Recent Experiments At Ndcx-II: Irradiation Of Materials Using Short, Intense Ion Beams

TL;DR

This paper reviews the NDCX-II accelerator's recent performance and experiments using intense, short ion beams to study material damage, synthesis, and plasma physics, highlighting improved capabilities and experimental results.

Contribution

It reports advancements in accelerator performance, diagnostics, and experimental techniques for irradiating materials with nanosecond ion pulses, enabling new scientific investigations.

Findings

Achieved ion bunches with over 3x10^10 ions and 2-30 ns pulse duration.

Demonstrated effective neutralization and focusing of ion beams for precise irradiation.

Validated particle-in-cell simulations against experimental data for accelerator optimization.

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.