KIP - Cryogenic particle detection - Superfluid helium detectors


Superfluid Helium Detectors

The use of superfluid helium as absorber in particle detectors is largely motivated by the fact, that liquid helium is the substance with the highest purity. Therefore liquid helium is favored as target material in particular in experiments for which a very low background is needed. There are two different concepts for using superfluid helium in the detection of particles. In one case the production of thermal excitations (Rotons and Phonons) in superfluid 4He by the energy deposition of an incident particle is used to identify an event and measure the energy. Below 100 mK the thermal excitations propagate ballistically through the liquid and can evaporate He atoms if they reach the surface. The evaporated atoms are condensed on thin wafer calorimeters (Fig. 1 left). The resulting temperature rise is a measure for the energy of the incident particle. The other type of liquid helium detector is based on superfluid 3He. The deposition of energy in superfluid helium leeds to the production of quasi-particles. The presence of these generated quasi-particles is measured via the increased damping of a vibrating wire (Fig. 1 right). Therefore the amplitude of the wire oscillation is a measure for the energy deposited in the liquid. Further details of the two concepts can be obtained at:
 
HERON, Brown University (USA)

Lancaster University (England)

CRTBT Grenoble (France)

Fig. 1: Sketch of the operational modes of a 4He detector (left) and a 3He detector (right).
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