IMPLOSION OF REACTOR-SIZE, GAS-FILLED SPHERICAL-SHELL TARGETS DRIVEN BY SHAPED PRESSURE PULSES

The implosion of a family of reactor-size targets for inertial confine ment fusion (ICF) is studied analytically and numerically. The targets consist of a deuterium-tritium (D-T) shell filled with D-T vapor and they are imploded by a multistep pressure pulse designed in such a way that the final hot spot is formed mainly from the initially gaseous f uel. The formation of the hot spot is described by means of a relative ly simple model, and scaling laws for the quantities that characterize the state of the initially gaseous part of the fuel prior to ignition are derived. The results of the model are compared with one-dimension al fluid simulations, and good agreement is found. A parametric study of the fuel energy gain is then presented; the dependence of the gain and of the hot spot convergence ratio on the pulse parameters and on t he filling gas density is analyzed. It is also shown that a substantia l increase in the gain (for a given target and pulse energy) can be ac hieved by replacing the last step of the pulse with an exponential ram p.