Beam-Cavity Interaction Measurements in a DAW Structure

Mode excitations induced by relativistic electron beams have been measured in a disk-and-washer (DAW) structure. The structure had three washers, each with four radial support stems, and half-disk end terminations. The design DAW operating frequency was 1300 MHz, the same as that used to accelerate the electron beam. Both short-pulse (35-ps, 800-Hz, 17-nC/pulse) and long-pulse (10-μs, 2-A average) conditions were used in the beam-excitation experiments. Mode spectra were measured and identified using low-power techniques employed after the high-power beam measurements. Mode frequency calculations for the complete three-washer geometry were performed using URMEL for up to m = 7. Calculated results are compared with data determined from low-power and beam-driven excitation of the DAW structure.