Author: Wang, E.
Paper Title Page
MOP156 Status of the Polarized SRF Photocathode Gun Design 385
 
  • J.H. Park, H. Bluem, M.D. Cole, D. Holmes, T. Schultheiss, A.M.M. Todd
    AES, Princeton, New Jersey, USA
  • I. Ben-Zvi, J. Kewisch, E. Wang
    BNL, Upton, Long Island, New York, USA
 
  Funding: This work was supported by the U.S. Department of Energy, under Contract No. DE-FG02-06ER84450.
A polarized SRF photocathode gun is being considered as a high-brightness electron injector for the International Linear Collider (ILC). The conceptual engineering analysis and design of this injector, which is required to deliver a large emittance ratio, is presented. The delivered beam parameters we predict are compared to the required performance after the ILC damping ring. The analysis indicates that it may be possible to save cost by eliminating the damping ring though higher values of the emittance ratio are still to be demonstrated.
 
 
MOP157 Testing a GAAS Cathode in SRF Gun 388
 
  • E. Wang, I. Ben-Zvi, A. Burrill, J. Kewisch, T. Rao, Q. Wu
    BNL, Upton, Long Island, New York, USA
  • D. Holmes
    AES, Medford, NY, USA
 
  Funding: Work supported by Brookhaven science Associates, LLC Contract No.DE-AC02-98CH10886 with the U.S.DOE
RF electron guns with a strained superlattice GaAs cathode are expected to generate polarized electron beams of higher brightness and lower emittance than do DC guns, due to their higher field gradient at the cathode’s surface and lower cathode temperature. We plan to install a bulk GaAs:Cs in a SRF gun to evaluate the performance of both the gun and the cathode in this environment. The status of this project is: In our 1.3 GHz 1⁄2 cell SRF gun, the vacuum can be maintained at nearly 10-12 Torr because of cryo-pumping at 2K. With conventional activation of bulk GaAs, we obtained a QE of 10% at 532 nm, with lifetime of more than 3 days in the preparation chamber and have shown that it can survive in transport from the preparation chamber to the gun. The beam line has been assembled and we are exploring the best conditions for baking the cathode under vacuum. We report here the progress of our test of the GaAs cathode in the SRF gun.
 
 
WEP161 Modeling and Simulations of Electron Emission from Diamond-Amplified Cathodes 1791
 
  • D.A. Dimitrov, R. Busby, J.R. Cary, D.N. Smithe
    Tech-X, Boulder, Colorado, USA
  • I. Ben-Zvi, X. Chang, T. Rao, J. Smedley, E. Wang, Q. Wu
    BNL, Upton, Long Island, New York, USA
 
  Funding: This work is supported by the U. S. Department of Energy under the DE-SC0004431 grant.
Emission of electrons from a diamond-amplified cathode was recently demonstrated*. This experiment was based on a promising new concept** for generation of high-current, high-brightness, and low thermal emittance electron beams. The measurements from transmission and emission experiments have shown the potential to realize the diamond-amplified cathode concept. However, the results indicate that the involved physical properties should be understood in greater detail to build diamond cathodes with optical properties. We have already made progress in understanding the secondary electron generation and charge transport in diamond with the models we implemented in the VORPAL computational framework. We have been implementing models for electron emission from diamond and will present results from 3D VORPAL simulations with the integrated capabilities on generating electrons and holes, initiated by energetic primary electrons, propagation of the charge clouds, and then the emission of electrons into diamond. We will discuss simulation results on the dependence of the electron emission on diamond surface properties.
* X. Chang et al., Electron Beam Emission from a Diamond-Amplified Cathodes, to appear in Phys. Rev. Lett. (2010).
** I. Ben-Zvi et al., Secondary emission enhanced photoinjector, Rep. C-A/AP/149, BNL (2004).
 
 
MOP155 Progress on Diamond Amplified Photo Cathode 382
 
  • E. Wang
    PKU/IHIP, Beijing, People's Republic of China
  • I. Ben-Zvi, X. Chang, J. Kewisch, E.M. Muller, T. Rao, J. Smedley, Q. Wu
    BNL, Upton, Long Island, New York, USA
  • T. Xin
    Stony Brook University, Stony Brook, USA
 
  Funding: Work supported by Brookhaven science Associates, LLC Contract No.DE-AC02-98CH10886 with the U.S.DOE
Two years ago, we obtained an emission gain of 40 from the Diamond Amplifier Cathode (DAC) in our test system. In our current systematic study of hydrogenation, the highest gain we registered in emission scanning was 178. We proved that our treatments for improving the diamond amplifiers are reproducible. Upcoming tests planned include testing DAC in a RF cavity. Already, we have designed a system for these tests using our 112 MHz superconducting cavity, wherein we will measure DAC parameters, such as the limit, if any, on emission current density, the bunch charge, and the bunch length.
 
 
WEP263 A Multiple Cathode Gun Design for the eRHIC Polarized Electron Source 1969
 
  • X. Chang, I. Ben-Zvi, J. Kewisch, V. Litvinenko, A.I. Pikin, V. Ptitsyn, T. Rao, B. Sheehy, J. Skaritka, Q. Wu
    BNL, Upton, Long Island, New York, USA
  • E. Wang
    PKU/IHIP, Beijing, People's Republic of China
  • T. Xin
    Stony Brook University, Stony Brook, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The future electron-ion collider eRHIC requires a high average current (~50 mA), short bunch (~3 mm), low emittance (~20 μm) polarized electron source. The maximum average current of a polarized electron source so far is more than 1 mA, but much less than 50 mA, from a GaAs:Cs cathode [1]. One possible approach to overcome the average current limit and to achieve the required 50 mA beam for eRHIC, is to combine beamlets from multiple cathodes to one beam. In this paper, we present the feasibility studies of this technique.
 
 
THP046 Characterization of an SRF Gun: A 3D Full Wave Simulation 2205
 
  • E. Wang
    PKU/IHIP, Beijing, People's Republic of China
  • I. Ben-Zvi
    BNL, Upton, Long Island, New York, USA
  • J. Wang
    CST of America, Wellesley Hills, Massachusetts, USA
 
  Funding: Work supported by Brookhaven science Associates, LLC Contract No.DE-AC02-98CH10886 with the U.S.DOE
We characterized a BNL 1.3GHz half-cell SRF gun is tested for GaAs photocathode. The gun already was simulated several years ago via two-dimensional (2D) numerical codes (i.e., Superfish and Parmela) with and without the beam. In this paper, we discuss our investigation of its characteristics using a three dimensional (3D) full-wave code (CST STUDIO SUITE™).The input/pickup couplers are sited symmetrically on the same side of the gun at an angle of 180⁰. In particular, the inner conductor of the pickup coupler is considerably shorter than that of the input coupler. We evaluated the cross-talk between the beam (trajectory) and the signal on the input coupler compared our findings with published results based on analytical models. The CST STUDIO SUITE™ also was used to predict the field within the cavity; particularly, a combination of transient/eigenmode solvers was employed to accurately construct the RF field for the particles, which also includes the effects of the couplers. Finally, we explored the beam’s dynamics with a particle in cell (PIC) simulation, validated the results and compare them with 2D code result.
 
 
TUP147 Rotating Dipole and Quadrupole Field for a Multiple Cathode System 1106
 
  • X. Chang, I. Ben-Zvi, J. Kewisch, V. Litvinenko, W. Meng, A.I. Pikin, V. Ptitsyn, T. Rao, B. Sheehy, J. Skaritka, Q. Wu
    BNL, Upton, Long Island, New York, USA
  • E. Wang
    PKU/IHIP, Beijing, People's Republic of China
  • T. Xin
    Stony Brook University, Stony Brook, USA
 
  A multiple cathode system has been designed to provide the high average current polarized electron bunches for the future electron-ion collider eRHIC. One of the key research topics in this design is the technique to generate a combined dipole and quadrupole rotating field at high frequency (700 kHz). This type of field is necessary for combining bunches from different cathodes to the same axis with minimum emittance growth. Our simulations and the prototype test results to achieve this will be presented.