hugh.radkins@LIGO.ORG - posted 08:17, Tuesday 07 November 2017 - last comment - 10:59, Tuesday 07 November 2017(39310)
WHAM4 ISI Balanced and left Unlocked with soft covers held away from table
I'll detail the rebalancing after I review the previous payload to document changes--Exec Summ: removed many kgs.
My tabulation of the payload results in a reduction of balance masses by 11.75Kgs.
Just wanted to outline my process for balancing the ISI:
1) With ISI still locked, reset RX RY target to LOCATIONMON value (cartesian LIGO global), set Z target to locked position plus 20um.
2) Unlocked ISI and balanced to get RESIDUALMON pretty close to zero so that locking was easy.
3) Relocked and unlocked a few times looking for repeatability.
4) Reset the RX RY and Z targets to new locked position. It is not unexpected for the locked position to change like this after lots of work on the table. These changed -46urad, +11urad, +0.7um for RX RY and Z.
5) unlocked and fine tuned the balance.
6) Relocked and consolidated and secured all masses. Unlock to lock change: RX -7.4urad, RY +0.6urad, Z -19um.
7) Updated SDF for RX RY and Z Target, e.g., H1:ISI-HAM4_CPS_RX_TARGET w/ Z set less the 20um for in air buoyancy effect.
FWIW--Locking the ISI at this balance condition was easy, unlike unlocking it when it was 11kg heavy. Lightest weight balance item is ~50grams.