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Title: ILC @ SLAC R&D Program for a Polarized RF Gun

Abstract

Photocathode rf guns produce high-energy low-emittance electron beams. DC guns utilizing GaAs photocathodes have proven successful for generating polarized electron beams for accelerators, but they require rf bunching systems that significantly increase the transverse emittance of the beam. With higher extraction field and beam energy, rf guns can support higher current densities at the cathode. The source laser system can then be used to generate the high peak current, relatively low duty-factor micropulses required by the ILC without the need for post-extraction rf bunching. The net result is that the injection system for a polarized rf gun can be identical to that for an unpolarized rf gun. However, there is some uncertainty as to the survivability of an activated GaAs cathode in the environment of an operating rf gun. Consequently, before attempting to design a polarized rf gun for the ILC, SLAC plans to develop an rf test gun to demonstrate the rf operating conditions suitable for an activated GaAs cathode.

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Stanford Linear Accelerator Center (SLAC)
Sponsoring Org.:
USDOE
OSTI Identifier:
875812
Report Number(s):
SLAC-PUB-11657
TRN: US0600801
DOE Contract Number:
AC02-76SF00515
Resource Type:
Conference
Resource Relation:
Conference: Contributed to 11th International Workshop on Polarized Sources and Targets (PST05), Tokyo, Japan, 14-17 Nov 2005
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; ACCELERATORS; CATHODES; DESIGN; ELECTRON BEAMS; LASERS; PHOTOCATHODES; STANFORD LINEAR ACCELERATOR CENTER; TARGETS; Accelerators,ACCPHY

Citation Formats

Clendenin, J.E., Brachman, A., Dowell, D.H., Garwin, E.L., Ioakemidi, K., Kirby, R.E., Maruyama, T., Miller, R.A., Prescott, C.Y., Wang, J.W., /SLAC, Lewellen, J.W., /Argonne, Prepost, R., and /Wisconsin U., Madison. ILC @ SLAC R&D Program for a Polarized RF Gun. United States: N. p., 2006. Web.
Clendenin, J.E., Brachman, A., Dowell, D.H., Garwin, E.L., Ioakemidi, K., Kirby, R.E., Maruyama, T., Miller, R.A., Prescott, C.Y., Wang, J.W., /SLAC, Lewellen, J.W., /Argonne, Prepost, R., & /Wisconsin U., Madison. ILC @ SLAC R&D Program for a Polarized RF Gun. United States.
Clendenin, J.E., Brachman, A., Dowell, D.H., Garwin, E.L., Ioakemidi, K., Kirby, R.E., Maruyama, T., Miller, R.A., Prescott, C.Y., Wang, J.W., /SLAC, Lewellen, J.W., /Argonne, Prepost, R., and /Wisconsin U., Madison. Wed . "ILC @ SLAC R&D Program for a Polarized RF Gun". United States. doi:. https://www.osti.gov/servlets/purl/875812.
@article{osti_875812,
title = {ILC @ SLAC R&D Program for a Polarized RF Gun},
author = {Clendenin, J.E. and Brachman, A. and Dowell, D.H. and Garwin, E.L. and Ioakemidi, K. and Kirby, R.E. and Maruyama, T. and Miller, R.A. and Prescott, C.Y. and Wang, J.W. and /SLAC and Lewellen, J.W. and /Argonne and Prepost, R. and /Wisconsin U., Madison},
abstractNote = {Photocathode rf guns produce high-energy low-emittance electron beams. DC guns utilizing GaAs photocathodes have proven successful for generating polarized electron beams for accelerators, but they require rf bunching systems that significantly increase the transverse emittance of the beam. With higher extraction field and beam energy, rf guns can support higher current densities at the cathode. The source laser system can then be used to generate the high peak current, relatively low duty-factor micropulses required by the ILC without the need for post-extraction rf bunching. The net result is that the injection system for a polarized rf gun can be identical to that for an unpolarized rf gun. However, there is some uncertainty as to the survivability of an activated GaAs cathode in the environment of an operating rf gun. Consequently, before attempting to design a polarized rf gun for the ILC, SLAC plans to develop an rf test gun to demonstrate the rf operating conditions suitable for an activated GaAs cathode.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Jan 25 00:00:00 EST 2006},
month = {Wed Jan 25 00:00:00 EST 2006}
}

Conference:
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  • The ILC requires a polarized electron beam. While a highly polarized beam can be produced by a GaAs-type cathode in a DC gun of the type currently in use at SLAC, JLAB and elsewhere, the ILC injector system can be simplified and made more efficient if a GaAs-type cathode can be combined with a low emittance RF gun. Since this type of cathode is known to be extremely sensitive to vacuum contamination including back bombardment by electrons and ions, any successful polarized RF gun must have a significantly improved operating vacuum compared to existing RF guns. We present a newmore » RF design for an L-Band normal conducting (NC) RF gun for the ILC polarized electron source. This design incorporates a higher order mode (HOM) structure, whose chief virtue in this application is an improved conductance for vacuum pumping on the cathode. Computer simulation models have been used to optimize the RF parameters with two principal goals: first to minimize the required RF power; second to reduce the peak surface field relative to the field at the cathode in order to suppress field emitted electron bombardment. The beam properties have been simulated initially using PARMELA. Vacuum and other practical issues for implementing this design are discussed.« less
  • Since the ITRP recommendation in August 2004 to use superconducting rf technology for a next generation linear collider, the former NLC Group at SLAC has been actively pursuing a broad range of R&D for this collider (the ILC). In this paper, the programs concerning linac technology are reviewed. Current activities include the development of a Marx-style modulator and a 10 MW sheet-beam klystron, operation of an L-band (1.3 GHz) rf source using an SNS HVCM modulator and commercial klystrons, design of a more efficient and less costly rf distribution system, construction of a coupler component test stand, fabrication of amore » prototype positron capture cavity, beam tests of prototype S-band linac beam position monitors and preparations for magnetic center stability measurements of a prototype SC linac quad.« less
  • No abstract prepared.
  • The Linac Group at SLAC is actively pursuing a broad range of R&D to improve the reliability and reduce the cost of the L-band (1.3 GHz) rf system proposed for the ILC linacs. Current activities include the long-term evaluation of a 120 kV Marx Modulator driving a 10 MW Multi-Beam Klystron, design of a second-generation Marx Modulator, testing of a sheet-beam gun and beam transport system for a klystron, construction of an rf distribution system with remotely-adjustable power tapoffs, and development of a system to combine the power from many klystrons in low-loss circular waveguide where it would be tapped-offmore » periodically to power groups of cavities. This paper surveys progress during the past few years.« less
  • The R and D program for the ILC electron focuses on three areas. These are the source drive laser system, the electron gun and photo cathodes necessary to produce a highly polarized electron beam. Currently, the laser system and photo cathode development take place at SLAC's 'ILC Injector Test facility', which is an integrated lab (laser and gun) that allows the production of the electron beam and is equipped with a set of diagnostics, necessary to characterize the source performance. Development of the ILC electron gun takes place at Jefferson Lab, where advanced concepts and technologies for HV DC electronmore » guns for polarized beams are being developed. The goal is to combine both efforts at one facility to demonstrate an electron beam with ILC specifications, which are electron beam charge and polarization as well as the cathode's lifetime. The source parameters are summarized in Table 1. The current schematic design of the ILC central complex is depicted in Figure 1. The electron and positron sources are located and laid out approximately symmetric on either side of the damping rings.« less