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Author Esposito, B. ♦ Granucci, G. ♦ Nowak, S. ♦ Martin-Solis, J. R. ♦ Gabellieri, L. ♦ Smeulders, P. ♦ Maraschek, M. ♦ Pautasso, G. ♦ Stober, J. ♦ Treutterer, W. ♦ Urso, L.
Source CiteSeerX
Content type Text
File Format PDF
Subject Domain (in DDC) Computer science, information & general works ♦ Data processing & computer science
Subject Keyword Asdex Upgrade ♦ Ex 7-3ra Disruption Control ♦ Ecrh Power ♦ Disruption Avoidance ♦ Plasma Current Quench ♦ Deuterium Gas ♦ Asdex Upgrade L-mode Plasma ♦ Strong Local Ecrh Heating ♦ Similar Set ♦ Magnetic Island ♦ Minimum Absorbed Power Value ♦ Toroidal Magnetic Field ♦ Coupled Mode ♦ Rational Surface ♦ Deposition Radius ♦ Mhd Mode ♦ Direct Heating ♦ Rutherford Equation ♦ Power Deposition Location ♦ Disruption Precursor ♦ Deposition Location ♦ Ecrh Launching Mirror ♦ Promising Technique ♦ Current Quench ♦ Dedicated Experiment ♦ Greenwald Limit ♦ Current Quench Delay ♦ Loop Voltage Signal ♦ Complete Discharge Recovery ♦ Ftu Experiment
Abstract Abstract. The use of ECRH has been investigated as a promising technique to avoid or postpone disruptions in dedicated experiments in FTU and ASDEX Upgrade. Disruptions have been produced by injecting Mo through laser blow-off (FTU) or by puffing deuterium gas above the Greenwald limit (FTU and ASDEX Upgrade). The toroidal magnetic field is kept fixed and the ECRH launching mirrors are steered before every discharge in order to change the deposition radius. The loop voltage signal is used as disruption precursor to trigger the ECRH power before the plasma current quench. In the FTU experiments (Ip=0.35-0.5 MA, Bt=5.3 T, PECRH=0.4-1.2 MW) it is found that the application of ECRH modifies the current quench starting time depending on the power deposition location. A scan in deposition location has shown that the direct heating of one of the magnetic islands produced by magnetohydrodynamic (MHD) modes (either m/n=3/2, 2/1 or 3/1) prevents its further growth and also produces the stabilization of the other coupled modes and current quench delay or avoidance. Disruption avoidance and complete discharge recovery is obtained when the ECRH power is applied on rational surfaces. The modes involved in the disruption are found to be tearing modes stabilized by a strong local ECRH heating. The Rutherford equation has been used to reproduce the evolution of the MHD modes. The minimum absorbed power value found for disruption avoidance is 0.4 MW at 0.5 MA with deposition on the q=2 surface. In the similar set of experiments carried out in ASDEX Upgrade L-mode plasmas (Ip=0.6 MA, Bt=2.5 T, PECRH =
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Learning Resource Type Article