Performance of a DC GaAs photocathode gun for the Jefferson lab FEL

Abstract

The performance of the 320kV DC photocathode gun has met the design specifications for the 1kW IR Demo FEL at Jefferson Lab. This gun has shown the ability to deliver high average current beam with outstanding lifetimes. The GaAs photocathode has delivered 135pC per bunch, at a bunch repetition rate of 37.425MHz, corresponding to 5mA average CW current. In a recent cathode lifetime measurement, 20h of CW beam was delivered with an average current of 3.1mA and 211C of total charge from a 0.283cm2 illuminated spot. The cathode showed a 1/e lifetime of 58h and a 1/e extracted charge lifetime of 618C. We have achieved quantum efficiencies of 5% from a GaAs wafer that has been in service for 13 months delivering in excess 2400C with only three activation cycles. © 2001 Elsevier Science B.V. All rights reserved.