The momentum resolution of the Cauchois-type spectrometer reaches 0.13 atomic units at the h i g h - e n e r g y i n e l a s t i c s c a t t e r i n g b e a m l i n e ( B L 0 8 W ) [ 1 ] . T h e s p e c t r o m e t e r i s e q u i p p e d w i t h a conventional Germanium detector with four slits in front to allow such observations as Fermi surface signatures of Sr 2 RuO 4 . Now the spectrometer is to be equipped with a one-dimensional microstrip Germanium detector so as to establish a higher detection efficiency around the 80 keV X-ray region as well as a high background rejection capability [2]. There are one hundred twenty eight cathode strips that are photo-chemically formed on the Germanium crystal, the width, the interstrip, and the length of which are 300 μ m, 50 μ m, and 50 mm, respec tively . When compar ed with the origin al system , the data-ta king speed is expect ed to be 30 t i m e s f a s t e r i n t h e n e w d e t e c t o r s y s t e m . O w i n g t o t h e h i g h m o m e n t u m r e s o l u t i o n a n d t h e h i g h detection efficiency, the spectrometer will yield a few dozen Compton profiles of, for example, heavy element metals or alloys, during a reasonable beamtime with a sufficient accuracy. Reconstructing the t h r e e - d i m e n s i o n a l m o m e n t u m d e n s i t i e s f r o m t h e m u l t i f o l d C o m p t o n p r o f i l e s o b s e r v e d s h o u l d significantly enrich knowledge about their Fermi surfaces. The one-dimensional microstrip Germanium detector mentioned above was constructed during the second stage of the R&D program on the position-sensitive detector for the beamline. In order to h a n d l e t h e l a r g e n u m b e r o f t h e r e a d o u t c h a n n e l s , f o u r 3 2 - p a r a l l e l - i n p u t f r o n t - e n d h y b r i d - b o a r d s Fig. 1. 128-channel microstrip Germanium detector with four 32-parallel-input front-end hybrid boards mounted. 113 Masayo Suzuki and Naoto Yagi SPring-8 / JASRI (IDEAS, VA32c-TA32cg ) were adopted as charge-sensitive pre-amplifiers and discriminators. These boards are currently controlled by a Windows-based PC data acquisition system (IDEAS, VADAQ ). Because of its A/D conversion time of 30 μ sec, however, the data-taking speed achieved with the new d e t e c t o r s y s t e m i s s t i l l l i m i t e d a n d i s o n l y f o u r t i m e s f a s t e r t h a n t h e o r i g i n a l s y s t e m . I n o r d e r t o improve the speed, a data acquisition system with flush ADC VME modules and a conversion time of 100 nsec maximum is currently under development. References [1] SPring-8 Research Frontiers 1998/1999, p. 77. [2] SPring-8 Research Frontiers 1998/1999, p. 98. Fig. 2. X-ray energy spectra observed at focal plane with a sample of Nb in 2-D representation. 114 50 100 150 200 250 300 350 400 50 60 70 80 90 100 110 0 0.05 0.10 0.15 0.20 0.25 0.30 Deposited En er gy (k eV ) Positi on along Fo cal Pla ne (Inde x Number ) X-ray Intensity (Arbitrary Units)
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