Research On Crystal Cooling Technique Of Monochromator In Synchrotron Radiation

Abstract: The Synchrotron Radiation (SR) has been developed from the firstgeneration to the fourth generation with widely used in the field of basic disciplinesand engineering applications. The electronic emission of SR continues to reduce, thebrightness and energy of SR is gradually increasing. Therefore, the heat load appliedto the crystals of monochromators in the beam line is increasingly becoming a keyfactor of restricting the performance of monochromators with the development of SR.As the spectral components, the thermal deformation of crystal would lead to manydefects such as reducing the energy resolution and luminous flux of monochromators.Because of these defects, the beam spot will be unable to meet the test requirementsor what’s more serious is the experimental station can’t gain light spot.Because that the domestic research to crystal cooling technique of monochrome--ators stated late, there has no much experience for the crystal cooling of high headload from high-power light source. Therefore, the crystal cooling techniques ofmonochromators are presented based on the full analysis of crystal cooling techniqueat home and abroad. They include the following several aspects.Firstly, according to the classification of SR source, the radiated power andpower density of SR are analyzed comprehensively; the calculation methods of powerand power density received by the surface of the first crystal of monochromators arepresented. Moreover, the thermal deformation of crystal has been analyzed and thetheoretical evaluation standards of crystal cooling are built.Secondly, according to the existing crystal cooling technique and method, theindirect cooling and direct cooling methods are modeled and analyzedcomprehensively. The heat transfer model of indirect cooling, the deformation modelof crystal and the calculation model of equivalent heat transfer coefficient are built.For indirect cooling, cooling on diffractive surface can reduce temperature gradient ofthe crystal and thermal deformation of the diffractive surface more effectively thanthe way of cooling on crystal bottom. A physical model of direct cooling and the calculation method of equivalent heat transfer coefficient are built. In addition, theother effective cooling technique can reduce the crystal deformation are presented.Thirdly, based on the detailed discussion of key techniques of crystal cooling, theprinciples of choosing crystal material and cooling media are discussed and proposed.The qualitative and quantitative analysis of the crystal surface error under thedifferent flow rate, flow, temperature and other characteristics of cooling media havebeen done; and the influence of crystal surface of the crystal structure such asdiffracting layer thickness, the cooling channel dimensions and clamping mechanismare qualitatively and quantitatively analyzed.Fourth, according to the requirements of the monochromator research projects intwo SR beam line for Shanghai Synchrotron Radiation Facility (SSRF), a directcooling structure and a new indirect cooling structure based on the top-side coolingmethod are designed. Theoretical analysis results for these two new cooling structuresshow: the two new structures designed in this thesis can effectively reduce the thermaldeformation of crystal. Especially the new indirect cooling structure has more obviousadvantages than previous indirect cooling structure. Therefore, the research anddesign in this thesis will provide a reliable theoretical analysis and structural referencefor the future monochromator research projects.