Author: Shaw, J.L.
Paper Title Page
THP205 Modeling the Performance of a Diamond Current Amplifier for FELs 2507
 
  • K. L. Jensen, B. Pate, J.L. Shaw, J.E. Yater
    NRL, Washington, DC, USA
  • J.J. Petillo
    SAIC, Billerica, Massachusetts, USA
 
  Funding: We gratefully acknowledge funding by the Joint Technology Office and the Office of Naval Research.
A diamond current amplifier concept can reduce demands made of photocathodes under development for high performance Free Electron Lasers (FELs) by augmenting the charge per bunch (i.e., increasing the apparent QE of the photocathode) by employing secondary emission amplification in a diamond flake*. The characteristics of the bunch that emerges from the diamond flake is dependent on properties of the diamond (e.g., impurity concentrations) and the conditions under which it is operated (e.g., voltage drop, space charge, temperature)**. A study of the electron bunches produced by an incident 3-5 keV beam striking a very thin diamond and its transport under bias subject to scattering and space charge forces is considered. The quantities of greatest interest are then the yield, the transit time, emittance, and the rise/fall characteristics of the emerging bunch. These are simulated using Monte Carlo techniques, the application of which shall be described as it applies to the initial generation of the secondary electrons followed by their scattering and transport in the presence of band bending and space charge.
*J.E. Yater, et al., IEEE IVNC (2009); J. L. Shaw, et al., ibid.
**K.L. Jensen, et al. J. Appl. Phys. 108, 044509 (2010).
 
 
WEOBS3 The Effects of a Density Mismatch in a Two-State LWFA 1421
 
  • B.B. Pollock, F. Albert, C. Filip, D.H. Froula, S.H. Glenzer, J.E. Ralph
    LLNL, Livermore, California, USA
  • C.E. Clayton, C. Joshi, K.A. Marsh, J. Meinecke, A.E. Pak, J.L. Shaw
    UCLA, Los Angeles, California, USA
  • K.L. Herpoldt
    Oxford University, Physics Department, Oxford, Oxon, United Kingdom
  • G.R. Tynan
    UCSD, La Jolla, California, USA
 
  Funding: Work performed under U.S. DOE Contract DE-AC52-07NA27344 and was partially funded by the Laboratory Directed Research and Development Program under project tracking code 06-ERD-056.
A two-stage Laser Wakefield Accelerator (LWFA) has been developed, which utilizes the ionization induced injection mechanism to produce high energy, narrow energy spread electron beams when the electron density is equal in both stages. However, when the densities are not equal these high quality beams are not observed. As the electron density varies across the interface between the adjacent stages the size of the ion cavity is expected to change; this results in either a reduction of the peak electron energy (for a density decrease), or in the exclusion of previously trapped charge from the first wake period (for a density increase). The latter case can be overcome if the interaction length before the density interface exceeds a threshold determined by the densities in each stage, and may provide a mechanism for enhanced energy gain.