Ⅲ-1

Accelerators andInstruments

BL1UⅢ -1. Accelerators and Instruments

BL1U

Improvement of Image Quality of Selective Isotope 3D-CT in UVSOR-BL1U
H. Ohgaki1, K. Ali1, H. Zen1, T. Kii1, T. Hayakawa2, T. Shizuma2, M. Fujimoto3, Y. Taira3and M. Katoh3,4Institute of Advanced Energy, Kyoto University, Kyoto 611-0011, Japan
Tokai Quantum Beam Science Center, National Institutes for Quantum and Radiological Science and Technology,
Ibaraki 319-1106, Japan
3
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
4
Hiroshima University, Higashi-Hiroshima 739-8511, Japan
1

2

Ⅲ -1
Nuclear Resonance Fluorescence (NRF) is a
powerful tool to identify the specific isotope, especiallyin combination with a Laser Compton Backscattering(LCS) gamma-ray beam which provides quasimonochromatic and energy variable gamma-rays. We
have been developed an NRF-CT technique by using
the LCS gamma-ray beam available at the beamline
BL1U in UVSOR and demonstrated a three-dimensional(3D) isotope-selective CT image of the enriched leadisotope distribution of 208Pb in a cylindrical holder (Fig.
1), so far [1]. However, we needed 48 h beam time toobtain a CT image with a 4 mm/pixel in the horizontal
plane and 8 mm/pixel in the vertical plane using the
LCS gamma-ray beam with a beam size of 2 mm and aflux density of 10 photons/s/eV.
To overcome this problem, we proposed a fusion
visualization (FV) technique by combining the NRF-CT
image which provides a rough distribution of targeting
isotope with a gamma-ray CT image which can beobtained by the same measurement system with NRFCT but can provide better pixel resolution with a shortmeasurement time (5 hours) [2]. We measured a 3D
gamma-CT image of the same CT target [1] with the 3D
NRF-CT in BL1U. The obtained 3D gamma-CT image(Fig. 2) has a 1 mm/pixel resolution with an LCS
gamma-ray beam size of 1 mm and a flux density of 0.7
photons/s/eV. The target consists of two enriched leadisotopes (206,208Pb), iron, and aluminum. As shown in
Fig. 2, two enriched lead isotopes can be obtained but
we cannot identify which one is the target isotope 208Pb.
After a few FV methods were applied to construct an
FV image between NRF-CT and gamma-ray CT images,
the post-multiply FV method which can keep thequantitative information of NRF interaction was
selected. Figure 3 shows the 3D isotope-selective fused
CT image. Consequently, we can improve the image
quality of 3D NRF-CT of 208Pb rods embedded in thealuminum cylinder with 206Pb rod as well as iron rods
with keeping quantitative information of NRF
interaction.
[1] K. Ali et al., “Three-Dimensional Nondestructive
Isotope-Selective Tomographic Imaging of 208Pb
Distribution via Nuclear Resonance Fluorescence.”
Appl. Sci. 11 (2021) 3415.
https://doi.org/10.3390/app11083415.

[2] K. Ali, et al., “Fusion Visualization TecFighniqueto Improve a Three-Dimensional Isotope-Selective CT
Image Based on Nuclear Resonance Fluorescencewith a Gamma-CT Image”, Appl. Sci. 11 (2021) 11866.
https://doi.org/10.3390/app112411866.

Fig. 1. 3D NRF-CT image measured in BL1U.

Fig. 2. 3D Gamma-ray CT image measured in BL1U.

Fig. 3. 3D FV NRF-CT image

33 1 Ⅲ01-

BL1U
Ⅲ -1. Accelerators
and Instruments

BL1U

Photon Counting Experiments of Young's Double-Slit Interference Using
Undulator Vortex Radiation

Ⅲ -1

S. Wada1,2, H. Ohta2, A. Mano3, M. Fujimoto4,3 and M. Katoh5,2,4

Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
2
Faculty of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
3
Synchrotron Radiation Research Center, Nagoya University, Nagoya 464-8603, Japan
4
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
5
Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima 739-0046, Japan

1

Recent theoretical and experimental progresses in thesynchrotron radiation technology reveal that highharmonics emitted from a helical undulator possesses
helical wave-front structure [1,2]. The undulator
beamline BL1U at UVSOR can produce fundamental
and its harmonics of circularly polarized radiation invisible and UV regions. Therefore, leading experiments
using vortex radiation from the undulator have been
conducted [3,4]. Especially, Young’s double-slit
interference experiments demonstrated the characteristic
nature of vortex radiation as a singularity in the middleof the interference pattern arising from helical wavefront structure. This phenomenon is quite interestingfrom the view point whether a single photon
spontaneously emitted from a high-energy electron canalso possess such a characteristic or not. In this study,
we demonstrated Youngs double-slit experiments underphoton-counting condition in order to confirm the above
nature of vortex radiation from a helical undulator [5].
Experiments were performed at UVSOR BL1U
under quite low-current mode (less than 1 mA).
Circularly polarized radiation centered at 355 nm ofsecond harmonics was extracted from a vacuum
beamline to atmosphere via a quart window, passed
through an iris and an interference filter (Alluxa 7057)
in order to extract center part and remove fundamental
710 nm light from the undulator radiation, and thenirradiated onto a double-slit (0.1 mm width and 1 mm
separation). By using as few optics as possible mentioned
above, we could achieve very low simultaneous
detection of two photons, that is single-photon counting
condition in keeping helical wave-front structure. Single
photons after interference were detected by a gated
ICCD camera system (Hamamatsu Photonics, M797101 and ORCA-05G) 1 m far from the double-slits.
After confirming the double-slit interference in thisexperimental setup under multiphoton detection modeusing a normal CCD camera, we could measureinterference pattern even by photon counting detection
as shown in Fig. 1(a). The figure was obtained byintegrating 5000 shots of images with an exposure timeof 200 us, and about 150 photons were randomly
detected in each image. As clearly shown in the figure,
we can find stripes due to interference by the double-slit
and the singularity, that is mismatch of stripes at thedark middle region. The result obviously demonstrates
that the interference patters of circularly polarizedradiation from a helical undulator exhibit characteristics
of optical vortex even under single-photon counting
condition. The nature of vortex radiation from theundulator in the photon-counting condition is also
confirmed by removing the double-slit as shown in Fig.
1(b), indicating the integrated beam profile like donutshaped with the center missing. This is characteristic ofvortex radiation with no light intensity due to a phasesingularity.

Fig. 1. (a) Young's double-slit interference pattern ofvortex radiation measured at BL1U under photoncounting condition. (b) Integrated beam profile
without the double-slit.

[1] S. Sasaki and I. McNulty, Phys. Rev. Lett. 100 (2008)
124801.
[2] J. Bahrdt et al., Phys. Rev. Lett. 111 (2013) 034801.
[3] M. Katoh et al., Sci. Rep. 7 (2017) 6130.
[4] T. Kaneyasu et al., J. Synchrotron Rad. 24 (2017)934.
[5] H. Ohta, B.Sc. Thesis, Hiroshima University (2021).

34 2 Ⅲ01-

Others

Ⅲ -1. Accelerators and Instruments

OthersDevelopment Mass Production Facilities of Nuclear Emulsion Films
I. Usuda, H. Rokujo and M. Nakamura

Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan

Nuclear emulsion is a kind of photographic films
that have sensitivity for ionizing radiation. The films
record tracks of charged particle with high angularresolution.
In Nagoya University, we have developed gel
production machine and developed several types of
emulsion by ourselves. We are planning someexperiments (e.g., gamma ray telescope, neutrino
interaction research, muon radiography) using morethan 500 m2 nuclear emulsion films.
Nuclear emulsion is made by coating emulsion gelon plastic base. Previously, it was difficult to makelarge amount of films because we have coatedemulsion gel by hand.
We have developed roll-to-roll coating machine in
Nagoya University (Fig. 1). For mechanical coating, wehave tried to add new chemicals to nuclear emulsion gel
and optimize the gel’s viscosity. We were the first in theworld to succeed in the mechanical coating of over 60
μm thickness of nuclear emulsion films. We also
introduced new gel production machine that can make30 times amount of nuclear emulsion gel compared withconventional machine.
Now, we can make about 100 m2 nuclear emulsion
films per month.
We checked the performance of new emulsion gel
and films. The index of sensitivity is Grain Density(GD) which is number of silver grains in the tracks ofminimum ionized particle. The index of noise rate is
Fog Density (FD) which is number of randomly
generated silver grains unrelated to tracks. After we
exposed electron beam to emulsion films at UVSOR(Fig. 2), we evaluated GD and FD.
We checked that GD and FD of nuclear emulsion
gel and films which made by mass production facilities
are comparable to that of conventional products. And
the performance is stable for repeated operation. (Fig.
3, 4)

Ⅲ -1

Fig. 1. Overview of roll-to-roll coating machine in
Nagoya University.

Fig. 2. Optical microscopic image of electron beam
(several tens of MeV) track. The electron beam was
exposed at UVSOR.

Fig. 3. Difference of Grain Density (GD) by emulsion
gel batch.

Fig. 4. Difference of Fog Density (FD) by emulsion
gel batch.

35 3 Ⅲ01-

BL1U
Ⅲ -1. Accelerators
and Instruments

BL1U

Laser Pulse Shaping and Transport at UVSOR-III
Y. Takashima 1,2, A. Mano1, G. Jang2, Y. Taira3, M. Fujimoto3, Y. Okano3 and M. Katoh4,3Synchrotron Radiation Research Center, Nagoya University, Nagoya 464-8603, Japan
2
School of Engineering, Nagoya University, Nagoya 464-8603, Japan
3
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
4
HiSOR, Hiroshima University, Higashi-Hiroshima 739-0046, Japan1

Ⅲ -1

We constructed the compact optics to shape a laser
pulse to develop advanced Laser-Compton scattering
gamma-ray source or sophisticated laser-synchrotron
radiation combination experiment. The optics is a kindof Michelson interferometer [1]. As the first step, we
tried to generate two temporally consecutive laser
pulses (double pulse) from one original laser pulse. We
confirmed generating double pulses.
Figure 1 shows the optics for the generation of the
double pulse of the short-pulse laser. The original laser
pulse is injected from the direction of arrow 1 in Fig.
1. The laser pulse is divided into the orthogonal
direction "A" and "B" by the beam splitter in Figure 1;
the laser pulses are reflected by the mirror 1 and 2.
Mirror 2 is mounted on the movable stage so that thepath length of the laser pulse along to "B" can bechanged. The reflected pulses are mixed in the beam
splitter and go throw the direction "C", and thenreflected the mirror 3 and exit to the direction "D".
We used an autocorrelator to measure the pulse
width and the interval of the double pulses. The
autocorrelator is installed downstream of the direction"D". According to the measurement using the
autocorrelator, when we interrupt the laser pulse
reflected on mirror 1, the FWHM of the pulse width ofthe laser of the single pulse is about 5.0 ps. Figure 2
showed the output signal from the autocorrelator when

we arranged the difference of the path length
appropriately by moving the stage of mirror 2. We
obtained the interval of the double pulse of about 3.0
ps. Fig. 3. shows the spectrum of the double pulse laser.
We successfully transported the laser pulse onto thecirculating electron beam in the UVSOR-III storage
ring by using the existing laser transport line for theLaser-Compton scattering.

Fig. 2. The output signal of the autocorrelator.

Fig. 3. The spectrum of the double pulse laser.

Fig. 1. Optics for the generation of the double pulse.

[1] G. Jang, Graduation thesis of School of Engineering,
Nagoya University (2021)

36 4 Ⅲ01-

BL1U

Ⅲ -1. Accelerators and Instruments

BL1U

Revival of UVSOR-FEL and Gamma Ray Generation
by Intra-cavity Laser Compton Scattering
H. Zen1, J. Yamazaki2, M. Fujimoto2,3, K. Hayashi2, H. Ohta2, Y. Taira2,3 and M. Katoh2,4Institute of Advanced Energy, Kyoto University, Uji 611-0011, JapanUVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
3
The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
4
Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima 739-0046, Japan
1

2

Compton scattering [2]. In this study, two small
current electron bunches were injected into 3 backets
behind the main bunches for generating gamma-ray by
colliding with intra-cavity FEL beams. The spectrumof the generated gamma-ray measured by a NaI
scintillator is shown in Fig. 2. The maximum gammaray energy was evaluated as 13 MeV. In thismeasurement, the optical cavity length was slightly
detuned to avoid the pile-up events in the scintillator.

Intensity [Arb. Units]

1.0
0.8
0.6
0.4
0.2
0.0
520

522

524

526

Wavelength [nm]

528

530

Fig. 1. Wavelength Spectrum and beam profile of
FEL observed at the downstream of the optical cavity.
100

Counts [# /s / 0.1 MeV]

The lasing of Free Electron Laser (FEL) at S5 section
was firstly achieved in 1992. The research activity
related to FEL had been continued until the end of
FY2011. Then the straight section used for activities of
FEL and coherent light source developments waschanged to S1, which has been newly created by moving
the injection point. Two APPLE-II type undulators with
an electromagnetic buncher magnet have been installedin the S1 section. The optical cavity used for FEL lasing
was removed from S5 section at the end of FY2010 andreconstructed at the beginning of FY2015. In FY2017,
we tried to have a first lasing of FEL at S1 section. At
that time, we could achieve storage of undulator
radiation in the optical cavity [1] but could not achieve
FEL lasing due to a mismatch between the optical cavity
length and the electron bunch interval. In the April-2021
shutdown of UVSOR, the position of the downstream
mirror chamber was shifted to make the roundtrip
frequency of the optical cavity the same as the electron
bunch interval. In February 2022, a commissioning
experiment of optical cavity and FEL was conducted toconfirm the FEL lasing at S1 section.
The commissioning experiment of FEL was performed
with an FEL cavity mirror pair which has highreflectivity around 520 nm. At first, the gap and thephase of the APPLE-II undulators are adjusted to havethe center wavelength of 520 nm with the electron beamenergy of 600 MeV. Next, the angles of the opticalcavity mirrors were adjusted to store the undulator
radiation in the optical cavity. Then the length of the
optical cavity was scanned for finding the matchingcondition between the roundtrip frequency of the opticalcavity and the electron bunch interval. This adjustment
was performed with two bunch equidistant filling mode.
The pulse duration of the stored light is strongly
depending on the cavity length. The cavity length
condition giving the shortest pulse duration of the stored
light should be corresponding with the matched
condition. After finding the matched condition of thecavity length, the electron beam current was increased
up to 20 mA/2 bunch and the excitation current of thebuncher magnet was increased up to 20 A. With a slightadjustment of the angle of the optical cavity mirror,
lasing of the FEL can be achieved. Figure 1 shows thephotograph of the FEL beam and its wavelength
spectrum. The bright green spot in the photograph was
the FEL beam having a central wavelength of 524.5 nm.
One of the interesting applications of UVSOR-FEL
is the gamma-ray generation by the intra-cavity laser

600 MeV, 524.4 nm
FEL bunch: 12.6 mA
LCS bunch: 3.9 mA
FEL Power: 0.3 mW
Collimator: 2.8 mm

80
60
40
20
0

0

2

4

6

8

10

Energy [MeV]12

14

Fig. 2. The spectrum of the generated gamma-ray
measured by a NaI scintillator.

[1] H. Zen et al., UVSOR Activity Report 2017 45(2018) 31.
[2] M. Hosaka et al., Nucl. Instrum. Meth. A 393 (1997)525.

37 5 Ⅲ01-

Ⅲ -1

BL1U
Ⅲ -1. Accelerators
and Instruments

BL1U

Evaluation of Analyzing Power of Gamma-ray Polarimeter
S. Endo1,2, T. Shizuma3, H. Zen4, Y. Taira5, K. Sugita5, O. Mohamed1, S. Kawamura2,
R. Abe2, T. Okudaira2, M. Kitaguchi2 and H. M. Shimizu2
Japan Atomic Energy Agency, Tokai 319-1195, Japan
2
Nagoya University, Nagoya 464-8062, Japan
3
National Institute for Quantum Science and Technology, Tokai 319-1195, Japan
4
Kyoto University, Uji 611-0011, Japan
5
Institute for Molecular Science, Okazaki 444-8585, Japan1

Ⅲ -1
A measurement of a circular polarization ratio of the
gamma-rays emitted from an un-polarized neutron
capture reaction of nuclei leads to the study for thecompound nuclei [1]. Furthermore, the total angularmomentum of neutron resonances can be determinedby measuring the circular polarization ratio of gammarays from a polarized-neutron capture reaction [2]. We
are aiming to conduct these measurements at JPARC/MLF. The degree of the circular polarization of
gamma-rays can be determined by measuring thetransmission ratio of the magnet, called a gamma-ray
polarimeter, because the cross-section of the Compton
scattering depends on the direction of the electron
polarization in the magnetized material and the
gamma-ray helicity, i.e., circular polarization [3]. We
developed a gamma-ray polarimeter and evaluated its
analyzing power using a circularly polarized gammaray beam generated by the inverse Thomson scatteringin the UVSOR BL1U [4].
The analyzing power is defined as�� ���

𝑃𝑃� � �� ��� ,where 𝑁𝑁 � and 𝑁𝑁 � are the transmission ratio of thepolarimeter for right- and left-circularly polarized
gamma-rays, respectively. Figure 1 shows the schematicof the experiment. The beam flux was monitored bydetecting gamma-rays scattered from brass with a LaBr
detector. Gamma-rays transmitting the polarimeter weredetected using a Ge detector. Figure 2 shows the
gamma-ray energy spectrum taken by the Ge detector.
Background measurement was performed with the laser
off. Therefore, it includes the environmental radiation
and backgrounds derived from the Bremsstrahlung. The
pile-up effect was corrected, and the transmission ratio
was obtained from the number of events for the LaBr
and Ge detectors.
Since the analyzing power depends on the magnetic
field, it depends on the current flowing the polarimeter.
Figure 3 shows the obtained analyzing power for eachcurrent for 100% circularly polarized gamma-rays.
The current up and down mean whether the current
was increased or decreased, respectively, reflecting theeffect of magnetic hysteresis. The analyzing power
was obtained as 𝑃𝑃� � 2.12 � 0.04% above 2 A.

Fig. 1. Schematic of experimental setup.

Fig. 2. Gamma-ray energy spectrum taken by the Ge
detector.

Fig. 3. Analyzing power for each current.

[1] V.V. Flambaum and O.P. Sushkov, Nucl. Phys. A
435 (1985) 352.
[2] L.C. Bindenharn et al., Phys. Rev. 83 (1951) 683.
[3] H.A. Tolhoek, Rev. Mod. Phys. 28 (1956) 277.
[4] Y. Taira et al., Nucl. Instrum. Meth. Phys. Res. A
637 (2011) 116.

38 6 Ⅲ01-

BL1U

Ⅲ -1. Accelerators and Instruments

BL1U

Development of Gamma ray Induced Positron Annihilation Spectroscopy
Y. Taira1,2, K. Sugita1,2, R. Yamamoto3, Y. Okano1 and T. Hirade4

UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
3
Graduate School of Engineering, Nagoya University, Nagoya, 464-8603, Japan
4
Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Tokai, 316-8511, Japan
1

2

Positron annihilation spectroscopy (PAS) is an
excellent method to detect lattice defects in solids suchas vacancies, dislocations, and clusters and freevolumes in polymers [1]. Conventional β+ radioisotopes
such as 22Na, a positron beam generated from anelectron accelerator, and a high energy gamma ray [2,3]are used for PAS. PAS using a high energy gamma ray,which is called gamma ray induced PAS (GiPAS), has
several advantages compared with PAS using
conventional radioisotopes. (i) It enables defect analysis
of a thick material in a few centimeters because
positrons are created throughout a bulk material via pair
production by irradiation with gamma rays having highpenetration into the material. (ii) Source contribution of
positrons annihilated in the covering material isnegligible. In conventional radioisotopes, about 10 % ~15 % of positrons annihilate in the source. This distorts
the positron lifetime spectra and complicates the data
analysis.
Inverse Thomson/Compton scattering is a scattering
process between high energy electrons and a laser,which can produce high energy gamma rays. A MeV
gamma ray can be generated by the scattering between a
1 GeV electron and a 1 eV photon. The generated gamma
rays possess features such as quasi-monochromatic andtunable energy, highly polarized, low divergence angle,
and low background. Inverse Thomson/Compton
scattered gamma rays have been generated at several
electron accelerator facilities in the world. We havedeveloped ultra-short pulsed gamma rays by inverse
Thomson scattering at UVSOR-III [4]. They are
generated via inverse Thomson scattering with 90
degree collisions between a 750-MeV electron beam
and a Ti:Sa laser pulse. The maximum energy is 6.6
MeV and the pulse width is calculated to be sub-ps to ps
ranges.
We are currently developing GiPAS using the ultrashort pulsed gamma ray [5]. Gamma ray induced
positron annihilation lifetime spectroscopy (GiPALS),
which is a technique to measure positron lifetime andevaluate type of defects at the nanometer scale andtheir concentrations inside material, is currently
available for users. The measured positron lifetime
spectrum of stainless steel distributed by National
Metrology Institute of Japan (NMIJ) as referencematerial for positron lifetime is shown in Fig. 1. The
positron lifetime spectrum was analyzed using LT9
program.
In addition to GiPALS, we have developed gamma

ray induced age-momentum correlation (GiAMOC),
which is a technique to measure time resolved
momentum distribution of an electron which is theannihilation counterpart of a positron. The measured
AMOC spectrum of the NMIJ stainless steel is shownin Fig. 2.

Fig. 1. Measured positron lifetime spectrum of NMIJ
stainless steel. Time resolution is 138 ps in full widthat half maximum.

Fig. 2. GiAMOC spectrum of NMIJ stainless steel.

[1] J. Cizek, J. Mat. Sci. Tech. 34 (2018) 577.
[2] F. A. Selim, Acta Phys. Pol. A 132 (2017) 1450.
[3] M. Butterling et al., Nucl. Instr. Meth. Phys. Res.
B, 269 (2011) 2623.
[4] Y. Taira et al., Nucl. Instr. Meth. A 652 (2011) 696.
[5] Y. Taira et al., Rev. Sci. Instr. 84 (2013) 053305.

39 7 Ⅲ01-

Ⅲ -1

BL1U
Ⅲ -1. Accelerators
and Instruments

BL1U

Single Electron Storage at UVSOR-III
R. Shinomiya 1, M. Shimada 2,3, H. Miyauchi 2,3, M. Fujimoto 4 and M. Katoh 3,1,4,2

School of Science, Hiroshima University, Higashi-hiroshima 739-8526, Japan
High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
3
Hiroshima Synchrotron Radiation Research Center, Hiroshima University, Higashi-hiroshima 739-0046, Japan
4
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
1

2

Ⅲ -1

Single electron storage in an electron synchrotron(electron storage ring) has been achieved at several
facilities, aiming to investigate electron dynamics in asynchrotron [1,2], to investigate electromagnetic
radiation from an electron [3,4], or to utilize theradiation as a primary standard [5,6]. However, in Japan,
as far as we know, there is no report on such studies.
We have tried the single electron storage at UVSORIII aiming to establish accelerator techniques for thisspecial operation mode toward novel experiments infuture.
The experimental procedure is as follows. First, we
accumulate an electron beam with relatively low current,
typically around 1 mA. Then, we reduce the beam
current by using a device called beam scraper, which isa movable copper rod installed on the beam pipe at astraight section. We can insert the rod into the beam pipe
close to the beam from the vertical direction. When we
make the distance between the rod and the beam around
1 mm, the beam lifetime becomes several minutes,
which is much shorter than the normal one, typicallyseveral hours. We observe the beam current by using
DCCT until around 0.1 mA. Below this beam current,
the DCCT cannot give reliable data. Then, we use aphotomultiplier tube (PMT) to measure the synchrotron
radiation intensity at BL1U, where ultraviolet radiation
can be produced from an undulator. The wavelength of
the fundamental radiation from the undulator was set tobe 355 nm. The PMT was set at a small dark room
surrounded by black curtains, where the undulator
radiation was extracted from the ultra-high vacuum
chamber of the beamline to the air through a sapphire
window. The signal from the PMT was analyzed with acounting unit and was recorded by a PC. We tried toapply various bandpass filters to improve the signal tonoise ratio. We found that a bandpass filter which had amoderately large bandwidth of about 60 nm and passed
almost all the fundamental component of the undulator
radiation gave the best result.
We mounted four ND filters with OD 2.0 on the PMTat the start of the measurement. As decreasing the beam
current, we removed them one by one as keeping thecounting rate of PMT lower than the limit of theprocessing rate of the counting unit. After removing all
the ND filters, we successfully observed step-functionlike jumps in the time history of the counting rate as
shown in Fig. 1, which indicated the loss of the electrons
one by one. The background rate is much smaller than
the step of the counting rate, which corresponds to theradiation intensity emitted from one electron. The
observed counting rate from one electron was consistent
with a preliminary evaluation of the photon flux basedon an analytic formula.
We do not describe the details here, but we also
succeeded in observing which RF backet the lastelectron existed in. Moreover, after confirming that
only one electron is circulating, we pulled out thebeam scraper and observed that the last electron wasstored for more than 2 hours, which is sufficiently longto carry out the experiments with single electron.
In conclusion, we successfully demonstrated thesingle electron operation at UVSOR-III and establish
the basic techniques for this special operating mode.
We are going to start novel researches utilizing thisnew mode.

Fig. 1. Synchrotron radiation intensity at BL1U.

[1] A. N. Aleshaev et al., NIM A 359 (1995) 80.
[2] I. V. Pinayev et al., NIM A 375 (1996) 71.
[3] I. V. Pinayev et al., NIM A 341 (1994) 17.
[4] A. Romanov et al., JINST 16 (2021) P12009.
[5] R. Klein et al., Phys. Rev. STAB 11 (2008) 110701.
[6] R. Klein et al., Metrologia 47 (2010) R33.

40 8 Ⅲ01-

BL1U

Ⅲ -1. Accelerators and Instruments

BL1U

Exploring Novel Application of Undulator Radiation Based on
Interferometric Technique
K. Kato1, M. Shimada2,3, H. Miyauchi2,3, A. Mano4 and M. Katoh3,1,5,2,4

School of Science, Hiroshima University, Higashi-hiroshima 739-8526, Japan
High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
3
Hiroshima Synchrotron Radiation Research Center, Hiroshima University, Higashi-hiroshima 739-0046, Japan
4
Synchrotron Radiation Research Center, Nagoya University, Nagoya 464-8603, Japan
5
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan1

2

The classical electromagnetic theory indicates thatradiation from a relativistic electron running in an
undulator forms a wave packet whose number ofcycles is exactly same as the number of magnetic
periods of the undulator. In case of the undulator at
BL1U, the number of the magnetic period is 10. If we
set the wavelength of the fundamental radiation at 355
nm, then the wave packet has a length of 3.5 micron
which corresponds to about 10 femtosecond. This“ultrafast” property of synchrotron radiation has
merely been considered useful for any applications
except for only a few previous works [1]. However,recently, at UVSOR, interesting applications of thisproperty has been demonstrated successfully [2,3,4].
Following these successes, we continue exploringother possible applications. We were inspired by aprevious study using interferometer, in which theundulator radiation showed a clear interferogram [5].
We started considering an application to the tomographic
imaging. In the optics technology field, a technology
called optical coherence tomography has beensuccessfully demonstrated and are widely usedparticularly in the medical field [6]. Its principle may bedescribed as follows. A low coherence light beam splits
into two by means of a beam splitter. Two beams arereflected by mirrors and come back to the beam splitterand merge. When the path lengths are exactly same,interference fringe is observed in the merged beam. If asample material is inserted on a path, because of therefractive index of the sample, the path length which
gives the interference changes. Moreover, if multireflection takes place in the sample, interference isobserved at several different path lengths. From suchobservation, one can get information on the inner
structure and its optical property of the sample. We havecarried out a proof of principle experiment on such atomography method using undulator radiation at BL1U[7]. Some preliminary results are presented here.
The wavelength of the undulator radiation was
selected at 355 nm, which is compatible with thewavelength range of the Mach–Zehnder interferometer,
which was constructed in a previous study [5]. We
utilized the existing interferometer to observe thechange of the interferogram as putting samples on its
light paths. We tried two configurations, transmitting
and reflecting ones. To minimize the modification of
the interferometer, in the former configuration, we justplaced the sample on the one of the path after the beam
splitter, and, in the latter, we placed the sample at thereflecting mirror.
We carried out the interferogram measurements onsome thin materials such as glass plates or films andseveral stimulated samples which has multilayer
structure. One example of the interference fringe isshown in Fig. 1. In this measurement, a thin film is placedin a transmitting configuration. The sample covered ahalf of the light path. By adjusting the optical path
length, we could observe interference fringe only for thehalf area where the film existed. More details will bepresented in future papers.

Fig. 1. Interference fringe observed for 25 micron
OPP film as a sample. In the upper side, the OPP filmis placed and in the lower none.

[1] S. Nakanishi et al., J. Synchrotron Rad. 5 (1998)
1702.
[2] T. Kaneyasu et al., Phys. Rev. Lett. 123 (2019)
233401.
[3] Y. Hikosaka et al., Nature Comm. 10 (2019) 4988.
[4] T. Kaneyasu et al., Phys. Rev. Lett. 126 (2021)
113202.
[5] e.g. D. Huang et al., Science 254 (1991) 1178
[6] A. Mano et al. UVSOR Activity Report 2020 48(2021) 38.
[7] K. Kato et al., presented at JSR 2022 (2022).

41 9 Ⅲ01-

Ⅲ -1

BL2A
Ⅲ -1. Accelerators
and Instruments

BL2A

Calibration of CMOS Sensor with Reflective-type Flux Reduction System
N. Narukage

National Astronomical Observatory of Japan, Mitaka 181-8588, Japan

Ⅲ -1

The solar corona is full of dynamic phenomena suchas solar flares. The understandings of these phenomena
have been progressing step-by-step with the evolutionof the observation technology in EUV and X-rays fromthe space. But there are fundamental questions remainunanswered or haven’t even addressed so far. Ourscientific objective is to understand underlying physics
of the dynamic phenomena in the solar corona, coveringsome of the long-standing questions in solar physics
such as particle acceleration in flares and coronalheating. To achieve this objective, we identify theimaging spectroscopy (the observations with spatial,
temporal and energy resolutions) in the soft X-ray range(from ~0.5 keV to ~10 keV) is a powerful approach forthe detection and analysis of energetic events [1]. This
energy range contains many lines emitted from below 1
MK to beyond 10 MK plasmas plus continuum
component that reflects the electron temperature.
The soft X-ray imaging spectroscopy is realizedwith the following method. We take images with ashort enough exposure to detect only single X-ray
photon in an isolated pixel area with a fine pixel
Silicon sensor. So, we can measure the energy of the
X-ray photons one by one with spatial and temporal
resolutions. When we use a high-speed soft X-ray
camera that can perform the continuous exposure witha rate of more than several hundred times per second,
we can count the photon energy with a rate of several
10 photons / pixel / second. This high-speed exposure
is enough to track the time evolution of spectra
generated by dynamic phenomena in the solar corona,
whose lifetimes are about form several ten seconds toseveral minutes. For the first imaging spectroscopic
observation of the solar corona in soft X-ray range, welaunched a NASA’s sounding rocket (FOXSI-3) on
September 7th, 2018 and successfully obtained theunprecedented data [2] using a high-speed X-ray
camera [3] with a back-illuminated CMOS sensor [4].
Calibration of CMOS detectors is essential forscientific data analysis. For this purpose, a completely
monochromatic X-ray light source is needed. In
addition, the flux must be adjusted so that individual
X-ray photons can be isolated. Therefore, so far, wehave controlled (reduced) the flux by adjusting thematerial and thickness of metal filters. However, in
this case, the lower energy was preferentiallyattenuated, so the contamination of higher-order (2nd,
3rd and 4th order) components could not be removed,
resulting in incomplete data for calibration.
In this time, we developed a mirror-based reflectivetype flux reduction system (see Fig. 1). In this system,
two flat mirrors aligned in parallel are mounted on arotating stage, and by changing the angle of incidence,
the reflectance, i.e., attenuation rate, can be flexibly

adjusted. The system worked well as expected andsuccessfully produced the completely monochromatic
light with the appropriate flux. As a result, theresponse of the CMOS detector used in the FOXSI-3
sounding rocket project could be completely
calibrated in the energy range of 830 eV to 4500 eV in
50 eV intervals (see Fig. 2).

Fig. 1. Photo (left) and schematic
drawing (right) of the reflectivetype flux reduction system.

Fig. 2. Measured (black data points) and modeled(colored lines) response of the CMOS sensor to themonochromatic X-rays (at 2905.1 eV in this case).
[1] N. Narukage et al., White paper of the “soft X-ray
imaging spectroscopy”, arXiv:1706.04536 (2017).
[2] N. Narukage and S. Ishikawa, UVSOR Activity
Report 2018 46 (2019) 36.
[3] S. Ishikawa et al., Nuclear Instruments andMethods in Physics Research Section A, 912 (2018)
191-194.
[4] N. Narukage et al., Nuclear Instruments andMethods in Physics Research Section A, 950 (2020)
162974.

42 10 Ⅲ01-

BL3B

Ⅲ -1. Accelerators and Instruments

BL3B

Photon Energy Resolutions of BL3B Evaluated by Appearance Energy
Measurements of Xe+ Ions
H. Iwayama1,2

UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan1

2

A beamline in s synchrotron facility generally works
as a monochromator and focus system. A photon
energy resolution of the beamline is one of the mostimportant parameters for various measurements. To
maintain the performance of the beamlines, it isdesirable to check the actual photon energy resolution
regularly.
The beamline BL3B can provide monochromatic
light in the range from visible to extreme ultraviolet
region. Previously the photon energy resolution of
BL3B was evaluated by vibration-rotation spectra ofoxygen molecules [1], which are significantly complex.
In this work, we estimate photon energy resolutions of
BL3B from appearance energy spectra, which havestep functional structure at an ionization threshold.
The photoelectron-photoion coincidence (PEPICO)
measurements for an ion time-of-flight mass spectrum
were performed at UVSOR BL3B. A schematic view of
PEPICO measurements is described in the previous
report [2]. Sample gas is xenon, whose ionizationthreshold is 12.130 eV [3]. The ion mass spectra wererecorded at photon energies ranging from 12.100 eV to
12.200 eV in 0.001 eV-increments. We used G1 gratingof BL3B. We estimate photon energy resolutions forthree slit configurations of (entrance slit, exit slit) = (500μm, 500 μm), (300 μm, 300 μm) and (100 μm, 100 μm).
Figure 1 shows a typical mass spectrum of Xe ions.
The peak structure results from an isotope distributionof Xe atoms. The corresponding mass resolution
m/Δm is 400.
Figure 2 shows Xe ions yield spectra for three slit
configurations. We find steep rises at the ionizationthreshold of 12.130 eV. With narrowing slit sizes, stepsof Xe ion yield spectra become steeper. This showsthat photon energy resolution become better. From
three spectra, we estimate photon energy resolutions
for three slit configurations and summarize Table 1. In
future, we also perform estimations of photon energy
resolutions for G2 and G3 gratings.

Ⅲ -1

Fig. 1. Typical time-of-flight mass spectrum of Xe ions.

Fig. 2. Xe ion yield spectra around the ionizationenergy of 12.130 eV for three slit configurations.
Table 1. Photon energy resolutions for G1 grating
Slit size(500 μm, 500 μm)(300 μm, 300 μm)(100 μm, 100 μm)

ΔE @ hv=12eV
20 meV
11 meV
4.2 meVE / ΔE
600
1000
3000

[1] K. Fukui, et al., J. Synchrotron Rad. 21 (2014) 452.
[2] H. Iwayama and T. Horigome, UVSOR Activity
Report 2020 48 (2021) 41.
[3]https://physics.nist.gov/PhysRefData/ASD/levels_
form.html.

43 11 Ⅲ01-

BL4B
Ⅲ -1. Accelerators
and Instruments

BL4B

BL4B Usage for Developing the Photoelectron Spectroscopy End-station for
Organic Materials
K. Fukutani, H. Iwayama, F. Matsui and S. Kera
Institute for Molecular Science, Okazaki 444-8585, Japan

Ⅲ -1

The field of organic electronics has been prolific in
the last couple of years. However, the study of themolecular function and property using the synchrotron
light sources has been limited so far due to difficulty inthe measurements for irradiation sensitive materials andlack of the suitable environment for the comprehensive
experiments.
The soft X-ray beamline BL4B, monochromator was
designed to cover the energy range of 35 – 800 eV andused for XMCD and XAS by setting the user apparatus.
To achieve the fundamental understanding of chargetransport properties, adsorption properties, interface
energetics, chemical reactivity and so on, we placed theend-station with the acceptance-cone- tunable electron
spectrometer (ACTES) for the highly efficient constantenergy photoelectron mapping based on the ARPES
system equipped with a hemispherical analyzer (MBSA-1 Lens4) [1].
In the initial process, we tested the figure of meritfor a typical experimental procedure, that is core-level
photoelectron spectroscopy, valence band energyband dispersion measurement, low-energy secondary
electron cut-off measurement with bias voltage, andnear-edge X-ray absorption fine structure (NEXAFS)
spectroscopy. The samples of Au(111) and molecular
films of OV-phthalocyanine (OVPc) are prepared.
The photon flux is moderate at BL4B, however it isstill high enough to make some troubles on the sample
of organic films, like an irradiation damage. We havechecked a typical measurement condition of photon
flux and analyzer parameters with energy resolution
and spectral intensity for optimizing the molecularsystems. The beam-spot size was set at 0.68 x 0.52 mm
at photon energy (hv) of 60 eV with a resolution power(E/ΔE) of 5,000. Effective low-hv range could startfrom 30 eV, and it would be very hard to obtain the
results at 25 eV for ARPES experiments. The high-hv
range could be useful up to 1,200 eV for XPS
experiments, though the monochromator covers up to
1,500 eV. The contribution of the second-order light isestimated less than 1 % for hv = 250 eV at the E/ΔE of
2,000 for grating G1.
XAS was demonstrated for C-, N-, and O- K edges. A
large photon-flux dropping due to a mirror contamination
is observed for C-K edge region, and the NEXAFS
experiments for bulk samples could be reasonable bychanging the irradiating position slightly for recording
the data by using a relatively clean area of the gratings,
however we request to clean up the mirror systems.
Moreover, the reference data of Au mesh must be
clarified to obtain the data for thin-film interfaces.
The beam stabilities of the photon energy and flux

have been carefully checked by repeatedly measuring
the binding energy and intensity of Au 4f and Fermiedge. The result confirms that the light will bestabilized after about 1 hour. The continuous scanning
for accumulating the data long time under the lowphoton flux should be confirmed again.
The beam damage on the molecular film sample ischecked for the annealed monolayer of OVPc
/Au(111) with hv = 60eV at the E/ΔE of 2,000, which
gives the sample current (Is) of 5.2 nA (corresponding
to the Au mesh current (I0) of 167 pA). We observed
discernible broadening of the HOMO spectral feature
over the 2 h irradiation as shown in Fig. 1. We find theirradiation effects are settled by reducing the photon
flux to the Is = 0.55 nA to give no remarkable change
in the features over 40 min. The impact will depend on
the hv range, hence the molecular film survived for 60
min. in XPS for hv = 500 eV at the E/ΔE of 2,000,
giving the Is = 0.28 nA (I0 = 32 pA), but not suitable
for a higher-photon flux of Is = 0.77 nA (I0 = 85 pA) as
an example.
The detailed experiments upon cooling the sample
will be continued in FY2022.

Fig. 1. Impacts of irradiation time on the ARPES of amonolayer of OVPc/Au(111) surface taken at 295 K
and hν = 60 eV.
[1] H. Yamane et. al., Rev. Sci. Instrum. 90 (2019)093102.

44 12 Ⅲ01-

BL4B

Ⅲ -1. Accelerators and Instruments

BL4B

Development of High Efficiency Liquid Cell in Total Electron Yield Using
Atomically-thin Graphene
I. Mitsuishi1, K. Kashiwakura1, Y. Niwa1, T. Ogawa1, Y. Tawara1, R. Kitaura2,
P. Solís-Fernández3, K. Kawahara3, H. Ago3, T. Taniguchi4, K. Nomoto4, H. Kodaka4,
T. Horigome5, E. Nakamura5, H. Iwayama5, M. Nagasaka5 and K Tanaka5
Graduate School of Science, Division of Particle and Astrophysical Science, Nagoya University,
Nagoya 464-8602, Japan2
Department of Chemistry, Nagoya University, Nagoya 464-8602, Japan3
Global Innovation Center, Kyushu University, Kasuga 816-8580, Japan
4
Optical Measurement Technology Development Department, R&D Division, USHIO INC.,
Yokohama 225-0004, Japan
5
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan

X-rays are a powerful probe to investigate material
properties through, e.g., X-ray absorption
spectroscopy (XAS) which can reveal local atomic andelectronic states of oxygen, carbon, etc.. Among the
XAS methods for liquid, total electron yield ispreferably utilized in some cases because shortelectron escape depth in this method makes it possible
to examine atomic and electron states of liquid surface
and solid-liquid interfaces. In order to realize highefficiency measurements through the total electron
yield method, high efficiency films with high electrontransmission are a key and therefore have beenstrongly desired.
To construct our original device for the total electron
yield measurements, we propose to utilize graphene
which is atomically thin and has high electrontransmission [1]. As a first step, we tried to establish our
original experimental setup to verify our idea as shownin Fig. 1. As a preliminary experiment, liquid water was
sandwiched by a silicon nitride window and freestanding 5-layer graphene on a quartz substrate withapertures of 0.5 x 0.5 mm. A high voltage system wasalso prepared between the entrance window of thesample and the X-ray source to reduce thecontamination of electrons produced by the surface ofthe substrate and sample holder. We obtained the spectra
around the O K-edge structure as shown in Fig. 2 andconfirmed the O K-edge absorption by the liquid water.
However, photoelectrons of oxygen were also detectedin background spectra without the sample. Thus, toreduce the contamination, voltages of 200, 400, 600,
and 800 eV were applied and the reduction of thecommination was confirmed successfully as shown in
Fig. 2. Although the high-voltage system worked welland the contamination level went down significantly,
we could not conclude that there is no significant
contribution to the observed photoelectrons with thesample. Thus, to evaluate the sensitivity of our liquid
cell, optimizations of our experimental setup based on
simulations are necessary.

Entrance

X-ray

Exit

Ⅲ -1

X-ray
Sample stage (Z-axis)

MCP
SamplePD
X-ray

Fig. 1 Experimental setup and an overview of thesample holder.

With the sample

105

Background(Without the sample)

104

0V
200 V

Intensity

1

400 V
600 V

103

800 V
102

500

520

Energy [eV]

540

560

Fig. 2 Examples of observed MCP spectra aroundthe O K-edge structure with / without the sample. The
spectra with voltages of 200, 400, 600, 800 eV are also
shown for comparison.

[1] G. Hassink, R. Wanke, I. Rastegar, W. Braun, C.
Stephanos, P. Herlinger, J. H. Smet and J. Mannhart,
APL Materials 3 (2015) 076106.

45 13 Ⅲ01-

BL5B
Ⅲ -1. Accelerators
and Instruments

BL5B

Development of a Fluorescence Polarimeter in Extreme Ultraviolet Region
T. Kaneyasu1, K. Hosaka2 and J. Adachi3

SAGA Light Source, Tosu 841-0005, Japan
National Institutes for Quantum Science and Technology, Takasaki 370-1292, Japan
3
Institute of Materials Structure Science, KEK, Tsukuba 305-0801, Japan
1

2

Ⅲ -1

Polarization is one of the most important characteristics
of synchrotron radiation. In addition to the use ofhorizontal linear polarization in the bending magnet
radiation, the recent advent of insertion devices allows
us to use arbitrarily polarized light in a wide spectral
range from vacuum ultraviolet to x-ray. For accurate
measurements using the polarization properties ofsynchrotron radiation, it is essential to evaluate thepolarization state of light at a sample point. Here, we
present a polarization measurement of synchrotron
radiation in the extreme ultraviolet (XUV) wavelength
region using a fluorescence polarimeter. This method isbased on the conversion of the XUV radiation to visible
radiation on the atomic resonance [1-3]. The fluorescencepreserves the polarization state of the excitation lightwhen it is observed along the light propagation axis.
Comparing with the optical polarimeters [3], thismethod has advantages in its simple apparatus and easy
operation.
The experiment was performed at the bending
magnet beamline BL5B in UVSOR synchrotron. Figure
1 shows the experimental layout of the present study.
The monochromatized synchrotron radiation interactedwith helium atoms provided by an effusive beam. The
pressure of the interaction chamber was around 1×10-3
Pa during the measurement. The excitation wavelength
was 51.56 nm, corresponding to the 1s5p resonance of
helium atom. We observed 361-nm-wavelength
fluorescence photons emitted in decays from 1s5p to
1s2s state of a helium atom. The fluorescence photons
emitted parallel to the light propagation axis (z-axis)
were detected by a photomultiplier tube equipped witha polarizer and a bandpass filter. To evaluate thepolarization state of XUV radiation, we measured
fluorescence intensity as a function of the rotation angleof the polarizer.
Figure 2 shows the fluorescence intensity measured
as a function of the polarizer angle which is defined by
the angle of the polarization axis with respect to thehorizontal axis (x-axis). The fluorescence intensity
shows a sinusoidal modulation reflecting the polarization
state of the XUV radiation. Assuming an ellipticalpolarization, the experimental data points are fitted by atheoretical curve. The linear polarization degree of lightis evaluated to be 0.74 which is somewhat smaller than
the ideal value of 0.84 [4]. This disagreement is probably
due to the detection solid angle for the fluorescencephotons, and it is expected that this instrumental effectcan be improved by reducing the detection solid angle.

The present work shows the capability of a fluorescencepolarimeter to evaluate the polarization state of XUVradiation. Although we evaluated the degree of linear
polarization only, this method has the potential todetermine Stokes parameters [3] by just introducing aquarter waveplate in the detector system.

Fig. 1. Experimental layout of the present study. The
fluorescence photon emitted along the light propagation
axis was detected.

Fig. 2. Fluorescence intensity measured as a functionof the polarizer angle. The experimental data points
are fitted by a theoretical curve.

[1] V. Bobahev and O. S. Vasyutinkii, Rev. Sci. Isturm.
63 (1992) 1509.
[2] C. J. Latimer et al., J. Electron Spectroscopy Relat.
Phenom. 101-103 (1999) 875.
[3] E. Allaria et al., Phys. Rev. X 4 (2014) 041040.
[4] Y. Hikosaka et al., J. Synchrotron Rad. 27 (2020)
675.

46 14 Ⅲ01-

BL5B

Ⅲ -1. Accelerators and Instruments

BL5B

Measurement of a Detection Efficiency of High-sensitivity Microchannel
Plates with Tapered Pores
S. Matoba1, H. Iwayama2,3 and T. Kaneyasu4

Institute of Materials Structure Science, KEK, Tsukuba 305-0801, Japan
Editorial Board, UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan3
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
4
SAGA Light Source, Tosu 841-0005, Japan
1

2

A microchannel plate (MCP) is a lead glass detector
with a two-dimensional array of electron-multiplying
pores of about 10 μm in diameter. When charged
particles or short-wavelength photons collide with theinner wall of the pore, secondary electrons are generated
and amplified in the pore to be detected as electron
pulses. MCPs are used in a very wide range of fields
from basic research to industry because of their large
area, high spatial resolution, and high-speed detection
capability. The maximum detection efficiency of an
MCP is at the upper limit of its open-area-ratio, andtypical MCPs have a detection efficiency of 50-60%.
This causes a problem of reduced detection efficiency
when used in coincidence measurement experiments.
For example, if an MCP with a detection efficiency of
60% is used in a triple coincidence experiment, the total
detection efficiency drops to about 20%. We havedeveloped a tapered MCP with an effective aperture of
89% by applying a tapered aperture to the incident area,
based on the idea that the detection efficiency can beincreased by increasing the aperture. The maximum
detection efficiency of the tapered MCP for monatomic
ions was improved to 90%, comparable to the openarea-ratio, demonstrating for the first time theeffectiveness of tapered processing in the detection ofmonatomic ions [1]. MCPs are also used as UV and Xray detectors, and are employed as imaging elements forplanetary atmosphere observation from satellites andspacecraft. It is known that a CsI coating on the surface
of an MCP improves the detection efficiency by several
tens of times in the wavelength region above 100 nm,
but below 100 nm, where emission lines from heliumand oxygen ions, which are major components of many
astronomical atmospheres, are concentrated, theimprovement is only 1.2 times [2]. Therefore, it is not adecisive observation method for understanding the
dynamic picture of celestial atmospheres. In thisexperiment, the detection efficiency of EUV ismeasured using a tapered MCP to verify its usefulness.
The wavelength range of about 32-190 nm was used forthe measurement. Spectrified EUV passes through apinhole with a diameter of 1 mm and is injected into the
MCP. Since the counting rate of the MCP saturates athigh intensity, a molybdenum mesh and a Kapton thinfilm were used to attenuate the light. A 300-nm-thickaluminum foil was inserted to attenuate higher-order
light. The MCP used for the measurement is a custommade type divided into four regions: normal type,tapered type, CsI-coated normal type, and CsI-coatedtapered type.
Figure 1 shows the intensity ratios of the measured
count rates of tapered MCP (T-MCP), CsI-coated MCP(CsI-MCP), and tapered CsI-coated MCP (TCsI-MCP)
to normal-type MCP (N-MCP). The detection efficiencyof the tapered MCP is higher than that of the normal
MCP in all the measured wavelength ranges. In the
short wavelength range, the tapered MCP has a higher
detection efficiency than the CsI-coated MCP. The
synergistic effect of tapered MCP and CsI coating on
the detection efficiency of MCP was confirmed. These
results demonstrate that tapered MCP is a powerfultool for UV detection.

Fig. 1. intensity ratio of measured count rates oftapered MCP (T), CsI-coated MCP (CsI) and tapered
CsI-coated MCP (TCsI) to normal type MCP (NMCP).

[1] S. Matoba et al., Jpn. J. Appl. Phys. 50 (2011)
112201.
[2] K. Yoshioka et al., Rev. Sci. Instrum. 83 (2012)083117.

47
III 01- 15 -

Ⅲ -1

BL5B
Ⅲ -1. Accelerators
and Instruments

BL5B

Study on the Source of Photon-Energy Drift of BL5B
H. Zen1, E. Nakamura2, K. Hayashi2 and K. Tanaka2,3Institute of Advanced Energy, Kyoto University, Uji 611-0011, JapanUVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan3
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI) Okazaki 444-8585, Japan12

M1 Holder Temp. [deg. C]

mechanics are considered to be a significant source ofthe photon-energy drift of BL5B. Further study should
be conducted to clarify whether the grating and its
holding mechanics are the significant sources of thephoton-energy drift or not.
60
50

2/25
Turn off Heateron M1 Holder

2/24
2/23

30

Turn on Heateron M1 Holder
Decrease Mirror Temp.
by Reducing SR amount on M1

09 10 11 12 13 14 15 16 17 18 19 20 21 2275

M1 Mirror Temp. [deg. C]

w/o M1 Mask

40

(a)

70

Time [hh]Turn off Heater on M1 Holder

2/25

w/o M1 Mask

65

2/23

60
55
50
45

Decrease Mirror Temp.
by Reducing SR amount on M1

40

2/24

Turn on Heateron M1 Holder

35

30
09 10 11 12 13 14 15 16 17 18 19 20 21 22

(b)

17.06
17.05

Wavelength [nm]Ⅲ -1

The stability of the photon beam properties, such as
beam position, beam intensity, photon energy, and soon, during user operation in beamlines, are very
important for the advanced application of synchrotron
radiation (SR) facilities. A photon-energy drift at
BL5B has been observed during user experiments [1].
We started the study on the source of this photonenergy drift in 2019. Although we have tried several
countermeasures to suppress the photon-energy drift[2], no significant improvement has been achieved.
In the study performed FY2020, we found a clear
correlation between the temperature of the M1 mirror
holder and the photon energy [3]. Therefore, in this FY,
a heater attached directly to the M1 mirror holder was
introduced to control the temperature of the M1 mirror
holder. By using the heater, the temperature of the M1
mirror holder can be stabilized as shown in Fig. 1 (a)black line. However, even with the stabilized M1
temperature, the wavelength of the SR exit the
monochromator continuously changes as shown in Fig.
1 (c) black line and red line.
To find the origin of the photon-energy drift, several
trials were made; 1: Turn off and on the heater on M1
holder, 2: Remove M1 mask to increase the M1 holder
temperature, 3: decrease mirror temperature by reducing
SR amount on M1 and successive optics. By trial 1, we
could confirm the correlation between M1 holder
temperature and the photon energy. By trial 2, wefound that the temperature variation of the M1 holder
has no significant influence on the trend of photonenergy drift. By trial 3, we found that the variation of
SR amount has a significant influence on the photon
energy drift. After reducing the SR amount, thetemperature of the M1 mirror gets stable within 3
hours (see Fig. 1 (b) red line) but the photon-energy
drift last for longer than 6 hours (see Fig. 1 (c) red line).
These results imply that the significant source of thephoton-energy drift should exist after the M1 mirror.
We checked our results obtained in FY2019. In
FY2019, grating #3 and mirror #23 (configuration ofG3M3) were used and roughly 0.1 eV photon-energy
drift was observed from 12 to 21 o’clock. In this FY,
roughly 0.24 eV photon-energy drift was observed
from 12 to 21 o’clock with grating #2 and mirror #24(G2M4). The sensitivity of the photon energy to the
angular variation for the G2M4 configuration isapproximately 1.2 times higher than that of the G3M3
configuration. The observed difference of photonenergy variation was much larger than the differenceof sensitivity. From this result, grating and its holding

17.04
17.03

Time [hh]Turn on Heateron M1 Holder
Turn off Heateron M1 Holder

17.02 w/o M1 Mask
17.01
17.00
16.99

2/25
2/23
2/24

Decrease Mirror Temp.
by Reducing SR amount on M1

16.98
16.97
09 10 11 12 13 14 15 16 17 18 19 20 21 22(c)Time [hh]Fig. 1. Trend of (a) temperature of M1 mirror holder,(b) temperature of M1 mirror, and (c) wavelength of
SR light exit monochromator of BL5B.

[1] K. Hayashi, UVSOR Activity Report 2011 39 (2012)121.
[2] H. Zen et al., UVSOR Activity Report 2019 47(2020) 42.
[3] H. Zen et al., UVSOR Activity Report 2020 48(2021) 47.

48
III 01- 16 -

BL7B

Ⅲ -1. Accelerators and Instruments

BL7B

Complex Refractive Index Measurement by Reflectance Spectra in
Different Polarization Configurations
M. Horiba1, K. Fukui1, K. Yamamoto1 and T. Saito2

Department of Electrical and Electronics Engineering, University of Fukui, Fukui 910-8507, Japan
Department of Electrical and Electronic Engineering, Tohoku Institute of Technology, Sendai 982-8577, Japan
1

2(Stokes parameter S1/S0 ~ 0.8), reflectance measured in
the horizontal and the vertical configuration are almost
equal to the reflectance of p- and s-polarization,
respectively.
The reliability of complex refractive index derived
from experimental values is directly related to themagnitude of the difference in reflectance in p- and spolarization configuration. Therefore, the angle ofincidence should be close to Brewster's angle, andexperiments have confirmed that the difference inreflectance spectra between the p- and s-polarization
configuration increases in the order of 8°, 45°, and 67°
angle of incidence. Therefore, results for 45° and 67°
are used for analysis. Figure 1 shows the photon
energy dependence spectra of complex refractive
index of Au mirror. The curves represent refractive
index n and extinction coefficient k derived from PS
method, and symbols from spectroscopic ellipsometry
measurement mode. The overall trend of n and kspectra from PS method are in good agreement withthose from spectroscopic ellipsometry measurement
mode. However, a marked difference in absolutevalues remains an issue to be solved.
3.0

Complex refractive index

Based on the basic design of the instrument by the
AIST group [1], we have been developing a complex
type refractive index spectrum measurement device(CRIMS-VUV) [2], which can continuously measure
not only in the visible region but also in the ultraviolet
and vacuum ultraviolet regions. CRIMS-VUV canperform spectroscopic ellipsometry measurements andreflection spectrum measurements under the sameenvironment.
The spectroscopic ellipsometry measurement modeof CRIS-VUV has the advantage of measuring thecomplex refractive index with high accuracy. However,this mode has the disadvantage that, due to its
measurement principle, it takes time to measure ateach measurement point (photon energy), making it
difficult to measure a continuous spectrum. In thisrespect, reflection spectrum measurement mode issuitable for measuring continuous spectrum. The wellknown Kramers - Kronig analysis method is used todetermine the complex refractive index spectrum fromthe reflectance spectrum. However, Kramers - Kronig
analysis method requires appropriate approximations
on both sides of the measured photon energy range,
since Kramers - Kronig analysis method uses theintegral of reflectance at photon energy from 0 to
infinity to obtain complex refractive index at eachphoton energy. Therefore, this method is useful, forexample, for obtaining qualitative complex refractive
index spectrum for limited photon energy region
around the absorption edge, but is not well suited for
obtaining quantitative complex refractive index
spectrum over a wide photon energy region. Unlike the
Kramers - Kronig analysis method method, there are
two methods to obtain the complex refractive index ateach photon energy from reflectance measurements
under different measurement conditions, one withreflectance measurements at different incident angles
and the other with different polarization configurations.
Therefore, we decided to use a method of measuringreflectance with p- and s-polarization configurations(PS method) to obtain the complex refractive index foreach photon energy, since CRIMS-VUV has amechanism that automatically changes the polarization
configuration as desired. In this report, we show the trial
results of PS method measurements on an Au mirror asa sample.
PS method measurements were carried out withCRIMS-VUV installed at BL7B. The photon energy
range was 2 to 20 eV. Since output light of BL7B (input
light of CRIMS-VUV) is highly linearly polarizedn (PS method)k (PS method)n (SE mode)k (SE mode)

2.5
2.0
1.5
1.0
0.5
0.0

2

4

6

8

10

12

14

16

18

20

Photon Energy (eV)Fig. 1. Complex refractive index of Au mirror[1] T. Saito, M. Yuri and H. Onuki, Rev. Sci. Instrum.
66 (1995) 1570.
[2] D. Imai et al., UVSOR Activity Report 2018 46(2019) 39.

49
III 01- 17 -Ⅲ -1

UVSOR User 3