J. Kissel, M. Evans

As the QUAD damping loops have evolved over the past few days, I've taken open loop gain TFs of the latest configuration that we believe to give us the most reduced motion thus fair (as measured by the TOP mass -- which may not be the right figure of merit). The first three attached are the results for the three degrees of freedom in question.

We can see that we have indeed significantly increased the amount of L damping, but P and Y have not changed that much, given the combination of adding boost filters at low frequency and decreasing gain.

The fourth attachment compares the components of each of the filters, just give a rough idea of the shape and frequency of the boost filters. 

I also add on as bonus information (pgs 4 and 5 of the fourth attachment) the filters used for the TMSY, designed by M. Evans. Granted, he's got a much more simple suspension to deal with so he can be more aggressive, but we could maybe learn a lesson or two from his design. Specifically, instead of the B. Shapiro tactic of fixing the elliptical filter at 50Hz and trying to gain damping gain by lowering the "turn-over" poles of the baseline AC-coupling filter (the FM1s), M. Evans fixes the poles and zeros of his baseline turn-over, then tailors his elliptic to push hard on the performance. The advantage there is that, if you don't care about noise, you always have a configuration (FM1 only) which is unconditionally stable with which you can turn the gain knob arbitrarily. This is not necessarily true for the B. Shapiro designs.

Back to the OLG TFs: The second attachment shows that we're probably squishing the Pitch just as much as before. As mentioned in my previous entry, this may mean we're locking the TOP mass to the Cage (in Pitch), and directly shorting the isolation of that stage. A quick fix to test this would be to lower the pitch gain by another factor of 3.

See if it helps!

Regarding the right figure of merit -- it seems like the UIM and below are showing little improvement. Perhaps, when one data mines the spectra for the times mentioned below, we should see how the UIM and PUM perform with respect to the TOP and the various configurations.

Note, that in the 4th page of the first 2 attachements I show the OLG TFs of not only L to L and P to P, but the cross degrees of freedom as well. These OLG TFs are a better way of comparing relative amplitudes, because they're in the same units. BUT the measurements were taken with the damping loops OFF, so the off-diagonal terms show the situation with no P damping -- which shows that the L to P cross-coupling is horrendous -- but it's not representative of the real situation.

The next measurement to do, would be to take the same measurement with damping loops CLOSED, and derive the open loop gains by measuring IN1/IN2 (another pioneering measurement). I'm out next week, so I may have to have someone do this one site .... or y'all can continue to play around, and see what you get. 

Best of luck!!

I've configured H2 SUS ITMY this morning in various states damping that we've developed over the past few days. I'll post the results later, but for future data mining:

All data taken with BSC8-HPI ON (IPS Loops only), and BSC8-ISI ON (Damping loops only).

    Time                              H2SUSITMY Damping Loop Status                Gains [L,T,V,R,P,Y]
(1) Jun 29 2012 (13:45 - 14:07) UTC   Damps ON, Baseline Filters and Boosts ON     [-20, -5, -2, -0.3, -0.033, -0.1]

(2) Jun 29 2012 (14:10 - 14:33) UTC   Damps ON, Baseline Filters and Boosts ON     [-10, -5, -2, -0.3, -0.033, -0.1]

(3) Jun 29 2012 (14:35 - 14:57) UTC   Damps ON, Baseline Filters only              [-10, -5, -2, -0.3, -0.033, -0.1]

(4) Jun 29 2012 (15:00 - 15:23) UTC   Damps ON, Baseline Filters only              [ -1, -5, -2, -0.3, -0.1, -0.1]

(5) Jun 29 2012 (15:25 - 15:40) UTC   Damps OFF


The hope is that measuring these configurations back-to-back, over the course of a quiet morning (times are ) will give a better representation of their relative amplitude difference.

Also, just an update from B Team think tank:
We took some open loop gains from this morning on ETMY as well. Data to come, but it looks like, after adding the low frequency boost, we're back at LOTS of pitch gain, even with -0.03. The theory now is that because we're squashing pitch so hard, we've effectively locked the TOP mass to the cage, therefore creating a triple pendulum in pitch the directly transmits ISI input motion.

Hence, another quick fix to try would be to reduce the Pitch by another factor of three (leaving all else the same as config (1) above), for a total reduction from original by a factor of 10, from -0.1 to -0.01.

(corey, eric)

With a morning window of crane access, the BSC7-SW & BSC4-SE Pier (Horiz & Vert) Actuators were removed.

(sorry for rotated image....on my phone and computer it looks fine)

JimW & Hugh

The 'locked' (w/ lockers) level of the Optical Table was measured with the Optical Auto Level.  The table is level to 0.7mm p-p.  We also assessed the LIGO global elevation and the Optical Table average is 1mm below design height.  This all may sound sloppy but given that the system was leveled using the exterior of the Support Tubes, we then connected those to the new HEPI Crossbeams, and then placed 8000 lbs on them.  So I for one, am very happy that the optical table is now where it is.

Next we'll float the system on HEPI and adjust the level and elevation.

I shuffled the new cabling for ACC, MAG and MIC on the h2tcsl0 AA chassis to fill in any gaps. I modified the h2peml0 model to add the new channels and also added a permanent IRIGB signal in channel 30 in prep for tomorrow's leap second addition to UTC testing.

Rick S, Michael R

After the low power transition and some first order alignment correction we had about 10.7W transmitted through the PMC and 2W at reflection. However, some peaks in the modescan indicated mode matching issues, so we decided to move the mode matching lenses L2 and L3 to improve this. We couldn't use the alignment ramp on the PMC screen so we instead ramped the PZT on the NPRO and adjusted the crystal temperature using the slow actuator to move between modes.

Our procedure was to first optimize the position of L2, then move L1 and L2 in iterative steps until the mode matching peak is minimized.

To optimize L2:

1. Scan NPRO PZT
2. Look at PMC reflection PD and ISS PDA on a scope
3. Adjust position of L2 by 1cm on rail
4. Move slow actuator to alignment peak, adjust pointing to minimize
5. Move slow actuator to mode matching peak (what faintly looked like a 02/20 on the camera) and measure voltage
6. Repeat steps 3-5 until the mode matching voltage is minimized

Once L2 position was optimized we then started adjusting L1 as well:

1. Adjust position of L1 by 1cm on rail
2. Move slow actuator to alignment peak, adjust pointing to minimize
3. Move slow actuator to mode matching peak and measure voltage
4. If the voltage decreased, then repeat steps 1-3 for L2. Otherwise adjust L1 in the opposite direction
5. Continue to iterate between moving L1 and L2 until the mode matching peak is minimized

We now have 11.6W in transmission and 0.8W in reflection. Visibility is 90% (going off of PD voltage readings). We did not fully minimize the peak so there is still more power to be gained. However, another mode appeared to grow as we minimized the 02/20 mode, which looks on a viewing card like a 02 hermite horizontal.

The attached spreadsheet shows positions of the lenses and the corresponding 02/20 mode voltages. Positions are measured at the North end (towards HAM1) of the lens mounting block.

FSS settings were checked again. UGF is at 400kHz with 55 degrees of phase margin. Common gain set to 23 dB.

Below is the checklist we are using to guide work at Xend. So far, we've only agreed on sequence of events through all grouting.

1. Retrofit chamber cleanroom-done
2. Position BSC9-done
3. Set BSC9-should be done today
4. Position/set BSC 9 HEPI piers
5. Build 1 Type C cleanroom
6. Cleanings
7. Stage for spool install
8. Install/set spool pieces and legs
9. Grout BSC9, HEPI piers, spool legs

The LHO alog disk had filled up with backups.  This caused problems creating entries.  This entry is a test that everything is working.

Elli, Thomas

In our attempt to decouple the motion of ETMY in pitch and yaw to the Hartmann sensor beam motion, we have been actuating on ETMY with a frequency of .35 HZ and an amplitude of 50 counts on the M0 stage and running a transfer function. Then changing the lenses on the table to alter the imaging path length till we get a nominal length so that the transfer function is at a minimum. The plot is attached below showing the actuation in yaw, we might need to do more measurements in yaw and then proceed on to pitch.  We're looking for a minimum coherence of at least .9

It's been locked for more than 30 minutes, and the beam spot is much brighter than yesterday! Another victory.

I'll attach my shoddy cell phone video later so you can see the beam motion on the ETMY. It's still moving, but it's not as bad as yesterday thanks to SUS people's effort (and of course that was essential to this long lock).

Detalis:

SUS people supplied us an updated analysis with new boost filters for each of big resonances. I played around with the gain of PIT and LONG gain a bit. When I increased the LONG gain by another factor of 10 (on top of a factor of 10 that I put in earlier), it immediately started oscillating and tripped the watchdog, but a factor of 2 (i.e. total of 20) was doing good, so I ended up with this:

H2:SUS-ETMY_M0_DAMP_L_GAIN: -20 (originally -1)

H2:SUS-ETMY_M0_DAMP_P_GAIN: -0.033 (originally -0.1)

I didn't touch Y gain even though it is with a new boost filter.

After this, I was able to see that the beam motion was reduced by maybe a factor of 1.5 or 2 by a highly scientific method of eyeballing the beam on the cage using my eyes. The DC level of the reflected beam was still fluctuating by about 20%, though (as opposed to 50 to 60% from yesterday) due to the beam motion.

Jax, Elli and I looked at the table and confirmed that the DC level of the Hartman path, which is just picked off of the main beam path upstream of the Faraday, does not fluctuate. 

After touching alignment, I felt as if the demod signal amplitude is much smaller than yesterday even though I was confident that the alignment was already reasonable. Yesterday we were getting something like 3-4Vpp, while today I got only 300-400mVpp.

I ignored that (modulation depth might have changed for some stupid reason), optimized the demod phase by using toggle switches on the delay line front panel, and plugged the CM board output to the VCO tune input. It didn't lock at first as the overall gain was too small (because the error signal is smaller), so I increaded the gain in Beckhoff world and voila!

Right now I can lock to 00 mode and 01 mode, and 01 mode is also sort of bright. Apparently we can refine alignment further, and it would be easier tomorrow as we can lock to 00 mode for however long we want.

Attached are plots of dust counts > .5 microns in particles per cubic foot.

JimW, Alex & Hugh---We forklifted and hefted in 800+lbs onto the HAM3 ISI Optical Table, enough to get it floating.  The Shipping Braces were removed and the Lockers were then locked.  We connected the CPS cabling to the feedthrus in preparation of floating and balancing.  The one missing bolt connecting the ISI to the East Support Tube, Corey noted during ISI Installation, was not successfully installed.  It remains loose and need to be removed and replaced.

HAM3 ISI had payload installed, and the ISI was floated.

HEPI acatuators were craned off of BSC7

Various tests/work done related to the OAT & SUS

EricA & HughR---Keita gave us a window to use the crane from 1130 to 1330, that was nice of him wasn't it!  At least it made for a shorter afternoon.
Anyway, no issues, removed the horizontal and vertical actuators on the two north piers of BSC7.  The main crane was out of position during that time and moving occasionally.  Just the SW corner left and then BSC4.  3/8ths done.

Afterfussing with the setup all afternoon yesterday and another few hours today, I finally glued the first primary prism to the HAM3 PR2. It looks to be off in the d-value disance, but the fixture/microscope setup is such that you cannot check any numbers once the prism is glued and being cured in the fixture.  So, I'll have to wait until tomorrow when the glue is mostly cured to remove the fixture and remeasure everything again.

[Michael R., Guido M., Rick S., Chris M.]

The input optics on the PSL table have been moved from H2 to H1.  The main beam path is aligned up to the bottom periscope mirror which has been left in the cabinet for safety.  All of the auxillary beams are aligned as well, but most of the electronics are yet to be installed (rfpd, dcpd, piezo mirror).  The alignment is as shown in D0902114.  

The periscope spacers have also been moved from H2 to H1 but are actually off in height by 1.25 inches.  New spacers are being machined and should be ready to be installed within the next month.  
We looked at the mode matching into the interferometer using beam scans with the WinCam.  The overap (in power) between the fitted beam and the mode cleaner mode is 98.7%.  The data wasn't robust enough (Rayleigh range is too large) to fit an M^2 value though.  The attached plot Mode_Matching_to_IMC.pdf shows the measured data with fits as well as the ideal beam.  

The H2 EOM has been moved to the H1 table which means that the sideband frequencies will all need to be modified.  Volker Q. will work on this when he is here in the middle of July. Hopefully the final RF system will be in place by then.  

For now we have checked out the AM/PM ratio for the 8.68 MHz sideband.  As usual with RFAM the measurement was not completely conclusive.  We initially measured a value of 4.9e-4, but were able to bring it down to 1.5e-4 by adjusting the alignment on the PD (without any significant change in the DC value).  We also put an iris in front of the PD and by adjusting the aperature size were able to bring it down to 4.9e-5 again without any significant change in the DC value.  Our hypothesis is that it is caused by scattered light possibly from the blocked s polarized beam from the EOM.

Methods of measurement and definitions of modulation indices can be found in an attachment to https://alog.ligo-la.caltech.edu/aLOG/index.php?callRep=2901.  The attached spreadsheet H1_PSL_Data.ods contains the data described above.  

J. Kissel, M. Evans

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These are the results and analysis from the Open Loop Gain TF measurements of H2 SUS ETMY mentioned below. For details of the measurement and setup, please check out the associated comments to that entry. 
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In order to check / confirm that the damping loops were "working as expected," I took Open Loop Gain TFs of the degrees of freedom of interest to the excess motion recently found in H2 SUS I/ETMY; Longitudinal (L), Pitch (P), and Yaw (Y). Attached are the results.

Each collection of plots shows the Open Loop Gain TF (in red), and a reference Plant TF (in black). 
The black traces are what we typically loosely call simply "TFs," which are taken from with the excitation point from the out-of-loop TEST bank. These are in OSEM repsonse [ct]s / COIL drive [ct]s, but because all frequency response in the analog signal chain is compensated, the calibration is merely a collection of scale factors; an even scale factor of 60 -- so we can consider it in [m/N] or [rad/N.m] which is indeed the "plant," P, of the damping control loop. 
The new red traces are taken by exciting through the DAMP filter bank, which means the measurement includes the damping filters and gains, -K, and is hence the Plant times the Filters, P*-K == G, or the Open Loop Gain. Here, because we're sensing and actuating from the same point in the loop (i.e. the input to the damp filters), the transfer function is dimensionless, and no calibration is necessary. Also, because the loop is defined with minus sign explicitly outside of the damping filters, the stability criteria is for Upper Unity Gain crossings to stay away from -180, and Lower Unity Gain crossings to stay away from +180. 

These plots confirm what was mentioned below, that with the gains as is [er was by now], the

- L is basically undamped for both SUS, especially its low frequency modes (where the dominant RMS motion lies), because the Open Loop Gain is below 1,
- P is totally squashed (over-damped), especially the higher frequency modes; not necessarily obvious from these plots -- because it's unclear from the open loop gain how much suppression one would get, it merely shows that you have lost of gain over all resonances -- but it certainly obvious from the closed loop TF plots in the previous log.
- Y could maybe use a little more juice at low frequency, but otherwise looks OK


It's from the combination of these plots and the previous plots our "quick fix" recommendation came: it looks like there was plenty of phase-margin head room to increase the gain of the L loop by 10, and decreasing the P gain by a factor of 3 looked like we could still get some gain at the resonances, without squashing them entirely.

Of course, while writing this log, I found that Keita had remeasured the performance using these new "quick fix" gains, and found that the motion has increased. So, I will tuck my tail between my legs and head back to the drawing board with my thinking cap on. l'*sigh*.