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

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 finite‐difference 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.