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Published byColin Cody McDowell Modified over 9 years ago
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S. Coda, MHD workshop, PPPL, 22 Nov. 2004 Advances in sawtooth control for NTM prevention in JET S. Coda 1, L.-G. Eriksson 2, J. Graves 1, R. Koslowski 3, F. Nave 4, P. Belo 4, R.J. Buttery 5, S. Cowley 6, P. de Vries 5,7, M.J. Mantsinen 8, M.-L. Mayoral 5, A. Mück 1, O. Sauter 1, E. Westerhof 7, and JET-EFDA contributors 1 CRPP, EPFL, Association Euratom-Fédération Suisse, Lausanne, Switzerland 2 Association Euratom-CEA, DRFC, Cadarache, France 3 Association Euratom-FZ Jülich, Institut für Plasmaphysik, TEC, Jülich, Germany 4 Associação Euratom-IST, Centro de Fusão Nuclear, Lisbon, Portugal 5 Euratom-UKAEA Fusion Association, Culham Science Center, United Kingdom 6 Department of Physics, Imperial College, London, United Kingdom 7 Association Euratom-FOM, FOM-Rijnhuizen, TEC, Nieuwegein, The Netherlands 8 Association Euratom-Tekes, Helsinki University of Technology, Finland
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Sawtooth control in JET S. Coda, MHD workshop, PPPL, 22 Nov. 2004 Outline NTM triggering by long sawteeth Sawtooth destabilization by ICCD Sawtooth destabilization by counter-NBI
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Sawtooth control in JET S. Coda, MHD workshop, PPPL, 22 Nov. 2004 Long sawteeth trigger (3,2) NTMs at low N O. Sauter et al., PRL 88, 105001 (2002) Avoidance strategy: destabilize sawteeth keep seed island small
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Sawtooth control in JET S. Coda, MHD workshop, PPPL, 22 Nov. 2004 Fishbones are less of a concern
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Sawtooth control in JET S. Coda, MHD workshop, PPPL, 22 Nov. 2004 Discrete jump in N at long T st …
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Sawtooth control in JET S. Coda, MHD workshop, PPPL, 22 Nov. 2004 …but N vs. T st not really so simple
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Sawtooth control in JET S. Coda, MHD workshop, PPPL, 22 Nov. 2004 ICRH control of sawtooth period +90 0 at center: max fast-ion stabilization -90 0 at q=1: max ICCD destabilization M.-L. Mayoral et al., PoP 11, 2607 (2004) Both effects increase with ICRH power
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Sawtooth control in JET S. Coda, MHD workshop, PPPL, 22 Nov. 2004 ICCD destabilization of fast-particle-stabilized sawteeth ITER simulation: -particles ICRH-accelerated fast ions ICCD at q=1 to keep sawteeth short: tested only without strong fast particle pressure (crash criterion different) need 2 ICRH frequencies (H minority) It works! Must still apply to NTM scenario (NBI) L.-G. Eriksson et al., PRL 92, 235004 (2004)
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Sawtooth control in JET S. Coda, MHD workshop, PPPL, 22 Nov. 2004 Control experiments: fast ions vs. ICCD
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Sawtooth control in JET S. Coda, MHD workshop, PPPL, 22 Nov. 2004 Control experiments: B-field scan
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Sawtooth control in JET S. Coda, MHD workshop, PPPL, 22 Nov. 2004 Sawtooth destabilization by counter-NBI Sawteeth shorter with counter- than co-NBI
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Sawtooth control in JET S. Coda, MHD workshop, PPPL, 22 Nov. 2004 Rotation scan in counter-NBI Sawtooth period is minimum at P~4 MW
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Sawtooth control in JET S. Coda, MHD workshop, PPPL, 22 Nov. 2004 Minimum T st found at finite rotation Explanation? NBCD unlikely Fast ions unlikely Promising candidate: internal kink stabilization by sheared rotation
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Sawtooth control in JET S. Coda, MHD workshop, PPPL, 22 Nov. 2004 Shape also affects sawteeth
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Sawtooth control in JET S. Coda, MHD workshop, PPPL, 22 Nov. 2004 Conclusions NTMs are expected to be excited in ITER by long sawteeth stabilized by -particles ICCD at q=1 has been proven to be an effective means of shortening sawteeth, even with large fast-ion pressure, thus preventing NTMs Additional sawtooth destabilization tools demonstrated on JET: rotation in counter-NBI and higher elongation
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Sawtooth control in JET S. Coda, MHD workshop, PPPL, 22 Nov. 2004 Plans for coming campaigns Demonstrate NTM prevention scenario with combined sawtooth stabilization/destabilization scheme –Attempt feedback on ICRH frequency for scenario optimization –Use new ICRH antenna for better coupling during ELMs Further characterize NTM triggering in a wider range of plasma parameters
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Sawtooth control in JET S. Coda, MHD workshop, PPPL, 22 Nov. 2004 N *N * Modified Rutherford equation: –small island effects cause a * dependence w pol * N * criterion –usually assumes a given seed size
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Sawtooth control in JET S. Coda, MHD workshop, PPPL, 22 Nov. 2004 New JET-EP ICRH antenna Better coupling esp. during ELMs
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