Synergy between neutral beam current drive and ICRH in TEXTOR
During combined heating experiments of NBI-Co (D(o) to D(+)) + ICRH (H minority scenario), a large increase of beam driven current was observed in TEXTOR (up to 70% increase depending on the mix of NBI and ICRH power). This, together with the enhancement of the bootstrap current, results in a large volt-second (Vs) saving which allows a substantial increase of the shot duration (e.g. by a factor of 5 at I(p) = 300 kA). Much of the synergistic increase of the beam driven current can be explained by the rise of the electron temperature produced by ICRH, which leads to an extension of the beam slowing down time. A smaller contribution is due to direct coupling of the RF power to the beam and to the decrease of the toroidal rotation velocity induced by the RF. The RF absorption with a realistic beam distribution function was theoretically computed. It is shown that in the case of minority heating about 20% of the total absorption can be due to beam components (omega = 2 x omega(CD) interaction). The initial deformation of the beam distribution function by the RF is also theoretically evaluated. The results of the non-ohmically driven current for a density scan and a total current scan are given and discussed, in the light of these theoretical considerations and of simulations made by the code-system TRANSP.
Bibliographic Reference: Article: Proceedings of the IAEA Technical Committee Meeting on Fast Wave Current Drive in Reactor Scale Tokamaks, Arles (1992) pp. 335-352
Record Number: 199210878 / Last updated on: 1994-12-02
Original language: en
Available languages: en