Electron Density Measurements on Radiographic Diodes

Summary form only given. A two-color, two-chord, quadrature, Mach-Zehnder interferometer is being applied to radiographic diode studies conducted on the high-impedance Mercury pulsed-power generator. The two interferometer chords are positioned independently, so that the more sensitive chord at 1064 nm can be used to probe regions of lower density than the chord at 532 nm. The quadrature arrangement uses polarization splitting to extract both the sine and cosine of the interference signal, removing ambiguity about the phase quadrant. Mercury is a magnetically-insulated inductive voltage adder designed to produce a 50-ns pulse at 6 MV and 360 kA across a vacuum diode. The electron density and corresponding X-ray, current, and voltage characteristics are measured for several diode configurations, including the self-magnetic-pinched diode and variations of the rod-pinch diode. These measurements are used to track the shape of the plasma around the electrodes as it expands to close the diode gap at the time of impedance collapse.