(Kiwamu, Chris, Alexa, Lisa, Matt, Stefan) We had to solve a series of mysteries today: - The green beam from ISCTEY was completely misaligned. However, HEPI, ISI and suspensions were all at the same location as last Friday. The beam was realigned on to the quadrant PDs on the TMSY. - The BSC cable running to the beat node monitor spectrum analyser was ripped out of its connector. Our forensic analysis team concluded that someone must have entered EY, stumbled over the cable and hit the ISCTEY hard enough to misalign it in yaw. - The IFR frequency synthesizer used for the fiber launch AOM had to be reset after the power outage. - The fiber connectors at the polarization controller in the MSR seem broken - the transmitted power changed by a factor of 5 when we wiggled the fiber connector. In the end we lost about a factor of 2 from what we expected. (That's on top of the factor of two loss in the reference cavity power.) - The ALS-Y PLL autolocker is completely messed up after the reboot. This needs to be looked at. - The MC x-over is currently set 10db too high - haven't tracked down why. - We also redid the PLL to tame our ALS-C frequency sensor: We currently have a SR560 with a gain of 5 in feed-back (resuling in a 60kHz UGF of the PLL). On top we have an SR560 with pole at 1Hz and a gain of 10 hooked up to the PLL control signal.
As for EY thing, HEPI, ISI, EY suspension are exonerated (OPLEV looks fine), TMSY suspension is also exonerated (once ISCTEY was aligned to TMSY, we were already hitting ITMY without changing TMS offset).
It should be some strange failure mode of ISCTEY (table moved, something on the table moved etc.) or more esoteric failure mode of TMSY (e.g. table/tele moved in relation to the top without affecting the top, in-vac steering mirror moved).
We had to physically turn a knob of a steering mirror downstream of the second PZT mirror on ISCTEY to relieve a huge YAW offset on the PZT mirror 2.
This was about a half turn of the knob of 100 TPI actuator (see the pictures showing before/after), and since this is a 2" mount, the angle change is
1"/200 / 2" = 2.5 mrad
which is huge.