1 / 18

Advances in sawtooth control for NTM prevention in JET

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.

harris
Télécharger la présentation

Advances in sawtooth control for NTM prevention in JET

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Advances in sawtooth controlfor NTM prevention in JET S. Coda1, L.-G. Eriksson2, J. Graves1, R. Koslowski3,F. Nave4, P. Belo4, R.J. Buttery5, S. Cowley6,P. de Vries5,7, M.J. Mantsinen8, M.-L. Mayoral5,A. Mück1, O. Sauter1, E. Westerhof7,and JET-EFDA contributors 1CRPP, EPFL, Association Euratom-Fédération Suisse, Lausanne, Switzerland 2Association Euratom-CEA, DRFC, Cadarache, France 3Association Euratom-FZ Jülich, Institut für Plasmaphysik, TEC, Jülich, Germany 4Associação Euratom-IST, Centro de Fusão Nuclear, Lisbon, Portugal 5Euratom-UKAEA Fusion Association, Culham Science Center, United Kingdom 6Department of Physics, Imperial College, London, United Kingdom 7Association Euratom-FOM, FOM-Rijnhuizen, TEC, Nieuwegein, The Netherlands 8Association Euratom-Tekes, Helsinki University of Technology, Finland S. Coda, MHD workshop, PPPL, 22 Nov. 2004

  2. Outline • NTM triggering by long sawteeth • Sawtooth destabilization by ICCD • Sawtooth destabilization by counter-NBI S. Coda, MHD workshop, PPPL, 22 Nov. 2004

  3. Long sawteeth trigger (3,2) NTMsat low bN Avoidance strategy:destabilize sawteeth]keep seed island small O. Sauter et al., PRL 88, 105001 (2002) S. Coda, MHD workshop, PPPL, 22 Nov. 2004

  4. Fishbones are less of a concern S. Coda, MHD workshop, PPPL, 22 Nov. 2004

  5. Discrete jump in bN at long Tst… S. Coda, MHD workshop, PPPL, 22 Nov. 2004

  6. …but bN vs. Tst not really so simple S. Coda, MHD workshop, PPPL, 22 Nov. 2004

  7. ICRH control of sawtooth period +900 at center: max fast-ion stabilization -900 at q=1: max ICCD destabilization Both effects increase with ICRH power M.-L. Mayoral et al., PoP 11, 2607 (2004) S. Coda, MHD workshop, PPPL, 22 Nov. 2004

  8. ICCD destabilizationof fast-particle-stabilized sawteeth L.-G. Eriksson et al., PRL 92, 235004 (2004) • ITER simulation:a-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) S. Coda, MHD workshop, PPPL, 22 Nov. 2004

  9. Control experiments:fast ions vs. ICCD S. Coda, MHD workshop, PPPL, 22 Nov. 2004

  10. Control experiments: B-field scan S. Coda, MHD workshop, PPPL, 22 Nov. 2004

  11. Sawtooth destabilizationby counter-NBI • Sawteeth shorter with counter- than co-NBI S. Coda, MHD workshop, PPPL, 22 Nov. 2004

  12. Rotation scan in counter-NBI • Sawtooth period is minimum at P~4 MW S. Coda, MHD workshop, PPPL, 22 Nov. 2004

  13. Minimum Tst found at finite rotation Explanation? • NBCD unlikely • Fast ions unlikely • Promising candidate: internal kink stabilization by sheared rotation S. Coda, MHD workshop, PPPL, 22 Nov. 2004

  14. Shape also affects sawteeth S. Coda, MHD workshop, PPPL, 22 Nov. 2004

  15. Conclusions • NTMs are expected to be excited in ITER by long sawteeth stabilized by a-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 S. Coda, MHD workshop, PPPL, 22 Nov. 2004

  16. 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 S. Coda, MHD workshop, PPPL, 22 Nov. 2004

  17. bNr* • Modified Rutherford equation: • small island effects cause a r* dependence wpolr* • bNr* criterion • usually assumes a given seed size S. Coda, MHD workshop, PPPL, 22 Nov. 2004

  18. New JET-EP ICRH antenna • Better coupling esp. during ELMs S. Coda, MHD workshop, PPPL, 22 Nov. 2004

More Related