Vacuum came down to ~7e-7 Torr. On startup, bias sparked over somewhere. Vacuum leak was caused. Later we found that HV had sparked through the source gas tubing, which was touching the beamline frame. Obviously an arc had formed within the tube and sparked through on the ground side. We also could not reset the bias interlock (ICR has efaulted this), so we ran in local. System is set up for 21Ne with about 28nA on FC6. Bias is off for the night, while plasma remains on. Bias can be turned on at will, preferably via EPICS. Fine-tuning will take place mid-morning Wednesday.

Other notes: Neon gas line checked for any sparkover leaks. None. It was closed down and pumped during the course of leak-checking today. Checked: bottle valve open, and line valve open. Plasma electrode in this mode is best near zero. About 3V is good, which locks in one plasma mode. At zero and with the quartz  liner "can" installed, the plasma could toggle through different modes as plasma wanders back and forth through the plasma chamber. Also, microwave power can walk the plasma. Goal: Move the plasma back as far as possible so that a clean beam exits the source, i.e. good beam on cups with relatively small spills on collimators. In an otherwise identical setup but without a liner, the plasma would form adjacent to the backplate, a different mode of operation altogether.