The method of contact ionization is used to produce a three-component plasma (Cs+, Cl-, e-) in the Q-device BARBARA using a beam of Cesium chloride. The end-plate temperature controls the concentration of Cl-, which can be varied in a wide range. The density of negative ions is obtained from the difference between the positive ion density given by a Langmuir probe and the electron density given by a microwave resonator. A high concentration of negative ions is achieved.

Previously obtained data on the Wega tokamak by lower hybrid heating (f = 500 MHz; PHF = 130 kW) are re-visited in the light of recent theories on ion stochastic heating and quasi-linear electron Landau damping. It is possible, with the help of these theories, to correctly estimate the fast-ion mean energy, the HF power density coupled to the ions and that coupled to the electrons. The values of the parallel index of refraction, N‖, which are necessary to obtain a good quantitative agreement between experiment and theoretical estimates, are the same for ions and electrons, although higher than expected.

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