DEMONSTRATION OF LOW-LOSS ELECTRON-BEAM TRANSPORT AND MM-WAVE EXPERIMENTS OF THE FUSION-FEM

In the Fusion-FEM electrostatic Free Electron Maser, an electron beam loss current of less than 0.2% is essential for long-pulse operation. At reduced beam current, 3 A instead of the nominal 12 A, we have demo nstrated electron beam acceleration and transport through the undulato r at current losses less than 0.02%. This paper summarizes the results of beam transport experiments and outlines the simple yet effective b eam diagnostics system. The status of the mm-wave cavity and low-power measurements are given. It is shown that cavity characteristics, such as losses, bandwidth, frequency-tuning and feedback coefficient, can be checked in situ via the output window, by injecting a low power tes t-signal into the mm-wave system and analyzing the reflected signal. ( C) 1998 Elsevier Science B.V. All rights reserved.