Dirac R-matrix calculations for the electron-impact excitation of neutral tungsten providing noninvasive diagnostics for magnetic confinement fusion

TL;DR

This paper presents advanced Dirac R-matrix calculations for electron-impact excitation of neutral tungsten, aiding noninvasive diagnostics crucial for the operation of fusion reactors like ITER.

Contribution

It introduces detailed atomic structure calculations and electron-impact excitation data for neutral tungsten, improving diagnostic line selection for fusion plasma monitoring.

Findings

Identification of alternative diagnostic lines to 400.88nm

Benchmarking results align with recent experimental measurements

Enhanced atomic data for tungsten improves impurity diagnostics

Abstract

Neutral tungsten is the primary candidate as a wall material in the divertor region of the International Thermonuclear Experimental Reactor (ITER). The efficient operation of ITER depends heavily on precise atomic physics calculations for the determination of reliable erosion diagnostics, helping to characterise the influx of tungsten impurities into the core plasma. The following paper presents detailed calculations of the atomic structure of neutral tungsten using the multiconfigurational Dirac-Fock method, drawing comparisons with experimental measurements where available, and includes a critical assessment of existing atomic structure data. We investigate the electron-impact excitation of neutral tungsten using the Dirac R-matrix method and, by employing collisional-radiative models, we benchmark our results with recent Compact Toroidal Hybrid measurements. The resulting comparisons highlight alternative diagnostic lines to the widely used 400.88nm line.