Experimental and theoretical investigation of waves and resonances of a bounded hot electron, cold ion magnetized plasma

A plasma column is produced by diffusion along a steady magnetic field by a helical microwave discharge source located at one end of a linear machine. Plasma parameters are: plasma density, 8 x 109- 8 x 1010cm-3; typical electron temperature, 8 eV; magnetic field, 800-2200 Gauss. Waves in the plasma are electrostatically excited by a split-cylindrical, slow-wave structure. Movable well-balanced RF double probes are used to measure RF electric field amplitude as a function of frequency. A small signal, quasi-static theoretical analysis of a warm-electron, cold-ion, collisional plasma column including the wave-exciting structure predicts, at fixed k parallel, resonances ie peaks in the RF field amplitude as a function of frequency in the 'magneto-ion domain'. This frequency domain includes the Trivelpiece-Gould (T-G) mode (fsub(LH)<f<fsub(pe), surface wave mode, electrostatic ion-cyclotron mode (fsub(ci)<f<fsub(LH) and ion-acoustic mode (f<=fsub(ci)). Experimentally we have found that it is, in general, difficult to impose a single k parallel over the entire frequency range mentioned above. It was nevertheless possible to do so for the T-G mode over a given frequency band. Experimentally observed resonances and dispersion curves of the bounded plasma system (f vs. k parallel) are in good agreement with theory for ion-acoustic waves, surface waves and T-G mode. Moreover, it has been experimentally demonstrated that well defined slow-waves can be excited by an external coupler in the T-G region which extends to the lower-hybrid frequency. (author)