used to make a trigger
for the data acquisition system and to generate the gate for the ADC module. The decay times of thesecrystals are rather long and the output signal does not form a single pulse in response to a single γ
ray. Therefore, the signal for the trigger was fed into a timing filter amplifier ORTEC 474 with an RC
shaping time of 200 ns, and was converted into a logic signal with a discriminator.
The background events were measured without the 137 Cs source to be subtracted. The pedestal
in each energy spectrum was measured with a 1 kHz clock trigger. Fig. 2 shows the typical energy
spectra for the BSO and BGO crystals. The input signal to ADC was attenuated by about 10 dB for BGO
since the light output of BGO is much higher than that of BSO. The attenuation factor was carefully
investigated by comparing the attenuated waveform with non-attenuated one, by utilizing an digital
phosphor oscilloscope Tektronix DPO4104, and was found to be 0.3155 with an error less than 0.0001.
The centroid µ of the photoelectric peak was obtained by fitting a sum of two Gaussians to the peak
and background components. Fitting was repeated several times in the region [µ − 10σ, µ + 3σ), where120

σ denotes the width of the peak. The obtained energy resolutions (FWHM) for 661.7 keV γ-rays were

300
250
200

S

150
100

Fitting Region

500

BGO

400
300

S

200
100

50
0

600

BSO

PedestalCounts / 10 channel

350

Fitting Region

Counts / 10 channel

Pedestal∼ 10.7% and ∼ 5.3% for BSO and BGO, respectively.

B
0

500

1000

1500

ADC (channel)

2000

0

B
0

500

1000

1500

2000

ADC (channel)

Fig.2. Typical energy spectra (S) for the BSO and BGO crystals in response to γ rays from137
Cs. The signal from BGO to ADC is attenuated by approximately 10 dB. The spectra(B) correspond to the background events triggered without 137 Cs. The pedestal data takenwith a clock trigger are also displayed. The solid lines show a sum of two Gaussians fitted
to the peak and the background components.

§ 3. Relative output of BSO to BGO
The relative light output LBSO /LBGO is now given with pedestal-subtracted centroids of photoelectric peaks µBSO and µBGO ,√µBSO,A,1st µBSO,B,2nd
LBSO= Ratt,LBGOµBGO,B,1st µBGO,A,2nd(5)

where Ratt = 0.3155 is the attenuation factor for the BGO signal. Fig. 3 shows the typical light output
ratio of BSO to BGO obtained as a function of the elapsed time after the high voltage to the PMT’s isturned on. The light output ratio gives a constant value of 0.210 with an error less than 0.001. To reduce
undesirable inconsistency that might come about especially in optical contact of the PMT to the crystals,
we performed four series of measurements. The light output ratio was found to be quite stable in allthese measurements. The details of the analysis for relative outputs are described elsewhere [11].

§ 4. Summary
BSO is one of the candidates for the detector element of a new EM calorimeter which we plan toconstruct at ELPH for the next generation meson photoproduction experiments. The relative output of
BSO to BGO scintillators is measured as one of the basic scintillation characteristics of BSO crystals.
The obtained values is found to be 0.210 with an error less than 0.001.

Ratio of Light Outputs BSO / BGO

121

0.225
0.220
0.215
0.210
0.205
0.200
0.195
0.190

0

10

20

30

40

50

Elapsed Time (min.)Fig.3. Typical light output ratio of BSO to BGO measured as a function of the time elapsed since
the high voltage to the PMT’s is turned on.

Acknowledgment
This work was supported in part by Grant-in-Aid for Scientific Research (B) (17340063) and forSpecially promoted Research (19002003).

References[1]

T. Nakano et al.: Phys. Rev. Lett. 91, 012002 (2003); D. Diakonov, V. Petrov, M. Polyakov: Z. Phys.
A 359, 305 (1997); V. Kuznetsov et al.: Phys. Lett. B 647, 23 (2007); F. Miyahara et al.: Prog. Theor.
Phys. Suppl. 168, 90-96 (2007); H. Shimizu: talk at NSTAR2007; I. Jaegle et al.: Phys. Rev. Lett.
100, 252002 (2008).

[2]

T. Ishikawa et al..: Research Report of LNS 42&43, Tohoku University, 1 (2011).

[3]

M.J. Weber and R.R. Monchamp: J. Appl. Phys. 44 (1973) 5495.

[4]

M. Kobayashi et al..: Nucl. Instr. and Meth. 205 (1983) 133.

[5]

M. Kobayashi et al..: Nucl. Instr. and Meth. A 372 (1996) 45.

[6]

M. Kobayashi et al..: Nucl. Instr. and Meth. A 400 (1997) 392.

[7]

M. Ishii et al..: J. Crystal Growth 205 (1999) 191.

[8]

M. Ishii et al..: Opt. Mater. 19 (2002) 201.

[9]

Futek Furnace website: ⟨http://www.futekfurnace.com/⟩.

[10] T. Ishikawa et al..: Research Report of LNS 42&43, Tohoku University, 176 (2011).
[11] T. Ishikawa: Internal GeV-γ Analysis Note No. 197D (2011).

ELPH Annual Report 2010, Tohoku University Vol. 1

123

Temperature dependence of the light output for BSO
scintillator
S. Takahashi1 , T. Ishikawa1 , H. Fujimura1 , R. Hashimoto1 , S. Kaida1 ,A. Nakamura1 , H. Shimizu1 , K. Suzuki1 , and H. Yamazaki1
1Research Center for Electron Photon Science (ELPH), Tohoku University, Sendai 982-0826,
Japan

BSO is one of the candidates for the detector element of a new electromagnetic (EM) calorimeter forthe next generation photoproduction experiments at ELPH. We have continued to investigate the basic
scintillation characteristics of BSO crystals with and without the beam. In this report, the temperaturedependence of the light output for BSO scintillator is presented.

§ 1. Introduction
The baryon resonance spectroscopy is an important testing ground for understanding low energy
QCD. Meson photoproduction is utilized for it complementary to π-N scattering. The excited resonances are intensively studied via η photoproduction on the neutron by using an electromagnetic (EM)calorimeter complex FOREST [1] in the GeV-γ experimental hall at ELPH. We plan to construct a
new EM calorimeter for the next generation photoproduction experiments. Bismuth silicate (Bi4 Si3 O12 :BSO) [2–6] would be the detector element of choice for EM calorimeters in the photon energy region from
100 MeV to a few GeV.
We have investigated the properties of the BSO crystals which were produced at Futek Furnace Co.,
Yokohama, Japan [7]. A small crystal is advantageous in some measurements of crystal properties since
light attenuation effects and non-uniformity of the internal temperature are relatively ignored, compared to a large crystal. We employed a small 17.3 mm cube for the measurements for the temperaturedependence of the BSO light output.

§ 2. Experimental setup
The temperature dependence of light outputs was measured for a 17.3 mm BSO cube by using
661.7 keV γ rays from 137 Cs. Employing a small crystal, we can save time in cooling the crystal sufficiently and get better internal temperature uniformity in the crystal. The BSO cube was wrapped with
Tyvek 1082D paper and cooled by a refrigerator AS-ONE LTB-250 through copper blocks and plates
as illustrated in fig. 1. One unwrapped side of the cube was coupled to a PMT, H6410, with an optical grease OKEN6262A. Temperatures on the BSO surface and the PMT window were monitored withcopper-constantan (T-type) thermocouples. A flow of dry air was provided to avoid water vapor on the
BSO surface. Fig. 2 shows the trend of the temperature at the crystal surface, for example.

124

FrontView
2 - M3

8.7

22.0
M3
17.3

M3

12.7 16.0

Cu block BSO

Cu pipeSide View

Top View
33.4

17.3

1

2 - M317.3
17.3

Cu pipe
POM

33.4

POM

POM

18.0
30.1

Temperature (K)Fig.1. Experimental setup for the measurement of the temperature dependence of light outputs.
The cube of BSO scintillator is wrapped with Tyvek paper, and is directly connected toa PMT H6410. Four sides of the BSO cube are surrounded with cooled copper blocks
and 1 mm thick plates. The unit of the lengths described in the figure is mm. The
polyoxymethylene (POM) blocks are used for the temperature isolation.

295
290
285
280
275
270
265
260
255

0

10

20

30

40 50 60
Time (Hours)

70

80

90

Fig.2. Trend of the temperature at the crystal surface. Each step corresponds to the stabilized
temperature after the setting of the refrigerator is changed.

125

We measured the charge distribution (energy spectra) of the output signals from the BSO crystal
in response to γ rays from 137 Cs with a CAMAC based data taking system. The anode signal from each
PMT was split into two equal parts. One part was sent into a LeCroy 2249W ADC module, and its
charge was integrated over a 1.5 or 2.0 µs ADC gate. The other split signal was used to make a trigger
for the data acquisition system and to generate the gate for the ADC module. The decay times of thesecrystals are rather long and the output signal does not form a single pulse in response to a single γ
ray. Therefore, the signal for the trigger was fed into a timing filter amplifier ORTEC 474 with an RC
shaping time of 200 ns, and was converted into a logic signal with a discriminator.
The background events were measured without the 137 Cs source to be subtracted. The pedestal
in each energy spectrum was measured with a 1 kHz clock trigger. Fig. 3 shows the typical energy
spectra of the BSO crystal for different crystal temperatures. The centroid µ of the photoelectric peak
was obtained by fitting a sum of two Gaussians to the peak and background components. Fitting was
repeated several times in the region [µ − 6σ, µ + 3σ), where σ denotes the width of the peak.

289.1K

774

285.0K

819

280.8K

268.4K

1029 264.5K

1071 260.5K

264.5K

1284 268.4K

285.0K

873

276.6K

924

272.5K

9781137 257.8K

1203 260.5K

1257

1311 272.5K

1344 276.6K

1386 280.8K

1419

1447 289.1K

1504 293.4K

1543 293.4K

1590 291.4K

1620

289.2K

1666 283.0K

1721 280.8K

1777 274.7K

1821 272.5K

1861

266.5K1913 264.5K

1957 258.8K

2005 258.0K

2045 262.4K

2086

1000
0
1000
0

Counts/10 Channel

1000
0
1000
0
1000
0
1000
0

0

1000

0

1000

0

1000
0
ADC (channel)

1000

0

1000

Fig.3. Typical energy spectra of the BSO crystal for different crystal temperatures in response to
γ rays from 137 Cs. The spectra corresponding to the background events triggered without
137
Cs are subtracted with proper normalization factors. The solid lines show a sum of two
Gaussians fitted to the peak and the background components. The crystal temperatureand run number are described in each panel.

126§ 3. Temperature dependence of the light output
The signal from the PMT was integrated over an ADC gate of 2.0 µs in the measurement. The light
output was given with the position of the pedestal-subtracted photoelectric peak. It took about one hourthat the temperature of the BSO crystal reached the setpoint of the refrigerator and got stable within±0.2 K. The position of the photoelectric peak was recorded after the peak position became stable within±5 channel. Fig. 4 shows the relative light output as a function of temperature. The light output becomeslarger as temperature goes down. The ratio of the light output at 258.0 K to that at 293.4 K is 1.75. The
overall temperature gradients of light outputs is found to be −1.49%/K and −1.57%/K for the 1.5 and2.0 µs ADC gate data collections by fitting an exponential function to the data of light output ratios. The
obtained temperature gradients include the effect of the temperature-dependent quantum efficiency inbialkali photocathodes (∼ −0.4%/K [9]). The details analysis for the temperature dependence of the light

2

2

1.8

1.8

1.6

1.4

Relative Light Output

Relative Light Output

output is described elsewhere [10].

1.6

1.4

1.2

1.2

1

1

250 255 260 265 270 275 280 285 290 295 300
Temperature(K)250 255 260 265 270 275 280 285 290 295 300
Temperature(K)Fig.4. Measured relative light output as a function of BSO temperature (the light output at
20◦ C is normalized to be 1). The left and right panels show the light outputs measured
with ADC gates of 1.5 and 2.0 µs, respectively. The solid line shows the fitted exponentialfunctions.

§ 4. Summary
BSO is one of the candidates for a new EM calorimeter for the next generation photoproduction
experiments at ELPH. The temperature dependence of BSO scintillator is investigated. The overalltemperature gradients of the light output is found to be ∼ −1.5%/K by fitting an exponential function to
the data of the relative light output.

Acknowledgment
This work was supported in part by Grant-in-Aid for Scientific Research (B) (17340063) and forSpecially promoted Research (19002003).

127

References[1]

T. Ishikawa et al..: Research Report of LNS 42&43, Tohoku University, 1 (2011).

[2]

M. Kobayashi et al..: Nucl. Instr. and Meth. 205 (1983) 133.

[3]

M. Kobayashi et al..: Nucl. Instr. and Meth. A 372 (1996) 45.

[4]

M. Kobayashi et al..: Nucl. Instr. and Meth. A 400 (1997) 392.

[5]

M. Ishii et al..: J. Crystal Growth 205 (1999) 191.

[6]

M. Ishii et al..: Opt. Mater. 19 (2002) 201.

[7]

Futek Furnace website: ⟨http://www.futekfurnace.com/⟩.

[8]

T. Ishikawa et al..: Research Report of LNS 42&43, Tohoku University, 176 (2011).

[9]

Hamamatsu Photonics, Photomultiplier Tube, 3rd Ed., 2005.

[10] S. Takahashi: Internal GeV-γ Analysis Note No. 198D (2011).

ELPH Annual Report 2010, Tohoku University Vol. 1

129

Precision measurement of the half-life of 99mTc
K. Takamiya1 , H. Kikunaga2 , K. Hirose3 , and T. Ohtsuki3
1
2
3

Research Reactor Institute, Kyoto University, Kumatori, Osaka 590-0494, Japan

Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan

Laboratory of Nuclear Science, Tohoku University, Sendai, Miyagi 982-0826, JapanThe half-life of 99m Tc in various chemical conditions has been measured precisely. The 99m Tc wasproduced by the reaction of 100 Mo(γ, n)99 Mo, followed by disintegration to 99m Tc. The half-life of 99m Tc
was determined within the good precision of the magnitude of 0.1%.

§ 1. Introduction
It was reported that decay constants of the some dozen of nuclides from 7 Be to 235m U were changed
with changing environmental factors such as chemical state [1]. Several studies have been measured thehalf-life of 7 Be with various chemical states in recent years to investigate the effects of environmental
condition on the decay constant [2, 3]. On the other hand, it is well known that the decay constantof 99m Tc is also affected by its chemical environment. Almost all 99m Tc nuclei decays via a 2.2-keVtransition from the 142.7-keV level to the 140.5-keV level in 99 Tc [4]. Because of the high internalconversion coefﬁcient and low transition energy, the probability of the transition is expected to vary withchanges in the chemical structure affecting the electron density at the nucleus.
However, the variation measurements of decay constant of 99m Tc were carried out with a few kindsof the chemical forms and indicate some different results [1]. The goal of our research is to clarify theeffects of chemical structure on the decay constants of 99m Tc. It is difﬁcult that the observation of thevariation of the decay constant because that is on the order of magnitude of 0.1% [1]. In the present
study, the half-life of 99m Tc was precisely measured by using a reference source method.

§ 2. Experimental Procedure
2.1 Measurement for the half-life of 99m Tc
The isotope 99m Tc was produced in the nuclear reaction 100 Mo(γ, n)99 Mo, followed by disintegration
to 99m Tc. A sample of about 5 mg of enriched 100 Mo was enclosed in a quartz tube for bremsstrahlung
irradiation. The irradiation was carried out with the Electron Linear Accelerator at Tohoku University.
The accelerator was operated at an electron energy of 50 MeV with a mean current of around 0.1 mA.
The 100 Mo target was placed in close contact with the back of a platinum converter and cooled withrunning tap water during the 8 h irradiation.
After the irradiation, the target was chemically treated described below. The 100 Mo target wasdissolved in 1 mL of 7 M (mol/dm3 ) HNO3 and then heated to dryness. The residue was dissolved in a

130

few drops of 7 M NH3 aq. and then added 0.1 M HCl to adjusted to neutral pH. The solution was passed
through an anion exchange resin column (Dowex 1×8, 200-400 mesh, 5.5 mmϕ × 40 mm) to eliminate
Tc from the Mo solution.
To allow the decay of 99 Mo (T1/2 = 66.0 h) and the growth of 99m Tc, the puriﬁed Mo solution wasleft to stand for about 22 h after the end of the puriﬁcation of the Mo solution. The solution containing
99m

Tc was passed through an anion exchange resin column (Dowex 1×8, 200-400 mesh, 5.5 mmϕ ×

40 mm) to adsorb the Tc isotopes. The resin was washed with 8 mL of 1 M HCl to remove Mo isotopes
from Tc fraction. The Tc isotopes were eluted from the column with 12 mL of 7 M HNO3 and adjusted
to 0.12 M KCl solution. The solution was passed through an alumina column (Wako Pure Chemical
Industries, Ltd., 300 mesh, 5.5 mmϕ × 40 mm) to reduce the content of 99 Mo. The alumina column
procedure was repeated twice using a fresh column each time. Additionally, the Tc isotopes was puriﬁedby the anion exchange column procedure, the alumina column procedure (three times), and the anion
exchange column procedure in this order. The puriﬁed Tc solution was ﬁnally adjusted to 7 M HNO3
solution and divided into several fractions. 500 μg per a counting source of 99g Tc was added to the
puriﬁed solution as carrier. The Tc isotopes were changed its chemical form to prepare counting sources.
To prepare pertechnetate sources, the Tc fraction were heated to dryness and then the residue wasdissolved in 0.7 M KCl solution. The solution was evaporated to dryness on a glass plate and then coatedwith parafﬁn.
The sulﬁde of heptavalent technetium Tc2 S7 was precipitated from the Tc fraction adjusted to
2 M HCl by bubbling hydrogen sulﬁde at about 80 ˚ C. The precipitate was collected on an alumina
membrane ﬁlter of Anodisc 25 (pore size, 0.02 mm, Whatman Co., Ltd.), heated to dryness, and coatedwith parafﬁn.
The two samples of KTcO4 and Tc2 S7 were set in an automated sample changer [2] and placed
alternately in front of a high-purity (HP) Ge detector at interval of 1800 s. The 140 keV γ-rays from99m

Tc were measured for a real time of 1750 s at one data point. The procedures were repeated over at

least 42 h (T / T1/2 > 7). A 137 Cs source was attached to near the HP-Ge detector as a reference source tocorrect for inﬂuential factors for determination of half-life such as pile-up effect. The internal clock timeof the computer for data acquisition was constantly calibrated by a time-standard signal distributed via
a long-wave radio transmission station in Japan.
2.2 Derivation of half-life
The half-life of 99m Tc was determined based on a reference source method [5]. The ratio R(t) is
given by the following equations:
R(t) =C 0 (t) =0
Csample
(t)
0
Cref
(t)

,

tR
λN
(1 − e−λt ) tL

(1)
(2)

0
0
(t) and Cref(t) are count rates of a sample and a reference source at beginning of data
, where Csample

acquisition, respectively. N is the net counts in the objective peak. tR and tL are real time and live time,

131
respectively. Using the slope of the graph ln R(t) versus time, aslope , the half-life of the radionuclide in
the sample, Tsample is described in the following equation:
Tsample =1
1/Tref − aslope / ln 2(3)

, where Tref is the half-life of the reference source, namely, 137 Cs (11018.3 ± 9.5 d [6]).

§ 3. Results and discussion
In all γ-ray spectrum obtained, the 99m Tc γ-line at Eγ = 140.5 keV and 137 Cs γ-line at Eγ = 661.5 keV
can be observed as two giant peaks. No peaks were seen at around Eγ = 181 keV, 739.5 keV, and
777.9 keV which are the expected energy regions for 99 Mo, followed by disintegration to 99m Tc. In
Fig. 1, a typical exponential curve for the R(t) obtained using a least-squares ﬁtting procedure andtheir residuals are plotted as a function of time. The residuals of the ﬁt of all the data remain within
the limit of approximately 1%. For the samples of KTcO4 , the measurements were repeated several
times using several detectors. The results were summarized in Fig. 2. The uncertainty is given by theuncertainty of the slope of the straight line ﬁtted to the logarithm of and the uncertainty of the half-lifeof 137 Cs (0.09% [6]) used as a reference source. The half-life values have the possibility to include asystematic errors originated in the performance of detection system. The systematic error is estimate
0.09%. As a results, the half-life of 99m Tc with the chemical form of KTcO4 is 6.0016 ± 0.0053 h, whichis in good agreement with recent values of other authors which were measured with the chemical formof pertechnetate (6.0072 ± 0.0010 h in normal saline solution [7] and 6.0071 ± 0.021 h in NaTcO4 [5]).
Relative differences in the decay constant of 99m Tc, {λ(TcO−
4 ) -λ(Tc2 S7 )}/ λ(Tc2 S7 ) obtained fromthis work and the previous reports [8, 9] are plotted in the Fig. 3. The previous values are not consistent
with each other within 2σ. Our result is consistent with the value reported by Mazaki et al. [9] within
1σ although the precision error of our value is larger than that of the previous values. Repetitive experiments by using the present methods will allow us to obtain good statistics and further information on
the variation of decay constant of 99m Tc with changing its chemical form.

§ 4. Conclusion
We have produced 99m Tc in the 100 Mo(γ, n)99 Mo, followed by disintegration to 99m Tc. The half-lifeof these nuclides was determined with good precision on the order of magnitude of 0.1%. The present
system will allow us to measure the half-life of 99m Tc with various chemical states.

Acknowledgement
The authors would like to thank the technical staff of Laboratory of Nuclear Science, Tohoku University for their excellent accelerator operation.

References[1]

G. T. Emery et al.: Ann. Rev. Nucl. Sci. 22 (1972) 165.

132
[2]

T. Ohtsuki et al.: Phys. Rev. Lett., 93 (2004) 112501.

[3]

Y. Nir-El et al.: Phys. Rev. C 75 (2007) 012801.

[4]

R. B. Firestone and V.S. Shirley: Table of Isotopes 8th ed., Wiley & Sons, (1996).

[5]

M.A.L. da Silva et al.: J. Radioanal. Nucl. Chem. 264 (2005) 571.

[6]

M. P. Unterweger et al.: Appl. Radiat. Isot. 56 (2002) 125.

[7]

R. L. Ayres et al.: Int. J. Appl. Radiat. Isot. 33 (1982) 835.

[8]

K. T. Bainbridge et al.: Phys. Rev. 90 (1953) 430.

[9]

H. Mazaki et al.: Phys. Rev. C 21 (1980) 344.

133

100
T1/2(KTcO4) = 6.0076 s 0.0022 h

R(t)

10

1

Residuals (%)

2.0
1.0
0
-1.0
-2.0
0

10

20
30
Elapsed time / h4050

Fig.1. A typical exponential curve for the R(t) obtained using a least-squares ﬁtting procedureand their residuals.

Tc (h)

6.04

Detector 1
Detector 2
Detector 3
Detector 4
Detector 5

99m

6.02

Half-life of

6
5.98
5.96

Fig.2. The half-life of 99m Tc with the chemical state of KTcO4 .

λ(Tc2S7)λ(TcO4-)-λ(Tc2S7)

 104

35

30

25
Bainbridge et al. [8]Mazaki et al. [9]This work

KTcO4

φ4AsTcO 4

KTcO4 (n=3)

Fig.3. Relative differences in the decay constant of 99m Tc between TcO−
4 and Tc2 S7 forms.

ELPH Annual Report 2010, Tohoku University Vol. 1

135(ELPH Experiment : #2707, #2734)

Photon Flux correction for Photon Activation Analysis
Yasuji Oura1 , Hirofumi Hamanaka1 , Yutaka Sasaki1 , Ayaka Wada1 ,Yuka Arai1 , and Mitsuru Ebihara1
1

Department of Chemistry, Tokyo Metropolitan University, Hachioji, 192-0364

In photon activation analysis using bremsstrahlung from an electron LINAC, samples to be irradiated are stacked along an electron beam. Since photon ﬂux comes down towards downstream samples,
photon ﬂux in each sample should be corrected to obtain an accurate determination value. In this study,
we compared some metal foil monitors to get effectual correction way. Decreasing rate of induced radioactivity in monitors was dependent on monitor reaction, and the rate was found to be correlated with
Q value of a reaction producing the radionuclide: the rate of decreasing became signiﬁcant with decreaseof absolute Q value. Appropriate monitor reaction should be selected to obtain an accurate determination
value.

§ 1. Introduction
We have been determining an elemental composition in geochemical, cosmochemical, and environmental samples by photon activation analysis (PAA) using bremsstrahlung with 20 - 30 MeV of end point
energy (E0 ) from electron LINAC. In PAA, since samples arrayed in a quartz tube along with a directionof electron beam are irradiated by bremsstrahlung, photon intensity comes down towards downstream
samples. Therefore, we usually monitor radioactivity of 196 Au produced by 197 Au(γ, n) reaction in gold
ﬂux monitor foils irradiated together with samples to correct variation of photon intensity among samples, assuming that induced radioactivity is proportional to photon ﬂux. When a large number of samples
are irradiated by bremsstrahlung, whole of samples and gold foils in a quartz tube come up to about 10
cm in length and 4 g in weight. In such case, energy distribution of bremsstrahlung photon going throughsamples may change at downstream samples in comparison with at upstream samples. So photon ﬂux
variation was monitored by several reactions including 197 Au (γ, n) 196 Au reaction, and an appropriate
ﬂux monitor for PAA was considered.

§ 2. Experimental
Gold, copper, nickel, stainless steel, nickel silver (alloy of Cu, Zn, and Ni) and carbon foils with 10
mm in diameter were used as a ﬂux monitor. Used monitor reaction are tabulated in Table 1. They wereplaced every 3 samples (10 mm in diameter) in quartz tube and were irradiated for 20 minutes to 423
minutes. After irradiation γ-ray was measured at appropriate cooling time.

136

Table 1. Monitor reactions for photon ﬂux
monitorgold
coppernickelnickel silver

stainless steel

carbonreactionAu(γ, n)196 Au
65
Cu(γ, n)64 Cu
62Cu(γ, n)61 Cu
58
Ni(γ, n)57 Ni
58Ni(γ, 2n)56 Ni
65
Cu(γ, n)64 Cu
62Cu(γ, n)61 Cu
64
Zn(γ, n)63 Zn
58Ni(γ, n)57 Ni
54Fe(γ, n)53 Fe
57
Fe(γ, p)56 Mn
56Fe(γ, pn)54 Mn
54Fe(γ, pn)52m Mn
58
Ni(γ, n)57 Ni
58Ni(γ, 2n)56 Ni
52Cr(γ, n)51 Cr
50
Cr(γ, n)49 Cr
12C(γ, n)11 C
197

half life
6.2 d
13 h
9.7 m
36 h
5.9 d
13 h
9.7 m
38.5 m
36 h
8.5 m
2.6 h
312 d
21 m
36 h
5.9 d
27 d
42 m
20 m

Q value [MeV]
-8.1
-9.9
-19.7
-12.2
-22.5
-9.9
-19.7
-11.9
-12.2
-13.4
-10.6
-20.4
-20.9
-12.2
-22.5
-12.0
-13.0
-18.7

§ 3. Results and discussion
As an example of variation in induced radioactivity at each monitor in quartz tube, relative radioactivity produced in ﬂux monitors irradiated at E0 = 25 MeV for 20 minutes and 423 minutes areshown in Fig.1. Three monitor sets (carbon, gold, stainless steel, and nickel silver) placed every 3 quarts
ﬁlters (about 6.5 mg each) were irradiated continuously for 20 min, and 5 monitor sets (gold, stainless steel, copper, and nickle) placed every 3 JB-1a (geochemical standard issued by Geological Survey ofJapan, basalt) samples (about 20 mg each) were irradiated intermittently for 423 min in net. All induced
radioactivity decreased with increasing of accumulated sample weight, and their decreasing rates depended on induced radionuclide. For irradiation for 20min, slope of ﬁtted exponential function changed
between -0.257 (52m Mn in stainless steel foil) and -0.560 (196 Au in gold foil). For irradiation for 423 min, arange of variation in the slope value (-0.115 to -0.169) was smaller than for 20 min. In both irradiations,radioactivity of 196 Au went down most signiﬁcantly among induced radionuclides. This inconsistency of
decreasing rate among radionuclides means that correction for ﬂux variation by Au ﬂux monitor which
we are using is not always exact, especially in more downstream samples.
The radioactivity induced by irradiation for 20 minutes decreased more steeply than irradiation for423 min. For instance, the value of relative radioactivity of 196 Au at 1 g of accumulated weight were0.571 and 0.845 for short and long irradiation, respectively. This tendency that decreasing rate for shorttime irradiation is greater than for long time irradiation was found also in past experiments by looking
anew their data.
Although decreasing rates of radioactivity of different radionuclides were not consistent, decreasingrate of same radionuclide in different monitors such as 57 Ni produced in Ni, stainless steel, and JB-1a,
were consistent each other as shown in Fig.2. Therefore, the difference of decreasing rate was not caused

137

Fig.1. Relative induced radioactivity in ﬂux monitor foils. (a) Quartz ﬁlter samples and monitors
were irradiated for 20 min. (b) JB-1a samples and monitors were irradiated for 423 min.

by materials of monitors but probably caused by difference of monitored nuclear reactions.
Correlation between Q values of monitored reaction and values of slope of exponential function ﬁtted
with ﬂux variation is shown in Fig.3. The value of slope of radioactivity variation seems to correlate with
Q values of nuclear reactions, and the degree of dependence for short time irradiation is heavier thanfor long time irradiation. It is guessed qualitatively that photon does not attenuate with keeping theirrelative energy distribution, but the energy distribution changes during bremsstrahlung going throughsamples, that is, photon with lower energy is easier to attenuates than higher energy photon. But, it isstrange that the dependency on Q value is dependent on irradiation time. Stimulation on attenuation ofbremsstrahlung by some calculation code is needed.

Fig.2. Comparison of relative radioactivity induced in different monitors. (a) 57 Ni in Ni, stainless steel and JB-1a. (b) 56 Ni in Ni and stainless steel.

In this study, we found that photon ﬂux correction by using only one kind of metal foil is not always
accurate and correction by 196 Au in gold monitor which we have been using is overestimate (10% in

138maximum) . Flux monitors including all elements to be determined such as standard reference materials
are recommended, and at least alloys consisting of multiple elements are preferable. Or 57 Ni in Ni
monitor, which has middling Q value, is relatively better.

Fig.3. Correlation between Q values and values of slope of exponential function ﬁtted with ﬂux
variation. Run 1 and run 2 were irradiation for 20 min and run 3 for 423 min.

Acknowledgment
The authors are indebted to Dr. T. Ohtsuki, Dr. K. Hirose, and the linac crew members of the
Research Center for Electron Photon Science, Tohoku University, for their invaluable assistance in irradiation, measurement, and accelerator operations.

ELPH Annual Report 2010, Tohoku University Vol. 1

139

Operation status of accelerator complex in 2010
Accelerator group§ 1. Low energy operation of linac
High average beam current with beam energies less than 30 MeV has been routinely supplied to produce radioisotopes for nuclear chemistry applications. In this mode a repetition rate and a macropulse
duration of the beam pulse are usually 300 Hz and ∼ 4 μs respectively, which is remarkably high duty.
Although the 80 kV DC gun can provides the beam current up to 200 mA, so that the average beam
current should be more than 200 μA, the on-target current is typically 120 μA because beam transmission in both accelerating structures and a transport line is pretty poor due to large beam emittance ofmore than 200 mm mrad (normalized) and less appropriate beam focusing system. Since the linac wasconstructed about 45 years ago, the accelerator technology and knowledge were not much sufﬁcient toavoid severe beam losses and unwanted longer tuning time. However these years we have made effort toimprove the control system and then machine tuning has been progressed, so that the high current beamwith minimum beam loss is now easily available within 30 min tuning time. Nevertheless we have beendeveloping a novel DC gun equipped very small size cathode of LaB6 crystal to provide low emittancebeam, which is described later in a section of machine development.

§ 2. Linac operation as an injector of booster synchrotron
Another role of 45-year-old linac is an injector for a 1.2 GeV booster synchrotron In 2010, the injector
operated at the beam energy of 150 MeV was also working well because of the well developed control
system and tuning experiences. Since stacking beam injection was not taken account in the injection
system of the booster ring, the beam current in the ring is limited. The maximum beam current in amacropulse of the 150 MeV beam is less than 80 mA due to beam brow-up, it is very difﬁcult to reachhigh ring current. Because of the time structure of the injection bump, the macropulse length longer
than 2 turns in the ring cannot be injected. Practically the maximum beam current stored in the ringis 20 mA at most, which means the injection efﬁciency is almost 25%. This value is, however, quite
acceptable because of the larger beam emittance and time jitters of the injection system, and has been
not serious problem for user experiments.

§ 3. 1.2GeV booster synchrotron
In addition to that nominal ramping time of the booster upto the maximum energy of 1.2 GeVfrom the injection one of 150 MeV is 1.2 s which is limited by the power supplies, a function of beam

140

storage is capable. In this sense this synchrotron is mostly storage ring, but fetal defect is a lack of
sextupoles. Because the length of the dispersive section is strictly short and the beta functions are verysmall, there is no solution to correct chromaticity A threshold current for head-tail instability has been
considered to be ∼ 5 mA at a beam energy of 150 MeV. Even if the injection system is improved thebeam stacking in the injection would be impossible. Accordingly the ramping is started after the beam
injection immediately.
Furthermore tracking ability of the power supplies to the ramping reference is not permissibleamount because the power supply for the dipoles is semiconductor (IGBT) switching one while those forquads are conventional thyristor ones. As a result of this mismatching of response times, variationsof tunes at the beginning of energy ramping are very much spread, which is crucial for beam storing.
In spite of these critical issues, the machine has been running well and the machine time for nuclear
physics experiments were properly consumed.

§ 4. Statistics of 2010
Monthly operating time is summarized in Fig. 1. Except for maintenance terms such as August,2010 and February, 2011, the accelerator complex was well operated. Variation of the total machinetime per months has strongly depended on the experimental situation. Approximately 3,000 hours weredevoted to user machine time, and 90% of it was for nuclear physics experiments using the booster ring.
Note the machine time in March, 2011 was miserably deducted because of the disaster of East
Japan earthquake, occurred on March 11, 2011

Fig.1. Monthly statistics of the operation time in FY 2010.

141§ 5. Developments of accelerators
A couple of years ago, it turned out that the old DC gun won’t be supported by a manufacturer any
longer, we have started to develop a DC gun with a novel concept. Though extraction voltage is relatively
lower such as 50 kV, the gun is very compact and then the ﬁeld gradient is very high, which has beenvery promising toward extremely low emittance beam. A single crystal LaB6 cathode with a diameterof less than 2 mm is employed and the maximum current density of 50 A/cm2 is expected. On a test-bed
experiment the normalized emittance of less than 1 mmmrad was already achieved at the beam currentof 300 mA. A speciﬁc feature of the gun is that the transvers particle distribution can be manipulated byfeeding bias voltage at the wehnelt. Since a longrun test with high repetition rate was already passed,
we are now studying matching conditions with the old linac.
Introducing the sextupole moment into the ring has been crucial and apparently desperate issue
for the 1.2 GeV booster. Surely there seems to be no chance to re-construct the lattice again because oflimited money, space and lack of strong motivation Our conclusion became to that quad-sext magnets
and nondispersion-free lattice shall be employed. Basically the booster consists of conventional 4 doublebend achromat cells. However there is no strong meaning for achromat lattice. The scenario is that someamount of dispersion would be introduced in the straight section, and combined function quads containing sextupole moment correct the chromaticities. This procedure was already successfully introduced in
MAX-II 1.5 GeV storage ring. At the present we have performed investigation for the dynamic apertureand optimum operating condition for chromatic abration and beam instabilities.

ELPH Annual Report 2010, Tohoku University Vol. 1

143

User Support Ofﬁce Report
T. Ishikawa

The User Support Ofﬁce coordinates communication with scientists at ELPH and management of
the beamtime. In this ﬁscal year, the electron and photon beams (including electron/positron beam
for testing detectors) have been provided without serious problems before the 2011 earthquake off the
Paciﬁc coast of Tohoku (東北地方太平洋沖地震) known as 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 utilized by the experimentalists in this ﬁscal
year 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 is basically no difference between the latter two in the operation of the accelerator complex.
Laboratory of Nuclear Science (LNS) belonging to Graduate School of Science was reorganized into
Research Center for Electron Photon Science (ELPH) on the ﬁrst December 2009. The beamtimes supplied to the users are presented both in this ﬁscal year and the previous one from December 2009 to
March 2010.

§ 2. Beamtime operated
The pattern operation system for the STB ring, which was based on Computer Aided Measurement
And Control (CAMAC), became out of order on the 19th November 2009. A temporary operation system,
which utilized some of the CAMAC modules working ﬁne, was constructed on 30th November by Quark
Nuclear Physics group in cooperation with technical staffs at ELPH. The beam came back just on thebirth day of ELPH, and the system was used till a brand new system is ready on 7th May 2010. No
other problem arose in the previous ﬁscal year (FY2009) for ELPH. Table 1 summarizes the radiation,and user beamtimes in FY2009 for ELPH.

144

Table 1. Radiation, and user beamtimes in FY2009 for ELPH. They are given by the sum of thetimes that the beam is coming to the beamline, and that the beam is provided to theusers. The beamtimes are classiﬁed to linac only and STB used ones.
month
DecemberJanuary
FebruaryMarchsumlinac only
radiation (h) user (h)
21.6
39.9
9.3
9.4
15.4
29.4
10.6
28.5
56.8
107.2

STB
radiation (h) user (h)
228.1
225.2
246.2
240.9
69.7
72.4
0.0
0.0
544.1
538.5

In this ﬁscal year (FY2010), the electron and photon beams (including electron/positron beam fortesting detectors) have been provided without serious problems before 2011 Earthquake. The patternoperation system for the STB ring has been recovered on the 7th May. The trouble on the thermionicgun took place in the high current operation on the 11th June, and was tested on the 21st on June. The
troubles on the operation of the QD magnets in the STB ring and the third Klystron occurred on the
15th June and the 20th June, respectively. The mis-operation of a staff for the control of electricity at
ELPH caused a blackout on 25th September 2010, and it takes two days for the beam to come back.
There was an electric arc in the third Klystron occurred on the 15th December. A large earthquakewith the seismic intensity of 4 at ELPH and the magnitude of 7.2 made a brief stop to conﬁrm thesafety for the accelerator operation in the morning on the 9th March. The 2011 Earthquake with theseismic intensity of 6+ at ELPH and the magnitude of 7.9, which is the most powerful earthquake, hit
the Tohoku area in Japan including our facility at 14:46 on 11th March 2011. The losses of our facility
is discussed in section 3.
The accelerator operated time (operation time) was 217.7 hours for the linac only operation and2707.5 for the STB one, and it was 2925.2 hours in total, which was slightly shorter than 3000 hours.
The beam provided time (user beamtime) was 283.6 and 2549.4 hours for the linac only and STB operations, and it was 2833.0 hours in total. When the several experimental groups use the beamtime, theuser beamtime is doubly counted. Table 2 summarizes the operation, radiation, and user beamtimes in
FY2010.

§ 3. 2011 Earthquake
The 2011 Earthquake took place at 14:46 on 11th March 2011. An experiment for an RI experimental group (spokesperson: K. Takamiya, Research Reactor Institute, Kyoto University) was being carriedout on that day, and the linac was in operation when the disaster of the earthquake hit. Another experimental group (spokesperson: K. Ozawa, Department of Physics, University of Tokyo), of which beamtime
ended on the day before, was just cleaning up and preparing for sending back the experimental devices
and tools. Fortunately, all the members for the two groups went back to their facility at last. No power
was supplied until 16th, and all the basic computer servers stopped during the blackout.
The damage to the two accelerators were serious. Many cracks on the waveguides and the accel-

145

Table 2. Operation, radiation, and user beamtimes in FY2010. They are given by the sum of thetimes that accelerators are in operation, that the beam is coming to the beamline, andthat the beam is provided to the users. The beamtimes are classiﬁed to linac only and
STB used ones.
month
April
May
June
July
AugustSeptember
OctoberNovember
DecemberJanuary
FebruaryMarchsum

operation (h)
66.4
11.2
12.9
22.5
13.3
11.2
10.5
11.5
22.5
22.4
0.0
13.2
217.7

linac only
radiation (h)
20.1
8.8
4.1
15.1
8.6
5.5
8.9
9.4
17.9
19.4
0.0
4.8
122.5

user (h)
63.1
29.8
0.0
37.4
20.9
8.5
29.0
10.3
40.5
36.9
0.0
7.2
283.6

operation (h)
126.2
277.8
403.4
283.5
0.0
492.6
660.6
159.4
161.8
81.0
0.0
61.1
2707.5

STB
radiation (h)
114.7
271.1
382.5
273.4
0.0
416.7
632.9
154.6
149.6
76.4
0.0
56.6
2528.4user (h)
99.7
259.1
390.6
252.6
0.0
480.8
639.9
126.3
172.8
70.0
0.0
57.4
2549.4

erator columns were found in 300 MeV linac. The elements of the STB ring slipped out of place, somemagnets hit by shield blocks, and several power suppliers 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 will be summarized elsewhere.

ELPH Annual Report 2010, Tohoku University Vol. 1

放射線安全管理室報告（平成 22 年 4 月〜平成 23 年 3 月）
放射線安全管理室

Radiation Protection Report 2010
Radiation Control Ofﬁce§ 1 . 許認可申請
2010 年度の変更許可申請はない。

§ 2 . 個人管理
2.1 放射線業務従事者登録196 人（内 女子 15 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 196 人
2.3 教育訓練
定期講習
平成 22 年 6 月 24 日 新規教育 16 人 再教育 54 人
特別講演の内容：東北大学大学院工学研究科量子エネルギー工学専攻 三村 均 教授
「高機能性吸着剤による原子力レアメタルの選択的分離・回収」
不定期の講習48 回 131 人§ 3 . 管理区域内作業33 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 22 年 9 月 21 日 異常無し
2 回目 平成 23 年 3 月 24 日

147

148

平成 23 年 3 月 11 日の地震による影響が大きく、放射線発生装置の直線加速装置およびシンクロトロンについては真空劣化やマグネットのずれ等のため使用できない状態となった。
点検結果のまとめは次のとおり。

1. 第 1 実験室及び第 2 実験室は震災の影響から立入禁止措置
2. クライストロン室天井ボードの一部に はがれあり
3. 管理区域境界標識 4 枚脱落あり
4. 第 3 実験室第 3 室フード内の遮蔽ブロックの崩れあり
5. 第 3 実験室第 3 室洗浄室出入り口扉上部ガラス窓にひびあり§ 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

6970

C-11

2000

Cl-34m

200

Co-57

200

Co-58

300

Cr-51

500

Ge-69

500

Mn-54

200

Na-22

800

Nd-147

1610

Ni-57

530

Sr-85

2020

Zn-63

500

Zn-65

20

全 14 核種

計 16,350 kBq

ELPH Annual Report 2010, Tohoku University Vol. 1

149

List of Publication (論文リスト) (2010)
Papers Published in Refereed Journals
Multi-layered parallel plate ionization chamber for cross-section measurements of minor actinides
K. Hirose, T. Ohtsuki, Y. Shibasaki, N. Iwasa, J. Hori, K. Takamiya, H. Yashima, K. Nishio,
Y. Kiyanagi
Nucl. Instr. and Meth. A 621, 379–382 (2010).
The second GeV tagged photon beamline at ELPH
T. Ishikawa, H. Fujimura, R. Hashimoto, T. Ishida, J. Kasagi, T. Kinoshita, S. Kuwasaki,
F. Miyahara, A. Miyamoto, K. Mochizuki, T. Nakabayashi, M. Nanao, K. Nawa, Y. Okada,K. Okamura, Y. Onodera, Y. Saito, K. Satou, M. Sengoku, H. Shimizu, K. Suzuki, S. Suzuki,
Y. Tajima, T. Takahashi, H. Yamazaki, H. Yonemura, H.Y. YoshidaNucl. Instr. and Meth. A 622, 1–10 (2010).
Expected Performance of a Planar Undulator Designed for the Terahertz Source Project at Tohoku University
F. Hinode, M. Kawai, K. Nanbu, F. Miyahara, H. Hama
Nucl. Instr. and Meth. A 637, S72–S75 (2010).
Intense Coherent THz Generation from Accelerator-Based Sources
H. Hama, M. Yasuda, M. Kawai, F. Hinode, K. Nanbu, F. Miyahara
Nucl. Instr. and Meth. A 637, S57–S61 (2010).
Dependence of barrier distribution and fusion-ﬁssion process on entrance channel
H. Ikezoe, S. Mitsuoka, K.Nishio, Y. Watanabe, S.C. Jeong, I. Nishinaka, T. Ohtsuki, K. Hirose
Nucl. Phys. B 834, 172c–175c (2010).
Nuclear orientation in the reaction 34 S + 238 U and synthesis of the new isotope 268 Hs.
K. Nishio, S. Hofmann, F.P. Hesberger, D. Ackermann, S. Antalic, Y. Aritomo, V.F. Comas,
Ch.E. Düllmann, A. Gorshkov, R. Graeger, K. Hagino, S. Heinz, J.A. Heredia, K. Hirose,
H. Ikezoe, J. Khuyagbaatar, B. Kindler, I. Kojouharov, B. Lommel, R. Mann, S. Mitsuoka,
Y. Nagame, I. Nishinaka, T. Ohtsuki, A.G. Popeko, S. Saro, M. Schädel, A. Türler, Y. Watanabe, A. Yakushev, A.V. Yeremin
Phys. Rev. C 82, 024611(1–9) (2010).
Evidence for qasiﬁssion in the sub-barrier reaction of 30 Si+238 U
K. Nishio, H. Ikezoe, I. Nishinaka, S. Mitsuoka, K. Hirose, T. Ohtsuki, Y. Watanabe, Y. Aritomo, S. Hofmann
Phys. Rev. C 82, 044604(1–5) (2010).

150
Energy calibration of tagged photons by the d(γ, π − pp) reaction
HAN Yun-Cheng, Nobuyuki Chiga, Yu Fujii, Kenta Futatsukawa, Osamu Hashimoto, Kentaro Hirose, Takatsugu Ishikawa, Hiroki Kanda, Masashi Kaneta, Daisuke Kawama, Yue Ma,
Kazushige Maeda, Tomofumi Maruta, Nayuta Maruyama, Akihiko Matsumura, Youhei Miyagi,
Koji Miwa, Satoshi N. Nakamura, Hajime Shimizu, Koutarou Shirotori, Koutaku Suzuki,
Tadaaki Tamae, Hirokazu Tamura, Kyo Tsukada, WANG Tie-Shan, and Hirohito Yamazaki
Chinese Physics C34 35 (2010).
Liquid H2 /D2 Target System Used for Photoproduction
HAN Yun-cheng, WANG Tie-shan, B. Beckford, T. Fujii, K. Futatsukawa, O. Hashimoto,
H. Kanda, M. Kaneta, T. Kawasaki, C. Kimura, K. Maeda, and A. Okuyama
Atomic Energy Science and Technology 44 873 (2010).
SCRIT: RI・電子散乱実験装置の建設
若杉昌徳、宮下裕次、戸ケ崎衛、竹原広樹、堀利匡、原雅弘、市川進一、高橋弘範、玉木聖一、小泉浩二、森屋誠、浦野恭輔、北沢僚也、栗田和好、玉江忠明、須田利美
加速器学会誌

7 271–277 (2010).

Short-Range Longitudinal Wake Field and Its Effect on the Energy Spectrum in a Linear Accelerator
Tetsuya Igo, Ryukou Kato, Shigeru Kashiwagi, Goro Isoyama
Jpn. J. Appl. Phys. 49 056301 (2010).

Papers Published in International Conference Proceedings
Inﬂuence of Deuterium Gas Permeation on Surface Elemental Change of 88 Sr Ion-Implanted Pd and
Pd/CaO multi-layer system
T. Hioki, J. Gao, N. Takahashi, S. Hibi, A. Murase, T. Motohiro and J. Kasagi
Proceedings of 14th International Conference on Condensed Matter Nuclear Science ICCF14,
203–211 (2010).
Development of New Detector System for Charged Particle Emission
Y. Toriyabe and J. Kasagi
ibid., 310–315.
Screening potential for nuclear reactions in condensed matter
J. Kasagi
ibid., 318–325.
Low-Energy Nuclear Reactions in Low-Temperature Dense Plasmas
J. Kasagi, Y. Toriyabe, E. Yoshida, K.H. Fang and H. Yonemura
Tours Symposium on Nuclear Physics and Astrophysics VII, AIP Conference Proceedings
1238, 151–156 (2010).
Linear Focal Cherenkov Camera for the t-ACTS Injector
K. Nanbu, H. Hama, M. Kawai, S. Kashiwagi. F. Hinode, T. Muto, F. Miyahara, Y. Tanaka
Proc of FEL2010, WEPB51, Sweden, (2010) (WEPB51).

151

A Direct Measurement of the Longitudinal Phase Space for a Low Energy Electron Beam Using Energy
Dependent Angular Distribution of Cherenkov Radiation
K. Nanbu, H. Hama, M. Kawai, S. Kashiwagi. F. Hinode, T. Muto, F. Miyahara, Y. Tanaka
Proc of IPAC10, 1002–1004, Japan, (2010) (MOPE019).
Development of a Thermionic RF Gun for Coherent THz Source at Tohoku University
F. Hinode, H. Hama, S. Kashiwagi, M. Kawai, K. Nanbu, F. Miyahara, T. Muto, H. Oohara,
Y. Tanaka
Proc of IPAC10, 1731–1733, Japan, (2010) (TUPEC010).
Production of Femtosecond Electron Pulse using Alpha Magnet together with Off-crest Acceleration for
Generation of Coherent THz Radiation
F. Miyahara, F. Hinode, M. Kawai, T. Muto, K. Nanbu, H. Oohara, Y. Tanaka, and H. Hama
Proc of IPAC10, 4509–4511, Japan, (2010).
Cherenkov Ring to Observe Longitudinal Phase Space of a Low Energy Electron Beam Extracted from
RF GunH. Hama, K. Nanbu, M. Kawai, S. Kashiwagi, F. Hinode, T. Muto, F. Miyahara, Y. Tanaka
Proc of BIW2010, TUCNB03, USA, (2010).
Effects of nuclear orientation on fusion and ﬁssion process for reactions using actinide target nuclei
K. Nishio, H. Ikezoe, S. Mitsuoka, I. Nishinaka, H. Makii, Y. Watanabe, Y. Nagame, T. Ohtsuki, K. Hirose, S. Hofmann
International Symposium on Exotic Nuclei Sochi (Russia), 28 September-2 October 2009 AIP
Conference Proceedings 1224, 301–310 (2010).
Effects of Nuclear Orientation on Fusion and Fission Process for Reactions Using 238 U Target Nucleus
K. Nishio, H. Ikezoe, S. Mitsuoka, I. Nishinaka, H. Makii, Y. Watanabe, Y. Nagame, T. Ohtsuki, K. Hirose, and S. HofmannTours Symposium on Nuclear Physics and Astrophysics-VII. AIP Conference Proceedings
1238, 307–311 (2010).
Effects of nuclear orientation on fusion and ﬁssion in the reaction using 238 U target nucleus
K. Nishio, H. Ikezoe, S. Mitsuoka, I. Nishinaka, Y. Nagame, T. Ohtsuki, K. Hirose, S. Hofmann
Second International Workshop on Compound Nuclear Reactions and Related Topics Bordeaux, France, October 05-08, 2009, EPJ Web of Conferences 2, 10001 (2010).
Strangeness photoproduction experiments at SENDAI
H. Kanda, B. Beckford, T. Fujii, Y. Fujii, K. Futatsukawa, Y.C. Han, O. Hashimoto, K. Hirose,
T. Ishikawa, M. Kaneta, S. Kiyokawa, C. Kimura, T. Koike, K. Maeda, T. Maruta, K. Miwa,
S.N. Nakamura, A. Okuyama, H. Shimizu, K. Suzuki, T. Tamae, H. Tamura, T.S. Wang, H. Yamazaki, and the NKS/NKS2 collaboration
Nucl. Phys. A 835 371 (2010).

152

Study of charged pion photoproduction on deuteron
HAN Yun-Cheng, 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, WANG Tie-Shan, and H. Yamazaki
Nucl. Phys. A834 596c (2010).
Present Status of the RIKEN RI Beam Factory
T. SudaJournal of Physics 267 012008(1-6) (2011).
DEVELOPMENT OF A PHOTOCATHODE RF GUN FOR THE L-BAND LINAC AT ISIR, OSAKA UNIVERSITY
S. Kashiwagi, K. Furuhashi, G. Isoyama, R. Kato, Y. Morio, N. Sugimoto, Y. Terasawa, H. Hayano,
H. Sugiyama, Y. Takahashi, T. Takatomi, J. Urakawa, H. Iijima and M. Kuriki
Proceedings of IPAC’10, (Kyoto, Japan, 2010), pp.1728-1730 (TUPEC009)
ELIMINATION OF HALL PROBE ORIENTATION ERROR IN MEASURED MAGNETIC FIELD OF
THE EDGE-FOCUSING WIGGLER
S. Kashiwagi, R. Kato, G. Isoyama, K. Tsuchiya and S. Yamamoto
Proceedings of IPAC’10, (Kyoto, Japan, 2010), pp.3159-3161 (WEPD030)
PULSE RADIOLYSIS WITH SUPERCONTINUUM PROBE GENERATED BY PCF
Y. Hosaka, R. Betto, A. Fujita, K. Sakaue, M. Washio, R. Kuroda, S. Kashiwagi and K. Ushida
Proceedings of IPAC’10, (Kyoto, Japan, 2010), pp.145-148 (MOPEA035)
PERFORMANCE OF THE L-BAND ELECTRON LINAC FOR ADVANCED BEAM SCIENCES AT OSAKA UNIVERSITY
G. Isoyama, R. Kato, S. Kashiwagi, Y. Morio, Y. Terasawa, K. Furuhashi, N. Sugimoto, J. Shen,
S. Hirata, M. Fujimoto, S. Suemine
Proceedings of IPAC’10, (Kyoto, Japan, 2010), pp.3221-3223 (WEPD056)
HIGH POWER TERAHERTZ FEL AT ISIR, OSAKA UNIVERSITY
R. Kato, S. Kashiwagi, Y. Morio, K. Furuhashi, Y. Terasawa, N. Sugimoto, S. Suemine, G. Isoyama,
K. Tsuchiya, S. Yamamoto
Proceedings of IPAC’10, (Kyoto, Japan, 2010), pp.2209-2211 (TUPE030)
DEVELOPMENT OF A HIGH AVERAGE POWER LASER GENERATING ELECTRON BEAM IN ILC
FORMAT FOR KEK-STF
M. Kuriki , H. Iijima, H. Hayano, Y. Honda, H. Sugiyama, J. Urakawa, G. Isoyama, S. Kashiwagi , R. Kato, E. Katin, E. Khazanov, V. Lozhkarev, G. Luchinin, A. Poteomkin, G. Shirkov,
G. Trubnikov
Proceedings of IPAC’10, (Kyoto, Japan, 2010), pp.4098-4100 (THPEC024)

153

DEVELOPMENT OF AN L-BAND RF GUN FOR HIGH-DUTY-CYCLE OPERATION
R. Kato, N. Sugimoto, G. Isoyama, S. Kashiwagi, H. Sugiyama, H. Hayano, J. Urakawa,T. Takatomi, M. Kuriki
Proceedings of Linear Accelerator Conference LINAC2010, (Tsukuba, Japan, 2010), pp.10251027 (THP121)
DEVELOPMENT OF A THERMIONIC ELECTRON GUN OF THE L-BAND LINAC FOR FEL OPERATION
N. Sugimoto, R. Kato, A. Tokuchi, S. Suemine, G. Isoyama, S. Kashiwagi
Proceedings of Linear Accelerator Conference LINAC2010, (Tsukuba, Japan, 2010), pp.965967 (THP121)

Oral Presentations at International Conferences
University-based Accelerator Facilities for Quark Nuclear Physics at Sendai
H. Shimizu
The ﬁrst ANPhA Symposium, J-PARC, Tokai, Jan. 18–19, 2010
Electron Accelerator Complex at Tohoku University, 42-Year- Operation and Future
H. Hama, M. Kawai, F. Hinode, Y. Shibasaki, S. Takahashi, K. Nanbu, I. Nagasawa, T. Muto,
M. Hiraga
The 7th International Workshop on Accelerator Operations, Daejeon, Korea April 12–16, 2010
Nuclear Science at Tohoku University with an Electron-Photon Beam
H. Shimizu
International Symposium on Nuclear Physics in Asia, Beihang University, Beijing, China,
Oct. 14–15, 2010
Quark Nuclear Physics with a Photon Beam at Elphs Lab
H. Shimizu
N-N Interaction & the Nuclear Many-Body Problem, Tata Institute, Mumbai, India, Nov. 18–
27, 2010
Electron scattering for exotic nuclei
T. SudaThe 11th Asia Paciﬁc Physics Conference Nov. 14-18, 2010, Shanghai, China
Present status of RIKEN RI Beam Factory
T. SudaThe 10th International SPRING Seminar on Nuclear Physics - New Quest in Nuclear Structure - May 21-15, 2010, Vietri Sul Mare, Italy
Electron Scattering - towards Hofstadter’s experiments for exotic nuclei T. Suda
JUSTIPEN-EFES conference
AIZU, JAPANCutting Edge Physics of Unstable nuclei Nov. 10-13, 2010,

154

Electron Scattering - towards Hofstadter’s experiments for exotic nuclei T. Suda
French-Japanese symposium on Nuclear Structure Problems Jan. 04-08, 2011, Wako, Japan

学位論文 (電子光理学研究センター所属)
修士論文 「π 0 光生成反応によるバリオン共鳴 N*(1670) の研究」
甲斐田 俊, 平成 22 年, 東北大学
修士論文 「π 0 -π 0 相互作用の研究」
高橋 真一郎, 平成 22 年, 東北大学

学位論文 (他機関所属)
博士論文「Study of charged-pion photoproduction on the deuteron」

Yun-Cheng HAN, (2010)，蘭州大学
博士論文「An Investigation of the Elementary Photoproduction of Strangeness in the Threshold Region」
二ツ川健太，平成 22 年，東北大学
博士論文「The R&D experiments for electron scattering off unstable nuclei」

WANG, Shuo, 2010，北京大学
修士論文「高強度荷電粒子ビーム飛跡解析用のシリコンストリップ検出器の開発」
浅野秀光, 平成 21 年度 (2010), 京都大学
修士論文「J-PARC E15 実験のための全反射型ガラスチェレンコフ検出器の開発」
佐田優太, 平成 21 年度 (2010), 京都大学
修士論文「中性Ｋ中間子スペクトロメーターにおける 3 次元飛跡解析法の開発」
山本郁也，平成 22 年，東北大学
修士論文「Development of GEM tracker for in-medium φ → e+ e− measurement」
小松雄哉, 平成 22 年度 (2011), 東京大学
修士論文「Performance of γ-ray calorimeter and neutron TOF detector for measurements of ω meson

mass in nuclear medium」
桝本新一, 平成 22 年度 (2011), 東京大学
修士論文「荷電粒子識別用ホドスコープのための波長変換ファイバー読み出し系の研究」
久保田 尚矢, 平成 22 年，山形大学

155

Steering Committee* Chairperson
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

156

General Advisory Committee* Chairperson
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

157

Program Advisory Committee* Chairperson
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

158

159

平成 22 年度前期採択課題一覧
課題番号

課

題

名

申込責任者

採択シフト数原子核関連分野

2708

電子ビームによる SOI/MOSFET への Total Ionizing Dose 効果

山本 均

5

の測定

2710

バリオン共鳴 N*(1670) の研究 (5)

清水 肇

60

2711

BSO、BGO、PWO、CsI クリスタル検出器の波形

石川 貴嗣

5

2713

γp → π 0 p 反応、γp → π + n 反応を用いた STB 1200 MeV 運転

神田 浩樹

6

における BM4 ガンマビームのエネルギー測定

2714

KOTO 実験荷電粒子検出器の性能評価

南條 創

3

2715

APD, MAPD 読み出しによる CsI(Tl) カロリメータの開発

今里 純

4

2716

Study of Neutral Kaon Photoproduction on Deuterium Target

金田 雅司

5

by NKS22717

4π 電磁カロリメータ BGO EGG のエネルギー分解能の測定

藤村 寿子

12

2718

SOI ピクセル検出器を用いた電子ビーム飛跡再構成性能試験

山本 均

3

放射化学関連分野

2700

99mTc の壊変定数の化学形に対する依存性

高宮 幸一

1

2701

光量子放射化分析による、地球・宇宙科学的試料中の微量元素の定

関本 俊

1

量

2702

超臨界水利用の MOX 燃料製造と核分裂生成物分離に関する研究

山村 朝雄

1

2703

放射化分析法による通信材料中の不純物評価

鹿野 弘二

1

2704

選択硫化を用いる使用済燃料の再処理法の研究

桐島 陽

1

2705

(γ, n) 生成核種の半減期精密測定

廣瀬 健太郎22706

固体抽出剤を用いた希土類元素とアクチノイド元素の分離に関する

鈴木 達也

1

研究

2707

宇宙化学的試料および環境試料の光量子放射化分析

大浦 泰嗣

3

2709

陽電子消滅γ線ドップラー拡がり測定装置の較正用線源 (Sr-85) 製

木野 康志

1

フィッション・トラック法による Pa-231 光核分裂反応断面積の測定

横山 明彦

2

2719

電荷分散型 GEM 検出器のテスト

小沢 恭一郎1

2720

KOTO 実験 CsI 波長変換ファイバー読み出しの電磁シャワーに対

南條 創

1

造

2712
随時申込

する応答試験

160

平成 22 年度後期採択課題一覧
課題番号

課

題

名

申込責任者

採択シフト数原子核関連分野

2722

ミューオン電子転換過程探索実験 COMET 用電磁カロリメーター

佐藤 朗

4

の開発

2723

J-PARC E16 実験用 GEM トラッカーの性能評価

小沢 恭一郎82725

ゲート機能付き TPC 飛跡検出器の性能試験

佐藤 進

4

2727

J-PARC P36 実験用エアロジェルチェレンコフ カウンターの開発

豊田 晃久

4

2728

波長変換ファイバーを用いた新電磁カロリメータ用電荷識別用ホド

石川 貴嗣

3

河合 秀幸

1

河合 秀幸

2

橋本 治

108

スコープの開発2729

シリカエアロゲル+WLS+PPD を用いたしきい値型チェレンコフカ
ウンターの性能評価

2730

多数の PPD を用いた正方形プラスチックシンチレーターの時間分
解能の測定

2731

Photo-production of a Neutral Kaon and/or a Lambda Hyperon
on a deuteron near the threshold2732

水素標的における πη 光生成反応の研究

藤村 寿子

62

2733

SOI ピクセル検出器を用いた電子ビーム飛跡再構成性能試験 2

山本 均

0

放射化学関連分野

2721

51Cr の壊変定数の化学形に対する依存性

高宮 幸一

1

2724

韓国原子力分野学生実験プログラム−核燃料サイクルにおける加速

佐藤 修彰

1

木野 康志

3

器利用と RI 製造

2726

陽電子消滅 γ 線ドップラー拡がり測定装置の陽電子および較正用線
源 (Na-22,Sr-85) 製造

2734

宇宙化学的試料および環境試料の光量子放射化分析

大浦 泰嗣

2

2735

光量子放射化分析による、地球・宇宙科学的試料中の微量元素の定

関本 俊

2

横山 明彦

2

量

2736

フィッション・トラック法による Pa-231 光核分裂反応断面積の測定

2737(γ, n) 生成核種の半減期精密測定

廣瀬 健太郎22738

超臨界水利用の MOX 燃料製造と核分裂生成物分離に関する研究

山村 朝雄

1

2739

放射化分析法による通信用材料中の不純物評価

鹿野 弘二

1

三連四極電磁石による検出器テスト用陽電子ビームの集束

石川 貴嗣

施設実施

随時申込

2740