J. Kissel

I've taken this week's effective bias voltage measurements that track accumulated charge on the test mass/reaction mass electrostatic drive system. 

The standard metrics:
- Monitoring the single-frequency actuation strength of each quadrant as a function of requested bias voltage using Pitch and Yaw optical optical lever signals to measure the response. 
- Monitoring the overall longitudinal strength comparing an ESD excitation against a photon calibrator excitation at adjacent single frequencies.

The conclusions from both these metrics have not changed from the last two measurements (LHO aLOGs 35553, 35366):

Just before we vent on May 8th, during last minute preparations as we bring the IFO down, let's 
    - Turn OFF the ETMX ESD bias completely, and leave it OFF 
    - Leave the ETMY bias ON at +400 [V], with the opposite sign as in observation (Negative in NLN, switch to Positive for vent)
for the duration of the vent (i.e. until we open back up to the arms)