Thermal analysis of YB66 crystal of BL15XU at SPring-8 by finite element method

Thermal analysis of YB66 crystal used at a third-generation light source was performed by the finite element method. It was confirmed that the effect of YB66 crystal thickness on maximum temperature on the surface was strongly dependent on the amount of heat load due to the irradiation by the beam and the heat transfer coefficient of the back surface. It was found that the heat load to the YB66 crystal for a practical use should be less than 0.1 W, 1.6 W/mm2 at 1.1 keV with a front-end (FE) slit size 0.2×0.2 mm2, or less than 0.4 W, 2.2 W/mm2 at 2 keV with an FE slit size 0.2×0.2 mm2. The photon flux was estimated to be ∼2×1010 photons/s/0.1% B.W./100 mA at the photon energy of 1.1 and 2 keV with an FE slit size 0.2×0.2 mm2 positioned downstream of the monochromator at the undulator beamline, such as SPring-8 BL15XU.