Analysis of the fusion-effectiveness of active and passive pulse-stackers

Isentropic compression of thermonuclear fuel pellets in laser fusion systems requires a laser pulse with a faster-than-exponential rise in intensity. One method of producing such pulses, known as pulse-stacking, consists of generating a sequence of pulses with appropriate amplitudes and recombining them with appropriate time delays to form an approximation to the required pulse shape. Numerous active and passive pulse-stacking systems have been proposed, although adequate documentation on these is almost entirely lacking. In this report we analyze the performance characteristics of several of the better-documented systems: the Thomas-KMS fusion pulse-stacker,1 the Pockels cell pulse-stacker of Harney,2 and the Emmett-LLL pulse-stacker.3 These systems are typical of the best suggestions to date and are shown schematically in Figs. 1(a)-(c).