Time Ordering Effects on Hydrogen Zeeman-Stark Line Profiles in Low-Density Magnetized Plasmas

Abstract

Stark broadening of hydrogen lines is investigated in low-density magnetized plasmas, at typical conditions of magnetic fusion experiments. The role of time ordering is assessed numerically, by using a simulation code accounting for the evolution of the microscopic electric field generated by the charged particles moving at the vicinity of the atom. The Zeeman effect due to the magnetic field is also retained. Lyman lines with a low principal quantum number n are first investigated, for an application to opacity calculations; next Balmer lines with successively low and high principal quantum numbers are considered for diagnostic purposes. It is shown that neglecting time ordering results in a dramatic underestimation of the Stark effect on the low-n lines. Another conclusion is that time ordering becomes negligible only when ion dynamics effects vanish, as shown in the case of high-n lines.

An intermediate distribution between Gaussian and Cauchy distributions

“…( 1), to describe the function g (ω − ω 0 ). Specifically, take [34] where p (x, µ, σ, ν) is defined by the Eq. ( 1).…”

“…We import a set of data of hydrogen Zeeman-Stark line broadening from Figure 2 (b) in Ref. [34] and fit them with the intermediate, Cauchy, and Gaussian distribution, respectively. The data and the fitting results are plotted in Figure 3.…”

“…Figure3: The fitting of the experimental line width data with the intermediate, the Gaussian, and the Cauchy distribution. The data are taken from Ref [34]. …”

Division Xii / Commission 14 / Working Group Collision Processes

“…Rosato et al (2009) have reexamined the Stark broadening of hydrogen lines in the presence of a magnetic field and developed an impact theory for ions, valid for low electron densities (N e 10 14 cm −3 ), which takes into account the Zeeman splitting of the atomic energy levels. Rosato et al (2010) have also studied numerically the role of time ordering in such plasmas, by using a simulation code that accounts for the evolution of the microscopic electric field generated by the charged particles moving close to the atom. Calisti et al (2010) have developed a very fast method to account for the dynamical effects of charged particles on the spectral line shape emitted by plasmas, based on a formulation of the frequency fluctuation model.…”