Heavy Ion Beam Inertial Confinement Research Articles

Study on target structure for direct–indirect hybrid implosion mode in heavy ion inertial fusion

The key issues in heavy ion beam (HIB) inertial confinement fusion (ICF) include particle accelerator, physics of intense beam, beam final transport, target-plasma hydrodynamics, etc. In this paper, we focus on fuel implosion. In order to realize an effective implosion, beam illumination non-uniformity on a fuel target must be suppressed less than a few percent. In this study a direct–indirect hybrid implosion mode is discussed in heavy ion beam inertial confinement fusion (HIF) in order to release sufficient fusion energy in a robust manner. In the direct–indirect hybrid mode target, a low-density foam layer is inserted, and the radiation energy is confined in the foam layer. In the foam layer, the radiation transport is expected to smoothen the HIB illumination non-uniformity in the lateral direction. In this paper, we study the influences of the foam thickness and the inner radiation-shield Al density on implosion uniformity. Two-dimensional fluid simulations demonstrate that the hybrid target contributes to the HIB non-uniformity smoothing and releases a sufficient fusion energy output in HIF.

Cross Sections for Charge Exchange and Ionization of High-Energy Ions in Noble Gases

Interactions of charge exchange and ionization of fast, low-charged heavy ions are very important in heavy ion beam inertial confinement fusion. These effects are crucial indetermination of the final focusing in the chamber. However, corresponding cross section data is very limited and/or not accurate over the entire range of energies and ions of interest. This paper reports on our recent studies of cross sections for interactions of heavy ions with noble gases. Since a quantum mechanical treatment encounters a complex many-body problem, a classical trajectory Monte Carlo method is employed. The distribution of inner electrons is estimated by a modified Hartree-Fock model for the purpose of decreasing the number of electron orbits calculated, a micro-canonical ensemble for the initial electron probability distribution is introduced to describe quantum mechanical uncertainty. Cross sections are evaluated over a limited energy range; then scaling laws are developed to reflect the change probability for the beam charge state over a larger energy range.

Three-dimensional study of radiation symmetrization in some indirectly driven heavy ion ICF targets

Symmetrization of the radiation field inside hohlraum targets for indirectly driven heavy ion beam inertial confinement fusion (ICF) is investigated numerically. The targets considered consist of a casing, enclosing the spherical fuel capsule, and a few cylindrical radiators, schematically representing ion beam irradiated converters. Radiation absorption and re-emission are dealt with as in the paper by Murakami and Meyer-ter-Vehn (Nucl. Fusion 31 (1991) 1333), but with the geometry extended to three dimensions and with the finite size of the radiators taken into account. It is found that, for a practical casing to capsule area ratio (of the order of ten) and practical converter aspect ratios, two converters (allowing for two-side axisymmetric irradiation) cannot provide the uniformity required for ICF. However, with a spherical casing with six converters (placed in couples along the axes of a Cartesian co-ordinate system) it would be possible to illuminate a capsule with a non-uniformity well below 2%, which could satisfy the ICF requirements. The effects of changing the area ratio, the size and position of the converters and the geometry of the hohlraum are also discussed