PLASMA CONTAINMENT IN A UNIT WITH A HIGH-FREQUENCY, TRAVELLING MAGNETIC FIELD

The unit consists of inductive elements surrounding a toroidal discharge chamber of quartz with an outer torus diameter of 70 cm and an inner diameter of 8 cm. A total of 12 high-frequency traveling waves at 2.5 x 10/sup 6/ cycles/sec with a phase velocity of 5 x 10/sup 7/ cm/sec are superimposed on each other. The pesk power is 60 Mw for a period of 300 to 600 mu sec. The direction of propagation of the traveling wave is fixed by the design of the generator. The gas is ionized by the electric field of the traveling wave. The amplitude of the magnetic wave H/sub z/ increases from the axis to the periphery of the torus so that magnetohydrodynamic stability is assured. The effective conductivity of the plasma was found to be sigma /sub eff/ = 2.5 x 10/sup 13/ CGSE units. This value is an order of magnitude less than the value of 4 x 10/sup 14/ CGSE units, which should be the conductivity for an electron temperature of 10 ev and an electron concentration of 1.7 x 10/sup 14/ cm/sup -3/, as determined experimentally. The anomalously high absorption of the energy of the traveling electromagnetic wave, andmore » the low effective conductivity of the plasma open up the possibility of heating a plasma to high temperatures by this method. The low value of the effective conductivity can be explained by magnitization of the plasma due to the observed directional drift of electrons. Further studies are being conducted on the effects due to break-away of the plasma from the walls of the chamber, where the strengih of the magnetic field is high. These effects tend to occur at low initial hydrogen pressures (2 x 10/sup -3/ mm), and are especially prominent during discharge in air at a pressure of 5 x 10/sup -4/ mm. (TTT)« less