BURN CHARACTERISTICS OF INERTIALLY CONFINED D-HE-3 FUEL

Many difficult technological problems encountered in fusion reactors could probably be solved if D-He-3 fuel would be used instead of D-T fuel. The paper examines the burn characteristics for inertial confinement fuel pellets, i.e. for pure D-He-3 fuel pellets and for D-T ignitor/D-He-3 fuel pellets, using a hydrodynamics code modified to include neutron transport and charged particle transport. The results indicate that it is difficult to ignite pure D-He-3 fuel pellets with a reasonable driver energy. However, the ignition conditions can be relaxed by using D-T fuel as ignitor. It is found that a fuel gain of approximately 480 can be obtained with D-T/D-He-3 pellets having a spark temperature of 5 keV, a D-T ignitor rho-R value of 3.0 g/cm2 and a total fuel rho-R value of 15.5 g/cm2. When the density of these pellets is assumed to be 10 000 times the liquid density, the internal energy of the configuration at ignition is approximately 1.2 MJ, which is still more severe than that in the case of D-T fuel. It is also shown that the transport of 14.7 MeV protons produced by the D-He-3 reaction plays a significant role in determining the burn characteristics of the pellets. Nuclear elastic scattering (NES) of 14.7 MeV protons enhances the ion heating, leading to a fuel gain which is higher by about 20% than that in the case without NES. The effect of nuclear spin polarization is also examined for an ideally polarized fuel pellet. It is found that the burn characteristics are improved and that the required driver energy is possibly decreased.