LASERS AND THE REACTOR IGNITION PROBLEM

Abstract

Some published estimates of the laser energy (W0) required to heat an inertially confined D–T target in a pulsed fusion reactor are summarized. Assuming a thermal efficiency of 1/3 and a laser heating efficiency (target energy/laser pumping energy) of 100%, most of these estimates of W0 range between 10 and 1000 MJ, depending on the various assumptions which are made about the degree of solid-state target compression, the possibility of target tamping, and the required reactor power gain. Any energy gain due to fusion reactions in material other than the target is omitted in these calculations. These estimates of W0 are then compared with the maximum fusion outputs which can be handled with and without damage to the structure and the low permissible cost of replacing damaged components is stressed. The possibility of using nonlinear absorption of repetitively pulsed CO2 lasers to start up a steady-state stellarator which is fueled by D–T pellet injection and has an output of ~10 GW(E) is then discussed. It is shown that laser energies as low as 80 kJ may be feasible and possible advantages and difficulties of such a hybrid inertial/magnetic confinement approach are outlined.