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ID Date Author Type Category Subjectup
  7279   Sun Aug 26 21:47:50 2012 KojiUpdateCDSC1LSC ooze

I came in to the lab in the evening and found c1lsc had "red" for FB connection.
I restarted c1lsc models and it kept hung the machine everytime.

I decided to kill all of the model during the startup sequence right after the reboot.
Then run only c1x04 and c1lsc. It seems that c1oaf was the cause, but it wasn't clear.

  14187   Tue Aug 28 18:39:41 2018 JonUpdateCDSC1LSC, C1AUX reboots

I found c1lsc unresponsive again today. Following the procedure in elog #13935, I ran the rebootC1LSC.sh script to perform a soft reboot of c1lsc and restart the epics processes on c1lsc, c1sus, and c1ioo. It worked. I also manually restarted one unresponsive slow machine, c1aux.

After the restarts, the CDS overview page shows the first three models on c1lsc are online (image attached). The above elog references c1oaf having to be restarted manually, so I attempted to do that. I connect via ssh to c1lsc and ran the script startc1oaf. This failed as well, however.

In this state I was able to lock the MICH configuration, which is sufficient for my purposes for now, but I was not able to lock either of the arm cavities. Are some of the still-dead models necessary to lock in resonant configurations?

Attachment 1: CDS_FE_STATUS.png
CDS_FE_STATUS.png
  7225   Sat Aug 18 17:09:01 2012 SashaUpdateSimulationsC1LSP MEDM Screens Added

C1LSP has been added to the site map. I'll work on filling in the structure some more today and tomorrow (as well as putting up PDH and REFL/AS MEDM screens).

NOTE: Does anyone know how to access channels (or if they're even there) for straight Simulink inputs and outputs (i.e. I have some sort of input, do something to it in the simulink model, then get some output)? I've been trying to add ADC MEDM screens to c1lsp, but channels along the lines of C1LSP-ADC0_0_Analog_Input or C1LSP-ADC0_A0 don't seem to exist.

  7227   Sat Aug 18 19:40:47 2012 SashaUpdateSimulationsC1LSP MEDM Screens Added

Quote:

C1LSP has been added to the site map. I'll work on filling in the structure some more today and tomorrow (as well as putting up PDH and REFL/AS MEDM screens).

NOTE: Does anyone know how to access channels (or if they're even there) for straight Simulink inputs and outputs (i.e. I have some sort of input, do something to it in the simulink model, then get some output)? I've been trying to add ADC MEDM screens to c1lsp, but channels along the lines of C1LSP-ADC0_0_Analog_Input or C1LSP-ADC0_A0 don't seem to exist.

 NVM. Figured out that I can just look in dataviewer for the channels. It looks like there aren't any channels for ADC0...I'll try reinstalling the model and restarting the framebuilder.

  6068   Mon Dec 5 02:55:30 2011 DenUpdateAdaptive FilteringC1OAF

I've added filter banks for correction path in the C1OAF model to use AA filters.  I compiled and installed the new version. I runs but does not sync. Probably, I've made a mistake in the some names of epics channels. Leave it for now, figure out tomorrow. If someone needs an old version, it is in the /opt/rtcds/caltech/c1/userapps/trunk/isc/c1/models/c1oaf_BACKUP20111204.mdl file. Corresponding medm screen is in the /opt/rtcds/caltech/c1/userapps/trunk/isc/common/medm/OAF_OVERVIEW.adl file.

  6070   Mon Dec 5 10:13:13 2011 JenneUpdateAdaptive FilteringC1OAF

Quote:

I've added filter banks for correction path in the C1OAF model to use AA filters.  I compiled and installed the new version. I runs but does not sync. Probably, I've made a mistake in the some names of epics channels. Leave it for now, figure out tomorrow. If someone needs an old version, it is in the /opt/rtcds/caltech/c1/userapps/trunk/isc/c1/models/c1oaf_BACKUP20111204.mdl file. Corresponding medm screen is in the /opt/rtcds/caltech/c1/userapps/trunk/isc/common/medm/OAF_OVERVIEW.adl file.

 The general rule in the 40m is that if it's not an 'emergency', i.e. something is wrong with the computers and preventing the main locking work, no model recompiling-type activities at nighttime. 

Also, if you do things and recompile, you need to do an svn check-in.  That's where backups are kept.  We don't want to clutter folders with backups anymore.

  6093   Fri Dec 9 13:28:09 2011 DenUpdateAdaptive FilteringC1OAF

I tried to figure out why red NO SYNC label became present in the C1OAF_GDS_TP screen after I added AA filters to the C1OAF model.

C1OAF model contains 8 libraries C1OAF_ADAPT for 8 DOF. I changed C1OAF_ADAPT library to C1OAF_ADAPT_AA library where I added 28 AA filters for 28 witness channels. It turns out that if I use this library for all 8 DOF then I see NO SYNC label, if only for one DOF (MCL) then I see green IOP label. This means that using AA filters for each DOF too much channels of filters are created for online system to operate. I think there is some number inside the code that one can not exceed. Analyzing compilation output after "make c1oaf" I figured out that without using AA filters we have 632 filters and using AA we have 856 filters.

For now I'll use AA filters for MCL only.

  6094   Fri Dec 9 14:33:16 2011 Alex IvanovUpdateAdaptive FilteringC1OAF

Quote:

I tried to figure out why red NO SYNC label became present in the C1OAF_GDS_TP screen after I added AA filters to the C1OAF model.

C1OAF model contains 8 libraries C1OAF_ADAPT for 8 DOF. I changed C1OAF_ADAPT library to C1OAF_ADAPT_AA library where I added 28 AA filters for 28 witness channels. It turns out that if I use this library for all 8 DOF then I see NO SYNC label, if only for one DOF (MCL) then I see green IOP label. This means that using AA filters for each DOF too much channels of filters are created for online system to operate. I think there is some number inside the code that one can not exceed. Analyzing compilation output after "make c1oaf" I figured out that without using AA filters we have 632 filters and using AA we have 856 filters.

For now I'll use AA filters for MCL only.

 I have a feeling we are not fitting into pre-allocated memory space in the shared memory between the front-end process and the epics process. Filter module data is overwriting some other data and that's why we are not getting a sync light. I suggest we upgrade to 2.4 code first and then we will figure out a way to expand memory areas to fit 856 filters.

  6100   Fri Dec 9 17:53:31 2011 DenUpdateAdaptive FilteringC1OAF

[Jenne, Den]

AA filters for witness channels are added to the oaf model. It is working now and the number of memory used is not critical.  NO SYNC is not present any more.

  15254   Thu Mar 5 11:27:48 2020 gautamUpdateElectronicsC1PSL acromag crate is no longer sitting on the floor

[jordan, gautam]

The C1PSL crate has now been installed in a more permanent way in the rack.

  • Top and bottom covers were re-attached after work yesterday.
  • +/- 24 V DC and +15 V DC power connectors were screwed on for better robustness (I had removed the fuse for the -24V supply as part of debugging yesterday, this was reconnected).
  • PSL diagnostics DB 25 cable was re-run appropriately over the cable tray and connected to the unit.
  • The chassis sits on some rails - these rails are mounted to the rack using rack nuts but that means the ears on the Acromag chassis no longer line up with any rack nut slots, and so the chassis is not bolted on to the rack.
  • We also took this opportunity to remove the c1iool0 VME chassis from 1X2 - given that the DAC and BIO cards of c1ioo (rtcds system) are unused, I felt comfortable disconnecting them and that made the removal relatively easy. The CDS overview MEDM screen reports no errors after this work.

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.

Quote:

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.

  15251   Wed Mar 4 20:42:53 2020 gautamUpdateElectronicsC1PSL acromag crate is sitting on the floor

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.

  12924   Mon Apr 3 17:09:47 2017 gautamUpdateCDSC1PSL burt-restored

When I came in this morning, Steve had re-locked the PMC and IMC - but I could see a ~1Hz intensity fluctuation on the PMC REFL video monitor. I unlocked the PMC and tried to re-lock it, but couldn't using the usual prescription of turning the servo gain down and moving the DC bias slider around. I checked the status of the slow machines - all were responding to pings and could be telnet'ed into, so that didn't seem to be the problem. In the past, this sort of behaviour was characteristic of the infamous "sticky slider" problem - so I simply burt-restored c1psl using a snapshot from 29 March, after which I could easily re-lock the PMC. The transmitted light level looked normal on the scope on the PSL table, and the PMC REFL video monitor also look normal now.

  15256   Thu Mar 5 19:45:23 2020 JonSummaryPSLC1PSL in-situ test results

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.

Post-installation modifications

  • All four channels connected to the sourcing BIO module were found to in fact require sinking I/O. They were reassigned to sinking BIO modules. Affected channels:
    • C1:PSL-FSS_FASTSWEEP
    • C1:PSL-FSS_SW1
    • C1:PSL-FSS_SW2
    • C1:PSL-PSL_Shutter
  • Added a new AI channel:
    • C1:PSL-FSS_MIXERM
  • Removed an unneccessary AI channel:
    • C1:PSL-FSS_LODET
  • Moved two AI channels from BNC connectors to a new Dsub connector (labelled DB25M-2 in the spreadsheet).
    • C1:PSL-FSS_RCTEMP
    • C1:PSL-FSS_RMTEMP_VOLTS

Issues identified during testing

  • Digital calibration. The following channels work, but we need to verify their EPICS calibration parameters (EGUF/EGUL):
    • C1:PSL-FSS_FASTGAIN
    • C1:PSL-FSS_FAST
    • C1:PSL-PMC_RFADJ
    • C1:PSL-PMC_MODET
  • IMC servo board. The Acromag channels themselves were found to work, but the linearity of the mbbo gain stages are in question (i.e., a potential problem with the board). GV is currently testing the servo board.
  • PSL QPD board apears to be dead. We connected a scope directly to the test points on the board and measured a high level of noise and no signal (for all four of the QPD channels). I understand this QPD has not been used in some time, so it may not have been noticed before.
  • WFS DC channels are saturating when the IMC is unlocked. The acceptance range of the Acromag ADC is only +/-10 V, but we measured sensor voltages as high as ~14 V. It appears that the old ADCs were somehow accepting a range of 0 to +20 V instead of -10 to +10 V. However, the Acromags do not support the input range 0-20 V. Since SNR is not critical for these channels (they're used only for initial alignment), I propose we simply install a voltage divider inside the chassis, just before the Acromag, for each of these signals.
Attachment 1: c1psl_feedthrough_wiring_-_By_Connector_(3).pdf
c1psl_feedthrough_wiring_-_By_Connector_(3).pdf c1psl_feedthrough_wiring_-_By_Connector_(3).pdf c1psl_feedthrough_wiring_-_By_Connector_(3).pdf c1psl_feedthrough_wiring_-_By_Connector_(3).pdf
  3921   Mon Nov 15 14:36:37 2010 KojiUpdatePSLC1PSL rebooted?

Has C1PSL rebooted? Has burtrestore been forgotten? Even without elog?

We found some settings are wrong and the PMC has pretty low gain.

  3922   Mon Nov 15 14:42:01 2010 AidanUpdatePSLC1PSL rebooted?

Yeah. Joe and I rebooted c1psl a couple of times this morning. I didn't realize the burtrestore wasn't automatic.

 

Quote:

Has C1PSL rebooted? Has burtrestore been forgotten? Even without elog?

We found some settings are wrong and the PMC has pretty low gain.

 

  17149   Wed Sep 21 10:10:22 2022 YehonathanUpdateCDSC1SU2 crashed

{Yehonathan, Anchal}

Came this morning to find that all the BHD optics watchdogs tripped. Watchdogs were restored but the all ADCs were stuck.

We realized that the C1SU2 model crashed.

We run /scripts/cds/restartAllModels.sh to reboot all machines. All the machines rebooted and burt restored to yesterday around 5 PM.

The optics seem to have returned to good alignment and are damped.

  16769   Mon Apr 11 11:00:30 2022 JancarloUpdateVACC1VAC Reboot and Nitrogen tanks

[Paco, JC, Ian, Jordan, Chub]

Checking in the morning, I walked over to the Nitrogen tanks to check the levels. Noticed one tank was empty, so I swapped it out. Chub came over to check the levels and to take note of how many tanks were left available for usage (None). Chub continued to put in a work order for a set of full Nitrogen tanks. We should be set on Nitrogen until Thursday this week (4/14/22).

As for C1VAC, this morning, Paco and I attempted to open the PSL shutter, but the interlock system was tripped so we didn't get any light into the IFO. We traced the issue down to C1VAC being unresponsive. We discussed this may have interlocked as a result of the Nitrogen tanks running out, but we do not believe this was the issue since we would have recieved an email. We tried troubleshooting as much as possible avoiding a reboot, but were unable to solve the issue. In response, we ran the idea of a reboot across Jordan and Ian, where everyone was in agreement, and fixed the system. Restarting c1vac seems to have closed V4, but this didn't cause any issues with the current state of the vacuum system.

After opening the PSL shutter again, we see the laser down the IFO, so we resume alignment work

  7214   Fri Aug 17 05:29:04 2012 YoichiConfigurationComputer Scripts / ProgramsC1configure scripts

 I noticed that the IFO restore scripts have some problems. They use burt request files to store and restore the settings. However, the request files contain old channel names.

Especially channels with _TRIG_THRES_ON/OFF are now _TRIG_THRESH_ON/OFF, note the extra "H".

These scripts reside in /opt/rtcds/caltech/c1/burt/c1ifoconfigure/.

I fixed the PRMI_SBres and MI scripts. Someone should fix all other files.

  1022   Fri Oct 3 12:15:21 2008 AlbertoConfigurationIOOC1iool0 rebooted
This morning, in order to update the threshold values of the alarm handler for the StochMon, I rebooted the C1iool0 computer following the procedure in the wiki, that is telnetting on it and typing CTRL+X. Apparently everything went well in the process.
  3834   Mon Nov 1 11:34:08 2010 josephbUpdateCDSCA.Client.Exception spam fixed

Problem:

CA.Client.Exception...............................................
    Warning: "Identical process variable names on multiple servers"
    Context: "Channel: "C1:SUS-ITMX_TO_COIL_0_3_INMON", Connecting to: 192.168.113.85:42367, Ignored: c1susdaq:42367"
    Source File: ../cac.cpp line 1208
    Current Time: Fri Oct 29 2010 18:07:39.132686519

The above exception gets thrown for each channel sent to the framebuilder when you start the frame builder.  Its the 192.168.113.xxx (main martian) and 192.168.114.xxx (DAQ) networks sending the same information.  This makes it hard to see real errors when starting the frame builder.

Solution:

Configure EPICS channel access to only use one network.  This is done by modifying the /etc/bash/bashrc and the /diskless/root/etc/bash/bashrc files with the following two lines:

export EPICS_CA_AUTO_ADDR_LIST=NO
export EPICS_CA_ADDR_LIST="192.168.113.255"

The first line tells the computers not to automatically search all attached network devices.  The second tells it to use the 192.168.113.xxx network for EPICS channel broadcasts.

  13654   Fri Feb 23 20:46:04 2018 Udit KhandelwalSummaryGeneralCAD Summary 2018/02/23

I have more or less finished cadding the test mass chamber by referring to the drawings Steve gave me. Finer details like lugs and bolts and window flaps can be left for later. Here's a quick render:

  14042   Fri Jul 6 19:39:37 2018 Udit KhandelwalSummaryGeneralCAD drawings of cantilever suspension required

Request to Koji to acquire the drawings or 3D CAD of the cantilever suspensions of the Tip-Tilt Assembly!

  1531   Wed Apr 29 04:03:51 2009 YoichiUpdateLockingCARM RF changed to REFL_2I
Yoichi, Peter

As Rob suggested, the optimal demodulation phase is easier to find for REFL_2I than POX_1I.
Moreover, for 166MHz LO, we have a phase shifter (delay line) already installed. So we can easily change the demodulation phase of REFL_2I.
Tonight, we switched the RF CARM signal to REFL_2I.
To do so, I changed the signal going to the REFL1 input of the common mode board from POX_1I to REFL_2I.
I moved a BNC-T installed at the output of POX_1I to the REFL_2I output to split the REFL_2I signal and send it to the CM board.
Since the gain of the REFL_2I was about 20dB lower than that of POX_1I, I increased the gain of the SR560, which is installed between the REFL_2 demodulation board and the CM board, from 1 to 10.

With some gain tweaks, we were able to hand off the CARM from REFL_DC to REFL_2I. We also succeeded in switching the REFL_2I ADC channel from PD11 to PD2_DC (the output of the length path from the CM board). This switching is necessary in order to engage the boost on the CM board.

There remains some offset in the CARM when the arm power is maximized. This is expected because the REFL_2I demodulation phase is probably not exactly right.
I will optimize the demodulation phase tomorrow.
  1535   Thu Apr 30 15:10:54 2009 robUpdateLockingCARM RF changed to REFL_2I

Quote:
Yoichi, Peter

As Rob suggested, the optimal demodulation phase is easier to find for REFL_2I than POX_1I.
Moreover, for 166MHz LO, we have a phase shifter (delay line) already installed. So we can easily change the demodulation phase of REFL_2I.
Tonight, we switched the RF CARM signal to REFL_2I.
To do so, I changed the signal going to the REFL1 input of the common mode board from POX_1I to REFL_2I.
I moved a BNC-T installed at the output of POX_1I to the REFL_2I output to split the REFL_2I signal and send it to the CM board.
Since the gain of the REFL_2I was about 20dB lower than that of POX_1I, I increased the gain of the SR560, which is installed between the REFL_2 demodulation board and the CM board, from 1 to 10.

With some gain tweaks, we were able to hand off the CARM from REFL_DC to REFL_2I. We also succeeded in switching the REFL_2I ADC channel from PD11 to PD2_DC (the output of the length path from the CM board). This switching is necessary in order to engage the boost on the CM board.

There remains some offset in the CARM when the arm power is maximized. This is expected because the REFL_2I demodulation phase is probably not exactly right.
I will optimize the demodulation phase tomorrow.



From Optickle simulations, it looks like the SRCL/CARM gain ratio at REFL I2 is about 8e-4. So a 1 nanometer offset in SRCL yields 0.8 picometers of offset in CARM.
  10971   Wed Feb 4 04:51:14 2015 diegoUpdateLSCCARM Transition to REFL11 using CM_SLOW Path

[Diego, Jenne, Eric]

Tonight we kept on following our current strategy for locking the PRFPMI:

  • the first few tries were pretty unsuccessful: the PRMI lock wasn't much stable, and we never managed to reduce CARM offset to zero before losing lock;
  • then we did some usual manteinance: we fixed the X arm green beatnote, fixed the phase tracker and given much attention to ASS alignment, since the X arm wasn't doing great;
  • the last few locks were consintently better: we managed to get to CARM offset zero "easily", but the arm power was not very high (~8);
  • then we tried to transition CARM to REFL11, both with the usual configuration and using CM_SLOW, using REFL11 as input for the Common Mode Board;
    • with the usual configuration, we lost lock right after the transition, because of MICH hitting the rail;
    • we did a very smooth CARM transition directly to REFL11 on the CM_SLOW path; we managed to take a spectrum with the SR785, but we couldn't take any more measurements before losing lock because of some weird glitch, as we can see from the lockloss plot;
  • another thing that helped tonight was changing the ELP of the MICH filter bank: it went from 4th order to 6th order, and from 40 dB suppression to 60 dB suppression;

both of the last two locks, the most stable ones (one transition to usual REFL11 and one transition to "CM_SLOW" REFL11) were acquired actuating on MC2;

 


EDITs by JCD:  At least one of the times that we lost PRMI lock (although kept CARM and DARM lock on ALS), was due to MICH hitting the rail, even after we increased the limiter to 15,000 counts.


 Here is the transfer function between CARM ALS (CARM_IN1) and REFL11 coming through the CM board (CARM_B), just before we transitioned over.  Coherence was taken simultaneously as usual, I just printed it to another sheet.

CARM_3Feb2015_CarmBwasCMslow_CarmAwasLiveALS.pdf

CARM_3Feb2015_CarmBwasCMslow_CarmAwasLiveALS_Coh.pdf


Here is the lockloss plot for the very last lockloss.  This is the time that we were sitting on REFL11 coming through the CM_SLOW path.  A DTT transfer function measurement was in progress (you can see the sine wave in the CARM input and output data), but I think we actually lost lock due to whatever this glitch was near the right side of the plots.  This isn't something that I've seen in our lockloss plots before.  I'm not sure if it's coming from REFL11, or the CM board, or something else.  We know that the CM board gives glitches when we are changing gain settings, but that was not happening at this time.


Q: Here's the SR785 TF of CARM locked through CM board, but still only digital control; nothing exciting. Excitation amplitude was only 1mV, which explains the noisy profile. 

Attachment 1: CARM_3Feb2015_CarmBwasCMslow_CarmAwasLiveALS.pdf
CARM_3Feb2015_CarmBwasCMslow_CarmAwasLiveALS.pdf
Attachment 2: CARM_3Feb2015_CarmBwasCMslow_CarmAwasLiveALS_Coh.pdf
CARM_3Feb2015_CarmBwasCMslow_CarmAwasLiveALS_Coh.pdf
Attachment 3: Glitch_in_CARM_and_PRCL_3Feb2015.png
Glitch_in_CARM_and_PRCL_3Feb2015.png
Attachment 4: slowCM_04-02-2015_042805.png
slowCM_04-02-2015_042805.png
  10979   Thu Feb 5 04:35:14 2015 diegoUpdateLSCCARM Transition to REFL11 using CM_SLOW Path

[Diego, Eric]

Tonight was a sad night... We continued to pursue our strategy, but with very poor results:

  • before doing anything, we made sure we had a good initial configuration: we renormalized the arm powers, retuned the X arm green beatnote, did extensive ASS alignment;
  • since the beginning of the night we faced a very uncooperative PRMI, which caused a huge number of locklosses, often just by itself, without even managing to reduce the MICH offset before reducing the CARM one;
  • we had to reduce the PRCL gain to -0.002 in order to acquire PRMI lock, but keeping it such or restoring it to -0.004 once lock was acquired either didn't improve the PRMI stability at all;
  • we also tweaked a bit the PRCL and MICH UGF servos (namely, their frequencies to ~80 Hz and ~40 Hz respectively) and that seemed to help earlier during the night, but not much longer;
  • we only managed to transition CARM to REFL11 via CM SLOW twice;
    • the first time we lost lock almost immediately, probably because of a non-optimal offset between CARM A and B;
    • the second time we managed to stay there a little longer, but then some spike in the PRCL loop and/or the MICH loop hitting the rails threw us out of lock (see the lockloss plot);
    • both times we transitioned at arm power ~18;
  • during the night we used an increased analog ASDC whitening gain, as from Eric's elog here http://nodus.ligo.caltech.edu:8080/40m/10972 ; even with this fix, though, MICH is still often hitting the rails and causing the lock losses;
  • the conclusion for tonight is that we need to figure what is going on with the PRMI...

 

Attachment 1: 4Feb2015_Transition_CARM_REFL11_CM_SLOW_AP_18.png
4Feb2015_Transition_CARM_REFL11_CM_SLOW_AP_18.png
  10982   Fri Feb 6 03:21:17 2015 diegoUpdateLSCCARM Transition to REFL11 using CM_SLOW Path

[Diego, Jenne]

We kept struggling with the PRMI, although it was a little better than yesterday:

  • we retuned the X Green beatnote;
  • we managed to reach lower CARM offsets than yesterday night, but we still can't keep lock long enough to perform a smooth transition to CM SLOW/REFL11;
  • we tweaked MICH a bit:
    • the ELP in FM8 now is always on, because it seems to help;
    • we tried using a new FM1 1,1:0,0 instead of FM2 1:0 because we felt we needed a little more gain at low frequencies, but unfortunately this didn't change much MICH's behaviour;
    • now, after catching PRMI lock, the MICH limiter is raised to 30k (in the script), as a possible solution for the railing problem; the down/relock scripts take care of resetting it to 10k while not locked/locking;

So, still no exciting news, but PRMI lock seems to be improving a little.

  10589   Thu Oct 9 16:31:53 2014 ericqUpdateLSCCARM W/N TFs

In my previous simulation results, I've always plotted W/m, which isn't exactly straightforward. We often think about the displacement that a given mirror actuator output will induce, but when we're locking the full IFO, radiation pressure effects modify the mechanical response depending on the current detuning, making the meaning of W/m transfer functions a little fuzzy.

So, I've redone my MIST simulations to report Watts of signal response due to actual actuator newtons, which is what we actually control with the digital system. Note, however, that these Watts are those that would be sensed by a detector directly at the given port, and doesn't take into account the power reduction from in-air beamsplitters, etc.

As an example, here are the SqrtInv and REFLDC CARM TFs for the anti-spring case:

carm2SQRTinv.pdfcarm2REFLDC.pdf

 

The units of the SqrtInv plot are maybe a little weird, these TFs are the exact shape of the TRX W/N TFs with the DC value adjusted by the ratio of the DC sweep derivatives of TRX and SqrtInv. 

All of the results live in /svn/trunk/modeling/PRFPMI_radpressure/

 

  10591   Thu Oct 9 18:30:59 2014 JenneUpdateLSCCARM W/N TFs

Okay, here (finally) is the optickle version.

I have the antispring case, starting at 501pm and going roughly every 10pm down to 1pm.  I also have the spring case, starting at -501pm and going down every 10pm to roughly -113pm.  Rossa crashed partway through the calculation, which is why it's not all the way.

In the .zip is a .mat file called PDs_vs_CARMoffset_WattsPerNewton.mat, which has (a) a list of the 50 CARM offsets, (b) a frequency vector, and (c) several transfer function arrays.  The transfer function arrays are supposed to be intuitively named, eg. REFLDC_antispring. 

In the .zip file are also the original .mat files that are a result of the tickle calculations, as well as a .m file for loading them and making the plots, etc.  For anyone who is trying to re-create the transfer function variables, I by-hand saved the variable called PD_WperN to the names like REFLDC_antispring.  Just kidding.  Those original mat files are over 100Mb each, and that's just crazy.  Anyhow, I think the .zip has everything needed to use the data from these plots.

Anyhow.  Here are plots of what are in the various transfer function arrays:

 TRX_antispring.pngTRX_spring.png

REFLDC_antispring.pngREFLDC_spring.png

REFL11I_antispring.pngREFL11I_spring.png

Attachment 6: ForElog.zip
  10593   Fri Oct 10 00:20:37 2014 ranaUpdateLSCCARM W/N TFs

 

 Assuming that these Watts/Newtons TFs are correct, I've modeled the resulting open loop gain for CARM. The goal is to design a loop that is stable under a wide range of offsets and also has enough low frequency gain.

The attached PDF shows this. I used a CARM OLG Simulink model:

carm40.png

I've replaced the 'armTF' block with a digital gain of zero. After measuring the open loop gain of all but this piece, I multiply that 'OLG' with the W/N that Jenne extracted from Optickle for CARM->TR (not sqrtInv)

I plot the resulting estimate of the actual OLG in the following plot. Since the CARM-RSE peak is moving down, we use the LP filter that Den installed for us several months ago. To account for the radiation pressure spring, we use some low frequency boosts but not the crazy FM4 filter.

As you can see, the loop is stable from 500 to 200 pm, but then goes unstable around 110 pm. I expect that we will want to do some fancy shaping there or switch from TRX+TRY into something else.

This assumes we have filters 0, 1, 3, 5, and 7 on in the CARM filter bank - still need to add the digital AA/AI to make the loop phase lag a little more accruate, but I think this is looking promising.

 

Attachment 2: carm.pdf
carm.pdf
  10608   Wed Oct 15 02:59:04 2014 ranaUpdateLSCCARM W/N TFs

 In my previous elog in this thread, I showed the CARM OLG given some new digital filters and the varying CARM plant (spring side, not anti-spring). Jenne has subsequently produced the TFs for all of the rest of the CARM offsets.

These attached plots for several CARM offsets show that the anti-spring side is much more stable than the spring side and so we should use that. Annecadotedally, we think that positive CARM offsets are more stable when going to arm powers of > 10, so perhaps this means that +CARM = -SPRING.

The first PDF shows the spring OLGs and the 2nd one shows the antispring OLGs. I have put in some gain changes to keep the UGF approximately the same as the offset is changed.

The PDF thumbnails will become visible once Q and Diego install the new nodus.

 UPDATE OCt 16: this is all wrong! bad conversion of filters within the invbilinear.m function.

Attachment 1: spring.pdf
spring.pdf
Attachment 2: antispring.pdf
antispring.pdf
  10609   Wed Oct 15 13:38:33 2014 JenneUpdateLSCCARM W/N TFs

Here are the same plots, but the legend also includes the arm power that we expect at that CARM offset.  


Here is what the arm powers look like as a function of CARM offset according to Optickle.  Note that the cyan trace's maximum matches what Q has simulated in Mist with the same high losses.  For illustration I've plotted the single arm power, so that you can see it's normalized to 1.  Then, the other traces are the full PRFPMI buildup, with various amounts of arm loss.  The "no loss" case is with 0ppm loss per ETM.  The "150 ppm loss" case is with 150 ppm of loss per ETM.  The "high loss" case is representative of what Q has measured, so I have put 500 ppm loss for ETMX and 150 ppm loss for ETMY.

ArmPower_vs_Loss.png


And, the transfer functions (all these, as with all TFs in the last week, use the "high loss" situation with 500ppm for ETMX and 150ppm for ETMY).

TFs_TRX_vsCARMoffset_PRFPMI_antispring.pngTFs_TRX_vsCARMoffset_PRFPMI_spring.png

TFs_REFLDC_vsCARMoffset_PRFPMI_antispring.pngTFs_REFLDC_vsCARMoffset_PRFPMI_spring.png

TFs_REFL11I_vsCARMoffset_PRFPMI_antispring.pngTFs_REFL11I_vsCARMoffset_PRFPMI_spring.png

  10620   Thu Oct 16 22:35:05 2014 ranaUpdateLSCCARM W/N TFs

In my last CARM loop modelling, all of the plots are phony, so don't trust them. The invbilinear function inside of StefanB's onlinefilter.m was making bogus s-domain representations of the digital filter coefficients.

So now I've just plotted the frequency response directly from the z-domain SOS coeffs using MattE's readFilterFile.m and FotonFilter.m.

Conclusions are less rosy. The anti-spring side is still easier to compensate than the spring side, but it starts to get hopeless below ~130 pm of offset, so there we really need to try to get to REFL_11/(TRX+TRY), pending some noise analysis.

** In order to get the 80 and 40 pm loops to be more stable I've put in a tweak filter called Boost2 (FM8). As you can see, it kind of helps for 80 pm, but its pretty hopeless after that.

Attachment 1: carm_spring.pdf
carm_spring.pdf
Attachment 2: carm_antispring.pdf
carm_antispring.pdf
  10626   Mon Oct 20 17:50:30 2014 JenneUpdateLSCCARM W/N TFs (Others were all wrong!)

I realized today that I had been plotting the wrong thing for all of my transfer functions for the last few weeks! 

The "CARM offsets" were correct, in that I was moving both ETMs, so all of the calculations were correct (which is good, since those took forever). But, in the plots I was just plotting the transfer function between driving ETMX and the given photodiode.  But, since just driving a single ETM is an admixture of CARM and DARM, the plots don't make any sense.  Ooops.

In these revised plots (and the .mat file attached to this elog), for each PD I extract from sigAC the transfer function between driving ETMX and the photodiode.  I also extract the TF between driving ETMY and the PD.  I then  sum those two transfer functions and divide by 2.  I multiply by the simple pendulum, which is my actuator transfer function to get to W/N, and plot.

The antispring plots don't change in shape, but the spring side plots do.  I think that this means that Rana's plots from last week are still true, so we can use the antispring side of TRX to get down to about 100 pm.

Here are the revised plots:

TFs_TRX_vsCARMoffset_PRFPMI_antispring.pngTFs_TRX_vsCARMoffset_PRFPMI_spring.png

TFs_REFLDC_vsCARMoffset_PRFPMI_antispring.pngTFs_REFLDC_vsCARMoffset_PRFPMI_spring.png

TFs_REFL11I_vsCARMoffset_PRFPMI_antispring.pngTFs_REFL11I_vsCARMoffset_PRFPMI_spring.png

Attachment 1: PDs_vsCARMoffset_20Oct2014.mat.zip
  9796   Fri Apr 11 01:02:07 2014 JenneUpdateLSCCARM and DARM both on IR signals!!!!!!!!!

[EricQ, Jenne]

We're still working, but I'm really excited, so here's our news:  We are currently holding the IFO on all IR signalsNo green, no ALS is being used at all!!!!  

PRCL and MICH in REFL33, CARM on 1/sqrt(trans), DARM on AS55 Q.

CARM actuating on MC2, DARM actuating +ETMY, -ETMX. 

CARM offset is 1.9 counts, TRX averages about .1 counts. At this offset, we are able to transition CARM from ALS to DC Transmission signals and DARM from ALS to AS55Q. 

onlyIRspectra.pdf

  9797   Fri Apr 11 02:09:31 2014 JenneUpdateLSCCARM and DARM both on IR signals!!!!!!!!!

[EricQ, Jenne]

A few more details on our work for the evening, of switching the PRFPMI completely to IR signals (although still with a pretty big CARM offset).


We did the same transition for CARM to 1/sqrt(trans) signals, as last night (elog 9793).  The only difference is that for CARM actuation, we were using a -1*MC in the output matrix, rather than +1's for both ETMs. 

We then had a look at the relative sign and gain between the ALS DARM signals, and AS55Q, using a calibration line in DARM.  Before doing so, we used the DARM line (521.3 Hz, 50 counts) to rotate the AS 55 phase from -60.7 degrees to -97.7 degrees, which gave us about 20dB separation between the I and Q signals.  This informed us that we needed a factor of about 400 less gain for AS55Q than for the ALS darm signal, as well as a minus sign, so I put -400 in the DC normalization place in the LSC for AS55, so that my input matrix would go from ALSY-ALSX (1's) to +1 in AS55Q. 

This transition to AS55 was very easy, and once we did it, we held lock for 5 or 10 minutes, until a large earthquake from Papa New Guinea hit us.  Note however, that we still had a large CARM offset, and our TRX and TRY signals were about 0.1 counts, when we expect several hundred at perfect resonance. 

After that, we relocked, made both CARM and DARM transitions again, and tried to look at a CARM calibration line to see if we see CARM information in any of the REFL RF signals.  We lost lock after a few minutes (so, not related to our calibration line), so we didn't finish, but it looks like REFL55I, normalized by TRX+TRY is the most promising.  Also, REFL55's phase was already very good, while REFL11's phase was not. 


There were some moderate changes to the LSC model that happened, and matching screen changes.  I put in a switch just before the input triggering place of the CARM servo.  This allows us to switch from the "regular" input matrix, and a CESAR signal.  The inputs to the CESAR block are sqrtinv(TRX), sqrtinv(TRY), ALSX, ALSY and the output of the CARM row of the input matrix (so that we can have dynamic normalization of the RF signals).  I have exposed all of these changes in the input matrix screens.

I also modified slightly the ALS watch scripts, to include CARM and DARM servo filter watching, so now we can use the actual CARM and DARM servos.  We should make restore configure scripts for these!


The 2 gps times for when we made the transition from ALS DARM to AS55 DARM were 1081238160 and 1081240217.  We want to go back tomorrow, and extract some nice time series.

Here's a spectrum though, of the difference in noise between DARM on ALS, and DARM on AS55.  The CARM was always on 1/sqrt(Trans) signals during these spectra.  We have an enormous gain in high frequency noise performance once we switch to the RF signal, which is great.

IRlocks.pdf

  9798   Fri Apr 11 10:30:48 2014 jamieUpdateLSCCARM and DARM both on IR signals!!!!!!!!!

Quote:

[EricQ, Jenne]

We're still working, but I'm really excited, so here's our news:  We are currently holding the IFO on all IR signalsNo green, no ALS is being used at all!!!!  

 Phenomenal!!  Well done, guys!

  9799   Fri Apr 11 11:58:24 2014 JenneUpdateLSCCARM and DARM both on IR signals!!!!!!!!!

 A few time series from last night's data. 

300 seconds, starting from 1081240100, showing that as we move from ALSY-ALSX to AS55Q, the DARM error signal gets smaller.

DARM_IN1_getsSmaller.png

The same 300 seconds, showing that the CARM error signal, and the arm transmissions, are not perturbed during this transition.

DARM_CARM_TRX_TRY.png

DARM in and out, for 300 seconds, showing that the control output also gets smaller.

DARMin_DARMout.png

A slightly longer time series, ending at about the same time, but starting a few minutes earlier, showing us (1) adding a 3 count CARM offset, (2) locking the PRMI (3) transitioning CARM to sqrtinv signals, and then (4) transitioning DARM to AS55Q.

CARMtransition_DARMtransition.png

CARM and DARM in and outs, for the 500 second time chunk showing all the transitions.  Unfortunately, it looks like CARM_OUT is more noisy when it's on the sqrtinv signals, than it was on the ALS signals.  Part of this may be that we have not yet swapped the resistor in the TRY QPD, to improve the SNR in the same way that we have already done for the TRX QPD.  [EDIT, JCD:  Also, we had hard-triggered the Trans switching, so we were only looking at the QPD sum for the TRX and TRY, and the QPDs only have a few ADC counts at low transmissions, so we had poor SNR for that reason too.]

CARM_DARM_in_out.png

  9800   Fri Apr 11 12:21:27 2014 KojiUpdateLSCCARM and DARM both on IR signals!!!!!!!!!

About the ADC range,

According to the elogs, DARM = AS55Q/400. So in the current level, the error has +/-40cntpp (even if I ignore the whitening).

The arm transmission this time was 0.1-0.3. This will go up to 100~300. So we potentially increase the AS55Q optical gain by factor of 1000.

So we get +/-40000. This is already too much. If we consider the whitening, the situation is more tough.

We need to lower the whitening gain. If it is not enough, we need to lower the power on the PD.

How much was the whitening gain for AS55 this time?

Quote:

 DARM_IN1_getsSmaller.png

 

  9801   Fri Apr 11 12:32:33 2014 ericqUpdateLSCCARM and DARM both on IR signals!!!!!!!!!

Quote:

How much was the whitening gain for AS55 this time? 

 21 dB. We played with the whitening gain a little bit; at around 30dB with the signal levels at TRX = .1ish, we were consistently saturating the ADC. 

  11136   Thu Mar 12 03:47:56 2015 JenneUpdateLSCCARM and DARM loop adjustments

No wins tonight.

I've tried playing with the shapes of the loops a little bit (mostly CARM so far), to no avail.  I think I made it to CARM RF-only only one time tonight.  I was able to turn on the REFL11 whitening, although I lost lock while about halfway through the DARM transition. 

I tried making a double integrator instead of a single integrator for CARM_B, since that would allow me to make a complex zero pair which could help win back some phase. I also tried just straight copying FM1 from CARM into CARM_B, so that it could be turned off for the ALS part of the loop, but left on for the REFL part, but that didn't work very well.  Like Rana and I saw last Friday, we really need the REFL signal to have a true integrator, to force the PDH signal toward zero, before we can complete the transition.

I moved the cavity pole compensator's zero back up to 120 Hz, since that was what had worked on Saturday night.  That helped me get farther before running into gain peaking problems at ~50Hz.  This is because, as seen in my simulation earlier tonight, I win back some gain margin by having the pole compensator more closely matched with the pole frequency.

I've been turning off both FM1 and FM2 in CARM and DARM.  I think this is helping a lot, when I can get far enough to do so.  I don't want to turn off the second boost until after I'm about 50/50 on REFL.  (When  I have that much REFL, with the true integrator, the PDH signal sticks to zero).

I tried once turning off the bounce/roll filters for CARM and DARM, rather than the FM1 boost, since the bounce roll filters eat lots of phase, but I got pushed off resonance.  I think not having that focused boost may have made my overall RMS larger, which caused me to randomly jump too far outside of the good PDH range.

Early on in the evening, I turned off the MC2 violin filters in the ETM LSC-SUS filter banks, since I am actuating on only the ETMs tonight. However, I saw a violin mode ring up at ~642, which showed up in POX but not POY.  This was causing up-conversion, beating against the 40-50Hz buzzing from the IR resonance.   The MC2vio1,2 filter covers this frequency (because it's an absurdly wide notch), but the EXYvio1 filter does not.  There seems to be some confusion on the wiki as to what the ETMX violin mode frequency is - it says 631 (638??).  The notch that is in the EXYvio1 filter is for 631 Hz, but this is not correct.  DAYTIME self: Make the MC2 violin filter smaller than 40Hz(!) wide, and move the ETMX notch up to the correct frequency.  For tonight, I just turned back on the MC2 filter, and the mode has rung down.

Idea:  MICH offset, or ETM misalignment, enough to keep the power recycling low-ish, so that the CARM cavity pole doesn't come down too far in frequency?  Daytime brain should think about this.

  11133   Wed Mar 11 18:02:02 2015 JenneUpdateLSCCARM and DARM loops marginal

I have looked at the CARM and DARM RF loops, assuming the loop shapes that we've been using, and it pretty much looks like a miracle that we were ever able to make the transition.  The CARM and DARM loops are very marginal.

The ALS CARM loop was already pretty close to marginal, but we lose an extra 12 degrees of phase with the REFL loop:

  • -4 deg because REFL has analog AA, but ALS does not.
  • -6 deg because FM1 is designed to have minimal phase loss at 100Hz, but the REFL integrator is not.
  • -2 deg because the cavity pole compensator must have a zero at finite frequency.

However, if our cavity pole compensator's zero frequency is too low, we get all of that phase back, at the sacrifice of 2dB of gain margin at both ends of the phase bubble.

I looked at an Optical simulation to check what the cavity pole frequencies are expected to be, with the losses that we've measured.  In both cases, I assume the Xarm has about 150ppm of loss.  The DARM cavity pole is about 4.5kHz no matter what the Yarm loss is.  The CARM cavity pole is about 172 Hz if the Yarm has 500ppm of loss, or 120 Hz if the Yarm has 200ppm of loss.

In the plots below, I use a CARM cavity pole frequency of 150 Hz, to roughly split the difference.

Edit, 13Mar2015, JCD:  Rana points out to me that I was using from Foton the analog design strings, without including the fact that these are actually digital filters. This means that I am missing some phase lag.  Eeek.

The ALS loop includes:

  • Actuator
    • 3 16kHz computation cycles (includes computer hops)
    • Pendulum
    • Analog anti-imaging
    • Digital anti-imaging
    • 1 64kHz computation cycle
    • Violin filters: ETM 1st, 2nd, 3rd order notches
  • Plant
    • Flat, not including the cavity pole at ~17kHz
  • Sensor
    • Closed loop response of phase tracker
    • Digital anti-aliasing
    • 1 64kHz computation cycle
    • 1 16kHz computation cycle
  • Servo (CARM filter bank)
    • FM1
    • FM2
    • FM3
    • FM5
    • FM6
    • 1 16kHz computation cycle

The REFL loop includes:

  • Actuator
    • 3 16kHz computation cycles (includes computer hops)
    • Pendulum
    • Analog anti-imaging
    • Digital anti-imaging
    • 1 64kHz computation cycle
    • Violin filters: ETM 1st, 2nd, 3rd order notches
  • Plant
    • 150 Hz cavity pole
  • Sensor
    • Analog anti-aliasing
    • Digital anti-aliasing
    • 1 64kHz computation cycle
  • Servo (CARM_B filter bank and CARM filter bank)
    • Cavity pole compensator
    • Integrator (20:0)
    • FM2
    • FM3
    • FM5
    • FM6
    • 1 16kHz computation cycle

The first plot is the case of perfectly matched cavity pole and compensating zero (150Hz, with compensator having 3kHz pole):

This next version is the case where the compensating zero is a little too low, which is the case I think we have now:

The last plot is a DARM loop.  Everything is the same, except that the RF plant has a 4.5kHz pole, and no compensation:

Attachment 1: CARMloop_ALSvsREFL_fcav150_fcomp150.png
CARMloop_ALSvsREFL_fcav150_fcomp150.png
Attachment 2: CARMloop_ALSvsREFL_fcav150_fcomp80.png
CARMloop_ALSvsREFL_fcav150_fcomp80.png
Attachment 3: DARMloop_ALSvsAS55_fcav4500_nocomp.png
DARMloop_ALSvsAS55_fcav4500_nocomp.png
  9817   Wed Apr 16 02:11:40 2014 JenneUpdateLSCCARM and DARM on IR signals, boosts engaged

[Jenne, EricQ]

Tonight, we transitioned CARM and DARM to IR signals, took loop transfer functions, and determined that we could engage the LSC boosts (FM4 in the CARM and DARM servos, which are the same as the XARM and YARM servos). 

Q is preparing spectra to post, and I will dig out time series.  Look for these tomorrow, if they aren't posted tonight.

For the time series data fetching, I have taken notes on what we were doing when, so that I can actually find the data.


11:09pm:  CARM's LSC boost on for the first time

11:14pm:  DARM transferred to AS55Q

11:21pm:  DARM's LSC boost on for the first time

(lockloss)

11:53pm:  CARM transition

12:02am:  DARM transition done, both LSC boosts on

12:04am:  lockloss after reducing CARM digital offset to 0.4

12:45am: PRMI + 2 arms flashing, with no CARM or DARM offsets (arms still on ALS) because we forgot to put in the CARM offset before restoring PRM alignment.  PRMI may have been actually locked, or we may just have been flashing....need to look through the data to see what our recycling looked like.

(lockloss)

1:05am:  pretty smooth transition completed (both CARM and DARM), but we lost lock while reducing the CARM offset.

1:19am: lockloss - why?? We were just sitting at a CARM offset of about 1.3nm (1.3 counts), holding on IR signals.  We were not touching any IFO things while looking at some plots, and just lost lock.  Want to see if we can understand why.

1:27am:  another nice smooth transition for both CARM and DARM to IR signals, but almost immediate lockloss when reducing the CARM offset.


Using the new ALS lock acquisition scripts (elog 9816) and our transition scripts, getting back to PRFPMI lock is pretty smooth and procedural.

* Align arms using ASS (ifo configure screen, restore xarm and yarm, run both arms' ass scripts).

* Align PRMI, no arms (ifo configure screen, restore prmi sideband)

* Find ALS beatnotes, with arm lasers on opposite sides of the PSL.  For both, when increasing the value of the temperature slider, the beatnote should increase in frequency.  (ifo configure screen, restore CARM and DARM als)

* Run ...../scripts/ALS/Lock_ALS_CARM_and_DARM.py

* Run "Find resonance" scripts from ALS screen for each arm.

* Put in a 3 count offset to CARM loop.

* Restore PRM alignment.  (PRMI should acquire lock immediately, although PRM may need some small alignment tweaking).  Enable PRCL and MICH outputs, PRM and BS actuation outputs.

* Reduce CARM offset to 2 counts. 

* Set offsets of 1/sqrt(TRX) and 1/sqrt(TRY) filter banks in the AUXERR section of the LSC screen.  The outputs of both should equal 2 counts (to match the 2 count offset in the CARM loop). 

* Run .../scripts/PRFPMI/Transition_CARM_ALS_to_TransSqrtInv.py , making sure to reduce the CARM digital offset if needed, to keep the arm transmissions at about 0.1 counts.

* Engage FM4 of the CARM filter bank, which is the LSC boost.

* Run .../scripts/PRFPMI/Transition_DARM_ALS_to_AS55.py , making sure to reduce the CARM (or should be DARM?) digital offset if needed, to keep the arm transmissions at about 0.1 counts.

* Engage FM4 of the DARM filter bank, which is the LSC boost.


Notes for going forward:

When we have small-ish digital CARM offsets, such that both of our arm transmitted powers are about 0.1 or higher, we see clear coherence between our CARM_IN1 (the 1/sqrt(trans) signals) and a normalized REFL11_I (again using a spare filter bank like XARM to get REFL11 normalized by (TRX+TRY) ).  We have not yet tried transitioning the CARM digital error signal to this normalized REFL11.

Even though we see that the IFO is much less noisy (as measured by significantly reduced RIN in TRX and TRY as visible by eye on Dataveiwer), we are still losing lock when we reduce the CARM offset.  I have noted above several times, for when we had locklosses, so that I can see if I see anything elucidating in the time series data.

  9818   Wed Apr 16 02:29:30 2014 ericqUpdateLSCCARM and DARM on IR signals, boosts engaged

 As Jenne mentioned, we took OLTF transfer functions, and determined that we had more than enough phase margin to switch on the LSC boosts in FM4. This improved the error signal noise spectra quite a lot, and noticeably reduced the TRX/TRY fluctuations, and actuation output. 

Here's the CARM OLTF (FM4 boost on in red, boost off in black)

carmOLTF.pdf

 

Here's what happened to the CARM and DARM spectra when we turned on the boosts. (ALS only in black, initial IR signal transitions in mid-color, boosted IR signals in bright color)

boostPlot.png 

  9819   Thu Apr 17 00:49:06 2014 JenneUpdateLSCCARM and DARM on IR signals, boosts engaged

I looked at 2 of the locklosses from last night, (1:19am and 1:27am), and saw that for both, the DARM loop started to oscillate just before we lost lock.  In the trials tonight, we were more watchful of gain peaking.

Here is the 1:19am lockloss

Lockloss_DARMgainTooHigh_119am.png

And here is the 1:27am lockloss

Lockloss_DARMgainTooHigh_127am.png


 So you can see what we were doing, and what the effect was, here is a few minutes of data just before the 1:27am lockloss. The times I note below are rough, but should give you an idea of what happened at which time.

0 sec:  Arms are held on resonance with ALS.

10 sec:  CARM offset of 3nm added.

20 sec:  PRM restored, one flash, then PRMI acquires lock.

30 sec:  CARM offset reduced to 2nm, transmitted powers are about 0.1

50 sec:  Transition CARM to 1/sqrt(trans) signals.  Note that we are using the high gain Thorlabs PD here, so the noise is better than last Thursday.

60-110 sec:  CARM offset reduction to about 1nm.

110 sec:  CARM's LSC low frequency boost engaged.

120 sec:  DARM transitioned to AS55Q.

170 sec:  DARM's LSC low frequency boost engaged.

SmoothCARMandDARMtransitions_LSCboosts.png

  11116   Sat Mar 7 22:01:12 2015 JenneConfigurationLSCCARM and DARM on RF signals!!!!!!!!!!!!!!!!!!!!

[Jenne, with Matt and Fujimi as witnesses]

It might be about time to throw that champagne in the fridge.  Nice. Not quite close enough to talk about popping it open, but we'll want it chilled just in case... yeslaugh

I still haven't logged yesterday's work, and I'm still working now, so no details, but I just handed both CARM and DARM over to non-normalized RF signals, and had the arms stable at powers of about 105.  I was workinig on the ETM alignment, and the power was increasing, so I think that's where the extra power will come from. I was lowering the DARM gain as I improved the alignment, because the optical gain was increasing so much.  I probably just didn't do that fast enough for the last aligning, which is why I lost lock.

Anyhow, here's a plot, because I'm excited:

Attachment 1: ARM_POWERS_100.png
ARM_POWERS_100.png
  11117   Sun Mar 8 00:05:37 2015 KojiConfigurationLSCCARM and DARM on RF signals!!!!!!!!!!!!!!!!!!!!

Exciting! How long was it?

  11118   Sun Mar 8 01:27:01 2015 JenneConfigurationLSCCARM and DARM on RF signals!!!!!!!!!!!!!!!!!!!!

I have in my notebook that at 9:49pm CARM was no longer using ALS as an error signal, and at 9:50pm, DARM was no longer using ALS as an error signal.  It looks like I was locked for 3+ minutes after getting to RF-only signals.

The increase in power near the end of the lock stretch was me trying to improve the dark port contrast by touching the ETMX alignment.  DARM was definitely oscillating as I improved the dark port contrast, so I was trying to hand-lower the gain as I worked on the alignment.

Attachment 1: RFlock3min.png
RFlock3min.png
  15015   Wed Nov 6 17:05:45 2019 gautamUpdateLSCCARM calibration

Summary:

A coarse calibration of the CARM error point (when on ALS control) is 7.040 +/- 0.030 kHz/ct. This corresponds to approximately 0.95nm/ct. I typically lose the PRMI lock when the CARM offset is ~0.2 cts, which means I am about 1kHz away from the resonance. This is >10 CARM linewidths.

Details:

The calibration was done by sweeping the CARM offset (no PRM) and identifying the arm cavity FSRs by looking for peaks in TRX / TRY. Attachment #1 shows the scan, while Attachment #2 shows a linear fit to the FSRs. In Attachment #2, the frequency axis is taken from the phase tracker servo, which was calibrated by injecting a "known" frequency with the Marconi, and there is good agreement to the expected FSR with 37.79 m long arm cavities. There is much more info in the scan (e.g. modulation depths, mode matching to the arm cavities etc) which I will extract later, but if anyone wants the data (pre-downsampled by me to have a managable filesize), it's attached as a .zip file in Attachment #3.

Attachment 1: CARMscan.pdf
CARMscan.pdf
Attachment 2: CARMcalib.pdf
CARMcalib.pdf
Attachment 3: scan.hdf5.zip
  10933   Fri Jan 23 02:11:40 2015 JenneUpdateLSCCARM filters modified slightly

[Jenne, Diego]

One of tonight's goals was to tweak the CARM filters, so that we could engage the lowpass filter, to avoid the detuned double cavity pole resonance disturbing the CARM loop.

I increased the Q of the zeros in the FM3 boost so that it eats fewer than the original 18 degrees of phase at 100 Hz.  We kept losing lock though, so for each lock I backed off on the Q a little bit.  In the end, the filter eats 9 degrees of phase at 100 Hz.  I also moved the lowpass from 700 Hz to 1kHz, although that doesn't change the phase at 100 Hz very much.

We modified the carm_up script re: PRMI locking a little bit.  The PRMI is not so enthusiastic about locking immediately at 25% MICH fringe, so I backed that off.  It now acquires lock at a few percent, and then ramps up the offset.  Also, the MICH FM6 bounce roll filter is now turned on after lock is acquired, effectively giving it an extra second or two of delay beyond the rest of the filters.

We were able several times to get to some MICH offset and turn on the lowpass filter, but starting to reduce the CARM offset makes us lose lock.  I think the problem is that the UGF servo demod phase is changing as we are changing offsets, filters and error signals.  We see that the I-phase is servoed successfully to 0dB, but that the Q-phase is starting to move around by 30 degrees or more.  We either need to monitor this much more closely, and add the changing demod phases to the carm_up script, or we need to go back to the sum-of-squares situation that we had last week.  Note that we saw failures with that method for a completely separate reason:  we were getting too close to the limiters, which cause the UGF servos to glitch and the outputs jump by a significant amount.  So, the issues that we were seeing last week when we had the sum-of-squares were a different thing, that we noticed and understood later.

Anyhow, nothing too exciting and glorious tonight, but progress has been made.

Also, from some Mist simulations that Q did, Diego made a sweet plot that is now posted in the control room, so we can translate arm power to CARM offset, at various MICH offsets. 

We also took some CARM loop measurements with the new filters.  We have a little more phase than we used to, which is nice.  These traces don't have the lowpass engaged, since I was trying to see how far we could get without it.  We lost lock right after the second measurement, but I think that was to do with the UGF servos.

Attachment 2: CARM_22Jan2015.pdf
CARM_22Jan2015.pdf
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