Volume ignition targets for heavy-ion inertial fusion

Abstract

Inertial confinement fusion (ICF) targets can be imploded by heavy-ion beams (HIBs) in order to obtain a highly compressed fuel microsphere. The hydrodynamic efficiency of the compression can be optimized by tuning the ablation process in order to produce the total evaporation of the pusher material by the end of the implosion. Such pusherless compressions produce very highly compressed targets for relatively short confinement times. However, these times are long enough for a fusion burst to take place, and burnup fractions of 30% and higher can be obtained if the volume ignition requirements are met. Numerical simulations demonstrate that targets of 1-mg DT driven by a few MJ can yield energy gains of over 70. Although direct drive is used in these simulations, the main conclusions about volume ignition are also applicable to indirect drive.

Collective alpha particle stopping for reduction of the threshold for laser fusion using nonlinear force driven plasma blocks

“…This result of the much shorter stopping length of the reaction products in laser fusion was the reason of the strong reheats in laser irradiated fusion pellets for DT at fully detailed inclusion of the adiabatic expansion dynamics of the spherical plasmas leading to the discovery of the volume ignition (Hora & Ray, 1978;Hora et al, 2003;Hora, 2007). This was confirmed later by Kirkpatrick and Wheeler (1981)-where the cooperation with John A. Wheeler should be underlined-and numerous other authors (Tahir & Long, 1983;Tahir, 1986Tahir, , 1994Basko, 1990;Martinez-Val et al, 1994;Atzeni, 1995) where the robustness of volume ignition was underlined by Lackner et al (1994) against spark ignition (Lindl, 1994) with nearly the same fusion gains, and using the ideal and natural adiabatic hydrodynamics of the reacting DT plasma was shown that only this volume process arrived at the highest measured fusion gains (Hora et al, 1998.…”

Review about acceleration of plasma by nonlinear forces from picoseond laser pulses and block generated fusion flame in uncompressed fuel

“…The confidence to reach such neutron numbers may be estimated also from the alternative compression scheme of volume ignition (Hora & Ray, 1978), which scheme was confirmed (Kirkpatrick & Wheeler, 1981) by evaluation of the "Wheeler modes" and applied with inclusion of self-heating by the generated neutrons (He & Li, 1994;Martinez-Val et al, 1994), and clarified as a rather uncomplicated "robust" method (Lackner et al, 1994). It was rather surprising that the highest measured laser produced yields (Hora et al, 1998, see Fig.…”

Measured laser fusion gains reproduced by self-similar volume compression and volume ignition for NIF conditions

“…A very slightly higher energy results in a faster rise of the temperature and faster expansion, causing a lower net gain. This temperature effect in volume ignition was essential also in the following work of Kirkpatrick and Wheeler (1981), and was most significant when too-rapid heating of the ions left the electrons at lower temperatures, as seen by Martinez-Val et al (1994) and He and Li (1994). This temperature jump due to self-heating causes a self-produced strong addition of driver energy, added to that of the laser, and leads to high gains, comparable to that of spark ignition (see Sec.…”