Open AccessSimultaneous diagnosis of radial profiles and mix in NIF ignition-scale implosions via X-ray spectroscopy
Author(s) -
O. Ciricosta,
H. A. Scott,
P. Durey,
B. A. Hammel,
R. Epstein,
Thomas R. Preston,
S. P. Regan,
S. M. Vinko,
N. C. Woolsey,
J. S. Wark
Publication year - 2017
Publication title -
physics of plasmas
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.75
H-Index - 160
eISSN - 1089-7674
pISSN - 1070-664X
DOI - 10.1063/1.5000774
Subject(s) - national ignition facility , physics , implosion , opacity , ignition system , hohlraum , hot spot (computer programming) , spectroscopy , plasma , spectral line , radiative transfer , plasma diagnostics , computational physics , inertial confinement fusion , optics , nuclear physics , thermodynamics , astronomy , quantum mechanics , computer science , operating system
In a NIF implosion hydrodynamic instabilities may cause cold material from the imploding shell to be injectedinto the hot-spot (hot-spot mix), enhancing the radiative and conductive losses, which in turn may lead toa quenching of the ignition process. The bound-bound features of the spectrum emitted by high-Z ablatordopants that get mixed into the hot-spot have been previously used to infer the total amount of mixed mass;however, the typical errorbars are larger than the maximum tolerable mix. We present here an improved 2Dmodel for mix spectroscopy which can be used to retrieve information on both the amount of mixed massand on the full imploded plasma profile. By performing radiation transfer, and simultaneously fitting all ofthe features exhibited by the spectra, we are able to constrain self-consistently the effect of the opacity of theexternal layers of the target on the emission, thus improving the accuracy of the inferred mixed mass. Themodel's predictive capabilities are first validated by fitting simulated spectra arising from fully characterizedhydrodynamic simulations, then the model is applied to previously published experimental results, providingvalues of mix mass in agreement with previous estimates. We show that the new self consistent procedureleads to better constrained estimates of mix, and also provides insight on the sensitivity of the hot-spotspectroscopy to the spatial properties of the imploded capsule, such as the in-ight aspect ratio of the coldfuel surrounding the hotspot