Session CO1 - Compression and Burn.
ORAL session, Monday afternoon, November 15
Room 201/202, SCC
Observations of rad-hydro-burn simulations of high-gain direct-drive and NIF ignition targets show that the common wisdom of isobaric (constant pressure) conditions around stagnation is incorrect. In particular, at ignition: (a) hotspot and cold fuel are not in pressure equilibrium, (b) fusion alpha energy produced up to this time can exceed the PdV work from the stagnating shell, (c) the cold fuel partitions into a stagnated tamp mass and a still-ingoing unstagnated portion that contains a substantial fraction of the fuel mass [Betti et al, Phys Plas. 9, 2277 (2002)], and (d) the hotspot criterion for ignition, rho-R*T, is not fixed but depends on the tamp conditions. We infer that hotspot formation, ignition and propagating burn is a dynamic process that necessitates a time-dependent description and, accordingly, have formulated a fully dynamic 0-D model based on six coupled ODEs that describe energy, momentum and mass balances across the hotspot/cold fuel system. We obtain fast (\sim10s) accounting of the processes through stagnation, ignition and burn, including full thermonuclear energy production under burn disassembly. Good agreement with 1-D simulations is obtained for integral quantities such as gain, yield and ignition margins.