Differential ablator-fuel adiabat tuning in indirect-drive implosions.

ABSTRACT

We propose a design adjustment to the high foot laser pulse [T. R. Dittrich et al., Phys. Rev. Lett. 112, 055002 (2014)] that is predicted to lower the fuel adiabat, increase compression and neutron production, but maintain similar ablation front growth. This is accomplished by lowering the laser power between the first and the second pulses (the "trough") so that the first shock remains strong initially but decays as it transits the ablator and enters the capsule fuel in a process similar to direct-drive "adiabat shaping" [S. E. Bodner et al., Phys. Plasmas 7, 2298 (2000)]. Integrated hohlraum simulations show that hohlraum cooling is sufficient to launch decaying shocks with adequate symmetry control, suggesting that adiabat shaping may be possible with indirect-drive implosions. Initial experiments show the efficacy of this technique.