A computer code to calculate then fast induced signals by electron swarms in gases

Abstract

To aid the data analysis of pulsed Townsend experiments, a special code has been developed to calculate the induced pulse by solving the electron continuity equation including growth, drift and diffusion. A realistic profile of the initial laser beam is taken into account as well as the boundary conditions at the cathode and the anode. The approach is either semi-analytic, based on the expression derived by P.H. Purdie and J. Fletcher, or fully numerical, using a finitedifference scheme introduced by J. de Urquijo et al. A new improved scheme is also proposed and compared with the other two methods under typical experimental conditions. A brief discussion on the stability of the numerical procedures is given. The new finite-difference scheme allows a detailed investigation of the importance of back diffusion to the cathode, a subject seldom tackled in the past.