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Study On The Gas Adsorption Capability On Cryogenic Superconductive Cavity Surface And Beam Loss Induced Gas Desorption

Posted on:2019-02-03Degree:DoctorType:Dissertation
Country:ChinaCandidate:C F HuFull Text:PDF
GTID:1362330590977924Subject:Nuclear technology and applications
Abstract/Summary:PDF Full Text Request
Superconducting technology has been widely used in superconducting linear accelerators after nearly half a century of rapid development.The application of superconducting technology provides a strong guarantee for the development of superconducting linear accelerators,and brings unprecedented challenges,such as beam matching between the normal temperature section and the superconducting section,protection of high power couplers,and gas migration between the room temperature and the low temperature section.A superconducting linear accelerator can usually be divided into normal temperature section and low temperature superconducting section.In this thesis,with the stable operation of superconducting linear accelerator as an ultimate goal,the author focused his research on the gas migration characteristics between the normal temperature section and the low temperature section of the superconducting linear accelerator and the effects it brings about.The specific research contents include gas adsorption capacity and transmission characteristics under cryogenic environments,the effect of superconducting cavity on the performance of gas adsorption on low temperature surface,the study of gas desorption caused by beam loss,and the gas isolation between normal temperature section and low temperature section.In this paper,the basic theoretical and experimental researches on the adsorption capacity of hydrogen gas and other gas on the surface of superconducting cavity under extremely low temperature conditions and the characteristics of adsorption process are carried out.According to the research results,a mathematical model for hydrogen and other gases migrating in the cryogenic pipelines are built.Such mathematical model of gas migration proposed in this paper is suitable for describing the migration of almost all gases in cryogenic pipelines.A series of experimental studies have been carried out on the performance degradation caused by gas adsorption on the surface of bulk niobium superconducting cavity.The experimental results show that the physical adsorption of carbon-free gas,such as hydrogen and nitrogen,on the low temperature surface of the superconducting cavity won't deteriorate the performance of the superconducting cavity.However,when methane or air is adsorbed on the surface of the superconducting cavity at low temperature,the presence of carbon element will reduce the surface work function of the SRF cavity,which ultimately leads to a decrease in the acceleration performance of the superconducting cavity.Experimental study on the desorption of low temperature surface gas caused by beam loss is presented in the second part of this thesis.The experimental results show that the key parameters about the desorption,the sputtering yield,is strongly related with beam incident angle,beam current intensity and cryogenic surface gas adsorption parameter.Through experimental research,not only the relationship between sputtering yield and related parameters is obtained,but also the characteristics of gas pressure change process during beam desorption of low-temperature surface gas by beam bombardment.Finally,according to the basic research results of gas adsorption and mitigation,aiming at the stable operation of superconducting linear accelerator,this thesis studies the problem of the performance degradation of SRF cavity caused by gas adsorption and the vacuum instability of cryogenic vacuum pipeline in the presence of beam loss.Meanwhile,a solution for isolating gas migration between normal temperature and low temperature section is also proposed.
Keywords/Search Tags:Superconducting linear accelerator, cryogenic gas adsorption and migration, superconducting cavity, gas desorption
PDF Full Text Request
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