[johannes, gautam]

Summary: Today we moved the suspended ETMY optic back into the chamber from the cleanroom. Once in the chamber, we positioned the optic using the stops that marked the previous position of the optic. We then shortened the arm length by 19mm (in order to match the X and Y arm lengths. The F.C. coat on the HR face was removed prior to the final placement of the optic. We then adjusted the OSEM positions in their holders to get the sensor outputs to half their maximum value.

We did not get to check where the input beam hits the optic or see if the pitch balance of the optic is such that the reflected beam makes it back to the ITM. The plan for tomorrow is to do this. 

Part 1: Cleanroom work

• We worked a little more on trying to adjust the rotational position of the OSEM coils in order to minimize the coupling of the bounce mode into the sensor signals. 
• We had limited success in this regard. After about an hour, we concluded that it made more sense to do this in the chamber itself. For one thing, the drive electronics for the Y end are different (in the cleanroom, we are using the X end electronics, satellite box etc.).
• We adjusted the position of the OSEMs till the sensor output readout was half the open value as best as we could. We also made sure that the wire was in the groove on both sides and that the magnets were well centered in the vertical direction relative to the OSEM coils and that there was no danger of knocking any magnets off (see attached pictures).
• We then engaged all the EQ stops, and transferred the suspension cage to a cart (topped with Al foil, wiped clean) for transportation to the Y-end (with OSEMs left in).

Part 2: Transportation of optic

• Nothing special here, just took great care while going over bumps near doors between the cleanroom and the IFO, and along the Y-arm itself.
• Definitely a 2 man job - one person can lift a pair of wheels over any bumps while the other can make sure there is no danger of the cage toppling over. 

Part 3: Chamber work

• PSL shutter was closed for this part of work. Earlier today, I found that C1SUSAUX had failed yet again (why are all the slow computers dying more often nowadays?!). I restarted the slow machine, and locked the mode cleaner. The alignment hadn't drifted so much from when EricQ had last aligned the IMC, and with only minimal tweaking, I was able to lock the IMC and see a beam on the REFL camera.
• First, I transferred the suspension cage onto the edge of the table inside the chamber. Care was taken not to accidentally place the cage onto the trailing OSEM wires.
• There were some specks of dust on the barrel of the optic, and also the cage. These were removed with clean wipes and isopropanol.
• I judged that it would be too precarious to remove the F.C. with the optic in its final desired position. So we decided to take the coat off with the optic at the edge of the table. The central part of the HR face looks pretty clean. Even though the whole HR face was cleaned with F.C., the part that was left uncovered prior to putting the optic back into the chamber has a few specks of dust on it (see attachments). These could not be removed just by blowing ionized air. I was hesitant to drag wipe the optic, so I left things as is. In any case, the optic as a whole is MUCH cleaner (to my eye at least) than prior to the cleaning. 
• Conveniently, the stops marking the previous position of the optic were on the far side and back.
• Since we wanted to shorten the Y arm length by 2 cm, we placed a clean steel ruler of width 19mm in front of the rear stop (see attached pictures). I then moved the cage back along the side stop till I hit the ruler.
• I then clamped the optic down, removed the spacing ruler, and re-adjusted the position of the rear stop to mark the new position of ETMY.
• We were concerned that the change of position of the cage on the table affected the leveling. Checking with a clean spirit level, we found evidence of a slight tilt in the direction towards the vertex of the IFO, as expected from the way the ETMY cage was moved. To compensate for this, I moved one of the counterweight masses (see attachments) till the spirit level showed the table to be level (to its resolution) in two perpendicular directions. 
• We then plugged in the OSEMs into the DB25 connectors on the table. We found that the Y-end electronics were giving different readouts from what we had been seeing in the cleanroom with the X end electronics (not surprising I guess). We resolved to pull out all the OSEMs, check their maximum sensor output values, and re-insert them till the sensor output was half this maximum as best as we could. NOTE TO SELF: UPDATE THE WIKI PAGE!
• We turned on the damping, and found that the exisiting input matrix performs fairly well.
• We took a quick look at the spectra of the sensor outputs - interestingly, with the suspension on the seismic stacks inside the chamber, the 16.4 Hz bounce mode peak showed up clearly (these were totally absent in the cleanroom). I did not attempt any fine rotation of the OSEMs in the holders (it is not even clear to me how good/bad the present configuration is) because I reasoned we first need to apply a pitch bias to get the beam back to the ITMY chamber and then re-adjust the OSEM coils. The bounce mode decoupling will be the last step. 
• For tonight, we decided to leave the optic freely swinging (with EQ stops close by) so that tomorrow, we can look at the offline spectra of sensor outputs and if necessary, re-diagonalize the suspension. 
• After checking nothing unwanted was left behind in the chamber, we closed it up for tonight.

Plan for tomorrow:

• Pitch balancing check (by looking at reflected beam at ITMY)
• Re-adjust OSEMs on ETMY, minimize bounce mode coupling into sensor outputs
• Make Y arm cavity by re-positioning ITMY

Attachments:

Attachment #1: Wire is in groove in side without OSEM

Attachment #2: Wire is in groove in side with OSEM (picture taken with OSEM coil removed)

Attachment #3: UL magent relative to OSEM coil

Attachment #4: LL magent relative to OSEM coil

Attachment #5: LR magnet relative to OSEM coil

Attachment #6: UR magnet relative to OSEM coil

Attachment #7: Side magnet relative to OSEM coil

Attachment #8: ETMY HR face with F.C. film removed. Non-covered part isn't super clean, but the covered part itself does not have any large specks of dust visible.

Attachment #9: Scheme adopted to shorten Y arm length by 19mm.

Attachment #10: Current situation inside EY chamber. Counterweight that was moved to balance the table is indicated.