THE POSITIVE COLUMN IN A LONGITUDINAL MAGNETIC FIELD (thesis)

Technical Report · Mon Feb 27 04:00:00 EST 1961

OSTI ID:4010959

Paulikas, G A

The positive column of a glow discharge is shown to become hydromagnetically unstable when immersed in a longitudinal magnetic field of the order of 1 kilogauss. The instabillty transforms the azimuthally symmetric column into a constricted, rotating, helical state; neither this new steady state nor lts properties are predicted by classical theories. The critical magnetic field, B, describing the onset of the instability, varies approximately inversely as the tube radius and directly as the squsre root of the ion mass; e.g., in a helium discharge at a pressure of 1 mm Hg and in a 0.9-cm-radius tube we find B/ sub c/ = 2.4 kilogauss. For B> B/sub c/ the longitudinal electric field increases with magnetic field and indicates particle losses in excess of tlassical predictions. The occurrence of this instability explains the previously mysterious anomalous diffusion observed by Lehnert. The properties of the helical state were measured in H/sub 2/, D/sub 2/, He, and Ne as functions of gas pressure and tube radius. For this example the angular frequency of rotation of the luminous spiral is 0.8 x 10/sup 5/ sec/sup -//sup 1/ with a wave length of about 40 cm. Frequency decreases with increasing pressure, increasing tube radius, and increasing ion mass. The wave length is found to decrease with increasing pressure. These dependences, as well ss the values of B/sub c/ are in good agreement with predictions of the perturbation theory of Kadomtsev and Nedospasov. The onset of instability as predicted by the entirely different sheath-instability theory of Hoh is not in as good agreement with the experimental results; Hoh's theory does not include a description of the nature or build-up of the presumed instability. A comparison of measurements of radial potential distributions with the theory of Ecker indicates the absence of anamolous effects for B < B/sub c/. (auth)

• Research Organization: California. Univ., Berkeley. Lawrence Radiation Lab.
• DOE Contract Number: W-7405-ENG-48
• NSA Number: NSA-15-018904
• OSTI ID: 4010959
• Report Number(s): UCRL-9588
• Country of Publication: United States
• Language: English

Related Subjects

CHARGED PARTICLES
DEUTERIUM
DIFFUSION
ELECTRIC FIELDS
FREQUENCY
GASES
GLOW DISCHARGES
HELIUM
HYDROGEN
IONS
LAYERS
LOSSES
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
MASS
MEASURED VALUES
NEON
PERTURBATION THEORY
PHYSICS
PLASMA
POSITIVE COLUMN
PRESSURE
ROTATION
STABILITY
SURFACES
TUBES
VARIATIONS