Reaction chain used to describe the process and mechanism of helium breakdown under high pressure

Abstract

In this study, we establish a two-dimensional axisymmetric fluid model and verify its efficacy via experiments. We analyze the reaction rates to introduce a concept that we have termed “reaction chain” to describe the process and mechanism of helium discharge at high pressure. We observe that the entire process of discharge can be perfectly described by the reaction chains, which indicates that the breakdown process of helium involves a series of chain reactions, just like the nuclear fission. The results revealed that ground-state ionization reaction predominates the early discharge stage, whereas with the quick accumulation of He2*, penning ionization reaction will eventually play a dominant role. Our study confirms that metastable atoms play an important role in helium discharge. We demonstrated that He* is converted into He2* as an intermediate and that the number density of He2* eventually influences the breakdown of helium.