Dynamic Control of a Cusped Plasma near the Ion Cyclotron Frequency

Plugging a decaying cusp plasma with a frequency feedback system

“…The experiments were carried out with the afterglow plasma confined in the cusp field of the TPD-II machine [1] (see Fig. l(b)).…”

“…Previous experiments have shown that an end loss of a steady-state cusp plasma is plugged most effectively by an electric field whose frequency is a little higher than the ion cyclotron frequency, and that the deviation from the cyclotron frequency depends on the plasma density [1]. A theory taking account of collective response of a plasma has been proposed to explain the experimental results [2].…”

Radio-frequency containment (RFC-XX-M)

“…The RF plugging experiments were initiated on the TPD-II device [2] which was constructed in 1967. The device had a spindle cusp configuration and was used to demonstrate the suppression of the cusp end losses.…”

“…(1) Plasma loss from the cusp ends was resonantly suppressed [ 1 ] when the applied frequency was equal to the eigenfrequency of the electrostatic ion cyclotron waves [2,4,5,13,15]. (2) A special ion species could be plugged preferentially [6].…”

“…By axial phasing we could control the propagation of the wave (either a unidirectional or a standing wave) and thereby control the power deposition profile [14]. (2) The plasma was heated by using a rotating type-III antenna in the ICRF range [14]. The maximum plasma parameters obtained were n = 2 X 10 13 cm" 3 , T ix = 1 keV and 0 = 4% when the antenna was excited with the m = -1 mode (lefthanded rotation).…”