On 30 January 2003, after reconfiguration of the target system and measurement line ready for high voltage, we were able to apply voltages up to 100kV on the source, and extract ions from the plasma. The ions were captured in a Faraday cup. An average current greater than 20mA was registered, at a repetition rate of 1/4 Hz. Only occasional breakdowns of the source high voltage was seen (at a rate of a few per hour)
The following day, the voltage could be increased to 110kV (but with some eventual external corona current) and ions were further measured. The repetition rate was increased to 1Hz for a short period (1 minute) before arcing in the laser stopped progress. The source potential was still being raised, but no problems were seen up to 105kV.
A longer run at 100kV source potential and 1/4 Hz laser operation, gave an average current again of 20mA, with a distribution sigma of 35%, over a period of 15 minutes running. Below are shown five ion current signals from this run, together with the nominal window for the region containing Pb25+. High frequency noise spikes on the traces have yet to be fully investigated.
