-
Longitudinal: +0.2 mm (North)
- Tolerance: ±3.0 mm
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Lateral: -0.9 mm (East)
- Tolerance: ±1.0 mm
-
Vertical: +2.8 mm (high)
- Tolerance: ±1.0 mm
I looked back through my notes of the pilot ITMx cartridge alignment from way back in September 2013 and the in-chamber alignment from November 2013 to see what the history of the height adjustments are with this quad. The ITMx height on the test stand is set with respect to the ISI table: we attach a calibrated height stick (with attached scale) to the ISI table and use that to set the total station 1742.0 mm below the ISI table; this is the desired distance the center of the ITMx should be from the ISI table. We then aligned the ITMx in height to this location. We started low by 1.6 mm, but adjusted to be high by 0.1 mm. The cartridge was then craned into WBSC3. I seem to remember Hugh setting the ISI table to its proper height prior to the alignment work (correct me if I'm wrong here Hugh). I then took the first set of numbers and found the ITMx to be 3.6 mm low. We still do not understand where this discrepancy between the cartridge alignment, Hugh's setting of the ISI table, and my 1st in-chamber look at ITMx comes from, but I should note that for the pilot ITMx we needed to raise HEPI by 3.6 mm, now for the production ITMx we need to lower HEPI by 2.8 mm; Betsy floated the idea that it is a possibility that the pilot suspension could have been long and the production suspension is correct, thereby causing the required HEPI adjustments.
At Betsy's suggestion I also looked back at ITMy to see if we could be walking into a similar situation with this optic. This suspension goes all the way back to WBSC8 in December of 2011. When this suspension originally left the test stand we were 1 mm low. After the in-chamber fiber break the ITMy was suspended by a wire for the H2OAT. In November of 2012 this suspension was moved to WBSC1 to be used for HIFO-Y and the most recent integration work. The ITMy on the test stand before install into WBSC1 had a height error of 0.2 mm low. Once installed in WBSC1, we began aligning in January 2013; the initial height error was high by 1.7 mm. We used HEPI to adjust the ITMy height error to 0.0 mm. This was the last time we looked at ITMy (~18 months). Looking at the other BSC chamber optics (BS, ETMx, ETMy), they all had initial height errors of <= 1.0 mm, and with the exception of the BS they all started high (BS was initially low by 0.4 mm, so no problems there). The pilot ITMx in WBSC3 had the largest initial height error we've seen here at LHO, and was 1 of 2 optics to have a negative initial in-chamber height error.
