Particle in cell simulations of low pressuresmall radius positive column discharges

Abstract

Improved positive column simulation techniques are needed because ofthe non-local nature of typical low-pressure discharges used for lighting. Ina local model, the power balance between Joule heating and collisionallosses must hold for each volume element of the discharge separately while anon-local model requires only a global power balance. The departurefrom locality increases as either gas density ng or radius R isdecreased. Despite this, most current fluorescent lamp software is based onthe local concept. We present a non-local kinetic particle-in-cell Monte Carlocollisions (PIC-MCC) code to simulate low-pressure, small-radius, positivecolumn discharges. This code is also compared to a non-local fluid code, anon-local kinetic Monte Carlo code and to experimental data. The PIC-MCC codemade the least approximations and assumptions and was accurate and stable overa wider parameter regime than the other codes. Also, 1d3v PIC-MCC simulationspeeds are quite competitive even on moderate workstations. Finally, weanalyse the PIC-MCC simulation results in detail, especially the power balanceand the radial electron kinetic energy flux Hr(r). We found that for lowngR< 1×1015 cm-2, the electron kinetic energy flux is directed radiallyoutward while for higher ngR, it is directed radially inward except rightnear the wall.