Beam dynamics of the Neutralized Drift Compression Experiment-II, a novel pulse-compressing ion accelerator

Abstract

Intense beams of heavy ions are well suited for heating matter to regimes of emerging interest. A new facility, NDCX-II, will enable studies of warm dense matter at ϳ1 eV and near-solid density, and of heavy-ion inertial fusion target physics relevant to electric power production. For these applications the beam must deposit its energy rapidly, before the target can expand significantly. To form such pulses, ion beams are temporally compressed in neutralizing plasma; current amplification factors of ϳ50-100 are routinely obtained on the Neutralized Drift Compression Experiment ͑NDCX͒ at the Lawrence Berkeley National Laboratory. In the NDCX-II physics design, an initial non-neutralized compression renders the pulse short enough that existing high-voltage pulsed power can be employed. This compression is first halted and then reversed by the beam's longitudinal space-charge field. Downstream induction cells provide acceleration and impose the head-to-tail velocity gradient that leads to the final neutralized compression onto the target. This paper describes the discrete-particle simulation models ͑one-, two-, and three-dimensional͒ employed and the space-charge-dominated beam dynamics being realized.

Nonlinear effects of beam-plasma instabilities on neutralized propagation of intense ion beams in background plasma

“…Similar simulations have also been carried out for parameters relevant to upcoming NDCX-II experiments [5]. In these simulations a singly-ionized lithium ion beam with velocity v b = c/30 propagates through a neutralizing singly-ionized background carbon plasma with density n p = 0.55 × 10 11 cm −3 .…”

Generalized Courant-Snyder Theory for Charged-Particle Dynamics in General Focusing Lattices

“…In realistic accelerators, there also exist bending magnets, torsion of the design orbit (fiducial orbit), and skew-quadrupole components introduced intentionally or by misalignment. In certain applications, such as the NDCX-II experiment [7], solenoidal magnets are also used. When these additional linear components are included, the transverse dynamics are coupled, and the dynamics of a charged particle relative to the fiducial orbit are governed by a general timedependent Hamiltonian [8] …”

Modeling warm dense matter experiments using the 3D ALE-AMR code and the move toward exascale computing

“…Figure 1 shows the layout of the NDCX-II facility. Extensive particle-in-cell computer simulation studies have enabled an attractive physics design that meets the stringent cost goal [1]. The blumleins (blue cylinders in the figure) can energize the ferrite cores in the induction cells with voltage pulses up to 250 kV for 70 ns.…”

“…The machine is an induction linac with custom voltage waveforms to control the longitudinal space charge forces and compress the pulse. Overall longitudinal compression factors of 500X are required to achieve a 1-ns pulse, but most of that compression occurs in the accelerator [1]. To be cost effective, NDCX-II reuses and modifies induction cores and cells and some of the pulsed power hardware from LLNL's decommissioned Advanced Test (electron) Accelerator (ATA).…”