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Three great possible descriptions steer the same plasma mechanics physical background towards different frameworks, while only adopting distinct angles. One can chose to focus on each particle the plasma is composed of and try to follow it in time. Doing so, he would perform a many body description, requiring to be able to embrace at any given time the 6N degrees of freedom of the N particles. With N above the billion, it is nowadays untractable for who is not a Laplace demiurge. And typically, N about 10(23) in ITER, the International Thermonuclear Experimental Reactor. Another possibility consists in fixing time and considering a snapshot of the plasma state. So as to describe this snapshot, statistical physics and mathematics come up with the distribution function intermediary concept. In this frame, the key notion rests on the dynamics (time evolution) of this distribution function, strongly dependant on the existing electrodynamic fields in the medium.
The so-called kinetic approach rests on a mean field approximation: the electric and magnetic fields are averaged on distances in between the interparticular distance and the Debye screening length. This approach has 6Ns degrees of freedom, where Ns refers to the number of species (electrons, ions, impurities) in the medium. In the non-collisional limit that will prevail in ITER, the dynamics of the distribution function can satisfactorily be described by the Vlasov equation , which has a Hamiltonian structure.

Additional information

Authors: SARAZIN Y, Département de Recherches sur la Fusion Contrôlée, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR)
Bibliographic Reference: An oral paper given at: Mémoire de stage 2005 Organised by: CEA Caderache, Saint-Paul-lez-Durance (FR) Held at: CEA Caderache, Saint-Paul-lez-Durance (FR)
Availability: Available from Association EURATOM-CEA, Département de Recherches sur la Fusion Contrôlée, 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:
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