Introduction

We consider here as cryogenic detectors the solid state or superfluid He detectors operated at temperature lower than 77 K. The principle of operation of these detectors is presented in Section 20.2. Liquid xenon, argon and neon detectors operated respectively at 165 K, 87 K and 20 K are described in the following chapter.

The first searches for dark matter particles were performed with ultrapure semiconductors, operated at liquid nitrogen temperature and installed in pure lead and copper shields in underground environments. Combining a-priori excellent energy resolutions (low energy thresholds) and very pure detector material, they produced the first limits on WIMP searches in the 1980s. It turns out that about 20 years later, such germanium detectors, reaching sub-keV thresholds, have produced the best limits at very low WIMP masses, i.e. lower than 10 GeV. Performances and results of these detectors are described in Section 20.3.1.

In the 1980s, the idea was also put forward in the United States, Europe and Japan of using very low temperature detectors to achieve the required excellent energy resolution and low threshold characteristic of semiconductors, but with different materials and then different nuclei. The idea was to detect particles in a crystal by measuring the increase of temperature induced by the energy deposition. As the heat capacity approximately follows a Debye law with a T3 dependence, it is possible to consider real calorimetric measurements down to very small energy deposition, by using the proper absorber and low enough temperature.