On the mechanism of RPM pulse shortening in oscillators driven by relativistic electron beams

Microwave pulse shortening affects RPM sources even if their efficiency is sufficiently low. In such devices the electrostatic field of the REB exceeds the microwave field on the wall of the slow wave structure so that the field emission of electrons is initially impossible. In this case the reason for plasma to appear is a bombardment of the surface by relativistic electrons. They may originate with the REB, which disrupted partially in the microwave field, or the reflection from the collector. Estimations show that a bombardment of the wall surface with the energy ∼ 10⁻³ J/cm² is sufficient for the microwave pulse shortening.