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Coleman, J.E.

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MOP031 Estimates of Energy Fluence at the Focal Plane in Beams Undergoing Neutralized Drift Compression 133
  • J.J. Barnard
    LLNL, Livermore, California
  • J.E. Coleman, D. Ogata, P.A. Seidl
    LBNL, Berkeley, California
  • D.R. Welch
    Voss Scientific, Albuquerque, New Mexico

Funding: Work performed under the auspices of the U.S. Department of Energy under contract DE-AC52-07NA27344 at LLNL, and University of California contract DE-AC03-76SF00098 at LBNL.
We estimate the energy fluence (energy per unit area) at the focal plane of a beam undergoing neutralized drift compression and neutralized solenoidal final focus, as is being carried out in the Neutralized Drift Compression Experiment (NDCX) at LBNL. In these experiments, in order to reach high beam intensity, the beam is compressed longitudinally by ramping the beam velocity (i.e. introducing a velocity tilt) over the course of the pulse, and the beam is transversely focused in a high field solenoid just before the target. To remove the effects of space charge, the beam drifts in a plasma. The tilt introduces chromatic aberrations, with different slices of the original beam having different radii at the focal plane. The fluence can be calculated by summing the contribution from the various slices. We develop analytic formulae for the energy fluence for beams that have current profiles that are initially either constant or parabolic in time. We compare with envelope and particle-in-cell calculations. The expressions derived are useful for predicting how the fluence scales with accelerator and beam parameters.

TH203 Beam Compression in Heavy-Ion Induction Linacs 754
  • P.A. Seidl, A. Anders, F.M. Bieniosek, A.X. Chen, J.E. Coleman, J.-Y. Jung, M. Leitner, S.M. Lidia, B.G. Logan, P.N. Ni, P.K. Roy, K. Van den Bogert, W.L. Waldron
    LBNL, Berkeley, California
  • J.J. Barnard, R.H. Cohen, D.P. Grote
    LLNL, Livermore, California
  • J.A. Calanog
    UCB, Berkeley, California
  • M. Dorf, E.P. Gilson
    PPPL, Princeton, New Jersey
  • D.R. Welch
    Voss Scientific, Albuquerque, New Mexico

Funding: This work was supported by the Office of Fusion Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231, DE-AC52-07NA27344, DE-AC02-76CH3073.
The Heavy-Ion Fusion Sciences Virtual National Laboratory is pursuing an approach to target heating experiments in the Warm Dense Matter regime, using space-charge-dominated ion beams that are simultaneously longitudinally bunched and transversely focused. Longitudinal beam compression by large factors has been demonstrated in the LBNL Neutralized Drift Compression Experiment (NDCX) experiment with controlled ramps and forced neutralization. The achieved peak beam current and energy can be used in experiments that generate plasmas of warm dense matter. Using an injected 30 mA K+ ion beam with initial kinetic energy 0.3 MeV, axial compression leading to ~100X current amplification and simultaneous radial focusing to beam radii of a few mm have led to encouraging energy deposition approaching the intensities required for eV-range target heating experiments. We discuss the status of several improvements to the experiment and associated beam diagnostics that are under development to reach the necessary higher beam intensities.


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