Breakdown analysis for electrodeless discharge in a magnetic field

A fluid model for an electrode-less, toroidal breakdown process in presence of a steady magnetic field is developed. Breakdown processes in the Extrap configuration are studied. Both particle balance and energy balance are solved to obtain breakdown voltages. A 2-dimensional particle balance is solved for the Extrap configuration, and the existence of the magnetic nulls seems to play an important role. The concept of the Townsend first coefficient α is found not to be applicable when the particle losses are severe, and the energy balance has to be solved in order to explain the very high low-threshold of the filling pressure observed in the Extrap breakdown experiments. The theoretical results are compared with experiments; a fairly good agreement is achieved. (author)