Attached are ASD and Coherence betwix the three corner station STS2s taken at 3am local Wednesday Thursday and Friday.  These three days look very similar.  I installed STS2-A aka HAM2 on Tuesday.  Recap:

STS2-C (HAM5) has been in place for long time.  STS2-B (ITMY) is the unit returned from Stanford replacing PEM STS2 which we were using to replace our original STS2-B which is still at Quanterra for repairs.  STS2-A returned from Quanterra after a couple months in their vault where they say there was no problem.  The A unit spent time in the BeirGarten near the ITMy unit undergoing cable and chassis swaps, see 18354 for recap but nothing was consistent.

To me, STS2-A still looks like this unit has a problem.  When I look at plots from back in May, 18354, it looks even worse now.  There was better coherence in Z and X with the other units and Y was equally poor.

RobertS--do you have an opinion?

Travis S, Darkhan

Yesterday, Aug 27, 2015, we took Pcal end-station calibration measurements at both end-stations. The measurement procedure is described in T1500063 (-v5).

The following steps from the procedure have been completed at both end-stations:

• 3.1  DAC calibration
• 3.2  Setting up the current amplifier
• 3.3  Additional checks
• Appendix A.  Taking the measurements.

Rough numbers from MEDM screen logged into the record sheet (provided in appendix A of T1500063) suggest that RxPD and TxPD calibrations as well as optical efficiencies of Pcal beams at LHO EY did not change significantly compared to numbers from calibration on 2015-05-22, however we saw ~1 - 2 % drop in the optical efficiency of Pcal beams at LHO EX compared to measurement taken on 2015-05-20.

Calibration results will be reported after completing the last part of the calibration procedure, running Matlab scripts that acquire data and calculate responses of TxPD and RxPD:

• 4.1  Data acquisition and plots
• 4.2  Committing results into SVN

Record sheet papershots are attached to this alog.

Jenne, Nutsinee

There was a suspecious lockloss at SWITCH_TO_QPD at 17:50 UTC. We went through lockloss plots and found ASC-MICH was unstable right before the lockloss.

J. Kissel, D. Barker

Dave found that H1SUSETMY L3 LOCK L FM 2 (which has and remains OFF all throughout lock acquisition and lownoise) had been changed by Evan from compensating for the ESD driver's low pass filter (which is now done in the H1 SUS ETMY L3 ESDOUT $(QUADRANT) FM2/FM7 banks) to some other filter, and sadly did not name it so it shows up (appropriately) as "Unknown." I;m not sure what his intent was with this filter, but because is OFF all the time, I loaded the coefficients so that the model doesn't have a "modified filter coefficients" message which sets off all sorts of SysAdmin alarms.

I'll find out from Evan what his intent, and probably clean it up later.

the attached files show the current status of the front end code.

ER8 Day 11. No restarts reported

(All times UTC)

Summery:

Evan and Stefan were working on recentering the AS WFS when I arrived. When they were done, Evan cleared out his changes in the SDF aside from some ASC diff that occurred from dark offset scripts. I accepted the ODC Master changes from alog 20915.

Guardian brought the IFO into a full lock really quick, Evan added some DCPD Whitening, and it has stayed in lock since.

Locking:

• 10:28 Locked NOMINAL_LOW_NOISE
• 10:48 Intent bit set (though the HWS SLED IX was ON)

Itbit set at 10:48 UTC with long lock hopes.

Stefan, Evan

We made another attempt at using 90 MHz to center WFS AS B.

This time we turned up the whitening gain to 45 dB, which gave a healthy number of counts on each quadrant. We then redid our dark offsets, which were significant at this whitening gain. [We actually redid the dark offsets for all the REFL and AS WFS signals using the script in the userapps repo.]

Then in DRMI, we phased each quadrant to put most of the power in I. At this point we saw that the centering signals provided by these 90 MHz quadrants (pitch and yaw) were slightly different than the dc centering signals for AS B, so we switched the centering over to these signals (a relative gain of −0.003 is required between these 90 MHz signals and the dc signals). Things seemed fine in DRMI (the sideband buildups all changed slightly, but it was hard to say whether they were better or worse), but when we tried the CARM reduction sequence, the new centering ran away on the DARM WFS step.

So instead, we went to full lock at 2 W with the old centering scheme and switched over again to the new 90 MHz AS B centering. Things again seemed fine.

We weren't quite sure what to do about the BS/SRM matrix elements. In the end we tried using AS B 36 I&Q only to control these loops (i.e., no mixture with AS A 36), and this was fine at 2 W, but we lost lock immediately when trying to power up.

C. Cahillane, D, Tuyenbayev

In a previous alog alog 20946 I showed preliminary carpet plots of ER7 strain uncertainty based on changes in the calibration parameters |kappa_tst|, φ_kappa_tst, |kappa_pu|, φ_kappa_pu, kappa_C, f_c.
Here are some updated plots.  (Plots 1 - 6)

The data is now low-noise, and is dewhitened.  This gives much nicer, more accurate results.
I have been working to reproduce Darkhan's carpet plots from T1500422.  The method he uses to find error in Delta_L_ext is as follows:

delta Delta_L_ext =  C_true / (1 + G_true)     
                             ------------------------------
                                        C / (1+G)

where C_true and G_true are the quantities where kappa_tst, kappa_C, and f_c are varied.

The method I use to find error in strain is:

delta strain = (1 / C_true) * d_err + A_true * d_ctrl
                      ----------------------------------------------
                                  (1 / C) * d_err + A * d_ctrl

Plot 7 is Darkhan's method of computing error from changes in kappa_tst reproduced by me.
Plot 1 is my method of computing error from changes in |kappa_tst|.  They should be the same.  They aren't.

We are searching for potential reasons behind the structure found in Darkhan's plot.  Something odd may be going on at the UGF of the CLG, causing the low magnitude error near 65 Hz and low phase error near 35 Hz.
My plot, on the other hand, has no low error region in phase, in fact it has a maximum near 35 Hz, and has a tilted low magnitude error region between 30 and 40 Hz.

I am investigating this difference now.

23:00 (16:00) Darkhan and Travis at end Y running PCAL measurements. Leo running charging measurements for ETMX.
23:36 (16:36) Kiwamu to electronics room to measure transfer function of whitening filter
23:40 (16:40) Evan to CER to run measurement with network analyzer
23:41 (16:41) Darkhan and Travis done at end Y, moving to end X
00:09 (17:09) Nutsinee to TCS X to take picture of control box
00:15 (17:15) Nutsinee back
00:44 (17:44) Evan done, Leo done
01:18 (18:18) Travis and Darkhan done at end X
01:37 (18:37) Travis and Darkhan back

02:13 (19:13) Kiwamu and I start locking
Trouble locking on DRMI
Ran through initial alignment starting with CHECK_IR
Lost lock engaging ASC WFS in LOCK_DRMI, Kiwamu had to revert phase settings for AS 36
Lock loss on bounce mode
03:17 (20:17) h1fw2 crashed and restarted
04:48 (21:48) Locked on Low Noise, Darkhan running calibration measurements

05:22 (22:22) Darkhan done, Stefan and Evan starting wiggling cables test
05:26 (22:26) Kiwamu to CER to clean up previous work
Kiwamu is back
06:22 (23:22) h1fw2 crashed and restarted
07:00 (00:00) handing off to TJ, Evan and Stefan are investigating RF

Other
end Y dust alarms
smelled a lot of smoke in hallway, went up to roof, didn't spot any fires

J. Kissel, K. Kawabe

Similar to what is shown and briefly mentioned in LLO aLOG 18406, I've done a comprehensive transfer function study between the DAC and ADC Duotone timing signals from the following IO chassis:
h1lsc0 (which houses the ADC for the OMC DCPDs),
h1susex & h1susey (which house the DACs for the ETM QUADs)
h1iscex & h1iscey (which house the ADC for the PCAL RXPDs)
h1oaf0 (which receives the DARM_ERR and DARM_CTRL channels from the OMC model over IPC)
Recall that these Duotone signals are merely *checks* on the system that is actually providing the time signals for the DAC / ADC cards, which is the 1 PPS signal from the local timing fanout in the building (which in in turn receives its 1 PPS from the timing master in the corner station which is GPS synchronized). The results indicate that -- although there is a few tens of micro-second offset between all of these front-ends, they appear to not *differ* by more than a few hundred nano-seconds, and typical in the tens of nano seconds. This is consistent with what Shivaraj found when making the comparison between his l1iscex and l1iscex against l1oaf0. Recall that our requirement is that the timing uncertainty is no greater than 25 [us], so at least the DuoTone signals between each IO chassis fall in well-below this. What we would need to do to confirm that the actual front end timing is to then compare this DuoTone against the "digital world" 1 PPS, as Keita has done for the ADC and DAC DuoTone signals for all of the above mentioned chassis in LHO aLOG 20962. His aLOG also indicates a ~100 [ns] difference between chassis, on top of the ~7 [us] offset.

So far, so good in timing land.

Details:
---------
For all measurements, I used h1lsc0 ADC and DAC duotone singals as the reference (TF denominator), and the others as the response (TF numerator). Below are the results for the phase relationship between each at 960 [Hz] (the results are the same within the precision stated for the 961 [Hz] line):
          xxxx ADC      xxxx DAC      xxxx ADC     xxxx DAC
          --------      --------      --------     --------
          LSC0 ADC      LSC0 ADC      LSC0 DAC     LSC0 DAC

h1lsc0       n/a         -26.42        +26.42         n/a
h1susex    +5.14         -21.27        +26.45       +5.14
h1susey    +5.13         -21.28        +26.44       +5.13
h1iscex   +0.008         -21.29        +26.45       +5.13
h1iscey   +0.028         -21.27        +26.47       +5.14
h1oaf0    -0.013         -21.34        +26.43       +5.07

which we can turn in to an equivalent delay (or advance) between the two front end timing signals, with 1e6 * (pi/180) * phase_deg * / (2*pi*961 [Hz])
          xxxx ADC      xxxx DAC      xxxx ADC     xxxx DAC
          --------      --------      --------     --------
          LSC0 ADC      LSC0 ADC      LSC0 DAC     LSC0 DAC
            [us]          [us]         [us]          [us]
h1lsc0       n/a         -76.4         76.4          n/a
h1susex     14.9         -61.5         76.5          14.9
h1susey     14.8         -61.6         76.5          14.8
h1iscex     0.023        -61.6         76.5          14.8
h1iscey     0.081        -61.5         76.6          14.9
h1oaf0     -0.038        -61.7         76.5          14.7

Templates live in 
/ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/ER8/H1/Measurements/Timing/
2015-08-27_H1LSC0_to_CALCS_DuoTone_TFs.xml
2015-08-27_H1LSC0_to_ISCEND_DuoTone_TFs.xml
2015-08-27_H1LSC0_to_SUSEND_DuoTone_TFs.xml
of which I attach an example.

New EXCITATION_OVERVIEW screen has been created:

$USERAPPS/sys/common/medm/EXCITATION_OVERVIEW.adl

Hopefully this can help in tracking down excitations that could be preventing the system from entering READY:

The two columns show the front-end excitation monitors (FEC, left) and the ODC monitors (ODC, right).

NOTE: ONLY ODC monitors count towards OBSERVATION READY at the moment.

The FEC monitors are there for reference, and for completeness.

The EXCITATIONS box in the OBSERVATION_OVERVIEW screen now contains a link to this screen.

Evan, Sheila

While the IFO was down for some calibration measurements, we made another attempt at phasing AS36. 

We first redid the dark offsets, this was an important step.  Then we locked the bright michelson with 22 Watts of input power. 

We steered the beam onto each quadrant of AS_A by maximizing the DC counts, then phased 36 to minimize Q.  There were several things that made this seem much more promising than any of our previous attempts to phase these WFS:

• The amplitudes of the signals in all quadrants were similar to within 5%
• The phases are all within 20 degrees of each other, as you would expect since the cable lengths are supposed to be matched.
• The phase that minimized Q also maximized I.
• The phasing was not very sensitive to the pointing onto the diode, as it is with DRMI locked.  
• When we turned on the centering, the phase required to minimize Q changed by 40 degrees, but the change was the same for all quadrants, and the signal levels were still similar on all 4 quadrants.  

Both of these things are firsts for these WFS as far as I'm aware, so this seemed like real progress.  

We started to do the same procedure for AS_B 36, but after we phased the first quadrant the phase jumped.  Kiwamu was in the rack working on the calibration measurements of the DC PDs at this time and reported that he had plugged a signal into the patch panel.  After this I looked at the A signals again, and they did not make sense any more. I tried repeating the procedure above for A, and found that the phases needed to minimize Q with the light maximized on each quadrant had changed by -15, -10, 0, and -20 degrees for quadrants 1,2,3,4.  

It seems like we need to make a thorough check of the HAM6 racks before we continue trying to make sense of AS WFS.  

Just for the record the momentarily sane phasings were:

I have created a DTT template that makes it easier to decide when it's okay to turn on more OMC DCPD whitening.

Evan wrote an alog some time ago about the new OMC DCPD whitening on/off guardian states (alog 20578), and Cheryl and Evan made some notes on when it's okay to go to these new states (alog 20787).

As of right now, the guardian will automatically turn on one stage of whitening, but we get better high frequency noise performance if we add a second stage.  However, if some mode (eg. a violin mode) is rung up, then we can't add the second stage of whitening without being in danger of saturating the ADC.  So.  The new DTT template should help decide when it's okay to add the second stage.

The template is /ligo/home/ops/Templates/dtt/DCPD_saturation_check.xml (screenshot below). The template should be run after we have arrived at NOMINAL_LOW_NOISE for the main lock sequence.  If the dashed RMS lines are below the green horizontal line, it's okay to add the second stage of whitening.  

To engage the second stage of DCPD whitening:

Open the full list of guardian states for the OMC_LOCK guardian, and select "ADD_WHITENING". It will take a minute or two, and automatically return to the nominal "READY_FOR_HANDOFF" state.

Evan Stefan Daniel

The second EOM driver was installed in the CER using the 9MHz control and readback channels. The first attached plot shows the DAQ readback signals. Both drivers show the similar noise levels for the in-loop and out-of-loop sensors. They are also coherent with each other as well as ASC-AS_C! The in-loop noise is clearly below which would indicate that the signal is suppressed to the sensor noise. The measured out-of-loop noise level is also a factor of 4 higher than the setup in the shop.

The second plot shows the same traces but this time the ifr is feeding the EOM driver in the CER. As expected its out-of-loop noise level is now consistent with measurements in the shop and no longer coherent with the unit in the PSL.

We were starting to suspect that we are looking at down-converted out-of-band noise...

This entry is meant to survey the sensing noises of the OMC DCPDs before the EOM driver swap. However, other than the 45 MHz RFAM coupling, we have no reason to expect the couplings to change dramatically after the swap.

The DCPD sum and null data (and ISS intensity noise data) were collected from an undisturbed lock stretch on 2015-07-31.

Noise terms as follows:

• Shot noise
  • For 20.0 mA dc on the DCPD sum, we expect a shot noise of 8.0×10⁻⁸ mA/Hz^1/2.
• Dark noise
  • Dan and I measured this a few months ago. In full lock we use one stage of whitening, which amounts to a dark noise of 1.5×10⁻⁸ mA/Hz^1/2 or so above 100 Hz. We have at times experimented with two stages of whitening, but it requires some vigilance regarding the violin modes.
• Intensity noise
  • Coupling was measured à la Kiwamu by leaving the outer loop off and driving the inner-loop excitation point. For the noise estimation, I used the outer loop out-of-loop sensor. Since Sudarshan et al. previously found that this is artificially high, this estimation is an upper limit (though probably no more than a factor of 3, given Sudarshan's plot).
• Frequency noise [CARM sensing noise only]
  • Previously (i.e., when we locked CARM using the in-air REFL sensor), I estimated the coupling by looking at the TF in-vac REFL to DARM, and for the frequency noise estimation I used the noise of in-vac REFL as an upper limit for the frequency noise. Since we now lock with in-vac REFL, which has more light on it than in-air REFL does, I do not expect that the noise of in-air REFL is a particularly useful upper limit for the frequency noise.
  • Therefore, I have tried to instead estimate the sensing noise in CARM (from in-vac REFL, the summing-node board, the common-mode board, and PDH shot noise) in V/Hz^1/2 and propagate it (using the Izumi/Sigg expression) into a frequency noise in Hz/Hz^1/2. For the CARM optical TF I use 12.7 W/Hz at dc, with a pole at 0.48 Hz.
  • Then I have injected noise into CARM and looked at the TF from the residual of the excitation into DARM. This is the coupling TF needed to propagate the estimated sensing noise to DARM, assuming the CARM gain is high (this isn't quite true at high frequencies; the ugf is 17 kHz or so, and the gain does not exceed 20 dB until 3 kHz).
  • Since this includes sensing noise only (and not, for example, FSS noise), I have labeled it as a lower limit. In fact, the coherence between REFL 9Q and the DCPD sum is about 0.04 around 7 kHz, perhaps suggesting a frequency noise contribution of 2×10⁻⁸ mA/Hz^1/2 or so. More investigation required.
• Oscillator phase noise [not included here]
  • Stefan and I measured the coupling of the 9 MHz RF source into DARM, and using the expected performance of the OCXO estimated the noise in DARM should be 2.8×10⁻¹⁰ mA/Hz^1/2 at 1 kHz. This is quite low (and not shown on the plot).
  • This number should be replaced with Alexa's and Daniel's measurements of the phase noise. An even more satisfying number could be made by trying to measure the 9 MHz and 45 MHz phase noises in situ, closer to the EOM (e.g., at the output of the distribution system on the ISC rack).
• Oscillator amplitude noise [45 MHz only]
  • In this case we know that the 45 MHz RFAM is the dominant contributor (other than shot noise) to the DARM noise above a few hundred hertz. Here I use Stefan's estimate of the RFAM-induced photocurrent (1.8×10⁻⁸ mA/Hz^1/2), which (as he notes) is not enough to explain the excess between sum and null.
  • However, based on tonight's measurements using the new EOM driver readback, it seems that 45 MHz RFAM is enough to explain the excess. Perhaps Stefan's measurement is an underestimate, since it was done at the output of the distribution system and did not include the final rf amplifier before the EOM.
  • As for 9 MHz RFAM, Stefan and I made an estimate of the coupling from the 9 MHz source into DARM. Based on the specified performance of the OCXO, the expected noise in DARM is quite small. However, it would be better to look somewhere further downstream, as Stefan did (although I think he said the measurement was not that clean). This noise is not estimated in the plot.

The downward slope in the null at high frequencies is almost certainly some imperfect inversion of the AA filter, the uncompensated premap poles, or the downsampling filter.