Parameterizing the deformation of LN2-cooled silicon monochromator crystals with modified linear power density funtion

The very low emittance and low energy spread source of a future Cornell energy recovery linac (ERL) will be equipped with long undulators of large numbers of short period magnets. The power density in the undulator radiation central cone will be much higher than that from normal undulators at current 3 rd generation sources. The deformation of liquid nitrogen (LN 2 ) cooled silicon crystal monochromators for ERL beamlines is evaluated by parameterizing the thermal problem with a modified linear power density function based on a simplified analytical model. This provides a clear and “universal” description of thermal deformation under different thermal footprints, variable loads and is independent of specific facility. The characteristics of thermal deformation of LN 2 -cooled Si crystals for Cornell ERL undulators is also given using finite element analysis (FEA).