aLIGO LHO Logbook

H1 SUS (SUS)

betsy.weaver@LIGO.ORG - posted 09:47, Monday 04 November 2013 - last comment - 13:11, Monday 04 November 2013(8367)

SRM rebalanced to aid in range of middle stage AOSEMs

Betsy, Travis

On Friday, we rebalanced the SRM suspension adding enough weight to the middle mass to bring it down such that the 2 AOSEMs which were maxed out in Z-position could be aligned. These AOSEM brackets were poorly designed and we have found that many of the HSTSes at LHO (and likely at LLO, but awaiting their response) are built with the brackets at a range extreme. So, while the SRM passed TFs the other week, we had to start over with balancing in order to bring these AOSEMs into alignment with a little bit of range adjustment. Previously, the SRM had been balanced to within tolerance at ~0.75mm high. Friday, we added enough weight to bring it to ~0.25mm low in order to bring the middle mass down a bit. Note none of the other 12 OSEMs were out of range, just the 2 top ones on the middle mass. Because of the rebalancing, Phase 2b TFs need to be run and evaluated again.

Comments related to this report

janeen.romie@LIGO.ORG - 12:24, Monday 04 November 2013 (8371)

Link

Danny, Gary & Matt agree that we have not seen this problem here at LLO on any suspensions. 
Matt has gone over all of the photos he has of the in situ HSTSs and there are none at the extremes. 
Matt & Betsy will talk

janeen.romie@LIGO.ORG - 13:02, Monday 04 November 2013 (8372)

Link

Matt, Betsy Jeff B & Janeen talked. Matt reminded that there were 2 different vendors for the HSTS weldments. It may be that the horizontals of the two different manufacturer's weldments are in different positions relative to the drawing. If, for example, some of the LHO crossbars are further apart than the LLO crossbars, then the range for those middle stage AOSEM brackets would be different. We are in agreement that if the suspensions meet the requirements - TF pass and optic center is in the right position relative to the optics table - then these differences are acceptable.

janeen.romie@LIGO.ORG - 13:11, Monday 04 November 2013 (8373)

Link

Matt has a couple of photos of HSTSs here at LLO, that show the relatively nominal position of these brackets.
The first photo is the back of LPR2. The second is the back of MC3. The last is the back of MC2. You'll need to zoom in on these photos to see the AOSEM mounting brackets.

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