Power deposition profile during lower hybrid current drive in Tore Supra
Extensive lower hybrid experiments at injected power up to 4 MW have been performed in Tore Supra in various regimes. Strong electron heating and creation of a suprathermal tail have both been observed. The fast electrons created may diffuse radially during their slowing down process and therefore may produce a non-local bulk heating. To analyse the power deposition profiles on the bulk electrons, a standard perturbed energy balance has been used, including the ohmic power modulation and the thermalisation process. The results of an LH square modulated experiment performed at relatively high density are presented. The thermal and fast electron responses are analysed simultaneously using a set of 4 diagnostics: - a soft X-ray camera measuring the photon emission in the 1-30 keV energy range along 43 chords, - an ECE diagnostic measuring the thermal (2 fce) as well as the non- thermal cyclotron emission (2 fce with relativistic shift), - a T(e) profile measurement by Thomson scattering, - a hard X-ray (0.06 to 1 MeV) spectrometer viewing the plasma along 5 chords. It is observed that the time response of the thermal population to the power modulation is longer than 100 ms, whereas the fast electron population is created in a much shorter time (less than 30 ms). This heating is dominated by a local deposition rather than by transport. At this high density the analysis of the T(e) perturbation shows a fairly uniform electronic power deposition profile; on the other hand, it is seen from hard X-rays that the energetic electrons are produced rather off axis. This difference can be explained by an inward diffusion of fast electrons on a time scale comparable with their slowing down time.
Bibliographic Reference: Paper presented: 18th European Conference of the EPS-Plasma Physics Division, Berlin (DE), June 3-7, 1991
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Record Number: 199110379 / Last updated on: 1994-12-02
Original language: en
Available languages: en