Charge Lifetime Study of K₂CsSb Photocathode Inside a Jlab DC High Voltage Gun

Conference · Thu Sep 01 00:00:00 EDT 2011

OSTI ID:1968867

Mammei, R. ^[1]; Suleiman, R. ^[1]; Poelker, M. ^[1]; Rao, T. ^[2]; Smedley, J. ^[2]; McCarter, J. L. ^[3]

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1. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2. Brookhaven National Lab. (BNL), Upton, NY (United States)
3. University of Virginia, Charlottesville, VA

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.

• Research Organization: Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP)
• DOE Contract Number: AC05-06OR23177
• OSTI ID: 1968867
• Report Number(s): JLAB-ACC-11-1435; DOE/OR/23177-1919
• Resource Relation: Conference: IPAC2011 - Proceedings San Sebastián, Spain, September 4-9, 2011
• Country of Publication: United States
• Language: English