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Title: Observation of Significant Quantum Efficiency Enhancement from a Polarized Photocathode with Distributed Bragg Reflector

Polarized photocathodes with higher Quantum efficiency (QE) would help to reduce the technological challenge associated with producing polarized beams at milliampere levels, because less laser light would be required, which simplifies photocathode cooling requirements. And for a given amount of available laser power, higher QE would extend the photogun operating lifetime. The distributed Bragg reflector (DBR) concept was proposed to enhance the QE of strained-superlattice photocathodes by increasing the absorption of the incident photons using a Fabry-Perot cavity formed between the front surface of the photocathode and the substrate that includes a DBR, without compromising electron polarization. Here we present recent results showing QE enhancement of a GaAs/GaAsP strained-superlattice photocathode made with a DBR structure. Typically, a GaAs/GaAsP strained-superlattice photocathode without DBR provides a QE of 1%, at a laser wavelength corresponding to peak polarization. In comparison, the GaAs/GaAsP strained-superlattice photocathodes with DBR exhibited an enhancement of over 2 when the incident laser wavelength was tuned to meet the resonant condition for the Fabry-Perot resonator.
Authors:
 [1] ;  [1] ;  [1] ;  [2] ;  [2]
  1. Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
  2. SVT Associates, Inc., Eden Prairie, MN (United States)
Publication Date:
OSTI Identifier:
1223480
Report Number(s):
JLAB-ACC--15-2034; DOE/OR/23177--3547
TRN: US1601446
DOE Contract Number:
AC05-06OR23177
Resource Type:
Conference
Resource Relation:
Conference: IPAC 2015, Richmond, VA (United States), 3-8 May 2015
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; PHOTOCATHODES; GALLIUM ARSENIDES; GALLIUM PHOSPHIDES; BRAGG REFLECTION; QUANTUM EFFICIENCY; STRAINS; SUPERLATTICES; LASER RADIATION; ELECTRON BEAMS; RESONATORS; COMPARATIVE EVALUATIONS; POLARIZED BEAMS; ABSORPTION; SPIN ORIENTATION; WAVELENGTHS; AUGMENTATION; SUPERLATTICES; MILLI AMP BEAM CURRENTS