Was unsuccessful in damping the mode.  It made the spectrum really terrible.  I tried increasing the ADS dithers so that they wouldn't get drown out, and that wasn't good.  I turned off the ADS, but we still lost lock.

Kara and I had a look, and the phase rotator filters in ITMX Mode 2 weren't at the correct phases (+40 deg and -70 deg, rather than +/- 60 deg, and their magnitudes weren't unity at the violin frequency).  She used Patrick's gui to put in +/-30 deg and +/-60 deg filters, so that we can hopefully find something that more reliably damps this mode.  For now, it is also commented out of the lscparams so that it won't turn on with totally different filters than it used to have.

Anamaria changed the Mode2 filter to also catch the Mode 4 frequency, and turned off the gain for Mode4. 

Also, we made the Mode3 filter much more narrow, so that the tail of it isn't hitting its neighbors and potentially driving them up.

Ensured that Mode9 is very narrow (it was already an 8th order butterworth), and made mode1 more narrow (4th order to be 6th order) to help prevent it from hitting the mode9 frequency.

I've adjusted the guardian damping settings for ITMX modes 2 and 4.  

Mode 2 now uses filters FM5, FM9, and FM10 with gain=-25.

Mode 4 now has gain=0.

I've commented out both ITMX modes 1 and 9 so that we can make it to NLN now, and find the best damping settings later after we've had a chance to check consistency.

Here I am trying to build a model of the scattering. If you don't have time to read all of it, jump directly to the last plot, which gives what I believe is a reasonably good model that we could use for noise projections.

Here's a spectrogram of DARM during times around the OMC ANG X injections. It is evident that even without any injection, there are scattering shelves in DARM going up to 20-30 Hz. 

I selected four periods: two before the injection (fist at T=100s in the spectrogram above: almost no scatter visible, second at T=600s, some scattering visible) and two during the injection (T=850s: low amplitude injection, T=1000s: high amplitude injection). 

Using H1:OMC-ASC_ANG_X_INMON as a proxy for the scatterer motion, I can fit a scattered light noise model based on the "phase wrapping" model (from Accadia 2010 and Canuel 2013), including a single bounce and a double bounce. The model simply assumes that the fringe wrapping gives a noise in h(t) that can be modeled by

where f_1 and f_2 are the two coupling coefficients for the single and double bounces (related to the amount of light which is scattered back) and k_1 is a factor converting the OMC_ANG_X into the actual length change in the scattering path. 

If I use the medium amplitude injection, I can find coefficients that described quite well the spectrum of scattered light. The parameters are f_1 = 1e-19, f_2 = 1e-21, k_1 = 22e-7. In the plot below I use those parameters to "project" the scattered light noise for all four periods. The bottom left plot shows that the fit is good for the medium amplitude injection, but clearly fails for all other cases.

I can't reproduce the scattered light noise for both medium and hgh amplitude using any of the H1:OMC-ASC_[AND/POS]_[X/Y]_INMON signals. In particular for the high amplitude injection I can't reproduce the rising edge of the shelf. Typically one gets such rising edges when the RMS of the motion is concentrated at almost a single frequency.

If we assume that only the 0.5 Hz motion is responsible for the scattering, we can proceed as follows:

1. First, I apply a narrow band filter to H1:OMC-ASC_ANG_X_INMON, composed of a zero at 0 Hz plus a complex pole at -0.1 +- 0.5j Hz, scaled to maintain a gai of 1 at 0.5 Hz. 
2. Then I can use the filtered signal to fit the high amplitude injection noise.

The best parameters are: f_1=3.5e-20, f_2=5e-22, k_1=1.6e-5. The resulting noise projects well for both the high and medium injection amplitude, and it is also in the right ballpark for the high scattering period without injection. So this seems to be a good model.

We can apply the same scattered light model to the noisy period reported in 47399. It looks like the same parameters over-estimate the up-conversion (i.e. the corner frequency of the scattered light is too high). So I had to reduce the k_1 coefficient from 1.5e-5 to 1.0e-5, while I could use the same coupling factors f_1 and f_2.

I ran some 0.5 Hz line injections in the other OMC ASC degrees of freedom to see if there were any differences in the coupling.

First attached figure shows DARM and the control signals for (clockwise from top left) POS_X, POS_Y, ANG_Y and ANG_X. Red is ambient noise, blue with a moderate excitation and yellow with a larger excitation. Apologies for the different excitation amplitudes. POS_X has the strongest coupling.

Second attached figure is the control signals and corresponding RMSs.

I haven't done the work of projecting these into DARM yet, but in case anyone wants to the template can be found here:

/ligo/cds/lho/exports/georgia.mansell/Scattering/20190311_OMC_ASC_to_DARMscatter2.xml

Ran some more injections into OMC ASC ANG X, this time with a BB Inj 0.1 to 1 Hz.  Stored at https://lhocds.ligo-wa.caltech.edu/exports/craig.cahillane/Scatter/
Continuing work on the scattering projection into DARM in the live noisebudget.  It's not too far away, needs more work though.

We found that we struggled getting through the locking when DRMI ASC had lower and noisier RF18. Spent some time finding an alignment which got us RF18~75 and that seems to get through much easier. RF18 drops a lot when engaging ASC but the PRG stays constant.

Bounce modes rung up a several times too and caused a few locklosses.

If you have an opportunity over the weekend, what you need to do is:

Set the laser power to 30W. Go to ISS_DC_COUPLED (IMC_LOCK guardian). Confirm that the VGA gain slider is at 7dB.

Go to the floor. At the back of the ISS 2nd loop chassis on the rightmost PSL rack, there are four BNC connectors labeled as ERR1, ERR2, EXC and board OUT.

Connect the excitation of SR785 to EXC, CHA to ERR2, CHB to ERR1.

In the MEDM screen, enable excitation input.

EXC voltage of 1000mV is OK. There's a 1/10 attenuation in the EXC path so this is not excessive. You'll have to integrate long (e.g. 0.1 sec or some such) to get a decent measurement.

Measure the OLTF. Note that the measured quantity is OLTF/10.

Disable EXC, disconnect EXC, connect ERR2 and ERR1 and OUT to a scope and measure the voltages. If you still see a huge gain peaking you want to lower the gain further.

This morning when H1 lost lock, I quickly went to the floor and made the same measurements, and things look OK.

At 30W with 7dB VGA slider, UGF~28kHz, phase margin~37deg, which look good to me (first attachment).

Moving the slider back up to 12dB, the servo immediately started the oscillation at about 50kHz. Bringing it down to 11dB already quenched the oscillation.

With the nominal gain of 7dB, the residual noise at around 50kHz was ~1Vpp after the x10 summation stage with maybe another 1+Vpp or so at around UGF (second attachment blue) which is larger than I'd like. However, the output of VGA with 7dB gain will be ~4.5+Vpp which would be large but OK. The output of the board was measured to be about 15~20mVpp or so (2nd attachment green), this is no problem for the 1st loop.

(The reason why the board output is small is because two fixed boost type filters downstream has about 2E-3 attenuation combined for f>20kHz.)

At a first look, DHARD_P coupling appears to be much more stationary. Comparing to 47274:

1. the coherence between DARM and DHARD_P during the injection is higher (see first plot)
2. a spectrogram of DARM during the injection appears much more stationary than before (see second plot and third plot for a whitened version)

I also ran the non-stationary noise subtraction code, and confirmed that most of the noise coupling is stationary (see 4th figure). The largest non stationary contribution comes from modulation due to PRC1_P

I've put these changes into the guardian, and they've worked for at least 2 locks so far. So far, the 0.5 Hz instability hasn't come back, although that is mostly luck and low ground motion, more than anything deliberate.

I took a spectrum with no lines (no Cal, no ADS), and we got up to 117 Mpc!

BruCo report available here:

https://ldas-jobs.ligo.caltech.edu/~gabriele.vajente/bruco_lho_1236049000/

During the Friday commissioning meeting several of us were wondering how H1 with 30 W and 2 dB sqz have the same shot noise as L1 with 40 W and 3 dB sqz.
I believe that the L1 curve shown in H1_DARM_FOM has low squeezing. The shot noise at 1 kHz is shown to be ~4e-20 m/rtHz. The attached plot shows a typical L1 noise curve with 40 W and ~3 dB sqz. 
The shot noise at 1 kHz is closer to ~3e-20 m/rtHz as one would expect from the factor ~sqrt(30/40)*10^-0.05=0.77. The L1 40 W 0dB sqz spectrum is also shown.

Associated with open-and-closed ticket LHO aLOG 12491, but may need a LONGTERMFIX to the OFS offset to fit the requested drive within the linear range.

Dan, Craig, Georgia

We git-committed the noise budget templates used here, and have rerun the noise budget templates for MICH_P, DHARD_P, DSOFT_P (increased the excitation by a factor of 30 to make it visible in DARM). We still need to re-run the CSOFT_P template to make the ASC contribution to the noise budget up-to-date. We have added DC centering loop templates to the folder however the excitation level needs to be tuned.

A preliminary look at the ASC budget, with the old CSOFT_P measurement, (attached figure) shows we've won a in the <15 Hz region, and we still have some sensitivity to gain by improving DHARD.

Dan, Danny, Alexi

To include the DC centering in the noise budget we excited the DC1 and DC2 pitch and yaw centering loops and DC3 yaw.  It took large amplitudes for us to see coherence in DARM that was mainly below 10 Hz. 

We also injected into the SRC1 yaw excitation point and didn't seem to see anything in DARM even with large amplitudes. 

Not sure if we are doing this right. Might be worth revisiting. We have templates made up for these. They live in /ligo/gitcommon/NoiseBudget/simple-noise-budget

Rich verbally confirms that he and Peter used the measurement setup as described in LHO aLOG 47225 and D1900027, using the coil driver test box as a differential driver. They *did not* gather the test setup's transfer function, however, so this will need to be done in order to analyze the data (attached above, DCPD_Whitening_v2.zip) to the desired precision. Also note that details of the measurement files can be found on the last page of the DCPDWhiteningChanges.pdf attachment.

Also -- I opened (and subsequently closed) FRS Ticket 12453 covering the problem of "changes in frequency response as a result of input signal level" that the solution in this aLOG fixes.

Since this issue will likely impact LLO as well, I've opened up an integration issue,  IIET Ticket 12454, such that the above mentioned change becomes an ECR to be implemented at LLO as well (assuming they have the same problem).

Updated the FM1,FM2,FM3 whitening compensation filters for PDA and PDB.
They are now matched at the +-0.15% level (see plot).
And we verified that they are no loner offset dependent.

Also, to be explicit: We disabled the 12dB, 6dB and 3dB whitening gain steps in both PDA and PDB. The 24dB step is still operational.

The new foton filters are:

PDA:
FM1: zpk([10.44],[0.996],0.9734,"n")
FM2: zpk([49.63],[497.5],-0.9995,"n")
FM3: zpk([10.372],[0.9865],1.002,"n")

PDB:
FM1: zpk([10.160],[0.969],0.975458,"n")
FM2: zpk([49.72],[497.7],-1.0004,"n")
FM3: zpk([10.467],[1.000],.9973,"n")

Using this filter, we injected pink noise into both DCPDs, and plotted the PD ratio in various configurations to verify the filter compensation. Specifically, plotted are:

A(FM1,FM2,FM3)/B(noFM)
A(FM1,FM2,FM3)/B(FM1,FM2)
A(FM1,FM2)/B(FM1,FM2)
A(FM1)/B(FM1)
A(FM1)/B(noFM)
A(noFM)/B(noFM)
A(FM1,FM2)/B(FM1)
B(FM1,FM2)/A(FM1) (opposite rat!)

The xml file with the data in the plot is in /ligo/home/controls/sballmer/20190303/DCPDfinal.xml

Finally, we still will have to re-match the photo diode light levels in lock (alog 47217).

All this was done to fix the problem identified in alog 47247.

Attached are plots of

- Transfer function wit- over-without offset. The insanity is indeed gone.

- PDA: FM1, FM1FM2, FM1FM2FM3 - all normalized with their compensation filter.

- PDB: FM1, FM1FM2, FM1FM2FM3 - all normalized with their compensation filter.

In short: the current compensation is good at the 0.02dB level. One could still improve it...

The plotting MATLAB code is here: /ligo/home/controls/sballmer/20190304/DCPD

I've moved the contents of Stefan's results from his home directory on the local file system into the calibration SVN (though I've not yet modified his plotting script for the new directories and/or to spit out the right file names).

I used the follow commands to do so:
Data:
    cd /ligo/svncommon/CalSVN/aligocalibration/trunk/Common/Electronics/H1/Data/OMCWhiteningChassis/2019-03-04/
    cp /ligo/home/controls/sballmer/20190304/DCPD/SRS00* ./
    cp /ligo/home/controls/sballmer/20190304/DCPD/srs00* ./
    cp /ligo/home/controls/sballmer/20190304/DCPD/47254_20190303213* ./

Script:
    cd /ligo/svncommon/CalSVN/aligocalibration/trunk/Common/Electronics/H1/Scripts/
    cp /ligo/home/controls/sballmer/20190304/DCPD/plotData.m plot_omcdcpdwhiteningmods_20190304.m

Results:
    cd /ligo/svncommon/CalSVN/aligocalibration/trunk/Common/Electronics/H1/Results/OMCWhiteningChassis/
    cp /ligo/home/controls/sballmer/20190304/DCPD/PD*.png ./
    rename 's/PD/2019-03-04\_H1OMC\_WhiteningChassisTFs\_PD/' PD*.png

Thus the new script name to plot the data is:
    /ligo/svncommon/CalSVN/aligocalibration/trunk/Common/Electronics/H1/Scripts/plot_omcdcpdwhiteningmods_20190304.m

which should be modified to analyze the following data:
    /ligo/svncommon/CalSVN/aligocalibration/trunk/Common/Electronics/H1/Data/OMCWhiteningChassis/2019-03-04/
        SRS00*.78D
        srs00*.asc
using the notes in the file
    /ligo/svncommon/CalSVN/aligocalibration/trunk/Common/Electronics/H1/Data/OMCWhiteningChassis/2019-03-04/
        47254_20190303213544_DCPDWhiteningChanges.pdf

and to produce plots and results with similar file tags as
    /ligo/svncommon/CalSVN/aligocalibration/trunk/Common/Electronics/H1/Results/OMCWhiteningChassis/
        2019-03-04_H1OMC_WhiteningChassisTFs_PD*.png
(or the code should be re-written to use your favorite fitting code [maybe in python using IIRrational] and produce plots and results with similarly explicit file names with indications of the date, the interferometer, and WhiteningChassisTFs in the file name.)

Lilli S.,

First, I have renamed the data files in dir /ligo/svncommon/CalSVN/aligocalibration/trunk/Common/Electronics/H1/Data/OMCWhiteningChassis/2019-03-04/, so that they match what is described in note /ligo/svncommon/CalSVN/aligocalibration/trunk/Common/Electronics/H1/Data/OMCWhiteningChassis/2019-03-04/47254_20190303213544_DCPDWhiteningChanges.pdf

The test box has been factored out. (Test box data: /ligo/svncommon/CalSVN/aligocalibration/trunk/Common/Electronics/H1/Data/CoilDriverTestBox/S1900070/)

The fitting script is /ligo/svncommon/CalSVN/aligocalibration/trunk/Common/Electronics/H1/Scripts/fit_OMCDCPDWhiteningChassis_20190304.py 

The results are in the table below. The fitting plots are in the attachments.

The low-freq poles/zeros roughly match Stefan's results. In O1 and O2 we used 1 stage of whitening (FM1), and the high freq poles were at [(14.34e3 + 14.60e3)/2, (18.68e3 + 18.57e3)/2, (98.94e3 + 100.45e3)/2] Hz. The new fitting for FM1 is consistent with O1 and O2.

Take PDA FM1FM2FM3 noDC as an example, manually build TF by removing the high-freq zeros, and plot the residual -> see diff.pdf 

By ignoring the high-freq zeros, there's little impact on magnitude, but there's phase difference at higher freq (~<1 deg below 5k Hz).

Concluding from the results of the fit above, I'll be updating the calibration model parameters to change from the previous measurement of the DCPD whitening chassis (before O2, when the nominal configuration was to only have the first stage of whitening -- "F1" or "FM1" -- on; see LHO aLOG 28087) from 
                          PDA            PDB              PDA          PDB             PDA            PDB
    uncompOMCpoles_whitening = [(14.34e3 + 14.60e3)/2, (18.68e3 + 18.57e3)/2, (98.94e3 + 100.45e3)/2];
to the new fitted measurement results, and choosing the new nominal configuration, with all three filters on (the 1st and 3rd stages, which are whitening and the 2nd stage which is a low pass, i.e. "FM1FM2FM3" or "3 filt"), and using the 5 V_DC offset fit results because it's more representative of the nominal running conditions of the chassis (with the poles rounded to the nearest Hz) 
                          PDA            PDB               PDA             PDB                 PDA             PDB
    uncompOMCpoles_whitening = [(11.346e3 + 11.521e3)/2, (32.875e3 + 32.863e3)/2, (32.875e3 + 32.863e3)/2];

Lilli S.,

The residual contribution plot is attached. This was generated using /ligo/svncommon/CalSVN/aligocalibration/trunk/Common/Electronics/H1/Scripts/fit_OMCDCPDWhiteningChassis_20190304-vsOriginal.py

(based on reference model modelparams_H1_20190118)

The results is averaged after using different poles/zeros in PDA and PDB, instead of using the same set of averaged poles/zeros in PDA and PDB.

Per Jeff's request that the original DCPD files be included, I am attaching the data extending down to 0.5Hz for the OMC DCPD Whitening chain as taken on the floor by signal injection into the front panel of the Split Whitening Chain via an SR785

Attached are two plots:

A) The comparison of TFs:

1. All low-freq z:p + high-freq p + out-of-band z from IIRrational fitting

2. Dead reckoned z:p = [500, 1, 1]:[50, 10, 10]

3. Low-freq z:p from Stefan's fitting in 47257

4. Low-freq z:p from Stefan's fitting in 47257 + high-freq p from IIRational

B) The comparison of contribution residuals, by using the latest H1 model 20190301

The scripts live in

/ligo/svncommon/CalSVN/aligocalibration/trunk/Common/Electronics/H1/Scripts/fit_OMCDCPDWhiteningChassis_20190304-compareTF.py

/ligo/svncommon/CalSVN/aligocalibration/trunk/Common/Electronics/H1/Scripts/fit_OMCDCPDWhiteningChassis_20190304-compareRes.py

Adding a plot of power levels of the two locks with mask and without.

PRG and arm power remain lower with CO2 ITMY mask on, but POP18 is higher.

The other night we put the mask on once the IFO had thermalized alog 47097. The effect of the mask looked to be leveling off. However when applying the mask at a later date we also saw an improvement in the coupling.

Here is the 9 MHz RIN line amplitude at the start of the lock, when we switched the mask on, and when we switched it off. Overall saw ~30% reduction in coupling.

Attached is a breakdown of the mask test with a thermalised IFO at 30W. We switched on the mask for two hours. Plotted is the OPD changes between several points:

1. OPD change during power up before any mask is applied
2. OPD change with the mask switched on
3. The change in the OPD due to the mask (Difference between 1 and 2)
4. The steady state OPD of the mask after 2 hours

What's confusing us is that we now see an OPD change that is different to when we applied the mask separately. i.e. case 4 does not look like this.

The magnitude of the optical depth change is completely different too. Case 4 has an OPD change of 40nm, whereas applying the mask out of lock gave us ~140nm. I can't think of why this would be the case, perhaps the mask induces a change in the beam which introduces a different OPD, so some non-linear effect is in play. If so, it will be difficult to predict what mask shape to actually use.

It does however have a crescent like shape similar to aidans model Aidan's model (top right image here), although that may be a coincidence.

The reference for the "140nm measurement" of the CO2Y mask thermal lens was not taken at a cold state but rather with 0.85W of CENTRAL heating on. This yields a strong positive lens. If this positive lens is taken as a reference (or zero) point and then central heating is turned off, we will see a strong negative lens in the measurement.

Probably best to repeat the calibration of the CO2Y mask from a genuine cold state.

So the "140nm OPD measurement" is looking at the difference between a reference state of "0.85W central + 0.0W custom mask" and "0W central + 0.45W custom mask".

Alexei, Dan

Pulled the data from OMC_DCPD_SUM_OUT_DQ corresponding to the injections of frequency and intensity noise lines as outlined in alog 47097.

The first black line is when the CO2 was switched on the second black line is when it got switched off. Looks like the mask increases intensity noise coupling but doesn't do much of anything to the frequency noise.

The ringing towards the end is likely some instability as there is a lock loss about 10 minutes after the data ends.