WP 5489

I have update the violin mode filters in CAL CS in order to make them more accurate. This will impact on the calibration at sub-percent level at around 30 Hz.

Joe B pointed me out that the way my matlab script (alog 21322) handles violin's zpk was not ideal (i.e. I was implicitly assuming certain ordering in the zeros and poles in zpk data format). I corrected the script as was already done in Livingston (LLO alog 20512). This resulted in somewhat better accuracy for PUM in 1-100 Hz . The attached screenshots are the new filters and discrepancy between the full ss model and the installed discrete filters. Compared with the one I previously reported in alog 21322, the magnitude of PUM is now somewhat better. The magnitude of PUM at 30 Hz is now more accurate with a very small discrepancy of 0.08 % (which used to be 0.2 % discrepancy ), and it is also more accurate at 100 Hz with a small discrepancy of 0.65 % (which used to be 2.4 %). I do not expect any noticeable change in the binary range with this update.

I have installed the new filters and loaded the coefficients in CAL-CS.

Bubba and John want to drive down the Xarm, so I've taken the IFO to commissioning/maintenance. Otherwise, no work is currently being done on the instrument.

• Title: 09/14 OWL Shift: 7:00-15:00UTC (00:00-8:00PDT), all times posted in UTC
  

• State of H1: Recently recovered from a lockloss due to a 4.7M earthquake in Oregon. Observing at 68 Mpc.
  

• Support:
  

• Shift Summary: Locked and observed most of the shift. The BNS range dropped from 73 Mpc down to 66 Mpc in ~5 hours. Only three ETMY saturations since shift started (not including the saturation caused by the earthquake).

• Incoming Operator: Jim

• Activity Log:

• 7:00 IFO locked. Intent bit commissioning. Jeff K. updating filters, Stefan and Evan working on calibration and OMC mode matching. Sorry I forgot the transition summary.

• 7:36 Intent bit set to Undisturbed.

• 7:49 Briefly went to commisioning to close the beam diverter before I realized it was already closed.

• 14:00 Lockloss due to 4.7M earthquake in Lakeview, Oregon. Only SUS OMC SW watch dog tripped.

• 14:28 Locked again at NOMINAL_LOW_NOISE. There's a tall peak around 18 Hz (another roll mode?). I watched to make sure it's being damped before setting intent bit to Undisturbed.

• 15:00 Handing off to Jim.

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There's a huge spike in seismic activity. No earthquake report from Terramon. Not sure what caused the lockloss.

The BNS range has been dropping slowly for the past three hours as the seismic noise goes up -- probably due to increasing wind speed (slightly above 20 mph at the moment). Saturation alarm complains very little. Hardly any glitches on DMT Omega. Nobody else on site. Quiet shift so far.

Stefan, Evan

We spent some time today trying to estimate the amount of carrier power (00 or otherwise) in HAM6 in full lock. Stefan had previously estimated about 270 mW of non-45-MHz light entering HAM6, based on AS_C calibration. This seemed high to us, since we should expect < 150 mW of carrier: 25 mW or so of 00 carrier (based on the DCPD sum), and 110 mW or so of other carrier (23 W input power × 0.88 input chain throughput × 37 W/W recycling gain × 150 ppm contrast defect, taken at low power).

[Does Dan have updated numbers for the contrast defect (and the 9 MHz AS port content) based on new 23 W modescans???]

According to Dan, there is a factor-of-two error in Stefan's AS_C calibration, which would bring the estimated carrier power down to 135 mW [but this is problematic; see below]. Since one can never have too many calibrations of the same diode, I'm going to use 60×10³ ct/W for the calibration [referred to watts of power entering HAM6], based on 1638.4 ct/V (ADC) × 0.78 A/W (responsivity) × 2 V/V (single/differential conversion) × 10^36/20 V/V (whitening) × 370 ppm (optical throughput to AS_C).

We did a few different measurements.

DARM offset sweep

We locked the IFO on RF at 23 W, locked the OMC (with dither on), and swept the DARM offset by a few tens of picometers (positive and negative). From these data it should be possible to compute a calibrated curve of current versus DARM offset, as Dan has done previously at lower power. But even without that, we can already infer 2700(640)×10³ ct on AS_C for 39.5(6) mA on the DCPD sum [= 68(16) ct/mA]. Assuming an AS_C calibration of 60×10³ ct/W, and noting that the amount of photocurrent at zero DARM offset is small (< 1 mA), this suggests that for 20 mA of DCPD sum we have 23 mW of carrier from the arms entering HAM6. This seems unphysically low, since we already expect 26 mW of carrier based on a DCPD responsivity of 0.75 A/W. Either way, something about the numbers in HAM6 doesn't hang together, which is a conclusion that Koji and Dan already came to based on single-bounce power budgeting.

I believe we expect at least 30 mW coming into HAM6 under normal operation, since we expect at least 14 % readout losses, not including the quantum efficiencies of the photodiodes or anything upstream of the OFI. [31 mW × (1 − 0.14) × 0.75 A/W = 20 mA.]

[For this measurement, we notched out the 332 Hz pcal line in the EX drive, so it is visible in the DCPDs. So this can be used to estimate the optical gain at each DARM offset.]

DCPDs vs AS_C vs OMC REFL

As a second test, we modulated DCPD sum at 8 Hz by driving OMC-READOUT_X0 while watching AS_C and OMC_REFL (we again opened the beam diverter for this). First, from the quiescent spectra alone we could already calibrate the PDs against each other; the calibrations are roughly 70 ct/mA for AS_C sum / DCPD sum and 2 ct/ct for AS_C sum / OMC REFL A sum. With AS_C and OMC REFL A calibrated (attachment), the strength of the line in OMC REFL A appears with a factor of 0.012 relative to the line in AS_C, suggesting that >98% of the modulated DARM light is coupled into the OMC.

J. Kissel, M. Evans

After downloading the work that Matt has done (LHO aLOG 21424)carefully fitting the nasty actuation function we'd discovered (LHO aLOG 21419), 
1) I've plotted it myself, to make sure I understand what Matt has given me
2) Inverted it, made sure I got the same residuals he did
3) Discovered the fit contained a pole at 15 [kHz], played around with the implications of moving the pole to the highest frequency foton accepts (8190 [Hz])
4) Painstakingly copied over to foton, because the fit poles and zeros did not all fit into one filter bank, and *I* wanted to control how they were divided between banks
5) Exported the foton filter, loaded it back into matlab, and fine tuned the necessary advance.

T'was a lot of work, but we have something installed and running. Now we beat the heck out of it to find the bugs, while we (in parallel) push injection through the photon calibrator forward.

In addition to this pain-in-the-tuckus inversion process, Joe Betz -- on the phone for other reasons -- brought up another excellent point: LHO does NOT use linearization on the H1SUSETMY electrostatic drive. While we get away with doing so during a quiescent lock, any loud control signal will expose the non-linearity (quadratic) nature of the ESD. We think we've already seen some evidence of this while measuring DARM open loop gain transfer functions. Yuck. PCAL has no such problems (in fact, though it uses an inherently quadratic AOM, it has analog electronics to ensure its linearity).

Note: Contrary to all of my suggestions, Matt *has* included and fit inverses to the notches in the actuation function. This means, while we will likely have the same amplification problems around the notch frequencies (see, e.g. LHO aLOG 20904), the phase reconstruction of all regions except this frequency is within 5 [deg]. Since there seemed to be competing interests in the CBC group on whether or not to include the inverse of the notches, I've left them in. If we need to remove them, and somehow retain the phase reconstruction in the surrounding frequency regain, then it'll be another day's worth of work between Matt and I. But honestly, if it comes to that, we're switching to PCAL.

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Details
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Not much to say on the design here -- Matt did almost all of the work. The only two gotchas were as mentioned above: I had to move the highest fitted pole down and I must split the filter in to two parts. For the splitting, I chose to put everything from the (inverse) beam-splitter violin mode notch at ~300 [Hz] into the first module ("O1.A" in FM3), leaving the (inverse) QUAD violin notches and 950 [Hz] elliptic low-pass for the next ("O1.B" in FM4).

After exporting the product back into matlab, I tuned the timing advance to account for the pole that I'd moved down from the "ideal" fit. 
Thus, all analysis should assume the waveforms need a timing advance of 255 [us]. 
Also, of course exactly surrounding the frequencies of the notches at ~300, 500, 1000, and 1500 [Hz] there is greater than 50% mismatch between the real SUS and the inverse actuation filter. 

The first .pdf attachment shows 
(pg 1) my reproduction of Matt's filter comparsion (over a little bit wider a frequency band), 
(pg 2) the inverse function, both of Matt's ideal fit, and of the reconstruction from foton, and 
(pg 3) a zoom in on the interesting region between 100 [Hz] and 2000 [Hz].

The second .pdf attachement shows a bode plot showing the breakdown of the filter between FM3 and FM4, and compares the filter against the ER7 filter. 

Noteably, there is *not* a sign difference between the new filter and ER7 or the H1 Mini-run filter, but the phase has rotated once around the unit circle.  For a clear demonstration of this, see the third .pdf attachment. Recall, folks have been worried about the hardware injection filter since ER7 (see LHO aLOG 19948 for complete summary). I'm not sure how this ~360 [deg] rotation could be mistaken for a sign flip -- but maybe I'm just carrying around the term that was used during the initial guess of what the problem was, even though the real problem was more subtle. I've confirmed that neither the design string nor the "alternate" (i.e. as what foton interprets your design) show a minus sign in the gain.

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Configuration control:
(1) Stefan and I updated the ODC state vector for the hardware injections, since flipping the FMs from 2 to 3&4 make the "HARDWARE filter stated OK" light go red. To make green, we changed the recently modified bit status check from 0x1602 to 0x160c. 
(2) I accepted the new filter bank state (and ODC bit word) into both the OBSERVE.snap and into the SAFE.snap for the CAL-CS front-end model.
I attach ascreenshot of the filter bank as I've left it.

• 9/13 @ 7:53utc Verbal_Log died on video5 (restarted on 9/14 @4:21) 
• 23:24:  NOMINAL_LOW_NOISE (first time post-big-quake)
• 1:25 LOCKLOSS
  • Restored SR3 Pitch value
  • Had issues Finding IR a few times tonight
  • During DRMI acquisition alignment/flashing looked bad
  • Locked PRMI & tweaked BS & PRM (did not do PR2)
    • When realigning SRM it tripped its Software Watchdog (Jim also mentioned having SRM saturations.  This is a new feature.)
    • Will try PRMI again, and this time try PR2 (& maybe PRE3?)
• Evan discovered high frequency noise for SRM
• 2:30  Went CER to power cycle (white button on back) of SRM Driver box (still high freq noise after power cycle)
• 5:28 NOMINAL_LOW_NOISE
• 5:36  Loading coefficients for hardware injection filter (jeff)
• 6:02  Lockloss
  • Had to help FIND_IR for ALS_DIFF
• 6:36  NOMINAL_LOW_NOISE & Evan/Stefan starting OMC measurements
  • Remember to Close OMC REFL Beam Diverter before going to OBSERVATION!!!

Addendum Notes

Bubba will address Chiller Yard alarm noted Sat night when he's in on Monday (change alarm setting?)

H1 Problems of the day:

• These are items Jim mentioned to me:
  • HAM5 ISI Watchdog rogue excitation watchdog was not trivial to reset
  • SRM saturating and tripping HAM5ISI:  This is a new feature
  • ALSy problems which were remedied by PR2 tweaks

SDF Diffs

• optical align offsets changed to not monitored for:  etmx, itmx
• PR3 was clicked to NOt Monitored, but sheila and I decided we should keep monitoring this channel
  • Idea is to Monitor SUS biases for optics we rarely touch (so that if they are touch, we get an SDF notification)
• SUSIM:  Cheryl changed alignment and then Jim changed back.  So I will go back to ACCEPTING their alignment in SDF(since these aren't changed much and we can monitor when they are changed)

SR3 Cage Servo

Locked H1 without this servo engaged (SR3 was saturating).  Sheila was able to slowly engage this while in lock.  The H1:SUS-SR3_M1_OPTICALALIGN_P_OFFSET SDF setpointpoint is 563.7, but to get this servo to go, it was moved to 562.2 (Sheila called this a "hot" state for SR3).  For future locks we want to go back to the "cold" value of 56.7.  This was done after the 1:27 Lockloss.  

I've made the GDS correction filters for the remaining of ER8 and O1.  These filters include only the corrections discussed in alog #21386 with the addition of the inverse DAQ downsampling filter which must be applied to the actuation chain (downsampled from 16kHz to 4kHz when written to frames).  They are meant to be applied as corrections to the output of the front-end CALCS channels {IFO}:DELTAL_CTRL_DQ (or {IFO}:DELTAL_CTRL_TST_DQ+{IFO}:DELTAL_CTRL_PUM_DQ+{IFO}:DELTAL_CTRL_UIM_DQ) and {IFO}:DELTAL_RESIDUAL_DQ.  In addition to the correction filters, the CALCS channels must also be dewhitened with dewhitening filters.  Plots comparing the frequency response of the FIR correction and dewhitening filters to the freuqency models they are based on are attached.  These filters are made using the following code checked into the calibraiton SVN:

aligocalibration/trunk/Runs/ER8/Common/MatlabTools/create_partial_td_filters_ER8.m

I've done a comparison of the spectrum of calibrated h(t) data from GPS times 1126003500-1126003700 from both the GDS pipeline and CALCS front-end calibration. Plots of the two spectra on top of each other and of the relative difference between the spectra are attached.  The differences between the spectra are consistent with the addition of the high-frequency corrections and accurate time delays in the GDS pipeline.  Note: For this comparision, the calibration factors have not been applied to h(t).

Cregg Yancey ran the hardware injection cross-checking code he has been developing, and noticed a curious discrepancy in the periods marked by the burst injection ODC bits at H1 versus L1 for the hardware injection at GPS 1125390500.  I investigated more closely, reading ODC bitmask time series from the recorded raw frame file along with the hardware injection excitation record, H1:CAL-INJ_HARDWARE_OUT_DQ.  I focused in on the bits which indicate burst hardware injections: bit 25 of H1:ODC-MASTER_CHANNEL_OUT_DQ (sampled at 16384 Hz) and bit 11 of H1:CAL-INJ_ODC_CHANNEL_OUT (sampled at 256 Hz).  What I found is rather startling: these ODC bits "flicker" between 0 and 1 around the time of the injection in a way that they definitely should not.  Each bit is supposed to equal 1 when there is no injection (meaning two or more consecutive samples with excitation amplitude less than 10^-200, according to LLO alog 18913) and 0 when there IS an injection.  The bit flickering pattern shows no obvious connection with the excitation time series.

The first three attached plots show what I found for the injection around GPS 1125390500, at three different time scales.  This is the "too-loud burst" injection which has been studied (see https://wiki.ligo.org/LSC/JRPComm/G181472) and seems to have been anomalous due to saturating the actuation chain.  However, the ODC bit setting should only be based on H1:CAL-INJ_HARDWARE_OUT_DQ, unrelated to saturation occurring anywhere later in the chain, so I believe this is a different problem.  Also, another injection at GPS 1125400500 seemed fine as an injected burst (it was a 69 Hz sine-gaussian) but still has the crazy ODC bit behavior, as shown in the last three plots.  There are even alternating "stripes" which are very odd.

Although I'm only showing plots here for H1, the problem occurs in a similar (though not identical) way in L1 data.  Therefore it is NOT restricted to one site.

Also, this bit problem did NOT occur for the ER7 injections; we checked the bitmask transitions and they all made sense.  It seems to have been introduced since then.  Perhaps the model code update described at LLO alog 18913 is not working as expected?

• Title: 9/13 Day Shift: 17:00-23:00UTC

• State of H1: Trying to lock

• Support: Jenne came in early, Sheila later

• Shift Summary: Bad shift. Spent most of it changing alignments, resetting alignments, watching futile atttempts to catch DRMI.

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• Activity Log:

• I came in and helped Cheryl reset HAM5 ISI, which is difficult, you have to reset the watchdog and the rogue excitation watchdog. Reisolating will probably require putting GS13s in low gain as well.

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• Otherwise I spent it redoing alignments, and didn't get around to keeping a log, but Jenne and I were the only ones doing anything on the IFO, mostly.

Dan, Evan

This evening we made a qualitative study of the coupling of beam jitter before the IMC into DARM.  This is going to need more attention, but it looks like the quiescent noise level may be as high as 10% of the DARM noise floor around 200Hz.  While we don't yet understand the coupling mechanism, this might explain some of the excess noise between 100-200Hz in the latest noise budget.

We drove IMC-PZT with white noise in pitch, and then yaw.  The amplitude was chosen to raise the broadband noise measured by IMC-WFS_A_I_{PIT,YAW} to approximately 10x the quiescent noise floor.  This isn't a pure out-of-loop sensor, and since we were driving the control point of the DOF3 and DOF5 loops of the IMC alignment channels we will need to work out the loop suppression to get an idea of how much input beam motion was being generated.  Unfortunately we don't have a true out-of-loop sensor of alignment before the IMC.  We may try this test again with the loops off, or the gain reduced, or calibrate the motion using the IMC WFS dc channels with the IMC unlocked.  Recall that Keita has commissioned the DOF5 YAW loop to suppress the intensity noise around 300Hz.

The two attached plots show the coherence between the excitation channel (PIT or YAW) and various interferometer channels.  The coupling from YAW is much worse: at 200Hz, an excitation 10x larger than normal noise (we think) generates coherence around 0.6, so the quiescent level could generate a few percent of the DARM noise.  Looking at these plots has us pretty stumped.  How does input beam jitter couple into DARM?  If it's jitter --> intensity noise, why isn't it coherent with something like REFL_A_LF or POP_A_LF (not shown, but zero)? 

The third plot is a comparison of various channels with the excitation on (red) and off (blue).  Note the DCPD sum in the upper right corner.  Will have to think more about this after getting some slpee.