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Reports until 17:14, Tuesday 29 July 2014
H1 SUS
betsy.weaver@LIGO.ORG - posted 17:14, Tuesday 29 July 2014 - last comment - 10:50, Wednesday 30 July 2014(13048)
ITMy status

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...

Comments related to this report
arnaud.pele@LIGO.ORG - 10:50, Wednesday 30 July 2014 (13052)
Link

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.

Images attached to this comment
jeffrey.kissel@LIGO.ORG - 20:02, Tuesday 29 July 2014 (13057)
Link 

A. Pele, J. Kissel, B. Weaver, T. Sadecki

Confused as to why the ITMY dynamics are affected by the ACB dynamics, we postulated that it's because the ISI is locked, with HEPI floating -- directly shorting ST0 (from which the ACB is suspended) to ST2 (from which the QUAD is suspended). 

While Betsy & Travis were on their way out to center the R0 OSEMs (not mentioned above, but the original reason for their TUES LATE PM into-chamber), Arnaud quickly grabbed an ISI Damped vs. Undamped comparison on M0 Pitch because he was on a roll with "it's the ISI's fault" (See LHO aLOG 12945 and 7625). We even bet bacon-wrapped jalapenos on it.

ISI damped vs. undamped made the spurious feature disappear -- see first attachment. Given that the ISI is locked, turning on the damping loops should have made no difference. Because it *did*, perhaps the ISI isn't locked "well"? Unfortunately, we didn't get enough data points to make a convincing argument before Betsy and & Travis locked up the ACB ... AND, as Arnaud didn't mention above, all of his comparisons are made with ISI *undamped*, and we see no feature. (Note "damped" means both ST1 and ST2 are damping loops were turned on. HEPI is floating, and isolated under "pos" blend filters in both scenarios.)

Totally baffled (pun intended) by this ISI damped vs. undamped improvement, I grabbed some data from ITMX, which -- if the theory holds -- we should see some resonant features appear and disappear with damping, because the ISI is free. I see no such features; see second and third attachment.

So apparently, as has been the case for lots of suspensions on this last install push, we're in some weird new state where the ISI is mostly-locked but free enough to be affected by damping loops HEPI. #sevenstageisolationsystem

HOWEVER -- the message: we've turned two knobs ("ISI damped vs. undamped" and "ACB unlocked vs. locked"), semi-simultaneously, both seem to get rid of the resonance in the SUS dynamics -- implying that the problem is not QUAD related. As Arnaud says above -- we'll confirm with the results from tonight's full set, but if they're clean I vote we move on with the remaining install activities for this chamber ('cause we'll have more configurations, and more measurements to ponder).
Non-image files attached to this comment
betsy.weaver@LIGO.ORG - 09:19, Wednesday 30 July 2014 (13064)
Link

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.

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