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Progress toward NIF opacity measurements
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Progress toward NIF opacity measurements T.S. Perry , R.F. Heeter , Y.P. Opachich , H.M. Johns , J.A. King , E.S. Dodd , B.G. DeVolder , M.E. Sherrill , B.G. Wilson , C.A. Iglesias , J.L. Kline , K.A. Flippo , T. Cardenas , M.B. Schneider , D.A. Liedahl , T.J. Urbatsch , M.R. Douglas , J.E. Bailey , G.A. Rochau PII: DOI: Reference:
S1574-1818(18)30104-6 https://doi.org/10.1016/j.hedp.2019.100728 HEDP 100728
To appear in:
High Energy Density Physics
Please cite this article as: T.S. Perry , R.F. Heeter , Y.P. Opachich , H.M. Johns , J.A. King , E.S. Dodd , B.G. DeVolder , M.E. Sherrill , B.G. Wilson , C.A. Iglesias , J.L. Kline , K.A. Flippo , T. Cardenas , M.B. Schneider , D.A. Liedahl , T.J. Urbatsch , M.R. Douglas , J.E. Bailey , G.A. Rochau , Progress toward NIF opacity measurements, High Energy Density Physics (2019), doi: https://doi.org/10.1016/j.hedp.2019.100728
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier B.V.
Progress toward NIF opacity measurements T.S. Perrya, R.F. Heeterb, Y.P Opachichb, H.M. Johnsa, J.A. Kingc, E.S. Dodda, B.G. DeVoldera, M.E. Sherrilla, B.G. Wilsonb, C.A. Iglesiasb, J.L. Klinea, K.A. Flippoa, T. Cardenasa, M.B. Schneiderb, D.A. Liedahlb, T.J. Urbatscha, M.R. Douglasa, J.E. Baileyd, and G.A. Rochaud a
Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM
bLawrence
Livermore National Laboratory, P.O. Box 808, Livermore, CA c
Nevada National Security Site, 161 S Vasco Rd #A, Livermore, CA d
Sandia National Laboratory, P.O. Box 5800, Albuquerque, NM
Abstract The opacities of iron and other mid-Z elements help to regulate the transport of energy in the sun. Recent experiments on the Sandia National Laboratories Z machine have shown large discrepancies between the measured and calculated opacities of iron at certain solar conditions. To replicate these opacity measurements a platform is being developed on the National Ignition Facility to measure the opacities of iron and other elements at the same conditions as in the Z experiments. The NIF platform consists of a hohlraum to heat the opacity sample to the desired conditions, a separate backlighter to radiograph the sample, and a spectrometer to give the spectrally resolved opacity. Not only must the opacity be measured but the temperature and density of the sample must also be accurately determined. This platform has now produced its first iron transmission measurements. These measurements will be presented along with plans for future measurements and details on how the measurements will be improved. Keywords: Opacity, Solar interior, Radiation hydrodynamics
Corresponding author: T. S. Perry, E-mail: [email protected], Phone: 925-423-2065 or 505-695-3420, Address: P.O. Box 808, MS L-473, Livermore, CA 94550
1. Introduction The discrepancies between theoretical calculations and the iron opacity measurements performed at the Sandia National Laboratory Z machine have been well documented [1-4]. Models agree with iron measurements at electron temperatures T e = 156-165 eV and electron densities ne = 7x1021 cm-3, but models are up to a factor of four lower than measurements at Te = 182-195 eV and ne = 3-4x1022 cm-3. These plasma conditions are interesting because they are similar to the conditions found in the interior of the sun. Energy produced in the sun moves radially outward from the center to the surface. In the center of the sun where temperatures are high and there are few bound electrons, the energy is more easily able to radiatively stream outward. Away from the center the temperature of the solar interior cools and the number of bound electrons increases. These bound electrons increase the opacity of the solar medium until the energy can no longer propagate radiatively and instead convective heat transport takes over as the mechanism for transporting energy to the surface. The place where this transition occurs is called the radiative-convective (R-C) boundary. This boundary is located at about 70% of the solar radius and its location has been accurately determined by helioseismic measurements [5]. When attempts are made to calculate the position of this boundary using standard theoretical opacities, the location is not predicted correctly [6]. A 15% increase in the overall opacity near the R-C boundary would be enough to bring the calculated location of this boundary into agreement with what is measured. The opacity of the solar interior is determined in large part by the opacity of higher atomic number trace elements such as iron. If the higher iron opacity measured by the Z experiments is used in the solar models, the location of the R-C boundary is matched much better by the simulations. A difficulty in accepting this higher measured opacity as a solution to the R-C boundary location problem is that no opacity theory has yet been able to replicate the observed higher opacities. The discrepancies between theory and measurement have been discussed in detail [2] but changing the theory to account for discrepancies in the quasi-continuum at short wavelengths appears to be difficult [7]. Recent research [8,9] describes ideas that may help to resolve the discrepancy, but the full evaluation of these ideas requires more effort. A second difficulty for the Z results to gain full acceptance is that such measurements require large-scale high energy density facilities and consequently the Z experiments have not been replicated elsewhere. The goal of the work described here is to provide alternative experiments that measure opacities at conditions similar to the Z experiments 2. Experiments To obtain more data to help guide the theories and to replicate the Z experimental results, an effort has been launched to make opacity measurements on the National Ignition Facility (NIF). The experimental techniques have been more fully described elsewhere [10-15]. A hydrodynamically tamped sample containing the material of interest is heated in a hohlraum. The hohlraum is designed so that the sample is only
heated by thermal x-ray radiation in order to help keep the sample in local thermodynamic equilibrium. A backlighter source of x-rays produced external to the hohlraum is passed through the sample. By measuring the spectrally resolved transmission of x-rays through the sample the opacity of the sample can be determined. Figure 1 shows a diagram of the experimental setup being used on the NIF.
Figure 1. Diagram of the targets used for the opacity experiments. The hohlraum consists of three sections. Laser energy is deposited in the upper and lower, larger diameter, chambers while the opacity sample is located in the center of the inner, smaller diameter chamber. The sample is not able to see directly any surface heated by the laser beams. The backlighter capsule is directly driven by other laser beams and implodes to produce a flash of x-rays. The collimator between the backlighter and the hohlraum serves to preferentially allow x-rays produced by the capsule implosion to pass through; x-rays produced by laser-plasma interactions with the plastic shell of the capsule are mostly blocked. The side access hole in the side of the hohlraum allows the expansion of the sample to be imaged and also allows a Dante temperature measurement [16] of the inner chamber of the hohlraum. A separate Dante measurement is made of the temperature of the lower outer chamber of the hohlraum. The grid lines on the diagram are 1 mm apart.
In order to measure the temperature of the sample a low atomic number element is mixed with the element of interest. By spectroscopically measuring the ion balance of the low atomic number element the temperature of the co-mixed sample can be determined. For the iron opacity measurements, the iron has been co-mixed with magnesium to provide the temperature diagnostic. In order to measure the density of the sample, the sample is imaged from the side. Knowing the expansion, the initial areal density, and composition of the sample, allows the density to be determined. 3. Results During the last year initial results on the transmission of iron have been obtained. While a final iron opacity measurement has not yet been completed, the results so far
indicate that spectral opacity data will soon be obtained although there are several improvements that still need to be made. Several tests of the initial data have been made to show the experimental technique is working. The first test was to show that the results from multiple spectrometers are mutually consistent. We have found that this is true only at photon energies above about 1100 eV. An example of this is shown in figure 2. The spectrometer used in the experiments has two crystals. The data from each of these crystals is independent and can therefore be analyzed independently. Details on how the data is analyzed have been described elsewhere [17]. Since the data are taken from the same sample, the measured transmission should be the same for data from both crystals. Figure 2 shows the results from a recent experiment. The blue curve is the data taken from one crystal and the black curve is the transmission taken from the other crystal. The red curve is the absolute difference of these two curves.
Figure 2. Consistency of NIF opacity data. At photon energies above 1100 eV, the data agree.
Notice that below about 1100 eV the red curve begins to rise dramatically. We believe that this rise is from problems with incorrectly subtracting the backgrounds caused by x-ray diffraction from alternate crystal planes in the spectrometer and also backgrounds from other possible sources. We are pursuing ways to eliminate the problem, but for the time being, this limits our ability to measure opacity to the spectral region above 1100 eV. A second test was performed to determine whether the transmission changes appropriately when the areal density of the sample is changed. The transmission of the sample is given by: T(h) = exp[-L(h)]
where his the photon energy, is the plasma mass density, L is the path length through the sample, and (h) is the opacity (mass absorption coefficient of x-rays) as a function of photon energy. Accordingly, the transmission should scale exponentially with the area density L of the sample. Two separate samples were shot having different areal densities. The second (thicker) sample had twice the Fe areal density of the first sample. Accordingly, taking the square root of the transmission of the thicker sample should give the same transmission as the thinner sample. This comparison is shown in figure 3. At photon energies between 1100 and 1700 eV the scaled transmission of the thicker sample agrees reasonably well with the transmission of the thin sample. In order for this comparison to be fully valid we also need to show that the temperatures and densities of the two samples were consistent. This work is still in progress. We have recently performed a preliminary study of the statistical and possible systematic errors. This evaluation shows that with additional experiments it will be possible to measure the iron opacity with an accuracy better than 10% in the key spectra regions [17].
Figure 3. Comparison of the transmission of two different samples. The black and blue curves are the measured transmission of the thinner iron sample. The lower red curve is the transmission of the thicker sample. The upper red curve was obtained by taking the square root of the lower red curve. There is reasonable overlap above 1100 eV. Note that the discrepancies in the spectral lines above 1300 eV is not significant. These lines are from the magnesium tracer element used to determine temperature and the amount of magnesium was not scaled for the two different samples.
4. Conclusion and future work While much progress has been made in developing a platform for opacity experiments on the NIF, much work still needs to be done. The data taken to date need
to be further analyzed to determine precisely the temperatures of the sample so that the measurements can be compared with theory. As noted above, the platform is currently only able to measure the opacity at photon energies in a limited spectral range. A full evaluation of the transmission and opacity uncertainties is in progress. A new spectrometer has been designed which should allow the measurements to be extended to lower and higher photon energies. Another major goal for the next year is to do experiments at higher temperatures. The current experiments have all been done at temperatures around 150 eV. The discrepancies between theory and measurements seen for the Sandia Z experiments occurred at higher temperatures, but experiments at these temperatures have only just begun at NIF. We look forward to reporting on these measurements at the next HEDLA conference. Declarations of Interest: none. 5. Acknowledgments This work was performed under the auspices of the US Department of Energy by the LLNL authors under Contract No. DE-AC52-07NA27344, by the LANL authors under Contract No. DE-AC52-06NA25396, by the Sandia authors under Contract No. DEAC04-94AL85000, and by the Nevada National Security Site authors under Contract No. DE-AC52-06NA25946. Los Alamos National Laboratory, an affirmative action/equal opportunity employer, is operated by the Los Alamos National Security, LLC for the National Nuclear Security Administration of the US Department of Energy. By approving this article, the publisher recognizes that the US Government retains nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or to allow others to do so, for US Government purposes. Los Alamos National Laboratory strongly supports academic freedom and a researcher’s right to publish; as an institution, however, the Laboratory does not endorse the viewpoint of a publication or guarantee its technical correctness. Declarations of Interest: none. References [1] JE Bailey, GA Rochau, CA Iglesias, et al., Phys Rev Lett, 99, 265002 (2007). [2] JE Bailey, T Nagayama, GP Loisel et al., Nature 517, 56 (2015). [3] RF Heeter, JE Bailey, RS Craxton, et al., J Plasma Phys 83, 595830103 (2017). [3] TS Perry, RF Heeter, YP Opachich, et al. High Energ Dens Phys 23, 223 (2017). [5] JN Bahcall & MH Pinsonneault, Rev Mod Phys 67, 781 (1995). [6] S Basu, WJ Chaplin, Y New, et al., Phys Rev 457, 217 (2008). [7] CA Iglesias, High Energ Dens Phys 15, 4 (2015).
[8] RM More, SB Hansen, T Nagayama, High Energ Dens Phys 24, 44 (2017). [9] P Liu, C Gao, Y Hou, et al. Commun Phys 1, 95 (2018). [10] TS Perry, PT Springer, DF Fields, et al., Phys Rev E 54, 5617 (1996). [11] PW Ross, MF Ahmed, JE Bailey, et al., Proc SPIE, 9591, 959101-1 (2015). [12] PW Ross, RF Heeter, MF Ahmed, et al., Rev Sci Instrum 87, 11D623 (2016). [13] YP Opachich, RF Heeter, M Barrios Garcia, et al., Phys Plasmas 24, 6 (2017). [14] ES Dodd, BG DeVolder, ME Martin, et al., Phys Plasmas 25, 063301 (2018). [15] JA King, YP Opachich, EJ Huffman, et al. Rev Sci Instrum 89, 10F101 (2018). [16] BV Beeman, AS Moore, A Wargo, et al. Proc SPIE, 10390, 1039005 (2017). [17] RF Heeter, TS Perry, HM Johns, et al. Atoms 6, 57 (2018).
Progress toward NIF opacity measurements T.S. Perry , R.F. Heeter , Y.P. Opachich , H.M. Johns , J.A. King , E.S. Dodd , B.G. DeVolder , M.E. Sherrill , B.G. Wilson , C.A. Iglesias , J.L. Kline , K.A. Flippo , T. Cardenas , M.B. Schneider , D.A. Liedahl , T.J. Urbatsch , M.R. Douglas , J.E. Bailey , G.A. Rochau PII: DOI: Reference:
S1574-1818(18)30104-6 https://doi.org/10.1016/j.hedp.2019.100728 HEDP 100728
To appear in:
High Energy Density Physics
Please cite this article as: T.S. Perry , R.F. Heeter , Y.P. Opachich , H.M. Johns , J.A. King , E.S. Dodd , B.G. DeVolder , M.E. Sherrill , B.G. Wilson , C.A. Iglesias , J.L. Kline , K.A. Flippo , T. Cardenas , M.B. Schneider , D.A. Liedahl , T.J. Urbatsch , M.R. Douglas , J.E. Bailey , G.A. Rochau , Progress toward NIF opacity measurements, High Energy Density Physics (2019), doi: https://doi.org/10.1016/j.hedp.2019.100728
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier B.V.
Progress toward NIF opacity measurements T.S. Perrya, R.F. Heeterb, Y.P Opachichb, H.M. Johnsa, J.A. Kingc, E.S. Dodda, B.G. DeVoldera, M.E. Sherrilla, B.G. Wilsonb, C.A. Iglesiasb, J.L. Klinea, K.A. Flippoa, T. Cardenasa, M.B. Schneiderb, D.A. Liedahlb, T.J. Urbatscha, M.R. Douglasa, J.E. Baileyd, and G.A. Rochaud a
Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM
bLawrence
Livermore National Laboratory, P.O. Box 808, Livermore, CA c
Nevada National Security Site, 161 S Vasco Rd #A, Livermore, CA d
Sandia National Laboratory, P.O. Box 5800, Albuquerque, NM
Abstract The opacities of iron and other mid-Z elements help to regulate the transport of energy in the sun. Recent experiments on the Sandia National Laboratories Z machine have shown large discrepancies between the measured and calculated opacities of iron at certain solar conditions. To replicate these opacity measurements a platform is being developed on the National Ignition Facility to measure the opacities of iron and other elements at the same conditions as in the Z experiments. The NIF platform consists of a hohlraum to heat the opacity sample to the desired conditions, a separate backlighter to radiograph the sample, and a spectrometer to give the spectrally resolved opacity. Not only must the opacity be measured but the temperature and density of the sample must also be accurately determined. This platform has now produced its first iron transmission measurements. These measurements will be presented along with plans for future measurements and details on how the measurements will be improved. Keywords: Opacity, Solar interior, Radiation hydrodynamics
Corresponding author: T. S. Perry, E-mail: [email protected], Phone: 925-423-2065 or 505-695-3420, Address: P.O. Box 808, MS L-473, Livermore, CA 94550
1. Introduction The discrepancies between theoretical calculations and the iron opacity measurements performed at the Sandia National Laboratory Z machine have been well documented [1-4]. Models agree with iron measurements at electron temperatures T e = 156-165 eV and electron densities ne = 7x1021 cm-3, but models are up to a factor of four lower than measurements at Te = 182-195 eV and ne = 3-4x1022 cm-3. These plasma conditions are interesting because they are similar to the conditions found in the interior of the sun. Energy produced in the sun moves radially outward from the center to the surface. In the center of the sun where temperatures are high and there are few bound electrons, the energy is more easily able to radiatively stream outward. Away from the center the temperature of the solar interior cools and the number of bound electrons increases. These bound electrons increase the opacity of the solar medium until the energy can no longer propagate radiatively and instead convective heat transport takes over as the mechanism for transporting energy to the surface. The place where this transition occurs is called the radiative-convective (R-C) boundary. This boundary is located at about 70% of the solar radius and its location has been accurately determined by helioseismic measurements [5]. When attempts are made to calculate the position of this boundary using standard theoretical opacities, the location is not predicted correctly [6]. A 15% increase in the overall opacity near the R-C boundary would be enough to bring the calculated location of this boundary into agreement with what is measured. The opacity of the solar interior is determined in large part by the opacity of higher atomic number trace elements such as iron. If the higher iron opacity measured by the Z experiments is used in the solar models, the location of the R-C boundary is matched much better by the simulations. A difficulty in accepting this higher measured opacity as a solution to the R-C boundary location problem is that no opacity theory has yet been able to replicate the observed higher opacities. The discrepancies between theory and measurement have been discussed in detail [2] but changing the theory to account for discrepancies in the quasi-continuum at short wavelengths appears to be difficult [7]. Recent research [8,9] describes ideas that may help to resolve the discrepancy, but the full evaluation of these ideas requires more effort. A second difficulty for the Z results to gain full acceptance is that such measurements require large-scale high energy density facilities and consequently the Z experiments have not been replicated elsewhere. The goal of the work described here is to provide alternative experiments that measure opacities at conditions similar to the Z experiments 2. Experiments To obtain more data to help guide the theories and to replicate the Z experimental results, an effort has been launched to make opacity measurements on the National Ignition Facility (NIF). The experimental techniques have been more fully described elsewhere [10-15]. A hydrodynamically tamped sample containing the material of interest is heated in a hohlraum. The hohlraum is designed so that the sample is only
heated by thermal x-ray radiation in order to help keep the sample in local thermodynamic equilibrium. A backlighter source of x-rays produced external to the hohlraum is passed through the sample. By measuring the spectrally resolved transmission of x-rays through the sample the opacity of the sample can be determined. Figure 1 shows a diagram of the experimental setup being used on the NIF.
Figure 1. Diagram of the targets used for the opacity experiments. The hohlraum consists of three sections. Laser energy is deposited in the upper and lower, larger diameter, chambers while the opacity sample is located in the center of the inner, smaller diameter chamber. The sample is not able to see directly any surface heated by the laser beams. The backlighter capsule is directly driven by other laser beams and implodes to produce a flash of x-rays. The collimator between the backlighter and the hohlraum serves to preferentially allow x-rays produced by the capsule implosion to pass through; x-rays produced by laser-plasma interactions with the plastic shell of the capsule are mostly blocked. The side access hole in the side of the hohlraum allows the expansion of the sample to be imaged and also allows a Dante temperature measurement [16] of the inner chamber of the hohlraum. A separate Dante measurement is made of the temperature of the lower outer chamber of the hohlraum. The grid lines on the diagram are 1 mm apart.
In order to measure the temperature of the sample a low atomic number element is mixed with the element of interest. By spectroscopically measuring the ion balance of the low atomic number element the temperature of the co-mixed sample can be determined. For the iron opacity measurements, the iron has been co-mixed with magnesium to provide the temperature diagnostic. In order to measure the density of the sample, the sample is imaged from the side. Knowing the expansion, the initial areal density, and composition of the sample, allows the density to be determined. 3. Results During the last year initial results on the transmission of iron have been obtained. While a final iron opacity measurement has not yet been completed, the results so far
indicate that spectral opacity data will soon be obtained although there are several improvements that still need to be made. Several tests of the initial data have been made to show the experimental technique is working. The first test was to show that the results from multiple spectrometers are mutually consistent. We have found that this is true only at photon energies above about 1100 eV. An example of this is shown in figure 2. The spectrometer used in the experiments has two crystals. The data from each of these crystals is independent and can therefore be analyzed independently. Details on how the data is analyzed have been described elsewhere [17]. Since the data are taken from the same sample, the measured transmission should be the same for data from both crystals. Figure 2 shows the results from a recent experiment. The blue curve is the data taken from one crystal and the black curve is the transmission taken from the other crystal. The red curve is the absolute difference of these two curves.
Figure 2. Consistency of NIF opacity data. At photon energies above 1100 eV, the data agree.
Notice that below about 1100 eV the red curve begins to rise dramatically. We believe that this rise is from problems with incorrectly subtracting the backgrounds caused by x-ray diffraction from alternate crystal planes in the spectrometer and also backgrounds from other possible sources. We are pursuing ways to eliminate the problem, but for the time being, this limits our ability to measure opacity to the spectral region above 1100 eV. A second test was performed to determine whether the transmission changes appropriately when the areal density of the sample is changed. The transmission of the sample is given by: T(h) = exp[-L(h)]
where his the photon energy, is the plasma mass density, L is the path length through the sample, and (h) is the opacity (mass absorption coefficient of x-rays) as a function of photon energy. Accordingly, the transmission should scale exponentially with the area density L of the sample. Two separate samples were shot having different areal densities. The second (thicker) sample had twice the Fe areal density of the first sample. Accordingly, taking the square root of the transmission of the thicker sample should give the same transmission as the thinner sample. This comparison is shown in figure 3. At photon energies between 1100 and 1700 eV the scaled transmission of the thicker sample agrees reasonably well with the transmission of the thin sample. In order for this comparison to be fully valid we also need to show that the temperatures and densities of the two samples were consistent. This work is still in progress. We have recently performed a preliminary study of the statistical and possible systematic errors. This evaluation shows that with additional experiments it will be possible to measure the iron opacity with an accuracy better than 10% in the key spectra regions [17].
Figure 3. Comparison of the transmission of two different samples. The black and blue curves are the measured transmission of the thinner iron sample. The lower red curve is the transmission of the thicker sample. The upper red curve was obtained by taking the square root of the lower red curve. There is reasonable overlap above 1100 eV. Note that the discrepancies in the spectral lines above 1300 eV is not significant. These lines are from the magnesium tracer element used to determine temperature and the amount of magnesium was not scaled for the two different samples.
4. Conclusion and future work While much progress has been made in developing a platform for opacity experiments on the NIF, much work still needs to be done. The data taken to date need
to be further analyzed to determine precisely the temperatures of the sample so that the measurements can be compared with theory. As noted above, the platform is currently only able to measure the opacity at photon energies in a limited spectral range. A full evaluation of the transmission and opacity uncertainties is in progress. A new spectrometer has been designed which should allow the measurements to be extended to lower and higher photon energies. Another major goal for the next year is to do experiments at higher temperatures. The current experiments have all been done at temperatures around 150 eV. The discrepancies between theory and measurements seen for the Sandia Z experiments occurred at higher temperatures, but experiments at these temperatures have only just begun at NIF. We look forward to reporting on these measurements at the next HEDLA conference. Declarations of Interest: none. 5. Acknowledgments This work was performed under the auspices of the US Department of Energy by the LLNL authors under Contract No. DE-AC52-07NA27344, by the LANL authors under Contract No. DE-AC52-06NA25396, by the Sandia authors under Contract No. DEAC04-94AL85000, and by the Nevada National Security Site authors under Contract No. DE-AC52-06NA25946. Los Alamos National Laboratory, an affirmative action/equal opportunity employer, is operated by the Los Alamos National Security, LLC for the National Nuclear Security Administration of the US Department of Energy. By approving this article, the publisher recognizes that the US Government retains nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or to allow others to do so, for US Government purposes. Los Alamos National Laboratory strongly supports academic freedom and a researcher’s right to publish; as an institution, however, the Laboratory does not endorse the viewpoint of a publication or guarantee its technical correctness. Declarations of Interest: none. References [1] JE Bailey, GA Rochau, CA Iglesias, et al., Phys Rev Lett, 99, 265002 (2007). [2] JE Bailey, T Nagayama, GP Loisel et al., Nature 517, 56 (2015). [3] RF Heeter, JE Bailey, RS Craxton, et al., J Plasma Phys 83, 595830103 (2017). [3] TS Perry, RF Heeter, YP Opachich, et al. High Energ Dens Phys 23, 223 (2017). [5] JN Bahcall & MH Pinsonneault, Rev Mod Phys 67, 781 (1995). [6] S Basu, WJ Chaplin, Y New, et al., Phys Rev 457, 217 (2008). [7] CA Iglesias, High Energ Dens Phys 15, 4 (2015).
[8] RM More, SB Hansen, T Nagayama, High Energ Dens Phys 24, 44 (2017). [9] P Liu, C Gao, Y Hou, et al. Commun Phys 1, 95 (2018). [10] TS Perry, PT Springer, DF Fields, et al., Phys Rev E 54, 5617 (1996). [11] PW Ross, MF Ahmed, JE Bailey, et al., Proc SPIE, 9591, 959101-1 (2015). [12] PW Ross, RF Heeter, MF Ahmed, et al., Rev Sci Instrum 87, 11D623 (2016). [13] YP Opachich, RF Heeter, M Barrios Garcia, et al., Phys Plasmas 24, 6 (2017). [14] ES Dodd, BG DeVolder, ME Martin, et al., Phys Plasmas 25, 063301 (2018). [15] JA King, YP Opachich, EJ Huffman, et al. Rev Sci Instrum 89, 10F101 (2018). [16] BV Beeman, AS Moore, A Wargo, et al. Proc SPIE, 10390, 1039005 (2017). [17] RF Heeter, TS Perry, HM Johns, et al. Atoms 6, 57 (2018).