Author: Montgomery, E.J.
Paper Title Page
MOPLH11 Nanostructured Photocathodes for Spin-Polarized Electron Beams 196
 
  • E.J. Montgomery, C. Jing, S. Poddar
    Euclid Beamlabs LLC, Bolingbrook, USA
  • A. Afanasev
    GWU, Washington, USA
  • R. Kumar, G.J. Salamo
    University of Arkansas, Fayetteville, Arkansas, USA
  • S. Zhang
    JLab, Newport News, Virginia, USA
  
  Funding: Work supported by US DOE Office of Science, Office of Nuclear Physics, SBIR grant DESC0019559. CNM work supported by US DOE Office of Science, Basic Energy Sciences, contract DE-AC02-06CH11357.
We present progress on incorporation of nanopillar arrays into spin-polarized gallium arsenide photocathodes in pursuit of record high tolerance to ion back-bombardment. Our goal is to exceed the 400 Coulomb record for a high polarization milliampere-class electron source set at Jefferson Laboratory in 2017, while maintaining high quantum efficiency (QE) and spin polarization with a superlattice. Because the Mie effect is resonant, uniformity and careful control over nanostructure geometry is key. We report excellent uniformity and straight sidewall geometry with improved optical absorption using a painstakingly optimized inductively coupled plasma reactive ion etch. We also report the application of Kerker theory to spin-polarized photocathode nanopillar arrays, setting new requirements on nanostructure dimensions to avoid spoiling spin polarization. Finally, we also report initial steps toward re-establishing U.S. production of strained superlattice photocathodes towards integration with nanopillar arrays. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH11  
About • paper received ※ 03 September 2019       paper accepted ※ 12 September 2019       issue date ※ 08 October 2019  
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MOPLO06 Black Gun Technologies for DC Photoinjectors 247
 
  • E.J. Montgomery, C. Jing, S. Poddar
    Euclid Beamlabs LLC, Bolingbrook, USA
  • J.E. Butler
    Euclid TechLabs, LLC, Solon, Ohio, USA
  • S. Zhang
    JLab, Newport News, Virginia, USA
  
  Funding: Work supported by the US DOE Office of Science, Office of Nuclear Physics, grant number DESC0019688. Work at Argonne CNM under Contract No. DE-AC02-06CH11357.
Euclid Beamlabs is developing a new "Black Gun" concept in direct current (DC) photoinjectors. To reduce electron-stimulated desorption indirectly influenced by stray photoemission, we are testing advanced optical coatings and low-scattering optics compatible with the extreme high vacuum (XHV) environment of modern DC photoinjectors. Stray light in DC photoinjectors (in proportion to the photoemitted charge) causes off-nominal photoemission, initiating electron trajectories which intercept downstream surfaces. This causes electron-stimulated desorption of atoms, which ionize and may back-bombard the cathode, reducing its charge lifetime. Back-bombardment is key for high average current or high repetition rate. First, we report on progress developing optical skimmers based on Butler baffles to collimate both incoming and outgoing laser beams. Second, we describe candidate coatings for reduction of scattered light. Requirements for these coatings are that they be conducting, optically black at the drive laser wavelength, conformally applied to complex geometry, and XHV-compatible with negligible outgassing. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO06  
About • paper received ※ 04 September 2019       paper accepted ※ 05 September 2019       issue date ※ 08 October 2019  
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