Keven, Steve

1Y4, 1X1,2,3,4 & 5 instrument racks floor space were cleaned.

 All normal.

As we've been seeing a bit lately, the MC will be locked happily for several hours, but then it will start misbehaving. 

Today, I measured the spots on the MC mirrors, and found that the MC2 spot was quite far off in yaw (about -3.5 cm).  I recentered the MC2 spot, and then (with the MCWFS on), moved MC1 and 3 until their WFS outputs were close to zero (they had gone up to 100+).  In the ~15 minutes since doing that, the MC refl signal is not oscillating like it was, the transmission is up, and the MC has not unlocked. 

To reiterate, I did not touch any settings of anything, except the alignment of the MC mirrors to center the MC2 spot, and then offload the WFS.  Next time the MC starts acting up, we should measure the spots, and roughly center them, before messing with any other settings.  Note however, that this is a ~10 minute procedure (including the fact that one spot measurement takes a little less than 5 minutes).  This need not be a several hour endeavour. 

Koji mentioned to me (and elogged) that he was unsuccessful locking the ALS using the LSC servos.  He suggested I look into this.

So, rather than just looking at the transfer function between POX or POY and the green beatnotes at a single frequency, I did a whole transfer function.  The point was to see if the TF is flat, and if we get any significant phase lag in the transfer from c1als to c1lsc.  (c1als is running on the IOO machine, so an RFM connection is involved in getting it over to the LSC machine.)

In the first figure, I have plotted POX vs. Beatnote_PHASE_OUT (ALS error signal, still in the c1als model), and POX vs. ALSX_IN1 (the ALS error signal, after transfer over to the c1lsc model).  You can see that we have a little phase lead in the blue transfer function, and fairly significant phase lag in the red (red is after transfer over to the lsc model).  In the grand scheme of things, the magnitude is fairly flat, however that is not perfectly true - the peaks seen near 50 Hz and 300Hz are repeatable.  The relative phase lag between the "BEATX" version of the signal in the ALS model, and the "ALSX" version of the signal in the LSC model is 15 degrees at 200 Hz, which corresponds to 33 usec.   

The second figure is the same as the first, except for the Yarm.  The relative phase lag between the ALS version of the error signal and the LSC version is 16 degrees at 200 Hz, which is about 35 usec.

As a side note, before trying any ALS locking, I took a spectrum of the beatnote (in the ALS model) while the arms were locked with IR:

To check things, I made sure that I could lock the Xarm ALS using the old ALS system - I was able to do so.  (Has someone put the "watch" script as a constantly-on thing?  It's kind of nice not to have to turn it on, although we'll need to change it to turn off the LSC versions of the servos eventually). 

Then, I tried locking the Xarm using the LSC system (using only FM5 of the regular LSC-XARM filter bank).  Like Koji, I was not able to acquire lock.  As a next step, I copied all of the LSC-XARM filters into an empty filter module, LSC-XXXDC (the first one on the list underneath LSC-XARM), and copied over the ALS Xarm filters to the LSC Xarm filter bank.  I then tried to acquire lock, but am unable to get it to stay.  Using the ALS system, when you put in a small gain, the beatnote starts to settle down, and as you increase the gain, the beatnote stops moving (as seen on the spectrum analyzer) almost completely.  However, using the LSC system, the beatnote never really stops moving or settles down.  And if I increase the gain, I push the ETM hard enough that I lose green lock.  I have put the regular LSC filters back for now.

Here is a plot from Foton comparing the FM5 filter modules from the LSC-XARM (regular IR locking) and the ALS-XARM servo.  They are pretty different, and have 10 degrees of phase difference at 200 Hz, because 2 of the 3 poles are complex in the LSC version, while the ALS version is just a single real pole.

Anyhow, I am declaring it to be dinnertime, and I plan to return in a few hours. Since I put the regular LSC filters back (since I'm going to have to realign after dinner anyway), the IFO should be in its nominal state if anyone wants to come in and play with it.

Hmm. Wierd. Can you look at the TFs between ETMX-EXC and the error signals so that we can identify which one has these structures.

It looks like its somehow a discrepancy between the TFs of each error signal, because features are similar, and present, in both error signals.

I'm really excited, so I'm posting this, even though I'm still working:

I currently have ALS locked using the LSC system, and have (by hand, coarsely) found IR resonance!  Hooray!

I looked at my error signals, as well as LSC-XARM_IN1 with dataviewer, and noticed that the XARM_IN1 signal was crazy when I was using the ALS signal as the error.  I soon realized that this is because there was a non-zero element in the power normalization matrix, and I'm overriding the trigger.  So, I was trying to divide by zero, and was getting crazy numbers.  After zeroing the power normalization matrix element for the Xarm, the XARM_IN1 signal matched the ALSX_OUT, and I was easily able to acquire lock.

I had already re-transferred over the ALS versions of the filters, so that's what I'm using right now.  Next up (on a 5 minute time-scale) is trying to acquire lock using the regular LSC filters. 

Oh, also, something I hadn't thought of before dinner:  I am setting the offset of the ALSX filter bank such that the output is centered around zero, so that I can lock, since these are not AC coupled servos.

Great. I indeed disabled all of the triggers and the normalization during my trial but in vain.
So I'm curious this is actually because of the filter shape or not.

I am also not able to lock the ALS using the 'regular' LSC filters.  To figure out what filters were doing what, I made several comparison plots from Foton.

The first one is the progression of ALS locking, using the filters from ALS-XARM.  FM5 is always engaged, then FMs 2, 3, 6, 7, and 8, and finally FM 10 (the low frequency boost) is engaged.

The next plot is a comparison between the ALS version of the filters, and the LSC-XARM equivalents. 

Finally, just so I remember which LSC filters do what, I made an equivalent of the first plot, but for the LSC filters.

When I try to lock the Xarm ALS using the regular LSC filters, I'm getting an oscillation somewhere, that grows and eventually knocks me out of lock.  It looks from dataviewer to be in the ~few Hz range, but it's hard to see it in DTT, since I don't stay locked all that long once the oscillation starts.  (If I catch it, I can back off the gain and turn off the servo without losing lock, but if I don't turn off the servo, I inevitably push the ETM too hard and lose green lock to the arm.)  I tried engaging the 3.2 Hz resonant gain filter, and it just makes things oscillate sooner, so that's not a solution with the current filter designs. 

Also, I'm not able to lock the IR using the ALS version of the XARM filters.  I'll have to meditate more on the situation, but the filters seem to be different enough that there's no crossover at this point.

No more progress tonight.  I am still unable to lock the ALS using the regular LSC filters.  I went back to putting the ALS filters into the LSC filter banks, and locked both arms with ALS, and found their IR resonances. I then held them off resonance, and tried to lock PRMI with REFL 55 I&Q, with no success.  Just before locking the arms, I had redone the whole IFO alignment (lock arms in IR, ASS, lock and align MICH, lock and align PRMI), and the PRMI was flashing very nicely.  I'm not sure why I wasn't able to catch lock, except that perhaps 3 or 6 ALS offset counts isn't far enough away from the IR resonance to make the 1f signals happy. The MC lost lock, which I then took as a sign that it's time to go home. (I was hoping to do a quick PRMI + 2arms, and see that we don't lose PRMI lock.  I was going to catch lock with REFL55, then transition to REFL33, although if I had thought about it before the MC lost lock, I would have tried just catching lock with REFL33).

I restored the regular LSC filters for the X and Y arms, and locked the arms in IR just to make sure it's all honkey-dory.  Which, it's not quite.  I don't know why, but right now, neither arm wants its boost (FM9) enabled.  It's part of the restore script that FM9 is triggered along with the rest of the filters, but even if I turn on the filters manually, I can turn on all but FM9, and then when I turn on the boost, the arm falls out of lock. Same behavior for both arms.  Anyhow, they lock, and they seem okay modulo the boost not being able to engage.

 All 40m laser safety glasses are cleaned and measured this morning.  Bring your own safety glasses if you have to enter the 40m IFO room.

Glasses were washed in 1% Liquinox water solution and  their transmission measured at  165 mW,  2 mm OD beam of 1064 nm

 Q EDIT: THIS IS WRONG. I LOCKED PRC ON THE CARRIER

 As Koji measured the other day: MICH and PRCL seem very degenerate in the 3f REFL PDs. 

I'm using this as a motivation to do some simulation in MIST and try to understand the best way to implement the 3F locking scheme. Hopefully my thinking below isn't nonsense...

First, I modeled the PRC with no arm cavities and the estimated cavity length I got with the PRM kick measurement, and looked at the REFL sensing matrix.

This agrees with the observed degeneracy. I then modeled the case of the PRC length that gives coincident SB resonance, again with no arm cavities.

Now there is good separation in REFL165. (REFL33 still looks pretty degenerate, however). This raised the question, "What does the angle between MICH and PRCL in REFL165 do as a function of macroscopic PRC length?" 

• We see ~90 degrees at coincident resonance
• Shortening the cavity, which we did to account for the arms, quickly shrinks the angle
• Presuming we moved to make the cavity 4cm shorter implies we had ~45 degrees between MICH and PRCL in REFL165 before the move. (Is this consistent with earlier observations?)

To me, this implies that locking the PRC on 3F from scratch won't be simple. However, the whole point of the PRC length choice is to have coincident SB resonance when the arms are resonating.

So: even if we're not spot on, we should be relatively close to the PRC length where having arms resonant gives us simultaneously resonant upper and lower sidebands, where MICH and PRCL should be orthogonal-ish. I.e. building up a little bit of IR power in the arms may start to break the degeneracy, perhaps allowing us to switch from 1F to 3F locking, and then continue reducing the CARM offset. 

So, I ultimately want to model the effect of arm power buildup on the angle between MICH and PRCL in the 3f PDs. This is what I'm currently working on. 

So far, I have reproduced some of the RC modeling results on the wiki to make sure I model the arms correctly. (I get 37.7949 m as the ideal arm length for a modulation freq of 11.066134 MHz vs. 37.7974m for 11.065399 MHz as stated on the wiki). Next, I will confirm the desired PRC length that accounts for the arms, and then look at the MICH vs PRCL angle in the REFL PDs as a function of arm power or detuning. 

We need to change several scripts for use with the new ALS-in-the-LSC paradigm:

* Watch arms (to turn off ALS if we lose the beatnote, before pushing optics too hard)

* Find IR resonance

* Offset from resonance

None of these should be difficult, just changing the filter bank names to match the new ones (ex. LSC-XARM rather than ALS-XARM, and LSC-ALSX rather than ALS-OFFSETTER1). 

So far, I have changed the "find resonance" script (ALSfindIRresonance.py).  I believe, in principle, to first order, that my modifications should work, however I have not yet tested the script.  So.  If you use it, watch the output of the script and ensure it's doing what it ought.  I'll check it after the lunch meeting and update this log entry.  (I changed the name of the "OFSFILT" variable, line 26, and also modified line 114.  Both of those lines have comments on how to revert the changes).

I have also changed the "offset from resonance" script (ALSchangeOffset.py).  Again, since I'm not locking right now, I have not tested this script either.  So, pay attention if you need to use it, before I check it.  (I changed the name of the OFSFILT variable, and the check which arm logic around line 37.  Again, both of those lines have comments on how to revert the changes.)

 Q EDIT: THIS IS WRONG. I LOCKED PRC ON THE CARRIER

Koji noted oddities in the sensing matrix results I had gotten; namely that the plots showed REFL33 not changing at all, when we know for a fact that this should not be the case. 

Gabriele lent his eyes to my code, and came up with the idea that the modulation depths I was using were maybe not ideal (.1 for both 11 and 55). This affects REFL33 in that it is not simply Carrier * 33Mhz + 11Mhz * -22Mhz but also 22MHz * 55MHz, etc. 

I got more realistic values from Jenne (0.19 for 11MHz and .26 for 55Mhz) and re-ran the code, with more realistic results. The behavior for 165 has remained the same, but the other signals are more well behaved. 

Moral of the story: the modulation depths affect the 3f signals in a complicated way.

Disregard previous ELOGs, I had the PRC locked on carrier 

Locked on the sideband, the MICH / PRCL angle is much less sensitive to the PRC length, and shouldn't in fact be as degenerate as we've seen in reality. 

So, my simulations no longer provide any reason for the 3F signals to be so degenerate. 

Watch arms script (ALSdown.py) has been modified and now watches the LSC-$ARM filter module instead of the ALS-$ARM filter module. Threshold has been kept the same +/-5000 counts to the ETM suspensions. The script has been tested and works just fine. It exists in the same place scripts/ALS/.

Jenne's modified versions of ALSfindResonance.py and ALSchangeOffset.py were tested and work just fine.

[Jenne, Koji, Manasa, EricQ]

Today we successfully locked the ALS using the LSC system, with filters that are good for both the IR PDH and the ALS locking.  We tried PRFPMI, but were unable to hold PRMI lock while the arms were held with ALS.  We combined the ALS signals into common and differential signals, and successfully transitioned over to a combined set of 1/sqrt(TRANS) signals for the common mode part of the lock (differential stayed with ALS). 

Locking the ALS using filters in the LSC system that are also good for IR PDH

The biggest difference between the ALS and LSC filters were the ones used for lock aquisition. At Koji's suggestion, I made FM5 of the LSC servos (for X and Y arms) the filter needed for ALS locking.  Then, I made FM4 into a combination of old LSC FM4 and FM5, as well as an inverse of the new FM5, so that when both FM4 and FM5 are engaged, the servo shape is the same as the old LSC.  I left the other LSC filters where they were.  I replaced the FM1 +6dB with the combined integrators (really, just gentle DC boosts) for the ALS, since we were never using this +6dB filter module.  The LSC resonant gain filter for the bounce mode also included a resgain for 18.5 Hz.  I don't know what that was for, and it was eating into phase that I needed, so I removed it.

The other filter that changed significantly was the Boost filter.  The ALS system had been using more DC gain than the LSC had.  However, the current ALS boost filter (in FM10 of the old ALS servos) was eating too much phase near my UGF.  So, I scooted the whole boost filter to lower frequencies, to give myself some extra phase margin.  The boost was set to "zero history", "zero crossing", with 0.01 tolerance and an 8 second timeout.  Setting it to zero crossing with a low tolerance, rather than just ramping it on, was the key to engaging the boost.

I had to be so careful about phase margin, since I lost ~15 degrees of phase at 200 Hz from the lag of going through the RFM network.  This was pretty frustrating, but I don't have a better plan yet, save moving the c1als model and ADC to the SUS machine, which has Dolphin access to the LSC.  I may back off my safety margin, and give myself some gain in the boost back at 10Hz, since we are now seeing too much noise at 10Hz in the closed-loop spectra.  I also "cheated" and lowered my UGF from the ~150Hz it used to be in the ALS model, to 100Hz, where I was closer to the top of the new phase bubble.

With the new filter situation, I was able to lock the Xarm (the one I was using for design work) with both IR and ALS.  To lock IR, the "restore" script still works. For the ALS, we should put in a separate "restore" script into the IFO_CONFIGURE screen. 

The ALS locking procedure is as follows:

* Prepare ALS and green locking.  Green locked to 00 mode, alignment all nice, etc, etc.  Beatnote within 100MHz on spectrum analyzer.  If doing both arms, try to get beatnotes on opposite sides of PSL, to keep crossbeatnotes at higher frequencies, and out of the way.

* Turn on Watch script.

* Set LSC parameters (this is where a new restore script will come in handy): 

       * Zeros in RFPD columns of input matrix (i.e. POX and POY).

       * Ones in AUX input matrix elements.

       * Zeros in power normalization matrix rows for arms.

       * All FM triggers for arms set to "Man" for manual.

       * Override main trigger, so that signals are always going through to the servo.

       * Only FM5 engaged in arm servo.

       * Gain of servo set to zero, output on, then engage main LSC master switch.  ETM output on.

* Clear history in phase tracker.

* Check sign of gain using + or - 0.1 in the servo.  You'll know if you got it wrong (the ETM will be kicked, and the beatnote will fly around).  If you didn't get it wrong, you probably got it right.

* Increase gain to about 12 (with correct sign).

* Engage FM1 (gentle DC boost), FM6,7,8 (resonant gains for stack, bounce, roll)

* Wait a few seconds for filters to settle, then engage FM9 (boost).

* Run find IR resonance script.

* Move off resonance by ~36 counts (12 times the +3 script).  This number comes from trying to be completely off the IR resonance, even when the PRMI was locked.

* Do whatever locking (ex. PRMI) you set out to do.

 PRFPMI attempt

After locking both arms with ALS using the LSC system, we attempted to lock the PRMI.  We were able to lock PRMI on REFL55 I&Q, REFL33 I&Q, and REFL55 I&AS55Q before the arms were locked, so we were hoping that we wouldn't have too much trouble.

We found the IR resonance for both arms, then moved off resonance.  Then, restored the PRM.  For REFL55, Koji coarsely turned the REFL 55 demod phase from 16 degrees to 87, while we were locked on the carrier.  After this, I stepped farther and farther from the IR resonance, since at first I found that our transmitted powers were something like 4, rather than almost zero, so the demod phase may not be totally correct.  

We were having trouble, so we locked the PRMI on carrier using REFL55 I and AS55 Q, with 1's in both elements in the input matrix.  MICH gain was about -10, PRCL +0.010.  We used this time to tweak up the alignment of the PRMI.  At some point, Koji tweaked the REFL33 demod phase from 124 to 134 degrees.  Then we switched back to sideband locking.  After some trials with REFL55 I&Q, and REFL55/AS55, we went to REFL33 I&Q.  REFL33I->PRCL was 1.556 in the input matrix, and REFL33Q->MICH was -0.487.  No other elements in the input matrix.  MICH gain was reduced to -6, PRCL gain to -0.020.  MICH FMs 3,6,9 triggered, PRCL FMs 2,3,6,8,9 triggered.  We were able to keep short locks on the order of ~10 seconds, but not longer. We played with every parameter we could think of (alignment being good is one of the most important!), but were not able to keep better lock.  The POP spot is moving around a lot, so the PRCL ASC needs to be examined, hopefully tomorrow.

We started losing the Xarm lock fairly regularly, I'm not sure why, but the Yarm was locked for almost 2 hours straight, held off resonance with ALS!

 ALS Common and Differential, transition to IR control

We set PRMI aside for the rest of the night, and looked at using ALS to control the arms in common and differential modes. 

Regular ALS locking procedures were used (see above), with the exception of the AUX input matrix:

 Since the beatnotes were on opposite sides of the PSL frequency, the common and differential modes look opposite of what you'd expect. 

We then used the regular find IR resonance scripts running simultaneously, which worked really well to find both arms' IR resonance points.

I put a 1 count offset in the Xarm servo (which was our proxy for common mode), although in retrospect this should have been +0.5 in ALSX, and -0.5 in ALSY, so that our signals going through the input matrix were at their zero crossings.  Anyhow, this offset put us at about half fringe on both arms (transmissions were about 0.6). 

Koji set the offsets in the 1/sqrt(trans) filter banks before the input matrix so that they would have zero crossings at this point (avg the IN1, put negative of that value into the offset). 

We then stepped the input matrix values until our common mode (Xarm) row was:

We left the differential (YARM) row alone, so that the ALS system would still be controlling the differential degree of freedom.  The values and sign for the 1/sqrt(trans) signals came from a transfer function of dividing the spectra of each error signal and noting the relative gain and sign.

After we swapped the error signals, we realized that we had to remove the offset from the XARM servo, which is why we should have put the offsets elsewhere in the first place.

Then, Koji took a spectrum, which is attached to this entry.  We note that the ALS signals are strongly correlated, and mostly common. 

To Do List

Going forward, we need to figure out what is going on with the PRMI, and why we're having trouble keeping lock.

We need to redo the PRCL ASC servo, with the anti-oplev trick that Rana mentioned a week or two ago.

We need to investigate the degeneracy of REFL165, now that Q's simulation doesn't justify / explain it. 

EQ UPDATE: Measured it wrong the first time, fixed now.

I measured the spectra of the SQRTINV channels from dark QPDs, with offsets adjusted to imitate various transmission levels. (While the dark noise stays constant in terms of, say, TRX counts, 1/sqrt(TRX) isn't linear, and so the noise coupling depends on the TRX offset). 

I did some calculations to turn this into the equivalent displacement noise when using SQRTINV as an error signal. This depends on where on the fringe you are locking, since the slope of SQRTINV vs. position is not constant, and can only really be treated as linear down to about 1/3 of a line width away from full resonance. In my calculations, I assumed a coupled arm line width of 38pm, and a full transmission of 700 counts in TRX/Y. 

The QPD dark noise RMS when two line widths away (TR = 40) is about 5fm, and only goes down from there. 

I measured the REFL 165 demod board's I/Q separation. 

Our 11MHz signal is currently 11.066092 MHz, so I put a signal to the RF input of the REFL165 demod board at 165.992380 MHz (15*11 MHz + 1kHz), with a signal of -13 dBm.

I then used the SR785 to measure the transfer function between the I and Q output channels. 

I got 82.7 degrees, at -0.64 dB. (I don't remember now if I had I/Q, or Q/I, not that it really matters). So, it seems that the REFL165 demod board has good separation, and at least isn't totally broken.

I noticed that the fb lights on all of the models on the c1lsc machine are red, and that even though the MC was locked, there was no light flashing in the IFO. Also, all of the EPICS values on the LSC screen were frozen.

I tried restarting the ntp server on the frame builder, as in elog 9567, but that didn't fix things.  (I realized later that the symptom there was a red light on every machine, while I'm just seeing problems with c1lsc. 

I did an mxstream restart, as a harmless thing that had some small hope of helping (it didn't). 

I logged on to c1lsc, and restarted all of the models (rtcds restart all), which stops all of the models (IOP last), and then restarts them (IOP first).  This did not change the status of the lights on the status screen, but it did change the positioning of some optics (I suspect the tip tilts) significantly, and I was again seeing flashes in the arms.  The LSC master enable switch was off, so I don't think that it was trying to send any signals out to the suspensions.  The ASS model, which sends signals out to the input pointing tip tilts runs on c1lsc, and it was about when the ass model was restarted that the beam came back.  Also, there are no jumps in any of the SOS OSEM sensors in the last few hours, except me misaligning and restoring the optics.  I we don't have sensors on the tip tilts, so I can't show a jump in their positioning, but I suspect them.

I called Jamie, and he suggested restarting the machine, which I did.  (Once again, the beam went somewhere, and I saw it scattering big-time off of something in the BS chamber, as viewed on the PRM-face camera).  This made the oaf and cal models run (I think they were running before I did the restart all, but they didn't come back after that.  Now, they're running again).  Anyhow, that did not fix the problem.  For kicks, I re-ran mxstream restart, and diag reset, to no avail.  I also tried running the sudo /etc/init.d/ntp-client restart command on just the lsc machine, but it doesn't know the command 'ntp-client'. 

Jamie suggested looking at the timing card in the chassis, to ensure all of the link lights are on, etc.  I will do this next.


The LSC machine isn't any better, and now c1sus is showing the same symptoms.  Lame.

The link lights on the c1lsc I/O chassis and on the fiber timing system are the same as all other systems.  On the timing card in the chassis, the light above the fibers was solid-on, and the light below blinks at 1pps. 

Koji and I power-cycled both the lsc I/O chassis, and the computer, including removing the power cables (after softly shutting down) so there was seriously no power.  Upon plugging back in and turning everything on, no change to the timing status.  It was after this reboot that the c1sus machine also started exhibiting symptoms. 

[Koji, Jenne]

Koji noticed that the time on the front-end detail screens was not correct, and that the GPS time was not matching up between different models.  Koji ran the following on all front-end machines, and on nodus:

sudo ntpdate -b -s -u pool.ntp.org

Now, everything is fine, and every status light on the cds overview screen is green.

 The X -arm fiber is in the high cable tray and it has has  coupler mounts.

 The Y -arm fiber is in the low cable tray and it has no coupler mounts.

 The fibers are only protected at entering and exiting the trays.

 We have only 68 ft spare 1.5"  ID protective plastic tubing.

 Demod boards should be at 90 deg, not 82.7 or 12 or yellow or ****. We should re-inject the RF and then set the D Phase in the filter module to make the signals orthogonal. 165 is a challenging one to get right, but its worth it since the signals are close to degenerate already.

We're exploring some effects which may give some funny macroscopic detuning and cause a near phase degeneracy in the REFL RF signals (see radar plot from Jenne below).

1) Alignment: we centered the oplevs to reduce fluctuations and then tweaked the BS and PRM alignment to build up the power. No significant change in the RF phases of the DOFs.

2) Measuring RAM: we set the dark offsets (by hand since the Masayuki script doesn't really work well anymore) to with 1 counts. We then locked the MC, misaligned the ITMs, and looked at the REFLOUT16 channels using the following command line:

z avg 12 C1:LSC-REFL11_I_OUT16 C1:LSC-REFL11_Q_OUT16 C1:LSC-REFL33_I_OUT16 C1:LSC-REFL33_Q_OUT16 C1:LSC-REFL55_I_OUT16 C1:LSC-REFL55_Q_OUT16 C1:LSC-REFL165_I_OUT16 C1:LSC-REFL165_Q_OUT16

C1:LSC-REFL11_I_OUT16     -12.04
C1:LSC-REFL11_Q_OUT16     -14.34
C1:LSC-REFL33_I_OUT16       0.43
C1:LSC-REFL33_Q_OUT16      -0.28
C1:LSC-REFL55_I_OUT16       2.84
C1:LSC-REFL55_Q_OUT16       5.64
C1:LSC-REFL165_I_OUT16      4.40
C1:LSC-REFL165_Q_OUT16      0.10

So these offsets are small in counts. In meters this corresponds to....less than 3 pm for any of the I signals.

Refl11I = 2.06e-12 meters

Refl11Q = 2.94e-10 meters

Refl33I = 5.28e-13 meters

Refl33Q = 1.07e-11 meters

Refl55I = 2.71e-12 meters

Refl55Q = 3.55e-11 meters

Refl165I = 3.07e-13 meters

Refl165Q = 8.63e-14 meters

3) Next we want to put large offsets into the error points of the loops

4) Change modulation depth

5) Check IMC length (todo for Q/Manasa for Tuesday - Wednesday)

[Jenne, Rana]

We put offsets in the PRCL and MICH loops, and measured sensing matrices for each condition. 

What we found was that PRCL offsets of order 1/20th a linewidth (calibration to be checked tomorrow) would give significant changes in the angles of the REFL signal sensing matrix elements.  We broke MICH lock before we were able to put in a significant enough offset to see the demod phases change.

Because there are so many plots, I've put them together in a pdf. Each page has a set of radar plots for sensing matrix elements.  On the bottom of each page I note what our MICH and PRCL offset values were, and where the data is saved (in the 40m scripts directory). To see the differences, make sure your pdf viewer is set to single-page, not scrolling.

One major thing that we noted was that putting in a PRCL offset also changed the MICH offset.  When we increased the PRCL offset, we saw the AS port get brighter (but not as bright as when we were putting in large MICH offsets). 

Tomorrow, I need to check the calibrations we were using, to see how many meters we were moving the optics.  Also, Q, Gabriele and I need to meditate and do some modelling to figure out why the length offset could be affecting the degeneracy so strongly. 

After speaking with Jenne and Gabriele, I did a little bit of simulating based on my earlier code that looked at the angle of MICH vs. PRCL, just with cavity detuning instead of macroscopic length change.

The zero point in the following plots is with the PRC locked on the sideband. The PRC detuning was done by changing the PRM-BS microscopic length (in terms of phase), and the MICH detuning was done by adding half of the detuning to the BS-ITMY distance, and subtracting half of it from the BS-ITMX distance. 

This plot is in terms of radians, so to roughly relate it to line width, here's a plot of the POP powers as a function of the PRC detuning. 

 And glossing over the MICH offset, here's the PRC offset plots in displacement, rather than radians.

The simulation is actually slightly different now. I now use nominal ITM T values (T=.014) instead of the random R=.99 I had in place. 

(correction: Field Power should be Field Amplitude in the first plot)

 We had our annual safety inspection today.  Our SOPs are outdated. The full list of needed correction will be posted tomorrow.

The most useful found was that the ITMX-ISCT ac power is coming  from 1Y1 rack. This should actually go to 1Y2 LSC rack ?

 Please test this so we do not create more ground loops.

I have recalibrated the REFL signals.

I first adjusted the demod phases until the I-signals lined up with the I-phase in the sensing matrix plot:

I then balanced the ITM drives by pushing on -1*ITMX and +1.015*ITMY, and seeing a minimum of MICH actuation in the I-phase of REFL55 (the PD I was locking with).

I then took a nice long measurement with DTT, and measured the peak heights in I and Q for each REFL diode.  I was driving PRM with 100 cts at 675.1Hz, and ITMX with 1000 cts at 452.1 Hz (and matching ITMY drive, to make pure MICH).  Knowing these numbers, and the actuator calibrations (PRM elog 8255, ITMs elog 8242), I know that I was driving PRCL by ~4.3 pm, and MICH by ~23 pm. 

For the I-phase calibrations, I find the peak height at the PRCL drive frequency, and divide 4.3 pm by that height.  For the Q-phase calibrations, I find the peak height at the MICH drive frequency, and divide 23 pm by that height.

This gives me the following calibrations:

 My calibrated REFL spectra then looks like:

Last night we noticed an excess in the GUR1Z seis BLRMS on the StripTool. It was in the 0.1 - 0.3 Hz band. The rumor in the control room was that "this kind of noise has been showing up at night recently".

AS it turns out, this was not some environmental noise around the 40m at night, but instead its some internal servo oscillation in the GUR1 Z channel. In the Guralp seismometers, each channel is a different mechanical sensor (unlike the STS or T240), so when a single channel gets noisy it doesn't always implicate the others.

My guess is that the oscillation came from the Z channel needing to be recentered. I power cycled the interface box just now. The oscillation had already gone away, but I thought this might reduce the excess noise. Maybe it did, but the effect is tiny. You can see in the oscillation reference that the low frequency noise is high, but in the new trace its still kind of high. Needs to be re-centered correctly with the paddle. Or add a centering button to the interface box.

I have measured the sensing matrix at a variety of PRCL offset values.

During this each measurement, I also took a 20 second average of the POP 2f signals and the ASDC signal:

All of this data was taken during a single lock stretch. 

If / when I do this again, I want to go out to larger offsets.  I won't take as many points, but I do want to see how far I can go before I lose lock, and what the phase separation looks like at larger offset values (this time, I stopped at +700 counts which is about 0.7nm, to start checking the negative values. MC has been unhappy, so I wasn't able to take very many negative offset values.) 

I conclude that these sensing matrix measurements do see changes in the phase separation with PRCL length offset (what we saw / said yesterday), but that they do not line up with Q's simulation from this afternoon in elog 9671.

The simulation says that we shouldn't be seeing large phase changes until we get out to several nanometers, however the measurement is showing that we get large phase chnages with picometer scale offsets.  Yesterday, Rana and I said that the offsets due to RAM were small (of order picometer), and that they were therefore likely not important (elog 9668).  However, now it seems that the RAM is causing significant length offsets which then cause poor MICH/PRCL phase separation.

To Do List:

* Confirm MIST simulation with Optickle.

* Look at sensing matrix data pre-lockins (in the raw sensors).

* Check that there is no clipping anywhere in the REFL path (at least out of vacuum), and that the beam is sufficiently small on all 4 REFL diodes.

* Calculate the new PRC g-factor with the new length.

I've asked Manasa and Q to have a look at the MC in the morning.  Rana and I have found it to be slightly uncooperative in relocking after a lockloss.

We have found that just letting the autolocker go doesn't seem to work very well, and sometimes the MC just doesn't want to re-lock.  Closing the PSL shutter or disabling the autolocker for a few minutes (5ish) doesn't do anything, but leaving it closed for a long time (30 ish minutes) helps a lot.  The MC  will relock immediately after a nice long break. 

 The MC is happy (but only for this tiny snapshot in time and most probably will go dysfunctional again as it has been for several months, as of this writing)

....fb timing issue happened again.

I thought that it was the thing that Koji and I saw the other day, where it was individual front end computers that had lost ntp sync, since it wasn't every core on every computer that was red, but reconnecting to the ntp server on c1lsc didn't do anything.  I then tried reconnecting to the ntp server on fb, and that fixed things right up.  Annoying.

[Jenne, Vivien]

We had an oplev tuning party this afternoon.  What we have learned is that we don't have a lot of intuition yet on tuning loops.  But, that was part of the point - to build some intuition. 

I took responsibility for the PRM, and Vivien took ITMX.  I think, in the end, all changes were reverted on ITMX, however Vivien took some data to try and make a computer-generated controller.  Before we got started, I locked and aligned the PRMI, and we centered the PRMI-relevant oplevs.

I moved my "boost bump" around a bit, to do more at higher frequencies, but had to sacrifice some of the "oomph", since it was starting to eat up too much phase at my UGF of ~8Hz.  I also made the stack resonant gain higher Q and lower height so that it didn't eat so much phase.  In the end, I have 25 degrees of phase margin, which isn't really great, but I do win a factor of 2 around 2 and 3 Hz.  Also, now I'm able to engage the 3.2 resgain at all, whereas with the previous filter shape I was not able to turn it on.

Maybe it's because I really want it to have helped, but I feel like the POP spot isn't moving as much when I'm locked on PRMI sidebands as it was earlier (we were seeing a lot of low frequency (few Hz) motion).  So, I think I did something good.

 Linus-1, Nodus and others  ac cords can be moved over to new blank yellow extension cord with multiple recepticals.

 Remove two red extension cords going to Smart UPS

  in order to Win in Loop Tuning, you must draw a cartoon of the cost function on the whiteboard before starting. Some qualitative considerations from our Workshop:

1. We want to use the oplev servo to reduce the motion of the mirror in the frequency band where the Oplev is quieter than the mirror, w.r.t. inertial space.
2. We can estimate the true mirror motion by some simple stack / pendulum model and compare it to the Oplev noise (not the dark noise). There are several contributions to the mirror angular motion due to the cross-coupling in the stacks and pendula.
3. Below ~0.2 Hz, we think that the oplev is not the right reference, but this is not quantitative yet.
4. The high frequency noise in the OPLEV ERROR is definitely electronics + shot noise.
5. We cannot increase the gain of the loop without posting some loop measurements (Bode + steps). Also have to post estimates of how much PRCL noise is being introduced by the Oplev feedback. Oplev feedback should make less length noise than what we have from seismic.

Give us a cost function in the elog and then keep tuning.

...yet again.

lsc and sus needed mxstream restarts after I restarted the ntp on fb.

We need to correctly setup crontab or rc.local for the frontend machines.

I wanted to check how the refl signals looked like.
I decided to measure the demod phase where PRCL and MICH appear, one by one.

The method I used is to actuate PRCL or MICH at a fixed frequency and rotate the demod phase such that
the signal at the actuating frequency disappears.

For the PRCL actuation, PRM was actuated by the lock-in oscillator with the amplitude of 100cnt.
For MICH, the ITMX and ITMY was actuate at the amplitude of 1000cnt and 1015cnt respectively.

The script I used was something like this

ezcaread C1:LSC-REFL11_PHASE_R
ezcaservo -r C1:CAL-SENSMAT_CARM_REFL11_Q_I_OUTPUT C1:LSC-REFL11_PHASE_R -g 100 -t 60
ezcaread C1:LSC-REFL11_PHASE_R

"11" should be changed according to the PD you want to test.
"Q" should be changed to "I" depending on form which quadrature you want to eliminate the signal

The option "-g" specifies the servo gain. This specifies which slope (up or down) of the sinusoidal curve the signal is locked.
Therefore, it is important to flip the signal angle 180degree if a negative gain is used.

Note: Original phase settings before touching them

REFL11  - 19.2
REFL33   135.4
REFL55    48.0
RELF165 -118.5

Here in the measurement PRMI was locked with AS55Q (MICH) and REFL55I (PRCL)


Without no serious reason I injected a peak at 503.1Hz. This peak is not notched out by the servo. There may have been
some residual effect of the feedback loops.

PRCL: By elliminating the peak from the Q quadrature, we optimize the I phase for PRCL.

REFL11,   minimize PRCL in "Q", gain, -1, -19.3659 deg
REFL33,   minimize PRCL in "Q", gain, -1, 132.813 deg
REFL55,   minimize PRCL in "Q", gain, -1, 20.9747 deg
REFL165, minimize PRCL in "Q", gain, -1, -119.004 deg

MICH: By elliminating the peak from the I quadrature, we optimize the Q phase for MICH.
If PRCL and MICH appears at the same phase, the resulting angles shows an identical number.

REFL11,   minimize PRCL in "I", gain, -1, -28.4526 deg
REFL33,   minimize PRCL in "I", gain, -1, 65.9148 deg
REFL55,   minimize PRCL in "I", gain, -1, 12.4051 deg
REFL165, minimize PRCL in "I", gain, -0.1, -143.75 deg

Then, the signal frequency was changed to 675Hz where the notch filters in the servo is active.

PRCL: By elliminating the peak from the Q quadrature, we optimize the I phase for PRCL.

REFL11,   minimize PRCL in "Q", gain, 1, -19.5224 deg
REFL33,   minimize PRCL in "Q", gain, -1, 135.868 deg
REFL55,   minimize PRCL in "Q", gain, 1, 48.5716 deg
REFL165, minimize PRCL in "Q", gain, 1, -122.398 deg

MICH: By elliminating the peak from the I quadrature, we optimize the Q phase for MICH.
If PRCL and MICH appears at the same phase, the resulting angles shows an identical number.

REFL11,   minimize PRCL in "I", gain, -10, -73.7153 deg
REFL33,   minimize PRCL in "I", gain, -10, 135.5 deg
REFL55,   minimize PRCL in "I", gain, 10, -2.55868 deg
REFL165, minimize PRCL in "I", gain, -5, -156.135 deg

This is just a test of the REFL channels for the arms signals. ETMX or ETMY were actuated.

YARM

REFL11, minimize ETMY in "Q", gain 100 => C1:LSC-REFL11_PHASE_R = 145.694
REFL55, minimize ETMY in "Q", gain 100 => C1:LSC-REFL11_PHASE_R = -60.1512

XARM

REFL11, minimize ETMX in "Q", gain 100 => C1:LSC-REFL11_PHASE_R = 142.365
REFL55, minimize ETMX in "Q", gain 100 => C1:LSC-REFL55_PHASE_R = -68.6521

I have installed Dropbox on the 40m workstations, using the foteee account. 

I put it in /users/Dropbox.

As a side note, I did the install while sitting on Pianosa, but since I put the folder on the mounted hard drive, I think we should be able to use it from any workstation, although I have not yet confirmed this.

 I was getting the Y Arm ready for Eric Q's loss measurements and so I looked at the noise and loop shape. The loop shape was strange:

You can see that the gain margin is too low at high frequencies. That's why we have >15 dB of gain peaking. Way too much! I think this is from Masayuki and Manasa increasing the phase margin at some point in the past. I lowered the gain by 3 dB from 0.1 to 0.07 and now the awful gain peaking is less. But what about the low frequency gain? Is there enough?

I calibrated the OUT channel with 14 nm/count (1/f^2) with a Q = 10 pole pair at 1 Hz. The error signal is done to cross over at 180 Hz. It looks like the resonant gain at 25 Hz is a little too much and the in-loop RMS is 10 pm. Jenne says the linewidth is ~1 nm, so this seems sort of OK. Except that the LIGO-I DARM RMS had to be <0.1 pm for ~the same linewidth. Do we need to do better before trying to bring the arms into resonance?

I've remove FM1 and FM8. I put the RollRG of FM8 into the BounceRG and renamed it BounceRoll. Also changed the Y-arm restore so that RollRG and the 5,5:0,0 are no longer triggered automatically since the double integrator was overkill and we already have a 1:0 in FM2. I also lowered the peak gain for the roll mode RG from 30 to 10 dB because it was also overkill. We've gained a few more degrees at the UGF.

 Keven, Steve

1X6, 1X7 and 1X9 instrument racks floor space were cleaned today

Not a whiteboard, but here's a cartoon of my oplev cost function cartoon.  For the "maximize this area" and "minimize this area", I plan to use ratios between the curves, and then give those ratios to a sigmoid function.

I measured the arm cavity losses as Kiwamu did way back in ELOG 5074.

I used the same logic as the ../scripts/LSC/armloss script, but did it manually. This meant:

1. Lock and ASS-Align both arms. 
2. Misalign the ITM of the arm that I'm not measuring, to get its spot off of AS
3. Take 10 seconds of ASDC_OUT data while the arm is locked. 
4. Unlock, misalign ETM of arm of interest, take another 10 seconds of ASDC_OUT
5. Relock, run ASS, goto #3

Analysis was done similar to ../scripts/LSC/armloss.m. This uses the nominal T values (.014 and 15e-6) to estimate the input power from the unlocked ASDC data, and the cavity reflectivity from the locked ASDC / input power. Then, loss is calculated by:

• Pin = ASDC(unlocked) / R1
• Rc = ASDC(locked) / Pin
• rc=sqrt(Rc), etc.
• Loss = 1 - (( 1 / r1r2)) * ( 1 - t1^2 r2 / (r1 - rc)) ^2

I did this for pairs of locked / unlocked data stretches. (Subsequent pairs maybe have slightly different things going on, but each pair was taken within a minute or so of each other)

Unfortunately, during the X Arm measurements, the MC was misbehaving with large REFL fluctuations, so I don't have confidence the results.

The Y Arm data seems fine, however. 

The Y arm loss is 123.91 +/- 10.47 ppm 

(Trial-to-Trial fluctuations dominate the fluctuations within each trial by far, and their standard deviation is what I report as the random error above)

This seems roughly in agreement with old values I've seen in the ELOG. I'll remeasure the x arm tomorrow during the day. Here's a plot showing the ASDC values of the Y Arm measurements. 

At today's meeting, it was suspected that these noise levels were far too low. (ELOG 9660)

I've attached the math I did to get the conversions, as well as the dark noise SQRTINV spectra at various imitated transmission values and the python script that does the converting. 

I've gone over my calculations, and think they're self-consistent. However, a potential source of misestimation is the treatment of the Lorentzian profile simply existing with the coupled arm line width (38pm). The conversion to m/rtHz is directly proportional to the line width of the transmission peak, so if it is much broader in practice (because of imperfect PRC buildup or something), the noise will be that much worse.

I'm open to any other feedback about what I may have done wrong!

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

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

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

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

I locked the arms using ALS error signals and the LSC filter modules. But when I try to acquire CARM and DARM using ALS, the arms lose lock when the matrix elements ALSX to Yarm and ALSY to X arm reach -/+0.9

What I did:

1. ALS locking of arms
(i) Found arm beat notes
(ii) Input matrix POX and POY elements set to '0'
(iii) Aux matrix elements ALSX to Xarm and ALSY to Y arm set to '1'
(iv) Power normalization matrix elements for TRX and TRY set to '0'
(v) Triggers for arm lock over ridden and the FM triggers were set to 'manual'
(vi) Arm servo gains set to '0'
(vii) All but FM5 were disabled
(viii) Phase tracker history reset and servo actuation set to ETMs
(ix) Servo gain increased in steps (+/-10 for the arms)
(x) FM1, FM6, FM7 enabled (see note 1 below)
(xi) FM9 enabled

Arms were locked with ~2000Hz rms

2. CARM and DARM locking
(i) Scanned the arms for IR resonance
(ii) Moved off-resonance (Stepped arm servo offsets by 30 counts)
(iiI) Stepped matrix elements ALSY to X arm and ALSX to Y arm ezcastep C1:LSC-PD_DOF_MTRX_6_29 +-0.1 C1:LSC-PD_DOF_MTRX_7_28 +0.1

Whenever the matrix elements reached -/+0.9, the arms were kicked out of lock. I don't see anything obvious as to why this is happening even after nearly 10+times of redoing.

Notes:
1. I found the filters for the arm servos different for X and Y. FM1 and FM8 were missing in one of the filter modules. Jenne remembered Rana modifying and removing the unnecessary filters in one arm. We put back FM1 (low pass filter) which might not be necessary for PDH lock but is necessary for ALS. FM8 is now added to FM7.
2. To self : Check ALS Y arm power outlets (60Hz frequency comb seen in the error signal)