The Physics of Implosion, Ignition and Propagating Burn

Abstract

The subject of inertial confinement fusion centres around the achievement of ignition and propagating burn in a fuel mass that has been imploded by some form of driver. Whether this driver is a laser, a hohlraum radiating soft x-rays, or a charged particle beam, this theme of implosion followed by ignition and propagating burn is a common one. In this chapter we shall consider the process by which the fuel is compressed, as well as looking at the process of ignition. We shall consider situations in which burning proceeds from a region that is at the same density as the surrounding fuel and also the more typical situation of central hotspot ignition, in which the ignition region is at a lower density than the surrounding material. Burn-up of fuels other than 50:50 deuterium-tritium will be briefly considered, and some discussion of burn wave propagation will be presented. Finally we shall consider some of the requirements placed upon the implosion, and show that in order to achieve the required high densities in the imploded fuel it is necessary to employ a series of shock waves to accelerate the shell.