Summary: ESD (EY) Actuation Strength 'may' have changed by about 10% at it max from ER7.

The actuation strength of the ESD can be calculated by comparing the height of Pcal lines to ESD lines.  We know the calibration of Pcal line and using the DARM_IN1 as an intermediate between ESD line and Pcal Line we can transfer this calibration to the ESD.

We have been using an assumption that the response function is same at close enough frequency (few Hz apart). This assumption is still under investigation and looks like it is not necessarily true to the level at which we want our calibration to be accurate.

However for this result we are only concerned with change in actuation strength from some initial configuration. We chose this initial configuration to be the start of ER7 and the result is attached below. In the plot below the first long set of data is the first half of ER7 and the a small chunk at the end of the plot is the lock stretch from the weekend. Using all four Pcal lines it shows the actuation strength has changed by about 5-10 % after ER7 (possibly a result of discharge). Note the actuation strength itself was changing with time during ER7.