TITLE: 03/08 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:

Locking went well with the exception of a couple of HEPI pump trips that were physically induced. It was a good exercise and allowed for a small update to the SEI>HEPI wiki instructions for those who are more in the dark about SEI than others
LOG:

16:45 Jeff out to LVEA - shooting pics of ITMs

17:16 Jeff Back

17:24 Kyle out to EY - mechanical room

17:35 Nominal Low Noise - 113.206 Mpc

17:49 LockLoss - EY mechanical room activity tripped HEPI

18:02 Hartmann team (TJ and Daniel) out to LVEA to check SLED

18:06 Jim and Fil to EY to recover HEPI

18:35 Hartmann team back

18:50 Kyle back

18:54 EY HEPI pump recovered - waiting for isolation to resume locking

19:10 EY SEI WDs tripped again

20:03 re-locking resumed

20:49 Nominal Low Noise - 100Mpc

21:33 LockLoss - high bounce mode

22:25 Begin Initial Alignment

22:52 Resume locking

23:50 H1 locked at NLN - 113Mpc

During last night lock, for a short period some excess noise appeared at around 185 Hz and 360-470 Hz. This is very visible in the spectrogram, and also in a direct comparison of the spectrum during the noisy period and a quiet period right after.

I ran two BruCo scans for the low and high noises. See

Low noise: bruco_lho_1236051018low
High noise: bruco_lho_1236050668high

The only noticeable difference is that in the high noise state, there is a teeny bit of coherence with squeezer signals. I picked one signal (H1:SQZ-SHG_PWR_RIN_OUT_DQ) and found that 

1. the signal is more noisy in coincidence with the time when DARM is noisy too
2. some wandering lines (like the 79 Hz) are common to both signals

    Got a minute this morning (thanks Jenne)to take some ITM photos under 30 watts laser. All frames were shot from a fixed point and focal length, so the images should be the same. I am looking into adding a grid or overlay to help with fixing location of the spots. Right now the best way to fix the spots locations is to use the image of the EQ stop, which one or two are visible in most frames. 

   These frames were shot varying the exposure and ISO to render a usable image. ITM-X frame #004 and ITM-Y frame #3 show the best resolution of the spots. However this is just my opinion. 

   Feedback to make these images more useful is always appreciated.         

Summary

Looking at one hour of data during the good lock of last night (47384) we can see that there is a lot of non-stationary noise at low frequency (below 30-40 Hz) most likely due to scatter light driven by the OMC ASC loops (47321)

Details

Here's a spectrogram of one hours of data from last night (using CAL-DELTAL_EXTERNAL and without compensating for the whitening, so that there's no spectral leakage from the low frequency motion).

A direct comparison of a "quiet" period and a "noisy" period is shown below (quiet is +500s from start, noisy is +3035s from start).

To better correlate the noise level with the OMC ASC motion, I computed band-limited RMS (BLRMS) of DARM in two regions: 10-14 Hz and 28-32 Hz. There is a correlation between the OMC ANG and POS signal RMS and the DARM noise. I compared the OMC ASC signals in the two "low" and "high" noise periods as above, and found that the main difference is in the amplitude of a 0.5 Hz peak:

Therefore I computed the BLRMS of the OMC ASC signals around 0.5 Hz (between 0.4 and 0.6 Hz), and compared it below with the DARM BLRMS. There is an obvious correlation between times when the OMC ASC signals move more at 0.5 Hz and higher scattered light noise in DARM.

(see WP #8111)

I accidentally blew a fuse within the HEPI panel this morning by plugging a drill into a power strip which was being powered by the HEPI panel.  Jim W. and Fil C. responded.  The fuse wasn't serviceable at the time so the affected power supply was plugged into an extension cord as an interim solution.

TITLE: 03/08 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: 7mph Gusts, 5mph 5min avg
    Primary useism: 0.03 μm/s
    Secondary useism: 0.16 μm/s
QUICK SUMMARY:

IFO unlocked. EQ around Phillippines hindering a bit. Jeff B recovered Green arm align and was waiting on DRMI. SRC (SR2) was found a bit off. It was corrected amd normal locking was resumed. We are currently at DC readout + 30W. Jeff B was in LVEA shooting the ITMs and Jenne is taking measurements.

Added the OMC ASC controls noise projections into the live noisebudget.

Projections are done by reading in the control signal of each OMC ASC loop (Pos X, Pos Y, Ang X, Ang Y), calibrating the control signal to DARM meters like a simple pendulum zpk during an excitation, then projecting the ambient control signal into DARM noise all the time.  

Each projection is shown in attachment one.
The quadrature sum of each projection (OMC ASC) is shown as the pink curve in the second attachment.

With the live noisebudget, we'll be able to tell if OMC ASC controls noise is ever unusually high.  cool

Problem with the live noisebudget: we cannot yet look at subnoisebudgets.  So I cannot look at the four traces that make up OMC ASC in a second plot.

I turned up the gains of ASC-MICH pit and yaw, and gave them each a different lowpass, and was able to get our BNS range up a few Mpcs.  I also switched to using a SOFT_P cutoff in both CSOFT and DSOFT with a corner at 10 Hz, rather than 14Hz.  These 2 things combined give us about 110 Mpcs. 

However, the ASC seemed more delicate in this situation.  I'm not sure if it was Keita in the LVEA for DIFF VCO tests (likely not) or a small amount more ground motion, but the IFO wobbled at 0.5 Hz a few times, and then eventually had a ring-up of this frequency and lost lock. 

In the attached plot, it seems like INP1, SOFT and the DC centering loops all saw this ring up at roughly the same time, starting a little more than 200 seconds before the lockloss.  It's hard to say if it's a pitch or a yaw problem.  INP1, DC3 and DC4 see the instability most stronly in yaw, while DC1 and DC2 see it more in pitch.  Other loops such as SRC2, DHARD, and CHARD all see the ring-up, but they mostly start later, after it's pretty clear in other degrees of freedom.

(Squeezing was on during this lock)

After Peter and I powered off the DBB, I ran PeterF's script to see whistles.

Probably because IFO noise was good, I was able to clearly see whistles in DCPD that correspond to the difference betwee IMC VCO and DIFF.

In the plots attached, white circles are the difference of the fundamental frequency of IMC VCO and diff VCO, yellow triangles are second harmonics.

There are visually apparent whistles in DCPD (leftmost top, 0-4 sec, 23-24 sec between 4000 and 6000Hz) and they agree pretty well with the fundamental of IMC-DIFF. There are less apparent whistles (12-13 sec between 2000 and 4000Hz, 15-16 sec between 2000 and 4000Hz) and they also agree with the fundamental of IMC-DIFF.

All visually apparent whistles in OMC PI channel (there are four such whistle traces) seem to agree well with fundamental and second harmonics of IMC-DIFF and IMC-COMM.

I went to the floor and started powering off the DIFF VCO, it was a paint to disconnect power connector from the back, and IFO lost lock (ASC instability?) about 80 second before I successfully removed both 17V and 24V connector.

I noticed that DBB interface was on,  PeterK and I went to the floor to turn it off.

For locking DBB PMC, it uses a 1MHz oscillator of some sort (probably just a canned crystal). The oscillator is ON all the time even when modulation is disabled as far as it is powered but its frequency is not monitored.

J. Kissel

I've process Craig's sensing function from last night (LHO aLOG 47354), in which he states, the data lives here:
     2019-03-07_H1DARM_OLGTF_5to1100Hz_20min.xml
     2019-03-07_H1_PCAL2DARM_TF_5t1100Hz_8min.xml
I had to finagle the exported data a bit -- the PCAL to DARM TF result appears to have 1 less frequency point (at ~5 Hz) than the DARM OLG TF result, so I just stripped the DARM OLG TF data of that frequency point. Also, there seems to have been a data point with coherence of identically zero which confused the data processing software, so I modified it to be some small non zero value.

The comparison of model to measurement is attached. The numerical answers are
   Optical gain, H_c (ct/m)                 | 3.426e+06 (+1799,-2153) or (+0.0525%,-0.06285%)
   Optical gain, H_c (mA/pm)                | 4.236     (+0.002224,-0.002662) or (+0.0525%,-0.06285%)
   Cavity pole, f_cc (Hz)                   | 394.6     (+1.418,-1.17) or (+0.3594%,-0.2965%)
   Detuned SRC spring frequency, f_s (Hz)   | 2.353     (+0.06679,-0.08249) or (+2.839%,-3.506%)
   Detuned SRC spring quality factor, Q_s   | 0.01186   (+0.003069,-0.001373) or (+25.87%,-11.58%)
   Residual time delay, tau_c (usec)        | -0.4223   (+0.9933,-0.8277) or (+-235.2%,--196%)

The systematic error above ~100 Hz is great -- likely attributed to Stefan's good work compensating the DCPDs (LHO aLOG 47257) and some further good results from fitting the high frequency poles of the OMC DCPD whitening chassis by Lilli (see LHO aLOG 47377). Impressively, the residual time delay (which can be either real unknown delay, or uncompensated high frequency poles) is consistent with zero, within 1 [us].

Low frequency is still a problem -- at the 5% level below 20 Hz, with a 1% wiggle around 80-100 Hz. The good news is -- due to my template tuning (mentioned at the tail end of LHO aLOG 47206), we're now able to resolve some of our detuning again -- and the message is, we definitely have it. given the wiggle at ~90 Hz, I'm wondering if we're on the opposite side of the SRC detuning such that we're seeing pro-spring -- so much so that the ~90Hz wiggle may be the right-half plane poles not perfectly canceling the left real zero, that normal reduce to a single pole frequency when the RSE detuning phase is very close to 90 deg (see discussion of this effect in P1600295, Section 5.2).

I'd like more data with more dense frequency points around 90 Hz and between 20 and 8 Hz to really make conclusive statements about all this, but the message is that the "simple" O2 model of the detuning is failing to replicate the features seen in this plant below 100 Hz -- at the 5% level below 20 Hz.

Most of you will argue this level of systematic error is "good enough" for the sensing function.

If you insist, then populate the CAL-CS_DARM_ERR filter (preferably in new pair of filter banks, please) with the following two filter modules.
    SRCD2N: zpk([394.6064;2.3389;-2.3668],[0.1;0.1;7000],1,"n")gain(553.54)
    Gain: gain(2.919e-07)
and set the CAL-CS_DARM_ERR gain to 1.0.

Since Craig updated the CAL-CS gains on the actuator paths (LHO aLOG 47354) with the numbers from LHO aLOG 47331 (which I argued were good on TST, but still bad on PUM), then we can also run and process the DARM Open Loop gain measurement against the model, and predict the level of systematic error that would remain if we updated the sensing function as above.

See that result attached second.
Unsurprisingy, the residual systematic error looks exactly the residual systematic error in the PUM stage reported in LHO aLOG 47331.

However, the flaws are are all below 30 Hz. So theoretically, this he above sensing function is pushed, we should have little-to-no remaining systematic error above that frequency region.

And one more thing -- you'll have to update the delay between the sensing and actuation paths to 7.0 clock cycles.
See that result attached 3rd. This is consistent with what we've used for O1 (LHO aLOG 22117) and O2 (LHO aLOG 33924). The real delay is 6.89 [16kHz clock cycles], and the difference shouldn't result in that much systematic error. I haven't yet had the time to figure out the Joe Betz / Shivaraj generation of a thiran filter (see hints at LLO aLOG 28268) that allows for non-integer delays.

Georgia, Craig, Danny, Sheila

Here are some updated noise budget plots, made for 9:30 UTC March 5th, when there was no squeezing injected. 

Some notes:

• shot noise: Although the pcal monitors at this time suggest that kappa_c (scale factor for optical gain) is  and that the DARM cavity pole, I found that the shot noise is more accurate based on the cross correlation with a cavity pole of 440 Hz, and kappa c of .  For the last few weeks I have consistenly been using cavity poles higher than the pcal monitors have said and optical gains lower than what the pcal monitor says.  
• The OMC length noise is Geogira's measurement posted here: 47286
• The frequency noise is based on Craig's projection 46864  Note that we are doing a pretty generous interpolation here, sometime we would like to get better frequency resolution for the measurement.  
• 73 Hz line: This was a time before the grounding change at EX got rid of 73 Hz line and some features around 280 Hz, so those peaks which are unexplained in this budget are no longer in DARM.  47323
• MICH P:  The MICH P ASC noise is very small in this noise budget, but will need to be updated again. We are rethinking this loop 47352 since we found that it was causing a lot of motion at 0.5Hz and contributing to the sidebands on the 60Hz line. 
• The centering loops haven't been re-measured so they aren't included here yet. neither is the SRC1 (AS 72 to SRM loop).
• MICH LSC coupling has been changing a bit while things thermalize, the ones that are included here are measured a few hours into a lock.47333

I wrote some python code to create cross-correlated DARM spectra over long, glitchy locks.
Stefan balanced the PDs recently, and we saw our correlated DARM noise was fairly high at high frequency.  Stefan supposed this was from glitches, but from this alog, this seems to not be the case.

The info we want from the cross-correlated DCPD spectrum is the correlated noise from the IFO.  We can average away the shot noise like 1/sqrt(N) where N = number of ASD averages.
The problem is we need many averages to integrate away the shot noise.  However, during these locks, we have frequent, strong ESD saturation glitches which spoil the spectrum.  
DTT is not able to "gate" the glitches, i.e. remove them from the timeseries.  This code solves this problem.

Attachment one shows a DARM ASD and DARM CSD between the OMC DCPDs during the lock last night.  I have 2000 averages with a binwidth of 0.2 Hz and 50% overlap, or 1.4 hours of data.  During this time there were 4 glitches which spoiled the spectra (the blue, purple, and green traces).  With gating we have the red and orange traces.
Attachment two shows a zoomed in gate function of one of these glitches.  The gate I apply is just a logistic function with the mean of the data added in.  The glitches are witnessed via the DARM BLRMS increasing to huge values, specifically H1:OAF-RANGE_RLP_3_OUT16 going above 100 counts.
Attachment three shows the DARM OMC DCPD data with and without the gate applied.  

Code lives in /ligo/home/craig.cahillane/Git/IFO/Crosscorrelations/scripts/gated_DCPD_CSDs.ipynb.  To run you'll have to run:
$ setupanaconda (or $ source /opt/rtcds/userapps/release/cds/h1/scripts/setup_anaconda if your .bashrc alias isn't set up)
$ source activate cragenv
$ jupyter notebook /ligo/home/craig.cahillane/Git/IFO/Crosscorrelations/scripts/gated_DCPD_CSDs.ipynb

Shoutouts to TJ Massinger for help with understanding gating.

Today, while doing some cabling for PSL Picomotors, I noticed that the clamping of hte PZT actuator doesn't look right (see attached photos).

It seems that the screws that apply the clamping force, thus constraining the PZT body between the upper vee and the lower vee (and compressing the viton damping cylinder in the process) were not sufficiently tightened.

The PZT actuator cylinder appears to be floating on top of the viton cylinder, lightly constrained by the upper vee, but not the lower one - there is an obvious 1-2 mm gap between the PZT cylinder and the lower vee, on both sides.

Stefan, Peter, Rich

It was found that the overall DC gain, and the pole-zero location associated with the second filter module of the OMC DCPD Whitening chain, was somehow dependent on input signal level.  A parametric study was done on the OMC DCPD whitening chain for different whitening filter combinations with and without DC offset.  Notes detailing the parametric study are attached to this entry.  

There were two causes of these phenomena:  
1.  Gain Change - As the DC input to the OMC DCPD Whitening amplifier (D1002559 Chassis S1101627) is varied, the DC level causes saturation in some of the DC coupled gain stages.  This saturation causes the normally high-impedance amplifier input to be fairly low due current flowing into the input protection diodes internal to each opamp stage.  This lower input resistance in conjunction with the series resistance of the FET switches produces a voltage divider with a division ratio dependent on signal level.
2.  Pole-Zero Change - The second filter module had an ECR (E1500252) performed that required a 1uF capacitor to be used.  This type of filter function is supposed to be implemented with a plastic film dielectric capacitor, but a ceramic capacitor was used instead.  The piezoelectric nature of ceramic capacitors can result in a capacitance that will change with applied voltage.  This caused the pole-zero location to vary as a function of DC level.  This capacitor was changed to the proper type and the problem went away.

Data (attached) was taken for both OMC DCPD chains by injecting signals into the input of the OMC whitening chassis (DCPD Preamps disconnected), and taking the output differentially from the analog output of the whitening chassis with the ADC cable still attached (to account for any loading effects).  This data was taken with and without a 5V DC offset to verify that there is no longer any effect on the signal path gain.

We note that the above were all small effects, but significant in the world of 1% calibratin uncertainty. The DC gain reduction with a 5 V offset (similar to the offset in NLN operation) was 0.2 dB. The errors in the filter stage with offset were -- phase: 0.6-1 degree at 50 Hz; magnitude: 0.15 dB gain difference between 50 Hz and 200 Hz.