For tuning the phase and amplitude of the mod. drive:
- since we don't have access to both RF phases, I just maximized the gain using the RF phase slider. First, I flipped the sign using the 'phase flip' button so that we would be near the linear range of the slider. Then I put the servo close to oscillation and adjusted the phase to maximize the height of the ~13 kHz body mode. For the amplitude, I just cranked the modulation depth until it started to show up as a reduction in the transmission by ~0.2%, then reduced it by a factor of ~3. That makes it ~5x larger than before.
* PMC + MC were unlocked when I came in.
* I fiddled around some more with the mcup/down scripts to make locking snappier. The locking was breaking the PMC lock often, so I re-enabled the MC servo board output limiter during acquisition. It is disabled in the MC UP script.
* Re-measured the MC OLG. Still OK.
* Measured the PZT / EOM crossover (aka the FAST / PC crossover) using the connectors on Koji's summing box. With the FAST gain at 18 dB, the crossover is ~10 kHz. Looks way to shallow. Plots to follow.
* I finally discovered today that the PMC PZT stroke is what's causing the main mis-alignment of the beam going to the IMC. By relocking at a few positions, I could see that the IOO QPDs have steps when the PMC relocks. So the IO beam wander is NOT due to temperature effects on the optics mounts of the PSL table. I wonder if we have a large amount of length to angle coupling or if this is the same as the OMC PZTs ?
P.S. I found that someone is using a temporary bench power supply to power the summing box between the TTFSS and the Thorlabs HV driver...whoever did this has ~48 hours to hook up the power in the right way or else Koji is going to find out and lose it and then you have to wear the Mickey Mouse hat.
The first attachment shows the OLG measurements with 2 different values of the fast gain (our nominal FG is 18 dB). You can see that the higher gains produce some crossover instability; when tuning the gain we notice this as an increase in the PCDRIVE rms channel.
The second attachment shows the measurement of the 'crossover'. Its really just the direct measurement of the IN1 / IN2 from the FAST summing box, so its the crossover measurement where the OLG is high.
A few things that I have neglected to ELOG yet:
scripts/offsets/LSCoffsets is a new script that uses ezcaservo to set FM offsets of our LSC PDs. It still warns about large changes, and lets you revert. It reads the FM gain to pick the right gain for the ezcaservo call.
We never, ever want to use ezcaservo to do this. IN fact, we twice have already deleted scripts where people have implemented these (sometimes) unstable servos. Also, since this change had never been committed to the SVN, I just deleted it and updated from the SVN to get back the script that doesn't use any servos.
I'm going to periodically delete locking scripts that are not committed to the SVN since anyone who is too lazy to use the SVN probably can't write code worth using.
The attached PDF shows the Mathematica notebook and the associated block diagram.
In the notebook, I have written the single hop connection gains into the K matrix. P is the optical plant, C is the Common electronic gain, F is the 'fast' NPRO PZT path, and M is the phase Modulator.
G is the closed loop gain matrix. The notation is similar to matlab SS systems; the first index is the row and the second index is the column. If you want to find the TF from node 2 to node 3, you would ask for G[[3,2]].
As examples, I've shown how to get the FAST gain TF that I recently made with the Koji filter box as well as the usual OLG measurement that we make from the MC servo board front panel.
Why AS55/(TRX + TRY) instead of just TRX? Isn't (TRX+TRY) controlled by CARM?
(question is secretly from Kiwamu)
This is good news. It means that the driver probably won't limit the response of the loop - I expect we'll get 20-30 deg of phase lag @ 100 kHz just because of the acoustic response of the AOM PZT + crystal.
Here is a lock loss from around 11 PM tonight. Might be due to poor PRC signals.
This is with arm powers of ~6-10. You can see that with such a large MICH offset, POP22 signal has gone done to zero. Perhaps this is why the optical gain for PRCL has also dropped by a factor of 30 .
This seems untenable . We must try this whole thing with less MICH offset so that we can have a reasonable PRCL signal.
No elog response from outside and no elogd process on nodus, so I restarted it using 'start-elog.csh'.
The nonlinearity in the LSC detection chain (cf T050268) comes from the photodetector and not the demod board. The demod board has low pass or band pass filters which Suresh installed a long time ago (we should check out what's in REFL33 demod board).
Inside the photodetector the nonlinearity comes about because of photodiode bias modulation (aka the Grote effect) and slew rate limited distortion in the MAX4107 preamp.
With the Y Arm locked, we checked that we indeed can get loop decoupling using this technique.
The guess filter that we plugged in is a complex pole pair at 1 Hz. We guessed that the DC gain should be ~4.5 nm count. We then converted this number into Hz and then into deg(?) using some of Jenne's secret numbers. Then after measuring, we had to increase this number by 14.3 dB to an overall filter module gain of +9.3.
The RED trace is the usual 'open loop gain' measurement we make, but this time just on the LSC-MC path (which is the POY11_I -> ETMY path).
The BLUE trace is the TF between the ALS-Y phase tracker output and the FF cancellation signal. We want this to be equal ideally.
The GREEN trace is after the summing point of the ALS and the FF. So this would go to zero when the cancellation is perfect.
So, not bad for a first try. Looks like its good at DC and worse near the red loop UGF. It doesn't change much if I turn off the ALS loop (which I was running with ~10-15x lower than nominal gain just to keep it out of the picture). We need Jenne to think about the loop algebra a little more and give us our next filter shape iteration and then we should be good.
The filters were already in the damping loops but missing the MC WFS path. I checked that these accurately cover the peaks at 16.5 Hz and 23.90 and 24.06 Hz.
In the drawing, the FF path should actually be summed in after the Phase Tracker (i.e. after S_ALS). This means that the slow response of the phase tracker needs to be taken into account in the FF cancellation filter. i.e. D = -A_REFL * P_ALS * S_ALS. Since the Phase Tracker is a 1/f loop with a 1 kHz UGF, at 100 Hz, we can only get a cancellation factor of ~10.
So, tonight we added a 666:55 boost filter into the phase tracker filter bank. I think this might even make the ALS locking loops less laggy. The boost is made to give us better tracking below ~200 Hz where we want better phase performance in the ALS and more cancellation of the ALS-Fool. If it seems to work out well we can keep it. If it makes ALS more buggy, we can just shut it off.
Its time to take this loop cartoon into OmniGraffle.
Depends on the plots of the whitening I guess; if its low freq sat, then we lower the light level with ND filters. If its happening above 10 Hz, then we switch off the whitening.
Went to zero CARM offset on ALS; transmission QPDs are still saturating :(
Maybe we need to switch off all whitening.
I wonder if DRMI can be locked on 3f using this lower 55 MHz modulation depth. It seems that PRMI should be unaffected, but that the 3*f2 signals for SRCL will be too puny. Is it really possible to scale up the overall modulation depths by 3x to compensate for this?
Following this entry, I have made the same change in the controls account on rossa:
In the ~/.grace/gracerc file (create one if it doesn't exist), put in a line which reads:
PAGE LAYOUT FREE
Now we can scale our dataviewer live and playback plots by stretching the window with our mouse. The attached screenshot shows how I filled up one of the vertical monitors with a DV window for arm locking.
Might have to also get the OL screens that go with this new code to see, but the calibrations don't go into the matrix, but rather into the OLPIT/OLYAW filter banks which follow the division, but before the servo filter banks.
The Schnupp asymmetry is definitely not an important parameter (no need for Koji to explode). It only serves to give us a bigger Q phase signal slope, but is not significant for the I phase signals.
The main anomaly is that the REFL33 optical gain (W/m) seems to have been reduced so much by the phase and amplitude adjustment of the 55 MHz modulation signal. One guess is that the true 3f signal is being made not by the (2*f1 - (-f1)) beat, but by some higher order beat. In addition to the usual RF fields produced by the 2 modulations, we must consider that the sidebands on sidebands produce intermodulation fields just after the EOM and so the fields with which we interrogate the PRMI are more complicated.
Jenne's Optickle calculation today should show us what the sensing matrix contribution is from each pair of fields, so that we can have a sensing matrix signal budget.
I have adapted one of Evan's python scripts into an ipython notebook for calculating our PRMI sensing matrix - the work is ~half done.
The script gets the data from the various PD channels (like REFL33_I) and demdoulates it at the modulation frequencies. At the moment its using just the sensing channels, but with the recent addition of the SUS-LSC_OUT_DQ channels, we can demod the actuation channels as well and not have to hand code the exc amplitudes and the basolute phase. Please ignore the phase for the moment.
The attached PDF shows the demod (including lowpass) outputs for a 2 minute stretch of PRMI locked on f2. Next step is to average these numbers and make the radar plots with the error bars. The script is scripts/LSC/SensingMatrix/PRMIsensMat.ipynb and is in the SVN now.
** along the way, I noticed that the reason this notebook hasn't been working since last night is that someone sadly installed a new anaconda python distro today without telling anyone by ELOG. This new distro didn't have all the packages of the previous one. I've updated it with astropy and uncertainties packages.
I've fixed the Radar plot making part, so that's now included too. The radial direction is linear, so you can see from the smearing of the blobs that the uncertainty is represented in the graphics due to each measurement being a small semi-transparent dot. Next, we'll put the output of the statistics on the plot: mean, std, and kurtosis.
Just in case there was some confusion, the champagne on my desk is not to be opened before I get back, no matter how many signals are transitioned to RF.
In the attached plot you can see that the MC REFL fluctuations started getting larger on Feb 24 just after midnight. Its been bad ever since. What happened that night or the afternoon of Feb 23?
The WFS DC spot positions were far off (~0.9), so I unlocked the IMC and aligned the spots on there using the nearby steering mirrors - lets see if this helps.
Also, these mounts should be improved. Steve, can you please prepare 5 mounts with the Thorlabs BA2 or BA3 base, the 3/4" diameter steel posts, and the Polanski steel mirror mounts? We should replace the mirror mounts for the 1" diameter mirrors during the daytime next week to reduce drift.
This has been done before:
Arm length measurements and g-factor estimates in 2012, but only with an accuracy of ~30 cm. However, Yuta was able to get many FSRs somehow.
MC Refl alignment follow up: the alignment from last night seems still good today. We should keep an on the MC WFS DC spots and not let them get beyond 0.5.
According to the official rules, we only need 8 seconds to declare it "locked".
I wonder if the double cavity pole compensation filter for CARM was on for all the attempts yesterday? IF it looks like it will not saturate, it would be more stable to have the whitening on for REFL11 / AS55. Since on Friday, I set the REFL165 demod phase just by minimizing the MICH control signal with the arms on resonance, we ought to check out the PRMI degeneracy with the ETMs misaligned.
Speaking of signal mixing: Although we weren't able to get the carrier term cancelled in the 3*f1 signals by the relative mod phase method, I wonder if we can do it by mixing the 3*f1 and 3*f2 signals in the input matrix. Might help to keep the PRMI more stable, if that's an issue.
P.S. I have done some scripts directory / SVN cleanup. Adding some directories that were not in (like lockloss) and then removing stuff from the repo using 'svn rm --keep-local filenames' for the image and data files.
Since the DARM_OUT signal is only 500 counts_peak, I don't see why AS55 whitening needs to be switched on. Maybe in a couple weeks after the lock is robust. In any case, its much better to do the switching BEFORE you're using AS55, not after.
Another thought about the mystery PCDRIVE noise: we've been thinking that it could be some slow death inside the NPRO, but it might also be a broken and intermittent thing in the MC servo or MC REFL PD.
Another possibility is that its frequency noise in the old oscillator used to drive the pre-PMC EOM (which is the Pockel Cell for the FSS). To check this, we should swap in a low noise oscillator for the PMC. I have one for testing which has 36 and 37 MHz outputs.
The oplev situation still seems unresolved - notice this DTT. I guess there are still inconsistencies in the screens / models etc.
Could use some some investigation and ELOGGING from Eric.
So, was there real shifting in the ITMX alignment as seen in the DV trend or just mis-diagnosis from the ETMX violin mode? Or how would the ETMX violin mode drive the ITMX with the LSC feedback disabled?
The rsync job to sync our frames over to the cluster has been on a 20 MB/s BW limit for awhile now.
Dan Kozak has now set up a cronjob to do this at 10 min after the hour, every hour. Let's see how this goes.
You can find the script and its logfile name by doing 'crontab -l' on nodus.
This is a very cool result. I'm surprised that it can work so good. Please post what frequency dependent weighting you used on the target before running the Wiener code.
I think its important to tune it to keep the low frequencies from getting amplified by a factor of 10 (as they are in your plots). The seismometers are all just noise acting like thermometers and tilt sensors below 0.1 Hz. Temperature and tilt do not couple to our interferometer very much.
It also seems weird that you would need 20th order filters to make it work good. In any case, you can always split the SOS up into pieces before making the digital filters. For LLO, we used 3 buttons in some cases.
Before locking for the evening, I wanted to try again implementing the Wiener filters that I had designed back in Jaunary (elog 10959).
Unfortunately, this kind of trend plot is not detailed enough to know if something has gone bad in a quantitative way. But at least we can tell that the suspension wire didn't break.
+1 to both Evan and Zach for prompt info and +2 to you for getting more stuff than you started looking for. -2 karma to whomever had swiped them and hoarded without signing. You should put a 40m sticker on both of them. Make sure to check / use fresh batteries. The Busby box is BJT based and works on low impedance sources, the Rai box works on anything, but (I am guessing) has less CMRR.
The Rai box was in the Cryo lab, and the Busby box was in the TCS lab. Neither had been signed out. Lame. Anyhow, thanks to Evan and Zach's memories of having seen them recently, they have been returned to the 40m where they belong. (Also, I grabbed a spare Marconi while I was over there, for the phase noise measurement).
It doesn't work with the lens in there, but it seems pretty close. Please leave it as is and I'll play with it after 5 today.
To test what the inherent angular noise of the HeNe 1103P laser is, we're testing it on a table pointing into the BS OL QPD with only a few steering mirrors.
From the setup that I found today, I've removed the lens nearest to the laser (which was used for the BS and PRM) as well as the ND filter (what was this for?) and the lens placed just before the BS QPD.
With the ND filter removed, the quadrant signals are now ~15000 if we misalign it and ~9000 each with the beam centered.
In order to calibrate the OLPIT_IN1 and OLYAW_IN1 signals into mm of beam motion, I misaligned the mirror just before the QPD. The knobs on there actuate the 100 TPI screws and the knurling on the knob itself has 10 ridges, so that's 36 deg per bump.
PIT cal ~ 1.55 (knob deg / count) -->> 10 microns / count --->>> 10 urad / count
YAW cal ~ 1 (knob deg / count) -->> 6.5 microns / count --->>> 6.5 urad / count
Distance from the 45 deg turning mirror to the QPD silicon surface is 23 cm. Distance between knob tip and fixed pivot point is ~4 cm. 1 knob turn = 0.01" = 0.254 mm = 0.254/40 radians of mirror angle.
So 360 deg of knob gives 2*0.254/40 = 0.012 radians of beam angle = 0.012 * 230 mm ~2.3 mm of beam spot motion. Or 6.4 microns of translation / deg of knob.
The distance from the face of the laser to the QPD is 96 cm.
The punchline is that the laser shows a level of noise which has a similar shape to what's seen at LLO, but 10x lower.
The noise at 0.05 - 0.2 Hz is ~2-3x worse than the PR3 at LLO. Not sure if this is inherent to the HeNe or the wind in our setup.
Just randomly found this old entry from 3 years ago. We should never have installed a GAP 2000 - they are an inferior type of InGaAs diode. We should add to our list replacing these with a 2 mm EG&G diode.
How many 2 mm EG&G InGaAs diodes do we have Steve? Can you please find a good clean diode case so that we can store them in the optics cabinet on the south arm?
We replaced the dead photodiode on MC REFL PD with a new one (GAP 2000). We measured the frequency response of the PD and tuned the resonant frequency using inductor L5 (in the circuit diagram) to be 29.575MHz - over an average of 10 measurements.
Q: please update this Wiki page with the go-back procedure:
For 1/4-20 bolts made of 18-8 Stainless Steel, the recommended torque varies from 65-100 inch-pounds, depending upon the application, the lubrication, how loose the bolt is, if there's a washer, etc.
For our case, where we are going into a tapped, ferromagnetic stainless table, its less clear, but it will certainly by in the 60-80 range. This is close to the 5-6 foot-lbs that I recommended on Wednesday.
I've ordered 3 torque wrenches with 1/4" drive so that we can have one at each end and one in the toolbox near MC2. We'll indicate the recommended torque on there so that we can tighten everything appropriately.
Recently, Steve replaced the HeNe which was sourcing the BS & PRM OL. After replacement, no one checked the beam sizes and we've been living with a mostly broken BS OL. The beam spot on the QPD was so tiny that we were seeing the 'beam is nearly the size of the segment gap' effect.
Today I removed 2 of the lenses which were in the beam path: one removed from the common PRM/BS path, and one removed from the PRM path. The beams on both the BS & PRM got bigger. The BS beam is bigger by a factor of 7. I've increased the loop gains by a factor of 6 and now the UGFs are ~6 Hz. The loop gains were much too high with the small beam spots that Steve had left there. I would prefer for the beams to be ~1.5-2x smaller than they are now, but its not terrible.
Many of the mounts on the table are low quality and not constructed stably. One of the PRM turning mirror mounts twisted all the way around when I tried to align it. This table needs some help this summer.
In the future: never try locking after an OL laser change. Always redo the telescope and alignment and check the servo shape before the OL job is done.
Also, I reduced the height of the RG3.3 in the OL loops from 30 to 18 dB. The BS OL loops were conditionally stable before and thats a no-no. It makes it oscillate if it saturates.
Upgraded python on megatron. Added lines to the crontab to run autoMX.py. Edited crontab to have a PYTHONPATH so that it can run .py stuff.
But autoMX.py is still not working from inside of cron, just from command line.
Since python from crontab seemed intractable, I replaced autoMX.py with a soft link that points at autoMX.sh.
This is a simple BASH script that looks at the LSC FB stat (C1:DAQ-DC0_C1LSC_STATUS), and runs the restart mxstream script if its non-zero.
So far its run 5 times successfully. I guess this is good enough for now. Later on, someone ought to make it loop over other FE, but this ought to catch 99% of the FB issues.
If it all possible, don't use links to your home directory. Its not robust. It would be like if you clicked on your Google Music and it told you to ask me to sing that song to you. Imagine that on auto-repeat next time your fancy-bone itches.
Since the nodus upgrade, Eric/Diego changed the old csh restart procedures to be more UNIX standard. The instructions are in the wiki.
After doing some software updates on nodus today, apache and elogd didn't come back OK. Maybe because of some race condition, elog tried to start but didn't get apache. Apache couldn't start because it found that someone was already binding the ELOGD port. So I killed ELOGD several times (because it kept trying to respawn). Once it stopped trying to come back I could restart Apache using the Wiki instructions. But the instructions didn't work for ELOGD, so I had to restart that using the usual .csh script way that we used to use.
Today I tried some things, but basically, lowering the input gain by 10 made the thing stable. In the attached screenshotstrip, you can see what happens with the gain at 1. After a few cycles of oscillation, I turned the gain back to 0.1.
There still is an uncontrolled DoF, but I that's just the way it is since we only have one mirror (the BS) to steer into the x arm once the yarm pointing is fixed.
Along the way, I also changed the phase for POX, just in case that was an issue. I changed it from +86 to +101 deg. The attached spectra shows how that lowered the POX_Q noise.
I also changed the frequencies for ETM_P/Y dither from ~14/18 Hz to 11.31/14.13 Hz. This seemed to make no difference, but since the TR and PO signals were quieter there I left it like that.
This is probably OK for now and we can tune up the matrix by measuring some sensing matrix stuff again later.
We want to have a VAC page in the summaries, so Steve - please put a list of important channel names for the vacuum system into the elog so that we can start monitoring for trouble.
Also, anyone that has any ideas can feel free to just add a comment to the summary pages DisQus comment section with the 40m shared account or make your own account.
Installed libmotif3 and libmotif4 on nodus so that we can run dataviewer on there.
Also, the lscsoft stuff wasn't installed for apt-get, so I did so following the instructions on the DASWG website:
Then I installed libmetaio1, libfftw3-3. Now, rather than complain about missing librarries, diaggui just silently dies.
Then I noticed that the awggui error message tells us to use 'ssh -Y' instead of 'ssh -X'. Using that I could run DTT on nodus from my office.
Still processing, but I think it should work fine once we have a day of data. Until then, here's the summary pages so far, including Vac channels:
Same thing again today. So I renamed the /etc/init/elog.conf so that it doesn't keep respawning bootlessly. Until then restart elog using the start script in /cvs/cds/caltech/elog/ as usual.
I'll let EQ debug when he gets back - probably we need to pause the elog respawn so that it waits until nodus is up for a few minutes before starting.
Looks like some of our seismometers are oscillating, not mounted well, or something like that. No reason for them to be so different.
Which Guralp is where? And where are our accelerometers mounted?
X arm was far out in yaw, so I reran the ASS for Y and then X. Ran OK; the offload from ASS outputs to SUS bias is still pretty violent - needs smoother ramping.
After this I recentered the ITMX OL- it was off by 50 microradians in pitch. Just like the BS/PRM OLs, this one has a few badly assembled & flimsly mounts. Steve, please prepare for replacing the ITMX OL mirror mounts with the proper base/post/Polaris combo. I think we need ~3 of them. Pit/yaw loop measurements attached.
Based on the PEM-SEIS summary page, it looked like GUR1 was oscillating (and thereby saturating and suppressing the Z channel). So I power cycled both Guralps by turning off the interface box for ~30 seconds and the powering back on. Still not fixed; looks like the oscillations at 110 and 520 Hz have moved but GUR2_X/Y are suppressed above 1 Hz, and GUR1_Z is suppressed below 1 Hz. We need Jenne or Zach to come and use the Gur Paddle on these things to make them OK.
From the SUS-WatchDog summary page, it looked like the PRM tripped during the little 3.8 EQ at 4AM, so I un-tripped it.
Caryn's temperature sensors look like they're still plugged in. Does anyone know where they're connected?