Short-Pulse, Compressed Ion Beams at the Neutralized Drift Compression Experiment

TL;DR

This paper reports on the development and initial experiments of short, intense ion beams at NDCX-II, focusing on beam compression, focusing techniques, and potential applications in material science and fusion research.

Contribution

Introduction of a novel short-pulse ion beam system with advanced neutralization and focusing methods for high-energy-density physics experiments.

Findings

Successful generation of 1.2 MeV ion beams with 2.5 ns pulse duration.

Implementation of plasma-based helium ion source with higher charge delivery.

Potential to study radiation damage and metastable material phases.

Abstract

We have commenced experiments with intense short pulses of ion beams on the Neutralized Drift Compression Experiment (NDCX-II) at Lawrence Berkeley National Laboratory, with 1-mm beam spot size within 2.5 ns full-width at half maximum. The ion kinetic energy is 1.2 MeV. To enable the short pulse duration and mm-scale focal spot radius, the beam is neutralized in a 1.5-meter-long drift compression section following the last accelerator cell. A short-focal-length solenoid focuses the beam in the presence of the volumetric plasma that is near the target. In the accelerator, the line-charge density increases due to the velocity ramp imparted on the beam bunch. The scientific topics to be explored are warm dense matter, the dynamics of radiation damage in materials, and intense beam and beam-plasma physics including select topics of relevance to the development of heavy-ion drivers for inertial fusion energy. Below the transition to melting, the short beam pulses offer an opportunity to study the multi-scale dynamics of radiation-induced damage in materials with pump-probe experiments, and to stabilize novel metastable phases of materials when short-pulse heating is followed by rapid quenching. First experiments used a lithium ion source; a new plasma-based helium ion source shows much greater charge delivered to the target.