First Results of the University of Maryland Electron Beam Transport Experiment

The University of Maryland electron beam transport experiment, in collaboration with the Rutherford Laboratory, is designed to study emittance growth in periodically focused intense beams. For initial studies, the electron gun consists of a 1-cm diam., dispenser-type cathode and an anode covered with a wire mesh. To avoid neutralization, 5 ¿s, 60 Hz pulses are used and the current is 230 mA at 5 kV. By varying the voltage from 10 kV to 500 volts the space charge depression, ¿/¿o, of the particle oscillation frequencies in the focusing channel can be changed from ~ 0.04 to ~ 0.2. Further increase of ¿/¿o should be possible with modified guns and the use of emittance control grids. Four prototype solenoids have been built, and the results of experiments with the first two are presented in this paper. Beam profile measurements show the nonlinear effects due to the space charge and the magnetic field, and also the effects of the anode mesh on the beam distribution.