Linear wave properties, parametric decay processes, and resulting heating in a bounded magnetized plasma

A plasma column along a steady magnetic field is produced by a helical microwave discharge source located at one end of a linear machine. Plasma parameters are: plasma density, 8 × 10⁹—8 × 10¹⁰ cm⁻³; typical electron temperature, 7 eV; magnetic field, 900–2200 Gauss. Waves in the plasma are electrostatically excited by a split‐cylindrical, slow‐wave structure. The frequency domain studied includes the Trivelpiece‐Gould (T‐G) mode (ƒ_LH < ƒ < ƒ_pe), the surface wave mode, the electrostatic ion‐cyclotron mode (ƒ_ci < ƒ < ƒ_LH), and the ion‐acoustic mode (ƒ≲ ƒ_ci). Experimentally observed resonance frequencies in the T‐G mode range and the dispersion curves of the bounded plasma system (ƒ vs. k_∥) are in good agreement with the bounded plasma theory for ion‐acoustic waves, the surface wave, electrostatic ion‐cyclotron and T‐G modes. Furthermore, parametric interactions have been studied on the present plasma setup which is characterized by the presence of many normal modes. Two types of resonant parametric instabilities have been simultaneously observed above a certain threshold of the pump power at a frequency ƒ_p (ƒ_LH < ƒ_p « ƒ_pe). In both processes the electron decay product is a Trivelpiece‐Gould mode. In the first case the ion decay product is an ion‐acoustic (IA) wave (ƒ < ƒ_ci) and electron and ion heating are observed. In the second case the ion decay mode is an ion‐cyclotron (IC) wave (ƒ_ci < ƒ < ƒ_pi) which is accompanied only by electron heating.