Occurrence of Thermoacoustic Phenomena at 0.8 K, 4 K and above

Thermoacoustics in cryogenics continues to be a very interesting phenomenon which is still poorly understood but often experienced unexpectedly in experiments where it causes unacceptable heat leaks. The authors report on the appearance and onset of this unwanted occurrence at temperatures below 35 K. A number of physical experiments are presented, where the authors had the means to take quantitative measurements of the heat leak caused by these pressure oscillations in apparatus with bent tubes ranging from 4.55 and 4.7 mm inner diameter, with heat stationing links. The parameters which indicate the likelihood of inadvertently developing these thermoacoustic oscillations are presented and means developed to avoiding them in that instance are given. Furthermore, we had the rare opportunity to record and analyze 4 K TAOs experienced on a test setup and present the simple method that was used to eliminate them.