Investigation of nested type X pinches with ∼ 1 MA current

Recent results of X pinch studies on the COBRA generator from Cornell University (peak current up to 1.2 MA and rise time of 100 ns) are presented. Preliminary experiments on COBRA generated a bright burst of soft X-ray radiation with an intensity that was much higher than the intensity of X pinch radiation obtained on generators with smaller current. Theoretical estimates show that energy yield of X-ray radiation could be proportional to the generator current to the power 34/9, i.e. grows with increasing current very quickly. A determination of the real scaling experiments on generators with a range of currents, but higher current requires the use of loads with higher mass per unit length. Such loads can be made by increasing the number of wires or the wire diameters. It is reasonable to expect that the configuration of the wire crossing point will influence X pinch neck formation processes. Using an initial configuration of wires (before their twisting), similar to nested arrays, enables the assembly of a symmetric configuration for the X pinch crossing region. It also enables an investigation of multilayered X pinches. X pinches of different configurations, including X pinches with different materials in the inner and outer wire layers, were tested. All diagnostics developed for the COBRA generator were used in the experiments. The results of the experiments were compared with results obtained in experiments with regular multi-wire X pinches.