A theoretical model for effect of electron radial diffusion on breakdown characteristics of DC Townsend discharge in uniform axial magnetic field

摘要

The breakdown characteristics of gas discharge between two parallel disks including the electron losses in the discharge process due to radial diffusion have been discussed. A theoretical approach was established to determine the fraction of electrons lost from the discharge cell due to radial diffusion. Then, the dependency of the effective secondary electron emission coefficient on the inter-electrode spacing d, the electrode radius R, and the axial magnetic field B was studied. A par-ticle-in-cell, Monte Carlo collision technique was employed to obtain the values of electron loss coefficient, δ, for d from 1 cm to 10 cm, R between 1 and 10 cm, B up to 300 G, and the gas pressures from 50 mTorr to 250 mTorr. The results show that the loss of the electrons increases exponentially with the distance d, while it decreases by increasing R. Based on the model, the applied magnetic field lowers the Paschen curve that is in agreement with the experimental data.