Multiple electron cyclotron power deposition location tracking by break-in-slope analysis in TCV plasmas

Abstract

Abstract. Modulation of the amplitude of externally injected electron cyclotron (EC) power is a frequent method used to determine the radial power deposition profile in fusion plasmas. There are many tools to analyze the plasma response to the power modulations in quasi-stationary conditions. This paper focuses on the unique ability of the break-in-slope (BIS) method to retrieve a quasi-instantaneous estimate of the power deposition profile at each power step in the modulation, an outcome particularly relevant to track the power deposition location in nonstationary conditions. Here, the BIS analysis method is applied to the signals of a fast and high radial resolution wire-chamber soft X-ray camera in the Tokamakà Configuration Variable (TCV) where the plasma magnetic configuration and thus the EC resonance location are varied during the plasma discharge. As a step to validate this technique before real-time control experiments, the time-varying EC power deposition location of a single beam is successfully monitored by off-line BIS analysis. Simultaneous tracking of two EC beams deposition locations gives promising results.

A versatile ray-tracing code for studying rf wave propagation in toroidal magnetized plasmas

“…Here again, the dispersion relation is well satisfied along the trajectory. This example illustrates the versatility of the C3P O code and its applicability to the EC wave propagation [46], even though effects such as beam focusing and diffraction are not described in this pure ray-tracing scheme and require a beamtracing formalism. It is important to note, however, that many features developed in this paper are also applicable to beamtracing numerical schemes.…”

Experimental and numerical investigations of electron transport enhancement by electron-cyclotron plasma-wave interaction in tokamaks

“…Measuring the absorbed power density profile is not always straightforward. In particular, in the Tokamak à Configuration Variable (TCV), direct measurements of the absorbed power density profile have been judged to be unreliable in sawtoothing plasmas [3], and its determination must rely heavily on modeling.…”