P.F. Peterson

An Updated Point Design for Heavy Ion Fusion

Abstract An updated, self-consistent point design for a heavy ion fusion (HIF) power plant based on an induction linac driver, indirect-drive targets, and a thick liquid wall chamber has been completed. Conservative parameters were selected to allow each design area to meet its functional requirements in a robust manner, and thus this design is referred to as the Robust Point Design (RPD-2002). This paper provides a top-level summary of the major characteristics and design parameters for the target, driver, final focus magnet layout and shielding, chamber, beam propagation to the target, and overall power plant.

Realistic modeling of chamber transport for heavy-ion fusion

Transport of intense heavy-ion beams to an inertial-fusion target after final focus is simulated here using a realistic computer model. It is found that passing the beam through a rarefied plasma layer before it enters the fusion chamber can largely neutralize the beam space charge and lead to a usable focal spot for a range of ion species and input conditions.

Chamber-transport simulation results for heavy-ion fusion drivers

The heavy-ion fusion community recently developed a power-plant design that meets the various requirements of accelerators, final focus, chamber transport and targets. The point design is intended to minimize physics risk and is certainly not optimal for the cost of electricity. Recent chamber-transport simulations, however, indicate that changes in the beam ion species, the convergence angle and the emittance might allow more-economical designs.

Chamber transport of "foot" pulses for heavy-ion fusion

Indirect-drive targets for heavy-ion fusion must initially be heated by “foot” pulses that precede the main heating pulses by tens of nanoseconds. These pulses typically have a lower energy and perveance than the main pulses, and the fusion-chamber environment is different from that seen by later pulses. The preliminary particle-in-cell simulations of foot pulses here examine the sensitivity of the beam focusing to ion–beam perveance, background-gas density, and pre-neutralization by a plasma near the chamber entry port.

X-Ray Ablation and Debris Venting for the HIF Point Design

Abstract This paper presents detailed design and analysis for x-ray ablation and venting in the 120-beam, 7-MJ heavy-ion fusion (HIF) “robust” point design. The HI Robust Point Design (“RPD-2002”) is a self-consistent, non-optimized system design that has been generated as a point of reference for ongoing research in the HIF program. The point design uses a thick-liquid protected chamber, derived from HYLIFE-II – no structural surfaces face the target. A ternary salt mixture called flinabe (LiNaBeF4) has been selected for the liquid structures. Detailed two-dimensional, axially symmetric TSUNAMI calculations have been performed to determine the mass of ablation debris generated by the target x-rays following ignition and to predict the venting of the debris from the inside of the pocket into the main chamber and beam lines. These calculations provide predictions of the impulse loading to the surfaces of the liquid pocket---The closest liquid structures will experience a somewhat strong impulse, but further optimization of the design will easily decrease this impulse. The integrated mass and energy fluxes of ablation and target debris reaching the beam-line magnetic shutters are given as well: A small and acceptable magnetic dipole will prevent any debris ingression up in the final focus magnet region.

Thick-Liquid Blanket Configuration and Response for the HIF Point Design

Abstract This paper describes the thick-liquid blanket system of the Robust Point Design (RPD-2002). RPD-2002 is the first self-consistent description of a heavy-ion fusion accelerator, final focus, target, magnet shielding, and thick-liquid blanket design. The 120 beams are delivered to the target from two sides, in 9x9 arrays, with 5.4° between rows giving a maximum beam angle from the target axis of 24°. The chamber employs thick-liquid protection, using liquid jets that have been demonstrated to have the required geometric precision in scaled water experiments. Other aspects of the chamber design, not directly related to the beam-line shielding, have been kept the same as the HYLIFE-II design.

Towards a Modular Point Design for Heavy Ion Fusion

Abstract We report on an ongoing study on modular Heavy Ion Fusion (HIF) drivers. The modular driver is characterized by ~20 nearly identical induction linacs, each carrying a single high current beam. In this scheme, one of the full size induction linacs can be tested as an “integrated Research Experiment” (IRE). Hence this approach offers significant advantages in terms of driver development path. For beam transport, these modules use solenoids, which are capable of carrying high line charge densities, even at low energies. A new injector concept allows compression of the beam to high line densities right after the source. The final drift compression is performed in a plasma in which the large repulsive space charge effects are neutralized. Finally, the beam is transversely compressed onto the target, using either external solenoids or current-carrying channels (in the assisted pinch mode of beam propagation). We report on progress towards a self-consistent point design from injector to target. Considerations of driver architecture, chamber environment as well as the methodology for meeting target requirements of spot size, pulse shape and symmetry are also described. Finally, some near-term experiments to address the key scientific issues are discussed.

IFE Chamber Technology - Status and Future Challenges

ABSTRACT Significant progress has been made on addressing critical issues for inertial fusion energy (IFE) chambers for heavy-ion, laser and Z-pinch drivers. A variety of chamber concepts are being investigated including drywall (currently favored for laser IFE), wetted-wall (applicable to both laser and ion drivers), and thick-liquid-wall (favored by heavy ion and z-pinch drivers). Recent progress and remaining challenges in developing IFE chambers are reviewed.

Visual TSUNAMI: A Versatile, User-Friendly, Multidimensional Ablation and Gas-Dynamics Design Code

Abstract Gas dynamics phenomena in thick-liquid protected inertial fusion target chambers have been explored since the early 1990’s with the help of a series of simulation codes known as TSUNAMI. The code has been recently redesigned entirely to make use of modern programming techniques, languages and software; improve its user-friendliness; and refine its ability to model thick-liquid protected chambers, while expanding its capability to a larger variety of systems. The new code is named “Visual Tsunami” to emphasize the programming language of its core, Fortran 95, as well as its graphics-based input file builder and output processors. It is aimed at providing a user-friendly design tool for complex systems for which transient gas dynamics phenomena play a key role.

Nonsinusoidal Nozzle Oscillation Functions for Generating Thick-Liquid Pockets for Heavy-Ion Fusion Chambers

Abstract Oscillating thick-liquid jets have been proposed to create pockets to provide neutron shielding and droplet clearing at high repetition rate for heavy-ion inertial fusion energy. A procedure is introduced to compute nonsinusoidal nozzle oscillation functions based on the desired pocket geometry at the time of target ignition. The primary goals for creating optimum pocket geometries are discussed, such as complete pocket closing at time of target ignition, avoidance of liquid-liquid collisions that could lead to jetting into the target region, maintenance of a uniform void distribution to avoid the propagation of strong shocks toward the injection nozzles, and consideration of mechanical limitations on the maximum nozzle acceleration. The equation of motion for a horizontally translating nozzle is derived that generates the desired pocket shape. Numerical results are compared to a sinusoidal oscillation function. The same procedure had been applied to a rotating nozzle.