ADVANCES TOWARDS FAST THERMAL DETECTORS OF INTERMEDIATE-MASS WITH HIGH-RESOLUTION AND LARGE DYNAMIC-RANGE

The limiting characteristics of intermediate mass bolometers cooled to low temperature for the detection of single events are analyzed over a large energy range with the contributions of inherent noise at low e nergy, of statistical effects at intermediate energy, and of nonlinear effects at high energy. The optimal design of a fast (time constant t au<1 ms) intermediate mass bolometer (10 mg<m<1 g) with high resolutio n (Delta(FWHM)<500 eV) and large dynamic range (E(max)>5 MeV) is descr ibed from functional block diagram ta the calculation of parameters fo r each element. This has been applied to the construction and successf ul tests of a 100 mg silicon bolometer. We obtained resolutions better than 1 keV on gamma-rays from 13 to 130 keV with a base line resoluti on of 300 eV and a measured time constant of less than 400 mu s. The s ame bolometer was also used for alpha particle spectrometry in the 5 t o 8 MeV range with a resolving power greater than 200. From measuremen ts of the short lived Po-214 atoms recoiled into the bolometer we dedu ced a half-life of 160+/-12 mu s, which extends the excellent time res olution possible with such bolometers.