Physics and applications of metallic magnetic calorimeters for particle detection

An increasing number of experiments and applications employ low temperature particle detectors. Following the calorimetric detection principles, the energy released in the detector leads to a temperature increase which is measured by a very sensitive sensor. Metallic magnetic calorimeters are composed by an energy absorber, optimized for the particles to be detected, in good thermal contact with a metallic paramagnetic sensor positioned in a weak magnetic field. A change in the sensor magnetisation follows the change of the detector temperature. High energy resolution can be obtained by using a low-noise, high-bandwidth DC-SQUID to measure the corresponding change of flux. We discuss the thermodynamic properties, the energy resolution, the microfabrication and general design considerations of magnetic calorimeters as well as their application in high resolution x-ray spectroscopy, beta spectroscopy and absolute activity measurements.