Reflected and Secondary Electrons from an Aluminum Target

Velocity distributions of secondary electrons from an aluminum target, bombarded with homogeneous streams of primary electrons, were examined with a magnetic analyser. The secondaries examined were those coming off approximately at right angles with the primary beam. The range of primary velocities used was from 5 volts to 175 volts. Sharply defined peaks, consisting of electrons reflected without loss of energy, constitute 2 percent of the whole distribution at 175 volts, 10 percent at 35 volts, 90 percent at 12 volts, and 95 percent at 7 volts. The coefficient of reflection at right angles is of the order of 10^-3 to 10^-2 per unit solid angle, increasing over twenty fold between 100 volts and 8 volts, attaining a maximum at 7 or 8 volts and decreasing sharply below that.