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38 results on '"Loisel, G. P."'

1. Experimental methods to test photoionized plasma models in emission.

Author

Cho, P. B., Loisel, G. P., Bailey, J. E., Nagayama, T., Fontes, C. J., Mayes, D. C., and Dunham, G. S.

Subjects
*ELECTRON density, *ELECTROMAGNETIC spectrum, *ELECTRON temperature, *BLACK holes, *GOVERNMENT laboratories
Abstract

The expanding foil photoionized plasma platform was developed on the Z-machine at Sandia National Laboratories to produce terrestrial photoionized plasmas at some of the same conditions as those observed in astrophysical black hole accretion disks. The specific scientific goals of the platform are motivated by long-standing astrophysical puzzles related to accreting black hole systems. Ultimately, the experimental goal is to inform the supersolar Fe abundance problem by testing photoionized plasma models in emission with at-parameter laboratory data. High quality high resolution emission data with absolute intensity calibration from a laboratory photoionized plasma have never been collected prior to the experiments described here, providing broader motivation. A robust test of the model predictions requires the successful production of a laboratory photoionized plasma along with measurements of the supporting model inputs including the radiation drive spectrum used to create the photoionized plasma, the electron density, and the temperature. The measured absolute spectral radiance in emission collected from the independently diagnosed plasma can be compared against model calculations performed using the measured inputs. In this paper, we focus on the experimental platform and the model inputs, specifically detailing the methodology used to measure the plasma conditions. The moderate electron temperature of ∼ 41 eV ± 15 eV and electron density of ∼ 1e19 ± 1.6e18 e−/cm3 and the ∼ 3e12 W/cm2 x-ray irradiance at the sample confirm that photoionization dominates the plasma ionization and spectra. [ABSTRACT FROM AUTHOR]

Published
2024
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2. Parallax diagnostics of radiation source geometric dilution for iron opacity experiments

Author

Nagayama, T., Bailey, J. E., Loisel, G., Rochau, G. A., and Falcon, R. E.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Solar and Stellar Astrophysics
Abstract

Experimental tests are in progress to evaluate the accuracy of the modeled iron opacity at solar interior conditions [J.E. Bailey et al., Phys. Plasmas 16, 058101 (2009)]. The iron sample is placed on top of the Sandia National Laboratories z-pinch dynamic hohlraum (ZPDH) radiation source. The samples are heated to 150 - 200 eV electron temperatures and 7e21 - 4e22 e/cc electron densities by the ZPDH radiation and backlit at its stagnation [T. Nagayama et al., Phys. Plasmas 21, 056502 (2014)]. The backlighter attenuated by the heated sample plasma is measured by four spectrometers along +/- 9 degree with respect to the z-pinch axis to infer the sample iron opacity. Here we describe measurements of the source-to-sample distance that exploit the parallax of spectrometers that view the half-moon-shaped sample from +/-9 degree. The measured sample temperature decreases with increased source-to-sample distance. This distance must be taken into account for understanding the sample heating., Comment: Published online 17 July 2014 (http://scitation.aip.org/content/aip/journal/rsi/85/11/10.1063/1.4889776)

Published
2014
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3. Control and diagnosis of temperature, density, and uniformity in x-ray heated iron/magnesium samples for opacity measurements

Author

Nagayama, T., Bailey, J. E., Loisel, G., Hansen, S. B., Rochau, G. A., Mancini, R. C., MacFarlane, J. J., and Golovkin, I.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Physics - Plasma Physics
Abstract

Experimental tests are in progress to evaluate the accuracy of the modeled iron opacity at solar interior conditions, in particular to better constrain the solar abundance problem [S. Basu and H.M. Antia, Physics Reports 457, 217 (2008)]. Here we describe measurements addressing three of the key requirements for reliable opacity experiments: control of sample conditions, independent sample condition diagnostics, and verification of sample condition uniformity. The opacity samples consist of iron/magnesium layers tamped by plastic. By changing the plastic thicknesses, we have controlled the iron plasma conditions to reach i) Te=167+/-3 eV and ne=(7.1+/-1.5)e21 e/cc, ii) Te=170+/-2 eV and ne=(2.0+/-0.2)e22 e/cc, and iii) Te=196+/-6 eV and ne=(3.8+/-0.8)e22 e/cc, which were measured by magnesium tracer K-shell spectroscopy. The opacity sample non-uniformity was directly measured by a separate experiment where Al is mixed into the side of the sample facing the radiation source and Mg into the other side. The iron condition was confirmed to be uniform within their measurement uncertainties by Al and Mg K-shell spectroscopy. The conditions are suitable for testing opacity calculations needed for modeling the solar interior, other stars, and high energy density plasmas., Comment: Published online 14 May 2014

Published
2014
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4. Fusion reactions initiated by laser-accelerated particle beams in a laser-produced plasma

Author

Labaune, C., Baccou, C., Depierreux, S., Goyon, C., Loisel, G., Yahia, V., and Rafelski, J.

Subjects
Physics - Plasma Physics, Nuclear Experiment, Physics - Accelerator Physics, Physics - Optics
Abstract

The advent of high-intensity pulsed laser technology enables the generation of extreme states of matter under conditions that are far from thermal equilibrium. This in turn could enable different approaches to generating energy from nuclear fusion. Relaxing the equilibrium requirement could widen the range of isotopes used in fusion fuels permitting cleaner and less hazardous reactions that do not produce high energy neutrons. Here we propose and implement a means to drive fusion reactions between protons and boron-11 nuclei, by colliding a laser-accelerated proton beam with a laser-generated boron plasma. We report proton-boron reaction rates that are orders of magnitude higher than those reported previously. Beyond fusion, our approach demonstrates a new means for exploring low-energy nuclear reactions such as those that occur in astrophysical plasmas and related environments., Comment: 7 pages, 5 figures

Published
2013
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5. Comparison of Fe and Ni opacity calculations for a better understanding of pulsating stellar envelopes

Author

Gilles, D., Turck-Chièze, S., Loisel, G., Piau, L., Ducret, J. -E., Poirier, M., Blenski, T., Thais, F., Blancard, C., Cossé, P., Faussurier, G., Gilleron, F., Pain, J. -C., Porcherot, Q., Guzik, J. A., Kilcrease, D. P., Magee, N. H., Harris, J., Busquet, M., Delahaye, F., Zeippen, C. J., and Bastiani-Ceccotti, S.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Physics - Atomic Physics, Physics - Plasma Physics
Abstract

Opacity is an important ingredient of the evolution of stars. The calculation of opacity coefficients is complicated by the fact that the plasma contains partially ionized heavy ions that contribute to opacity dominated by H and He. Up to now, the astrophysical community has greatly benefited from the work of the contributions of Los Alamos [1], Livermore [2] and the Opacity Project (OP) [3]. However unexplained differences of up to 50% in the radiative forces and Rosseland mean values for Fe have been noticed for conditions corresponding to stellar envelopes. Such uncertainty has a real impact on the understanding of pulsating stellar envelopes, on the excitation of modes, and on the identification of the mode frequencies. Temperature and density conditions equivalent to those found in stars can now be produced in laboratory experiments for various atomic species. Recently the photo-absorption spectra of nickel and iron plasmas have been measured during the LULI 2010 campaign, for temperatures between 15 and 40 eV and densities of ~3 mg/cm3. A large theoretical collaboration, the "OPAC", has been formed to prepare these experiments. We present here the set of opacity calculations performed by eight different groups for conditions relevant to the LULI 2010 experiment and to astrophysical stellar envelope conditions., Comment: 15 pages, 10 figures

Published
2012
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6. On plasma radiative properties in stellar conditions

Author

Turck-Chièze, S., Delahaye, F., Gilles, D., Loisel, G., and Piau, L.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Physics - Plasma Physics
Abstract

The knowledge of stellar evolution is evolving quickly thanks to an increased number of opportunities to scrutinize the stellar internal plasma properties by stellar seismology and by 1D and 3D simulations. These new tools help us to introduce the internal dynamical phenomena in stellar modeling. A proper inclusion of these processes supposes a real confidence in the microscopic physics used, partly checked by solar or stellar acoustic modes. In the present paper we first recall which fundamental physics has been recently verified by helioseismology. Then we recall that opacity is an important ingredient of the secular evolution of stars and we point out why it is necessary to measure absorption coefficients and degrees of ionization in the laboratory for some well identified astrophysical conditions. We examine two specific experimental conditions which are accessible to large laser facilities and are suitable to solve some interesting questions of the stellar community: are the solar internal radiative interactions properly estimated and what is the proper role of the opacity in the excitation of the non radial modes in the envelop of the $\beta$ Cephei and the Be stars ? At the end of the paper we point out the difficulties of the experimental approach that we need to overcome., Comment: 7 pages, 6 figures, published in HEDP 2009

Published
2012
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7. Iron and Nickel spectral opacity calculations in conditions relevant for pulsating stellar envelopes and experiments

Author

Gilles, D., Turck-Chièze, S., Busquet, M., Thais, F., Loisel, G., Piau, L., Ducret, J. E., Blenski, T., Blancard, C., Cossé, P., Faussurier, G., Gilleron, F., Pain, J. C., Porcherot, Q., Guzik, J. A., Kilcrease, D. P., Magee, N. H., Harris, J., Bastiani-Ceccotti, S., Delahaye, F., and Zeippen, C. J.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Physics - Atomic Physics, Physics - Plasma Physics
Abstract

Seismology of stars is strongly developing. To address this question we have formed an international collaboration OPAC to perform specific experimental measurements, compare opacity calculations and improve the opacity calculations in the stellar codes [1]. We consider the following opacity codes: SCO, CASSANDRA, STA, OPAS, LEDCOP, OP, SCO-RCG. Their comparison has shown large differences for Fe and Ni in equivalent conditions of envelopes of type II supernova precursors, temperatures between 15 and 40 eV and densities of a few mg/cm3 [2, 3, 4]. LEDCOP, OPAS, SCO-RCG structure codes and STA give similar results and differ from OP ones for the lower temperatures and for spectral interval values [3]. In this work we discuss the role of Configuration Interaction (CI) and the influence of the number of used configurations. We present and include in the opacity code comparisons new HULLAC-v9 calculations [5, 6] that include full CI. To illustrate the importance of this effect we compare different CI approximations (modes) available in HULLAC-v9 [7]. These results are compared to previous predictions and to experimental data. Differences with OP results are discussed., Comment: 4 pages, 3 figures, conference Inertial Fusion Sciences and Applications, Bordeaux, 12th to 16th September 2011; EPJ web of Conferences 2012

Published
2012
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8. Radiative properties of stellar plasmas and open challenges

Author

Turck-Chièze, S., Loisel, G., Gilles, D., Piau, L., Blancard, C., Blenski, T., Busquet, M., Caillaud, T., Cossé, P., Delahaye, F., Faussurier, G., Fariaut, J., Gilleron, F., Guzik, J. A., Harris, J., Kilcrease, D. P., Magee, N. H., Pain, J. C., Porcherot, Q., Poirier, M., Soullier, G., Zeippen, C. J., Bastiani-Ceccotti, S., Reverdin, C., Silvert, V., Thais, F., and Villette, B.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Physics - Plasma Physics
Abstract

The lifetime of solar-like stars, the envelope structure of more massive stars, and stellar acoustic frequencies largely depend on the radiative properties of the stellar plasma. Up to now, these complex quantities have been estimated only theoretically. The development of the powerful tools of helio- and astero- seismology has made it possible to gain insights on the interiors of stars. Consequently, increased emphasis is now placed on knowledge of the monochromatic opacity coefficients. Here we review how these radiative properties play a role, and where they are most important. We then concentrate specifically on the envelopes of $\beta$ Cephei variable stars. We discuss the dispersion of eight different theoretical estimates of the monochromatic opacity spectrum and the challenges we need to face to check these calculations experimentally., Comment: 6 pages, 5 figures, in press (conference HEDLA 2010)

Published
2011
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9. Theoretical and experimental activities on opacities for a good interpretation of seismic stellar probes

Author

Turck-Chièze, S, Loisel, G, Gilles, D, Thais, F, Bastiani, S, Blancard, C, Busquet, M, Caillaud, T, Cosse, P, Blenski, T, Delahaye, F, Ducret, J E, Faussurier, G, Gilleron, F, Guzik, J, Harris, J W, Kilcrease, D P, Magee, N H, Piau, L, Pain, J C, Poirier, M, Porcherot, Q, Reverdin, C, Silvert, V, Villette, B, and Zeippen, C

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

Opacity calculations are basic ingredients of stellar modelling. They play a crucial role in the interpretation of acoustic modes detected by SoHO, COROT and KEPLER. In this review we present our activities on both theoretical and experimental sides. We show new calculations of opacity spectra and comparisons between eight groups who produce opacity spectra calculations in the domain where experiments are scheduled. Real differences are noticed with real astrophysical consequences when one extends helioseismology to cluster studies of different compositions. Two cases are considered presently: (1) the solar radiative zone and (2) the beta Cephei envelops. We describe how our experiments are performed and new preliminary results on nickel obtained in the campaign 2010 at LULI 2000 at Polytechnique., Comment: 6 pages, 4 figures, invited talk at SOHO24

Published
2011
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11. Domination of the K-Radiation at a Z-Pinch Stagnation on Z by Numerous Tiny Spots and the Properties of the Spots Inferred by Experimental Determination of the K-Line Opacities

Author

Maron, Y., primary, Bernshtam, V., additional, Zarnitsky, Y., additional, Fisher, V., additional, Nedostup, O., additional, Ampleford, D. J., additional, Jennings, C. A., additional, Jones, B., additional, Cuneo, M. E., additional, Rochau, G. A., additional, Dunham, G. S., additional, and Loisel, G. P., additional

Published
2022
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12. Development and integration of photonic Doppler velocimetry as a diagnostic for radiation driven experiments on the Z-machine

Author

Swanson, K. J., primary, Jaar, G. S., additional, Mayes, D. C., additional, Mancini, R. C., additional, Ivanov, V. V., additional, Astanovitskiy, A. L., additional, Dmitriev, O., additional, Klemmer, A. W., additional, De La Cruz, C., additional, Dolan, D., additional, Porwitzky, A., additional, Loisel, G. P., additional, and Bailey, J. E., additional

Published
2022
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17. Review of pulsed power-driven high energy density physics research on Z at Sandia

Author

Sinars, D. B., primary, Sweeney, M. A., additional, Alexander, C. S., additional, Ampleford, D. J., additional, Ao, T., additional, Apruzese, J. P., additional, Aragon, C., additional, Armstrong, D. J., additional, Austin, K. N., additional, Awe, T. J., additional, Baczewski, A. D., additional, Bailey, J. E., additional, Baker, K. L., additional, Ball, C. R., additional, Barclay, H. T., additional, Beatty, S., additional, Beckwith, K., additional, Bell, K. S., additional, Benage, J. F., additional, Bennett, N. L., additional, Blaha, K., additional, Bliss, D. E., additional, Boerner, J. J., additional, Bourdon, C. J., additional, Branch, B. A., additional, Brown, J. L., additional, Campbell, E. M., additional, Campbell, R. B., additional, Chacon, D. G., additional, Chandler, G. A., additional, Chandler, K., additional, Christenson, P. J., additional, Christison, M. D., additional, Christner, E. B., additional, Clay, R. C., additional, Cochrane, K. R., additional, Colombo, A. P., additional, Cook, B. M., additional, Coverdale, C. A., additional, Cuneo, M. E., additional, Custer, J. S., additional, Dasgupta, A., additional, Davis, J.-P., additional, Desjarlais, M. P., additional, Dolan, D. H., additional, Douglass, J. D., additional, Dunham, G. S., additional, Duwal, S., additional, Edens, A. D., additional, Edwards, M. J., additional, Evstatiev, E. G., additional, Farfan, B. G., additional, Fein, J. R., additional, Field, E. S., additional, Fisher, J. A., additional, Flanagan, T. M., additional, Flicker, D. G., additional, Furnish, M. D., additional, Galloway, B. R., additional, Gard, P. D., additional, Gardiner, T. A., additional, Geissel, M., additional, Giuliani, J. L., additional, Glinsky, M. E., additional, Gomez, M. R., additional, Gomez, T., additional, Grim, G. P., additional, Hahn, K. D., additional, Haill, T. A., additional, Hamlin, N. D., additional, Hammer, J. H., additional, Hansen, S. B., additional, Hanshaw, H. L., additional, Harding, E. C., additional, Harvey-Thompson, A. J., additional, Headley, D., additional, Herrmann, M. C., additional, Hess, M. H., additional, Highstrete, C., additional, Hurricane, O. A., additional, Hutsel, B. T., additional, Jennings, C. A., additional, Johns, O. M., additional, Johnson, D., additional, Johnston, M. D., additional, Jones, B. M., additional, Jones, M. C., additional, Jones, P. A., additional, Kalita, P. E., additional, Kamm, R. J., additional, Kellogg, J. W., additional, Kiefer, M. L., additional, Kimmel, M. W., additional, Knapp, P. F., additional, Knudson, M. D., additional, Kreft, A., additional, Laity, G. R., additional, Lake, P. W., additional, Lamppa, D. C., additional, Langston, W. L., additional, Lash, J. S., additional, LeChien, K. R., additional, Leckbee, J. J., additional, Leeper, R. J., additional, Leifeste, G. T., additional, Lemke, R. W., additional, Lewis, W., additional, Lewis, S. A., additional, Loisel, G. P., additional, Looker, Q. M., additional, Lopez, A. J., additional, Lucero, D. J., additional, MacLaren, S. A., additional, Magyar, R. J., additional, Mangan, M. A., additional, Martin, M. R., additional, Mattsson, T. R., additional, Matzen, M. K., additional, Maurer, A. J., additional, Mazarakis, M. G., additional, McBride, R. D., additional, McLean, H. S., additional, McCoy, C. A., additional, McKee, G. R., additional, McKenney, J. L., additional, Miles, A. R., additional, Mills, J. A., additional, Mitchell, M. D., additional, Moore, N. W., additional, Myers, C. E., additional, Nagayama, T., additional, Natoni, G., additional, Owen, A. C., additional, Patel, S., additional, Peterson, K. J., additional, Pointon, T. D., additional, Porter, J. L., additional, Porwitzky, A. J., additional, Radovich, S., additional, Raman, K. S., additional, Rambo, P. K., additional, Reinhart, W. D., additional, Robertson, G. K., additional, Rochau, G. A., additional, Root, S., additional, Rose, D. V., additional, Rovang, D. C., additional, Ruiz, C. L., additional, Ruiz, D. E., additional, Sandoval, D., additional, Savage, M. E., additional, Sceiford, M. E., additional, Schaeuble, M. A., additional, Schmit, P. F., additional, Schollmeier, M. S., additional, Schwarz, J., additional, Seagle, C. T., additional, Sefkow, A. B., additional, Seidel, D. B., additional, Shipley, G. A., additional, Shores, J., additional, Shulenburger, L., additional, Simpson, S. C., additional, Slutz, S. A., additional, Smith, I. C., additional, Speas, C. S., additional, Specht, P. E., additional, Speir, M. J., additional, Spencer, D. C., additional, Springer, P. T., additional, Steiner, A. M., additional, Stoltzfus, B. S., additional, Stygar, W. A., additional, Ward Thornhill, J., additional, Torres, J. A., additional, Townsend, J. P., additional, Tyler, C., additional, Vesey, R. A., additional, Wakeland, P. E., additional, Webb, T. J., additional, Weinbrecht, E. A., additional, Weis, M. R., additional, Welch, D. R., additional, Wise, J. L., additional, Wu, M., additional, Yager-Elorriaga, D. A., additional, Yu, A., additional, and Yu, E. P., additional

Published
2020
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19. Systematic Study of L -Shell Opacity at Stellar Interior Temperatures

Author

Nagayama, T., primary, Bailey, J. E., additional, Loisel, G. P., additional, Dunham, G. S., additional, Rochau, G. A., additional, Blancard, C., additional, Colgan, J., additional, Cossé, Ph., additional, Faussurier, G., additional, Fontes, C. J., additional, Gilleron, F., additional, Hansen, S. B., additional, Iglesias, C. A., additional, Golovkin, I. E., additional, Kilcrease, D. P., additional, MacFarlane, J. J., additional, Mancini, R. C., additional, More, R. M., additional, Orban, C., additional, Pain, J.-C., additional, Sherrill, M. E., additional, and Wilson, B. G., additional

Published
2019
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22. A 7.2 keV spherical x-ray crystal backlighter for two-frame, two-color backlighting at Sandia’s Z Pulsed Power Facility

Author

Schollmeier, M. S., primary, Knapp, P. F., additional, Ampleford, D. J., additional, Harding, E. C., additional, Jennings, C. A., additional, Lamppa, D. C., additional, Loisel, G. P., additional, Martin, M. R., additional, Robertson, G. K., additional, Shores, J. E., additional, Smith, I. C., additional, Speas, C. S., additional, Weis, M. R., additional, Porter, J. L., additional, and McBride, R. D., additional

Published
2017
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25. Direct measurement of the inertial confinement time in a magnetically driven implosion

Author

Knapp, P. F., primary, Martin, M. R., additional, Dolan, D. H., additional, Cochrane, K., additional, Dalton, D., additional, Davis, J.-P., additional, Jennings, C. A., additional, Loisel, G. P., additional, Romero, D. H., additional, Smith, I. C., additional, Yu, E. P., additional, Weis, M. R., additional, Mattsson, T. R., additional, McBride, R. D., additional, Peterson, K., additional, Schwarz, J., additional, and Sinars, D. B., additional

Published
2017
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29. A higher-than-predicted measurement of iron opacity at solar interior temperatures

Author

Bailey, J. E., primary, Nagayama, T., additional, Loisel, G. P., additional, Rochau, G. A., additional, Blancard, C., additional, Colgan, J., additional, Cosse, Ph., additional, Faussurier, G., additional, Fontes, C. J., additional, Gilleron, F., additional, Golovkin, I., additional, Hansen, S. B., additional, Iglesias, C. A., additional, Kilcrease, D. P., additional, MacFarlane, J. J., additional, Mancini, R. C., additional, Nahar, S. N., additional, Orban, C., additional, Pain, J.-C., additional, Pradhan, A. K., additional, Sherrill, M., additional, and Wilson, B. G., additional

Published
2014
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31. ZAPP: The Z Astrophysical Plasma Properties collaboration

Author

Rochau, G. A., primary, Bailey, J. E., additional, Falcon, R. E., additional, Loisel, G. P., additional, Nagayama, T., additional, Mancini, R. C., additional, Hall, I., additional, Winget, D. E., additional, Montgomery, M. H., additional, and Liedahl, D. A., additional

Published
2014
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32. Model uncertainties of local-thermodynamic-equilibrium K-shell spectroscopy.

Author

Nagayama, T., Bailey, J.E., Mancini, R.C., Iglesias, C.A., Hansen, S.B., Blancard, C., Chung, H.K., Colgan, J., Cosse, Ph., Faussurier, G., Florido, R., Fontes, C.J., Gilleron, F., Golovkin, I.E., Kilcrease, D.P., Loisel, G., MacFarlane, J.J., Pain, J.-C., Rochau, G.A., and Sherrill, M.E.

Abstract

Local-thermodynamic-equilibrium (LTE) K-shell spectroscopy is a common tool to diagnose electron density, n e , and electron temperature, T e , of high-energy-density (HED) plasmas. Knowing the accuracy of such diagnostics is important to provide quantitative conclusions of many HED-plasma research efforts. For example, Fe opacities were recently measured at multiple conditions at the Sandia National Laboratories Z machine (Bailey et al., 2015), showing significant disagreement with modeled opacities. Since the plasma conditions were measured using K-shell spectroscopy of tracer Mg (Nagayama et al., 2014), one concern is the accuracy of the inferred Fe conditions. In this article, we investigate the K-shell spectroscopy model uncertainties by analyzing the Mg spectra computed with 11 different models at the same conditions. We find that the inferred conditions differ by ±20–30% in n e and ±2–4% in T e depending on the choice of spectral model. Also, we find that half of the T e uncertainty comes from n e uncertainty. To refine the accuracy of the K-shell spectroscopy, it is important to scrutinize and experimentally validate line-shape theory. We investigate the impact of the inferred n e and T e model uncertainty on the Fe opacity measurements. Its impact is small and does not explain the reported discrepancies. [ABSTRACT FROM AUTHOR]

Published
2016
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34. Radiative properties of stellar envelopes: Comparison of asteroseismic results to opacity calculations and measurements for iron and nickel.

Author

Turck-Chièze, S., Gilles, D., Le Pennec, M., Blenski, T., Thais, F., Bastiani-Ceccotti, S., Blancard, C., Busquet, M., Caillaud, T., Colgan, J., Cossé, P., Delahaye, F., Ducreta, J.E., Faussurier, G., Fontes, C.J., Gilleron, F., Guzik, J., Harris, J.W., Kilcrease, D.P., and Loisel, G.

Abstract

Abstract: The international OPAC consortium consists of astrophysicists, plasma physicists and experimentalists who examine opacity calculations used in stellar physics that appear questionable and perform new calculations and laser experiments to understand the differences and improve the calculations. We report on iron and nickel opacities for envelopes of stars from 2 to and deliver our first conclusions concerning the reliability of the used calculations by illustrating the importance of the configuration interaction and of the completeness of the calculations for temperatures around 15–27 eV. [Copyright &y& Elsevier]

Published
2013
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35. Comparison of Fe and Ni opacity calculations for a better understanding of pulsating stellar envelopes.

Author

Gilles, D., Turck-Chièze, S., Loisel, G., Piau, L., Ducret, J.-E., Poirier, M., Blenski, T., Thais, F., Blancard, C., Cossé, P., Faussurier, G., Gilleron, F., Pain, J.C., Porcherot, Q., Guzik, J.A., Kilcrease, D.P., Magee, N.H., Harris, J., Busquet, M., and Delahaye, F.

Subjects
COMPARATIVE studies, OPACITY (Optics), OPTICAL properties of metals, STELLAR oscillations, OPTICAL constants, ASTROPHYSICS, ABSORPTION spectra, TEMPERATURE effect, CIRCUMSTELLAR matter
Abstract

Abstract: Opacity is an important ingredient of the evolution of stars. The calculation of opacity coefficients is complicated by the fact that the plasma contains partially ionized heavy ions that contribute to opacity dominated by H and He. Up to now, the astrophysical community has greatly benefited from the work of the contributions of Los Alamos , Livermore and the Opacity Project (OP) . However unexplained differences of up to 50% in the radiative forces and Rosseland mean values for Fe have been noticed for conditions corresponding to stellar envelopes. Such uncertainty has a real impact on the understanding of pulsating stellar envelopes, on the excitation of modes, and on the identification of the mode frequencies. Temperature and density conditions equivalent to those found in stars can now be produced in laboratory experiments for various atomic species. Recently the photo-absorption spectra of nickel and iron plasmas have been measured during the LULI 2010 campaign, for temperatures between 15 and 40 eV and densities of ∼3 mg/cm3. A large theoretical collaboration, the “OPAC”, has been formed to prepare these experiments. We present here the set of opacity calculations performed by eight different groups for conditions relevant to the LULI 2010 experiment and to astrophysical stellar envelope conditions. [Copyright &y& Elsevier]

Published
2011
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36. Theoretical interpretation of X-rays photo-absorption in medium-Z elements plasmas measured at LULI2000 facility.

Author

Blenski, T., Loisel, G., Poirier, M., Thais, F., Arnault, P., Caillaud, T., Fariaut, J., Gilleron, F., Pain, J.-C., Porcherot, Q., Reverdin, C., Silvert, V., Villette, B., Bastiani-Ceccotti, S., Turck-Chièze, S., Foelsner, W., and de Gaufridy De Dortan, F.

Subjects
LIGHT absorption, PLASMA gases, NUCLEAR facilities, HEAT radiation & absorption, OPACITY (Optics), COMPUTER software, WAVELENGTHS, PHASE transitions, RELATIVITY (Physics), TEMPERATURE effect
Abstract

Abstract: We analyzed the spectra of X-ray transmission through radiatively heated medium-Z plasma (Fe, Ni, Cu and Ge) measured at LULI2000 facility in the wavelength range of 2p–nd transitions. The analysis was performed using the statistical superconfiguration code SCO, two line-by-line opacity codes based on the HULLAC and FAC packages and a new hybrid statistical-detailed code SCORCG. The temperature and mass density of the samples were estimated from hydrodynamic simulations based on the cavity radiative temperature measurements. The theory–experiment agreement is relatively good in the wavelength range corresponding to the 2p–3d transitions except in the germanium case. In the wavelength range of the 2p–2d, n > 3 transitions a relatively good theory–experiment agreement was found in the copper case. As predicted by calculations the separation of the characteristic spin-orbit-split 2p–3d structures, absent in the iron measured spectrum, appears in the nickel spectrum and is visible in the copper and germanium spectra. Comparisons of the experimental transmission with calculations confirm the importance of the relativistic configuration interaction. The absorption strength of the measured germanium 2p–3d transition is much larger than that obtained from the codes. Spatial temperature and density gradients, relatively high in the germanium sample, may be at the origin of this discrepancy. [Copyright &y& Elsevier]

Published
2011
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37. Absorption spectroscopy of mid and neighboring Z plasmas: Iron, nickel,copper and germanium.

Author

Loisel, G., Arnault, P., Bastiani-Ceccotti, S., Blenski, T., Caillaud, T., Fariaut, J., Fölsner, W., Gilleron, F., Pain, J.-C., Poirier, M., Reverdin, C., Silvert, V., Thais, F., Turck-Chièze, S., and Villette, B.

Subjects
ABSORPTION spectra, LASER plasmas, METALS, PHYSICAL measurements, TEMPERATURE effect, WAVELENGTHS, ULTRASHORT laser pulses, SIMULATION methods & models, OPACITY (Optics)
Abstract

Abstract: Opacities of four medium Z element plasmas (iron, nickel, copper and germanium) have been measured at the LULI-2000 facility in similar conditions: temperatures between 15 and 25eV and densities between 2 and 10mg/cm3, in a wavelength range (8–18Å) including the strong 2p–3d structures. Two laser beams from the LULI facility were used in the nanosecond-picosecond configuration. The NANO-2000 beam (at λ =0.53μm) heated a gold hohlraum with an energy between 30 and 150J with a duration of 0.6ns. Samples covering half a hohlraum hole were thus radiatively heated. The picosecond pulse PICO-2000 beam (at λ =1.053μm) has been used to produce a short (about 10ps) X-ray backlighter in order to reduce time variations of temperatures and densities during the measurement. A crystal high-resolution spectrometer was used as the main diagnostic to record at the same time the non-absorbed and the absorbed backlighter spectra. Radiation temperatures were measured using a broadband spectrometer. 1D and 2D simulations have been performed in order to estimate hydrodynamic plasmas parameters. The measured spectra have been compared with theoretical ones obtained using either the superconfiguration code SCO or the detailed term accounting code HULLAC. These comparisons allow us to check the modeling of the statistical broadening and of the spin-orbit splitting of the 2p–3d transitions and related effects such as the interaction between relativistic subconfigurations belonging to the same non-relativistic configuration. [Copyright &y& Elsevier]

Published
2009
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38. On plasma radiative properties in stellar conditions.

Author

Turck-Chièze, S., Delahaye, F., Gilles, D., Loisel, G., and Piau, L.

Subjects
PLASMA radiation, STELLARATORS, SIMULATION methods & models, STELLAR dynamics, HELIOSEISMOLOGY, MASS attenuation coefficients, LASERS in physics, PHYSICS experiments
Abstract

Abstract: The knowledge of stellar evolution is evolving quickly thanks to an increased number of opportunities to scrutinize the stellar internal plasma properties by stellar seismology and by 1D and 3D simulations. These new tools help us to introduce the internal dynamical phenomena in stellar modeling. A proper inclusion of these processes supposes a real confidence in the microscopic physics used, partly checked by solar or stellar acoustic modes. In the present paper we first recall which fundamental physics has been recently verified by helioseismology. Then we recall that opacity is an important ingredient of the secular evolution of stars and we point out why it is necessary to measure absorption coefficients and degrees of ionization in the laboratory for some well identified astrophysical conditions. We examine two specific experimental conditions which are accessible to large laser facilities and are suitable to solve some interesting questions of the stellar community: are the solar internal radiative interactions properly estimated and what is the proper role of the opacity in the excitation of the non-radial modes in the envelop of the β Cepheids and the Be stars? At the end of the paper we point out the difficulties of the experimental approach that we need to overcome. [Copyright &y& Elsevier]

Published
2009
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