Edgard, Conor and Brian.

We are investigating the feasibility of implementing feedforward control from the suspension point longitudinal motion (as seen by the GS13s) to longitudinal drive at the Top Mass. The evidence suggests that it could reduce the coupling to DARM in the band from 0.1 to 0.3 Hz.

However, to do this, we need to understand and compensate for the DC cross coupling to pitch at the top mass.

Details can be found here: dcc.ligo.org/LIGO-G1800467


As a way to track the variability of the cross coupling we took a set of measured transfer functions from 2017 (thanks for putting these together!). A summary of results here:

1) The figure attached shows the top mass Length to top mass Pitch transfer function at different times during 2017. The two outliers (light blue and green traces) correspond to measurements taken in air. 

2) The discrepancy of the measurements could not be traced back to a simple (linear) relation with the vertical position of the top mass. 

3) We don't understand why the cross coupling is so much smaller in air than in vacuum, need to check for other suspensions.

The complete version of this log post can be found here: SEI alog 1316

Today, we performed a few iterations of weld annealing with the goal of reducing the differential pitch offset of the PUM-to-ETM from the initial welded value of ~3mRad.  After 2 iterations, we had the pitch down to ~1.6 mRad.  As we were preparing to break for lunch, I noticed that the PUM prism crack (referenced in aLog 41111) seemed to have grown from what I recalled.  During the break, I looked at Betsy's pictures that were taken shortly after removal from chamber which confirmed my suspicions that the crack had increased in length.  We decided this warranted a discussion with several of the decision making staff (Dennis, Peter, Calum, Fred, and Garilynn).  Together we concluded that it was probably fine to carry on since the crack only seemed to lengthen when exposed to heat from welding (the initial cause of the crack and the cause of this case of extension) and that this side of the PUM would not need to see any more heat for the annealing that was continuing.  (Note that the copper prism shield that was designed to protect this from happening again after the first instance WAS installed, but apparently enough radiative heat was present to affect the crack anyways.)  We continued on with another iteration of annealing which resulted in a final differential pitch of ~350 µRad.  This concludes the final post-O2 monolithic welding session.  Check.

Shelia, TVo, Nutsinee, Alexei, Dan

Today we continued trying to align the beam into HAM6. The beam going into HAM6 leaking from the OFI was ~15mm too low on the SQZ apertures. To try and correct this we adjusted SR2 and SR3 pitch within the ranges we found yesterday (alog 41197) to avoid any OFI clipping. We were unable to find a suitable alignment that avoided the OFI clipping and pitched the beam up enough to make it through the center of the SQZ apertures.

The procedure was:

1. Pick an SR3 pitch value in the unclipped range we found yesterday
2. Re-center the beam through the OFI by adjusting SR2 pitch and finding the clipping points
3. Measure the offset at the SQZ aperture

SR3 pitch of 1100 was causing clipping yesterday so we stopped here. We tried to improve on -7mm by pitching ZM2 but this railed before being able to sufficiently correct it. The beam going into HAM6 had an angle of 7mrad toward the SQZ aperture (The beam dropped ~5mm over ~68.6cm) which is too much for ZM2.

Shelia and Terry have gone back into HAM6 to look at alignment further.

We've never made this official and there is always some evolution of things but we should get something in writing; so, here goes.

0) Chamber is under vacuum.  0.1) Things are vented, chamber is opened.

1) Lock the ISI (before anything happens to the platform), see attached from D071450 (which has lots more detail of the assembly):

a) Keep things quiet, don't disturb Stage1 (the suspended platform)

b) Lock the lockers turning them counter-clockwise; Squirting Isopropyl onto the locker sleeve is permissible but should not be needed.

i) always lock A B C & D in order for repeatability

ii) Locker letters are embossed on Stage0 of ISI, but not HAM6 (it's the same as HAM5)

iii) I have part of a locker in my office if you want to see one

2) Sit back, wait for others to do their thing and alter the table balance.

3) Rebalance the Platform.  Display ...CART_BIAS.adl available from ISI CHAMBER OVERVIEW(2nd attachment)

3.1) Record the current, locked cartesian position of Z, RX & RY from the ISI Cart Bias medm.

a) Record to micron precision; screen displays to nanos

b) Load these as Requested Setpoints to get residual calculation

c) Residuals should now be a few microns at worst

3.2) Unlock the ISI, with payload change, may be difficult: lift, push, pull

as needed to ease, use Isopropyl if necessary:

a) Not critical but usually easier to reverse locking order--D C B then A

b) Residual now tells where things need correction

c) Medm graphic indicates Add, Remove, or Move Mass to & from

3.3) Change mass as required

a) our smallest mass is 50g

b) this will move the Z position a few um

c) this will swing the add/remove location more than you'd think

d) If you get the residuals to less than 5 micros, great, go to the next step

e) Given tradeoffs, leave Z high (buoyancy) get tilts close

4) Re-rebalance the ISI

4.1) Carefully relock the ISI as above

a) Record the positions

b) Are they much different from above step 3.1,more than a few micros?

c) If not different, pretty much done

d) If the the position is different, start over beginning with Step 3

5) Confirm locking and unlocking the ISI does not shift the tilts more than a few urads.

6) Runs some TFs to insure things are not rubbing badly or shorting.

TITLE: 03/29 Day Shift: 15:00-23:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY:

Here are notes on morning activities up until lunch time (bold items below were still ongoing at lunch).
LOG:

• 13:09-15:05 PSL Work begins (Peter K)
  • PSL_FSS Guardian set to NONE (from "READY_FOR_MC_LOCK")
• 15:02 Working on HAM6 Suspensions (Jeff K)
• 15:15 Cleaning complete for EY/MY & heading into LVEA now (Karen)
• 15:46 SR3 Thermocouple cabling @HAM5 (Fil & Marc)
• 16:02 Venting Y Beam Manifold, WP7445 (Chandra)
• 16:06 Turning off fans/hvac for h1psl (Ed)
• 16:22 HAM6 squeezer teamwork (Sheila, Thomas, Nutsinee)
• 16:23-18:15 ETMy AMD work (Georgia, Betsy, Seb, Slawek)---> No NOISEY Work at EY until Friday at noon!
• 16:42 CER inventory (marc)
• 16:49 Washington Crane @ Large Equip Access
• 17:12 Weld crew heading to EX
• 17:40 M&M IP6 GateValve work (via Chandra)
• 19:04 Handing off shift to Jim.

Slawek, Betsy, Sebastien, Georgia

We finished installing the remaining AMDs (AMD 3 and 4) on ETMY this morning. Everything went smoothly, no issue to report. The required force was applied and we observe a nice ring of epoxy around the AMD bases, as expected. The epoxy has to cure 24h with the jig in place (we will remove it tomorrow).

We also inspected AMD1 and 2, installed two days ago. Bond looks uniform, as we observe few fringes between the base and the test mass (Betsy will put pictures later). Find attached a little sketch (not to scale) showing the rough locations of the AMDs on the flats. We will have more precise numbers by looking at the pictures.

Commissioning team requested that the PZT high voltage power supply be turned on. PZT power supply was turned on and the fast shutter power supply was left off.

Vertex pump down is not trending down (just one turbo is pumping since X&Y beam manifolds are vented. Attached is plot over 10 days.

So have had a continuous exponential spectra of the WHAM6 CPS signals running on the desktop watching for the grounding or whatever-it-is noise on the Corner3 sensors.  The attached snap shows this new noise.  The reference and the thicker traces are the corner3 signals, which look fine.  The other four fine traces are the corners 1 & 2 signals.  This isn't even the worse of it but it looks very similar to the corner3 noise seen previously while messing with the cabling there the last few days.  Note that the corner3 channels are in one satellite crate and corners 1 & 3 are in the other.  I'm suspicious activity around the chamber has disturbed the ground of that crate and made it iffy.

I went back to about 1pm yesterday (1900 utc 28 March) and watched the spectra until it went noisy like this.  First time I spotted was 0130 pdt this morning. Will check with EE to see if they know of anything.

I tried to open the GV2 gate annulus valve to pump out that volume while valve is hard closed (so we don't have to hook up a pump cart later), but it won't recover with annulus valve open. It's acting like there is an o-ring leak. Valve is closed an AIP current is a little higher now.

TITLE: 03/29 Day Shift: 15:00-23:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Planned Engineering
OUTGOING OPERATOR: None
CURRENT ENVIRONMENT:
    Wind: 7mph Gusts, 5mph 5min avg
    Primary useism: 0.03 μm/s
    Secondary useism: 0.13 μm/s
QUICK SUMMARY:

• I'm covering morning for Jim W. 
• Peter has been out on the floor for PSL work (FSS guardian set to "NONE" so he doesn't have to fight Guardian trying to lock the IMC).
• Jeff K working HAM6 suspensions (heard Hugh say his Corner 1 & 2 CPS are now displaying oddities...it had been the Corner 3's last week.)
• Amber staging for 9am Virtual Visit w/ South Carolina high school.
• CDS Overview:  MY is almost all INVALID/WHITE, edcu RED, TIMING RED

I have cleaned up the ISC guardian code (ISC_LOCK, ISC_DRMI, OMC_LOCK, ALIGN_IFO, ALS_XARM, ALS_YARM, ALS_COMM, ALS_DIFF, ISC_GEN_STATES, ISC_library and lscparams). 

My goals were to remove depricated code (it's been growing since ~2014, and many functions clearly haven't been used since about then), merge nearly-identical functions (we don't need 15 different functions to determine if a cavity is locked), ensure that functions from sub-files (eg. ISC_library) are clearly called out (by removing all "from _______ import *", which Sheila had already done a lot of work toward), and make the code generally easier to read. 

I was going to do a bit more syntax checking, but since we have IR light into the vacuum earlier than had been anticipated and several people have been working on locking the IMC, I deployed the new code this afternoon.  All guardians were checked in before I did anything, and then I copied over my files from a side folder into the main userapps guardian folders. 

So far, the IMC guardian is able to lock the IMC (after a few boost changes from Sheila, TVo, DanielBrown and Alexei...they'll write a separate alog).  The ALIGN_IFO guardian is able to change the SUS configurations, although it hasn't been tested farther than that, since PeterK is working on the PSL. 

This cleanup has removed ~4,000 lines of unnecessary guardian user code.  I think it'll help make things easier as we go forward with a new commissioning phase.