Inferring Hot-Spot Electron Temperature from X-Ray Continuum Emission

The measured burn-weighted hot-spot ion temperature (T_i) is used as a key implosion performance metric, but it can be biased by motional blurring. To avoid this effect, the inverse slope of the x‑ray continuum emission spectrum will be used instead to infer a hot-spot electron temperature (T_e). At a chosen photon energy, this inferred Te is exactly equal to the emission-weighted harmonic mean of the hot-spot T_e. Near 15-keV spectral energy, the emission weighting is closest to burn weighting. For OMEGA-scale implosions, however, simulations indicate that correlation is too poor between the inferred T_e and burn-weighted T_i for T_i measurement surrogacy because of the non-equilibrium state between T_e and T_i. The inferred T_e will therefore be treated as an independent metric to constrain post-shot simulations. Absolute emission measurements will also be used to infer the amount of hot-spot mix. In contrast to previous methods,^1,2 a non-equilibrium temperature state and the inclusion of a T_e measurement will be assumed. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

¹ R. Epstein et. al., Phys. Plasmas 22, 022707 (2015).

² T. Ma et al., Phys. Rev. Lett. 111, 085004 (2013).