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Kirby, R.E.

Paper Title Page
TPPE057 An Experimental Study of the Quantum Efficiency and Topology of Copper Photocathode Due to Plasma Cleaning and Etching
 
  • D.T. Palmer, F. King, R.E. Kirby
    SLAC, Menlo Park, California
 
  We have developed an experimental research program to the study of the photoemission properties of copper photocathodes as a function of various plasma cleaning/etching parameters. The quantum efficiency, QE, and topology, Ra and Rpp, of Copper Photocathodes, , will be monitored while undergoing plasma cleaning/etching process. We will monitor the QE as a function of time for the various test coupons while we optimize the various plasma processing parameters. In addition, surface topology, will be studied to determine the suitability of the cleaning/etching process to produce an acceptable photoemitter. We propose to use two metrics in the evaluation of the plasma cleaning process as an acceptable cleaning method for metallic photocathodes, Quantum Efficiency versus Wavelength and Surface roughness: Ra and Rpp represent the Average Roughness and Peak to Peak Roughness parameters, respectively.  
TPPE063 Improved Electron Yield and Spin-Polarization from III-V Photocathodes Via Bias Enhanced Carrier Drift 3603
 
  • G.A. Mulhollan, J.C.B. Bierman
    Saxet, Austin, Texas
  • A. Brachmann, J.E. Clendenin, E.G. Garwin, R.E. Kirby, D.-A.L. Luh, T.V.M. Maruyama
    SLAC, Menlo Park, California
  • R.X.P. Prepost
    UW-Madison/PD, Madison, Wisconsin
 
  Funding: Work at Saxet Surface Science, SLAC and the University of Wisconson is supported by the following U.S. DOE grants respectively: DE-FG02-04ER86231, DE-AC02-76SF00515 and DE-AC02-76ER00881.

Spin-polarized electrons are commonly used in high energy physics. Future work will benefit from greater polarization. Polarizations approaching 90% have been achieved at the expense of yield. The primary paths to higher polarization are material design and electron transport. Our work addresses the latter. Photoexcited electrons may be preferentially emitted or suppressed by an electric field applied across the active region. We are tuning this forward bias for maximum polarization and yield, together with other parameters, e.g., doping profile Preliminary measurements have been carried out on bulk GaAs. As expected, the yield change far from the bandgap is quite large. The bias is applied to the bottom (non-activated) side of the cathode so that the accelerating potential as measured with respect to the ground potential chamber walls is unchanged for different front-to-back cathode bias values. For a bias which enhances emission, the yield nearly doubles. For a bias which diminishes emission, the yield is approximately one half of the zero bias case. The size of the bias to cause an appreciable effect is rather small reflecting the low drift kinetic energy in the zero bias case.

 
WPAP058 The ILC Polarized Electron Source 3420
 
  • A. Brachmann, J.E. Clendenin, E.G. Garwin, R.E. Kirby, D.-A.L. Luh, T.V.M. Maruyama, D.C. Schultz, J. Sheppard
    SLAC, Menlo Park, California
  • R.X.P. Prepost
    UW-Madison/PD, Madison, Wisconsin
 
  Funding: This work is supported by U.S. DOE contracts DE-AC02-76SF00515 (SLAC) and DE-AC02-76ER00881 (UW).

The SLC polarized electron source (PES) can meet the expected requirements of the International Linear Collider (ILC) for polarization, charge and lifetime. However, experience with newer and successful PES designs at JLAB, Mainz and elsewhere can be incorporated into a first-generation ILC source that will emphasize reliability and stability without compromising the photocathode performance. The long pulse train for the ILC may introduce new challenges for the PES, and in addition more reliable and stable operation of the PES may be achievable if appropriate R&D is carried out for higher voltage operation and for a simpler load-lock system. The outline of the R&D program currently taking shape at SLAC and elsewhere is discussed. The principal components of the proposed ILC PES, including the laser system necessary for operational tests, are described.

 
ROAC004 High Gradient Performance of NLC/GLC X-Band Accelerating Structures 372
 
  • S. Doebert, C. Adolphsen, G.B. Bowden, D.L. Burke, J. Chan, V.A. Dolgashev, J.C. Frisch, R.K. Jobe, R.M. Jones, R.E. Kirby, J.R. Lewandowski, Z. Li, D.J. McCormick, R.H. Miller, C.D. Nantista, J. Nelson, C. Pearson, M.C. Ross, D.C. Schultz, T.J. Smith, S.G. Tantawi, J.W. Wang
    SLAC, Menlo Park, California
  • T.T. Arkan, C. Boffo, H. Carter, I.G. Gonin, T.K. Khabiboulline, S.C. Mishra, G. Romanov, N. Solyak
    Fermilab, Batavia, Illinois
  • Y. Funahashi, H. Hayano, N. Higashi, Y. Higashi, T. Higo, H. Kawamata, T. Kume, Y. Morozumi, K. Takata, T. T. Takatomi, N. Toge, K. Ueno, Y. Watanabe
    KEK, Ibaraki
 
  Funding: Work Supported by DOE Contract DE-AC02-76F00515.

During the past five years, there has been an concerted effort at FNAL, KEK and SLAC to develop accelerator structures that meet the high gradient performance requirements for the Next Linear Collider (NLC) and Global Linear Collider (GLC) initiatives. The structure that resulted is a 60-cm-long, traveling-wave design with low group velocity (< 4% c) and a 150 degree phase advance per cell. It has an average iris size that produces an acceptable short-range wakefield in the linacs, and dipole mode damping and detuning that adequately suppresses the long-range wakefield. More than eight such structures have operated over 1000 hours at a 60 Hz pulse rate at the design gradient (65 MV/m) and pulse length (400 ns), and have reached breakdown rate levels below the limit for the linear collider. Moreover, the structures are robust in that the breakdown rates continue to decrease over time, and if the structures are briefly exposed to air, the rates recover to their low values within a few days. This paper presents a final summary of the results from this program, which effectively ended last August with the selection of ‘cold’ technology for a next generation linear collider.

 
ROPB001 Suppressing Electron Cloud in Future Linear Colliders 24
 
  • M.T.F. Pivi, R.E. Kirby, T.O. Raubenheimer
    SLAC, Menlo Park, California
  • F. Le Pimpec
    PSI, Villigen
 
  Funding: Work supported by the U.S. DOE under contract DE-AC02- 76SF00515.

Any accelerator circulating positively charged beams can suffer from a build-up of an electron cloud in the beam pipe. The cloud develops through ionization of residual gases, synchrotron radiation and secondary electron emission and, when severe, can cause instability, emittance blow-up or loss of the circulating beam. The electron cloud is potentially a limiting effect for both the Large Hadron Collider (LHC) and the International Linear Collider (ILC). For the ILC positron damping ring, the development of the electron cloud must be suppressed. This paper presents the various effects of the electron cloud and evaluates their significance. It also discusses the state-of-the-art of the ongoing international R&D program to study potential remedies to reduce the secondary electron yield to acceptably low levels.