Thermonuclear burn characteristics of compressed deuterium-tritium microspheres

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 $Y_0$ from uniform 10, 1, and 0.1 $\mu \mathrm{g}$ microspheres with densities $\text{ρ\hspace{0.17em}=\hspace{0.17em}1\hspace{0.17em}}\mathrm{to}{\text{\hspace{0.17em}4\hspace{0.17em}×\hspace{0.17em}10}}^4\mathrm{\hspace{0.17em}g/}{\mathrm{cm}}^3$ and temperatures $T_e{\mathrm{\hspace{0.17em}=\hspace{0.17em}T}}_i\text{\hspace{0.17em}=\hspace{0.17em}1.8\hspace{0.17em}}\mathrm{to}\text{\hspace{0.17em}100\hspace{0.17em}}\mathrm{keV}$ are given. It is shown that $Y_0\text{\hspace{0.17em}∼\hspace{0.17em}ρR,\hspace{0.17em}ρR\hspace{0.17em}<\hspace{0.17em}0.3}$ ($R$ is the microsphere radius) or, equivalently, $Y_0{\mathrm{\hspace{0.17em}\sim \hspace{0.17em}\rho }}^{\text{2/3}}$ for spheres of fixed mass $m$ . The gain‐factor $G_0{\mathrm{\hspace{0.17em}\equiv \hspace{0.17em}Y}}_0{\mathrm{/mI}}_0$ ($I_0$ 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.