SLOW WAVE LOWER HYBRID COUPLERS FOR HEATING AND CURRENT DRIVE IN LARGE SCALE TOKAMAK PLASMAS
According to the original "Grill" concepts, in most of the lower hybrid heating or current drive experiments, each guide of the "grill" in the toroidal direction is fed independently in phase and amplitude. The extrapolation of such a concept to large scale Tokamaks where a R.F. power level of several megawatts will be required leads to a very complex and cumbersome structure. Recently the use of E plane multijunctions and geometrical phase shifters has been proposed in order to simplify the S.W.L.H. coupler. In this paper we shall point out some important properties of the resulting compact antenna the so called "Multijunction grill" as far as coupling of the R.F. power to the plasma is concerned. Especially we shall estimate for some practical cases of waveguide phasing the electric field enhancement due to multiple reflexions of the wave between the antenna aperture and the guides junction ? plane. The small perturbation of the n-// power spectrum due to these reflexions is then evaluated. We also show how the reflected power of the "Travelling wave multijunction grills" can be made very small( approximately equal to 1%) in a large range of edge plasma parameters compared to that of the "conventional Grill". Finally we give an example of a S.W.L.H. coupler designed according to the multijunction concept.
Bibliographic Reference: COURSE AND WORKSHOP ON APPLICATIONS OF RF WAVES TO TOKAMAK PLASMAS, VILLA MONASTERO, VARENNA (ITALY), SEPT. 5-14, 1985 PP. 829-834, VOL. II 908 P., 1985, VOL. I AND VOL. II WRITE TO MONOTYPIA FRANCHI, VIALE UMBRIA 28/C, 06012 CITTA DI CASTELLO, PERUGIA (I
Record Number: 1989124100900 / Last updated on: 1987-01-01
Available languages: en