Abstract and subjects
This Letter reports on a series of high-adiabat implosions of cryogenic layered deuterium-tritium (DT) capsules indirectly driven by a "high-foot" laser drive pulse at the National Ignition Facility. High-foot implosions have high ablation velocities and large density gradient scale lengths and are more resistant to ablation-front Rayleigh-Taylor instability induced mixing of ablator material into the DT hot spot. Indeed, the observed hot spot mix in these implosions was low and the measured neutron yields were typically 50% (or higher) of the yields predicted by simulation. On one high performing shot (N130812), 1.7 MJ of laser energy at a peak power of 350 TW was used to obtain a peak hohlraum radiation temperature of similar to 300 eV. The resulting experimental neutron yield was (2.4 +/- 0.05) x 10(15) DT, the fuel rho R was (0.86 +/- 0.063) g/cm(2), and the measured T-ion was (4.2 +/- 0.16) keV, corresponding to 8 kJ of fusion yield, with similar to 1/3 of the yield caused by self-heating of the fuel by a particles emitted in the initial reactions. The generalized Lawson criteria, an ignition metric, was 0.43 and the neutron yield was similar to 70% of the value predicted by simulations that include alpha-particle self-heating.