jeffrey.kissel@LIGO.ORG - posted 08:25, Tuesday 31 January 2012 - last comment - 15:32, Monday 06 February 2012(2109)
Update on SUS Sign Conventions and Status
Earlier this month, we had made a complete assessment of all aLIGO SUS signs and flips across suspension types (see T1200015) and currently functional builds of those types (see SignStatus_120111.pdf). In doing so we identified: - Some suspensions had a few of their magnets flipped - The BSFMs had some mistakes in their Basis Transformation Matrices - Some suspensions had there OSEMINF sat-amp compensation filters defined with more poles than zeros For the most part, we have now rectified these problems. I attach a new assessment. The remaining action items are - Fix H2 ITMY M0's F2 and F3 magnet sign; to fix when we swap out for real ITM Optic - Figure out what's wrong with X2 PR3's SD OSEM; currently under investigation.
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In regards to the issue with PR3's SD OSEM: Because of the arrangement and tight quarters in HAM2, it has been decided (RODA pending!) that some suspensions have their OSEMs Sensor/Coils over on "opposite side" (as opposed to the "side"), i.e. -Trans side of the suspension -- see E1100109 for which is which. It turns out PR3 is one of those suspensions. We therefore expect the magnet polarity to be [N] not [S], which means the COILOUTF gain should be [+] not [-]. Once this COILOUTF gain was flipped, the Transverse damping loop closed and was stable, just the like the rest of the DOFs. Mystery solved! *achoo!*