29 results on '"S. P. Preval"'
Search Results
2. Mind the gap – Part 1: Accurately locating warm marine boundary layer clouds and precipitation using spaceborne radars
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Katia Lamer, Pavlos Kollias, S. P. Preval, and Alessandro Battaglia
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Atmospheric Science ,Virga ,010504 meteorology & atmospheric sciences ,lcsh:TA715-787 ,Cloud top ,Cloud cover ,lcsh:Earthwork. Foundations ,0211 other engineering and technologies ,02 engineering and technology ,01 natural sciences ,lcsh:Environmental engineering ,law.invention ,law ,Cloud base ,Environmental science ,Clutter ,Sensitivity (control systems) ,Precipitation ,lcsh:TA170-171 ,Radar ,021101 geological & geomatics engineering ,0105 earth and related environmental sciences ,Remote sensing - Abstract
Ground-based radar observations show that, over the eastern North Atlantic, 50 % of warm marine boundary layer (WMBL) hydrometeors occur below 1.2 km and have reflectivities of −17 dBZ, thus making their detection from space susceptible to the extent of surface clutter and radar sensitivity. Surface clutter limits the ability of the CloudSat cloud profiling radar (CPR) to observe the true cloud base in ∼52 % of the cloudy columns it detects and true virga base in ∼80 %, meaning the CloudSat CPR often provides an incomplete view of even the clouds it does detect. Using forward simulations, we determine that a 250 m resolution radar would most accurately capture the boundaries of WMBL clouds and precipitation; that being said, because of sensitivity limitations, such a radar would suffer from cloud cover biases similar to those of the CloudSat CPR. Observations and forward simulations indicate that the CloudSat CPR fails to detect 29 %–43 % of the cloudy columns detected by ground-based sensors. Out of all configurations tested, the 7 dB more sensitive EarthCARE CPR performs best (only missing 9.0 % of cloudy columns) indicating that improving radar sensitivity is more important than decreasing the vertical extent of surface clutter for measuring cloud cover. However, because 50 % of WMBL systems are thinner than 400 m, they tend to be artificially stretched by long sensitive radar pulses, hence the EarthCARE CPR overestimation of cloud top height and hydrometeor fraction. Thus, it is recommended that the next generation of space-borne radars targeting WMBL science should operate interlaced pulse modes including both a highly sensitive long-pulse mode and a less sensitive but clutter-limiting short-pulse mode.
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- 2020
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3. What can ISM and non-photospheric highly ionised lines in white dwarf spectra reveal about the β CMa tunnel?
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Nicolle L. Finch, Thomas R. Ayres, S. P. Preval, Matthew Bainbridge, N. Reindl, Sarah L. Casewell, Martin A. Barstow, and B. Welsh
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Physics ,Photosphere ,010308 nuclear & particles physics ,White dwarf ,Astronomy and Astrophysics ,Astrophysics ,01 natural sciences ,Spectral line ,Galaxy ,Interstellar medium ,Supernova ,Stars ,Space and Planetary Science ,Ionization ,0103 physical sciences ,010303 astronomy & astrophysics - Abstract
White dwarfs are useful objects with which to study the local interstellar medium (ISM). High ionisation state absorption features that cannot be attributed to the photosphere or the ISM have been observed along the line-of-sight to a number of white dwarf stars. Suggested origins of these lines include ionisation from past supernovae, stellar winds, circumstellar disks, photoionisation from nearby hot stars or also from the white dwarf itself. In this study we consider the origin of these non-photospheric highly ionised lines in two stars towards a rarefied region of the galaxy known as the extended β CMa Tunnel. We present preliminary results from our analysis of the first of these two stars.
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- 2019
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4. A far-UV survey of three hot, metal-polluted white dwarf stars: WD0455-282, WD0621-376, and WD2211-495
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S. P. Preval, Nicole Reindl, Jay B. Holberg, John K. Webb, Chung-Chi Lee, Matthew Bainbridge, Thomas R. Ayres, Jiting Hu, John D. Barrow, and Martin A. Barstow
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Physics ,Foundation (engineering) ,Astronomy ,White dwarf ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Spitzer Space Telescope ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics - Abstract
Using newly obtained high-resolution data ($R\sim{1\times{10}^{5}}$) from the \textit{Hubble Space Telescope}, and archival UV data from the \textit{Far Ultraviolet Spectroscopic Explorer} we have conducted a detailed UV survey of the three hot, metal-polluted white dwarfs WD0455-282, WD0621-376, and WD2211-495. Using bespoke model atmospheres we measured $T_{\mathrm{eff}}$, log $g$, and photospheric abundances for these stars. In conjunction with data from Gaia we measured masses, radii, and gravitational redshift velocities for our sample of objects. We compared the measured photospheric abundances with those predicted by radiative levitation theory, and found that the observed Si abundances in all three white dwarfs, and the observed Fe abundances in WD0621-376 and WD2211-495, were larger than those predicted by an order of magnitude. These findings imply not only an external origin for the metals, but also ongoing accretion, as the metals not supported by radiative levitation would sink on extremely short timescales. We measured the radial velocities of several absorption features along the line of sight to the three objects in our sample, allowing us to determine the velocities of the photospheric and interstellar components along the line of sight for each star. Interestingly, we made detections of circumstellar absorption along the line of sight to WD0455-282 with three velocity components. To our knowledge, this is the first such detection of multi-component circumstellar absorption along the line of sight to a white dwarf., 19 pages, 23 figures, 8 tables. Accepted for publication in the Monthly Notices of the Royal Astronomical Society
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- 2019
5. Rate Coefficients for Dielectronic Recombination of Carbon-like 40Ca14+
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Z. K. Huang, W. Q. Yang, Wenchao Ma, Shu-Xing Wang, N. R. Badnell, H. B. Wang, Chongyang Chen, Weiqiang Wen, C. Y. Zhang, You-Jin Yuan, Meitang Tang, J.C. Yang, X. Liu, J. J. Li, S. P. Preval, X. H. Ma, Xiao-Ming Ma, Lijun Mao, Da-Yu Yin, N. Khan, Lin-Fan Zhu, Dongmei Zhao, and Die-yan Chen
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Physics ,chemistry ,Space and Planetary Science ,chemistry.chemical_element ,Astronomy and Astrophysics ,Atomic spectroscopy ,Atomic physics ,Spectroscopy ,Carbon ,Recombination - Published
- 2020
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6. Constraining the magnetic field on white dwarf surfaces; Zeeman effects and fine structure constant variation
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Nicole Reindl, Chung-Chi Lee, Julian C. Berengut, John D. Barrow, Matthew Bainbridge, V. A. Dzuba, Jay B. Holberg, Thomas R. Ayres, Robert F. Carswell, Victor V. Flambaum, Jiting Hu, W. Ü. L. Tchang-Brillet, Martin A. Barstow, S. P. Preval, John K. Webb, Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA (UMR_8112)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-CY Cergy Paris Université (CY), Barrow, John [0000-0002-6083-9751], and Apollo - University of Cambridge Repository
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Physics ,atomic processes ,Library science ,FOS: Physical sciences ,Astronomy and Astrophysics ,line: profiles ,General Relativity and Quantum Cosmology (gr-qc) ,magnetic fields ,01 natural sciences ,General Relativity and Quantum Cosmology ,Royal Commission ,Scholarship ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,0103 physical sciences ,[PHYS.GRQC]Physics [physics]/General Relativity and Quantum Cosmology [gr-qc] ,Astrophysics::Solar and Stellar Astrophysics ,010306 general physics ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,010303 astronomy & astrophysics ,Data archive ,Solar and Stellar Astrophysics (astro-ph.SR) ,white dwarfs - Abstract
White dwarf atmospheres are subjected to gravitational potentials around $10^5$ times larger than occur on Earth. They provide a unique environment in which to search for any possible variation in fundamental physics in the presence of strong gravitational fields. However, a sufficiently strong magnetic field will alter absorption line profiles and introduce additional uncertainties in measurements of the fine structure constant. Estimating the magnetic field strength is thus essential in this context. Here we model the absorption profiles of a large number of atomic transitions in the white dwarf photosphere, including first-order Zeeman effects in the line profiles, varying the magnetic field as a free parameter. We apply the method to a high signal-to-noise, high-resolution, far-ultraviolet HST/STIS spectrum of the white dwarf G191-B2B. The method yields a sensitive upper limit on its magnetic field of $B < 2300$ Gauss at the $3\sigma$ level. Using this upper limit we find that the potential impact of quadratic Zeeman shifts on measurements of the fine structure constant in G191-B2B is 4 orders of magnitude below laboratory wavelength uncertainties., Comment: 10 pages, 5 figures
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- 2019
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7. Dielectronic recombination of lanthanide and low ionization state tungsten ions: W$^{13+}$ - W$^{1+}$
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S. P. Preval, N. R. Badnell, and M. G. O'Mullane
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Physics ,Atomic Physics (physics.atom-ph) ,Divertor ,FOS: Physical sciences ,chemistry.chemical_element ,Plasma ,Tungsten ,Condensed Matter Physics ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Physics - Plasma Physics ,010305 fluids & plasmas ,Ion ,Physics - Atomic Physics ,Plasma Physics (physics.plasm-ph) ,chemistry ,Impurity ,Sputtering ,Physics::Plasma Physics ,Ionization ,0103 physical sciences ,Beryllium ,Atomic physics ,010306 general physics - Abstract
The experimental thermonuclear reactor, ITER, is currently being constructed in Cadarache, France. The reactor vessel will be constructred with a beryllium coated wall, and a tungsten coated divertor. As a plasma-facing component, the divertor will be under conditions of extreme temperature, resulting in the sputtering of tungsten impurities into the main body plasma. Modelling and understanding the potential cooling effects of these impurities requires detailed collisional-radiative modelling. These models require a wealth of atomic data for the various atomic species in the plasma. In particular, partial, final-state resolved dielectronic/radiative recombination (DR/RR) rate coefficients for tungsten are required. In this manuscript, we present our calculations of detailed DR/RR rate coefficients for the lanthanide-like, and low ionization stages of tungsten, spanning charge states W$^{13+}$ to W$^{1+}$. The calculations presented here constitutes the first detailed exploration of such low ionization state tungsten ions. We are able to reproduce the general trend of calculations performed by other authors, but find significant differences between ours and their DR rate coefficients, especially at the lowest temperatures considered., 23 pages, 23 figures, 3 tables. Accepted for publication in Journal of Physics B: Atomic, Molecular, and Optical Physics
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- 2018
8. Multi-wavelength observations of the EUV variable metal-rich white dwarf GD 394
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Seth Redfield, Boris T. Gänsicke, Jay Farihi, P. Wilson Cauley, Jay B. Holberg, David J. Wilson, S. P. Preval, Paul Chote, Claudia Belardi, Matthew R. Burleigh, Mark Hollands, Sarah L. Casewell, Knox S. Long, Martin A. Barstow, Detlev Koester, and Odette Toloza
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Library science ,FOS: Physical sciences ,Astrophysics::Cosmology and Extragalactic Astrophysics ,01 natural sciences ,Mauna kea ,Spitzer Space Telescope ,Observatory ,Hubble space telescope ,0103 physical sciences ,William Herschel Telescope ,media_common.cataloged_instance ,Astrophysics::Solar and Stellar Astrophysics ,European union ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics ,media_common ,Physics ,Earth and Planetary Astrophysics (astro-ph.EP) ,geography ,Summit ,geography.geographical_feature_category ,010308 nuclear & particles physics ,European research ,Astronomy and Astrophysics ,Astrophysics - Solar and Stellar Astrophysics ,13. Climate action ,Space and Planetary Science ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics - Earth and Planetary Astrophysics - Abstract
We present new Hubble Space Telescope (HST) ultraviolet and ground-based optical observations of the hot, metal-rich white dwarf GD 394. Extreme-ultraviolet (EUV) observations in 1992-1996 revealed a 1.15d periodicity with a 25 percent amplitude, hypothesised to be due to metals in a surface accretion spot. We obtained phase-resolved HST/Space Telescope Imaging Spectrograph (STIS) high-resolution far-ultraviolet (FUV) spectra of GD 394 that sample the entire period, along with a large body of supplementary data. We find no evidence for an accretion spot, with the flux, accretion rate and radial velocity of GD 394 constant over the observed timescales at ultraviolet and optical wavelengths. We speculate that the spot may have no longer been present when our observations were obtained, or that the EUV variability is being caused by an otherwise undetected evaporating planet. The atmospheric parameters obtained from separate fits to optical and ultraviolet spectra are inconsistent, as is found for multiple hot white dwarfs. We also detect non-photospheric, high-excitation absorption lines of multiple volatile elements, which could be evidence for a hot plasma cocoon surrounding the white dwarf., Accepted for publication in MNRAS
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- 2018
9. Dielectronic and trielectronic recombination rate coefficients of Be-like Ar14+
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S. P. Preval, Bobing Wu, Lin-Fan Zhu, Terrence Xu, Shu-Xing Wang, Ji Yang, Xiaolong Zhu, H. B. Wang, Lijun Mao, X. H. Ma, Stefan Schippers, Xiao-Ming Ma, Yi Yang, Ke Yao, H. S. Xu, Li-Jun Dou, Weiqiang Wen, J. J. Li, N. Khan, Xin Xu, L. N. Sheng, Sultan Mahmood, X Y Chuai, Ruishi Mao, Z. K. Huang, Dongmei Zhao, N. R. Badnell, W. Q. Xu, and You-Jin Yuan
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Physics ,QC717 ,Recombination rate ,Astronomy and Astrophysics ,Plasma ,Atmospheric temperature range ,01 natural sciences ,symbols.namesake ,Space and Planetary Science ,Ionization ,0103 physical sciences ,Rydberg formula ,symbols ,Atomic physics ,010306 general physics ,010303 astronomy & astrophysics ,Recombination ,Storage ring ,Atomic data - Abstract
Electron–ion recombination of Be-like 40Ar14+ has been measured by employing the electron–ion merged-beams method at the cooler storage ring CSRm. The measured absolute recombination rate coefficients for collision energies from 0 to 60 eV are presented, covering all dielectronic recombination (DR) resonances associated with 2s 2 → 2s2p core transitions. In addition, strong trielectronic recombination (TR) resonances associated with 2s 2 → 2p 2 core transitions were observed. Both DR and TR processes lead to series of peaks in the measured recombination spectrum, which have been identified by the Rydberg formula. Theoretical calculations of recombination rate coefficients were performed using the state-of-the-art multi-configuration Breit–Pauli atomic structure code AUTOSTRUCTURE to compare with the experimental results. The plasma rate coefficients for DR+TR of Ar14+ were deduced from the measured electron–ion recombination rate coefficients in the temperature range from 103 to 107 K, and compared with calculated data from the literature. The experimentally derived plasma rate coefficients are 60% larger and 30% lower than the previously recommended atomic data for the temperature ranges of photoionized plasmas and collisionally ionized plasmas, respectively. However, good agreement was found between experimental results and the calculations by Gu and Colgan et al. The plasma rate coefficients deduced from experiment and calculated by the current AUTOSTRUCTURE code show agreement that is better than 30% from 104 to 107 K. The present results constitute a set of benchmark data for use in astrophysical modeling.
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- 2018
10. Dielectronic recombination of the open 4d-shell of tungsten: W$^{37+}$ to W$^{28+}$
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M. G. O'Mullane, N. R. Badnell, and S. P. Preval
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Physics ,Range (particle radiation) ,Tokamak ,Atomic Physics (physics.atom-ph) ,Divertor ,FOS: Physical sciences ,chemistry.chemical_element ,Plasma ,Tungsten ,Atmospheric temperature range ,Condensed Matter Physics ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Physics - Atomic Physics ,010305 fluids & plasmas ,law.invention ,Ion ,chemistry ,Physics::Plasma Physics ,law ,Ionization ,0103 physical sciences ,Atomic physics ,010306 general physics ,QC - Abstract
Tungsten is an important element for magnetically confined fusion plasmas but has the potential to cool, or even quench the plasma due to it being an efficient radiator. Total and level-resolved dielectronic recombination (DR) rate coefficients, for all ionization stages, are essential to model tungsten. We describe a set calculations performed using the distorted wave code AUTOSTRUCTURE for the tungsten ions W$^{37+}$ to W$^{28+}$. We demonstrate the importance of relativistic configuration mixing in such calculations. In particular, we show that the partial DR rate coefficients calculated in level and configuration resolution can differ by as little as 5%, and up to as much as 75%. Using the new data, we calculate a revised steady-state ionization fraction for tungsten. We find that, relative to the ionization fraction calculated using the recombination rate coefficients of Putterich et al. (Plasma Phys. Control. Fusion, 50, 085016), the peak temperatures of W$^{37+}$ to W$^{28+}$ ionization states are shifted to lower temperatures spanning 0.9-1.6keV. This temperature range is important for understanding the performance of large tokamaks, such as ITER, because the temperatures in the pedestal, edge, scrape-off-layer and divertor region fall in this range., 15 pages, 16 figures, 3 tables. Accepted for publication in Journal of Physics B: Atomic, Molecular, and Optical Physics. Updated with DOI and bibliographic information
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- 2018
11. Iso-nuclear tungsten dielectronic recombination rates for use in magnetically-confined fusion plasmas
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N. R. Badnell, Won Ae Lee, Chris Fontes, T. Nakano, James Colgan, M. G. O'Mullane, S. P. Preval, Bowen Li, Y.B. Fu, Hyun-Kyung Chung, D.-H. Kwon, Ehud Behar, Bastiaan J. Braams, Connor Ballance, Xiaobin Ding, Chenzhong Dong, and Multiscale Dynamics
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Nuclear and High Energy Physics ,Chemistry ,Fusion plasma ,Experimental data ,chemistry.chemical_element ,Tungsten ,7. Clean energy ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,010305 fluids & plasmas ,Ion ,Nuclear physics ,0103 physical sciences ,Atomic physics ,010306 general physics ,QC ,Recombination ,Atomic data - Abstract
Under the auspices of the IAEA Atomic and Molecular Data Center and the Korean Atomic Energy Research Institute, our assembled group of authors has reviewed the current state of dielectronic recombination (DR) rate coefficients for various ion stages of tungsten (W). Subsequent recommendations were based upon available experimental data, first-principle calculations carried out in support of this paper and from available recombination data within existing atomic databases. If a recommendation was possible, data were compiled, evaluated and fitted to a functional form with associated uncertainty information retained, where available. This paper also considers the variation of the W fractional abundance due to the underlying atomic data when employing different data sets.
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- 2018
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12. Partial and Total Dielectronic Recombination Rate Coefficients for W$^{55+}$ to W$^{38+}$
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S. P. Preval, M. G. O'Mullane, and N. R. Badnell
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Physics ,Atomic Physics (physics.atom-ph) ,FOS: Physical sciences ,chemistry.chemical_element ,Plasma ,Tungsten ,Condensed Matter Physics ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Physics - Plasma Physics ,010305 fluids & plasmas ,Ion ,Physics - Atomic Physics ,Plasma Physics (physics.plasm-ph) ,chemistry ,Yield (chemistry) ,Ionization ,0103 physical sciences ,Spontaneous emission ,Atomic physics ,010306 general physics ,Wave function ,QC ,Recombination - Abstract
Dielectronic recombination (DR) is the dominant mode of recombination in magnetically confined fusion plasmas for intermediate to low-charged ions of W. Complete, final-state resolved partial isonuclear W DR rate coefficient data is required for detailed collisional-radiative modelling for such plasmas in preparation for the upcoming fusion experiment ITER. To realize this requirement, we continue {\it The Tungsten Project} by presenting our calculations for tungsten ions W$^{55+}$ to W$^{38+}$. As per our prior calculations for W$^{73+}$ to W$^{56+}$, we use the collision package {\sc autostructure} to calculate partial and total DR rate coefficients for all relevant core-excitations in intermediate coupling (IC) and configuration average (CA) using $\kappa$-averaged relativistic wavefunctions. Radiative recombination (RR) rate coefficients are also calculated for the purpose of evaluating ionization fractions. Comparison of our DR rate coefficients for W$^{46+}$ with other authors yields agreement to within 7-19\% at peak abundance verifying the reliability of our method. Comparison of partial DR rate coefficients calculated in IC and CA yield differences of a factor $\sim{2}$ at peak abundance temperature, highlighting the importance of relativistic configuration mixing. Large differences are observed between ionization fractions calculated using our recombination rate coefficient data and that of P\"{u}tterich~\etal [Plasma Phys. and Control. Fusion 50 085016, (2008)]. These differences are attributed to deficiencies in the average-atom method used by the former to calculate their data., Comment: Accepted for publication in Journal of Physics B. Manuscript contains 21 pages, 30 figures, and 7 tables
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- 2017
13. The Tungsten Project: Dielectronic Recombination Data For Collisional-Radiative Modelling In ITER
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M. G. O'Mullane, S. P. Preval, and N. R. Badnell
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Physics ,Atomic Physics (physics.atom-ph) ,Nuclear engineering ,Divertor ,FOS: Physical sciences ,chemistry.chemical_element ,Tungsten ,File format ,Physics - Atomic Physics ,chemistry ,Calculated data ,Radiative transfer ,Nuclear fusion ,Atomic physics ,QC - Abstract
Tungsten is an important metal in nuclear fusion reactors. It will be used in the divertor component of ITER (Latin for 'the way'). The Tungsten Project aims to calculate partial and total DR rate coefficients for the isonuclear sequence of Tungsten. The calculated data will be made available as and when they are produced via the open access database OPEN- ADAS in the standard adf09 and adf48 file formats. We present our progress thus far, detailing calculational methods, and showing comparisons with other available data. We conclude with plans for the future., Seven pages, four figures. To appear in the proceedings of the 19th International Conference on Atomic Processes in Plasmas, Paris 2016
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- 2016
14. Probing the Gravitational Dependence of the Fine-Structure Constant from Observations of White Dwarf Stars
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Nicole Reindl, Victor V. Flambaum, Jiting Hu, S. P. Preval, Thomas R. Ayres, John D. Barrow, John K. Webb, Jay B. Holberg, Julian C. Berengut, Vincent Dumont, V. A. Dzuba, Matthew B. Bainbridge, Martin A. Barstow, W.-Ü Lydia Tchang-Brillet, Wim Ubachs, Laboratoire Univers et Théories ( LUTH ), Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université Paris Diderot - Paris 7 ( UPD7 ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique ( LERMA ), École normale supérieure - Paris ( ENS Paris ) -Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université de Cergy Pontoise ( UCP ), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique ( CNRS ), Laboratoire Univers et Théories (LUTH (UMR_8102)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA (UMR_8112)), PSL Research University (PSL)-PSL Research University (PSL)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), Barrow, John [0000-0002-6083-9751], Apollo - University of Cambridge Repository, Atoms, Molecules, Lasers, and LaserLaB - Physics of Light
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High Energy Physics - Theory ,Cosmology and Nongalactic Astrophysics (astro-ph.CO) ,gravitation: model ,[ PHYS.ASTR ] Physics [physics]/Astrophysics [astro-ph] ,FOS: Physical sciences ,General Physics and Astronomy ,General Relativity and Quantum Cosmology (gr-qc) ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,7. Clean energy ,01 natural sciences ,General Relativity and Quantum Cosmology ,Spectral line ,[ PHYS.GRQC ] Physics [physics]/General Relativity and Quantum Cosmology [gr-qc] ,[ PHYS.HTHE ] Physics [physics]/High Energy Physics - Theory [hep-th] ,Gravitation ,High Energy Physics - Phenomenology (hep-ph) ,Gravitational field ,varying constants ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,quasar ,010306 general physics ,white dwarf ,010303 astronomy & astrophysics ,Multiplet ,Astrophysics::Galaxy Astrophysics ,Space Telescope Imaging Spectrograph ,varying alpha ,Physics ,fundamental constant: fine structure ,hot white dwarf stars ,[PHYS.HTHE]Physics [physics]/High Energy Physics - Theory [hep-th] ,absorption: spectrum ,White dwarf ,Fine-structure constant ,Quasar ,absorption spectra analysis ,High Energy Physics - Phenomenology ,High Energy Physics - Theory (hep-th) ,multiplet ,[PHYS.HPHE]Physics [physics]/High Energy Physics - Phenomenology [hep-ph] ,atomic physics ,atmosphere ,[PHYS.GRQC]Physics [physics]/General Relativity and Quantum Cosmology [gr-qc] ,[ PHYS.HPHE ] Physics [physics]/High Energy Physics - Phenomenology [hep-ph] ,Astrophysics::Earth and Planetary Astrophysics ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
Hot white dwarf stars are the ideal probe for a relationship between the fine-structure constant and strong gravitational fields, providing us with an opportunity for a direct observational test. We study a sample of hot white dwarf stars, combining far-UV spectroscopic observations, atomic physics, atmospheric modelling and fundamental physics, in the search for variation in the fine structure constant. This variation manifests as shifts in the observed wavelengths of absorption lines, such as quadruply ionized iron (FeV) and quadruply ionized nickel (NiV), when compared to laboratory wavelengths. Berengut et al. (Phys. Rev. Lett. 2013, 111, 010801) demonstrated the validity of such an analysis using high-resolution Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph (STIS) spectra of G191-B2B. We have made three important improvements by: (a) using three new independent sets of laboratory wavelengths, (b) analysing a sample of objects, and (c) improving the methodology by incorporating robust techniques from previous studies towards quasars (the Many Multiplet method). A successful detection would be the first direct measurement of a gravitational field effect on a bare constant of nature. Here we describe our approach and present preliminary results from nine objects using both FeV and NiV., Comment: 6 pages, 1 figure, published on 30th March 2017 in Universe as part of VARCOSMOFUN'16 proceedings
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- 2016
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15. Partial and total dielectronic recombination rate coefficients forW73+toW56+
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M. G. O'Mullane, S. P. Preval, and N. R. Badnell
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Physics ,Divertor ,chemistry.chemical_element ,Plasma ,Fusion power ,Tungsten ,Coupling (probability) ,01 natural sciences ,Maxwell–Boltzmann distribution ,010305 fluids & plasmas ,Ion ,symbols.namesake ,chemistry ,Ionization ,0103 physical sciences ,symbols ,Atomic physics ,010306 general physics - Abstract
Dielectronic recombination (DR) is a key atomic process which affects the spectroscopic diagnostic modelling of tungsten, most of whose ionization stages will be found somewhere in the ITER fusion reactor: in the edge, divertor, or core plasma. Accurate DR data is sparse while complete DR coverage is unsophisticated (e.g. average-atom or Burgess General Formula) as illustrated by the large uncertainties which currently exist in the tungsten ionization balance. To this end, we present a series of partial final-state-resolved and total DR rate coefficients for W$^{73+}$ to W$^{56+}$ Tungsten ions. This is part of a wider effort within {\it The Tungsten Project} to calculate accurate dielectronic recombination rate coefficients for the tungsten isonuclear sequence for use in collisional-radiative modelling of finite-density tokamak plasmas. The recombination rate coefficients have been calculated with {\sc autostructure} using kappa-averaged relativistic wavefunctions in level resolution (intermediate coupling) and configuration resolution (configuration average). The results are available from OPEN-ADAS according to the {\it adf09} and {\it adf48} standard formats. Comparison with previous calculations of total DR rate coefficients for W$^{63+}$ and W$^{56+}$ yield agreement to within 20\% and 10\%, respectively, at peak temperature. It is also seen that the J\"{u}ttner correction to the Maxwell distribution has a significant effect on the ionization balance of tungsten at the highest charge states, changing both the peak abundance temperatures and the ionization fractions of several ions.
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- 2016
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16. Electron–ion Recombination Rate Coefficients of Be-like 40Ca16+
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X Y Chuai, Dongmei Zhao, Lijun Mao, N. R. Badnell, You-Jin Yuan, Meitang Tang, Xiaolong Zhu, Sultan Mahmood, J C Yang, Xin Xu, Ruishi Mao, Li-Jun Dou, N. Khan, Shu-Xing Wang, S. P. Preval, X. H. Ma, H. B. Wang, Weiqiang Wen, Da-Yu Yin, Stefan Schippers, Z. K. Huang, J. J. Li, Xiao-Ming Ma, and Lin-Fan Zhu
- Subjects
Physics ,Range (particle radiation) ,Resonance ,Astronomy and Astrophysics ,Electron ,Plasma ,01 natural sciences ,Ion ,Space and Planetary Science ,Ionization ,Metastability ,0103 physical sciences ,Center of mass ,Atomic physics ,010306 general physics ,010303 astronomy & astrophysics ,QC - Abstract
Electron–ion recombination rate coefficients for beryllium-like calcium ions in the center of mass energy from 0 to51.88 eV have been measured by means of the electron–ion merged-beam technique at the main cooler storage ringat the Institute of Modern Physics in Lanzhou, China. The measurement energy range covers the dielectronicrecombination (DR) resonances associated with the 2s2 1S0 -> 2s2p 3P0,1,2, 1P1 core excitations and the trielectronicrecombination (TR) resonances associated with the 2s2 1S0 -> 2p2 3P0,1,2, 1D2, 1S0 core excitations. In addition,the AUTOSTRUCTURE code was used to calculate the recombination rate coefficients for comparison with theexperimental results. Resonant recombination originating from parent ions in the long-lived metastable state 2s2p 3P0 ions has been identified in the recombination spectrum below 1.25 eV. A good agreement is achievedbetween the experimental recombination spectrum and the result of the AUTOSTRUCTURE calculations whenfractions of 95% ground-state ions and 5% metastable ions are assumed in the calculation. It is found thatthe calculated TR resonance positions agree with the experimental peaks, while the resonance strengths areunderestimated by the theoretical calculation. Temperature dependent plasma rate coefficients for DR and TR inthe temperature range of 103–108 K were derived from the measured electron–ion recombination rate coefficientsand compared with the available theoretical results from the literature. In the temperature range of photoionizedplasmas, the presently calculated rate coefficients and the recent results of Gu & Colgan et al. are up to 30% lowerthan the experimentally derived ones, and the older atomic data are even up to 50% lower than the presentexperimental result. This is because strong resonances situated below electron–ion collision energies of 50 meVwere underestimated by the theoretical calculation, which also has a severe influence on the rate coefficients inlow-temperature plasmas. In the temperature range of collisionally ionized plasmas, agreement within 25% wasfound between the experimental result and the present calculation as well as the calculation by Colgan et al. Thepresent result constitutes a set of benchmark data for use in astrophysical modeling.
- Published
- 2018
- Full Text
- View/download PDF
17. Hot DA white dwarf model atmosphere calculations: Including improved Ni PI cross sections
- Author
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Ivan Hubeny, N. R. Badnell, Jay B. Holberg, Martin A. Barstow, and S. P. Preval
- Subjects
Physics ,Opacity ,010308 nuclear & particles physics ,Atomic Physics (physics.atom-ph) ,Stellar atmosphere ,White dwarf ,Flux ,FOS: Physical sciences ,Astronomy and Astrophysics ,Context (language use) ,Photoionization ,01 natural sciences ,Spectral line ,Physics - Atomic Physics ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Ionization ,0103 physical sciences ,Atomic physics ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,QB - Abstract
To calculate realistic models of objects with Ni in their atmospheres, accurate atomic data for the relevant ionization stages needs to be included in model atmosphere calculations. In the context of white dwarf stars, we investigate the effect of changing the Ni {\sc iv}-{\sc vi} bound-bound and bound-free atomic data has on model atmosphere calculations. Models including PICS calculated with {\sc autostructure} show significant flux attenuation of up to $\sim 80$\% shortward of 180\AA\, in the EUV region compared to a model using hydrogenic PICS. Comparatively, models including a larger set of Ni transitions left the EUV, UV, and optical continua unaffected. We use models calculated with permutations of this atomic data to test for potential changes to measured metal abundances of the hot DA white dwarf G191-B2B. Models including {\sc autostructure} PICS were found to change the abundances of N and O by as much as $\sim 22$\% compared to models using hydrogenic PICS, but heavier species were relatively unaffected. Models including {\sc autostructure} PICS caused the abundances of N/O {\sc iv} and {\sc v} to diverge. This is because the increased opacity in the {\sc autostructure} PICS model causes these charge states to form higher in the atmosphere, moreso for N/O {\sc v}. Models using an extended line list caused significant changes to the Ni {\sc iv}-{\sc v} abundances. While both PICS and an extended line list cause changes in both synthetic spectra and measured abundances, the biggest changes are caused by using {\sc autostructure} PICS for Ni., Comment: 14 pages, 9 figures, 7 tables. Accepted for publication in MNRAS
- Published
- 2016
- Full Text
- View/download PDF
18. The Tungsten Project : Dielectronic Recombination data for the International Thermonuclear Experimental Reactor (ITER)
- Author
-
M. G. O'Mullane, S. P. Preval, and N. R. Badnell
- Subjects
Quenching ,History ,Thermonuclear fusion ,Materials science ,Physics::Instrumentation and Detectors ,chemistry.chemical_element ,Plasma ,Tungsten ,equipment and supplies ,Computer Science Applications ,Education ,Nuclear physics ,chemistry ,Physics::Plasma Physics ,Sputtering ,Physics::Space Physics ,Physics::Accelerator Physics ,Spontaneous emission ,Recombination ,QC - Abstract
The plasma facing components in ITER will be constructed using Tungsten. Sputtering of plasma against these walls introduces Tungsten impurities into the plasma, possibly causing quenching. As data for Tungsten in the relevant charge states is historically poor, this project aims to calculate this data, providing partial and total Dielectronic/Radiative Recombination rates for use in collisional-radiative modelling of the ITER plasma.
- Published
- 2015
19. Distorted wave photoionization cross sections for use in NLTE model atmospheres: Ni – Ni10+
- Author
-
N. R. Badnell and S. P. Preval
- Subjects
History ,Valence (chemistry) ,Opacity ,Chemistry ,Stellar atmosphere ,Photoionization ,Computer Science Applications ,Education ,Ion ,Atmosphere ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Atomic physics ,QC ,Astrophysics::Galaxy Astrophysics ,Atomic data - Abstract
Synopsis The Opacity Project is a highly successful venture in which energy levels, oscillator strengths, and photoionization cross sections were calculated for astrophysically important elements up to iron. However, metals heavier than iron are being discovered in stellar atmospheres. The photoionization cross sections for elements and ions not covered by the Opacity Project are usually approximated with hydrogenic formulae. We present a series of valence and inner-shell distorted wave photoioniza-tion cross section calculations for use in model atmosphere calculations covering Ni-Ni10+. We discuss current progress, and future work.
- Published
- 2017
- Full Text
- View/download PDF
20. The Tungsten Project: A complete set of isonuclear dielectronic recombination rate coefficients for use in magnetically confined fusion plasmas
- Author
-
S. P. Preval, N. R. Badnell, and M. G. O’Mullane
- Subjects
Nuclear physics ,Set (abstract data type) ,History ,Chemistry ,Recombination rate ,Fusion plasma ,chemistry.chemical_element ,Atomic physics ,Tungsten ,Computer Science Applications ,Education - Published
- 2017
- Full Text
- View/download PDF
21. Limits on a Gravitational Field Dependence of the Proton-Electron Mass Ratio fromH2in White Dwarf Stars
- Author
-
John D. Barrow, S. P. Preval, Edcel J. Salumbides, Michael T. Murphy, J. Bagdonaite, Wim Ubachs, and Martin A. Barstow
- Subjects
Physics ,Gravitational field ,Hubble space telescope ,Hydrogen molecule ,General Physics and Astronomy ,White dwarf ,Local environment ,Sensitivity (control systems) ,Astrophysics ,Mass ratio ,Proton-to-electron mass ratio ,Mathematical physics - Abstract
Spectra of molecular hydrogen (${\mathrm{H}}_{2}$) are employed to search for a possible proton-to-electron mass ratio ($\ensuremath{\mu}$) dependence on gravity. The Lyman transitions of ${\mathrm{H}}_{2}$, observed with the Hubble Space Telescope towards white dwarf stars that underwent a gravitational collapse, are compared to accurate laboratory spectra taking into account the high temperature conditions ($T\ensuremath{\sim}13\text{ }000\text{ }\text{ }\mathrm{K}$) of their photospheres. We derive sensitivity coefficients ${K}_{i}$ which define how the individual ${\mathrm{H}}_{2}$ transitions shift due to $\ensuremath{\mu}$ dependence. The spectrum of white dwarf star GD133 yields a $\mathrm{\ensuremath{\Delta}}\ensuremath{\mu}/\ensuremath{\mu}$ constraint of $(\ensuremath{-}2.7\ifmmode\pm\else\textpm\fi{}4.{7}_{\text{stat}}\ifmmode\pm\else\textpm\fi{}0.{2}_{\text{syst}})\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}5}$ for a local environment of a gravitational potential $\ensuremath{\phi}\ensuremath{\sim}1{0}^{4}$ ${\ensuremath{\phi}}_{\text{Earth}}$, while that of $\mathrm{G}29\ensuremath{-}38$ yields $\mathrm{\ensuremath{\Delta}}\ensuremath{\mu}/\ensuremath{\mu}=(\ensuremath{-}5.8\ifmmode\pm\else\textpm\fi{}3.{8}_{\text{stat}}\ifmmode\pm\else\textpm\fi{}0.{3}_{\text{syst}})\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}5}$ for a potential of $2\ifmmode\times\else\texttimes\fi{}1{0}^{4}$ ${\ensuremath{\phi}}_{\text{Earth}}$.
- Published
- 2014
- Full Text
- View/download PDF
22. Limits on a gravitational field dependence of the proton-electron mass ratio from H2 in white dwarf stars
- Author
-
J, Bagdonaite, E J, Salumbides, S P, Preval, M A, Barstow, J D, Barrow, M T, Murphy, and W, Ubachs
- Abstract
Spectra of molecular hydrogen (H2) are employed to search for a possible proton-to-electron mass ratio (μ) dependence on gravity. The Lyman transitions of H2, observed with the Hubble Space Telescope towards white dwarf stars that underwent a gravitational collapse, are compared to accurate laboratory spectra taking into account the high temperature conditions (T∼13 000 K) of their photospheres. We derive sensitivity coefficients Ki which define how the individual H2 transitions shift due to μ dependence. The spectrum of white dwarf star GD133 yields a Δμ/μ constraint of (-2.7±4.7stat±0.2syst)×10(-5) for a local environment of a gravitational potential ϕ∼10(4) ϕEarth, while that of G29-38 yields Δμ/μ=(-5.8±3.8stat±0.3syst)×10(-5) for a potential of 2×10(4) ϕEarth.
- Published
- 2014
23. Limits on the dependence of the fine-structure constant on gravitational potential from white-dwarf spectra
- Author
-
John D. Barrow, Jay B. Holberg, Julian C. Berengut, Martin A. Barstow, A. Ong, S. P. Preval, Victor V. Flambaum, and John K. Webb
- Subjects
Physics ,High Energy Physics - Theory ,Cosmology and Nongalactic Astrophysics (astro-ph.CO) ,Physical constant ,Atomic Physics (physics.atom-ph) ,General Physics and Astronomy ,White dwarf ,FOS: Physical sciences ,Fine-structure constant ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,General Relativity and Quantum Cosmology (gr-qc) ,Spectral line ,General Relativity and Quantum Cosmology ,Physics - Atomic Physics ,Stars ,Gravitational potential ,Gravitational field ,High Energy Physics - Theory (hep-th) ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics::Galaxy Astrophysics ,Dimensionless quantity ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
We propose a new probe of the dependence of the fine structure constant, alpha, on a strong gravitational field using metal lines in the spectra of white dwarf stars. Comparison of laboratory spectra with far-UV astronomical spectra from the white dwarf star G191-B2B recorded by the Hubble Space Telescope Imaging Spectrograph gives limits on the fractional variation of alpha of (Delta alpha/alpha)=(4.2 +- 1.6)x10^(-5) and (-6.1 +- 5.8)x10^(-5) from Fe V and Ni V spectra, respectively, at a dimensionless gravitational potential relative to Earth of (Delta phi) ~ 5x10^(-5). With better determinations of the laboratory wavelengths of the lines employed these results could be improved by up to two orders of magnitude., Comment: 8 pages, 2 figures. v2: minor corrections
- Published
- 2013
- Full Text
- View/download PDF
24. Dielectronic recombination of lanthanide and low ionization state tungsten ions: W13+–W1+.
- Author
-
S P Preval, N R Badnell, and M G O’Mullane
- Subjects
- *
ION recombination , *RARE earth metals , *TUNGSTEN ions - Abstract
The experimental thermonuclear reactor, ITER, is currently being constructed in Cadarache, France. The reactor vessel will be constructed with a beryllium coated wall, and a tungsten coated divertor. As a plasma-facing component, the divertor will be under conditions of extreme temperature, resulting in the sputtering of tungsten impurities into the main body plasma. Modelling and understanding the potential cooling effects of these impurities requires detailed collisional-radiative modelling. These models require a wealth of atomic data for the various atomic species in the plasma. In particular, partial, final-state resolved dielectronic/radiative recombination (DR/RR) rate coefficients for tungsten are required. In this manuscript, we present our calculations of detailed DR/RR rate coefficients for the lanthanide-like, and low ionization stages of tungsten, spanning charge states W13+–W1+. The calculations presented here constitutes the first detailed exploration of such low ionization state tungsten ions. We are able to reproduce the general trend of calculations performed by other authors, but find significant differences between ours and their DR rate coefficients, especially at the lowest temperatures considered. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
25. Electron–ion Recombination Rate Coefficients of Be-like 40Ca16+.
- Author
-
S. X. Wang, X. Xu, Z. K. Huang, W. Q. Wen, H. B. Wang, N. Khan, S. P. Preval, N. R. Badnell, S. Schippers, S. Mahmood, L. J. Dou, X. Y. Chuai, D. M. Zhao, X. L. Zhu, L. J. Mao, X. M. Ma, J. Li, R. S. Mao, Y. J. Yuan, and M. T. Tang
- Subjects
BERYLLIUM ,ALKALINE earth metals ,SPECIAL relativity (Physics) ,CALCIUM ions ,ABSORPTION coefficients - Abstract
Electron–ion recombination rate coefficients for beryllium-like calcium ions in the center of mass energy from 0 to 51.88 eV have been measured by means of the electron–ion merged-beam technique at the main cooler storage ring at the Institute of Modern Physics in Lanzhou, China. The measurement energy range covers the dielectronic recombination (DR) resonances associated with the core excitations and the trielectronic recombination (TR) resonances associated with the core excitations. In addition, the AUTOSTRUCTURE code was used to calculate the recombination rate coefficients for comparison with the experimental results. Resonant recombination originating from parent ions in the long-lived metastable state ions has been identified in the recombination spectrum below 1.25 eV. A good agreement is achieved between the experimental recombination spectrum and the result of the AUTOSTRUCTURE calculations when fractions of 95% ground-state ions and 5% metastable ions are assumed in the calculation. It is found that the calculated TR resonance positions agree with the experimental peaks, while the resonance strengths are underestimated by the theoretical calculation. Temperature dependent plasma rate coefficients for DR and TR in the temperature range of 10
3 –108 K were derived from the measured electron–ion recombination rate coefficients and compared with the available theoretical results from the literature. In the temperature range of photoionized plasmas, the presently calculated rate coefficients and the recent results of Gu & Colgan et al. are up to 30% lower than the experimentally derived ones, and the older atomic data are even up to 50% lower than the present experimental result. This is because strong resonances situated below electron–ion collision energies of 50 meV were underestimated by the theoretical calculation, which also has a severe influence on the rate coefficients in low-temperature plasmas. In the temperature range of collisionally ionized plasmas, agreement within 25% was found between the experimental result and the present calculation as well as the calculation by Colgan et al. The present result constitutes a set of benchmark data for use in astrophysical modeling. [ABSTRACT FROM AUTHOR]- Published
- 2018
- Full Text
- View/download PDF
26. Dielectronic and Trielectronic Recombination Rate Coefficients of Be-like Ar14+.
- Author
-
Z. K. Huang, W. Q. Wen, X. Xu, S. Mahmood, S. X. Wang, H. B. Wang, L. J. Dou, N. Khan, N. R. Badnell, S. P. Preval, S. Schippers, T. H. Xu, Y. Yang, K. Yao, W. Q. Xu, X. Y. Chuai, X. L. Zhu, D. M. Zhao, L. J. Mao, and X. M. Ma
- Published
- 2018
- Full Text
- View/download PDF
27. Dielectronic recombination of the open -shell of tungsten:.
- Author
-
S P Preval, N R Badnell, and M G O'mullane
- Subjects
- *
TUNGSTEN metallurgy , *RADIATORS , *ION recombination , *RATE coefficients (Chemistry) , *TUNGSTEN ions ,DESIGN & construction - Abstract
Tungsten is an important element for magnetically confined fusion plasmas but has the potential to cool, or even quench the plasma due to it being an efficient radiator. Total and level-resolved dielectronic recombination (DR) rate coefficients, for all ionisation stages, are essential to model tungsten. We describe a set calculations performed using the distorted wave code autostructure for the tungsten ions –. We demonstrate the importance of relativistic configuration mixing in such calculations. In particular, we show that the partial DR rate coefficients calculated in level and configuration resolution can differ by as little as 5%, and up to as much as 75%. Using the new data, we calculate a revised steady-state ionisation fraction for tungsten. We find that, relative to the ionisation fraction calculated using the recombination rate coefficients of Putterich et al (2008 Plasma Phys. Control. Fusion50 085016), the peak temperatures of – ionisation states are shifted to lower temperatures spanning 0.9–1.6 keV. This temperature range is important for understanding the performance of large tokamaks, such as ITER, because the temperatures in the pedestal, edge, scrape-off-layer and divertor region fall in this range. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
28. Distorted wave photoionization cross sections for use in NLTE model atmospheres: Ni – Ni10+.
- Author
-
S. P. Preval and N. R. Badnell
- Published
- 2017
- Full Text
- View/download PDF
29. The Tungsten Project: Dielectronic Recombination data for the International Thermonuclear Experimental Reactor (ITER).
- Author
-
S P Preval, N R Badnell, and M O'Mullane
- Published
- 2015
- Full Text
- View/download PDF
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