ANL, Lemont, Illinois, USA
Silicon crystals have been widely applied for x-ray monochromators. It is an anisotropic material with temperature dependent properties. Values of its thermal properties from cryogenic to high temperature are available in literature for expansion, conductivity, diffusivity, heat capacity, but neither elastic constants nor Young’s modulus. X-ray monochromators may be liquid-nitrogen cooled or water cooled. Finite Element Analysis (FEA) is commonly used to predict thermal performance of monochromators. The elastic constants and Young’s modulus over cryogenic and high temperature are now collected and derived from literature, with the purpose of assisting in providing accurate FEA predictions.
ANL, Lemont, Illinois, USA
Wavefront preservation is essential for numerous X-ray science applications. Research is currently underway at the Advanced Photon Source to characterize and minimize Bragg-plane slope errors in diamond crystal optics*. Understanding the effect of cooling the optics to cryogenic temperatures on Bragg-plane slope errors is of interest to this research. Through the use of a finite element model a custom, compact vacuum chamber with liquid nitrogen cooling of samples was designed and manufactured. The design process and initial results are discussed in this paper.
*P. Pradhan et al., J. of Synchrotron Radiation 6, 1553 (2020)