Switched to true integrator: FM1: zpk([0.01],[0],0.01,"n") FM2: zpk([],[0.01],-1,"n") (was old FM1) Gain 0.1 Added all of this to Guardian and SDF.
It seems like Detchar must already be aware of this, but we are having huge glitches durring this lock long lock stretch, which show up in auxiallary degrees of freedom. We were wondering if anyone has checked for things like DAC crossings, or saturations.
Note, we're on a 20 hour lock stretch!
And the previous lock was also long at around 18 hrs.
The relock time between these 2 long stretches took ~1 hour.
Nice.
(Now we just need a trendable range channel...)
Since this was a feature we had in iLIGO, why did we devolve?
I have set the Intent Bit to Commissioning for some measurements by Elli.
Sudarshan reports that a PCal line was turned off sometime last night. He is turning it back on at 17:53.
Darkhan, Sudarshan
Pcal Lines got turned off last night during a pcal sweep measurements (LHO alog 20734 and 20732) because the optical follower servo got unlocked. We turned two lines one at 36.7 Hz and the other one at 331.9 Hz back on. We ramped it slowly to avoid any lock loss but we still saw some drop in the range. We left the higher frequency line at 1083.7 Hz off for now. We will turn this back on during the comissioning period or next lockloss opportunity.
Attached is a trend of Optical Follower Servo error signal showing when the lines got turned off. (around 2015-08-21 07:20:00 UTC)
Are we meant to be able to see the PCal lines in the normalised spectrogram of DARM? You can see them disappear and turn on again at about the times you mention, see the first plot (this is GDS strain). Also PCal End Y doesn't look so happy, see second plot. Plots were taken from the PCal part of the summary pages
Yes, Pcal line are supposed to appear in h(t).
Also, the third line at 1083.7 Hz is turned back on after the lockloss.
What's the best way for Operators to confirm whether PCal (and DARM) Cal Lines are present? (seeing Excitation on CDS Overview? looking for lines on DARM spectra? Navigating to Calibration Line medms?)
Let us know and we can put this in checklists for operators to check.
I made a DTT template which has all the calibration lines on it. May be we can arrange to display this on the screen (A screenshot is attached.). The template sits on the following location.
/ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/ER8/H1/Scripts/Templates/ Calibration_line_template.xml
The other way is to head to PCAL medm screen and look at the OFSPD plot on the screen. If there is no excitation this plot should be flat.
With Vern's approval, Commissioners have opened some shutters to return to a closer state to yesterday's. This resulted in a very brief (couple of minute) Intent Bit switch at 17:40. It is back to Undisturbed.
ER8 Day 4
No restarts reported
At 17:07, I accidentally clicked a Guardian state request while doing some Dataviewer work. While this did not effect the state of the IFO (since there is no path out of Low Noise), it did trip the Intent Bit out of Undisturbed. During this brief downtime, Betsy and Stefan took the opportunity to update a few SDF diffs. We are back to Undisturbed as of 17:27. This is a good reminder of the power of a stray mouse click.
(Keita writing)
While Betsy was checking SDF status she found that some ASC signals were routed to ASC-DC5 only in YAW while output matrix elements for DC5 are all zero.
It seems to me that somebody used DC5 matrix elements to write down the previous SRC1 sensing matrix when they had to change it, knowing that DC5 is not used at LHO, and forgot to delete the "memo". Sensing matrix doesn't look like a good place to store this kind of stuff.
It is a very convenient method for looking at different linear combinations of WFSs in real time (e.g., with striptool) when trying to pick out a new error signal. But certainly we should clean up after ourselves when done.
Went through the SDF to see if I could make sense of the differences on there. I did not make anything GREEN (i.e. I did not ACCEPT or REVERT anything because I'm not sure whether we want Operators to do this or Detector Engineers to do that).
Here are some of my notes of Differences we have by subsystem:
SUSITMY
SUSITMX
SUSETMX
SUSETMY
SUSSR3
LSC
ASC
OMC
CALCS
Lots of channels here. Seems like many can be ACCEPTED
As usual, the SDF stuff just needed some investigation. During the last few Intent drops, I cleared some SDF stuff in Corey's alog 20736. Usually we don't have to go into such detail, but since there were a lot of question marks by each, I am adding a few notes of why things were accepted below.
Here's what I have found after hunting things down and double checked a few things with TEAM-COMMISS:
ACCEPTED New violin stuff SUSITMY
ACCEPTED New violin stuff SUSETMX
ACCEPTED New violin stuff SUSETMY
ACCEPTED This is the revert to turn the CAGE servo OFF and the OLDAMP servo ON SUSSR3
ACCEPT Tramps are not a big deal. If they are, then they are written into the Guardian and therefore can be ignored anyways. LSC
CLEARED ASC
ACCEPTED See attached snap - an additional stage of whitening is ON (the 2nd of 3), Stefan says this will likely stay on. OMC
OMC DCPD - In fact, we have now just set SDF to NOT MON these switches since Evan/Stefan say they will be switching whitening states during different lock stretches as needed, in Guardian.
The ASC control of the SRC hasn't been making sense. I did some calculations to see if the SRC might head towards an unstable condition if we run the IFO at high power (24W). We were interested in whether thermal lensing effects in the ITMs could cause a big enough gouy phase shift to cause us troubles.
At 24W there is 120kW of power in the arms and that the surface absorption of the ITMs is 0.5ppb (galaxy). The HR surface curvature of the ITMs changes by 1.06 udiopter/mW absorbed power (LLO alog 14634). This means we could expect a change in ITM curvature of 120e3*0.5e-6*1.06e3=65udiopters, or a change in the radius of curvature from 2000m to roughly 1750m as we go from cold state to 24W input power. I haven't considered substrate absorption, and G060155, slide16, indicates change in index of refraction due to bulk heating is roughly 10% of the surface absorption effect.
Putting this hot state ITM ROC into an aLaMode model of the interferometer (based on Lisa's model T1300960 with Dan's additions, alog 18915), the round trip gouy phase decreases from 32 to 22 degrees. Calculating the stability parameter for the SRC using the round trip transfer matrix, the cavity goes unstable. (A stable cavity occurs when -1<1/2*(A+D)<1. This parameter changes from 0.8 to 1.3.)
These numbers are just estimates, but the take away message is that as we increase the power, the SRC becomes less stable, and could be pushed into an unstable regime around about now. Turning on the ITM ring heaters would make the SRC more stable. (see comment) A ring heater on SR3 would also make the SRC more stable.
An additional note on transverse mode spacing: The SRC mode spacing is 240kHz in the cold state and 180kHz in the hot state. The cavity Finesse is 13.5, the free spectral range is 2.67MHz, so the full-width-half-maximum is 200kHz. So heating of the ITMs also pushes the SRC closer to degeneracy.
Paul F pointed out that I had neglected to look at the substrate lensing effect due to coating absorption. His calculations indicate this means that the SRC becomes more stable as we go to higher power. I will update my caculations too....
This is a follow up analysis of Robert's anthropogenic noise injections on August 12th. So far I don't see any convinving evidence that these activities were actually coupled into DARM. There were couple of injections ("human in optics lab" and "jumping in the change room") that seemed to coincide with DARM noise around 20-100Hz but it was unclear whether those injections were actually causing the noise. The noise *blobs* started prior to the injection and the PEM seismic sensor only coincided with one of them. Plus I would expect to see a coupling at much lower frequency if human jumping up and down the change room actually injects noise into DARM.
Note that the first injection time (15:05) is still unconfirmed. The time in the original table was wrong.
Adding SUS and SEI tags so I can locate entry. Seems like good news for the isolation crowd. (I note that just because a coupling only happens > 10 Hz does note mean SUS and SEI are off the hook. Robert and Anamaria have shown that loud drive at > 100 Hz can couple into HAM6 optics. So I would say this knocks SEISUS off the top of the list, but not off the list completely.)
Most injections lasted about 1s so the time series used for each tile should be about that long. These look like averages of time stretches almost an order of magnitude longer. I'll bet the signals will be more obvious if you zoom in in time on the individual injections instead of trying to see all 1s events in a singe 30 minute spectrogram.
I can see the injected signal clearly after I zoomed in. Below are the spectrograms for the truck horn injection. The signal can't be seen in the PEM-CS_MIC_LVEA_VERTEX channel. I'm working on the rest.
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:
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.
* What is the reasoning behind the updated suspension thermal noise plot?
* Its weird that cHard doesn't show up. At LLO, cHard is the dominant noise from 10-15 Hz. Its coupling is 10x less than dHard, but its sensing noise is a lot worse.
I remade this plot for a more recent spectrum. This includes the new EOM driver, a second stage of whitening, and dc-lowpassing on the ISS outer loop PDs.
This time I also included some displacement noises; namely, the couplings from the PRCL, MICH, and SRCL controls. Somewhat surprising is that the PRCL control noise seems to be close to the total DCPD noise from 10 to 20 Hz. [I vaguely recall that the Wipfian noise budget predicted an unexpectedly high PRCL coupling at one point, but I cannot find an alog entry supporting this.]
Here is the above plot referred to test mass displacement, along with some of our usual anticipated displacement noises. Evidently the budgeting doesn't really add up below 100 Hz, but there are still some more displacement noises that need to be added (ASC, gas, BS DAC, etc.).
Since we weren't actually in the lowest-noise quad PUM state for this measurement, the DAC noise from the PUM is higher than what is shown in the plot above.
If the updated buget (attached) is right, this means that actually there are low-frequency gains to be had from 20 to 70 Hz. There is still evidently some excess from 50 to 200 Hz.
Here is a budget for a more recent lock, with the PUM drivers in the low-noise state. The control noise couplings (PRCL, MICH, SRCL, dHard) were all remeasured for this lock configuration.
As for other ASC loops, there is some contribution from the BS loops around 30 Hz (not included in this budget). I have also looked at cHard, but I have to drive more than 100 times above the quiescient control noise in order to even begin to see anything in the DARM spectrum, so these loops do not seem to contribute in a significant way.
Also included is a plot of sensing noises (and some displacement noises from LSC) in the OMC DCPDs, along with the sum/null residual. At high frequencies, the residual seems to approach the projected 45 MHz oscillator noise (except for the high-frequency excess, which we've seen before seems to be coherent with REFL9).
Evidently there is a bit of explaining to do in the bucket...
Some corrections/modifications/additions to the above:
Of course, the budgeted noises don't at all add up from 20 Hz to 200 Hz, so we are missing something big. Next we want to look at upconversion and jitter noises, as well as control noise from other ASC loops.
We're currently checking for DAC glitches, hopefully have an answer shortly
I checked for correlations of the glitches with the ASC error signals residual motion around zero, and with suspension witness sensors and optical levers. I couldn't find anything convincing.