Phase diffusion in high-power microwave sources

Autocorrelation of electromagnetic fields emitted by high-power microwave sources makes it possible to determine the phase diffusion coefficient $D$. The value of $D$ imposes significant constraints on synchronization of several HPM sources. It is clearly demonstrated by the example of a relativistic reflex triode operating at $f\approx 3.3$ GHz and having the phase diffusion coefficient equal to $D\approx 0.06$ rad${}^2\cdot$ns${}^{-1}$.