Calorimeters with proximity-effect thermometers and lead and tin absorbers

Taking advantage of the low critical temperatures of proximity-effect phase transition thermometers, superconductors with low Debye temperatures can be used as absorber materials for calorimetric detectors. We performed experiments with lead and tin absorbers of a mass of about 1 g. The energy resolutions for 6 keV X-rays are 1000 eV and 230 eV FWHM, respectively. A model which includes the effect of both thermal and non-thermal phonons explains the measured pulse shapes. The observed heat capacity of the absorbers agrees with that given by the Debye law. A comparison of heat pulses and of radiation induced pulses shows a thermalization efficiency close to 100%. No evidence for trapping of energy as quasiparticles is observed.