Georgia Sheila Jeff K Craig Daniel S
We made an attempt to check that the ITM ESDs were functioning before putting the doors on by using the ITMX driver bias channel to drive quadrants of ITMY. (we left the ITMY bias at 400V, and drove +/-400V at 0.6Hz out of the ITMX driver bias channel, which we temporarily connected the signal electrodes on ITMY). This means that we were applying voltages to the ITM that are similar to what we use for the ETM oplev charge measurements. From alog 38656 the actuation strength is 2(gamma-alpha)*Vbias newtons/volt, for the ITMs this is about 1e-10N/V and for the ITMs it is about 2e-11N/V, so the ITMs are a factor of 5 weaker actuators than the ETMs.
However, the ITM optical levers are 3 orders of magnitude noisier than the ETM optical levers, even though we turned the purge down. For this reason we did not see any signals and lost a bet with Jeff K.
Fil had bypassed the interlock on the pressure for us, we turned off the high voltage supplies when we were finished and removed the pressure sensor bypass. When we turned the purge air back up, the soft door cover partially came off of the ITMY chamber. We turned the butterfly valve on the y purge air to about 45 degrees, added an extra clamp to the door cover, which is on but billowing a lot.
Note on the high optical lever noise:
It looks like when we're under vacuum the optical lever noise on the ITMs is comparable to the ETMs. This means we can most likely run this kind of test again to do charge measurements on the ITMs when we're under vacuum, even with the factor-of-5 penalty in actuation strength. Attaching spectra of the optical lever pitch and yaw signals from a couple of days ago, and a year ago (I also checked in dataviewer that we were on the op levs for the in-vacuum spectrum), these can be compared with the spectrum from ETMY in alog 41772. More data from ETMY, with bias drive and optical lever response, coming soon.