Atomic Physics and Thermonuclear Fusion Research

Drawin, H. W.

doi:10.1088/0031-8949/24/4/002

Cited by 59 publications

(32 citation statements)

References 210 publications

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“…Heavy impurity atoms in a plasma give rise to strong electromagnetic radiation via bremsstrahlung and characteristic line emission [1]. At the low density of a magnetically confined fusion plasma, short-wavelength radiation cannot be efficiently reabsorbed and, therefore, leaves the plasma.…”

Section: Introductionmentioning

confidence: 99%

“…Understanding the influence of tungsten as an impurity and its impact on the plasma requires detailed knowledge about atomic processes and atomic structures of tungsten atoms and ions in all stages of ionization [1,5]. While available plasma-related data bases for elements with low and intermediate atomic number Z have become relatively reliable during recent decades, there are still large uncertainties for heavier multi-electron ions, where even the most fundamental atomic collision processes are not yet sufficiently well understood [6].…”

Section: Introductionmentioning

confidence: 99%

“…In particular, ionization and recombination determine the tungsten ion charge-state distribution in a plasma. The ion charge-state distribution at a given electron temperature directly influences the power of bremsstrahlung losses from the plasma while direct and resonant excitation together with the population of excited states in recombination processes are responsible for the emission of electromagnetic line radiation and the associated energy losses [1,7].…”

Section: Introductionmentioning

confidence: 99%

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Fusion-Related Ionization and Recombination Data for Tungsten Ions in Low to Moderately High Charge States

Müller

2015

Atoms

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Collisional processes and details of atomic structure of heavy many-electron atoms and ions are not yet understood in a fully satisfying manner. Experimental studies are required for guiding new theoretical approaches. In response to fusion-related needs for collisional and spectroscopic data on tungsten atoms in all charge states, a project has been initiated in which electron-impact and photon-induced ionization as well as photorecombination of W q+ ions are studied. Cross sections and rate coefficients were determined for charge states q ranging from q = 1 to q = 5 for photoionization, for q = 1 up to q = 19 for electron-impact ionization and for q = 18 to q = 21 for electron-ion recombination. An overview, together with a critical assessment of the methods and results is provided.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Fusion-Related Ionization and Recombination Data for Tungsten Ions in Low to Moderately High Charge States

Müller

2015

Atoms

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“…The H-H collisional ionization rate coefficient can also be derived using the semi-empirical method described in Drawin (1968Drawin ( , 1969. Following the interpretation of Drawin's results given in Soon (1992), we can write the rate coefficient as…”

Section: Collisional Ionization Of H By H (Reaction 10)mentioning

confidence: 99%

Simulating the formation of massive seed black holes in the early Universe – II. Impact of rate coefficient uncertainties

Glover

2015

Mon. Not. R. Astron. Soc.

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We investigate how uncertainties in the chemical and cooling rate coefficients relevant for a metal-free gas influence our ability to determine the critical ultraviolet field strength required to suppress H 2 cooling in high-redshift atomic cooling halos. The suppression of H 2 cooling is a necessary prerequisite for the gas to undergo direct collapse and form an intermediate mass black hole. These black holes can then act as seeds for the growth of the supermassive black holes (SMBHs) observed at redshifts z ∼ 6. The viability of this model for SMBH formation depends on the critical ultraviolet field strength, J crit : if this is too large, then too few seeds will form to explain the observed number density of SMBHs. We show in this paper that there are five key chemical reactions whose rate coefficients are uncertain enough to significantly affect J crit . The most important of these is the collisional ionization of hydrogen by collisions with other hydrogen atoms, as the rate for this process is very poorly constrained at the low energies relevant for direct collapse. The total uncertainty introduced into J crit by this and the other four reactions could in the worst case approach a factor of five. We also show that the use of outdated or inappropriate values for the rates of some chemical reactions in previous studies of the direct collapse mechanism may have significantly affected the values of J crit determined by these studies.

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“…One of the major aspect is the calculation of the ratio of spectral line intensities from different excitation stages of the highly stripped ions. These data are essential for high temperature plasma diagnostics [4][5][6][7][8][9]. In this regard doubly excited states, which are observed in solar flare [10] and in solar corona [11], play a significant role to the excitation cross sections required to determine the rate coefficients, particularly in dielectronic recombination processes [8] between ionic states.…”

Section: Introductionmentioning

confidence: 99%

Doubly excited states of highly stripped ions: a time dependent perturbation approach

Mukherjee

1997

Z Phys D - Atoms, Molecules and Clusters

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Doubly excited singlet states have been calculated for the astrophysically important highly stripped He like ions Al>, Si>, P>, S> and Cl> for the transitions 2s: S , 2p: D , 2snp: P, 2snd: D and 2pnd: F for n45. The transition energies are obtained from the position of resonances in the oscillations of the two electron charge cloud under an external harmonic perturbation. Linearised version of a suitably constructed variational functional is used for obtaining the response properties of the system. Most of the results are new. Agreement with the only few existing experimental data along this line is very reasonable. Analytic representations of the doubly excited states are obtained and the Coulomb repulsion integral in these states are estimated for checking the consistency of the wavefunctions. The doubly excited state wavefunctions so obtained may be used for evaluating other physical properties connected with transitions.

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Atomic Physics and Thermonuclear Fusion Research

Cited by 59 publications

References 210 publications

Fusion-Related Ionization and Recombination Data for Tungsten Ions in Low to Moderately High Charge States

Fusion-Related Ionization and Recombination Data for Tungsten Ions in Low to Moderately High Charge States

Simulating the formation of massive seed black holes in the early Universe – II. Impact of rate coefficient uncertainties

Doubly excited states of highly stripped ions: a time dependent perturbation approach

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