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Pérez-Callejo G, Marley EV, Liedahl DA, Jarrott LC, Kemp GE, Heeter RF, Emig JA, Foord ME, Schneider MB, Rose SJ, Wark JS. Demonstration of Geometric Effects and Resonant Scattering in the X-Ray Spectra of High-Energy-Density Plasmas. PHYSICAL REVIEW LETTERS 2021; 126:085001. [PMID: 33709744 DOI: 10.1103/physrevlett.126.085001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Revised: 11/30/2020] [Accepted: 01/19/2021] [Indexed: 06/12/2023]
Abstract
In a plasma of sufficient size and density, photons emitted within the system have a probability of being reabsorbed and reemitted multiple times-a phenomenon known in astrophysics as resonant scattering. This effect alters the ratio of optically thick to optically thin lines, depending on the plasma geometry and viewing angle, and has significant implications for the spectra observed in a number of astrophysical scenarios, but has not previously been studied in a controlled laboratory plasma. We demonstrate the effect in the x-ray spectra emitted by cylindrical plasmas generated by high power laser irradiation, and the results confirm the geometrical interpretation of resonant scattering.
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Affiliation(s)
- G Pérez-Callejo
- Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
| | - E V Marley
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - D A Liedahl
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - L C Jarrott
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - G E Kemp
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - R F Heeter
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - J A Emig
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - M E Foord
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - M B Schneider
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - S J Rose
- Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
| | - J S Wark
- Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
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Renner O, Kerr FM, Wolfrum E, Hawreliak J, Chambers D, Rose SJ, Wark JS, Scott HA, Patel P. Radiation transfer effects on the spectra of laser-generated plasmas. PHYSICAL REVIEW LETTERS 2006; 96:185002. [PMID: 16712368 DOI: 10.1103/physrevlett.96.185002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2005] [Indexed: 05/09/2023]
Abstract
Experimental x-ray spectra of the H-like 2p --> 1s (Lyman-alpha) doublet have been obtained using time-integrated high-resolution spectroscopy of a constrained-flow, laser-generated aluminum plasma. These spectra show monotonic alteration of the relative intensities of the doublet components with distance from the target surface. Excellent agreement between experiment and theory is found only if the modeling includes both ion collisional rates between the fine-structure components of the level and, more importantly, the radiative pumping of one Lyman-alpha component by the other component along the direction of the major velocity gradient (i.e., perpendicular to the direction of spectra observation). Understanding radiation transfer in plasmas with high velocity gradients is important in modeling many astrophysical objects, and this experiment acts as a benchmark for such complex calculations.
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Affiliation(s)
- O Renner
- Institute of Physics, Czech Academy of Sciences, 18211 Prague, Czech Republic.
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