Measurement of beam-loaded resonant frequency and quality factor in a gyroklystron input cavity using noise emissions

The spectral shape of noise emissions from a 35-GHz gyroklystron input cavi ty is used to directly measure the cavity resonant frequency and quality fa ctor under beam-loaded conditions. The quality factors obtained with this t echnique at a number of magnetic fields are found to be consistent with qua lity factors obtained from reflection coefficient measurements made at the identical operating points. The measured variation in quality factor is use d to identify various regimes of operation based on input cavity coupling. Comparisons between the measurements and simulations are in good agreement in resonant frequency, but moderate discrepancies in quality factor exist.