Experiment on the use of an auxiliary discharge to investigate plasma properties in a theta pinch with a trapped reverse magnetic field

An experimental and theoretical study has been made of the hydromagnetic instability of an axisymmetric bulged region in the midplane of a theta pinch 8 m long. The bulged region was generated adiabatically after the initial implosion in such a way that it fulfilled most of the assumptions of the theoretical model; in particular, it was free of end effects for the time of observation. At a filling pressure of 20 m Torr D2 and with a peak magnetic field of 20 kG the plasma, which was collision dominated, had values of temperature, density, and beta on the axis of 120 eV, 3 × 1016cm−3, and 0.7 ± 0.2. The predicted m = 1 instability was observed and for a range of bulge amplitudes its measured growth and propagation along the column agreed to within a factor of less than 2 with the theoretical values. It is concluded that the m = 1 instability of such bulged plasmas is well described by ideal hydro-magnetic theory. Modes with m ≥ 2 were not observed during the m = 1 growth and their absence is attributed to finite Larmor radius stabilization.

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Rotation during the Implosion of a Theta Pinch

Benford

1972

The Physics of Fluids

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Measurements of fields and pressure gradients during the collapse of a theta pinch allow determination of the ion azimuthal velocity from the radial component of Ohm's law. In hydrogen and nitrogen discharges Vθ was found to change sign across the current sheet. Ions rotated so as to carry an appreciable fraction of the current in the front of the sheet and moved so as to oppose current flow in the rear. The total angular momentum was approximately zero. These results agree well with the Düchs calculations of the influence of small transverse fields. Measurements of small transverse fields in the current sheet are presented.

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Experiment on the use of an auxiliary discharge to investigate plasma properties in a theta pinch with a trapped reverse magnetic field

Cited by 9 publications

References 2 publications

Some conditions for the existence of a ?Pinch? structure of the current sheet in plasma

Some conditions for the existence of a ?Pinch? structure of the current sheet in plasma

Stability of a Bulged Theta Pinch

Rotation during the Implosion of a Theta Pinch

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