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ID Date Authorup Type Category Subject
  8348   Tue Mar 26 00:17:47 2013 JenneUpdateLockingREFL pickoff fraction

To see how much of the light that comes out of the REFL port actually goes to the PDs, I measured the power immediately after leaving the vacuum (~575mW) and in front of REFL11 (~5mW) and REFL55 (~6mW).

So, 0.01 of the power leaving the vacuum actually goes to the REFL PDs. This number will be useful when calculating the actual signals (in volts) that we expect to see.

  8351   Tue Mar 26 11:08:03 2013 JenneUpdateLockingPRMI locking should be possible - let's get it done!

[Jenne, Gabriele, Jamie]

We have looked at Koji's old Finesse code, and determined that the PRMI sensing matrix that he calculated was for the sideband-resonant case.  Thus, this is the sensing matrix we are interested in for locking. Gabriele has confirmed this using independently written code with his software, Mist.

Pics or it didn't happen:

 PRMI_SBres_plot_allTheFs_LowRes.png

The sensing matrix is:

LSC_sigmatrix_PRMI.pdf

Numerical values are on the wiki:  https://wiki-40m.ligo.caltech.edu/IFO_Modeling/SensingMatrix

For any of the REFL PDs (1*f1, 1*f2, 3*f1, 3*f2), the PRCL signal is a factor of ~100 larger than the MICH signal.  Rana assures us that, with some clever triggering, we should be able to lock the PRMI. 

This means that we will not be venting in the next few days to flip the SRC folding mirror.  We will work on PRMI lock (probably first with 1*f, but then quickly moving on to 3*f), and as soon as Annalisa and Manasa have the new ETMY table ready for us, we will then do PRFPMI.  (We can also play with the Xarm green until Yarm green is back).

  8360   Wed Mar 27 15:46:13 2013 JenneUpdateLockingPRMI progress

[Gabriele, Jenne]

We have achieved PRMI locks of the order ~5 seconds! Here is an example lock:

PRMI_sb_27Mar2013.png

This was actuating MICH on the ITMs (+1 for ITMY, -1 for ITMX in the output matrix), and PRCL on PRM (+1). 

PRCL gain was +1, MICH gain was -10.

PRCL signal was normalized with POP22I with a matrix value of 0.003 . (No normalization of MICH).

Both PRCL and MICH were triggered on POP22I with high thresh of 200, low of 50.  MICH and PRCL FM2 (integrators) were triggered on POP22I with thresh of 400 and low thresh of 50.  FMs 4 and 5 were on for both MICH and PRCL always.

We zoomed in on the MICH_OUT signal, and the instability looks like it is around 300 Hz.  We aren't sure what this is.  I think this is a similar frequency to an oscillation that Yuta saw, but I'll have to check the old elogs.

PRM and BS SUS_LSC_POS filter banks both have notches between 1280-1290Hz.  The ITMs do not have this "Vio2" filter.

This is one of the first locks with the new triggering of both the INPUT and OUTPUT of the control filter banks.  I modified the lsc model before lunch. 

To do:  Where is this 300Hz coming from, and what can we do about it?  Why are we losing lock?  It's not due to the oscillation - maybe too much afternoon seismic?  Steve says he went next door and the rock monster / river is on medium/high.

 

  8362   Thu Mar 28 00:31:11 2013 JenneUpdateSUSPRMI optics' oplev servos tuned

[Rana, Gabriele, Jenne, Jamie, Lisa, Rana]

We have tuned the oplev servos for PRM, BS, ITMX, ITMY.  For each, we measured the servo transfer function.  Most had a UGF ~ 3Hz.  For those, we increased the gain by a factor of 2, and engaged the 3.3Hz resonant gains. The other case, such as PRM yaw, the gain was already okay, we just needed to engage the resonant gain.  We also checked the new phase margin, and for some of them switched the elliptic lowpass to 50Hz rather than 30 or 35.

Before and afters:

PRM_OLPIT_tuning_27Mar2013_RedIsAfter.pdf

PRM_OLYAW_tuning_27Mar2013_RedIsAfter.pdf

bs_pit.pdf

bs_yaw.pdf

ITMY_OLPIT_tuning_27Mar2013_RedIsAfter.pdf

ITMY_OLYAW_tuning_27Mar2013_RedIsAfter.pdf

itmx_pit1.pdf

itmx_yaw.pdf

We need to, as a last check, look at the spectra before and after to ensure that no modes (like bounce or roll) are newly excited.

  8363   Thu Mar 28 01:59:33 2013 JenneUpdateLockingPRMI progress - even better!

[Gabriele, Rana, Jenne, Jamie, Lisa, Zach]

We tweaked some things after dinner, and our locks got longer (~10sec) and more frequent!

What happened / notes:

* Increased analog gain from 15dB to 27dB for REFL55 I&Q.

* No analog whitening during lock acquisition.  (Need trigger + wait so whitening comes on after ~1sec...but this is not our limitation right now).

* Limit MICH and PRCL control to 5000, so that we don't kick optics too much, which makes them take too long to settle.

* ITMX and ITMY Vio2 filters turned off (PRM still has it on) in the SUS-optic_LSC module.

* MICH and PRCL DoFs triggering on POP22I, with levels 200 & 50.  FMs 4&5 always on.

* MICH and PRCL FM2 triggering on POP22I with levels 400 & 50.

* MICH gain = -0.200

* PRCL gain = +0.150

* MICH and PRCL normalization using POP22I, with matrix values 0.00160 .  This value is ~1/600, where 600 was the peak value of POP22I_ERR.

* REFL 55 phase set back to -15, to minimize PRCL signal in I phase.

* Checked signs for ITMX and ITMY in output matrix for MICH.  Lock MICH using only ITMX or ITMY, find sign to hold on the dark fringe for each.  +1 for ITMY, -1 for ITMX was correct.

* Tweaked up the oplev servos.  See separate elog 8362.  May need more tweaking, such as increasing the UGF, engaging 1Hz resonant gain.

* May need better coil actuator balancing on suspensions at 1Hz.

* Found a weird thing in DTT, which went away after closing and reopening, when looking at time series.  Sometimes we would see a square wave-like jump in the signals, all signals at the same time, with a frequency of 16.6Hz.  This was not present in other data retreival programs, like Jamie's getdata python script.

* We are not sure right now why we are falling out of lock.  We need to investigate more signals, to try to figure out what our current problem is.

* Reduced the amount of misalignment with the "misalign" script, to reduce hysteresis.

To Do / ideas:

* Calibrate oplev signals - see if one optic is moving more than others.

* Calibrate ERR and CTRL  - look at CTRL in meters, see if cavities are moving around like crazy.

* Calibrate POP22 using something like an AM laser modulation trick into units of PRCL SB gain. Compare with expectation - are we locked optimally, or do we have more power that we can be getting out?

* Try feeding back PRCL CTRL to MC2, to make the laser to follow the power recycling cavity, in hopes of reducing angular motion.  Rana tried this quickly with a 1 in the output matrix, but this kicked the MC out of lock - need to try smaller values.

 

  8367   Thu Mar 28 12:50:52 2013 JenneUpdateComputersc1lsc is fine

 Manasa told me that she did things in a different order than her old elog. 

She had

(1) ssh'ed to c1lsc and did a remote shutdown / restart,

(2) restarted fb,

(3) restarted the mxstream on c1lsc,

(4) restarted each model individually in some order that I forgot to ask.

However, with the situation as in her "before" screenshot, all that needed to be done was restart the mxstream process on c1lsc. 

Anyhow, when I looked at the OAF model, it was complaining of "no sync", so I restarted the model, and it came back up fine.  All is well again.

  8380   Mon Apr 1 09:25:35 2013 JenneMetaphysicsLSCLock of PRMI on sidebands

[Gabriele, Jenne]

I put a notch in FM10 for both MICH and PRCL at 628Hz, to try to prevent us from exciting the mode that Gabriele saw on Friday.  Since those filter banks were all full, I have removed an ELP50 (ellip("LowPass",4,1,40,50)).  I write it down here, so we can put it back if so desired.

  8385   Mon Apr 1 17:59:04 2013 JenneUpdateLockingPRMI videos

[Gabriele's work, I'm just spectating]

Annalisa is working on finding the PSL/AUX laser beatnote, so the PSL temp is changing, but Gabriele is still able to lock.  Here are some videos:

 

 

  8389   Tue Apr 2 15:58:40 2013 JenneUpdateSUSoplev calibration for ITMX, BS

[Jenne, Gabriele]

Optical lever calibrations:

ITMX pit calibration = -9.07 cts/mrad

ITMX yaw calibration = -12.33 cts/mrad

ITMX plot:opl_itmx.png

BS pit calibration = -22.86 cts/mrad

BS yaw calibration = -24.14 cts/mrad

BS plot:opl_bs.png

 

Method:  Similar to Manasa and Yuta's method last month.  We mounted each oplev QPD on a micrometer translation stage, centered the beam using the steering mirror, then used tdsavg to get 10 second averages of the _INMON channel for various settings of the micrometer stage.  For BS, we had to take out the PRM oplev to make room for the translation stage.  All QPDs were remounted in their original positions, within less than 1mm.  Measured the out-of-vac distances with the laser disto-meter, and the invac distances from the optic to the window from the CAD drawing.

Copying from other elog entries,

elog 8232:

We calibrated oplev for ITMY. Calibration factor for C1:SUS-ITMY_OL(PIT|YAW)_IN1 are;
  OLPIT: 6.29 +/- 0.11 counts/mrad
 
OLYAW: 5.74 +/- 0.09 counts/mrad

 

elog 8221:

We calibrated oplev for PRM. Calibration factor for C1:SUS-PRM_OL(PIT|YAW)_IN1 are;
  OLPIT: 15.6 +/- 0.3 counts/mrad
  OLYAW: 17.8 +/- 0.3 counts/mrad

  8391   Tue Apr 2 16:55:34 2013 JenneUpdateSUSoplev calibration online for ITMs, BS, PRM

[Jenne, Gabriele]

We have put in a new EPICS input into the SUS library part, just before the OL_PIT and OL_YAW filter banks, so that the IN1 point is calibrated to microradians.  I recompiled all SUS-related models.  The OPTLEV_SERVO screen has been changed, so that you can see the calibration, and enter a value.  The gains have been reduced by a factor reciprocal to the calibration, so the loop gain is the same.

ETMs, SRM and MCs all have "calibration" numbers of 1, so the numbers aren't really calibrated, they're just the same as always.

It looks like the PRM and the BS are moving significantly (factor of ~30) more than the ITMs at a few Hz!  (Y-axis of plot is urad/rtHz)

comparison_opl.pdf

EDIT JCD:  We need to fix up the MEDM QPD indicators, and the OpLev red lights on the watchdog screen, so they match the new numbers.  Also, Rana turned on the output limiters to 2000 for all oplev servos.

  8393   Tue Apr 2 18:19:30 2013 JenneUpdateSUSBS, PRM oplev servos improved

 

[Gabriele, Jenne]

We have implemented 4Hz resonant gains for both PRM and BS yaw.  The filter was already in place for PRM Yaw, so we just turned it on, but we also copied the filter over to BS Yaw.  We also changed the 3.3Hz res gain and the ELP for the PRM servo to match the BS servo, since after implementing the 4Hz gain, PRM was still much noisier than BS.  Now the 2 servos match, and PRM is a little quieter.  We hope that tonight's locking might be a little more stable after this work.

PRM_servo_matches_BS.pdf

prm_bs_optical_levers_comparison.pdf

  8398   Wed Apr 3 01:32:04 2013 JenneUpdateComputersupdated EPICS database (channels selected for saving)

I modified /opt/rtcds/caltech/c1/chans/daq/C0EDCU.ini to include the C1:LSC-DegreeOfFreedom_TRIG_MON channels.  These are the same channel that cause the LSC screen trigger indicators to light up. 

I vaguely followed Koji's directions in elog 5991, although I didn't add new grecords, since these channels are already included in the .db file as a result of EpicsOut blocks in the simulink model.  So really, I only did Step 2.  I still need to restart the framebuilder, but locking (attempt at locking) is happening.

The idea here is that we should be able to search through this channel, and when we get a trigger, we can go back and plot useful signals (PDs, error signals, cotrol signals,....), and try to figure out why we're losing lock. 

Rana tells me that this is similar to an old LockAcq script that would run DTT and get data.

EDIT:  I restarted the daqd on the fb, and I now see the channel in dataviewer, but I can only get live data, no past data, even though it says that it is (16,float).  Here's what Dataviewer is telling me:

Connecting to NDS Server fb (TCP port 8088)
Connecting.... done
read(); errno=0
LONG: DataRead = -1
No data found

read(); errno=9
read(); errno=9
T0=13-03-29-08-59-43; Length=432010 (s)
No data output.

 

  8399   Wed Apr 3 03:18:23 2013 JenneUpdateLockingPRMI locked with REFL55 I&Q for more than 1 minute

[Rana, Gabriele, Jenne]

We have now locked the PRMI using REFL55 I&Q for more than one minute!!!!!

PRMI_sb_80sec_2Apr2013.png

This isn't really the most useful plot as is, but it was created using:

/opt/rtcds/caltech/c1/scripts/general/getdata C1:LSC-POP22_I_ERR_DQ C1:LSC-REFL55_I_ERR_DQ C1:LSC-REFL55_Q_ERR_DQ C1:LSC-MICH_IN1_DQ C1:LSC-MICH_OUT_DQ C1:LSC-PRCL_IN1_DQ C1:LSC-PRCL_OUT_DQ -d 80 -s 1049013520 -c

This is just one of several long lock stretches.  If I can get the TRIG_MON channels to be saved, we can automatically (versus my by-hand search) find lock stretches and make this kind of plot.  Although we want them saved in some raw format so we can zoom in on selected axes, I think.  This might require some python-fu from Jamie, or learning of python-fu for Jenne.

The secret sauce:

* The big key was changing REFL55's phase.  It was -4 when we looked at the I&Q signals, and minimized the PRCL information in the Q-phase.  We were able to get short lock stretches with this.  During these stretches, Rana changed the REFL55 phase until the lock sounded (audibly) quieter.  The final phase we settled on was +26. As we changed the phase, the lock stretches got longer and longer. 

* We also tweaked up the POP22 phase.  It was close from our previous efforts of looking at non-locked time series, but we perfected it by minimizing the signal in the Q-phase during lock stretches.  We also found that it drifted (according to this method) by ~5 degrees over ~half an hour (I don't remember the exact time between our phase tunings).

* POP22's low pass filters (both options, ELP10 and ELP50) must be OFF for any lock to be acquired.  Turning on either filter prevents locking.

* Normalization helped a lot.  Without normalization we weren't really able to catch any locks, certainly not of any significant length. (0.004, using POP22I, for both MICH and PRCL). 

* Parameters:

       ** Normalization:  use POP22I for both MICH and PRCL, value = 0.004

       ** Input matrix:  MICH with REFL55Q, value = 0.01; PRCL with REFL55I, value = 0.01  (we used the small number in the matrix so our servo gains weren't too tiny).

       ** POP22 lowpass filters OFF

       ** Analog whitening OFF for REFL55, POP22.

       ** Analog gain for REFL55 I&Q = 27 dB

       ** Analog gain for POP22 I&Q = 15 dB

       ** Output matrix:  MICH with -1 to ITMX, +1 to ITMY.  PRCL with +1 to PRM.

       ** Servo gains:  PRCL = 0.75;  MICH anywhere between -3 and -20.  Best in the -8 to -15 range.

       ** Vio2 filters in ITMX, ITMY, PRM (all actuated-on mirrors) were OFF. (Still need to lower the Q on these so they don't ring).

      ** PRCL and MICH triggering on POP22I.  The trigger-off was always 20, but the trigger-on changed throughout the night from ~170 to ~50.  I think 130 was a trigger value for at least some of the long-time locks.

      ** Low frequency seismic was small (i.e. no anomalous 0.1 Hz - 1 Hz noise) during successful lock times.  (Not to say it must be low, but it was low when we were able to lock for long stretches).

Things we had looked at and thought about throughout the evening:

* Oplev calibration.  See elog 8391 and 8393.  Optimized BS and PRM to reduce yaw angular motion.

* Actuators all functioning as expected.  We checked transfer functions of MICH_OUT/MICH_IN1 for locking with different optics, to ensure that at high frequency the response was 1/f^2.  Also, we locked MICH with (a) both ITMs, (b) BS, (c) ITMX and (d) ITMY.  We locked the PR-ITMY half-cav with (a) PRM and (b) ITMY.  We locked the PR-ITMX half-cav with (a) PRM and (b) ITMX.  Thus, we conclude that all of the PRMI-related optics are functioning as expected.

* Realigned REFL55 beam onto PD.  It was clipping a bit, so the DC power wasn't steady (when ITMs were misaligned, PRM aligned).  After alignment, the DC power as seen on a 'scope was much smoother.

* Turning off the limiters for the MICH and PRCL control signals allowed us to hear a high-pitched whine.  From looking at the time series, it's predominantly in MICH_OUT.  Rana speculates that perhaps the normalization is causing the UGF to wander temporarily to an unstable place.  For a time there was a high-Q peak between 500 and 600Hz, but reducing the gain (of MICH?) eliminated that.  Then we heard several times, irrespective of gain setting, the ~400Hz broad peak (I say broad because I was able to see it on DTT looking at the error and control signals, and it spanned +/-100Hz).

Things to investigate:

* Is there a good reason that we should switch to triggering on POP110, rather than the current POP22?  From Gabriele, Jamie and my Finesee/Mist modelling last week, without the arms, the 11MHz and 55MHz resonate at different PRC lengths.  If this difference is very small, then we are fine, but if the difference is large, it could be causing trouble - we're trying to catch the lock at the linear part of the 55MHz signal, but if that does not coincide with the linear part of the 11MHz signal, we're doing the wrong thing.  

* For the POP normalization, should we be using the amplitude or the power ( POP22 or sqrt(POP22) )?  Why?  Look at this with a modelling sweep and/or analytically.

* Look at different noise sources, potentially sensing noise, coil actuator noise,.....  We should check these out, and make sure we're not limited by anything obvious. 

Other To-Do:

* Make a "restore" medm screen, rather than restore script.  IFO Configure restore script can pull in values from the screen (EPICS values).  One screen per configuration. 

* Get TRIG_MON signals saved, write script to search for triggered lock times (between given gps times), then plot interesting signals for just before lock, during lock, and until just after a lockloss.

  8405   Wed Apr 3 18:22:00 2013 JenneUpdateElectronicsPOP110 re-implemented

I have re-implemented POP110.  The cable coming from the AS110 diode is disconnected, labeled, and sitting in the cable tray next to the LSC rack. 

Now the POP diode path is:

 

Thorlabs 10CF ----many meters of heliax cable-----> Bias Tee ------> RF amplifier ------> Splitter ------> Bandpass 21.7MHz --------> POP22 demod board

                                                                                                                   |                                                                                    |

                                                                                                                   |                                                                                    |

                                                                                                                   V                                                                                  V

                                                                                                            POP DC                                                                        High pass 100MHz

                                                                                                                                                                                                        |

                                                                                                                                                                                                        |

                                                                                                                                                                                                       V

                                                                                                                                                                                              Lowpass 150MHz

                                                                                                                                                                                                       |

                                                                                                                                                                                                       |

                                                                                                                                                                                                      V

                                                                                                                                                                                        POP110 demod board

  8422   Mon Apr 8 10:19:46 2013 JenneUpdatePSLLSC left enabled

 

 Note: The TRY PD isn't installed and normalized properly yet, so the IFO OVERVIEW screen indicates lock for the Yarm constantly, which is not true.  Hopefully in the next day or so the screen will be back to telling the truth.

Also, the LSC Locking was left ENABLED (presumably over the weekend).   This is not so good.  It can kick optics around, so we should all take a look when we walk through the control room, and if no one is locking, please disable the LSC master switch. 

  8432   Tue Apr 9 21:27:48 2013 JenneUpdate40m Upgrading TRY temporarily in place

Quote:

I've used a Y1 mirror to steer the Y transmission to an R98% BS. The reflected beam falls on PDA520 and the transmitted beam is steered to the camera. The earlier normalization of TRY is no more valid as the power distribution at the PD has changed.

 To take this into account, last night, I reduced the TRY gain by a factor of 2.  This is not exactly correct - when the layout is finalized we need to figure out what the pickoff situation used to be (we think, based on the Xend, that it could have been 0.5*0.9), and do the correct normalization.

  8433   Wed Apr 10 01:10:22 2013 JenneUpdateLockingConfigure screen and scripts updated

I have gone through the different individual degrees of freedom on the IFO_CONFIGURE screen (I haven't done anything to the full IFO yet), and updated the burt snapshot request files to include all of the trigger thresholds (the DoF triggers were there, but the FM triggers and the FM mask - which filter modules to trigger - were not).  I also made all of the restore scripts (which does the burt restore for all those settings) the same.  They were widely different, rather than just different optics chosen for misaligning and restoring.

Before doing any of this work, I moved the whole folder ..../caltech/c1/burt/c1ifoconfigure to ..../caltech/c1/burt/c1ifoconfigure_OLD_but_SAVE , so we can go back and look at the past settings, if we need to.

I also changed the "C1save{DoF}" scripts to ask for keyboard input, and then added them as options to the CONFIGURE screen.  The keyboard input is so that people randomly pushing the buttons don't overwrite our saved burt files.  Here's the secret:  It asks if you are REALLY sure you want to save the configuration.  If you are, type the word "really", then hit enter (as in yes, I am really sure).  Any other answer, and the script will tell you that it is quitting without saving.

I have also removed the "PRM" option, since we really only want the "PRMsb" for almost all purposes.

Also, I removed access to the very, very old text file about how to lock from the screen.  That information is now on the wiki:  https://wiki-40m.ligo.caltech.edu/How_To/Lock_the_Interferometer

I have noted in the drop-down menus that the "align" functions are not yet working.  I know that Den has gotten at least one of the arms' ASSes working today, so once those scripts are ready, we can call them from the configure screen.

Anyhow, the IFO_CONFIGURE screen should be back to being useful!

  8438   Thu Apr 11 02:00:21 2013 JenneUpdateLockingTRY gone???

TRY signals are all gone!  Both the PD and the camera show no signal.  I went down there to turn off the lights, and look to see what was up, and I don't see any obvious things blocking the beam path on the table.  However, Steve has experimentally bungeed the lids down, so I didn't open the box to really look to see what the story is.

Absent TRY, I redid the IFO alignment.  Yarm locked, so I assumed it was close enough.  I redid Xarm alignment pretty significantly.  Transmission was ~0.5, which I got up to ~0.85 (which isn't too bad, since the PMC transmission is 0.74 instead of the usual 0.83).  I then aligned MICH, and PRM.  After fixing up the BS alignment, the POP beam wasn't hitting the POP PD in the center any more.  I centered the beam on the PD, although as Gabriele pointed out to me a week or two ago, we really need to put a lens in front of POP, since the beam is so big.  We're never getting the full beam when the cavity flashes, which is not so good.

Den is still working on locking, so I'll let him write the main locking report for the night.

We see that the PRC carrier lock seems to be more stable when we lock MICH with +1 for ITMY and -1 for ITMX, and PRCL with -1 for both ITMs.  This indicates that we need to revisit the systematic problem with using the PRM oplev to balance the coils, since that oplev has a relatively wide opening angle.  I am working on how to do this.

  8441   Thu Apr 11 03:25:29 2013 JenneHowToSUSIdea for how to properly balance SUS actuators
We have calibrated the overall actuators of each suspension independent of the optical levers. So, we know how much we are 
moving the optic in POS in real units as a result of the dither we inject for the lockin measurement. The amount the oplev beam 
appears to move if there is only POS motion is
d/cos(theta)
where theta is the oplev's angle of incidence and d is the distance the optic has moved in POS.  None of the of the steering mirrors in the 
oplev path matter. 

I propose that I will add an option in the lockin path to subtract away the apparent angle from the oplev output just before the signal 
goes into the lockin module.  Then we will be balancing the actuators based on only the actual angular motion.

The success of this technique depends on how well we know our actuator calibration and the oplev angle of incidence. This also 
assumes that the oplev beam is centered on the optic, so we don't have beam displacement from A2L of the oplev beam, which then 
makes another apparent angular motion.  I suspect that we are close enough that we won't have to worry about this effect.
  8444   Thu Apr 11 11:58:21 2013 JenneUpdateComputersLSC whitening c-code ready

The big hold-up with getting the LSC whitening triggering ready has been a problem with running the c-code on the front end models.  That problem has now been solved (Thanks Alex!), so I can move forward.

The background:

We want the RFPD whitening filters to be OFF while in acquisition mode, but after we lock, we want to turn the analog whitening (and the digital compensation) ON.  The difference between this and the other DoF and filter module triggers is that we must parse the input matrix to see which PD is being used for locking at that time.  It is the c-code that parses this matrix that has been causing trouble.  I have been testing this code on the c1tst.mdl, which runs on the Y-end computer.  Every time I tried to compile and run the c1tst model, the entire Y-end computer would crash.

The solution:

Alex came over to look at things with Jamie and me.  In the 2.5 version of the RCG (which we are still using), there is an optimization flag "-O3" in the make file.  This optimization, while it can make models run a little faster, has been known in the past to cause problems.  Here at the 40m, our make files had an if-statement, so that the c1pem model would compile using the "-O" optimization flag instead, so clearly we had seen the problem here before, probably when Masha was here and running the neural network code on the pem model.  In the RCG 2.6 release, all models are compiled using the "-O" flag.  We tried compiling the c1tst model with this "-O" optimization, and the model started and the computer is just fine.  This solved the problem.

Since we are going to upgrade to RCG 2.6 in the near-ish future anyway, Alex changed our make files so that all models will now compile with the "-O" flagWe should monitor other models when we recompile them, to make sure none of them start running long with the different optimization. 

The future:

Implement LSC whitening triggering!

  8462   Thu Apr 18 19:54:11 2013 JenneUpdateLSCLSC whitening triggering working

I have implemented automatic triggered switching of the analog whitening (and digital dewhitening). 

The trigger is the same as the degree of freedom trigger.  On the LSC RFPD screen there is a space to enter the amount of time (in seconds) you would like to wait between receiving a trigger and actually having the whitening filter switch. 

The trigger logic is as follows: 

* For each column of the LSC input matrix (e.g. AS11 I), check if there is a non-zero element.  If there is a non-zero element (indicating that we are using that PD as the error signal for a degree of freedom), check if the corresponding DoF has been triggered.  Repeat for all columns of the matrix. 

* If either the I or the Q signal from a single PD is being used, send a trigger in the direction of the PD signal conditioning / phase rotation blocks.  (Since the whitening happens before the phase rotation, we want to have the whitening state be the same for both the I and Q signals coming from the demod boards.

* Before actually changing the whitening state, wait for the amount of time indicated on the RFPD overview screen.

* Switch the digital dewhitening.  If the digital dewhitening is on, send a bit over to the binary I/O to switch the analog whitening on.

LSC_triggers.png

LSC_SigCond.png

 

This required changing the LSC RF_PD library part so that you can send the trigger to the filter bank from outside that part..  This part is in use by all LSC models, so I'll make sure the LLO people are aware of this change before I commit it to the svn.

RF_PD_block.png

 

While I was working on the LSC model, I also put in a wait between the time that the filter module trigger is received, and when it actually switches the filter modules.  So far, this time is defined for a whole filter bank (so all filters for a given DoF still switch at the same time).  If I need to go back and make the timing individual for each filter module, I can do that.  This new EPICS variable (the WAIT) defaults to zero seconds, so the functionality will not change for anyone who uses this part.

LSC_FM_Trig.png

These changes also require 2 pieces of c-code:  {userapps}/cds/common/src/wait.c and {userapps}/isc/c1/src/inmtrxparse.c

  8467   Fri Apr 19 16:58:59 2013 JenneUpdateASCArm A2L measurement scripts 90% working again

After Den's work with the ASS model this week, all of the channel names were changed (this wasn't pointed out in his elog....grrr), so none of the A2L scripts worked. 

They are now back, however there is still some problem with the plotting that I'm not sure I understand yet.  So, the measurement works, but I don't think we're saving the results and we certainly aren't plotting them yet. 

I wanted to check where the spots are on the mirrors, to make sure Den's stuff is doing what we think it's doing.  All of the numbers were within ~1.5mm of center, although Rossa keeps crashing (twice this afternoon?!?), so I can't copy and paste the numbers into the elog.

A near-term goal is to copy over Den's work on the Yarm to the Xarm, so that both arms will auto-align.  Also, I need to put the set of alignment scripts in a wrapper, and have that wrapper call-able from the IFO Configure screen.

Also, while thinking about the IFO Configure screen, the "save" scripts weren't working (on Rossa) today, even though I just made them work a week or so ago. Rossa, at least, was unhappy running csh, so I changed the "save" script over to bash.

  8473   Mon Apr 22 19:48:56 2013 JenneUpdate40m Upgrading4 pins enough?

Are 4 of these spring loaded pins enough?  I'm not sure how one pin can hold 2 lids at each point.  It seems like we need 8 pins.

  8475   Tue Apr 23 15:00:20 2013 JenneUpdate40m Upgrading4 pins enough?

Quote:

Are 4 of these spring loaded pins enough?  I'm not sure how one pin can hold 2 lids at each point.  It seems like we need 8 pins.

 Steve has explained to me that the pins will go in between the 2 lids, with a big washer, so that one pin holds both lids at the same time.  4 is the right number.

  8481   Wed Apr 24 00:42:07 2013 JenneUpdateSUSPRMI locked, ITMX pitch OpLev ringing up

Koji is working on PRMI locking, and while he was doing that I glanced at the oplevs' spectra for the ITMs and PRM.

I found that when the PRMI was locked (for only 1 second or so max lock time) on the 55MHz sideband, and the error signals show a big peak around 400Hz (definitely audible in the control room), the only OpLev that I see a similar peak in is ITMX pitch. 

In the plot below, I have grabbed a time when the PRMI was flashing as the black reference traces, and then a time when the PRMI was locked as the active traces.  You can see that there is a similar peak in both REFL55I and ITMX_OL_PIT when the cavity is locked. 

PRMI_locked_ITMXpitOpLevRingingUp.pdf

  8485   Wed Apr 24 14:36:06 2013 JenneUpdateRF SystemPD frequency response

I think you have the splitter that splits the RF signal from the network analyzer in the wrong place. 

Usually you split the signal immediately after the RF Out, so that half of the signal goes to the A-input of the Analyzer, and the other half goes to your controller (here, the laser diode controller).  Then you would take the output of your controller and go straight to the actual laser diode, with no splitting in this path.

  8489   Thu Apr 25 03:35:28 2013 JenneUpdateLockingAngular motion does not explain RIN

Den made a nice elog about the PRMI RIN that we see a few weeks ago:  8464.  The RIN that we're seeing is typically about ~30%.  The question at hand is: what is causing this power fluctuation, and more specifically, is it the angular motion of the mirrors?

I find that no, the angular motion that we see does not explain the RIN that we see.

In the attached Mathematica notebook, I calculate the power lost due to angular misalignments of one or more mirrors.  (Math comes from Appendix A of Keita's thesis.)

From calibrated oplev spectra, our mirrors are moving about 1 microradian (RMS, which is dominated by low frequencies).  From a super sophisticated "draw on the TV, then measure" method (details below), I have estimated that the maximum static misalignment that we're seeing is about 2 microradians.

With all of this, I find that for a g-parameter of 0.94, the power lost due to misalignments should, at maximum, be 0.6%.  I need a g-parameter of 0.995 to get a power loss of 23%.  Alternatively, if I take the derivative of the power coupling function, to find the static misalignment at the steepest slope of the curve (and thus, the place where any AC misalignment would have the most effect), for 1urad of AC misalignment, I get 40% power loss. 

So, in order for the AC angular motion that we see to explain the RIN that we see, either our mirrors are very, very misaligned (so much so that we couldn't really be locking), or our cavity is much closer to unstable than expected from Jamie's calculations.  Since both of these cases (static misalignment or incorrect g-parameter calculation) have to be taken to extremes before they approximate the RIN that we see, I do not think that this power loss is due to angular fluctuations.

This means that we have to think of another potential cause for this RIN that we're seeing.

Details on the "draw on TV and measure" technique for determining static cavity misalignments:  Looking at the POP camera view, with the PRM significantly misaligned, I traced the straight-through beam spot.  I then restored the PRM, and during several momentary locks, I traced the beam spot, which I took to be the saturated area of the camera.  The idea here is that the straight-through beam represents the incident beam axis, while the locked beam represents the cavity axis.  I'm assuming that the camera image plane is at the face of PR2. I approximately found the center of each of my tracings, and found them to be ~1/4 inch apart.  I also measured the "spot size" of the sideband-locked PRMI, and found it to be ~3.5 inches.  So, very roughly, the ratio of (distance between spots)/(size of beam) is ~0.07. This corresponds to a static misalignment of either the ITM or the PRM of ~2urad, rounding up. (I use the Jamie's calculated g-parameters from elog 8316, the case of flipped PR2, tangential = 0.94 to calculate the effective RoC of the PRM). 

  8490   Thu Apr 25 04:10:09 2013 JenneUpdateLockingMICH_CTRL drifting away??

Koji is elogging separately of his exploration of different configurations.  The lock stretch that I'm looking at here uses the same parameters as Koji had for PRMI sb lock, using AS55Q for MICH and REFL33I for PRCL, with MICH gain of -0.8 and PRCL gain of 0.05 .

All of these plots are the same few second lock stretch, with different zooming.  Jamie's super-sweet getdata python script only accepts integers for the start time and duration parameters, so lots of this zooming happened by hand, but I tried to always keep the time axis aligned within each screenshot.  Sometimes the plot axis labels say differently, but they're lying to you.

Plot 1:  gps start time is 1050915916, duration = 6 seconds.  Overall view of the lock stretch.

1050915916-6.png

Plot 2:  gps start time is 1050915921, duration = 1 second.  We're looking at the lockloss that happens at the left side of the plots.

1050915921-1.png

Plot 3:  zoomed in (along the time-axis) version of plot 2, so much shorter time duration.  Some zooming on y-axes.

1050915921-zoom.png

Plot 4:  zoomed in (along y-axes) version of plot 2.

1050915921-1-zoom.png

It seems to me from these plots that maybe MICH CTRL is drifting away?  It seems like we lose the MICH lock, and that destroys the whole thing. 

Koji made some comments to me earlier, regarding his work this evening, that the MICH signal quality is poor in general, and that we should calculate/think about changing our schnupp asymmetry. 

  8498   Fri Apr 26 20:43:51 2013 JenneUpdateLSCRemeasuring the Schnupp asymmetry

[Jenne, Annalisa, with guidance from Koji]

We took data to remeasure the Schnupp asymmetry, using the Valera method that Jamie described in elog 4821

1  First, we locked the arms each with their PO(X,Y) signals, to get the alignment of each arm. 

2.  Then, we locked the Xarm with AS55I (Yarm optics, and PRM very misaligned, more than the misalign script).  Since AS55 was saturating, I changed the analog gain from 24dB to 21dB. (After work was completed, the analog gain was put back to the nominal 24dB for both I&Q.)

3.  We set up the Lockin similar to Jamie's description, with a few differences.  We used the same f = 103.1313, but used ampl=10cts.  Sin and cos gain were each 100.  We changed the lowpass filter from 0.1Hz to 0.05Hz (so each measurement had a settling time of at least 20sec).  We were using LSC-Lockin4, so the Lockin matrix was set so Lockin4 was reading from AS55Q, and the LSC output matrix was such that we were actuating on the ETM (X, then Y when we switched arms later).

4.  By hand, we roughly found the zero crossing of the lockin-q output (which corresponded also to zero of the lockin-I, since this is the place where all of the PDH signal was in AS55I, and the lockin was reading AS55Q). 

5.  We took points separated by 0.2 degrees, plus and minus 1 degree from the zero-crossing phase we had found (i.e., for the Xarm, we roughly found the zero crossing at -14.39 deg, so took data from -15.39 to -13.39degrees).  For each phase, we took 5 measurements (using ezcaread), at least 20 seconds apart.  After moving the phase, we waited at least ~40 seconds (watching the lockin outputs on striptool, they had completely settled after 30 or 40 seconds).

6.  We then repeated steps 2, 4 and 5 for the Y arm.  The lockin setup didn't change, except that now we actuate on ETMY.

We did a quick estimate calculation, from our rough zero-crossings to get a rough measurement of the Schnupp asymmetry.  DeltaPhi = (-14.39 -   -19.79) = 5.40 . This gives us (using F_sideband = 5*11066134, the current 11MHz marconi freq) a rough Schnupp asymmetry of 4 cm. 

Analysis to follow.

EDIT, JCD:  The Xarm gain at this time was -0.160, and the Yarm gain was -0.170

  8499   Fri Apr 26 21:38:06 2013 JenneConfigurationRF SystemPD frequency response

I was sad to see that there wasn't a photo of the POX situation after the fiber work was done on Thursday.

Also, I was out looking at something else, and noticed that the fibers aren't in a very good/safe place from the POX table over to your splitter.  Getting to the POX table is certainly more tricky than the AP table, since the fiber splitter is right next to the AP table, but we should go back and try to make sure the fibers to the more distant tables are laid in a nice, safe way.

Is there a reason that we're not using the clear plastic tubing that Eric bought to put the fibers into?  It seems like that would help a lot in keeping the fibers safe.

I took a few photos of the things that I'm sad about:

1. We should not be keeping fibers on the floor in an area where they can be stepped on.  This will be fixed (I hope) as part of putting the extra coiled length over by the splitter.

IMG_0498.JPG

2. Again, in an area where we semi-regularly walk, the fibers should not be a tripping hazard.  Behind the table legs (rather than under the middle of the table) is safer, and will help tuck them out of the way.

IMG_0499.JPG

3.  It's not obvious when we're pumped down, but we remove the access connector (top right side of this photo), and need to walk in this area.  I can pretty much guarantee that within 1 day of the next time we vent, these fibers will be stepped on, tripped over, and broken if they are not moved to a different location.  I'm not yet sure what the best way to route these fibers is, but this is not it. 

IMG_0500.JPG

Riju, since Eric will be away next week, please let one of us "40m Regulars" know when you plan to come over (at least a few hours ahead of time), and we can give you a hand in protecting these fibers a little bit better.  Thanks!

  8507   Mon Apr 29 18:53:03 2013 JenneUpdateElectronics1pps timing fiber to OMC rack may be bent

While helping Riju out this afternoon, I noticed that the timing fiber that goes to the OMC rack (near the AP table) was bent, and is now possibly kinked, after the installation of the fiber splitter box. 

The fiber was hanging from the back of the rack, and had been strain relieved.  However, the path that the fiber was taking is now occupied by the fiber splitter for the RF PD diagnostic stuff.  So, the installation of the fiber splitter box put the old timing fiber under tension, causing the fiber to be bent at a little over 90 degrees, since it was pulled tightly against the corner of the splitter's front panel. 

I adjusted the strain relief so that the fiber is loose again, although there is still a bit of a kink that you can feel.  Things (for now) seem to be working, since the 1pps light on the front of the box at the top of the OMC rack is still blinking happily, indicating that the 1pps is still getting there. 

We are not using most of the stuff in that rack right now, but if we have problems in the future, we should check out the fiber to make sure it is still good.

  8510   Tue Apr 30 10:54:35 2013 JenneUpdateSUSETMX restored

I'm not sure why or when it was tripped, but I have restored the ETMX watchdog.

  8513   Tue Apr 30 21:24:15 2013 JenneConfigurationRF SystemPOX fiber laying

Nice work.  That was a lot of effort, but having done it so nicely will definitely pay off, since it is now much harder to break the fibers.

2 small issues:  In your attachment 3, I see a coil of fiber just outside the POX table.  I thought Koji had asked that all spare coiled-up length of fiber always be at the splitter side.  Also, in securing the plastic tubing as it comes down near the PSL table, you have zip-tied the tubing to the PSL table.  Since that is a space that we need to access to align the Xgreen beatnote stuff, please disconnect that zip tie, and secure the tubing on the north side somewhere, underneath the AP table, rather than the PSL table (when you look closer, you may notice that no cables in that bundle are attached to the PSL side at the bottom, for this same reason). 

  8514   Tue Apr 30 22:40:57 2013 JenneUpdateSUSoplev XY-plots reflect new calibration

Back when Gabriele was here, he and I implemented online calibration of the oplevs, into microradians.  A consequence of this is that all of the XY-plots on the medm screens were too small. 

I have gone through all the screens that I could think of (SUS_SINGLE, SUS_SINGLE_OPTLEV_SERVO, OPLEV_MASTER, OPLEV_SUMMARY, OPLEV_SUMMARY_SMALL_SCALE, IFO_OVERVIEW) and made the range of the XY-plots +/- 100, rather than the old scale of +/-1. 

I have also added red boxes behind the numbers on many (but not yet all) of these screens, so that you can see when (a) the oplev sum is too low, or (b) either the pit or yaw value is over 50 microradians. 

While I was putzing around on the IFO overview screen, I also made the oplev sum numbers clickable, with the related display being that optic's oplev servo screen.

  8515   Tue Apr 30 23:04:23 2013 JenneConfigurationRF SystemOnly 4 25m cables ordered

I have found in the depths of the elog the (original?) list of fibers and lengths that were decided upon:  elog 6535.

In Suresh's elog, we were assuming that POP22 & POP110 would be served by a single PD.  This is still the nominal plan, although we (Rana is maybe still thinking about this in the back of his head?) think that it might not be feasible.  Riju and I were hoping to put a 4th fiber in the tubing so that we wouldn't have to add it later if POP22 & POP110 are eventually 2 separate PDs.  Anyhow, for now, all we have available are 3 fibers for the POX table, so that is what was installed this afternoon.

  8516   Tue Apr 30 23:17:25 2013 JenneUpdateLSCPRCL LSC filters copied to CARM bank temporarily

Koji is working on PRMI locking with different photodiodes, and rather than typing different numbers into the input matrix, it is more convenient to just be able to click on/off buttons for different filter banks.  So, the CARM filter bank in the LSC model is currently being borrowed as a secondary PRCL filter bank.  I have copied all of the current PRCL filters over to the CARM filter bank. 

Just for reference, although we have not yet used CARM for CARM, the previous filters were the "default" set, +6dB, 0:1, 1:5, 1:50, 1000:10, RG3.2, RG16.5, RG24, empty, empty.  These are currently the same in the DARM and MC filter banks, so we can copy them back over in the future.

  8519   Wed May 1 14:42:45 2013 JenneUpdateLSCPOP now has lens in front of PD

Quote:

- At the end of the session, Jenne told me that the POP PD still has a large diameter beam. (and a steering mirror with a peculiar reflection angle.)
==> THIS SHOULD BE FIXED ASAP
because the normalization factor can be too much susceptible to the misalignment of the spot.

 Koji set the IFO in a PRM-ITMY configuration for me, while I went to put a lens on the POP path.  Before putting the lens, the maximum average output that I saw from the diode (on a 'scope) was 4.40mV.  After putting in the lens and realigning the beam onto the diode, the new max DCvalue that I saw was 21.6mV.  This is a factor of 4.9. 

EDIT:  The dark value was -3.20mV, so actually the ratio is ~3.25 .

I have not yet done anything to fix the situation of the large angle of incidence on the first out-of-vac steering mirror.

  8528   Fri May 3 17:32:59 2013 JenneUpdateLSCRemeasuring the Schnupp asymmetry

I have looked at / analyzed the Schnupp data that Annalisa and I took last week, as well as some more Yarm data that I took this week.

I only have one set of Xarm data, but 3 sets of Yarm data.  I had intended to do careful error analysis of the data, but from the 3 sets of Yarm data, the variance in the answer I get using any one of the Yarm sets is much larger than the error in a single measurement.

 Xarm_SchnuppData_April2013.png

Yarm_SchnuppData_April2013.png

Using the central Yarm zero crossing, I get a Schnupp asymmetry of 3.9cm.  The other 2 Yarm data points give Schnupp asymmetries of 3.7cm and 4.1cm, so I'm claiming a value of 3.9 +\- 0.2cm . This is within error of Jamie's measurement of 3.64 ± 0.32 cm (elog 4821).

  8532   Tue May 7 03:08:12 2013 JenneUpdate PRM yaw responsible for RIN

Koji spent some time earlier this evening exploring where the excess RIN that we see in the PRC is coming from. 

He did this by locking the PRMI (MICH on AS55Q, PRCL on REFL33I, Pnorm for MICH = sqrt(POP110) with 0.1, Pnorm for PRCL = sqrt(POP110) with 10, MICH gain = -30, PRCL gain = 8), and then exciting each relevant optic, one at a time, in yaw.  The excitation was always using the ASCYAW excitation point on each of the optics (BS, PRM, ITMX, ITMY), with a frequency of 4.56 Hz, and an amplitude of 30 counts.

He also took reference traces with no optics excited.

Here, I plot (for each excited optic separately) the reference traces and traces during excitation for POP110_I_ERR, POPDC, and the OPLEV_YERROR for the optic that is being excited.

What we are looking for (only in yaw, since we see on the cameras that the dominant motion is in yaw) is an increase in POPDC and POP110 at the same frequency as an optic's excitation. 

We see that neither ITM is contributing a noticeable amount to either POPDC or POP110.  BS is contributing a little bit, but PRM is clearly contributingNo this entry should be read. (KA)

A week or two ago, I calculated in elog 8489 that the angular motion that we see does not explain the RIN that we're seeing, unless our cavity is much more unstable than Jamie calculated in elog 8316

I think that I need to install one of the T240's on the new granite slab, and see what kind of coherence we have between seismic and PRM yaw motion, and if FF can get rid of it.

BS_excited.pdf

ITMX_excited.pdf

ITMY_excited.pdf

PRM_excited.pdf

 

  8533   Tue May 7 03:14:06 2013 JenneUpdateSUSPRM SUS_LSC violin (FM5) set to correct frequency

While looking over Koji's shoulder earlier, I noticed the big peak in the PRM yaw spectrum (and I was starting to get annoyed by the hum....the fibox is so useful in motivating tasks that otherwise get looked over!) 

I used DTT's peak find feature (cursor tab, enable both cursors, select Peak X/Y as your 'statistic', set the 2 cursors to be on either side of the desired peak) to find the frequency of the PRM's violin mode.  It is 627.75 Hz. I adjusted FM5 of the C1:SUS-PRM_LSC filter bank (the "violin" filter) to be centered around this frequency, with the start and stop freqs +\- 4Hz.  I plotted the filter linearly in frequency to ensure that my target freq was not too close to either side of the bandstop.  After loading and engaging the new filter, the hum slowly started to go away. 

Note, for posterity:  The bandstop used to be centered around ~645 Hz or so.  I assume this is a copy-and-paste situation, where we hadn't gone through to check the exact frequency for each optic.

  8534   Tue May 7 03:25:28 2013 JenneUpdateIOOMC WFS drifting??

I'm not sure why, but starting ~3.5 hours ago, the WFS seem to not be holding the MC in optimal alignment. 

The WFS are definitely engaged and the loops are closed, but every time the MC locks, the WFS pitch and yaw values start drifting off.  In particular, the WFS loop actuation pushing on MC2 is in the many hundreds of counts after ~90 minutes of drift time.  I tried offloading those values by moving the MC2 slider, but then I unlocked the MC to check what that did to the alignment, and it was decidedly bad.  So, I'm not sure what's up with the WFS, but I need to look at it tomorrow.

  8537   Tue May 7 16:21:01 2013 JenneSummaryLSCError signal simulation in PRMI

I asked Gabriele why it looked like for the PRCL sweep REFL 55 I&Q were zero at zero, but for the MICH sweep only REFL55 I was zero.  He took a look at his code, and found that he was not at the correct locking point.  Here is his email back to me:

I found the reason for the not zero value. Indeed, if you could zoom into the PRCL sweep, you would see that the error signals does not cross zero exactly at PRCL=0, but instead some 50 pm away from zero. This is enough to change a lot the PRCL signal when sweeping MICH. If I put PRCL to the correct zero point, and I sweep MICH, I now get everything at zero. I'm sending again the plots.

The fact that such a small detuning is enough to change PRCL signal when sweeping MICH is due, I believe, to the fact that MICH optical gain is much smaller than PRCL one.

Here are the redone plots:

Phase not tuned:

michsweep_errsigs_phasenottuned.pngprclsweep_errsigs_phasenottuned.png

 

Phase tuned:

michsweep_errsigs_tunedphase.pngprclsweep_errsigs_tunedphase.png

POP22 resonance for MICH and PRCL:

michsweep_pop22.pngprclsweep_pop22.png

POP110 resonance for MICH and PRCL:

michsweep_pop110.pngprclsweep_pop110.png

  8538   Tue May 7 17:13:30 2013 JenneUpdateRF SystemIdeal PRMI RF frequency

Koji asked me to look at what the ideal RF modulation frequency is, for just the PRMI case (no arms).  If we had a perfect interferometer, with the sidebands exactly antiresonant in the arms when the arms resonate with the carrier, this wouldn't be an issue.  However, due to vacuum envelope constraints, we do not have perfect antiresonance of the sidebands in the arm cavities.  Rather, the sideband frequencies (and arm lengths) were chosen such that they pick up a minimum amount of extra phase on reflection from the arms.  But, when the arms are off resonance (ex, the ETMs are misaligned), the sideband frequencies see a different amount of phase.   

We want to know what a rough guess (since we don't have a precise number for the length of the PRC since our last vent) is for the ideal RF modulation frequency in just the PRMI. 

If I take (from Manasa's kind measurements from the CAD drawing yesterday) the relevant distances to be:

L_P[meters] = 1.9045 + 2.1155 + 0.4067

L_X[meters] = 2.3070 + 0.0254*n

L_Y[meters] = 2.2372 + 0.0359*n + 0.0254*n

L_PRCL = L_P + (L_X + L_Y)/2 = 6.7616 meters.

The *n factors (n=1.44963) are due to travel through glass of the BS, and the substrate of the ITMs. 

I find the FSR of the PRC to be 22.1686 MHz. For the sidebands to be antiresonant, we want them to be 11.0843 MHz. This would correspond to a mode cleaner length of 27.0466 meters.  Our current modulation frequency of 11.066134 MHz corresponds to a MC length of 27.091 meters.  So, if we want to use this 'ideal' modulation frequency for the PRC, we need to shorten the mode cleaner by 4.4cm!  That's kind of a lot.

  8557   Thu May 9 02:19:53 2013 JenneUpdateLocking50% BS installed in POP path

Koji had the good idea of trying to measure the motion of the POP beam, and feeding that signal to PRM yaw to stabilize the motion.  To facilitate this, I have installed a 50% beam splitter before the POP 110/22 PD (so also before the camera). 

Before touching anything, I locked the PRM-ITMY half-cavity so that I had a constant beam at POP.  I measured the POP DC OUT to be 58.16 counts.  I then installed a 1" 50% BS, making sure (using the 'move card in front of optic while watching camera' technique) that I was not close to clipping on the new BS.  I then remeasured POP DC OUT, and found it to be 30.63.  I closed the PSL shutter to get the dark value, which was -0.30 .  This means that I now have a factor of 0.53 less light on the POP110/22 PD.  To compensate for this, I changed the values of the power normalization matrix from 0.01 (MICH) to 0.0189, and 100 (PRCL) to 189.

After doing this, I restored the ITMX and am able to get several tens of seconds of PRMI lock (using AS55Q and REFL33I). 

I found several QPDs in the PD cabinet down the Y arm, but no readout electronics.  The QPD I found is D990272.  I don't really want to spend any significant amount of time hacking something for this together, if Valera can provide a QPD with BNC outputs. For now, I have not installed any DC PD or razor blade (which can be a temporary proxy for a QPD, enough to get us yaw information).

 

  8558   Thu May 9 02:47:23 2013 JenneUpdatePEMT240 at corner station - cabling thoughts

Something that I want to look at is the coherence between seismic motion and PRM motion.  Since Den has been working on the fancy new seismometer installations, I got caught up for the day with getting the new corner seismometer station set up with a T240.  Later, Rana pointed out that we already have a Guralp sitting underneath the POX table, and that will give us a good first look at the coherence.  However, I'm still going to write down all the cable thoughts that I had today:

The cables that came with the electronics that we have (from Vladimir and tilt meter -land) are not long enough to go from the seismometer to 1X7, which is where I'd like to put the readout box (since the acquisition electronics are in that rack). I want to make a long cable that is 19pin MilSpec on one end, and 25pin Dsub on the other.  This will eliminate the creative connector type changes that happen in the existing setup.  However, before making the cable, I had to figure out what pins go to what.  So.

25pin Dsub          19pin MilSpec

1                   P

2                   N

3                   E

4                   No conn

5                   D

6                   R and V

7                   H

8                   J

9                   No connection

10                  T

11                  F

12                  L

13                  No conn

14                  B

15                  A

16                  R and V

17                  No conn

18                  C

19                  G

20                  G

21                  K

22                  U

23                  No conn

24                  S

25                  M 

I am not sure why R and V are shorted to each other, but this connection is happening on the little PCB MilSpec->ribbon changer, right at the MilSpec side.  I need to glance at the manual to see if these are both ground (or something similar), or if these pins should be separate. Also, I'm not sure why 19 and 20 are shorted together.  I can't find (yet) where the short is happening. This is also something that I want to check before making the cable.

Den had one Female 19 pin MilSpec connector, meant for connecting to a T240, but the cable strain relief pieces of the connector have 'walked off'.  I can't find them, and after a solid search of the control room, the electronics bench, and the place inside where all of Den's connectors were stored, I gave up and ordered 2 more.  If we do find the missing bits for this connector, we can use it for the 2nd T240 setup, since we'll need 2 of these per seismometer. If anyone sees mysterious camo-green metal pieces that could go with a MilSpec connector, please let me know.

  8559   Thu May 9 15:07:51 2013 JenneUpdateGeneralDistances from CAD drawing

Since I keep asking Manasa to "measure" distances off of the CAD drawing for me, I thought I might just write them all down, and quit asking.

So, these are only valid until our next vent, but they're what we have right now.  All distances are in meters, angles in degrees.

05091301.PDF

  8563   Mon May 13 17:24:38 2013 JenneUpdateWienerFilteringPRM YAW Wiener filtering

I have done a quicky offline Wiener filter to check how much PRM yaw motion we can subtract using a seismometer in the corner station.  This work may be redundant since Koji got the POP beam shadow sensor feedback loop working on Friday night.

Anyhow, for now, I used the GUR2 channels, since GUR2 was underneath the ITMX chamber (at the north edge of the POX table).  Note that Zach is currently borrowing this seismometer for the week.

I used GUR2_X, GUR2_Y and GUR2_Z to subtract from the PRM_SUSYAW_IN1 channel (the filename of the figure says "GUR1", but that's not true - GUR1 is at the Yend).  All 4 of these channels had been saved at 2kHz, but I downsampled to 256 (I probably should downsample to something lower, like 64, but haven't yet).  There is no pre-filtering or pre-weighting of the data, and no lowpass filters applied at the end, so I haven't done anything to remove the injected noise at higher freqs, which we obviously need to do if we are going to implement this online.

PRM_SUSYAW_subtractUsing_GUR1_xyz.png

If I compare this to Koji's work (elog 8562), at 3.2Hz, he gets a reduction of 2.5x, while this gets 10x.  At all other frequencies, Koji's work beats this, and Koji's method gets reduction from ~0.03Hz - 10Hz, while this is only getting reduction between 0.4Hz and 5Hz.  Also, this does not include actuator noise, so the actual online subtraction may not be quite as perfect as this figure.

  8564   Mon May 13 18:44:04 2013 JenneUpdateLockingprcl angular motion

I want to redo this estimate of where RIN comes from, since Den did this measurement before I put the lens in front of the POP PD. 

While thinking about his method of estimating the PR3 effect, I realized that we have measured numbers for the pendulum frequencies of the recycling cavity tip tilt suspensions. 

I have been secreting this data away for years.  My bad.  The relevant numbers for Tip Tilts #2 and #3 were posted in elog 3425, and for #4 in elog 3303.  However, the data for #s 1 and 5 were apparently never posted.  In elog 3447, I didn't put in numbers, but rather said that the data was taken.

Anyhow, attached is the data that was taken back in 2010.  Look to elog 7601 for which TT is installed where. 

 

Conclusion for the estimate of TT motion to RIN - the POS pendulum frequency is ~1.75Hz for the tip tilts, with a Q of ~2.

  8567   Mon May 13 23:05:51 2013 JenneUpdatePEMGUR1 masses recentered

[Evan, Jenne]

Evan brought the Guralp handheld readout paddle and cables back from the ATF (Zach is using GUR2 and one of the T240s for gyro stuff this week), and we recentered the GUR1 masses.  N/S and Vert were okay (within 0.1 V), but E/W was at -0.5 V, so we set it at zero.  We then plugged the Guralp back in, and turned on the readout box.

There isn't much of a change on the BLRMS on the wall, so it's possible that we weren't actually having any trouble anyway. 

  8568   Tue May 14 01:13:35 2013 JenneUpdate40m UpgradingTRY realigned

Koji noticed that earlier this afternoon the Yarm ASS was working, but then after dinner it was no longer working.  I saw that the ETMY trans camera beam was clipped.  These things precipitated a visit to the Yend station. 

I saw that the beam on the optic that steers the camera beam to the camera was very, very low, almost falling off the optic.  The only mirror which steers to this optic is the harmonic separator which reflects the IR, and transmits the green.  I turned the pitch knobs on the harmonic separator until the beam was roughly centered on all 3 optics between the separator and the camera (BS to QPD, BS to TRYDC and Y1 for camera).  The yaw was fine, so I didn't touch it.

I then adjusted the steering mirror to the camera, and the BS pointing to the DC PD.  I have not touched the BS pointing to the QPD.  Once the beam was on the TRY PD, Koji ran the ASS script, and I recentered the beam on the DC PD.  During this time, Koji had the Yarm triggering using -1 in the POYDC element of the matrix.

The harmonic separator is not mounted in a nice way (I'm assuming that Annalisa is in the middle of things, and she'll get back to it after the green work), so the TRY PD and camera will need to be aligned again, so I didn't do any ASS-recentering-ASS iteration tonight.

The Yarm ASS works nicely again, getting TRY to ~0.89 . 

ELOG V3.1.3-