Thermal physics of transition edge sensor arrays

Thermal transport in transition edge sensor (TES)-based microcalorimeter arrays is reviewed. The fundamentals of thermal conductance in Si3N4 membranes are discussed and the magnitude of the electron–phonon coupling and Kapitza coupling in practical devices is summarized. Next, the thermal transport in high-stopping power and low-heat capacity absorbers, required for arrays of TES microcalorimeters, is discussed in combination with a performance analysis of detectors with mushroom-absorbers. Finally, the phenomenology of unexplained excess noise, observed in both Mo- and Ti-based TESs, is briefly summarized and related with the coupling of the TES to the heat bath.