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Title: Milliampere Beam Studies using High Polarization Photocathodes at the CEBAF Photoinjector

Abstract

Extending the charge lifetime of today's spin polarized GaAs photoelectron guns from tens to thousands of Coulombs is a requirement for long-duration operation at milliampere beam current. There are two main approaches frequently considered to achieve this goal. The first is improving photo-gun vacuum, which provides a direct means to minimize the ill effects of ion bombardment and associated QE decay. In this contribution, we demonstrate the second: enhancing the charge lifetime at milliampere beam current by using large laser spots which serves to distribute ion damage over a larger region of the photocathode. The efficacy of this approach was presented at past workshops, but using bulk GaAs and green laser light without RF structure. In this contribution, highly polarized beam was produced from strained-superlattice GaAs/GaAsP photocathodes inside the 130 kV photo-gun at the CEBAF photoinjector, at beam currents from 0.5 to 1.5 mA and with a clear indication of lifetime enhancement using laser beams as large as ~8 mm2. However, when the laser beam size was increased beyond this diameter, further lifetime enhancement was not observed which highlights the importance of proper cathode/anode design to maintain loss-free beam delivery and the preservation of static vacuum conditions. In addition, thismore » contribution presents electron beam polarization measurements at currents to 1 mA.« less

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1]
  1. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
Publication Date:
Research Org.:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
OSTI Identifier:
1467040
Report Number(s):
JLAB-ACC-18-2784; DOE/OR/23177-4516
DOE Contract Number:  
AC05-06OR23177
Resource Type:
Conference
Journal Name:
PoS PSTP2017
Additional Journal Information:
Conference: 17th International Workshop on Polarized Sources, Targets, and Polarimetry (PSTP2017) : Kaist, South Korea, October 16-20, 2017
Country of Publication:
United States
Language:
English

Citation Formats

Grames, Joseph M., Adderley, Philip A., Hansknecht, John C., Poelker, Matthew, Moser, Daniel G., Stutzman, Marcy L., and Zhang, Shukui. Milliampere Beam Studies using High Polarization Photocathodes at the CEBAF Photoinjector. United States: N. p., 2018. Web. doi:10.22323/1.324.0014.
Grames, Joseph M., Adderley, Philip A., Hansknecht, John C., Poelker, Matthew, Moser, Daniel G., Stutzman, Marcy L., & Zhang, Shukui. Milliampere Beam Studies using High Polarization Photocathodes at the CEBAF Photoinjector. United States. doi:10.22323/1.324.0014.
Grames, Joseph M., Adderley, Philip A., Hansknecht, John C., Poelker, Matthew, Moser, Daniel G., Stutzman, Marcy L., and Zhang, Shukui. Sun . "Milliampere Beam Studies using High Polarization Photocathodes at the CEBAF Photoinjector". United States. doi:10.22323/1.324.0014. https://www.osti.gov/servlets/purl/1467040.
@article{osti_1467040,
title = {Milliampere Beam Studies using High Polarization Photocathodes at the CEBAF Photoinjector},
author = {Grames, Joseph M. and Adderley, Philip A. and Hansknecht, John C. and Poelker, Matthew and Moser, Daniel G. and Stutzman, Marcy L. and Zhang, Shukui},
abstractNote = {Extending the charge lifetime of today's spin polarized GaAs photoelectron guns from tens to thousands of Coulombs is a requirement for long-duration operation at milliampere beam current. There are two main approaches frequently considered to achieve this goal. The first is improving photo-gun vacuum, which provides a direct means to minimize the ill effects of ion bombardment and associated QE decay. In this contribution, we demonstrate the second: enhancing the charge lifetime at milliampere beam current by using large laser spots which serves to distribute ion damage over a larger region of the photocathode. The efficacy of this approach was presented at past workshops, but using bulk GaAs and green laser light without RF structure. In this contribution, highly polarized beam was produced from strained-superlattice GaAs/GaAsP photocathodes inside the 130 kV photo-gun at the CEBAF photoinjector, at beam currents from 0.5 to 1.5 mA and with a clear indication of lifetime enhancement using laser beams as large as ~8 mm2. However, when the laser beam size was increased beyond this diameter, further lifetime enhancement was not observed which highlights the importance of proper cathode/anode design to maintain loss-free beam delivery and the preservation of static vacuum conditions. In addition, this contribution presents electron beam polarization measurements at currents to 1 mA.},
doi = {10.22323/1.324.0014},
journal = {PoS PSTP2017},
number = ,
volume = ,
place = {United States},
year = {2018},
month = {4}
}

Conference:
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