Particle detection with semiconductor thermistors at low temperatures

The authors studied the use of neutron-transmutation-doped (NTD) Ge thermistors as phonon sensors at dilution refrigerator temperatures. In addition to measuring their thermal and electrical properties the authors observed pulses generated by X-rays incident on a thermistor thermally well clamped to a heat sink. It is found that during these pulses the lattice temperature of the thermistor apparently does not change. This is interpreted as evidence of a strong coupling between the high-energy phonons generated by the interactions and the charge carriers in the thermistor. The phonons appear to be absorbed within a fraction of a millimeter. It is concluded that the thermistors have several desirable properties for a high-energy phonon sensor. It remains to be seen, however, if a composite detector consisting of a large crystal and attached phonon sensors can be developed. >