Performance of direct-drive cryogenic targets on OMEGA

The success of direct-drive-ignition target designs depends on two issues: the ability to maintain the main fuel adiabat at a low level and the control of the nonuniformity growth during the implosion. A series of experiments was performed on the OMEGA Laser System [T. R. Boehly, D. L. Brown, R. S. Craxton et al., Opt. Commun. 133, 495 (1997)] to study the physics of low-adiabat, high-compression cryogenic fuel assembly. Modeling these experiments requires an accurate account for all sources of shell heating, including shock heating and suprathermal electron preheat. To increase calculation accuracy, a nonlocal heat-transport model was implemented in the 1D hydrocode. High-areal-density cryogenic fuel assembly with ρR>200 mg/cm² [T. C. Sangster, V. N. Goncharov, P. B. Radha et al., 'High-areal-density fuel assembly in direct-drive cryogenic implosions', Phys. Rev. Lett. (submitted)] has been achieved on OMEGA in designs where the shock timing was optimized using the nonlocal treatment of the heat conduction and the suprathermal-electron preheat generated by the two-plasmon-decay instability was mitigated