The physics issues that determine inertial confinement fusion target gain and driver requirements: A tutorial

This paper presents a simplified, tutorial approach to determining the gains of inertial confinement fusion (ICF) targets, via a basic, zero-dimensional (“0-D”), energy “bookkeeping” of input (parametrized by ICF drivers’ coupling efficiencies to the target, and subsequent hydrodynamic efficiencies of implosion) versus output (thermonuclear burn efficiency and target fuel mass). Physics issues/constraints such as hydrodynamic instabilities, symmetry and implosion velocity requirements will be discussed for both the direct drive (driver impinging directly on the target) and indirect drive (x-ray implosion within a driver heated hohlraum) approaches to ICF. Supplementing the 0-D model with simple models for hohlraum wall energy loss (to predict coupling efficiencies) and a simple one-dimensional (1-D) model of the implosion as a spherical rocket (to predict hydrodynamic implosion efficiencies) allows gains to be predicted that compare well with the results of complex two-dimensional (2-D) radiation hydrodynamic simulations.