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ID Date Author Type Categoryup Subject
  8992   Fri Aug 9 22:51:37 2013 KojiUpdateLSCPRMI(sb) lock recovered

PRMI(sb) lock was recovered

PRMI lock

- Stared at the time series data of the REFL demod signals, and decided to use REFL165I&Q for the locking.

- Jiggled the demodulation phase of REFL165 and POP110. Changed the servo gains.

- Finally found a short lock. Further optimized the parameters.

- PRM ASC was turned on by giving the identity matrices for the input and output matrices.
  Now just hitting the up button is sufficient to engage the ASC servo.

- Under the presence of the ASC, the PRMI is indefinitely locked as before.

- Reacquisition is also instantaneous. (It acquires even if the ASC is left "on".)

- Actually the lock is somewhat robust even when the PRM ASC is not used.
  This is VERY GOOD as we can skip one of the steps necessary for the full lock.

  Although, the seismic on Friday night is very quiet.
  The spot motion at POP seems to be somewhat pitch/yaw mixed, in stead of previous "totally-dominated-by-yaw" situation.

- We are ready to implement ASS for PRM

Demod phase adjustment

- Shook PRM at 580Hz / 100cnt

- Swept the demod phase of REFL165 such that the PRM peak is minimized in the Q signal

- Open DTT. Measured transfer functions between REFL165I and the Q signals of each PD.

- Minimized the PRCL signal coupling in the signals.

- The resolution of the adjustment was ~1deg.

Locking test with PRM/BS

Tried the lock acquisition only with PRM and BS. (cf. http://nodus.ligo.caltech.edu:8080/40m/8816)

This just worked nicely.

Today's locking parameters:

PRMI(sb) lock:

MC Trans: 17500
POP110I (in lock): 150

PRCL Source: REFL165(I) 106deg / 45dB / Normalization SQRT(10 POP110I) / Input MTRX 1.0
PRCL Trigger: POP110I x 1.0 50up 25down
PRCL Servo: G=+3.5 Acq: FM4/FM5 Opr: FM2/FM3/FM6/FM7
PRCL Actuator: PRM +1.0

MICH Source: REFL165(Q) 106deg / 45dB / Normalization SQRT(0.1 POP110I) / Input MTRX 1.0
MICH Trigger: POP110I x 1.0 50up 25down
MICH Servo: G=-10 Acq: FM4/FM5 Opr: FM2/FM3/FM6
MICH Actuator: (ITMX -1.0 / ITMY +1.0) or (BS 0.5 / PRM -0.267)

Demod phases:

AS55 -17deg
REFL11 135deg
REFL33 -18deg
REFL55 120deg
REFL165 106deg

  8994   Mon Aug 12 10:44:22 2013 ranaUpdateLSCPRMI(sb) lock recovered

  In the past, we used to use Stefan's 'ezcademod' or Matt's 'ezlockin' to do auto phase adjustment.

JoeB / Jamie are working on python replacements for these tools, but in the near term possibly I can make a bash script to use ezcaservo and the existing LOCKINs to do this.

  9036   Mon Aug 19 23:08:31 2013 JenneUpdateLSCDRMI sensing signals

Here are a bunch of sensing signals.  The configuration is always DRMI.  Except for the optic noted in the title and the x-axis of any individual plot, other optics are held in their nominal position.  DRMI condition is sidebands resonant in PRCL, 55MHz sideband resonant in SRCL.  Each plot has an error signal, as well as the 2f signals at POP and AS.

 The phases of POP22 and POP110 have been adjusted so that the I signal is maximized when everything is at the nominal positions (sideband resonant for PRMI).  The phase of AS110 has been adjusted so that the I signal is maximized when the DRMI is in the nominal position (f2 resonant in SRC).  The phases of the 1f1, 1f2, 2f1 and 2f2 REFL signals were all adjusted to have max PRCL signal in the I phase.  AS55 was adjusted to have max SRCL signal in the Q phase.













  9037   Tue Aug 20 00:19:23 2013 ranaUpdateLSCPRMI / DRMI investigations

While Jenne was plotting, I locked and aligned the MICH with AS55_Q. Then I aligned the PRM and locked PRMI using REFL55_I/Q with triggering on POP22, but no power normalization.

I used this to set the phase for REFL11 and REFL55 (driving PRM at 111.3 Hz and minimizing the Q response using the DTT Sine Response tool). I flipped the sign on REFL11 by 

The REFL11 gain is ~50x larger than REFL55; this is with the 15 dB whitening gain on REFL55 and none for REFL11. What's going on here? The attached PDF shows the two time series with the free swinging PRMI and both phases set to ~ +/- 2 deg. The REFL55 signals have been scaled up by 50x.

So then we went in and looked at the RF signals at the demod boards. To do this we disconnected the RFPD test cables and hooked the RF Mon outputs into the 50 Ohm inputs on a scope. The following PNG images show the scope traces. The REFL11 (yellow) traces are too big!! See how small the REFL55 (green) are. REFL11 is saturating - need to fix.



Attachment 1: REFL.pdf
Attachment 6: REFL-2.pdf
  9038   Tue Aug 20 01:28:47 2013 JenneUpdateLSCREFL investigations

According to the wiki, REFL 11 has a transimpedance of 4.08kV/A, and REFL 55 has a transimpedance of 615V/A.  This is a ratio of ~6.5 .  My optickle simulations from earlier this evening indicate that, at maximum, there is a ~factor of 2 more signal in REFL 11 than REFL 55.  This is a factor of order 10-15.  Then, REFL 55 has 15dB whitening gain, which is a factor of ~4.  So, this explains why we're seeing so much more digital signal on REFL11 than REFL55.

Tomorrow, I need to replace the 50/50 beam splitter that splits the beam between REFL55 and REFL11 (33 and 165 have already had their light picked off at this point).  I want to put in a 10% reflector, 90% transmission beamsplitter.  Steve, can you please find me one of these, and if we don't have one, order one? This will give us a little more light on 55, and less light on 11, so hopefully we won't be saturating things anymore.


  9040   Tue Aug 20 11:41:30 2013 KojiUpdateLSCREFL investigations

As I always tell everyone: Don't use a 10% reflector which produce ghost beams. Use a 90% reflector.

  9041   Tue Aug 20 11:52:20 2013 JenneUpdateLSCREFL investigations


As I always tell everyone: Don't use a 10% reflector which produce ghost beams. Use a 90% reflector. 

 Hmmm, yes, I forgot (bad me).  I'll find a 90% refl BS, and swap the positions of REFL11 and REFL55.

  9043   Tue Aug 20 18:42:57 2013 JenneUpdateLSCREFL investigations

I have done the swap in the REFL path.  First, I swapped the positions of REFL11 and REFL55.  Then, I swapped out the 50/50 BS for a 90% reflection BS.  (90% goes to REFL55, 10% goes to REFL11).  I also changed the aluminum dump that was dumping the old REFL165 path into a razor dump.

Before: REFL11 had 4.0mW, REFL55 had 3.1mW.  Now, REFL11 has 0.53mW, and REFL55 has 6.9mW.  REFL165 still has around 61mW of light, and REFL33 has 3.3mW (the things that were changed were after 165 and 33 in the REFL path). 

Now, the DC value of the REFL PDs are:  REFL165 = 10.4V, REFL33 = 110mV, REFL55 = 232mV, REFL11 = 18.6mV. 

As I was finishing aligning the beams onto all of the REFL diodes, Manasa asked for the IFO so she and Masayuki could continue their work on the Xarm, so I'll check the signals acquired a little later.

  9049   Thu Aug 22 02:40:12 2013 JenneUpdateLSCDRMI Locked for 1+ minute!!!!!!

[Jenne, Koji]

The DRMI has been locked!!  And at least one time, it was for more than one minute!! 


We are not 100% sure yet that it's correctly sideband locked.  The test of this was to put a 50% BS in front of the AS camera (so after the beam has gone to AS55), and send the light over to a PDA10CF Thorlabs PD.  I locked the Michelson on carrier for the alignment of this diode.  Then I strung a cable to the control room, and plugged it into the RF spectrum analyzer.  (First, I had turned off the green beat PD power, so there wasn't any RF stuff on the line that I unplugged).  It's hard to watch the screen and a tv / dataviewer at the same time, so I've taken a video, so that we can see the nicely locked round DRMI beam on the AS camera, and the spectrum analyzer.  My phone is working very hard at uploading the video, but we may have to wait until tomorrow for that.  However, I think that we're locked on the 55MHz sideband. (Also, maybe I'm too tired or excited or something, but how do you make the real cameras take video??)

EDIT:  Video uploaded.  Pause the video at 10 seconds, and you'll see that we've got a strong 110MHz peak!!  Hoooray!  The TV in the upper right side of the video is AS.  You can see as we flash, the peaks go up and down.  When there's no resonance, the 110 peak goes away. (Ex., when I'm PRMI locked on the sideband, there isn't a visible peak).


Alignment procedure was as normal:  Lock and align the arms. Misalign ETMs. Check that MICH fringes look good (ASS does a nice enough job that I don't actually lock and align the Michelson anymore).  Restore the PRM.  Lock PRMI.  Tweak PRM alignment to maximize POP110I.  At this point, Koji and I played a little with the PRMI, but when we finished with that, we restored the SRM, and tweaked its alignment by making nice overlap on the AS camera.

Then, we tried some DRMI settings, started seeing some locks, and played a bit with trying to optmize the settings that we have. 


PRMI settings: 

PRCL ASC is on (with loop triggering).  MICH gain = -0.8, PRCL gain = +0.05.  FM4, FM5 always on, FM2 triggered.  Loop and filter module triggering on POP22I.  No power normalization.  MICH and PRCL locked on REFL55 I&Q, with 1's in the LSC input matrix.  PRCL actuating on PRM with +1, MICH actuating on BS with +0.5, PRM with -0.267. 

I took transfer functions between REFL55 I&Q and REFL11 I&Q, to determine the relative gains and signs.  REFL11I's gain should be -18dB relative to REFL55I, with the opposite sign.  We tried PRMI locking with MICH = 1*REFL55Q and PRCL = -0.125*REFL11I for the input matrix.  Still no power normalization (we haven't used power norm at all today, so I'll quit writing that).

I took transfer functions between REFL55 I&Q and REFL33 I&Q.  REFL33I's gain is -8dB relative to REFL55I, but they have the same sign.  We tried locking PRMI with MICH = 1*REFL55Q and PRCL = +0.6*REFL33I.  Success.

Next up, some Optickle simulations, to help us go in the right direction for DRMI locking.  I checked the signs of the error signals REFL55I (PRM sweep), REFL11I (PRM sweep) and REFL55Q (MICH sweep) in both PRMI and DRMI configurations.  For all of these cases, the signs were the same (i.e. no sign flips needed to happen for DRMI locking, relative to PRMI locking).  I checked the sensing matrices for DRMI and PRMI for those same signals, and took the ratios of the sensing matrix elements.  This gave me the ratio of optical gains for each error signal, in the DRMI case vs. PRMI case, so any servo gain changes should be the inverse of these numbers.  These numbers are all DRMI/PRMI:  REFL55I PRCL response = 0.76, REFL11I PRCL response = 0.99, REFL55Q MICH response = 18.  So, when trying to lock the DRMI, we wanted to keep the gains for PRCL about the same, reduce the servo gain for MICH by a factor of ~20, but keep the same signs for everything.

In doing that, we started seeing some short DRMI locks, so we twiddled some parameters (mostly the elements in the LSC input matrix) a bit.  We eventually settled on:  PRCL = -0.125*REFL11I, MICH = 0.1*REFL55Q, and SRCL = 1.0 * REFL55I.  The output matrix was the same (MICH pushing on BS and PRM, PRCL on PRM), with the addition of a +1 in the SRCL -> SRM element.  For all 3 degrees of freedom (PRCL, MICH, SRCL), FMs 4 and 5 were always on.  For PRCL, FMs 2,3,6 were triggered to come on after 0.5 seconds of delay.  The PRCL FM triggers helped enormously.  I tried several other things, including changing the MICH input matrix element up and down in value, changing the SRCL input matrix element up and down in value, and engaging triggering for a few different filters in the MICH and SRCL degrees of freedom.  However, none of these made things better, and several made things worse.  Most notably, for SRCL, engaging triggering for FMs 2 and 3 kicked the cavities out of lock, which implies that perhaps our gain isn't high enough yet (and thus our UGF isn't very high yet).  I changed FM1 of SRCL to be +3dB of gain (from +10dB), and it would live through that coming on (trigger delayed by 1 sec, then ramping up over 1 second), but within a second after the filter finishing coming on, the cavity would fall out of lock (not violently kicked, just not locked anymore). 

At this point, we were trying to figure out a way to confirm what kind of lock we had.  I checked Optickle again, and we do not expect to see a significant change in POP110I between the PRMI and DRMI cases, so that isn't a useful check.  We dreamed of having our AS110 demod board, or the AS OSA set up, but neither of those was going to happen tonight.  Instead, Koji suggested hooking up the PD, and looking directly at the output. 

To-do:  Set up the AS OSA.  Also, perhaps temporarily borrow the 110 demod board from POP.  We were triggering on POP22 tonight, and that seemed to work okay.



  9050   Thu Aug 22 07:57:57 2013 LisaUpdateLSCDRMI Locked for 1+ minute!!!!!!

  Very nice!!  I was wondering, shouldn't the driving matrix be such that MICH pushes on SRM as well?

  9051   Thu Aug 22 10:20:32 2013 kiwamuUpdateLSCDRMI Locked for 1+ minute!!!!!!

Wonderful ! I like the video -- the spatial mode looks pretty clean and much cleaner than what I observed in the old days.

  9052   Thu Aug 22 13:03:40 2013 JenneUpdateLSCDRMI Locked for 1+ minute!!!!!!


  Very nice!!  I was wondering, shouldn't the driving matrix be such that MICH pushes on SRM as well?

 Hmmm, yes, that's a very good point.  I think you're right, and I'll give that a try today.

  9053   Thu Aug 22 13:20:54 2013 KojiUpdateLSCDRMI Locked for 1+ minute!!!!!!

Don't go for a hacky solution. We want to climb a staircase step by step.
Prepare an independent 110MHz demod ports.


To-do:  Set up the AS OSA.  Also, perhaps temporarily borrow the 110 demod board from POP.  We were triggering on POP22 tonight, and that seemed to work okay. 


  9060   Sat Aug 24 00:11:07 2013 KojiUpdateLSCDRMI Locked with improved lock streatches

Friday night locking

Much more stable DRMI lock was achieved, partly thanks to the Friday-night quiet seismic,
and partly because of the improved servo gain and LF boosts

55MHz thru-put

I wanted to confirm the enhancement of the 110MHz signal at the AS port.

As the AS110 PD is placed in the CCD path, there is nothing visible with PRMI.
The Thorlabs PD was moved to the main AS path. Now the AS110 PD is receiving 50% of the power.

With PRMI 110MHz peak was -30dBm (As it was fluctuating, anything more precise number did not make sense)
When the DRMI was locked, the peak was enhanced to 0dBm.

The 2f signal comes from the beat between the sidebands.
Thus the amplitude of the intensity is proportional to the power of the sidebands (assuming the +1 and -1 order sidebands have the same amplitude)
-30dBm -> 0dBm means 31.6 times amplitude of the intensity. Therefore the amplitude transmission of the sidebands is 5.6 times more. (Is this true?)

According to the wiki, the AS port thru-put (i.e. power transmission) for the 55MHz sideband is 0.0026 and 0.43 for PRMI and DRMI respectively.
This corresponds to the amplitude difference of ~13. So we still have only half of the sidebands leaking out from the IFO. This could be attributed
to both the smaller PR gain and SR gain.

Locking setup

Same as the one Jenne used the other day. Later I engaged several additional triggers.
The following is the trigger setting I used

MICH: Delay 2 sec, FM1/FM2/FM3/FM6/FM7

PRCL: Delay 0.5 sec, FM2/FM3/FM6

SRCL: Delay 5 sec, FM1/FM2/FM3/FM6

SRCL FM1 was modified from +3dB to +6dB

Lock stability

Once lock is acquired, it lasts tens of minutes. (see the attached striptool chart.)
Even the lock is lost, it reacquires quickly.

The videos to show the lock acquisition and the in-lock stability are attached below.
The AS port beam is very round. It is not so shaky, but some yaw motion is visible.
The mode at the AS port is defined by the SRM, putting a QPD at the AS port would help to
stabilize the spot.

IFO state upon leaving

I left the 40m with the arms aligned, PRM and SRM slightly misaligned, and LSC setting is for the DRMI locking.


- AS110I/Q for triggering

- PRCL/MICH/SRCL normalization

- We should resurrect the IFO config scripts.

- Remove BS->SRCL actuation coupling

- Handing off to 3f signals (preparation for the full lock)

- Improve ALS stability

- SRM ASC: AS QPD for SRM control

Lock Acquisition Video
LL (AS) / LR (PRM Face)

In-lock video
LL (AS) / LR (PRM Face)


Attachment 1: Screenshot-Untitled_Window.png
  9061   Sun Aug 25 06:07:11 2013 ranaUpdateLSCDRMI Locked with improved lock streatches

 We're ready for using the auto configure.

We can put our scripts for the MICH, PRMI, and DRMI into the IFO CONFIGURE screens for now and then it should be easy to get them into the Guardian once Jamie has the bugs worked out.

This screen can also be used to setup and start the dither alignment for each configuration (once we have one working for DRMI / SRM).

Also, now that the notches/bandstop filters for the violin modes have been move from the SUS into the LSC, we should fix the triggering to engage them a few seconds after the boosts.

  9063   Mon Aug 26 18:59:08 2013 MasayukiUpdateLSCLSCoffset script updated

I made scripts/LSC/LSCoffsets2.py which is the script to zero the dark offset of all the LSC PD.  The list of PDs is same as the list in scripts/LSC/LSCoffsets. New script average all outputs of PDs parallelly, so we can zero the offsets much faster.

You can define the averaging time, and you can choose the channel for getting the dark offset from INMON or OUT16. You should know that if you use OUT16 channel, the effect of the unwhite filter is not taken into account.

Example usage (at scripts/LSC):

   ./LSCoffsets2.py -d 20 --out16

you can find the help by calling this script with option -h or --help

  9064   Mon Aug 26 19:13:38 2013 KojiUpdateLSCLSCoffset script updated

What do you mean???

What is the effect of the anti-whitening filter?


You should know that if you use OUT16 channel, the effect of the unwhite filter is not taken into account.


  9068   Tue Aug 27 02:18:28 2013 JenneUpdateLSCPRMI, DRMI sensing matrices

I have made a measurement of the PRMI and the DRMI sensing matrices. 

Keiko pointed out to me in an email a little while ago that I wasn't zeroing elements in the oscillator drive matrix after using them, so I was effectively driving all the degrees of freedom at once, which is why some of the recent sensing matrices looked a little bullshitty.  Anyhow, I put in a few lines to zero that row of the LSC  output matrix, so that we don't do that any more. 

PRMI sensing matrix:


DRMI sensing matrix, first-ever measurement, after the optic flipping / recent locking success:


Note that we don't have any error bars in the DRMI case, since the IFO fell out of lock during the error bar measurements.  So, we got the "real" data from the degrees of freedom, but not extra data for making error bars.  Also, the MICH / SRCL coupling hasn't been balanced out in the output matrix yet, but since the notches are engaged in the degrees of freedom during this measurement, that shouldn't be a significant effect.

To get the DRMI sensing matrix measured, I added the SRM's actuator calibration to SensMatDefinitions.py (data from elog 5637).  I also created a new file runDRMI_sens, to be the equivalent of runPRMI_sens.  In the new runDRMI_sens, I reduced the actuation from the oscillator by a factor of 10.  I had several attempts at higher oscillator amplitudes that kept kicking the IFO out of lock.

The DRMI was pretty good, but I wasn't getting ~10s of minutes like Koji was on Friday.  I also wasn't able to engage all of the FM triggers that he was.  The 10-30 Hz seismic BLRMS is a little higher than a usual night, but other than that, seismic looks pretty quiet.

My settings for the night:

LSC input matrix:  +0.1*REFL55Q = MICH, -0.125*REFL11I = PRCL, +1.00*REFL55I = SRCL.

Filter settings:  MICH, PRCL, SRCL all had FM4,5 always on.  MICH had FM2,3 triggered.  PRCL had FM2,3,6 triggered.  SRCL had FM2 triggered.  In particular, engaging FM 6 for MICH or SRCL made some loud low-ish frequency oscillation.  Engaging anything other than FM2 for SRCL kicked the IFO out of lock. 

Gains:  MICH = -0.800, PRCL = +0.050, SRCL = -0.100

Triggering:  All triggered on POP22I, upper = 50, lower = 10 (lower = 25 for SRCL).

FM trigger thresholds: MICH on = 35, off = 2, delay = 2 sec.  PRCL on = 35, off = 2, delay = 0.5 seconds.  SRCL on = 80, off = 25, delay = 5 sec.

Power normalization:  None, for any degree of freedom.

LSC Output matrix:  MICH = -0.267 for PRM, +0.50 for BS.  PRCL = +1.0 for PRM.  SRCL = +1.0 for SRM. 

LSC SUS filters:  BS, PRM, SRM all had FM1,2,3,6 engaged for the BS, PRM and SRM violin filters, as well as the 3rd order harmonic for one of them.

Other notes: 

I tried locking the SRMI, so that I could do the same kind of actuator calibration that Koji did for the PRMI in elog 8816, but was unsuccessful.  I checked optickle, and found that for REFL 55 I&Q locking, MICH and SRCL keep the same signs for SRMI as DRMI.  Also, for both, the optical response is a factor of ~15 lower for SRMI than DRMI, so the gains should be higher by a factor of 15 for both MICH and SRCL.  I think my big problem here is that I don't have anything to trigger on.  There isn't any signal to speak of in the POP PDs, with the PRM misaligned.  Hopefully we'll have AS110 shortly, and that will help.

I updated the IFO Configure restore scripts to our latest versions of locking.  I have also tested them, and restoring the Michelson, PRMI and DRMI all seem to work. (MICH restores to locking with AS55Q.  PRMI restores to locking with REFL165 I&Q.  DRMI restores to the settings noted above in this entry.)  The X and Y arm restores have been working, and I have been using them (semi-)regularly since I announced them in elog 8433 back in April.  Still to-do though:  Add PRCL ASC to the PRMI up script, and make the dither options work for at least the arms and PRM.  (Just need to point the drop down menu options to the new ASS scripts.)



  9078   Wed Aug 28 03:28:00 2013 JenneUpdateLSCPlaying with DRMI, some ASS automation prep

[Rana, Jenne]

We did lots of poking around with the DRMI tonight.  I should elog more in the morning, but the most important points are:

Locking settings same as elog 9068, except PRCL gain changed to 0.035, and the FMs that are triggered.  PRCL tonight had FM2,3,6 triggered.  MICH had FM1,2,3,7 triggered.  SRCL had FM1,2 triggered.  Engaging the MICH boosts helped make things more quiet, so that some of the SRC boosts could be enabled.  Still not as good of lock stretches as Koji got last Friday (elog 9060). 

REFL55 and REFL11 were still saturating (only during acquisition), after the optical path changes I did last week (elog 9043).  We reduced the REFL55 whitening slider from 15 dB to 6 dB (but forgot to compensate with digital gain), to keep the counts (as seen on DTT time series, binning off) to less than ~20,000 counts.  REFL11 is still saturating, and we're not sure why, since it's slider gain is 0 dB.  To be investigated.

I was prepping the ASS to be more conveniently put into a wrapper script, which could be called from the IFO Configure screen.  This involved adding PRCL to the burt .req and .snap files, as well as modifying the scripts a little bit to include PRCL as an option.  I ended up changing the script names from DITHER_Arm_ON.py and DITHER_Arm_OFF.py to DITHER_ASS_ON.py adn DITHER_ASS_OFF.py, since they are no longer restricted to being arms-only.  You must still provide an argument to the script, to tell it which degree of freedom you want to activate.  I also changed the save offsets scripts.  The way they were, the X and Y arms just had separate hard-coded scripts, with no convenient way to incorporate PRCL.  I merged them (including PRCL) into WRITE_ASS_OFFSETS.py, which you must now provide the DoF as an argument.  I tested these new scripts on all 3 of the DoFs, and made changes to the ASS screen, so it now calls only the new scripts.  It should now be easy to incorporate future ASS modifications.

Rana was in the middle of modifying the ASS model to include SRCL, and we also need to include MICH.  The ASS model is not compile-ready, so don't compile it!!  If you need to compile the ASS, please save what's there as a different name, and do an "svn up" to get the latest working version.

We suspected that there might be angular drive issues with the SRM (it was wiggling a lot). We checked the damping via step responses - all Qs were less than 10. Then we found that the INPUT button on the SRM PIT OL was OFF (why ???). After turning this back on it behaved better. We measured the loop shape and found that the UGF was 7 Hz; good. Need to work on some loop shaping for this guy. Its just 1/f out to 300 Hz right now. UGF should be made a little lower so that we can stably turn on the Bounce/Roll notches and a ~50 Hz low pass filter.

Most importantly, the F2A filters need to be measured and implemented. They are a few years old.

  9082   Wed Aug 28 07:33:51 2013 manasaUpdateLSCMICH locking

I wanted to measure the OLTF of MICH.

What I did:
1. Ran LSC offsets script to zero all the offsets.

2. Restored the IFO configure settings for locking Michelson (locked on AS55Q).

3. MICH wouldn't lock on these settings.

4. The MICH servo was hitting its limits (10000 counts). I checked the filter module. After a little bit of looking into things, I disabled FM3 (0,0:5,5), FM4 (1:10) and FM7 (1:5). FM3 and FM7 were filter modules that were switched ON at the trigger. I set these to manual. Enabling any of the filters (FM3, FM4, FM7) caused MICH to lose lock.

5. MICH gain was changed from -20 to -30. MICH locked with ASDC suppressed to 0.01 counts. I looked at the power spectrum of C1:LSC-MICH_OUT on dtt. //edit: Manasa// The plot (uncalibrated) now shows MICH_OUT power spectrum with MICH PSL shutter closed, free-running MICH and loop-enabled MICH.

6. I then wanted to measure the OLTF of MICH using dtt. A channels were set to C1:LSC-MICH_IN1/C1:LSC-MICH_IN2 and excitation given through C1:LSC-MICH_EXC. But I have not been able to get any good coherence for the measurement as yet.

Attachment 1: MICH.pdf
  9103   Wed Sep 4 17:22:09 2013 JenneUpdateLSCDemod phases for RFPDs

I checked the demod phases for AS55, POP110, and all the REFL PDs. 

AS55:  I locked MICH, and shook the ITMs (+1 for Y, -1 for X), and watched the AS55 I & Q spectra at 580Hz (notch in the servo was enabled).  I rotated the phase from -32.0 to +13.0 to get the signal entirely in the Q phase.

POP110:  I locked the PRMI (triggering on POP22), and maximized POP22.  I then rotated the phase of POP110 until the signal was maximally positive.  I forgot what the starting phase was, but it is now 84.  The POP11_I signal was entirely negative when I started, so the new phase is about 180 from the old phase.  I also checked by unlocking the cavity, and seeing that a large peak in POPDC corresponded to large negative dips in POP110_I and POP22_I.

REFL PDs:  I locked the PRMI, and shook the PRM (notches in the servos were enabled for both MICH and PRCL).  Maximized the peak in the I phase.  REFL11 was fine, REFL33 was fine.  REFL55 was changed from 120 to 45.  REFL165 was changed from 106 to 96.

I restored the SRM on the IFO_ALIGN screen, but the saved value was almost 2 full integers off in yaw from actual DRMI resonances.  It looks like it was saved when Rana and I were working late last week.  We must have accidentally saved it when it was misaligned, since hysteresis can't do that much.

I want to check the phases for POX and POY with arm locking, just in case.  Also need to set the AS110 phase (which is plugged into the AS11 channels - need to fix the channel names).


  9105   Wed Sep 4 20:47:15 2013 manasaUpdateLSCCalibrated in-loop MICH noise

To estimate in-loop MICH noise:

(a) Calibrate MICH_ERR:

1. Lock the arms for IR using POX11 and POY11.
2. Misalign the ETMs.
3. Obtain the average peak-to peak (bright to dark fringe) counts from the time series of AS55_Q_ERR. I measured this to be d = 6.358 counts.
4. This gives the calibration factor for AS55_Q_ERR [Calibration factor = 2*pi*d/1064/10^-9 = 3.7546x10^7 counts/m]

(b) In-loop MICH noise:

1. Lock MICH using AS55_Q.
2. Since LSC input matrix sets MICH_IN1 = 1* AS55_Q_ERR, the power spectrum measured using dtt and calibrated using the calibration factor from step 4 in (a) gives us the calibrated in-loop MICH noise.

The plot below shows the in-loop MICH noise and the dark noise (measured by closing the PSL shutter):

Compared with old measurements done by Keiko elog 6385 the noise levels are much better in the low frequency region below 100 Hz.
(No, no, no... this is not an apple-to-apple comparison: KA)

Attachment 1: MICH_noise.pdf
  9109   Thu Sep 5 01:55:29 2013 JenneUpdateLSCLSC model upated to have AS110 channels, violin filter triggering

I have modified the c1lsc model so that I have access to the AS110 channels in the triggering and power normalization matrices. 

I also put in a few blocks so that we can have triggering on the violin notches that we moved to the LSC model a week or so ago. 

Here is my svn comment, so I don't have to retype things:

2 changes:  AS110 channels added, and Violin filter triggers added.

AS110:     We recently installed a    new demod board    and PD for an AS110 signal.  Since we will not    be using AS11 in the forseeable    future,    the AS110 demod    board outputs use the former AS11 channels.  I    have left the AS11 channels in the model so that we can easily    add them back if we want to, but they are grounded rather than    connected to the ADC.  I've added digital demodulation for AS110, power normalization,    and then added the I&Q signals to both the trigger matrix and the main    power normalization matrix.  NOTE that these slide the matrix columns around.    Since the AS110    is also    using the former AS11 whitening    channels, swapped those on the    BIO block also.

Violins:  Recently, Rana and I moved the SUS LSC violin    filters    from the individual suspension    models over to the LSC model.  Giving every optic every    optics' violin    notch helps eliminate bad cross-coupling between servo loops.  Here, I have enabled triggering    for these notches, so that the violin filters can come on after a cavity is locked.  Since the    filter banks SHOULD BE THE SAME    for all LSC_SUS banks,    the "mask" is common to    all optics.

I also edited several medm screens, to show the new changes:  the lsc overview screen has a button to the violin notch triggering screen, in addition to being able to get to the new screen from the regular triggering matrix screen.  I made the trigger and normalization matrix screens bigger, since there are now 2 new columns. 

I added AS110 to both the LSCoffsets script, and Masayuki's new, better, LSCoffsets2.py. 

I added new lines to the .req files for the ifo configure burt restores for the new matrix columns, and the violin triggering.

I restored, checked out, and saved the Xarm, Yarm, MICH, PRM_sb, and DRM configurations. 


I tried locking the DRMI, but haven't really been successful.  I'm not 100% sure how to do the phasing for AS110, so that could be a problem.  For POP, I can watch POPDC to see if something is a carrier or a sideband flash, but I don't have something quite as convenient at the AS port.  I have set the AS110 phase to 60 degrees for now, since during free swinging DRMI flashes, it looks like most of the buildup is in the I phase with 60 degrees.  Even with the same configurations as a week or so ago, I'm not getting much more than ~1 second locks.

I also tried locking the SRMI, but am not getting anything at all.  I think I need to go back to simulation-land to figure out what good signals might be.


Other thoughts:

Stefan modified the LSC filter module triggering blocks, so now we have a new epics variable, "_INVERT", which sends the trigger through a NOT or not.  I think that we want to keep this variable set to 0 to be the same as things were, but I do need to expose this new variable on the screens.

The trigger and normalization matrices pictured on the LSC overview screen need to be expanded by the 2 new columns.  The actual matrix screens are good, but I forgot to fix up the little Kissel buttons.

When I have a free swinging SRMI, MICH and SRCL should have the same sign for the gain, if I'm using AS55 I&Q for locking.

LLO is using REFL 9I for SRCL, and ASDC for MICH for the SRMI, but I don't have any REFL beam with a misaligned PRM, so I don't think I can copy what Den and Lisa did on Monday night.

I have figured out / rediscovered why the "sqrt" buttons on the power normalization screen aren't restored when you restart the LSC model - They are controlled by momentary epics records, which go to embedded c-code to do some toggling.  I don't know yet of a good way to save the configuration of these guys for burt restore-type restoration.  This will be a problem for anything that is using these toggle c-codes.

  9113   Thu Sep 5 15:18:41 2013 JenneUpdateLSCFree swinging DRMI power buildups

I have the DRMI free swinging right now, since it's not really locking.  Looking at these time series in the attached pdf, particularly around time=1.15, it would be super handy to trigger the SRCL degree of freedom on AS110 after the PRMI is triggered on POP22.

Attachment 1: DRMI_free_swing_power_buildups.pdf
  9114   Thu Sep 5 21:07:09 2013 JenneUpdateLSCStarted work on logic for triggering

I want something like an "AND" for the degree of freedom triggers.  Koji and I talked through an idea, and I have it running in the c1tst model, but the logic isn't working like I expect, so I need to look into it more before I can put it into the lsc model.

  9116   Fri Sep 6 23:01:08 2013 KojiUpdateLSCStable DRMI lock was recovered from the impact on the RF system modification


Stable DRMI lock was recovered. The AS110 phase was adjusted. PRCL and MICH were locked with REFL33I and REFL165Q.
Still SRCL is controlled with REFL55Q.

PRMI sensing matrix

Thursday night, Jenne and I found DRMI can not be locked at all. Also the PRMI lock with REFL55 showed change in the optical gain.

In order to investigate what is happening, the PRMI sensing matrix was measured and compared with the previous one taken in the night of 8/26.


It shows that some signals are unchanged, some are partial change, and some are completely different.
My intuition saids something is wierd with the sensing matrix measurement.
Right now I can't trust these plots.

- Jenne and I have adjusted REFL55 demod angle so that REFL55Q has no PRCL. And I have confirmed with DTT that this is still true.
  However, the radar chart shows that REFL55Q is almost correct phase for PRCL instead of MICH.

- REFL11 shows the same amplitude and angle as before. But POX11/POY11 shows different MICH angle.

- I have rotated REFL55 demod phase and remearsured the sensing matrix. Evrything else looked same but REFL55.
  Since REFL55I&Q were not used for the control for this measurement, what we expect is to see no change of the sensing matrix and
  only see the angle of "I"&"Q" rotates. But the result was different from the expectation.

DRMI locking

Since no real info was obtained from the sensing matrix, I had to make a fight without any weapon.
After sevral hours of work, stable DRMI lock was recovered.

Basically I gave larger gains to REFL55 signals: REFL55I for SRCL was 100 instead of 1, and REFL55Q for MICH was 2 instead of 0.1.
This was enough to get a second locking. Using this short sections, I have optimized the FM triggers and the gain boosts (i.e. FM1)
as well as the mirror alignment.

Then, PRM ASS was left running during the lock. This actually stabilized the lock a lot.
This made thee lock indefinite.

The demod phase of AS110I was adjusted so that AS110Q fluctuates around zero.
In this condition, the nominal AS110I was 7300 with the whitening gain of 30dB.

Note that the AS110I&Q were also measured with PRMI. With the same phase and gains, AS110I and Q were -35,  -170, respectively.
Do we expect to have this phase shift? If I believe these numbers, the aplitude of 110MHz at the optimal phase is 173,
The ratio of AS110 between DRMI and PRMI is 7300/173 = 42. This corresponds to the ratio of the 110MHz sideband power at the AS port.
According to the wiki, this ratio shoud be ~160.

AS110I was in fact glitchy as you can see in the StripTool chart. I wonder this signal is suitable for the normalization or not.

=== SENSING ===

REFL11 -67deg / whitening gain 0dB
REFL33 -20deg / whitening gain 30dB
REFL55 45deg / whitening gain 6dB
REFL165 96deg / whitening gain 45dB

POP110 69deg whitening on / 15dB
POP22 102.2deg whitening on / 21dB
AS110 145deg whitening off / 30dB (seems to be related to AS11 whitening setting)


REFL11I x -0.125 => PRCL (REFL33I x 2.5 was also OK)
REFL55I x 100 => SRCL
REFL55Q x 2 => MICH (REFL165Q x 0.1 was also OK)


No normalization

Trigger settings


MICH x -0.8 FM4/5 ON, no limitter
FM Trigger: delay 2sec, FM1 (modified from 6dB to 20dB), FM2, FM3

PRCL x +0.035 FM4/5 ON, no limitter
FM Trigger: delay 0.5sec, FM2/3/6

SRCL x -0.1 FM4/5 ON, no limitter
FM Trigger: delay 5sec, FM1, FM2


MICH => PRM -0.267 / BS +0.5

PRCL => PRM +1.0

SRCL => SRM +1.0


delay 1sec: FM1/FM2/FM3/FM6

=== ASC/ASS ===

PITCH&YAW: FM1/9 (ALWAYS ON) + FM2/3 (turned on by the up-script)

PRM ASS left turned on for slow tracking

Attachment 1: DRMI.png
  9118   Mon Sep 9 20:46:28 2013 MasayukiUpdateLSCMICH calbration

[Manasa, Masayuki]

We took a bunch of measurements. Transfer function and power spectrum using DTT. They will be used to obtain calibrated MICH in-loop and free-running noise. Detail Elog with plots will follow very soon.

  9121   Tue Sep 10 17:35:50 2013 Masayuki, ManasaUpdateLSCMICH calbration


[Manasa, Masayuki]

We took a bunch of measurements. Transfer function and power spectrum using DTT. They will be used to obtain calibrated MICH in-loop and free-running noise. Detail Elog with plots will follow very soon.

 [Masayuki, Manasa]

Estimation of free-running MICH displacement noise:

Method 1. Assuming AS55_Q_err to be a linear sensor, as shown in (1) of figure below, free-running MICH noise (V_d) can be estimated by measuring V_err and the OLTF G. H can be estimated by using method explained in elog

 Method 2. Considering that the AS55_Q signal might be distorted or saturated, method 1 may not be precise. In method 2, we will use the ASDC as the sensor (S' in (3)) instead and lock MICH using ASDC in mid-fringe to calibrate the ITM actuators.




What we did:

1. Estimate H' from free-running ASDC signal (bright to dark fringe).
2. With MICH locked on ASDC, give an excitation signal to C1:LSC-SUS_XXXX_EXC (XXXX could be ITMX or ITMY) and measure R'. [(3) of schematic]
3. Measure OLTF of MICH locked on ASDC (hence estimate L). [(3) of schematic]
4. With MICH locked on AS55_Q, give an excitation signal to C1:LSC-SUS_XXXX_EXC (XXXX could be ITMX or ITMY) and measure R1. [(2) of the schematic] 



OLTF of MICH locked on ASDC




Actuator excitation to MICH transfer function (MICH locked using ASDC) 


* y axis (no units)

Figure 3:
Actuator excitation to MICH transfer function (MICH locked using AS55Q)


* y axis (no units)

Figure 4:
Free-running MICH noise



1. By using the second sensor, we also eliminate the effect of the MICH servo loop locked on AS55_Q (Estimated V_d does not depend on G but only on G').

2. The free-running MICH noise is still suppressed at 1Hz. This should be coming from the effect of the UGF of the loop at ~10Hz and the vicinity to the pendulum frequency at 1Hz.


Edit/Masayuki// This noise curve is not collect, especially in low frequency region. We used the measured OLTF for compensating the free running noise, but that is not collect in low frequency region. So we should model the OLTF and fit that into the measured OLTF. We will fix this soon.



  9122   Wed Sep 11 17:35:38 2013 JenneUpdateLSCALS requirement

I have done a quickie look at Optickle to see how the linewidth of an arm cavity changes versus the configuration. 

To do this, I make different configurations, and do a sweep of ETMX.  For each configuration, I find the max peak value, and then find the points that are at half that value.  The distance between them is the full width at half max.

I get:

FWHM_DRFPMI = 3.8750e-11  meters

FWHM_PRFPMI = 3.8000e-11  meters

FWHM_SRFPMI = 2.3200e-09  meters

FWHM_FPMI =   1.1900e-09  meters

So, for the ALS to hold within 1/10th of a linewidth for the full IFO configuration, we want the ALS noise to be on the order of 3 picometers RMS.  If I recall correctly, that's about an order of magnitude better than we currently have.



                 use LOG y-scale

EDIT 8 Nov 2013, JCD:  New log-y plot:


  9127   Thu Sep 12 23:36:25 2013 MasayukiUpdateLSCMICH calbration

For Modelling of the OLTF, I measured the response of the BS suspension. I used the OSEM sensor for measurement. The attatchment1 is the measured TF from C1:SUS-BS_LSC_EXC to C1:SUS-BS_SUSPOS_IN1 with exciting with random force. The measured data was fitted and the resonant frequency is 1.029(±0.005) Hz and quality factor is 12.25 (± 0.2).  Additionally I did same measurement for ITMX and ITMY. The attachment 2 and 3 are the results for ITMX and ITMY. Each eigenfrequency and Q are 1.063 (±0.008) Hz and 7.33 (±0.13) (ITMX), 1.022 (±0.005) Hz and 9.41 (±0.09) (ITMY).

 After that, I locked the MICH with AS55, and measured the PSD of error signal. I compensated the that PSD by the modelled OLTF with this suspension TF and the servo TF. The result is in attachment 4. Above 1 Hz it is quite close to the previous data by Keiko (elog#6385) But below 1 Hz there is a large dip. The error signal has also this dip. I looked for a integral filter between 0.2 Hz and 1 Hz, but I connot find a such filter. And when I locked MICH with using ASDC, there was same dip at same frequency. I don't think it's true free running noise, and I will try to fix it.

I completely forgot to mention that I fitted the modelled OLTF into the measured OLTF. I used the fitted OLTF for compensation. 



Attachment 1: BSsus.PNG
Attachment 2: ITMXsus.PNG
Attachment 3: ITMY.PNG
Attachment 4: free_running.PNG
  9128   Fri Sep 13 19:22:01 2013 MasayukiUpdateLSCMICH calbration


 I made sure the yesterday's result was collect. I measured not only the error signal but also the feedback signal. And I compared those signals and measured the TF in order to confirm my servo filter model is not wrong.

The reason of dip at low frequency region is maybe the coherence of the ground motion. The ITMX and ITMY suspensions are put close. If ground motion has coherence, the mirrors move in common mode. That will suppress the free running noise. The attachment is the free running noise of Sep 13rd and Sep 12nd.

Attachment 1: noise.PNG
  9131   Mon Sep 16 14:11:47 2013 ranaUpdateLSCMICH calbration

  There doesn't seem to be any coherence among the different directions of ground motion (as expected from seismic theory), so I am suspicious of such a low MICH noise.

Attachment 1: Screen_Shot_2013-09-16_at_2.10.31_PM.png
Attachment 2: Screen_Shot_2013-09-16_at_2.18.47_PM.png
  9134   Tue Sep 17 00:50:42 2013 MasayukiUpdateLSCMICH calbration

I found the bug in my calibration code, and I fixed it.

And I put the white Gaussian noise on the BS actuator, and calibrated to the differential length with my new code. We already know the efficiency of the actuator(elog#8242), so I could estimate how much I put the disturbance and compare the two values. The result is in attachment 1.  x_exc means the value of the disturbance. 

You can see the PSD of the differential motion decrease factor of 3 by decreasing the disturbance by factor of 3 (except for the region from 1 Hz to 5 Hz), and the value at lower frequency than resonant frequency of the suspension is comparable to the value estimated with the actuator efficiency. Also there is no dip when I put the larger disturbance than free running noise.

Between 1 Hz and 5 Hz there seems to be a resonance of something (seismic stack?). And also on resonance of the suspension there seems to be some other noise source. One possibility is the active damping of each suspension.

Actually still there seems to be a dip between 0.1 Hz and 1 Hz. But if you consider about those effect, I think this result doesn't seems to be so strange. But according to the documentation of LIGO document-T000058, which I found the seismic motion in 40 m Lab is written in, the seismic motion at 0.1 Hz is 10^-7. I'm not sure about this factor of 10 difference. One possibility is the geophone doesn't have good sensitivity at low frequency. I'm still not sure this result is really collect.



Attachment 1: noise.PNG
  9136   Tue Sep 17 18:44:29 2013 MasayukiUpdateLSCLSC calibration screen

I update the LSC calibration screen. This screen is for real time calibration of each DOF with using error signal and control signal. The formula of the calibration is

x_dis = V_err/H + A V_fb

,where x_dis is the disturbance without surpression, V_err and V_fb are error signal and control signal, H is the transfer function from the displacement to output and A is the efficiency of the actuator.

I will put the filter of 1/H into the CINV filter bank and actuator efficiency into the A filter bank.


Attachment 1: calibration_screen.png
  9149   Fri Sep 20 22:49:10 2013 MasayukiUpdateLSCLSC calibration screen


I update the LSC calibration screen. This screen is for real time calibration of each DOF with using error signal and control signal. The formula of the calibration is

x_dis = V_err/H + A V_fb

,where x_dis is the disturbance without surpression, V_err and V_fb are error signal and control signal, H is the transfer function from the displacement to output and A is the efficiency of the actuator.

I will put the filter of 1/H into the CINV filter bank and actuator efficiency into the A filter bank.


 I fixed the filter of the MICH real-time calibration. You can find C1CAL screen from the LSC menu 'calibration' of sitemap.

*Filter explanation

    C1CAL_MICH_CINV : the servo to convert  the error signal to displacement.

Sen_MICH :

the inverse of the transfer function from the distance to the error signal, which has the unit of count/m. In the formula this filter is represented by 1/H.

I assume this H is independent of frequency and time, and I calculated by the amplitude of the fringe of error signal. But it may change every day by drift of laser intensity and so on.  So we should follow the actual H somehow.  The temporary value of H is 3.76*10^7 count/m .

    C1CAL_MICH_A : the servo to convert the feedback signal to displacement. In formula This transfer function is represented by A


the transfer function of the suspension of the BS. This is modeled from the measurement in elog#9127. The resonant frequency is 1.029 Hz and Q is 12.25.

 Res_A :

the response of the actuator on BS_SUS, which has the unit of m/count. The value is 1.99*10^-8 m/count. This value is measured in the measurement in elog#9121.

     C1CAL_MICH_W : the servo to handle the calibrated signal.

  m->um ;

the filter to convert the unit of signal from m to um. When this filter is on, the output is written in unit of um.


 I measured the power spectrum of the calibrated free running noise. The measured port was C!CAL_MICH_W_OUT. The result is in attachment 1. Also in this figure there are the plots of the Verr/H and Vfb*A.

 In low frequency region, where control loop suppresses the disturbance, you can see that the displacement is equal to the displacement of actuation (I'm not sure what happens at the point of 0.03Hz), and in high frequency region, where control loop doesn't work, the displacement is equal to the value of the Verr divided by MICH sensitivity. Also this result is similar to the my calibration result.elog#9131

Attachment 1: plot.pdf
  9158   Wed Sep 25 08:11:01 2013 MasayukiSummaryLSCLSC calibration screen


  The real time calibration system is not correct in high frequency.

The attachment are the plot of two free running noise. Blue curve is the plot of noise calibrated with OLTF. Green one is the just fft analysed signal of the real time calibration system output. You can see the ripple in high frequency region in green curve. That is because the anti-aliasing filter and digital anti-aliasing filter. I assume the sensitivity of MI as constant but Rana mentioned that we should take these filters into account.

modeled OLTF and sensitivity H
 I put the AA filter and DAA filter effects into matlab calibration script. The attachment 2 is the modeled sensitivity of the MICH. You can find each filter properties in  elog#8555 (analog AA filter) and in elog#3961. I estimate the H gain by measuring the fringe. The attachment 3 is the plot of fringe and I averaged with green points. The actual number is 3.48e7 count/m

attachment 2: the sensitivitiy of MICH


 attachment 3: fringe of the MICH


I modeled OLTF with this H and the fitted into the measurement data. That is in attachment 4. In this OLTF I also included the DAI filter and AI filter, and ' sample and hold circuit' of DAC TF . These are  mentioned in two references. Additionally I added the time delay 309.6 us.  Yuta mentioned that in C1SUS has 125us time delay. In MICH control we have also C1LSC , so I think this time delay is reasonable. I compensated the error signal with these OLTF and MICH sensitivity.

attachment 4: OLTF of the MICH control


You can see that the ripple is gone in blue curve and after 5 kHz the curve is flat.

Next step

I'm trying to put the inverted AA filter and DAA filter in C1CAL_INCV servo. But the ploblem is the difference of sampling frequency, so I couldn't fix yet. One possibility is putting approximated filter. I hope I will find some good way to design these filters.



Other thing

I esitimated the FPMI noise propagated from the residual noise of IR PDH control of both ARMS. I will summarize and write these staff in this afternoon.

Attachment 1: plot.pdf
  9167   Thu Sep 26 23:02:40 2013 ranaUpdateLSCFPMI noise caused by ARM locking

Hidden in Nakano-kun's previous entries was that the phase margin of the X-Arm was only 9 degrees!! This extremely close to instability and makes for huge gain peaking. The feedback loop is increasing noise above 100 Hz rather than suppress. After some tweaks of the LSC filters we got a much more stable loop/.

So we today started to examine the sources of phase lag in the arm cavity sweeps. There were a few unfortunate choices in the XARM LSC filter bank which we tuned to get less delay.

Then I wrote a bunch of detail about how that worked, but the ELOG ate my entry because it couldn't handle converting my error signal noise plot into a thumbnail. Then it crashed and I restarted it. We also have now propagated the changes to the Y arm by copy/paste the filters and the result there is pretty much the same: low phase margin is now 38 deg phase margin. Noise is less bad.


Attachment 1: Xarm_sweep_130926.pdf
Attachment 2: lsc.pdf
Attachment 3: err.png
  9168   Fri Sep 27 00:48:53 2013 MasayukiUpdateLSCFPMI noise caused by ARM locking


Hidden in Nakano-kun's previous entries was that the phase margin of the X-Arm was only 9 degrees!! This extremely close to instability and makes for huge gain peaking. The feedback loop is increasing noise above 100 Hz rather than suppress. After some tweaks of the LSC filters we got a much more stable loop/.

So we today started to examine the sources of phase lag in the arm cavity sweeps. There were a few unfortunate choices in the XARM LSC filter bank which we tuned to get less delay.

Then I wrote a bunch of detail about how that worked, but the ELOG ate my entry because it couldn't handle converting my error signal noise plot into a thumbnail. Then it crashed and I restarted it. We also have now propagated the changes to the Y arm by copy/paste the filters and the result there is pretty much the same: low phase margin is now 38 deg phase margin. Noise is less bad.


[Rana, Masayuki

 I made the plot of the phase of the digital filters which Rana change and also  of the AA, AI, DAA, DAI filters. Now the biggest phase delay come from the timedelay of the digital system.


The UGF is around 150 Hz at that frequency the time delay has biggest phase  delay. Second one is the FM9 filter (this filter is BOOST filter). Then we have the AA filter, AI filter and so on, but these delay is roughly 5 degree.

As I said in previous entry, the time delay of the XARM control is roughly 300 usec, and we have 120 usec even only in C1SUS. Also between the C!SUS and C1LSC we have another 120 usec time delay. We want to increase the UGF to 300 Hz but because of the time delay of the digital system we cannot increase. So we should fix this problem.


After changing these filters, the FPMI noise is become better at high frequency. Before we have peak around the 100 Hz (because of 8 degree phase margin...), but they are gone. i attached the noise spectrum. This plot is measured by the real time calibration output. But even then, you can see the extra noise around 100 Hz in FPMI conpare to only MICH.




  9169   Fri Sep 27 13:55:11 2013 MasayukiUpdateLSCLSC calibration screen

  I added the DAQ channel to all output of calibration servo. The name of channels are C1CAL_(plant name)_W_OUT_DQ.

I recompiled and restarted the model. Also I committed the changes to the svn of the calibration model.

  9172   Fri Sep 27 21:01:50 2013 MasayukiUpdateLSCLSC calibration screen


 I fixed the XARM and YARM real time calibration servo.

I also change the C1CAL_MICH_A servo. Now the actuator response and the suspension TF are combined together and that filter name is BS_act. C1CAL_XARM_A and C1CAL_YARM_A have same kind of filters, ETMX_act and ETMY_act.

There are AI filter in each A servo and inv_AA, inv_DAA filters in CINV servo, but it's doesn't work correctly yet.

  9174   Mon Sep 30 11:33:15 2013 ranaUpdateLSCLSC calibration screen


  I fixed the XARM and YARM real time calibration servo.

I also change the C1CAL_MICH_A servo. Now the actuator response and the suspension TF are combined together and that filter name is BS_act. C1CAL_XARM_A and C1CAL_YARM_A have same kind of filters, ETMX_act and ETMY_act.

There are AI filter in each A servo and inv_AA, inv_DAA filters in CINV servo, but it's doesn't work correctly yet.

 These aren't servos. What he means is that he's changed some filters in the real time calibration screens so as to make the actuation and sensing parts more accurate, but the inversion of the AA filters is not accurate yet.

  9187   Thu Oct 3 00:01:59 2013 rana, jenneHowToLSCsteps to full IFO

In moving now to full IFO locking, there are a number of sub-states to diagnose:

  1. PRMI + 1 arm
  • Measure sensing matrix as arm is scanned into resonance. Compare time series of sensing matrix elements with New LoopTickle simulation. But first, we need more than 1 LOCKIN screen in the LSC! That will allow us to measure all of the elements of front_matrix.jpg simulataneously.
  • Measure 3f PRMI noise spectra as a function of arm position. Look for trouble.
  1. DRMI + 1 arm
  • Same as PRMI above.
  • Want to find why this is unstable sometimes. Make stable for t > 10 minutes.
  • Maybe add some QPD->ASC for SRC angular control, but how? Will this still work after the arms are resonant or will it be swamped by carrier contrast defect? Will Berlusconi ruin all of the Italian gelateria? Only time can tell...
  1. FPMI (non optically recombined) for ALS diagnosis
  2. PRFPMI (iLIGO configuration)
  • this ought to be easier than DRFPMI
  • will let us tell if our ALS is good enough to handle the coupled cavity pole
  1. DRFPMI (aLIGO style)

Which to do first and in what order?

  9189   Thu Oct 3 01:18:57 2013 KojiHowToLSCsteps to full IFO

I vote on PRMI+1arm -> PRFPMI

  9191   Thu Oct 3 02:43:34 2013 rana, jenneSummaryLSCPRMI: comparison of 1f and 3f signals w/ calibration

The attached plot shows the spectra of all the REFL signals with the PRMI SB lock.

We excited the ITMY_LSC with 3000 counts. We used the Masayuki calibration of ITMY (5 nm / count * (1/f^2)) to estimate this peak in the REFL spectra.

To correctly scale the REFL spectra we account for the fact that the DTT BW was "0.187 Hz" and we turn off the "Bin" radio box before measuring the peak height with the cursor.

Since the ITMY motion is 3000 * 5e-9 / (580.1 Hz)^2 = 44.6 pm_peak, we want the DTT spectrum of the REFL spectra to report that too.

i.e. to convert from peak height to meters_peak, we use this formula:

meters_peak = peak_height * sqrt(BW) * sqrt(2)

I *think* that since the line shows up in multiple bins of the PSD, we should probably integrate a ~0.5 Hz band around the peak, but not sure. Need to check calibration by examining the time series, but this is pretty close.

Mystery: why are the REFL_I 3f signals nearly as good in SNR as the 1f signals? The modelling shows that the optical gain should be ~30-100x less. Can it be that our 1f electronics are that bad?

Bonus: notice how we have cleverly used the comb of bounce frequencies around the calibration line to determine that REFL11 is clipping!

Attachment 1: REFL_signals_CalLinesLinedUp.pdf
  9193   Thu Oct 3 02:51:26 2013 JenneUpdateLSCPRMI locked "forever", some ALS fiddling

First up for me this evening was getting the PRMI locked.

I used the IFO configure screen to lock the X and Y arms, then aligned them using the ASS scripts.  Then used the IFO config screen to restore the Michelson, and did some fine tune tweaking of the BS alignment by looking at the AS camera.  Then, I restored the PRMI from the IFO config screen, tweaked the PRM a little bit in yaw, and was able to get a lock using REFL 165 I&Q for ~25 minutes before I got bored and unlocked things.  I used the ASS for the PRM to align the PRM, then turned off the ASS.  POP110 and POP22 both drifted down, but by a small amount, and at the end (when I turned the ASS back on for PRM), they picked back up to about their original levels.


(Note to self: to get it to print both plots, chose custom paper size, make it 14.5 by 11.  Don't ask why, just do it, because it works.  Also, in PNG device properties, increase the compression to 9.)


After I played with the PRMI, I started looking at the ALS system. 

I had both arms locked on IR using the regular LSC system (so POX and POY for the error signals).  Then I opened up the green shutters, and got both arms locked on green (so the green lasers were just following the arms...no digital ALS business).  I went out to the PSL table and tweaked up the alignment of the green beams (didn't need much at all, just an itsy bitsy bit in yaw, mostly).  I saw a very strong peak for the Yarm vs. PSL (around -19dBm), and there was a harmonic of that beat.  Opening and closing the Xarm green shutter had no effect on these peaks, so there wasn't any kind of X-Y cross beat sneaking around that I could see.  That's really as far as I got - I think (but haven't checked) that Manasa may have removed the power splitter / combiner, so that the RF analyzer is only looking at the Y beat PD (she mentioned earlier today that she was going to give that a try to narrow things down). 

After that, Rana and I went back to the PRMI for some noise stuff, and worked on the PMC.  See those separate elogs for info on those activites.

  9213   Mon Oct 7 13:55:26 2013 JenneUpdateLSCArms locked in IR for many hours

Someone left the arms aligned, and the LSC engaged, so the arms have been locked almost continuously for several days hours.  The trend below is for 4 days hours.  What is most impressive to me is that we don't see a big degredation in the transmitted power over this time.

EDIT: Okay, I got excited without paying attention to units.  It was only several hours, which is not too unusual.  Although the lack of transmission degredation is still unusual.  However, this may be due to improved oplevs?  I'm not sure why, but we're not seeing (at least in this plot) the degredation to ~0.7 after an hour or so.


  9214   Mon Oct 7 14:15:10 2013 JenneUpdateLSCPRMI alignment is also excellent

Something is really excellent with the alignment today, or something has changed with the POP path / electronics.  While usually we see ~120 counts on POP22_I and ~175 counts on POP110_I (cf elog 9193), today I have ~175 counts on POP22_I and ~265 counts on POP110_I.


  9215   Mon Oct 7 14:24:10 2013 JenneUpdateLSCPRMI Config settings re-saved

I have resaved the PRMI locking settings in the IFO Config screen.  Nothing has changed, except that I have put a 1e-4 into the PRCL matrix elements for REFL11I, REFL33I and REFL55I.  So, PRMI still locks on REFL165 I&Q, but the other 3 REFL diodes' whitening gets triggered when the cavity is locked.  I think this will help the LSC sensing matrix measurements, which I'm going to test out now.

  9217   Mon Oct 7 18:36:39 2013 JenneUpdateLSCSensing Matrix scripts updated

I discovered that I was not getting enough SNR on all the refl RFPDs when I actuated using the Sensing Matrix script.  The problem was that the ITMs have actuation constants that are a factor of 5 lower than the PRM.  So, I need to push on the ITMs (for MICH) about 5 times as hard as I push on the PRM (for PRCL).  I have modified the sensing matrix scripts to allow different actuation amplitudes for each degree of freedom.  If I watch the REFL PD spectra while the script is running, I see that I now have some actual SNR (as in, more than 1, which is what the SNR was for some diodes previously). 

A consequence of this is that the script to analyze past data will no longer work on sensing matrix data taken before this afternoon.  On the other hand, that data isn't very useful, since there was no SNR.

  9218   Mon Oct 7 18:39:29 2013 JenneSummaryLSCPRMI: REFL11 beam realigned


Bonus: notice how we have cleverly used the comb of bounce frequencies around the calibration line to determine that REFL11 is clipping!

 Rana and I noticed last week that it looked like the REFL11 beam was clipping.  This afternoon, I locked the PRMI with REFL 165 I&Q, and checked the REFL 11 path.  The beam looks fine through all of the optics going to the diode, so I just realigned the beam onto the diode using the itty bitty steering mirror.  I have not yet checked the change (hopefully improvement) in the REFL11 spectrum.

ELOG V3.1.3-