Collective Thomson scattering model for arbitrarily drifting bi-Maxwellian velocity distributions

Abstract

In this paper we derive the equations of collective Thomson scattering (CTS) for an arbitrarily drifting magnetized plasma described by a bi-Maxwellian distribution. The model allows the treatment of anisotropic plasma with different parallel and perpendicular temperatures (with respect to the magnetic field) as well as parallel and perpendicular plasma drift. As could be expected, parallel observation directions are most sensitive to the parallel temperature and drift, whereas perpendicular observation directions are most sensitive to the perpendicular temperature and the perpendicular drift along the observation direction. The perpendicular drift can be related to the radial electric field. Measurements with a spectral resolution better than 0.5 MHz are necessary for the inference of the radial electric field. This spectral resolution and the required scattering geometry are attainable with the current setup of the CTS diagnostic on Wendelstein 7-X.

Optimization of the Collective Thomson scattering diagnostic for future operation

“…CTS diagnostics are in operation at the LHD device [5,6] and ASDEX Upgrade [7] and will be an important diagnostic at ITER [8]. The measured spectra at W7-X were extensively compared with numerical simulations made by the forward model eCTS [9,10] whose input parameters were inferred by the Bayesian Maximum-A-Posterior method in the Minerva framework [11]. The obtained value of T i is in agreement with the result obtained by the X-ray imaging spectroscopy [12], and agreement was obtained between synthetic and measured spectra, yet a few discrepancies in spectral shape and width were noted [2].…”

Collective Thomson Scattering Diagnostic for Wendelstein 7-X at 175 GHz

“…140 GHz heating gyrotrons are used as a source of probing radiation [1]. Here eCTS, a java code integrated into the Bayesian analysis framework Minerva, has been developed and used for the analysis of experimental data [2][3][4]. The first experimental results on ion temperature measurements in the bean-shaped cross-section are reported in reference [1].…”