Ⅲ-1

Accelerators andInstrumentsⅢ -1. Accelerators and Instruments
BL1U
BL1U

Reconstruction of Free-Electron-Laser Optical Resonator at BL1U
H. Zen1, J. Yamazaki2, M. Fujimoto2, 3, M. Hosaka4, K. Hayashi2, M. Katoh2, 3 and H. Ohgaki1
Institute of Advanced Energy, Kyoto University, Uji 611-0011, JapanUVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan3
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585,
Japan
4
Nagoya University Synchrotron radiation Research center, Nagoya 464-8603, Japan1

2

An electron storage-ring-driven Free Electron Laser(FEL) had been developed at the straight section #5, of
the UVSOR using an optical klystron and FEL opticalresonator until 2009 [1]. The straight section #5 hadbeen also used for developing new coherent lightsources, such as the coherent synchrotron radiation,
the coherent harmonic generation by combining thehigh energy electron beam circulating in the storage
ring and the high-power femtosecond laser. In 2010,
dedicated undulators with an electromagnet-based
bunching section were installed in the straight section#1 of the UVSOR. Then the above activities have been
moved from straight section #5 to #1.
In this work, we tried to reconstruct the FEL opticalresonator at the straight section #1 and BL1U to restart
the FEL which will be used for the generation of highintensity gamma-rays as same as the HIγS in Duke
University [2].
The new layout of the FEL optical resonator mirrors(M1 and M2) and the optical klystron at the straightsection #1 is depicted in Fig. 1. The optical klystronhas been already installed in 2012. In this work, theoptical resonator mirrors were installed in thebeamline and some commissioning experiments of the
optical resonator were carried out.
The photographs of the vacuum chamber of the
optical resonator mirrors are shown in Fig. 2. The
vacuum chambers are supported by large gimbal
mounts equipped with a motorized actuator to control
the angle of mirrors. The resonator mirrors with thediameter of 1 inch are installed in the vacuum chamber.
The downstream side gimbal mount is placed on thelinear stage which enables us to change the total cavity
length.
The commissioning experiment was performed at

the wavelength of 540 nm. As a result, we could store
the undulator radiation lights inside the opticalresonator and observed strong lights from theresonator mirror as shown in Fig. 3. This indicates thatthe optical cavity mirrors has good alignment in thetransverse direction. In the next machine time, thelength of the optical resonator will be optimized toachieve the lasing of UVSOR-FEL with this new
configuration.

Fig. 2. Photograph of the vacuum chamber for FEL
optical resonator mirrors.

Fig. 3. Photograph of the strong lights from theoptical resonator.
[1] H. Zen et al., Proc. of FEL2009 (2009) 576.
[2] http://www.tunl.duke.edu/web.tunl.2011a.higs.php

Fig. 1. Layout of FEL optical resonator mirrors (M1 and M2) and the optical klystron at the straight section #1 of
UVSOR.

31 1 Ⅲ01-

Ⅲ -1

Ⅲ -1. Accelerators and Instruments
BL1U
BL1U

Observation of XUV Vortex Beam from a Helical Undulator
T. Kaneyasu1, Y. Hikosaka2, M. Fujimoto3, 4, H. Iwayama3, 4, M. Hosaka5, E. Shigemasa3, 4 and
M. Katoh3, 4
SAGA Light Source, Tosu 841-0005, Japan
Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama 930-0194, Japan
3
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
4
The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
5
Synchrotron Radiation Research Center, Nagoya University, Nagoya 464-8603, Japan
1

2

Ⅲ -1
An optical vortex beam carries orbital angularmomentum (OAM), as well as spin angularmomentum associated with its circular polarization.
Recently it has been reported that the spiral motion ofa relativistic electron naturally leads to the emission ofphotons carrying OAM [1]. A typical example of thevortex radiation is found in the harmonic radiation ofa helical undulator in synchrotron light sources [2, 3].
Since the helical undulators are widely used in modern
synchrotron light sources, the optical vortex beam
generated as harmonic radiation may open up newopportunities in synchrotron radiation researches.
Here we report on the observation of the extreme
ultraviolet (XUV) vortex beam at 60 nm wavelength,
produced as the second harmonic radiation from ahelical undulator [4].
The experiment was carried out at the BL1U. To
characterize experimentally the optical vortex beam,
we observed an interference pattern between thephoton beams from two helical undulators. The
reference beam without OAM was produced as thefundamental radiation from the upstream undulator,
while the optical vortex beam was produced as thesecond-harmonic radiation from the downstream
undulator. The radiation wavelengths were set to 60
and 120 nm for the fundamental radiation from the
upstream and downstream undulators, respectively.
The spatial distribution of the photon beam wasmeasured by scanning a pinhole.
Figure 1(a) compares the interference patterns
measured for the left and right circular polarization
modes. The direction of the spiral pattern changes withthe helicity, as predicted in theoretical studies. The
dotted curves in Fig. 1(b) show the calculated
interference patterns, which agree with theexperimental results. Thus, it is reasonable to conclude
that optical vortex beams carrying an OAM of lħ(l=±1) per photon are produced in the XUV region. In
the present experiment, the electron beam emittance is17.5 nm-radian, which is about four times larger than
the 4.8 nm-radian corresponding to the diffractionlimited emittance at 60-nm wavelength Consequently,
the measured spiral patterns are blurred, owing to therelatively large electron beam emittance, whereas anindividual electron emits an optical vortex with aphase singularity and zero-intensity minimum. To
reveal the overall features of the interference patternsmeared by the finite emittance, we performed asimulation using the SRW code [5] as in Fig. 1(c). It
can be clearly seen that the simulation reproduces theexperiments, which confirms the reliability of themeasurement.

Fig. 1. Interference patterns at 60-nm wavelength
produced by interfering the optical vortex beam withthe reference beam without OAM. Left column: left
circular polarization. Right column: right circularpolarization. (a) Measurement results. (b) Same as (a)with the dotted curves representing the constructive
interference patterns predicted by the theoreticalmodel. (c) Simulation results by SRW code.
[1] M. Katoh et al., Sci. Rep. 7 (2017) 6130.
[2] S. Sasaki and I. McNulty, Phys. Rev. Lett. 100(2008) 124801.
[3] J. Bahrdt et al., Phys. Rev. Lett. 111 (2013) 034801.
[4] T. Kaneyasu et al., J. Synchrotron Rad. 24 (2017)934.
[5] O. Chubar et al., Nucl. Instrum. Meth. A 435(1999) 495.

32 2 Ⅲ01-

Ⅲ -1. Accelerators and Instruments
BL2A
BL2A

Evaluation of a Flight High-Speed Back-Illuminated CMOS Sensor in a
Soft X-Ray Range for FOXSI-3 Sounding Rocket Project
N. Narukage1 and S. Ishikawa2

1
National Astronomical Observatory of Japan, Mitaka 181-8588, Japan
Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara 252-5210,
Japan

2

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 1,000 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.
As the first imaging spectroscopic observation of
the sun in soft X-ray range, we plan to launch theNASA’s sounding rocket (FOXSI-3) in the summer of
2018.
In this time, we evaluated quantum efficiency (QE)of a flight back-illuminated high-speed CMOS sensor
at UVSOR BL2A (see Fig. 1). The sensor was driven
with a flight camera electronics board [2]. As areference sensor, we used the photodiode AXUV100G.
The preliminary result of the measured QE is shown in

Fig. 2. The measured QE of the flight sensor is within
the expected range that is calculated with the material
and thickness of the sensor. Based on this QE
measurement, we will finalize the thickness of theattenuation filter to adjust the incident X-ray flux into
the sensor suitably for the photon counting.

Fig. 1. Setting of CMOS sensor evaluation with aflight camera system. Left: CMOS sensor andphotodiode deployed in a vacuum chamber. Right:
Flight camera electronics board (green board in thispicture).

Fig. 2. Preliminary result of the measured quantum
efficiency (QE) of the flight CMOS sensor. The solidand dotted lines show the measured and expected QE,
respectively.
[1] N. Narukage et al., White paper of the “soft X-ray
imaging spectroscopy”, arXiv:1706.04536 (2017).
[2] S. Ishikawa et al., arXiv:1711.04372 (2017).

33 3 Ⅲ01-

Ⅲ -1

Ⅲ -1. Accelerators and Instruments
BL4U
BL4U

Development of a Cryo-Cooling System for Scanning Transmission X-ray
Microscopy
T. Ohigashi1, 2, F. Kaneko3, Y. Inagaki1, T. Yano1, H. Kishimoto3 and N. Kosugi1, 2

2

Ⅲ -1

1
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
School of Physical Sciences, SOKENDAI (The Graduate University for Advanced Studies), Okazaki 444-8585,
Japan
3
Sumitomo Rubber Industries, Kobe, 651-0072, Japan

A scanning transmission X-ray Microscope(STXM) is a powerful tool to obtain 2-dimensional
chemical states with high spatial resolution. By using
the STXM in the soft X-ray region, core-levelabsorption edges of light elements, carbon, nitrogenand oxygen, are available for the measurement.
Generally speaking, the radiation damage by X-rays islower than that by electron beams [1]. This means thateven organic materials, such as polymers, carbon
nanotubes and biological specimens that are very
sensitive to radiations, can be targets of the STXM.
However, in spite of the lower radiation damage of Xrays, some samples show chemical or morphologicalchanges during the measurement. For example, rubber,
one of reasonable targets for the STXM analysis [2, 3],
is easily damaged by the irradiation of X-rays. It is
known that the cooling of rubber samples reduces
radiation effects [4]. In the present work, therefore, wehave developed a cryo-cooling system.
A Dewar vessel is placed on the STXM. Liquid
nitrogen in the vessel cool a sample mounting platethrough copper braids. A sample holder is equippedwith two sets of a heater and a temperature sensor. Oneof these combinations is for the temperature control ofsamples and the other one is for keeping thetemperature of stages constant. These heaters areoperated by PID controllers. Main issues of the cryocooling system for STXM are the vibration generated
by bubbling of liquid nitrogen and the thermal stability.
In the present work, by optimizing thermal insulationand stiffness of the copper braids, the vibration at the
sample is successfully reduced down to 50 nm (peakto valley). By using this system, the sample mounting
plate can be cooled down to -90C.
A thin specimen (thickness of 250 nm) ofvulcanized rubber was used as a sample. Aftermeasuring an energy stack at nitrogen K-edge bychanging dwell time as 1, 2 and 4 ms, the energy stackat carbon K-edge was measured to evaluate damages
on the sample. NEXAFS spectra around carbon Kedge at RT and at cryo contion of -85C and an STXM
image of a damaged sample are shown in Fig. 1. In Fig.
1(a) and 1(b), main peaks are 285.4 and 288.0 eV,corresponded to C=C * and C-H * transition
respectively. The damage by X-ray irradiation mainly
appears on 285.4 and 288.0 eV as decrease of intensity
and as broadening of peak width. Especially, the peaks

at 288.0 eV show apparent difference between RT andcryo conditions. In RT condition, peaks at 288.0 eV are
dull and low rather than those in cryo condition
although the lowest dose by the dwell time of 1 ms.
Furthermore, height of the peaks at 285.4 in RT arelower than those in cryo condition. These differences
show that using the cryo-cooling system is effective to
reduce the damage on the sample. Currently, criticaldose to analyze the vulcanized rubber andimprovement of cryo temperature are under discussion.

(a)Damaged
area
1 µm

(b)

Fig. 1. NEXAFS spectra of pristine and damaged
vulcanized rubber around carbon K-edge (a) at RT and(b) at -85C. An inset in (a) is an STXM image of thedamaged vulcanized rubber acquired at 285.4 eV.
[1] H. Ade et al., Science 258 (1992) 972.
[2] D. A. Winesett et al., Rubber. Chem. Technol. 76(2003) 803.
[3] D. A. Winesett et al., Rubber. Chem. Technol. 80(2007) 14.
[4] G. Schneider, Ultramicroscopy 75 (1998) 85.

34 4 Ⅲ01-

Ⅲ -1. Accelerators and Instruments
BL4U
BL4U

High Pressure STXM Cell
P. –A. Glans1, Y. S. Liu1, R. M. Qiao1, T. Ohigashi2, 3 and J. –H. Guo1

Advanced Light Source, Lawrence Berkeley Nat’l Lab. 1 Cyclotron Road, Berkeley, CA 94720, USA
2
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan3
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585,
Japan
1

Measurements of the electronic structure ofmaterials in vacuum or even at atmospheric pressure
are becoming more and more common. Some catalytic
reactions, however, occur at, or create, higher
pressures: gas evolution (such as water splitting),
some catalytic processes are more efficient at higher
pressures, some batteries operate at pressures higher
than 1 atm, High pressures are also necessary toinvestigate phase transitions of gasses.
A high-pressure cell for the STXM has been
designed and tested at the BL4U at UVSOR, see Fig.
1. The body of the cell is made out of PEEK for
maximum chemical compatibility. Windows similar towhat is usually used at the STXM but with a custom
window size were made at the Lawrence Berkeley Lab.
The window size was 75μm x 75μm, set in frames of
5 mm x 5 mm and 10 mm x 10 mm. The cell was tested
off-line and could reliably hold gauge pressures up to
10 bar. Liquid can flow through the cell through PEEK
tubing. Once the system is filled, a valve on the drain
end is closed and the system is pressurized by runningthe pump until required pressure has bee achieved.

Fig. 1. Partially assembled high-pressure cell. The
cell is mounted on the standard STXM sample holder.

The back window (5 mm x 5 mm frame) is visible
together with Teflon spacers and the outer o-ring. A
larger window (10 mm x 10 mm frame) will bemounted on top and the lid – visible to the right in thephoto – will finish the ‘sandwich.’ The large window
is rotated 45 degrees with respect to the smaller one.
The cell was loaded with water or CaCl2 solutions
with concentrations ranging from 0.5 M to 3.0 M. The
pressure was controlled with a syringe pump andmeasured by a pressure gauge. In the STXM chamber
we did not go past 2.0 bar gauge pressure for safety
reasons. Figure 2 shows example data of the Ca L2,3
edge XAS from 1.5 M solution of CaCl2 in water at 0
bar gauge pressure and 2.0 bar gauge pressure.
The cell performed very well and we could collectspectra at elevated pressures. However, the next
iteration needs a way to measure I0 and a solution tominimize the bulging of the windows. A future versionof the cell will also include electrodes to allow forelectrochemical reactions.

Fig. 2. STXM images of 1.5 M CaCl2 solution at a) 0
bar gauge pressure, and at b) 2.0 bar gauge pressure.
c) Cl L2,3 XAS extracted from the images.
Unfortunately, i) there was no access to an I0 channel
to normalize the spectra, and ii) the optical density was
too high at higher pressures due to bulging cells so the
XAS is saturated at 2.0 bar.

35 5 Ⅲ01-

Ⅲ -1

Ⅲ -1. Accelerators and Instruments
BL7B
BL7B

Performance Verification of the VUV Coating for the CLASP2 Flight
Mirrors
D. Song1, R. Ishikawa1, R. Kano1, K. Shinoda1 and M. Yoshida2

National Astronomical Observatory of Japan, Mitaka 181-8588, Japan
Department of Astronomical Science, Graduate University for Advanced Studies (SOKENDAI), Tokyo 1818585, Japan
1

2

Ⅲ -1

We are developing an ultraviolet spectropolarimeter (SP) for a sounding rocket experimentnamed Chromospheric LAyer Spectro-Polarimeter(CLASP2). The CLASP2 is re-flight project of the
Chromospheric Lyman-Alpha Spectro-Polarimeter(CLASP1), which successfully observed the Lymanalpha polarization in 2015 [1], but will observe thepolarization in 2019 with the different lines from the
CLASP1 after a small modification in the optics. It
mainly aims to achieve the high-sensitivity (< 0.1%)
spectro-polarimetric observations in the Mg II h & klines (near 280 nm) for deriving the magnetic
information in the upper chromosphere of the Sun andalso to get solar images in the Lyman-alpha line (121.6nm) with the high temporal resolution. Therefore, it
requires the high throughput not only near 280 nm but
also around 121.6 nm wavelengths.
In this fiscal year, we prepared all CLASP2 flightmirrors. On the primary mirror of the telescope (TL),a dual-band pass “cold mirror” coating targeting boththe 121.6 nm (R > 40%) and 280 nm (R > 70%) was
performed by Acton Optics. In addition, the highreflectivity mirror coating (Al+MgF2 coating) was
done by Acton Optics on the new fabricated SP mirrors(R > 80% near 280 nm for convex hyperbolic mirrors
and folder mirrors, and R > 75% near 121.6 nm for aslit mirror.
To evaluate their coating performance, we measured
the reflectivity of witness samples (WSs) for the p- ands-polarized beam (hereafter, Rp and Rs) at the UVSOR
BL7B. The WSs are 1-inch flat mirrors simultaneously
coated with the flight mirrors during the coatingprocesses [2]. For the primary mirror coating, WSs
were spread over the area corresponding to theeffective area of the primary mirror to check theuniformity of the reflectivity.
Figure 1 shows the reflectivity of the WSs for the
primary mirror in the wide wavelength ranges. The
measured reflectivity is larger than 55% near the 121.6
nm wavelength and also larger than 76% near the 280
nm wavelength. Meanwhile, the average reflectivity inthe visible light wavelength ranges is less than 5%,
which had been measured by the Acton Optics. This
indicates that the “cold mirror” coating performed on
the primary mirror not only has high reflectivity near
our required UV wavelengths, but also efficiently
eliminates unwanted lights such as visible light.
From Fig. 2, we can verify the performance of thehigh reflectivity coating at Angle of Incidence (AOI)

as required by our SP mirrors. Note that, more
information is given in Table 1.
Based on our measurements with WSs of the flightmirrors, we confirmed the following three: (1) The
coatings performed on the flight mirrors (TL and SP)
well satisfy our specifications. (2) The coating of the
primary mirror (diameter: 290 m) is sufficiently
uniform. (3) Finally, the computed throughput is about
1.8%, which is three times larger than the value of
CLASP1 instrument (0.6%).

Fig. 1. Measured reflectivity of 10 witness samples
for the primary mirror as a function of wavelengths.

Fig. 2. Measured reflectivity of witness samples for
the SP mirrors.
Table 1. Measured reflectivity of WSs for SP mirrors
AOI (º)Rp
Rs(Rp+Rs)/2
MirrorMHyperbolic
11-18
87% 87.5%
87.3%
MFolder
24-33
87%
88%
87.5%
MSlit
22-30
73%
81%
77%
[1] R. Kano et al., ApJL, 839 (2017), L10.
[2] N. Narukage et al., UVSOR Activity Report 40(2012) 46.

36 6 Ⅲ01-

Ⅲ -1. Accelerators and Instruments
BL7B
BL7B

Stokes Parameters Measurements of the BL7B by Using
VUV Ellipsometry (III)F. Sawa1, 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

1

Since it is difficult to construct vacuum ultraviolet
region (VUV) ellipsometers, there exists only one
beamline equipped with VUV spectroscopic
ellipsometer (SE) at BESSY [1] in the world to ourknowledge. Saito et al. proposed the other idea for
VUV SE, which is dedicated to the synchrotron
radiation (SR) and used an oblique incidence detector[2, 3]. Compared with the standard SE, this type of SE
has an advantage in obtaining not only opticalconstants of the sample, but also Stokes parameters(S1/S0, S2/S0, S3/S0) (SPs) of the incident beam. We
installed this type of SE at the BL7B of UVSOR. Since
these SPs must be invariant even if the sample changes,
we can use this characteristics as an indicator of thereliability of unknown sample experiment results.
Therefore, we have been continuing to improve thereproducibility by eliminating the causes to reducethem. On the other hand, we have not confirmed thecorrectness of the absolute value for these SPs. In thisreport, we have compared the results of our VUV SE
against the results obtained by using dichroic dye film
type polarizers in the visible region (300 ~ 500 nm) for
the SPs of BL7B output beam to further confirm thecorrectness of the absolute SPs based on our SE.
Figure 1 shows schematic layout of our VUV SE
with Au mirror as a standard sample. Measurement
system using the VIS polarizer is shown in Fig. 2. In
Fig. 2, since the polarizer set at the sample position
instead of a Au mirror is a transmission type, opticalconditions are the same between two methods. Figure
3 shows SPs of BL7B output beam as a function of
wavelength obtained by our VUV SE (solid circles)
and polarizers (open circles). It is noted that S3/S0 and
unpolarized components cannot be distinguished in
the experiment by using the polarizer. As expectedfrom both the characteristics of SR and the opticalconfiguration of the BL7B, the results of bothexperimental methods show that S1/S0 values are close
to 1 and both S2/S0 and S3/S0 have small values. The
agreements between the two methods for both S2/S0
and S1/S0 in all wavelength region validates our SE.
[1] W. Budde and R. Dittmann, PTB-Mitt. 83 (1973) 1.
[2] T. Saito, M. Yuri and H. Onuki, Rev. Sci. Instrum.
66 (1995) 1570.
[3] T. Saito, K. Ozaki, K. Fukui, H. Iwai, K.
Yamamoto, H. Miyake and K. Hiramatsu, Thin Solid
Films 571 (2014) 517.

Ⅲ -1

Fig. 1. Schematic layout of VUV SE.

Fig. 2. Schematic layout of Stokes parameters
measurement system using a polarizer.

Fig. 3. Stokes parameters of BL7B.

37 7 Ⅲ01-UVSOR User 1