Methods for response stabilization in bolometers for rare decays

Massive bolometric detectors operated at very low temperatures (≃10 mK) can be used to search for rare events, such as Double Beta Decay and interactions of Dark Matter candidates. In experiments of this type it is important to keep the detector response steady within 0.1% level over periods of the order of one year or more, often in conflict with the intrinsic instabilities of the cryogenic setups. Here, a powerful method to stabilize detector response is described: using calibrated amounts of energy, injected by means of alpha particles or resistive heaters, a correlation between pulse amplitude and detector bias can be established. This correlation can be used to correct off-line the amplitudes of every pulse. The satisfactory results achieved with this technique are reported and discussed. For this purpose heavily doped Si heaters with steady resistances at cryogenic temperatures were designed and succesfully tested.