Eur. Phys. J. D (2013) 67: 12
https://doi.org/10.1140/epjd/e2012-30608-0

Regular Article

Analysis of the quasicontinuum band emitted by highly ionised tungsten atoms in the 4–7 nm range

¹ Centro de Física Atómica e Departamento de Física da Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal
² Centro de Física Atómica e Departamento de Física da Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Monte da Caparica, 2829-516 Caparica, Portugal
³ Laboratoire Kastler Brossel, École Normale Supérieure, CNRS, Université Paris 6, 4 place Jussieu, 75252 Paris Cedex 5, France

^a e-mail: tiamorim@fc.ul.pt

Received: 2 October 2012
Received in final form: 16 November 2012
Published online: 31 January 2013

Abstract

Spectra emitted by highly ionized tungsten atoms from magnetically confined plasmas show a common feature: a narrow structured quasi-continuum emission band most prominent in the range 4−7 nm, which accounts for 40−80% of the radiated power. This band has been fairly well explained by unresolved transitions from groups 4d-4p, 4f-4d (Δn = 0) and 5d-4f, 5g-4f and 5p-4d (Δn = 1). In this work we use a Multi-Configuration Dirac-Fock code in Breit self-consistent field mode to compute level energies and transition probabilities for W²⁷⁺ to W³⁷⁺ ions contributing to this emission band. Intra-shell correlation was introduced in the calculation for both initial and final states and all dipole and quadrupole radiative transitions have been considered. The wavefunctions in the initial and final states are optimized separately and the resulting non-orthogonality effect is fully taken into account. The importance of some satellite lines was assessed. Together with the ionic distributions obtained by using the FLYCHK application and assuming that the initial states population depends statistically on the temperature we were able to synthesize plasma emission spectrum profiles for several electron temperatures.