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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Abstract.We report on measurements of angular differential cross sections for the excitation of multiply charged ions by electron impact. An ion beam is crossed by an electron beam; electrons which are inelastically scattered at different angles are identified by their energy loss due to the excitation process. Absolute excitation cross sections are obtained by comparing the signals of the elastic and the inelastic electron-ion scattering. Results obtained for the 3s---, 3p excitation of Ar v+ are discussed.

A _s~nthesized plasma containing no electrons but only positive H+ and negative H Ions has been made from a very intense H-ion source. A rectilinear H-ion beam, extracted from a Penning-type source through a magnetic shield, crosses a gaseous target. By two-electron collisional detachment, positive ions are created which, ~ccord~ng to the gas pressure and target depth, can balance the negative current mtenslty of the negative remaining ions. Precautions have been taken to avoid any pollution by electrons. Such purely ionic plasma beams have a density in the range 10 12 _10 13 m-3 , with a velocity of the order of 10 6 m/sec. This particular kind of plasma was first obtained in 1970 and reported in 1971.