The quantum noise curves here are not correct. c.f. amplitude quadrature noise budget.
In the style of the KA characterization of the CM board, the AO path gain EPICS slider (IN2) of the IMC servo board was stepped by 1 dB through the full available range of -32 dB to +31 dB. For each value of the requested gain, I measured the TF from the injected signal (to IN2) to TP1A on the IMC servo board. I used the BNC connector for this test, whereas we use the LEMO connector for the AO path. The source was tee-d off at the SR785 side, with one leg going to IN2 of the IMC servo board, and the other going to CH1A of the SR785. TP1A of the IMC board was connected to CH2A of the SR785.
Attachment #1 - Measured gain vs requested gain.
Attachment #2 - Frequency dependent transfer functions
The motivation here is to try and figure out why I cannot engage the AO path smoothly in the CARM handoff part of lock acquisiton. I plan to use this information to do some loop modeling and project laser frequency noise coupling in various stages of the lock acquisition process.
In 1X1, there is a box labelled "FSS REF" below a KEPCO HV supply. This box had a power cable that wasn't actually connected to any power. I removed said cable.
in prep for the install tomorrow, we did the following:
Barring objections, tomorrow (Friday 28 Feb 2020) morning I will commence the switch (I still want to work on the IFO tonight).
While my checks of the AO signal path have thrown up some unanswered questions, I don't think there's any evidence in those measurements to suggest the AO crossover can't be realized. Thinking about it today though - I was wondering if it could be that the IN1 gain slider of the CM board is configured optimally. Looking back at some data, when the ALS CARM offset is zeroed, the CM_SLOW digitized data has a peak-to-peak range of ~200 cts. This is paltry. One possibility is that as I am upping the AO path gain, I'm simply injecting the electronics noise of the CM board into the IMC error point. I'd say it is safe to up the IN2 gain by 20dB to -12 dB, in which case the peak-to-peak would be ~2000 cts, still only 10% of the ADC range. It'll be straightforward to re-scale the CARM_B loop gain to account for this. Let's see if this helps.
I'd also like to measure the spectrum of the REFL11_I signal in a few different states. I think I should be able to do this using the OUT2 of the CM servo board. These are the things to try tonight:
There was some UNELOGGED work at EX today. The DFD outputs were also hijacked for loss measurement. Unclear who the culprit was, but there is now a broad noise bump centered around ~180 Hz in the ALS X noise curve, which certainly wasn't there yesterday. Maybe let's keep the few working systems working, it is annoying to have to deal with these auxiliary issues every night. I'll push ahead with locking, hopefully the ALS noise is "good enough".
And so it begins.
Barring objections, tomorrow (Friday 28 Feb 2020) morning I will commence the switch
There are several problems evident already.
For now, I've returned the old c1psl connections, the PMC and IMC are both locked. Need to do some debugging on the bench.
On Monday, we will remove the old c1psl and c1iool0 machines from the electronics rack and install the Acromag crate in a more permanent way. We will also clean up some of the old cabling and cross connects, althoug the situation seems so complicated (some cross connects are also used by the rtcds c1ioo expansion chassis) that I am inclined not to remove any cables.
The area around 1X1/1X2 has a lot of dangling cables and general detritus. Be careful if you are walking around there. We will clean up on monday.
$TARGET_DIR = /cvs/cds/caltech/target
It remains to (Jon is taking care of these)
[JV, JWR, YD, GV]
Channel list with test status
== Test Status ==
[done] Lock PMC and IMC
[done] IMC Servo board test
[done] IMC LO Det Mon channel check
[0th order] WFS quadrant DC mon
[none] WFS I/F monitors
[0th order] WFS attenuators
[none] IOO QPD channels
[done] FSS readbacks
[done] PMC readbacks
Some more detailed elogs about the individual tests will follow.
Basically, I have characterized the IMC Servo board in detail. The summary finding is that the IN2 (=AO gain) slider needs to be investigated.
All other channels need to be verified in a more thorough fashion than my basic checks which were just to guarantee the core interferometer functionality, which is important to me.
Had to reboot both end machines and the c1rfm model to get the TRX and TRY signals to the LSC models. Now both arms can be locked using POX/POY respectively.
Updated noise budget curves, now computed using the latest version of pygwinc. This resolves the inconsistency between the gwinc quantum noise curves and Gautam's analytic calculations. As before, the key configuration parameters are listed in the figure titles.
Attachment 1: Phase quadrature
Attachment 2: Amplitude quadrature
Attachment 3: Comparison to aLIGO design (phase quadrature)
Jordan and I removed another 10 kg of cabling from 1X2. The c1iool0 crate now has all cabling to it disconnected - but it remains in the rack because I can't think of a good way to remove it without disturbing a bunch of cabling to the fast c1iool0 machine. We can remove it the next time the vertex FEs crash. Cross connects have NOT been removed - we will identify which cross connects are not connected to the fast system and trash those.
Do we want to preserve the ability to use the PZT driver in 1X2?
I used existing BNC cables running from the PSL table to the PSL rack and reassigned them to the PSL Shutter and PMC transmission PD channels.
The PSL shutter turned out to be a sinking channel. Jordan reconnected the PSL shutter wires to a sinking BIO Acromag. Channel list is updated.
Both channels have been tested to be working as expected.
gautam add on about EPICS:
P.S - there is a problem we noticed - if the modbus process is started with the local subnet not having a fixed IP address, then all the EPICS channels will not be responsive. The way to fix this is to run the following sequence of commands:
Revised noise estimates, correcting a couple of factor of 2 and factor of pi errors found in the coil driver noise calculation. Also resolves a strain vs. displacement units confusion using the new pygwinc. Gautam and I have checked these noises against the analytical predictions and believe they are now accurate. Attachments are again:
Attachment 1: Phase quadrature
Attachment 2: Amplitude quadrature
Attachment 3: Comparison to aLIGO design (phase quadrature)
Allegra had no network cable and no mouse. We found Allegra'snetwork cable (black) and connected it.
I found a dirty old school mouse and connected it.
I wiped Allegra and now I'm currently installing debian 10 on allegra following Jon's elog.
04/01 update: I forgot to mention that I tried installing cds software by following Jamie's instruction: I added the line in /etc/apt/sources.list.d/lscsoft.list: "deb http://software.ligo.org/lscsoft/debian/ stretch contrib". But this the only thing I managed to do. The next command in the instructions failed.
deb http://software.ligo.org/lscsoft/debian/ stretch contrib"
I realigned the input pointing into the PMC this morning. Usually, the way I do this is to minimize any discernible mode structure in the PMC reflection CCD image. Today, I noticed that making the DC reflection go down also makes the DC transmission go down. Possibilities:
There was some work done on the Acro crate this morning. Unclear if this is independent, but I found that the IMC servo board IN1 slider doesn't respond anymore, even though I had tested it and verified it to be working. Patient debugging showed that BIO1 (and only that acromag unit with the static IP 192.168.114.61) doesn't show up on the subnet in c1psl. Hopefully it's just a loose network cable, if not we will switch out the unit in the afternoon.
Jon is going to make a python script which iteratively pings all devices on the subnet and we will put this info on an MEDM screen to catch this kind of silent failure.
After discussing with Koji, I removed the PZT driver and associated AI card from the Eurocrate at 1X2. The corresponding backplane connectors were also removed from the cross connects. An additional cable going from the DAC to IDC adaptor on 1X2 was removed. Finally, some cables going to the backplane P1 and P2 connectors for slots in which there were no cards were removed.
Finally, there is the IMC WFS whitening boards. These were reconfigured in ~2016 by Koji to have (i) forever whitening, and (ii) fixed gain. So the signals from the P1 connector no longer have any influence on the operation of this board. So I removed these backplane cables as well.
Some pics attached. The only cross connect cabling remaining on the south side of 1X2 is going to the fast BIO adaptor box - I suspect these are the triggered fast whitening switching for the aforementioned WFS whitening board. If so, we could potentially remove those as well, and remove all the cross connects from 1X1 and 1X2.
Update 1720: indeed, as Attachment #2 shows, the RTCDS BIO channels were for the WFS whitening switching so I removed those cables as well. This means all the xconnects can be removed. Also, the DAC and BIO cards in c1ioo are unused.
To debug a problem with the new c1psl (later elog), we needed a Supermicro EPICS server that was using the shared EPICS/modbus/asyn binaries rather than a local install. Of those available in the lab (c1iscaux, c1vac, c1susaux being the others), this was the only one which uses the shared install. So I
At which point Jon reset the software end, I restored the slow bias voltage and re-enabled the local damping. The optic seems to have damped okay. The Oplev spot is back in ~center of the QPD and the green beam can be locked to a TEM00 mode (so the alignment is okay - the IR beam is unavailable while c1psl issues are being sorted but I judge that things are back to the nominal state now).
Jon is going to write up the details of todays adventures. But the C1PSL Acromag chassis is sitting on the floor between the IMC beamtube and the 1X1 electronics rack, and is very much a trip hazard. Be careful if youre in that area.
We are going to replace the old Sun c1ioo with a modernized supermicro. At the opportunity, remove the DAC and BIO cards to use them with the new machines. BTW I also have ~4 32ch BIO cards in my office.
I investigated the problem reported earlier today with the BIO1 channels. By logging the systemd messages generated when the IOC starts, I was immediately able to determine that the problem was not limited to BIO1. The modbus communications were failing for several other units as well.
Because some in-situ rewiring of a handful of channels had recently been done (more on this soon), I initially suspected that one of the Acromags had been damaged in the process. However, removing BIO1 (or other non-communicating modules) did not restore communications with the rest of the modules. To test whether the chassis was the source of the problem at all, we set up a fresh ADC (new out of the package) and directly connected it to the secondary Ethernet interface of c1psl. With only the one new ADC connected, the modbus IOC failed in exactly the same way.
To confirm that the new ADC did in fact work, we connected it to c1auxex in the same configuration. The unit worked fine connected to c1auxex. This established that the source of the problem was the c1psl host. After some extensive debugging, I traced the problem to a pre-execution script (part of the modbus IOC systemd service) which resets the secondary network interface (the one connected to the Acromag chassis) prior to launching the IOC. This was to ensure the secondary interface always had the correct IP address. It appears this reset was somehow creating a race condition that allowed the modbus initializations (first communications with the Acromags) to sometimes start before the network interface had actually come back up.
I still don't understand how this was happening, or why the pre script worked just fine up until yesterday, but eliminating the network interface reset fixes the problem in 100% of the trials we ran. Unfortunately we lost the entire day to debugging this problem, so the final round of testing is still to be completed. We plan to pick it back up tomorrow afternoon.
The C1PSL crate has now been installed in a more permanent way in the rack.
After this work, I disabled logging and restarted the modbus service (and copied the current version of the systemd service file to the target directory for backup). The PMC and IMC lock alright. The system is now ready to be tested in-situ. I will separately continue my IMC Servo board tests in the evening.
One thought about how to protect against this kind of silent failure - how about we always run the modbus service with logging enabled, and then send out a warning email and stop the service if the logfile size suddenly blows up (which is characteristic of when the communications process dies)? This should be done in addition to the ping-ing of the individual IPs.
Regarding the burt-restore step that the systemd service runs after starting up the IOC - this is not even that useful, at least in the way it is currently setup (restore the "latest" burt snapshot file). If the maintenance takes >1hour as it often does, the "latest" snapshot for the system under maintenance is just garbage. So either the burt-restore should be for a "known good time" (dangerous because this will require frequent updates of the systemd service every time we find a new safe state) or we should just do it manually (my preference). Then there is no need to install custom packages on the server machine. Anyway, for now, I have not commented this step out.
Jordan is going to take pictures of all the electronics racks and update the relevant wiki pages.
With the Acromag chassis now permanently installed, we tested the C1PSL channels going over the channel list one by one, excluding the IMC channels which Gautam is taking responsibility for (the servo board itself is also in question).
The strategy is to check the response of input channels to specific output channels for expected behaviour whenever is possible.
We marked on the channel list spreadsheet the status of the channels that were tested.
In more detail
PMC Servo Card
Unlocked the PMC by switching C1:PSL-PMC_SW1. Tweaked C1:PSL-PMC_RAMP and observed a change in C1:PSL-PMC_PZT.
We misaligned MC1 to get a measurable signal in WFS channels. NDScoped the corresponding C1:IOO-WFS*_SEG*_I&Q channels and observed a change in those channels in response to switching the attenuation on and off.
The signals were compared to previous values for consistency. Then they were unplugged from the Acromag chassis to confirm their values went to 0 and returned to the same values after being reconnected.
We've completed almost all of the in-situ testing of the c1psl channels. During this process, we identified several channels which needed to be rewired to different Acromags (BIO sinking v. sourcing). We also elected to change the connector type of a few channels for practical advantages. Those modifications and other issues found during testing are detailed below. Also attached are the updated channel assignments, with a column indicating the in-situ testing status of each channel.
I am running some tests on the IMC servo board with an extender card so the IMC will not be locking for a couple of hours.
It seems like the AO path gain stages on the IMC Servo board work just fine. The weird results I reported earlier were likely a measurement error arising from the fact that I did not disconnect the LEMO IN2 cable while measuring using the BNC IN2 connector, which probably made some parasitic path to ground that was screwing the measurement up. Today, I re-did the measurement with the signal injected at the IN2 BNC, and the TF measured being the ratio of TP3 on the board to a split-off of the SR785 source (T-eed off). Attachments #1, #2 shows the result - the gain deficit from the "expected" value is now consistent with that seen on other sliders.
Note that the signal from the CM board in the LSC rack is sent single-ended over a 2-pin LEMO cable (whose return pin is shorted to ground). But it is received differentially on the IMC Servo board. I took this chance to look for evidence of extra power line noise due to potential ground loops by looking at the IMC error point with various auxiliary cables connected to the board - but got distracted by some excess noise (next elog).
Sometime between 1PM and 6PM on Tuesday, excess laser frequency noise shows up in MCF at around 800 Hz, as shown in Attachment #1. Sigh.
While I show the MCF spectrum here, I confirmed that this noise is not injected by the IMC loop (with the PSL shutter closed, and the IMC servo board disconnected from the feedback path to the NPRO, the PMC error and control points still show the elevated noise, see Attachment #2). I don't think the problem is from the PMC loop - see Attachment #3 which is the ALS beat out-of-loop noise with the PMC unlocked (the PSL beam doesn't see the cavity before it gets to the ALS setup, and we only actuate on the cavity length for that loop, so this wasn't even really necessary).
Was there some work on the PSL table on Tuesday afternoon that can explain this?
I did some preliminary debugging of this, and have localized the problem to the output path (after MC slow) on the IMC Servo card. Basically, I monitored the spectrum of the ALS beat frequency fluctuations under a few different conditions:
Toggling C1:IOO-MC_FASTSW, which supposedly isolates the post-MC slow (a.k.a. MCL) part of the servo, I see no difference. I am also reasonably confident this switch itself works, because I can break the IMC lock by toggling it. So pending a more detailed investigation, I am forced to conclude that the problem originates in the part of the IMC servo board after the MCL pickoff. Some cabling was removed at 1X2 on Tuesday between the times when there was no excess and when it showed up, but it's hard to imagine how this could have created this particular problem.
An earthquake around 330 UTC (=730pm yesterday eve) tripped ITMX, ITMY and ETMX watchdogs. ITMX got stuck. I released the stuck optic and re-enabled the local damping loops just now.
ETMX was grossly misaligned.
I re-aligned it and the X arm now locks.
7:00PM with Koji
Both the alignment of the X and Y arms was recovered.
~>z avg 10 C1:LSC-TRX_OUT C1:LSC-TRY_OUT
We are running ass for the X arm to recover the X arm alignment.
Meanwhile, i want to block the Y arm trans PD (Thorlabs). To do it, the PD<->QPD thresholds were changed from 5.0/3.0 to 0.5/0.3.
I returned the triggering threshold to normal values (5/3).
I want to measure the transfer function of the arm cavities to extract the pole frequencies and get more insight into what is going on with the DC loss measurements.
The idea is to modulate the light using the PSL AOM. Measure the light transmitted from the arm cavities and use the light transferred from the IMC as a reference.
I tried to start measuring the X arm but the transmission PD is connected to the QPD whitening filter board with a 4 pin Lemo for which I couldn't find an adapter.
Could this be because of the PDA520 limited BWs? I tried playing with the PD gain/bandwidth switch but it seems like it was already set to high bandwidth/low gain.
In any case, the extracted pole frequency ~ 2.9kHz implies a finesse > 600 (assuming FSR = 3.9MHz) which is way above the maximal finesse (~ 450) for the arm cavities.
I disconnected the source from the AOM. But left the other two BNCs connected to the SR785. Also, TRY PD is still teed off. Long BNC cable is still on the ground.
My old scheme was flawed as I used pitch as the readback. The pitch signal could not distinguish the cross-coupling due to coil imbalance and that due to the natural suspension L2P. A new scheme based on yaw alone has been developed and will be integrated into ifo_test. For now we revert the C1:SUS-MC2_UL/UR/LR/LLCOIL gains back to 1, -1, 1, -1.
We did some quick DC balancing of the MC2 coil drivers to reduce the l2a coupling. We updated the gains in the C1:SUS-MC2_UL/UR/LR/LLCOIL to be 1, -0.99, 0.937,-0.933, respectively. The previous values were 1, -1, 1, -1.
The procedures are the following:
Drive UL+LR and change the gain of LR to zero pitch.
Drive UR+LL and change the gain of LL to zero pitch.
Lastly, drive all 4 coils and change UR & LR together to zero yaw.
We used C1:SUS-MC2_LOCKIN1_OSC to create the excitations at 33 Hz w/ 30,000 cts. The angular error signals were derived from IMC WFSs.
While this time we did things by hand, in the future it should be automated as the procedure is sufficiently straightforward.
Attachment #1 shows the relevant parts of the schematic of the WFS demod board (not whitening board).
Before removing the boards from the eurocrate:
After Koji effected the fix, the boards were re-installed, HV supplies were dialled back up to nominal voltage/currents, and the PMC/IMC were re-locked. The WFS DC channels now no longer saturate even when the IMC is unlocked 👏 👏 . I leave it to Yehonathan / Jon to calibrate these EPICS channels into physical units of mW of power. We should also fix the MEDM screen and remove the un-necessary EPICS channels.
Later in the evening, I took advantage of the non-saturated readbacks to center the beams better on the WFS heads. Then, with the WFS servos disabled, I manually aligned the IMC mirrors till REFLDC was minimized. Then I centered the beam on the MC2 transmission QPD (looking at individual quadrants), and set the WFS1/2 RF offsets and MC2 Trans QPD offsets in this condition.
WFS DC channels are saturating when the IMC is unlocked.
I opened the packages send from Syracuse.
- The components are not vacuum clean. We need C&B.
- Some large parts are there, but many parts are missing to build complete SOSs.
- No OSEMs.
- Left and right panels for 6 towers
- 3 base blocks
- 1 suspension block
- 8 OSEM plates. (1 SOS needs 2 plates)
- The parts looks like old versions. The side panels needs insert pins to hold the OSEMs in place. We need to check what needs to be inserted there.
- An unrelated tower was also included.
It's been a while since I've attempted any locking, so tonight was mostly getting the various subsystems back together.
when doing the AM sweeps of cavities
make sure to cross-calibrate the detectors
else you'll make of science much frivolities
much like the U.S. elections electors
Came this morning to find the PMC was unlocked since 6AM. Laser is still on, but PMC REFL PD DC shows dead white constant 0V on PMC screen. All the controls on the PMC screen show constant 0V actually except for the PMC_ERR_OUTPUT which is a fast channel.
Is PSL Acromag already failing?
I restarted the IOC but it didn't help.
I am now rebooting c1psl... That seemed to help. PMC screen seem to be working again. I am able to lock the PMC now.
IMC was locking easily once some switches on the MC servo screen were put to normal states.
TTs were grossly misaligned. Onces they where aligned, arm cavities were locking easily. Dither align for the X arm is very slow though...
Of course the reboot wiped any logs we could have used for clues as to what happened. Next time it'll be good to preserve this info. I suspect the local subnet went down.
P.S. for some reason the system logs are priveleged now - I ran sudo sysctl kernel.dmesg_restrict=0 on c1psl to make it readable by any user. This change won't persist on reboot.
the long DB25 cable to connect the Acromag chassis to the temperature sensor interface box arrived. We laid it out today. This cable does the following:
Both signals now show up in the EPICS channels, but are noisy - I suspect this is because the return pin of the Acromag is not shorted to ground (this is a problem I've seen on the bench before). We will rectify this tomorrow as well.
We took this opportunity to remvoe the bench supply and temporary Acromag crate (formerly known as c1psl2) from under the PSL table. While trying to find some space to store the bench supply, we came across a damaged Oscilloscope in the second "Electronics" cabinet along the Y-arm, see Attachment #1.
After this work, I found that the IMC autolocker was reliably failing to run the mcup script at the stage where the FSS gains are ramped up to their final values. I was, however, able to smoothly transition to the low-noise locked state if I was manipulating the EPICS sliders by hand. So I added an extra 2 seconds of sleep time between the increasing of the VCO gain to the final value and the ramping of the FSS gains in the mcup script (where previously there was none). Now the autolocker performs reliably.
Finally, some RF only CARM, see Attachment #1. During this time, DARM was also on a blend of IR and ALS control, but I couldn't turn the ALS path off in ~4-5 attempts tonight (mostly me pressing a wrong button). Attachment #2 shows the CARM OLTF, with ~2kHz UGF - for now, I didn't bother turning any boosts on. PRCL and MICH are still on 3f signals.
The recycling gain is ~7-8 (so losses >200ppm), but there may be some offset in some loop. I'll look at REFL DC tomorrow.
Can we please make an effort to keep the IFO in this state for the next week or two
- it really helped tonight I didn't have to spend 2 hours fixing some random stuff and could focus on the task at hand.
Updated the cert in /etc/httpd/ssl. The new cert is good until March 12, 2022.
I want to monitor the PMC TRANS and REFL levels on the PSL table - previously there were some cables going to the oscilloscope on the shelf but someone had removed these. I re-installed them just now. While there, I disconnected the drive to the AOM - there must've been some DC signal going to it because when I removed the cable, the PMC and IMC transmission were recovered to their nominal levels.
Today I finished implementing loopback monitors of the up/down state of the slow controls machines. They are visible on a new MEDM screen accessible from Sitemap > CDS > Slow Machine Status (pictured in attachment 1). Each monitor is a single EPICS binary channel hosted by the slow machine, which toggles its state at 1 Hz (an alive "blinker"). For each machine, the monitor is defined by a separate database file named c1[machine]_state.db located in the target directory.
Sitemap > CDS > Slow Machine Status
This is implemented for all upgraded machines, which includes every slow machine except for c1auxey. This is the next and final one slated for replacement.
The blinkers are currently implemented as soft channels, but I'd like to ultimately convert them to hard channels using two sinking/sourcing BIO units. This will require new wiring inside each Acromag chassis, however. For now, as soft channels, the monitors are sensitive to a failure of the host machine or a failure of the EPICS IOC. As hard channels, they will additionally be sensitive to a failure of the secondary network interface, as has been known to happen.
Each slow machine's IOC had to be restarted this afternoon to pick up the new channels. The IOCs were restarted according to the following procedure.
The intial recovery of c1susaux did not succeed. Most visibly, the alignment state of the IFO was not restored. After some debugging, we found that the restart of the modbus service was partially failing at the final burt-restore stage. The latest snapshot file /opt/rtcds/caltech/c1/burt/autoburt/latest/c1susaux.snap was not found. I manually restored a known good snapshot from earlier in the day (15:19) and we were able to relock the IMC and XARM. GV and I were just talking earlier today about eliminating these burt-restores from the systemd files. I think we should.
I measured the cross-calibration of the two PDs on the PSL table.
I used the existing flip mounted BS that routes the beam into a PDA255, the same as in the IMC transmission.
I placed a PDA520, the same as the one measuring TRY_OUT on the ETMY table, on the transmission of the BS (Attachment 1).
I used the SR785 to measure the frequency response of PDA520 with reference to PDA255 (Attachment 2). Indeed, calibration is quite significant.
I calibrated the Y arm frequency response measurement.
However, the data seem to fit well to 1/sqrt(f^2+fp^2) - electric field response - but not to 1/(f^2+fp^2) - intensity response. (Attachment 3).
Also, the extracted fp is 3.8KHz (Finesse ~ 500) in the good fit -> too small.
When I did this measurement for the IMC in the past I fitted the response to 1/sqrt(f^2+fp^2) by mistake but I didn't notice it because I got a pole frequency that was consistent with ringdown measurements.
I also cross calibrated the PDs participating in the IMC measurement but found that the calibration amounted for distortions no bigger than 1db.