OMC PZT driver

• This afternoon around 4pm local time Fil replaced the modified OMC PZT driver with the old driver.
• We retook the measurements for the OMC length noise, measuring the DCPD spectra when locked on the carrier and sideband, on resonance and detuned from resonance. Stay tuned for a length noise spectrum. Looking at the raw data we took today compared to the same spectra from yesterday (top and bottom plots of the first attachment respectively) it's clear that the 180 Hz is much narrower with the new driver. The right colum of plots are the same as the left but zoomed into the 180Hz. The height of the 60Hz line was not reduced. The 10Hz comb of lines is also no longer present.
• We have not yet got to re-measure the RF9 coupling or look at the DARM spectrum with the old driver returned, as we have had trouble locking.

4.5 Hz DARM oscillation

• We've lost lock many times today due to the 4.5 Hz ring up in DARM, which occurs during or shortly after the transition to from {ITMX L3 and ETMY L1+L2} to {ETMX L1+L2+L3}.
• Plots from example lockloss shown in second attachment, showing what looks like L2 and L3 fighting for control at this frequency.
• Later this evening Sheila tried to complete the DARM actuator transition with new filters and gains in the ETMY LOCK L1 filter bank, to better match it to ETMX (i.e. the same filters as installed in EX by Sheila and Keita last week). We still lost lock during the transition however, and the changes were not put in guardian.
• Craig tried increasing the ETMX L2 gain further than what Sheila and I tried on Monday. Initially we tried going from 15 to 22 - the actuator signals, and DARM IN and OUT looked better, but still marginally stable. We next increased the gain to 30, and managed to make it to nominal low noise.
• Once we were locked with this higher ETMX L2 gain it was clear we needed to retune the MICH-FF, Craig started this measurement and got the MICH to DARM transfer function, but not the MICH-FF to DARM transfer function. An oversealous excitation caused us to lose lock. We have left the high ETMX L2 gain in the guardian in LOWNOISE_ESD_ETMX, but are not 100% confident we actually solved the problem or if this was just another fluke.

I manually locked the FSS by disabling the autolocker, moving the temperature to where it was when the FSS was previously locked, then engaging the loop.
Looking at the FSS time series, it seems as though the temperature never actually reaches the top of it's range.  When the FSS sees flashes, it triggers some FSS_OSCILLATION state in the PSL_FSS guardian, which ramps up and down the common gain in an attempt to unrail the PZT.  It's possible that these common gain ramps were too small, happen too quickly or jerk the temperature around too quickly.
I adjusted the FSS_OSCILLATION state so the gain goes down to 0 dB from 28 dB, then ramps back up.  Unclear if this will actually help, probably would be smarter to tune the autolocker settings to slow things down around the flashes.

A BruCo scan for the "improved spectrum" mentioned in 47011 is available at the link below:

https://ldas-jobs.ligo.caltech.edu/~gabriele.vajente/bruco_lho_1234697418b/

I didn't use exactly the same time as in the posted spectrum, but instead used a quiet period with good range.

Some highlights:

• Coherence with SRCL at low frequency (<13 Hz) and around 25-30 Hz (fig 1)
• Angular noise as witnessed by ITMX_L2 below 40 Hz (fig 2)
• High coherence with OMC_A_PIT_OUT below 20 Hz and around the big lines (fig 3) Not sure how to interpreter this
• At high frequency, there's coherence with ISS signals (fig 4)
• Also, there's coherence with PEM-CS_ADC_5_20_2K_OUT_DQ and PEM-CS_ADC_5_21_2K_OUT_DQ. What are those? (fig 5)

Leaving Y-mid instrument-air energized until further notice.

Also ,

1415 -1445 hrs. local -> Ran HEPTA pump (testing) at Y-mid.  I expect to be running this pump intermittently over the next few days for various testing purposes and will record the Start/Stops in the aLOG at the end of the day(s). 

TITLE: 02/20 Day Shift: 16:00-00:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Commissioning
INCOMING OPERATOR: None
SHIFT SUMMARY:

Made it to NLN once (for a couple of minutes) & then lost lock multiple times around the LOWNOISE_ESD_ETMX step.  Performed an alignment (had issues with PRC & SRC, but Jenne walked me through them).

LVEA Dust Monitor #6 is down.
LOG:

• 15:30 PSL FSS measurements (PeterK)
• 23:04-23:50 Power supply swap for OMC PZT (Fil)

The main benefit of doing radiation pressure compensation is that we only need to handle a single suspension plant. If the plant is unchanged, we can invert it or utilizing its features in the digital control filter banks to improve the loops' noise performance.

For example, we can use optimal control techniques (specifically, the H-infinity design) to optimize the DHARD PIT loop, which enables x10 less sensing noise injection to DARM at 10 Hz yet with the same phase margin (30 deg) and a good enough residual rms level (< 1 nrad). 

Please see the attached plots for details:

    1. In oltf_Hinf_fit.pdf we compare the oltf using H-inf (the red trace) and the one currently used (the black trace; based on the model in LHO:46179 with a 10 W plant which  seemed to match measurements done at both 10 W no RPC and at 20 W w/ RPC). The red trace has a ugf of 2.3 Hz with 30 deg phase margin (same as the black trace; the margin can be further increased if we slightly reduce the DC gain of the loop).  On the other hand, the roll-off for the H-inf design is much faster than the one used currently, and it should enable about a factor of 10 more reduction of sensing noise injection to DARM in the 10-20 Hz band.  At the same time, there is less phase delay at ~ 1 Hz, so the H-inf design might actually be more robust than the current filter at 1 Hz against cross-couplings.

    2. We extract from the overall oltf the control filter should go into the DHARD_P filter module in ctrl_Hinf_fit.pdf. Again a comparison between how the H-inf vs. current should look like is shown in the plot. 

        In case people were interested in implementing it, we also provide the foton file that can be directly put into the filter in dh_p_ctrl.txt. (Only need to change the ctrl filter bank while leaving the DC gain the same, which was 30 in the model we adopted).

    3. The anticipated closed-loop noise performance is shown in cl_noise_hinf_fit.pdf. The low-freq rms is ~ 0.7 nrad < 1 nrad that we need (here we assumed no reduction of input noise from the ISIFF). As a comparison, using the original loop design the rms is 0.4 nrad for the same input noise. Therefore in terms of motion stabilization the two loops should be similar. Also shown is the requirement on roll-off so that it equals to the aLIGO design noise. Here we have assumed a sensing noise of 1e-14 rad/rtHz for DHARD (LHO:46178) and an a2l coupling of 1 mm/rad. 

[Jenne, Nutsinee]

We've added an empty state in ISC_LOCK, called INJECT_SQUEEZING.  Once the SQZ automation is ready, this state should be able to tell the squeezer guardian to do the final steps for injection of squeezing.

This is an update on my previous entry 46952. 

Field content

Using the optical path distortion measured by the HWS (provided by Aidan, see also 46127 and 46888) I simulated the mode content at various ports in a dual recycled Fabry-Perot Michelson interferometer. The simulation is done with MIST, using Hermite Gauss modes up to order 10, and locking the interferometer using simulated error signals. In the original entry 46952, the path distortion was about half of what we expect at 26 W (because the wavefront map provide by Aidan corresponds to a power step of about 15 W). So in the results considered here I multiplied the map by two.

Only the optical path distortion in the ITM is included, there is no deformation of the HR surface.

Each of the attached plots show the distribution of power into each modes, assuming 26 W of input power, 60ppm or round trip losses per arm. The orange traces are there for comparison, to show that in a ideal IFO, all power is in the fundamental TEM00 mode.

Interestingly, the point absorber seems to create some 9MHz sideband power in modes of order 9 at the AS port, which we believe are the culprit for the high RF9 modulation noise coupling.

RIN coupling

Using the same simulation described above, I could compute the coupling of input RIN to DARM. The result is shown below, compared with Craig's measurement from 46817. The distortion produced by the point absorber seems to explain qualitatively (even though not quantitatively) the increased coupling at high frequency. The magnitude of the coupling is larger in simulation, but roughly ok. The coupling scales with the amplitude of the optical path distortion, and it's likely to change if the point absorber is moved by a cm or two, probably within the uncertainty of the beam center position in the HWS map.

Sidebands RIN 

According to the simulation, there is about 1 mW of 9MHz sidebands power in the modes of order 9. Assuming that all of this mode is transmitted through the OMC, we can compute the DARM noise corresponding to sideband RIN:

DARM = SB_RIN * SB_POWER / (OMC_DC / DARM) 

From 46985 I estimate a DARM noise at a level of DARM ~= 5e-20 m/rHz at 100 Hz. From the simulation I have OMC_DC / DARM ~= 1.2e10 W/m, from which 

SB_RIN ~= 4e-7 /rHz

is the level of 9 MHz sidebands RIN that would explain the DARM noise, assuming it's all due to RF9 TEM9 mode leakage.

Small step in EX pressure a few weeks ago.  Followed by a slightly larger step up for EY.  (see attached)

All oplevs within nominal levels (ITMx was centered yesterday during Maintenance by EdM).

There was an FSS measurement this morning; other than that No Issues to report.
Laser Status:
Front End Power is 32.46W (should be around 30 W)
70W Output Power is 70.84W
Front End Watch is GREEN
70W Watch is GREEN

PMC:
It has been locked 0 days, 1 hr 59 minutes (should be days/weeks)
Reflected power = 10.56Watts
Transmitted power = 54.41Watts
PowerSum = 64.97Watts.

FSS:
It has been locked for 0 days 0 hr and 35 min (should be days/weeks)
TPD[V] = 2.961V (min 0.9V)

ISS:
The diffracted power is around 2.2%
Last saturation event was 0 days 0 hours and 36 minutes ago (should be days/weeks)

Addressed TCS Chillers (07:50 - 8:00 AM PST today/Wed)

• TCSx Chiller:  Had level of 30.0cm.  No water added, woo woo!
• TCSy Chiller:  Had level of 10.0 cm.  No water added, woo woo!

TITLE: 02/20 Day Shift: 16:00-00:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Commissioning
OUTGOING OPERATOR: None
CURRENT ENVIRONMENT:
    Wind: 13mph Gusts, 12mph 5min avg
    Primary useism: 0.05 μm/s
    Secondary useism: 0.29 μm/s
QUICK SUMMARY:

• H1 locked overnight (range up to 93 Mpc), went down when Peter went to make FSS measurements around 13:30utc (5:30am).
• Jenne is currently locking H1. 
• Only light snowing here and there on drive in.

Sheila, Georgia, Craig

After improving the broad shoulders on the power lines by increasing the OMC dither, 47007, and finding that our 9 MHz coupling to DARM is reduced 47008 and that the DCPD cross correlation shows improved noise around 50-60Hz 47012, we decided to inject squeezing again since we know from 47006 that it can improve our sensitivity.  The attached screenshot shows the reference, anti-squeezing and DARM with squeezing.  The sensmon range is between 93-94Mpc, and we think that this is underestimating the range by about 12% according to the PCAL sweep that Jeff did this morning 47003. 

Sheila, Nutsinee

Today we took our time to carefully map out phase vs. amount of squeezing we get. Turned out the best squeezing can't simply be judged by looking at QMON (although I believe this works for asqz). In the end we were able to get 2.02 dB of sqz and 4.5 dB of asqz at a nonlinear gain of 2.39. This measurement still indicates a significant amount of loss. Optimizing the CFL phase is probably what helped the phase noise here. We think we could be limited by some technical noise (to be calculated). But attached below a usual sqz/asqz fit. It seems like our loss is approximately the same as last time (30-40%,  alog46814) with better phase noise. We also got a little more RF3 today (-14.7dBm compared to -15.5 dBm last time). We used the same amount of CLF power as last time.

J. Kissel, E. Goetz

Since we haven't had a number to reflect the answer to perennial question  "what's the status of the calibration?" in what *feels* like a long time (the last time we were able to quantify its badness was on on 2019-01-31, based on a measurement from 2019-01-18, see LHO:46723), I've been given time to take a PCAL to DELTAL_EXTERNAL sweep today.

As a result of successfully gathering this sweep, I was able to -- offline -- correct all* systematic errors in the DELTAL_EXTERNAL ASD, and compute the range -- at one time -- 120 seconds of data starting at 2019-02-19 23:00 UTC. This time was a thermally stabilized, and otherwise undisturbed with all calibration lines on. The plot aide is attached, but the sweep indicated a frequency dependent systematic error with excursions as high as 20%. 
The conclusion is that DELTAL_EXTERNAL is under-reporting H1's range by (85.45 - 75.35)/85.45 = 0.1182 ~ 12%.
*This is, of course, assuming PCAL is a perfect calibrator. It should be damn close as the PCAL Y recently had a tune-up and remeasure of its force coefficient -- see LHO:46695, but I only balk a bit because of the recent evidence for clipping -- see LHO:46847.

While I can't specifically attribute the systematic error to any one thing, I can point you to an aLOG in which I describe the current (well -- 2 weeks ago now) status of what I believe I need to do in order to correctly *remove* this systematic error: LHO:46806. Sadly, because of the snow-blizzard and lack of person power, I haven't made much *tangible* progress at all.

The data lives here:
    (1) 2019-02-19_H1_PCAL2DARM_TF_5t1100Hz_8min.xml [Contains both DELTAL / PCAL and C/(1+G) measurements]
    (2) 2019-02-19_H1DARM_OLGTF_5to1100Hz_20min.xml [Contains both G and 1/(1+G) measurements]
    (3) 2019-02-19_H1_OMCDCPDSUM_to_DARMIN1.xml [Contains information to turn DARM IN1 counts roughly into DCPD SUM Current in "mA"]
Note -- I only *need* needed measurement (1), but I was generously given a bit more time.

I've worked my way through using Evan's command line function,
    /ligo/svncommon/CalSVN/aligocalibration/trunk/Common/pyDARM/correct_bns_range.py

It required I create a new loop model,
    /ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/O3/H1/params
        modelparams_H1_20190219.py

The exact command line sequence I used for the function is 
python3.6 correct_bns_range.py --run='O3' --IFO='H1' --GPSstart='1234652418' --GPSend='1234652538' --PCAL2DARMTF='/ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/O3/H1/Measurements/FullIFOSensingTFs/2019-02-19_H1_PCAL2DARMTF_A_PCALYRX_B_DELTALEXT_tf.txt' --PCAL2DARMCOH='/ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/O3/H1/Measurements/FullIFOSensingTFs/2019-02-19_H1_PCAL2DARMTF_A_PCALYRX_B_DELTALEXT_coh.txt' --DARMmodelfile='modelparams_H1_20190219' --modelFunction='modelPars'

The following is a short summary of an approach to commissioning the H1 ITMY CO2 mask, D1900030. The purpose of the mask is to reduce the scattering of sidebands into higher order spatial modes. However, when the mask is simply applied by itself, it creates a strong positive quadratic lens. A combination of the ITMY RH, ITMX CO2 central heating and ITMX RH must be used to minimize the overall effect of the COMMON & DIFFERENTIAL MICH lenses and the COMMON and DIFFERENTIAL ITM curvatures.

First Step: Mask application to reduce HOM and maintain current quadratic lens in ITMY 

The application of the mask is illustrated in the attached PDFs. An example of the application is shown here:

• Upper left: The single-pass (SP) optical path distortion from self-heating (point absorbers) scaled to 30W of input power and assuming PRG of 40. The Gaussian weighted RMS OPD of this distortion is 25nm (where the Gaussian beam radius = 54mm). Contour spacing is 5nm.
• Upper middle: "OPD Now": The SP OPD plus 0.75W of RH power. RMS OPD = 22nm. This is what we currently have on ITMY - hence the name "OPD Now". The scatter from this OPD to LG10 is calculated (i.e. the effective lens of this OPD) as that's a number that we're going to come back to.
• Upper right: The steady-state SP OPD from the CO2 mask when a total of 450mW is applied to the ITM. The RMS distortion from this is 25nm. Note that this is the power applied to the test mass (not the power transmitted through the mask. i.e. be sure to account for the efficiency of transmission from the mask to the ITM).
• Lower left: The "OPD Now" distortion plus the CO2 mask OPD. This removes a lot of the intermediate HOM but leaves some of the very high spatial frequencies. As can be seen, there is a strong positive lens in the OPD now. 
• Lower middle: The amount of additional RH OPD required to be added to the previous plot so that the scatter into LG10 (or the effective lens of the new OPD) is the same as what we currently have in "OPD Now".
• Lower right: the sum of "OPD Now", the CO2 mask OPD and the additional RH power. This has the same effective lens as "OPD Now" but has a much lower overall RMS wavefront error of approximately 8nm.

Note that (a) the color scales have been set to the same level [-70, 70]nm for comparison between different plots [so there is some saturation in some of the plots], (b) contours are set to 5nm spacing in all plots, (c) DC levels have been subtracted from each image so that the Gaussian weighted mean value is 0nm.

Once this step has been applied, the ITMY substrate lens should be same as it currently is. This will maintain the COMMON and DIFFERENTIAL MICH lenses. However, the application of ITMY RH will change the ITMY ROC and, hence, the COMMON and DIFF ITM ROC will need to be corrected. Which will be dealt with in step 2.

The attached PDFs show the effect for differing CO2 powers ranging from 50mW to 750mW. The minimum RMS OPD is achieved around 450mW.