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A transport equation for dipole radiation is derived from quantum electrodynamics. The radiation field is described in terms of a space-time Wigner function, which accounts for the position-momentum and time-energy Heisenberg uncertainty relations on an equal footing. The formalism involves the Heisenberg equations of motion for the quantized electric field and the polarization density. It is shown that the radiative transfer equation introduced phenomenologically in textbooks holds at the large spectral band limit, which is characteristic of a slowly varying radiation field in a medium with slowly varying emission and absorption coefficients. [ABSTRACT FROM AUTHOR]

We present a formulation of the radiative transfer theory based on the quantum phase space formalism. The formalism employs the Wigner function relative to the electric field in ( r , t , k , ω ) space. It is shown that this quantity obeys a transport equation with source and loss terms nonlocal in space and time. This delocalization is a feature of the Heisenberg uncertainty relation, both relative to position and momentum and to time and energy. A discussion of the theory, together with links to the standard radiative transfer formalism, is done. [ABSTRACT FROM AUTHOR]

We report on a transport model for the Lyman line radiation in optically thick divertor plasma conditions encountered in exhaust systems in magnetic fusion devices. The model is designed to switch automatically between a kinetic and a continuum description according to the plasma conditions and to the spectral range. A kinetic treatment is retained for photons with a large mean free path (line wings), whereas a continuum description of the radiation field is invoked in highly absorbing or scattering regions (core photons). Prototypical calculations of this so-called δ f Monte Carlo type of the Lyman α photo-excitation rate in slab geometry are performed as an illustration. The hybrid method is suggested as a candidate for speeding up the kinetic transport codes currently involved in magnetic fusion research for ITER and DEMO divertor (power and particle exhaust system) design. [ABSTRACT FROM AUTHOR]

A recent model for radiative transfer that accounts for spatial coherence is extended in such a way as to retain temporal coherence. The method employs Bogoliubov-Born-Green-Kirkwood-Yvon hierarchy techniques. Both spatial and temporal coherence are shown to affect the formation of atomic line spectra. Calculations of Lyman a radiation transport in optically thick divertor plasma conditions are reported as an illustration of the model. A possible extension of the formalism to dense media involving correlations between atoms is discussed in an appendix. A link to partial frequency redistribution modeling is also discussed. [ABSTRACT FROM AUTHOR]

A recent transport model for partially coherent light is reexamined. In its original formulation, this model involves a transport equation for the one-photon Wigner function with nonlocal source and loss terms. We show here that under suitable approximations this equation can be reformulated in a compact form involving the Moyal star product and the related symmetric and antisymmetric brackets. This formulation provides a general framework for the establishment of opacity models accounting for radiation coherence. An investigation of anomalous dispersion in magnetic fusion plasma conditions is reported as an illustration of the model. [ABSTRACT FROM AUTHOR]

A quantum transport model for atomic line radiation in plasmas is developed and analyzed. It is found that the Wigner phase space formulation of QED provides a consistent way to address the wave-particle duality in radiative transfer problems. If the photons' thermal de Broglie length is much smaller than all of the spatial scales of the problem under consideration (large-spectral-band limit), the radiation is not coherent and radiative transfer can be addressed with the usual treatments. In the general case, the Heisenberg uncertainty relation yields ambiguities in the description of the radiation-matter interaction mechanisms. We examine this issue and show that an accurate description of radiative transfer should involve a model with nonlocal interactions and requires an appropriate coarse-graining procedure. Calculations of transmission factors and absorption spectra in ideal cases are performed and indicate that significant misinterpretations can be made in spectroscopic diagnostics if the radiation coherence is not well accounted for. Applications to laser physics are also discussed. [ABSTRACT FROM AUTHOR]

The quantum phase space formalism proposed by Wigner is applied to radiation transport problems. It is shown that a generalization of the radiative transfer equation, which accounts for coherence effects, can be obtained within the second quantization formalism. A simplification in the case of stationary medium and slab geometry is considered and applied to low- and high-density plasmas. The obtained results indicate that spectra can be misinterpreted if the light's spatial coherence is neglected. [ABSTRACT FROM PUBLISHER]

Abstract: Ion dynamics is revisited in the presence of a magnetic field. This problem is of interest for the characterization of the ITER divertor plasmas, where Zeeman–Stark line shapes are both a diagnostic tool and an ingredient in the transport codes used for radiative transfer simulations. Comparisons between ab initio simulations of Zeeman–Stark profiles and calculations performed using the computationally efficient frequency fluctuation model are presented for the Lyman α and Balmer α lines. [Copyright &y& Elsevier]

Abstract: Hydrogen line radiation can be trapped in some spatial regions within magnetic fusion experiments at high density, typically when N H(∼N e)∼1015 cm−3. The corresponding photoexcitation yields a significant additional source of ionization that must be properly characterized by numerical simulations. Kinetic Monte-Carlo codes provide a capability to study this subject; however, these codes require accurate physical models for the reaction rates, including spectral line shapes. In this paper we deal with the Zeeman–Stark model used for the Lyα transition in the EIRENE code [D. Reiter, M. Baelmans, P. Börner, Fusion Sci. Technol. 47 (2005) 172; www.eirene.de] and we address the influence of ion dynamics, which can affect these line profiles. The impact theory for ions, that we first consider, is shown to be suited for description of the lateral components of the Lorentz triplet. By contrast, comparisons to numerical simulations show that this theory is not well suited for description of the central component, which is significantly affected by incomplete and non-binary collisions. A refinement of the model in the framework of the unified theory is proposed and discussed. [Copyright &y& Elsevier]