Abstract
The concept and structure of the Simulation of Spectra (SOS) code is described starting with an introduction to the physics background of the project and the development of a simulation tool enabling the modeling of charge-exchange recombination spectroscopy (CXRS) and associated passive background spectra observed in hot fusion plasmas. The generic structure of the code implies its general applicability to any fusion device, the development is indeed based on over two decades of spectroscopic observations and validation of derived plasma data. Four main types of active spectra are addressed in SOS. The first type represents thermal low-Z impurity ions and the associated spectral background. The second type of spectra represent slowing-down high energy ions created from either thermo-nuclear fusion reactions or ions from injected high energy neutral beams. Two other modules are dedicated to CXRS spectra representing bulk plasma ions (H+, D+, or T+) and beam emission spectroscopy (BES) or Motional Stark Effect (MSE) spectrum appearing in the same spectral range. The main part of the paper describes the physics background for the underlying emission processes: active and passive CXRS emission, continuum radiation, edge line emission, halo and plume effect, or finally the charge exchange (CX) cross-section effects on line shapes. The description is summarized by modeling the fast ions emissions, e.g., either of the α particles of the fusion reaction or of the beam ions itself.
Highlights
Introduction to the Simulation of Spectra (SOS) ProjectThe need for quantitative evaluation of complex line emission spectra as observed in hot fusion plasmas initiated a challenging development of sophisticated interpretation tools based on integrating advanced underlying atomic modeling [1] with detailed treatment of the plasma environment.The successful merging of the relevant plasma and atomic physics has led to routine diagnostic procedures which have contributed enormously to the understanding of plasma processes and to a wide acceptance of spectroscopy as a reliable diagnostic method [2]
The background is a comprehensive data base gained from the JET charge-exchange recombination spectroscopy (CXRS) diagnostic [10] which uses advanced spectral analysis codes (CXSFIT, [11]) and charge exchange (CX) data processing code Charge Exchange Analysis Package (CHEAP)
In the case of CXRS reaction the synthetic line shapes need to be reconstructed from a convolution of emission rate function and the original particle velocity distribution function projected into the direction of observation
Summary
The need for quantitative evaluation of complex line emission spectra as observed in hot fusion plasmas initiated a challenging development of sophisticated interpretation tools based on integrating advanced underlying atomic modeling [1] with detailed treatment of the plasma environment. In the case of CXRS reaction the synthetic line shapes need to be reconstructed from a convolution of emission rate function and the original particle velocity distribution function projected into the direction of observation. This requires a three-dimensional integration in velocity space. A second class of non-Gaussian synthetic line shape arises in the case of passive CX line emission [17], which represent the non-local, line-of-sight integrated, measurement of spectra induced by the interaction of neutral hydrogen streaming from the wall into the plasma and fully stripped confined impurity ions: Ne10+ ,. Active spectra simulated by SOS is that of fast-ion-CX-spectra, i.e., slowing-down fusion alpha particles [26,27,28,29,30], fast beam ions [31,32,33,34,35,36] or minority ions accelerated by Ion Cyclotron Resonance
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