Radio frequency phase shifters for launching waves in a magnetized plasma

Abstract

A variable phase-shifting system, able to generate phase-shifted replicas of the same reference input signal, has been designed to properly feed the antenna system within a plasma device. The system is based on a phase-locked loop used as a voltage controlled phase shifter and is able to provide four phase-shifted output signals. The phase differences between adjacent outputs can be varied between 0° and 100°, and are maintained equal to each other, with a precision of less than 3° in the range 2.5–10 MHz.

Ion resonance cones in a magnetized plasma

“…The experimental analysis of ion resonance cones has been performed in the Thorello device [9][10][11][12], which is a toroidal system producing a steady-state magnetized plasma with the following operating parameters: n e < 10 11 cm −3 , B toroidal = 2150 G, T e < 10 eV, T i < 2 eV. Details of the equipment set-up of the device are given in [12].…”

“…The Green function, the solution of (1), can be written as (11) where the integration must be performed numerically.…”

“…The definition ρ(k ) depends mainly upon the geometrical characteristics of the antenna employed. From the experimental point of view, we used a point source antenna and 'slow-wave antennae' (figure 7(b)), formed by one or more plates aligned along the toroidal coordinate and symmetrical with respect to the equatorial plane [11]. The length of one plate is l = 11 cm, while the distance between two consecutive plates is d = 13.8 cm.…”

“…The theory, discussed in section 2, concerns the analysis of the wave potential emitted from different kinds of source, considering both the cold and warm plasma approximations [8]. The experimental analysis has been performed in the Thorello device, a toroidal system producing a steady-state magnetized plasma [9][10][11][12]. The ion resonance cones have been excited with different antenna systems and plasma parameters and have been detected using an interferometric system.…”