Interpretation of the millimeter wave generation in the orbitron as stimulated emission of bremsstrahlung

Experimental results on the operation of the Orbitron maser for helium (at pressures ranging from 0.01-2 Torr) and for neon (at pressures only up to 0.08 Torr) are presented. The rise time of the emitted microwave pulses and the delay were found to be pressure dependent and greater, for a given pressure, at higher frequencies. It is also noted that the microwave pulse disappears when the voltage on the tube becomes sufficiently low. These observations are shown to be consistent with the stimulated-bremsstrahlung model of millimeter wave generation in the Orbitron.