Surface Science Analysis of GaAs Photocathodes Following Sustained Electron Beam Delivery

Journal Article · Tue Jun 12 04:00:00 EDT 2012 · Physical Review Special Topics - Accelerators and Beams, 15(6):063501

DOI:https://doi.org/10.1103/PhysRevSTAB.15.063501· OSTI ID:1044486

Shutthanandan, V; Zhu, Zihua; Stutzman, Marcy L; Hannon, Fay; Hernandez-Garcia, Carlos; Nandasiri, Manjula I; Thevuthasan, Suntharampillai; Hess, Wayne P

Degradation of the photocathode materials employed in photoinjectors represents a challenge for sustained operation of nuclear physics accelerators and high power Free Electron Lasers (FEL). Several photocathode degradation processes are suspected, including defect formation by ion back bombardment, photochemistry of surface adsorbed species and irradiation-induced surface defect formation. To better understand the mechanisms of photocathode degradation, we have conducted surface and bulk analysis studies of two GaAs photocathodes removed from the FEL photoinjector after delivering electron beam for a few years. The analysis techniques include Helium Ion Microscopy (HIM), Rutherford Backscattering Spectrometry (RBS), Atomic Force Microscopy (AFM) and Secondary Ion Mass Spectrometry (SIMS). In addition, strained super-lattice GaAs photocathode samples, removed from the CEBAF photoinjector were analyzed using Transmission Electron Microscopy (TEM) and SIMS. This analysis of photocathode degradation during nominal photoinjector operating conditions represents first steps towards developing robust new photocathode designs necessary for generating sub-micron emittance electron beams required for both fourth generation light sources and intense polarized CW electron beams for nuclear and high energy physics facilities.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1044486
• Report Number(s): PNNL-SA-82424; 45795; 40992; 40990
• Journal Information: Physical Review Special Topics - Accelerators and Beams, 15(6):063501, Journal Name: Physical Review Special Topics - Accelerators and Beams, 15(6):063501 Journal Issue: 6 Vol. 15; ISSN 1098-4402
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
ACCELERATORS
ATOMIC FORCE MICROSCOPY
DEFECTS
ELECTRON BEAMS
Environmental Molecular Sciences Laboratory
FREE ELECTRON LASERS
HELIUM IONS
HIGH ENERGY PHYSICS
LIGHT SOURCES
MASS SPECTROSCOPY
MICROSCOPY
NUCLEAR PHYSICS
PHOTOCATHODES
PHOTOCHEMISTRY
RUTHERFORD BACKSCATTERING SPECTROSCOPY
TRANSMISSION ELECTRON MICROSCOPY