Plasma evolution and continuum lowering in hot dense matter generated by X-ray free electron lasers
<p>The advent of the 4th generation X-ray sources paves the way for a new phase of experimental investigation of Hot-Dense plasmas. At the Linac Coherent Light Source (LCLS), pulses of keV X-rays, shorter than 100 fs, and with intensities up to 10<sup>18</sup> W·cm<sup>-2<...
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| Format: | Thesis |
| Language: | English |
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2014
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| _version_ | 1817932598304833536 |
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| author | Ciricosta, O |
| author2 | Wark, J |
| author_facet | Wark, J Ciricosta, O |
| author_sort | Ciricosta, O |
| collection | OXFORD |
| description | <p>The advent of the 4th generation X-ray sources paves the way for a new phase of experimental investigation of Hot-Dense plasmas. At the Linac Coherent Light Source (LCLS), pulses of keV X-rays, shorter than 100 fs, and with intensities up to 10<sup>18</sup> W·cm<sup>-2</sup>, are routinely produced, allowing for the production of uniform samples of solid-density plasmas. The simple single-photon X-ray absorption mechanism can be easily modelled, so that the plasma conditions can be accurately retrieved, without relying on diagnostic techniques that are not benchmarked in this high density regime.</p> <p>The work presented here describes the results of the first experiment where the LCLS interacts with a solid Al target, isochorically heating it at temperatures up to 190 eV. The system is described by the SCFLY non-LTE model, where the density and temperature are computed self consistently, as a consequence of the detailed atomic processes, rather than imposed by the user. The approximations affecting the simulations are discussed in detail.</p> <p>The code is first validated, by modelling the charge state distribution measured in a previous experiment (L. Young <em>et. al</em>), where the LCLS interacts with a Ne gas, a simplified (collisionless) problem. Then it is used to model the K-alpha spectroscopic data obtained for Al. The plasma evolution, explained by SCFLY simulations, is found to be primarily determined by collisions, whose visible effects on the experimental spectra are discussed.</p> <p>By varying the wavelength of the laser and observing the change in the K-alpha fluorescence, the K-edges for different ions in the plasma were determined, leading to a charge resolved measurement of continuum lowering in the HDM system. The results disagree with the widely used Stewart-Pyatt model, with the disagreement increasing for higher charge states, but are consistent with the older Ecker-Kroell model. These results have profound implications for dense plasma modelling.</p> |
| first_indexed | 2024-03-06T20:26:23Z |
| format | Thesis |
| id | oxford-uuid:2f872e7c-80dd-43d5-b171-b1d14957c0e6 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-12-09T03:40:27Z |
| publishDate | 2014 |
| record_format | dspace |
| spelling | oxford-uuid:2f872e7c-80dd-43d5-b171-b1d14957c0e62024-12-07T11:21:59ZPlasma evolution and continuum lowering in hot dense matter generated by X-ray free electron lasers Thesishttp://purl.org/coar/resource_type/c_db06uuid:2f872e7c-80dd-43d5-b171-b1d14957c0e6Atomic and laser physicsEnglishOxford University Research Archive - Valet2014Ciricosta, OWark, J<p>The advent of the 4th generation X-ray sources paves the way for a new phase of experimental investigation of Hot-Dense plasmas. At the Linac Coherent Light Source (LCLS), pulses of keV X-rays, shorter than 100 fs, and with intensities up to 10<sup>18</sup> W·cm<sup>-2</sup>, are routinely produced, allowing for the production of uniform samples of solid-density plasmas. The simple single-photon X-ray absorption mechanism can be easily modelled, so that the plasma conditions can be accurately retrieved, without relying on diagnostic techniques that are not benchmarked in this high density regime.</p> <p>The work presented here describes the results of the first experiment where the LCLS interacts with a solid Al target, isochorically heating it at temperatures up to 190 eV. The system is described by the SCFLY non-LTE model, where the density and temperature are computed self consistently, as a consequence of the detailed atomic processes, rather than imposed by the user. The approximations affecting the simulations are discussed in detail.</p> <p>The code is first validated, by modelling the charge state distribution measured in a previous experiment (L. Young <em>et. al</em>), where the LCLS interacts with a Ne gas, a simplified (collisionless) problem. Then it is used to model the K-alpha spectroscopic data obtained for Al. The plasma evolution, explained by SCFLY simulations, is found to be primarily determined by collisions, whose visible effects on the experimental spectra are discussed.</p> <p>By varying the wavelength of the laser and observing the change in the K-alpha fluorescence, the K-edges for different ions in the plasma were determined, leading to a charge resolved measurement of continuum lowering in the HDM system. The results disagree with the widely used Stewart-Pyatt model, with the disagreement increasing for higher charge states, but are consistent with the older Ecker-Kroell model. These results have profound implications for dense plasma modelling.</p> |
| spellingShingle | Atomic and laser physics Ciricosta, O Plasma evolution and continuum lowering in hot dense matter generated by X-ray free electron lasers |
| title | Plasma evolution and continuum lowering in hot dense matter generated by X-ray free electron lasers |
| title_full | Plasma evolution and continuum lowering in hot dense matter generated by X-ray free electron lasers |
| title_fullStr | Plasma evolution and continuum lowering in hot dense matter generated by X-ray free electron lasers |
| title_full_unstemmed | Plasma evolution and continuum lowering in hot dense matter generated by X-ray free electron lasers |
| title_short | Plasma evolution and continuum lowering in hot dense matter generated by X-ray free electron lasers |
| title_sort | plasma evolution and continuum lowering in hot dense matter generated by x ray free electron lasers |
| topic | Atomic and laser physics |
| work_keys_str_mv | AT ciricostao plasmaevolutionandcontinuumloweringinhotdensemattergeneratedbyxrayfreeelectronlasers |