DESIGN AND CHARACTERIZATION OF THE DC ACCELERATION AND TRANSPORT-SYSTEM REQUIRED FOR THE 1-MW FREE-ELECTRON MASER EXPERIMENT

A Free Electron Maser (FEM) has been constructed and is soon to be tes ted at the FOM Institute (Rijnhuizen) Netherlands with the ultimate go al of producing 1 MW long pulse to CW microwave output in the range 13 0 to 250 GHz. The DC acceleration and beam transport systems is eventu ally to be used in a depressed collector configuration requiring 99.8% beam transmission in order that the high voltage 2 MV supply be requi red only to supply 20 mA of body current. A relativistic version of th e Herrmann optical theory originally developed for microwave tube beam s is used to take into account thermal electrons far out on the Gaussi an distribution tail which can translate into beam current well outsid e the ideal beam edge. This theory is applied to the FOM beamline desi gn and predicts that the beam envelope containing 99.8% of the current can be successfully transported through the undulator for the expecte d range of assumed emittance values.