Observation of microsecond heat pulses in large magnetic fields

By means of a new type of heat pulse detector based on the avalanche phenomenon in a doped semiconductor, phonon pulses as short in duration as 0.1 μsec have been studied in magnetic fields up to 30 kOe. Measurements of phonon mean free path as a function of magnetic field have been made in MgO+. This detector should make it possible to determine the frequency spectrum of a heat pulse for the first time. © 1968 The American Institute of Physics.