Effects of thermal acoustic oscillations on LCLS-II cryomodule testing

Cryogenic Engineering Conference 2017

材料科学;物理学

Hansen, B.J.^1 ; Al Atassi, O.^1 ; Bossert, R.^1 ; Einstein-Curtis, J.^1 ; Holzbauer, J.^1 ; Hughes, W.^1 ; Hurd, J.^1 ; Kaluzny, J.^1 ; Klebaner, A.^1 ; Makara, J.^1 ; Pischalnikov, Y.^1 ; Schappert, W.^1 ; Stanek, R.^1 ; Theilacker, J.^1 ; Wang, R.^1 ; White, M.J.^1

Fermi National Accelerator Laboratory, Batavia

IL

60510, United States^1

关键词: Cryogenic system;    Distribution systems;    Subcritical pressure;    Super-critical pressures;    Systematic study;    Thermal acoustics;    Thermoacoustic oscillations;    Undesirable effects;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/278/1/012188/pdf
DOI  :  10.1088/1757-899X/278/1/012188

学科分类：材料科学（综合）

来源: IOP

【 摘 要 】

Thermoacoustic Oscillations (TAOs) is a commonly experienced phenomenon in helium cryogenics and in most cases, is an undesirable effect. During LCLS-II prototype Cryomodule (pCM) testing, TAOs were observed in both the Cryogenics Distribution System and in the LCLS-II Cryomodule JT and Cooldown Valves. The TAOs manifested themselves through the usual effect of added heat load to the cryogenic system and ice formation on the oscillating device. However, during cavity testing, the TAOs were also found to significantly contribute to microphonics detuning of the SRF cavities. Systematic studies were carried out and it was discovered that the TAOs could be "turned-off" or substantially decreased by operating at subcritical pressures on the LHe supply. Lastly, various TAO dampening/mitigation techniques were employed to allow operations at supercritical pressure with greatly reduced static heat load and microphonics levels.