Sometime between the SUS and ISI payloading mid-week last week the alignment of the ITMy QUAD wandered off. The ACB install and alignment proceeded late last week. On Monday (yesterday) we resumed realignment of the ITMy SUS. This involved the usual many day effort of realigning all 3 stages of sensors during the test mass and CP pointing alignment. By COB on Monday we had good sensor alignment and good IAS pointing, however we had a strange 2.6Hz peek on V and P DOF TFs. Overnight TFs confirmed these peeks. Today, we have again spent all day trying to understand and mitigate crosscoupling of this peek via shifting the sensor mounting box around and realigning the OSEMs each time. No help.
WED
SUS and ISI Payloaded
Good IAS alignment, Good sensor alignment, Main Chain rubbing
THUR/FRI
ACB Install and alignment
Closed the ring heater.
MON
Main chain rubbing had been alleviated, IAS and sensor pointing ongoing
2.6Hz in some DOF TFs of M0 and R0
TUES AM
Sensor mounting table cloth realigned in an attempt to improve sensor centering along x - pushed towards main chain, all BOSEMs realigned.
Major L1 and L2 OSEM alignment coupled with both chain pointing alignments.
Checked a few flags that possibly were crooked. None found bad.
No problems with cables, EQ stops or flags found between chains.
2.6Hz peek found to have moved to 2.4Hz.
TUES AFTERNOON
Sensor mounting table cloth realigned in an attempt to change any coupling seen by the sensors to mis-pitched/mis-yawed/mis-rolled top mass flags. All 12 top BOSEMs realigned.
Tweeked slightly miscentered L1 Upper and Left BOSEM centering.
No problems with cables, EQ stops or flags found between chains.
Opened the ring heater (grasping at straws).
2.4Hz still there on both main and reaction.
TUES LATE PM
Locked ACB with 1 bracket in an attempt to stop what we observed to be a 2-3Hz bounce resonance.
Story TBC...
I attached tfs of top mass main and reaction chain undamped itmy showing the difference with ACB LOCKED/UNLOCKED. Suprisingly it does change the response, and the resonance at ~2.42Hz disappears when the ACB is locked.
Full tfs will be ran tonight, on the main and reaction chain of ITMY, in order to confirm that extra resonances seen this morning in the tfs ran yesterday night are independant of the suspension.
Note, particle counts before we started work for the day in BSC1 yesterday (the day of the above post) was:
0.3um 10
0.5um 0
1.0um 0
Then the PC ran out of batteries so we didn't take any more counts. WIll try to be more dilligent today.