Overview of ignition conditions and gain curves for the fast ignitor

Fast ignited inertially confined fusion targets have potentials for high gain at moderate laser energy. Gain estimates are based on simulations of separate aspects of target evolution and on gain models, and depend critically on ignition requirements and assumptions concerning coupling of the igniting beam to the compressed fuel. In this paper, we review and discuss ignition requirements, burn studies, and gain models. We present selected gain results, illustrating the dependence of the gain on the parameters of the ignition beam. We discuss the requirements for very large gain, as well as for substantial gain at small driver energy.