Experimental and simulated neon spectra in the 10-nm wavelength region from tokamak and reversed field pinch plasmas

Abstract

Experimental neon spectra (in the 10-nm region), from the tokamak Tore Supra and the reversed field pinch experiment RFX, have been simulated. The spectra include lines from three neon ionization states, namely Ne(7+), Ne(6+), and Ne(5+) ions. Collisional radiative models have been built for these three Ne ions, considering electron collisional excitation and radiative decay as populating processes of the excited states. These models give photon emission coefficients for the emitted lines at electron density and temperature values corresponding to the experimental situations. Impurity modelling is performed using a one-dimensional impurity transport code, calculating the steady-state radial distribution of the Ne ions. The Ne line brightnesses are evaluated in a post-process subroutine and simulated spectra are obtained. The parts of the spectra corresponding to a single ionization state do not depend on the experimental conditions and show good agreement with the simulated single ionization state spectra. On the other hand, the superposition of the three spectra depends on the experimental conditions, as a consequence of the fact that the ion charge distribution depends not only on the radial profiles of the electron density and temperature, but also of the impurity transport coefficients. Simulations of the Ne spectra (including transport) give confidence in the atomic physics calculations; moreover, they allow the determination of the transport coefficients in the plasma region emitting the considered ionization states.

CHIANTI—An Atomic Database for Emission Lines. VI. Proton Rates and Other Improvements

“…However, it has been found that resonances play an important role in the calculation of Be-like n = 2 effective collision strengths (Landi et al 2001), so the distorted wave data for the n = 2 transitions in the whole sequence have been replaced with close coupling results, as described below. The accuracy of the R-matrix data in the case of Ne VII was demonstrated from laboratory spectra by Mattioli et al (1999).…”

HULLAC-based Simulations of Non-LTE Emission Spectra

“…The DWA is a very good scheme for calculating the impact excitation rates between the levels of highly charged, high Z ions (that is, for all the cases considered here). The DWA misses resonance contributions to the excitation cross section ( [23]); in certain cases, at low temperatures, resonance effects can contribute noticeably to the excitation cross section [24,25,26]. The fact that our collisional-radiative level population calculations (described below) include autoionization into excited levels of the final ion can (partially) account for this contribution [25].…”

Spectral Line Shapes as a Diagnostic Tool in Magnetic Fusion

“…on the determination of the electron temperature, electron density and elemental abundances. In most cases atomic data are supposed to be valid and the simulations give D(r) and V(r), like, e.g., in Refs [20,21]. But with high quality and large amount of spectroscopic data, it is possible to go further and to verify also S ion and α rec .…”

“…Until recently, simulations of full spectra were less frequent. These include, e. g., full simulation in the XUV range of n=2 to n=2 L-shell Ne, Ar and Fe spectra [18,19], of n=3 to n=2 L-shell Ne and Ar spectra [20,21], and of n=3 to n=3 M-shell Fe and Ni spectra [22,23]. The analysis of spectra emitted by hot and well-diagnosed magnetic fusion plasmas is important since it touches on atomic physics issues to be used in the analysis of high spectral resolution astrophysical observations, i.e.…”

“…After evaluation of radial CSD, post-process subroutines are used to produce simulated spectra, using line photon emission coefficients (PECs) from collisionalradiative models (CRM). Like for Refs [18][19][20][21][22][23], the PECs have been obtained using the HULLAC code.…”