Speaker
Enrique Henestroza
Description
E. Henestroza and B.G. Logan
Lawrence Berkeley National Laboratory, Berkeley, California, 94720, USA
A new inertial-fusion target configuration, the X-target, using one-sided axial illumination has been explored [1]. This class of target uses annular and solid-profile heavy ion beams to compress and ignite deuterium-tritium (DT) fuel that fills the interior of metal cases that have side-view cross sections in the shape of an “X”. X-targets that incorporate inside the case a propellant (plastic) and a pusher (aluminum) surrounding the DT fuel are capable of assembling higher fuel areal densities ~2 g/cm2 using two MJ-scale annular beams to implode quasi-spherically the target to peak DT densities ~100 g/cm3. A 3MJ fast-ignition solid ion beam heats the high-density fuel to thermonuclear temperatures in ~200 ps to start the burn propagation, obtaining gains of ~300. These targets have been modeled using the radiation-hydrodynamics code HYDRA [2] in two- and three- dimensions to study the properties of the implosion as well as the ignition and burn propagation phases. The main concern for the X-target is the amount of high-Z atomic mixing at the ignition zone produced by hydro-instabilities, which, if large enough, could cool the fuel during the ignition process and prevent the propagation of the fusion burn. At typical Eulerian mesh resolutions of a few microns, the aluminum-DT interface shows negligible Rayleigh–Taylor (RT) and Richtmyer–Meshkov (RM) instability growth; also, the shear flow of the DT fuel as it slides along the metal X-target walls, which drives the Rayleigh–Taylor (RT) and Kelvin Helmholtz (KH) instabilities, does not have a major effect on the burning rate. An analytic estimate of the RT instability process at the Al-DT interface shows that the aluminum spikes generated during the pusher deceleration phase would not reach the ignition zone in time to affect the burning process. Also, preliminary HYDRA calculations, using a higher resolution mesh to study the shear flow of the DT fuel along the X-target walls, indicate that metal-mixed fuel produced near the walls would not be transferred to the DT ignition zone (maximum ρR) located at the vertex of the X-target. These preliminary studies need to be extended by further hydrodynamic calculations using finer resolution, complemented with turbulent mix modeling and validated by experiments, to ascertain the stability of the X-target design.
[1] E. Henestroza and B. G. Logan, Phys. Plasmas 19, 072706 (2012).
[2] M. M. Marinak et al., Phys. Plasmas 8, 2275 (2001)
This work was performed under the support of the U.S. Department of Energy by the Lawrence Berkeley National Laboratory under Contract No. DE-AC02-05CH11231.
Primary author
Enrique Henestroza
