[Georgia, Patrick]

We ran the usual charge measurements today - the quadrant-by-quadrant effective bias voltage measurements on both ETMX and ETMY, and the additional measurements of combinations of the four parameters on ETMX (measured by driving combinations of the signal and bias electrodes).

The ETMY effective bias trend remains consistent with ~50 V offsets on the UL quadrant (coupling to pitch), the UR quadrant (coupling to yaw), and the LL quadrant (both pitch and yaw). The first attachment shows this over the last few months.

The ETMX effective bias is trending back towards zero after the bias was switched on September 11. The second screen shot shows the quadrant-by-quadrant measurement for ETMX.

This trend is also seen in the four-parameter measurement which makes sense. The third attachment shows the alpha and gamma parameters in the first column, these are associated with the ESD actuation strength and should not change over time. The second column is the beta+beta2 parameters, as measured by driving the bias and measuring the response on the op lev, and by driving the signal electrodes and measuring the response on the op lev. This measurement should be immune to space-charge polarisation which we assume is symmetric. The bias-driven beta+beta2 seems to have taken a jump recently (though I don't want to jump to conclusions based on two data points), while the longitudinal signal drive did not. This is strange. The third column shows beta-beta2 and the Veff, which are sensitive to space charge polarisation and consistent with the quadrant-by-quadrant measurements.

Note when running these measurements - it can be hard to tell if the HV is on or off. Even with the HV off a small signal is seen in the ESDAMON channels whin driving the quadrants. These channels are calibrated into volts and should see a large excitation from the charge measurements (100s of volts, exact numbers depend on the measurement). Up until today the ETMY L3 ESDAMON and LVESDAMON filters were turned off, leaving those channels in counts, not volts. I have switched those filters on now.