KIP - Cryogenic particle detection - Calorimeters


Fundamentally, the calorimetric detection of particles is based on the discovery of Mayer and Joule that heat is a form of energy.The general scheme of a calorimetric detector is shown in Fig. 1. In principle, a calorimeter is a simple device, consisting of an absorber suited for the particles being detected, which is weakly coupled to a thermal reservoir, and a thermometer with which the temperature of the absorber can be monitored with high precision. The deposited energy E is determined by the temperature rise δT = E/C. Here C denotes the heat capacity of the calorimeter.

The use of calorimeters for particle detection has a long tradition in physics, starting in 1903 with the famous experiments by Curie and Laborde, in which they were able to demonstrate the production of heat associated with the radioactive decay of radium. The idea of cooling calorimeters for particle detection to very low temperatures can be traced back to the paper of Simon in 1935.The obvious advantage of operating a calorimeter at low temperatures lies in the signal enhancement due to the decrease of heat capacity and the reduction of noise originating from thermodynamic fluctuations. For a long time this idea did not attract much attention, but driven by the need for new types of detectors for certain applications, the work on cryogenic detectors intensified significantly about twenty years ago. Since then, a wide variety of such detectors has been developed, some of which we will briefly describe below.
Semiconductor Thermistors

Superconducting Transtion Edge Sensors

Magnetic Calorimeters

Fig. 1: Scheme of a calorimeter for particle detection, consisting of an absorber, weakly coupled to a thermal bath and a thermometer to monitor the temperature of the absorber.