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Accelerators andInstruments

Ⅲ-1 Accelerators and Instruments

BL1U

Spectral Phase Interferometry for Direct Electric-field Reconstruction of
Undulator Radiation
T. Fuji1, T. Kaneyasu2, M. Fujimoto3, Y. Okano3, E. Salehi3, M. Hosaka4,5, Y. Takashima4,
A. Mano4, Y. Hikosaka6, S. Wada7 and M. Katoh8,31

Laser Science Laboratory, Toyota Technological Institute, Nagoya 468-8511, Japan
2
SAGA Light Source, Tosu 841-0005, Japan
3
Institute for Molecular Science, Okazaki 444-8585, Japan
4
Synchrotron Radiation Research Center, Nagoya University, Nagoya, 464-0814, Japan
5
National Synchrotron Radiation Laboratory, University of Science and Technology of China,
Hefei 230029, China
6
Institute of Liberal Arts and Sciences, University of Toyama, Toyama 930-0194, Japan
7
Graduate School of Advanced Science and Engineering, Hiroshima University,
Higashi-Hiroshima 739-8526, Japan
8
Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima 739-0046, Japan

An undulator is a device widely used in modern
synchrotron light sources to produce quasimonochromatic light. The waveform of the electricfield produced by a relativistic electron in the undulator
is primarily determined by the number of magnets andthe gap between them. Although a simple
electromagnetic theory predicts a square-shaped
waveform, it has never been measured due to the lackof a suggested method. Therefore, it is crucial tocharacterize the electric field produced by the undulator
for the development of synchrotron sources.
SPIDER is a femtosecond pulse characterization
method that has been widely used since its invention in1998 [1]. It involves retrieving the spectral phase byanalyzing the fringes of the interferogram between atest pulse and a spectrally sheared replica. At the
UVSOR-III synchrotron light source, a tandem
undulator produces two wave packets whose
wavelengths can be individually adjusted by changing
the gap between the permanent magnets of each
undulator. A phase shifter consisting of three pairs ofelectromagnets forms a small chicane for the electron
beam and controls the delay between the wave packets
in the femtosecond regime with attosecond accuracy.
The twin tandem undulator produces a pair of
wavelength-shifted wave packets with a delay, and theinterferogram between them can be regarded as a
“SPIDER” interferogram. Consequently, we can use
the same algorithm as SPIDER to analyze theinterferogram and reconstruct the electric field
generated by the undulator [2].
The experiment took place at the 750-MeV UVSORIII storage ring, where a tandem undulator was installed
as shown in Figure 1. The undulator consisted of twin
APPLE-II type variable polarization devices that
operated in the horizontal linear polarization mode,with 10 magnetic periods and a period length of 88 mm.
The central photon energy of the fundamental radiation

was adjusted to 35 eV. Figure 2 displays the retrieved
electric field, which shows 10-cycle field oscillations
with a rectangular envelope of the wave packet that are
accurately reproduced.
This method is advantageous for shorter wavelength
synchrotron radiation, including soft and hard x-rays,
as it does not require nonlinear wavelength conversion.
Additionally, it holds potential for the characterizationof FEL pulses.

Fig. 1. Conceptual diagram of the tandem undulator.
ω0 and ω0 +Ω represent the carrier frequencies of the
upstream and downstream wave packets, respectively.

Fig. 2. Waveform of the wave packet retrieved using
the SPIDER algorithm.
[1] C. Iaconis and I. A. Walmsley, Opt. Lett. 23 (1998)
792.
[2] T. Fuji et al., Optica 10 (2) (2023) 302.

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BL1U

Construction of Laser Transport Line and Light Measurement Setup for
Coherent Harmonic Generation Experiment at BL1U
F. Sakamoto 1, H. Zen2, T. Tanikawa3, Y. Taira4, Y. Okano4, H. Ohta4,
J. Yamazaki4, K. Hayashi4, Y. Takashima5, A. Mano5 and M. Katoh4,61National Institute of Technology, Akita College, Akita 011-8511, Japan
Institute of Advanced Energy, Kyoto University, Kyoto 611-0011, Japan
3
Innovation Center for Applied Superconducting Accelerators (iCASA), High Energy Accelerator Research
Organization (KEK) Ibaraki 305-0801, Japan
4
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
5
Synchrotron Radiation Research Center, Nagoya University, Nagoya 464-8603, Japan
6
HiSOR, Hiroshima University, Higashi-Hiroshima 739-0046, Japan
2

Coherent Harmonic Generation (CHG) is a method
to imprint external laser information to an electron
beam and generate temporally coherent and short VUVradiations from it [1]. Since the properties of the CHG
such as polarization, temporal and spectral distribution
are completely dependent on the external laser [2], they
can be optimized by changing the laser and electron
beam conditions. These features of the CHG havepossibilities for some applied experiments. So far,some experiments on CHG have been performed at
UVSOR-II and important features of CHG wereobserved [3, 4].
We plan to resume detailed studies of CHG using an
optical klystron and an ultrashort Ti:Sapphire laser
pulse at BL1U. The optical klystron of BL1U consistsof two APPLE-II variable polarization undulators and abuncher magnet which is located between the undulators[5]. The laser pulse is injected into the first undulator
and an energy exchange between the laser pulse andelectron beam that circulates in the storage ring occurs.
This leads to an energy modulation inside the electron
beam. In the buncher magnet, the energy modulation isconverted to a density modulation with a period of thelaser wavelength (micro-bunching). Temporally
coherent radiations are generated from the microbunched electrons in the second undulator.
In order to perform the CHG experiment, we have
newly constructed a laser transport line and lightmeasurement setup at BL1U. Schematics of the setup
are shown in Fig. 1. The laser pulse is transported about
10 m from laser hutch and injected to the vacuum tube
connected to the storage ring. The polarization state iscontrolled by a λ/2 waveplate and a polarization beam
splitter (PBS). We also set a monitoring system toadjust spatial and temporal overlaps between the laserand electron beam using CMOS and streak cameras.
After the construction of the setup, we have performed
the first CHG experiment at BL1U.
The experiment was performed with an electron
beam energy of 600 MeV. A resonant wavelength of theundulators was set to 800 nm which corresponds to thewavelength of Ti:Sapphire laser. Figure 2 shows thestreak camera images. From these images, we canconfirm the laser pulse of 1 ps was well overlapped on
the undulator radiation (i.e., electron beam) of 100 ps.

We also observed the spatial overlap by using CMOS
camera that was focused in the first undulator. The firsttarget wavelength for the observation was set to 267 nm
which was 3rd harmonics of the radiation from themicro-bunching. For the purpose, CHG and Ti:Sapphirepulses were separated by using a dichroic mirror and aband pass filter (BPF) at a downstream of undulators. A
photo-multiplier tube (PMT) was used to monitor an
intensity of the CHG signals but unfortunately no CHG
signals was observed. We are considering the spatial
overlap between the laser pulse and electron beam in
the first undulator was not good enough. For the next
experiment, we plan to remodel the alignment optics
for the spatial overlap.

Fig. 1. Schematics of laser transport line and lightmeasurement setup.

Fig. 2. Streak camera images of laser pulse andundulator radiation. The vertical scale corresponds
between right and left images and is synchronized withRF signal of accelerator.
[1] G. Vingnola et al., Nucl. Instrum. Methods Phys.
Res., Sect. A 239 (1985) 43.
[2] H. Zen et al., Proc. FEL2010 TUPB16 (2010) 286.
[3] M. Labat et al., Eur. Phys. J. D 44 (2007) 187.
[4] T. Tanikawa et al., Appl. Phys. Express 3 (2010)
122702.
[5] Y. Uematsu et al., Proc. PASJ 2012 WEPS066(2012) 551.

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Ⅲ-1 Accelerators and Instruments

BL1U

Impact of the Temperature on the Non-Destructive Nuclide Assay in theTransmission NRF Method
M. Omer1, T. Shizuma2, M. Koizumi1, Y. Taira3, H. Zen4, H. Ohgaki4 and R. Hajima2
1
Japan Atomic Energy Agency, Tokai 319-1195, Japan
National Institutes for Quantum Science and Technology, Kizugawa 619-0215, Japan
3
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
4
Institute of Advanced energy, Kyoto University, Uji 611-0011, Japan
2

Nuclear resonance fluorescence (NRF) is thephotoexcitation of a nuclide using high energy γ-rays.
The resonating levels excited by NRF are a fingerprintof each nucleus. Therefore, NRF can be employed as a
non-destructive assay technique for nuclear materials
such as fissile isotopes. There are two schemes for NRF
measurement. The first one is scattering NRF
measurement, by which the sample is irradiated by a
γ-ray beam, and the scattered NRF photons aremeasured. The second scheme is the transmission NRF
measurement, by which the absorption of NRF photons
by the sample is measured. To realize absorption
measurement, a second target (witness target of thesame sample located downstream the sample target) isused to estimate the amount of γ-ray absorption in thesample. In transmission NRF, γ-ray detector ispositioned close to the witness target. So, themeasurement is possible without the shadow ofbackground radiation from the sample target. [1].
The emission and absorption rate of NRF γ-rays
depend on the temperature of the scattering and witness
targets via the Doppler broadened widths of NRF
levels. Therefore, the temperature of the scattering andwitness targets may aﬀect the time and sensitivity ofthe measurement. Based on the level widths, many
isotopes are possible candidates to study the eﬀect oftemperature on transmission NRF, such as 27Al, 48Ti,
51
V, 206Pb, and 208Pb. In the present measurement, 208Pb
target was irradiated with laser Compton scattering(LCS) γ-ray beam at BL1U of UVSOR. LCS γ-rays of
maximum energy of 5.54 MeV were produced from thecollision of 746-MeV electrons with laser photons of awavelength of 1.98 μm. A lead collimator with 20-cm
thickness and 3-mm aperture size was used to confine
the generated γ-rays energy width to approximately 8%(FWHM). Three 140% HPGe detectors, locatedhorizontally, were used to detect NRF γ-rays. Two ofthem were positioned at a scattering angle of 135° andthe third at a scattering angle of 70° with respect to theincident γ-ray direction, as shown in Fig. 1.
A typical γ-ray spectrum measured using 208Pb isshown in Fig. 2. NRF peaks of 208Pb were observed asindicated in Fig. 2. We also observed substantial
background lines at energies higher than the maximum
energy of the LCS γ-ray beam. These lines probably
originate from the neutron capture interactions withmaterials surroundings the experimental setup. The

neutron capture background aﬀects the accuracy of
NRF peaks. We applied a 10-cm thickness lead shieldaround one detector to decrease the background. As
shown in Fig. 2 (green spectrum), the background was
eﬀectively suppressed. The shielding configuration will
be applied in the planned transmission NRF
experiments. This work is a contribution of the JAEA
to the International Atomic Energy Agency (IAEA)
under the agreement of the coordinated research
program (CRP), J02015 (Facilitation of Safe andSecure Trade Using Nuclear Detection Technology Detection of RN and Other Contraband).

Fig. 1. Photo of the experimental setup used for the
cryo-NRF experiment at BL1U.

Fig. 2. Typical γ-ray spectra observed for 208Pb before(red) and after (green) heavy shield. NRF levels arelabeled with resonance energies. Also, single anddouble escape peaks are labeled. The high energy
background was eﬀectively suppressed.
[1] C.T. Angell et al., Nucl. Instrum. Methods Phys.
Res. B 347 (2016) 11.

− 37 −BL1U

Basic Study on Compton Camera for Detection of Polarized gamma-rays
K. Shimazoe 1, M. Uenomachi2, T. Ueki1, Q. Shu1, A. Takeda3, K. Magata3,
K. Nagayanagi3 and Y. Taira4
1

Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan
2
Space Unit, Kyoto University, Kyoto 606-8502, Japan
3
Miyazaki University, Miyazaki 889-2192, Japan
4
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan

Compton imaging is a promising technology
visualizing the distribution of gamma-rays by using theCompton kinetics principle. Measuring the energies inscatterer and absorber determines the scattering angleof gamma-rays and enables the localization of radiation
source. Compton imaging is now widely investigated
for the application of astronomy, medical imaging [1]and environmental monitoring [2]. Although the
gamma-ray imaging is possible through Compton
imaging, but the information of polarization in gammaray is not well utilized till now. The polarization
information can be used to improve the image quality
in positron emission tomography (PET) scanners with
its quantum entanglement nature [3].
In the previous research, we have been working on
developing silicon on insulator (SOI) based monolithic
sensor integrating the silicon sensor and readout
electronics in one chip [4]. SOI device can be used todetect the track of Compton recoil electrons for theadvanced Compton imaging. In this research weinvestigated the possibility of extracting the polarization
information of incoming linearly or circularly polarized
gamma-rays through the pattern of electron tracks andCompton scattering angles.
Figure 1 shows the experimental setup for detecting
the polarization of gamma-rays. Two SOI pixel sensor
are used as scatterers and Compton electron trackers.
Eight 8×8 GAGG arrays (pixel size is 3.2 mm andthickness is 9 mm) coupled with SiPM array are used asabsorber. All the detectors are synchronized for
detecting the coincidence events between detectors.
Figure 2 shows the picture of detector setup aligned
to the beam. In this setup 31-47 degree and 45-61
degree scattering events can be acquired for SOI1/
GAGG and SOI2/GAGG coincidence respectively.

Figure 3 shows the expected scattering angle ofpolarized photon with a Monte Carlo simulation code
(GEANT4).
In the first analysis, the coincidence events are
successfully acquired between laser trigger and SOI
and between laser trigger and GAGG as shown in
Figure 4. The more detail analysis is ongoing.
()

Fig. 2. the detector setup in the beamline BL1U

Fig. 3. Simulated scattering angle of polarized photon

Fig. 4. time diﬀerence histogram of SOI and laser

Fig. 1. Two SOI sensors and eight GAGG arrays areused to detect polarized gamma-rays.

[1] M. Uenomachi, M. Takahashi, K. Shimazoe, et al.,Sci Rep 11 (2021) 17933 .
[2] Jianyong Jiang, et al., Journal of Nuclear Scienceand Technology 53.7 (2016) 1067.
[3] D. P. Watts, et al., Nature Communications 12.1
(2021) 2646.
[4] Y. Yoshihara, et al., Journal of Instrumentation 12.01(2017) C01045.

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Ⅲ-1 Accelerators and Instruments

BL1U

Development of gamma-ray-induced Positron age-momentum Correlation
Y. Taira1, 2, Y. Okano1 and T. Hirade3
1
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
Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Tokai, 319-1195, Japan
2

In UVSOR-III, gamma-ray-induced positronannihilation spectroscopy using the ultra-short pulsed
gamma rays is developed. The ultra-short pulsed
gamma rays with a pulse width of ps range are generated
via inverse Thomson scattering with 90 degreecollisions between an electron beam and a laser pulse at
BL1U [1]. Gamma-ray-induced positron annihilation
lifetime spectroscopy (GiPALS) is currently available
to users. In addition to GiPALS, gamma-ray-induced
age-momentum correlation (GiAMOC) is being
developed. GiAMOC is an approach to measure theemission time and the energy shift of annihilation
gamma rays with an energy of 0.511 MeV
simultaneously for observing the time-resolved
momentum distribution of an electron, which is theannihilation counterpart of a positron. For that, one of
the two annihilation gamma rays produced from asample is detected using a barium fluoride (BaF2)
detector with high time resolution and the other isdetected by a high purity germanium detector (Mirion
Technologies, GC4018, 40% relative eﬃciency) withhigh-energy resolution. A BaF2 detector comprises a
BaF2 scintillator and a photomultiplier tube (Hamamatsu
Photonics K.K., H3378-51). GiAMOC using one
detector pair was presented in Ref. [2]. In this report,
we present the results of quartz measurements using
two detector pairs.
The GiAMOC measurement system is shown in
Figure 2 of Ref. [2]. Two sets of this system were used
to improve the counting rate by a factor of two, asshown in the picture in Fig. 1. The measured time
evolution of a fraction of low-momentum annihilation(S-parameter) of synthetic silica glass (Tosoh SGM
Corp., ED-C) is shown in Fig. 2. As shown in Fig. 2,
S-parameter decreased with time. Around time 0, theannihilation process of para-positronium, which has ashort annihilation lifetime and a small energy spread, isdominant, and as time passes, the annihilation processesof free positrons and ortho-positronium, which have
longer lifetimes and larger energy spreads than thepara-positronium, is dominant. The time evolution of
the measured S-parameter is consistent with thatmeasured using a slow positron beam at AIST [3].

Fig. 1. Detector arrangement of GiAMOC.

Fig. 2. The time evolution of S-parameter for synthetic
silica glass.
[1] Y. Taira et al., Nucl. Instr. Meth. A 652 (2022) 696.
[2] Y. Taira et al., Rev. Sci. Instr. 93 (2022) 113304.
[3] Y. Komuro et al., Rad. Phys. Chem. 76 (2007) 330.

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BL1U

Study on Generation of F-LCS Gamma-rays for Absolute Cross-section
Measurement of NRF using BL1U Undulator
H. Ohgaki1, H. Zen1, T. Kii1, T. Hayakawa2, T. Shizuma2, M. Fujimoto3 and Y. Taira3
1
Institute 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

2

Fig. 1. Schematic drawing of the LCS beamline BL1U,UVSOR. PM: power meter, W: window, SM: Spherical
Mirror. A Ge detector was added after the collimator in
the POP experiment.

Fig. 2. LCS gamma-ray energy distribution in thevertical axis with the undulator K-value of K=0.2.
㻝㻚㻞㻝Normalized Count

Laser Compton Scattering Gamma-ray beam
(F-LCS), which has a flat distribution in the energy
spectrum and the spatial distribution with a few mm
diameter beam size, has been developed to study an
isotope selective CT Imaging application in thebeamline BL1U in UVSOR. By using a circular motionof the electron beam which is excited by a helicalundulator installed in a storage ring, and collision withan intense laser beam, an F-LCS beam can be generated.
The principle is that the electron beam divergence
could be enlarged by the undulator field that enlarges
the beam divergence of the Compton backscatteredgamma-ray (LCS) beam. At the same time, the LCS
beam energy is also spread.
An Electron Gamma Shower version 5 (EGS5) [1]simulation study assumed in the LCS beamline BL1U
(Fig.1) with the collimator diameter of 2 mm .has
been carried out. Figure 2 shows the energy spectra of
the LCS beams with K-values from 0 to 0.4. The
boarder energy spread peak is observed with a larger
K-value. The energy spread is widened from 2.7 to
22% (FWHM), and the peak energy is shifted from5.53 MeV to 5.01 MeV by increment of the K-value
from 0 to 0.4 On the other hand, the F-LCS beam yieldat the top energy region decreases with the increase of
the undulator field. Therefore, K-value of 0.2 could berecommended for practical applications in BL1U.
A POP experiment was carried out at the BL1U in
UVSOR. The experimental setup was the same as thatshown in Fig. 2 except for a high-purity germanium(Ge) detector with a relative eﬃciency of 120% wasadded after the 2-mm collimator. The stored electronwith an energy of 746 MeV and a current of about 6 mA
was used. The laser beam from a Tm-fiber laser system(TLR-50-AC-Y14, IPG Laser GmbH) whose
wavelength was 1.896 μm with random polarization
was used at around 1 W CW power. The spectra of the
LCS beams were measured for diﬀerent K-values from
K=0 to 0.3. Although the Ge detector response madecomplicated energy spectra, we observed peak the shift
toward lower energy according to larger K value, as
shown in Fig. 3.
As a result, the larger K-value, the broader energy
bandwidth of the LCS was observed as predicted by
EGS5 simulation. This result supports the successful
generation of the F-LCS beam.

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Energy (MeV)

Fig. 3. Measured LCS beam spectra with the undulator
K-value of 0, 0.1, 0.2, and 0.3.
[1] H. Hirayama, Y. Namito, A.F. Bielajew, S.J. Wilderman and W.R. Nelson, The EGS5 code system, SLAC
Report number: SLAC-R-730, KEK report number:2005-8 (2005).

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Ⅲ-1 Accelerators and Instruments

BL1U

Double-Pulsed Light Wave Packets Emitted from a Tandem Undulator
T. Kaneyasu1,2, M. Hosaka3,4, A. Mano4, Y. Takashima4, M. Fujimoto2,4, E. Salehi2,
H. Iwayama2,5, Y. Hikosaka6 and M. Katoh2,4,7
1

SAGA Light Source, Tosu 841-0005, Japan
Institute for Molecular Science, Okazaki 444-8585, Japan
3
University of Science and Technology of China, Hefei 230029, China
4
Synchrotron Radiation Research Center, Nagoya University, Nagoya, 464-8603, Japan
5
Sokendai (The Graduate University for Advanced Studies), Okazaki 444-8585, Japan
6
Institute of Liberal Arts and Sciences, University of Toyama, Toyama 930-0194, Japan
7
Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima 739-0046, Japan2

The waveform of electromagnetic radiation from anultra-relativistic electron reflects the motion of theelectron. We report on a fully-optical characterizationof double-pulsed wave packets emitted by individual
relativistic electrons passing through a tandem
undulator in a synchrotron light source [1]. The
experiment was carried out at the undulator beamline
BL1U. The light source of BL1U consists of two
identical APPLE-II undulators, between which a threepole electromagnetic phase shifter is installed (Fig. 1).
The period length and number of periods for each
undulator were 88 mm and 10, respectively. A
relativistic electron passing through the undulators
emits a wave packet with a waveform expected to be
characterized by time-separated 10-cycle oscillations.
The time delay between the double-pulsed components
can be controlled by adjusting the length of electron
orbit between the undulators using the phase shifter
magnet.
Using a Mach-Zehnder interferometer [2] operating
at ultraviolet wavelengths, we measured the
autocorrelation trace for the spontaneous radiationfrom the tandem undulator. The double-pulsed wave
packets were randomly distributed within the overall
300 ps radiation pulse corresponding to the length ofthe electron bunch. Figure 2(a) shows the interferograms
obtained by setting the field strength of the phase shifter
magnet to four diﬀerent values. The central wavelengthof the radiation was 357 nm for both undulators. Theinterferograms measured at a phase shifter current of
10.0 A or more show approximately 20-cycle
oscillations with triangular envelopes in the range of-12 – +12 fs, as well as weaker 20-cycle oscillations
lying on both sides. The side oscillation structuresapproach the central structure as the phase shifter
current decreases, and they are unified at a phase shifter
current of 0 A.
The observed interferograms can be understood as
autocorrelation traces of double-pulsed wave packet.
The calculated autocorrelation trances for a doublepulsed 10-cycle sinusoidal wave packet at 357 nm
wavelength are shown in Fig. 2(b). Over the whole
range of phase shifter currents, one finds excellent
agreement between the experiments and calculations.

This fact confirms that each of the relativistic electron
emits a double-pulsed 10-cycle wave packet which
well reflects the magnetic field in the tandem undulator.

Fig. 1. Schematic illustration of the tandem undulator.
A relativistic electron passing through the undulators
emits a wave packet with a waveform expected to be
characterized by time-separated 10-cycle oscillations.

Fig. 2. Autocorrelation measurements of spontaneousradiation from the tandem undulator at various valuesof the phase shifter current. The wavelength of thefundamental undulator radiation was set to 357 nm. (a)Measurement. (b) Calculation.
[1] T. Kaneyasu et al., Sci. Rep. 12 (2022) 9.
[2] A. Mano et al., UVSOR Activity Report 2020, 48(2020) 38.

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BL1U

Progress in Single Electron Storage Experiment
A. Asai 1, M. Shimada 2,3, H. Miyauchi 2,3 and M. Katoh 3,1,4,2
1School of Science, Hiroshima University, Higashi-hiroshima 444-8585, 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
2

Single electron storage has been achieved at several
electron synchrotrons, aiming to investigate electron
dynamics in a synchrotron [1,2,3], to investigate
electromagnetic radiation from an electron [4], or toutilize the radiation as a primary standard [5,6,7]. In
FY2021, we have started an experimental study on
single electron storage at UVSOR-III and successfully
demonstrated it [8, 9]. In FY2022, we continued
improving the operation technique for the single
electron storage and also have started some basic
studies on undulator radiation [10]. Here, we report
some preliminary results. The final results will be
published elsewhere in future.
We have established the following procedure for the
single electron storage. First, we accumulate an electron
beam with very low current, typically 0.1 mA. Indeed,this current corresponds to one shot of the injector. At
this low beam current, we could observe and adjust the
optical axis by eye from the undulator at BL1U, which
is tuned at 355 nm wavelength. Then, we reduce thebeam lifetime to several minutes by using beam scraper.
We use a photomultiplier tube (PMT) to measure thesynchrotron radiation intensity. The PMT signal was
analyzed with a counting unit and recorded by a PC.
Single electron storage corresponds to about 1 pA beam
current. Therefore, we have to observe very wide rangeof the intensity for many orders of magnitudes.
Therefore, we set ND filters in front of the PMT toadjust the radiation intensity and remove them as theintensity reduces. To make the operation simpler, we
examined an ultra-wide range PMT and obtained agood result. The details will be described elsewhere in
future.
We could observe step function like changes in theintensity as shown in Figure 1, which corresponds to aloss of one electron. We also observed the timing of the
PMT output relative to the revolution signal provided
by the RF system, as also shown in Figure 1. We could
observe in which RF bucket the electrons exists. We
confirmed that the last electron survives for more than
2 hours after we pulled out the beam scraper to theoriginal position. This allows us to observe some basic
properties of synchrotron radiation. An example ispresented in Figure 2, which shows that the photon
statistics is well represented by Poisson distribution.
Other interesting results will be presented somewherein future.

Fig. 1. Synchrotron radiation intensity

Fig. 2. Photon Statistics observed 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] A. Romanov et al., 2021 JINST 16 (2021) P12009.
[4] I. V. Pinayev et al., NIM A 341 (1994) 17.
[5] R. Klein et al., Phys. Rev. STAB 11 (2008) 110701.
[6] R. Klein et al., 2010 Metrologia 47 (2010) R33.
[7] T. Saito et al., Bulletin of the ElectrotechnicalLaboratory (in Japanese) (1985) 431.
[8] R. Shinomiya et al., UVSOR Activity Report 2021,(2022) 39.
[9] R. Shinomiya, Bacholor Thesis (Hiroshima University)(in Japanese) (2022).
[10] Y. Asai, Bacholor Thesis (Hiroshima University)(in Japanese) (2023).

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Ⅲ-1 Accelerators and Instruments

BL2A

Calibration of the Soft X-ray Response Matrix of CMOS Detector Used inSounding Rocket Experiment FOXSI-3
N. Narukage 1, 2, R. Shimizu2, 3, Y. Sato1, 2 and S. Kashima3
1
National Astronomical Observatory of Japan (NAOJ), Mitaka, 181-8588, Tokyo, JapanThe Graduate University for Advanced Studies, SOKENDAI, Hayama, 240-0193, Kanagawa, Japan
3
Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA),
Sagamihara, 252-5210, Kanagawa, Japan2

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 powerfulapproach for the 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 realized withthe following method. We take images with a shortenough exposure to detect only single X-ray photon in
an isolated pixel area with a fine pixel Silicon detector.
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 performthe continuous exposure with a rate of more thanseveral hundred times per second, we can count thephoton 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 areabout form several ten seconds to several minutes. For
the first imaging spectroscopic observation of the solar
corona in soft X-ray range, we launched a NASA’ssounding rocket (FOXSI-3) on September 7th, 2018 andsuccessfully obtained the unprecedented data [2] using
a high-speed X-ray camera [3] with a back-illuminated
CMOS detector [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, we havedeveloped a mirror-based reflective-type flux reduction
system [5].
In this time, using this system, the response of the
CMOS detector aboard the FOXSI-3 sounding rocket iscompletely calibrated in the energy range of 840 eV to4500 eV in 20 eV intervals (see Fig. 1).

Fig. 1. Measured response matrix of the FOXSI-3
CMOS detector from 840 eV to 4500 eV. In the colormaps, the horizontal axis shows the values of output
signals from the detector, when the detector detects the
monochromatic X-ray photons with the energy shownin the vertical axis. The colors indicate, in log scale,
how frequently each signal value is output. The topright panel shows the number of monochromatic X-ray
photons used to create this matrix.
[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 (2018) 36.
[3] S. Ishikawa et al., Nucl. Instrum. Methods Phys.
Res., Sect. A 912 (2018) 191.
[4] N. Narukage et al., Nucl. Instrum. Methods Phys.
Res., Sect. A 950 (2020) 162974.
[5] N. Narukage, UVSOR Activity Report 2022, 49(2021) 42.

− 43 −BL2A

Development of a Transfer Vessel for NEXAFS Spectroscopy
E. Kobayashi 1 and A. Inoishi 2
1
2

Kyushu Synchrotron Light Research Center, 8-7 Yayoigaoka, Tosu, Saga 841-0005, Japan
Institute for Materials Chemistry and Engineering, Kyushu University 6-1 Kasuga-koen,
Kasuga-Shi 816-8580, Japan

Battery materials are contaminated with oxygen,carbon dioxide and water when exposed to theatmosphere. Therefore, we developed a sample transfer
vessel that can transport the sample to the analyzer
without exposing it to the atmosphere [1, 2].
Furthermore, in order to perform more precise analysis,
we developed a transfer vessel with a small ion pump[3]. In recent years, analysis of battery materials using
soft X-ray absorption spectroscopy has been performed.
However, it was diﬃcult to analyze across the beamline
without atmospheric exposure. This is because thesample holders are diﬀerent depending on the beamline.
Therefore, we have developed a transfer vessel that canmeasure the soft X-ray absorption spectrum across thebeamline without exposing the sample to theatmosphere, based on the apparatus that we havedeveloped.
The ZrO2 powders was attached to the transfer vessel
in a glove box under an argon atmosphere. NEXAFS
spectra of the ZrO2 powders using both total electron
yield (TEY) and partial fluorescence yield (PFY)
modes were measured at the beamline 2A of the
UVSOR in the Institute of Molecular Science. For
TEY, the drain current of the sample was measured. For
PFY, fluorescence X-rays were collected using anenergy dispersible silicon drift detector (SDD). All
experiments were performed at room temperature.
Fig. 1 shows a photograph of the developed transfer
vessel. The sample is fixed to the lower part of thevessel using carbon tape. The sample current ismeasured using the Bayonet Neill-Concelman (BNC)
connector on the upper part of the vessel. Fig. 2 shows
the Zr L-edge NEXAFS spectra of ZrO2 powder
obtained from TEY and PFY. The shape of the spectrum
measured in the TEY mode was almost the same as thatmeasured in the PFY mode. The TEY is surfacesensitive whereas the PFY is sensitive to the bulk. The
result indicates that the sample could be transported
without air contamination.

Fig. 1. Photograph of the transfer vessel.

Fig. 2. Zr L-edge NEXAFS spectra of ZrO2 powder
obtained from TEY and PFY.
[1] E. Kobayashi, J. Meikaku, T. Okajima, and H.
Setoyama, Japanese Patent No. 5234994.
[2] E. Kobayashi, J. Meikaku, H. Setoyama, T. Okajima,
J. Surf. Anal., 19 (2012) 2.
[3] E. Kobayashi, S. Tanaka, T. Okajima. J. Vac. Soc.
Jpn. 59 (2016) 192.

− 44 −

Ⅲ-1 Accelerators and Instruments

BL3U

Soft X-ray Transmission Measurements of Polymer Films for Soft X-ray
Absorption Spectroscopy of Liquids in Low-Energy Regions
M. Nagasaka1, 2, S. Fujikawa3, H. Takaya1,4 and Y. Uozumi1,2
1
Institute for Molecular Science, Okazaki 444-8585, JapanThe Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
3
International Institute for Carbon-Neutral Energy Research (WPI-I2CNER) and Research Center for Negative
Emissions Technologies, Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan
4
Department of Life Science, Faculty of Life & Environmental Sciences, Teikyo University of Science,
Main Buld #15-05, 2-2-1 Senjyusakuragi, Adachi-ku, Tokyo 120-0045, Japan
2

Soft X-ray absorption spectroscopy (XAS) is anelement-specific method to investigate electronic
structures of liquids. The soft X-ray regions below 2
keV have chemically and biologically absorption edges
such as K-edges of C, N, and O and L-edges of transition
metals such as Mn, Fe, Co, and Ni. Recently, we havedeveloped a transmission-type liquid cell, where aliquid layer is sandwiched between two Si3N4
membranes with the thickness of 100 nm, and measured
XAS spectra of several liquid samples in transmission
mode by adjusting the liquid thicknesses precisely from20 nm to 2000 nm [1].
The low-energy regions below 200 eV include
absorption edges for the investigation of chemical andbiological phenomena in solutions such as K-edges of
Li and B and L-edges of Si, P, S, and Cl. Since soft
X-ray transmission in the low-energy region isextremely lower than that in the high-energy region
above 200 eV [2], transmitted soft X-rays below 200
eV include many high-order X-rays. Recently, we haveused an argon gas window for removing high-order
X-rays by using the Ar L-edge (240 eV) [3] anddeveloped the soft X-ray detector that removes highorder X-rays [4]. However, the XAS measurements inthe low-energy regions are still diﬃcult since soft
X-rays are strongly absorbed by Si3N4 membranes with
the Si L-edges (100 eV). In this study, we havesynthesized polymer films that include no Si atoms
with the thickness of 100 nm and evaluated the soft
X-ray transmission of the polymer film.
The experiments were performed at BL3U. The
polymer film was settled under an ultrahigh vacuum
condition, which directly connected to the beamline.
The transmitted soft X-rays through the polymer film
were measured by using a photodiode detector.
Figure 1 shows the soft X-ray transmission of thepolymer film in the soft X-ray region from 50 eV to 560
eV. Since the polymer film includes the C=C and C=N
groups, the sharp absorption peaks such as the transition
from C 1s electrons to C=C π* orbitals at the C K-edge
and the transition from N 1s electrons to C=N π*orbitals at the N K-edge are observed. Note that the soft
X-ray beamline BL3U includes three monochromatic
gratings for covering wide photon energy regions. The

photon intensities are also maximized by adjusting theundulator gap. That is why several photon energy
regions are not continuous due to the diﬀerent gratings
and the orders of the undulator gap. Since the polymer
film includes no Si atoms, there is no peaks at the Si
L-edge. Soft X-ray transmission of the polymer filmshows a still high value below 200 eV, indicating thepresent polymer film is suitable to measure XAS ofliquids in the low-energy region.
In the present, we have developed an ultrathin liquidcell to reduce the optical pass length of Ar gas. We will
include the present polymer films to the ultrathin liquidcell for improving the soft X-ray transmission of liquidsamples in the low energy region below 200 eV.

Fig. 1. Soft X-ray transmission of the polymer film.
[1] M. Nagasaka and N. Kosugi, Chem. Lett. 50 (2021)
956.
[2] C. T. Chantler, J. Phys. Chem. Ref. Data 29 (2000)
597.
[3] M. Nagasaka, J. Synchrotron Rad. 27 (2020) 959.
[4] M. Nagasaka and H. Iwayama, Rev. Sci. Instrum.
91 (2020) 083103.

− 45 −

BL3B

Dissociation Channels of Molecules for a Use of Plasma Etching Processes
T. T. Nguyen1, K. Ishikawa1 and H. Iwayama2
1

2
Nagoya Univeersity Center for low-temperature plasma sciences, Nagoya 464-8601,
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan

Plasma etching is indispensable for the fabrication ofsemiconductor devices. In recent years, there has been
an urgent need to develop etching gases that meet therequirements for manufacturing three-dimensional
devices and high aspect ratio structures. For the plasmaetching, hydrofluorocarbon molecules are uesd. Plasma
dissociates and ionizes gas molecules. The plasmarelated reactions are complicated significantly, howeverthese reactions of dissociated and ionized fragments ofmolecules should be controlled on the basis of scientificunderstanding. First, we predicted dissociation andionization channels of gas moledules using
computational chemistry. As the results, we calculated
precisely the excited state of perfluorocarbon, c-C4F8[1]. In order to improve the accuracy of the reaction
prediction,
experimental
verificationofphotodissociation is required.
In this study, experimental verification of dissociationof perfluorocarbons, which are not in the database forplasma-etching gases, mainly hydrofluorocarbon
molecules, has been performed with precision andaccuracy using beamlines owned by the Institute for
Molecular Science (IMS). Through this study, we will
pioneer the future development of the world’s best
plasma etching gas by combining coincidence
spectroscopy and computational chemistry.
This study conducted coincidence spectroscopy
experiments on photoionization and photodissociation
using vacuum ultraviolet light region from 40 nm to
400 nm from beamlines of BL3B in the IMS. This lightsource is the only facility in Japan.
In the etching process plasmas, abundances fordissociated ions are reported by C3F5+ > CF3+ > CF+ >C2F4+, which are diﬀerent C2F4+ > C3F5+ > CF+ > CF3+ inmass spectra taken at 70 eV electron energy. The
calculation results showed that a secondary process of
c-C4F8+ to C2F4 + C2F4+ disscociation route is a potential
barrier of 12.05 eV (Fig. 1, Table 1), which is wellcorresponded with the calculated energy barrier of 12.0
eV along the C2F4+ dissociation route [1]. The C3F5+ ion
production channel is the lowest energy barrier due tointramolecular rearrengement reaction, that is
c-C4F8+→C3F5+ + CF3 and additionally c-C4F8+ ions
C2F4+ channel is the second lowest energy barrier. The
other fragments such as C3F5+, CF3+, CF+, are producedbyintermolecularrearrangement
reactions.

Consequently, the ionization process of C3F5+ channel
is abundant due to the lowest potential barrier.

Fig. 1.
Typical mass spectral intensities byphotoionization of c-C4F8 measured vacuum ultraviolet
ranges from 10 to 30 eV.
Table 1. Ionization potential (IP) and appearance
potentials(AP)for c-C4F8.
p
( )
Ions
IP
AP

c-C4F8+c-C4F7+

Potential
Calc. [1]
11.5
15.1

C3F5+

12.0

C2F4+

12.4
12.0*

CF3+

12.5

CF2+

14.8

+

13.6

CF

(eV)
Exp.
11.55
15.45
12.1
11.85
12.35
12.05
14.4
16.6
17.9
18.4
17.1

References
This study
This study
Lifshitz[2]This study
Lifshitz[2]This study
Lifshitz[2]This study
This study
Lifshitz[2]This study* vertical ionization potential[1] T. Hayashi, et al. Jpn. J. Appl. Phys. 61 (2022)
106006.
[2] C. Lifshitz, et al. Int. J. Mass Spectrum Ion Phys. 10(1972) 25.

− 46 −

Ⅲ-1 Accelerators and Instruments

BL3B

Study of Luminescence Characteristics of Diamond Scintillator
for Dark Matter Search
A. Umemoto
Division of Physics, University of Tsukuba, Tennoudai, Tsukuba, Ibaraki, 305-8571, Japan

Direct detection of dark matter is one of the highest
priorities in astroparticle physics. The dark matter inMilky Way Galaxy can be detected via elastic scatteringfrom nuclei in a detector on the earth. For the direct
dark matter search, diamond is one of the promisingdetector. The highest Debye temperature among
crystals (2200 K) and optical centers due to defects andimpurities are unique physical properties of diamond,and they might make good performance of a diamondscintillating bolometer [1][2].
With the goal of developing a diamond scintillating
bolometer for dark matter search, we constructed anexperimental system to measure a photoluminescence
property of synthetic diamond at BL3B in UVSOR.
Usually, the measurements at BL3B are conducted by
the following setup: the excitation light is incident on asample surface at an angle of 45°, and fluorescence is
detected with a CCD placed at right angles to theexcitation light. But this measurement setup will notwork well for diamond due to the total internal reflection
because the refractive index of diamond (n = 2.42) ismuch larger comparing with that of air (also vacuum).
Therefore, a measurement system using a right angle
prism as shown in the schematic diagram of Fig.1 wasdesigned. The excitation deviated a light path by 90°by
entering one side of the prism will be made incident on
the diamond attached on the other side of the prism byvacuum grease. The system makes it possible for the
CCD to detect the photoluminescence of diamond
emitted in a direction perpendicular to the diamondsurface. We used a UV fused silica right angle prismwith length of 10 mm manufactured by Thorlabs, whichtransmits more than 90% of light with wavelengths
more than 185 nm.
Fig.2 shows a photoluminescence spectrum of adiamond excited by ultra violet light with wavelengthof 200 nm. The diamond is a commercially available
synthetic crystal with a size of 3 x 3 x 0.3 mm
manufactured by a method of high-pressure hightemperature. Nitrogen impurities of the diamond is lessthan 200 ppm. Although a peak due to the second-orderdiﬀraction of the excitation light was also observed, theshape of the spectrum detected in the wavelength of

500<λ<700 nm was consistent with our previous resultof X-ray radio luminescence spectrum. It wasdemonstrated that the measurement system is useful for
detecting a photoluminescence of diamond. In FY2023,
we plan to perform low-temperature measurementswith this setup to quantify the luminescence propertiesof diamond scintillators.

Fig. 1. A design of the experimental setup forphotoluminescence measurement of diamond.

Fig. 2. Photoluminescence spectrum of a commerciallyavailable HPHT diamond measured by using the system
shown as Fig.1. Ultra violet light with wavelength of
200 nm was used for photoluminescence excitation.
[1] T.L. Nam et al., Appl. Radiat. Isot. 40 (1989) 8.
[2] L. Canonica et al., J. Low. Temp. Phys, 189 (2020)
606.

− 47 −

BL4B

Current Photon Flux and Focus Size of BL4B
H. Iwayama 1, 2
1
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, Japan2

Beamline BL4B has three holographically ruled
laminar profile plane gratings (G1: 800 lines/mm, G2:
267 lines/mm, G3: 100 lines/mm) and covers soft X-ray
regions ranging from 40 eV to 1000 eV. This soft x-ray
region includes K-edge energies of light elements such
as C, N, and O and L-edge energies of transition metals
such as Mn, Fe, and Co. Since an endstation of BL4B
is not fixed for specific equipment, users can bring intheir equipment and connect them to BL4B. The main
experiments at BL4B are X-ray magnetic circulardichroism (XMCD), angular resolved photoemission
spectroscopy (ARPES), and X-ray absorption finestructure (XAFS) measurements.
The BL4B uses synchrotron radiation from a bending
magnet, and its photon flux and focus size are weak andlarge compared to undulator beamlines. While BL4B isdiﬃcult to measure in tiny samples, it is suitable fororganic molecules, which are fragile against radiation
damage. Thus photon density is an important parameterfor estimating radiation damage on the sample.
This work measured photon flux and focus image at
the focus point. We use a photodiode and Ce:YAG
scintillator for photo flux and focus image
measurements.
Figure 1 shows photon flux curves for each grating.
Entrance and exit slits of the beamline are set to 50 μm.
The photon flux is almost the same as the previous one
measured in 2005, and a photon flux is higher than theprevious one for a high photon energy region of morethan 400 eV. In 2012, our facility improved the optics
of electron storage ring, such as bending magnets, andupgraded from UVSOR-II to UVSOR-III. Whileelectron trajectories in the storage ring were significantly
changed after the major update of UVSOR synchrotron,
the photon flux curves measured this time indicate thatbeamline optics were optimized well and the throughput
and photon flux of the beamline was maintained.
Figure 2 shows a photo of measurement equipment
for a focus image. The equipment comprises Ce:YAG
scintillator, ultra-long working distance lens, and
CMOS camera. The scintillator is in a vacuum chamber
and irradiated by soft X-ray beam of BL4B. The
irradiated scintillator emits ~ 550 nm fluorescence, andwe observed them by the ultra-long working distancelens and CMOS camera. This lens’s working distanceand optical magnification are 305 mm and 0.37 ~ 4.48,
respectively. The highest space resolution is 7 μm.
Figure 3 shows a typical focus image. Photon energy
and flux are 400 eV and 8×109 photons/s. An exposure

time is 30 seconds. This image exhibits a focus size ofφ ~ 500 μm.

Fig. 1. Photon flux curves for G1, G2 and G3.
Entrance and exit slits are set to 50 μm.

Fig. 2. Photo of focus image measurement equipment
at an endstation of BL4B.

Fig. 3. Focus image at the Ce:YAG scintillator. The
photon energy is 400 eV.

− 48 −

Ⅲ-1 Accelerators and Instruments

BL4B

Low Radiation Damage XAFS Measurements at BL4B
H. Iwayama1, 2
1
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

2

Recent developments in synchrotron radiation andfocusing optics technologies yield highly brilliant lightsources. This high bright synchrotron radiation enables
us to measure tiny samples and perform nano-structure
analysis such as scanning transmission x-ray
microscope (STXM) and photoemission electron
microscope (PEEM). In addition, photon-hungry
experiments such as resonant inelastic x-ray scattering
benefit from the recent higher brightness of synchrotron
radiations.
However, the higher brightness causes severe
problems of radiation damage to the samples. In
particular, soft X-rays has weak penetration power, andonly a several-100 nm thickness of the sample almost
absorbs them. Thus radiation damage problem for soft
X-ray regions is much more severe than that for hard
X-ray regions. If a photon flux, focus size, and photon
energy are 1013 photons/s, 10 μm, and 300 eV, thecorresponding dose is estimated to be at 10 GGy/s forsamples mainly composed of carbon. Critical dose forchemical change are 80, 280, and 1230 MGy forpolymethyl methacrylate, fibrinogen, and polystyrene,
respectively [1]. It means that irradiation of suchbrilliant synchrotron radiation destroys soft mattersamples in a moment.
Low photon flux measurements are also important toavoid radiation damage on fragile samples such as soft
matter. In this case, signals of XAFS measurements are
weak in proportion to the photon flux. For good SN
ratio data, noise levels should be pretty small. A total
electron yield (TEY) measurement is one of the mostpopular X-ray absorption fine structure analysis
methods. In the TEY measurements, we measure
currents in the sample irradiated by soft X-rays. The
current means the total electrons ejected from thesample, corresponding to absorption cross sections.
Thus we measure the sample current for each photon
energy by using a pico-amperemeter. In this case, thenoise of signals mainly comes from electric noise. In
particular, noise from the ground level of theexperimental hall is critical.
In this work, we estimate radiation damages for
XAFS measurements and verify the lower limit ofphoton flux, which is enough to obtain XAFS spectrawith good SN ratios. Our TEY equipment at BL4B issimple. A sample is fixed on a sample holder of analuminum board in a vacuum chamber using carbon
tape. We connect a current output terminal of thevacuum chamber to a pico-amperemeter (Keythleyelectrometer 617) with a low-noise BNC cable. The
sample is FePO4 powders.

Figure 1 shows (a) sample currents and (b) the
histogram of our TEY equipment when no soft X-ray
irradiates the sample. The Full-width half maximum(FWHM) is 2 fA. In this measurement, we observe an
oﬀset of 6 fA. It may be because the ground voltages ofthe pico-amperemeter and sample holder are slightly
diﬀerent. When we use a standard BNC cable instead ofthe low-noise cable, the FHWM of noise levels becomes
2 fA.
Figure 2 shows TEY spectra of FePO4 powders at
diﬀerent photon fluxes. The resolution of photon
energies is set to E/ΔE of 2000, and it takes 8 minutes
to obtain one spectrum. When photon flux is more than
4×107 photons/sec, SN ratios are enough to find finestructure of XAFS spectra. However, at the photon fluxof 8×106 photons/sec, while we observe the prominent
peak at the photon energy of 710 eV, sample current
intensities are about 10 fA, and their fine structures
around 723 eV are drowned in noise. From this, a lower
limit of photon flux is around 4×107 photons/sec at the
Fe L edge, and the corresponding dose is only 20 kGy.
This work demonstrates that our TEY system enables
us to perform low radiation damage XAFS
measurements.

Fig. 1. Noise levels of our TEY equipment at BL4B.

Fig. 2. TEY spectra of FePO4 powders for various
photon fluxes.
[1] J. Wang et al., J. Electron Spectrosc. Relat. Phenom.
170 (2009) 25.

− 49 −

BL5B

Transmission Characteristics of an Optical Filter for UV Observations
A. Yamazaki1, K. Goda1, T. Matsumoto2, S. Teramoto2 and K. Yoshioka2
1

Department of Earth and Planetary Science, Graduate School of Science,
The University of Tokyo, Tokyo 113-0033, Japan2
Department of Complexity Science and Engineering, Graduate School of Frontier Sciences,
The University of Tokyo, Chiba 277-8561, JapanThe hydrogen absorption cell is a unique type of filter
that functions as an optical band-stop filter for hydrogen
Lyman-α. The Lyman-α is absorbed by hydrogencontained in the cell when thermally dissociated into
the atomic state. The shape of this cell is cylindrical(φ35 mm, L40 mm), and the windows on each side are
made of magnesium fluoride (MgF2) for UV lighttransmission. Therefore, the cell simply acts as an
MgF2 filter without hydrogen gas. Overall, the cell isknown for its narrow bandwidth, lightweight, small
size, and thus suited to mount on a small spacecraft. We
plan to use this filter in the ongoing Comet Interceptor
Mission, in which the filter is used to observe theatomic hydrogen coma of the target comet remotely.
However, there is a diﬃculty regarding this filter: thedegradation of MgF2 transmittance. The transmittanceof MgF2 drops over time as it alters by UV lightirradiation, and this filter is no exception. Since wehave been using this filter in past experiments, thecenter of the MgF2 window is more altered comparedto the edges. To better understand the characteristic, inthis experiment, we mainly focused on evaluating theposition dependence of the MgF2 transmittance and thechange in the transmittance after polishing the surface
with ethanol. The latter aims to retrieve the transmittancelost due to alteration. Since the experiments aim tounderstand the characteristics of the filter window, we
did not fill hydrogen gas in the cell and thus was not
functioning as a band-stop filter.
In the experiment, we measured the position
dependence of the filter transmittance. The cell was set
on a motorized stage, and the transmittance wasmeasured at multiple incident positions by moving it
vertically against the beam. Microchannel plates and a
resistive anode encoder were used for the detector. For
each measurement, a wavelength scan was performed
using the G3M5 grating system with the range of 110135 nm at an interval of 1 nm. Later, the samemeasurement was done after polishing the MgF2
surface with ethanol.
Figure 1 shows the transmittance of the cell filter.

The solid and dashed lines show the result before andafter polishing the surface with ethanol. The plots’colors describe the diﬀerent incident positions as shownin the upper right illustration. The area below 116 nm is
shaded since the data in this range has a low S/N ratio
due to the MgF2 cutoﬀ wavelength at 115 nm.
The result implies that the transmittance increases
from the center towards the edge, and also increases bypolishing the MgF2 surface with ethanol. However, theincrease in transmittance varies significantly among theincident positions. At the center of the cell, thetransmittance increases no more than a few percent, butaround the edges, it increases by ~20%. One possible
explanation is that polishing the surface is eﬀective forsurface dust and smears, but not for degradation caused
by intensive UV light irradiation. Since the center ofthe cell has suﬀered irradiation throughout the pastexperiments, the alteration is discernible. Polishing thecell surface proved eﬀective in increasing thetransmissions, but we could not fully retrieve those lost
due to UV-induced alteration.

Fig. 1. Transmission spectra of MgF2 windows on ahydrogen absorption cell.

− 50 −

Ⅲ-1 Accelerators and Instruments

BL5B

Evaluation of the Pressure Dependence of the Krypton Absorption Cell
M. Kuwabara 1, K. Kato1, K. Arakawa1 and M. Taguchi1
1

Department of Physics, College of Science, Rikkyo University, Tokyo 171-8501, Japan

In planetary upper atmospheres, hydrogen atoms
originating from hydrogen molecules in lower
atmospheres expand to an altitude equivalent to several
planetary radii. These hydrogen atoms resonantly
scatter the solar Lyman-alpha radiation (121.567 nm),forming planetary hydrogen coronae. Since thebrightness of the hydrogen coronae depends on thenumber density of hydrogen atoms, the spatial
structures can be obtained by imaging the coronae.
A hydrogen absorption cell is eﬃcient tool for remotesensing of the density and temperature distribution of
the exospheric hydrogen atoms. Additionally, thistechnique has advantages over other techniques interms of geometrical size, weight, and simplicity.
Therefore, this technique is expected to be eﬀectively
used for exploration using ultra-small spacecraft andother applications [1].
One of the drawbacks of the absorption cell techniqueis the diﬃculty of calibration. Since the absorption
linewidth of the hydrogen absorption cell is a few pm at
most, the calibration system must have high wavelengthstability. However, it is revealed that the measurement
wavelength of BL5B beam line drifts as the temperatureof the mirror changes, so it is necessary to know thecorrect wavelength for each measurement. This

problem can be overcome by placing a krypton
absorption cell in front of the hydrogen absorption cell.
This is because krypton has a strong absorption line at
123.584 nm, which is close to the Lyman-alpha line of
the hydrogen atom. By measuring the light transmitted
through both cells, the peak of the absorption of thehydrogen Lyman-alpha line can be determined.
In this experiment, we evaluate the pressure
dependence of the absorption line profile of the krypton
cell to establish a calibration method for the hydrogen
absorption cell. Figure 1 shows the result of theexperiment. The absorption line of krypton is 123.584
nm, but the measurement wavelengths of the calibration
system are oﬀ, and the peaks are seen a little beyond
124 nm. In addition, the positions of the peak vary ineach measurement. Regarding the pressure dependence,as the pressure of krypton gas increases, both the depth
and the width of absorption also increase. The result
will be used to determine the optimum pressure for the
krypton absorption cell needed for the BL5B calibration
system in the future.
[1] M. Kuwabara et al., Rev. Sci. Instrum. 89 (2018)023111.

Fig. 1. Pressure dependence of the krypton cell absorption.

− 51 −BL5B

XUV Polarization Measurement using Visible Fluorescencefrom Neon Atoms
T. Kaneyasu1,2, K. Hosaka3 and J. Adachi4,5
1
SAGA Light Source, Tosu 841-0005, Japan
Institute for Molecular Science, Okazaki 444-8585, Japan
3
National Institutes for Quantum Science and Technology, Takasaki 370-1292, Japan
4
Institute of Materials Structure Science, KEK, Tsukuba 305-0801, Japan
5
The Graduate University for Advanced Studies (SOKENDAI), Tsukuba 305-0801, Japan
2

Polarization is one of the most importantcharacteristics of synchrotron radiation. For accurate
measurements using the polarization properties ofsynchrotron radiation, it is essential to evaluate thepolarization state of light at a sample point. Fluorescencepolarimetry is a useful technique to determine thepolarization state of the extreme ultraviolet (XUV)
radiation. This method is based on the conversion of
XUV radiation to visible light on the atomic resonance[1,2]. The fluorescence preserves the polarization stateof the excitation light when it is observed along thelight propagation axis. Comparing with the opticalpolarimeters [3,4], this method has advantages in its
simple apparatus and easy operation. Up to the present,
however, this method has been only applied to helium
atoms [2,4,5], and the wavelength range is restricted toaround 50 nm. In this study, we show that neon atoms
can be used to measure the polarization state of XUVradiation at 60 nm wavelength.
The experiment was performed at the bending magnet
beamline BL5B. Figure 1 shows the experimental
layout of the present study. The wavelength of
monochromatized synchrotron radiation was set to 59.6
nm. Neon atoms were provided by an eﬀusive beam.
The XUV radiation resonantly excites the neon atom to
the 4d’[3/2]o1 state. This state decays to the 3p[1/2]o1
state with the emission of 511.4 nm fluorescencephoton. The fluorescence photons emitted parallel tothe light propagation axis (z-axis) were detected by aphotomultiplier tube equipped with a polarizer and a
bandpass filter. The fluorescence photon basicallypreserves the polarization state of the XUV radiation.
The only diﬀerence between them is that the polarization
angle of the fluorescence photon is expected to rotate
by 90 degrees with respect to the polarization angle ofthe incident XUV radiation.
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). In accordance with the
expectation, the fluorescence intensity shows asinusoidal modulation reflecting the vertically linear
polarization of the fluorescence photon. Assuming an
elliptical polarization, the experimental data points are

fitted by a theoretical curve. The linear polarization
degree and polarization angle of XUV radiation areevaluated to be 0.67±0.02 and 10±2 degrees,
respectively. This is roughly in agreement with theresults obtained by helium atoms [5, 6], suggesting thecapability of fluorescence polarimeter using neon
atoms.

Fig. 1. Experimental setup. The visible fluorescencephoton 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] D. Cubric et al., Meas. Sci. Technol. 10 (1999) 554.
[4] E. Allaria et al., Phys. Rev. X 4 (2014) 041040.
[5] T. Kaneyasu, K. Hosaka and J. Adachi, UVSOR
Activity Report 2020 49 (2021) 46.
[6] Y. Hiosaka, H. Iwayama and T. Kaneyasu, J.
Synchrotron Rad. 27 (2020) 675.

− 52 −

Ⅲ-1 Accelerators and Instruments

BL5B

A Position-sensitive Microchannel Plate Detector with Resistive AnodeS. Matoba1, S. Kanda1, H. Ohshita1, K. Hirata2, H. Iwayama3, 4 and T. Kaneyasu5
1Institute of Materials Structure Science, KEK, Tsukuba 305-0801, Japan
National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology,
1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan
3
Editorial Board, UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
4
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI),
Okazaki 444-8585, Japan
5
SAGA Light Source, Tosu 841-0005, Japan2

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.
We are developing a system that enables easymeasurement of imaging techniques using quantum
beams regardless of the beam type and location, which
can be used for trial experiments prior to the use ofadvanced devices. The most common method of twodimensional detectors for MCP anodes is opticaldetection of emission from fluorescent anodes using a
CCD camera or the like. However, the diﬃculty of
inserting a detector in the middle of the beamline andthe upper limit of the frame rate of the camera limit theuse of this method for accelerator beamlines. Anothermajor method, the delay-line anode[1], requires a highspeed circuit that can detect time diﬀerences between
wires, making it expensive and diﬃcult to implementin small-scale experiments.
We are developing a position-sensitive detector using
resistive anodes as a two-dimensional detector forvarious particles such as neutrons, ultraviolet light,
muons, and ions. The advantages of this system are that
position detection can be easily performed by using a
4-channel waveform analyzer and that the resistive
anodes are only about 2 mm thick, so they can beassembled into a compact assembly. Resistive anodes
as two-dimensional detector elements have beendeveloped for a long time[2], but there is no simple
system that can be used by researchers who are notdetector experts, and we are developing one.
In this experiment, the “solid chamber” of BL5B was
removed and a pinhole, a four-quadrant slit, and a lightreducing filter made of aluminum foil and tungsten
mesh were installed to detect the incident position of

the MCP with a wavelength of 130 nm UV light ofapproximately 1 mm in diameter. The charge of theelectron pulses generated by the MCP, which has aneﬀective diameter of 40 mm and consists of two stages,
is dispersed and transferred to the electrodes at the four
corners of the resistive anode. The two-dimensional
position information is calculated from the current
flowing to each electrode as x/d = (I1 + I4) /I, y/d = (I1+ I2) /I (where d is the full width or height of one sideof the resistive anode and I = I1+I2+I3+I4). The current
flowing to each electrode was measured with a
4-channel amplifier, shaper and waveform analyzer.
Figure 1 shows an example of the measured light
positions. In this experiment, the measurement system
was verified and confirmed to be capable of soundposition detection. In the future, the position resolution
and detection eﬃciency distribution will be investigatedusing patterns, etc.

Fig. 1. Position reconstruction on the resistive anode.
[1] S. E. Sobottka and M. B. Williams, IEEE Trans.
Nucl. Sci., 35 (1988) 348.
[2] M. Lampton and R. F. Malina, Rev. Sci. Instrum.,47 (1976) 1360.

− 53 −

BL6U

Progress of Photoelectron Momentum Microscopy for Revealing Complex
and Detailed Electronic Structures of Materials
S. Suga 1, 2 and F. Matsui 3, 4
1

SANKEN, Osaka University, Osaka, 567-0047, Japan
2
PGI-6, Jülich Research Center, Germany
3
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
4
The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan

The photoelectron momentum microscope (often
abbreviated as 2D-PMM) is installed already in 2020 at
BL6U of UVSOR in the form of single hemisphericaldeflection electron energy analyzer (HDA) behind the
PEEM type objective lens, which can easily be switchedbetween the real space to the momentum spacedetection mode. EB(x,y) or EB(kx,ky) constant energy
contour (CEC) can be simultaneously detected by a 2D
detector behind the focusing lens optics installed after
the exit of the HDA[1]. The detection eﬃciency of theEB(kx,ky) is very high in comparison with theconventional HDA detection due to the simultaneously
covered wide acceptance angle owing to the use of
PEEM, where the sample rotation is not necessary forEB(kx,ky) detection and excitation light focusing is notnecessary to probe micro-nano regions. Then very
reliable gigantic data set is obtained by this instrument
in rather short measuring time [2−4]. Temperature
down to 10 K can be measured.
Since the best quality sample surface region down to~10 μm can be selected by the proper sized field
aperture in the objective lens, high quality andreproducible data can be obtained by this instrument.
The beam focusing is not necessary in this system byusing the PEEM and several tens of nm resolution canbe realized without noticeable radiation damage.
Detailed behaviors of CECs of graphite are shown in
Fig.1 [3]. Resolutions are ΔE~40 meV and Δk~0.01
Å-1. Band dispersions along any kx-ky direction can be
immediately derived from the big data.
Since 2022 upgrading is progressing. In addition to
68° incidence of light from the surface normal direction, 0° incidence is soon available. HDA is upgraded to
2 HDAs to realize this configuration. 2D spin filter will
be installed within a few months to realize themultichannel figure of merit FoM~102. Then the spin
detection eﬃciency becomes 104 times higher than the
single channel spin detection and 102 times higher thanusing the W (tungsten) 2D spin filter.
Various additional upgrading of the SP-2D-PMM
system in UVSOR will be made in the next few years,
producing the world best heavy data on micro-nanoregions of exotic and/or functional materials supporting
the new device development.

Fig.1. CECs of graphite (0001) at various hν reproduced
from Ref.[3]. Thus EB(kx,ky,kz) as well as band
dispersions along any kx-ky directions can be easily
derived from gigantic data.
[1] S. Suga, A. Sekiyama, C. Tusche, Photoelectron
Spectroscopy, Springer, Springer Series of Surface
Science 72 (2021) 1−503.
[2] F. Matsui, S. Makita, H. Matsuda, T. Yano, E.
Nakamura, K. Tanaka, S. Suga, and S. Kera, Jpn. J.
Appl. Phys. 59 (2020) 067001.
[3] F. Matsui and S. Suga, Phys. Rev. B 105 (2022)
235126.
[4] F. Matsui, Y. Okano, H. Matsuda, T. Yano, E.
Nakamura, S. Kera and S. Suga, J. Phys. Soc. Jpn. 91(2022) 094703.

− 54 −

Ⅲ-1 Accelerators and Instruments

BL6B

Low-frequency Photocarrier Response in Semiconductors Based on
ns-visible-pump broadband-infrared-probe Spectroscopy
J. Nishida 1* and T. Kumagai 1
1

Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki 444-8585, Japan

Optical responses of photoinduced carriers in mid- to
far-infrared encode their scattering times as well as trap
and polaronic states, which are all directly relevant to
the mobility of the carriers. Yet, due to the spectrally
broad nature of such responses, the time-resolved studyof such photoinduced carriers is often diﬃcult andrequires advanced laser sources for ultrafast experiments[1]. While mid-infrared thermal light source with fastelectronics covers important subsets of the spectral
range and time resolution [2], the full characterizationof the low-frequency carrier response has remained
elusive.
An extremely broadband output of a synchrotron
provide unique opportunities to tackle such problems.
With the combination of broad spectrum extending
from mid- (~100 meV) to far-infrared (~ meV), as well
as a reasonable pulse duration of < 1 ns, it may bepossible to address the scattering and polaronicstabilization of photoinduced carriers on the nanosecond
time scale. Such an information is particularly relevant
to address the photoinduced carrier responses in lead
halide perovskites, where the interaction of carriers
with surrounding lattice has been intensely debated [3].
We thus attempted to combine the mid-infraredsynchrotron output at BL6B beam line as a probe pulse
with a 10s-ns visible laser as a pump pulse (Fig. 1a).
We mainly focused on the application in the singlebunch operation (~5 MHz) to enforce the relaxation ofphotoinduced carriers as much as possible. The TTL
output synchronized with the synchrotron laser is used
to trigger our commercial and duration-tunable (6 – 40ns) pulsed nanosecond laser. In collaboration with
Equipment Development Center, we developed timedelay generator and modulator to control the timing
between the visible and broadband mid-infrared pulse,
as well as to modulate the visible pump pulse intensity.
The modulation frequency is used for the lock-in
detection of the photoinduced change in the intensitythat transmits a sample. We implemented a Michelsoninterferometer for spectral measurements.
We first demonstrated the photo-modulation
absorption spectroscopy on the low-frequency responseof silicon. In Fig. 1b, we show an acquired interferogramin the ground-state (I), and its photoinduced change(ΔI). With the average time of ~30 min, we demonstrated
the sensitivity of ΔI/I ~ 10-3. The Fourier transform(Fig. 1c) shows the divergent response toward the lowfrequency side, consistent with the Drude-like behavior

expected for the photo-carriers in silicon.
We then attempted to extend the approach toperovskite quantum dots dispersed in solution. While
we observed a photoinduced change in the transmitted
intensity, the response was strongly dependent on themodulation frequency (Fig. 1d), likely pointing to athermal eﬀect. Such a thermal contribution can bealleviated by modulating the pump pulse rapidly at 100
kHz. We scanned the pump-probe delay to identify any
relaxation processes related to the photoinduced
carriers, but so far could not identify any such responses(Fig. 1d, inset; 5 min average each point).
To observe photoinduced carriers in a broad range ofsemiconductor materials, we estimate another order ofmagnitude improvement is necessary for the signal-tonoise ratio. We confirmed that the current signal-tonoise level is limited by the HgCdTe detector,
potentially due to the large element size. With the
optimization of the electronics, we may attain enoughsensitivity to be combined with the time resolution andspectral range that we demonstrated.

Fig. 1. (a) Timing scheme, (b) photo-modulated
interferogram and (c) spectrum on silicon, (d)modulation-frequency dependence of photo-induced
modulation.
[1] T. T. Yeh et al., Sci. Rep. 7 (2017) 1.
[2] K. Furuhashi et al., J. Phys. Chem. C 117 (2013)
19101.
[3] K. Munson T. et al., Chem, 4 (2018) 2826.

− 55 −

BL7B

Study on the Reflective Properties of Black Coatings Used in UV
Observation Equipment.
T. Matsumoto2, K. Goda1, A. Yamazaki1, K. Inoue1, S. Liu2 and K. Yoshioka2
1

Department of Earth and Planetary Science, Graduate School of Science,
The University of Tokyo, Tokyo 113-0033, Japan2
Department of Complexity Science and Engineering, Graduate School of Frontier Sciences,
The University of Tokyo, Chiba 277-8561, JapanThe emission angle dependence of scattered lightintensity (Experiment 1) and reflectance (Experiment2) were measured for three diﬀerent, black-coatedaluminum plates (Samples A, B, and C) and a mirror.
The reflectance of the samples was determined basedon their relative reflectance to the mirror. This
experiment aimed to optimize the black coating to be
applied to the optics of the hydrogen imager (HI) on
board the Comet Interceptor (CI) mission to be launchedin 2029. To do this, we quantitatively determine theblack coating that minimizes stray light caused byreflections inside the equipment. These measurements
are also crucial for the quantitative estimation of the
expected performance of CI/HI.
The setup for both Experiment 1 and Experiment 2
was the same. Samples A, B, and C and a mirror were
mounted on the inner rotating stage, while the detector
was mounted on the outer rotating stage (Fig. 1). The
detector used was a photodiode with an eﬀective areaof 10 mm × 10 mm. The slit width was adjusted toprevent saturation of the measured values at each
incident angle. A G3 diﬀraction grating was used.
The following g12 measurements were performed.
p

4 targets3 incident angles
×(A, B, C, Mirror)(30°, 45°, 60°)
In Experiment 1, the wavelength was set to 121.4 nm.
The detector was positioned with the direction of theincoming beam as 0° and rightward as positive. Anglescans were performed from 45° to 180° with an intervalof about 13.5°, followed by angle scans near the peakwith an interval of about 2°. In Experiment 2, thedetector was fixed, and wavelength scans were
performed from 112 nm to 133 nm with an interval of 1
nm without summing.
Experiments 1 and 2 are summarized below with
their results (Fig. 2 and Fig. 3.).
The results found that, at any incident angle, thereflectance was A, B, and C from the lowest to thehighest, with Sample A being the most optimal.
However, the reflectance of Samples A and B was
negative only at 45° incident angle, which might havebeen due to the dark noise and the positional accuracyof the detector. Further experiments are needed toconfirm reproducibility and evaluate the consistency of
the incident angle dependence of reflectance withtheoretical values.

Fig.1. The setup of the measurements.

Fig. 2. Experiment 1: The emission angle dependenceof the scattered light intensity

Fig. 3. Experiment 2: Reflectance− 56 −

Ⅲ-1 Accelerators and Instruments

BL7B

Complex Refractive Index Measurement by Reflectance Spectra in Diﬀerent
Polarization Configurations (II)K. Shinkai1, K. Fukui1, K. Yamamoto1 and T. Saito2
1
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, Japan2

configuration can be easily changed with the system.
These features make the PS method suitable for thissystem. The following are the intermediate results ofcomplex refractive index measurements of fused silica
glass substrate using this PS method.
Figure 1 shows reflectance spectra both in p- ands-polarization configurations. The dots are reference
points which represent the reflectance calculated fromthe complex refractive index obtained from the ES
mode, and the lines are reflection spectra of the OR
mode in p- and s- polarization configurations corrected
for the reference points. Note that the eﬀect of surface
roughness is taken into account in the optical model ofthe ES mode and reflectance calculations. The
dispersion after the band edge is well shown by thecontinuous spectrum.
0.5㻌㻾㻜㼻㻔㻻㻾㻌㼙㼛㼐㼑㻕㻌㻾㻥㻜㼻㻔㻻㻾㻌㼙㼛㼐㼑㻕㻌㻾㻜㼻㻔㻿㻱㻌㼙㼛㼐㼑㻕㻌㻾㻥㻜㼻㻔㻿㻱㻌㼙㼛㼐㼑㻕

0.4

ReflectanceBased on the basic design of the instrument by agroup at AIST [1], a combined refractive index
spectrum measurement system (CRIMS-VUV) [2] hasbeen developed specifically for BL7B, which cancontinuously measure from the visible region (VIS) at
2 eV to the vacuum ultraviolet (VUV) region at 20 eV.
CRIMS-VUV is composed of two measurement modes(spectroscopic ellipsometry measurement (SE) modeand reflection spectrum measurement (OR) mode),both of which can be performed in the sameenvironment.
SE mode has the advantage of measuring the complex
refractive index with high accuracy. However, thismode has the disadvantage that, due to its measurement
principle, it takes time to measure at each measurement
point (photon energy), making it diﬃcult to measure acontinuous spectrum. In this respect, OR mode issuitable for measuring continuous spectrum. The wellknown Kramers - Kronig analysis (KKA) method isused to determine the complex refractive index
spectrum from the reflectance spectrum. However, as
mentioned our previous work [2], KKA method isuseful, for example, for obtaining qualitative complex
refractive index spectrum for limited photon energy
region around the absorption edge, but is not well suitedfor obtaining quantitative complex refractive index
spectrum over a wide photon energy region. Therefore,
we decided to use the method for determining thecomplex refractive index from the reflectance in p- ands-polarization configurations (PS method) as a methodfor determining the complex refractive index from thereflectance for each photon energy. This method
requires the linear polarization of the incident light(Stokes parameter S1), which can be measured from theSE mode of the system. The S1 can be measured fromthe SE mode of the system, and the polarization

0.3
0.2
0.1
0.0

0

2

4

6

8

10 12 14 16 18 20

Photon Energy(eV)Fig. 1. Reflectance spectra in p- and s-polarization
configurations of fused quartz glass[1] T. Saito, M. Yuri and H. Onuki, Rev. Sci. Instrum.
66 (1995) 1570.
[2] M. Horiba et al., UVSOR Activity Report 2021 49(2022) 49.

− 57 −

Others

Performance of the Refreshable Large Crystal Nuclear Emulsion
for the NINJA Experiment
T. Fukuda 1, 2, H. Kobayashi2, Y. Hirobe2, Y. Morimoto2 and M. Nakamura1,3
1

F-lab., Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
2
Institute for Advanced Research, Nagoya University, Nagoya 464-8601, Japan
3
Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya 464-8601, Japan

In neutrino oscillation studies, it is important todetect short-range hadrons in the energy range of about
1 GeV in order to understand neutrino-nucleus
interactions. The Emulsion Cloud Chamber (ECC) is asandwich structure consisting of a special photographic
film nuclear emulsion film with sensitivity to minimum
ionizing particles, with a thickness of several hundred
microns (composed of two sensitive emulsion gel
layers each tens of microns thick and plastic baselayer), and a thin target material with a thickness ofseveral hundred microns to several millimeters, stacked
alternately. The NINJA experiment, which uses ECC as
the main detector, has been publishing measurement
data on low-energy hadrons for neutrino-iron andneutrino-water interactions since 2014, while expanding
the scale of the experiment.
This autumn to winter, we plan to conduct a largescale statistical experiment on neutrino-H, O, C, and Fe
nuclear interactions using about 250 square meters of
nuclear emulsion films. The tracks on the nuclear
emulsion films are automatically scanned by the track
selecting device HTS, but 250 square meters is twice
the amount of the previous experimental run that tookapproximately 20 months for track scanning, and weare developing the track selecting device HTS2, which
has five times the scanning speed of HTS. With the
expansion of the field of view, the pixel size of HTS2
has been increased, and it is necessary to increase thesize of the developed silver grains compared to theconventional nuclear emulsion.
We have created a nuclear emulsion with AgBrI
crystal size of 320 nm, which is larger than theconventional 240 nm, and added a group of chemicals
that have a proven eﬀect in suppressing latent image
fading and fogging. After irradiating the emulsion films
with electron beams using UVSOR, we performed arefresh process to eliminate unwanted tracks byexposing it to high temperature and humidity conditions(30℃, 95%RH). We have newly discovered that therefresh which removes unwanted tracks is insuﬃcient(Fig. 1.). The left image of Fig. 1. has a grain density of
53.5±1.5 grains/100 μm and has not undergone arefresh process. The image on the right of Fig. 1. hasundergone a refresh process with a grain density of
29.8±1.7, but the disappearance of tracks due to therefresh process is insuﬃcient.
Based on our experience in the OPERA experiment,
we conducted experiments to determine the appropriate

amount of 5-methylbenzotriazole (5-MBT, Fig. 2.),
which promotes refreshment by oxidizing latent image
nuclei in high humidity conditions. The results ofcomparing the GD of emulsion film samples withvarying amounts of 5-MBT added, using UVSOR to
apply an electron beam and comparing with and without
refresh processing, are shown in Fig. 3. The initial
sensitivity decreased depending on the amount of
5-MBT added to the emulsion. However, when 5-MBT
was added at 1.0×10-3 or more moles per mole of silverin the emulsion, the refresh eﬀect was enhanced. A
suitable amount of balance between the refresh eﬀect
and initial sensitivity was found through this addition.

Fig. 1. Microscopic images of large crystal emulsion
films. (left) unrefreshed film. (right) refreshed film.

Fig. 2. The chemical formula of 5-MBT.

Fig. 3. GD of electron beam tracks. The solid anddashed lines show the data of unrefreshed films andrefreshed films, respectively.

− 58 −

Ⅲ-1 Accelerators and Instruments

Accelerators

Lattice Design of the UVSOR-IV Storage Ring
E. Salehi1, Y. Taira1, M. Fujimoto1,3 and M. Katoh1,2
1
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-hiroshima 739-0046, Japan
3
NUSR, Nagoya University, Nagoya, Japan

2

In this study, we have designed a new lattice for
UVSOR storage ring to provide diﬀraction-limited
light in the vacuum ultraviolet range which requires asmall emittance at least a few nm. UVSOR is a low
energy synchrotron light source. After some major
upgrades [1-4], it is now called UVSOR-III, which has
a moderately small emittance of about 17 nm andprovide vacuum ultraviolet light of high brightness.
In order to provide diﬀraction-limited light, at thefirst step, we have analyzed the present magnetic latticeof UVSOR based on tie diagram to explore thepossibility to get a lower emittance with some minorchanges in the configuration of magnets. We havefound a few optics which has smaller emittance around
10 nm than the present value [5]. To reach the low
emittance around a few nm, we have designed a new
storage ring of 1 GeV electron energy, which is higher
than the present value, 750 MeV. The magnetic lattice
is based on a compact double bend achromat cell. This
cell consists of two bending magnets and four focusing
magnets, all of which are of combined function
magnets. In this lattice two sextupole families arelocated in between two combined dipoles for thechromaticity correction and two harmonic sextupolefamilies are also employed to correct the high ordergeometric aberrations. The circumference is 82.5 m.
This lattice has twelve DBA cells with six long straightsections about 4 m and six short straight sections
around 1.5 m long. Among 12 straight sections, twosections will be used for the injection and RF cavity,
and ten sections will be used for insertion devices.
These lengths are same as those of UVSOR-III. This
may enable us to use the undulators at UVSOR_III in
the new ring. The undulators can radiate nearlydiﬀraction-limited light in VUV.
A tune survey was performed to optimize the magnet
arrangement and the working point by ELEGANT [6].
We found an optic with a small natural emittancearound 4.2 nm in the achromatic condition, whichbecomes lower in the non-achromatic condition.
Occupying three short straight sections with 2T
multipole wigglers in symmetry can reduce theemittance to 3.6 nm-rad. Moreover, these wigglers
provide intense tender X-rays. Figure 1 shows (left) the
lattice functions in the achromatic condition and (right)
the dynamic aperture for on- and oﬀ energy particles atthe straight section after optimizing the strengths of theharmonic sextupoles.
Intra-beam and Touschek scattering which dominate
the lifetime in low emittance storage rings, particularlyof low energy has been studied. Figure 2 shows that
IBS eﬀect increases the Touschek lifetime, while theemittance is increased. One possible technique todecrease the IBS eﬀect is lengthening the bunches byusing harmonic cavity which is routinely used at
UVSOR-III. Our simulation shows that the increasingof the bunch length by 80 mm can reduce IBS eﬀect on
the emittance to an acceptable level with to ߳଴ = 4.3 ݊݉[7].

Fig. 1. (Left)Lattice function of 1 GeV storage ring
whit a small emittance of 4.2 nm for UVSOR-IV, (right)
dynamic aperture of optic for diﬀerent energy deviation.

Fig. 2. IBS eﬀect on Touschek lifetime (top) andlongitudinal emittance (bottom) versus bunch charge.
[1] M. Katoh, K. Hayashi, et al., Nucl. Instr. Meth. A
467 (2001) 68.
[2] M. Katoh, M. Hosaka, et al., AIP Conf. Proc. 705(2004) 49[3] M. Adachi, H. Zen, et al., J. Phys. Conf. Ser. 425(2013) 042013.
[4] M. Katoh, M. Adachi, et al., AIP Conf. Proc. 1234
(2010) 531.
[5] E. Salehi and M. Katoh, in Proc. IPAC’21,
Campinas, Brazil, May 2021, 3970.
[6] M. Borland, APS LS-287 (2000). https://www.aps.
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