FREE-ELECTRON MASER EXPERIMENT WITH A PREBUNCHED BEAM

An experimental project aimed at demonstrating Free Electron Maser (FE M) operation with prebunching is under way at Tel-Aviv university. The FEM utilizes a 1.0 A prebunched electron beam obtained from a microwa ve tube. The electron beam is bunched at 4.87 GHz and is subsequently accelerated to 70 keV. The bunched beam is injected into a planar wigg ler (B-w = 300 G, lambda(w) = 4.4 cm) constructed in a Halbach configu ration with 17 periods, The wiggler utilizes a new scheme for horizont al focusing based on the use of two long permanent magnets at the side s of the wiggler. We plan to study FEM gain enhancement and radiation features due to the prebunched (superradiant) mode of operation. In an oscillator configuration the experiment should be enable study of see d injection by prebunching. Simulation of FEL operation shows an expec ted gain of approximately 100% and an rf output power of 5 kW. In this paper we review the design of the main parts of the experimental set- up, and present recent analytical, numerical, and experimental results .