Energy distribution of transmitted secondary electrons from porous KCl films

Energy distribution of secondary electrons from three types of porous films (porous KCl films, porous KCl films with intermediate thin Al layer, porous KCl films containing small amount of amorphous Al) was measured by an ac retarding-field method. The half-width of each energy distribution curve was found to be about 10–20 eV. The surface potential of these films was also obtained from the rising point of the energy distribution curve. A single relationship between surface potential and yield and independent of collector voltage was found for constant primary energy. Decay characteristics of the surface potential of three films after ceasing the primary electron bombardment were similar to each other. Secondary currents from a porous KCl film containing a small amount of amorphous Al were found to be considerably more stable compared to those from two other films. A secondary electron emission mechanism is proposed using a channel electron multiplier model.