(Betsy, Jason, Oli)
Today Jason setup to see Pitch and Yaw of the BBS in the suspension cage on the cartridge. We were a ways off in Yaw and some Pitch. I spent a few hours walking YAW but the mechanics are rough. 5 bolts lock down the whole Top Blade assy and then you can use a push or a pull screw to pivot the whole Top Blade mechanism. Repeat for the second Top Stage blade assy. Of course when you pop the 5 locking screw the entire chain sags and grounds on stops yeilding confusing beams to look at. So a few iteration of this and that got us kinda no where. Part way thru I discovered that the push/pull thingy was totally out of range on both. No idea why. So back to starting over tomorrow and maybe trying to go around this "yaw" adjustment and just push the stages in the mounting slop or something.
Seems like I wrote this alog 10 years ago. Probably did since the mechanics from the BS are the same and we struggled with them at that time too. Will need to read back and also check how LLO faired with this.
Meanwhile, Oli and I also struggled to get Pit damping working so a few hours of parallel brain straining on that, swapping out the quad cable and it seems to be working. Weird tho because this is the same cable we used on the BS just a couple weeks earlier.
Yeah this yaw adjustment was no fun. Here at Livingston, it took us a decent part of a day but we think we got a good system going by the end.
We adjusted only one side at a time. We tried to keep the way we unlocked/torqued the 5 bolts of the top blade assembly consistent (see photo attached). When we unlocked we tried to only get the bolts barely loose and back them out as little as possible. Each time we locked the 5 bolts down, we found that the structure moved around 0-4 minutes in a consistent direction. By following the attached photo procedure, the yaw seemed to settle consistently 2ish arcminutes off of its unlocked value in the same direction each time. For example, unlocked we would set the BBSS at 45 degrees - 5 arcminutes, and when we locked it down we would get 45 degrees - 3 arcminutes. We repeated the process until we got lucky and the suspension locked in the right place. This took a lot of trial and error. There is some hysteresis in the push/pull screw adjustment. The yaw adjustment is not very good or repeatable.
To make matters worse, the LF and RT OSEM plates have the circular inset that houses the disk that the magnet flag of M1 sits on. This is a place where it is very easy to get subtle rubbing and it is hard to verify by eye. We did this alignment with the QOSEMs which was somewhat of a blessing because the Y direction readback of the QOSEM can act as a guide to tell you if you should start to be concerned about rubbing. It might be worth removing the LF and RT OSEM plates and see if you can to the alignment without roll or vertical damping to avoid this rubbing. If the suspension is moving too much to not have V and R damping, you must frequently adjust the LF and RT OSEMS to ensure that there is no rubbing at that location.