Cross-point coronal plasma dynamics in two- and four-wire x-pinches

Abstract

Studies of the late time diode gap formation in two- and four-wire tungsten x-pinches using an 80kA, 50ns current pulse are presented. Quantitative measurements of the coronal plasma density are recovered using interferometry simultaneously with laser shadowgraphy. Axial expansion of the gap occurs at ∼106cm∕s for both two- and four-wire systems and is likely to be driven by an axial J×B force resulting from radial current flow in the plasma minidiode “electrodes.” Radial density profiles suggest repinching of the low density plasma occurs after the main pinch resulting in secondary x-ray emission peak >10ns after the first, which is recorded with a pair of pin diodes.