Using time-resolved penumbral imaging to measure low hot spot x-ray emission signals from capsule implosions at the National Ignition Facility

We have developed and fielded a new x-ray pinhole-imaging snout that exploits time-resolved penumbral imaging of low-emission hot spots in capsule implosion experiments at the National Ignition Facility. We report results for a series of indirectly driven Be capsule implosions that aim at measuring...

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Bibliographic Details
Published in:Review of scientific instruments 2018-10, Vol.89 (10), p.10G111-10G111
Main Authors: Bishel, D. T., Bachmann, B., Yi, A., Kraus, D., Divol, L., Bethkenhagen, M., Falcone, R. W., Fletcher, L. B., Glenzer, S. H., Landen, O. L., MacDonald, M. J., Masters, N., Neumayer, P., Redmer, R., Saunders, A. M., Witte, B. B. L., Döppner, T.
Format: Article
Language:English
Subjects:
Emissions control
Filtration
Ignition
Implosions
Inertial confinement fusion
OTHER INSTRUMENTATION
Pinholes
Scientific apparatus & instruments
Shot
Stagnation
Thomson scattering
Variation
X ray flashes
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Summary:We have developed and fielded a new x-ray pinhole-imaging snout that exploits time-resolved penumbral imaging of low-emission hot spots in capsule implosion experiments at the National Ignition Facility. We report results for a series of indirectly driven Be capsule implosions that aim at measuring x-ray Thomson scattering (XRTS) spectra at extreme density conditions near stagnation. In these implosions, x-ray emission at stagnation is reduced by 100–1000× compared to standard inertial confinement fusion (ICF) implosions to mitigate undesired continuum background in the XRTS spectra. Our snout design not only enables measurements of peak x-ray emission times, to, where standard ICF diagnostics would not record any signal, but also allows for inference of hot spot shapes. Measurement of to is crucial to account for shot-to-shot variations in implosion velocity and therefore to benchmark the achieved plasma conditions between shots and against radiation hydrodynamic simulations. Additionally, we used differential filtering to infer a hot spot temperature of 520 ± 80 eV, which is in good agreement with predictions from radiation hydrodynamic simulations. We find that, despite fluctuations of the x-ray flash intensity of up to 5×, the emission time history is similar from shot to shot and slightly asymmetric with respect to peak x-ray emission.
ISSN:0034-6748
1089-7623
DOI:10.1063/1.5037073