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ID Date Author Type Categoryup Subject
  8215   Sun Mar 3 22:16:46 2013 JenneUpdateLSCLSC whitening triggering started

[Jenne, Annalisa]

We have started working on writing the c-code to parse the LSC input matrix, to see which PD is used for what degree of freedom, and to output a trigger for the PD.  The code is in ..../isc/c1/src, and there is a little block in the LSC code to the left of the triggering stuff.  Right now, the output of the c-code just goes to some temporary EPICS channels, so that we can see if things are working before we actually implement it.  At this time, there is no change to how the LSC model runs.

I can't figure out a bug in my c-code though.  Right now it's all commented out, so that the LSC model would start, but if I try to sum all of the elements in an array, the model compiles fine, but it won't start running.  I'm going to ask Jamie about it tomorrow.  I have a less-tidy backup plan if we can't get this figured out.

If I have time on the IFO to check that this works tomorrow, I expect another few hours of work (2?  3?), and then we'll have whitening filter triggering.

  8217   Mon Mar 4 09:55:33 2013 ranaUpdateLSCLSC whitening triggering started

  How about posting a logic flow diagram? Is the idea to trigger only on the power signals to determine the lock state? Is the hysteresis going to be done in the same way as the main filter bank triggers?

  8230   Tue Mar 5 06:27:14 2013 yutaUpdateLSCintra-cavity power dependence on mirror misalignment

I measured intra-cavity power dependance on mirror misalignment.
Intra-cavity power of PRC in PRMI degrates roughly 20 % when there's 0.5 mrad 5 urad misalignment. (edited by YM)
Currently, PRMI lock is not so stable, so it is hard to do this measurement and error bars are huge.

Measurement method:
  0. Align the cavity and lock.
  1. Misalign one optic and measure oplev output value and intra-cavity power.
  2. Also, dither the optic in pitch or yaw in 8.5 Hz and get demodulated amplitudes at 8.5 Hz of oplev output and intra-cavity power using tdsdmd.
  3. Misalign the optic again and do the same things.

  1. gives intra-cavity power dependence on mirror misalignment directly, but 2. should give better S/N because of dithering.


Scripts:
  /opt/rtcds/caltech/c1/scripts/dither/dithergfactor.py does these things, and ./plotgfactor.py plots the result.
  They work quite well, but it should be made better so that

  - it checks if the cavity is locked
  - automatically change the oplev calibration factor for each optic
  - automatically adjusts the region and modulation amplitude
  - read data with better error evaluation

  etc...


PRMI alignment:
  Y green looks like it drifted quite a lot somehow. If we start aligning Yarm to Y green, we get AS and POP beam at different spot on camera compared with last week. Also, TRY and TRX only goes as high as ~0.7. Since we have A2L now (elog #8229), let's start using Yarm spot positions as input pointing reference.


PRMI locking details:
  Same as in elog #8212, but I changed gains in the lock acquisition mode.

  == PRMI carrier ==
  MICH: AS55_Q_ERR, AS55_PHASE_R = -12 deg,  MICH_GAIN = -0.2, feedback to ITMX(-1),ITMY(+1)
  PRCL: REFL55_I_ERR, REFL55_PHASE_R = 70 deg, PRCL_GAIN = 1.0, feedback to PRM

  I made gainx5 in LSC_MICH filter bank so that it increases the overall gain when locked by trigger.
  I also made gainx0.3 in LSC_PRCL filter bank so that it reduces the overall gain when locked by trigger.


Result for PRC in PRMI:
  For PRMI, I couldn't done dithering method because dithering takes time to measure and I could not hold PRMI locking during the measurement.
  Below is the result when reading just the DC values. Mirror angle is calibrated by oplev (elog #8221). Error bars are huge because of beam motion mainly in yaw.


PRM in pitch: PRM_PIT_20130305a.png    PRM in yaw:PRM_YAW_20130305b.png


Results for the arms:
  For the arms, I could do both in DC and dithering. Below are the results, but ITMs misalignments are not calibrated because we don't have calibrated oplev yet.
  Results for the arms can be used to verify this method because we know g-factors of the arms from mode scan.


ITMX in yaw: ITMX_YAW_20130305.png    ITMY in yaw: ITMY_YAW_20130305.png



By the way:
  I found C1:SUS-ITMY_LSC_GAIN is somehow set to be 2.895 recently. I think this should be 1.0. Maybe this is why we had actuation imbalance in ITMs(elog #8212).


Next:
 - more stable lock
 - calibrate ITM oplevs to apply this method to the arms
 - derive g-factor from these measurements
 - measure PRM angular motion spectra using calibrated oplev

  8234   Tue Mar 5 18:36:27 2013 JenneUpdateLSCLSC whitening triggering started

More effort at debugging the LSC whitening. 

Today I tried moving things over to the c1tst model, which runs on the y-end computer, but I crashed c1iscey.  I rebuilt the TST model to a known good state, then cycled the power on c1iscey, and the computer came back up fine. 

I have now backed off and am just writing the code inside a little wrapper script, so that I can just compile and test the code completely independent from the realtime system.  Then once I get all the bugs out, I can try again installing on the actual system.

Still, there are no changes to the functionality of the c1lsc model.  There will not be until I get the c-code for matrix parsing debugged.

The logic, in non-diagram form (I'll make a diagram, but so you can read without waiting):

*** C-code

* Inputs is an array of degree of freedom triggers, the same schmidt triggers used for main LSC locking. (This means it also uses the same thresholds as main triggers.  Side note, now that the WAIT command (see below) works, I want to change the filter module triggers to use the same main trigger, and then just wait a specified time before turning on.)

* Parse the LSC input matrix (internal to the c-code).

     * This tells you which photodiode is being used to control which degree of freedom.

* Multiply rows of the LSC input matrix by the degree of freedom triggers (the same trigger as the main LSC triggers, which is a schmidt trigger).

     * This gives a matrix, where non-zero elements indicate that a photodiode is supposed to be used for a degree of freedom, AND that DoF has been triggered (is locked or has flashed).

* Sum along the columns of the matrix.

     * If a column has a non-zero element, that means that that PD quadrature is used, and has been triggered (by any DoF).

* Apply OR to I and Q quadratures of each PD. 

      * Since the phase rotation happens after whitening and dewhitening, if either I_ERR or Q_ERR is requested (used and triggered), we need to turn on the whitening for both channels.  I am hopeful that this doesn't cause problems for cases when we want to use both quadratures of a PD to control 2 degrees of freedom, but I haven't yet put much thought into it.  COMMENTS WELCOME on this point.

*  Output of c-block is array of PD triggers.  So if either AS11I or AS11Q is triggered, output a "1" for the first element, which corresponds to AS11, etc.

*** LSC model

* Give GoTo/From flag for each DoF trigger to the mux of inputs.

* Go through c-code

* Demux outputs into GoTo/From flags, one per PD (one flag for AS11, one for AS55, and one for ASDC...DC elements count separately, even though they're derived from the same physical PD).

* For each PD, trigger flag goes through WAIT c-code

   * This allows you to define a wait time, in seconds, with an EPICS variable. 

   * Starts counting the wait time as soon as it receives a "1".  Resets counter each time it receives a "0".

    * Output of wait function is ANDed with the current (non-delayed) trigger.

         * This allows for cavity to flash, but if it's not still locked after the wait time, don't actually flip any switches.

* Use delayed ANDed trigger to flip the FM1 switch on both the I and Q filterbank for that PD.

  8235   Tue Mar 5 23:00:08 2013 yutaUpdateLSCYarm and PRC g-factor from misalignment measurement

I fitted intra-cavity power dependance on mirror misalignment plot with parabola to get the g-factor.

  Y arm (tangential) g = 0.44 +0.01 -0.01  (measured value before was 0.3765 +/- 0.003 elog #6938)
  PRC (sagittal)       g = 0.97 +0.01 -0.04 (expected value is 0.939 elog #8068)
  PRC (tangential)   g = 0.96 +0.02 -0.05 (expected value is 0.966 elog #8068)

Error bars are just statistical errors from the fitting. Estimated systematic error is ~0.04 (or more).
Here, I assumed PR2/PR3 to be flat to make the calculation simple. I assumed PRC to be curved PRM - flat ITM cavity, and Y arm to be curved ETMY - flat ITMY cavity.

g-factor calculation:
  Intra-cavity power decrease can be written as

dP/P = (dx/w0)**2 + (dt/a0)**2

where dx and dt are translation and tilt of the beam axis introduced by mirror misalignment. w0 is waist size and a0 is divergence angle (= lamb/(pi*w0)).

  When considering a flat-curved cavity with cavity length L, dx and dt can be expressed as;

(dx)    1  ( L*g     L ) (a2)
(  ) = --- (           )*(  )
(dt)   1-g ( -(1-g)  0 ) (a1)


using misalignments of mirrors(a1,a2). Here, mirror1 is curved, and mirror2 is flat. See Kakeru document /users/OLD/kakeru/oplev_calibration/oplev.pdf for derivation.

  So, power decrease by flat mirror misalignment can be expressed as

dP/P = pi*L/lamb * g/(1-g)/sqrt(g*(1-g)) * a2**2

  For curved mirror is

dP/P = pi*L/lamb * 1/(1-g)/sqrt(g*(1-g)) * a1**2

  We can derive g-factor by measuring dP dependance on a1/a2.


Script:
  My script lives in /opt/rtcds/caltech/c1/scripts/dither/gfactormeasurement/plotgfactor.py.
  It least fitts data with parabola (scipy.optimize.leastsq) and gets g-factor value from bisection (scipy.optimize.bisect).


Result:
  Below are the plots of fitted curves.

ITMY_YAW_20130305_DC.pngPRM_PIT_20130305a_DC.pngPRM_YAW_20130305b_DC.png


Systematic effect:
  [oplev calibration] We noticed QPD rotation when calibration oplevs (elog #8232). ~5 deg of rotation makes 10% of systematic error to the oplev calibration and this introduces ~0.04 of error to g-factor values. This

  [oplev linear range] Oplev linear range is ~100 urad, so this is OK.

  [assumption of flat PR2/PR3] Result here doesn't tell you g-factor of PRM itself, but some "effective g-factor" of PRM/PR2/PR3 combination. We can compare with FINESSE result.

  [intra-cavity power drift] If there's significant intra-cavity power drift during the measurement, if effects parabola fitting. We can make this affect small by sweeping the mirror alignment in both direction and take average.


By the way:
  I kept getting PRC g-factor of something like 0.999999 because I had power normalization mistake in my calculation. My script worked for Yarm because TRY is already normalized.
  Also, I was multiplying the oplev calibration factor wrong last night (see elog #8230).

Next:
  - Compare with FINESSE result.
  - Is this g-factor enough? Is this presicion enough? Calculate from mirror angluar motion.
  - More stable lock of PRMI.
  - Try dithering method to measure g-factor to check consistency and also to study systematic effect.

  8237   Wed Mar 6 02:46:20 2013 ManasaUpdateLSCPRMI locking for g-factor measurement

 [Yuta, Manasa]

PRMI alignment procedure for carrier locking has been kept the same except that a couple of issues that have persisted are now taken care of.

We were able to keep PRMI locked for over a minute (POPDC measures 2200) .

1. Trigger levels to MICH and PRCL for PRMI locking have been changed
Whenever we enabled LSC controls to lock PRMI, ITMY moves haphazard if PRM is not aligned. This is because of the low trigger levels of POPDC which keeps MICH triggered all the time while we align PRM. Increasing POPDC trigger (Upper level : 1000 and Lower level:20) for both MICH and PRCL solved this problem and resulted in a more stable ITMY. Also this has stabilized locking greatly if the alignment is fair enough.

2. C1:SUS-ITMY_LSC_GAIN reset
Quoting Yuta's elog "  I found C1:SUS-ITMY_LSC_GAIN is somehow set to be 2.895 recently. I think this should be 1.0. Maybe this is why we had actuation imbalance in ITMs(elog #8212)."
This has been reset to 1.0 and it has not affected PRMI locking.


Mystery

1. Filter module (FM1) on PRCL and MICH show significant delay while enabling and disabling.

2. I tried to fix PMC alignment (PMC trans was 0.76). I was not able to get PMC trans more than 0.79.
PMC has been this way since yesterday.

3. MICH is still bright when locked (ASDC_OUT reads 0.08 for dark and 2.0 for bright). We suspect it is because of the AS55_I error offset that persists even after running LSCoffsets script.

4. PRMI shows some dither at 3Hz when locked.
POPDCspec_PRMIlocked.png

  8239   Wed Mar 6 09:44:29 2013 KojiUpdateLSCPRMI locking for g-factor measurement

- What about normalizing POPDC to indicate the carrier recycling gain?

- When you align the PMC, confirm FSS SLOW DC is around zero. Some region of the slow thermal actuation makes the laser source emit at multiple frequencies. In the case, the cavity visibility get worse.

- Do you guys think we can determine if the TT is longitudinally quiet enough? Is there any comparison between the simple Michelson and the PRC motion in m/rtHz?

  8242   Wed Mar 6 18:14:33 2013 ManasaSummaryLSCCalibration of BS, ITMX and ITMY actuators

[Yuta, Manasa]

Measured actuator response between 50Hz and 200 Hz in (m/counts).

BS     = (20.7 +/- 0.1)    x 10 -9 / f2

ITMX = (4.70 +/- 0.02) 
x 10 -9/ f2

ITMY = (4.66 +/- 0.02)
x 10 -9/ f2

Actuator response differs by 30% for all the 3 mirrors from the previous measurements made by Kiwamu in 2011.

Calibration of BS, ITMX and ITMY actuators

We calibrated the actuators using the same technique as in Kiwamu's elog.

A) Measure MICH error

1. Locked Y-arm and X-arm looking at TRY and TRX.
2. Misaligned ETMs
3. Measured  MICH error using ASDC and AS55_Q err (MICH_OFFSET = 20 - to compensate for offset in AS_Qerr which exists even after resetting LSC offsets)

MICHerrCalibration.png

B) Open loop transfer function for MICH control

1. Measured the transfer function between C1:LSC-MICH_IN1 and C1:LSC-MICH_IN2 by exciting on  C1:LSC-MICH_EXC.
MICH filter modules used for measurements(0:1 , 2000:1, ELP50). ELP50 used so that actuation signals above 50 Hz are not suppressed.

MICHOLTF.png

C) Calibration of BS/ ITMX/ ITMY actuators

1. Measured transfer function between actuation channels on BS/ ITMX/ ITMY and C1:LSC-AS55_Q_ERR.

actcalibITMBS.png
 

  8248   Thu Mar 7 01:43:35 2013 yutaUpdateLSCcalibrated MI differential length spectra

Free swing MI differential length is 86 nm RMS and residual length when locked is 0.045 nm RMS(in-loop).
Looks very quiet. Comparison with PRMI is the next step.

Openloop transfer function:
  OLTF of simple MI lock using AS55_Q_ERR as error signal and ITMs as actuators is below.
  UGF ~ 90 Hz, phase margin ~ 40deg
  I added 16 Hz resonant gain to suppress bounce mode.
LSCMICHOLTF_MI.png

MI differential length spectra:
  Below. Calibration was done using calibrated AS55_Q_ERR and actuator response(elog #8242)
MImotion.png


  Expected free swing is calculated using

x_free = (1+G)/G * A * fb

where G is openloop transfer function, A is actuator response, fb is feedback signal(C1:LSC_ITMX/Y_IN1) spectrum. I used A as simple pendulum with resonant frequency at 1 Hz, Q = 5. Since free swing RMS is dominated by this resonance, RMS depends on this Q assumption.

  8255   Fri Mar 8 02:17:04 2013 yutaUpdateLSCcalibration of PRM actuator

[Manasa, Yuta]

We measured AC response of PRM actuator using PRM-ITMY cavity.
Result is

PRM:  (19.6 +/- 0.3) x 10^{-9} (Hz/f)^2 m/counts

It is almost the same as in 2011 (elog #5583). We took the same procedure as what Kiwamu did.

What we did:
  1. Aligned PRMI in usual procedure, mis-aligned ITMX and locked PRM-ITMY cavity using REFL55_Q_ERR. POP DC was about 18 when locked.

  2. Made UGF of PRM-ITMY cavity lock at 10 Hz and introduced elliptic LPF at 50 Hz(OLTF below).
OLTF_PRCL.png


  3. Measured transfer function from C1:LSC_ITMY_EXC to C1:LSC_REFL55_Q_ERR. Dividing this by ITMY actuator response(measured in elog #8242) gives calibration of REFL55_Q.

  4. Measured transfer function from C1:LSC_PRM_EXC to C1:LSC_REFL55_Q_ERR to calibrate PRM actuator.

Result:
  Calibration factor for REFL55_Q for PRM-ITMY cavity was (1.37 +/- 0.02) x 10^9 counts/m (plot below). Error is mainly from statistical error of the average.
calibREFL55Q.png


  Measured AC response (50-200 Hz) of PRM is below.
actcalibPRM.png


Next:
  - Measure free-run length spectrum of PRM-ITMY cavity and compare with MICH free-run.

  8256   Fri Mar 8 03:07:19 2013 yutaUpdateLSCcalibrated PRM-ITMY length spectra

Measured free swing PRM-ITMY length was 230 nm RMS.
MI differential length was 85 nm RMS(elog #8248). This tells you that PR2, PR3 are not so noisy compared with usual suspensions.

Openloop transfer function:
  OLTF of PRM-ITMY cavity lock using REFL55_Q_ERR as error signal and PRM as actuator is below.
  UGF ~ 120 Hz, phase margin ~ 50 deg.
  Somehow, phase delay was 460 usec, which is smaller than the empirical value 550 usec.
LSCPRCLOLTF_PRITMY.png


PRM-ITMY length spectra:
  Below. Calibration was done using calibrated REFL55_Q_ERR and actuator response(elog #8255).
PRITMYmotion.png

  8332   Fri Mar 22 19:46:29 2013 KojiSummaryLSCDiode impedance test result

I've tested Perkin-Elmer InGaAs PDs at OMC Lab.

- The diode impedances were measured with the impedance measurement kit. Reverse bias of 5V was used.

- Diode characteristics were measured between 10MHz and 100MHz.

- 4-digit numbers are SN marked on the can

- Ls and Rs are the series inductance and resistance

- Cd is the junction capacitance.

- i.e. Series LCR circuit o--[Cd]--[Ls]--[Rs]--o

C30665GH, Ls ~ 1nH

0782 Perkin-Elmer, Rs=8.3Ohm, Cd=219.9pF
1139 Perkin-Elmer, Rs=9.9Ohm, Cd=214.3pF
0793 Perkin-Elmer, Rs=8.5Ohm, Cd=212.8pF

C30642G, Ls ~ 12nH

2484 EG&G, Rs=12.0Ohm, Cd=99.1pF
2487 EG&G, Rs=14.2Ohm, Cd=109.1pF
2475 EG&G glass crack, Rs=13.5Ohm, Cd=91.6pF
6367 ?, Rs=9.99Ohm, Cd=134.7pF
1559 Perkin-Elmer, Rs=8.37Ohm, Cd=94.5pF
1564 Perkin-Elmer, Rs=7.73Ohm, Cd=94.5pF
1565 Perkin-Elmer, Rs=8.22Ohm, Cd=95.6pF
1566 Perkin-Elmer, Rs=8.25Ohm, Cd=94.9pF
1568 Perkin-Elmer, Rs=7.83Ohm, Cd=94.9pF
1575 Perkin-Elmer, Rs=8.32Ohm, Cd=100.5pF

C30641GH, Perkin Elmer, Ls ~ 12nH

8983 Perkin-Elmer, Rs=8.19Ohm, Cd=25.8pF
8984 Perkin-Elmer, Rs=8.39Ohm, Cd=25.7pF
8985 Perkin-Elmer, Rs=8.60Ohm, Cd=25.2pF
8996 Perkin-Elmer, Rs=8.02Ohm, Cd=25.7pF
8997 Perkin-Elmer, Rs=8.35Ohm, Cd=25.8pF
8998 Perkin-Elmer, Rs=7.89Ohm, Cd=25.5pF
9000 Perkin-Elmer, Rs=8.17Ohm, Cd=25.7pF

 

Note:  Calculated Ls&Rs of straight wires
  1mm Au wire with dia. 10um -> 1nH, 0.3 Ohm
20mm BeCu wire with dia. 460um -> 18nH, 0.01 Ohm

  8375   Fri Mar 29 19:23:49 2013 Gabriele, JenneFrogsLSCAnalog whitening filter of REFL55 not switching

We discovered that the analog whitening filter of the REFL55_I board is not switching when we operate the button on the user interface. We checked with the Stanford analyzer that the transfer function always correspond to the whitening on.

The digital one is actually switching. We decided to keep the digital de-whitening on to compensate for the analog one. Otherwise we get a very bad shape of the PDH signal. Sorry Rana...

  8376   Fri Mar 29 19:56:02 2013 GabrieleMetaphysicsLSCLock of PRMI on sidebands

I finally managed to get long stretches of PRMI lock, up to many minutes. The lock is not yest very stable, it seems to me that we are limited by some yaw oscillation that I could not trace down. The oscillation is very well visible on POP.

Presently, PRCL is controlled with REFL55_I, while MICH is controlled with AS55_Q. This configuration is maybe not optimal from the point of view of phase noise couplings, but at least it works quite well. I believe that the limit on the length of locks is given by the angular oscillation. I attach to this entry few plots showing some of the lock stretches. The alignment is not optimal, as visible from a quite large TEM01 mode at the dark port.

Here are the parameters I used:

MICH gain -10   PRCL gain -0.1

Normalization of both error signal on POP22_I with factor 0.004

Triggering on POP22: in at 100, out at 20 for both MICH and PRCL.

POP55 demodulation phase -9

MICH and PRCL control signal limits at 2000 counts

 

There is a high frequency (628 Hz) oscillation going on when locked (very annoying on the speakers...), but reducing the gain made the lock less stable. I could go down to MICH=-1.5 and PRCL=-0.02, still being able to acquire the lock. But the oscillation was still there. I suspect that it is not due to the loops, but maybe some resonance of the suspension or payload (violin mode?). There is still some room for fine tuning...

Lock is acquired without problems and maintained for minutes.

Have a nice week-end!

Attachment 1: lock_prmi5.pdf
lock_prmi5.pdf
Attachment 2: lock_prmi6.pdf
lock_prmi6.pdf
Attachment 3: lock_prmi7.pdf
lock_prmi7.pdf
Attachment 4: oscillation.pdf
oscillation.pdf
Attachment 5: lock_prmi8.pdf
lock_prmi8.pdf
  8377   Fri Mar 29 19:58:24 2013 Gabriele, JenneFrogsLSCAnalog whitening filter of REFL55 not switching

Quote:

We discovered that the analog whitening filter of the REFL55_I board is not switching when we operate the button on the user interface. We checked with the Stanford analyzer that the transfer function always correspond to the whitening on.

The digital one is actually switching. We decided to keep the digital de-whitening on to compensate for the analog one. Otherwise we get a very bad shape of the PDH signal. Sorry Rana...

 I forgot to say that the analog gain of the REFL55 channels has been reduced to 9db

  8378   Sun Mar 31 17:26:32 2013 ranaUpdateLSCLock of PRMI on sidebands

 

 Our first move has to be fixing the whitening switching for REFL55. That's the configuration we need to start and then move onto REFL165 to get to FPPRMI.

  8379   Mon Apr 1 09:05:09 2013 Jenne, GabrieleConfigurationLSCPOP22 configuration

On Friday we modified the POP22 set up: now the PD output goes to a bias tee. The DC output goes to the ADC board, while the RF output goes to an amplifier (Mini-circuits ZFL-1000LN+), to a band pass filter at 21.4 MHz and then to the ADC

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

[Gabriele, Jenne]

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

  8383   Mon Apr 1 16:24:09 2013 JamieFrogsLSCPD whitening switching fixed (loose connection at break-out box)

Quote:

We discovered that the analog whitening filter of the REFL55_I board is not switching when we operate the button on the user interface. We checked with the Stanford analyzer that the transfer function always correspond to the whitening on.

This turned out to just be a loose connection of the ribbon cable from Contec board in the LSC IO chassis at the BIO break-out box.  The DSUB connector at the break-out box was not strain relieved!  I reseated the connector and strain relieved it and now everything is switching fine.

20130401_161917.jpg

20130401_161858.jpg

I wonder if we'll ever learn to strain relieve...

  8387   Tue Apr 2 10:22:37 2013 Rana, Gabriele, JenneUpdateLSCPRMI lock

We locked the PRMI, this time really on the sidebands, using the two REFL55 signals.

Here are the parameters: triggering on POP22_I in at 140, out at 20. No normalization. MICH gain -0.15, PRCL gain 0.1

It seems that the lock is not very stable. It seems likely to come from some large angular motion of one of the mirrors. We'll need to calibrate the optical lever signals to understand which one is moving too much.

 

Attachment 1: lock_prmi_sb.pdf
lock_prmi_sb.pdf
  8388   Tue Apr 2 11:08:16 2013 KojiUpdateLSCPRMI lock

> The two REFL55 signals

Wow! It's a good news.
I think this is our first ever lock of PRMI with the REFL I/Q signals.

We kept having difficulty to obtain MICH from the REFL beam.

Next time could you make calibration of REFL55 MICH and AS55 MICH and compare the ratio with any simulation?

  8397   Tue Apr 2 23:14:02 2013 ranaUpdateLSC22/110MHz path for POP

Quote:

We could not find a power supply slot for the amplifiers on the LSC rack. We had to put a temporary power supply in contradiction to our 'no temporary power supply' policy.

 After 1 month, its hard to imagine that this could not have been fixed by putting in a proper fuse and fuse block. I will remove this tomorrow if I still find it this way in the bottom of the rack.

There are also 2 Sorensen switching supplies in the bottom of the LSC rack (with all of our sensitive demod boards). These should also be moved over to the old 'digital' LSC rack tomorrow for the post meeting lab cleanup.

Use fuse blocks with fuses with appropriate ampacity.

  8401   Wed Apr 3 14:46:17 2013 GabrieleSummaryLSCError signal simulation in PRMI

Here is a summary of a simulation of the error signal behavior in the PRMI configuration. The main parameters are:
L_PRC = 6.7538 m
Schnup = 0.0342 m
fmod1 = 11.065399e6 Hz
fmod2 = 5 * fmod1

prmi_prclsweep_pop22.pngprmi_prclsweep_pop110.png

These two plots shows the response of the POP22 and POP110 signals (in almost arbitrary units) to a PRCL sweep around the resonance. The splitting of the 55 sideband peaks is well visible in the second plot. It is due to the fact that the 55MHz sidebands are not perfectly matched to the PRC length

prmi_michsweep_pop22.pngprmi_michsweep_pop110.png

The same thing when sweeping MICH. The peaks are wider and it is not possible to see the splitting.

prmi_prclsweep_errsig_not_tunedphase.pngprmi_michsweep_errsig_not_tunedphase.png

These are the error signals (REFL11_I/Q and REFL_55_I/Q) as a function of the PRCL (left) and MICH (right) sweep. Here the demodulation phases are not properly tuned. This is just to show that when the phase is wrong, you can get multiple zero crossings (in this case only in the Q signals, but in general also in I) close to resonance.

prmi_prclsweep_errsig_tunedphase.pngprmi_michsweep_errsig_tunedphase.png

If the phases are tuned in order to maximize the slope of the I signals with respect to PRCL, one gets these "optimized phase" responses. It is that the phase does not correspond to the one that makes the PRCL peak to peak signal small in Q. The Q signals are indeed flat around resonance for a PRCL motion, but they deviate quite a lot from zero when moving more far from resonance. Moreover, both the REFL_55 error signals (I for PRCL and Q for MICH) are crossing again zero at two additional positions, but those are quite far from the resonance point.

prmi_prclsweep_triggering.pngprmi_michsweep_triggering.png

These plots just show the PRCL and MICH error signals together with the POP22 and POP110 signals, to give an idea of the level of triggering that might be needed to be inside the linear range. It seems that if we trigger on POP22 when using the REFL55 signal we loose a bit of linear range, but not that much.

prmi_prclsweep_linearized_signals.pngprmi_michsweep_linearized_signals.png

If you reached this point it means you're really interested in this topic, or maybe you have nothing better to do... However, this plot shows the effect of linearization of the error signal, obtained dividing them by the proper POP22/110 signal. The linear range is increased, but unfortunately for the 55 signals, the additional zero crossing I was mentioning before creates two sharp features. Those are however quite outside the triggering region, so they should not be harmful.

Attachment 1: prmi_michsweep_pop22.png
prmi_michsweep_pop22.png
Attachment 2: prmi_michsweep_pop110.png
prmi_michsweep_pop110.png
  8411   Thu Apr 4 10:12:55 2013 GabrieleSummaryLSCPOP22 and POP110

I had a look at the POP110 signal, with the PRMI flashing.

1) The LSCoffset script does not zero any more POP22_I_ERR offset. I did it by hand

2) The gain of POP22 is changed a lot, as well as the sign: now sidebands are resonant when POP22_I is negative

3) POP110 seems to deliver good signals. The plot attached shows that when we cross the sideband resonance, there is a clear splitting of the peak. If we rely on the simulations I posted in entry 8401, the full width at half height of the POP_22 peak is of the order of 5 nm. Using this as a calibration, we find a splitting of the order of 7 nm, which is not far from the simulated one (5 nm)

Attachment 1: pop110_2.pdf
pop110_2.pdf
  8412   Thu Apr 4 10:32:42 2013 GabrieleSummaryLSCREFL55 error signals

The attached plot shows that also the behaviour of the REFL11 and 55 signals is qualitatively equal to the simulation outcome.

Attachment 1: prmi_refl_signals.pdf
prmi_refl_signals.pdf
  8413   Thu Apr 4 10:46:54 2013 KojiSummaryLSCREFL55 error signals

Beautiful double peaks. I don't see the triple zero-crossings. Is this because you adjusted the phase correctly (as predicted)?

Don't you want to have a positive number for POP22? Should we set the demod phase in the configuration script for the positive POP22, shouldn't we?

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

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

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

The trigger logic is as follows: 

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

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

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

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

LSC_triggers.png

LSC_SigCond.png

 

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

RF_PD_block.png

 

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

LSC_FM_Trig.png

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

  8491   Thu Apr 25 10:19:10 2013 KojiSummaryLSCLocking activity on Apr 24th

Last night I worked on the several locking configurations:

General preparations / AS table inspection

- The AS beam looked clipped. I went to the AP table and confirmed this is a clipping in the chamber.
  This may be fixed by the invacuum PZTs.

Modulation frequency tuning

RFPD Mon of the MC demodulator was check with the RF analyzer. Minimized the 25.8MHz (=55.3-29.5MHz) peak by changing the marconi freq.
This changed the modulation freq from 11.066147MHz to 11.066134MHz. This corresponds to the change of the MC round-trip length from
27.090952m to 27.090984m (32um longer).

Michelson tests

- I wonder why I could not see good Michelson signal at REFL ports.

- I roughly aligned the Michelson. On the AP table, the RF analyzer was connected to the REFL11 RF output.
  By using "MAX HOLD" function of the analyzer, I determined that the maximum output of the 11.07MHz peak
  was -61.5dBm.

- I went to the demodboard rack. I injected -61dBm from DS345 into the RFEL11 demodboard. This produced
  clean sinusoidal wave with the amplitude of 4 count. The whitening gain was 0dB.

- The output from the PD cable was -64.0dBm. So there is ~2.5dB loss in the cable. Despite this noise, the demodulation
  system should be sufficiently low noise. i.e. the issue is optical

- The Michelson was locked with AS55Q. And the REFL11 error signals were checked.Fringe like feature was there.
  This suggested the scattering from the misaligned PRM. The PRM was further misaligned. Then some reasonable
  (yet still noisy) Michelson signal appeared. (Usual misaligned PRM is not at the right place)

  Q. How much scattering noise (spurious cavity between PRM and the input optics) do we have when the PRM is aligned?
  Q. Where should we put the glass beam dumps in the input optics?
  Q. Can we prepare "safe" misaligned place for the PRM with the beam dump?

- The Michelson was locked with REFL11Q. From the transfer function measurement, the gain difference between AS55Q (whitening gain 24dB)
  and REFL11Q was 32dB. The whitening gain was 0dB. In fact I could not lock the Michelson with the whitening gain 33dB (saturation???)
  The element in the Input matrix was 1, The gain of the servo was +100. BS was actuated.

Coupled cavity tests

- At least REFL11 is producing reasonable signals. So what about the other REFL ports? The Michelson signals in the other frequencies
  were invisible. So I decided to use three-mirror coupled cavity with the loss PRC.

- Aligned X arm, Misaligned ETMX, ITMY. Aligned PRM.

- Locked the PRM-ITMX cavity with REFL11 and REFL33.

- Aligned ETMX. If I use REFL11I for the PRC locking, I could not lock the coupled cavity. But I could with REFL33I.
  This is somewhat familiar to me as this is the usual feature of the 3f signal.

- The coupled cavity could be locked "forever". To realize this I needed to tweak the normalization factor from 1.0 to 1.6.
  Q. How does the coupled cavity change the response of the cavity? Can we compensate it by something?
  Q. Measure open loop transfer functions to check if there is any issue in the servo shapes.

- Transmission during the lock is 3.2 while the nominal TRX with PRM misaligned was 0.93.
  This corresponds to power recycling gain of 0.17.

 - X arm:

    - Source: POX11I, phase 79.5 deg, whitening gain 36dB
    - Input matrix: POX11I->1.0->XARM, Normalization TRX*1.60
    - XARM servo gain +0.8, actuation ETMX
    - XARM trigger 0.25 up, 0.05 down. XARM Filter trigger untouched.

- PRC: (sideband locking)
    - Source: REFL33I, phase -34.05 deg, whitening gain 30dB
    - Input matrix: REFL33I->1.0->PRCL, Normalization None
    - PRCL servo gain +4.0, actuation PRM
    - PRCL trigger None

- Same test for the Y arm. At the moment ETMY did not have the OPLEV.
  Same level of transmission (~3.3)

 - Y arm:

    - Source: POY11I, phase -61.00 deg, whitening gain 36dB
    - Input matrix: POY11I->1.0->YARM, Normalization TRX*2.1
    - YARM servo gain +0.25, actuation ETMX
    - YARM trigger 0.25 up, 0.05 down. YARM Filter trigger untouched.

- PRC: (sideband locking)
    - same as above

Sideband PRMI attempt

    - Now I got some kind of confidence on the REFL33 signal.
    - So I tried to get any stable setup for sb PRMI, then to find any reasonable MICH signals anywhere else than AS55Q.
    - With REFL33I(PRCL) & AS55Q(MICH), I got maximum ~10sec lock. It regularly locked. It was enough long to check
      the spectrum on DTT. But it was not enough long to find anything about the MICH signals at the REFL ports.

    - I tried REFL33Q for MICH. The lock was even shorter but could lock for 1~2 sec.

    Q. What is the cause of the lock loss? I did not see too much angluar fluctuation. The actuation was also quiet (below 10000).

- PRCL: (sideband locking)
    - Same as above except for
      - the PRCL servo gain +0.05, No limitter at the servo output.
      - Trigger POP22I (low pass filtered by LP10) 20 up, 3 down

- MICH:
    - AS55Q -24.125 24dB -> x1.0 -> MICH -0.7, No limitter -> ITMX/Y differential
    or
    - REFL33Q -34.05dB -> x2.0 -> MICH same as above
    - For both case, trigger POP22I (low pass filtered by LP10) 20 up, 3 down

 

At this point Jenne came back from dinner. Explained what I did and handed over the IFO.

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

[Jenne, Annalisa, with guidance from Koji]

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

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

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

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

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

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

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

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

Analysis to follow.

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

  8500   Sat Apr 27 00:21:06 2013 KojiUpdateLSCLocking activity on Apr 26th

When I talked with Den via phone, he recommended to use the trigger and normalization with POP110I.
So I decided to try this approach. Also I investigated how the REFL33 signals are useful.

I could find the state where the PRMI(sb) locks regularly, although the lock is ~1min at most.

PRCL: REFL33I
whitening gain 30dB, -14.0deg (finely tuned in lock)
-> x1.0 -> Triggered by POP110I (20up, 1down)
-> Normalized by POP110I x0.04
-> Gain 0.2~0.12 FM3, 4, 5, 6 always on, no triggered FMs
-> PRM

MICH: REFL33Q
whitening gain 30dB, -14.0deg (finely tuned in lock)
-> x1.0 -> Triggered by POP110I (20up, 1down)
-> Normalized by POP110I x0.04
-> Gain -20 FM4, 5 always on, no triggered FM
-> ITMX (-1.0) and ITMY (+1.0)

I needed to tune the phase very precisely to reach this state. Also the alignment of the michelson and PRM
was very crtiical to acquire the lock.

Later in the same night I was plagued by PRM alignment drift. It seems that the PRM alignment is bistable or
slightly drifting in pitch. I had to align PRM continuously. When the PRMI is locked, the alignment fluctuation
was mainly in yaw. This was as people commented before.

Attachment 1: Screenshot.png
Screenshot.png
  8501   Sat Apr 27 00:29:40 2013 KojiUpdateLSCLSCoffset script fixed

Prior to the locking trials...

scripts/LSC/LSCoffset script had behaved peculiarly:

This script spawns LSC/offset3 in order to remove the dark offset from the channels.
How ever the offsets had been nulled every other PDs
(i.e. The offsets REFL11 I&Q were nulled.
The offsets REFL33 I&Q had been left untouched
The offset REFL55 I&Q had been nulled
and so on.)

I found that the script run many instances of "offset3" scripts in background.
It seemed that tdsavg did not like too many averaging channels at once.

So the "&"s in the LSCoffsets were removed and now the script runs much more slowly,
but works for all of the PDs listed.

I think I have never seen the offsets in REFL33 and REFL165 nulled down to this level before.

  8508   Mon Apr 29 22:13:41 2013 KojiUpdateLSCLocking with ASDC

Today the locking was not as easy as that was last Friday.
So I tried something new. Today Rana talked about the ASDC locking with POPDC normalization.
This technique was tried. (This is somewhat similar to DC readout.)

PRCL
Signal source: REFL33I / Normalization POP110I x 0.04 / Trigger POP110I 20up 3down, otherwise  untouched from Friday locking
Servo: input matrix 1.00 -> PRCL Servo FM3/4/5/6 Always ON G=+0.06
Actuator: output matrix 1.00 -> PRM

MICH
Signal source: ASDC Offset -109.5 (nominal of the day -49.5) / Normalization POPDC x 1.00 / Trigger POP110I 20up 3down
Servo: input matrix 1.00 -> MICH Servo FM5 Always On G=+10000
ActuaroL output matrix -1.00 -> ITMX / +1.00 -> ITMY

Observation

- POP110I was ~120 during the lock (cf 170 on Friday). So there is some small leakage from the dark port.

- Lock was easier when FM4 of the MICH loop was turned off.

- During the lock horizontal motion of the intracavity mode was visible as usual.

Screenshot.png

  8509   Mon Apr 29 23:02:48 2013 KojiConfigurationLSCQuestons

Q. How much Schnupp asymmetry we want in order to improve the signal ratio between PRCL/MICH in REFL ports?

Q. How much can we increase Schnupp asymmetry in the practical constraints?

Q. How PRCL/MICH ratio is different the REFL ports?
=> My modeling (many years ago) shows the ratio of {115, 51, 26, 23} for REFL{11, 33, 55, 165}.
These numbers should be confirmed by modern simulation of the 40m with updated parameters.
I should definitely use 55MHz but also prepare better 165MHz too.

Q. How the TT/PRM motions are affecting the lock stability? How can we quantify this effect? How can we mitigate this issue?

Q. Can we somehow change the sensing matrix by shifting the modulation frequency?

Q. Is normalization by POP22 or POP110 actually working well?
=> Time series measurement of error signals & servo inputs

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

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

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

  8517   Wed May 1 00:05:03 2013 KojiUpdateLSCMore stable lock of PRMI (REF33I and AS55Q)

[Jenne Koji]

- Today the spots were moving more than the usual. The OPLEV screens showed that the spots are too much off from the center.

- Each vertex OPLEVs were checked and OPLEV wonderland was discovered: Other than the usual misalignment of the spots,
it was found that PRM/ITMX/ITMY beams were clipped somewhere in the paths, BS/PRM oplevs had many loose components
including the input lenses (they are still clamped by a single dog clamp THIS SHOULD BE FIXED ASAP).

- On the ITMY table there were so many stray optics. They were removed and put on the wagon next to the ITMY table.
THIS SHOULD BE CLEARED ON THE WEDNESDAY CLEANING SESSION.

- During this OPLEV session, LSCoffset nulling was run.

- After the OPLEV session, the locking became really instantaneous. We wonder which of the OPLEV cleaning, LSC offset nulling,
and the usual seismic activity decay in the evening was effective to make it better.

- Initially the lock was attempted with REFL33I/Q and some ~10sec lock streches were obtained. During this lock,
  the optical gain of AS55Q was measured in relative to REFL33Q. In deed they were calibrated to be the same
  gain at the input matrix.

- After the MICH signal source was switched to AS55Q, the lock streches became more regular and the minutes long.
We precisely tuned the phase of AS55 and REFL55 in terms of the differential excitation of ITMX/Y using lockin (FREQ 250, AMP 1000).

- We noticed that the AS port spot with AS55Q MICH was darker than the REFL33Q MICH. This suggests the existence of residual offset
in REFL33Q. In deed we observed +30cnt offset in REFL33Q when the PRMI is locked with AS55Q MICH.

- Phases and relative gains of the signals were as follows:

PRCL: REFL33I 1.00 =REFL55I +0.4
MICH: AS55Q 29deg x1.00 = REFL33Q -14deg x1.00 = REFL55Q 118deg 0.03?

- We tried to lock PRMI with AS55Q. The acquisition was not as easy as that with REFL33I. This might be from the saturation of the
REFL55I signal. This configuration should tested with different whitening gain. Handing off using the input matrix went well once the
lock was obtained by REFL33I.

- Handing off from AS55Q to REFL55Q was not successful.

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

- The configuration of the filters:

PRCL FM3/4/5/6 G=+0.05 / NORM 0.04 POP110I
MICH FM4/5 G=-5.00 / NORM 0.01 POP110I (or none)

Screenshot.png

  8518   Wed May 1 10:42:35 2013 SteveUpdateLSCcleanup

 

 Optics from the car were placed into glass door cabinet E0

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

Quote:

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

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

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

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

  8521   Thu May 2 00:34:57 2013 KojiUpdateLSClocking

- Routine alignment

Locked the arm cavties. Ran ASS. As this was not enough precise alignment for PRMI locking, Yarm alignment was re-adjusted by sliders.
Xarm was also aligned in the same way.

- OPLEV alignment

Once the arms were aligned, OPLEV spots were adjusted. For this adjustment, PRM had to be aligned and OPLEV servos needed to be turned off.

- LSC offset nulling

While Jenne was measuring the dark output of the POP PD, LSC offset nulling script was executed.

- Compensation of the POP spot size fix

As Jenne reported the POP path now has a lens and the denominator for the normalization got bigger.
To compensate this change, PRMI(sb) was locked by the same configuration as yesterday (i.e. AS55Q for MICH, REFL33I for PRCL). 
After some try and error, configuration for stable locking was found. 

PRCL
Signal source: REFL33I / Normalization POP110I x 1.00 / Trigger POP110I 80up 10down
Servo: input matrix 1.00 -> PRCL Servo FM3/4/5/6 Always ON G=+8.00
Actuator: output matrix 1.00 -> PRM

MICH
Signal source: AS55Q / Normalization POP110I x 0.01 / Trigger POP110I 80up 10down
Servo: input matrix 1.00 -> MICH Servo FM4/5 Always On G=-30
Actuator output matrix -1.00 -> ITMX / +1.00 -> ITMY

This suggests that POP110I signal is 5~6 times more than before the lens was installed. 

- SQRTing option for POP110I was implemented

The PRMI optical gain is derived from (Carrier)x(1st order Sideband) or (2nd order SB)x(1st order SB).
Here the carrier and the 2nd order sidebands are nonresonant.
Therefore the optical gain is proportional to the amplitude power recycling gain of the 1st order sidebands.
On the other hand, POP 2f signals are derived from the product of the 1st and -1st order sidebands.
This means that we should take a sqrt of the POP signals to compensate the recycling gain fluctuation.

Screenshot.png

- Locking with SQRT(POP110I)

PRCL
Signal source: REFL33I / Normalization SQRT(POP110I) x 10 / Trigger POP110I 10up 3down
Servo: input matrix 1.00 -> PRCL Servo FM3/4/5/6 Always ON G=+8.00
Actuator: output matrix 1.00 -> PRM

MICH
Signal source: AS55Q / Normalization SQRT(POP110I) x 0.1 / Trigger POP110I 10up 3down
Servo: input matrix 1.00 -> MICH Servo FM4/5 Always On G=-30
Actuator output matrix -1.00 -> ITMX / +1.00 -> ITMY

The lock seems not so different from the ones without SQRTing.

The spot was still moving in yaw direction. If I chose a correct alignment, I could minimize the modulation of the internal power
by misalignment. As you can see in the following plot.

Screenshot2.png

When the alignment was deviated from the optimum, the misalignment induced RIN was much worse although this was the longest lock I ever had with the PRMIsb. (more than 8 min)

Screenshot3.png

- Locking with other signal sources

REF55I/Q trial:

Demodulation phase was adjusted to make the difference of the peak heights for MICH maximized.
After the lock is acquired, I tried to swap the signal source at the input matrix. PRCL swapping was successful but
MICH swapping was not successfull.

It is much more hard to lock the interferometer with REFL55I compared with REFL33I.

REFL165I/Q trial:

As REFL165 PD never produced any useful signal, I tried to swap it with the BBPD used in the green setup.

- Borrowed the PD, power supply from the green setup.

- Put REFL165PD aside. Placed the BBPD in the path. The DC output was 0.8V. This corresponds to the input power of ~5mW.

- Checked the signal but it was very litte (several counts even at the maximum whitening gain).

- Decided to use the power reduction pick off to introduce much more light on the PD.
  This PO mirror is 90% reflector. Therefore I had to be careful no to fry the diode.
  Currently there are OD1.3 (x1/20) power attenuator to reduce the input power down to 6.5V (40mW).

- The resulting signal is very wiered suggesting the saturation of the PD at the RF stages.

- Probably I need to make a new PD circuit which has the high pass filter to reject other low frequency components.

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

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

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

 Xarm_SchnuppData_April2013.png

Yarm_SchnuppData_April2013.png

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

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

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

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

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

Here are the redone plots:

Phase not tuned:

michsweep_errsigs_phasenottuned.pngprclsweep_errsigs_phasenottuned.png

 

Phase tuned:

michsweep_errsigs_tunedphase.pngprclsweep_errsigs_tunedphase.png

POP22 resonance for MICH and PRCL:

michsweep_pop22.pngprclsweep_pop22.png

POP110 resonance for MICH and PRCL:

michsweep_pop110.pngprclsweep_pop110.png

  8553   Wed May 8 19:31:17 2013 JamieConfigurationLSCLSC: added new SQRT_SWITCH to power normalization DOF outputs

This removes the old sqrt'ing from the inputs to the POW_NORM matrix (was only on the POP110 I/Q) and moves it to the DOF outputs.  Koji wanted this so that he could use the DC signals for normalization both sqrt'd and not sqrt'd.

The POW_NORM medm screen was updated accordingly.

  8555   Thu May 9 00:05:12 2013 rana, Koji, JenneSummaryLSCAA and AI change

We would like to increase the UGF of the PRC loop so as to allow more suppression of the PRC signal and less pollution of the MICH signal (remember that the PRC/MICH optical gain ratio is huge).

We were already losing phase because of delay in the LSC - SUS digital link. In addition to that, a major source of delay is the analog anti-aliasing (on the LSC error signals before they enter the ADC) and the analog anti-imaging (between the SUS DAC and the coil driver).

 IN addition to these, the other major sources of phase lag in the system are the FM5 filter in the LSC-PRC filter bank, the digital upsampling and downsampling filters, and the DAC sample and hold.

In the near term, we want to modify these analog filters to be more appropriate for our 64 kHz ADC/DAC sample rate. Otherwise, we are getting the double phase lag whammy.

 

Staring at the schematics for the AA (D000076-01) and the AI (D000186-A), we determined a plan of action.

For the AA, we want to remove the multi-pin AA chip filter from Frequency Devices, Inc. and replace it with a passive LC low pass. Hopefully, these chips are socketed. Rana will design an appropriate LC combo and elog; we should make the change on a Wednesday afternoon so that we have enough soldering help.

For the AI, the filter is a dual bi-quad using discrete components and LT1125 opamps. Not so clear what to do with these. The resistors are all the noisy thick film kind and maybe should be replaced. Koji will find some online design tool for these or do it in LISO. Changing the TF is easy; we can just scale the capacitors. But we also want to make sure that the noise of the AI does not destroy the noise reduction action of the dewhitening board which precedes it.

Jenne should figure out how low the noise needs to be at the input to the coil driver.

 

P.S. the matlab code which defines these filters

>> [z,p,k] = ellip(4,4,60,2*pi*7570,'s');
>> misc.ai = zpk(z,p,k*10^(4/20)) * zpk([],-2*pi*13e3,2*pi*13e3);
>>
>> % Fudged Anti-Imaging Filter
>> [z,p,k] = ellip(8,0.001,80,2*pi*7570,'s');
>> misc.aa = zpk(z,p,k*10^(0.001/20)) * zpk([],-2*pi*32768,2*pi*32768);

Attachment 1: AAAI.pdf
AAAI.pdf
  8566   Mon May 13 23:05:26 2013 KojiConfigurationLSCPRMI locking

- Disabled MCL path in mcdown/mcupscript.

Nominal gain in mcdown/mcup was -50 and -100 respectively.

- Confirmed the stable lock was just because of the quiet seismic of the Friday night.

- Improvement of the PRM ASC servo
RG3.2 (3.2Hz Q=2 Height 30dB)
=>
RG3.2 (3.2Hz Q=10 Height 30dB) +  zero[f, 1, .5] pole[f, 2, 3] zero[f, 4.5, .5] pole[f, 3.5, 3]

Filter shape comparison is found in the second plot attached.

The resulting spectra (freerun vs controlled) is found in the first plot.

Nominal PRM ASC gain is +70

- Openloop TF measurement

OLTF PRCL 250Hz 30deg / MICH 200Hz 45deg

- REFL55/REFL33 phase adjustment (in lock)

REFL55 phase fine tune (95.25deg) (x1,x0.3)
REFL33 phase (-13.0deg) (x1, x2)

Attachment 1: 130513_PRC_ASC.pdf
130513_PRC_ASC.pdf
Attachment 2: 130513_PRC_ASC_servo.pdf
130513_PRC_ASC_servo.pdf
  8574   Tue May 14 20:27:19 2013 KojiConfigurationLSCOpenloop gain for PRMI lock May 13

The OLTFs for PRCL and MICH for the last night's lock were modelled using Yuta's python script.

Attachment 1: LSCPRCLOLTF.png
LSCPRCLOLTF.png
Attachment 2: LSCMICHOLTF.png
LSCMICHOLTF.png
Attachment 3: 130513.zip
  8577   Wed May 15 00:45:28 2013 ranaConfigurationLSCOpenloop gain for PRMI lock May 13

 

 Pfft. Why 500 usec delay? We should be using the known parameters for the hardware and software AA/AI.

  8589   Thu May 16 04:46:37 2013 JenneUpdateLSCKiwamu's sensing matrix measurement script revived

Kiwamu had an old set of scripts for measuring the sensing matrices, but they were hidden away in ..../scripts/general/kiwamuscripts/pyplant . I have moved them to a more useful place, and updated them.

The useful scripts (the main one is SensResp.py, and the PRMI-specific one, runPRMI_SENS.py, which calls SensResp.py) have been moved to .../scripts/LSC .  I have also created a folder within the LSC scripts folder called SensMatData for the data.

The 2 big changes to Kiwamu's scripts:  The ezca library that he was calling wasn't working.  I switched it over to using the one that Yuta wrote, in ..../scripts/pylibs.  Also, Kiwamu's script was written back during a time where we must have only had one total lockin for the whole LSC model.  Now we have one per PD in the input matrix.  This meant that several of his channel names were wrong.  I have fixed this, and also made it measure all the sensors at once using tdsread of the _OUT16 channels (the OUT16's have some AA action, other EPICS channels don't).

So, now (after you're locked), it shakes one "mirror" (the ITMs are shaken differentially at the same time, as one "mirror"), and reads out all of the RF PD lockin values.  Then it moves to the next mirror.  (For the PRMI case, there are only 2 "mirrors":  The ITM set and the PRM.)  All of the information is stored in a dictionary, which is written to a text file. 

The format of the dictionary is:

{ OPTIC_1: [Photodiode_1, Lockin_I, Lockin_Q], [Photodiode_2, Lockin_I, Lockin_Q], OPTIC_2: [Photodiode_1, Lockin_I, Lockin_Q], [Photodiode_2, Lockin_I, Lockin_Q] }

At this point, I am too tired to actually do a measurement, although next time the PRMI is locked, we should just have to run the runPRMI_SENS.py, and look at the data.  I'm also not quite sure how to extract the information from a dictionary after it has been written to a text file.  This may not be a good way to store data, and I'll ask Jamie about it tomorrow.

OTHER NOTES:

* I need to set up another iteration of the sensing matrix measurement with no drive, measuring several times, to get an estimate of the error in a single measurement.

 

* I had the PRMI locked on AS55Q/REFL33I for more than half an hour.  Then the MC started unlocking semi-regularly.  Seismic was good except for one EQ ~2 hours ago.  After the earthquake (unlocked MC, but no tripped optics), the MC has remained locked.

* The LSC Lockin Overview screen does not click-through to the _SIG individual screens.  We need to fix the path to these screens.

* All of the _SIG filters are band passes around 285 Hz, but the names of the filters all say 238Hz.  I need to fix all 27 of these.

* We can perhaps change the LSCoffsets script someday to use tdsread a few times, and average the results (since the PDs don't have lowpass filters, and we're measuring the offset of the IN1 location, not the OUT).  This way we can hopefully measure all the PDs at once and speed up the script, without having failed tdsavg runs.

  8592   Thu May 16 22:03:16 2013 KojiConfigurationLSCY Green BBPD returned to the PSL table

I borrowed the GTRY BBPD  for the REFL165 trial before.

Now the PD is back on the PSL table.

The PD is intentionally misaligned so that anyone can find it is not aligned.

  8593   Thu May 16 23:48:39 2013 JenneUpdateLSCKiwamu's sensing matrix measurement script revived

Koji locked the PRMI for me, and I took some data.  I haven't finished figuring out what to do with it / writing a processing script.

Here is the data, in a python dictionary (not for you to read, but so that it's here and you can use it later if you want).

{'AS55_Q': [['ErrorBarData0', '-1.60826e-05', '0.000154774'], ['ErrorBarData1', '-1.61949e-05', '-9.69142e-05'], ['ITMs', '-0.134432', '0.00240338'], ['PRM', '0.0525864', '0.145516']], 'REFL55_Q': [['ErrorBarData0', '-0.00088166', '-0.00294315'], ['ErrorBarData1', '0.00298076', '-0.000466507'], ['ITMs', '-0.573825', '-0.0865747'], ['PRM', '1.94537', '0.534968']], 'REFL33_Q': [['ErrorBarData0', '0.000868208', '0.000785702'], ['ErrorBarData1', '-0.00136268', '-0.000288528'], ['ITMs', '-0.0653009', '-0.0112035'], ['PRM', '0.875275', '0.419765']], 'REFL11_I': [['ErrorBarData0', '-0.147347', '0.136075'], ['ErrorBarData1', '0.351823', '0.160556'], ['ITMs', '-12.0739', '-80.1513'], ['PRM', '6991.11', '7073.74']], 'REFL33_I': [['ErrorBarData0', '-0.00100624', '0.00134366'], ['ErrorBarData1', '0.00373581', '0.000783243'], ['ITMs', '-0.399404', '-0.774793'], ['PRM', '67.4138', '68.8886']], 'REFL11_Q': [['ErrorBarData0', '-0.0173368', '0.0141987'], ['ErrorBarData1', '0.100048', '0.0882165'], ['ITMs', '6.46585', '-26.2841'], ['PRM', '1653.42', '1663.96']], 'AS55_I': [['ErrorBarData0', '-1.87626e-05', '2.24596e-05'], ['ErrorBarData1', '-5.46466e-05', '-2.96552e-07'], ['ITMs', '-0.00531763', '0.00130579'], ['PRM', '-0.100501', '-0.0706334']], 'REFL55_I': [['ErrorBarData0', '-0.000774208', '-5.32631e-05'], ['ErrorBarData1', '0.00347621', '0.0025103'], ['ITMs', '-0.115633', '-0.83847'], ['PRM', '72.8058', '74.2347']]}

The structure is that each sensor has some "error bar" measurements, when there was no drive to any optics (I, then Q of the lockin), and then response to different optics' drives (waiting 20sec after turning on the oscillator before making a measurement, since the lockin has 0.1Hz lowpasses.  ).

The amplitude that Kiwamu had of 4000 cts in the LSC lockin was fine for MICH, but made PRCL unlock, so this data was taken with an amplitude of 1000 counts, at a frequency 283.1030 Hz. 

Since this is only barely above the UGF for both MICH and PRCL loops, I also have OLTF information at 283Hz from DTT:  PRCL mag = -1.05264 dB, phase = 24.6933 deg, MICH mag = -8.50951 dB, phase = 31.3948 deg.

I have started writing a script SensMatAnalysis.py in the scripts/LSC directory to do the analysis, but after having talked to Koji, I need to do more thinking to make sure I know what I'm doing.  Stay tuned for actual analysis later.

  8600   Mon May 20 17:49:36 2013 JenneUpdateLSCPRMI sensing matrix - not high quality data

Just so we have some numbers, I did a by-hand analysis of the PRMI sensing matrix numbers I posted here in the elog the other day.  This analysis is ignoring the error bar data.

For each sensor (PD_I or PD_Q), I do loop compensation, since these measurements were taken fairly close to the UGFs of the loops, and notches were not in use at the drive frequency.  To do the loop compensation, I multiply the complex value (lockin_I + i*lockin_Q) by (1-G), where G is the (complex) open loop gain of the degree of freedom I'm shaking.

 When I'm shaking a single degree of freedom (ex. shaking the PRM to get PRCL information), for each PD_I or PD_Q, we get 2 numbers, the lockin_I and lockin_Q values.    I check the phase between the lockin_I and lockin_Q values, since that phase (after loop compensation) should be either 0 or 180, and if it is not, something is wrong. 

Of the 16 sensors I measure (where PD_I and PD_Q count as 2 sensors), 11 sensors had phases more than 20 degrees away from either 0 or 180.  This is not good, and indicates that something is wrong with my measurement.  I suspect that I may not be driving hard enough -  I was using an amplitude 4x smaller than the previous value.  Next time the PRMI is locked, I will turn on the drive oscillation, and ensure that I can see the line in all of the PD signals.

The results of my quickie analysis script:

Bad REFL11_I_MICH phase!  Phase is -82.0185 degrees!
Bad REFL11_Q_MICH phase!  Phase is -35.9697 degrees!
Bad REFL33_I_MICH phase!  Phase is -134.952 degrees!
Bad REFL55_I_MICH phase!  Phase is -79.7997 degrees!
Bad AS55_I_PRCL phase!  Phase is -142.6016 degrees!
Bad AS55_Q_PRCL phase!  Phase is 90.6194 degrees!
Bad REFL11_I_PRCL phase!  Phase is 52.471 degrees!
Bad REFL11_Q_PRCL phase!  Phase is 52.2324 degrees!
Bad REFL33_I_PRCL phase!  Phase is 52.909 degrees!
Bad REFL33_Q_PRCL phase!  Phase is 25.14 degrees!
Bad REFL55_I_PRCL phase!  Phase is 52.8113 degrees!

Sensing Matrix, calculated even though most of the measurement data isn't any good:
AS55: MICH = 0.13502, -1.6122deg.  PRCL = 0.14993, -2.245deg
REFL11: MICH = 29.6373, -2.6365deg.  PRCL = 7376.3206, -2.9098deg
REFL33: MICH = 0.35649, -2.9633deg.  PRCL = 69.5133, -3.1302deg
REFL55: MICH = 0.62084, -2.0261deg.  PRCL = 75.0214, 3.1176deg

Attachment 1: PRMIsensMatQuickAnalysis.m.gz
  8601   Mon May 20 18:47:47 2013 KojiUpdateLSCPRMI sensing matrix - not high quality data

For now forget about the demodulation phase and assume all of the ports are independent.
I want to know the numbers in the following format.

          PRCL     MICH   (unit: cnt/m)
REFL11I:  x.xxxEx x.xxxEx
REFL11Q:  x.xxxEx x.xxxEx
REFL33I:  x.xxxEx x.xxxEx
REFL33Q:  x.xxxEx x.xxxEx
REFL55I:  x.xxxEx x.xxxEx
REFL55Q:  x.xxxEx x.xxxEx
REFL165I: N/A     N/A
REFL165Q: N/A     N/A
AS55I:    x.xxxEx x.xxxEx
AS55Q:    x.xxxEx x.xxxEx

If you really want to resolve the TF phase difference between the I and Q  demod-signals,
you need to look at the transfer functions between the excitation and these ports.
We can't understand what is happening only from the single point measurement.

ELOG V3.1.3-