VELOCITY SPREAD MEASUREMENTS ON A MAGNETRON INJECTION GUN BEAM

The parallel electron velocity distribution function has been measured on an electron beam from a magnetron injection gun (MIG) using an E p arallel to B energy analyzer. The magnetic field, beam voltage, and be am current were scaled down from normal operating parameters. The perp endicular velocity spread, inferred under the assumption that the elec trons are monoenergetic, is relatively constant for electron velocity ratios beta(perpendicular to)/beta(parallel to)>0.7 and increases appr oximately linearly with the beam current. The current scaling of the p erpendicular velocity spread is also consistent with electron-loss cur rents measured at the control anode of the MIG. Observed perpendicular velocity spreads for the gun design parameters are substantially larg er than computational values.