Selective heating of high-pressure vapour elements by ion-cyclotron resonance

Abstract

The heating at ion-cyclotron resonance of various species of pure metallic plasmas (Mg, Ca, Zn, Ba and Yb) is measured experimentally with various diagnostics (using an energy analyser, Fabry-Pérot interferometry, laser absorption and induced fluorescence) and compared with the theory. The selectivity of the heating is found to be very sensitive to the characteristics of the plasma source. At each ion-cyclotron resonance, the refractive index of the fast wave exhibits an increase proportional to the square root of the abundance of the corresponding isotope, leading to a decrease of the exciting electric field and of the heating that is checked experimentally. The experiments and the theory show that the selective heating is proportional to the square of the antenna current. Also the increase of the heating measured with the static axial magnetic field is due to the increase of the fast-wave component as and to the decrease of the slow-wave component of the electric field by the space-charge effect. The decrease of the ionic heating with the plasma radius is due to the slow wave radial profile whose characteristic absorption length (3 cm) is about half the plasma radius.