Diagnosis of x-ray heated Mg/Fe opacity research plasmas

Bailey, James E.; Rochau, G. A.; Mancini, Roberto; Iglesias, Carlos A.; Macfarlane, J. J.; Golovkin, I.; Pain, Jean‐Christophe; Gilleron, F.; Blancard, C.; Cossé, Ph.; Faussurier, G.; Chandler, G. A.; Nash, T. J.; Nielsen, D. S.; Lake, P.

doi:10.1063/1.3020710

Cited by 39 publications

(39 citation statements)

References 41 publications

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“…Thus, similar iron charge states exist over a broad range of the solar interior. The conditions corresponding to recent Z facility iron experiments 19,20 are superimposed on the solar interior results in Fig. 5.…”

Section: Opacity Experiments Designmentioning

confidence: 99%

Experimental investigation of opacity models for stellar interior, inertial fusion, and high energy density plasmas

et al. 2009

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Theoretical opacities are required for calculating energy transport in plasmas. In particular, understanding stellar interiors, inertial fusion, and Z pinches depends on the opacities of mid-atomic-number elements over a wide range of temperatures. The 150–300 eV temperature range is particularly interesting. The opacity models are complex and experimental validation is crucial. For example, solar models presently disagree with helioseismology and one possible explanation is inadequate theoretical opacities. Testing these opacities requires well-characterized plasmas at temperatures high enough to produce the ion charge states that exist in the sun. Typical opacity experiments heat a sample using x rays and measure the spectrally resolved transmission with a backlight. The difficulty grows as the temperature increases because the heating x-ray source must supply more energy and the backlight must be bright enough to overwhelm the plasma self-emission. These problems can be overcome with the new generation of high energy density (HED) facilities. For example, recent experiments at Sandia’s Z facility [M. K. Matzen et al., Phys. Plasmas 12, 055503 (2005)] measured the transmission of a mixed Mg and Fe plasma heated to 156±6 eV. This capability will also advance opacity science for other HED plasmas. This tutorial reviews experimental methods for testing opacity models, including experiment design, transmission measurement methods, accuracy evaluation, and plasma diagnostics. The solar interior serves as a focal problem and Z facility experiments illustrate the techniques.

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Section: Opacity Experiments Designmentioning

confidence: 99%

Experimental investigation of opacity models for stellar interior, inertial fusion, and high energy density plasmas

et al. 2009

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“…3 Based on the conditions inferred for the past experiments, the dominant Mg and Al ionization stages are He-like, Li-like, and H-like. The electron density, n e , can be inferred by the He-like β, γ , and δ Stark-broadened line shapes.…”

Section: Spectral Models To Infer T E and N Ementioning

confidence: 99%

“…K-shell line absorption from Mg uniformly doped into the iron sample provides the independent temperature and density measurements, which are required to benchmark opacity models. 3 The iron sample is heated by radiation supplied from one side (Fig. 1), raising the concern that the sample may not be uniform.…”

Section: Introductionmentioning

confidence: 99%

Investigation of iron opacity experiment plasma gradients with synthetic data analyses

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Bailey

Rochau

et al. 2012

Review of Scientific Instruments

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Experiments have been performed at Sandia National Laboratories Z-facility to validate iron opacity models relevant to the solar convection/radiation zone boundary. Sample conditions were measured by mixing Mg with the Fe and using Mg K-shell line transmission spectra, assuming that the plasma was uniform. We develop a spectral model that accounts for hypothetical gradients, and compute synthetic spectra to quantitatively evaluate the plasma gradient size that can be diagnosed. Two sample designs are investigated, assuming linear temperature and density gradients. First, Mg uniformly mixed with Fe enables temperature gradients greater than 10% to be detected. The second design uses Mg mixed into one side and Al mixed into the other side of the sample in an attempt to more accurately infer the sample gradient. Both temperature and density gradients as small as a few percent can be detected with this design. Experiments have successfully recorded spectra with the second design. In future research, the spectral model will be used to place bounds on gradients that exist in Z opacity experiments.

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“…OpSpec is designed to fit into NIF's polar (axial) diagnostic instrument manipulator (Polar DIM). A convex, cylindrically curved crystal is used, similar to the Sandia TIXTL opacity spectrometers used on Z (Bailey et al 2008) and in the tradition of the Henway design fielded on Nova and Omega (Koppel & Eckels 1977).…”

Section: Instrumentation and Diagnosis Of Plasma Conditionsmentioning

confidence: 99%

Conceptual design of initial opacity experiments on the national ignition facility

et al. 2017

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Accurate models of X-ray absorption and re-emission in partly stripped ions are necessary to calculate the structure of stars, the performance of hohlraums for inertial confinement fusion and many other systems in high-energy-density plasma physics. Despite theoretical progress, a persistent discrepancy exists with recent experiments at the Sandia Z facility studying iron in conditions characteristic of the solar radiative-convective transition region. The increased iron opacity measured at Z could help resolve a longstanding issue with the standard solar model, but requires a radical departure for opacity theory. To replicate the Z measurements, an opacity experiment has been designed for the National Facility (NIF). The design uses established techniques scaled to NIF. A laser-heated hohlraum will produce X-ray-heated uniform iron plasmas in local thermodynamic equilibrium (LTE) at temperatures 150 eV and electron densities 7 × 10 21 cm −3. The iron will be probed using continuum X-rays emitted in a ∼200 ps, ∼200 µm diameter source from a 2 mm diameter polystyrene (CH) capsule implosion. In this design, 2/3 of the NIF beams deliver 500 kJ to the ∼6 mm diameter hohlraum, and the remaining 1/3 directly drive the CH capsule with 200 kJ. Calculations indicate this capsule backlighter should outshine the iron sample, delivering a point-projection transmission opacity measurement to a time-integrated X-ray spectrometer viewing down the hohlraum axis. Preliminary experiments to develop the backlighter and hohlraum are underway, informing simulated measurements to guide the final design.

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Diagnosis of x-ray heated Mg/Fe opacity research plasmas

Cited by 39 publications

References 41 publications

Experimental investigation of opacity models for stellar interior, inertial fusion, and high energy density plasmas

Experimental investigation of opacity models for stellar interior, inertial fusion, and high energy density plasmas

Investigation of iron opacity experiment plasma gradients with synthetic data analyses

Conceptual design of initial opacity experiments on the national ignition facility

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