BEGIN:VCALENDAR VERSION:2.0 PRODID:-//wp-events-plugin.com//6.4.7.2//EN TZID:Europe/Paris X-WR-TIMEZONE:Europe/Paris BEGIN:VEVENT UID:1-450@lptms.universite-paris-saclay.fr DTSTART:20161018T110000Z DTEND:20161018T120000Z DTSTAMP:20160929T075146Z URL:http://www.lptms.universite-paris-saclay.fr/seminars/seminaire-lptms-f riedrich-wagner/ SUMMARY:Séminaire du LPTMS: Friedrich Wagner *** commun avec l'IPN *** - I PN-batiment 100\, Auditoriurm - 18 Oct 16 11:00 DESCRIPTION:\nOptimized and self optimized magnetic confinement\n\n\n\n\n\n Friedrich Wagner (Max-Planck-Institut für Plasmaphysik\, Teilinstitut Gr eifswald)\n\n\n\n\nMagnetic confinement in toroidal fusion systems has bee n developed to a degree\, which allows building the first fusion reactor\, ITER. The goal of ITER is the operation of a Deuterium-Tritium plasma und er conditions\, which allow the production of 500 MW fusion power with a p ower amplification of Q=10. But ITER is still an experiment and it will so lve for its basic concept – the tokamak – many fundamental research is sues. As the tokamak concept has drawbacks – prone to current driven ins tabilities and intrinsically pulsed – alternatives are pursued in parall el. The stellarator is the second most advanced toroidal magnetic confinem ent concept whereat the largest and most advanced device of this line\, We ndelstein 7-X\, has just started operation in Greifswald\, Germany. Wendel stein 7-X is an experiment for basic research\, which nevertheless should demonstrate the reactor viability of this concept. The major difference be tween tokamak and stellarator is the way the poloidal field\, essential fo r confinement\, is produced. In case of the tokamak\, it is generated by a strong toroidal current induced within the toroidal plasma ring. In stell arators\, it is produced externally by currents within strongly shaped coi ls.\n\n\n\n\nThe system optimization aims i.a. at the quality of the therm al insulation of the plasma to reach high core temperatures by economic me ans. The tokamak benefits from the reduced system symmetry with continuous symmetry in toroidal direction. The stellarator plasma is unavoidably 3-d imensional and toroidally periodic with the corollary of insufficient coll isional confinement. But with a rigorous system optimization those field p roperties which are decisive for the “laminar” radial transport can be made 2-dimensional. Systems with these features are called quasi-symmetri c and they should have similar collisional transport like truly symmetric systems\, be more stable and intrinsically suitable for steady-state opera tion.\n\n\n\n\nOn the other hand\, fusion plasmas are thermodynamically op en systems where turbulent processes govern radial transport in symmetric and quasi-symmetric systems. Like in other open systems also\, self-organi zed processes can determine important and relevant plasma characteristics. Under high plasma pressure giving rise to a large turbulence level\, the turbulent eddies can develop a coherence where ultimately the energy of th e turbulence field is transformed into the kinetic energy of a macroscopic flow. This flow turns out to be sheared acting back onto its original dri ve\, the turbulence field. Within a sub-millisecond time scale\, the turbu lence is quenched in a highly non-linear process and a quiescent regime wi th good confinement emerges. This regime is called high-confinement mode ( H-mode) and is the basis to reach the goals of ITER. Some of these mechani sms play also a role in other open systems with classical turbulence.\n\n\ n\n\nIn this seminar the physics of plasma optimization and self-optimizat ion will be presented.\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n CATEGORIES:seminars LOCATION:IPN-batiment 100\, Auditoriurm\, 15 Rue Georges Clemenceau\, orsay \, France GEO:48.698196;2.181773 X-APPLE-STRUCTURED-LOCATION;VALUE=URI;X-ADDRESS=15 Rue Georges Clemenceau\, orsay\, France;X-APPLE-RADIUS=100;X-TITLE=IPN-batiment 100\, Auditoriurm: geo:48.698196,2.181773 END:VEVENT END:VCALENDAR