Brushing/touching cables were fixed by Betsy.

PZT cable on the OMCS cage was resting on one of the OMC DCPD cables at the top (PZTcablebefore.jpg). Betsy rerouted the OMC DCPD cables at the top to make more space for the PZT cable (pztcableafter1 and 2.jpg). This was possible because the part of the DCPD cable wasn't directly going to the breadboard, it was between DB9 and the cable retainer.

One of the QPD cables on the OMCS cage was touching the shroud panel yesterday, today it wasn't touching but was close. (QPDcablesbefore.jpg). Betsy used metal ribbon to tie the QPD cables to BOSEM cables at the top to raise them (QPDcablesafter.jpg)

After this was done, Betsy and Rahul ran TFs undamped to check rubbing and it was good.

Realignment.

OMC cable handling affected the OMC alignment a bit. That was big enough of a change for OM1/2/3 alignment offset to go bigger than we wanted, so we physically rebalanced OM2, twisted OM2 and OM1 cage, to relieve OM1/2/3 alignment offset. See slidervalues.png for the current good OM slider values as well as DAC outputs.

At this point, centering on the small 45deg mirror for OMCR is not perfect but nothing was clipping.

We then recentered WFS path (lens_for_wfs.jpg), ASC-AS_C path and OMCR path again.

We relocated two beam dumps for OMCR too (BD_relocation.jpg), because the ghost beam from 99:1 splitter looked almost parallel to the 1% transmission after the lens, but the beam size becomes smaller as you go closer to the OMCR DCPD, so it made sense to make the beam dump closer to the DCPD. (We could not photograph this ghost beam though I was able to see it on the IR viewer card through the blue IR viewer.) BD_clearance.jpg shows the distance between the BD for the ghost beam from 99:1 and the main 1% transmission beam.

I checked the FS clearance and there wasn't much change, so made no adjustment.

No ground loop.

The shield ground for OMC DCPD/PZT/QPD were grounded to the chamber somewhere. Sometimes the slightest motion of some cable somewhere somehow breaks it, but it will come back when touching something else. Betsy spent some time isolating the cable coil for OMC DCPD/PZT/QPD from other cables (because the shield for these three are tied together on the OMC breadboard anyway and we cannot fix it). We don't know if that is the reason the ground loop was broken, but anyway it was. From outside of the chamber at the feedthrough, I disconnected in-air cables one by one and confirmed that none of the in-chamber cables' shield ground (which is tied to the pin 13 of DB25) is connected to the chamber.

No ground loop. Success.

For Monday.

I haven't removed temporary optics on HAM6, so that needs to be done first thing in the morning. Then HAM7 team can inject light from HAM7 to HAM6. If they need to scan OMC length, they need to enable HV for that. HV for FS is already on.

In parallel, Jim needs to look at cable routing.

After that we can do the final ground loop check for ISC from outside of the chamber.