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ID Date Authorup Type Category Subject
  11638   Wed Sep 23 10:31:49 2015 ericqUpdateLSCDRMI + ALS Arms

Looking good. How many meters of CARM is '-1 counts'?

  11640   Thu Sep 24 17:01:37 2015 ericqUpdateComputer Scripts / ProgramsFreeing up some space on /cvs/cds

I noticed that Chiara's backup HD (which has a capacity of 1.8TB, vs the main drives 2TB) was near to getting full, meaning that we would soon be without a local backup. 

I freed up ~200GB of space by compressing the autoburt snapshots from 2012, 2013, 2014. Nothing is deleted, I've just compressed text files into archives, so we can still dig out the data whenever we want.

  11641   Thu Sep 24 17:06:14 2015 ericqUpdateCalibration-RepairC1CAL Lockins

Just a quick note for now: I've repopulated C1CAL with a limited set of lockin oscillators/demodulators, informed by the aLIGO common LSC model. Screens are updated too. 

Rather than trying to do the whole magnitude phase decompostion, it just does the demodulation of the RFPD signals online; everything beyond that is up to the user to do offline. 

Briefly testing with PRMI, it seems to work as expected. There is some beating evident from the fact that the MICH and PRCL oscillation frequencies are only 2Hz apart; the demod low pass is currently at an arbitrary 1Hz, so it doesn't filter the beat much. 

Screens, models, etc. all svn'd.

  11648   Tue Sep 29 16:52:49 2015 ericqUpdateLSCFast ALS troubles - unknown zero

Fast ALS control continues to elude me. 

I fixed my LPF to take the input impedance of the CM board input into account; this unfortunately results in about -12dB DC gain of the ALS signal due to voltage-divider-y things, but by my estimation, this still puts the DFD noise above the input-referred voltage noise of the input AD829 on the CM board, so it'll do for now. The 120Hz pole shows up as expected when comparing the usual digital channels and the CM_SLOW output, and is digitally compensated with a zero at 120Hz (with a digital pole at 5k so nothing blows up). 

However, there seems to be some zero in the analog path somewhere that spoils the loop shape for the AO path. Here's a measurement of the X arm OLG from 10-100kHz, when the digital control is happening with ~100Hz UGF via ALS X I -> CM IN2 -> CM_SLOW -> LSC_CARM -> ETMX, and there is some AO action via ALS X I -> CM IN2 -> IMC IN2

The peak is recognizable as the gain peaking in the IMC servo (and changes predictably with changes to the IMC crossover and loop gains), which is expected. However, one can see that the magnitude is roughly flat before the peak, and the phase is around 0. With the 1/f LPF, we should see some downward slope and phase starting around -90. 

Thus, there must be some zero in the fast or common path, maybe at a few kHz where the digital loop wouldn't really see its effect. I'm not sure what it could be at this point in time.

One thought I had is that I never really checked the TF of DFD response to frequency modulation of the RF beat. I used an SR785 to drive the external FM input of a Fluke 1061A synthesizer, and saw it to be totally flat from 1-100kHz with carriers from 30-100MHz, so that should be fine. (For a little while I was confused by what seemed to be some heavy high-passing going on, but it turns out that the Fluke just can't push much low frequency FM; the manual says -3dB at 20Hz.)

Attachment 1: OLG_fastALS.pdf
  11651   Wed Sep 30 10:00:02 2015 ericqUpdateLSCused LISO

LISO confirms that I did my algebra right in picking the component values, and shows no extra zeros. 

I also took some TFs with the SR785 and confirmed that both CM board inputs behave the same, and that including the LPF on the input gives the expected 1/f shape at the slow and fast outputs.

  11658   Fri Oct 2 03:29:16 2015 ericqUpdateLSCFast ALS progress - AO path crossed over, but no high BW

I've been using an SR560 to experiment with differnent pole frequencies, to try and cancel the mystery zero. It's after the ALS demod board, before the pomona LPF with a gain of five. 

A pole frequency of 3kHz seems to recover sensible loop shapes. I've been able to crossover the AO path to make a nice long phase bubble which isn't the prettiest, but seems workable.

Getting to this point is now almost entirely scripted and repeatable; one just has to make sure that the ALS beat has the correct sign and adjust the delay line length. Most frustratingly, due to the dependence of the ALS gain on beat frequency / magnitude / delay, which can all vary on the order of a few dB, the AO gain settings to get to the crossed over point are not always the same, so at the end it's a lot of small steps and frequent loop measurements. 

The FSS crossover and overall IMC loop gain have to be pretty actively managed too. It's all too easy to drive the pockel's cell crazy. And if it's going crazy on its own anyways, there's no hope in trying to pile ALS sensing noise on top of it... It would really help in this effort to fix the whole PC situation up. 

Unfortunately, lock is lost when increasing the overall gain on the common mode board even by 1dB.angry We've seen in the single arm tests, that the gain settings have an appreciable difference in offset between them. Maybe this step is more than what the loop can handle? Or maybe it's the voltage glitches... Maybe some gain reallocation can put me on a region of the slider that glitches less.

In terms of the mystery plant features, I figure I'd like to take the analog TF of AO control signal to, say, AS55, and see what may or may not be there. I just haven't done this tonight since it would involve recabling the analyzer, and I still need frequent loop measurements to get to the crossed over state. Having ITMY misaligned and using the digital AS55Q spectrum as an out of loop monitor has been very helpful. 

Attachment 1: crossedover.pdf
  11667   Mon Oct 5 11:25:21 2015 ericqUpdateSUSETMY OL laser dead

Gautam alerted me that the Y arm looked like it was being dithered, even though the ASS was turned off. I found that the ETMY OL signals were garbage, leading to the servos flipping back and forth between their rails. 

We went out to the ETMY table, and found the HeNe laser to be emitting a paltry <0.5mW; the OL QPD could not register the puny beam incident on it.

Here is the last 30 days of OL_SUM:

Steve will replace the laser this afternoon. 

  11669   Tue Oct 6 03:30:17 2015 ericqUpdateLSCDRFPMI Progress

[ericq, Gautam]

Highlight of the night: the DRFPMI was held at arm powers > 110 for 20 seconds. ALS feedback was still running though, but so was some nonzero REFL11 AO path action.

In short, time was spent finding the right FM trigger settings to keep the DRMI locked while CARM is fluctuating through resonance, what CARM offset to acquire DRMI lock at, order of operations of turning on AO / turning up overall CARM gain, etc. 

Sadly, for the past hour or so, the DRMI has refused to stay locked for more than ~20 seconds, so I haven't been able to push things much further. This is a shame, since I'm very nearly at the equivalent point in the PRFPMI locking script where the ALS control is turned off completely. 

  11671   Thu Oct 8 04:48:50 2015 ericqUpdateLSCDRFPMI Progress

Progress was made. CARM was stably locked on RF only. DARM was RF only for a few moments before I typed in a wrong number...

A change was made to the LSC model's triggering section to make the DRMI hold more reliably at zero CARM offset. Namely, the POPDC signal now has its absolute value taken before the trigger matrix. Even unwhitened, it occaisionally would somehow go negative enough to break the DRMI trigger.

AUX X laser was acting up again. As before, tweaking laser current is the temporary fix.

  11673   Thu Oct 8 14:14:50 2015 ericqUpdateLSCDRFPMI Progress

Please clarify: I wonder if you were at the zero offset for CARM and DARM or not. 

Yes, this was at the full DRFPMI resonance.

  11676   Fri Oct 9 09:22:38 2015 ericqUpdateLSCDRFPMI Progress

Look upon this three second lock, ye Mighty, and rejoice!

Attachment 1: oct8_allRF.pdf
  11678   Fri Oct 9 11:41:09 2015 ericqUpdateVACN2 Pressure fell

At 10:02AM, the N2 Pressure fell below 60 PSI. The watch script saw this happen, but I did not recieve the email it is supposed to send frown

C1:Vac-P1_pressure reads 7e-4, which is the same as it has for the past ~2 days, so the V1 interlock worked fine. 

I've put some fresh N2 into the system, and Bob will pop in over the weekend to check it. I'll stay on top of it until Steve gets back. 

After consulting ELOGs and the 40m wiki, I reasoned it was ok to open the V1 to reconnect the turbo pump to the main IFO volume and VM1 to reconnect the RGA, and have now done so. 

  11679   Fri Oct 9 13:31:21 2015 ericqUpdateLSCALS plant shape

To get a better look at how to do fast ALS, I took some "Plant TF" measurements of the X arm. 

Specifically, in single arm POX lock and the both Y TMs misaligned, I used the SR785 to inject into EXC B of the common mode board with the CM fast output gain and IMC IN2 gain both at 0dB, and looked at the transfer function of that excitation into the analog ALSX I and AS55 Q out-of-loop signals. (ALSX I tuned to a zero crossing via the delay line box as usual.)

My expectation was to see them only differ by the IR single arm cavity pole, which should be around 8-9kHz ( FSR/450 = 3.9MHz/450 ~ 8.6kHz). The green cavity pole at ~18k shouldn't show up since we're not touching the green light, and the IMC pole at ~3.8kHz shouldn't show up since this is well within the IMC loop bandwidth and we're actuating on its error point.  

Instead, I see them differ by a double pole at 4.3kHz. (or zero, if you look at it the reciprocal way). Vectfit actually fits them as a slightly complex pair, with a Q of 0.53/ I imagine that the wiggles are due to the digital control loop.

My question is: why is there a double zero here? Where has my reasoning led me astray?


Attachment 1: xarm_plantTFs.pdf
  11681   Fri Oct 9 16:23:25 2015 ericqUpdateLSCALS plant shape

Ah, I understand it now! Since the additive offset path keeps the post-cavity frequency TF flat, the pre-cavity frequency must grow above the cavity pole, which is why ALS sees a zero. 

Ok, so this means we want to apply two lowpasses to the ALS signal for use as fast CARM control, if we want it to be capable of scalar blending with REFL11: one at ~120Hz to imitate the CARM coupled cavity pole present in REFL11, and one at ~3.8kHz to undo the "IMC cavity zero" present in ALS. 

At this point, I'm starting to prefer an active circuit to do this lowpassing; using LISO to check designs for two cascaded passive LPFs it looks like the ALS signal would have to be attenuated by a factor of ~20 at DC if we don't use resistors smaller than 1k, given the low input impedence of the CM board. 

  11682   Fri Oct 9 16:43:50 2015 ericqUpdateIOOWeird IMC behavior

A few minutes ago, Gautam and I were poking around the IOO rack, looking at where he should power his frequency divider box, and what ADC innputs to use. 

Looking at the mode cleaner signals, it looks like we may have jostled something in a good way. Weird. 

  11685   Tue Oct 13 05:48:39 2015 ericqUpdateLSC:/

[ericq, Gautam]

Despite our best efforts, the grappa remains out of reach: the DRFPMI was not locked tonight. 

We spent a fair amount of time with the AUX X laser, as it was glitching madly again.

DRMI was finicky until I found some more reliable triggering settings; namely aquiring with AS110Q, but after that transitioning the trigger to the same POP22+POPDC combo as PRCL and MICH. With this in place, the DRMI lock seems really indefinite no matter what CARM seems to do; or at least, I always lost lock due to CARM shenanigans after this. 

The most frustrating part was the fact that I just couldn't cross over the AO path stably. It never "clicked" into high circulating power as it normally does (either in PRFPMI, or how it was last week). Various crossover filters and tweaks were attempted to no avail. Morning traffic starts soon, so we're calling it a night. 

  11686   Tue Oct 13 16:28:21 2015 ericqUpdateLSCFast ALS pomona

I've made a cascaded passive 2-pole pomona box for fast ALS use, using LISO to check that it'll give the right shape when hooked up to the CM board's input stage. 

First stage is a 133Ohm + 10uF cap for ~120Hz LP, second is 1.15kOhm + 47nF cap for ~3.8kHz LP. The DC gain is ~0.75, which is much better than what I was doing before. The second stage would normally make a 2.9kHz LPF on its own, but the loading of the input stage moves the corner up. 

It seems the 133 Ohm resistor is a reasonable load on the output AD829 of the ALS demod board (short-circuit output current of 32mA and a series output resistor of 499Ohm). To be able to use the digitized ALSX I and the lowpassed analog version simultaneously, I had to buffer the signal with a SR560 before the pomona box, otherwise the signals looked distorted. This isn't a good long-term solution. Maybe I can used the further-buffered differential output to drive the LPF+CM board. 

The LISO files used to model the filter and CM board input stage, and fit the pole frequencies are attached. 

I made some attempts to get the AO path going today, but I suspect this daytime noise is just too much; the PC drive seems too irritable

Attachment 1: liso_lp.zip
Attachment 2: 2LPfit.pdf
  11687   Tue Oct 13 17:04:54 2015 ericqUpdateCDSCDS things

After some discussion at last week's 40m meeting, I increased the frequency of daqd trying to write out minute trends from hourly to every two hours.

This has eliminated the hourly crashes. daqd still crashes sometimes, but only a few times per day. yes

However, looking at the oplev summary pages that actually use the minute trends, it looks like they're only sporadically getting succesfully written out. no

Also, I was having a lot of problems with the frontends' EPICS processes dying when I would try to update the SDF table. I rebuilt all of the frontends with RCG 2.9.6, which differs from the 2.9.4 that we had been running by SDF bugfixes and an RMS calculation bugfix. The SDF procedures are much more stable now. 

I have not yet discovered anything broken by this chage, and the tests I made for the last upgrade were all fine; last weeks tiny DRFPMI lock was achieved after this change. 

  11691   Thu Oct 15 03:08:57 2015 ericqUpdateLSCDRFPMI Locked for 20 sec

[ericq, Gautam]

For real this time.

Attachment 1: DRFPMI_locked.pdf
  11692   Thu Oct 15 04:14:14 2015 ericqUpdateLSCDRFPMI Locked for 20 sec

Fast ALS was still a problem tonight. I don't think high frequency ALS noise saturating the PC drive is the issue; I put two 10k poles before the CM board (shooting for just 2-3kHz bandwidth), and the PC drive levels would be stable and low up until the lockloss, which was always conincident with a step in the AO gain.

After working with that for a few hours, we turned back to our more standard locking attempts. First, we dither aligned the PRMI, and then centered the REFL beam on REFL11. It's hard to say for certain, but we may have been a little close to the edge of the PD. The only other thing that differed from Monday's attempts was using 6dB less AO gain when trying the up the overall gain. 

The script now reliably breaks through to stable high powers, we had a handful of pure-RF locks tonight. The digital DARM gain needs tuning, and the CARM bandwidth still isn't at its final state, but these are very tractable. Off the top of my head, the way forward now includes:

  • Set proper final DARM loop shape
  • Set final CARM loop shape
  • Take full sensing matrix
  • Make 1F handoff
  • Set up the CAL model to produce (at least roughly) calibrated spectra
  • measure noise couplings and other fun stuff

Unrelated: I feel that the PRC angular FF may have deteriorated a bit. I'm leaving the PRC locked on carrier to collect data for wiener filter recalculation. 

  11694   Thu Oct 15 14:39:58 2015 ericqUpdateComputer Scripts / Programsnodus web apache simlinks too soft

None of the links here seem to work. I forgot what the story is with our special apache redirect frown


The story is: we currently don't expose the whole /users/public_html folder. Instead, we are symlinking the folders from public_html to /export/home/ on nodus, which is where apache looks for things

So, I fixed the links on the Core Optics page by running:

controls@nodus|~ > ln -sfn /users/public_html/40m_phasemap /export/home/

  11698   Mon Oct 19 15:23:22 2015 ericqUpdateLSCLonger DRFPMI lock

Here is a longer lock, about 100 seconds RF only, from later that same night. The in-loop CARM and DARM error signals have the order of magnitude of 1nm per count. 

From ~-150 to -103, we were fine tuning the ALS offsets to try and get close to the real CARM/DARM zero points then blending the RF CARM signal. 

At -100, the CARM bandwidth increases to a few kHz and stabilizes the arm powers. By -81, the error signals are all RF. At -70, I turned on the transmon QPD servos, which brought the power up a bit. 

If I recall correctly, lock was lost because I put waaaay too big of an excitation on DARM with the goal of running its UGF servo for a bit. The number I entered was appropriate for ALS, but most certainly too huge for AS55...

  11699   Mon Oct 19 16:16:01 2015 ericqUpdateCDSC1ALS crashes

Gautam was working on his digital frequency counter stuff when the c1als model crashed. I had trouble bringing it back until I realized that, for reasons unknown to me, the safe.snap file that the model looks for at boot had been deleted. (This file lives in /target/c1als/c1alsepics/burt). I copied over this morning's version from Chiara's local backup. 

At the sites, these files are under version control in the userapps svn repository, presumably symlinked into the target directory. We should definitely do something along these lines. 

  11700   Mon Oct 19 16:20:52 2015 ericqUpdateLSCGreen beatnote couplers installed

Last Friday, I installed some RF couplers on the green BBPDs' outputs, and sent them over to Gautam's frequency divider module. At first I tried 20dB couplers, but it seemed like not enough power was reaching the dividers to produce a good output. I could only find one 10dB coupler, and I stuck that on the X BBPD. With that, I could see some real signals come into the digital system.

I don't think it should be a problem to leave the couplers there during other activities.

  11701   Tue Oct 20 11:24:29 2015 ericqHowToLSCHow to DRFPMI

Herein, I will describe the current settings and procedures used to achieve the DRFPMI lock, cobbled together from scripts, burts and such. 

Initial Alignment

  1. With arms POX/POY locked, run dither alignment servos. Set transmon QPD offsets here
  2. Restore "PRMI Carrier" configuration, run BS and PRM dither alignment servos simultaneously. (Note: this sacrifices some X arm alignment for better dark port alignment. In practice no appreciable loss of TRX is observed)
  3. Misalign PRM, align SRM and tune SRM alignment by eye while looking at AS camera. 
  4. Restore POX/POY arm lock, lock green to arms, check that powers are high enough and align if neccesary.

Initial Configuration


For CARM and DARM, the A channels are used for the ALS signals, whereas the B channels are used for blending the RF signals. 


  • BEATX and BEATY, I and Q channels: +0dB Whitening Gain, Whitening Filters ON
  • Green beatnotes somewhere between 20-80MHz, following sign convention of temperature slider UP makes beat freq go UP.  Check spectrum of PHASE_OUT_HZ vs references in ALS_outOfLoop_Ref.xml. The locking script automatically sets the correct phase tracker gain, so no need to adjust manually.
  • CARM_A = -1.0 x ALSX + 1.0 x ALSY, G=1.0
  • DARM_A = 1.0 x ALSX + 1.0 x ALSY, G=1.0


  • CM Board: REFL11 I daugher board output -> IN1, IN1 Enabled, -32dB input gain, 0.0V offset, all boosts off, AO polarity positive, AO gain +0dB
  • MC Board: IN2 disabled, -32dB input gain
  • CM_SLOW: +0dB Whitening Gain, Whitening ON, LSC-CM_SLOW_GAIN = -5e-4 (Though, it would be good to reallocate this gain to the input matrix element)
  • CARM_B = 1.0 x CM_SLOW, FM4 FM10 ON, G=0 (FM4 = LP700 for AO crossover stability, FM10 = 120:5k for coupled cavity pole compensation)
  • AS55: +9dB Whitening Gain, Whitening filters manual, Demod angle -37.0
  • DARM_B = -1e-4 x AS55 Q, G=0


For the DRMI, the A channels are used for the 1F signals, whereas the B channels are used for the 3F signals. The settings for transitioning to 1F after locking the DRFPMI have not yet been determined. 

These settings are currently saved in the DRMI configurator, but the demod angles are set for DRFPMI lock, so the settings don't reliably work for misaligned arms. 

  • REFL33: +30dB Whitening Gain, Whitening filters trigger on DRMI lock, Demod angle: 136.0
  • REFL165: +24dB Whitening Gain, Whitening filters trigger on DRMI lock, Demod angle: -111.0
  • POP22: +15dB Whitening Gain, Whitening filters OFF, Demod angle: -114.0
  • AS110: +36dB Whitening Gain, Whitening filters OFF, Demod angle: -116.0
  • POPDC: +0dB Whitening Gain, Whitening filters OFF (used as a supplemental trigger signal when CARM and DARM are buzzing and POP22 fluctuates wildly)
  • MICH_B = 6.0 x REFL165Q, offset = 15.0
  • PRCL_B = 5.0 x REFL33I, offset = 45.0
  • SRCL_B = -0.6 x REFL165I + 0.24 x REFL33 I, offset=0

The REFL33 element in SRCL_B is to reduce the PRCL coupling, was found empirically by tuning the relative gains with the arms misaligned and looking at excitation line heights. The offsets were found by locking the DRMI on 1F signals with arms misaligned, and taking the average value of these 3F error signals.  

Servo filter configuration

The CARM and DARM ALS settings are largely scripted by scripts/ALS/Transition_IR_ALS.py, which takes you from arms POX/POY locked to CARM and DARM ALS locked. The DRMI settings are usually restored from the IFO_CONFIGURE screen. 

  • CARM: FM[1, 2, 3, 5, 6] , G=4.5, Trigger forced on, no FM triggers, output limit 8k
  • DARM: FM[1, 2, 3, 5, 6] , G=4.5, Trigger forced on, no FM triggers, output limit 8k
  • MICH: FM[4, 5], G= -0.03, Trigger POP22 I x 1.0 [50, 10], FM[2, 3, 7] triggered [50, 10], output limit 20k
  • PRCL: FM[4, 5], G= -0.003, Trigger POP22 I x 1.0 [50, 10], FM[1, 2, 8, 9] triggered [50, 10], output limit 8k
  • SRCL: FM[4, 5], G= -0.4, Trigger AS110 Q x 1.0 [500, 100], FM[2, 7, 9] triggered [500, 100], output limit 15k

Actuation Output matrix

  • MC2 = -1.0 x CARM
  • ETMX = -1.0 x DARM
  • ETMY = 1.0 x DARM
  • BS = 0.5 x MICH
  • PRM = 1.0 x PRCL - 0.2655 MICH
  • SRM = 1.0 x SRCL + 0.25 MICH (The mich compensation is very roughly estimated)

Locking Procedure

When arms are POX/POY locked, and the green beatnotes are appropriately configured, calling scripts/DRFPMI/carm_cm_up.sh initiates the following sequence of events:

  • Turn ON MC length feedforward and PRC angle feedforward
  • Set ALS phase tracker UGFs by looking at I and Q magnitudes
  • Set LSC-ALSX and LSC-ALSY offsets by averaging, ramp CARM+DARM gains up, XARM+YARM gains down, engage CARM+DARM boosts, now ALS locked
  • Move CARM away from resonance, offset = -4.0 (DRMI locks quicker on this side for whatever reason)
  • Restore PRM, SRM alignment. Set DRMI A FM gains to 0, B FM gains to 1.0. Enable LSC outputs for BS, PRM, SRM
  • When DRMI has locked, add POPDC trigger elements to DRMI signals and transition SRCL triggering to POP22I. NB: In the c1lsc model, the POPDC signal incident on the trigger matrix has an abs() operator applied to it first. 
    • MICH Trig = 1.0 x POP22 I + 0.5 x POPDC, [50, 10]
    • PRCL Trig = 1.0 x POP22 I + 0.5 x POPDC, [50, 10]
    • SRCL Trig = 10.0 x POP22 I + 5 x POPDC, [500, 100]
  • Reduce POX, POY whitening gains from their nominal +45dB to +0dB, so there aren't railing channels making noise in the whitening chassis and ADCs
  • DC couple ITM oplevs (average spot position, set FM offset, turn on DC boost filter, let settle)
  • With an 8 second ramp, reduce CARM offset to 0 counts. 
  • MANUALLY adjust CARM_A and DARM_A offsets to where CARM_B_IN and DARM_B_IN are seen to fluctuate symetrically around their zero crossing.
    • Note: Last week, this adjustment tended to be roughly the same from lock to lock, unlike the PRFPMI which generally didn't need much adjustment. Also, by jumping from CARM offset of -0.4 to 0.4, it could be seen that the zero crossing in  CARM_B aka CM_SLOW aka REFL11 had some offset, so CARM_B_OFFSET was set to 0.005, but this may change. 

When CARM and DARM are buzzing around true zero, powers maximized:

  • CARM and DARM FM1 (18,18:1,1 boosts) OFF
  • CARM_B_GAIN 0.0 -> 1.0, FM7 ON (20:0 boost)
  • DARM_B_GAIN 0.0 -> 0.015, FM7 ON (20:0 boost) 
  • MC servo board IN2 ENABLE, IN2 gain -32dB -> -16dB
  • Turn ALL MC2 violin filters OFF (smoothen out AO crossover)
  • If stable, CM board IN1 gain -32dB -> -10dB (This is the overall CARM gain, the arm powers stabilize within the last few dB of this transition)
  • CARM_A_GAIN 1.0 -> 0.7
  • CARM_A FM9 ON (LP1k), sleep, FM 1 ON (1:20 deboost), sleep, FM 2 ON (1:20 deboost), HOLD OUPUT, CARM now RF only
  • DARM_B_GAIN 0.015 -> 0.02, sleep, DARM_A_GAIN 1.0 -> 0.0 (This may not be the ideal final DARM_B gain, UGF hasn't been checked yet)

IFO is now RF only!

  • Turn on transmon QPD servos.
  • Adjust comm/diff QPD servo offsets to correct any problems evident on AS/REFL cameras. This usually brings powers from ~100-120 to ~130-140. 

This is as far as we've taken the DRFPMI so far, but the CARM bandwidth is still only at a few kHz. Based on PRFPMI locking, the next steps will be:

  • CM BOARD +12dB or so additional IN1 gain, more AO gain may be needed to get crossover to final position of ~100Hz
  • MC2 viollin filters back on
  • CM boost(s) on
  • AS55 whitening on
  • Transition DRMI to 1F
  11702   Tue Oct 20 15:51:44 2015 ericqUpdateSUSMC2 F2P tuned

Using a modified version of Hang's deMod_deCoup scripts, I tuned the MC2 coil output matrix to minimize the appearance of POS drive in the SUSPIT signal at 28Hz. Up until now, there was no F2P compensation. This reduced the force to pitch coupling at 28Hz by 8dByes

Old: POS -> 1 x UL, 1 x UR, 1 x LL, 1x LR

New: POS -> 1.1054 x UL, 1.1054 x UR, 0.8946 x LL, 0.8946 LR

I checked the MCL spectrum before and after this change with OAF on, this did not spoil the feedforward length subtraction in any noticible way. 

The script lives in userapps/release/isc/c1/scripts/decoup, but I've symlinked it to /opt/rtcds/caltech/c1/scripts/decoup.

The script modification I made had to do with how the I and Q data is collected. Before, it was sporadically probing the I and Q FM output monitor EPICS values; I changed it to use the avg function of cdsutils, which calculates the mean and std from the 16kHz data and have seen it improve results by 1dB or so. I've been in touch with Jenne to propagate this to the sites. 

  11703   Tue Oct 20 16:27:04 2015 ericqUpdateVACvacuum VME machines rebooted

[ericq, Gautam, Steve]

Following roughly the same procedure as ELOG 11354, c1vac1 and c1vac2 were rebooted. The symptoms were identical to the situation in that ELOG; c1vac1 could be pinged and telneted to, but c1vac2 was totally unresponsive. 

The only change in the linked procedure was that we did not shut down the maglev. Since I unwittingly had it running for days without V4 open while Steve was away, we now know that it can handle shorter periods of time than that...

Upon reboot, many channels were readable again, unfortunately the channels for TP2 and TP3 are still blank. We were able to return to "Vacuum normal state," but because of unknowned communication problems with VM1's interlock, we can't open VM1 for the RGA. Instead we opened VM2 to expose the RGA to the main IFO volumn, but this isn't part of the "Normal" state definite, so things currently read "Undefined state".

  11716   Tue Oct 27 03:46:26 2015 ericqUpdateSUSMC2 F2P mis-tuned

D'oh. Good point.

Reverted for now; I'm thinking about doing laser pointer->MC2 QPD...

  11718   Tue Oct 27 03:56:52 2015 ericqUpdateLSCDRFPMI work

A handful of DRFPMI locks tonight, longest one was ~7 minutes. 

EPICS/network latency has been a huge pain tonight. The locking script may hang between commands at an unstable place, or fail to execute commands altogether because it can't find the EPICS channel. This prevented or broke a number of locks. 

I made some CARM OLG and crossover measurements, and found the AO gain for the right crossover freq (~100Hz) to be ~8dB different than what's in the PRFPMI script, which is weird. Right now, the CARM bandwidth / ability to turn on boosts is limited by the gain peaking in the IMC CLG due to the high-ish PC/PZT crossover frequency we're using. 

Gautam turned on some sensing excitations during the last couple of locks, but they weren't on for very long before the lock loss. Hopefully I can pull out at least some angles from the data. 

I'm also more convinced that the PRC angular FF needs retuning; there is more residual motion on the cameras than I'm used to seeing. I've taken more data that I'll use to recalculate a wiener filter tomorrow. 

The PMC, ALSX beat and ITMX oplev all needed a reasonable pitch realignment tonight. 

  11721   Wed Oct 28 17:06:30 2015 ericqUpdateASCNew PRC Angular FF filters installed

I've installed new filters for the T240 -> PRM static online angular feedforward that were trained after some of the recent changes to the signal chain of the relevant signals (i.e. the counts->velocity calibration that Rana did for the seismometers, and fixing the improper dewhitening of the POP QPD channels used as the Wiener target.)

Quickly trying them out now shows about the same level of performance as the previous ones, but the real performance I care about is during after-hours locking-time, so I'll take more measurements tonight to be posted here. 

  11722   Thu Oct 29 03:25:49 2015 ericqUpdateLSCDRFPMI work

[ericq, Gautam]

The length of DRFPMI lock did not increase much tonight, but we got a ~80 second sensing matrix measurement, and got the CARM bandwidth up to 10k with two boosts on. 

NB: I did not measure the CARM loop gain at its excitation frequency, so the plotted sensing element is supressed by the CARM loop. However, this is still useful for gauging the size of the PRCL signal vs. the residual CARM fluctuations. The excitations are fairly closely spaced between 309 and 316 Hz. 

For comparison, I'm also re-plotting the DRMI sensing measurement from a few weeks back taken at CARM offset of -4. We can see some change in the PRCL sensing, likely due to the CARM-coupled path. MICH/PRCL sadly looks pretty degenerate, but REFL55 looks more reasonable. 


I think the main limitation tonight was SRC stability. Even before bringing CARM to zero offset, we would see occasional sharp dives in AS110 power. One lockloss happened soon after such an occurance, but I checked the values, and it was not sufficient to trigger the Schmitt trigger down; instead it may have been a real optical loss of signal. The SRCL OLTF looks sensible. 

Random notes:

  • Aux X laser was glitching yet again, twiddled laser current to 1.90A from the 1.95A that I twiddled it to on Monday from the nominal 2.0A. 
  • When aligning the PRMI, I saw both ITMs' oplevs shift by a few urad in both pitch and yaw when engaing/breaking the lock, but this was not repeatable.
  • I reduced the AS110 whitening gain by 9dB, since the DC values were a few thousands, and I wanted to make sure there were no stray ADC saturations. This didn't change lock stability though. 
Attachment 1: DRFPMI.pdf
Attachment 2: DRMIarms.pdf
  11726   Tue Nov 3 03:12:46 2015 ericqUpdateLSCDRFPMI work

Tonight was kind of a wash. 

We spent some time retaking single arm scans with Gautam's frequency counting code to confirm the linewidths he measured before his most recent round of code improvements. During this, ETMX was being its old fussy self, costing us gentle realignment time. For the time being, we started actuating on ITMX for single arm locks. Also, out of superstition, I changed the static position offset that had been at +1k for the last N months to -1k. 

ETMX broke us out of a few DRFPMI lock trials as well, as did poor SRM alignment. I finally set up dither alignement settings for SRM in DRMI though, which helped (even in the arms-held-off-resonance situation). I still prefer doing the PRM/BS dither alignment in a carrier PRMI lock, because I think the SNR should be better than DRMI. 

We know that the ETMX excursions can happen without length drive exciting them, but also that length drives certainly can excite them. For future locks, I'm going to try out avoiding ETMX drive altogether; the sites use a single ETM for their DARM actuation and let the CARM loop take care of the resultant cross coupling, so hopefully we can do the same without angering the mode cleaner.

Anyways, we didn't really ever make it far enough to do anything interested with the DRFPMI tonight frown

  11729   Wed Nov 4 14:44:00 2015 ericqUpdateSUSETMX oplev servo disabled

I've turned the ETMX oplev servos off for the time being. (At the input side, so that no scripts will accidently turn it on).

Thus, only the local damping is being applied, let's see if we see any kicks...

  11731   Wed Nov 4 16:12:07 2015 ericqUpdateCDSOPTIMUS

There is a new machine on the martian network: 32 cores and 128GB of RAM. Probably this is more useful for intensive number crunching in MATLAB or whatever as opposed to IFO control. I've set up some of the LIGO analysis tools on it as well. 

A successor to Megatron, I dub it: OPTIMUS

  11733   Wed Nov 4 22:42:02 2015 ericqUpdateSUSETMX oplev servo disabled

During this time period, it looks like there was maybe one excursion. Here are the individual OSEM signals, which I think to be calibrated to microns. 

When I'm doing other things, I'm going to intentionally leave the watchdog tripped, and see if anything happens. 

  11742   Mon Nov 9 15:59:06 2015 ericqUpdateLSCFSR and linewidth measurements with phase tracker

- modulation depth = 0.390 +/- 0.062

There are two modulation frequencies that make it to the arm cavities, at ~11MHz and ~55MHz. Each of these will have their own modulation depth indepedent of each other. Bundling them together into one number doesn't tell us what's really going on. 

  11744   Mon Nov 9 23:22:18 2015 ericqUpdateSUSETMX oplev servo disabled

During a ETMX kick that just occured, with only local damping on, the slow VMon channels didn't show any noticable change. 

  11758   Thu Nov 12 10:47:17 2015 ericqUpdateSUSETMX oplev servo disabled

By looking at the oplev and Vmons before and after a step of 90 counts in SUS-ETMX_PIT_OFFSET, I observe:

  • UL: +1.53mV / urad
  • UR: -1.94mV / urad
  • LR: -1.54mV / urad
  • LL: +1.92mv / urad

The random error associated with these measurements is ~0.02mV

So, the ~7urad urad shift seen in my earlier post would mean a change of around 10mV in the Vmon signals, which isn't evident in the traces. So, this is possibly a piece of evidence in favor of a real mechanical shift, rather than an electronic glitch. 

  11759   Thu Nov 12 16:00:55 2015 ericqUpdateIOOPSL Laser turned back on

We found the PSL laser switched off. Looking at the wall StripTool, it looks like this happened about 4 hours ago. Gautam was working at and around the PSL table, and I suspect he accidently ran into the Big Red Button. 

We turned the laser back on.

  11770   Tue Nov 17 00:57:21 2015 ericqUpdateSUSITMX UL calmed?

After running dither alignment for all mirrors, all oplevs were recentered. (Except ETMY, since we did that earlier today.)

Looking at Koji's template for OSEM signals, the ITMX UL sensor noise floor seems more in line with the LL sensor, though there continues to be more noise than in other mirrors. 


Trending the sensor signals over the past 7 days, Koji's measurement looks to have been taken during a time when the UL sensor voltage had jumped down. Did someone squish the satellite box cable? I have not done so. 

I think that the step right at the end is due to a new POS offset of -2k counts, which I think Koji put into place earlier today. 

According to the wiki, the Vmax/2 values and the current values are: 



















Attachment 1: TM_nov17.pdf
  11772   Tue Nov 17 14:31:25 2015 ericqUpdateCDS16Hz frame writing temporarily disabled

To test the effect on EPICS latency, I've restarted daqd with modified ini files which disable all frame writing of 16Hz channels. 

This happened at GPS:1131835955 aka Nov 17 2015 22:52:18 UTC

Last night, I started running a script written by Dave Barker that monitors a specified EPICS channel (in this case C1:IOO-MC_TRANS_SUM), to look for seconds in which it does not update the expected number of times. This is still running, so I will be able to compare the rate of EPICS slowdowns before and after this change. 

I will revert back to the nominal state of things in a few hours, or until someone asks me to. 

  11777   Tue Nov 17 20:57:43 2015 ericqUpdateCDS16Hz frame writing running again

Back to nominal FB configuration at 1131857782, aka Nov 18 2015 04:56:05 UTC.

Weirdly, during this time, the script watching MC_TRANS_SUM from pianosa saw tons of freezes, but another instance  watching LSC-TRY_OUT16 on optimus saw no freezes. 

  11778   Wed Nov 18 10:10:53 2015 ericqUpdateCDSc1iscey IO chassis missing brackets

Steve and I inadvertently discovered that the c1iscey IO chassis doesn't have brackets to secure the cards where the ADC/DAC cables are connected, making them very easy to knock loose. All other IO chassis have these brackets. Pictures of c1iscey and c1lsc IO chassis to compare:

  11786   Wed Nov 18 23:18:07 2015 ericqUpdateComputer Scripts / Programsnodus /boot cleared up

The /boot partition was filling up with old kernels. Nodus has automatic security updates turned on, so new kernels roll in and the old ones don't get removed. 

I ran apt-get autoremove, which removed several old kernels. (apt is configured by default to keep two previous kernels around when autoremoving, so this isn't so risky)

Now: /dev/sda1                    236M   94M  130M  42% /boot

In principle, one should be able change a setting in /etc/apt/apt.conf.d/50unattended-upgrades that would do this cleanup automatically, but this mechanism has a bug whose fix hasn't propagated out yet (link). So, I've added a line to nodus' root crontab to autoremove once a week, Sunday morning. 

  11789   Thu Nov 19 15:16:24 2015 ericqUpdateCDSc1iscey IO chassis now has brackets

[Steve, ericq]

Brackets for the c1iscey IO chassis cards have been installed. Now, I can't unseat the cards by wiggling the ADC or DAC cable. yes

  11799   Mon Nov 23 14:45:39 2015 ericqUpdateComputer Scripts / ProgramsNew software

COMSOL 5.1 has been installed at: /cvs/cds/caltech/apps/linux64/comsol51/bin/comsol

MATLAB 2015b has been installed at: /cvs/cds/caltech/apps/linux64/matlab15b/bin/matlab 

This has not replaced the default matlab on the workstations, which remains at 2013a. If some testing reveals that the upgrade is ok, we can rename the folders to switch. 

  11803   Mon Nov 23 23:42:56 2015 ericqUpdateLSCALSY recovered

[ericq, gautam]

Gautam couldn't observe a Y green beatnote earlier, so we checked things out, fixed things up, and performance is back to nominal based on past references. 

Things done:

  • Marconi carrier output switched back on after Koji's excellent RF maintence
  • BBPD power supplies switched on
  • Removed a steering mirror from the green beatY path to do near/far field alignment. 
  • Aligned PSL / Y green beams 
  • Replaced mirror, centered beam on BBPD, moved GTRY camera to get the new spot.
  • POY locked, dither aligned, beatnote found, checked ALS out-of-loop noise, found to be in good shape. 
  11825   Mon Nov 30 14:12:14 2015 ericqUpdateLSCLO level check for the LSC RF distribution box

I checked the RF levels at the LSC LO distribution box, with the agilent scope and a handful of couplers. This was all done with the Marconi at +13dBm. 

I only checked the channels that are currently in use, since the analyzer only measures 3 channels at a time, and rewiring involves walking back and forth to the IOO rack to make sure unpowered amps aren't driven, and I was getting hungry. 

For the most part, the LO levels coming into the LSC demod boards are all around +1.5dBm (i.e. I measured around -18.0dBm out of the ZFDC-20-5 coupler, which has a nominal 19.5dB coupling factor)

The inputs piped over from the IOO rack, labeled as "+6dBm" were found to be 4.7dBm and 2.9dBm for 11Mhz and 55MHz, respectively. 

The 2F signals were generally about 40dB lower, with two exceptions:

  • REFL165's ~332MHz signal was around -18dBc
  • POP22 had many more visible harmonics than any other LO signal
    • 11MHz: -32 dBc
    • 33MHz: -32 dBc
    • 44Mhz: -15dBc 

Here are the raw numbers I measured out of the couplers, all in dBm:

  • 11MHz in: -14.8
  • 55MHz in: -16.6
  • POX11:    -18.7
  • POY11:    -18.0
  • REFL11:   -18.0
  • REFL33:   -18.3
  • POP110:   -17.9
  • AS110:    -18.1
  • POP22:    -19.9
  • REFL165:  -18.5
  • AS55:     -18.6
  • POP55:    -18.8 (this port is used as the REFL55 LO)
  11827   Mon Nov 30 16:33:06 2015 ericqUpdateLSCstrange behavior of ASDC

One possible explanation of this behavior is simply poor centering of the AS beam on AS55 (whose DC level provides ASDC, if memory serves me correctly).

I misaligned ETMY, and moved ITMY through its current nominal alignment while looking at the POYDC and ASDC levels. 

In both pitch and yaw, the nominal alignment is fairly close to the "plateau" in which the AS beam is fully within the PD active surface. I.e. it doesn't take much angular motion to start to lose part of the beam, and thus introduce a first order coupling of angle to power. (Look at the plateaus at around -2min and -0.5min, and where the rapidly changing oplev trace crosses zero)

Furthermore, POYDC seems to be in some weird condition where it is actually possible to increase the reported powerwhen misaligning in pitch, but somehow there is more angular coupling in this state. 

In any case, I would advise that the POY11 and AS55 RFPDs have their spots recentered with optics in their nominal aligned states. In fact, given how we found REFL11 alingment to be less-than-ideal not so long ago, all of the RFPDs could probably use a checkup. 

  11836   Wed Dec 2 03:34:30 2015 ericqUpdateLSCSRCL OLG weirdness

[gautam, ericq]

Since ETMX seems to have been on good behavior lately, we tried to fire the IFO back up. 

We had a fair amount of trouble locking the DRMI with the arms held off resonance. For reasons yet to be understood, we discovered that the SRCL OLG looks totally bananas. It isn't possible to hold the DRMI for very long with this shape, obviously. 

With the arms misaligned and the DRMI locked on 1F, the loop shape is totally normal. I haven't yet tried 3F locking with the arms misaligned, but this is a logical next step; I just need to look up the old demod angles used for this, since it wasn't quickly possible with the 3F demod angles that are currently set for the DRFPMI. 

Attachment 1: weirdSRCLG.pdf
ELOG V3.1.3-