Further investigations of thermal cryogenic detectors in the field of ionizing radiation metrology

Thermal cryogenic detectors (bolometers, microcalorimeters) have been operated in the pulse mode to quantify ionizing radiation. These detectors exhibit considerable promise for applications in high resolution spectrometry and integral counting. A compact cryogenic system has been developed that can easily be operated for 15 h at 300 mK. This temperature is probably low enough for α-particle spectrometry. We have recently installed a composite-composite bolometer into this cryostat. The detector consists of two cubic crystals (a sapphire target and a diamond scatterer) coupled to a chemically doped Ge temperature sensor. The time constants of the bolometric signal are such that processing and digital filtering of the pulses is required. Careful examination and processing of the recorded pulses permits the elimination of some causes of the loss in energy resolution (pile-up, microphonics, collection defect). Moreover, the very strong dependence of the gain on the temperature has led us to define stability criteria and to select, a posteriori, measurement periods showing sufficient stability.