Charge exchange spectroscopy as a fast ion diagnostic on TEXTOR

Abstract

An upgraded charge exchange spectroscopy diagnostic has been taken into operation at the TEXTOR tokamak. The angles of the viewing lines with the toroidal magnetic field are close to the pitch angles at birth of fast ions injected by one of the neutral beam injectors. Using another neutral beam for active spectroscopy, injected counter the direction in which fast ions injected by the first beam are circulating, we can simultaneously measure a fast ion tail on the blue wing of the D ␣ spectrum while the beam emission spectrum is Doppler shifted to the red wing. An analysis combining the two parts of the spectrum offers possibilities to improve the accuracy of the absolute ͑fast͒ ion density profiles. Fast beam modulation or passive viewing lines cannot be used for background subtraction on this diagnostic setup and therefore the background has to be modeled and fitted to the data together with a spectral model for the slowing down feature. The analysis of the fast ion D ␣ spectrum obtained with the new diagnostic is discussed.

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

“…The rapid decay of excitation rate coefficient as (~1/n 3 ) where n is the principal quantum number prevents the appearance of plume in all other impurities except of He (see also PEC values for HI, HeII, and CVI in Figure 2h). Finally, the type of synthetic 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 Heating (ICRH). In all three examples of FICX (Fast-Ion-CXRS), the range of energies of the fast ions exceeds by far the width of the CX emission rate function which typically peaks around 50 keV/amu, and contributes dominantly to measurable signals for relative collision velocities less than 100 keV/amu.…”

Fast-ion D-alpha measurements at ASDEX Upgrade

“…The FIDA technique, which is similar to spectroscopic measurements of fast alpha particles [8], was first implemented at DIII-D [9] and has become a widely used method due to its relatively good spatial and temporal resolution. It is now used as well in TEXTOR [10], LHD [11] and NSTX [12] and has yielded results on the fast-ion distribution due to micro-turbulence [13], Alfven waves [14] and different injection geometries [15].…”

Conceptual design of a fast-ion D-alpha diagnostic on experimental advanced superconducting tokamak

“…One powerful diagnostic method is the fast-ion D-alpha (FIDA) technique, which is based on charge-exchange between injected neutral beam particles and the high energetic deuterium ions, similar as the measurements of energetic helium ions reported on Joint European Torus (JET) in 1993. 1 Since it was first successfully exploited in Doublet-III-D (DIII-D), 2 now it has been applied to several tokamaks (National Spherical Torus Experiment (NSTX); 3 Tokamak EXperiment for Technology Oriented Research (TEXTOR); 4 Axially Symmetric Divertor EXperiment Upgrade (ASDEX-U) 5 ). Similar experiments based on Fast Ion Charge eXchange Spectroscopy (FICXS) have been applied on Large Helical Device (LHD).…”