ENERGY SCALING OF INERTIAL CONFINEMENT FUSION-TARGETS FOR IGNITION AND HIGH-GAIN

The dependence of the ignition threshold on the velocity nu(imp) and c ompressibility of an imploding fuel mass is central to establishing th e driver requirements and implosion strategy for inertial confinement fusion (ICF). Using a series of LASNEX calculations, it is found that ke(imp) proportional to nu(imp)(-alpha)beta(a), where ke(imp) is the k inetic energy in the imploding fuel at the ignition threshold, alpha = 5.5+/-0.5, a = 1.7+/-0.2 and nu(imp) is the implosion velocity. Here, the compressibility parameter beta is related to the pressure P and d ensity rho of the DT fuel by the relation P = beta rho(5/3). These res ults are obtained by starting at the peak implosion velocity for a fue l shell of a high gain ICF capsule and scaling the isentrope, mass and velocity of the fuel shell. In the presence of a mix of hot and cold material at the edge of the central hot spot, it is also found that th e results can be fitted by assuming that the reduced clean fuel radius for a mixed capsule requires a velocity increase of the same magnitud e as that which would be required if the entire capsule had been resca led in size by the same ratio.