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DE-NA0003874Principal Investigator: M. Koepke

Department of Physics and Astronomy, West Virginia University

Start Date: 1 October 2018, End Date: 30 September 2021Performance Location: Org 1683, Sandia National Laboratories

Z Machine

Spectroscopic methods to obtain n, T applied to soft x-ray absorption spectra from radiatively heated Z-pinch plasmas

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The pinch’s x-rays both drive and backlight a plasma, yielding absorption spectra.

CH4 µm

CH4 µm

NaFMgO0. 4 µm

Z Pinch Foil Limiting Aperture Slits

Kodak 2492 X-Ray film

KAP Crystal

2.65 cm 307 cm 152 cm

CH7 µm

CH7 µm

NaFMgO0. 4 µm

CH15 µm

CH15 µm

NaFMgO0. 4 µm

8 cm

Hotter and Sparser Cooler and Denser

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Many absorption features of 3 elements acquired, thanks to uniquely broadband backlighter and spectrometer range.

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Project is split into 3 complementary studies: 1)Test iso-electronic line-ratio technique in absorption as a Te diagnostic for HEDLP. 2) Acquire data on multi-element Stark broadening to diagnose ne and utilize this dataset as a testbed for Stark broadening codes. 3) Study sensitivity of soft-x-ray satellite lines to electron temperature and electron density.

Goal: Quantify consistency of determining Te and ne from a soft x-ray absorption spectrum

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List of students and postdocs since 15 Feb 2019:•Ted Lane (PhD, July 2019), now at Southern Utah Univ.•David Dunkum (grad student), left graduate school•Greg Riggs (grad student), M.S., May 2019, PhD underway•Ripudaman Nirwan (grad student), left High-Energy-Density Laboratory Plasmas topic

Four WVU grad studentshave participated in ZAPP projects over past year.

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List of 5 publications since 15 Feb 2019

•Maser radiation from collisionless shocks: Application to astrophysical jets, Speirs, Bingham, Ronald, Phelps, Koepke, Cairns, Rigby, Cruz, Trines, Bamford, Kellett, Albertazzi, Cross, Fraschetti, Graham, Kozlowski, Kuramitsu, Miniati, Morita, Oliver, Reville, Sakawa, Sarkar, Spindloe, Koenig, Silva, Lamb, Tzeferacos, Lebedev, Gregori, High Power Laser Science and Engineering (2019) 7, e17.•Interrelationship between lab, space, astrophysical, magnetic-fusion, and inertial-fusion plasma expts, Koepke, Atoms 7, 35 (2019), doi: 10.3390/atoms/7010035.•Laboratory experiments: Putting space into the lab, M. Koepke, AGU Books on Magnetospheres (accepted in 2019; to appear in 2020).•Synergy of physics-based reasoning and machine learning in biomedical applications: Towards unlimited deep learning with limited data, V. Gavrishchaka, O. Senyukova, M. Koepke, Advances in Physics: X (2019) 4, 1582361 (53 pp)•Basic factors for acquiring, correcting, and interpreting, probe current-voltage characteristic in medium-pressure plasma for determining non-equilibrium electron energy distribution, V. Demidov, M. Koepke, I. Kurlyandskaya, M. Malkov, Physics of Plasmas 27, 020501 (2020); https://doi.org/10.1063/1.5127749•Communication between solar wind and magnetosphere: Collisionless information exchange responsible for nonlinear cascade-like mechanism mediated by plasma flow encountering a magnetic obstacle, Savin, Amata, Belakhovsky, Sharma, Legen, Zelenyi, Safrankova, Nemecek, Wang, Li, Tang, Pilipenko, Pallocchia, Kozak, Rauch, Koepke, Budaev, Blecki, Kronberg, Nature Communications (to be submitted in Spring 2020).

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List of 3 invited talks since 15 Feb 2019

•Priorities in Connecting Heliophysics and Laboratory Plasma Studies, Solar, Heliospheric, & Interplanetary Environment (SHINE) Workshop, Boulder, CO, 4-8 August 2019.•The importance of OMEGA Laser Users Group (invited address to NNSA Administrator L. Gordon-Haggerty), LLE, U. Rochester, 20 Aug 2019.•Alfvén wave experiments in the Large Plasma Device-Upgrade at UCLA, Interrelationship between Plasma Experiments in the Laboratory and in Space, Univ. Tokyo, Japan 2-8 Sep 2019.

•Upcoming invited talk at Royal Society “Prospects for High-Gain ICF” Factors influencing the commercialisation of inertial fusion energy•Upcoming invited talk at ICPP2020, First statistical survey of discrete auroral arc lifetimes challenges all arc-generation models

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List of 2 seminars and 4 posters/talks since 15 Feb 2019

•Interrelationship between Lab, Space, Astrophysical, Magnetic-Fusion, and Inertial-Fusion plasma experiments, Plasma Seminar, Aerospace and Energetics Research Lab, Univ. WA, Seattle, 14 Oct 2019.•Development of an isoelectronic line-area-ratio electron-temperature diagnostic in soft x-ray absorption spectroscopy, P-24 Plasma Seminar, Los Alamos National Lab, NM, 23 Sept 2019.

Contributed Posters and Talks•Interfacial instabilities and turbulent plasma mixing in the lab and in geospace (mini-conference talk), M. Koepke, S. Nogami, V. Demidov, K. Gentle, APS DPP 2019. •Acceleration of electrons and maser radiation from collisionless shocks (poster), Bingham et al. NP10.00071, APS Div. Plasma Physics conference, 21-25 Oct 2019.•The effect of species mix and fast-ion distribution on emission of fast magnetosonic waves near the ion cyclotron frequency (poster), Vincena et al. TO8.00006, APS Div. Plasma Physics conference, 21-25 Oct 2019.•An experiment to investigate parametric interaction and mixing of microwaves in plasma (poster), Ronald et al. TP10.00095 , APS Div. Plasma Physics conf, 21-25 Oct 2019.

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List of new findings since 15 Feb 2019

• Old finding #1: Uncertainty quantification (UQ) benefits from further analysis of synthetic data.

• New finding: Data-based range for density and temp values is being chosen to improve UQ and overall self consistency.

• Old findings #2 and #3: Preliminary results show that nonzero density or temp gradient matches experimentally obtained spectra better.

• New finding: Modifying/rewriting the density & temp gradient analysis codes extends our simulations to N-layers of varying density & temperature.

• Additional new finding: Individual-shot processing, rather than configuration-average processing, avoids one-size-fits-all error analysis of wavelength calibration and shot jitter.

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Mean ± standard deviation of all lineshape-area ratios yield the quoted temperature ± uncertainty.

56.9 eV ± 3.2 eV (isoelectronic) 59.9 eV ± 2.6 eV (iso-element)

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Progress made since 15 Feb 2019 with respect to milestones

• Milestone #1: Fabricate Mg-NaF foils, tamped by low-Z materials, e.g., CH or Be, designed to produce uniform plasma at desired density. Completed.

• Milestone #2: Predict relationship between ne and Stark broadening for a specific Te. In progress.

• Milestone #3: Predict and evaluate prospective line pairs for Te sensitivity of line ratio. Completed.

• Milestone #4: Vary charge-state distribution in all 3 elements. Completed.

• New Milestone: Quantifying target-incident Planckian fraction associated with re-radiation from proximity hardware ... is the subject of a manuscript in preparation.

• New Milestone: Quantifying uncertainty in n & T gradients ... is expedited with larger PrismSpect-simulations stockpile of n & Tvalues and by optimizing WVU n-layer gradient-analysis code.

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Comparison of single-temperature simulations with uniform-temperature-gradient simulation.

Agreement between the temperature gradient simulation and the shot data suggests an existing temperature gradient in the shot plasma

Measured spectrum vs. simulated spectrum based on ten-layer gradient

Measured spectrum vs. gradient-free simulated spectrum

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Investigation of arbitrary T profile suggests a sudden jump in T between thinner hot edge and thicker cooler region

Normalized Chi-Squared Best-Fit Temperature Profile

80706050403020100

Tem

pera

ture

(eV)

Nth layer is hot. The other N-1 layers are designated the cooler layer. For N=8, the hot layer is one-eighth as thick as the cooler layer.

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Nth layer is hot. The other N-1 layers are designated the cooler layer. For N=3, the hot layer is half as thick as the cooler layer.

N-layer gradient analysis distinguishes effects of ∆T, ∆n, ∆x

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Comparison of single-temperature simulation with thin 75-eV layer + thick 46-eV layer simulation.

Foil is divided into 45, 47.5, and 75 eV layers to represent one-third hot and two-thirds cooler layering

Previously quoted values of temperature and uncertainties are being reformulated using this localized-gradient approach.

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Sabbatical leave spent at SNL (Fall 2019) & IC-L (Spring2020)

• SNL research at SNL: CAPP/ZAPP data using low-Z-tamped Mg-NaF foils, for ne and Te determination. Almost completed; manuscript in preparation.

• SNL research at SLAC: Conductivity of warm-dense iron. 1st data acquired.

• SNL research at LANL: Relationship between ne and Stark broadening for a specific Te and magnetic field will be predicted. In progress.

• Lab Astro research at IC-L: Fast-streaming, magnetized plasmas collide to induce MHD shocks, B turbulence, reconnection, wave-particle interaction. Plasma-flow encounters with magnetized objects. In progress.

• Lab Astro research at IC-L: High-Energy-Density rotating plasma with pulsed-power driving and intense lasers.* In progress.

• IFE roadmapping at U. Oxford: Royal Society event, 2-3 March, is organized.https://royalsociety.org/science-events-and-lectures/2020/03/inertial-fusion-energy/

*Plasma flows are formed by ablation of 8 aluminum wires and are accelerated by radial and azimuthal components of JxB force. Because of the relative azimuthal shift of two concentric annular wire arrays, an azimuthally-rotating and vertically-rising magnetized-plasma jet forms, which is relevant to accretion disks and astrophysical jets.

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• Step #1: Iso-electronic line analysis including Oxygen ratiosfrom Line-Of-Sight 130 on Z.

• Step #2: Assessment of Gradient Effects on Soft X-ray Spectral Measurements on the Z.

• Step #3: Models for interpreting density from multi-element Stark broadening are being tested.

• Step #4: Line-dissolution & continuum-lowering from plasma-microfields affecting the bound electrons at high ne, low Te.

• Step #5: Application of iso-electronic line-ratio technique to physics/astrophysics, in support of ZAPP/CAPP collaboration.

• Step #6: Apply established iso-electronic technique to validate satellite line formation models used at SNL & LLNL.

List of next steps (in 2020)

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Spectroscopic methods to obtain n, T applied to soft x-ray absorption spectra from radiatively heated Z-pinch plasmas

DE-NA0003874Principal Investigator: M. Koepke

Department of Physics and Astronomy, West Virginia UniversityStart Date: 1 October 2018, End Date: 30 September 2021

Performance Location: Org 1683, Sandia National Laboratories

End

This material is based upon work supported by the U.S. Department of Energy, Office of Science,Office of Workforce Development for Teachers and Scientists, Office of Science Graduate StudentResearch (SCGSR) program. The SCGSR program is administered by the Oak Ridge Institute forScience and Education (ORISE) for the DOE. ORISE is managed by ORAU under contract numberDE‐AC05‐06OR23100.This material is also based upon work supported by the U.S. DOE, Office of Science under contract number DE-SC0012515 and U.S. DOE NNSA under contract DE-NA0003874.Sandia National Laboratories is a multi-mission laboratory managed and operated by NationalTechnology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of HoneywellInternational, Inc., for DOE’s National Nuclear Security Administration under contract DE-NA-0003525.

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Stark broadening dominates all observed linewidth contributions, well above our instrument resolution.

Total

KAP Crystal

Source

Detector

F-Heδ (1s2->1s15p1)

Even smallest density ne shown here hasthe width of the line as ~20mÅ, wellabove our instrument resolution ~9mÅ

**

Density (x1021 cm-3) 0.775 −−−−2.25 −−−−−3.67 −−−−−5.00 −−−−−

Tran

smiss

ion

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He-like charge state is the highest observed charge state in the plasma.

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Agreement between F-Heγand F-Heδ, and F-Heε and F-Heγsuggests that electron density lies ~2.3X1021

electrons/cc

Thus each line’s width (Δλ) translates into an electron density (ne).

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Voigt profile is used to determine lineshape area.

”Line Ratio” is lineshape area of one Voigt-fit spectral line divided by the lineshape area of a second Voigt-fit line.