Molecular beam probing of electron beams

Empirical electron-beam characterization by molecular beam probing has been applied to the interaction space of a gridded Injected Beam Crossed-Field Amplifier (IBCFA) and a nongridded M-Backward Wave Oscillator. A small gas stream, preferably helium or argon, is injected through a capillary into the electron beam. The interaction of the gas molecules with electrons in the beam results in the release of far ultraviolet photons which are collected and counted as a function of position by means of a solar blind, photon detector. The spatial resolution is as small as 15 × 15 × 15 µm
³
. Application of this technique to the beam injection in IBCFA's is presented, and applications to TWT's, gyrotrons, and cathode emission studies are discussed.