Observations of vacuum spark dynamics from its X-ray emission

The behavior of a medium energy (similar to 1 kJ) pulse-power-driven vacuum spark is shown to depend on the electrode material and form of the anode in otherwise similar conditions of operation. The dynamical evolution of the discharge is followed from its soft X-ray emission. The electrode materials compared are titanium and aluminum with a form of anode that is tubular or conical. The use of a tubular anode favors a more uniform sheath and a better formation of a dense Z-pinch and the ensuing hot spots are found to be at least twice as bright. The position of the brightest spots differs according to the material and the electrode shape, and is found to coincide with the shape of the sheath. The energy output is measured and the density of the plasma in the hot spots may be calculated.