Onset of Thermoacoustic Oscillations in Flexible Transfer Lines for Liquid Helium

Thermoacoustic oscillations in flexible transfer lines result in an increased evaporation rate of stored cryogen. This kind of os- cillation is barely regarded since it only occurs in idle state, i.e. no liquid helium is transferred and a considerable part of the transfer line is close to ambient temperature. The examination of prototype transfer lines with built-in sensors has resulted in a unique knowledge of the oscillation characteristics. As a consequence thermoacoustic oscillations are considered as a common phenomenon in idle flexible transfer lines. The presented paper discusses the conditions for the establishment and a strategy for mitigating thermoacoustic oscillations.