This morning whilst aligning the ISS AOM there was no diffracted beam irrespective of the AOM
orientation.  The 80 MHz signal in to and out from the AOM driver was measured.  The output
of the driver was too low [~18.4 dBm (3.4 dBm + 15 dB attenuation)] for any noticeable diffraction.
The RF amplifier gain simply was not there.

    As a side note, the RF spectrum was measured.  80MHzIn2.tif shows the input RF spectrum
from 10 MHz to 120 MHz and is relatively clean.  The output spectrum is in 80 MHzOut2.tif
where a number of extra peaks are present.

    The AOM driver, which should produce at least 33 dBm, was examined in the EE Lab.  For a
power supply voltage of +18 V, it could not produce more than ~30 dBm regardless of modulation
input.  Increasing the power supply voltage to the nominal +24 V, the AOM driver easily produced
33 dBm.  Keeping the modulation input voltage fixed, as it is whilst the ISS is unlocked, and
reducing the power supply voltage by 1 V reduced the AOM driver RF output power.  The
suspicion is that either the power supply voltage was reduced some how and the AOM driver
latched.  The same behaviour was observed in a different unit that was, until now, thought
to be faulty.

    A dedicated power supply line will be pulled some time next week just for the AOM driver.

WP 7710

The EFM chassis was removed from EX and inspected. Interface board is a v6 which does not contain the whitening stage. CIT will ship correct v7 board next week. Unit was reinstalled at EX.S1102829

ECR E1800202

Both the installed and spare SR3 Heater drivers was modified per ECR E1800202:

1. Increase the current monitor gain
2. Decrease the voltage monitor gain

SN S1700597 and S1700598.

J. Kissel, H. Yu

Having seen a good amount of success with the recently installed H1 SUS ETMY ISI ST2 L to M0 P feed forward filtering (see LHO aLOG 42875), I was curious if we would gain any benefit from installing a similar L to Y feed-forward path, since only L2P paths were installed (LHO aLOG 42851). 

    As such, I've measured the ISI ST2 Longitudinal motion (as measured by the calibrated, projected GS13s) to Test Mass (L3) Yaw motion (as measured by the calibrated optical lever), both with and without a drive of ISI ST2 in the Y direction (not Yaw, Y, as in X, Y ,Z, or aligned with the Y arm).

    The message: if the ISI ST2 L to L3 Pitch coupling (improved by the ISI ST2 to Mo P feed-forward) is good enough, the as-is L3 Yaw is comparable to it. So -- we don't need to implement a feed-forward path.

The first attachment (2141) shows the comparison between (driven) ST2 Long to L3 Pit with the feed-forward ON vs. OFF against the ST2 Long to L3 Yaw, shoing the the improved L to P transfer function is comparable to the existing L to Y coupling. As a side benefit to this confirmation, we also confirm that the ISI ST2 to M0 P feed forward is stable over the ~1 day time scale, with similar improvements in the driven transfer function as was seen yesterday.

The second attachment (2205) shows the comparison between the quiescent ST2 Long to L3 Yaw against driven ST2 Long to L3 Yaw. This shows there's little coherence in the quiescent state.

The driven template can be found here:
    /ligo/svncommon/SusSVN/sus/trunk/QUAD/H1/ETMY/Common/Data/
        2018-07-13_2141_H1SUSETMY_M0_ISIFF_FilterDesign_ISIST2L_2_L3PY.xml

We have made a branch of the ALIGN IFO guardian which should replace the manual alignment of the beam splitter in MICH dark.  This is finishing up work that was started here and here

It locks the bright michelson, engages the AS centering loops, uses ADS to maximize the AS air build up dithering the beam splitter, waits for the loops to converge, and offloads both the beam splitter and OM alignments to the sliders.  There is a bit of an oscillation, but this seems to work well enough for an initial alignment servo.  

Instead of aligning the Michelson by hand, from now on we should just need to request MICH_BRIGHT_OFFLOADED from the ALIGN_IFO guardian.  

This is checked into the SVN as 17552

We did the M0 stage L2A decoupling for ETMY (similar to what we did in LHO:42723 for EX). It was motivated by that we saw some excess coherence between ETMY (where DARM actuation went) and C/DHARD than ETMX with C/DHARD at the microseismic band (LHO:42751).

The result is attached. The pink (cyan) trace is the L2P (L2Y) coupling with the old l2a filters, and the red (blue) one is with the new l2a filters.

When designing the filter we focused on the microseismic band ~ 0.2 Hz. For pitch we should be able to reduce the actuation L2P by about a factor of 2, and for yaw we should be able to essentially eliminate the L2Y coupling.

Helium removal during business hours

TITLE: 07/13 Day Shift: 15:00-23:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Commissioning
OUTGOING OPERATOR: None
CURRENT ENVIRONMENT:
    Wind: 4mph Gusts, 1mph 5min avg
    Primary useism: 0.01 μm/s
    Secondary useism: 0.12 μm/s
QUICK SUMMARY:

Peter out of PSL  just after 8am (15:00utc) and ready to hand over to Commissioners with the caveat power stabilization won't be available until later today.  IMC GRD attempts to lock the IMC, but while doing so I have been getting an "IMC WFS not centered" and "FSS unlocked" message.

Stefan, Danny, Thomas

At the beginning of the day we found that the annulus mask was not very well aligned to the incoming CO2 beam but the central mask was pretty good, so we slightly moved the annulus mask to get the beam relatively well centered but it was quite difficult because it's very sensitive, mostly due to the 7 shims sitting underneath the base.  We also re-centered on the two Irises just before the periscope and was hitting the center of the bottom periscope

Before lunch we turned on the CO2 for one minute and saw that we still had an edge of the annulus mask on the HWS.  After lunch we saw that the beam was clipping on top periscope and not very well centered at all on the viewport.  Chandra came out with us and gave the OK to remove the coupling between the table and the outer ZnSE to put the laser card closer to the injection point.  We then tried to walk the beam closer to the center of the viewport with the bottom periscope and compensate with the top periscope (only in yaw to begin with).  Unfortunately, when we tried this, the HWS didn't register another CO2 injection, so we attempted to walk back the same way to get our orientation again, and we've gotten some fringe heating back again so we still have some work left to get the pointing correct to the test mass and will go back out to the table tomorrow morning.

Most of today was spent with me trying to figure out the lensing mentioned in previous update log. Turns out, I was not suppose to mirror the EY setup exactly. Dang, my fault. So I reverted back to the original layout (D1201448) but with an added path for the LED source. I realigned back to ALS-M11 and placed the lenses very roughly in their positions according to T1000717. HWS-L2 (PLCC 1" roc257.5) seemed to make the beam much larger than the diameter of HWS-M1, the next optic. This seemed to be the case unless I placed the lens very near the M1 mirror, but ~400mm away from where T100717 says it should be.

Tomorrow we will work on more of this mode matching before moving on to replacing ALS-M11 with the PBS. If all else fails I would at least like to have this in place so when the arm is opened, HWS work won't hold back commissioners too much.

Attachment 1 - My proposed layout, though due to space it was slightly changed.

Attachment 2 - Current layout.

Attachment 3 - Current layout side view.

P. King, J. Oberling

Peter worked to recover the PMC, FSS, and ISS this morning.  For details, see his alog here.

After Peter was finished, I re-installed the MOPA lid and the FE power monitor pick-off; I then worked on aligning the pick-off, finishing in the afternoon.  The power out of the FE was measured using the roving 300W power meter to be 33.6W; I calibrated the pick-off to this value.  At this point I noticed something strange.  The output of the pick-off takes a long time (10s of minutes) to settle down and level off; the power reading on the power meter did not change during this "warm up" period.  I don't remember it doing this upon first installation, so this is something to keep an eye on.  After a lengthy warm-up period I checked the pick-off to make sure it wasn't getting hot (an indication of the pick-off being misaligned) and it was cool to the touch.  With the pick-off installed, a slight realignment into the 70W amp was required.  Most of the alignment was off in pitch, which holds together with the first time we installed this pick-off.  Upon realignment the output of the 70W amplifier was 75.8W; I re-calibrated the 70W power monitor PD to this value.

I then proceeded to reinstall the ISS AOM.  Using low power, I roughly aligned the AOM to the beam using the aperture in the AOM cover.  This done, I looked for a diffracted beam, but couldn't find one.  In addition, the beam on the AOM looks much larger than I remember it being.  Not wanting to damage anything when we're so close to having the beam back, I stopped here for the day.  So the only things left to do before the PSL is ready is to align the ISS AOM and close the ISS loop.  I left the FE and 70W amplifier OFF overnight.

Jeff K., Edgard, Hang

Today we continued to implement the ISI to top mass (M0) FF and the results looked promising.

In the first plot we showed the ISI_SUSPOINT_L to ETMY L3 oplev pitch transfer function (left panels), coherence (top-right), and oplev asd (bottom-right). The pink and cyan curves were without the ISI2M0 FF and the red curves with the FF on. A broad band reduction in the pitch motion from 0.1 Hz to 1 Hz was achieved with the rms pitch motion reduced by a factor of ~ 2.5.

The measurement was done using the passive data (i.e. excitation from the sei motion). To make sure the rms between measurements were comparable we also showed the ISI suspoint asd in the second plot. No significant difference between the SEI motion was noticed, and thus the reduction achieved should be real.

We will try to use some interferometric data to validate the result when the beam is back, and test the robustness of the FF filter over time in the future.

=====================================================================

Details:

We first tried to use the scalar FF (LHO:42866) to simultaneously reduce the M0 length and pitch motion. After made sure that we measured the M0 motion relative to the ground instead of ISI, the measured FF coefficients were consistent with the prediction in that they were essentially constants in the low freq band. However, after we turned on the FF, somehow we created an unstable feedback loop.

See the third image. The FF was turned on at around -0.7 min in the strip tool. First we excited the local damping ctrl, presumably due to that as we tried to stabilize the M0 to the ground, we intentionally created differential motion between M0 and ISI which made the local damping loops unhappy. Moreover, somehow the suspoint input started to oscillation and grew exponentially... Somehow we formed a feed back loop in the SEI chain...

Instead, we tried an alternative approach. Since we were mostly interested in reducing the L3 stage pitch motion, we directly measured the (SUS-ETMY_SUSPOINT_ETMY_EUL_L_DQ --> SUS-ETMY_L3_OPLEV_PIT_OUT_DQ) transfer function, and FF the negative of this TF to the M0 P drive (using the SUS-ETMY_M0_ISIFF_L2P filter module). Specifically, the filter we put in was

- (SUS-ETMY_SUSPOINT_ETMY_EUL_L_DQ --> SUS-ETMY_L3_OPLEV_PIT_OUT_DQ) / (SUS-ETMY_M0_TEST_P_OUT --> SUS-ETMY_L3_OPLEV_PIT_OUT_DQ),

(which was the standard way of designing FF filters), and the resultant improvement was shown in the first attached image with passive data.

For completeness, we also actively shook the ISI so that we could see the performance up to 2 Hz. Again a broadband reduction was achieved.

The potential drawback for this new scheme (stabilizing only L3 pitch) relative to simultaneously stabilizing M0 length and pitch was that it could inject extra longitudinal noise at low frequencies. This would not be an issue in full lock as the longitudinal loops have sufficient bandwidth to suppress this noise, yet it might affect the lock acquisition. To address this issue we looked at the L2 stage osem length response (without the main or the ALS beam we could not extract L3 stage's length motion unfortunately). The result was shown in the last figure's bottom right panel. Again red and blue curves were FF off and pink and cyan ones FF on. The L2 L asd looked essentially the same thus hopefully our FF would not be an issue for the L3 stage also.

Robert, Philippe, Kara

-Attached accelerometer to periscope in PSL in Y direction.

It looks like someone changed the IMC-MC2_TRANS_SUM_OFFSET on July 10th around 23:30:00 UTC.  Was there a reason for this?  The input to the filter bank is off, and the offset is on and set, which seems like it's meant to make the sum look like the IMC is locked with 10W of input power. 

The consequence of this change is that the IMC guardian was unable to recognize that the IMC had lost lock (since it looks at this sum channel to determine if the IMC is locked), and so the loops were still engaged, and the integrator at the top stage of MC2 was just integrating up, railing the top stage actuators of MC2.  Not the end of the world, but not so great either.

I'm reverting the settings back to their nominal values.

I've also added a clause to the is_locked() function for the IMC case that if the power injected into the vacuum is less than 0.1W, assume that the IMC is unlocked - hopefully this will catch situations like this in the future.