Study And Optimization Of Ultratrace Krypton Measurement System In PandaX Experiment

As is known to us all,in addition to ordinary baryonic matter,there is a large amount of invisible dark matter in the universe.The dark matter contributes up to 26.8%of the total content of the universe.Therefore,dark matter detection is one of the most challenging basic physics research topics in the world.Currently,physicists have five hot hypotheses about the dark matter,and the most widely accepted candidate is Weakly Interaction Massive Particles?WIMPs?.So,how to detect WIMPs will become an important challenge for scientists.In order to support the detection of dark matter,the government has established the first extremely deep China Jinping Underground Laboratory?CJPL?in jinping mountain,Sichuan province.The 2400 m depth of the rock gives the lab the most favorable conditions to shield cosmic rays and their from background effects.However,in the dark matter detection experiments,the impurities of xenon will spread to the entire detector,and krypton?decay of krypton-85 can't block,the?particles will influence our experiment electronic recoil signals.So the existence of krypton for dark matter detection experiment is a big problem that cannot be ignored.The main research object of this thesis is the ultratrace krypton measurement system,which is used to measure the content of krypton in xenon.The article begins with an intro-duction to the dark matter and the series of experiments of PandaX.Then,under the condition of controlling the flow rate by the flow meter.The known gas was calibrated and the other gas was measured in this system.Krypton measurement system,carried on the detailed design and simulation studies,achieve krypton precision of ppt(Kr/Xe=10^-12mol/mol)level.It provide high purity xenon gas for the four ton liquid xenon detector experiment,which laid a foundation for the research and application of the experiment.