A DOUBLE CRYSTAL MONOCHROMATOR FOR SOFT X-RAY BEAM LINE OF UVSOR

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A DOUBLE CRYSTAL MONOCHROMATOR FOR SOFT X-RAY BEAM LINE OF UVSOR

T. Murata, T. Matsukawa, M. Mori, M. Obashi, S.-I. Nao-E, H. Terauchi, Y.

Nishihata, O. Matsudo, J. Yamazaki

To cite this version:

T. Murata, T. Matsukawa, M. Mori, M. Obashi, S.-I. Nao-E, et al.. A DOUBLE CRYSTAL MONOCHROMATOR FOR SOFT X-RAY BEAM LINE OF UVSOR. Journal de Physique Col- loques, 1986, 47 (C8), pp.C8-135-C8-137. �10.1051/jphyscol:1986824�. �jpa-00226145�

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JOURNAL DE PHYSIQUE

Colloque C8, supplement au no 12, Tome 47, decembre 1986

A DOUBLE CRYSTAL MONOCHROMATOR FOR SOFT X-RAY BEAM L I N E OF W S O R

T. MURATA, T. MATSUKAWA', M. MORI'('), M. OBASHI*,

S.-I. NAO-E", H. TERAUCHI*", Y. NISHIHATA"", 0. MATSUDO' and J.I. YAMAZAKI'

Department of Physics, Kyoto University of Education, Fushimi-ku, Kyoto 612, Japan

"Department of Physics, College of General Education, Osaka University, Machikaneyama, royonaka 560, Japan

* * Department of Physics, College of General Education, Kanazawa University, Kanazawa 920, Japan

""~epartment of Physics, Faculty of Science, Kwansei-Gakuin University, Nishinomiya 662, Japan

'Institute for Molecular Science, Myodaiji, Okazaki 444, Japan

-Abstract A simple, constant offset, high vacuum compatible double crystal mpno- chromator has been constructed for the soft x-ray beam line of UVSOR storage ring.

Na K-edge XANES and EXAFS spectra are presented as examples of the performances of the monochromator.

1. Introduction

The UVSOR is a 6OOMeV (750MeV max.) dedicated electron storage ring in the Institute for Molecular Science at Okazaki. Japan, constructed mainly for the use of VUV photonsl). The calculated intensity distributidn of the radiation is shown in Fig. 1. As shown in the figure, the intensity of the soft x-ray around 10i are not negligible especially in 750MeV operation. Moreover, a 4T superconducting three- pole horizontal wiggler is installed in the straight section.

Fig. 1 Calculated intensity distri- bution of the radiation from ordinary bending section and the superconducting wiggler of the UVSOR storaqe ring.

("present address : Department of Physics, College of General Education, Nagoya University. Nagoya 464, Japan

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1986824

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C8-136 JOURNAL DE PHYSIQUE

In order to utilize the soft x-ray and normal x-ray photons from the U V S O R ring, w e designed and constructed a double crystal monochromator (DXM) with following characteristics; (a) constant offset, (b) monochromator crystals with small size, (c) simple mechanism, (dl high vacuum compatible. In this paper, the mechanism and several performances of the DXM are presented.

2. Mechanism of DXM

In order to realize the constant offset, i.e. constant output beam position during the rotation of the crystals, we chose a simple mechanism of linear movements of the two crystals, perpendicular with each other. The principle of the mechanism is shown in Fig. 2. The t w o crystals are placed on the each side of a L-shaped base. The center of rotation (point 0 in the figure) is placed at the position whose distances to both input and output beam level are the same. The positions of the each crystal are controlled by two linear guides placed on both levels to be at the input and the output beam positions . The mechanical movement was found to be very smooth through a full rotation of 60' (between 15' and 75O of Bragg angle), and a constant offset was successfully achieved. The principle of the mechanism is that discovered by Golovchenko et a12). The mechanism is similar to that of Cowan et a13). Light beam irradiates the fixed small area of each crystal in any incident angle. Therefore it is not necessary to use monochromator crystals with large area.

The actual area of the crystal surface is 20mmx20mm. For fine adjustments of the crystal plane, two piezo-electric transducers (Berley Inchworm, vacuum compatible version) are used for the second crystal.

Fig. 2 Schematic diagram of the mechanism of the DXM. Lines AA' and BB' are input and output beam levels, respectively. Point 0 denotes the center of rotation.

3. Performances

The monochrom~tor crystals such as beryl(lOIO), mica(001) and KAP(100) whose 2d value are 15.98A, 19.801;', and 26.64;, respectively were tested. In Figs. 3(a) and (b) are shown the throughput transmission spectrum of the DXM for beryl crystal at the operating condition of the ring of 750MeV and about 30 mA. No radiation damage was observed for both beryl and mica crystals. The KAP crystal, however, suffered a serious damage on the surface even in the 6OOMeV operation.

Figs. 4(a) and (b) show the Na K-edge XANES and EXAFS spectrum of a thin film of NaCl which was evaporated in situ on a collodion film in a sample chamber.

Despite the presence of many structures due to impurities and constituent atoms in t6e monochromator crystal in the throughput transmission spectrum, no structure appears in the absorption spectrum of NaC1. All the structures were eliminated by the division of signals without and with a sample. From the doublet separation of the spectrum in Fig. 4(a) we can estimate the resolution of about 1 eV which is practically sufficient for this energy range.

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A monochromator chamber i s evacuated w i t h an i o n pump f o r t h e use of t h e s o f t x-ray. To a v o i d t h e i n f l u e n c e t o t h e u l t r a high vacuum i n t h e s t o r a g e r i n g , a l i g h t t i g h t Be f o i l w i t h a t h i c k n e s s of 10um i s placed i n t h e upstream o f o t h e monochroma- t o r i n t h e beam l l n e . A s a r e s u l t , t h e long wavelength l i m i t i s 18A.

000 1200 1600 2000 700 1100 1500 1900 2300 PHOTON ENERGY / e V PHOTON ENERGY / e V

Fig. 3 T h r o u g h p u t t r a n s m i s s i o n s p e c t r a o f D X M f o r m o n o c h r o m a t o r c r y s t a l o f ( a ) b e r y l and ( b ) mica.

0 ilba 1150 12 PHOTON ENERGY / e V

( b ) NRCL/HI CFI 3. 0.-

2.0--

1280

PHOTON ENERGY / e V

Fig. 4 K-edge (a)XANES and (b)EXAFS s p e c t r a of evaporated NaCl f i l m on c o l l o d i o n a t room temperature.

O t h e r c r y s t a l s s u c h a s I n S b (111) a n d Q u a r t z ( 1 0 i O ) a r e a l s o p r e p a r e d . They a r e planned t o be used a l o n g w i t h a superconducting h o r i z o n t a l wiggler.

Acknowledgments The a u t h o r s a r e indebted t o a l l t h e s t a f f s of t h e UVSOR f a c i l i t y , e s p e c i a l l y t o P r o f e s s o r M. Watanabe f o r h i s c o n t i n u o u s s u p p o r t a n d e n c o u r a g e m e n t throughout t h e work. They a r e a l s o g r a t e f u l t o Messrs. K. Sakai and T. Horigome of IMS f o r d r a f t i n g t h e p a r t s of t h e monochromator.

References

1) M. Watanabe e t a l . : IEEE Trans. Nucl. S c i . NS-28 (1981) 3175.

2 ) J. A . Golovchenko, R. A. Levesque and P. L. Cowan: Rev. Sci. I n s t . 52 (19811 51.

3 ) P. L. Cowan, J. B. H a s t i n g s , T. J a c h and J. P. K i r k l a n d : Nucl. I n s t r u m . Meth. 208 (1983) 349.