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ID Date Authordown Type Category Subject
  10719   Fri Nov 14 19:28:33 2014 JenneUpdateSUSASS gain reduced for Yarm

[Koji, Jenne]

We noticed last night that the yarm couldn't handle the old nominal gain for the ASS servos.  We were able to run the ASS using about 0.3 in the overall gain.  So, I have reduced the gain in each of the individual servos by a factor of 3, so that the scripts work, and can set the overall gain to 1.

  10724   Mon Nov 17 23:04:51 2014 JenneUpdatePSLAligned PMC

I aligned the beam into the PMC, mostly in yaw.  Don't know why it drifted, but it was annoying me, so I fixed it.

  10725   Tue Nov 18 15:20:58 2014 JenneUpdateLSCSome lockloss plots from PRFPMI

Elog from ~5am last night:

Tonight was just several trials of PRFPMI locking, while trying to pay more attention to the lockloss plots each time.

General notes: 

I tried once to acquire DRMI on 1f while the arms were held off resonance.  I wasn't catching lock, so I went back to PRMI+arms.  I aligned the PMC, which I noted in a separate elog.  

I was able to hold the PRMI on REFL33I&Q, and have ALS CARM and DARM at zero CARM offset.  The arm would "buzz" through the resonance regularly.  I use the word buzz because that's kind of what it sounded like.  This is the noise of the ALS system.

I think we want to add the transmission QPD angular signals to the frames.  Right now, we just keep the sums.  It would have been handy to glance at them, and see if they were wiggling in the same way that some other signal was waggling. 

All the data files are in /opt/rtcds/caltech/c1/scripts/LSC/LocklossData.  Each folder is one lockloss.  It includes text files for each trace, as well as any plots that I've made, and any notes taken.  The text files are several MB each, so I'm not going to bog the elog down with them.  There are a few folders that end in "_notInteresting".  These ones are, as one might guess, not interesting.  2 were MC locklosses (I'm not actuating on MC2, so I declared these independent from my work) and one was when I knew that my ALS was bad - the beatnotes weren't in good places, and so the ALS noise was high.


 Folder:  1100342268_POP22goesLow

Working notes:  Lost lock because POP22 went too low.  PRCL and MICH triggered off.  After this, changed PRCL and MICH "down" thresholds to 0.5, from 10.
 

Plots:

ErrorSignals_NothingObviouslyOscillating.pngErrorSignals_Zoom_MICHprclWeird.pngPowers_POP22goesLow.png

Conclusion:  Easy fix.  Changed the down thresholds for MICH and PRCL to be lower, although still low enough that they will trigger off for a true lockloss.  Why though do we lose so much sideband power when the arm transmission goes high?  POP22 dipped below 10 when TRX went above 29.  Does this happen on both sides of the CARM offset?  Quick simulation needed.

------------------------------------------------------------------------

Folder:  1100330534_maybePRCLangular

Working notes:  PRFPMI, reducing CARM offset to arm powers of 7.  CARM on sqrtInv, DARM on DCtrans. PRMI on REFL33 I&Q. Don't know why I lost lock.  Maybe angular stuff in PRC? I think POP spot was moving in yaw as it started to go bad.
Note, later:  regathered data to also get POP angular stuff. Don't think it's POP angular.  Not sure what it is.

Plots:

ErrSigs_NothingJumpingAtMe.pngNotPOPangular.png

Conclusion:  I'm not sure what this lockloss was caused by, although it is not something that I can see in the POP QPD (which was my initial suspicion).  It is, like many of the rest of the cases, one where I see significant bounce and roll mode oscillations (error and control signals oscillating at 16 and 24 Hz).  I don't think those are causing the locklosses though.

--------------------------------------------------------------------

Folder:  1100334680_unknown_highArmPowers

Working notes:  PRFPMI, carm_up script finished, sitting at arm powers of 8.  CARM, DARM on DC trans.  PRMI on REFL33.   Don't know why lost lock.

Plots:

[Don't have any? - I'll make some]

Conclusion:  Again, I see 16 and 24 Hz oscillations, but I don't think those are causing the lockloss.

---------------------------------------------------------------------

Folder: 1100331950_unknown

Working notes: PRFPMI, arms about 8.  CARM, DARM on DC trans.  PRMI on REFL33.  Don't know why I lost lock.

Plots:

More16and24Hz.png

Conclusion: Don't have an answer.

--------------------------------------------------------

Folder: 1100345981_unknown

Working notes: Lockloss while going to arm powers of 7ish from 6ish.  Not POP angular, POP22 didn't go low.

Plots:

ErrSigs_16and24Hz.pngNotPOPsFault.png

Conclusions:  This one wasn't from POP22 going too low, but again, I don't see anything other than 16 and 24Hz stuff.

 

  10726   Tue Nov 18 17:11:30 2014 JenneUpdateLSCSome lockloss plots from PRFPMI

I am still staring at / trying to figure out the latter 4 locklosses posted earlier.  But, I have just included the transmission QPD angular output signals to the frames, so we should be able to look at that with locklosses tonight. 

To get the lockloss plots:  in ..../scripts/LSC/LocklossData/ , first run ./FindLockloss.sh <gps time> .  This just pulls the TRX and TRY data, and doesn't save it, so it is pretty quick.  Adjust the gps time until you capture the lockloss in your plot window.  Then run ./LockLossAutoPlot.sh <gps time> to download and save the data.  Since it has become so many channels, it first makes a plot with all of the error and control signals, and then it makes a plot with the power levels and angular signals.  The data folder is just called <gps time>.  I have started also including a text file called notes inside of the folder, with things that I notice in the moment, when I lose lock.  Don't use .txt for the suffix of the notes file, since the ./PlotLockloss.py <folder name> script that will plot data after the fact tries to plot all .txt files.  I have also been appending the folder name with keywords, particularly _notInteresting or _unknown for either obvious lockloss causes or mysterious lockloss cases.

 

  10727   Tue Nov 18 22:34:28 2014 JenneUpdateLSCSome other plots from PRFPMI

Quote:

I was able to hold the PRMI on REFL33I&Q, and have ALS CARM and DARM at zero CARM offset.  The arm would "buzz" through the resonance regularly.  I use the word buzz because that's kind of what it sounded like.  This is the noise of the ALS system.

Here is a plot of when the arm powers went pretty high from last night.  CARM and DARM were on ALS comm and diff, PRMI was on REFL33 I&Q.  I set the CARM offset so that I was getting some full arm resonances, and it goes back and forth over the resonance.

The Y axes aren't perfect when I zoom, but the maximum TRX value was 98 in this plot, while the max TRY value was 107. 

MICH_OUT was hitting its digital rails sometimes, and also it looks like PRCL and MICH occasionally lost lock for very brief periods of time. 

Glitch-like events in PRCL_OUT are at the edges of these mini-locklosses. I don't know why POPDC has glitch-y things, but we should see if that's real.

TRXmax98_TRYmax107_CARMdarmOnALS_0carmOffset.png

Okay, I've zoomed in a bit, and have found that, interestingly, I see that both POP22 and POP110 decrease, then increase, then decrease again as we pass through full resonance.  This happens in enough places that I'm pretty sure we're not just going back and forth on one side of the resonance, but that we're actually passing through it.  Q pointed out that maybe our demod phase angle is rotating, so I've made some zoom-in plots to see that that's not a significant effect.  I plot the I and Q phases individually, as well as the total=sqrt(I**2 + Q**2), along with TRY (since the increases and decreases are common to both arms, as seen in the plot above).

For POP 22:

Zoom_with_POP22.png

For POP 110:

Zoom_with_POP110.png

I also plot the MICH and PRCL error signals along with TRY and POP22 total.  You can see that both MICH and PRCL were triggered off about 0.1msec after POP22 total this it's first super low point.  Then, as soon as POP22 becomes large enough, they're triggered back on, which happens about 1.5msec later. (The triggering was actually on POP22I, not POP22tot, but the shapes are the same, and I didn't want to overcrowd my plots).

Zoom_with_ErrSigs.png

I am not sure if we consistently lose sideband signal in the PRC more on one side of the CARM resonance than the other, but at least POP22 and POP110 are both lower on the farther side of this particular peak.  I want to think about this more in relation to the simulations that we've done.  One of the more recent things that I see from Q is from September:  elog 10502, although this is looking specifically at the REFL signals at 3f, not the 2f circulating PRCL power as a function of CARM offset.

  10734   Tue Nov 25 02:04:19 2014 JenneUpdateLSCPRFPMI tonight - need some PRCL and MICH tuning at high arm powers

Take-away for the night:  We need to do some more fine-tuning of the PRCL and MICH loops when we have arm resonance.

Koji sat with me for the first part of the night, and we looked back at the data from last week (elog 10727), as well as some fresh data from tonight.  Looking at the spectra, we noticed that last week, and early in the evening today, I had a fairly broad peak centered around ~51Hz.  We are not at all sure where this is coming from.  The PRMI was locked on REFL 33 I&Q, and CARM and DARM were both on ALS comm and diff.  This peak would repeat-ably come and go when I changed the CARM offset.  At high arm powers (above a few tens? I don't know where exactly), the peak would show up.  Move off resonance, and the peak goes away.  However, later in the night, after an IFO realignment, I wasn't able to reproduce this effect.  So.  We aren't sure where it comes from, but it is visible only in the CARM spectra, so there's some definite feedback funny business going on. 

Anyhow, after that, since I couldn't reproduce it, I went on to trying to hold the PRMI at high arm powers, but wasn't so successful.  I would reduce the CARM offset, and instead of a 50Hz peak, I would get broadband noise in the PRMI error signals, that would eventually also couple in to the CARM (but not DARM) error signal, and I would lose PRMI lock. I measured the PRCL and MICH transfer functions while the arms were at some few units of power, and found that while MICH was fine, PRCL was losing too much phase at 100Hz, so I took away the FM3 boost.  This helped, but not enough. I had 1's in the triggering matrix for TRX and TRY to both PRCL and MICH, so that even if POP22 went low, if the arms were still locked then the PRMI wouldn't lose lock unnecessarily, but I was still having trouble.  In an effort to get around this, I transitioned PRMI over to REFL 165 I&Q. 

While the arms were held around powers of 2ish, I readjusted the REFL 165 demod phase.  I found it set to 150 deg, but 75 deg is better for PRMI locking with the arms.  For either acquiring or transitioning from REFL33, I would use REFL165I * -1.5 for PRCL, and REFL 165Q * 0.75 for MICH.  (Actually, I was using -2 for REFL165I->PRCL, and +0.9 for REFL165Q->MICH, but I had to lower the servo gains, so doing some a posteriori math gives me -1.5 and +0.75 for what my matrix elements should have been, if I wanted to leave my servo gains at 2.4 for MICH and -0.02 for PRCL.) I don't always acquire on REFL165, and if it's taking a while I'll go back to putting 1's in the REFL33 I&Q matrix elements and then make the transition. 

With PRMI on REFL 165 I&Q, I no longer had any trouble keeping the PRMI locked at arbitrarily high arm powers.  I was still using 1*POP22I + 1*TRX + 1*TRY for triggering PRCL and MICH.  My thresholds were 50 up, 0.1 down.  The idea is that even if POP goes low (which we've seen about halfway up the CARM resonance), if we're getting some power recycling and the arms are above 1ish, then that means that the PRMI is still locked and we shouldn't un-trigger anything.  I didn't try switching over to POP110 for triggering, because POP22 was working fine.

Earlier in the night, Koji and I had seen brief linear regions in POX and POY, as well as some of the REFL signals when we passed quickly through the CARM resonance.  I don't have plots of these, but they should be easy to reproduce tomorrow night.  Koji tried a few times to blend in some POY to the CARM error signal, but we were not ever successful with that.  But, since we can see the PDH-y looking regions, there may be some hope, especially if Q tells us about his super secret new CESAR plan. 

Okay, I'm clearly too tired to be writing, but here are some plots.  The message from these is that the PRMI loops are causing us to fluctuate wildly in arm transmission power.  We should fix this, since it won't go away by getting off of ALS.  The plots are from a time when I had the PRMI locked on REFL165, and CARM and DARM were still on ALS comm and diff.  All 3 of these colored plots have the same x-axis.   They should really be one giant stacked plot.

HighPower_7pt3sec_Powers.png

HighPower_7pt3sec_ErrAndCtrls.png

HighPower_7pt3sec_AuxErrs.png

Also, bonus plot of a time when the arm powers went almost to 200:

CARMDARMonALScommdiff_StayingAbove5_upTo175_24Nov2014.png

  10736   Wed Nov 26 05:15:48 2014 JenneUpdateLSCPRFPMI tonight PRMI 100Hz osc?

[Jenne, EricQ]

Just to get our day started right, we tweaked up the alignment of the Ygreen to the Yarm (after IR alignment), and also touched up the X beatnote alignment on the PSL table.  Ran the LSC offsets script, and then started locking. 

All of the locking tonight has been based on CARM and DARM held on ALS comm/diff, and PRMI held on REFL165.  Today, CARM was actuated using MC2.  No special reason for the switch from ETMs. The AS port is noticeably darker when using REFL165 instead of REFL33. 

Around 12:33am(ish), we were able to hold the arms at powers of about 100, for almost a minute.  The fluctuations were at least 50% of that value, but the average was pretty high.  Exciting.

Q and I tried a few times to engage the AO path while the arms were held at these high powers.  Q hopefully remembers what the gain and sign values were where we lost lock.  We didn't pursue this very far, since I was seeing the 50Hz oscillation that Koji and I saw the other day.  I increased the CARM gain from 6 to 10, and that seemed to help significantly.  Also, messing with the PRMI loops a bit helped.  Q increased the pole frequency in FM 5 for both MICH and PRCL from 2k to 3k.  While he had Foton open, he made sure that all of the LSC DoF filters use the z:p notation. 

I then did a few trials of trying to transition CARM over to normalized REFL11I.  Now that I'm typing, it occurs to me that I should have checked REFL11's demod phase.  Ooops.  Anyhow, using the phase that was in there, I turned on a cal line pushing on ETMs CARM, and found that using -0.002*REFL11I / (TRX + TRY) was the right set of elements.  I also put an offset of 0.05 into the CARM CESAR RF place, and started moving.  I tried several times, but never got past about 30% normalized REFL11 and 70% ALS comm. 

During these trials, Q and I worked also on tweaking up the PRMI lock.  As mentioned last night, PRCL FM3 eats too much phase (~30deg at 100Hz!), so I don't turn that on ever.  But, I do turn on FM1 (which is new tonight), FM2, 6, 8 and 9.  FM8 is a flat gain of 0.6 that I use so I can have higher gain to make acquisition faster, but immediately turn the gain down to keep the loop in the center of the phase bubble.  MICH needed a lowpass, so in addition to FM2, I am now also triggering FM 8, which is a 400Hz lowpass that was already in there. 

Now, my MICH gain is 2.4, with +0.75*REFL165Q, and PRCL gain is -0.02 with -3*REFL165I.  Triggering for both MICH and PRCL is 1*POP22I + 5*TRX with 50 up, 0.1 down. 

In my latest set of locks, I have been losing lock semi-regularly due to a 100Hz oscillation in either the PRCL or MICH loops.  If I watch the spectra, most times I take a step in CARM offset reduction, I get a broad peak in both the MICH and PRCL error signals.  Most of the time, I stay locked, and the oscillation dies away.  Sometimes though it is large enough to put me out of lock.  I'm not sure yet where this is coming from, but I think it's the next thing that needs fixing.

Here is a shot of the spectra just as one of these 100Hz oscillations shows up.  The dashed traces are the nominal error signals when I'm sitting at some CARM offset, and the solid traces are just after a step has been made. The glitch is only happening in the PRMI, not CARM and DARM. 

PRFPMI_currentErrSigs_25Nov2014.pdf

  10737   Wed Nov 26 22:24:28 2014 JenneUpdateLSCDARM loop improved, other work

[Jenne, Koji]

We have done several things this evening, which have incrementally helped the lock stability.  We are still locking CARM and DARM on ALS, and PRMI on REFL165.

  • Saw peaks in CARM error signal at 24Hz and 29 Hz, so put in moderate-Q resonant gains. 
  • DARM at low frequency was much noisier than CARM.  We discovered that we had put in a nice boost at some point for CARM in FM1, but hadn't transferred that over to DARM.  Copying FM1 from CARM to DARM (so replacing an integrator with a boost below ~10Hz) dropped the DARM noise down to match the CARM noise at low frequencies.
  • Koji noticed that we were really only illuminating one quadrant of the Xend QPD, so we aligned both trans QPDs.  Also, I reset the transmission normalization so that all 4 diodes (Thorlabs and QPDs at each end) all read 1 with good alignment.
  • We've got some concerns about the ASS.  It needs some attention and tuning.
    • The X ASS needs an overall gain of about 0.3.  This may be because I forgot to put the new lower gains into the burt restore after Rana's oplev work, or this may be something new.
    • When Koji did a very careful arm alignment, we turned on the Y ASS and saw it methodically reduce the transmitted power.  Mostly it was moving ETMY in yaw.  Why is the DC response of the ASS not good?  The oplev work shouldn't have affected DC.
    • We don't like the way the ASS offloads the alignment.  Maybe there's a better way to do it overall, but one thought is to have an option to offload (for long-term alignment fixing, so maybe once a day) and another option to just freeze the current output (for the continual tweak-ups that we do throughout the evening).  We'd want the ASS to start up again with these frozen values, and not clear them.
  • ETMY was being fussy, in the same way that ETMX had been for the last few months.  I went down to squish the cables, and found that it was totally not strain-relieved, and that the cable was pulling on the connector.  I have zip tied the cable to the rack so that it's not pulling anymore.
  • At high arm powers, it is hard to see what is going on at the AS port because there is so much light.  Koji has added an ND filter to the AS camera so that we can more easily tweak alignment to improve the contrast.

Something that has been bothering me the last few days is that early in the evening, I would be able to get to very high arm powers, but later on I couldn't.  I think this has to do with setting the contrast at the AS port separately for the sideband versus the carrier.  I had been minimizing the AS port power with the arms held off resonance, PRMI locked.  But, this is mostly sideband.  If instead I optimize the Michelson fringes when the arms are held with ALS at arm powers of 1, and PRM is still misaligned, I end up with much higher arm powers later.  Some notes about this though:  most of this alignment was done with the arm cavity mirrors, specifically the ETMs, to get the nice Michelson fringes.  When the PRM is restored and the PRMI locked, the AS port contrast doesn't look very good.  However, when I leave the alignment alone at this point, I get up to arm powers above 100, whereas if I touch the BS, I have trouble getting above 50.


Around GPS time 1101094920, I moved the DARM offset after optimizing the CARM offset.  We were able to see a pretty nice zero crossing in AS55, although that wasn't at the same place as the ALS diff zero offset (close though).  At this time, the arm powers got above 250, and TRY claimed almost 200.  These are the plots below, first as a wide-view, then zoomed in.  During this time, PRCL still has a broadband increase in noise when the arm powers are high, and CARM is seeing a resonance at a few tens of Hz.  But, we can nicely see the zerocrossing in AS55, so I think there's hope of being able to transition DARM over. 

DARMcrossing_Power.png

DARMcrossing_ErrCtrl.png

DARMcrossing_AuxErr.png

DARMcrossing_Angles.png

Now, the same data, but zoomed in more.

DARMcrossing_Power_Zoom.png

DARMcrossing_ErrCtrl_Zoom.png

DARMcrossing_AuxErr_Zoom.png

DARMcrossing_Angles_Zoom.png


During the 40m meeting, we had a few ideas of directions to pursue for locking:

  • Look into using POX or POY as a proxy for POP and instead of REFL, for CARM control.  Maybe we have some nice juicy SNR.
  • Check the linearity of our REFL signals by holding the arms on (or close to) resonance, then do a swept sine exciting CARM ctrl and taking a transfer function to the RF signals.
  • Q is going to look into the TRX QPD, since he thought it looked funny last week, although this may no longer be necessary after we put the beam at the center of the QPD.
  • Koji had a thought for making it easier to blend the CARM error signals.  What if we put a pole into the ALS CARM signals at the place where the final coupled cavity pole will be, and then compensate for this in the CARM loop.  Since any IR signals will naturally have this pole, we want the CARM loop to be stable when it's present.
  • Diego tells us that the Xarm IR beatnote is basically ready to go.  We need to see how big the peak is so we can put it into the frequency counter and read it out via EPICS.  The freq counter wants at least -15dBm, so we may need an amplifier.
  10740   Mon Dec 1 16:34:20 2014 JenneUpdateGeneralIFO wake-up

 

 After its' several days of rest, it is time to wake up the IFO. 

  • FSS temp was railed at +10, which was making the MC not want to lock.  Set it to zero, locked the MC, and ran the MC WFS relief scripts.
  • PMC trans is down to 0.686, so I'll probably want to tweak that up before I get too carried away for tonight. 
  • c1iscex computer was frozen, which I suspect is why Steve found ETMX tripped this morning.  Soft reboot, and we're back to normal.

With that, it's time for a new week of locking, and trying to catch up with the big kids at the sites.

  10742   Mon Dec 1 17:19:22 2014 JenneUpdateGeneralPMC align

[Diego, Jenne]

Tweaked up the input alignment to the PMC.  Now we're at 0.785.

  10743   Mon Dec 1 17:43:22 2014 JenneUpdateLSCReset Yarm trans normalization

After Koji and I reset the transmission normalizations last Friday, he did some alignment work that increased the Yarm power.  So, I had set the transmission normalization when we weren't really at full Yarm power.  Today I reset the normalization so that instead of ~1.2, the Y transmission PDs read ~1.0.

  10746   Tue Dec 2 02:44:45 2014 JenneUpdateLSCTried cav pole compensation trick - fail

[Jenne, Diego]

First, random notes:

  • saw a violin peak in CARM / DARM at 638.0Hz.  Assumed it was one of the ETMs, even though it doesn't match any of the frequencies in our handy-dandy chart: wiki resonances
    • Put an extra notch in the ETM violin filters.
    • Just now realized that I was actuating MC2 at the time for CARM (although 638 is also not what we have in the chart for MC2).  The MC2/ETM violin filters should be shared between eachother.
  • Measured CARM and DARM loops on ALS comm and diff, gains should be 8, not 6.  Fixed in Lock_ALS_CARM_and_DARM script. 
  • MC has been fussy tonight.  I started actuating CARM on ETMs, and that helped, but we've still had several unexplained MC locklosses. 
    • PC and FSS Slow are okay right now, but they have been mad earlier tonight.  Do we need to check the PID tuning for FSS slow?
  • When I first started locking this evening, I was able to hold nice high arm powers (with the usual factor of 2+ RIN), so the IFO seemed okay except for the fussy MC.

Koji suggested last week that we put a cavity pole filter into the ALS error signals, and then compensate for that in the CARM and DARM servos.  The idea is that any RF signals we want to transfer to will have some kind of frequency dependence, and at the final zero CARM offset that will be a simple cavity pole. 

I put a pole at 200 Hz, with a zero at 6 kHz into the LSC-ALS[X,Y] filter banks in FM1, and then also put a zero at 200 Hz with a pole at 6 kHz into both the CARM and DARM servos at FM7.  Ideally I wouldn't have the 6kHz in there, but the compensation filter in the CARM/DARM servos needs a pole somewhere, so I put in the zero in the ALS signals so that they match.  Foton thinks that multiplying the two filters should give a flat response, to within 1e-6dB and 1e-6 deg. 

We can lock CARM and DARM on ALS with the new filters, but it seems to be not very stable.  We've measured transfer functions in both configurations, and between 50-500Hz, there is no difference (i.e., our matching filters are matching, and cancelling each other out).  We sometimes spontaneously lose lock when we're just sitting somewhere with the new configuration, and we cannot run any find IR resonance scripts and stay locked.  We've tried the regular old script, as well as Diego's new gentler script.  We always fail with the regular script during the coarse scan.  With Diego's script, we made it through the coarse scan, but spontaneously lost lock while the script was calculating the location of the peak.  So, we determine that there is something unstable about the new configuration that we don't understand.  Turning off all the new filters and going back to the old configuration is just as robust as always.  Confusing. 

 

  10751   Wed Dec 3 21:41:12 2014 JenneUpdateComputer Scripts / ProgramsMatlab license updated

It seems that the old Matlab servers went down a week or so early, so I have updated the Matlab license information in 

/cvs/cds/caltech/apps/linux64/matlab/licenses/

per the instructions on https://www.imss.caltech.edu/content/updating-matlab-license-file

EDIT: Q did this also for the control room iMac

  10752   Thu Dec 4 00:26:07 2014 JenneUpdateASCPOP yaw razor blade installed

We would like the option of feeding back the POP beam position fluctuations to the PRM to help stabilize the PRC since we don't have oplevs for PR2 and PR3.  However, we cannot just use the DC QPD because that beam spot will be dominated by carrier light as we start to get power recycling. 

The solution that we are trying as of today is to look at yaw information of just the RF sidebands.  (Yaw is worse than pitch, although it would be nice to also control pitch).  I have placed a razor blade occluding about half of the POP beam in front of the POP PD (which serves POPDC, POP22 and POP110).  I also changed the ASS model so that I could use this signal to feed back to the PRM.  Loop has been measured, and in-loop spectra shows some improvement versus uncontrolled.


Optical table work:

The POP beam comes out of the vacuum system and is steered around a little bit, then about 50% goes to the DC QPD.  Of the remaining, some goes to the Thorlabs PD (10CF I think) and the rest goes to the POP camera.  For the bit that goes to the Thorlabs PD, there is a lens to get the beam to fit on the tiny diode.

There was very little space between the steering mirror that picks off the light for this PD, and the lens - not enough to put the razor blade in.  The beam after the lens is so small that it's much easier to occlude only half of the beam in the area before the lens.  (Since we don't know what gouy phase we're at, so we don't know where the ideal spot for the razor is, I claim that this is a reasonable place to start.)

I swapped out the old 50mm lens and put in a 35mm lens a little closer to the PD, which gave me just enough room to squeeze in the razor blade.  This change meant that I had to realign the beam onto the PD, and also that the demod phase angles for POP22 and POP110 needed to be checked.  To align the beam, before placing the razor blade, I got the beam close enough that I was seeing flashes in POPDC large enough to use for a PRMI carrier trigger.  The PRMI carrier was a little annoying to lock.  After some effort, I could only get it to hold for several seconds at a time.  Rather than going down a deep hole, I just used that to roughly set the POP22 demod phase (I -phase maximally negative when locked on carrier, Q-phase close to zero).  Then I was able to lock the PRMI sideband by drastically reducing the trigger threshold levels.  With the nice stable sideband-locked PRMI I was able to center the beam on the PD. 

After that, I introduced the razor blade until both POPDC and POP22 power levels decreased by about half. 

Now, the POP22 threshold levels are set to up=10, down=1 for both MICH and PRCL, DoF triggers and FM triggers.


ASS model work:

POP22 I and POP110 I were already going to the ASS model (where ASC lives) for the PRCL ASS dither readbacks.  So, I just had to include them in the ASC block, and increased the size of the ASC input matrix.  Now you can select either POP QPD pit, POP QPD yaw, POP221 or POP110I to go to either PRCL yaw, PRCL pit, CARM yaw or CARM pit. 

Compiled, installed and restarted the ASS model.


Engaging the servo:

I took reference spectra of POP QPD yaw and POP 22, before any control was applied.  The shapes looked quite similar, but the overall level of POP22 was smaller by a factor of ~200.  I also took a reference spectra of the POP QPD in-loop signal using the old ASC loop situation.

Q looked at Foton for me, and said that with the boost on, the UGF needed to be around 9 or 10 Hz, which ended up meaning a servo gain of +2.5 (the old POP QPD yaw gain was -0.063).  We determined that we didn't know why there was a high-Q 50Hz notch in the servo, and why there is not a high frequency rolloff, so right now the servo only uses FM1 (0:2000), FM6 (boost at 1Hz and 3Hz) and FM7 (BLP40). 

The in-loop residual isn't quite as good with POP22 as for the QPD, but it's not bad. 

Here's the loop:

ASC_PRCLloop_POP22err.pdf

And here's the error spectra.  Pink solid and light blue solid are the reference traces without control.  Pink dashed is the QPD in-loop.  Red and blue solid are the QPD and POP22 when POP22 is used as the error signal.  You can definitely see that the boosts in FM6 have a region of low gain around 1.5Hz.  I'm not so sure why that wasn't a problem with the QPD, but we should consider making it a total 1-3Hz bandpass rather than a series of low-Q bumps.  Also, even though the POP22 UGF was set to 9 Hz, we're not seeing any suppression above about 4Hz, and in fact we're injecting a bit of noise between 4-20Hz, which needs to be fixed still. 

PRC_YAW_QPDvs22_3Dec2014.pdf

  10753   Thu Dec 4 01:24:47 2014 JenneUpdateSUSPRM volin 3rd harmonic

Earlier this afternoon, while locking PRMI, I saw a big peak at 1883.48 Hz.  This comes closest to the PRM's 627.75 Hz *3, so I infer that it is the 3rd order harmonic of the PRM violin mode. 

While putting this in, I noticed that my addition of ETM filters the other day (elog 10746) had gotten deleted.  Koji pointed out that Foton can do this - it allows you to create and save filters that are higher than 20th order, but secretly it deletes them.  I went into the filter archive and recovered the old ETM filters, and split things up.  I have now totally reorganized the filters, and I have made every single optic (ETMs, ITMs, PRM, SRM, BS, MC2) all the same. 

FM1 is BS 1st and 2nd harmonics, and FM6 directly below that is a generic 3rd order notch that is wide enough that it encompases 3*BS. 

FM2 is the PRM 1st and 2nd order, and FM7 below it is the PRM 3rd order. 

FM3 is the SRM 1st order, FM4 is the ETMs' 1st order, and FM5 is the MC2 1st and 2nd order filters. 

All of these filters are triggered on if any degree of freedom is triggered.  They all have a ramp time of 3 sec. We may want to consider having separate trigger options for each optic, so that we're not including the PRM notch on the ETMs, for example, and vice versa. 

When all of these filters are on, according to Foton we lose 5.6 degrees of phase at 100 Hz.

  10755   Thu Dec 4 03:09:06 2014 JenneUpdateLSCBump in Darm Plant: Lockloss after measurement

We were sitting around arm powers of 6, and that loop measurement had finished.  I was about to go down to arm powers of 5ish, but we lost lock.  I'm not sure why.  There's some slow stuff going on in some of the servos, but nothing jumps out at me as a loop oscillation.  It does however kind of look like the PRMI lost lock just before the arm powers went down?  Perhaps this somehow triggered a lockloss?

The time is 1101721675.

Wide view plots:

Arms6_3Dec2014_powers.png

Arms6_3Dec2014_errctrl.png

Arms6_3Dec2014_auxerr.png

Arms6_3Dec2014_angles.png

Zooms:

Arms6_3Dec2014_powers_Zoom.png

Arms6_3Dec2014_errctrl_Zoom.png

Arms6_3Dec2014_auxerr_Zoom.png

Arms6_3Dec2014_angles_Zoom.png


We're stopping for tonight because ETMX is back to its lame-o jumping around.  I went in and squished the cables, but it's still happening.

Also, the FSS PC drive has been high the last few minutes (only starting after we quit for the night).  When the MC re-locks, it sounds like an ocean wave dying out as the noise goes down a little bit.  But, after a few minutes, it'll get mad again and unlock the MC.

Also, also, I noticed this on Monday with Diego, but the LSC-ALS[x,y] filter module gains sometimes mysteriously get set to zero.  WTF?  Eric and I have both independently checked, and we cannot find a single script in the scripts directory with the string "LSC-ALS", so we aren't deliberately changing those.  Does anyone know what might be going on here?

  10756   Thu Dec 4 23:45:30 2014 JenneUpdateCDSFrozen?

[Jenne, Q, Diego]

I don't know why, but everything in EPICS-land froze for a few minutes just now.  It happened yesterday that I saw, but I was bad and didn't elog it.

Anyhow, the arms stayed locked (on IR) for the whole time it was frozen, so the fast things must have still been working.  We didn't see anything funny going on on the frame builder, although that shouldn't have much to do with the EPICS service.  The seismic rainbow on the wall went to zeros during the freeze, although the MC and PSL strip charts are still fine. 

After a few minutes, while we were still trying to think of things to check, things went back to normal.  We're going to just keep locking for now....

  10757   Fri Dec 5 00:52:51 2014 JenneUpdateSUSETMX 2nd order violin

We looked at the spectra of POX and POY during IR lock, and Q saw a peak at 1285 in POX only.  We're actuating on the ETMs, so it must be an ETMX violin mode, although it doesn't match the others that are in the table.

Anyhow, I added it to FM9.  While I was doing that, I realized that yesterday I had forgotten to put back the 3rd order ETM violin notch, so that is also in FM9.

  10758   Fri Dec 5 02:44:43 2014 JenneUpdateGeneralIFO alignment shenanigans

[Jenne, Q, Diego]

OMG, today sucked alignment-wise.  Like, wow. 

I think that the problem with the ASS is with the input pointing part of the system.  I found that if I disable the TTs for the Yarm (iin practice, the outputs are held at zero), I could run the Yarm ASS at full gain of 1, and it would do an awesome job.  The first time I did this, I by-hand optimized the TTs by running the test mass loops to make them follow the input pointing.  After that, I haven't touched the TT pointing at all, and we've just been running the test mass loops for the Yarm ASS.  The Xarm seems to not have this problem (or at least not as drastically), so I left it as it was, touching BS as well as ITMX and ITMY, although the gain still needs to be about 0.3.

I feel pretty good about the IFO alignment now, although it is slightly different than it has been.  The transmitted arm powers are higher than they were before I changed the ASS procedure, and there seems to be a little less power fluctuation with alignment.  Q points out that I don't have concrete evidence that this is a good alignment, but it feels right. 

It was a significant enough change that I had to go down to the Yend to realign the green to the new arm axis.  Xgreen we did with the remote PZTs.  I also realigned both of the beatnotes on the PSL table. 

While I was on the PSL table, I quickly touched up the PMC alignment.

The biggest problem, the one that sucked up more hours and energy than I'd like to admit, is ETMX's jumping.  So frustrating.  Sometimes it is time-coincident with engaging the LSC, sometimes not.  I thought that it might be because there are too many violin filters, but even if I turn off all violin filters to ETMX, it jumped a few times while the cavity was locked.  Sometimes it moves when the cavity is just locked and seems happy, sometimes it moves when nothing is resonating except for the green.  It takes a few minutes to recover the alignment enough to lock, and then it'll jump again a few minutes later.  I haven't gone down to squish the cables today, although I did it yesterday and that didn't seem to do anything. 

We had a few hours of time when it wasn't jumping, so we tried a few times to lock the IFO.  The last several times we have lost lock because the PRC loop rang up.  We measured the loop at low-ish arm powers, but it kept losing lock at higher powers before we could measure.  At least 3 times, the PRC lockloss took out CARM and DARM too.

Anyhow, it has been a long day of not accomplishing anything interesting, but hopefully the IFO will feel better tomorrow.

  10759   Fri Dec 5 15:41:45 2014 JenneUpdateComputer Scripts / ProgramsNodus on fast GC network

Apparently, some time ago Larry Wallace installed a new, fast ethernet switch in the old nodus rack. Q and I have just now moved nodus' GC ethernet cable over to the new switch.  Dan Kozak is going to use this faster connection to make the data flow over to the cluster not so lag-y.

  10768   Tue Dec 9 03:34:52 2014 JenneUpdateASCPOP yaw razor tuning

With the re-do of the IFO alignment last week, I think that the beam was no longer about halfway on the POP22 razor blade.  To fix this, I locked the PRMI on sideband, removed the razor blade, and then put it back in such that it occluded about half of the light.  

I'm not entirely sure why, but when I put the razor in, POP22 went from 104(ish) to 45(ish) but POPDC  went from 5200(ish) to 1600(ish).  [The 'ish'es are because the PRC wasn't angularly stabilized, so there was some motion changing the power levels that leaked out to the POP port].  The ETMs were misaligned, so this should not be a carrier vs. sideband effect, since they'll both share the cavity axis defined by the ITMs and the PRM.  It is possible, although I didn't check, that there is some oplev light scattered into the POP photodiode that is now blocked by the razor blade.  This light would only be at DC and not the 2f frequencies.  Since the signal levels for POP22 vs. POPDC didn't change with and without the table top on (and with and without room lights on), I don't think that it is an effect of ambient light getting into the diode.  To check if it is oplev light I should (a) just look, and (b) try to lock the PRMI without the ITMX oplev laser being on to see if there is a difference in the POPDC signal.

Anyhow, under the assumption that the POP22 signal level is correct, I tuned up the PRCL ASC a little bit.  These changes are now in the carm_cm_up script, and the carm_cm_down script resets things.  Before the PRC is locked, I have FM1 and FM7 (the basic servo shape and a 40Hz lowpass) on, the gain set to zero, and the input off.  After lock is acquired, the input is turned on, and the gain ramps from 0 -> 10 in 3 seconds.  Then FM2 and FM6 (boosts at 1 and 3Hz) are engaged.

In the plot below, the dark blue and red curves were taken when there was no angular control on the PRC.  Pink was taken last week with the old QPD yaw ASC on.  Light blue is today's version of the in-loop performance of the POP22 yaw ASC loop.  I didn't save the trace unfortunately, but the DC QPD saw out-of-loop improvement between about 0.8Hz - 4 Hz. 

Also, has anything happened with the LSC rack in the last few weeks that might be causing lots of 60Hz noise? I saw these large lines last week, but I don't think I remember them from the past.

PRC_YAW_QPDvs22_8Dec2014.pdf

After I got the PRCL ASC working, I tried several iterations of locking.  ETMX is still being annoying, although the last hour or so have been okay.  CARM keeps getting rung up right around the transition to the sqrtInv error signal.  Since CARM and DARM are kind of entangled, it took me a few iterations to figure out that it was CARM that is ringing up, and not DARM.  I'm a little worried about the phase loss from the 1kHz lowpass that we turn on just before the transition to sqrtInv.  I want to keep the lowpass off until after we have transitioned DARM also over to DC transmission.  I tried once, but I lost lock before starting the CARM transition.  Anyhow, the ETM alignment issue is annoying.

Also, Jamie, Q, Diego and I were discussing last Friday, but none of us elogged, that we think there might be something wrong with one of the Martian network switches.  I'll start a separate thread about that right now, but it slows things down when you can't trust EPICS channels to be current, and I (without evidence) am a little worried that this might also affect the fast signals.

  10769   Tue Dec 9 03:41:06 2014 JenneUpdateCDSEPICS running slow - network issue?

[Jamie, EricQ, Jenne, Diego]

This is something that we discussed late Friday afternoon, but none of us remembered to elog. 

We have been noticing that EPICS seems to run pretty slowly, and in fact twice last week froze for ~2 minutes or so (elog 10756). 

On Friday, we plotted several traces on StripTool, such as C1:SUS-ETMY_QPD_SUM_OUTPUT and C1:SUS-ETMY_TRY_OUTPUT and C1:LSC-TRY_OUTPUT to see if channels with (supposedly) the same signal were seeing the same sample-holding.  They were.  The issue seems to be pretty wide spread, over all of the fast front ends.  However, if we look at EPICS channels provided by the old analog computers, they do not seem to have this issue. 

So, Jamie posits that perhaps we have a network switch somewhere that is connected to all of the fast front end computers, but not the old slow machines, and that this switch is starting to fail. 

My understanding is that the boys are on top of this, and are going to figure it out and fix it.

  10774   Wed Dec 10 15:05:32 2014 JenneUpdateElectronicsXend QPD whitening board modified already

In April, Koji logged that he had made some changes to the Yend QPD whitening board (elog 9854).  Today, I pulled the Xend board to see if it had the same modifications.  The filter shapes all seem to be the same (as in, the capacitors at the output filters were removed, etc.), and the final gain is the same.  I just realized that I didn't explicitly check if the whitening switches were pulled to ground to permanently turn on the whitenening, but hopefully I'll be able to see that in the photo. 

I have not made any changes today (yet) to the board, so the overall gain is still accessible via EPICS.  I wanted to do a quick check that we won't be saturating things at full power with the maximum gain, before I make a change.

IMG_1776.JPG

EDIT:  After comparing the photos here and in elog 9854, the X end board has the filter shape modifications that were done some time ago, but the whitening is not permanently enabled.  For the Yend board, Koji added a jumper wire connecting (for example) R97 and R106 to the grounded side of C69.  This jumper wire is not in place on the X qpd board.

Before I re-pull the board and modify it, I want to make sure I know what I'm going to do for the gain slider override.

  10782   Thu Dec 11 16:42:12 2014 JenneUpdateElectronicsXend QPD whitening board plan

Here is a little PDF of what I plan to do to both of the transmission QPD whitening boards later today.  The idea is to take away the remote gain slider inputs, and force the gains to always be at +30dB.

The red and blue notes are from Koji's elog 9854, and the green are my plans for today. 

I will cut the traces from the gain slider inputs, and pull the negative input of the AD620 to ground.  The positive input will be connected to the +5 voltage line, with a divider so that the positive input to the AD620 is about 666mV. 

The AD602 will be maxed out at +30dB with anything over 625mV. 

QPDwhiteningModification_11Dec2014.pdf

Unless there are objections, I will start these modifications in an hour or so.  I will also make the Xarm whitening always-on, just like Koji has already done for the Yend.

EDIT, JCD, 12Dec2014:  These are not the modifications that were made.  Please see ____ for actual modifications.

  10788   Fri Dec 12 02:30:25 2014 JenneSummaryGeneralPSL table optical layout

Quote:

 

 I missed to elog this earlier. I have temporarily removed the DC photodiode for GTRY to install the fiber holder on the PSL table. So GTRY will not be seeing anything right now.

 

 After some confusion, I discovered this a few hours ago.

  10789   Fri Dec 12 04:33:49 2014 JenneUpdateASCASS retuned

[Rana, Jenne]

We decided that tonight was the night for ASS tuning. 

We started from choosing new frequencies, by looking at the transmission and the servo control signals spectra to find areas that weren't too full of peaks.  We chose to be above the OpLev UGF by at least a factor of ~2, so our lowest frequency is about 18Hz.  This way, even if the oplevs are retuned, or the gains are increased, the ASS should still function. 

We set the peak heights for the lowest frequency of each arm to have good SNR, and then calculated what the amplitude of the higher frequencies ought to be, such that the mirrors are moving about the same amount in all directions. 

We re-did the low pass filters, and eliminated the band pass filters in the demodulation part of the servo.  The band passes aren't strictly necessary, as long as you have adequate lowpassing, so we have turned them off, which gives us the freedom to change excitation frequencies at will.  We modified the lowpass filter so that we had more attenuation at 2Hz, since we spaced our excitation frequencies at least ~2.5 Hz apart.

The same lowpass filter is in every single demodulator filter bank (I's and Q's, for both length and transmission demodulation).  We are getting the gain hierarchy just by setting the servo gains appropriately. 

We ran ezcaservos to set the demodulation phase of each lockin, to minimize the Q-phase signal. 

We then tuned up the gains of the servos.  Rana did the Y arm, but for the X arm I tried to find the gains where the servos went unstable, and then reduced the gain by a factor of 2.  The Xarm is having trouble getting good alignment if you start with something less than about 0.7, so there is room for improvement.

Rana wrote a little shell script that will save the burt snapshot, if the gains need adjusting and they should be re-saved. 

The scripts have been modified (just with the new oscillator amplitudes - everything else is in the burt snapshots), so you should be able to run the start from nothing and the start from frozen scripts for both arms.  However, please watch them just in case, to make sure they don't run away.

  10794   Fri Dec 12 19:54:21 2014 JenneUpdateElectronicsXend QPD whitening board modified

Okay, I have finished modifying the Xend QPD whitening board, although I will likely need to change the gain on Monday.

Rather than following my plan in elog 10782, I removed the AD602's entirely, and just use the AD620's as the amplifiers.  We don't need remotely adjustable gains, and the AD620s are a less noisy part.

I set the gain to be 30dB using a 1.65k resistor for R_G, which turns out to be too high.  After I installed the board and realized that my counts were much higher than they used to be, I realized that what we had been calling +30dB was in fact +13.2dB. ( I am assuming that the ADC for the gain sliders were putting out a maximum of +10V.  The AD620 used to have a 1/10 voltage divider at the input, and an overall gain of 1, so the output of the AD620 was 100mV.  This goes into pin 16 of the AD602, which has gain of 32*V_set + 10.  Which gives 32*0.1+10=13.2dB.  Ooops.  We've been lying to ourselves. )

Anyhow, before I made the gain realization, I was happily going along, setting the AD620s' gains all to 30dB. I also copied Koji's modification from April of this year, and permanently enabled the whitening filters.

Here is the schematic of what ended up happening.  The red modifications were already in place, and the greens are what I did today.

QPDwhiteningModification_XtransCompleted_12Dec2014.pdf

You can see the "before" picture in my elog Wednesday, elog 10774.  Here is an "after" photo:

IMG_1779.JPG

Here is a spectrum comparing the dark noise of the Xend QPD after modification to the current Yend QPD (which is still using the AD602 as the main instrumentation amplifier).  I have given the Yend data an extra 16.8dB to make things match.

QPD_Xtrans_Ytrans_12Dec2014.pdf

And, here is a set of spectra comparing both ends, dark noise versus single arm lock.  While I'll have to sacrifice a lot of it, there's oodles more SNR in the Xend now.  The Yend data still has the "gain fixing" extra 16.8dB.

QPD_Xtrans_Ytrans_DarkVsLock_12Dec2014.pdf

The Xend quadrant input counts (before the de-whitening filters) now go up to peak values of about 1,000 at single arm lock.  If (optimistically) the we got full power recycling and the arms got to powers of 300, that would mean we would have 300,000 counts, which is obviously way more than we actually have ADC range for.  Currently, the Yend quadrant input counts go as high as 50, which with arm powers of 300 would give 15,000 counts.  I think I need to bring the Xend gain down to about the level of the Yend, so that we don't saturate at full arm powers.  I can't remember right now - are the ends 14-bit or 16-bit ADCs?  If they're 16-bit, then I can set the gain somewhere between the current X and Y values.

 Finally, I added a section of the 40m's DCC document tree for the QPD whitening:  E1400473, with a page for each end.  Xend = D1400414, Yend = D1400415.

  10799   Mon Dec 15 22:30:50 2014 JenneUpdateElectronicsYend QPD modified

Details later - empty entry for a reply.

Short story - Yend is now same as Xend filters-wise and lack of gain sliders -wise.  Both ends have 13.7k resistors around the AD620 to give them gains of ~4.5.

Xend seems fine.

Yend seems not fine.  Even the dark noise spectrum sees giganto peaks.  See Diego's elog 10801 for details on this investigation.

  10801   Mon Dec 15 22:45:59 2014 JenneUpdateElectronicsYend QPD modified

 

 [Jenne, Rana, Diego]

We did some test on the modified QPD board for the Yend; we saw some weird oscillations at high frequencies, so we went and check more closely directly within the rack. The oscillations disappear when the cable from the QPD is disconnected, so it seems something is happening within the board itself; however, looking closely at the board with an oscilloscope in several locations, with the QPD cable connected or disconnected, there is nothing strange and definitely nothing changing if the cable is connected or not. In the plots there are the usual channels we monitor, and the 64kHz original channels before they are downsampled.

Overall it doesn't seem being a huge factor, as the RMS shows at high frequencies, maybe it could be some random noise coming up, but anyway this will be investigated further in the future.

Attachment 1: QPD_Ytrans_oscillating_15Dec2014.pdf
QPD_Ytrans_oscillating_15Dec2014.pdf
Attachment 2: QPD_IOPchannels_Ytrans_oscillating_15Dec2014.pdf
QPD_IOPchannels_Ytrans_oscillating_15Dec2014.pdf
  10804   Tue Dec 16 03:43:09 2014 JenneUpdateLSCPRMI loops need help

[Jenne, Rana, Diego]

After deciding that the Yend QPD situation was not significant enough to prevent us from locking tonight, we got started.  However, the PRMI would not acquire lock with the arms held off resonance. 

This started some PRMI investigations.

With no arms, we can lock the PRMI with both REFL55 I&Q or REFL165 I&Q.  We checked the demod phase for both Refl 55 and 165.  REFL55 did not need changing, but REFL165 was off significantly (which probably contributed to the difficulty in using it to acquire lock).  I didn't write down what REFL165 was, but it is now -3 degrees.  To set the phase (this is also how Rana checked the 55 phase), I put in an oscillation using the sensing matrix oscillators.  For both REFL165I and 165Q, I set the sensing matrix demod phases such that all of the signal was in the I phase (so I_I and Q_I, and basically zero in I_Q and Q_Q).  Then, I set the main PD demod phase so that the REFL165Q phase (the Q_I phase) was about zero.

Here are the recipes for PRMI-only, REFL55 and REFL165:

Both cases, actuation was PRCL = 1*PRM and MICH = (0.5*BS - 0.2625*PRM).  Trigger thresholds for DoFs and FMs were always POP22I, 10 up and 0.5 down.

REFL55, demod phase = 31deg.

MICH = 2*R55Q, gain = 2.4, trig FMs 2, 6, 8.

PRCL = 12*R55I, gain = -0.022, trig FMs 2,6,9.

REFL165, demod phase = -3deg.

MICH = -1*R165Q, gain = 2.4, trig FMs 2,6,8.

PRCL = 2.2*R165I, gain = -0.022, trig FMs 2,6,9.

These recipes assume Rana's new resonant gain filter for MICH's FM6, with only 2 resonant gains at 16 and 24 Hz instead of a whole mess of them: elog 10803.  Also, we have turned down the waiting time between the MICH loop locking, and the filters coming on.  It used to be a 5 second delay, but now is 2 sec.  We have been using various delays for the PRCL filters, between 0.2s and 0.7s, with no particular preference in the end.

We compared the PRCL loop with both PDs, and note that the REFL 165 error signal has slightly more phase lag, although we do not yet know why.  This means that if we only have a marginally stable PRCL loop for REFL55, we will not be stable with REFL165. Also, both loops have a non-1/f shape at a few hundred Hz.  This bump is still there even if all filters except the acquisition ones (FM4,5 for both MICH and PRCL) are turned off, and all of the violin filters are turned off.  I will try to model this to see where it comes from.

PRMI_55vs165_15Dec2014.pdf

To Do list:

Go back to the QPDY situation during the daytime, to see if tapping various parts of the board makes the noise worse.  Since it goes up to such high frequencies, it might not be just acoustic.  Also, it's got to be in something common like the power or something, since we see the same spectra in all 4 quadrants. 

The ASS needs to be re-tuned. 

Rana was talking about perhaps opening up the ETMX chamber and wiggling the optic around in the wire.  Apparently it's not too unusual for the wire to get a bit twisted underneath, which creates a set of places that the optic likes to go to.

Diego is going to give us some spectra of the MC error point at various levels of pockel's cell drive.  Is it always the same frequencies that are popping up, or is it random?

  10810   Wed Dec 17 14:42:13 2014 JenneUpdateLSCPRMI loops need help

EricQ's crazy people filter has been deleted.  I'm trying to lock right now, to see if all is well in the world.

  10818   Fri Dec 19 15:59:49 2014 JenneUpdateLSCLockloss from Wed

I swapped out one of the channels on Q's lockloss plotter - we don't need POP22Q, but I do want the PC drive.  

So, we still need to look into why the PC drive goes crazy, and if it is related to the buildup in the arms or just something intrinsic in the current FSS setup, but it looks like that was the cause of the lockloss that Q and Diego had on Wednesday.

1102929772_PCdriveRailed.png

  10821   Fri Dec 19 18:08:46 2014 JenneUpdateCDSSOS!!! HELP!! EPICS freeze 45min+ so far!

[Jenne, Diego]

The EPICS freeze that we had noticed a few weeks ago (and several times since) has happened again, but this time it has not come back on its own.  It has been down for almost an hour so far. 

 So far, we have reset the Martian network's switch that is in the rack by the printer.  We have also power cycled the NAT router.  We have moved the NAT router from the old GC network switch to the new faster switch, and reset the Martian network's switch again after that.

We have reset the network switch that is in 1X6.

We have reset what we think is the DAQ network switch at the very top of 1X7.

So far, nothing is working.  EPICS is still frozen, we can't ping any computers from the control room, and new terminal windows won't give you the prompt (so perhaps we aren't able to mount the nfs, which is required for the bashrc).

We need help please!

  10824   Fri Dec 19 20:44:23 2014 JenneUpdateComputer Scripts / ProgramsFSS Slow servo moved to megatron

Today Q moved the FSS slow servo over to some init thing on megatron, and some time ago he did the same thing to the MC auto locker script.  It isn't working though.

Even though megatron was rebooted, neither script started up automatically.  As Diego mentioned in elog 10823, we ran sudo initctl start MCautolocker and sudo initctl start FSSslow, and the blinky lights for both of the scripts started.  However, that seems to be the only thing that the scripts are doing.  The MC auto locker is not detecting lockloses, and is not resetting things to allow the MC to relock.  The MC is happy to lock if I do it by hand though.  Similarly, the blinky light for the FSS is on, but the PSL temperature is moving a lot faster than normal.  I expect that it will hit one of the rails in under an hour or so. 

The MC autolocker and the FSS loop were both running earlier today, so maybe Q had some magic that he used when he started them up, that he didn't include in the elog instructions?

  10853   Mon Jan 5 18:15:18 2015 JenneUpdateCDSiscex reboot

Rana noted last week that TRX's value was stuck, not getting to the lsc from iscex.  I tried restarting the individual models scx, lsc and even scy (since scy had an extra red rfm light), to no avail.  I then did sudo shutdown -r now on iscex, and when it came back, the problem was gone.  Also, I then did a diag reset which cleared all of the unusual red rfm lights.

Things seem fine now, ready to lock all the things.

  10859   Tue Jan 6 17:41:20 2015 JenneConfigurationCDSDTT doesn't do envelopes??

[Jenne, Diego]

We are working on trying out the UGF servos, and wanted to take loop measurements with and without the servo to prove that it is working as expected.  However, it seems like new DTT is not following the envelopes that we are giving it. 

If we uncheck the "user" box, then it uses the amplitude that is given on the excitation tab.  But, if we check user and select envelope, the amplitude will always be whatever number is the first amplitude requested in the envelope.  If we change the first amplitude in the envelope, DTT will use that number for the new amplitude, so it is reading that file, but not doing the whole envelope thing correctly.

Thoughts?  Is this a bug in new DTT, or a pebkac issue?

  10860   Wed Jan 7 02:54:09 2015 JenneUpdateLSCFiddling with DARM filters

One of the things that we had talked about last night was the totally tiny amount of phase margin that we have in the CARM and DARM loops.  DARM seemed to be the most obnoxious loop last night, so I focused on that today, although the CARM and DARM loops are pretty much identical.

(Q tells me via email that the phase budget has the same ~14 degree discrepancy between what we expect and what we measure as his estimate last night.  However, the Caltech network issues prevented his posting an elog.)

So, we definitely need to figure out where this 14 deg is going, but for now, I wanted to see if I could recover a couple of extra degrees just by modifying the filters.

The original filters do seem to eat a lot of phase:

DARM_design_orig.pdf

The short version of the story is that I didn't leave the filters changed at all.  I reverted back to the last version of the filter file from Monday night, so currently everything is as it was.

I tried increasing the Q of the zeros on the cyan and brown filters, which would sacrifice some gain at ~20 Hz, but hopefully win us 10+ degrees of phase.  This gave me a dip of about a factor of 2 between the new and old filters (all servo filters combined added up to this factor of 2 in magnitude) between ~20Hz - 70Hz. 

When we were locked using DARM for just the Yarm (for the UGF servo commissioning), I took a spectra of the error signal (which was POY) as a reference, then loaded in my new filters.  For the most part, the spectra didn't change (which is good, since the magnitude of the filter didn't change much.).  The spectra was bigger though between 50-70Hz, in kind of a sharp bandpass-looking shape that I wasn't expecting.    I don't know exactly why that's happening.

Anyhow, we tried the new filters once or twice with the full IFO, but kept losing lock.  Since I clearly haven't put in enough thought yet for these (particularly, how much suppression do we really need? what are our requirements???), I reverted back to the filter file from last night.  We continued locking, and checking out the new UGF servo that Diego is elogging about.

  10862   Wed Jan 7 03:04:13 2015 JenneUpdateLSCTRY (thorlabs pd) weird noise

[Jenne, Diego, Rana]

This is a note about work done last night. 

We were starting to lock, and saw glitches in the Thorlabs TRY PD about once every 1/60th of a second.  It is not a sine wave, so it is not 60Hz line noise directly.  It looks like this:

TRY_60Hz_peaks_5Jan2015.pdf

Rana pointed out that this looks like it could be from a power supply that is converting AC to DC. 

We went down to the Yend, and noticed some weird symptoms.  So far, we do not know where the noise is coming from.  Rather, we are just using the QPD for locking.

* The noise comes and goes, particularly if someone is moving around at the end station.

* Moving the Thorlabs power supply farther from the HeNe power supply didn't do much.  Turning off and disconnecting the HeNe supply didn't make the noise go away, so we conclude that it is not the HeNe's fault.

* We suspected the loops of excess cable that were sitting on top of iscey, but moving the coils away from the computer did not make the noise go away.

* We removed a few disconnected BNC cables that were near or touching the end table, but that didn't fix things.

* We disconnected the PD's signal cable and pulled it out of the table enclosure, and then put it back.  Noise was gone when cable was disconnected (good), but it was back after plugging the cable back in.

* The noise still comes and goes, but we don't have to use the Thorlabs PD for locking, so we leave it for another day.

RXA: also moved the Thorlabs power supply to a different power strip and tried putting it closer/farther to the Uniblitz shutter controller. Another suspect is that its some PWM type noise from the doubler crystal temperature driver. Need to try turning off the heater and the Raspberry PI to if it effects the noise.

  10863   Wed Jan 7 03:09:15 2015 JenneUpdateLSCPRFPMI status & IFO status

As a warm-up after the holidays, before the real locking began, I installed 1064nm bandpass filters in front of the transmission QPDs to eliminate the stray green light that is there.

The Yend had threads epoxied to it, so that end should be good.  Steve is going to repeat that for the Xend QPD at some point.  Right now, the filter is just on a lens mount about 2cm away from the PD box aperture, since that's as close as I could get it.

Also, while I was at the Xend, I noticed that the transmission camera is gone.  I assume that it was in the way of Manasa's fiber work, and that it'll get put back somehow, sometime.  She elogged that she had removed it, but I mistakenly thought that it was already replaced.  We don't use that camera much, so I'm not worried.

  10869   Wed Jan 7 14:16:27 2015 JenneUpdateLSCtrans QPDs realigned

Now that both end transmission QPDs have the line filters, I aligned them.

I locked and aligned the IR using the ASS, then went to each end table and put the beam in the center of the QPD.

  10872   Wed Jan 7 15:53:01 2015 JenneUpdateLSCDC PD analog settings exposed

I have added another block to the LSC screen (and made the corresponding sub-screen) to expose the analog settings for the DC photodiodes. 

Note that we have 2 open channels there, which are still called something like "PD2" and "PD3" from olden times.

If we ever chose to use those, we will probably want to change their names, in /cvs/cds/caltech/target/c1iscaux2/LSC_aux2.db and /cvs/cds/caltech/target/c1iscaux/LSC_aux.db

  10876   Thu Jan 8 03:09:07 2015 JenneUpdateLSCToward variable finesse locking

[Jenne, EricQ, Rana]

Tonight we started prepping for an attempt at variable finesse locking. 

The idea is to put in a MICH offset and hold the lock with ASDC/POPDC (so that the offset can be larger than if we were just using RF signals).  This reduces the PRC buildup, which reduces / removes the double cavity resonance problems while reducing the CARM offset. 

  • So.  Today, I pulled out the POP22 razor blade so that we can use the Thorlabs PD as POPDC, without the yaw coupling.  Our other option is to use the POP QPD SUM, but that would require some model changes and more importantly it's not a particularly low noise readout path.
  • We re-set the analog whitening gains for ASDC and POPDC.
    • For ASDC, we want the half-fringe in the PRMI case to be not saturating.  We chose 18dB (it had been the default 0dB).
    • For POPDC, Rana and I saw that it was saturating all the time with the 33dB that it had when the carrier became resonant.  This was never really a problem in the past, but if we use it for normalization, we get glitches that knock us out of lock every time POPDC saturated.  So, now POPDC is at 0dB.  It still occasionally saturates when the PRMI is flashing, but we can't get lower than 0dB without going and putting an ND filter on the PD.
  • We turned off the analog whitening filters and digital unwhitening for both ASDC and POPDC.  We can consider turning them back on later after we have acquired lock if we need them, but we need them off for acquisition.
  • Locked MICH with ASDC/POPDC.  Good.  Stays locked even if PRM is flashing.
  • Locked PRMI with PRCL on REFL33I and MICH on ASDC/POPDC.
  • Locked arms, held off resonance with ALS, lock MICH with ASDC/POPDC. 
  • Failed to lock PRMI with arms held off resonance, using the new scheme (no transition, trying to directly acquire)
  • Locked PRMI on REFL33 I&Q with the arms held off resonance, and tried to transition MICH over to ASDC/POPDC, failed.
  • Confusion about the relative phase between REFL33Q and ASDC.  It looks like it is ~45deg at 100 Hz, or ~90 deg at 375 Hz.  Why isn't it 0 or 180?
  • Went back to PRMI-only, tried to map out fringe by changing MICH offset (tried while MICH was on both REFL33 and ASDC/POPDC).  Not really sure where we are on the fringe.

MICH locked on ASDC normalized by POPDC, PRM and ETMs (and SRM) all misaligned.

MICH offset of -20

MICH input = -0.04*ASDC normalized by 0.1*POPDC.

MICH gain = +5

MICH always triggered on (no triggering for DoF), but FM8 (CLP400) triggered to come on after lock (didn't write down the values).

 

PRMI locked with MICH on ASDC normalized by POPDC, PRCL on REFL33I, ETMs and SRM misaligned.

MICH offset of -10

MICH input = -0.04*ASDC normalized by 0.1*POPDC.

PRCL input = 1*REFL33I

MICH gain = +5

PRCL gain = -0.4 (factor ten times the regular value)

MICH always on, PRCL triggered on POP22.  MICH FM8 and PRCL FM1,2,6,9 triggered on.

Gives POPDC of about 20 counts, POP22 of about 12 counts, ASDC of about 500 counts.

 

Arms held at 3nm, MICH locked on ASDC/POPDC, PRM and SRM misaligned.

MICH offset of -10

MICH input = -0.04*ASDC normalized by 0.1*POPDC.

MICH gain = +5

MICH always on, PRCL triggered on POP22.  MICH FM8 and PRCL FM1,2,6,9 triggered on.

 

Arms held at 3nm, attempt at PRMI lock with MICH on ASDC/POPDC.

Failed.  Tried mostly same MICH gains as arms+mich, and PRCL at 10* normal gain.

 

Arms held at 3nm, PRMI locked with REFL 33 I&Q, attempt at transition to MICH on ASDC/POPDC.

Failed.  At first, I was putting in the TF line at ~375Hz, but we looked at the full transfer function between 100Hz and 1kHz, and there was a weird dip near 300Hz from PRCL-MICH loop coupling.  Here we were seeing that the phase between REFL33Q and ASDC was ~90 degrees.  What?

Tried putting the TF line at ~100 Hz (since MICH UGF is in the few tens of Hz anyway, so 100 is still above that), but still get weird relative phase.  Here it seems to be about 45 degrees when I inject a single line, although it didn't seem like a weird phase when we did the full swept sine earlier.  Maybe I was just not doing something right at that point??

Anyhow, no matter what values I tried to put into the input matrix (starting with REFL33I&Q, trying to get MICH to ASDC/POPDC), I kept losing lock.  This included trying to ramp up the MICH offset simultaneously with the matrix changing, which was meant to help with the PRCL gain change.  Q has since given us MICH and PRCL UGF servos.

 


Tomorrow:

  • Why is there some weirdo phase between REFL33Q and ASDC at 100Hz?  Was I just being a spaz?
  • With PRMI-only, figure out how to transition from REFL33 I&Q over to MICH on ASDC/POPDC.
  • Then hold the arms off resonance, and do the same transition.  (First make sure we're at a good place on the fringe)
  • Lower the CARM and DARM offsets, transition them to RF, engage CARM AO path.
  • Reduce MICH offset, transition to RF.
  • Celebrate (maybe).
  10885   Fri Jan 9 19:18:51 2015 JenneUpdatePSLPMC realigned

A few hours ago I tweaked up the alignment to the PMC.  It was really bad in pitch, and the transmission was down to about 0.711.

  10887   Tue Jan 13 00:42:15 2015 JenneUpdateLSCError signals for MICH with variable finesse technique

In order to know where we should try to make the transition from REFL##Q to ASDC for MICH, I did a quick Optickle simulation to see what the error signals will look like.

The idea is to try to lock the PRMI on a single REFL diode (ex. REFL33 I&Q) with some MICH offset, and then transition over to ASDC.  As soon as we have completed the transition, we can engage the normalization matrix to normalize ASDC by POPDC, and also increase the MICH offset if we want.  Unfortunately, we do not as yet have the ability in our model to independently normalize different error signals, and then blend them, so we have to turn on the normalization after we've transitioned.

Here is the situation for PRMI-only:

You can see that REFL33Q has a slightly wider range than REFL165Q.  It seems like we can perhaps try to make the transition around -15nm or so.  Note that the error signals are not quite symmetric about 0nm, so we can use that to help determine what + and - mean.  We expect that we need to add about 1nm offset to REFL33Q to get a true minimum in ASDC, so the sign of the digital offset that we need will tell us if there is a sign flip or not between the digital offset and this x-axis. 

After we get this to work (hopefully in the next hour or so....), we will want to try the same thing with the arms held off resonance. 

Usually we lock the PRMI at an offset of about 3nm:

However we could do it lower, perhaps around 1nm (which is where we currently are doing our CARM/DARM ALS->IR signals transitions):

At some point, we will arrive at 0nm CARM offset, when we'll want to transition back to RF signals (although probably we could jump straight to a 1f signal, not plotted):

The moral of the story here is that I'm not sure how we were ever successfully locking MICH on REFL165Q, unless my phase-setting in Optickle is way off.  Certainly it looks like we should be sticking with REFL33 for PRFPMI.  Also, since we have an offset in REFL33Q anyway (which we have seen and have commented on before), at 3nm CARM offset it looks like we could try to just do the jump without any extra digital offset.  Here's a zoom of the 3nm situation:

  10891   Tue Jan 13 03:58:27 2015 JenneUpdateLSCTransitioned to ASDC MICH (PRMI and PRFPMI)

[Jenne, Diego, EricQ]

Hopefully there will be more later, but Chiara just went down (network? other?  Q is in there right now looking at it), so this is a so-far-tonight elog.

We have successfully transitioned MICH over from REFL33Q to ASDC in both the PRMI and PRFPMI configurations.  Next up is to start reducing the CARM offset.


Resetting the REFL demod phases

I have been unable to lock the PRMI for more than teeny blips since Thursday.  So, tonight I finally got it to lock with MICH on AS55Q and PRCL on REFL33I, and used that to set the demod phases. 

PRMI, AS55Q and REFL33I MICH PRCL
Input matrix 1*AS55Q 1*R33I
Gain -7 -0.022
DoF trigger POP22I; 80up, 2down POP22I; 80up, 2down
FM trigger FM 2,6,8; 100up, 2down; 0.3sec FM 2,6,9; 100up, 2down; 0.01sec
Normalization n/a n/a
Output matrix 0.5*BS, -0.2625*PRM 1*PRM
UGF servo n/a

n/a

Setting the demod phases, I used an oscillation of 100 cts to PRM, at 400.123 Hz.

REFL 33 demod phase started at 148deg, now 133.2deg.

REFL165 phase started at -105.53, now -172.

No signal in REFL55????  Time series and spectra both look just like noise.  Need to check alignment of beam on PD, or if cables unplugged!!

REFL11 phase started at 16.75, now 18.9deg.

Was then able to lock on REFL 33 I&Q, like normal.

PRMI, REFL33I&Q MICH PRCL
Input matrix 1*R33Q 1*R33I
Gain 2.5 -0.02
DoF trigger POP22I; 80up, 2down POP22I; 80up, 2down
FMs FM 4,5 on FM 4,5 on
FM trigger FM 2,6,8; 100up, 2down; 0.3sec FM 2,6,9; 100up, 2down; 0.01sec
Normalization n/a n/a
Output matrix 0.5*BS, -0.2625*PRM 1*PRM
UGF servo n/a

n/a



Transitioning PRMI from REFL33Q to ASDC

With the PRMI locked on REFL33 I&Q, I found that a MICH offset of -5 counts gives a minimum in ASDC.  From my earlier elog this evening (http://nodus.ligo.caltech.edu:8080/40m/10887), I expect the minimum to be at +1.4nm.  This is only one point though, so I don't know the calibration of the MICH offset yet (we should get this calib during the day by looking at MICH-only).  Anyhow, this informed which side was positive and negative relative to my Optickle plots, so I know that I wanted positive offset in the MICH servo.

I was able to comfortably hold lock at +20 counts.  Looking at a calibration line at 143.125 Hz, I determined that I wanted the matrix element for ASDC to be -0.05.  After I made that transition using ezcastep, I put the POPDC normalization in.  At the time, POPDC was about 151counts, so I put 1/151 in the POPDC->Mich matrix element.

So, here were the final lock parameters.  Note that in PRMI-only, you can acquire lock like this, and with a variety of MICH offsets:

PRMI, ASDC and REFL33I MICH PRCL
Input matrix -0.05 * ASDC 1*R33I
Gain 2.5 -0.02
DoF trigger POP22I; 80up, 2down POP22I; 80up, 2down
FMs FM 4,5 on FM 4,5 on
FM trigger FM 2,6,8; 100up, 2down; 0.3sec FM 2,6,9; 100up, 2down; 0.01sec
Normalization  0.0066 n/a
Output matrix 0.5*BS, -0.2625*PRM 1*PRM
UGF servo n/a

n/a


Locking PRMI part of PRFPMI

Since the PRMI has been fussy, I'm including a brief note on the PRMI settings when the arms are held with ALS off by roughly 3nm.  To get to this point, we just ran the usual carm_cm_up script, and didn't let it run anymore when it asked for confirmation that PRMI was locked.

PRFPMI, Arms=ALS, PRMI=REFL33I&Q MICH PRCL CARM DARM
Input matrix 1*R33Q 1*R33I -1*alsX+1*alsY 1*alsX+1*alsY
Gain 2.5 -0.012 8 8
DoF trigger POP22I; 80up, 2down POP22I; 80up, 2down n/a n/a
FMs FM 4,5 on FM 4,5 on FM 1,2,3,5,6 FM 1,2,3,5,6
FM trigger FM 2,6,8; 50up, 2down; 0.3sec FM 1,2,6,9; 50up, 2down; 0.01sec n/a n/a
Normalization n/a n/a n/a n/a
Output matrix 0.5*BS, -0.2625*PRM 1*PRM 1*etmx+1*etmy -1*etmx+1*etmy
UGF servo n/a set to 150Hz n/a n/a

With MICH offset of -30 counts, AS port is pretty bright.  ASDC dark offset is set to -475.4 by the LSCoffsets script. with MICH offset = 0, ASDC_OUT is around 300counts.  But, with MICH offset = -30, ASDC_OUT is about 525 counts.  So, I put that 525 counts into the ASDC filterbank offset (so it is now the dark offset + this extra offset), so the ASDC offset is currently around -1,000.  This makes the ASDC signal roughly zero when I am ready to transition MICH over to it.  In principle I should probably set it so the average is the same as the MICH offset, but the noise is so high relative to that offset, that it doesn't matter.

After this, we engaged the CARM and DARM UGF servos.  MICH was gain peaking, so I think we might want to turn that one on too, rather than my by-hand turning down the gain.

The transition has been successful 4 or 5 times with the arms held off resonance at 3nm.  Once, we reduced the CARM offset as low as 1.7 (and had to lower the MICH gain to 1.5), but we were still hearing a woomp-woomp sound.  Not sure what that was from.  At this point, Chiara died, so we lost lock.  After that, we re-acquired lock a few more times, but MC keeps losing it.  We are still able to make the MICH to ASDC transition though, which is good.

The transition won't work if the PRCL UGF servo is not on.  The gain multiplier goes from about 1.1 up to 2.4, so the PRCL gain is certainly changing through the transition.

Diego has written up scripts for the individual UGF servos (look for an elog from him separately), so now the carm_cm_up script goes as far as locking the PRMI on REFL33 I&Q, and then it starts to transition.  PRCL UGF is engaged, MICH offset is set to -30 counts, MICH is transitioned to ASDC, POP normalization engaged, CARM UGF servo turned on, and DARM UGF servo turned on.  There are "read"s in the script before each step, so you can stop whenever you like.

Here's the final configuration for the PRFPMI while the arms are held at 3nm, with MICH on ASDC (so after the transition):

PRFPMI, Arms=ALS, PRCL=REFL33I, MICH=ASDC MICH PRCL CARM DARM
Input matrix 0.27*ASDC 1*R33I -1*alsX+1*alsY 1*alsX+1*alsY
Gain 2.5 -0.015 8 8
DoF trigger POP22I; 80up, 2down POP22I; 80up, 2down n/a n/a
FMs FM 4,5 on FM 4,5 on FM 1,2,3,5,6 FM 1,2,3,5,6
FM trigger FM 2,6,8; 50up, 2down; 0.3sec FM 1,2,6,8,9; 50up, 2down; 0.01sec n/a n/a
Normalization 0.0042*POPDC n/a n/a n/a
Output matrix 0.5*BS, -0.2625*PRM 1*PRM 1*etmx+1*etmy -1*etmx+1*etmy
UGF servo n/a set to 150.001Hz set to 115.1Hz set to 110.1

 

The transition for MICH to ASDC has been successful with the arms held off resonance several times tonight. It's all part of the carm_cm_up script now. I think that if we hadn't lost about an hour of time and our momentum, we would have gotten farther.  I have high hopes for tomorrow night!

  10894   Tue Jan 13 13:22:54 2015 JenneUpdateGeneralAUX Y + PSL beat note at 1064nm: needs work

I'm super excited about this new frequency readbacklaugh, but I'm not sure that it's reliable yetfrown.  Without touching any settings, the readback is currently saying 78.6MHz, and is changing slightly (as is the FSS Slow Temp), so something is working.  However, the beatnote as measured on the spectrum analyzer is 158.2MHz.  So, either the calibration or the tracking or something isn't quite finished being tuned yet.cheeky

It's going to be super awesome when we have this though!!cool

  10900   Wed Jan 14 03:42:31 2015 JenneUpdateLSCThoughts on going forward with variable finesse

[Jenne, Rana]

We tried locking with the variable finesse MICH offset technique again today. 

A daytime task tomorrow will be to figure out where we are in MICH and CARM offset spaces.  This will require some thinking, and perhaps some modelling.

We were using the UGF servos and checking out their step resonses, and had the realization that we don't want the gain multiplication to happen before the offsets are applied, in the case of MICH and CARM.  Otherwise, as the UGF servo adjusts the gain, the offset is changed.  I think this is what ChrisW and I saw earlier on in the evening, when it seemed like the CARM offset spontaneously zoomed toward zero even though I didn't think I was touching any buttons or parameters.  Anyhow, we no longer used the MICH and CARM UGF servos for the rest of the night.  We need to think about where we want the offset to happen, and where we want the UGF servo multiplication to happen (maybe at the control point, with a very low bandwidth?) such that this is not an issue.

Also, I'm no longer sure that the sqrt(I^2 + Q^2) instead of the usual demodulation is going to work for the UGF servos (Q made this change the other day, after we had talked about it).  When the numbers going into the I and Q servo banks are small (around 1e-5), the total UGF servo gets the answer wrong by a factor of 10 or so.  If I made the "sin gain" and "cos gain" 1000 instead of the usual 1, the numbers were of the order 1e-2, and the servo worked like normal.  So, I think we were perhaps running into some kind of numerical error somehow.  We first noticed this when we lowered the DARM excitation by a factor of 10, and the servo no longer functioned.  We should take out this non-linear math and go back to linear math tomorrow.

During the evening tomorrow, we should try locking the PRMI with a large MICH offset, and then leaving CARM and DARM on ALS, and seeing how far we can get.  Is it possible to just jump over to RF signals, since we won't have to worry about the detuned cavity pole?

Tonight, the locking procedure was the same as usual, but stopping the carm_up script before it starts to lower the CARM offset at all.  Only difference was that MICH triggered FMs were 2,3,7 rather than the usual 2,6,8. 

So, assuming you have the IFO with CARM and DARM on ALS held at +3 CARM offset counts (which we think is about 3nm), and the PRMI is locked on REFL33I&Q with no offsets, here's what we did:

  • PRCL UGF servo on
  • MICH offset goes to -20
  • MICH transitions to ASDC (0.27*ASDC, then normalize by POPDC)
  • DARM UGF servo on
  • CARM offset to 1 (arms about 0.25)
  • CARM transition to SqrtInvTrans
  • Lower CARM gain to 4
  • CARM offset to 0.6 (arms about 1)
  • DARM transition to DC transmission
  • Increase MICH offset to about -650 or -670
  • Lower CARM offset, see what happens

Something else to think about:  Should we normalize our DC transmission signals by POPDC, so that the arm powers will change when we change the MICH offset (for a constant CARM offset)?

The best we got was holding for a few minutes at arm powers of 7.5, but since the MICH offset was large and the power recycling was low, this was perhaps pretty far.  This is why we need some calibration action.

Also, earlier today I copied the CARM and DARM "slide" filter module screens so that we have the same thing for MICH.  Now all 3 of these degrees of freedom have slider versions of the filter module screens, which are called from the ctrl_compact screen.

  10903   Thu Jan 15 04:41:01 2015 JenneUpdateLSCThoughts on going forward with variable finesse

[Jenne, Diego]

Life would be easier with the UGF servos working.  As Diego already elogged, we aren't sure why the demod phases are changing, but that is certainly causing the I-signals to dip below zero, which the log function can't handle (there is a limiter before the log, so that the signal can't go below 1e-3).  Anyhow, this is causing the UGF servos to freak out, so we have not been using them for tonight's locking.

Our goal tonight was to see if we could introduce a nice big MICH offset, and then lower the CARM offset while keeping the arms locked on ALS.  We hope to see some kind of sign of a PDH signal in some RF PD. 

In the end, the highest we got to was -460 MICH offset counts, which we think is about 29nm (if our rough calibration is accurate). The MICH half fringe should be 188nm. With this offset, we got down to 0.3 CARM offset counts while locked on ALS.  We think that this is around 300pm, plus or minus a lot.  Note that while yesterday I had a pretty easy time getting to -660 counts of MICH offset, tonight I struggled to get past -200.  The only way we ended up getting farther was by lowering the CARM offset.  Although, as I type this, I realized that last night's work already had a lower CARM offset, so maybe that's key to being able to increase the MICH offset. 

We watched REFL11I and REFL11I/(TRX+TRY) on striptool, but we didn't see any evidence of a PDH signal.  We lost lock when I tried to transition CARM over to REFLDC, but I wasn't careful about my offset-setting, so I am not convinced that REFLDC is hopeless.

So.  Tonight, we didn't make any major locking progress (the MC started being fussy for about an hour, right after I ran the LSC offsets script, just before we started locking in earnest).  However, we have some ideas from talking with Rana about directions to go:

* Can we transition CARM over to REFL11I, and then engage the AO path?

* Then, while the MICH offset is still large, can we transition DARM over to POX or POY, actuating on a single arm?  If CARM is totally suppressed, this is DARM-y.  If CARM doesn't have the AO path yet, this is halfsy-halfsy, but maybe we don't care.

* Then, can we lower the MICH offset and transition back to a REFLQ signal?

* Separately, it seemed like we kept losing PRC lock due to PRC motion.  If the MICH offset is very large, are we sideband-limited at the POP port, such that we can use the POP DC QPD?  Is it even worth it?

 

MICH calibration:

A single mirror (ITM) moving by lambda/2, in the MICH-only situation is the full range, from bright to dark fringe.  So, half fringe should be lambda/4, or about 133nm.  If we are thinking about pushing on the BS, there's an extra factor of sqrt(2), so I think the half fringe should be at 188nm of BS motion.

When we had MICH locked on ASDC/POPDC, we put in a line at 143.125Hz, at 20 counts to (0.5*BS-0.2625*PRM), so a total of 10 counts to the BS at 143Hz.  Given the BS calibration in http://nodus.ligo.caltech.edu:8080/40m/8242, this is 10.1pm of actuation.  We saw a line in the error signal of 0.1 counts, so we infer that the MICH error signal of ASDC/POPDC has a calibration of 94pm/count. This number was invariant over a few different MICH offsets, although the ones I measured at were all below about 100 counts of MICH offset, so maybe this number changes as we start to get farther from the MICH dark fringe.

 

IFO left flashing (all mirrors aligned except SRM) in case anyone wants fresh data for that.

  10904   Thu Jan 15 14:28:14 2015 JenneUpdateLSCLSC model change idea

Something that kind of drives me crazy with our current LSC model setup is that I can't make "finished" error signals before blending them.  The blending happens before the normalization matrix, and there is no place to put an offset to help match a new error signal to the current offset.  So.  While I'm sure this is not going to be immediately popular, here's a cartoon of a proposed model change to the LSC. 

The most important difference between this and the ramping matrix that is used at the sites is that you can put in offsets before the blend.  Also useful is the fact that the normalization can happen before the blend.  This proposal would make the LSC input matrix  and the normalization matrix have twice as many rows, and add an extra "selector matrix" just before the triggering at the error point of the loops. 

I've only drawn one degree of freedom in my cartoon, but assume that they all have the same capability (maybe we don't have to do XARM, YARM and MC this way).  One row is currently being used for the error signal, while the other row is just used to prep a new singal.  For a first transition (say, ALS to DC transmission), maybe the ALS signals are on row 1, and the DC trans is on row 2.  Once the transition is complete, row 1 is available to prep for the next transition (such as AS55Q).

 

Thoughts?  Is there a better way to achieve what I'm going for here?

Attachment 1: SwitchableErrorSignalProposal_Jan2015.pdf
SwitchableErrorSignalProposal_Jan2015.pdf
  10905   Thu Jan 15 18:06:34 2015 JenneUpdateComputer Scripts / ProgramsInstalled kerberos on Rossa

I have installed kerberos on Rossa, so that I don't have to type my name and password every time I do an svn checkin, since I'm making some modifications and want to be sure that everything is checked in before and afterwards. 

I ran sudo apt-get install krb5-user.  I didn't put in a default_realm when it prompted me to during install, so I went into the /etc/krb5.conf file and changed the default_realm line to read default_realm = LIGO.ORG

Now we can use kinit, but we must (as usual) remember to kdestroy our credentials when we're done.

As a reminder, to use:

> kinit albert.einstein

Password for albert.einstein@LIGO.ORG: (type your pw here)

When you're finished, run

> kdestroy

The end.

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