Single Wire Electrode Contacts ABD their Effects on Energy Deposition

Abstract

Summary form only given. When single wires are driven with short, high-current pulses the energy deposited is terminated by a voltage collapse that occurs when coronal plasma forms along the wire. It has been shown that the formation of this plasma and the amount of energy deposited can be affected by the way electrical contact is established between a wire and the electrodes. It has also been shown that soldered contacts or improved mechanical contacts can delay the plasma formation and increase the energy deposited. We present here more detailed experiments using a new approach for improving the electrical connection between the wires and electrodes. Large diameter, 50 mum, 5056 aluminum wires were chemically etched down to 25 mum except for regions at the ends where the wire-electrode contact occurred. Initial wire diameters were determined and placement between the electrodes was adjusted using diffraction techniques. Care was taken so that the extension of the thicker portion of the wires into the anode-cathode gap region was minimized. Energy deposited before voltage collapse using these types of wires was compared to the energy deposited in uniform diameter 25 mum wires with simple mechanical electrode contacts and also with 25 mum wires using soldered contacts. Similar experiments are planned starting with larger wires of, for example 75 and 100 mum. Detailed time dependent measurements of the plasma at the ends of the wires, near the electrodes, was made using 532 nm laser interferometry. Time dependent laser backlighting was used to observe the wire expansion after the voltage collapse.