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In order to produce fully non inductive, lower hybrid (LH) driven discharges in a systematic and reproducible manner, new operation modes have been studied on the superconducting TORE SUPRA tokamak. To cope with some uncertainties in the LH current drive efficiency (eg profile dependencies), the plasma current is not imposed a priori, but it evolves freely until the equilibrium is reached. The voltage applied on the primary circuit no more controls the plasma current. In an open loop scenario in which this voltage is preset and constant, the time scale required to attain the equilibrium is the longest charactersitic time of the coupled plasma poloidal field coils system. In order to obtain a stationary state faster, a new feedback scheme has been implemented in which the primary circuit voltage is controlled in such a way that the flux consumption vanishes. It is shown that this operation mode allows to reach full steady state within a characteristic time of a few seconds. The underlying physics is described and a detailed analysis of the experiments is made. It is shown, in particular, that this operation scenario generates stable stationary plasmas with improved confinement, so that the so called LHEP regime can be extrapolated to continuous operation.

Additional information

Authors: KAZARIAN-VIBERT F, CEN, CEA Cadarache, Saint-Paul-lez-Durance (FR);LITUADON X, CEN, CEA Cadarache, Saint-Paul-lez-Durance (FR);MOREAU D, CEN, CEA Cadarache, Saint-Paul-lez-Durance (FR);ARSLANBEKOV R, CEN, CEA Cadarache, Saint-Paul-lez-Durance (FR);HOANG G T, CEN, CEA Cadarache, Saint-Paul-lez-Durance (FR);PEYSSON Y, CEN, CEA Cadarache, Saint-Paul-lez-Durance (FR)
Bibliographic Reference: Report: EUR-CEA-FC-1574 EN (1996) 19pp.
Availability: Available from Association Euratom-CEA, CEN Cadarache 13108 Saint-Pual-lez-Durance (FR)
Record Number: 199610886 / Last updated on: 1996-09-16
Original language: en
Available languages: en