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Nielsen, K.

Paper Title Page
ROAB001 DARHT-II Long-Pulse Beam-Dynamics Experiments 19
 
  • C. Ekdahl, E.O. Abeyta, R. Bartsch, L. Caudill, K.-C.D. Chan, D. Dalmas, S. Eversole, R.J. Gallegos, J. Harrison, M. Holzscheiter, E. Jacquez, J. Johnson, B.T. McCuistian, N. Montoya, S. Nath, K. Nielsen, D. Oro, L. Rodriguez, P. Rodriguez, L.J. Rowton, M. Sanchez, R. Scarpetti, M. Schauer, D. Simmons, H.V. Smith, J. Studebaker, G. Sullivan, C. Swinney, R. Temple
    LANL, Los Alamos, New Mexico
  • H. Bender, W. Broste, C. Carlson, G. Durtschi, D. Frayer, D. Johnson, K. Jones, A. Meidinger, K.J. Moy, R. Sturgess, A. Tipton, C.-Y. Tom
    Bechtel Nevada, Los Alamos, New Mexico
  • R.J. Briggs
    SAIC, Alamo, California
  • Y.-J. Chen, T.L. Houck
    LLNL, Livermore, California
  • S. Eylon, W.M. Fawley, E. Henestroza, S. Yu
    LBNL, Berkeley, California
  • T.P. Hughes, C. Mostrom, Y. Tang
    ATK-MR, Albuquerque, New Mexico
  • M.E. Schulze
    GA, San Diego, California
  
  Funding: This work was supported by the U.S. National Nuclear Security Agency and the U.S. Department of Energy under contract W-7405-ENG-36.

When completed, the DARHT-II linear induction accelerator (LIA) will produce a 2-kA, 18-MeV electron beam with more than 1500-ns current/energy "flat-top." In initial tests DARHT-II has already accelerated beams with current pulse lengths from 500-ns to 1200-ns full-width at half maximum (FWHM) with more than1.2-kA, 12.5-MeV peak current and energy. Experiments are now underway with a ~2000-ns pulse length, but reduced current and energy. These pulse lengths are all significantly longer than any other multi-MeV LIA, and they define a novel regime for high-current beam dynamics, especially with regard to beam stability. Although the initial tests demonstrated absence of BBU, the pulse lengths were too short to test the predicted protection against ion-hose instability. The present experiments are designed to resolve these and other beam-dynamics issues with a ~2000-ns pulse length beam.

 
FOAA002 Technological Improvements in the DARHT II Accelerator Cells 169
 
  • B.A. Prichard, R.J. Briggs
    SAIC, Alamo, California
  • J. Barraza, M. Kang, K. Nielsen
    LANL, Los Alamos, New Mexico
  • F.M. Bieniosek, K. Chow, W.M. Fawley, E. Henestroza, L. R. Reginato, W. Waldron
    LBNL, Berkeley, California
  • T.E. Genoni, T.P. Hughes
    ATK-MR, Albuquerque, New Mexico
  
  Funding: This work was supported by the U.S. National Nuclear Security Agency and the U.S. Department of Energy under contract W-7405-ENG-36.

DARHT employs two perpendicular electron Linear Induction Accelerators to produce intense, bremsstrahlung x-ray pulses for flash radiography. The second axis, DARHT II, features an 18 MeV, 2-kA, 2-microsecond accelerator. DARHT II accelerator cells have undergone a series of test and modeling efforts to fully understand their sub par performance. These R&D efforts have led to a better understanding of Linear Induction Accelerator physics for the unique DARHT II design. Specific improvements have been identified and tested. Improvements in the cell oil region, the cell vacuum region, and the PFNs have been implemented in the prototype units that have doubled the cell’s performance. A series of prototype acceptance test are underway on a number of prototype units to demonstrate that the required cell lifetime is met at the improved performance levels. Early acceptance tests indicate that the lifetime requirements are being exceeded. The shortcomings of the previous design are summarized. The improvements to the original design, their resultant improvement in performance, and various test results are included. The final acceptance test results will also be included.