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 energy, of statistical effects at intermediate energy, and of nonlinear effects at high energy. The optimal design of a fast (time constant τ < 1 ms) intermediate mass bolometer (10 mg < m < 1 g) with high resolution (ΔE_FWHM < 500 eV) and large dynamic range (E(max) 5 MeV) is described from functional block diagram to the calculation of parameters for each element. This has been applied to the construction and successful tests of a 100 mg silicon bolometer. We obtained resolutions better than 1 keV on γ-rays from 13 to 130 keV with a base line resolution of 300 eV and a measured time constant of less than 400 μs. The same bolometer was also used for α particle spectrometry in the 5 to 8 MeV range with a resolving power greater than 200. From measurements of the short lived ²¹⁴Po atoms recoiled into the bolometer we deduced a half-life of 160 ± 12 μs, which extends the excellent time resolution possible with such bolometers.