Second Sound in Solid Helium-3

An experiment on temperature pulse propagation in a bcc crystal of ³He grown at 95.9 atm shows the existence of second sound in the solid below about 0.58^∘{}K. In the temperature range 0.42^∘K<T<0.58^∘K, reflections of the received pulses were observed. In the range 0.58^∘K<T<1.2^∘K, the temperature pulses were observed to propagate diffusively.