Shock Timing and Yield Sensitivity Studies for NIF Ignition Capsules

A cryogenic, β-layered NIF ignition capsule with a beryllium ablator that employs a BeO dopant (2% O) for opacity control is described. The design has an optimized yield of 12 MJ and uses a “reduced drive” hohlraum temperature pulse shape that peaks at ∼250 eV. Shock timing sensitivity calculations have been performed for this capsule design. Individual uncertainties of: 1) ∼200 ps in the timing of the foot pulse; 2) ∼5% in the x-ray flux of the foot pulse and first step; 3) ∼10% in the ablator EOS; or 4) ∼ 5 μm in the DT ice layer thickness each have a significant impact on thermonuclear yield. Combined uncertainties have greater impact than isolated, individual issues. For example, a combination of uncertainties of: 200 ps in the foot, 2 eV in the foot, and 5 μm in the DT thickness results in a calculation that produces only ∼1% of the original design yield. A second, more speculative, capsule concept utilizing a liquid DT ablator is also discussed. This design produces a 2 MJ yield in a 250 eV peak drive calculation.