40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  40m Log, Page 122 of 341  Not logged in ELOG logo
ID Date Author Type Category Subjectup
  14755   Fri Jul 12 07:37:48 2019 gautamUpdateSUSM4.9 EQ in Ridgecrest

All suspension watchdogs were tripped ~90mins ago. I restored the damping. IMC is locked.

ITMX was stuck. I set it free. But notice that the UL Sensor RMS is higher than the other 4? I thought ITMY UL was problematic, but maybe ITMX has also failed, or maybe it's coincidence? Something for IFOtest to figure out I guess. I don't think there is a cable switch between ITMX/ITMY as when I move the ITMX actuators, the ITMX sensors respond and I can also see the optic moving on the camera.

Took me a while to figure out what's going on because we don't have the seis BLRMS - i moved the usual projector striptool traces to the TV screen for better diagnostic ability.

Update 16 July 1515: Even though the RMS is computed from the slow readback channels, for diagnosis, I looked at the spectra of the fast PD monitoring channels (i.e. *_SENSOR_*) for ITMX - looks like the increased UL RMS is coming from enhanced BR-mode coupling and not of any issues with the whitening switching (which seems to work as advertised, see Attachment #3, where the LL traces are meant to be representative of LL, LR, SD and UR channels).

  13739   Mon Apr 9 08:39:39 2018 SteveUpdatePEMM5.3 eq Souther CA

Earth quake M5.3    2018-04-05 19:29:16UTC          Santa Cruz Island, CA


  13302   Fri Sep 8 07:54:04 2017 SteveUpdatePEMM8.1 eq

Nothing tripped. No obvious damage.

  11572   Fri Sep 4 04:12:05 2015 ericqUpdateComputer Scripts / ProgramsMATLAB down on all workstations

There seems to be something funny going on with MATLAB's license authentication on the control room workstations. Earlier today, I was able to start MATLAB on pianosa, but now attempting to run /cvs/cds/caltech/apps/linux64/matlab/bin/matlab -desktop results in the message: 

License checkout failed.
License Manager Error -15
MATLAB is unable to connect to the license server. 
Check that the license manager has been started, and that the MATLAB client machine can communicate
with the license server.

Troubleshoot this issue by visiting: 

Diagnostic Information:
Feature: MATLAB 
License path: /home/controls/.matlab/R2013a_licenses:/cvs/cds/caltech/apps/linux64/matlab/licenses/license.dat:/cv
Licensing error: -15,570. System Error: 115

  320   Fri Feb 15 22:16:04 2008 AndreyUpdateComputersMATLAB is not working: "Licence checkout failed"

For some unknown to me reason,

Matlab stopped working about 20 minutes ago on all computers in the control room (both UNIX control machines and Windows).

It says: "License checkout failed. License Manager Error -15. MATLAB is unable to connect to the license server."

I do not know how to revive Matlab.

At the same time, I consider that I made a significant progress in building my theoretical/computational model in the last 2 days. I was able to compute the time-evolution of accelerometer signals through stacks and pendulums using Matlab command "lsim", and I am now able to calculate RMS of spectrum of differential arm length in different frequency intervals. It seemed to me that everything is ready in my program to make the three-dimensional theoretical/computational plot (RMS as a function of Q-factors of ETMX and ITMX), but unfortunately Matlab stopped working. It seemed to me that all that was remaining was to run a loop with all possible values of Q-factors. Let's hope that Matlab will be working after the weekend.

  15207   Tue Feb 11 19:11:35 2020 shrutiUpdateComputer Scripts / ProgramsMATLAB on donatella

Tried to open MATLAB on Donatella and found the error:

MATLAB is selecting SOFTWARE OPENGL rendering.


License checkout failed.
License Manager Error -9
This error may occur when: 
-The hostid of this computer does not match the hostid in the license file. 
-A Designated Computer installation is in use by another user. 
If no other user is currently running MATLAB, you may need to activate.

Troubleshoot this issue by visiting: 

Diagnostic Information:
Feature: MATLAB 
License path: /home/controls/.matlab/R2015b_licenses/license_donatella_865865_R2015b.lic:/cvs/cds/caltech/apps/lin
Licensing error: -9,57.

So I used  my caltech credentials to get an activation key for the computer. I could not find the option for a campus license so I used the individual single machine license.

Now it can be run by going to the location:


and running


On opening MATLAB, there were a whole bunch of other errors including a low-level graphics error when we tried to plot something.

  6294   Sat Feb 18 12:23:09 2012 DenUpdateIOOMC

When I came to the 40m this afternoon, the MC was unlocked. Here is the trend of MC_F for last 2 hours



Should I just disable the auto locker or try to realign it?

  8343   Mon Mar 25 23:17:11 2013 ranaSummaryIOOMC

I measured the dark noise and regular intensity noise in MC trans tonight to get some estimate for the free running spectrum that the Chas ISS must overcome. PDF is attached.

XML file is /users/rana/dtt/MC-trans_130325.xml

The RIN normalization was done by using the mean of the SUM time series. The dark noise was measured by misaligning MC2 and making the same measurement with the bright normalization.

  9211   Sun Oct 6 23:50:14 2013 ranaConfigurationSUSMC filters adjusted
  1. Found the low pass filters OFF in a couple of the MC SUS damping loops. This allows injection of OSEM noise all the way up to ~100 Hz. I deleted unused ones and turned on the 'Cheby' for all SUS DOFs: cheby1("LowPass",2,0.1,3)cheby1("LowPass",6,1,12)gain(1.13501)
  2. Tuned the Bounce/Roll filters to catch the bounce and roll modes for all 3 MC SUS (based on the Mech Res Wiki page). These are now engaged on ALL MC SUS DOFs. They have been deleted from the ASCPIT/YAW filter banks and moved into the WFS screen into the MC1,2,3 filter banks there to be more in line with our knowledge of multi loop instability from notches in individual loops:ellip("BandStop",4,1,40,15.9,17.2)ellip("BandStop",4,1,40,23.5,24.7)gain(1.25893)
  9697   Thu Mar 6 09:47:11 2014 SteveUpdateIOOMC trend of 20 days


The IMC has not been behaving well since this morning and totally not happy when Q was finishing his measurements. The WFS servo had large offsets in pitch. Looking back at the trend and using ezcaservo to restore the suspensions did not help.

I realigned the IMC and brought TRANS SUM to ~18000 and MCREFL to < 0.5. The spot positions are not very good; nearly 2 mm off in pitch on MC1 and MC3. But after the alignment of MC, the WFS servo offsets were below +/-20.

The MC has been locked stably with WFS servo ON for the last few hours.

P.S. I did not touch the WFS pointing or reset the WFS offsets.


  10225   Thu Jul 17 01:24:35 2014 ranaUpdateIOOMC / EOM Stability Mystery Solved!

MC loop is near unstable. Common gain reduced. Needs more loop tuning.

We've often seen that the MC gets into a state where it keeps losing lock and the EOM drive shows a large RMS. We've usually been looking at the noise spectrum to diagnose this.

Tonight we finally just measured the OLG. The attached plot shows the loop gain measured with the 4395 on the MC servo board

Although the phase margin is a healthy 45 degrees, its close to instability at 1 MHz. For this plot, I reduced the gain by 3 dB and now the margin is ~7 dB. So usually its pretty close to unstable and at least its always making a noise peak.

That whole TF above a few hundred kHz is weird. We should tune out whatever makes it so flat and also remove the resonance that makes the 1 MHz peak; maybe its from some post mixer low pass?

Anyone interested in helping in the investigation ought to measure the TF of the MC demod board, the MC servo board, and the FSS box.

Silver lining: if we fix this loop shape, we might be able to have a much more stable IMC and IFO.

  5167   Wed Aug 10 11:22:55 2011 SureshUpdateIOOMC A2L alignment

[Kiwamu, Suresh]

We attempted to minimise the A2L coupling in the MC mirrors (centering the beam spot on the actuation node on each optic).  While it was easy to minimise the coupling in the pitch for all the three optics and yaw of MC2, the yaw alignment of MC1 and MC3 proved to be difficult.  For one the adjustment required was quite large, so much so that PSL alignment into the MC is often lost during this adujstment.  We had to align the PSL coupling several times in order to proceed.   And the MC settles into a new position when the MC-PSL servo loop was disturbed by random denizens in the lab.  Requiring us to start over again.

Kiwamu wrote a script to measure the MC(optic)(Pitch/yaw) -> Lockin(#1 to #6) matrix.  Inverting this matrix gave us the linear combination of the offsets to put on the MC# PIT/YAW  inorder to minimise a specific Lockin output.  However the cross couplings were not completely eliminated.  This made it very hard to predict what a given set of offsets were going to do to the Lockin outputs.

Net result:  the spots are centered in vertical direction (pitch) but not in the horizontal (yaw)

Day time tasks have started so I am quitting now.

  9205   Sun Oct 6 17:05:49 2013 ranaSummaryIOOMC ASC problems

MC unlocked over the weekend and also got severely mis-aligned. It all started around midnight on Saturday.

At first I thought that this was due to the MCS CPU meter being railed at 60 us, so I deleted a bunch of filters in MC1,2,3 that are unused and left over from Den's quantization noise investigations. This reduced the CPU load somewhat, but didn't make any real improvements. Turning on the ASC filter banks in the MC SUS still mis-aligned the MC.

With the MC WFS and MC ASS turned off, there is still some digital junk coming in and misaligning things. Plot attached.

Similar stuff coming in on ITMX, but not ITMY.

Tried restarting various FEs, but there was no effect. Also tried rebooting c1lsc, c1ioo, & c1sus. Finally did 'shutdown -r now' on all 5 computers on the CDS overview screen and simultaneously (almost) pressed the reset button on the RFM switch above the old c1pem crate. Everything came back OK except for c1oaf (I had to manually button his BURT button) and now the ASC inputs on all the SUS are zero when they should be and MC is well locked and aligned.

Rob and I used to do this trick when he thought that a cosmic ray had corrupted a bit in the RFM network.

  7289   Mon Aug 27 18:59:24 2012 jamieUpdateIOOMC ASC screen was confusing - Jenne is not stupid


We have figured out that some of these measurements, those with the WFS off, were also not allowing the dither lines through, so no dither, so no actual measurement.

Jamie is fixing up the model so we can force the WFS to stay off, but allow the dither lines to go through.  He'll elog things later.

In the c1ioo model there were filter modules at the output of the WFS output matrix, right before going to the MC SUS ASCs but right after the dither line inputs, that were not exposed in the C1IOO_WFS_OVERVIEW screen (bad!).  I switched the order of these modules and the dither sums, so these output filters are now before the dither inputs.  This will allow us to turn off all the WFS feedback while still allowing the dither lines.

I updated the medm screens as well (see attached images).

  357   Tue Mar 4 20:14:02 2008 ranaConfigurationIOOMC Alignment
The MC alignment was pretty far off. We were getting TEM01 mode locks only.
Rather than inspect what happened I just aligned the MC suspensions to get
the transmission higher. Now Matt should be able to lock the X arm and collect
adaptive filter data.
  1166   Tue Dec 2 17:56:56 2008 Alberto, RanaConfigurationPSLMC Alignment
In the attempt to maximize the Mode Cleaner transmission and minimize the reflection from the steering mirrors of the MC periscope, we could not get more ~2 V at the MC Trans PD and ~ 0.5 V at MC REFL_DC. As it turned out from the SUS Drift Monitor, the reason was that the MC optics had been somehow displaced from the optimal position.

After restoring the reference position values for the mirrors and tweaking again the periscope, we got ~3V at the MC TransPD and 0.5V at the reflection.
The beam was then probably clipped at the REFL PD so that we had to adjust the alignment of one of the BS in the transmitted beam path on the AS table.
We also zeroed the WFS PDs, but not before reducing the power from the MZ, for their QPDs not to saturate.

After relocking, the transmission was 3V and the reflection ~0.3V.

The beam isnow centered on the Trans PD and REFL PD and the Mode Cleaner locked. More details on the procedure will follow.
  1169   Wed Dec 3 11:58:10 2008 AlbertoUpdatePSLMC Alignment
Rana, Alberto,

more details on the MC alignment we did yesterday.

Last week Rana re-aligned the Mach Zender (MZ) on the PSL table to reduce the power at the dark port (see elog entry #1151). After that, the beam was aligned to the MZ but not properly aligned to the Mode Cleaner (MC) anymore. As a result the MC could not lock or did it on unwanted transverse modes. To fix that we decided to change the alignment of the MC input periscope on the PSL table.

The ultimate goal of the operation was to align the MC transmitted beam to the IFO and to maximize the power.
Such a condition depends on:
a) a good cavity alignment and
b) input beam matching to the cavity TEM00 mode.

Since the MZ alignment had only affected the input beam, we assumed the cavity alignment was still good, or at least it had not changed, and we focused on the input beam.

The IOO computer, by the MC autolocker script, is able to change the cavity alignment and the length to match the input beam and lock the cavity. Although both the length servo (LSC) and the alignment servo (WFS) have a limited effective operating range. So for the script to work properly and at best, input beam and cavity matching have to be not far from that range.

The MC periscope has two mirrors which control the pitch and yaw input angles. By changing either yaw or pitch of both mirrors together (“two-knob" technique) one can change the input angle without moving the injection point on the cavity input mirror (MC1). So this is the procedure that we followed:

  • 1) turned of the autolocker running the MC-down script
    2) brought the reflected beam spot back on the MC-reflection camera and on the reflection photodiode (REFL-PD)
    3) turned on the LSC servo
    4) tweaked the periscope's mirrors until the cavity got locked on a TEM00 mode
    5) tweaked the periscope aiming at ~0.3V from the REFL-PD and ~3V on the transmission photodiode (TRANS-PD).

Following the steps above we got ~0.5 V on the REFL-PD and ~2V on the TRANS-PD but no better than that.

Looking at the Drift Monitor MEDM screen, we found that the cavity was not in the reference optimal position, as we initially assumed, thus limiting the matching of the beam to the MC.

We restored the optics reference position and repeated the alignment procedure as above. This time we got ~3V on the TRANS-PD and ~0.5 on the REFL-PD. We thought that the reason for still such a relatively high reflection was that the beam was not well centered on the REFL-PD (high order modes pick-up?).

On the AS table we centered the REFL-PD by aligning a beam splitter in the optical path followed by the light to reach the photodiode.

We also centered the beam on the reflection Wave Front Sensors (WFS). To do that we halved the power on the MZ to reduce the sidebands power and prevent the WFS QPD from saturating. We then aligned the beam splitters on the QPD by balancing the power among the quadrants. Finally we restored the power on the MZ.

As a last thing, we also centered the transmitted beam on the TRANS-QPD.

The MC is now aligned and happily locked with 3V at the TRANS-PD and 0.3V at REFL-PD.
  1774   Wed Jul 22 10:49:40 2009 AlbertoUpdatePSLMC Alignment Trend

Trying to track the MC positions back for a few days, it seems that the data hasn't been recorded properly for a while. Something happened yesterday after my boot fest and then the record got restored. Attached here are the readbacks showing the event for MC1.

Is anything wrong with the data record?

  12691   Thu Dec 29 21:48:32 2016 ranaUpdateIOOMC AutoLocker hung because c1iool0 asleep again

MC unlocked, Autolocker waiting for c1iool0 EPICS channels to respond. c1iool0 was responding to ping, but not to telnet. Keyed the crate and its coming back now.

There's many mentions of c1iool0 in the recent past, so it seems like its demise must be imminent. Good thing we have an Acromag team on top of things!

Also, the beam on WFS2 is too high and the autolocker is tickling the Input switch on the servo board too much: this is redundant / conflicting with the MC2 tickler.

  12818   Fri Feb 10 13:04:32 2017 ranaUpdateIOOMC AutoLocker hung because c1iool0 asleep again

c1iool0 was down again. Rather than key the crate, this time I just pushed the reset button on the front and it came back.

As move towards the wonderfulness of AcroMag, we also have to buy a computer  to handle all of these IOCs. Let's install the new c1iool0 over by the SUS computer.

  3345   Sun Aug 1 21:04:45 2010 ranaSummaryComputer Scripts / ProgramsMC Autolocker fixed

Someone had left a typo in the MC autolocker script recently while trying to set the lock threshold to 0.09. As a result, the autlocker wouldn't run.

I repaired it, made a few readability improvements, and checked in the new version to the SVN. If you make script changes, check them in. If you think its too minor of a change for a SVN checkin, don't do it at all.

  11773   Tue Nov 17 15:49:23 2015 KojiConfigurationIOOMC Autolocker modified

/opt/rtcds/caltech/c1/scripts/MC/AutoLockMC.csh  was modified last night.

1. Autolocker sometimes forget to turn off the MC2Tickle. I added the following lines to make sure to turn it off.

    echo autolockMCmain: MC locked, nothing for me to do >> ${lfnam}
    echo just in case turn off MC2 tickle >> ${lfnam}

2. During the lock acquisition, Autolocker frequently stuck on a weak mode. So the following lines were added
so that the Autolocker toggles the servo switch while waiting for the lock.

    echo autolockMCmain: Mon=$mclockstatus, Waiting for MC to lock .. >> ${lfnam}
    # Turn off MC Servo Input button
    ezcawrite C1:IOO-MC_SW1 1
    date >> ${lfnam}
    sleep 0.5;
    # Turn on MC Servo Input button
    ezcawrite C1:IOO-MC_SW1 0
    sleep 0.5;

  10116   Tue Jul 1 13:57:33 2014 ericqUpdateComputer Scripts / ProgramsMC Autolocker on Megatron

 Just a quick update on the status of the auto locker:

The auto locker now runs and respawns automatically on megatron, through ubuntu's "upstart" init system, instead of cron. 

  • The autolocker script itself is:/opt/rtcds/caltech/c1/scripts/MC/AutoLockMC.csh
  • The startup script called by the upstart system is: /opt/rtcds/caltech/c1/scripts/MC/AutoLockMC.init
  • The upstart configuration is: /etc/init/MCautolocker.conf
  • The auto locker is started by executing this command on megatron: sudo initctl start MCautolocker

This was pretty simple to set up, once I figured out how to provide the necessary environment variables in AutoLockMC.init 

  7264   Thu Aug 23 22:41:04 2012 KojiUpdateIOOMC Autolocker update

[Koji Rana]

MC Autolocker was updated. (i.e. mcup and mcdown were updated)


  • Turn on the MCL input and output switches
  • Change the MCL gain from 0 to -300 with nominal ramp time of 5sec
  • Turn on FM2, FM5, MF7 after a sleep of 5sec. Note: FM1 FM8 FM9 are always on.
  • Set the offset of 42 counts
  • Turn on the offset

# Turn on MCL servo loop
echo mcup: Turning on MCL servo loop...
ezcawrite C1:SUS-MC2_MCL_GAIN -300
sleep 5
ezcaswitch C1:SUS-MC2_MCL FM2 FM5 FM7 ON
# Offset to take off the ADC offset of MC_F
ezcawrite C1:SUS-MC2_MCL_OFFSET 42
ezcaswitch C1:SUS-MC2_MCL OFFSET ON

This offset of 42 count is applied in order to compensate the ADC offset of MC_F channel.
The MCL servo squishes the MC_F signal. i.e. The DC component of MC_F goes to zero.
However, if the ADC of MC_F has an offset, the actual analog MC_F signal, which is fed to FSS BOX,
still keep some offset. This analog offset causes deviation from the operating point of the FSS (i.e. 5V).


  • Basically the revese process of mcup.
  • This script keeps FM1 FM8 FM9 turned on.

# Turn off MCL servo loop
echo mcdown: Turning off MCL servo loop...
ezcawrite C1:SUS-MC2_MCL_GAIN 0
# Remove Offset to take off the ADC offset of MC_F
ezcawrite C1:SUS-MC2_MCL_OFFSET 0

  10940   Mon Jan 26 17:43:52 2015 ericqConfigurationIOOMC Autolocker update

The MC autolocker hasn't been so snappy recently, and has been especially fussy today. Previously, the mcup script was triggered immediately once the transmission was above a certain threshold. However, this could waste time if it was just an errant flash. Hence, I've added a 0.5 second delay and a second threshold check before mcup is triggered. 

After breaking the lock 5ish times, it does seem to come back quicker.

  10039   Sat Jun 14 18:43:15 2014 ranaUpdateIOOMC Autolocker upgrades

 Somehow the caget/caput commands are really slow. I'm not sure if this is new behavior or not, but after changing values, it takes ~1-2 seconds to move on to the next command.

On op340m, once I ran autolockMCmain40m in the foreground, I could see that there were a lot of error messages that weren't being caught in the log file. On Solaris, the TDS and EZCA binaries work well, but the caget/pu stuff is missing a lot of the new flags and the new CDSUTILS python scripts are not there. So I decided to stop running on there and move over to running the MC autolocker on megatron. I also changes the mcup and mcdown scripts to BASH from CSH. There are still some PERL commands in there from Rob/Matt/Sam, so I also added the proper commands so that the pick up the scripts/general/perlmodules/ directory.

Yes, yes, I know. You would all feel warm in your tummy if we did everything in python because its the best language ever, but how about we lock the interferometer first and then we can rewrite all the last decades worth of scripts?

Looked at the trend from the last time the MCWFS were one (2 weeks ago!) and aligned the MC suspension back to that point. After that the WFS come on fine and MC looks good. I fixed the nameserver/DNS/fstab stuff on megatron, asia, and belladonna.

I've left AutoLockMC.csh (too painful to convert to BASH) running on megatron via an open terminal on pianosa. If it looks OK for the weekend, Q should move the crontab line from op340m over to megatron and then update the Wiki appropriately.

CDSUTILS is also gone from the path on all the workstations, so we need Jamie to tell us by ELOG how to set it up, or else we have to use ezcaread / ezcawrite forever.

  577   Thu Jun 26 18:29:44 2008 JenneUpdate MC Back online
Jenne, Rob, Yoichi

I was playing with the Mode Cleaner earlier today, working on measuring the effect of the new filter (see next post for loop gain measurements etc.), and bumped something which made it so the Mode Cleaner would not lock.

After much poking around by Rob and Yoichi, we found that the TNC-to-2 pin LEMO from Out1 of the MC Servo Board to Ch1 of the Pentek Generic board to the right of the MC Servo Board was bad. If we touched the cable, the MC would lock, but as soon as we let go, the MC would fall out of lock. The LEMO end of the cable was not heat shrink wrapped, so the 2 wires could have been touching. I replaced the cable, and the MC locked immediately after plugging it in, so I think that has fixed the problem.
  496   Sun May 25 19:33:16 2008 ranaUpdateIOOMC Bad after Re-alignment
The MC pointing was off and the transmitted power was down after John and Andrey brought it back after the bootfest.

I tried getting it back on Friday but was unsuccessful. Today, after the Phoenix Landing, I got it back to someplace
reasonable, but it still seems to be far off. I will check with Rob before we recenter and of the QPDs.

I had to move all of the MC SUS and also align the beam using the IOO periscope. The attached PDF shows some trends
over the last 80 days. You can see that the drop in MC TRANS is about the same as the drop in PMC TRANS.
  1345   Mon Mar 2 16:27:40 2009 AlbertoConfigurationElectronicsMC Drum Mode SR560 Preamplifier Replaced

Today I checked out the SR560 around the lab. I confirmed that the one with the label "channel A noisy" is effectively mulfuctioning.

It was coonected to the lock-in amplifier set up for the drum mode peak readout.

I repleaced that with a working one.

  1814   Thu Jul 30 21:26:16 2009 ranaUpdateIOOMC Drumhead mode
I used COMSOL 3.5a to do a FEA of one of the MC flat mirrors. Should be close to the same for all the mirrors.

The model is very simple- it includes just the cylindrical shape (no magnets, curvature, or coating or bevels).
This is good enough, since we don't really know all of the material properties at the 1% level.

The attached plot shows the MC drumhead mode. The color scale shows the displacement along the optic axis.
The model predicts 28.855 kHz and the measured value was 28.2 kHz.

I used COMSOL in the multiphysics mode which includes the Structural Mechanics and Heat Transfer modules at the
same time. For the material I used the built in properties of Corning 7940 (fused silica). In reality we have
7980 (I don't know all of the material differences). In any case, this model includes the temperature dependence
of the Young's modulus, so it should be possible to use this to predict the absorption numbers.

The model file (mc2.mph) has been added to our COMSOL SVN directory.
  1322   Wed Feb 18 21:10:21 2009 ranaUpdateIOOMC Drumhead mode lost again
In early December, Caryn and I noticed that the MC Drumhead mode was visible at the Qmon point of
the MC demod board using a spectrum analyzer and no external excitation of the MC mirrors. We then
started tracking the MC Drumhead modes.

Today I found that it is gone again. It also wasn't there when I looked for it in 2007. Mad

I looked at the MC error point spectrum and it seemed reasonable. Changing the gains in the MZ, ISS, PMC, & FSS
had no good effect on the noise spectrum.

The voltage noise above 10 kHz in the MC error point is increasing like ~f. I think that this means that
the leftover is the noise from the FSS. Below 10 kHz it is the noise of the VCO (10 mHz/rHz).

One possibility is that the high frequency noise changes with the mood of the NPRO. There should be no
frequency noise induced by the decay of the PA diode power. We can do an NPRO SLOW scan to see if there
is some kind of mode hop noise happening.
  10826   Sun Dec 21 18:46:06 2014 diegoUpdateIOOMC Error Spectra

The error spectra I took so far are not that informative, I'm afraid. The first three posted here refer to Wed 17 in the afternoon, where things were quiet, the LSC control was off and the MC was reliably locked. The last two plots refer to Wed night, while Q and I were doing some locking work; in particular, these were taken just after one of the locklosses described in elog 10814. Sadly, they aren't much different from the "quiet" ones.

I can add some considerations though: Q and I saw some weird effects during that night, using a live reading of such spectra, which couldn't be saved though; such effects were quite fast both in appearance and disapperance, therefore difficult to save using the snapshot measurement, which is the only one that can save the data as of now; moreover, these effects were certainly seen during the locklosses, but sometimes also in normal circumstances. What we saw was a broad peak in the range 5e4-1e5 Hz with peak value ~1e-5 V/rtHz, just after the main peak shown in the attached spectra.

  10828   Mon Dec 22 15:11:08 2014 ranaUpdateIOOMC Error Spectra

che tristezza  

What we want is to have the high and low noise spectra on the same plot. The high noise one should be triggered by a high PC DRIVE signal.

  15573   Tue Sep 15 17:19:09 2020 gautamUpdateIOOMC F spectrum

There was an abrupt change in the MC_F spectrum between August 4 and August 5, judging by the summary pages - the 1 and 3 Hz resonances are no longer visible in the spectrum. Possibly, this indicates some electronics failure on the MC servo board / whitening board, the CDS settings don't seem to have changed. There is no record of any activity in the elog around those dates that would explain such a change. I'll poke around at 1X2 to see if anything looks different.

Update 1740: I found that the MCL / MCF cables were disconnected. So since August 5, these channels were NOT recording any physical quantity. Because their inputs weren't terminated, I guess this isn't a clean measurement of the whitening + AA noise, but particularly for MC_F, I guess we could use more whitening (see Attachment #1). Probably also means that the wandering ~10-30Hz line in the spectrogram is a electronics feature. The connections have now been restored and things look nominal again.

  15574   Tue Sep 15 19:17:30 2020 ranaUpdateIOOMC F spectrum

that's a very curious disconnection

the "Pentek" whitening board that carries the MC channels has jumpers to enable either 1 or 2 stages of 15:150 whitening. Looks lik MC_F has 2 and MC_L has 1.

I guess the MC_F signal is so low because of the high gain on the FSS board.  We could lower the FSS common gain and increase the IMC board's VCO gain to make up for this. Maybe 6 dB would be enough. IF that is risky, we could also up the analog gain on the whitening board.

  15576   Wed Sep 16 09:43:41 2020 gautamUpdateIOOMC F spectrum

This elog suggests that there is uniformly 1 stage engaged across all channels. I didn't look at the board to see what the jumper situation is, but only 1 stage of whitening is compensated digitally for both _F and _L. The Pomona box attached to the NPRO PZT input is also compensated digitally to convert counts to frequency.

I tried the gain re-allocation between VCO gain and FSS COMM (and also compensated for the cts to Hz conversion in MCF), but it doesn't seem to have the desired effect on the MCF SNR in the 5-50Hz band. Since the IMC stays locked, and I had already made the changes to mcup, I'll keep these gains for now. We can revert to the old settings if the IMC locking duty cycle is affected. Explicitly, the changes made were:

VCO gain: +7dB ---> +13 dB

FSS COMM: +6 ddB ---> +0 dB

The mcdown script wasn't modified, so the lock acquisition gains are the same as they've been. 


the "Pentek" whitening board that carries the MC channels has jumpers to enable either 1 or 2 stages of 15:150 whitening. Looks lik MC_F has 2 and MC_L has 1.

  10931   Thu Jan 22 18:36:11 2015 diegoUpdateIOOMC Flashes

I've been looking into the data of Jan 06 and Jan 15 taken during daytime, as the night before we left the PRC aligned in order to allow the IFO to flash; the purpose is to find out if some flashes from the IFO could propagate back to the IMC and cause it to lose lock; I will show here a sample plot, all of the others are in the archive attached.

My impression is that these locklosses of the IMC are not caused by these flashes: the signals MC_[F/L] seem quite stable until the lock loss, and I don't see any correlation with what happens to REFLDC that could cause the lockloss (apart from its drop as a consequence of the lockloss itself); in addition, in most occasions I noticed that the FSS started to go crazy just before the lock loss, and that suggests me that the lockloss source is internal to the IMC.

I can't see anything strange happen to MC_TRANS either as long as the IMC is locked, no fluctuations or weird behaviour. I also plotted the MC_REFL_SUM channel. but it is too slow to be useful for this kind of "hunt".

  12857   Tue Feb 28 21:05:44 2017 ranaSummaryIOOMC Length offset changes MCWFS offsets

The input offset on the MC length servo board changes the lock point of the length loop (by how much? need to calibrate this slider into meters & Hz).

The SUM signal on the MC WFS is ~few 1000. This is several times larger than the pit/yaw signals. This is bad. it means that the TEM00 mode on the WFS (or what the WFS interperets as a TEM00) is larger than the TEM01/10 that its supposed to measure.

So if the beam moves on the WFS head it will convert this large common mode signal into a differential one.

We moved the MC Servo offset around from -3 to +3 V today and saw that it does affect the transmitted light level, but we need to think more to see how to put the offset at the real center of the resonance. This is complicated by the fact that the MCWFS loops seem to have some several minutes time constant so things are essentially always drifting.

  1. Characterize and juice up the WFS loops.
  2. Figure out how to set the MC length loop offset. Is this bad offset changing the zero point of the MC WFS loops?
  3. If so, it may be a source of excess jitter noise in the interferometer.

I changed the McREFL SMOO to make it easier to use this noisy channel to diagnose small alignment changes:


  2236   Wed Nov 11 12:29:44 2009 AlbertoFrogsPSLMC Locked on the wrong mode?

This morning, after Steve pointed out that the readout RFAMPD_DC was zero, I thought of realigning the beam on the photodiode. Maybe I touched the lens or the beam splitter that send the beam on the diode when I installed an other beam splitter to make the measurement of the calibration between two ThorLabs PDA255 photodiodes.

After aligning the beam on the RFAMPD, the voltage of the DC readout was lower than it used to be (C1:IOO-RFAMPD_DC ~ 0.4 now vs. 4 as it was on November 4th).

I maximized the DC readout but the problem seems to be that the beam spot is not a round TEM00. In particular the spot looks like that of a TEM10 mode.

Since we're looking at the MC transmitted beam, is it possible that the MC is locked on the wrong mode?

Check out the attached picture.

  4620   Tue May 3 18:46:06 2011 ranaUpdateIOOMC Locking not working

I found that the MC autolocker was OFF. Kiwamu says he turned it off because its slow. Suresh says that he has some feelings that maybe something is wrong. I'll let them describe what they know about the MC in an elog.

I checked the trend of the MC and PMC transmissions for the past 30 days:


Looks like the alignment has been drifitng. PMC was corrected recently by Koji, but the alignment of the input beam to the MC or the MC itself has to be fixed. Has someone been twiddling the MC SUS alignment biases??

  4621   Wed May 4 11:48:01 2011 SureshUpdateIOOMC Locking not working

[Valera, Suresh]

The first time I noticed that the MC was not locking was after I had finished switching the RF source installation.  Before this change the RF modulation frequency (for MC) was 29.485 MHz as read from the Marconi RF Source.  We replaced this with a Wenzel crystal source at 29.491 MHz.  This may have changed the loop gain. 

Today, I changed the MC alignment to optimise the MC lock.  Valera pointed out that this is not a desirable solution since it would shift the beam pointing for all components downstream.  However, since we are not sure what was the last stable configuration, we decided to stay with the current settings for now and see the trends of several parameters which would tell us if something is drifting and causing the autolocker to fail.

The MC Auto locker is now working okay.  However to obtain lock initially we reduced the loop gain by decreasing the VCO gain.  We then increased the gain after the autolocker had locked the MC.




  3049   Fri Jun 4 11:32:51 2010 Alberto, kiwamuUpdateIOOMC MMT1 Mirror Tests
[Alberto, Kiwamu]
Last Wednesday, we measured the beam profile after the MC mode matching telescope n.1 (MMT1). We found that the reflected beam had an irregular profile when observed with the beam scan. Fringes also appeared on an IR card.
We thought that such effect could be due to interference of the main reflected beam with the beam reflected by the back surface of the mirror.
To test the hypothesis we checked the transmitted and the reflected beams of a spare optic identical to MMT1. (This was the same optic that got dropped during the cleaning/baking process.)
We tested it on the PSL table, using a 200mW beam coming from the new 2W Innolight  laser. To maximize the separation between the two beams, we tested MMT1 at 45 degrees. The setup we used is shown here:
We looked at the beam reflected by MMT1 about 5 meters from the mirror. At that distance the beam spot had a size of about 1-2cm. it didn't look perfectly round, but it showed no fringes, as it had happened with original MMT1 inside the MC chamber.
At the transmission, the second ghost beam due to the back surface reflection (see picture above) was very week. In order to be able to see it on an IR card, we had to increase the laser pumping current from 1A to about 1.5A.
We are now thinking of a way to measure the relative power between the two. The problem is that they run very close to each other and it's not easy to resolve them with a power meter or a photodiode.
  1997   Thu Sep 24 15:45:27 2009 robUpdateIOOMC OLG

I measured the mode cleaner open loop gain with the HP3563A

The UGF is 64kHz, phase margin is 28 deg.

  2144   Mon Oct 26 18:15:57 2009 robUpdateIOOMC OLG

I measured the mode cleaner open loop gain.  It's around 60kHz with 29 degs of phase margin.

  4582   Thu Apr 28 15:31:36 2011 kiwamuUpdateIOOMC PDH lock : readjustment of demodulation phase

Since Suresh has installed the RF source box and changed the cable configuration somewhat,

the demodulation phase for the MC locking became off by about 10 degree.

I changed the length of some cables and obtained a good demodulation phase by the same technique as Suresh and Koji did before (see here for detail).

I maximized the Q signal. The lock of the MC looks healthy.


Quote from #4578

RF Source box has been mounted in the 1X2 rack. 

  1162   Tue Nov 25 18:38:03 2008 Alberto, RobUpdatePSLMC Periscope Alignment
This morning when I came in I found the MC cleaner unlocked and the autolocker script could not lock it. The reflected beam was quite off and showed in the bottom left corner of the IMCR camera. After turning off the WFS locking, I started slightly changing the alignment of the steering mirrors on the MC periscope, waiting for the LSC servo to lock the cavity. It didn't work. At some point I lost the beam from the IMCR camera and that is how someone might have found it when I left it for about one hour.

When I came back and tried again adjusting the steering mirrors, I noticed that the autolocker was working and was trying to lock the cavity. After just a bit of adjustment, the MC got easily locked.

After that, I spent a couple of hours trying to improve the alignment of the periscope to minimize the reflection and maximize the transmission. I started with a transmission of 0.4 V but, despite all the tweaking (I used the technique of turning both yaw knobs at the same time), I couldn't get more than 1.2 V (and 2.4 V at the reflection) if only the LSC servo was on. Looking at the camera, I moved the beam around to look for a more favorable spot but the MC wouldn't lock with the beam in other places. Maybe I could do better or maybe not because the cavity is not aligned. I'm going to try again tomorrow.
  8138   Fri Feb 22 17:33:25 2013 ManasaUpdateElectronicsMC REFL PD back from the dead


 [Yuta, Manasa]

We replaced the dead photodiode on MC REFL PD with a new one (GAP 2000). We measured the frequency response of the PD and tuned the resonant frequency using inductor L5 (in the circuit diagram) to be 29.575MHz - over an average of 10 measurements.

Riju is measuring the characteristics of the PD and will be posting an elog in detail.

  11237   Wed Apr 22 17:04:11 2015 ranaUpdateElectronicsMC REFL PD back from the dead

Just randomly found this old entry from 3 years ago. We should never have installed a GAP 2000 - they are an inferior type of InGaAs diode. We should add to our list replacing these with a 2 mm EG&G diode.

How many 2 mm EG&G InGaAs diodes do we have Steve? Can you please find a good clean diode case so that we can store them in the optics cabinet on the south arm?


 [Yuta, Manasa]

We replaced the dead photodiode on MC REFL PD with a new one (GAP 2000). We measured the frequency response of the PD and tuned the resonant frequency using inductor L5 (in the circuit diagram) to be 29.575MHz - over an average of 10 measurements.


  877   Mon Aug 25 11:43:55 2008 YoichiFrogsIOOMC REFL PD cable had been disconnected through out the weekend
Most of my morning was wasted by the MC REFL PD cable, which was disconnected on the generic LSC PD interface board.
I know who did this. *ME*. When I pulled out the MC board, which is sitting next to the PD interface, on Friday, I must have
disconnected the PD cable accidentally. The connector of the PD cable (D-Sub) does not have screws to tighten and easily comes off.
I wrote this entry to warn other people of this potential problem.
  8137   Fri Feb 22 13:03:49 2013 ManasaUpdate MC REFL PD murder


[Yuta, Manasa]

We turned IFO power back to 1.25W by removing the attenuator and forgot that the Y1 mirror before the REFL PD must be replaced with BS 10% before getting to full power. The PD is dead  and now we are in the process of fixing it. Forgive us for all our sins!

On the other note, we have changed the mech shutter mode from N.O back to N.C. So the shutter now works as usual from the medm screen.


ELOG V3.1.3-