Superconducting transition edge thermometers for calorimetric detectors

Transition edge thermometers combined with a SQUID readout system are developed for the thermometry of calorimetric particle detectors. A calorimeter is tested, consisting of 1.1 g of silicon as absorber with a cadmium thermometer, showing an energy resolution of delta E/E = 1 percent for 5.8 MeV alpha-particles at an operating temperature of T = 455 mK. A sapphire calorimeter with a mass of 280 g is also built using an iridium thermometer. Operated at 135 mK an energy resolution of delta-E/E = 1.2 percent for 5.8 MeV alpha-particles is obtained. This corresponds to a measurement of the radiation-induced change in temperature with an accuracy of 54 nK.