Speaker
Description
Measurements of plasma parameters in the core of magnetic fusion devices represent a challenging task. Expected emission of x-ray lines of highly charged ions of W will be used in ITER or DEMO for derivation of electron and ion temperature, plasma rotation and finally the plasma control. In spite of considerable efforts to design the x-ray instruments operating in extreme harsh environment of future plasma devices [1], the accurate modelling of such spectra is still far from been complete [2].
The aim of this work is to provide the accurate effective rate coefficients for the lines in the spectral region of 1.35 Å to 1.5 Å of the contributing charged stages of W necessary in plasma modelling. The synthetic spectra are decomposed in contribution from Mg-, Na-, Ne-, F-, and O-like ions. This work provides probably the most complete set of atomic data for interpretation of the future X-ray spectra. Indeed, whereas the Ne-like ions are in general responsible for the line formation at the core of plasma devices, e.g., in the temperature range of 15-25 keV, the contribution from Na- and F-like ions remains considerable. We demonstrate here an overlooked impact of inner-shell ionization of Na-like W ions on the line formation of some of Ne-like lines. The intensity of some of the lines increase by up to 30 % which challenge the selection of the X-ray line to be measured in ITER or DEMO.
The calculations were performed with the collisional-radiative model NOMAD [3] using the FAC code [4] calculations of elementary atomic processes such as electron-impact rates, radiative and autoionization rates, etc. The model includes about 103 - 104 levels in each ion. We identified 51 lines in this interval which we describe in terms of effective rate coefficients of excitation Q$^{exc}$, recombination Q$^{rec}$ and inner-shell ionization Q$^{ion}$:
\begin{equation}
I(T)λ\propto N_e N{[Ne]} Q^{exc} (T)+N_e N_{[Na]} Q^{ion} (T)+N_e N_{[F]}Q^{rec}(T),
\end{equation} where T is the electron temperature, I is the line intensity, λ is the wavelength corresponding to the specific bound-bound transition, N$_{[He]}$, N$_{[Na]}$ and N$_{[F]}$ are the fractions of the Ne-, Na- and the F-like W ions, respectively. The tabulated values of fit results for the effective rate coefficients are presented. The errors of such decomposition remain on the order of 1 % and below in comparison to exact calculations and should provide a reliable basis for integrated plasma modelling of X-ray spectra from W ions.
References
Cheng Z. et al, Review of Scientific Instruments 93 073502 (2022)
Beiersdorfer P. et al, J. Phys. B: At. Mol. Opt. Phys. 43 144008 (2010)
Ralchenko Yu. V. and Maron Y J. Quant. Spectrosc. Radiat. Transfer 71 609 (2001)
Gu, M. F. ApJ, 582, 1241 (2003)
| Presenting Author | Marchuk |
|---|---|
| Presenting Author Email Address | o.marchuk@fz-juelich.de |
| Presenting Author Affiliation | Forschungszentrum Jülich |
| Country | Germany |
| Presenting Author Gender | Male |
