Cryocooler Contamination Study

S.W.K. Yuan, D.T.Kuo, and A.S. Loc

BEI Technologies, Cryocooler Group

Sylmar, CA 91342

ABSTRACT

Eliminating or reduction of contamination is essential for the success of cryocoolers as far as performance and cooler life is concerned.Contaminants in a cooler can be defined as any foreign material that results in the rubbing of mechanical parts or blockage of flow, which in turn reduces cooler life and / or degrades performance.In this paper, we will limit the scope of our study to gaseous and liquid contaminants, which may freeze and are detrimental to cooler performance.It was found that most of the contaminants in BEIs coolers consist, carbon dioxide, water, cleaning solvents (acetone and alcohol), nitrogen and oxygen.Five 0.5 watt coolers (B512) were used for the study.These coolers were baked out continuously at 71°C for one week.Gas analysis was performed on the cooler working gas every day during the one-week period.Outgassing curves have been constructed on the contaminants listed above.Based on the analysis, optimum bake-out time of the cooler components can be derived.Optimum purge and fill procedure will also be discussed in this paper.