Discharge of ETMy WBSC10 (in chamber)
Using the ETM / ERM Gap discharge procedure https://dcc.ligo.org/LIGO-T1500101 we discharged the optics in chamber at ETMy. Remember that this procedure includes a swing back of the ERM i.e. an increase in the gap between the optics. Using the electrometer https://www.trifield.com/content/ultra-stable-surface-dc-volt-meter/ mounted centrally (on an X brace) 1" from the back of the ERM (i.e. between the ERM and TMS) we measured the following voltage: -
Note:- The humidity at 10:00 am was 30%.
Note: - Prior to starting we zeroed the electrometer (11:12 am) with the cap on.
1) At start (after electrometer was mounted 1" from back of ERM and prior to swing back) = 6.8 V (this was steady over couple of minutes).
2) During mounting of swing back tooling = 6.7 V.
3) Electrometer was moved 5mm away from the ERM to allow for space during swingback = 6.4 V.
4) During swingback went up to peak of = 25.2 V.
5) Once Electrometer was moved back to being 1" from optic (and in chamber team in home position) = 24.9 V.
6) At this pont we broke for lunch. Once everyone out the chamber and soft door cover on = 23.1 V.
7) When we came back from lunch (1 hour later) = 13.7 V.
8) When the soft door cover came off = 12.2 V (with slow decay).
Note: - We had a first round failed discharge procedure. Panel was not flapping in gap. Decided to stop and start again. More details to follow.
9) After completion of ETM / ERM Gap discharge procedure (2nd time) = 3.8 V (and decaying). This was done at 2:56 pm.
10) After swing back of ERM (back to original position) and with electrometer reset to being 1" from optic = 9.3 V (and decaying). This was at around 3:04 pm.
Note: - At this point team started to suspend the chains and run transfer functions on both the main chain and the reaction chain. We left the electrometer in place during this time.
11) At end (prior to doors on) at 4:12 pm = 4.2 V * (and decaying).
12) Final number - At the end we put the cap back on the electrometer and it was now reading 1.3 V. Therefore we are calling the final number = 2.9 V (i.e. 4.2V - 1.3V).
Note:- The humidity got as high as 41% during efforts. At end before doors on it was 32%.
Note: - Doors were finally in place at around 5 pm.
Kate Gushwa, Gary Traylor, Danny Sellers, Travis Sadecki, Betsy Weaver and Calum Torrie