Influence of nitrogen impurities on the characteristics of helium discharge at high pressure. (15th June 2022)

• Record Type: Journal Article
• Authors: Yang, Chuping; Geng, Yinan; Wang, Jie
• Is Part Of: Annals of nuclear energy. Volume 171(2022)
• Publication Date: 2022-06-15
• Subjects: Nitrogen impurities -- High pressure -- Helium -- Discharge characteristics; Nuclear energy -- Periodicals; Nuclear engineering -- Periodicals; 621.4805
• DOI: 10.1016/j.anucene.2022.109024
• Languages: English
• ISSNs: 0306-4549

Abstract

Highlights: The establishment of a two-dimensional axisymmetric fluid model for helium gas with nitrogen impurities. Numerical verification of the breakdown voltages of high pressure helium. The analysis of dominant chemical reactions and the introduction of a concept named "reaction chain" Elucidating the influence of nitrogen impurities on the process and mechanism of helium breakdown under high pressure. Abstract: In this paper, a helium model with nitrogen impurities was established by COMSOL Multiphysics. In order to validate the model, the results of this model were compared with those of the pure helium model and the experimental data. A concept named "reaction chain" was applied to investigate the effects of the nitrogen impurities and elucidate the underlying mechanisms. In terms of discharge mechanisms, the Penning ionization of the He* and N2 can consume He* constantly and directly, which can shorten the reaction chain for the production of dominant ions. The direct ionization of ground state nitrogen molecules can produce more electrons to strengthen the effects of electron avalanche, which will further intensify the reactions. Therefore, the presence of nitrogen impurities can simplify the reaction pathways and intensify the reactions. As a result, the presence of nitrogen impurities can decrease the breakdown voltage remarkably.