Towards an Absolute Determination of the Particle Energy Thermalized in Bolometers

We describe a procedure to derive the absolute energy thermalized in the bolometer's target after a particle interaction. It relies on the comparison of the theoretical responsivity in stationary regime (deduced from the I-V curves) and the area of the pulse. Full thermalization in metals is addressed at high cryogenic temperatures (over 400 mK). Taking them as reference materials when glued to a target, they can be used to estimate the thermalization efficiency of particles in dielectrics and superconductors. We have applied the procedure to our current detectors for dark matter and neutron, alpha and X-ray spectroscopy (LiF, Li6Gd(BO3)(3), Ge, Cu and Ta) at different cryogenic temperatures (from 20 to 570 mK). The procedure permits also to measure the loss of sensitivity due to the deviation from an ideal isothermal bolometer model. Previous works on thermalization reported by other teams are reviewed and applications are discussed.