Irradiation of Materials with Short, Intense Ion pulses at NDCX-II

TL;DR

This paper reviews the NDCX-II accelerator's ability to produce intense, short ion pulses for material experiments, demonstrating beam-driven melting and energy loss measurements with detailed simulations aiding optimization.

Contribution

It introduces the use of NDCX-II for generating nanosecond ion pulses with high fluence and discusses the neutralization and compression techniques crucial for achieving these conditions.

Findings

Successful generation of 10^11 ions pulses with 2-30 ns duration

Effective neutralization and compression techniques demonstrated

Simulations closely match experimental results for optimization

Abstract

We present an overview of the performance of the Neutralized Drift Compression Experiment-II (NDCX-II) accelerator at Berkeley Lab, and report on recent target experiments on beam driven melting and transmission ion energy loss measurements with nanosecond and millimeter-scale ion beam pulses and thin tin foils. Bunches with around 10^11 ions, 1-mm radius, and 2-30 ns FWHM duration have been created with corresponding fluences in the range of 0.1 to 0.7 J/cm^2. To achieve these short pulse durations and mm-scale focal spot radii, the 1.1 MeV He+ ion beam is neutralized in a drift compression section, which removes the space charge defocusing effect during final compression and focusing. The beam space charge and drift compression techniques resemble necessary beam conditions and manipulations in heavy ion inertial fusion accelerators. Quantitative comparison of detailed particle-in-cell simulations with the experiment play an important role in optimizing accelerator performance.