Particle beam interactions with plasmas and their application to inertial fusion

Present day target designs indicate that particle beams with 1-10 MJ and 100-500 TW, focused to intensities around 100 TW/cm2 will be required to ignite targets with gains of 10-100. Due to uncertainties about the symmetry and stability of the implosion, these requirements may change by as much as an order of magnitude as more is learned. The particle beams will interact with target plasmas which have temperatures of several hundred electron volts and densities up to solid density. Under these conditions the main energy-loss mechanism is colli- sional, however, in the case of electrons, the orbits can be substantially altered by electric and magnetic fields. Experiments with thin foils have measured energy deposition enhancement by a factor of 5-10 with foils mounted in the anode, and by a factor of 20 or more with foils mounted on a stalk extending into the diode. Introduction. - About 1963, J. C. Martin and his colleagues in Aldermaston, England started a branch of pulse-power technology which today is capable of producing extremely powerful electrical pulses. Pulse power generators can now produce pulses with 10 TW and several hundred kilojoules. Major pro- grams at the Kurchatov Institute in Moscow and at Sandia Laboratories, along with smaller programs at about ten other laboratories throughout the world, are investigating the application of this technology to inertial confinement fusion. Generators producing 100 TW, multimegajoule pulses are planned for the early to mid-1980's at Kurchatov and Sandia. The pulse power generators have two principle advantages over lasers : they are efficient (20 % to 50 %) and inexpensive ($ 10/J). The first pulse-power approach to inertial fusion used electron beams to ablate the surface of a spheri-