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Abstract

Preventing the type I ELM heat pulses, in ITER Q-10 plasmas, from eroding the divertor target in a very short time will be a challenging, if not impossible task. This arises because high fusion power output requires a large plasma temperature near to the edge; around 4keV being a typical estimate. Thus, at density >10E 20m{-3}, as type I ELMs peel off the plasma edge they will take tens of megajoules with them. In addition, present data indicates that the proportion of the plasma energy, lost with each ELM, increases as the collisionality decreases towards ITER values. Current estimates are that each ELM will eject as much as 40MJ towards the target plates, in a time of about one millisecond. Various operating regimes have been found in which type I ELMs are not present but these suffer from lack of scalability or do not overlap with the conditions of the standard ITER operating scenario.
This work started from the point of view that a robust way of actively suppressing type I ELMs is both mandatory and practical in ITER. We report some considerable and experimental success in exploring this proposition, using a magnetic perturbation generated by the I-coils in DIII-D. The hypothesis was tested that an external magnetic perturbation, whose torodial and poloidal spectrum is in resonance with field lines at the edge, increases transport there, reduces the pressure gradient and, thereby, eliminates the drive for the mhd instabilities that cause ELMs. Holding the pressure gradient just below the threshold at which ELMs are triggered, should bring good fusion performance without the penalty of ELMs. JFT2-M and Compass had already made a start in this direction but neither obtained an unambiguous, robust suppression of type I ELMs.

Additional information

Authors: THOMAS P, Departement de Recherches sur la Fusion Controlee, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR);ET AL, Departement de Recherches sur la Fusion Controlee, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR)
Bibliographic Reference: An oral paper given at: 31st EPS Conference on Controlled Fusion and Plasma Physics Organised by: CCLRC Rutherford Appleton Laboratory (GB); EURATOM/UKAEA Fusion Association (GB); Imperial College London Held at: Imperial College London (
Availability: Available from Association EURATOM-CEA, Departement de Recherches sur la Fusion Controlee, CEA Cadarache, F-13108 St Paul-Lez-Durance, France Tel: (+33) 4 42 25 70 01; Fax: (+33) 4 42 25 64 21 E-mail: dirdrfc@drfc.cad.cea.fr
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