(Alexa, Kiwamu, Keita, Daniel, Sheila, Robert, Stefan) Last night, at 17:50 local time, we turned off the BSC6 clean room... We observed a sharp step shortly afterward (probably due to a quick realignment) on both green reflected light and transmitted light, followed by a 15h slow drift. We then decided to realign the REFL diodes at EY. But surprisingly, to lock the green light, we had to move the ITM pitch by 0.7urad, ETM pitch by -1.6urad, and TMSY by -8urad to get back to a good alignment. Meanwhile we also had to flip the EY PDH servo sign. We don't know why that happened. Image A: The the green refl diode, ALS-Y_REFL_A_DC power is falling off the PD over the duration of about 15h. Image B: We are also losing a little bit on ALS-Y_REFL_B_DC Image C & D: The clean room transient is also visible in the TMSY OSEMs as a step. The HPI IPS's show a glitch, but no step. (The large step on HEPI is the lock loss.) Image E: The corner green power (ALS-C_TRY_A_DC_VOLTS) and beat note RFMON actually stepped up initially, but then dropped over ~15h. For tonight we switched the clean room on again around 5pm
Remember that the clean room is also a large heater ~ 10KW
Temperature zone 202D shows a step change in temperature at that time. I am unable to post a plot from home for some reason but if you look at the FMCS signals for ENDY and look for the 4 temperature sensors in the VEA - these are labelled 202A,202B,202C,and 202D; you will see that zone D in room 202 took a dive when you turned off the cleanroom. This sensor is low on the wall near the return air grills. The temperatures inside the cleanroom were probably impacted even more.
Plot now attached.
Also, the cleanroom will impart a very small positive pressure inside the plastic curtains - hence the flow out of the cleanroom. This may account for the step change while the temperature change has given you the slow drift???
John
