Sheila, TVo

We measured the ITMY ISI RX motion to DARM using different Bias Voltages and found that there was no change in the coupling when going from +380 Volts to -380 Volts with a few increments in between.

Then we tried to move the vertical position of the optic by changing the offset in M0_DAMP in increments up to 73.36 micrometers and there was no appreciable change in DARM as well.  It is possible that we didn't move far enough to induce a change, but we also didn't want to break lock.

These null measurements could indicate that the ISI-to-Darm coupling is caused by image charges, which do not depend on the bias voltage.  This particular type of noise cannot be fixed by unplugging the ESD since the interaction is between the test mass charge and the suspension cage image charge, however, the TMDS would be able to make a difference.

The DTT template is in /ligo/home/thomas.vo/LIGO/ISC