The hydrogenmigration in cryogenic tubes of superconductive accelerator with gas source

Background In superconductive linear accelerator,the performance and stability can be impacted by gas adsorbed on cryogenic surfaces adversely.The cryogenic devices usually work at 4.2 K or 1.9 K and are refrigerated by normal or super fluid liquid helium,respectively.Purpose The purpose of this paper is to study the character of gas migration in cryogenic tubes.Method Adsorption coefficient for hydrogen at 4.2 K is measured by experimental study.Then,a gas migration model is established based on the experimental results to depict the hydrogen migration process in cryogenic tubes.Results The experimental results and model analysis indicated that at cryogenic temperature(4.2 K),adsorption coefficient for hydrogen is very close to 1,which is several orders higher than the adsorption coefficient at room temperature,resulting in a unique pressure distribution pattern in cryogenic tubes when compared with the pressure distribution in room temperature tubes.Conclusions At 4.2 K or 1.9 K,the gas migration process is obviously different from the process at room temperature and is significantly affected by the gas adsorption on the cryogenic surfaces.The model established in this article can be applied not only to hydrogen migration in cryogenic tubes but also to other gas migration in tubes with high adsorption coefficient.