EXPERIMENTAL INVESTIGATION OF MODE BUILDUP AND MODE COMPETITION PROCESS IN A PREBUNCHED FREE-ELECTRON MASER OSCILLATOR

A unique experimental set up at Tel-Aviv University (TAU) enables the study, observation and quantitative measurements of the mode competiti on process in a Free-Electron Maser (FEM) oscillator. The experimental results provide data on the mode build-up from noise level to steady- state saturation and on mode competition. The experimental results are recorded with the aid of a fast digital oscilloscope and are analyzed to obtain the Fourier components by use of a computer program, which we developed. The Fourier analysis shows clearly the build-up and comp etition of the longitudinal modes (eigenfrequencies) excited in the os cillator. We studied mode competition for two cases (I) free-running o scillator (no beam prebunching) (2) oscillator with prebunching of the e-beam. We also compared the experimental results with the results of the multi frequency simulation code MALT1D3, and found good agreement . (C) 1998 Elsevier Science B.V. All rights reserved.