Simulation of Spectra Code (SOS) for ITER Active Beam Spectroscopy

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.

Measurement of Absolute Carbon Ion Density Profile Based on CXRS Diagnostic on HL-2A Tokamak

“…where P is the total NBI power in unit of W, f is the power proportion of each beam energy component, E is the beam atom energy in keV/amu, v is the beam velocity in m/s, θ is the angle between the l.o.s and the beam axis, and w ⊥ is the horizontal beam e −1 radius (beam half-width at 1/e height) [16]. One of the methods for determining the beam components is the Doppler shift of D α Balmer lines.…”

Data for Beryllium–Hydrogen Charge Exchange in One and Two Centres Models, Relevant for Tokamak Plasmas

“…The figures in this section show the data for the cross sections for reaction (2), taken from the OPEN-ADAS database [6,7], and their comparison with cross sections from various sources, depending on the relative velocity v and the collision energy E, expressed in units of eV/amu (amu stands for the atomic mass unit). Collision energy E = 2.5 eV/amu corresponds to the relative velocity of colliding particles v ≈ 0.01 a.u.…”

“…Figures 3-5 show the data from the qcx#h0_en2_kvi#be4.dat file from OPEN-ADAS for charge exchange from excited hydrogen with a population of levels with different n and l. In Figure 3, one can see a comparison of these data with cross sections from several other sources, while Figures 4 and 5 show a detailed l-resolved comparison with calculations with the ARSENY code. (2) with excited hydrogen for the population of levels with different n, according to the data from the qcx#h0_en2_kvi#be4.dat file [6,7] (yellow curves), [8] (green curves), [9] (red curves) and calculations using the ARSENY code (blue curves). (2) with excited hydrogen, according to the data from the qcx#h0_en2_kvi#be4.dat file [6,7] and calculations using the ARSENY code.…”

“…It plays an important role for the Charge eXchange Recombination Spectroscopy (CXRS) diagnostics that Russia will supply to the ITER [1], as well as for other diagnostics of the Active Beam Spectroscopy type as a process that strongly affects the background signal (for more information, see, e.g., [2]). For such diagnostics, a diagnostic beam of neutral atoms is injected into the plasma.…”

“…Besides the active signal produced by the CX of diagnostic neutral hydrogen beam with impurity ions in the plasma, the passive signal produced by the CX of impurity ions with atoms in the cold edge plasma is also important, as follows from the available observational data from the JET (Joint European Torus) tokamak with ITER-like beryllium wall (see, e.g., comments and references in [2]).…”