Room-temperature, ignition-scale hohlraum experiments on NIF

We have fielded six shots (symmetry capsules and convergent ablators) to develop a room-temperature (``warm'') ignition-scale platform. These have lower cost than cryogenic (\textless~30 K) shots, and allow higher-Z hohlraum and capsule fill gases. Compared to the cryo He hohlraum fill, the warm neopentane fill (C$_{5}$H$_{12})$ produces comparable x-ray drive, but requires less cross-beam energy transfer to achieve a round implosion ``hot spot.'' The higher Z results in a hotter plasma, which appears to reduce Raman scattering from the inner beams. Warm shots also have more outer-beam Brillouin scattering. In-flight measurements of the shell show a positive P$_{4}$ Legendre mode (diamond shape) in both warm and cryo shots, consistent with predictions from the radiation-hydrodynamics code Hydra. The code also predicts a negative P$_{4}$ (square) hot spot shape for both warm and cryo shots, but only warm shots typically exhibit this. Improved Hydra modeling is being applied to the warm shots, including a self-consistent, inline package for energy transfer and backscatter. The warm capsule fill has been nominal or deuterated (C$_{3}$D$_{8})$ propane, giving \textgreater\ 2x10$^{11}$ neutrons. The hot spot is cooler in warm than in cryo shots (D-He$^{3}$ fill) due to increased radiation from hot-spot C.