Plasma are a source of unbound electrons for charge neutralizing intense heavy ion beams to focus them to a small spot size and compress their axial length. To produce long plasma columns, sources based upon ferroelectric ceramics with large dielectric coefficients have been developed. The source utilizes the ferroelectric ceramic BaTiO_3 to form metal plasma. The drift tube inner surface of the Neutralized Drift Compression Experiment (NDCX) is covered with ceramic material. High voltage (~;8kV) is applied between the drift tube and the front surface of the ceramics. A BaTiO_3 source comprised of five 20-cm-long sources has been tested and characterized, producing relatively uniform plasma in the 5x10^(10) cm^(-3) density range. The source has been integrated into the NDCX device for charge neutralization and beam compression experiments. Initial beam compression experiment yielded current compression ratios ~; 120. Recently, an additional 1 meter long source was fabricated to produce a 2 meter source for NDCX compression experiments. Present research is developing higher density sources to support beam compression experiments for high density physics applications.

The Neutralized Drift Compression Experiment-II (NDCX-II) is an induction linac that generates intense pulses of 1.2 MeV helium ions for heating matter to extreme conditions. Here, we present recent results on optimizing beam transport. The NDCX-II beamline includes a 1-m-long drift section downstream of the last transport solenoid, which is filled with charge-neutralizing plasma that enables rapid longitudinal compression of an intense ion beam against space-charge forces. The transport section on NDCX-II consists of 28 solenoids. Finding optimal field settings for a group of solenoids requires knowledge of the envelope parameters of the beam. Imaging the beam on the scintillator gives the radius of the beam, but the envelope angle is not measured directly. We demonstrate how the parameters of the beam envelope (radius, envelop angle, and emittance) can be reconstructed from a series of images taken by varying the B-field strengths of a solenoid upstream of the scintillator. We use this technique to evaluate emittance at several points in the NDCX-II beamline and for optimizing the trajectory of the beam at the entry of the plasma-filled drift section.

We have commenced experiments with intense short pulses of ion beams on the Neutralized Drift Compression Experiment-II at Lawrence Berkeley National Laboratory, by generating beam spots size with radius r<1 mm within 2 ns FWHM and approximately 10¹⁰ ions/pulse. To enable the short pulse durations and mm-scale focal spot radii, the 1.2 MeV Li⁺ ion beam is neutralized in a 1.6-meter drift compression section located after the last accelerator magnet. An 8-Tesla short focal length solenoid compresses the beam in the presence of the large volume plasma near the end of this section before the target. 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 selected topics of relevance to the development of heavy-ion drivers for inertial fusion energy. Here we describe the accelerator commissioning and time-resolved ionoluminescence measurements of yttrium aluminum perovskite using the fully integrated accelerator and neutralized drift compression components.

The most recent, and highly innovative, proposal for a next, integrated beam experiment in the U.S. Heavy Ion Fusion Virtual National Laboratory (HIF-VNL) is the Neutralized Drift Compression Experiment (NDCX). NDCX will develop novel, still unexplored beam manipulation techniques in order to establish the physics limits on compression of heavy ion beams for creating high energy density matter and fusion ignition conditions. As a major advance for the HIF-VNL, NDCX could also provide significant beam pulse energy on target (1011 J/m3). The main components of NDCX are discussed, in particular a new injector concept, the load-and-fire injector, and the neutralized drift compression section. NDCX will compress the beam within neutralizing plasma, therefore significantly extending the transportable beam current into high-intensity regimes not reachable in the absence of background plasma. To validate these essential components experimentally NDCX will be built in several phases, which are described in more detail.