Onset of Thermoacoustic Oscillations in Flexible Transfer Lines for Liquid Helium

Abstract 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.