Local Magnetohydrodynamic Characteristics of the Plasma Stream generated by MPC

This paper investigates the spatial distributions of electrical current which flows inside the plasma stream generated by a magnetoplasma compressor (MPC). Two different modes of MPC operation with different gas supply scenarios have been applied in the experiments presented here. The first is the operation mode with a pulse injection of xenon into the interelectrode space, and the second is the operation mode with residual helium in the chamber and local injection of xenon directly into the compression zone. The maximum value of the electric current observed outside the MPC channel is 15 ÷ 20% of the total discharge current. Electric current vortices were discovered in the plasma stream. The amplitude of the current in the vortices reaches 50% of the total discharge current. The maximum EUV radiation power was measured in the mode of MPC operation with local xenon injection. Power in the wave range 12.2 ÷ 15.8 nm achieves up to 16 ÷ 18 kW.

The Formative Phase of a Low Pressure, High Voltage Z Pinch

The formative phase of a 40 kV Z pinch has been investigated for pressures from 10 to 80 mTorr in H2. The energy spectrum of the electrons on the axis of the vessel, the spatial distribution of the current at the face of the anode, and the total discharge current were monitored. At the initiation of the discharge, a current of electrons with energies in excess of 20 keV is observed on the axis. This observation is in contrast to the normally accepted mode of ionization in which ionization initiates at the wall. The current is observed to switch from the axial region to the wall where it forms a current layer which collapses in accordance with the snow-plough model. The exact nature of the switching mechanism is not understood. The formative phase of the pinch typically takes a few hundred nanoseconds. The observations indicate that the detailed process of current sheet collapse may be affected by the formative phase.