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, 3A instead of the nominal 12A, we have demonstrated electron beam acceleration and transport through the undulator at current losses less than 0.02%. This paper summarizes the results of beam transport experiments and outlines the simple yet effective beam diagnostics system.