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ID Date Author Typedown Category Subject
  9585   Wed Jan 29 16:36:37 2014 KojiSummaryGeneralHigh power beam blasting of the aLIGO RFPD

[Rich, Jay, Koji]

We blasted the aLIGO RF PD with a 1W IR beam. We did not find any obvious damage.
Rich and Jay brought the PD back to Downs to find any deterioration of the performance with careful tests.

The power modulation setup is at the rejection side of the PBS in front of the laser source.
I checked the beams are nicely damped.
As they may come back here tomorrow, a power supply and a scope is still at the MC side of the PSL enclosure.

  9586   Wed Jan 29 21:01:03 2014 GabrieleSummaryLSCPRC length measurement analysis

 [Manasa, EricQ, Gabriele]

We managed to measure the PRC length using a procedure close to the one described in slog 9573.

We had to modify a bit the reference points, since some of them were not accessible. The distances between points into the BS chamber were measured using a ruler. The distances between points on different chambers were measured using the Leica measurement tool. In total we measured five distances, shown in green in the attached map.

We also measured three additional distances that we used to cross check the results. These are shown in the map in magenta.

The values of the optical lengths we measured are:

LX    = 6828.96 mm
LY    = 6791.74 mm
LPRC  = 6810.35 mm
LX-LY = 37.2196 mm  

The three reference distances are computed by the script and they match well the measured one, within half centimeter:

M32_MP1  = 117.929 mm   (measured = 119 mm)
MP2_MB3  = 242.221 mm   (measured = 249 mm)
M23_MX1p = 220.442 mm   (measured = 226 mm)

See the attached map to see what the names correspond to.

The nominal PRC length (the one that makes SB resonant without arms) can be computed from the IMC length and it is 6777 mm. So, the power recycling cavity is 33 mm too long w.r.t. the nominal length. This is in good agreement with the estimate we got with the SB splitting method (4cm).

According to the simulation in the wiki page the length we want to have the SB resonate when the arms are there is 6753 mm. So the cavity is 57 mm too long.

Attached the new version of the script used for the computation.

Attachment 1: map.pdf
Attachment 2: script.zip
  9588   Thu Jan 30 19:00:25 2014 GabrieleSummaryLSCPRC length changed

 [Manasa, EricQ, Gabriele]

Today we changed the PRC length translating PR2 by 27 mm in the direction of the corner. After this movement we had to realign the PRC cavity to get the beam centered on PRM, PR2, PR3, BS (with apertures) and ITMY (with aperture). To realign we had to move a bit both PR2 and PR3. We could also see some flashes back from the ETMY . //Edit by Manasa : We could see the ETMY reflection close to the center of the ITMY but the arm is not aligned or flashing as yet//. 

After the realignment we measured again the PRC length with the same method of yesterday. We only had to change one of the length to measure, because it was no more accessible today. The new map is attached as well as the new script (the script contains also the SRC length estimation, with random numbers in it).

The new PRC length is 6753 mm, which is exactly our target!


The consistency checks are within 5 mm, which is not bad.

We also measured some distances to estimate the SRC length, but right now I'm a bit confused looking at the notes and it seems there is one missing distance (number 1 in the notes). We'll have to check it again tomorrow.




Attachment 1: map_jan30.pdf
Attachment 2: survey_v3_jan30.m
clear all

global sos_lx sos_ly sos_cx sos_cy tt_lx ...
       tt_ly tt_cx tt_cy sos_sx sos_sy sos_dy

%% Survey of the PRC+SRC lengths %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%% measured distances
d_MB2_MY  = 2114 + 27 + 9;
... 446 more lines ...
  9590   Fri Jan 31 19:29:36 2014 GabrieleSummaryLSCPRC and SRC lengths

 Today we measured the missing distance to reconstruct SRC length.

I also changed the way the mirror positions are reconstructed. In total for PRC and SRC we took 13 measurements between different points. The script runs a global fit to these distances based on eight distances and four incidence angles on PR2, PR2, SR2 and SR3. The optimal values are those that minimize the maximum error of the 13 measurements with respect to the ones reconstructed on the base of the parameters. The new script is attached (sorry, the code is not the cleanest one I ever wrote...)

The reconstructed distances are:

Reconstructed lengths [mm]:
LX    = 6771
LY    = 6734
LPRC  = 6752
LX-LY = 37
LSX   = 5493
LSY   = 5456
LSRC  = 5474

The angles of incidence of the beam on the mirrors are very close to those coming from the CAD drawing (within 0.15 degrees):

Reconstructed angles [deg]:
aoi PR3 = 41.11 (CAD 41)
aoi PR2 = 1.48  (CAD 1.5)
aoi SR3 = 43.90 (CAD 44)
aoi SR2 = 5.64  (CAD 5.5)

The errors in the measured distances w.r.t. the reconstructed one are all smaller than 1.5 mm. This seems a good check of the global consistency of the measurement and of the reconstruction method.

NOTES: in the reconstruction, the BS is assumed to be exactly at 45 degrees; wedges are not considered.



Attachment 1: map_jan31st.pdf
Attachment 2: survey_v3.zip
  9613   Fri Feb 7 17:52:41 2014 KojiSummaryGeneralSome cleaning up
  • Adjusted the PMC alignment
  • Adjusted the IMC length offsets for the MC servo and the FSS servo
  • Adjusted the MC alignment. Ran /opt/rtcds/caltech/c1/scripts/MC/WFS/WFS_FilterBank_offsets
  • The Yarm servo was oscillating. Reduced the servo gain from 0.2 to 0.08.
  • AS Camera & AS port alignment was adjusted. Now the spot is at the center of the AS camera.
  • Cleaned up the ASC offsets on the suspensions (i.e. C1:SUS-***_(PIT|YAW)_OFFSET) by replacing them by the BIAS adjustment.
  • Saved the alignment values
  • Locked the PRMI with SB with REFL55I for PRCL and AS55Q for MICH
  • Aligned the PRM, then checked the alignment of the REFL PDs
  • The best POP110I was 500cnt.
  • Found REFL165 output was disconnected. It is now restored.
  • Used the LSC lockins to figure out the demod phases and the signal amplitudes (relative)

PRCL: 100cnt -> PRM 567.01Hz

Signal in demod Q ch were minimized

REFL11I -19.2deg demod I, Lockin I out (C1:CAL-SENSMAT_PRCL_REFL11_I_I_OUTPUT) 12.6 cnt
REFL33I +130.4deg 1.70cnt
REFL55I +17.0deg 2.30cnt
REFL165I -160.5deg 27.8cnt

MICH: 1000cnt -> ITMX(-1) & (ITMY +1.015 => Minimized the signal in REFL11I to obtain pure MICH)

REFL11I   +0.0     REFL11Q   +0.119
REFL33I   +0.023 REFL33Q   -0.012
REFL55I   +0.023 REFL55Q   -0.113
REFL165I +0.68   REFL165Q +0.038

It seems that REFL165 has almost completely degenerated PRCL and MICH.

  • Try to replace ITMX/Y with BS (+0.16) / PRM (-0.084)

 ITMX(-1)/ITMY(+1.015) actuation was cancelled by BS (+0.16). This introduces PRCL in REFL11I. This was cancelled by PRM (-0.084)


REFL11I   +0.0     REFL11Q   +0.13
REFL33I   -0.012  REFL33Q   0.025
REFL55I   +0.041 REFL55Q   -0.45
REFL165I +0.69   REFL165Q +/-0.02

Again, It seems that REFL165 has almost completely degenerated PRCL and MICH.

Locking info:

[Signal source] REFL11I (-19.2deg) x 0.16, OR REFL33I (+130.4deg) x 2.0, OR REFL55I (+17.0deg) x1.0, OR REFL165I (-160.5deg) x0.05
[Trigger] POP110I(-81deg) 100/10, FM trigger 35/2, delay 0.5sec FM2/3/6/9
[Servo] FM4/5 always on. G=-0.02, Limitter ON
[Output] PRM x+1.00

[Signal source] AS55Q (-5.5deg) x 1, OR REFL11Q x 0.25, OR REFL55Q x-0.06
[Trigger] POP110I 100/10, FM trigger 35/2, delay 5sec FM2/3/9
[Servo] FM4/5 always on. G=-10, Limitter ON
[Output] ITMX -1.0 / ITMY +1.0 (or +1.015), OR PRM -0.084 / BS +0.16



  9634   Thu Feb 13 19:36:36 2014 KojiSummaryLSCPRM 2nd/4th violin filter added

Jenne and I noticed high pitch sound from our acoustic interferometer noise diagnostic system.
The frequency of this narrow band noise was 1256Hz, which is enough close to twice of the PRM violin mode freq.
After putting notch filter at 1256+/-25Hz at the violin filters, the noise is gone. Just in case I copied the same filters to all of the test masses.

Later, I found that the 4th violin modes are excited. Additional notch filters were added to "vio3" filter bank to mitigate the oscillation.

  9667   Mon Feb 24 23:43:10 2014 ranaSummaryGeneralToDo

1) Fixup REFL165: remove ND filters, get box for PD, dump diode reflections, put less light on diode, change DC transimpedance (?), max power dissipation on BBPD < 0.5 W w/ 25 V bias. Perhaps replace OP27 with TLE2027.

2) Make plan for fixing fiber layout up and down the arms. Need tubing for the whole run. Don't make it cheesy. Two fibers per arm.

3) Fix LSC model to allow user switching of whitening. Get back to working on AutoLock scripts (not Guardian).

4) Manasa, Q, Jenne, tune Oplev servos Tuesday morning/afternoon.

5) Reconnect the other seismometers (Steve, Jenne). For real.

6) Balance PRMI coils at high frequency.

  9674   Tue Feb 25 18:16:22 2014 JenneSummaryLSCEven more violin filters

A new violin mode at 1303 Hz was ringing up this afternoon.  Rana and I added a notch for this.

RXA: while the mode at 1303.6 Hz was ringing down, I used the narrowband DTT technique to measure the Q (after turning on the notch in SUS-PRM_LSC). So its another frequency in the PRM (not the BS).

The time that it takes for 2 -foldings is 652 s, which implies that Q = pi*f*tau = 1.3e6. This seems too high by a factor of ~10, so my guess is that there is still some feedback path happening. The previous bandstop filter was centered around 1285 Hz and seems also weird that the PRM would have 2 violin modes with such different frequencies. Is the mirror rotated around the optic axis such that the standoffs are not at the same height?

Attachment 1: PRMvio2.png
  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


  9691   Wed Mar 5 11:33:10 2014 KojiSummaryLSC2 arm ALS->LSC transition - road map

Step by step description of transition from 2arm ALS to Common/Differential LSC for FPMI

- Step 0: Place the frequencies of the arm green beams at the opposite side of the carrier green.

- Step 1: Activate stablization loops for ALSX and ALSY simultaneously.
  (Use LSC filter modules for the control. This still requires correct handling of the servo and filter module triggers)

- Step 2: Activate stablization loops for ALS Common and Differential by actuating ETMX and ETMY

- Step 2 (advanced): Activate stabilization loops for ALS Common by actuating MC2 and ALS Differential by ETMX and ETMY

- Step 3: Transition from ALS Common to 1/SQRT(TRX)+1/SQRT(TRY). Make sure that the calibration of TRX and TRY are matched.
  The current understanding is that the offset for 1/SQRT(TRX)+1/SQRT(TRY) can't be provided at the servo filter. Figure out
  what is the correct way to give the offsets to the TR signals.

- Step 4: Lock Michelson with AS55Q and then POP55Q (PD not available yet) or any other PD, while the arms are kept off-resonant using ALS.

- Step 5: Reduce the TR offsets. Transition to RF CARM signals obtained from POP55I or REFL11I in the digital land.

- Step 5 (advanced): Same as test6 but involve the analog common mode servo too.

- Step 6: Transition from ALS Differential to AS55Q

Independent test: One arm ALS (To be done everyday)

- ALS resonance scan

- Measurement of out-of-loop displacement (or frequency) stability 

- Check openloop transer function

Independent test: Common Mode servo for one arm

- Reproduce Decmber CM servo result of transition from one arm ALS to CM servo
  Insert 1/sqrt(TRY) servo in between?

- How can we realize smooth transition from ALS to POY11?

  9694   Wed Mar 5 19:15:39 2014 JenneSummaryLSCALS offset moving script modified


- Step 3: Transition from ALS Common to 1/SQRT(TRX)+1/SQRT(TRY). Make sure that the calibration of TRX and TRY are matched.
  The current understanding is that the offset for 1/SQRT(TRX)+1/SQRT(TRY) can't be provided at the servo filter. Figure out
  what is the correct way to give the offsets to the TR signals.

 I have modified the script ALSchangeOffsets.py (in ..../scripts/ALS/) to also handle a "CARM" situation.  There is a new button for this on the ALS in LSC screen.  This script takes the desired offset, and puts half in the ALSX offset, and half in the ALSY offset.  Whatever offset you ask for is given the sign of the input matrix element in the ALS->CARM row of the input matrix.  For example, if you ask for a CARM offset of 1, and the matrix elements are ALSX->CARM=+1 and ALSY->CARM=-1 (because your beatnotes are on opposite sides of the PSL), you will get an offset of +0.5 in ALSX and -0.5 in ALSY, which should be a pure CARM offset. The offsets get set as expected, but I haven't had a chance to test it live while the arms are locked. 

I also want to write a script that will average the IN1 of the 1/sqrt(TR) signals, and put that number into the 1/sqrt(TR) offsets.  If this is run when we are at about half fringe, this will set the zero point of the 1/sqrt(TR) signals to the half fringe (or where ever we are).  Then, we need a script similar to the ALS CARM one, to put offsets into the CARM combination of 1/sqrt(TR)s. 

I think that putting the offsets in before the servo filters will mean that the signals coming out of the input matrices will already be at their zero points, so we won't have as much trouble shifting from ALS to IR.

  9698   Thu Mar 6 11:15:32 2014 KojiSummaryLSCStuck at step 2

You don't need to make transition from ALS X/Y to ALS C/D. Just stabilize the arms with ALS C/D from the beginning.

  9708   Mon Mar 10 21:12:30 2014 KojiSummaryLSCComposite Error Signal for ARms (1)

The ALS error (i.e. phase tracker output) is linear everywhere, but noisy.
The 1/sqrt(TR) is linear and less noisy but is not linear at around the resonance and has no sign.
The PDH signal is linear and further less noisy but the linear range is limited.

Why don't we combine all of these to produce a composite error signal that is linear everywhere and less-noisy at the redsonance?

This concept was confirmed by a simple mathematica calculation:

The following plot shows the raw signals with arbitorary normalizations

1) ALS: (Blue)
2) 1/SQRT(TR): (Purple)
3) PDH: (Yellow)
4) Transmission (Green)

The following plot shows the preprocessed signals for composition

1) ALS: no preprocess (Blue)
2) 1/SQRT(TR): multiply sign(PDH) (Purple)
3) PDH: linarization with the transmission (If TR<0.1, use 0.1 for the normalization). (Yellow)
4) Transmittion (Green)

The composite error signal

1) Use ALS at TR<0.03. Use 1/SQRT(TR)*sign(PDH)*(1-TR) + PDH*TR at TR>0.03
2) Transmittion (Purple)

Attachment 1: composite_linear_signal.nb.zip
  9709   Mon Mar 10 21:13:43 2014 nicolasSummaryLSC Composite Error Signal for ARms (2)

In order to better understand how the composite signal would behave in the presence of noise, I decided to do a simple analysis of the cavity signals while sweeping through resonance.

My noise model was to just assume that a given signal has some rms uncertainty (error bars) and use linear error propagation to propagate from simple signals to more complicated ones.

I used the python package uncertainties to do the error propagation.

I assumed that the ALS signal, the cavity transmission, and the cavity PDH error signal all have some constant noise that is independent of the cavity detuning. Below is a sweep through resonance (x axis is cavity detuning in units of radians).


The shaded region represents the error on each signal.

Next I calculated the 'first order' calculated error signals. These being a raw PDH, normalized PDH, an inverse square root trans, and the normal ALS again. I tuned the gains so they match appropriately.

Here, one can see how the error in the trans signal propagates to the normalized and trans signals and becomes large are the fractional error in the trans signal becomes large.


Next I did some optimization of linear combinations of these signals. I told the code to maximize the total signal to noise ratio, while ensuring that the overall signal had positive gain. I did this again as a function of the cavity detuning.

Each curve represents the optimized weight of the corresponding signal as a function of detuning.


So this is roughly doing what we expect, it prefers ALS far from the resonance, and PDH close to the resonance, while smoothly moving into square root trans in the middle.

It's a little fake, but it gives us an idea of what the 'best' we can do is.

Finally I used these weights to recombine the signals into a composite, to get an idea of the noise of the overall signal. At the same time, I plot the weighting proposed by Koji's mathematica notebook (using trans and 1-trans, and a hard switch to ALS).


So as one can see, at least for the noise levels I chose, the koji weighting is not much worse than the 'optimal' weighting. While it is much simpler.

The code for all this is in the svn at 40mSVN/nicolas/workspace/2014-03-06_compositeerror

  9710   Mon Mar 10 21:14:58 2014 ericqSummaryLSCComposite Error Signal for ARms (3)

Using Koji's mathematica notebook, and Nic's python work, I set out to run a time domain simulation of the error signal, with band-limited white noise added in. 


Basically, I sweep the displacement of the cavity (with no noise), and pass it to the analytical formulae with the coefficients Koji used, with some noise added in. I also included some 1/0 protection for the linearized PDH signal. I ran a sweep, and then compared it to an ALS sweep that Jenne ran on Monday; reconstructing what the CESAR signal would have looked like in the sweep. 

The noise amounts were totally made up. 

They matched up very well, qualitatively! [Since the real sweep was done by a (relatively) noisy ALS, the lower noise of the real pdh signal was obscured.]


Given this good match, we were motivated to start trying to implement it on Monday. 

At this point, since we've gotten it working on the actual IFO, I don't plan on doing much more with this simulation right now, but it may come in handy in the future...

  9711   Mon Mar 10 21:16:13 2014 KojiSummaryLSCComposite Error Signal for ARms (4)

The LSC model was modified for CESAR.

A block called ALSX_COMBINE was made in the LSC block. This block receives the signals for ALS (Phase Tracker output), TRX_SQRTINV, TRX, POX11 (Unnormalized POX11I).
It spits out the composite ALS signal.

Inside of the block we have several components:

1) a group of components for sign(x) function. We use the PDH signal to produce the sign for the transmission signal.

2) Hard triggering between ALS and TR/PDH signals. An epics channel "THRESH" is used to determine how much transmission
we should have to turn on the TR/PDH signals.

3) Blending of the TR and PDH. Currently we are using a confined TR between 0 and 1 using a saturation module. When the TR is 0, we use the 1/SQRT(TR) signal for the control,
    When the TR is 1, we use the PDH signal for the control.

4) Finally the three processed signals are combined into a single signal by an adder.

It is important to make a consideration on the offsets. We want all of ALS, 1/SQRT(TR), and PDH to have zero crossing at the resonance.
ALS tends to have arbitorary offset. So we decided to use two offsets. One is before the CESAR block and in the ALS path.
The other is after the CESAR block.
Right now we are using the XARM servo offset for the latter purpose.

We run the resonance search script to find the first offset. Once this is set, we never touch this offset until the lock is lost.
Then for the further scanning of the arm length, we uused the offset in the XARM servo filter module.

Attachment 1: ss1.png
Attachment 2: ss2.png
Attachment 3: CESAR_OFFSETS.pdf
  9712   Mon Mar 10 21:16:56 2014 KojiSummaryLSCComposite Error Signal for ARms (5)

After making the CDS modification, CESAR was tested with ALS.

First of all, we run CESAR with threshold of 10. This means that the error signal always used ALS.
The ALS was scanned over the resonance. The plot of the scan can be found in EricQ's elog.
At each point of the scan, the arm stability is limited by the ALS.

Using this scan data, we could adjust the gains for the TR and PDH signals. Once the gains were adjusted
the threshold was lowered to 0.25. This activates dynamic signal blending.

ALS was stabilized with XARM FM1/2/3/5/6/7/9. The resonance was scanned. No glitch was observed.
This is some level of success already.

Next step was to fully hand off the control to PDH. But this was not successfull. Everytime the gain for the TR was
reduced to zero, the lock was lost. When the TR is removed from the control, the raw PDH signal is used fot the control
without normalization. Without turning on FM4, we lose 60dB of DC gain. Therefore the residual motion may have been
too big for the linear range of the PDH signal. This could be mitigated by the normalization of the PDH signal by the TR.

  9713   Tue Mar 11 14:49:01 2014 KojiSummaryLSCImportant notice on the XARM servo

The nominal gain of the XARM for the POX11 error signal is 0.03 (instead of previous 0.3)

This is due to my increase of the gain in FM4 by 20dB so that we can turn of FM4 without changing the UGF when it is at 150Hz.

The YARM servo was not yet touched.

  9715   Tue Mar 11 15:14:34 2014 denSummaryLSCComposite Error Signal for ARms (1)


The composite error signal


 Very nice error signal. Still, I think we need to take into account the frequency shape of the transfer function TR -> CARM. 

  9717   Tue Mar 11 15:21:08 2014 KojiSummaryLSCComposite Error Signal for ARms (1)

True. But we first want to realize this for a single arm, then move onto the two arms case.
At this point we'll need to incorporate frequency dependence.

  9731   Mon Mar 17 12:02:55 2014 KojiSummaryGeneralIFO recovery / confirmed ETMX in trouble

I confirmed that we need to vent the chambers.

All of the mirrors have been aligned except for ETMX.

ETMX does not respond to the excitation by the UR and LR coils. Likely that the magnets are knocked off, or stuck in the coil.

PRM/SRM oplevs are too much off and can't be turned on. Need realignment of the beams on the QPDs.

- FB was down. FB restarted ("telnet fb 8087", then type shutdown)

- Aligned the MC mirrors.

- Aligned PRM. Look at the REFL. It was slightly mislisligned.

- AS has no beam. The Y arm was resonating with the green. So I determined that the TTs were the misaligned guys.

- Touched TT2 pitch with an increment of 0.1. Immediately the AS beam spot for ITMY was found. And the arm was resonating.

- The RM was further aligned. The bias sliders were saved and then the PRM was misaligned.

- Yarm was locked on TEM01. The ASS maximized the transmission for TEM01, and then the arm was locked on TEM00.
  The ASS aligned the arm and TTs. These values were saved.

- Yarm was aligned and I can see the AS spot. So I believe the BS is still well aligned.

- Aligned the PRM to reduce the ghost beams.

- Moved the ITMX to have Michelson fringes properly.

- Also aligned the SRM.

- Now ETMX was checked. Played with the alignment biases to see if the mirror was sticking on the coils. The mirror can rock a little, but it did not come back.

- Then, checked each magnets. 0.8Hz 1000cnt signals were injected to each coils (cf. C1:SUS-PRM_**COIL_EXC) to see how the mirror could react.
  The OSEM output and green spot on the ETMX cage were observed.

- Saw some response by actuating the UL, LL, SD coils.

- Saw no response from the UR and LR coils. They show the OSEM output of zero. Does this mean the magnets fell in the coils?

//Manasa// MC spot positions measured and they look alright with not much change from before the earthquake (attach)

Attachment 1: MCspots.png
  9733   Mon Mar 17 20:14:34 2014 KojiSummaryGeneralIFO recovery / confirmed ETMX in trouble

I tried to take the photos of the magnets from outside. So far most suspicious was LL.
Otherwise, the magnets are OK.
(The SD magnet is the one with most reasonable response.)
Steve will try to take much more zoomed photo with Olympus. But the LL coil already showed some response in my observation in the morning.


  9739   Tue Mar 18 21:19:22 2014 KojiSummaryIOOMC spot positions checked

MC spot sposition script was ran


Found no notable beam position change before and after the earthquake


Attachment 1: MCASS.png
  9740   Wed Mar 19 21:37:45 2014 manasaSummaryLSCAttempt to lock PRMIsb with REFL165I&Q

I tried to repeat Koji's PRMI lock using REFL165I/Q. I was not able to lock PRMI stably. All I could get was momentary PRMI sb locks (few seconds) using AS55Q for MICH and REFL165Q for PRMI. I tried to transition MICH locks from AS55Q to REFL165I/Q and this did not work well; I lost even the momentary locks.

The demod phases for both AS55 and REFL165 were also very different. 

Input ports:
AS55       WHTN: 21dB  demod phase -78.7deg
REFL165 WHTN: 45dB demod phase -80.7deg

Input matrix:
AS55Q x1.00 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 0.0 / Gain -10 / Limiter ON
PRCL OFS 0 / Gain -0.023 / Limiter ON

Output matrix:
MICH ITMX -1.0 / ITMY +1.0


  9751   Wed Mar 26 11:16:59 2014 ericqSummaryLSCComposite Error Signal for ARms (3)

Extending the previous model, I've closed a rudimentary CESAR loop in simulink. Error signals with varying noise levels are combined to bring a "cavity" to lock.  


There are many things that are flat out arbitrary at this point, but it qualitatively works. The main components of this model are:

  • The "Plant": A pendulum with f0 = 2Hz, Q = 10
  • Some white force noise, low passed at 1Hz before input to the plant.
  • The Controller: A very rough servo design that is stable...
  • ALS signal: Infinite range Linear signal, with a bunch of noise
  • Transmission and PDH signals are computed with some compiled C code containing analytic functions (which can be a total pain to get working), have less noise than ALS
  • Some logic for computing linearized PDH and SqrtInv signals
  • A C code block for doing the CESAR mixing, and feeding to the servo

And it can lock! 



Right now, all of the functions and noise levels are similar to the previous simulation, and therefore don't tell us anything about anything real...

However, at this point, I can tune the parameters and noise levels to make it more like our interferometer, and thus maybe actually useful. 

  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.

  9759   Fri Mar 28 20:23:02 2014 ranaSummaryIOOMC2 moved

I aligned MC2 suspension by 0.01 in pit and yaw to align the MC better to the PSL beam. Then I turned the WFS back on. The beams are not centered on the WFS heads.

Nic and Gabriele ought to send their SURF some example code (in April) for how to start redesigning the WFS telescopes so that we can order some optics in early June.

I've also turned on the MC2 TRANS path to gather some data over the weekend on how well or bad it works. Please turn it off on Monday.

  9764   Mon Mar 31 11:34:00 2014 manasaSummaryIOOMC2 moved


I've also turned on the MC2 TRANS path to gather some data over the weekend on how well or bad it works. Please turn it off on Monday.

 MC2_TRANS path in WFS servo turned OFF.

  9765   Mon Mar 31 13:15:55 2014 manasaSummaryLSCAlignment update


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)


POP path

The POP PD was showing only ~200 counts which was very low compared to what we recollect from earlier PRMI locks (~400 counts). Also, the POP ASC QPD was also not well-aligned.
While holding PRMI lock on REFL55, I aligned POP path  to its PD (maximize POP DC counts) and QPD (centered in pitch and yaw).

X and Y green

The X green totally lost its pointing because of the misaligned PZTs from last week's power failure. This was recovered.
Y arm green alignment was also recovered.

  9767   Mon Mar 31 17:47:57 2014 ericqSummaryLSCMICH sensing oddities in REFL 3F

Last week, while I had the PRMI locked on REFL33, I did some poking around with mirror excitation to RFPD quadrature transfer functions. I got some indication of weird things with sensing MICH with the 3F REFL signals, but it should be explored more before taken as a real thing. I just figured I would show what I saw. 

With that disclaimer out of the way, here's what I did:

  • Locked PRMI on PRCL:REFL33_I and MICH:REFL33_Q, as detailed in my earlier ELOG
  • Created PRCL and MICH excitations at two different frequencies, notched said frequencies out of the control filters
  • Took transfer functions from mirror LSC output signals to 33 I, 33 Q, 165 I, 165 Q in DTT
  • For each DOF, look at the measured transfer functions only at the excitation frequency. (Assuming good coherence, which was there)

The basic idea was, some PRCL motion (for instance), has a transfer function to both the I and Q quadratures at a given PD. As the PRCL excitation sine wave goes through one cycle, the REFL signals at the excitation frequency go through some coherent cycle. Thus, the excitation traces out some trajectory in the I vs. Q plane. I believe this is analogous to the typical "radar plot" that we make for sensing matrix elements. 

However, the straight line that we normally plot in the radar plots assumes a certain phase relationship between the DOF-> I and DOF->Q transfer functions that results in a straight line. Here are the trajectories I actually measured, normalized by the excitation amplitudes.


The plotted traces are (x,y) = (H_prcl->I * prcl, H_prcl->Q * prcl) and  (x,y) = (H_mich->I * mich, H_mich->Q * mich) where H_prcl->I is the measured complex transfer function from prcl to REFL I, for instance, and prcl and mich are the excitation signals, normalized to unit amplitude.

PRCL looks like a nice straight line in both of these, and pretty well phased, but not only is MICH not very orthogonal to PRCL, there is quite a bit of ellipticity present, which means we can't fully decouple the two DOFs, even if they were nominally orthogonal. 

I'm not sure what may cause this. To back up this measurement/interpretation, I tried to take measurements of these transfer functions across different excitation frequencies via swept sine DTT, but seismic activity kept me from staying locked long enough...

  9768   Mon Mar 31 21:23:30 2014 GabrieleSummaryLSCMICH sensing oddities in REFL 3F

I'm not sure what may cause this. To back up this measurement/interpretation, I tried to take measurements of these transfer functions across different excitation frequencies via swept sine DTT, but seismic activity kept me from staying locked long enough...

I guess that you get an ellipse when the transfer functions to I and Q have a different phase. One mechanism could be that when driving MICH we make some residual PRCL and this couples with a different transfer function to both I and Q. However, I would expect no phase lag in the PRMI configuration, since there is no enough optical delay in the system to give significant dephasing at few hundreds Hz. This effect might come from mechanical resonances.

It is worth measuring the optical transfer functions from both PRCL and MICH to REFL signals at all frequencies, to see if we have strange features in the TFs.

  9769   Mon Mar 31 23:57:22 2014 KojiSummaryASCPRM ASC characterization / design

A series of measurements / calculations for the PRM ASC characterization and servo design

1) Actuator characterization

The actuator responses of the PRM in pitch and yaw were measured (attachment figure 1). I believed the calibration of the oplev QPD to be
1 count/urad. The oplev servo loops were turned off at the FM inputs, and the filter banks were turned off so that the response has the open
loop transfer function except for the servo filter.

The measured transfer functions were fitted with LISO. The LISO results (c.f. the source codes) were shown in the figure. The responses also
include the 60Hz comb filter present in the input filters. The responses are well approximated by the single pendulum with f0 of 0.6-0.8 and q of 3.5 and 6.3.

From this measurement, the actuator responses of the PRM at DC are estimated to be 2.2 urad/cnt and 1.8 urad/cnt in pitch and yaw, respectively.

2) Sensor response of the POP QPD

As we already know how the actuators respond, the QPD optical gain can be characterized by measuring the actuator response of the QPD
(attachment figure 2). The QPD signals are such noisy that the response above 1Hz can't be measured with sufficient coherence. Below 1Hz,
the response is well represented by the actuator response measured with the oplev. From this measurement, the optical gains of the QPD
with respect to the PRM motion are 650 cnt/urad and 350 cnt/urad.

3) Open loop transfer function of the current ASC servo

By combining the above information with the servo setting of the servo filters, the open loop transfer functions of the PRM QPD ASC loops
were estimated (attachment figure 3). Actually the expected suppression of the fluctuation is poor. The yaw loop seems to have
too low gain, but in fact increasing gain is not so beneficial as there is no reasonable phase margin at higher frequency.

With the estimated openloop transfer functions and the measured free-running angular fluctuation, the suppressed angular spectra can be
estimated (attachment figure 4). This tells us that the suppression of the angular noise at around 3Hz is not sufficient in both pitch and yaw.
As there is no mechanical resonance in the actuator response at the frequency, intentional placement of poles and zeros in the servo filter is necessary.

4) Newly designed ASC filter

Here is the new design of the QPD ASC servo (attachment figure 5). The target upper UGF is 10Hz with the phase margin of 50 to 60deg.
The servo is AC coupled so that we still can tweak the alignment of the mirror.

As this servo is conditionally stable, at first we should close the loops with stable filter and then some boosts should be turned on.
Estimated suppressed fluctuation is shown in the attachment figure 6. We can see that the fluctuation was made well white between 0.5Hz to 10Hz.

The filter design is shown as follows:

FM1: zero at 0Hz, pole at 2000Hz, gain at 2000Hz = 2000

FM3: (boost)
zero: f: 0.5Hz q: 1  /  4.5Hz, q: 1 / f: 1Hz, q: 3
pole: f: 2Hz q: 3  / f: 2.7Hz, q: 2  / f: 1Hz, q: 15

FM9: (HF Roll-off)
pole: f: 40Hz q: 1.7
Servo gain: -0.028

FM1: zero at 0Hz, pole at 2000Hz, gain at 2000Hz = 2000

FM3: (boost)
zero: f: 0.7Hz q: 2  /  3Hz, q: 7 / f: 2Hz, q: 6
pole: f: 1.02Hz q: 10  / f: 4.5Hz, q: 0.8  / f: 1.5Hz, q: 10

FM9: (HF Roll-off)
pole: f: 40Hz q: 1.7
Servo gain: -0.0132


Attachment 1: PRM_OPLEV.pdf
Attachment 2: PRM_QPD.pdf
Attachment 3: OLTF_design.pdf
Attachment 4: QPD_spe.pdf
Attachment 5: OLTF_design2.pdf
Attachment 6: QPD_spe2.pdf
Attachment 7: 140328.zip
  9772   Tue Apr 1 21:45:01 2014 JenneSummaryLSCPRM violin notch not at correct freq?

Koji and I have the PRMI locked right now, and we hear a very strong violin mode ringing up, at 628Hz.  This is, according to Koji's elog 9634, what we expect the PRM's violin mode to be.  However, the current PRM violin mode notch is really more of a bandstop filter, between 622-670Hz.  At 628Hz, it has a suppression of about -20dB.  If I try to increase the width of this notch by making it 612-670Hz, the PRMI won't hold lock.

We're leaving this as a daytime task for tomorrow, since we're in the middle of taking data to show that Koji's new ASC filter design (slightly tuned from his elog 9769) works well.

Edit:  I have moved the PRM violin notch frequency over to 612-660 Hz, and after letting it sit for a while (while locked on PRMI), the violin mode has settled down.  Interestingly, if I compare the spectrum with and without the 1st order violin mode notch, it looks like the 2nd order mode changes from 1256Hz to 1303Hz.  I don't know what is going on here, but we already have notches for both of those frequencies.

  9773   Tue Apr 1 22:03:44 2014 KojiSummaryASCNew PRM ASC is running

[Koji Jenne]

New PRM ASC was implemented. [to be cnt'd]

  9777   Wed Apr 2 19:50:12 2014 KojiSummaryASCNew PRM ASC is running

As the designed ASC filters in this entry had too little phase margins (~10deg), I had to compromise the servo design.

The design was modified and tested again. This will be reported by a following entry.

Incidentally, I have adjusted the demodulation phases of REFL33/55/165 for PRMIsb so that the PRCL is eliminated from the Q signals.

REFL33    125.5 deg -> +136.5 deg
REFL55      45.0 deg -> +  25.0 deg
REFL165   -79.5 deg -> +  44.5 deg

This change of the demod phase for REFL165 was a bit surprising.
I did not check the sign, so it could be -135.5 deg. But still this is a bit change.

  9779   Wed Apr 2 23:08:51 2014 KojiSummaryASCNew PRM ASC is running

The new PRM ASC design

FM1: zero at 0Hz, pole at 2000Hz, gain at 2000Hz = 2000

FM5: (boost)
zero: f: 0.5Hz q: 1  /  4Hz, q: 2 / f: 1Hz, q: 3
pole: f: 2Hz q: 3  / f: 2.7Hz, q: 2  / f: 1Hz, q: 15

FM9: (HF Roll-off)
pole: f: 40Hz q: 1/Sqrt(2) (2nd order butterworth)

Servo gain: -0.023

FM1: zero at 0Hz, pole at 2000Hz, gain at 2000Hz = 2000

FM5: (boost)
zero: f: 0.5Hz q: 1  /  4Hz, q: 2 / f: 1.5Hz, q: 10
pole: f: 1.02Hz q: 10  / f: 3Hz, q: 5  / f: 2Hz, q: 6

FM9: (HF Roll-off)
pole: f: 40Hz q: 1/sqrt(2)
Servo gain: -0.027

The loop gains were adjusted to have the UGFs of 10Hz. The measured openloop transfer functions were compared with the model.
The transfer functions for yaw are well matched. However, the pitch ones don't. It seems that the pitch loop has extra low pass
which I can't locate. The possibility is the analog electronics of the pitch loop.

The effect of the control between 0.3Hz to 3Hz are well represented by the model. The attachment 2 shows the free running
angle fluctuation, the ones with the control engaged, and the estimated spectra. Indeed, the estimated spectra well represent
the measured angular spectra.

Attachment 1: PRM_QPD.pdf
Attachment 2: QPD_spe.pdf
  9784   Thu Apr 3 18:55:10 2014 ericqSummaryLSCSome CARM related modeling

 The other day, Jenne and I were comparing my MIST simulation to her Optickle simulation for the CARM transfer functions I posted some days ago. She told me that the arms are not exactly where they should be for the whole "PRC length tuning to account for sideband reflection phase off resonant cavity" deal. 

Specifically, as in the wiki (but with newer modulation frequencies), I calculated the ideal arm length to be 37.795 m some time ago, when doing PRC length simulations, and Jenne has told me that the X arm is more like 37.6m, and Y is 37.9. So, I updated my simulations, and found the following:

This does weird things to the f2 sideband buildup on resonance in the PRFPMI configuration:

asIsPRCRes.pdf idealPRCRes.pdf

(POP is way huger than than the TR's, because the POP pd's are artificially "inside" the cavity, whereas TRX/Y is actually transmitted through an ETM)

This is not necessarily directly something to worry about, but I think the following may be. It looks like this arm length mismatch actually causes the PRCL demodulation phase in REFL 165 to change dramatically with the CARM offset. (REFL33 seems fine, though. 5 degrees causes less than a 1% effective gain change.) 


My simulations don't include any signal recycling yet, so I don't have anything to show if there is a similar effect for SRCL, but it wouldn't surprise me... 


  9785   Fri Apr 4 18:51:29 2014 ericqSummaryLSCMORE CARM related modeling

In today's ISC call, Kiwamu was comparing two ways to approach resonance: 

  • "C-Type": The scheme we currently think about; zero DARM offset and slowly reduce the CARM offset
  • "D-Type": Start with no CARM offset, but a DARM offset and reduce that. 

D-type might be interesting to check out, since things change a little less dramatically when you reduce the DARM offset. Maybe this makes signal hopping easier? Signal recycling may complicate things, though. 

So, I've simulated CARM and DARM offset effects on CARM and DARM signals. (As with the previous plots, this is for the PRFPMI configuration.) From moving both offsets around, it looks like the resonance peak is about 5x wider in DARM than in CARM, so I simulated a 50pm offset range for CARM and a 250pm offset range for DARM. 

Here are some CARM signal transfer functions subject to CARM offsets in the top plot, and DARM offsets in the bottom plot. 




It's looks like the DARM offset changes cause much less dramatic changes in the CARM plant features. It's conceivable that this would make CARM locking easier. 

Here are some DARM plant transfer functions. 



In these plots, I did something kind of artificial: when we move the CARM offset, it changes the proper demodulation phase to get DARM in the Q of the AS 1F RFPDS. So, at each CARM offset, I re-phased the AS 1F demodulators, to show the total DARM information available at the AS RFPDs at each offset, rather than what one would actually see in them with a static demod phase. 


  9794   Thu Apr 10 10:52:15 2014 manasaSummaryIOOMC2_TRANS path in WFS servo



I've also turned on the MC2 TRANS path to gather some data over the weekend on how well or bad it works. Please turn it off on Monday.

 MC2_TRANS path in WFS servo turned OFF.

[From yesterday]

The MC had not been stable lately with WFS drifting constantly. I checked the servo and found that the MC_TRANS path was still running. It turned out that the autolocker script enables the TRANS path in the locking process. I have turned the MC_TRANS path servo inputs OFF and now it is no more a part of the WFS servo.

P.S. Jenne fixed the PMC alignment mostly in pitch to bring it up to 0.81 from 0.77. But the temperature fluctuations have still not got us to the sweet spot for optimum PMC trans.

  9837   Mon Apr 21 23:33:57 2014 ranaSummaryGreen LockingHP 8591E reads low by 140 Hz out of 10 MHz

To check the basolute frequency stability of the old monochrome HP 8591E RF Spectrum analyzer that we're using for the ALS beat readout, I hooked its 10 MHz reference output (from its rear panel) into the A channel of the SRS SR620 frequency counter. The SR620 is locked to the FS 720 Rubidium clock via the 10 MHz connections in their rear panels.

So, we can assume that this is a good absolute readout. It reads 9.999860.7 +/- 0.3 Hz. So its 139.1-139.4 Hz lower than 10 MHz. The +/- 0.3 is just a slow drift that I see over the course of 10 minutes.

So, let's say that the analyzer is low by 10 ppm, so the arm length estimates are short by ~0.4 mm. A negligible correction, so there's no need to use atomic clocks to measure our arm lengths.

  9857   Fri Apr 25 23:08:57 2014 ranaSummaryIOOMC2_TRANS QPD Servo re-re-engaged again

We turned on the MC2_TRANS paths for both PIT/YAW tonight.

I turned off the BLP200 and turned on the RLP7 (RLP always are better than BLP). G_PIT = -0.111, G_YAW = 0.111. On Monday, let's let Steve look at the trends and determine if this centering servo is bad or good.

  9858   Sat Apr 26 13:19:59 2014 ericqSummaryIOOMC2_TRANS QPD Servo re-re-engaged again


We turned on the MC2_TRANS paths for both PIT/YAW tonight.

I should've included this in my Thursday night ELOG... That evening, I aligned the mode cleaner with reasonable MC1/3 spot positions, and the MC2 spots very close to centered, and recentered the WFS and MC2 Trans QPDs. The mode cleaner held up very well over the course of that evening, even when actuating CARM on MC2 with WFS engaged (which previously wasn't very stable when the WFS weren't well aligned).

  9869   Mon Apr 28 15:47:57 2014 manasaSummaryIOOMC2_TRANS QPD Servo trend


We turned on the MC2_TRANS paths for both PIT/YAW tonight.

I turned off the BLP200 and turned on the RLP7 (RLP always are better than BLP). G_PIT = -0.111, G_YAW = 0.111. On Monday, let's let Steve look at the trends and determine if this centering servo is bad or good.

The MC was showing slow but periodic alignment drifts and eventually unlocked around noon. I looked up the alignment trend (Attach: 2 day trend)

MC_TRANS_PIT_ERR and MC_TRANS_Y_ERR show that the MC_TRANS servo slowly drifted the IMC alignment causing it to lose lock from time to time (mostly in yaw).

To confirm that the drift was NOT due to off-centering in the MC2_TRANS QPD, I turned off the WFS servo, moved MC2 to recenter the trans beam on the QPD, and re-enabled WFS servo.

MC_TRANS path in WFS is still left enabled.

Attachment 1: MC_TRANSservoApr28.png
  9871   Mon Apr 28 20:31:38 2014 ranaSummaryIOOMC2_TRANS QPD Servo trend

This is a 4-day trend. I don't see any difference here which is significant. My guess is that the MC_TRANS servo gain is so low that its not really doing anything.

I'll turn it on periodically this week and then on Monday people can look at the trend again to see if they can identify when the servo is ON and when its OFF.

Attachment 1: Untitled.png
  9886   Wed Apr 30 21:57:07 2014 ranaSummaryIOOMC2_TRANS QPD Servo now on for real


During a lull in Koji vs. The Arm, I switched on the MC2_TRANSQPD feedback path to check out its UGF. In the past months, when its been on, it has had a gain of ~0.03 - 0.1.

Today, I found that with the gain turned up to 11, it has a ~1 minute step response time (as you see in the above Strip chart). So its had a UGF of ~2 hours or so during the times when we thought it might be doing bad or good or magic.

I leave it on now to see if it behaves well over the next days. Let's see if Steve thinks its good or not based on his trend monitoring.

** also touched up the PMC pointing (using the PMC REFL image / please never align the beam into the PMC without this camera image)

  9925   Wed May 7 23:09:06 2014 rana, jamieSummaryComputer Scripts / ProgramsOttavia back on network

After Jamie fixed the third party repo issue with Ottavia, he was able to upgrade it to Ubuntu 12.04 Precise Pangolin. But its network stopped working.

I tried to fix its issues by ifconfig and GUI, but what it really wanted was for me to put the network cable back into its eth0 slot. The eth1 network card appears not be working anymore.

All seems fine now. Next I will mount the shared user disk from linux1 and put in a .bashrc.

  9932   Thu May 8 17:00:56 2014 rana, QSummaryLSCREFL_DC handoff didn't work last night

Last night after checking cabling and turning on ISS, we tried several times to handoff to REFL_DC but it didn't work at all.

Some issues:

  1. The ISS was injecting a lot of very low frequency power fluctuations because of bad AC coupling.
  2. The SR560 @ LSC rack was saturating a lot with the x10 gain that Jenne and Rana put in; we turned it back to G = 1.
  3. The ISS was also saturating a lot. We turned it off around 4 AM, but still no success.
  4. The ALS sequence for finding the Red Resonance takes too long (~2 minutes), so we're trying a faster scheme tonight.
  9934   Fri May 9 01:36:28 2014 ranaSummarySUSOptical Lever QPD Sum trends: they're almost all too weak

 We want there to be ~16000 cts of signal per quadrant on the optical levers. I think that most of the QPDs have been modified to have 100k transimpedance resistors.

From the attached 90 day trend, you can see that the ETMX, BS, PRM, and SRM are really low. We should figure out if we need to change the lasers or if the coating reflectivities are just low.

Steve, can you please measure the laser powers with a power meter and then reply to this entry?

Another possibility is that we are just picking a dim beam and a brighter one is available.

Attachment 1: OLtrend.png
ELOG V3.1.3-