Thermal Acoustic Phenomena In A Cryogenic Helium Distribution System

During normal operation of the cryogenic helium distribution system for the TPS superconducting radio frequency (SRF) cavities, thermal acoustic oscillations (TAO) occur leading to pressure fluctuations in the cold helium gas processing lines up to 65 mbar at a high frequency. The thermal acoustic phenomena present an additional heat load and affecting the operational stability of the SRF cavities. Three gas buffers were attached to the exhaust pipelines of the helium gas processing lines and the isolation valve of the gas buffers was kept half open to prevent pulsation in the flow. These buffers successfully suppressed the TAO phenomena without modifying the exhaust pipelines. The pressure fluctuations were reduced to not more than 7 mbar satisfying the operational requirements for the SRF cavities. In this paper, we present and discuss the solution for the thermal acoustic phenomena in the cryogenic distribution system.