Speaker
Description
Electron sources capable of high polarization and quantum efficiency (QE) are critical to the operation of electron accelerators such as the Continuous Electron Beam Accelerator Facility (CEBAF) at Thomas Jefferson National Accelerator Facility. Strained superlattice photocathodes containing pairs of strained GaAs/GaAsP are currently the standard for beam production at CEBAF, capable of more than 80% polarization and 1.5% QE [1]. In order to increase the quantum efficiency, several devices were grown by MOCVD with varying number of superlattice pairs and the effects on quantum efficiency and polarization were studied. All devices were tested using a microMott polarimeter at Jefferson Lab using a heat clean at 550°C and a cesium/NF3 activation process. Our initial test results seem to indicate that increasing the number of pairs beyond 30 provides minimal benefits for the QE, while the polarization remained constant. A brief discussion of the MOCVD growth process will be presented along with the results of the parametric study.
References
[1] P. Adderley, J. Clark, J. Grames, J. Hansknecht, M. Poelker, M. Stutzman and R. Suleiman, "CEBAF 200kV Inverted Electron Gun," in Particle Accelerator Conference, New York, NY, 2011.
Acknowledgments
This material is based upon work supported by the U.S. Department of Energy, Office of Nuclear Physics, Contract Number DE-SC0023369.
