Cryogenically Cooled Monochromator with Multi-crystal Switching System on BL11XU at SPring-8

We developed a multi-crystal switching system on a cryogenically cooled monochromator of the JAERI materials science beamline, BL11XU at SPring-8. In order to make progress in our science, it is necessary to ensure at least the energy range of 6 ~ 70 keV which is achieved by employing Si(111) and Si(311) crystals. The principle of the crystal switching is that, two crystals is arranged side by side, and they are translated in the horizontal direction for exchanging the crystals. Indium sheets were inserted between the crystals in order to improve the thermal contact. Four adjustment stages of the SPring-8 standard type monochromator were removed to avoid the crystal vibration. A sheet heater was installed on the -axis stage to prevent the over-cooling of the residual adjustment stages. The cryogenically cooled monochromator provides the 7.4 times higher flux intensity at 14.4 keV in comparison with a previous indirect water-cooling diamond (111) crystal monochromator. It takes only 5 minutes to exchange the crystal from Si(111) to Si(311) and adjust crystals geometry. This mechanism will be easily applied to other crystals, for example asymmetrical-cut crystals or more pair of the crystals.