IPAC2015 - List of Authors (Stutzman, M.L.)

Paper	Title	Page
TUPMA020	PEPPo: Using a Polarized Electron Beam to Produce Polarized Positrons	1878
	A.H. Adeyemi, P.L. Gueye Hampton University, Hampton, Virginia, USA P.A. Adderley, M.M. Ali, H. Areti, J. F. Benesch, L.S. Cardman, J. Clark, S. Covert, C. Cuevas, A. Freyberger, S. Golge, J.M. Grames, P.L. Gueye, J. Hansknecht, P.L. Harrell, C. Hyde, R. Kazimi, Y. Kim, D. Machie, K.L. Mahoney, R.R. Mammei, J.L. McCarter, M.D. McCaughan, M. Poelker, M.L. Stutzman, R. Suleiman, C.-Y. Tsai, D.L. Turner, Y.W. Wang JLab, Newport News, Virginia, USA M.A. Baylac, E. Froidefond, M. Marton, J-F. Muraz, J-S. Real, E. J-M. Voutier LPSC, Grenoble Cedex, France P. Cole, D. Dale, T.A. Forest ISU, Pocatello, Idaho, USA O. Dadoun, A. Variola LAL, Orsay, France D. Dale, Y. Kim IAC, Pocatello, Idaho, USA EF. Fanchini INFN Genova, Genova, Italy S. Golge NCCU, , North Carolina, USA S. Golge, C. Hyde ODU, Norfolk, Virginia, USA J.L. McCarter UVa, Charlottesville, Virginia, USA C.-Y. Tsai Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA A. Variola IN2P3-CNRS, Orsay, France
	Polarized positron beams have been identified as either an essential or a significant ingredient for the experimental program of both the present and next generation of lepton accelerators (JLab, Super KEK B, ILC, CLIC). An experiment demonstrating a new method for producing polarized positrons has been performed at the Continuous Electron Beam Accelerator Facility at Jefferson Lab. The PEPPo (Polarized Electrons for Polarized Positrons) concept relies on the production of polarized e⁻/e⁺ pairs from the bremsstrahlung radiation of a longitudinally polarized electron beam interacting within a high Z conversion target. PEPPo demonstrated the effective transfer of spin-polarization of an 8.2 MeV/c polarized (P~85%) electron beam to positrons produced in varying thickness tungsten production targets, and collected and measured in the range of 3.1 to 6.2 MeV/c. In comparison to other methods this technique reveals a new pathway for producing either high energy or thermal polarized positron beams using a relatively low polarized electron beam energy (~10MeV) .This presentation will describe the PEPPo concept, the motivations of the experiment and high positron polarization achieved.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA020
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TUPMA038	Observation of Significant Quantum Efficiency Enhancement from a Polarized Photocathode with Distributed Brag Reflector	1923
	S. Zhang, M. Poelker, M.L. Stutzman JLab, Newport News, Virginia, USA Y. Chen, A. Moy SVT Associates, Eden Prairie, Minnesota, USA
	Funding: This project was supported by the U.S. DOE Basic Energy Sciences under contract No. DE-AC05-060R23177. 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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA038
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WEPWI024	Vacuum Characterization and Improvement for the Jefferson Lab Polarized Electron Source	3540
	M.L. Stutzman, P.A. Adderley, M. Poelker JLab, Newport News, Virginia, USA M.A. Mamun Old Dominion University, Norfolk, Virginia, USA
	Operating the JLab polarized electron source with high reliability and long lifetime requires vacuum near the XHV level (<=1x10^-12 Torr). This paper describes ongoing vacuum research at Jefferson Lab including characterization of outgassing rates for surface coatings and heat treatments, ultimate pressure measurements, investigation of pumping including an XHV cryopump, and characterization of ionization gauges in this pressure regime.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI024
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Paper

Title

Page

PEPPo: Using a Polarized Electron Beam to Produce Polarized Positrons

1878

A.H. Adeyemi, P.L. Gueye
Hampton University, Hampton, Virginia, USA
P.A. Adderley, M.M. Ali, H. Areti, J. F. Benesch, L.S. Cardman, J. Clark, S. Covert, C. Cuevas, A. Freyberger, S. Golge, J.M. Grames, P.L. Gueye, J. Hansknecht, P.L. Harrell, C. Hyde, R. Kazimi, Y. Kim, D. Machie, K.L. Mahoney, R.R. Mammei, J.L. McCarter, M.D. McCaughan, M. Poelker, M.L. Stutzman, R. Suleiman, C.-Y. Tsai, D.L. Turner, Y.W. Wang
JLab, Newport News, Virginia, USA
M.A. Baylac, E. Froidefond, M. Marton, J-F. Muraz, J-S. Real, E. J-M. Voutier
LPSC, Grenoble Cedex, France
P. Cole, D. Dale, T.A. Forest
ISU, Pocatello, Idaho, USA
O. Dadoun, A. Variola
LAL, Orsay, France
D. Dale, Y. Kim
IAC, Pocatello, Idaho, USA
EF. Fanchini
INFN Genova, Genova, Italy
S. Golge
NCCU, , North Carolina, USA
S. Golge, C. Hyde
ODU, Norfolk, Virginia, USA
J.L. McCarter
UVa, Charlottesville, Virginia, USA
C.-Y. Tsai
Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
A. Variola
IN2P3-CNRS, Orsay, France

Polarized positron beams have been identified as either an essential or a significant ingredient for the experimental program of both the present and next generation of lepton accelerators (JLab, Super KEK B, ILC, CLIC). An experiment demonstrating a new method for producing polarized positrons has been performed at the Continuous Electron Beam Accelerator Facility at Jefferson Lab. The PEPPo (Polarized Electrons for Polarized Positrons) concept relies on the production of polarized e⁻/e⁺ pairs from the bremsstrahlung radiation of a longitudinally polarized electron beam interacting within a high Z conversion target. PEPPo demonstrated the effective transfer of spin-polarization of an 8.2 MeV/c polarized (P~85%) electron beam to positrons produced in varying thickness tungsten production targets, and collected and measured in the range of 3.1 to 6.2 MeV/c. In comparison to other methods this technique reveals a new pathway for producing either high energy or thermal polarized positron beams using a relatively low polarized electron beam energy (~10MeV) .This presentation will describe the PEPPo concept, the motivations of the experiment and high positron polarization achieved.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA020

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPMA038

Observation of Significant Quantum Efficiency Enhancement from a Polarized Photocathode with Distributed Brag Reflector

1923

S. Zhang, M. Poelker, M.L. Stutzman
JLab, Newport News, Virginia, USA
Y. Chen, A. Moy
SVT Associates, Eden Prairie, Minnesota, USA

Funding: This project was supported by the U.S. DOE Basic Energy Sciences under contract No. DE-AC05-060R23177.
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.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA038

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WEPWI024

Vacuum Characterization and Improvement for the Jefferson Lab Polarized Electron Source

3540

M.L. Stutzman, P.A. Adderley, M. Poelker
JLab, Newport News, Virginia, USA
M.A. Mamun
Old Dominion University, Norfolk, Virginia, USA

Operating the JLab polarized electron source with high reliability and long lifetime requires vacuum near the XHV level (<=1x10^-12 Torr). This paper describes ongoing vacuum research at Jefferson Lab including characterization of outgassing rates for surface coatings and heat treatments, ultimate pressure measurements, investigation of pumping including an XHV cryopump, and characterization of ionization gauges in this pressure regime.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWI024

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)