Recent Experiments at NDCX-II: Irradiation of Materials Using Short, Intense Ion Beams

Abstract

Author(s): Seidl, PA; Ji, Q; Persaud, A; Feinberg, E; Ludewigt, B; Silverman, M; Sulyman, A; Waldron, WL; Schenkel, T; Barnard, JJ; Friedman, A; Grote, DP; Gilson, EP; Kaganovich, ID; Stepanov, A; Treffert, F; Zimmer, M | Abstract: We present an overview of the performance of the Neutralized Drift Compression Experiment-II (NDCX-II) accelerator at Berkeley Lab, and summarize recent studies of material properties created with nanosecond and millimeter-scale ion beam pulses. The scientific topics being explored include the dynamics of ion induced damage in materials, materials synthesis far from equilibrium, warm dense matter and intense beam-plasma physics. We summarize the improved accelerator performance, diagnostics and results of beam-induced irradiation of thin samples of, e.g., tin and silicon. Bunches with over 3x10^10 ions, 1- mm radius, and 2-30 ns FWHM duration have been created. To achieve these short pulse durations and mm-scale focal spot radii, the 1.2 MeV He+ ion beam is neutralized in a drift compression section which removes the space charge defocusing effect during final compression and focusing. Quantitative comparison of detailed particle-in-cell simulations with the experiment play an important role in optimizing accelerator performance; these keep pace with the accelerator repetition rate of ~1/minute.