Two-dimensional positive column structure in a discharge tube with radius discontinuity

The low-pressure (40 and 90 Pa) low-current (4 and 10 mA) direct current discharge in a tube with a sharp change of its radius is studied both numerically and experimentally. A fully self-consistent hybrid numerical model of a two-dimensional non-uniform positive column in neon is developed using a nonlocal approach. The model combines kinetic simulation of the electrons (under two-terms approach) and fluid description of the neon ions and permits to calculate the distribution of all plasma parameters in the direct current discharges in the cameras with cylindrical geometry and radius discontinuity. The simulation results are compared with the measured 585.3 nm neon spectral line absolute intensities and excited 1s(3) metastable neon atom number densities. Non-local electron kinetics in the transition region and formation of standing strata are discussed. (C) 2014 AIP Publishing LLC.