Optimization Method for TES Microcalorimeters With Absorbers

Large absorbers and a high counting rate is required for high energy resolution transition-edge sensor (TES) microcalorimeters for future X-ray astronomical missions. However, these two requirements have a relation of a trade-off in terms of energy resolution. Thus, study of the effect of thermal diffusion in large absorbers on energy resolution is essential. Therefore, we performed 3 dimensional FEM simulations for TES microcalorimeter with Bi/Au absorber, where a role of Au layer is boost the thermalization of slow thermalizing Bi, using SPICE to calculate the effect of thermal diffusion in the absorber on energy resolution. The simulation results for square absorbers of size 500 mum and 750 mum with Au thickness 0.5 mum indicate that energy resolution of 3 eV and 5 eV can be achieved, respectively, with a fast response time of 100 mus, provided the residual resistivity ratio of Au is higher than ~10.