Computer designs for beam pentodes

A computer program for the solution of Poisson´s equation in two dimensions with mixed boundary conditions has been used to solve for electron trajectories in beam pentodes with circularly cylindrical cathode contours and round wire grids in the general configuration of many Pierce guns in parallel. Such designs can have nearly uniform cathode current density over the entire cathode surface and zero grid interception under all conditions of interest, including positive grid conditions. Operation with the plate voltage as low as 5 per cent of the screen grid voltage provides satisfactory secondary electron retention in a typical design for which complete transfer characteristics are computed.