Lower hybrid wave coupling in TORE SUPRA through multijunction launchers

Abstract

The TORE SUPRA lower hybrid current drive experiments (8 MWi3.7 GHz) use large phased waveguide arrays, four rows of 32 active waveguides and two passive waveguides for each of the two grills, to couple the waves to the plasma. These launchers are based on the 'multijunction' principle which allows them to be quite compact and is therefore attractive for the design of efficient multi-megawatt antennas in NETIITER. Extensive coupling measurements have been performed in order to study the radiofrequency (RF) characteristics of the plasma loaded antennas. Measurements of the plasma scattering coefficients of the antennas show good agreement with those obtained from the linear coupling theory (SWAN code). Global reflection coefficients of a few per cent have been measured in a large range of edge plasma densities (0.3 X 10" m-3 I neg I 1.4 X 10l8 m-3) or antenna positions (0.02-0.05 m from the plasma edge) and up to a maximum injected RF power density of 45 MWlm'. When the plasma is pushed against the inner wall of the chamber, the reflection coefficient is found to remain low up to distances of the order of 0.10 m. The coupling measurements allow us to deduce the 'experimental' power spectra radiated by the antennas when all their modules are fed simultaneously with variable phases. Thus, the multijunction launcher is assessed as a viable antenna for high power transmission with good coupling characteristics and spectrum control.

Investigation of lower hybrid wave coupling and current drive experiments at different configurations in experimental advanced superconducting tokamak

“…34,35 Preliminary studies indicate that LHW-plasma coupling and current drive efficiency are both affected by the plasma configuration. The best coupling is obtained in the limiter configuration, then the SN plasma, and the worst is the DN plasma.…”

New signal processing technique for density profile reconstruction using reflectometry

“…Direct measurements of density in front of the grid are usually conveniently given by fixed Langmuir probes. 21 This diagnostic offers the advantage of having low cumbersome features; however, it provides a single radial point measurement. Moreover, due to the very low LH cut-off density, measurement in the private zone of the launcher is highly demanded.…”

Design criteria and current status of LHCD system on SST1 machine

“…Fig. 3 shows the power flux handling capabilities for various machines like Versator-II [7], JFT-2 [8], PLT [9], WT-2 [10], JT-60U [11], TRIAM-1M [12], JET [13], Tore Supra [14,15], Asdex [16], Alcator-C [17] and FTU [18] and its dependence on frequency and the width of the grill channel. The magnetic field for the machines is also shown in brackets in the same figure to show the growing trend with operating frequency and magnetic field.…”