Observation of plasma motion in a coaxial plasma opening switch with a chordal laser interferometer

Electron densities in a coaxial plasma opening switch were measured at many lines-of-sight. In the present experiment, electron density was measured by a He-Ne laser interferometer with chordal lines-of-sight. In order to observe the motion of the POS plasma, the electron density contours during the conduction, opening and post-opening phases were drawn by combining the results of interferometer experiments. Seeing the density contours, the radial and axial motion of POS plasma was understood. As conduction time progressed, the POS plasma moved toward downstream. At 800 ns, which corresponds to the time of opening in the current waveform, low-density region as less than 10/sup 14/ cm/sup -2/ is seen at 10 mm from the cathode. After the opening completed, the low-density gap disappeared and the shape of the corn-shape-like plasma was distorted. The interferometer experiment was followed by the additional spectroscopic experiment. The result of spectroscopic experiment was in the good agreement with the result of interferometer experiment.