Shock focusing in implosions of inertial fusion model targets

Abstract

Implosions of high-gain targets for inertial confinement fusion must be highly spherically symmetric for efficient ignition. Using a single relativistic electron beam at low power (∼0.3 TW) and cylindrical targets, we have experimentally shown that loading asymmetries generate strong implosion asymmetries, resulting in poor convergence ratios. By introducing a nonspherical variation in the shell radius and thickness (shimming), the implosion symmetry is radically improved at one time during the implosion. The effect is explained by a shock focusing mechanism whereby ultrahigh pressure—0.9 Tpa (9 Mbar) —is achieved on one side of the target.