Author: Mammei, R.R.
Paper Title Page
TUPC178 Charge Lifetime Study of K2CsSb Photocathode Inside a Jlab DC High Voltage Gun 1443
 
  • R.R. Mammei, M. Poelker, R. Suleiman
    JLAB, Newport News, Virginia, USA
  • J.L. McCarter
    UVa, Charlottesville, Virginia, USA
  • T. Rao, J. Smedley
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE
Two photocathodes are frequently considered for generating high average current electron beams and/or beams with high brightness for current and future accelerator applications: GaAs:Cs and K2CsSb. Each photocathode has advantages and disadvantages, and need to demonstrate performance at “production” accelerator facilities. To this end a K2CsSb photocathode was manufactured at Brookhaven National Lab and delivered to Jefferson Lab within a compact vacuum apparatus at pressure ~ 5x10-11 Torr. This photocathode was installed inside a dc high voltage photogun biased at voltages up to 200 kV, and illuminated with laser light at 440 or 532 nm, to generate beams up to 20 mA. Photocathode charge lifetime measurements indicate that under some conditions this cathode has exceptionally high charge lifetime, without measurable QE decay, even from the center of the photocathode where operation using GaAs photocathodes is precluded due to ion bombardment. These studies also suggest a complex QE decay mechanism likely related to chemistry and localized heating via the laser beam.