Experimental investigation of wire array Z-pinches on the cobra accelerator

Summary form only given. Wire-array Z pinches have been studied on the 1.2 MA peak current, 100 ns rise time COBRA generator at Cornell University using a wide range of diagnostics. In addition to the X-ray and electrical diagnostics, two framing cameras with 5 ns temporal resolution, a three frame laser shadowgraphy system with 170 ps temporal resolution and optical and X-ray streak cameras have been used in the experiments. Wire-arrays made with Al, W and Invar wires with 16, 8 and 4 mm array diameters and interwire gaps from 4.6 mm to 0.8 mm have been studied. The investigations include dynamics of the wire-array implosion and hot spot formation in the on-axis stagnation plasma. The experiments showed that the wire-arrays with 4 mm diameter have an X-ray energy yield 1.5-2 times higher than larger diameter arrays for all wire materials studied. The study also shows a complicated structure of the hot spots in space and in time. Measurements with spatial and temporal resolution using the X-ray streak- camera have shown the beginning of the hot spot formation starts near the time of maximum compression of the arrays. Hot spots that last 1-5 ns are observed within a time interval of 30 - 40 ns. Energy measurements using filtered PCDs show that the hot spots radiate a major part of the wire-array energy yield for all wire materials and array diameters.