An idea was proposed to eliminate the possibility that charge build up on optics could be due to UV photons from new hot ion gauges installed at end stations. We (Jeff K., Betsy W., and I) may pursue this during O2 break by turning off IGs for extended periods of time while measuring charge rate.

Attached is a schematic showing the location of the two new hot ion gauges (IG) at each end station (and one 250 meters down on each arm) AND now we have a updated VE GUI on MEDM, thanks to Gerardo, showing these gauges (names have changed):  X4,Y4 are attached to the top of the very end BSC. X5,Y5 are right next to NEG pump, which is at about head level, also bolted to the very end BSC. X4 and Y4 are interlocked with high voltage, so if we turn them off, we need to  immediately turn HV back on manually. We can leave the gauges off for a week or more; however, we lose HV safety interlocks. X5,Y5 next to NEGs can be turned off for as long as we need. 

X6,Y6 are 250 meters down from end stations next to the ion pumps (IP) that were installed to compensate for the valved out large IP at end station. Those IPs and IGs should be far enough away to avoid charging issues, but they are on valves and we could valve the pump out for a day if we absolutely need to (we will see a pressure rise but it will recover when we turn pump back on).