Ⅲ-1

Accelerators andInstrumentsⅢ -1. Accelerators and Instruments

Light sources

Light sources

Measurement of Temporal Response of Transmission-type Spin-Polarized
Photocathodes （PCs） -II
1

N. Yamamoto1, K. Yamaguchi2, A. Mano2, M. Hosaka2, X. G. Jin1,
Y. Takashima2 and M. Katoh3, 2High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
2
Nagoya University, Nagoya 464-8601, Japan
3
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan

In order to study the temporal response directly andprecisely, A radio-frequency (rf) deflection cavity was
designed and constructed [1].
The measurement system consists of a pump laser
system, a 20-kV DC electron gun, a 2.6-GHz rf
deflection cavity [2] and a beam profiling system(shown in Fig. 1). A mode-locked Ti:Sapphire laser(COHERENT, MIRA) with 90.1 MHz pulse reputation
rate was used to illuminate the PC. A screen monitor witha thin fluorescent coating was located 0.6 m downstreamof the deflection cavity.
For synchronizing the electron bunch with the rf
phase of the deflection cavity, the rf signal was
passively generated from pump laser signals by using
a silicon photodetector (EOS, ET-2030A) and a band
pass filter. The obtained rf signal was converted to2612.9 MHz by using a 29-times frequency multiplier.
Finally, the rf signal passing through a phase shifter toadjust between the beam and rf phases was amplified
up to 50 W and was fed to the deflection cavity. The
laser pulse length convoluted with the timing jitter ofsynchronization system was measured by a streak
camera and was confirmed to around 0.6 ps in rootmean-square.
The temporal distribution of the electron beam
extracted from the transmission-type GaAs/GaAsP
strained-SL PC [3] was shown in Fig. 2, where the data
points with open circles and a solid line indicate theexperimental data and fitted curve with assumed theconvolution integral of the laser pulse length andtransverse beam size at the screen monitor and electron
retardation mechanisms with the decay constant τ inthe semiconductor. [4]. It is found that the intensity
increases exponentially at earlier time around the zeroreference time then decays with relative slow time
constants. The characteristic time of 90 and 98 % of
the pulse charge are contained, were evaluated to be
14.0 ± 0.2 ps and 27.0 ± 0.2 ps, respectively.
The decay constant of 4.6 ps ± 0.2 ps was derived
by the fitting procedure. This value could beunderstood by assuming the electron diffusion
constant of 7 cm2/s [5]. Then it is confirmed that theelectron emission process from the PC is mainly
dominated by the electron diffusion process in thesemiconductor.

Ⅲ -1

Fig. 1. Schematic view of the measurement systemand timing diagram.

Fig. 2. Measured temporal charge distribution and thefitted decay curve (solid line).
[1] T. Inagaki, UVSOR Activiy Report 42 (2014) 33.
[2] T. Niwa, master’s thesis, Nagoya University (2013).
[3] X. G. Jin, F. Ichihashi, A. Mano, et. al., JJAP 51(2012) 108004.
[4] N. Yamamoto et. al., Proc. of the 13th Annual
Meeting of PASJ (2016) WEPMY039.
[5] X. G. Jin et. al., Ultramicroscopy 130 (2013) 44.

33 1 Ⅲ01-

Ⅲ -1. Accelerators and Instruments
Light sources

Light sources

Angular Momentum Carried by Radiation from an Electron in Circular
MotionM. Katoh1, 2, M. Fujimoto1, 2, H. Kawaguchi3, K. Tsuchiya4, K. Ohmi4, T. Kaneyasu5,
Y. Taira6, M. Hosaka7, A. Mochihashi7 and Y. Takashima7
Institute for Molecular Science, Okazaki 444-8585, Japan
Sokendai (the Graduated University for Advanced Studies), Okazaki 444-8585, Japan3
Muroran Institute of Technology, Muroran 050-8585, Japan
4
High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
5
Saga Light Source, Tosu 841-0005 Japan
6
National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8568, Japan
7
Nagoya University, Nagoya 464-0814, Japan
1

2

Ⅲ -1

Optical vortex or twisted photons possess spiralphase structure and carry orbital angular momentum
other than spin angular momentum [1]. In these years,
such strange photons can be produced by using lasers
and special filters in laboratories and they are widely
investigated towards applications on nano-, imaging,and information/communication technologies [2]. On
the other hand, it was theoretically predicted that theharmonic components of helical undulator radiation
has vortex nature possessing helical phase structures[3]. Later, this was experimentally verified [4, 5].
However, the origin of this interesting phenomenon
has not been clearly discussed in these previous works.
Electrons in a helical undulator undergo a spiralmotion in its periodic magnetic field. This motion canbe decomposed to a drift motion with a relativistic
velocity along the undulator and a circular motion. In
this sense, the undulator radiation can be considered asradiation from an electron in circular motion but
Lorentz-transformed to the laboratory frame. Because
the phase of the electromagnetic field is Lorentzinvariant, the spiral phase structure seen in theundulator radiation should be found in the radiationfrom an electron in circular motion.
We have recently re-analyze the radiation from anelectron in circular motion [6]. This is one of the mostfundamental radiation processes as the basis of various
important processes, such as cyclotron radiation,synchrotron radiation or electron scattering of circularly
polarized light. This process has been addressed in many
scientific papers and textbooks. However, its vortex
nature has not been discussed explicitly in these
literatures.
We started from the retarded potential. For theradiation from an electron in circular motion, we
obtained the Fourier component of the vector potential
as follows;

where J1 is the Bessel function, l is the harmonic
number, k and ω the wave number and angularfrequency, r, θ and φ the position of the observer in a
spherical coordinate, β the electron velocity divided by
the light velocity, e the elementary charge. It should be
noted that the vector potential has a spiral phase term.
By using this result, we could obtain the ratio between
the angular momentum and the energy carried by theradiation field. The result can be expressed as follows;

dJ lz
dt
dU l
dt

kl
2
(1) (1)*(1) (1)*
 r d Al Al  Al Al
N p l4
 2

ck
N p lr 2 d Al(1) Al(1)*  Al(1) Al(1)*

4









where the denominator is the energy and the numerator
is the angular momentum carried away by the radiation
field for unit time. Np the number of photons and ħ the
reduced Plank constant. This equation indicates that nth harmonic photon carries well-defined energy andangular momentum which are given by ħω and ħl,
respectively. Since the angular momentum along theaxis of the drift motion is Lorentz invariant, the radiation
field in the laboratory frame also possesses the welldefined angular momentum.
[1] L. Allen, M. W. Beijersbergen, R. J. C. Spreeuw and
J. P. Woerdman, Phys. Rev. A. 45 (1992) 8185.
[2] G. Molina-Terriza, J. P. Torres and L.Torner, Nat. Phys.
3 (2007) 305.
[3] S. Sasaki and I. McNulty, Phys. Rev. Lett. 100 (2008)
124801.
[4] J. Bahrdt et al., Phys. Rev. Lett. 111 (2013) 034801.
[5] M. Hosaka et al., Proc. IPAC2016 (2016) 2036.
[6] M. Katoh et al., Phys. Rev. Lett. 118 (2017) 094801.

 J l (l sin  )  ei kr  lt  l  
1
Al (r , t )  e cot J l (l sin  )   o 2 rr  iJ ' (l sin  ) 
l

r

34 2 Ⅲ01-

Ⅲ -1. Accelerators and Instruments

OthersOthersDevelopment of Large Grain Size Nuclear Emulsion
for Cosmic-ray Radiography
A. Nishio1, M. Moto1, Y. Manabe1, K. Kuwabara1, K. Morishima1, 2 and M. Nakamura1, 3Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
Institute for Advanced Research, Nagoya University, Nagoya, 464-8602, Japan
3
Institute of Materials and Systems for Sustainability, Nagoya Universuty, Nagoya, 464-8602, Japan
1

2

Cosmic ray radiography is the a new nondestructive inspection technique of large-scaleconstructions with cosmic ray muon. Cosmic ray
muon has high penetrating power and it always comesfrom the whole sky. In the same way of taking a X-ray
photograph, we can obtain integrated density of
constructions which thickness are several tens toseveral hundreds. We had ever applied this techniqueto pyramids, nuclear reactors, volcanos, and so on [1].
In these observations, we used nuclear emulsion asa detector. Nuclear emulsion is a kind of photographic
film and has sensitivity for ionizing radiation. The film
record tracks of charged particle with angular accuracy
under several mrad. Nuclear emulsion is made bycoating emulsion gel on plastic base. In Nagoya
University, started a emulsion gel production machinein 2010. It was enable us to develop new-type
emulsion gel by ourself. Emulsion gel is mainly
consisted by silver bromide crystal and gelatin.
We developed a Large Crystal Nuclear Emulsion forthe purpose of improving sensitivity, contrast, andlong-term characteristics. We have succeeded in
producing nuclear emulsion with the diameter of silver
bromide crystals at 350, 450, 800 nm, in addition to
the conventional 200 nm one. Electron microscopic
image of the silver bromide crystal are shown in Fig.
1. Optimum gold-sulfur sensitization was performed
to each crystal size [2]. For the developing solution,
XAA developer (FUJIFILM Co., Ltd.) was used. pH of
the developing solution was optimally adjusted to eachcrystal size. Figure 2 shows the optical microscopic
image of minimum ionized particle tracks. Table 1
shows the evaluation results of sensitivity (Grain
Density) and noise (Fog Density). The volume
occupancy of silver bromide was 30%.
We succeeded in increasing the sensitivity withoutchanging the noise level compared to the conventional
200 nm one. Furthermore, as contrast improved as the
crystal size was larger, it is suitable for future low
magnification / wide field scanning.

Ⅲ -1

Fig. 1. Electron microscopic image of the conventional
200 nm silver bromide crystal and new-type 350, 450,
800 nm crystal (SEM image).

Fig. 2. Optical microscopic image of minimum ionizedparticle tracks. The larger the silver bromide crystals, thehigher the contrast.

Table 1. Sensitivity and noise of large crystal size
nuclear emulsion. Sensitivity is evaluated by Grain
Density (G.D) which is linear density of developed
crystals. Noise is evaluated by Fog Density which isvolume density of randomly developed crystals. G.Dof 800 nm crystals was shown with parenthesis due toreproducibility problem.
[1] K. Morishima et al., RADIATION DETECTORSAND THEIR USES (2012) 30.
[2] M. Moto et al., 2nd Fall meeting of Federation of
Imaging Societies (2015) 29.

35 3 Ⅲ01-

Ⅲ -1. Accelerators and Instruments
BL1U

BL1U

Design of NRF-CT Experimental Setup for 2D Isotope Imaging at BL1U
H. Zen1, H. Ohgaki1, Y. Taira2, T. Hayakawa3, T. Shizuma3, I. Daito4, J. Yamazaki5, T. Kii1,
H. Toyokawa2 and M. Katoh5, 6Institute of Advanced Energy, Kyoto University, Uji 611-0011, Japan
National, Institute of Advanced Industrial Science and Technology, Tsukuba 305-8560, Japan
3
National Institutes for Quantum and Radiological Science and Technology, Tokai 319-1195, Japan
4
Nippon Advanced Technology Co., Ltd., Amagasaki 661-0001, Japan
5
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
6
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
1

2

Ⅲ -1

Three-dimensional isotope imaging is an emerging
technology which has very wide applications in areas of
nuclear security, non-destructive inspection, nuclear
plant decommissioning and so on. A novel method
named as Nuclear Resonance Fluorescence Computer
Tomography (NRF-CT) which will enable us tomeasure the three-dimensional isotope image of ashielded target has been proposed [1-3]. Most nuclei canbe resonantly excited by the absorption of a gamma-ray.
The excited nucleus de-excites to the ground state by theemission of a gamma-ray with the same energy. Thissequential process is called NRF. Because each isotope
has characteristic NRF energy levels, the isotopes canbe identified by measuring NRF energies. The proposed
method in [1-3] utilizes the resonance attenuationinduced by photon- absorption in a sample target andthus available for imaging application directly. In thisstudy, we designed a setup for the first demonstration
experiment of the two-dimensional isotope imaging of
208
Pb by the NRF-CT method at BL1U.
At first, we designed a test sample target as shown in
Fig. 1. The test target consists of an 8-mm-diameter
natural lead rod and a 10-mm-diameter iron rod wrappedby a 30-mm-diameter aluminum cylinder and a 35-mmdiameter iron cylinder.
Next, the imaging measurement setup was designed
as shown in Fig. 2. The flux of the incident andtransmitted gamma-rays will be monitored by aplastic scintillation detector (PL) and a LaBr3(Ce)scintillation detector (LB), respectively. The NRF
gamma-rays from a witness target (WT) with a 208Pb
excitation energy of 5292 keV will be measured by
two high purity germanium detectors (HPGe). Whenthe same isotopes in the witness target (208Pb in thiscase) exist on the gamma-ray beam path between the
gamma-ray source and the witness target, the gammaray with the energy of 5292 keV is resonantly
attenuated by the photon-absorption. The amount of
the resonant attenuation can be evaluated from thevariation of the NRF yield measured by the HPGe
detectors and the transmittance of non-resonant
gamma-rays measured by the LaBr3(Ce) detector [1].
The sample target is placed on a three-axis movablestage which can change the horizontal position,
vertical position, and rotation angle. To obtain a CT
image, the amount of the resonant attenuation will bemeasured by changing the position and angle of thesample target.
By using the designed sample target and experimental
setup, a 2D image of the 208Pb contained in the lead rod
shielded by the iron cylinder and the aluminum cylinder
will be measured in forthcoming experiment.

Fig. 1. Schematic diagram of the designed sample
target.

Fig. 2. Designed setup of the NRF-CT 2D isotope
imaging experiment. PL: Plastic scintillation detector,
ST: Sample target, SB: Shielding block, HPGe: Highpurity germanium detector, WT: Witness target, AS:
Absorber, LB: LaBr3(Ce) scintillation detector.
[1] C. P. Barty et al., LLNL-CONF-515893 (2011).
[2] W. Bertozzi and R. J. Ledoux, US Patent 8180019
B2 (2012).
[3] I. Daito et al., Energy Procedia 89 (2016) 389.

36 4 Ⅲ01-

Ⅲ -1. Accelerators and Instruments

BL1U

BL1U

Observation of Longitudinal Coupled Bunch Instability in UVSOR Storage
Ring
A. Mochihashi1, J. Hasegawa2, M. Hosaka1, M. Fujimoto4, 5, Y. Takashima1, 2, K. Imao2,
K. Takahashi3 and M. Katoh4, 5Synchrotron Radiation Research Center, Nagoya University, Nagoya 464-0814, Japan
2
Graduate School of Engineering, Nagoya University, Nagoya 464-0814, Japan3
School of Engineering, Nagoya University, Nagoya 464-0814, Japan
4
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
5
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
1

In UVSOR electron storage ring, we have longitudinal
coupled bunch instability in multi-bunch operation. To
suppress the instability, we have used a 3rd harminic
cavity (HCV) whose resonant frequency is 270.3 MHz,and almost Landau-damped the harmful instability.
However, the source of the instability has not yet been
completely understood. Moreover, we now plan tofabricate a new HCV because of overage problem such as
vacuum failure. For the new HCV, we have started toinvestigate the source of the beam instability and estimate
systematically the Landau damping effect of HCV. As
one of the leading candidates of an impedance source forthe londitudinal coupled bunch instability, we havepointed out a higher order mode (HOM) in the HCV.
According to the 2-demensional electromegnetic
simulation by Superfish [1], R/Q value for TM010 modeis 149; on the other hand, the R/Q for TM020 mode (780
MHz) is 13 which is not negligible value.
To investigate this, we have observed the longitudinal
coupled bunch instability in multi-bunch operation(uniform filling). In the experiment, we have used
BL1U mirror port and observed a visible edge radiationfrom the bending magnet BM8 which is just upstreamof the undulator U1. To observe temporal beam
oscillation, we have used a dual time based streak
camera (Hamamatsu, C5680). In the experiment, wehave stored 300 mA beam and gradually decreased thebeam current by a beam scraper. Because of the Landau
damping of the passive HCV, the instability was
suppressed up to about 150 mA; however, below 150
mA the beam induced voltage in the HCV decreased andthe instability started. When the beam current was
decreased further, the instability ceased below the beam
current of 7.4 mA. Figure 1 shows the longitudinal
profile of the bunches by the streak camera at the beam
current of 300, 100 and 7.4 mA. In the experiment, theHCV was tuned moderately to suppress the instability inthe higher beam current, and the tuner position was
fixed. In the higher beam current, the Laudau damping
by the beam induced voltage in the HCV overcomes thegrowth of the longitudinal coupled bunch instability; thebalance turns over below 150 mA because the voltage inthe HCV decreases and the Laudau damping effectbecomes weak. In the weak beam current condition, theLaudau damping already becomes negligible but thegrowth rate of the instability also becomes small andcomparable to the longitudinal radiation damping rate.
We have estimated the growth rate of the longitudinal
coupled bunch instability due to the HOM of the HCVat the weak beam edge of 7.4 mA. In the calculation we
have applied LCR resonant cavity impedance model.
The Q factor and the shunt impedance value were
estimated by Superfish [1] calculation. The growth rateof the instability was estimated to be 64.3 [sec-1] at 7.4
mA; on the other hand, the longitudinal radiation
damping rate is 60.3 [sec-1] which is comparable to theinstability growth rate. From above estimation, it is
supposed that the longitudinal coupled bunch instability
at lower beam current condition is caused by the HOM
in the HCV; however, we are now considering a
possibility that the cause of the instability in higher
beam current condition is different from that in lower
beam current condition. To investigate this, we now plansystematic measurements for the characteristics of the
Laudau damping by the HCV. Based on thesemeasurements we plan to design and fabricate new
HCV which can overcome the longitudinal coupled
bunch instability in the wide range of the beam current
condition.

Fig. 1. Longitudinal coupled bunch instability in(upper)300 mA, (middle)100 mA and (lower)7.4 mA.
[1] K. Halbach and R. F. Holsinger, Particle Accelerators
7 (1976) 213.

37 5 Ⅲ01-

Ⅲ -1

Ⅲ -1. Accelerators and Instruments
BL2B

BL2B

Evaluation of Photon Counting Capability of a High-Speed BackIlluminated CMOS Sensor in a Soft X-ray Range of 0.8 keV – 4.5 keV
N. Narukage1 and S. Ishikawa2

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

2

Ⅲ -1

The solar corona is full of dynamic phenomena. They
are accompanied by interesting physical processes,
namely, magnetic reconnection, particle acceleration,
shocks, waves, flows, evaporation, heating, cooling, andso on. The understandings of these phenomena andprocesses have been progressing step-by-step with theevolution of the observation technology in EUV and Xrays from the space. But, there are fundamental questions
remain unanswered, or haven’t even addressed so far.
Our scientific objective is to understand underlying
physics of dynamic phenomena in the solar corona,covering some 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 (the observations withspatial, temporal and energy resolutions) in the soft X-ray
range (from ~0.5 keV to ~10 keV) is a powerful approachfor 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 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.
In this time, we evaluated the photon counting
performance of a back-illuminated high-speed CMOS
sensor, which is a key device of the high speed camera,in a soft X-ray range from 0.8 keV to 4.5 keV using
the BL-2A as shown in Fig. 1. On the basis of thisevaluation, we confirmed that this CMOS sensor has
the enough photon counting (2D imaging
spectroscopic) capability. So, we decided to use thissensor for the imaging spectroscopic observations of
the solar corona in the soft X-ray range. Thisobservation will be executed with the NASA’ssounding rocket (FOXSI-3 project) in the summer of
2018.
[1] T. Sakao, N. Narukage, M. Shimojo, K. Watanabe,
Y. Suematsu, S. Imada and S. Ishikawa, Proc. SPIE
8862 (2013) 12.

Fig. 1. Evaluation of the back-illuminated CMOS sensor. The CMOS was illuminated by the monochromatic Xrays (including higher-order diffraction lights). The right plots are the measured X-ray spectrum with the CMOS
sensor using photon counting methods. The bottom panel is an example of imaging spectroscopy for 830 eV Xray light. These results show that this CMOS has a capability of 2D imaging spectroscopy.

38 6 Ⅲ01-

Ⅲ -1. Accelerators and Instruments

BL4U

BL4U

Development of a 3-Dimensional Quantitative Observation Method in
Scanning X-ray Transmission Microscopy
T. Ohigashi1, Y. Inagaki1, A. Ito2, K. Shinohara2 and N. Kosugi1

UVSOR Synchrotron, Institute for Molecular Science, Okazaki 444-8585, Japan
2
School of Engineering, Tokai University, Hiratsuka 252-1292, Japan

1

Computed Tomography (CT) is a powerful methodby using X-rays to observe 3-dimensional internal
structure of a sample without any destructive process.
A reconstructed image of CT shows distributions ofliner absorption coefficients (LACs). In the soft X-ray
region, CT can be combined with X-ray microscopic
techniques regarding the relationship between
relatively short penetration depth of the soft X-rays
and high spatial resolution. Generally, full-fieldimaging X-ray microcopy is used for performing CT
because of its short measurement time. On the other
hand, scanning transmission X-ray microscopy(STXM) has an advantage in tuning of the X-ray
energy and is typically used to perform CT withlimited-angle rotation to reduce the measurement time
[1, 2] though this method loses quantitative values on
the reconstructed images. We have been developing
CT by using STXM with full-rotation (180 or 360)to get quantitative values and performing 3dimensional spectromicroscopy, though the working
distance, which is defined by distance between anorder select aperture and sample, is too short. We haveovercome this difficulty by developing a special
sample cell and adjusting an optical system of STXM
and performed a feasibility test of CT.
A sample cell for full-rotation CT developed (Fig.
1) is equipped with a small two-phase stepping motor(AM-1020, Faulhaber) and a spur gearhead (12/5,
Faulhaber) for the rotation of the sample. The samples
are set on a tip of a needle and the needle is fixed by aclamp. Motion of the sample is controlled by aprogrammable stepping driver (AD PM 00, Faulhaber)
via a feedthrough. Shape of the sample cell iscompatible with ALS-based STXM systems.
Polystyrene spheres of diameter of 5 µm as a test
sample were attached on a tip of a tungsten needle byglue. 50 STXM images (100100 pixels, 150 nm step)
were acquired with rotating the sample 3.6 each (180
rotation in total). Then, the X-ray energy of 280 eV,
below the C K-edge, was used and dwell time was 3
ms. The STXM images were aligned manually andsinograms were extracted. 2-dimensional crosssectional image was reconstructed by using homemade
convolution-backprojection algorithm with assuming
parallel beam projection. The reconstructed crosssectional image and 3-dimensional volume image areshown in Figs. 2(a) and (b), respectively. The 3dimensional volume image was obtained by stacking
the cross sectional images. A histogram of LACs of thereconstructed image is shown in Fig. 2(c). A main peak

at 0.173 µm-1 showspolystyrene and its FWHM
is 0.016 µm-1, 9.3% of thepeak LAC. That FWHM
degradesqualityofspectrum in spectroscopy so
it should be decreased. As
perspective, a Fresnel zone
plate with proper parametershould be used to obtain the
STXM images with goodquality and a number of the
STXM images will be
increased [3].

(a)

Ⅲ -1

Sample10 mm

Fig. 1. The sample
cell for CT

(b)

5 µm

Fig. 2. Tomographic reconstructed images ofpolystyrene spheres, (a) a cross sectional image, (b) 3dimensional volume image and (c) a histogram of
LACs of the cross sectional image[1] M. Obst, J. Wang and A. P. Hitchcock, Geobiol. 7(2009) 577.
[2] V. Berejnov, D. Susac, J. Stumper and A. P. Hitchcock,
ECS Transac. 50 (2012) 361.
[3] T. Ohigashi et al., accepted.

39 7 Ⅲ01-

Ⅲ -1. Accelerators and Instruments
BL5B

BL5B

Performance Evaluation of C/Al/C Metallic Thin Filters for Observation of
the Earth’s PlasmasphereⅢ -1

M. Kuwabara1, R. Hikida2, F. Suzuki2, K. Yoshioka1, 2 and I. Yoshikawa1

Department of Complexity Science and Engineering, Graduate School of Frontier Sciences, The University ofTokyo, Chiba 277-8561, Japan2
Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Tokyo
113-0033, Japan

A small telescope in extreme ultraviolet (EUV)
named PHOENIX (Plasmaspheric Helium ion
Observation by Enhanced New Imager in eXtreme
ultraviolet) will be boarded on the world’s smallest
spacecraft to explore the Earth-Moon Lagrange point.
By flying far from the Earth, PHOENIX can obtain
the entire image of the Earth’s plasmasphere. The
image from the equatorial plane helps us to understandthe dynamics of plasmas along the magnetic field. The
behavior of plasmas which is related to the solar
activity is the key for understanding physics andevolution of the Earth’s environment.
PHOENIX consists of an entrance mirror, metallic
thin filter, photon counting detector (microchannel
plates and resistive anode encoder), and electronics.
The optical system is optimized for the emission lineof He ion (wavelength of 30.4 nm), which is theimportant component of the Earth’s plasmasphere.
The column density of He ion along the field of viewof the instrument can be obtained because the intensityof the emission is proportional to it under theassumption that observational region is optically thin.
Therefore, the accuracies of the efficiencies of the
optical system of the instrument are critical for
estimation of the density and to achieve the scientificgoals of our mission.
The contaminations from other sources (He I 58.4
nm, O II 83.4 nm, H I 121.6 nm and etc.) should be
eliminated by the metallic thin filter. Therefore, thefilter materials which provide high transmittance at thetarget wavelength of 30.4 nm, while attenuating theunwanted emissions are required. For the reason noted
above, the C/Al/C (15 nm/165.2 nm/15 nm) filter waschosen for the PHOENIX mission [3].
In this experiment, we evaluated the transmittancesof two C/Al/C filters (No.1 and 2) at the wavelengthsof 30.4 nm and 58.4 nm by using the photo diode andthe microchannel plates. In order to achieve the pure30.4 nm and 58.4 nm lights, we installed an Al/Mg/Alfilter and an Sn filter at the entrance of the SOR beam
[1, 2, 4, 5].
The results are shown in Fig. 2 and the transmittancesof C/Al/C filters are 16% and 2% at the wavelengths of
30.4 nm and 58.4 nm, respectively.
For the next step, in addition to the 30.4 nm line and58.4 nm line, we plan to measure the transmittance at
83.4 nm line. O ion has an emission line at 83.4 nm
and is known as one of the main components in the

Earth’s plasmasphere.

Fig. 1. The setup of the measurements. C/Al/C filters
are installed on the central stage.
100

Transmittance1

Calculation
Measurement (No.1)
Measurement (No.2)

10-1

10-2
20

30

40

50

Wavelength [nm]6070Fig. 2. The transmittances of two C/Al/C filters. The
solid lines with dots show the results of the measurements
and the dashed line shows the calculation.
[1] K. Yoshioka et al., UVSOR Activity Report 35 (2007)
55.
[2] G. Ogawa et al., UVSOR Activity Report 36 (2008)
127.
[3] I. Yoshikawa et al., Earth Planets Space 60 (2008) 407.
[4] G. Murakami et al., UVSOR Activity Report 37(2009) 47.
[5] K. Sakai et al., UVSOR Activity Report 38 (2010) 45.

40 8 Ⅲ01-

Ⅲ -1. Accelerators and Instruments

BL6B

BL6B

Feedback Stabilization of Synchrotron Radiation Beam Path at BL6B
H. Zen1, T. Iizuka2, F. Teshima3, E. Nakamura3 and K. Tanaka3, 4

Institute of Advanced Energy, Kyoto University, Uji 611-0011, Japan2
Toyota Technological Institute, Nagoya 468-8511, Japan
3
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
4
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan1

Beamline 6B (BL6B) is an Infrared-THz beamline
which has confocal type micro-spectroscope station,reflection/transmission station, and IR microscope
imaging station. This beamline can provide
measurement techniques which are not available inconventional IR sources, utilizing the characteristics
of synchrotron radiation (SR) such as high brilliance,
polarization, or broad spectrum.
After the introduction of top-up operation of the
UVSOR storage ring, serious long term drift of SR
beam path in BL6B has been recognized. Our grouphas been investigated the cause of this long term driftof the SR beam path and found that the long-term driftof the M0 magic mirror angle is the main source of thedrift [1]. In this study, a feedback control system of M0
mirror angle was developed for stabilizing the SR
beam path in BL6B.
The schematic diagram of the feedback control
system of the M0 mirror angle is shown in Fig. 1. A
visible laser is injected into the vacuum chamber ofbending magnet and reflected by the M0 mirror. The
position of reflected laser light is monitored by a CCD
camera. The CCD camera image is processed in a PC
and the position of laser light is calculated from theimage. The angle variation of the M0 mirror can beevaluated from the measured position of the reflected
laser light. The angle of the M0 mirror can becontrolled by stepping motors to keep the readout
value of real-time angle monitor constant.
The feedback control system has been developed
and demonstration experiments were conducted. The
results are shown in Fig. 2 and Fig. 3. As shown in Fig.
2, the reflected laser light position, i.e. the M0 mirror
angle, can be stabilized by using the developed
feedback control during the 300-mA top-up operationof UVSOR. The small oscillation in Y direction wascaused by the backlash. And then the SR intensity
which is measured by an FT-IR spectrometer and an
MCT detector can be also stabilized by using the
feedback control as shown in Fig. 3.
After the successful demonstration, the developed
feedback control system is routinely operated tosupply stable SR beam for user experiments. This
feedback system has already significantly increased
the usability of BL6B beamline.

Ⅲ -1

Fig. 1. Schematic diagram of the feedback control
system of M0 mirror angle.

Fig. 2. The stability of the reflected laser position
with and without feedback control.

Fig. 3. The stability of SR intensity with and without
feedback control.
[1] T. Iizuka et al., UVSOR Activity Report 43 (2016) 38.

41 9 Ⅲ01-

Ⅲ -1. Accelerators and Instruments
BL7B

BL7B

Characterization of Optical Components for Polarization Spectroscopy
at the Large Helical Device
M. Goto1, 2, 3, N. Nimavat2, R. Makino1, 2, T. Oishi1, 2 and R. Kano3
1
National Institute for Fusion Science, Toki 509-5292, Japan
Department of Fusion Science, SOKENDAI, Toki 509-5292, Japan
3
National Astronomical Observatory of Japan, Mitaka 181-8588, Japan2line measurement. In this case, characterization ofthese optical components at 154.9 nm is required.
We have therefore made measurements of thepolarization-resolved reflectivity of the highreflectivity mirror and the polarization analyzer for154.9 nm at BL7B of UVSOR. An example of theresults is given in Fig. 1, which shows the dependenceof the reflectivity on the incident angle of the p- and spolarized lights at 154.9 nm for the polarization
analyzer. It is found that Brewster’s angle at thiswavelength is approximately 56° while the incident
angle in our measurement is 68°. The extinction ratio
at 68° is approximately 0.2, which is rather large when
it is recalled that linear polarizers available as acommercial product for visible light typically realize
an extinction ratio of 10-4. However, this relatively
large extinction ratio just reduces the sensitivity anddoes not deny the possibility of the polarization
detection. As for the high reflectivity mirror, the resultshows that their reflectivity is about 0.8 at 154.9 nm
and at the incident angle 23° used in our measurement.
We conclude from these results that a polarization
measurement at 154.9 nm with using the opticalcomponents for Lyman-α is possible although thecondition is not optimized. After detecting any sign ofpolarization in the CIV line at the LHD experiment, we
will consider preparing a high reflectivity mirror and apolarization analyzer optimized at 154.9 nm.
50

P Polarization
S Polarization

45
40
35

Reflection %Ⅲ -1

Excitation due to anisotropic collisions gives rise to
an inhomogeneous population distribution over themagnetic sublevels of ions in plasma, and emission
lines from those ions are generally polarized. When
Larmor motion of electrons in a plasma for the nuclear
fusion research of magnetic confinement are
selectively accelerated by means of microwave
injection, electrons could have a velocity distributionfunction (VDF) different in the parallel andperpendicular directions regarding the magnetic field.
Because the confinement characteristics of electrons
depend on their pitch angle with the magnetic field
direction, the anisotropic VDF of electrons is one of
the key issues which govern the performance ofplasma confinement. However, no reliable method has
been established for measuring the anisotropy in theelectron VDF to date.
We launched a project to earn information on theanisotropy in the electron VDF in the Large Helical
Device (LHD) at the National Institute for Fusion
Science through detection of polarization in emission
lines. The first observation target was the Lyman-α lineof neutral hydrogen, the dominant constituent of thenuclear fusion plasma. It was fortunate that we could
borrow optical components such as a 1/2-waveplate, ahigh reflectivity mirror, and a polarization analyzer
developed and elaborately characterized in CLASP(Chromospheric Lyman- Alpha SpectroPolarimeter)
project led by a group of National Astronomical
Observatory of Japan [1]. These optics wereincorporated into an existing spectrometer at LHD andactual measurements were started from February in
2017.
Some preliminary results have been alreadyobtained and the measurement itself looks successful.
However, there is a limitation in the Lyman-α line thatits emissions are localized at the outermost boundaryof the plasma and hence the results do not reflect thestate in the plasma core region that is more important
for the plasma confinement study. Therefore, in thenext stage of our project, we plan to use a CIV line
(1s22s 2S1/2 - 1s22p 2P1/2, 3/2) at 154.9 nm instead of
Lyman-α.
The best solution is naturally replacing all the
optical components with those optimized at 154.9 nm,
but that is unfortunately difficult with the presently
available budget for the project. Instead, we only
prepare a 1/2-waveplate for 154.9 nm and the highreflectivity mirror and the polarization analyzer
optimized for Lyman-α are tentatively used for the CIV

30
25
20
15
10
5
0

10

20

30

40

50

60

70

80

Theta (Degree)

Fig. 1. Incident angle dependence of the reflectivityof p- and s-polarized lights at 154.9 nm for thepolarization analyzer.
[1] UVSOR Activity Reports from 2009 to 2015.

4210 Ⅲ01-

Ⅲ -1. Accelerators and Instruments

BL7B

BL7B

Axis Measurement of Polarizer and Waveplate for CLASP2 Light Source
R. Ishikawa, K. Shinoda, H. Hara, R. Kano and N. Narukage
National Astronomical Observatory of Japan, Mitaka 181-8588, Japan

Ⅲ -1

Fig. 1. Experimental setup for the polarizer axis
measurement.

Fig. 2. Experimental setup for the waveplate axis
measurement.
1.0
0.8
Normalized intensity

The Chromospheric LAyer Spectro-Polarimeter 2(CLASP2) is the second flight of the CLASP(Chromospheric Lyman-Alpha Spectro-Polarimeter,
CLASP) sounding rocket experiment [1], which
succeeded in the first measurement of the linear
polarization signals in the hydrogen Lyman-α line
(121.6 nm) emitted from the Sun (e.g., [2]). In
CLASP2, we will measure all four Stokes parameters(i.e., intensity, two linear polarizations, and one
circular polarization) in the Mg II h & k lines around280 nm to obtain the magnetic field information in theupper solar chromosphere by refitting the existing
CLASP instrument. After the integration, thepolarization calibration of the instrument will be
performed with a well-calibrated light source byfeeding purely polarized light at least six different
polarization states (four for linear polarization and twofor circular polarization). The input light for the linear
polarization will be produced with a linear polarizer of
the transmissive type same as the sample that we tested
before [3]. The input light for the circular polarization
will be produced via a 1/4-waveplate installed
immediately after the polarizer. The polarizer andwaveplate are installed on the rotating motor androtated to emit the different polarization state. For the
precise polarization calibration, the direction of theprinciple axes of the polarizer and waveplate withrespect to the instrument has to be known precisely.
We measured a relative angle between the polarizer(or waveplate) and motor at the UVSOR BL7B in the
wavelength of 280 nm. Our goal is to measure theangle with the precision better than 0.1-degree. Figures
1 and 2 show the experimental setups for the polarizer
and waveplate, respectively. Using a high-reflective(Hi-R) polarizer, the linearly polarized 280 nm beamin the horizontal direction was directed on to the
waveplate/polarizer, and intensity modulation inducedby rotating the waveplate/polarizer was measured witha photodiode. One example of the intensity modulation
for the polarizer is shown in Fig. 3, where themeasurement was done every 5-degree step of rotating
motor. The principle axis of the analyzer can be
represented by the angle where the intensity becomesminimum (vertical dashed line in Fig. 3), and therelative angle with respect to the motor is estimated tobe 45.0-degree. We performed the same measurement
at several times, and found that the repeatability isquite good (the angle differences between themeasurements are less than 0.1-degree). The
waveplate axis was also measured with the sameaccuracy. Therefore, we conclude that the waveplate
and polarizer angles are successfully measured withthe accuracy less than our requirement.

0.6
0.4
0.2
0.0

0

100

200
Angle [deg]300

Fig. 3. Example of the intensity modulation for thepolarizer axis measurement. Triangles show themeasurement and solid line shows the result of fitting.
[1] N. Narukage et al., UVSOR Activity Report 43 (2016)31.
[2] R. Kano et al., ApJ, in press[3] R. Ishikawa et al., UVSOR Activity Report 43 (2016)40.

4311 Ⅲ01-

Ⅲ -1. Accelerators and Instruments
BL7B

BL7B

Stokes Parameters Measurements of the Beamline BL7B by Using VUVEllipsometry
Y. Fujii1, Y. Nasu1, K. Fukui1, K. Yamamoto2, T. Saito3 and T. Horigome4

55

100

200

300

 [nm]

100

G3 O53
G3 Py

90

G3 Qz

80

and[deg.]

G2 LiF

70

G2 B
G1 B

60
50
40
30
20

5

10

15

20

Photon energy [eV]

 [nm]

55

200

300

1.0

100

Fig. 1. Photon energy dependences of ellipsometricparameters of Au mirror.
600

Ellipsometers are known as powerful tools todetermine optical constants of materials. However,
because no solid materials can have transparency in thevacuum ultraviolet (VUV) region, an ellipsometer in
VUV region must consist of both reflection type polarizer
and analyzer in vacuum. Since these requirements makeit difficult to construct VUV ellipsometers, there exists
only one beamline (at BESSY) equipped with VUVspectroscopic ellipsometer (SE) [1] in the world to ourknowledge. Saito et al. proposed the other idea for VUVSE, which is dedicated to the synchrotron radiation (SR)and used an oblique incidence detector [2, 3]. Although
this type of SE requires much longer measuring time thanthat of the standard SE, this type of SE has an advantage
in obtaining not only optical constants of the sample
through the sample ellipsometric parameters, Ψ and Δ,
but also both detector Ψ and the Stokes parameters of theincident beam, which are completely independent of theellipsometric parameters of the sample. In this report, we
focus on the photon energy dependence of these sample
independent parameters at each sample measurement,
specifically an Au mirror (standard sample), two bulk
AlN substrates with different surface roughness.
Figure 1 shows ellipsometric angles Ψ andΔ of Au
mirror. Multiple measurement results are plotted andeach color corresponds to the BL7B conditions: thecombination of the grating (G1 - G3) and low energy
pass filter (blank, LiF2 crystal, Quartz plate, Pyrex
glass, 530nm-cut LPF). Figure 1 represents that the
reproducibility of this SE is within a few percentage
except for G2 region where there is a known problem
and it will be fixed in the near future. Figure 2 shows
the normalized S1 at Au mirror and two bulk AlN
substrates measurements as a function of the photon
energy. Although noted variation in S1 among samples
is found in G1 region, the very good fits are observedin G3 region. The variation in short wavelength (G1)region may be attributed to the scattering due to thesurface roughness of samples. In contrast, good fits on
S1 in G3 region independent of different samples prove
not only the high measurement accuracy for the Stokes
parameters, but also the reliability of the ellipsometricparameters of the sample.

0.8
0.6
0.4
0.2

S1/S0

Ⅲ -1

600

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 Facility, Institute for Molecular Science, Okazaki 444-8585, Japan1

G3 O53■ Au▲ c-AlN● m-AlN

0.0
-0.2

G3 Py

G3 Qz

G2 LiF

-0.4

G2 B

-0.6

G1 B

-0.8
-1.0

5

10

15

20

Photon Energy (eV)Fig. 2. Photon energy dependences of S1/S0 of multiple
samples.
[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.

4412 Ⅲ01-UVSOR User 3

UVSOR User 4