The authors consider the behaviour of the boundary of a plasma column in a strong, constant, inhomogeneous magnetic field and a high-frequency (HF) E-wave field. An azimuthal current is produced in the plasma by the HF-field. The direction of the azimuthal current depends on the direction of the constant, longitudinal magnetic field Hz. In all cases, however, this current causes the longitudinal magnetic field in the plasma to increase (paramagnetic effect). Stabilization is produced through compensation of the polarization currents by paramagnetic currents due to the HF-fields. The behaviour of the plasma column in a magnetic field of mirror-trap configuration was investigated experimentally. The high-frequency field was a rotating dipole, homogeneous along the constant magnetic field. The direction of the angular velocity vector for the HF-field coincided with the direction of the constant field.The studies showed that the behaviour of a plasma in a magnetic mirror trap depends largely on the curvature of the lines of force of the constant magnetic field. In the pinched regime, when the column-formation process has been completed, the level of the observed fluctuations increases with increasing curvature of the mirror-trap field. Tongue-shaped plasma streams are produced at the surface of the plasma column, perpendicular to the magnetic field. The “tongue” rotates in a direction which matches the rotation direction of the constant magnetic field. The frequency of the “tongue” rotation is in the range of 100–300 kHz. In addition to the intense deformation corresponding to the m = 1 mode, there are also other modes of higher orders. It is shown that the centrifugal effects caused by plasma rotation contribute to the instability.To control the rotation effect, use was made of a constant magnetic field of octupole configuration, which behaved in the same way as a high-frequency magnetic field rotating in the direction opposite to the plasma rotation.The experimental results provide sufficiently convincing evidence of the possibility of stabilizing convective-type instabilities arising in a plasma.
The paper presents theoretical calculations and the results of experimental studies of the behaviour of a plasma contained in a strong constant magnetic field when a rotating high-frequency field of dipole configuration with frequency Ω is superimposed upon it. It is shown that for υei > Ω (where υei is the frequency of collisions between electrons and ions) the high-frequency field excites an azimuthal electric current jφ on the plasma surface. The interaction between the current jφ and the constant magnetic field Hz generates a dynamic force, which forms the plasma into a column.The plasma is compressed into a column when the vector of the angular velocity of rotation of the high-frequency field and that of the constant magnetic field H⃗0 coincide in direction. When the plasma is compressed into a column, there is no contact with the walls of the vacuum chamber and the degree of ionization is close to total. Probe and microwave measurements have shown that the time of compression of a plasma into a column for Hz = 8 × 103 – 1 × 104 Oe is ∼ 300 μs and the rate 6 × 103 cm/s. The diameter of the column was of the order of 2–3 cm. The charged-particle concentration measured with the help of superhigh-frequency waves (λ = 2 mm, 8 mm and 32 mm) was greater than 2 × 1014 cm−3 and decreased by more than two orders at a distance of 1−1.5 cm from the column centre.When the vectors and H⃗0 are opposite in direction, the force is directed away from the axis, and in this case, the plasma in the form of a hollow cylinder is situated at the vacuum-chamber walls.The maximum strength of the rotating high-frequency field at 1.25 MHz was 100 Oe. The results obtained show good agreement with the theoretical calculations.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.