Longitudinal Magnetic Flux Research Articles

Measurement of the plasma energy in a Tokamak machine by the change in longitudinal magnetic flux

The results are described of measurements of the magnitude of the transverse plasma energy in a Tokamak machine, from a diamagnetic signal. It is shown that, for conditions in which the discharge current axis coincides within the limits of experimental error with the axis of the discharge vessel, the electron temperature measured by this method agrees with that calculated from the conductivity. A difference is observed only when the discharge is heated at low initial hydrogen pressures and the current axis is displaced towards the inside wall of the vessel.

Bewegungsvorgänge beim linearen Pincheffekt und Runaway-Elektronen

The time dependence of plasma radius and current is calculated on the assumption of homogeneous plasma in the case of the linear stabilised pinch effect. The comparison with the experiment shows a good conformity in regard to the contraction times. Especially it is found by theory and by experiments that the contraction times are independent of the stabilising magnetic field. Measurements of the longitudinal magnetic flux give the temporal and spatial dependence of the induced azimutal electric field in good agreement with the theory. A deviation at the beginning of the compression is attributed to the paramagnetic effect. A comparison with the theory of DREICER shows that the measured field strengths are sufficient for the production of runaway-electrons. This gives an explanation for the hard X-rays which are found in the experiments.

The Maximum Disturbance Growth Rate for an Unstable Plasma Column

A dispersion relation for a self-pinched plasma column enclosed by a conducting wall is derived for the case of a model with both surface sheet current and uniform volume current. On the basis of this dispersion relation the maximum disturbance growth rate for the instability is calculated. Both the uniform volume current and longitudinal magnetic flux outside the plasma column decrease the stability and make the growth rate faster. the effect of the magnetic flux being larger. (auth)