• I. Kaganovich, R.C. Davidson, M. Dorf, A.B. Sefkow, E. Startsev
  PPPL, Princeton, New Jersey
• J.J. Barnard
  LLNL, Livermore, California
• A. Friedman, E. P. Lee, S.M. Lidia, B.G. Logan, P.K. Roy, P.A. Seidl
  LBNL, Berkeley, California
• D.R. Welch
  Voss Scientific, Albuquerque, New Mexico

Funding: Research supported by the US Department of Energy.

Neutralized drift compression offers an effective means for particle beam focusing and current amplification. In neutralized drift compression, a linear radial and longitudinal velocity drift is applied to a beam pulse, so that the beam pulse compresses as it drifts in the focusing section. The beam intensity can increase more than a factor of 100 in both the radial and longitudinal directions, totaling to more than a 10,000 times increase in the beam density during this process. The optimal configuration of focusing elements to mitigate the time-dependent focal plane is discussed in this paper. The self-electric and self-magnetic fields can prevent tight ballistic focusing and have to be neutralized by supplying neutralizing electrons. This paper presents a survey of the present numerical modeling techniques and theoretical understanding of plasma neutralization of intense particle beams. Investigations of intense beam pulse interaction with a background plasma have identified the operating regimes for stable and neutralized propagation of intense charged particle beams.

Slides

• P.A. Seidl, A. Anders, F.M. Bieniosek, J.E. Coleman, J.-Y. Jung, M. Leitner, S.M. Lidia, B.G. Logan, P.N. Ni, D. Ogata, P.K. Roy, W.L. Waldron
  LBNL, Berkeley, California
• J.J. Barnard, R.H. Cohen, D.P. Grote
  LLNL, Livermore, California
• M. Dorf, E.P. Gilson
  PPPL, Princeton, New Jersey
• D.R. Welch
  Voss Scientific, Albuquerque, New Mexico

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 Neutralized Drift Compression Experiment (NDCX) with controlled ramps and forced neutralization. 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 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 NDCX to reach the necessary higher beam intensities, including:

1. greater axial compression via a longer velocity ramp;
2. beam steering dipoles to mitigate aberrations in the bunching module;
3. time-dependent focusing elements to correct considerable chromatic aberrations; and
4. plasma injection improvements to establish a plasma density always greater than the beam density, expected to be >10¹³ cm^-3.

Slides