Reduced model of plasma evolution in hydrogen discharge capillary plasmas

Abstract

A model describing the evolution of the average plasma temperature inside a discharge capil-lary device including Ohmic heating, heat loss to the capillary wall, and ionisation/recombinationeffects is developed. Key to this approach is an analytic quasi-static description of the radial tem-perature variation which, under local thermal equilibrium conditions, allows the radial behaviourof both the plasma temperature and the electron density to be specified directly from the averagetemperature evolution. In this way, the standard set of coupled partial differential equations formagnetohydrodynamic (MHD) simulations is replaced by a single ordinary differential equation,with a corresponding gain in simplicity and computational efficiency. The on-axis plasma tem-perature and electron density calculations are bench-marked against existing 1D MHD simulationsfor hydrogen plasmas under a range of discharge conditions and initial gas pressures, and goodagreement is demonstrated. The success of this simple model indicates that it can serve as a quickand easy tool for evaluating the plasma conditions in discharge capillary devices, particularly forcomputationally expensive applications such as simulating long-term plasma evolution, performingdetailed input parameter scans, or for optimisation using machine-learning techniques.

G. J. Boyle et al., Reduced model of plasma evolution in hydrogen discharge capillary plasmas, Phys. Rev. E