Device for Measuring Heat Capacities of Microcalorimeter Absorber Materials

We are developing a device for measuring the heat capacity of candidate absorber materials for gamma‐ray microcalorimeters with the goal of finding materials with low heat capacity and high stopping power to improve detector efficiency. To date, only Sn has been effective as an absorber, and speculation is that other materials suffer from anomalously high heat capacities at low temperatures. The key component of the measurement device is a 17 mm×17 mm low heat capacity silicon platform suspended by Kevlar fibers designed for accepting 1 g to 2 g samples, and whose heat capacity can be characterized prior to attaching a sample. The platform has a thin film Pd/Au heater deposited directly on the silicon, and a semiconducting thermometer bonded to the surface. The heat capacity is determined from C = Gτ, where G is the in‐situ measured conductance and x is the measured temperature decay time from a step change in applied heat. For a platform without samples, decay periods on the order of 0.3 to 0.05 seconds ...