• S.M. Lidia, E. P. Lee, D. Ogata, P.A. Seidl, W.L. Waldron
  LBNL, Berkeley, California
• S.M. Lund
  LLNL, Livermore, California

Funding: This work was supported by the Director, Office of Science, Office of Fusion Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

Longitudinally compressed ion beam pulses are currently employed in ion-beam based warm dense matter studies. Compression arises from an imposed time-dependent longitudinal velocity ramp followed by drift in a neutralized channel. Chromatic aberrations in the final focusing system arising from this chirp increase the attainable beam spot and reduce the effective fluence on target. We report recent work on fast correction optics that remove the time-dependent beam envelope divergence and minimizes the beam spot on target. We present models of the optical element design and predicted ion beam fluence, as well as benchtop measurements of pulsed waveforms and response.

• 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