Noise measurements on a magnetron injection gun beam

The results of noise measurements conducted on a helix-type traveling-wave amplifier containing a magnetron injection gun are described. A minimum noise figure of 15.3 dB was observed at 760 MHz with an approximate beam power of 1600 watts. The noise figure was minimized by an adjustment of the magnetic field, which determines the transit time of the electrons through a drift region. This optimizes the magnitude and phase of the standing noise waves at the helix input.