Ⅲ-1

Accelerators andInstrumentsⅢ -1. Accelerators and Instruments
BL1U
BL1U

Generation of Vector Beam with Tandem
andem Helical Undulators at BL1U
1S. Matsuba 1, K. Kawase1, A. Miyamoto1, S. Sasaki1, M. Fujimoto2, T. Konomi2,
N. Yamamoto3, M. Hosaka3 and M. Katoh2

Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-hiroshima 739-0046, Japan
2
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
3
Nagoya University Synchrotron Radiation Research Center, Seto 489-0965, Japan

Some sorts of lights which have spatially structured
in intensity, polarization, and/or phase, called"structured light", have stimulated significant interests
for a range of applications. Optical vortices and vector
beams which have a donuts-shaped intensity with spiralphase structure or spatially dependent polarization that
direction rotates around its beam axis have long beeninterest in laser community [1, 2]. Figure 1 shows
schematic illustration of vector beams.
In accelerator-based light sources, several ways togenerate optical vortices has been proposed anddemonstrated [3]. In addition, edge radiation andtransition radiation belong a category of vector beam. In
these situations, we devise a scheme to produce a vector
beam based on synchrotron radiation technology, whichenables the generation of vector beams in the VUV or
x-ray range [4]. The scheme is similar to the idea of“cross undulator” [5] but we expanded it into twodimensions to superpose second harmonics fromtandem helical undulators at their polarizations were
opposite to each other. It was well known in the laser
community that the vector beams can be generated bysuperposing optical vortices.
The experiment was carried out at the BL1U. The firstharmonic of the undulators light was set to 496 nm, andthe second harmonic to 248 nm. The intensity wasmonitored with a CCD camera 7.5 m downstream fromthe center of the downstream undulator after through the
band-pass filter with a center wavelength of 248 ±1 nm
and rotatable linear polarizer for analysis of polarization
direction.
The experimental results and the numericalsimulations results done by using the Synchrotron
Radiation Workshop [6] are shown in the Fig. 2. In thevicinity of the center, distributions of polarization are
well approximated as a vector beams of Fig.1. Obtained
degree of linear polarization is distributing in the rangeof 60-80%. This scheme may form the basis ofgenerating vector beam in diffraction-limited
synchrotron light sources in future.
In the next machine time, Stokes parameters ofundulator radiation including vector beams will bemeasured for obtaining all polarization parameters.

Ⅲ -1

Fig. 1. Schematic illustration of intensity
polarization structure of vector beams.

andFig. 2. Distribution of direction of linear polarizationon the observed plane. The observed area is 6 mm 6
mm square. Top and bottom rows show experimental
and simulation results respectively. The experimental
condition of results in right column have relative phaseretardation of downstream undulator radiation from thecondition of left column. The relative phase retardationis controlled approximately 180° by buncher magnets
between undulators.
[1] H. Rubinsztein-Dunlop et al., J. Opt. 19 (2017)013001.
[2] Q. Zhan, Adv. Opt. Photon. 1 (2009) 1.
[3] M. Katoh et al., Sci. Rep. 7 (2017) 6130.
[4] S. Matsuba et al., Appl. Phys. Lett. 113 (2018)
021106.
[5] K. J. Kim, Nucl. Instrum. Meth. Phys. Res. 219(1984) 425.
[6] O. Chubar et al., Nucl. Instrum. Meth. Phys. Res.
A 435 (1999) 495.

31
Ⅲ01- 1 -Ⅲ -1. Accelerators and Instruments
Accelerators
Accelerators

The Performance Evaluation of Nuclear Emulsion
2

Ⅲ -1

T. Takao1, T. Fukuda1,2 and M. Nakamura1,2

Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya 464-8601, Japan
1

Nuclear emulsion is a kind of photographic film
having sensitivity for ionization. The film is made bycoating emulsion gel, consisting mainly of silver
bromide crystals and gelatin, on plastic base (Fig. 1).
When a charged particle passes through the film, its
track is recorded by silver grains, for the particle runsin the film with silver bromides around it ionized. Ourgroup uses the film to find neutrino interactions. It is
not easy because the tracks we try to find are very fine.
Nuclear emulsion resolves this difficulty. Because thesilver bromide crystal’s diameter is 200 nm, we candetect them. We produced the films by ourselves andchecked their performance.
Grain density (GD) is a reference index of its
sensitivity. This value is counts of silver grains per 100µm. The larger the value is, the thicker the track is.
Then, I use the films exposed electron beam at
UVSOR which has equivalent energy with minimum
ionizing particle. Figure 2 shows the deference ofgrain densities by product batches. These values are
not extraordinary and it suggests that the films can beused safely.
The film has accumulated tracks since it is produced.
It means the film keep on recording cosmic ray, naturalradiation, and so on. These tracks recorded before an
experiment become noise. We want to fade noise
tracks because our targets contain fine tracks. Then,
we make the films “refresh”. Refresh is a process tofade tracks in the film. The film is filled with silver
bromide crystals. If a charged particle flies near them,
they are ionized and become silvers. The reaction thatsilver bromide turns to be silver is reversible. It
suggests that the tracks may fade away. We call thisphenomenon “fading”, and try to inhibit it. Refreshuses the characteristics of fading. I checked that
refresh is effective for our films to use in the neutrino
experiment. Then, I use the films exposed electron
beam at UVSOR. I make the film refresh and measuregrain density. Figure 3 shows the result. It is
recognized that electron tracks and cosmic ray tracks
faded after refresh.
We check the film’s performance by using electron
beam at UVSOR. After figuring out it, we use the filmin experiments.

Fig. 1. The structure of nuclear emulsion

Fig. 2. The diference of GD by product batches

Fig. 3. microscope views of films (left: unrefreshedfilm, right: refreshed film)

32
Ⅲ01- 2 -Ⅲ -1. Accelerators and Instruments
BL1U
BL1U

Laser Compton Scattering Gamma-ray Generation for Nonlinear Effect in
QED
T. Hayakawa1,2, K. Kawase1, T. Shizuma1, J. K. Koga3, H. Zen4, T. Kii4, H. Ohgaki4,
M. Fujimoto5 and M. Katoh5

Tokai Quantum Beam Science Research Center, National Institutes for Quantum and Radiological Science andApplications, Tokai 319-1106, Japan
2
National Astronomical Observatory of Japan, Mitaka 181-8588, Japan
3
Kansai Photon Science Institute, National Institutes for Quantum and Radiological Science and Applications,
Kizugawa 619-0215, Japan
4
Institute of Advanced Energy, Kyoto University, Uji 611-0011, Japan
5
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan

Although QED is considered to be established yet,
QED predicted unresolved nonlinear effects, such as
photon-photon interactions. However, because theircross sections are extremely small, the interactions
have not been well studied [1,2]. Recently, thescattering of virtual photon – virtual photon scatteringhas been measured for the first time [1]. One of thephoton- photon interactions is Delbrück scattering.
Delbrück scattering, in which a gamma-ray interactingwith a Coulomb field creates an electron-position pair,which subsequently annihilates to generate a gammaray whose energy is almost identical with the incident
gamma-ray, is one of important phenomena to study
nonlinear effects by QED and vacuum polarization.
However, there was a critical problem that one cannot
derive only the amplitude of Delbrück scattering by
the interference with other elastic scattering such as
nuclear Tomson scattering and Giant Dipole
Resonance.
Koga and Hayakawa [3] have presented that it ispossible to measure selectively the amplitude ofDelbrück scattering using linearly polarized gammaray beams. Furthermore, if one uses a linearlypolarized beam with energies lower than 1.022 MeV,
which is the threshold of the pair creation, it is possible
to measure only the virtual process of Delbrück
Scattering, namely vacuum polarization. For such a
purpose, we have developed a laser Compton
scattering (LCS) gamma-ray beam with a CO2 laser
having a wavelength of 10.6 μm at the UVSOR-III
synchrotron radiation facility, in which the energy ofthe electron beam stored in top-up mode isapproximately 750 MeV. We have demonstrated the 1MeV LCS gamma-ray beam generation using arandom polarization CO2 laser [4].
We newly installed a linearly polarized CW CO2
laser with power of up to 130 W in order to generatelinearly polarized LCS gamma-ray beam (see Fig. 1).
We measured the energy spectra of the generated LCS
gamma-ray beam using 3.5”  4” LaBr3(Ce)scintillation detector. Figure 2 shows the measured
energy spectra. The LCS gamma-ray intensity
increases with increasing laser power.

Fig. 1. Photo of the newly installed high power
linearly polarized CO2 laser.
5000
Counts per Channel

1

4000

114 W

3000
2000
1000
0
0

60 W
10 W
500

1000
1500
Energy [keV]

2000

Fig. 2. Measured energy spectra of the generated LCS
gamma-ray beam. The gamma-ray intensity increases
with increasing laser power.
[1] ATLAS Collaboration, Nature Physcs 13 (2017)852.
[2] T. Inada et al., Phys. Lett. B 732 (2014) 356 .
[3] J. K. Koga and T. Hayakawa, Phys. Rev. Lett. 118(2017) 204801.
[4] H. Zen et al., J. Phys.: Conf. Ser. 1067 (2018)
092003.

33
Ⅲ01- 3 -Ⅲ -1

Ⅲ -1. Accelerators and Instruments
BL1U
BL1U

Study on Isotope 3D Imaging Using NRF Absorption Method in
UVSOR-BL1U
H. Ohgaki1, H. Zen1, T. Kii1, K. Ali1, T. Hayakawa2, T. Shizuma2, H. Toyokawa3, Y. Taira3,
V. Iancu4, V. G. Turturica4, M. Fujimoto5 and M. Katoh5

1
SInstitute of Advanced Energy, Kyoto University, Kyoto 611-0011, Japan
Tokai Quantum Beam Science Center, National Institutes for Quantum and Radiologicl Science and Techonology,
Tokai 319-1106, Japan
3
National Institute of Advanced Industrial Science and Technology (AIST) Tsukuba Central 2-4,
Tsukuba 305-8568, Japan
4
Extreme Light Infrastructure - Nuclear Physics, s/ Horia Hulubei National Institute for R&D in Physics andNuclear Engineering, Bucharest-Magurele, Judet Ilfov, RO-077125, Romania
5
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan

2

Ⅲ -1

A Nuclear Resonance Fluorescence (NRF) method
is a powerful tool for investigation not only of thenuclear physics, but also of isotope imaging inside thespent nuclear fuel canisters and nuclear wastes. We
have been developing an isotope imaging technique by
using NRF [1]. The absorption can be measured bysample material and “witness target”[2].
A demonstration experiment of the NRF-CT
imaging by using LCS gamma-ray beam has been
carried out at the LCS gamma-ray beamline, BL1U
(Fig. 1), at UVSOR-III where 5.4 MeV LCS gammarays with a flux of 1×107 photons/s can be available [3].
In 2018, we upgraded the energy of LCS gamma-rays
up to 5.5 MeV and about 10 times higher flux byreplacing the IR fiber laser.
By using NRF absorption method a NRF-CT image
has been taken for a sample target consists ofaluminum, stainless steel, and lead rods (shown in Fig.
2 (a)). The NRF signals from the witness target(natural lead) were measured by a Ge detector. At thesame time, transmission gamma-rays have beenmeasured by a LaBr3(Ce) detector which gives adensity distribution of the sample target. The
segmented CT reconstruction method has beendeveloped and we obtained clear 208Pb distribution asshown in Fig. 2 (b) [4].
After the upgrade of the UVSOR-III BL1U beamline,
we have been trying to take a real isotope image byusing enriched targets, 206Pb and 208Pb. The experimenthas been performed and the isotope CT image
reconstruction is under processing. To obtain a highresolution image and 3D CT have also been planned.
[1] N. Kikuzawa et al., Appl. Phys. Express 2 (2009)
036502.
[2] H. Ohgaki et al., Proceedings of IPAC2016, Busan,
Korea, 2007-2010 (2016).
[3] H. Zen et al., Energy Procedia 89 (2016) 335-345.
[4] H. Zen et al., AIP Advanced 9 (2019) 35101.

Fig. 1. BL1U LCS gamma-ray beamline with the
setup for NRF-CT measurement.

Fig. 2. (a) Arrangement of the sample target.
(b) Result of NRF-CT measurement.

34
Ⅲ01- 4 -Ⅲ -1. Accelerators and Instruments
BL1U
BL1U

Study on Oxygen Vacancy in TiO2 Using Photon Induced Positron
Annihilation Spectroscopy at UVSOR-BL1U
H. Toyokawa1, S. Dohshi2, T. Ehiro2, K. Maeda2, Y. Taira1, T. Hirade3,
M. Fujimoto4 and M. Katoh4

National Institute of Advanced Industrial Science and Technology
Tsukuba Central 2-4, Tsukuba 305-8568, Japan
2
Osaka Research Institute of Industrial Science and Technology, Izumi 594-1157, Japan
3
Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan
4
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan1

Titanium dioxide (TiO2) is one of the mostimportant catalysts and catalyst supports for industrialuse. It is sometimes used under harsh chemical or
physical conditions, such as in water or chemical
vapors under high temperature and pressure. We havebeen interested in a mechanism of catalytic activity of
TiO2 to improve its performance.
Our recent studies showed formation of oxygen
vacancies and titanium ions (Ti3+) gave strong effecton the surface wettability and catalytic activity of TiO2
under irradiation of UV light or gamma-rays [1]. It isalso recently reported that very high oxidative
decomposition activity for organic molecules such as
toluene was observed by an excitation of valence
electrons with applying heat, instead of light orionizing radiation [2]. While these mechanisms are notunderstood in detail yet, we believe oxygen vacancy
plays an important role.
Our research proposal is to study the mechanism of
the catalytic activity of TiO2 under heat application, by
an observation of oxygen vacancy concentration as afunction of temperature of sample material. In thisstudy, a contactless and noninvasive material analysis
method, so called the photon induced positronannihilation spectroscopy method was applied [3]. The
method is based on a positron annihilation gamma-ray
spectroscopy, triggered by a high-energy photon beamincident on a sample material.
When photons of a few MeV or higher are incident
on a sample material, a part of them decays into
electron-positron pair (pair creation), and intense
monochromatic gamma-rays of 511 keV are emitted
following to the positron annihilation with theircounterpart electrons (positron annihilation). In thepresent research study, we measured an energy spreadof annihilation gamma-rays, which contains
information on the atomic vacancy concentration of
the sample material.
While the energy of the annihilation gamma-rays is
simply monochromatic, it slightly shifts as themomentum of the counterpart electrons with which thepositrons annihilate. It is called the doppler broadeningof the annihilation gamma-rays. When a momentum of
the counterpart electrons was large, the energy spreadof the annihilation gamma-rays is also large, and it issmall when the momentum was small. The energy

spread is usually small, typically on the order of keV,and it can be measured with high energy-resolution
gamma-ray spectrometer, such as high-purity
germanium detector (HPGe).
We have set up a gamma-ray spectroscopy systemat the laser-Compton scattering (LCS) beamline of
BL1U at UVSOR-III [4], and measured the energy
spectra of the annihilation gamma-rays as we changed
the sample temperature, from room temperature to 600
degree Celsius. The data acquisition was successful,and their analysis is being undergone. We also prepare
for the experiment of the positron lifetime
measurement in next fiscal year, to study themechanism in detail.

Fig. 1. Measurement system for doppler broadening
spectroscopy at LCS beamline at BL1U in UVSOR-III.

[1] S. Dohshi et al., Top Catal. 35 (2005) 327.
[2] H. Nishikawa, Appl. Surf. Sci. 225 (2009) 7468.
[3] H. Toyokawa et al., Proc. AccApp'07 (2007) 331.
[4] H. Zen et al., Energy Procedia 89 (2016) 335.

35
Ⅲ01- 5 -Ⅲ -1

Ⅲ -1. Accelerators and Instruments
BL2A
BL2A

Unprecedented Data of the Solar Corona Taken by a High-Speed X-ray
CMOS Camera aboard FOXSI-3 Sounding Rocket
N. Narukage1 and S. Ishikawa2

National Astronomical Observatory of Japan, Mitaka 181-8588, Japan
Institute for Space-Earth Environmental Research (ISEE), Nagoya University, Nagoya 464-8601, Japan
1

2

Ⅲ -1

The solar corona is full of dynamic phenomena.
They are accompanied by interesting physicalprocesses, namely, magnetic reconnection, particle
acceleration, shocks, waves, flows, evaporation,
heating, cooling, and so on. The understandings ofthese phenomena and processes have been progressing
step-by-step with the evolution of the observation
technology in EUV and X-rays from the space. But,
there are fundamental questions remain unanswered,or haven’t even addressed so far. Our scientificobjective is to understand underlying physics ofdynamic phenomena in the solar corona, coveringsome of the long-standing questions in solar physics
such as particle acceleration in flares and coronalheating. In order to achieve these science objectives,
we identify the imaging spectroscopy (theobservations with spatial, temporal and energy
resolutions) in the soft X-ray range (from ~0.5 keV to~10 keV) is a powerful approach for the detection andanalysis 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, we launched aNASA’s sounding rocket (FOXSI-3) on September 7th,2018 [2] and successfully obtained the unprecedented
data (see Fig. 1) [3] using a high speed X-ray camera
with a back-illuminated CMOS sensor [4].
The performances (especially, the photon counting
capability) of this CMOS sensor was evaluated at
UVSOR BL2A [5]. We deeply thank Mr. Kondo, Mr.
Nakamura and Dr. Tanaka for their kind help.
[1] N. Narukage et al., White paper of the “soft X-ray
imaging spectroscopy”, arXiv:1706.04536 (2017).
[2] Web Release:https://hinode.nao.ac.jp/en/news/topics/foxsi-3180907/[3] Web Release:https://hinode.nao.ac.jp/en/news/topics/foxsi-3-datarelease-en-20190115/[4] S. Ishikawa et al., Nucl. Instrum. Methods Phys.
Res. Sec. A 912 (2018) 191.
[5] N. Narukage and S. Ishikawa, UVSOR Activity
Report 45 (2017) 33.

Fig. 1. Focusing imaging spectroscopic data in soft X-rays obtained by the FOXSI-3 sounding rocket. Panel (a)shows real FOXSI data. Each white dot in these images is an individual X-ray photon. From these images, we cansimultaneously obtain information about the position, timing, and energy of each X-ray photon. Using thisinformation, we can construct a solar corona image (see Panel (b)). We can also investigate the temporal evolution
and spectrum of the X-ray photons, as shown in Panels (c) and (d), respectively.

36
Ⅲ01- 6 -Ⅲ -1. Accelerators and Instruments
BL4U
BL4U

Development of a Secondary Electron Detector for a Scanning Transmission
X-ray Microscope
T. Ohigashi1,2 and H. Yuzawa1

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
1

2

Analysis of interactions of X-ray with matters, suchas absorption, scattering, fluorescence, photoemission,phase transition, photo- and secondary electron etc.,brings unique information according to its mechanism.
Basically, a scanning transmission X-ray microscope(STXM) uses X-ray absorption to acquire integrated
information of a sample along its optical axis (i.e. bulk
information) and sometimes uses X-ray fluorescenceor photo- and secondary electron to obtain additional
information simultaneously. Detection of the electrons
is useful to analyze near surface information of thesample since escape depth of the electrons is limited toa few nm. Furthermore, the detection of the electrons
also enables to measure a thick sample which cannot
be penetrated by the X-rays. STXM beamline BL4U
can use low energy region from 50 to 770 eV [1] sothat the detection of the secondary electrons is moresuitable than that of X-ray fluorescence in regard totheir yields. Therefore, we have been developing an
optical system for STXM with using a channeltron to
detect the secondary electrons.
A schematic image of an optical system of STXM
with a channeltron (C4831, Photonis Inc.) is shown in
Fig. 1. Typically, the channeltron for STXM is placeddownstream of the sample in parallel with a detector
for a transmitted X-ray [2] because gap between anorder select aperture (OSA) and the sample is notenough to set the channeltron to detect the electrons
from top surface of the sample. Even though, in thisreport, the channeltron was placed upstream of thesample, set toward between the sample and OSA, toanalyze front-surface of the sample. A focusing
element, a Fresnel zone plate, with outermost zone
width of 45 nm and diameter of 240 µm was used for
longer focal length instead of higher spatial resolution.
Then, the gap between the OSA and the sample wasabout 1 mm at the X-ray energy of 400 eV.
An ultra thin section of blended polymer supported
by a copper grid was used as a test sample. The sample
was tilted about 30 towards the channeltron. 50 V for
input end and 2000 V for output end were applied to thechanneltron. Degree of vacuum was ~310-6 mbar. A
secondary electron image by the channeltron and an Xray transmission image were obtained simultaneously(shown in Fig. 2). Then, energy of the X-ray was 400
eV and dwell time per a pixel was 500 ms. From edge

profiles of the copper grid in each image, spatial
resolutions are almost similar. In the secondary electron
image in Fig. 2 (b), open space shown by a dashed circle,
where signals should be zero, produces some signals
more than the polymer. This result is under discussion.
Fresnel zone plate
X-ray

Photomultiplier
tube

Centralstopper
SampleOrder select aperture

Channeltron

Fig. 1. A schematic image of a optical system of
STXM with a channeltron.

(a)

(b)

Fig. 2. (a) An X-ray transmission and (b) a secondary
electron images of a thin section of blended polymer
on a copper grid. White color shows more signals.
Scale bars are 5 µm.
[1] See beamline section of this activity report[2] C. Hub, W. Wenzel, J. Raabe, H. Ade and R. H.
Fink, Rev. Sci. Instrum. 81 (2010) 033704.

37
Ⅲ01- 7 -Ⅲ -1

Ⅲ -1. Accelerators and Instruments
BL7B
BL7B

Pre-flight Verification of CLASP2 Throughput
D. Song1, R. Ishikawa1, R. Kano1, M. Yoshida2 and K. Shinoda1

National Astronomical Observatory of Japan, Mitaka 181-8588, Japan
Department of Astronomical Science, Graduate University for Advanced Studies (SOKENDAI),
Mitaka 181-8588, Japan
1

2

Ⅲ -1

We have developed a high precision (<0.1%) UV
spectro-polarimeter called Chromospheric LAyer
Spectro-Polarimeter (CLASP2), and it is in a final stepfor the launch whose expected date is on April 1st, 2019.
CLASP2 is a NASA sounding rocket experi- ment, whichaims to advance our knowledge of the magnetic fields inthe upper solar chromosphere by spectro-polarimetricobservations at the Mg II h & k lines (near 280 nm) andimaging observation with high cadence at the Lymanalpha line (121.6 nm) [1]. For this, the high throughput of
the instrument in both the UV lines is required.
To obtain the high throughput of CLASP2, we had
carried out a dual-band pass “cold mirror” coatingtargeting at both the lines to the primary mirror of thetelescope, and also performed the high reflectivity (R)mirror coating (Al+MgF2) to other mirrors. After coating,
we have frequently checked its coating performance at
UVSOR [2], and monitored their reflectivity by using thewitness samples (WSs) which are 1-inch flat mirrors
coated simultaneously with the flight mirrors.
On November, 2018, we moved our instrument fromJapan to USA for the final preparation of the launch. At
that time, we attached six WSs on our instrument tomonitor the contamination during the transportation andexperiment. We brought the monitored WSs back toJapan, and carried out the pre-flight verification of thehealthiness of the CLASP2 flight mirrors at the UVSOR
BL7B by using the WSs. In particular, we measured thereflectivity of each WS not only near 280 nm (G3 grating)but also at 121.6 nm (G2 grating). Finally, we compared
the results with those of previous UVSOR measurements
and derived the final throughput of CLASP2.
Figure 1(a) shows one of the results of our reflectivity
measurement of the primary mirror (M1) from the 115
nm to the 850 nm wavelengths. The measured reflectivity
is 50% at the 121.6 nm and 71% near the 280 nm
wavelengths, both of which meet the specification. The
average reflectivity in the visible light is about 5%. The
difference between this measurement and the previous
measurement is only about 1% near the 280 nm and about
3% at the 121.6 nm wavelengths. It indicates that thedual-band pass cold mirror coating performed on the M1still keeps sufficient performance even 15 months after
the coating.
We also confirmed that the coating performance ofother flight mirrors is well maintained as our required
specification. Figure 1(b) presents results of reflect- ivityof each mirror, and Table 1 represents the results in detail.
Finally, we calculated throughput of the spectropolarimeter and updated the radiometry of CLASP2
based on our measurements at the UVSOR. From thecalculation of radiometry, we confirmed that our
minimum required time for the observations of eachtarget is still less than the planned observing time.
In summary, we have measured the reflectivity of WSs
which were simultaneously coated with flight mirrors andaccompanied with the instrument during the integrationin Japan and shipment from Japan to USA through the
UVSOR experiment. From this experiment, we
confirmed: (1) There is no significant degradation of thecoating performance of all the flight mirrors. (2) The final
throughput of SP is satisfied for the solar observations werequired.
Recently, we moved our instrument of CLASP2 to thelaunch site "US White Sands Missile Range" in New
Mexico. It is ready for the launch.

Fig. 1. Measured reflectivity of witness samples of (a)the primary mirror (M1) and (b) other mirrors: M3 - Offaxis parabolic mirror (black solid line), M4 - Hyperbolic
Mirror (back dashed line), M5 - Folder mirror (black dotdashed line), Grating (black three dots-dashed line), Slitmirror (red solid line), Slit-jaw cold coating mirror (reddashed line), and M2 – Secondary mirror of telescope(red dot-dashed line). Red doted lines represent the
Lyman-alpha line and black doted lines show the Mg IIline near 280 nm wavelength.
Table 1. Reflectivity of CLASP2’s flight mirrors: Spec.:
specification, Prev.: previous UVSOR measurements, andU#38: pre-flight measurements (M1 & M2 are flightmirrors of telescope, From M3 to M5 and Grating are SP
mirrors, SM and SC represent a slit mirror and a slit-jaw
cold mirror). Note that, black color indicates the value ofreflectivity at 280 nm and red color represents the valuesof reflectivity at 121.6 nm
M1
Spec.
Prev.
U#38

>70%
>40%
72%
53%
71%
50%

M2/
M3

>80%
>80%
89%
84%
88%
80%

M4

M5

SM

SC

Grating

>80%

>80%

>75%

>35%

-

87%

87%

78%

36%

89%
(HJY)

88%

87%

76%

36%

84%

[1] N. Narukage et al., SPIE 9905 (2016) 99052U.
[2] D. Song et al., UVSOR Activity Report 2017 45(2018) 36.

38
Ⅲ01- 8 -Ⅲ -1. Accelerators and Instruments
BL7B
BL7B

The Composite Type Measurement System for VIS-VUVComplex Refractive Index
1

D. Imai 1, S. Takashima1, K. Fukui1, K. Yamamoto2, T. Saito3 and T. Horigome4

Department of Electrical and Electronics Engineering, University of Fukui, Fukui 910-8507, Japan2
Far-infrared region Development Research Center, University of Fukui, Fukui 910-8507, Japan3
Department of Environment and Energy, Tohoku Institute of Technology, Sendai 982-8577, Japan
4
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan

Since the ultraviolet (UV) - vacuum UV (VUV)
region generally has strong absorption, for example, thecorrect complex refractive index (CRI) of thephotodetector material is necessary, for example, for thedesign of the UV - VUV region photodetector. Based on
the instrument designed by Saito et al. [1], we havedeveloped a synchrotron radiation (SR) dedicatedvisible (VIS) - VUV spectroscopic ellipsometer (SE)which is installed at BL7B. Although this type of SE has
an advantage in obtaining not only optical constants ofthe sample, but also Stokes parameters of the incident
beam [2], but in principle the wavelength continuous
complex refractive spectrum can not be measured.
Furthermore, ellipsometry requires a layered model ofthe sample to calculate the CRI from the measured
ellipsometric parameters. Another way to obtain the
wavelength continuous CRI spectrum is the Kramers Kronig transformation method applied to thereflectance spectrum (KK method). In this method, it is
not difficult to measure the wavelength continuousreflectance spectrum and KK method does not require
the layered model, but it is not so easy to measure thereflectance spectrum quantitatively. In short, it can beseen that the SE method and KK method arecomplementary to each other. Then, we have beenreconstructing our VIS-VUV SE to the composite typemeasurement system for VIS - VUV CRI. In this report,
we will discuss the mechanical remodeling in our VIS VUV SE by the incorporating a reflectometer.
Specifically, in addition to the insertion of thereflectometer, the sample alignment mechanism wasredesigned that does not interfere with the reflectometerrotation.
Figure 1 shows the schematic layout of VIS - VUV
SE with the incorporated reflectometer. In order tocancel the wavelength sensitivity dependence of thephotodiode, both light source and reflected light fromthe sample must be measured with the same photodiode.
The 3D layout of the reflectometer considering theabove condition is shown in fig. 2a. All parts of thisreflectometer are equipped on one ICF203 flange. The
renewed sample position adjustment mechanism withthe sample holder is shown in fig. 2b. Precise rotationand translation adjustments of the sample can be madewith the rotary ball spline device (red color part). Figure.
2c represents the positional relationship in the mainchamber of our SE among the reflectometer, the samplealignment mechanism with the sample holder, and the βrotation mechanism. Figures 3a and 3b shows theexperimental results of the ellipsometric parameters andthe reflectivity under the same experimental conditions(without the incidence angle) after reconstruction,
respectively. Since sample is 1 μm AlN thin film,
interference is clearly observed at the lower photon
energy side of fig. 3b. We are currently working on theestablishment of analytical methods for deriving the
CRI from the measurement results of ellipsometory andreflection measurement.

Fig. 1. Schematic layout of VIS-VUV SE.

Fig. 2. 3D layouts of reflectometer (a), sample
mechanism (b), and their relationship (c).

Fig. 3. Experimental results. (a) ellipsometricparameters, (b) reflectance[1] T. Saito, M. Yuri and H. Onuki, Rev. Sci. Instrum.
66 (1995) 1570.
[2] F. Sawa et al., UVSOR Activity Report 2017 45(2018) 37.

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