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

Summary form only given, as follows. A coaxial plasma opening switch is used with the inductive-voltage-adder generator to realize pulse sharpening by an inductive energy storage scheme. The POS has the conduction time over 1 /spl mu/s and provides 200 kA with less than 50 ns of rise time of the load current into Z-pinch load. In the present experiment, two cable guns mounted symmetrically on the outer electrode were used as a plasma source. The diameter of the inner cathode, outer anode, and the distance between the electrodes were 80 mm, 140 mm and 30 mm, respectively. 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 was measured at many measurement locations in all over the POS region. From the result, the contours of the electron density at conduction, opening and post-opening phase were drawn. In the early time of the conduction phase, the plasma density became higher with time and stayed in the initial position. As conduction phase progressed, the high-density plasma spread downstream near the cathode and anode. The distance of plasma motion was larger near the cathode and smaller near the anode. At 800 ns, low-density region is seen at 10 mm from the cathode. After opening completed, the low-density gap disappeared and the shape of the corn-shape-like plasma was distorted. The plasma density after opening became higher with time. Through the experiment, the motion of POS plasma was understood and the low-density region was observed at the time of opening.