Wide band energy beamline using Si(111) crystal monochromators at BL22XU in SPring-8

Shobu, Takahisa  ; Tozawa, Kazukiyo*; Shiwaku, Hideaki   ; Konishi, Hiroyuki; Inami, Toshiya; Harami, Taikan; Mizuki, Junichiro

BL22XU with undulator is consisted of one optical hutch and three experimental hutches and about 120m in length. The aim of this beamline is to perform diffraction and absorption experiment with anomalous dispersion, the high pressure experiments at high or low temperature with multi-anvil type and diamond-anvil type high pressure system and stress measurements. The energy region from 3 to 70keV and high flux of X-rays were required to satisfy these experimental conditions. Then we installed two kinds of monochromator by employing Si (111) crystals. One is SPring-8 "standard" double crystal monochromators to make low-energy X-rays from 3 to 37keV (L-mono), the other is double crystal monochromators, mechanically separated, but combined with calculation to make high-energy X-rays from 36 to 72keV (H-mono). These monochromators were arranged in the tandem for optics. L-mono can be used by lowering the first crystal of the H-mono, on the other hand the H-mono can be used by lifting the whole of L-mono. The liquid nitrogen is used for cooling the crystals, and as a result the high quality monochromatized X-rays is obtained. At the position of 115m from undulator, the beam size is 2.5 mm (vertical) 3.5 mm (horizontal) (FWHM) and the flux is estimated to be 3 10 photon/s. But the stability of X-rays is rather poor because of the vibration caused by nitrogen liquid cooling system. The vertical position of X-rays changes by about 0.2 mm in a few minutes of periods, and the intensity of X-rays varies at about 10%. The stable X-rays within a limitation of accuracy can be obtained by using Monochromator stabilization, so called MOSTAB, which is a feedback control system.