J. Kissel

Attached are the weekly charge measurements on the H1 ETMs. 

While the effective bias voltage remains low ( > +/- 10 [V]) for most quadrants of both test masses, ETMY is showing a consistent negative trend. This may be a result of H1's incredibly high duty cycle of the past few weeks (see O2 Time Accounting Page, weeks 8-10), which means 
    > the ESD is always in use with one requested bias voltage sign, and 
        >> little time is spent with the opposite sign requested bias voltage, 
            >>> free ions of a particular signed voltage continue to accumulate

Sheesh! We can't win when it comes to maintaining minimal charge accumulation: If we flip the bias when in use, we're liable to screw up the calibration (e.g. LHO aLOG 29868). If we flip the bias when not in use, we need a medium observing duty cycle in order to split the time between in-and-out- of use evenly (see evidence in this aLOG).

Perhaps we should resume thinking about what are the remaining *source* of free ions in the chamber...