Inertial Confinement Fusion: Ignition of Isobarically Compressed D-T Targets

Ignition of initially isobaric D-T plasmas, triggered by a hot spot, surrounded by denser, cold fuel, is studied both analytically and numerically. It the conditions for self-heating of the not spot are met, then a burn wave propagates, at first through deflagration driven by α-particles, and eventually through detonation. After an initial transient phase and the self-heating stage, burn in propagated mainly by α-particle transport, while the burning region is cooled at comparable rates by heat conduction and hydrodynamic expansion. The whole process is described by means of three dimensionless quantities (related to α-particle production, thermal conductivity and α-particle transport, respectively), and, as suggested by ID numerical results, an ignition criterion is given in terms of two of them. Examples of applications show, its usefulness in target design. A condition for burn propagation is also derived.