On July 28, Sheila and I increased the ESD bias, report in 86027. We noticed that despite rescaling the drivealign gain to match, there was a frequency-dependent change in the response function.

I used data from the simulines measurement on 7/19 (nominal bias time) and on 7/31 (double bias time) to make some comparisons. For reference, the calibration model we are currently using was generated from the 7/19 report.

The four plots attached show the ratio of the double bias measurement over the nominal bias measurement for the DARM loop suppression, response function, sensing function, and L3 actuation function.

The L3 actuation function is unchanged, indicating that we have appropriately adjusted the drivealign gain to compensate for the bias change.

The DARM loop suppression function (1/1+G) shows a frequency dependent change, which is expected.

The sensing function (C) shows some frequency dependent change. It's unclear if this is due to the change in bias, or unrelated.

The response function change (1+G /C) follows the change in both the loop suppression and sensing together.

I think a good follow up measurement is to rerun simulines with multiple ESD biases and corrected drivealign gains.