The capture of many electrons by Ar !7+ ions, at low velocity, near a metallic surface, has been studied. Multiexcited bound states with many electrons in the outermost shells (hollow atoms) have been observed. The surrounding of an ionic excited core by many outermost electrons greatly decreases the lifetimes of the states. This characteristic decrease explains the main striking features of the relaxation of the ions.

The hot electrons in the plasma of an electron-cyclotron-resonance ion source are investigated by three passive diagnostics: bremsstrahlung, electron cyclotron emission, and diamagnetism. For this type of plasma the feasibility of the second diagnostic is an innovative development, as is the simultaneous use of two independent plasma diagnostics for either steady-state or transient experiments. In the steady-state experiments the bremsstrahlung and the electron cyclotron emission are interpreted by comparing the experimental spectra with simulated spectra calculated for the first time from a non-Maxwellian electron distribution. The ‘‘perpendicular temperatures’’ obtained by the two diagnostics are in good agreement. In the transient experiments the electron cyclotron emission and the diamagnetic signals are recorded to study the electron density and the electron lifetime. All these experiments performed using the Minimafios ion source working at 18 GHz with oxygen gas demonstrate trends and saturation effects when the gas injection pressure and the radio-frequency power are varied.

A new multijunction grill-type launcher has been tested on the Petula-B tokamak. In this new launcher, the RF power is divided by means of an E-plane junction, and the phase between each resultant wave is obtained by a suitable reduction in the height of the waveguides. Data obtained on Petula-B indicate that both the heating efficiency (4.5 eV × 1013 cm−3·kW−1) and the parametric dependences of the reflection coefficient are very similar to those of a conventional grill. Therefore, such a multijunction grill may greatly simplify the construction of grills considered for use in future large-scale tokamaks.

This article emphasizes a confinement model for electrons and ions in an ECR source for multicharged ions, on the basis of specific measurements performed on the 16.6 GHz MINIMAFIOS and 10 GHz CAPRICE facilities. The conclusions partially support the above model.

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