Diagnostic development for current density profile control at KSTAR

Atomic Data for Calculation of the Intensities of Stark Components of Excited Hydrogen Atoms in Fusion Plasmas

“…It is the presence of the coherence terms in Eqs. (4)(5)(6)(7)(8)(9) that explains the asymmetry between the red-and blue-shifted lines for Stark effect measurement (note that the influence of field ionisation is still low [32] under these conditions). Therefore, for instance, depending on the orientation between the cathode rays and the vector direction of the electric field (e.g., parallel, α = 0; transverse, α = π/2; or anti-parallel, α = π) blue-shifted, red-shifted, or symmetric patterns were detected for Balmer-α components of the emission [17].…”

“…Here we report the line intensities of the Lyman-α, β and Balmer-α lines for different values of α (Figs. [4][5][6]. The angle between the line-of-sight and the direction of the electric field is θ = π/2.…”

“…≈ 25 keV) play a dominant role [1]. Local measurements of ion temperature, concentration of impurity ions, plasma rotation, and electric field measurements including polarisation coherence, or control of the plasma current density profile, are the most representative examples of the use of injection of heating or diagnostic beams in fusion plasmas [2][3][4][5][6]. So, for instance, charge-exchange recombination spectroscopy, which is based on the capture of bound electrons of the beam atoms by impurity ions, has been exploited for the last few decades on practically all former and present tokamaks and stellarators, including JET, ASDEX, W7-X, KSTAR, etc., [7].…”

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

“…KSTAR recently show cased its capabilities by setting a new record for long pulse Hmode operation [3], however to support the ITER project in exploring advanced scenarios, current profile measurements are of essence. For this reason, a 25 chord MSE polarimeter has been installed in 2015 [4] and commissioned during the 2015 plasma campaign. Owing to the digital data acquisition system combined with digital lockin analysis, the full Stokes vector is reconstructed on a millisecond timescale.…”

“…In this report, after giving an overview of the experimental setup at KSTAR, a generic twostep calibration and verifica tion method is presented: First the bandpass filters used to single out the redshifted Stark peak are calibrated such, that the measured pitch angle displays a physically reasonable slope. In the second step it is investigated whether systematic offsets are present by comparing the reconstructed qprofile 1,4 (constrained by MSE) against rational qvalues obtainable from independent diagnostics during MHD instabilities in the plasma. After successful calibration, the qprofile evolution of a sawtooth crash is analysed in section 4.…”