BigFoot program and projections: the basics of indirect drive ICF*

We report a set of DT layered implosions used to test and quantify the experimental tradeoffs between velocity, coast, and adiabat at two physical scales. The laser power and energy were adjusted to maintain implosion symmetry at velocities from 330 to 430 um/ns, at adiabats 3 and 4, at a “coast time” from 700 ps to 2 ns (the time between peak radiation temperature in the hohlraum and capsule stagnation). For all tests the performance is found to be monotonic and consistent with simple theory, except in the case of adiabat. The highest adiabat configuration (4) resulted in the highest neutron yield to-date at the National Ignition Facility (NIF), and can be used to project the energy and power requirements for ignition [1].