Evolution of the central safety factor during stabilized sawtooth instabilities at KSTAR

Abstract

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Optimal MSE polarisation angle and q-profile estimation using Kalman filters and the plasma simulator RAPTOR

“…Flow diagram of the implemented coupling between RAPTOR and CHEASE. 7 Note that equation (2.15) is a reduced form which neglects contributions from electric fields, which can lead to high uncertainties in advanced plasma scenarios [24]. The radial electric fields cannot be obtained from RAPTOR.…”

“…A continuous challenge of the MSE diagnostic is to record data with sufficient accuracy for a good q-profile reconstruction. For a precise reconstruction, for example to accurately resolve the evolution of the central safety factor during sawtooth events, a measurement accuracy of 0.1°on a millisecond timescale is required [6,7]. In this article we propose a novel way to use a modelbased observer to obtain accurate estimates of the magnetic pitch angles.…”

Sawtooth inducedq-profile evolution at ASDEX Upgrade

“…Sawteeth were first observed in 1974 [4,5]. Measurements of the sawtooth induced qprofile changes were performed at TEXTOR [6], TFTR [7], DIIID [8], and KSTAR [9,10]. Various reconnection models and various values for q 0 after the sawtooth event have been proposed.…”