Study of intrapulse phase stability of 34 GHz magnicon for Yale project of weakly interacting sub-eV particle searches

The intrapulse phase instability of the 34 GHz magnicon that will be used as a high-power RF source for the Yale project “Weakly interacting sub-eV particle searches” was measured using a heterodyne technique. The measured intrapulse RMS phase deviation averaged over a series of runs is approximately 22.1±6.8 degrees. This is shown to be due mainly to magnicon modulator ripples. The ripples cause variable beam loading of the magnicon cavities resulting in frequency modulation of the magnicon output signal. Simulation of the beam dynamics (considering variations of the modulator voltage and the magnicon gun current) demonstrates a good agreement with the measured RMS value of the phase deviation for the magnicon steady-state regime. Measured RMS values of the phase deviations for similar parameter sets demonstrate good repeatability from one run to another one.