Thermonuclear burn characteristics of compressed deuterium-tritium microspheres

Abstract

The phenomenology of thermonuclear burn in deuterium-tritium microspheres at high densities is described, and numerical results characterizing the burn for a broad range of initial conditions are given. The fractional burnup, bootstrap-heating, and depletion of the DT fuel, its expansive disassembly, and thermonuclear ignition by propagating burn from central hot spots in the microspheres are discussed. Extensive numerical results from a 3 T Lagrangian simulation code are presented. The yields Y0 from uniform 10, 1, and 0.1 μg microspheres with densities ρ = 1 to 4 × 104 g/cm3 and temperatures Te = Ti = 1.8 to 100 keV are given. It is shown that Y0 ∼ ρR, ρR < 0.3 (R is the microsphere radius) or, equivalently, Y0 ∼ ρ2/3 for spheres of fixed mass m. The gain-factor G0 ≡ Y0/mI0 (I0 is the internal energy) is shown to measure burn efficiency in uniform microspheres. More than a four-fold increment in the gain factor is shown to derive from apportionment of the internal energy in a central hot spot. The limiting effects of electron degeneracy on the gain factor are outlined. As a guideline, the experimental observation of 1013 neutrons/kJ of input laser energy is established as proof of good absorption; 1015/kJ will imply yields exceeding break even.