Photocathode lifetime improvement by using a pulsed high voltage on the photocathode gun of the polarized electron source at NIKHEF

The first result on a dramatic improvement of the photocathode lifetime of the polarized electron source at NIKHEF is presented. The improvement was obtained after replacing the original DC power supply with a pulsed power supply for the photocathode gun high voltage. The pulsed high voltage power supply provides a negative Gauss-like pulse, with an amplitude of 100 kV, and a full-width of 600 μs, with repetition rates up to 10 Hz. Contrary to using DC high voltage, no deterioration of the vacuum in the acceleration chamber is observed. A photocathode lifetime of 180 h has been measured, using a strained layer InGaAsP photocathode. The lifetime is independent of whether or not the photocathode gun is operated at the pulsing rate of 1 Hz.