Atomic Physics and Non-Maxwellian Plasmas

We have calculated the degree of linear polarization of the Ly-α 1 (2p 3/2 → 1s 1/2 ) and Ly-β 1 (3p 3/2 → 1s 1/2 ) lines emitted after radiative recombination of spinless bare nuclei with unidirectional, unpolarized electrons. These calculations have been performed for various recombined H-like ions with atomic numbers in the range 10 Z 92. Several incident-electron kinetic energies ε 0 ranging from 0.01 to 10 times the electron binding energy in the 1s 1/2 ground state were considered and the radiative cascades following recombination into states with principal quantum number up to n = 6 were included. Three sets of cross sections for radiative recombination to individual magnetic sublevels of the excited levels of the recombined H-like ions were computed: the first two in the electric-dipole approximation with the nonrelativistic and relativistic electron wavefunctions and the third one in the exact relativistic method including all multipole orders of the radiation field. Results for the polarization calculated using these three sets of cross-section data were compared in order to stress the relative importance of relativistic and multipole effects as Z or ε 0 increases.

Section: Numerical Computationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Polarization of the Lyman line emission following radiative recombination of bare ions: effects of relativity and radiation multipoles

Bettadj¹,

Inal²,

Benmouna³

2014

“…In practically all cases these methods assume a Maxwellian electron distribution function. However, it has been shown that even rather small fractions of hot electrons (only some per cent) may alter the diagnostic properties drastically (Gabriel and Phillips 1979, Hammel and Jones 1984, Bartiromo et al 1985, Inal and Dubau 1989, Gabriel et al 1991, Lamoureux 1993, 1997, 1995, Rosmej 1994, 1996, Matte et al 1994, Rosmej and Vikhrev 1997. The neglection of hot electrons results, in almost all cases, in a considerable overestimation of the electron temperature (due to the enhanced collisional excitation of resonance lines) and in an overestimation of the electron density (due to the decreasing exchange cross section with high impact energies).…”

mentioning

confidence: 99%

Hot electron x-ray diagnostics

Rosmej¹

1997

A new method for the determination of hot electrons in high-temperature plasmas is proposed. The presence of hot electrons leads not only to a balance shift of the ion abundance but also to a qualitative distortion. In experiments the distortion is observable through the emission of H-like Ly α and the K α series satellites of Li-to F-like ions. The wide range of application is demonstrated and holds even for optically thick plasmas. Transient numerical calculations are carried out for typical parameters of fusion plasmas.

“…However, in general, most plasmas exist in a state quite far from thermal equilibrium. For example, in laboratory plasmas, the coupling of the injected external energy with the target system most often generates superthermal electrons escaping from the Maxwellian distribution [9,10]. Non-Maxwellian plasmas [11][12][13] are usually generated when electrons are injected from outside the plasma and whenever they are produced by strong external interactions.…”

Section: Introductionmentioning

confidence: 99%

Dynamic orientation effects on electron-impact excitations in kappa-Maxwellian plasmas

Kim

Jung

2005

The orientation phenomena for the 1s → 2p±1 transitions in electron–ion collisional excitations in kappa-Maxwellian plasmas are investigated by using the dynamic interaction potential. The plasma dielectric function in kappa-Maxwellian plasmas is used to obtain the scaled transition probabilities for the 1s → 2p±1 excitations. The semiclassical straight-line trajectory approximation is applied to the motion of the projectile electron in order to visualize the variation of the dynamic orientation parameter as a function of the impact parameter, collision energy, projectile energy and spectral index κ. It is found that the probability of the m = −1 transition is suddenly increased for 1.5 < κ < 2 and is slightly decreased for κ > 2 for the small velocity ratio (v/v∥). It is also found that the probability of the m = −1 transition is decreased for v/v∥ < 2 and increased for v/v∥ > 2. The probability of the m = −1 transition is found to be maximum near the first Bohr radius of the target ion. In addition, the probability of the m = −1 transition is also found to decrease with decreasing Debye length.