Using multiple secondary fusion products to evaluate fuel ρr, electron temperature, and mix in deuterium-filled implosions at the NIF

In deuterium-filled inertial confinement fusion implosions, the secondary fusion processes D(³He,p)⁴He and D(T,n)⁴He occur, as the primary fusion products ³He and T react in flight with thermal deuterons. In implosions with moderate fuel areal density (∼5-100mg/cm²), the secondary D-³He reaction saturates, while the D-T reaction does not, and the combined information from these secondary products is used to constrain both the areal density and either the plasma electron temperature or changes in the composition due to mix of shell material into the fuel. The underlying theory of this technique is developed and applied to three classes of implosions on the National Ignition Facility: direct-drive exploding pushers, indirect-drive 1-shock and 2-shock implosions, and polar direct-drive implosions. In the 1- and 2-shock implosions, the electron temperature is inferred to be 0.65 times and 0.33 times the burn-averaged ion temperature, respectively. The inferred mixed mass in the polar direct-drive implosions is in agreement with measurements using alternative techniques.