BL1B

BL1B: A Dedicated THz Coherent Synchrotron Radiation Beamline
S. Kimura1, 2, E. Nakamura1, K. Imura1, M. Hosaka3, T. Takahashi4 and M. Katoh1, 2
1

2

UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585,
Japan
3Synchrotron Radiation Research Center, Nagoya University, Nagoya 463-8603, Japan
4Research Reactor Institute, Kyoto University, Kumatori, Osaka 590-0494, Japan

Infrared (IR) and terahertz (THz) spectroscopies
The 3D-MM, which is located 880 mm from thehave now become conventional methods for thecenter of the source, reflects the THz-CSR to themeasurement of vibration modes and low-energy
focal point (F0) on the outside of the bending-magnet
electronic structures. IR/THz synchrotron radiationchamber, as shown in Fig. 1 (1200 mm from M0).
(SR) is also used as a light source for spectroscopy andThe THz-CSR collected by the 3D-MM is intercepted
microscopy throughout the world. So far, manyby a plane mirror (M1) located in the bending-magnet
advanced types of spectroscopy have been developed
chamber and guided to the beamline. The focal pointsuch as IR imaging, pressure-dependent and(F1) is located on the outside of the bending-magnet
magnetic-field-dependent THz spectroscopy, and sochamber through a tapered z-cut quartz window (24on. However, to realize further advances in
mm in diameter and 5 mm thickness at the center).
spectroscopy, intense tunable light sources must be
After F1, the light is formed into a parallel beam by adeveloped. One candidate for an intense broadband
parabolic mirror (M1) and guided to the outside of theTHz source is coherent synchrotron radiation (CSR).
radiation shielding wall. The emitted THz-CSR andThen we planned to construct a dedicated beamline
normal THz-SR light are measured by afor THz coherent radiation at BL1B.
Martin-Puplett type Fourier transform interferometer
A top view of the THz beamline is shown in Fig. 1.
(FARIS-1, JASCO ltd.) installed. Reflection and
The emitted THz light is collected by atransmission measurements can be performed in thethree-dimensional magic-mirror (3D-MM, M0) of thebeamline.
same type as those already successfully installed at
BL43IR in SPring-8 [1] and BL6B in UVSOR-II [2].
[1] S. Kimura et al., Nucl. Instrum. & Meth. Phys.
The 3D-MM was installed in the bending-magnet
Res. A 467-468, (2001) 437.
chamber and is controlled by a 5-axis pulse motor[2] S. Kimura et al., Infrared Phys. Tech. 49 (2006)
147.
stage (x, z translation; Tx, Ty, Tz rotation). To extractthe emission at 34 degrees, the 3D-MM is located at
the short distance of 55 mm from the electron orbit.
The 3D-MM is made of aluminum and was fabricatedby an NC length milling machine at the Equipment
Development Center ofInstitute for Molecular
Science. The surface
roughness is less than
r1 Pm, which iscomparable
tothevisible wavelength but
much smaller than thewavelength of THz light.
Visible light is scatteredby the surface of the3D-MM, but THz light
can be focused.
To eliminate the heatload from the SR, weemployed a copper rod(6 mm in diameter) withFig. 1. Schematic top view of the beam extraction part of the THz-CSR beamline,
water cooling on theBL1B. The three-dimensional magic mirror (3D-MM, M0) and a plane mirror
emission plane because(M1) are located in the bending-magnet chamber. A parabolic mirror (M2) isthe power from the SR
installed to form a parallel beam. The straight section (BL1U) is used for coherent
is concentrated in theharmonic generation (CHG) in the VUV region.
emission plane.

39

BL3B

Present Status of a New VIS-VUV Photoluminescence Beamline BL3B
K. Fukui1, Y. Imoto1, M. Kitaura2, K. Nakagawa3, T. Ejima4, E. Nakamura5, N. Kondo5,M. Sakai5, M. Hasumoto5 and S. Kimura5
1Fac. Engi., Univ. Fukui, Fukui 910-8507, Japan
Fac. Sci., Yamagata Univ., Yamagata 990-8560, Japan
3Grad. Sch. Human Dev. Enviro., Kobe Univ., Kobe 657-8501, Japan
4IMRAM, Tohoku Univ., Sendai 980-8577, Japan
5
UVSOR facility, Institute for Molecular Science, Okazaki 444-8585, Japan
2The solid-state optical devices in ultraviolet (UV)region will bring dramatic improvements in not only
the telecommunication applications but also theilluminating, environmental and medical applications.
To achieve both technological and scientificinvestigations on such industrially importantmaterials, the light sources which cover a wide
photon energy region from visible (VIS) to vacuum
ultraviolet (VUV) are required. In order to study
photoluminescence (PL) of such materials in theVIS-VUV regions, a new bending-magnet beamline
BL3B with a 2.5 m normal incidence monochromator(NIM) has been constructed. For the PL
measurements in the wide energy region from VIS toVUV, two PL monochromators, one covers the VIS –UV regions and the other VUV region, are equipped.
The schematic layout of the BL3B which mainly
consists of a 2.5 m off-plane Eagle-type
monochromator is shown in Figs. 1(a) and 1(b). The
actual parameters of the mirrors and gratings arelisted in Table 1. The design concept has beenreported in the previous report [1]. Fig. 2 shows thethroughput using a Si photodiode (IRD AX-UV100),with S1 (entrance slit) = S2 (exit slit) = 100 Pm. Fig.
3 shows the beam spot profile at the sample position(Q in Figs. 1(a) and 1(b)) using the G2 grating (at ~12eV) with S1 = S2 = 100 Pm. The FWHM of this spot
is 0.25 mm (V) u 0.75 mm (H). The present status ofthe BL3B is as follows: photon energy coverage
range: 1.7 ~ 31 eV, E/'E > 12000 (G1, ~ 7 eV), 0.8 ~2.8 u 1010 photons/s (E/'E | 1000, G3), beam size (atQ) 0.25 mm (V) u 0.75 mm (H).

Table 1. Actual parameters of the mirrors andgratings.

G3
G2
G10.8

9Photon Number (x10 /s/100mA)

1.00.6

0.4

0.2

0.0

010203040

Photon Energy (eV)Fig. 2. Throughput from the off-plane Eagle typenormal incidence monochromator beamline on BL3B.
[1] R. Ikematsu, K. Fukui, T. Ejima, E. Nakamura, M.
Hasumoto and S. Kimura, UVSOR Activity Report38 (2011) 44.

㪌㪎㪅㪇㪱㩷㪸㫏㫀㫊㩷㩿㫄㫄㪀㪌㪍㪅㪌㪌㪍㪅㪇㪌㪌㪅㪌

㪌㪌㪅㪇㪐㪅㪌㪈㪇㪅㪇㪈㪇㪅㪌㪈㪈㪅㪇㪯㩷㪸㫏㫀㫊㩷㩿㫄㫄㪀

Fig. 1. Schematic layout of the BL3B: top view and side view.

40

Fig. 3. Beam spot profile at thesample position [the point Q inFigs. 1(a) and 1(b)].

BL3B

Estimation of High Energy Limit of the 2.5 m Normal Incidence
Monochromator Constructed at BL3B by Reflectivity Measurements
Y. Imoto1, S. Watanabe2, M. Kitaura3, K. Fukui1, K. Nakagawa4, T. Ejima5, E. Nakamura6,M. Sakai6, M. Hasumoto6 and S. Kimura6
1

Department of Electric and Electronics Engineering, University of Fukui, Fukui 910-8507, Japan
2
EcoTopia Science Institute, Nagoya University, Nagoya 464-8603, Japan3
Department of Physics, Faculty of Science, Yamagata University, Yamagata 990-8560, Japan
4
Graduate School of Human Development and Environment, Kobe University, Kobe 657-8501, Japan
5
IMRAM, Tohoku University, Sendai 980-8577, Japan
6
UVSOR facility, Institute for Molecular Science, Okazaki 444-8585, JapanThe 2.5-m normal incidence monochromator forthe photoluminescence spectroscopy was newly
constructed at the BL3B beamline. Thismonochromator was designed to cover the photon
energy range from 2 eV to 30 eV. It is necessary toevaluate whether the monochromator works as
expected or not. We have investigated the actual
high-energy limit of this monochromator through thereflectivity measurements of alkaline and alkali-earth
halides. It is well known that these materials exhibit
the sharp peaks in the vacuum ultraviolet regionspectra [1, 2]. These sharp peaks are due to theabsorption of the cation’s np core excitons (n = 2-5).
An observation of such core exciton peaks isexpected to be an indication to grasp the high-energy
limit that can be measured with a monochromator.
The single crystals of alkali and alkali-earth halides
were cleaved in air, and quickly placed in a vacuum.
The samples were attached at the cold finger of aliquid helium flow-type cryostat, and cooled down at
10 K. Both incident and reflected light were detectedusing a calibrated silicon photodiode sensor in themeasurement chamber. The incident and reflected
angles were fixed to be 15o for the direction
perpendicular to the surface of samples.
Figure 1 shows the reflectivity spectrum of a PbCl2
single crystal measured in the 5-30 eV range. There
are three peaks between 21-25 eV, and the feature ofthese peaks is seen at two places in the low energy
side. Since these values are about one half and one
third, this result shows that the higher-order light has
been observed, which was also observed with KCl
single crystal. Therefore, we need to note thehigher-order light, especially in the G1 and G2
grating regions.
Figure 2 shows the reflectivity spectrum of a MgF2
single crystal measured in the 50-60 eV range. One
can see two peaks split by 0.34 eV, which are of Mg
2p core excitons. From this result, the higher side
limit of the photon energy coverage is set to be atleast 55 eV at present.

Fig. 1. Reflection spectrum of a PbCl2 single crystal
measured at 10 K.

Fig. 2. Reflection spectrum of a MgF2 single crystal
measured at 10 K.
[1] G. W. Rubloff, Phys. Rev. B 5 (1972) 662.
[2] O. Aita et al., Phys. Rev. B 93 (1989) 10266.
Many thanks to Prof. M. Itoh (Shinshu Univ.) for
providing alkali and alkali-earth halides single
crystals.

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BL4U

Scanning Transmission X-ray Microscope Project at BL4U
T. Ohigashi1, T. Araki2, E. Nakamura1, N. Kondo1, E. Shigemasa1, N. Kosugi1 and M. Kato1
1

2

Institute for Molecular Science, Okazaki 444-8585, Japan
TOYOTA Central R&D Labs., Inc. Nagakute Aichi 480-1192, JapanThe soft x-ray spectroscopy gives plenty of
information about the electronic structure of materials
containing low Z elements and metals. By analyzing
the photoabsorption and photoionization cross section
near the soft X-ray absorption edges in detail, thechemical states of molecules and solids can bedetermined. Since a high brilliant soft X-ray source
and advanced focusing optical elements haveprogressed in recent years, several microscopic
methods have been combined with soft X-ray
spectroscopy, such as XAFS (X-ray Absorption FineStructure)
andXPS(X-rayphotoelectronspectroscopy), to obtain the 2-dimentional (2D)
mapping of the chemical states with high spatial
resolution. A scanning transmission X-ray
microscopy (STXM) combined with XAFS is one ofthe promising tools in the soft X-ray spectroscopy.
In the STXM system, the incident X-rays arefocused onto the sample by using a focusing opticalelement, such as a Fresnel zone plate (FZP), and theintensities of the transmitted X-rays through thesample are monitored by using a detector. By
scanning the sample, the 2D mappings are obtained.
The advantages of the STXM are the high penetrating
power and the non-destructive property of the X-rays.
That enables the STXM to apply to rather thick
and/or rather radiation-sensitive samples incomparison with the electron-based microscopy.
Therefore, even the 3-dimensional structural analysisof the sample can be performed by using the
tomographic technique without any destructiveprocess. The high penetrating power of the X-rays
also allows us to observe the sample in air or wet
condition (i.e. the vacuum is not necessary).
Especially, the soft X-ray energy region from 282 to540 eV, between the K edges of carbon and oxygen,is called the “water window” region. By using theX-rays in this energy region, carbon-based samples inwater, such as living cells, can be observed without
any staining. The STXM could be a unique technique
to observe a living biological sample like cells inwater with high resolution. Thanks to these features,
the STXM has advantages over the electron
microscopy and the optical one.
In 2011, the STXM beamline project has been

X-raySlit

Toroidalmirror

Plane mirrorand Grating

launched with the upgrade project from theUVSOR-II ring to the UVSOR-III ring. A schematic
image of the beamline is shown in Fig. 1. The soft
X-ray source of the BL4U is equipped with anin-vacuum undulator. This undulator has 26 magnetic
periods and the period length of 38 mm pitch and its
gap width can be set from 13 to 40 mm. The
monochromator is a Monk-Gillieson type with avaried line spacing plane grating. The energy range
from 100 to 700 eV is available. The theoreticalresolving power (E/'E) is 10000 at a maximum. In
practical use for spectromicroscopy, the resolving
power of 2000~4000 will be routinely utilized. The
fixed exit slit is used as a virtual source of thefocusing optics of the STXM (the third Bruker systemfollowing SLS and BESSY) and the FZP is placed at1334 mm downstream from the slit. Two focusing
FZPs of different pattern materials are in preparing.
One is made of gold supported by Si3N4 membrane of
100 nm thick, and the other is made of hydrogensilsesquioxane (HSQ) supported by Si3N4 membraneof 50 nm thick. Their calculated efficiencies of +1
order diffraction including the absorption by thesupport membranes are plotted against the photon
energy in Fig. 2. These plots show that better
efficiencies are available by using the HSQ FZP for
the carbon K-edge (around 285 eV) and the gold one
for the oxygen K-edge (around 540 eV), respectively.
Operation of the BL4U is due to start in the end of2012. Carbon nanotube will be used as a firstreference sample to estimate the characteristics of thebeamline; spectral resolution, spatial resolution, andpolarization of the monochromatized radiation.
HSQ patternGold patternFig. 2. Calculated efficiencies of the Fresnel zone
plates of gold pattern and HSQ pattern.

CylindricalmirrorFixedexit slit

STXMFig. 1. Schematic imageof the optical system ofBL4U

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BL7B

Measurement of Transmissivity and Ghost Image Created by Ly-Alpha
Filters for CLASP Slit-Jaw Unit
M. Kubo1, Y. Katsukawa1, N. Narukage2, R. Kano1, T. Bando1, T. Kobiki1, R. Ishikawa1 andS. Tsuneta1
12

National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo 181-8588, Japan
Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku,Sagamihara, Kanagawa 252-5210, Japan A sounding  rocket program called theChromospheric Lyman-Alpha Spectro-Polarimeter(CLASP) will observe the upper solar chromospherein Ly-alpha (121.567 nm), aiming to detect the linearpolarization signal produced by scattering processes
and the Hanle effect for the first time [1,2]. The solar
image is focused at a slit by telescope mirrors, and thespectropolarimeter that measures the linear
polarization with high accuracy of 0.1% order islocated after the slit [3]. The solar image outside theslit is reflected to the slit-jaw unit and is monitored
during flight. It is used to confirm the instrument
pointing during flight and to obtain Ly-alpha context
images for the interpretation of the data obtained by
the spectropolarimeter. The images are also needed
for co-alignment with other observations.
The slit-jaw unit consists of a fold mirror, amatched pair of off-axis parabolic mirrors, a pair of
Ly-alpha narrow band filters, and a CCD detector.
The Ly-alpha filter is the key to good quality
Ly-alpha images. The prime candidate of theLy-alpha filter is a 122-XN-1D developed by theActon Optics & Coatings.
First of all, we have to know the transmissivity of
the 122-XN-1D filter and its visible light rejection
performance. Figure 1 shows the transmissivity of the
122-XN-1D filter as measured with the synchrotron
radiation at the UVSOR BL7B. The transmission
profile from 115nm to 200nm is consistent with thatprovided by the Acton Optics & Coatings, and thetransmissivity is 7% in the wavelength of Ly-alpha(121.567nm). We find the transmissivity for thevisible light is 0.01%. It is highest visible lightrejection performance in the three types of 122nm
narrowband filters developed by the Acton Optics &Coatings. From this measurements, we conclude thattwo 122-XN-1D filters are necessary for the slit-jaw
unit to have the visible light contamination less than
1% in the Ly-alpha image.
Another issue on the Ly-alpha filter is a ghost
image created by the filters. The ghost images are
created by the reflection on the back and front
surfaces of a filter and by the reflection between twofilters. We take images of a main beam and ghost
beams by using CCD camera. We plan to use the two
Ly-alpha filters at the angle of incidence (AOI) of 0
degree in the slit-jaw unit. We have confirmed neither
unexpected ghost image nor strange pattern createdby the two filters at the AOI of 0 degree. Furthermore,

43

we take images at some AOIs of the two filters inorder to obtain the intensity ratios of the ghost beams
to the main beam (Fig. 2), although it is a different
configuration with the filters in the slit-jaw unit. The
intensity ratio is less than 4% in every case, which isconsistent with the expected value in ourinvestigation of ghost images.

Fig. 1. Transmissivity of the 122-XN-1D filter.
2nd ghost
Main beam

1st ghostFig. 2. Main beam and ghost beams created by two
Ly-alpha filters at the AOI of 10 degree.
[1] R. Ishikawa et al., ASP Conference Series, 287(2011) 437.
[2] N. Narukage et al., SPIE, 8148 (2011) 81480H.
[3] H. Watanabe et al., SPIE, 8148 (2011) 81480T.

BL7B

Verifications of CLASP Polarimeter at an Oblique Incidence
R. Ishikawa1, M. Kubo1, D. Song2, N. Narukage3, T. Bando1, R. Kano1, T. Kobiki1,S. Tsuneta1 and H. Watanabe41National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo 181-8588, Japan
Department of Physics and Astronomy, Seoul National University, Gwanak-gu, Seoul 151-742, Korea
3
Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku,Sagamihara, Kanagawa 252-5210, Japan
4
Kwasan and Hida observatories, Kyoto University, Yamashina-ku, Kyoto 607-8417, Japan2

A team consisting of Japan, USA, Spain, France,and Norway is developing a high-throughput
Chromospheric Lyman-Alpha Spectro-Polarimeter(CLASP), which is proposed to fly with a NASAsounding rocket [1, 2]. CLASP will explore themagnetic fields of the upper chromosphere andtransition region via the Hanle effect of the Ly-alphaline (121.567 nm) for the first time. This experimentrequires specrtopolarimetric observations with highpolarimetric sensitivity (<0.1%) and wavelength
resolution of 0.01 nm.
CLASP polarimeter consists of a rotating MgF2
half-waveplate and MgF2 polarization analyzers atBrewster’s angle [3]. The linear polarization in theLy-alpha line is measured as the intensity modulationby the rotation of the waveplate. The CLASP
polarimeter is located in the converging beam with acone angle of 3-4 degree. Due to the oblique
incidence, the retardation angle (G) of thehalf-waveplate slightly deviates from 180 degree. As
to polarization analyzer, the purity of s-polarization isreduced and the direction of s-polarization slightlyrotates from that for a normal incidence. Theseeffects will appear on the modulation patterns.
We developed a prototype of the CLASPpolarimeter in 2010 [4] (Fig. 1). In this time weverified its response to an oblique incidence at theUVSOR BL7B. Using a MgF2 plate mounted at
Brewster’s angle, we created a source beam which ishighly linearly polarized in the horizontal direction,and the output signal was measured with a silicon
photodiode or CCD camera. At a normal incidence,with the waveplate of G=180 degree and thepolarization analyzer at the Brewster’s angle, thesinusoidal modulation must be observed as shown inFig.2 (a). The minimum value in the modulation at a
normal incidence is ~0 (comparable to the noiselevel) as expected [Fig. 2 (b)]. However, when werotate the whole polarimeter by 3 degree horizontally,
the minimum value becomes non-zero. This is due tothe incident angle into the analyzer different fromBrewster’s angle and non-180 degree retardation
angle of the waveplate. When we tilt the elevation
angle of polarization analyzer by 6 degree (bluearrow in Fig. 1) without rotating the wholepolarimeter, the phase is shifted by 3.7 degree fromthe normal incidence case [Fig. 2 (d)]. This is causedby the change of direction of s-polarization due to theoblique incidence to the polarizer.
Based on this experiment, we investigate thegreater detail of the effect of an oblique incidence on
the polarimetric observation with <0.1% accuracy,and refine the final design of the CLASP polarimeter.

Fig. 1. Prototype of CLASP polarimeter.

Fig. 2. (a) Ideal modulation in our experiment withnormal incidence. Observed modulations around 0degree at normal (b) and oblique (c, d) incidences.
X-axis represents a rotation angle of the waveplate.
[1] R. Ishikawa et al., ASP Conference Series, 287(2011) 437.
[2] N. Narukage et al., SPIE, 8148 (2011) 81480H.
[3] H. Watanabe et al., SPIE, 8148 (2011) 81480T.
[4] H. Watanabe et al., UVSOR Activity Report 38(2010) 49.

44