2
Instrumental
developments

41

BL3U

High-Resolution Soft X-ray Emission Studies
Using a Transmission-Grating Spectrometer
T. Hatsui1,2,3, T. Horigome1, H. Setoyama4, N. Kosugi1,2
1Institute for Molecular Science, Okazaki 444-8585 Japan
2
Graduate University for Advanced Studies, Okazaki 444-8585 Japan
3
PRESTO, JST, Kawaguchi, Saitama, 332-0012, Japan
4
Kyushu Synchrotron Light Research Center, Tosu, Saga 841-0005, Japangrating manufactured by NTT-ATN is made of siliconcarbide and has a free-standing structure with athickness of 800 nm. A detector together with thetransmission grating and the focus of the 0th orderdiffraction is positioned on a circle with a radius of
719.5 mm. The detector consists of a CCD (e2v CCD
42-40-A33) with a 2048 x 2048 pixel format with
13.5 x 13.5 mm and a preamplifier (Meisei Co.)
inside the vacuum chamber. After the installation of
the optical elements, the CCD chamber and the pipe
between the CCD detector and the TG are baked at
100 °C. The pressure in the chamber is in the 10-7 Pa
range.

Introduction
Soft x-ray emission studies in combination withsynchrotron radiation sources have been a subject ofincreasing and broad interest as it provides
information on the electronic structure on gas, liquidand solid materials. We have previously reported our
new design of a transmission-grating spectrometer(TGS) for high resolution soft X-ray emission studies[1]. The optical design incorporates the basic concept
for x-ray imaging and spectroscopy telescopes [2]into a compact and easy-to-use layout with higher
energy resolving power. One of the advantage of thepresent TGS is its high light gathering capability
without sacrificing the energy resolution, which isenabled by the introduction of the Wolter type-I
mirror and the transmission grating (TG).
The present TGS is installed in the soft x-ray
emission spectroscopy (XES) endstation of theundulator beamline BL3U of the UVSOR facility. In
this report we describe the apparatus and its
performance.

Optical Design and Apparatus
The present optical layout is a modification of the
Rowland torus mount with facet gratings [1]. The
design is adopted by Chandra x-ray satellite
observatory. In the ideal Rowland torus mount, thefacet TGs should be mounted onto Rowland torus
while keeping their normal to point the focus of theincoming x-rays. In the present spectrometer, thefacet TGs are positioned onto a single Si wafer. Suchsimplification may degradess optical properties.
However, we demonstrated by ray-tracing simulations
that the aberration in the geometry of the present
spectrometer is small enough to realize the energy
resolving power better than 5000 [2].
The TGS is pictured in Fig. 1. The soft x-rays
emitted from the sample are collected by a type I
Wolter mirror with a magnification of 10. The Wolter
mirror is a tube-shaped composite mirror withhyperboloidal and elliptical inner-surfaces, which are
27 and 33 mm long, respectively. The incident anlgeof 89 degree at the interconnection of the two mirror
surfaces yields an acceptance angle as large as 1.5 ×
10-3 sr. The slope error for each mirror estimated by
the imaging property was better than 2.0 mrad rms [3].
The collected soft x-rays with a focus of 1500 mm
downstream of the interconnection of the two mirror
surfaces are dispersed by a transmission grating witha groove density of 6250 lines/mm. The transmission

Fig. 1 Schematic layout of the transmission-grating
spectrometer at the XES endstation of the undulator
beamline BL3U.
The spectrometer is installed at the XES endstationof the undulator beamline BL3U. Schematic layout of
the XES endstation of the undulator beamline BL3U
is illustrated in Fig. 2 [4]. A soft x-ray emission
spectrometer generally requires small beam size at the
sample position, because a smaller opening of thespectrometer entrance slit is needed to achieve higher
energy resolution. Beamline BL3U is designed togive small beam size of order of 10 x 40 m2 byplacing sample 23 mm downstream of the beamline
exit slit, S1X. This configuration is enabled by theconstant exit-arm length of BL3U, where the x-rays
from the undulator are dispersed by one of three planevaried-line-spacing grating, which have central
groove densities of 240, 600, and 1200 lines/mm. The
distance between the grating and the focal plane is2703 mm. The slit opening as small as 10 mdiffracts soft x-ray significantly. The typical verticalbeam size is 5-20 m depending on the photon
energy and the energy resolution of the incident
x-rays. In the horizontal direction, the focusing mirror

42

M2X of the XES endstation images the undulator
source with a demagnification of 23.4. Under
operating condition, the horizontal beam profile has agaussian profile with FWHM of 41.2 mdamage is frequently problematic as well as thehigher resolution studies which was out of the reachby using conventional x-ray emission spectrometers.

Fig. 3 1st order diffraction peak of the diffuse
scattering from aluminum sample. Energy resolving
power of 4600 is demonstrated.

Fig. 2 Schematic Layout of XES endstation of theundulator beamline BL3U.

Results and Discussion
The stray light contamination is estimated bymeasuring the profile of the 0th order diffraction.
Typically the stray light intensity is less than 1 % of
the 1st diffraction order intensity. The energy
resolution is estimated by measuring diffuse
scattering from aluminum sample illuminated by 60
eV soft x-rays. Fig. 3 shows 1st order diffraction peak.
The peak width was FWHM of 3 pixels, whichcorresponds to the energy resolving power of 4600.
To our knowledge, the achieved resolving power byusing TG is more than 4 times higher than the bestrecord reported so far [5].
The spectrometer was employed to measureresonant XES spectra of a single crystal of silicon.
The sample is illuminated with a grazing-angle of 20
degree. Fig. 4a shows the Si L-edge absorption
spectrum of the sample together with the excitationenergies. An image of the CCD detector taken by
exciting at the resonance d is shown in Fig.4b. The
vertically dispersed image where the lower direction
corresponds to the higher photon energy clearlyshows a sharp elastic peak with two bumped structure
due to the x-ray emission. Horizontal length of thesignal band is confined within about 1 mm, which is amagnified image of the sample area where theincident soft x-rays illuminated. Fig. 4c shows the
XES spectra excited at the resonances, where each
spectrum was taken within 30-120 min. with incident
soft x-ray flux of 1011 photons/sec. The entrance slit
opening was 20 m. The spectrum clearly shows
coherent and incoherent structure as reported in theprevious work [6].
These results indicate that the present TGS iscapable of carrying out high-resolution soft x-ray
emission studies. Although rather low photon density
is used in the current experiment, the results clearlyshow that the XES study is feasible with the present
TGS. Large acceptance angle will give an advantage
to the studies of organic samples where the sample

Fig. 4 Si L-edge Absorption spectra (a), and a CCD
detector image when excitated at the resonance d.Thelabels a-d shows the excitation energies applied inresonant XES spectra (c).

Acknowledgements
The authors gratefully thank NTT-ATN,
Hamamatsu Photonics, and Meisei Co. for thedevelopment of the TG and the Wolter mirror, andCCD electronics, respectively. This work is partly
supported by the Japan Society for the Promotion of
Science (JSPS), Special Coordination Funds for
Promoting Science and Technology (MEXT), andInternational Collaboration Program (IMS).
[1] K.P. Beuermann, et.al., H. Bräuninger, J.
Trümper, J. Applied Optics 17 (1978) 2304.
[2] T. Hatsui, E. Shigemasa, N. Kosugi, J. Electron
Spectrosc. and Relat. Phenom., 144 (2005) 1059.
[3] A. Ohba, S. Onoda, Y. Sugiyama, private
communication.
[4] T. Hatsui, E. Shigemasa, N. Kosugi, AIP Conf.
Proc. 705 (2004) 921.
[5] C. R. Canizares, et.al., Publ. Astron. Soc. Pac.
117 (2005) 1144.
[6] S. Eisebitt, et.al., J. Electron Spectrosc. Relat.
Phenom. 93 (1998) 245

43

BL2B

Construction of an End Station of BL2B to Study the Dissociative
Photoionization of Fullerenes and VUV Spectroscopy of Ionic Liquids
1

H. Katayanagi1,2, B. P. Kafle2, S. I. Prodhan2, H. Yagi1, K. Mitsuke1,2
Department of Vacuum UV Photo-Science, Institute for Molecular Science,
Okazaki 444-8585 Japan
2
Graduate University for Advanced Studies, Okazaki 444-8585 JapanA new vacuum chamber for the end station of beamline 2B (BL2B) in UVSOR was constructed. The
chamber was designed for the gas phase spectroscopyof refractory materials such as fullerenes,
metallofullerenes and ionic liquids. The following
three subjects are now under way: (1) the velocity map
imaging of the ionic photofragments from fullerenes[1, 2], (2) threshold photoelectron – photoion
coincidence measurements of the fullerenes, and (3)photoelectron and photoabsorption spectroscopy ofionic liquids.
Drawing of the chamber is shown in Fig. 1. The
twofold -metal shield is put inside the chamber toprevent penetration of the geomagnetic field. The
effective volume surrounded by the shield is five times
as large as that of the previous chamber used at BL2B.
The new chamber is equipped with 14 ports facing theionization region, i.e. the focal point of thesynchrotron radiation. This larger volume andversatile port arrangement enable us to incorporate
many complicated devices. We designed this chamber
to adapt not only to BL2B but also to BL7U. In order
to compensate the difference of the heights of opticalaxes, we placed a stage of 50 cm in height at BL2B
and put the chamber on the stage. Additionally thechamber was mounted on a micromotion stage to alignits optical axis readily with the beam lines when thechamber is relocated.
The installation of the chamber at BL2B was
accomplished. We observed TOF spectra of fragments
and parent ions produced by the dissociative
photoionization of fullerenes (C60). We have obtained
spectra using the previous setup at BL2B. In
comparison with signal intensities and resolutions ofthese spectra, we can examine the performance of the
new setup. The TOF spectrum at the photon energy of
90 eV obtained by the new setup is shown in Fig. 2.
Intense three peaks in the spectrum correspond toC60+, C602+ and C603+ parent ions. Progressions ofsmall peaks in shorter TOF side of doubly and triply
charged parent ion peaks are fragments which lost C2units successively. From these results, we concluded
that we succeeded in reproducing the results obtainedwith the previous setup.
Using the chamber with small modifications ofsignal processing electronics, we can perform morequantitative experiments than those using theprevious setup. Prior to the new subjects (1) - (3), we
resumed quantitative comparison of photoion yield
spectra between the fullerene and higher fullerenes(C70 [3], C84). This will give us a clue to understandextraordinary stability of fullerenes. Moreover, in theenergy range available using BL7U (6 – 40 eV), thefullerenes have strong absorption (> 100 Mb)
associated with structures which originate frommolecular nature of the fullerenes. Although a part ofthe structure was observed using BL2B, it is subtle
because the structure is out of practical coverage ofthe monochromator of BL2B. Observation of thefullerene absorption spectra in the energy range of
BL7U using the new chamber will enable us tounderstand the ionization mechanism of fullerenes.

Fig. 1 Top view (drawing) of a new chamber for theend station of BL2B in UVSOR. Numbers in the
figure are in mm.

Intensity (arb.)

150

2+

C60

100
n=

20

10

0

+

C60
3+

50

0
15

C60

20

25

30

35

40

45

TOF / sFig. 2 TOF mass spectra of ions produced by the
dissociative photoionization of the fullerene (C60)[1] A. T. J. B. Eppink and D. H. Parker, Rev. Sci. Instrum. 69(1997) 3477.
[2] B. P. Kafle et al., AIP Conf. Proc. 879 (2007) 1809.
[3] J. Kou et al., J. Chem. Phys. 120 (2004) 6005.

44

BL3U

The Development of Sub-Pixel Spatial Resolution toSoft X-rays Using Electron-Multiplying CCD Detectors
T. Hatsui1,2,3, N. Kosugi1,2, A. Holland4, R. Ingley4, K. Holland5
1Institute for Molecular Science, Okazaki 444-8585 Japan
2
Graduate University for Advanced Studies, Okazaki 444-8585 Japan
3
PRESTO, JST, Kawaguchi, Saitama, 332-0012, Japan
4
Brunel University, Uxbridge, Middlesex,UB8 3PH, United Kingdom
5
XCam Ltd, Northampton, NN3 7TG, United Kingdom
from the undulator beamline BL3U. The spatial
resolution has been estimated by measuring soft
x-rays (380 eV) transmitted through 10 micron slit
(Fig. 1a). Single pixel events are rejected as they
originate from thermal electrons. Centroid in serialtransfer direction (horizontal direction in Fig. 1) of all
events that are spread over more than 2 pixels areanalyzed. The resulting image is shown in Fig. 2b.
The distance between the slit and the CCD sensor was
1.62 mm, which causes diffraction from the edge ofthe slit. The line profile across the slit image wassimulated based on the Fresnel theory assuming theGaussian profile of the point spread function (PSF) of
the detector. By fitting the experimental results (Fig.
2), we obtained the PSF of the detector with FWHM
of better than 3 m, which represents 1/5th of a pixel
resolution.

Introduction
We have developed a transmission-grating
spectrometer (TGS) for high-resolution soft-X-ray
emission studies. This spectrometer is designed torealize a resolution E/E beyond 5000 in the energy
region of 50-600 eV with a high throughput. One of
the key optical elements for this spectrometer is the
charge-coupled device (CCD) detector. Here we
report the development and performance of the CCD
detector. The transmission grating has lower linear
dispersion compared with reflection gratings. The
detector is mounted in normal incidence geometry inorder to obtain high quantum efficiency. These
configurations demand the detector to have spatial
resolution better than 5 m. By measuring the centerof the electron charge cloud generated in depletion
layer of CCD, sub-pixel resolution detection wasdemonstrated for hard x-rays by Hiraga et.al [1]. In
the case of soft X-rays, one photon produces a charge
cloud, of which the total intensity is about 10 times
weaker than hard x-rays (20-300 electrons). In orderto analyze the centroid of the charge cloud, theintensity of the nearby pixels (1-10 electrons) must be
accurately measured. This requirement is out of thereach of the conventional scientific CCD. In thisstudy, we have introduced electron multiplying CCD
technology in order to reduce the effective readout
noise substantially lower than the intensity of thecharge cloud tail, while increasing the readout rate ashigh as 400 kHz/pixel (10 frame/sec).

Acknowledgements
The authors gratefully thank Peter Pool (e2v) ande2v for the provision of the un-coatedback-illuminated L3V sensors. This work is partly
supported by Special Coordination Funds for
Promoting Science and Technology (MEXT), andInternational Collaboration Program (IMS).
[1] J. Hiraga et.al., Jpn. J. Appl. Phys. 40 (2001)1493.

Experimental
The CCD detector is assembled with an un-coatedback illuminated CCD sensor with L3Vision
technology (CCD97-00) with 16 x 16 m square
pixels. The active area is 512 x 512 pixels (8.2 x 8.2mm2). The sensor is cooled by thermoelectric coolers
and mounted on a conflat flange. The assembled andfinely tuned CCD is illuminated by soft x-rays fromthe undulator beamline BL3U. The CCD detector isoperated at 400 kHz/pixel (10 Hz/frame) readout ratewith electron multiplication of about 100.

Fig. 1 An image before (a) and after the centroid
analysis (b).

Results and Discussion
In the spectroscopic application, the one
dimensional spatial resolution is of interest. Therefore,
the CCD detector was operated in the binning modeof 4x1 pixels. The size of the charge clouds isevaluated by illuminating monochromatic soft x-rays

Fig. 2 Experimental line profile across the 10 m slit
image after the centroid analysis (+) and simulatedline profile (blue line).

45

BL4B

Performance of the Double Toroidal Electron Analyzer forElectron-Ion Coincidence Experiments
T. Kaneyasu1, M. Ito1,2, Y. Hikosaka1, E. Shigemasa1
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585 Japan
2
Graduate School of Science and Technology, Niigata University, Niigata-shi 950-21 Japan1

A double toroidal electron analyzer (DTA) has been
constructed for realizing electron-ion coincidence
experiments. It has been planned to study the decay
dynamics of core-excited or ionized molecules byusing the DTA with an ion momentum imaging
spectrometer. The molecule with a core hole is very
unstable due to its high internal energy andsubsequent electronic relaxation processes often leadto dissociation. A correlation analysis among theparticles ejected during the relaxation process gives
access to proper understanding on the decay
dynamics. Detailed descriptions of the electron-ion
coincidence spectrometer and the DTA had alreadybeen given elsewhere [1-3]. The DTA is suitable forelectron-ion coincidence experiment because of its
high angular acceptance (5% of 4 sr) and moderateenergy resolution (less than 1% of the pass energy)
for electron analysis. Additionally, the DTA allows
the angular distribution measurement of electrons,with the use of a two-dimensional position sensitive
detector (PSD: Roentdek DLD40).
Prior to the coincidence experiments [4], we haveevaluated energy resolution achieved by the DTA
under the present condition. The experiment was
performed at soft x-ray beamline BL4B with anenergy resolving power Eph/Eph~800 at 300 eV
photon energy. We have detected Ne 2s
photoelectrons for the performance test. The sample
gas was effused through an aperture of 0.2 mm
diameter on the repeller plate. The photoelectronsejected at 54.7° with respect to the electric vector of
the photon beam were analyzed in energy. The DTA
pass energy Epass was set to 200 eV which allows thesimultaneous observation of electrons with the energy
range of 248 - 270 eV. Photoelectron spectrum wasdeduced from the electrons’ arrival positions on the
PSD.
Figure 1(a) shows a Ne 2s photoelectron image
obtained at 302.6 eV. A concentric circle on the image
corresponds to the photoelectrons. The anisotropic
intensity along the circumference of the circle resultsfrom the unevenness of the transmission efficiency.
The radial intensity distribution corresponding to thephotoelectron spectrum is shown in Fig. 1(b). A leastsquare fit with a Gauss function gives the peakwidth of 1.34 eV (FWHM). Considering themonochromator bandwidth, the instrumental energy
resolution is estimated to be E=1.3 eV (FWHM),
which corresponds to the resolving power of the DTA
Epass/E=154. We have measured Ne 2s photoelectron
spectra by changing the photon energy and estimatedthe resolving power. In Fig. 2, the electron energy

resolution and the resolving power are plotted as afunction of the kinetic energy. The resolving power
better than 100 is achieved within an energy range
corresponding to 7% of the pass energy. For the
lower/higher kinetic energy electrons, the resolving
power is somewhat worse than that for 254.1 eVelectrons, which results from an imperfection of theelectric field at the exit plane of the toroidal surfaces.
tic e
nerg
K in e10

Y / mm

0

y

(a)

0

0.25

0.50



0.75

1.00

1.25

-10

Intensity / arb. units

20

1.50

1.75

-20
2.00

-20

-10

0

10

20

X / mm
600

(b)

500

FWHM
1.34eVCounts

400
300
200
100
0
246

248

250

252

254

256

258

260

Electron kinetic energy / eV

Fig. 1 (a) Two-dimensional image of Ne 2s
photoelectrons measured at 302.6 eV photon energy.
(b) Ne 2s photoelectron spectrum deduced from theimage.
6
5

200

EpassE

100

3Epass/EE (FWHM) / eV

150
4

2
50
1
0
245

E
0
250

255

260

265

270

Electron kinetic energy / eV

Fig. 2 The energy resolution and resolving power ofthe DTA plotted as a function of the kinetic energy.
[1] T. Kaneyasu et al., AIP conf. proc. 978 (2007)
1793.
[2] T. Kaneyasu et al., J. Electron Spectrosc. Relat.
Phenom., in press.
[3] C. Miron et al., Rev. Sci. Instrum. 68 (1997) 3728.
[4] T. Kaneyasu et al., in this report.

46

BL5B

Measurement of Absolute Efficiency for Micro Channel Plates
by Using Pure-Calibrated EUV Beam
G. Murakami1, K. Yoshioka1, K. Hikosaka1, A. Yamazaki2, I. Yoshikawa1
1
Department of Earth and Planetary Science, Graduate School of Science,
The University of Tokyo, Tokyo 113-0033 Japan
2Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency,
Sagamihara, Kanagawa 229-8510 Japanmeasurement shows that the quantum efficiency of
the MCPs is 7.4% at 30.4nm line.
As the next step, in addition to the 30.4nm line, weplan to measure the quantum efficiency at the 83.4nm
line, which is another observational object of
UPI-TEX. Then the purity of 83.4nm line is essential,
and must be investigated for the next machine time.

Introduction
We study to optically observe the Earth’s
plasmasphere, which is filled with cold plasmas(mainly H+, He+, O+ and electrons). The He+ and O+
ions have resonance scattering emission lines in theextreme ultraviolet (EUV) region, at 30.4nm (HeII)
and 83.4nm (OII) respectively. The intensity of each
emission is proportional to column density of eachscattered particle under the assumption of the
optically thin condition.
The SELenological and ENgineering Explorer(SELENE) satellite will be launched in 2007 and put
into the orbit around the moon. The Telescope for
EXtreme ultraviolet light (TEX) of the Upper
atmosphere and Plasma Imager (UPI) onboard the
SELENE satellite will observe the plasmasphere at
30.4nm and 83.4 nm lines from the lunar orbit. In thisexperiment, in order to calibrate the sensitivity of the
UPI-TEX we measure the quantum efficiency of the
micro channel plates (MCPs), which we use as thestandard detector, at 30.4nm line.

(a)Measurement and Result
We install an Al/Mg/Al (744Å/3958Å/747Å) filteron the entrance of the SOR beam to eliminate themulti-order lines from the 30.4nm line with PGM35.
At first, we investigate the purity of the 30.4nm line
through the Al/Mg/Al filter. We judge the purity fromtheconsistency
betweenthewavelengthcharacteristics of an Al/C (1201Å/54Å) filter and an
Al/Mg/Al (744Å/3958Å/747Å) filter for theparticular lines at the EUV facilities of Institute ofSpace and Astronautical Science (ISAS) and those forthe continuous lines at UVSOR. The former ismeasured for the emission lines of the gas (He, Ne)with the discharge light source. Fig. 1 shows thetransmittances of the two filters measured at ISAS
and UVSOR. It is clear that both profiles of eachfilter are consistent in the wavelength region of
25-50nm. We interpret from the result that the pure30.4nm can be introduced through the Al/Mg/Al filterby using PGM35.
With the available pure 30.4nm line, then wemeasure the quantum efficiency of the MCPs. The
quantum efficiency is calculated by the rate of the
MCPs count to the electron yield of the photo diodewhich is absolutely calibrated. The result of the(b)Fig. 1 The transmittances of (a) an Al/C (1201Å/54Å)filter and (b) an Al/Mg/Al (744Å/3958Å/747Å) filter.
The red dots show the results of the measurements atthe EUV facility of ISAS and the solid lines show
those at UVSOR. The solid line in (b) is discrete at
38nm and 49nm because the incident beam
introduced by PGM35 is weak at the wavelengths andthe results have large error.

47

BL5B

Calibration of Optics for Extreme Ultra-Violet Region
M. Yamamoto, H. Habara, K. A. Tanaka
Graduate School of Engineering Osaka University, 2-1 Yamadaoka, Suita 565-0871, Japan
reflectivity and difrractivity hardly depend onpolarization in VUV/XUV region light [3]. From theresults, we can evaluate the total optical loss for the
spectrometer.

Introduction
We’re developing a new spectrometer in order tomeasure the high-order harmonics in vacuum
ultra-violet (VUV) and extreme ultra-violet (XUV)
generated in ultra-intense laser-plasma interactions.
Optical system of spectrometer for VUV/XUV lightshould compose of reflective optics which arespherical mirror (SM) and spherical grating mirror(GR) because the harmonics can not propagate in thetransmittive optics for examples CaF2 (cut-off 120nm) and MgF2 (cut-off 115 nm). We investigated thereflectivity of SM and the ±1st diffractivity of GR.

Experimental
We utilize SM (ACTON Research Corp.
#1200-VUV coating) and GR (Horiba Jovin Yvon
monochrometer concave grating) for the spectrometer.
These properties are shown in Table 1 and Table 2. Asvarying the incident angle, the dependence ofreflectivity of SM and the ±1st diffractivity of GR on
pump wavelength were measured using s-polarizationsynchrotron radiation of multi-bunch operation at
BL5B line with a photodiode (IRD AXUV-100). In
the experiments, we measured the reflected light fromspherical optics irradiating into the photodiodeaperture monitoring maximum photodiode currents.

Fig. 1 The reflectivity of SM was measured usings-polarization synchrotron light.

Table 1. Properties of spherical mirror [1].
Coating
Wavelength
Reflectivity
Al - MgF2
115 – 300 nm
70 -90 %Table 2. Properties of spherical grating mirror [2].
Coating
Groove density
Deviation
Al - MgF21200 gr/mm
64 degFig. 2 The -1st diffractivity of GR was measured
using s-polarization synchrotron light.

Results and Discussion
Reflectivities of SM for the harmonics from 9th(@117 nm) to 15th (@70.2 nm) with s-polarization
incidence are shown in Fig. 1. It is found that our
results are significantly different from Ref. [1]. Alsoat the smaller incident angle, the difference ofreflectivity becomes larger by the wavelength. In
addition reflectivity of 9th is insensitive to theincident angle compared with 13th (@75.2 nm).
The ±1st diffractivities of GR for the 9th to 15th
harmonics with s-polarization incidence are shown in
Fig. 2 and Fig. 3. Only the +1st relative diffractivities
from 100 to 300 nm were calculated and thiscalculation shows particularly decrease from 100 to
140 nm in Ref. [2]. Our experiment found that the±1st difrractivity roughly increased with shorter
wavelength.
The experiments were carried out usings-polarization light. However, it is well known that

Fig. 3 The +1st diffractivity of GR was measured
using s-polarization synchrotron light.
[1] Catalog, ACTON Research Corp.
[2] Catalog (Ref. 522 00 250), Horiba Jobin Yvon.
[3] C. Palmer, ”Diffraction grating handbook (fifth
edition)”, Thermo RGL, 2002.

48

BL5B

Calibration of Phosphors for Extreme Ultra-Violet Region
M. Yamamoto, H. Habara, K. A. Tanaka
Graduate School of Engineering Osaka University, 2-1 Yamadaoka, Suita 565-0871, Japan
Introduction
We’re developing a new spectrometer in order tomeasure the high-order harmonics in vacuum
ultra-violet (VUV) and extreme ultra-violet (XUV)
generated in ultra-intense laser-plasma interactions.
Instead of expensive light detector such as a
micro-channel plate (MCP) and a charge coupleddevice (CCD), we utilized phosphors (Zn2SiO4:Mn,
BaMgAl10O17:Eu) for plasma display panel of thatproperty is well known above VUV (>120 nm)
region. We experimentally evaluated luminous
fluorescent characteristics at the shorter wavelengthfrom the rear side of the phosphor films in thecondition of actual uses.
Fig. 1 Luminescence spectra of Zn2SiO4:Mn excited
by VUV/XUV region light of synchrotron radiation.

Experimental
The sample films on the glass plate are made by
the coagulation sedimentation method. The properties
are shown in Table 1. Measurements of luminous
fluorescent spectra and quantum efficiency
dependence on pump wavelength were measured
using synchrotron radiation of multi-bunch operation
at BL5B line. Each property was measured with aspectrometer (Jobin Yvon HR320) and a photodiode(IRD AXUV-100).
Table 1. Properties of phosphor sample films.
SampleThickness Fluorescent center
Zn2SiO4:Mn
30 um
9.03 % (Mn)
BaMgAl10O17:Eu
50 um
9.31 % (Eu)

Results and Discussion

Fig. 2 Luminescence spectra of BaMgAl10O17:Eu
excited by VUV/XUV region light of synchrotron
radiation.

Luminous fluorescent spectra of phosphors wereshown in Fig. 1 and Fig. 2. In spite of different pumpwavelength, the luminous fluorescence spectra show
no difference between VUV/XUV and over 120 nm[1]. It is clear that it is impossible to distinguish thepump wavelength from the spectra in uses an imaging
detector for VUV/XUV region.
Luminous fluorescent quantum efficiency ofphosphors excited by VUV/XUV light corresponding
to the high order harmonics is shown in Fig. 3. T
luminescent fluence for both phosphors is estimatedby multiplying the simulation results of harmonics
intensity at 20 J/ 1019W/cm2 laser (@1.05 um) lightirradiated to a solid target [2], resulting that theluminescence of 210 mLux for 105 nm (10thharmonic) can be detected with 144 msr solid view
angle. As the result, it experimentally examines thatthe harmonics could be measured with phosphorsbecause a general astronomical CCD, which has morethan a few mLux sensitivity, could detect the
VUV/XUV harmonics.

Fig. 3 Quantum efficiency of phosphors excited by
VUV/XUV region light of synchrotron radiation.
[1] Catalog, Kasei Optonix LTD.
[2] P. Gibbon, Phys. Rev. Lett. 76 (1996) 50.

49

BL7U

Construction of a VUV Angle-Resolved Photoemission Beamline BL7U
S. Kimura1,2, T. Ito1,2, M. Sakai1, E. Nakamura1, N. Kondo1, T. Horigome1, M. Hosaka1,3, A.
Mochihashi1,2, M. Katoh1,2, T. Ejima4, H.J. Im1,5, H. Miyazaki1,3, K. Soda1,3
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
3
Graduate School of Engineering, Nagoya University Nagoya 464-8603, Japan
4
IMRAM, Tohoku University, Sendai 980-8577, Japan
5
Department of Physics, Sungkyunkwan University, Suwon 440-746, South Korea
employed changeable nine mirrors including Mo/Si
multilayer mirrors which have high reflectivity in thephoton energy range of 30-40 eV to increase thephoton flux [4].

Recently, the energy resolution of photoemission
experiments is drastically improved by using helium
discharge lamps and VUV lasers. Due to theimprovement, the thermodynamical properties ofsolids can be understood by the change of theelectronic structure detected by photoemission. In the
case
of
the
angle-resolved
photoemission
spectroscopy (ARPES) using such light sources, themomentum along the normal direction of sample
surface (kz) cannot be set at a high symmetry point
because the excitation photon energy that directly
connects to kz cannot be tuned. To determine thethree-dimensional band structure at the highsymmetry points by ARPES with tunable photons isimportant to compare with the band structure
calculation. Since synchrotron radiation (SR) is
suitable for the use of the various photon energies,
some photoemission beamlines have been constructedin the world up to now. Because of the low photon
flux of SR, however, the energy-resolution in ARPES
was lower than the other sources mentioned above.
Then we constructed a new undulator beamline in the
VUV region at UVSOR-II for the purpose of thehigh-energy resolution ARPES with the total energy
resolution less than 1 meV in the whole excitationenergy of 6 - 40 eV and with the various (vertically /horizontally linear and circular) polarizations ofphotons.
We employed a various polarized APPLE-II-type
undulator light source [1], a Wadsworth-type VUVmonochromator [2] and a high-energy-resolution
photoelectron analyzer with a liquid-He-cooled
cryostat with 6-axes manipulator. Since theWadsworth monochromator has no entrance slit andthe light source size (2) of 0.04(H)1.2(H) mm2 inthe 1-% coupling machine operation of UVSOR-II [3],the VUV light with high photon flux and with highenergy resolution can be obtained. The overall pictureof the beamline is shown in Fig. 1. The undulator
radiation is guided to 10-m-radius spherical gratingsby two plane mirrors (M0, M1). The light is focusedon the exit slit (S) by the spherical gratings. The
monochromatized light is focused again on a sample
by a toroidal mirror (M3). Because of no entrance slit,
the photon flux on the sample becomes very high.
However the near-normal incident mirror M1 reduces
the photon flux in the higher energy region. Then we

Fig. 1. Top view of the VUV photoemission beamline
BL7U of UVSOR-II.
[1] S. Sasaki, K. Miyata, and T. Takada, Jpn. J. Appl.
Phys. 31, L1794 (1992).
[2] S. Kimura, T. Ito, E. Nakamura, M. Hosaka, and
M. Katoh, AIP Conf. Proc. 879, 527 (2007).
[3] M. Katoh, M. Hosaka, A. Mochihashi, J.
Yamazaki, K. Hayashi, Y Hori, T. Honda, K. Haga,
Y Takashima, T. Koseki, S. Koda, H. Kitamura, T.
Hara, and T. Tanaka, AIP Conf. Proc. 705, 49(2004).
[4] T. Ejima, A. Yamazaki, T. Banse, K. Saito, Y
Kondo, S. Ichimaru, and H. Takenaka, Appl. Opt.
44, 5446 (2005).

50

BL7U

Performance Test of The VUV Monochromator at BL7U
S. Kimura1,2, M. Sakai1, T. Ito1,2
1
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
2
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI),
Okazaki 444-8585, Japan
BL7U is a new VUV undulator beamline at
UVSOR-II constructed in FY2006. The main purposeof the beamline is to elucidate the origin of the exotic
physical properties of functional materials including
strongly correlated electron systems by determinationof the electronic structure by an angle-resolved
photoemission experiment. To perform theexperiment, both of the high energy resolution andhigh photon flux of the monochromatized light are
simultaneously required. Then we checked the energy
resolution and the photon flux at the same
monochromator condition with the exit slit size of
100 m.
The energy resolution is tested by using rare gases.
The helium 1s np (h  24.5 eV) and argon 3s3p6 np(h  29 eV) absorption lines are shown in Figure 1.
The helium absorption spectrum was recorded using
the grating (3600 lines/mm) for the highest energy
range. The energy resolution was evaluated to be
E/E > 19,000. On the other hand, the argon
spectrum was obtained by using the medium region
grating (2400 lines/mm) and the energy resolution
was E/E > 9,000.
The obtained and the geometrically calculated
energy resolution are plotted in Figure 2. The energy
resolution of this beamline depends on the electron
beam parameter of the storage ring, particularly, thebeam size at the emission point. At present, thestorage ring is operated with 5-% coupling. The
obtained energy resolutions at 24.5 and 29 eV are
higher than the calculated lines. In the top-up
operation, the coupling percentage will be reduced to
1 %. Then the energy resolution becomes 2.2 times
higher than the 5-% coupling operation because of the
reduction of the electron beam size.
With the same beamline parameter, the photon
flux was obtained as shown in Figure 3. The spectra
were recorded by using the different undulator gap
size, two M1 mirrors, Au and SiC and different
gratings. If the quantum efficiency of the gold film isassumed to be 5 %, the photon flux at h = 10 - 22 eV
is more than 1012 ph/sec at 200 mA beam current. In
the energy region above 30 eV, the intensity rapidly
decreases with increasing photon energy because of
the poor reflectivity of gold. In the energy region, we
will employ four Mg/SiC multilayer mirrors.[1] Since
the reflectivity is about a few 10 times higher thanthat of a gold film, the photon flux in the energy
region will recover to at least 1011 ph/s.

Fig. 1. Absorption spectra of helium and argon gaseswith the exit slit size of 100 m. The
narrowest width of the absorption lines isregarded as the energy resolution.

Fig. 2.

Experimentally evaluated (marks) andcalculated (lines) energy resolution (E/E) of
three installed gratings as a function of photon
energy and the coupling of the electron beam.
The present coupling is 5 %.

Fig. 3. The throughput spectra of BL7U detected by adrain current of a gold film. The undulator gap,
M1 mirrors and gratings are changed. The exit
slit size was 100 m.

[1] T. Ejima et al., Appl. Opt. 44 (2005) 5446.

51

BL7U

Performance of the Three-Dimensional VUV Angle-Resolved Photoemission
Apparatus at BL7U
T. Ito1,2, S. Kimura1,2, M. Sakai1, N. Kondo1, T. Horigome1,
H.J. Im1,3, H. Miyazaki1,4, K. Soda1,4
1
UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
2
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI),
Okazaki 444-8585, Japan3
Department of Physics, Sungkyunkwan University, Suwon 440-746, South Korea
4
Graduate School of Engineering, Nagoya University Nagoya 464-8603, Japanmm.

The investigation of the anisotropic interaction at
the Fermi surface (FS) of inter-metallic compounds,
namely “Fermiology”, is one of the most facilitating
research field in recent days, since the interactions
between carriers, local spins, and lattice vibrations
play a dominant role for the functionality(superconductivity, magnetism, etc.) of materials.
Angle-resolved
photoemission(ARPES)
spectroscopy is a powerful tool to observe thequasiparticles which form FS’s. The recent
technological innovation of synchrotron radiation
instruments makes that it is possible to observe
three-dimensional (3D) FS’s [1]. However, there arefew 3D-ARPES apparatuses meeting demands ofhigh-energy/momentum
resolution,
enoughbulk-sensitivity, and high-photon-flux in the world.
To investigate the anisotropic interaction at FS ofsolids, we have constructed a bulk-sensitive
three-dimensional angle-resolved photoemission
apparatus (Fig. 1) using VUV light with high-energy
resolution and high photon flux from an undulator
beamline BL7U at UVSOR-II [3]. The main part of
the apparatus consists of a 200-mm-radiushemispherical photoelectron energy analyzer(MBScientific AB; ‘Peter’ A-1) and a liquid-helium
flow cryostat with 6-axes manipulation system (R-dec
Co. Ltd.; i-Gonio). To obtain ARPES spectra alonghigh-symmetry lines of a sample, the sample
manipulator is equipped with three-independent
rolling mechanism; two of them are rotations (x andy) with respect to the sample surface normal and theother an in-plane rotation (). In addition, to befeasible to obtain a complete data set, not only of FS,
but also of quasi-particle band dispersion within 12hours (e.g., user beam operation time in a day), we
will develop a computational multidimensionalscanning system.
Finally, we briefly introduce the present
performance of the PES measurement. From theenergy-distribution-curve of evaporated gold at the
Fermi level (Fig. 2(a)), the total energy resolution
with the angle-integrated mode is about ETotal = 1.5
meV with h= 10 eV photons at T = 15 K. The
horizontal spot size on the sample estimated from theposition distribution curve (Fig. 2(b)) is about 0.5

Fig. 1. Three-dimensional VUV angle-resolved
photoemission apparatus at BL7U. Purple arrow
indicates a path of SR light. Inset shows thedefinitions of 6-axes of the manipulater.

Fig. 2. Energy- (a) and position- (b) distribution
curves of gold at the Fermi level at T = 15K obtainedby using h= 10 eV photons.
[1] T. Ito et al., J. Mag. Magn. Mater. 310, 431(2007).
[2] S. Kimura et al., AIP Conf. Proc. 879, 527 (2007).

52