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ID Date Author Type Category Subjectup
  8039   Fri Feb 8 17:41:34 2013 JenneUpdateLockingPRMI work


 [Yuta, Jenne]

After much tweaking of the alignment using TT1, TT2 and PRM sliders, we were able to get a TEM00 mode locked with the half PRC!

PRCL gain is -0.010

FM4, 5 are always on.  FM2,3,6 (boosts and stack res-gains) are triggered to come on after the cavity is locked.

We see a little clipping of POPDC, even though there are 2 BSs in the beam path, to dump 50% and then 67% of the beam.  But it's not so much that we can't align. 

REFLDC goes from 28.5 to 24.5, so we don't have great visibility.

Please watch our awesome video of the cavity, where we demonstrate that the half cavity is stable:

The cavity is flashing for the 1st 15 sec, then locks.  Upper right is REFL, Lower right is POP, Upper left is back of the Faraday, Lower left is MC2F.   Note that we definitely see some not so beautiful modes flashing, but most of that is due to the half cavity length and thus greater degeneracy of modes.  Jamie is posting a HOM plot presently.


The beam is moving way more than it should be.  Right now the PRM oplev is not coming out of the vacuum, since the flat test mirror mount is obstructing it.  However, as we saw with other half-cavity tests, turning on the PRM oplev helps, but does not completely eliminate the beam motion.  We should consider putting oplevs on one of the passive TTs, at least temporarily, so we know what kind of motion is coming from where.

  8042   Fri Feb 8 19:39:02 2013 KojiUpdateLockingPRMI work

It seems that the cavity trans looks much better than before. Cool.

At least the optical gain is ~x5 of the previous value. This means what we did was something good.

Looking forward to seeing the further analysis of the caivty...

  8043   Fri Feb 8 20:05:15 2013 JenneUpdateLockingPRMI work

I fixed up the POP path so that there is no clipping, so that Yuta can take a cavity mode scan.

  6886   Thu Jun 28 00:50:48 2012 yutaUpdateLockingPRMI work started, commissioning plan

My goal for tonight was to lock PRMI,
 grasp the current situation by my eye,
  and capture some images using Sensoray.

They are done, but what are we going to do to solve the problem? The beam looks terrible than I had expected.

What I did:
  1. DC output of POP55 PD was plugged out from 1Y2 rack, so we plugged it in.

  2. Aligned POP beam to POP25 PD and moved POP camera position at ITMX table.
  3. Mis-aligned PRM and SRM, aligned both arms, aligned FPMI as usual.

  4. Mis-aligned PRM and ETMs, aligned MI and locked MI.

  5. Aligned PRM, and carrier locked PRMI. PRM alignment was not saved since June 7, so slider values which give good alignment was pretty much drifted (~0.4 in C1:LSC_PRM_(PIT|YAW)_COMM).

  6. Took some images of POP, REFL, AS during PRMI lock.


PRMI commissioning plan:
  From the beam shape at POP, REFL, and AS, the problem clearly comes from the mode-matching, including clipping, longitudinal mismatch, and alignment mismatch. Koji's idea of flipped-PRM seems reasonable, so I think we should better measure something to prove this.
  To prove this,

  1. Simulate what the beam look like in POP, REFL, AS if PRM was flipped. Compare them with actual captured images. I need to study on unstable cavities.
  2. Calculate power recycling gain and compare.
  3. Misalign PRM and capture the image of primary, secondary, ... reflections like Koji did in elog #6421. Measure the beam sizes of these reflections using some image analysis(Python Imaging Library? Is there anyone good at this?) and calculate PRM curvature.
  4. Can we do come characterization by making PRM-ITMY cavity? ITMX will be mis-aligned, BS will be the loss port to PRC.
  5. Beamspot on POP, REFL, AS looks woblby when PRMI is locked. Why?
  6. Open the vaccum chamber and see PRM. Simple.

  Any other ideas? I have to lock PRFPMI, at least, by July 13!

  6887   Thu Jun 28 01:44:57 2012 KojiUpdateLockingPRMI work started, commissioning plan

To be fair, this is Kiwamu's idea. And nothing is reasonable before it is confirmed quantitatively.


Koji's idea of flipped-PRM seems reasonable, so I think we should better measure something to prove this.

  6888   Thu Jun 28 15:21:02 2012 ranaUpdateLockingPRMI work started, commissioning plan


 Cycling the vacuum is easy. Why not vent starting Thursday evening and pop the doors on Friday morning? Inspect on Friday and pump on Monday morning.

  8992   Fri Aug 9 22:51:37 2013 KojiUpdateLSCPRMI(sb) lock recovered

PRMI(sb) lock was recovered

PRMI lock

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

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

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

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

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

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

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

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

- We are ready to implement ASS for PRM

Demod phase adjustment

- Shook PRM at 580Hz / 100cnt

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

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

- Minimized the PRCL signal coupling in the signals.

- The resolution of the adjustment was ~1deg.

Locking test with PRM/BS

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

This just worked nicely.

Today's locking parameters:

PRMI(sb) lock:

MC Trans: 17500
POP110I (in lock): 150

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

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

Demod phases:

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

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

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

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

  10068   Thu Jun 19 00:02:48 2014 JenneUpdateLSCPRMI+2 arms recovery

Arms locked in comm and diff with ALS. PRMI locked with REFL33 I&Q while arms off resonance. Having trouble reducing CARM offset, even to get to arm powers of 1.

After Manasa installed the new Xgreen PD, Koji looked at the PSL table alignment with me.  I saw only a very weak beatnote with the X BBPD, even though I could see the beatnote on the Y PD from the leakage of the X beam to the Y PD  (Yend shutter was closed, so just PSL and X greens were on the table).  I had thought that my near-field and far-field alignments were pretty good (actually, I checked them, but didn't feel that I needed to tweak them since Manasa did the alignment this afternoon).  Anyhow, it was just a matter of tweaking up the alignment a bit, and then the X beatnote got up to about -25dBm at a few tens of MHz.  I am starting to question myself if the other BBPD is broken, or if I just not well enough aligned.  Anyhow, the spare is in, we can still have a look at the previous X BBPD, but it may be okay, and it's just me embarrassing myself by not catching an alignment problem.

Anyhow, after the X beat was found, I was able to (on my first try) lock the arms using ALS comm and diff.  (I already had a nice strong Y beatnote, so that didn't need finding, other than temp adjustment of the end laser).  I ran the carm_cm_up.sh script, and it did everything nicely.  I did a quickie check of the phase tracker loop gains, but that should be redone in the morning.

PRMI was a little reluctant to lock, so I played around with the MICH and PRCL gains, but didn't really find any combination that was any better than the usual (+0.8 for MICH, -0.04 for PRCL as I had last night, although I needed to reduce the PRCL gain back to -0.02 to eliminate loop osc). 

After an arm lockloss, I relocked just the PRMI and used awggui to put a line into C1:LSC-PRM_EXC to check the RF PD phasing.  I changed REFL33 from 133.5 to 138.5, and REFL 165 from -142.5 to -152.5.  I didn't think that REFL11 needed changing, and I didn't check REFL55.  I also checked that I could lock PRMI without arms, using both REFL33 and REFL165 - they seemed about the same to me, both stable.  REFL33 has 1's in the input matrix, and I was using 0.07's for REFL165.  The demod phase adjustment didn't really improve PRMI locking while the arms were held off resonance, even if I moved the arms even farther from resonance (usually we do 3nm, I went out to 5nm to see if that helped - it didn't).  I tried REFL165 locking, but that wasn't any good either.  I tried using REFL165 with the arms held off resonance, but that didn't seem to catch at all (at least with REFL33 I was getting short lock blips). 

Anyhow, of the 3 or 4 times that I caught REFL33 PRMI lock and tried to reduce the CARM offset, only one time did I even get to arm powers of about 1 (CARM digital offset of -0.1, with CARM held on sqrt transmission signals), and then it didn't stay for more than a few tens of seconds.  The other few times, it broke lock on the way up to arm powers of 1. 

So, carm_cm_up.sh works pretty well, although perhaps the arm powers of 1 offset reduction needs to be a little slower.  PRMI doesn't catch and hold lock very easily with REFL33, and even less so with REFL165.  It may be useful to try catching lock with REFL11 or 55, and doing a transition over to 3f.  No real progress forward, but we're pretty much recovered.


  9251   Thu Oct 17 18:29:28 2013 KojiUpdateLSCPRMI+2arm attempt (not really yet)

While Manasa, Jenne, and Masayuki are working on the preparing the interferometer, I write the elog for them.

- 6PM-ish: X and Y arms were was locked. They were aligned with ASS.

- PRMI was locked. The PRM was aligned with ASS.

- Jenne went into the lab and aligned the PRM ASC QPD.

- Jenne also aligned all of the oplev spots except for the SRM.

- 6:40PM Then, Manasa and Masayuki checked the out-of-loop stability of the arms.
The X and Y arms have the rms of 2.2kHz and 600Hz, respectively.
The X arm is significantly worse than the Y arm.

Masayuki saved the plot somewhere in his directory.

- 7:20PM X beat: 41.2MHz, Y beat: 14.8MHz

- 7:22PM PRMI locked POP110 115-120 

- 7:30PM Lost lock of everything. Start over. Taking the arm alignment.

- 7:45PM start the 2nd trial. PRMI+one arm ready.

- 8:00PM explosion! Lost lock.

- 8:30PM The Xarm ALS is not stable anymore. It loses the control in ~10sec.
We are investigating the out-of-loop stability of the Yarm ALS.
(i.e. Look at the beat note error signal while locking the Yarm with the IR PDH)

  9413   Tue Nov 19 17:47:17 2013 JenneUpdateLSCPRMI+2arms attempt

So far this afternoon, I have redone the IFO alignment, locked both arms with ALS, moved both arms off resonance, locked PRMI, and started bringing one arm back to resonance. 

The alignment was really not good, which I knew yesterday, but the ASS wasn't working yesterday.  I hand-did the alignment, and tried locking, which was easier with the slightly better alignment.

I locked both arms with ALS, found the resonances, and then moved them off resonance using Masayuki's scripts.

I then restored the PRM alignment, and locked the PRMI. 

I started bringing the Yarm back, but I kept losing lock when I got to about 0.1 transmission.

After losing lock several times, I switched over to looking at the ASS. I have figured out the problem, and fixed it.  The ASS for the arms now works again.

Looking at the StripTool plots of the lockin outputs for each arm, it was clear that the "L" traces were their usual size, but the "T" traces, which are demodulated versions of the transmission DC PDs, were tiny.  I investigated in the model, and the answer is obvious:  both the LSC and the ASS get the transmission information directly from the end sus computers.  Since we recently moved the normalization gain for the transmission diodes into the SUS models from the LSC model, this means that the ASS was seeing a differently sized signal than it had in the past. 

To fix this, I put a gain into the T_DEMOD_SIG filter banks for all 8 lockins that use info from the transmission DC PDs.  I used 1/g , where g is the gain that is in the C1:SUS-ETM#_TR#_GAIN channels.  For TRX, that number is -0.003, and for TRY that number is 0.002 .  So, in the .snap file that is used when turning on the ASS, I have given the Xarm lockins a gain of -333, and the Yarm lockins a gain of 500.  I chose this place, because the only thing that has happened to the signal until this point is a bandpass, so the rest of the servo gains can remain the same. 

I tested the ASS, and it works just like it used to.  I let it run, and align all of the optics, then I misaligned by a small amount each of the ETMs, saw that the lockin output values changed, and then were servoed back to zero.  So, it seems all good. 

  8871   Thu Jul 18 15:55:31 2013 JenneUpdateLSCPRMI+Y arm ALS Sensing Matrices

Last night, I took sensing matrix data at various different offsets for the Yarm.  The sensing matrices I measured were of the PRMI, while the Yarm was (a) Held off resonance, (b) Held at ~50% peak power, and (c) Held on resonance.

The dither lines were clear in the MICH and PRCL spectrum, so I think I'm driving hard enough, but something else seems funny, since clearly the REFL165 I and Q signals were not completely overlapping last night.  If they were, we wouldn't have been able to lock the PRMI using REFL 165 I&Q.

Anyhow, here's the data that was taken.  Data folder is ...../scipts/LSC/SensingMatrix/SensMatData/

Yarm off resonance, SensMat_PRMI_1000cts_580Hz_2013-07-18_012848.dat


Yarm at ~50% resonance, SensMat_PRMI_1000cts_580Hz_2013-07-18_013937.dat


Yarm on resonance, SensMat_PRMI_1000cts_580Hz_2013-07-18_013619.dat



  8872   Thu Jul 18 16:30:08 2013 KojiUpdateLSCPRMI+Y arm ALS Sensing Matrices

Hmm. I agree that something was funny.
Let's take the matrix without the arms and confirm the measurement is correct.

  8867   Thu Jul 18 02:21:41 2013 KojiUpdateLSCPRMI+Y arm ALS success!

[Koji, Jenne, Manasa, Annalisa, Rana, Nic]

PRMI locked using 3f signals and Y arm brought to resonance using ALS



- After we checked the functionarity of the Yarm ALS, both arms were locked with the IR, and aligned by ASS.

- Disengaged the LSC feedback. Approximately aligned the PRM.

- Recorded the current alignment biases. Turned off all of the oplevs.

- Went into the lab, aligned all of the oplevs on the QPDs (except for the SRM).

- Check the locking of the PRMI.

- Once it is locked, go into the lab again and align the POP QPD.

- Check everything of the PRMI LSC/ASC works.

- Misalign PRM by 0.2

- Lock the arm again. Run ASS again.

- Miaslign ETMX.


- Lock the Xarm with green. Adjust the beat freq between 30-50MHz.

- Reset Phase Tracker history.

- Check if there is any offset for the ALS. If there is, adjust it to zero.

- Stabilize the arm with the ALS. We should check the sign of the servo before it is cranked up to the nominal.

- Confirm if the offset FM has LPF (30mHz LPF).

- Run excastep for the ALS offset until we find the TEM00 resonance of the IR

- Record the offset at the resonance.

- Step back by 5 count (=100kHz)


- Started from the offset of -5.

- Aligned the PRM and the PRMI was locked by REFL165I(x0.8)nadQ(x0.2).

- PRM ASC engaged

- Moved the offset to -4 by ezcastep C1:ALS-OFFSETTER2_OFFSET +0.01,100 -s 0.1

- Moved to -3, -2, -1.5, -1. During the sweep PRCL/MICH gain was tweaked so that the gain is reduced.
  Nominal locking gain was PRCL x+2.5/MICH -30 . During the sweep they were +2.2 / -12
  PRCL FM2/4/5 ON, Later FM3/6 turned on and no problem.

- Moved to -0.9, .... , and finally to 0.


- Automation of the PRMI+one arm

- PRMI locking with BS/PRM

- Better sensing matrix

- PRMI+two arms

- Use of the DC signals form the transmission monitors. (High power /low power transmon).



  8868   Thu Jul 18 10:47:21 2013 JamieUpdateLSCPRMI+Y arm ALS success!

AWESOME!  You guys rock.

  8869   Thu Jul 18 10:50:54 2013 LisaUpdateLSCPRMI+Y arm ALS success!


[Koji, Jenne, Manasa, Annalisa, Rana, Nic]

PRMI locked using 3f signals and Y arm brought to resonance using ALS

Fantastico! :-)

  8879   Fri Jul 19 12:02:18 2013 manasaUpdateLSCPRMI+Y arm ALS success!

Data retrieved using getdata (30 minutes trend) saved at


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

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

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

PRMI sensing matrix:


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


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

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

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

My settings for the night:

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

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

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

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

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

Power normalization:  None, for any degree of freedom.

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

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

Other notes: 

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

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



  9460   Thu Dec 12 21:30:52 2013 JenneUpdateASCPRMI-relevant oplevs centered

The ITM oplevs were pretty close to the edge of their ranges, and none of the oplevs have been centered in a while, so I centered ITMX, ITMY, BS, PRM after having done alignment (arms, then PRMI).

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


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

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

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

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

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

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

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

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

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

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

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

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

  9687   Mon Mar 3 22:21:43 2014 KojiSummaryLSCPRMIsb locked with REFL165I&Q

Successful PRMIsb locking with REFL165I/Q

My previous entry suggested that somehow the REFL165 signals show reasonable separation between PRCL and MICH, contrary to our previous observation.
I don't know what is the difference now. But anyway I took this advantage and tried to lock sideband resonant PRMI.

REFL165I was adjusted so that the signal is only sensitive to PRCL. Then REFL165I and Q were mixed so that the resulting signal shows.
(Next time, we should try to optimize the Q phase to eliminate PRCL and just use the I phase for PRCL.

At first, I used AS55Q for lock acquisition and then switched the MICH input matrix to REFL165.
Later I found that I can acquire PRMI just turning on AS55Q without turning off REFL165.

The REFL165 MICH signal had an offset of 15cnt. The lock was more robust and the dark port was darker once the MICH input offset was correctly set.

Turn on AS55Q only / or AS55Q + REFL156I/Q
Once it is locked and all of the FMs are activated, give -15.0OFS to MICH.
Turn off AS55Q.

Input ports:
AS55       WHTN: 21dB  demod phase -5.5deg
REFL165 WHTN: 45dB demod phase -156.13deg

Input matrix:
AS55Q x1.00 MICH
REFL165I x-0.035 + REFL165Q -0.050 MICH

REL165Q x+0.14

MICH POP110I 100up/10down / FM Trig FM2/3/6/7/9 35up 2down 5sec delay
PRCL POP110I 100up/10down / FM Trig FM2/3/6/9 35up 2down 0.5sec delay

MICH OFS -15.0 / Gain -10 / Limitter ON
PRCL OFS 0 / Gain -0.02 / Limitter ON

Output matrix:
MICH ITMX -1.0 / ITMY +1.0


  9753   Wed Mar 26 14:54:32 2014 KojiSummaryLSCPRMIsb locked with REFL165I&Q again

[Manasa, Eric, Koji]

PRMIsb was locked with REFL165I&Q.

- Aligned the arms with ASS. The misaligned ETMX and ETMY

- Configured PRMIsb with IFO_Configure screen

- Immediately PRMIsb was locked with REFL55I&Q

- Checked the REFL165 phase in terms of the REFL165Q vs PRCL. It was already well adjusted at -82.5deg. We tuned the phase a bit more and got -83.5deg.

- With DTT, relative gain between REFL55I and REFL165I was measured. REFL165I is about x10 higher than REFL55I and has the same sign.

- The transition of PRCL with the input matrix was just easy.

- With DTT, relative gain between REFL55Q and REFL165Q was measured. REFL165Q is about x3 higher than REFL55Q and has the same sign.

- The transition of MICH was flakey, but after careful adjustment of the PRM alignment, ~10s lock was achieved. It seemed that the PRM alignment fluctuation
  was bug enough to unlock the interferometer.

- Eric went into the lab and aligned all of the oplevs except for the SRM's one.

- Now the lock with REFL55 and also with REFL165 became more robust. Less MICH offset and darker AS port.

Input ports:
REFL55   WHTN: 45dB demod phase +45.0deg
REFL165 WHTN: 45dB demod phase -83.5deg

Input matrix: for acquisition:
REFL55I x 1.0 -> PRCL
REFL55Q x 1.0 -> MICH

Input matrix: PRCL Transition:
REFL55I x 1.0 + REFL165I x 0.0 -> x0.5 + x0.0 -> x0.5 + x0.05 -> x0.3 + x0.05 -> x0.2 + x0.05 -> x0.1 + x0.05 -> x0.0 + x0.05

Input matrix: MICH Transition:
REFL55Q x 1.0 + REFL165Q x 0.0 -> x0.5 + x0.0 -> x0.5 + x0.3 -> x0.3 + x0.3 -> x0.2 + x0.3 -> x0.1 + x0.3 -> x0.0 + x0.3

MICH POP110I 100up/10down / FM Trig FM2/3/9 35up 2down 5sec delay
PRCL POP110I 100up/10down / FM Trig FM2/3/6/9 35up 2down 0.5sec delay

MICH OFS 0 / Gain 1.3 / Limitter ON
PRCL OFS 0 / Gain -0.04 / Limitter ON

Output matrix:
MICH PRM -0.2625 / BS 0.5

  9754   Wed Mar 26 21:51:42 2014 ericqSummaryLSCPRMIsb locked with REFL165I&Q again

Incidentally, while messing around with transfer functions and sensing matrix elements this evening, I was able to sideband lock straight onto REFL33 I&Q.  The settings were all identical to Koji's ELOG, with the following differences:

Input ports:
REFL33   WHTN: 30dB demod phase +125.5deg (tweaked from 135.5 to minimize MICH in I)

Input matrix:

REFL33I x +1.0 -> PRCL
REFL33Q x +3.0 -> MICH

MICH OFS 0 / Gain 1/ Limitter ON (Oscillations occurred at 1.3)
PRCL OFS 0 / Gain -0.04 / Limitter ON

Output matrix:

MICH ITMX -1.0 / ITMY 1.0


  9758   Fri Mar 28 17:22:55 2014 KojiSummaryLSCPRMIsb locked with REFL165I&Q again

While I'm looking at the PRM ASC servo model, I tried to use the current servo filters for the ASC
as Manasa aligned the POP PDs and QPD yesterday. (BTW, I don't find any elog about it)

I found no issue for locking PRMIsb with the REFL165I&Q signals if the PRM ASC is employed.
See this entry for the IFO settings.

It is just stable. The IFO is ready for the arm scanning.

=== ASC setting ===

PRCL_PITCH: FM1/3/9 x-0.004
PRCL_YAW: FM1/3/9 x-0.001

The PRM OPLEV has to be off when the PRM ASC is engaged. Actually, it turned out that we don't need OPLEV for locking.

  15983   Thu Apr 1 00:50:06 2021 gautamUpdateSUSPRMdiag

I spent some time investigating the PRM this evening, trying out some of the stuff we discussed in the meeting.

  1. I used one of the SUS lockin oscillator to drive the butterfly mode (UL=+1, UR=-1, LL=-1, LR=+1) of the optic, @4.45 Hz, Amplitude=450cts (Oplev loops were engaged during the measurement).
  2. Used the sensing matrix infrastructure to demodulate the Oplev PIT/YAW error signals, using the other lockin channel (so that oscillator is just for demodulation, it doesn't actuate on the suspension).
  3. The digital demod phase was adjusted to put all of the demodulated signal in one ("I") quadrature.
  4. The balancing of the coils was perturbed by adding small amounts of the naive PIT (YAW) DoF to the pringle-mode actuation, while simultaneously looking to minimize the demodulated signal in YAW (PIT). 

Basically, my finding tonight was that I could not improve (make the pringle mode actuation witnessed by the Oplev QPD smaller) by +/- perturbing the butterfly actuation with of 0.05%, 0.5% and 1% of PIT (I didn't try YAW, or other values of PIT, as none of these seemed to do any good). It seems highly unlikely that the existing coil gains (these come after the output matrix) and the actual coil/magnet pairs are so perfectly tuned, so there must be something wrong with my method. I'll try more combos tomorrow. Separately, I verified that the naive PIT (YAW) moves the optic mainly, i.e. to the eye), in PIT(YAW) as judged by the REFL spot on the camera and the readback of the Oplev QPD.

For this work, I made a few changes to filter banks:

  1. Added 2Hz wide BPs centered around 4.45 Hz to the "SIGNAL" FM of the BS and PRM suspension lockins.
  2. Added 100mHz LPFs to the I and Q demodulated outputs.
  3. Made a copy of Kiwamu's perturbcoilbalance_fourosem.py (in scripts/SUS) to add little bit of PIT/YAW to the pringle actuation.

I noticed that the filters/switch states/gains for LOCKIN1 and LOCKIN2 are not consistent within either PRM or BS suspension, or across suspensions. Several filter INs/OUTs were also disabled - something for the SUSdiag team to note, whenever this is scripted, the script should check that the signal is indeed making it end-to-end.

  7921   Sat Jan 19 16:02:28 2013 ranaOmnistructureElectronicsPS cleanup

During our 'Women in Physics' tours today, we were reminded that there are several bench power supplies being used as permanent inside.

Some are being used to power PZTs, AOMs, VCOs, RFPDs, etc. On Wednesday, after the meeting, we will all go inside and remove one and replace it with a fused, professional wiring to the rack power supplies. The temporary ones must be removed.

  9467   Fri Dec 13 16:34:20 2013 SteveUpdateVACPS will be replaced next week


Instrument rack power supplies checked and labeled at present loads.

The vacuum rack Sorensen is running HOT! Their is only 0.3A load at 24V There is plenty of space around it.

It is alarming to me because all vacuum valve positions are controlled by this 24V

 The temperature went down to room temp with temporary fan in the back. Voltage and current are stable.

Regardless, it will be replaced early next week.

  10151   Tue Jul 8 09:02:02 2014 AkhilUpdateElectronicsPSD Plots for different sampling times of the Frequency Counter

 Although there were few timing issues with the FC and the Raspberry Pi at the lowest sampling time of the FC (0.1s) even after adding an external trigger circuit, it turned out that most of these issues are not prevalent at higher sampling times(>0.5 s)(narrow peaks of PSD seen for higher sampling times). Rana suggested me to look at the PSD plots at different sampling times of the FC so that we can decide which would be the optimal sampling time to work with the FC before replacing the spectrum analyzer. I took the measurements with the setup discussed in my previous elog(http://nodus.ligo.caltech.edu:8080/40m/10129) . However, the  noise of the R Pi- FC interface should be taken care of (I will discuss it with my mentors).

Attached are the plots at 100 MHz carrier frequency at  different sampling times of the FC( 0.1s, 0.2s, 0.3s, 0.5s, 1s) (pdfs and code attached in a zip file)

RXA: Put all the plots in a single PDF file and use the same axis limits for all plots so that its easy to compare.      (Attached in PSD.pdf)



  11458   Wed Jul 29 11:15:21 2015 JessicaSummaryLSCPSDs of Arms with seismometer subtraction

Ignacio and I downloaded data from the STS, GUR1, and GUR2 seismometers and from the mode cleaner and the x and y arms. The PSDs along the arms have the most noise at frequencies greater than 1 Hz, so we should focus on filtering in that area. The noise levels start dropping at around 30 Hz, but are still much higher than is seen at frequencies below 1 Hz. However, because the spectra is so low at frequencies below that, Wiener filtering alone injected a significant amount of noise into those frequencies and did not do much to reduce the noise at higher frequencies. Pre-filtering will be required, and I have started implementing a pre-filter, but with no improvements yet. So far, I have tried making a bandpass filter, but a highpass filter may be ideal in this case because so much of the noise is above 1 Hz. 

  81   Wed Nov 7 16:07:03 2007 steveUpdatePSLPSL & IOO trend
1.5 days of happy psl-ioo with litle bumps in C1:PSL-126MOPA_HTEMP
  14645   Fri May 31 15:55:16 2019 gautamUpdateALSPSL + X beat restored

Coupling into the fast axis of the fiber:

The PM couplers I bought require that the light is coupled to the fast axis. The Thorlabs part that Andrew ordered, and which Anjali was using for the MZ experiment, was the opposite configuration, and so the input coupler K6XS mount was rotated to accommodate this polarization. The HWP was also rotated to cut the power into the fiber. I undid these changes. Mode-matching is ~65% (2.42mW/3.70mW) which isn't stellar, but good enough. The PER is ~15dB (ratio of power in fast axis to slow axis is ~40), which I verified using another collimator at the output, and a PBS + two photodiodes. Again isn't stellar but good enough.

EX laser temperature adjustment:

Rana adjusted the temperature of the main laser to 30.61 C. According to the calibration, the EX laser temperature needed to be ~32.8 C. It was ~31.2 C. I made the change by rotating the dial on the front panel of the EX laser controller. Fine adjustment was done using the temperature slider on the ALS screen. With an offset of ~+610 counts, I found a beat at ~80 MHz.

First look at PM beamsplitters:

From my initial test, the beat amplitude was stable to my moving of the fibers yes. The NF1611 DC monitor reports 2.6 V DC with only the EX light, and 3.15 V DC with only the PSL light. So I should probably cut the PSL power a little to improve the contrast. Assuming the 10 kohm DC transimpedance spec can be believed, this means the expected signal level is 4*sqrt(260uA * 315uA)*700V/A ~0.8 Vpp, and I see ~0.9 Vpp, so roughly things add up (this is actually more consistent with an RF transimpedance of 800V/A, which is maybe not unreasonable). The RF amps for routing this signal to the delay line has been borrowed for the 2um frequency noise experiemnt - I will reacquire it today and check the ALS noise performance.

So overall, I am happy with the performance of the current iteration of the BeatMouth.

  14519   Fri Apr 5 11:49:30 2019 gautamUpdateALSPSL + X green beat recovery

Since we haven't been using it, the PID control was not enabled on the doubling oven on the PSL table (it is disabled after every power outage event in the lab). I re-enabled it just now. The setpoint according to the label on the TC200 controller is 36.9 C. The PID paramaters were P=250, I=200, D=40. These are not very good as the overshoot when I turned the control on was 44 C, seems too large. The settling time is also too long, after 10 minutes, the crystal temperature as reported by the TC200 front panel is still oscillating. I can't find anything in the elog about what the nominal PID parameter values were. The X end PID seems much better behaved so I decided to try the same PID gains as is implemented there, P=250, I=60, D=25.

With the Ophir power meter, I measured 60mW of IR light going into the doubling oven, 110uW green light coming out, for a conversion efficiency of 2.7%/W, seems pretty great.

Next, I went to EX and tweaked the steering mirror alignment - I wasn't able to improve the transmission significantly using the PZT sliders on the EPICS screen, and the dither alignment servo isn't working. It required quite a substantial common mode yaw shift of the PZT mirrors to make GTRX ~ 0.5. 


I plan to recover the green beat note as well and digitize it using the second available DFD channel (eventually for the Y arm) - then we can simultaneously compare the the green and IR performance (though they will have different noise floors as there is less green light on the green beat PDs, and I think lower transimpedance too).

  6324   Mon Feb 27 14:35:37 2012 JenneUpdateGreen LockingPSL Beat Setup

Xarm is aligned for both IR and green. 

Here is a photo of the beam paths of the PSL beat setup.  I want to make sure that the X-green BBPD sees a nice beam from both the PSL and the Xarm, without disturbing the currently working Y setup.  I keep getting confused with all the beamsplitters, especially the green PBSes, which operate at ~56deg, not 45deg, so I made a diagram.


  1013   Wed Oct 1 02:47:53 2008 ranaUpdatePSLPSL ERR & LODET: Too much offset
Looks like there is an anomolous mixer offset correlated with the increase in the LO level. This may be leading to crazy offset locking in the FSS and too much coupling from ISS to FSS.
  3488   Mon Aug 30 18:22:00 2010 ranaSummaryPSLPSL Enclosure is UNSTABLE

The lifting and resetting of the BLUE PSL enclosure has made it unstable somehow. When I push on it a little it rocks back and forth a lot.

Steve, please look into what's happening and stiffen it if you can. Its too unstable right now.

  10777   Thu Dec 11 09:11:18 2014 manasaUpdatePSLPSL FSS Slow actuator

I am not sure if people have been noticing it lately; but the slow actuator on the PSL FSS has been railing up quite often these days. I found it at >0.8 and as high as 1.5 on certain occasions before resetting it to nominal zero.

It could be because the PMC alignment needs to be tweaked. The night crew should consider doing this before starting to lock.

  4258   Mon Feb 7 21:23:11 2011 ranaConfigurationPSLPSL FSS Temperature Sensor Interface box removed

I noticed that the RMTEMP channel was spiking myteriously when Kiwamu opened the PSL door. We found out that the LEMO connectors would intermittently short to the case and cause ~1 deg steps in the temeprature.

We have removed the case and examined it. Not only were the connections to the box intermittent, there was a cold solder joint inside on an unsecured flying add-on opamp. The whole thing is a giant hack.

PK was the last person to work on this box, but I'm sure that he wouldn't have left it in this state. Must be gremlins.


The LEMO connectors on the front are the ones touching. The LT1021 is the badly soldered part.

  17605   Fri May 26 15:04:12 2023 JCUpdatePSLPSL Fans Replaced

We Changed The Fans on the PSL

To start, the part Koji ordered is 259-1818-ND from DigiKey. This is a Maglev fan from SUNON that should give us less noise. We have 3 spare replacement fans in case these go bad which are stored in the ___ Cabinet along the Y arm (This will be updated once I find a suitable storage spot for the part.)

Starting the replacement process.

Removing the PSL 

    1. Our first step to doing this was to prepare for removing PSL. We began by doing a 60s MC WFS Relief. This will allows us to turn off WFS and close the PSL Shutter next. This is to prevent a large kick once we place the PSL back in its place. 
    2. Went to the PSL and mushed the off button and turned the key. After this, begin by removing the external fan which is shown in elog 17595. After, continue by unplugging the cables from the back beginning with the power cable. Attachment #1 shows the original positions of the cables connected before removing any. Keep in mind, DO NOT TO TOUCH THE KNOBS. If the inputs are changed, this will throw off the beatnotes of the AUX lasers.
        a. There is a black plug at the bottom with a screw hat is hard to reach. Be very patient taking this off because the position of the cable blocks a screqwdriver from untightening the screw. 
        b. A second person should be on the other side of the table to push the module back into arm's reach. Also to make sure the module does not slide back and fall. 
    3. After removing the module, bring into the control room and place onnto the workbench. Make sure all of the red lights are off and the PSL table is closed properly.

Changing the Fan 
    1. We removed the top cover of the module and opened it all up. Similar to what is shown in elog 17452.
        a. Keep in mind to wear a grounding wristband when working on this.
    2. After removing the old fans and attempting to install the new ones, the holes did not line up correctly (Shown in Attachment #2). To accomodate for this, we used 6-32 screws which gave us just enough slack to fit in all 4 corners.
    3. Ones the fans were bolted down onto the aluminum plate, I soldered the cables to connecting the fan cable to the cables those of the original PSL fans.
    4. Next I used heat shrinks to cover the bare soldered areas and placed the fans into the module. 
    5. We tested the fans by plugging intp the PSL and turning the key. The fans turned on nicely and we proceeded to put it module back together.

Placing the PSL back in its place. 

    1. We place the PSL back into its original spot and began to connect the cables. Make sure the Power cables is put in LAST. 
    2. After the module was put back, we DID NOT put the external fan back into its place. This is to see if the fans which were installed are good enough to maintain the PSL.
    3. Turn the key and press the on Button.

The noise from the external fan is no longer appearing as shown in attachment #3. The PSL has been on for ~2 hrs now and has not turned off. It seems that the fans are doing their jobs well. 


  13223   Thu Aug 17 08:42:27 2017 SteveUpdatePSLPSL HEPA

The PSL HEPA was running noisy at 100V   The bearing is wearing out. I turned it down to 30V It is quiet there.

  16058   Wed Apr 21 05:48:47 2021 ChubUpdateGeneralPSL HEPA Maintenance

Yikes!  That's ONE filter.  I'll get another from storage.

  16065   Wed Apr 21 13:10:12 2021 KojiUpdateGeneralPSL HEPA Maintenance

It's probably too late to say but there are/were two boxes. (just for record)


  16002   Tue Apr 6 21:17:04 2021 KojiSummaryGeneralPSL HEPA investigation

- Last week we found both of the PSL HEPA units were not running.

- I replaced the capacitor of the north unit, but it did not solve the issue. (Note: I reverted the cap back later)
- It was found that the fans ran if the variac was removed from the chain.
- But I'm not certain that we can run the fans in this configuration with no attendance considering fire hazard.

@3AM: UPON LEAVING the lab, I turned off the HEPA. The AC cable was not warm, so it's probably OK, but we should wait for the continuous operation until we replace the scorched AC cable.

The capacitor replacement was not successful. So, the voltages on the fan were checked more carefully. The fan has the three switch states (HIGH/OFF/LOW). If there is no load (SW: OFF), the variac out was as expected. When the load was LOW or HIGH, it looked as if the motor is shorted (i.e. no voltage difference between two wires).

I thought the motors may have been shorted. But if the load resistance was measured with the fluke meter, it showed some resistance

- North Unit: SW LOW 4.6Ohm / HIGH 6.0Ohm
- South Unit: SW LOW 6.0Ohm / HIGH 4.6Ohm (I believe the internal connection is incorrect here)

I believed the motors are alive! Then the fans were switched on with the variac removed... they ran. So I set the switch LOW for the north unit and HIGH for the south unit.

Then I inspected the variac:

  • The AC output has some liquid leaking (oil?) (Attachment 1)
  • The AC plug on the variac out has a scorch mark (Attachments 2/3)

So, this scorched AC plug/cable connected directly to the AC right now. I'm not 100% confident about the safety of this configuration.
Also I am not sure what was wrong with the system.

  • Has the variac failed first? Because of the heat? I believe that the HEPA was running @30% most of the time. Maybe the damage was already there at the failure in Nov 2020?
  • Or has the motor stopped at some point and this made the variac failed?
  • Was the cable bad and the heat made the variac failed (then the problem is still there).

So, while I'm in the lab today, I'll keep the HEPA running, but upon my taking off, I'll turn it off. We'll discuss what to do in the meeting tomorrow.


  1057   Mon Oct 20 09:45:56 2008 steveUpdatePEMPSL HEPA on
The PSL HEPA filter was turned on.
It should be running all times.
The 0.5 micron particle count is up to 20,000 this morning.
  11453   Tue Jul 28 15:06:27 2015 SteveUpdateIOOPSL HEPA turned on


  15627   Wed Oct 14 18:16:27 2020 gautamUpdateGeneralPSL HEPA-->50%

Per Koji's suggestion, I turned the PSL HEPA Variac to 50% just now, so that the power load through the burnt electrical cable is reduced by 75%.

  16966   Thu Jun 30 19:04:55 2022 ranaSummaryPSLPSL HEPA: How what when why

For the PSL HEPA, we wanted it to remain at full speed during the vent, when anyone is working on the PSL, or when there is a lot of dust due to outside conditions or cleaning in the lab.

For NORMAL conditions, the policy is to turn it to 30% for some flow, but low noise.

I think we ought to lock one of the arms on IR PDH and change the HEPA flow settings and plot the arm error signal, and transmitted power for each flow speed to see what's important. Record the times of each setting so that we can make a specgram later

  10658   Fri Oct 31 15:34:47 2014 SteveUpdatePSLPSL HEPAs are running again


The PSL HEPA stopped working while it was running at 80%. I have closed the PSL enclosure.

Steve is working to fix this.

 The Variac burned out and it was replaced. Each unit was checked out individually. HEPA -north is still noisy at full speed.

  1107   Mon Nov 3 09:59:47 2008 steveUpdatePSLPSL HEPAs turned on
The psl enclosure HEPAs were tuned on.

Loose paper drawing was found on the psl inside shelf.
This can fall down into the beam and ignite a tragedy.

Thanks for the color coded correction. My spell checker is not reliable
  2191   Fri Nov 6 09:17:53 2009 steveOmnistructurePEMPSL HEPAs turned on

The PSL enclosure HEPAs turned on at 30%

ELOG V3.1.3-