In situ measurements in a crossed-field amplifier and comparisons with numerical simulations

In situ measurements of the electron density, electron energy distribution, and RF electric field have been made in a low-frequency (100 to 200 MHz) crossed-field amplifier. The amplifier is physically large with a length of 40 cm, a width of 20 cm, and an anode to sole spacing of 2 to 3 cm. Two-dimensional measurements have been made of the electron density and the RF electric field using collection probes and RF pick-up probes. The RF measurements clearly show gain in the local RF field comparable to the measured circuit gain. Electron density measurements of the highly cycloidal beam show that the beam trajectories shift spatially during amplification. This shift is believed to be due to the loss of energy the electrons experience during the amplification process. As they lose energy they are drawn to the anode, and they move on a different cycloidal path. In addition, preliminary energy analyzer measurements show a change in the energy distribution of the electrons during amplification. Some electrons appear to gain energy while others appear to lose energy.