40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  40m Log, Page 124 of 341  Not logged in ELOG logo
ID Date Author Type Category Subjectup
  5668   Sat Oct 15 04:53:41 2011 SureshUpdateIOOMC WFS Output Matrix determination

After we had a rough idea of what the output matrix looks like (see this elog),
I tried to measure the transfer function coefs (TFCs) between mirror degrees of freedom and the WFS sensors (WFS1, WFS2 and MC_Trans QPD)
I found that the TFCs that I obtained at 10.15 Hz did not have any resemblance to the previously identified output matrix.

The problem, I realised, arises because the various lockins used
in the C1IOO model do not have the same relative phase; So if we try to excite a mirror with one of them
and demodulate a sensor signal on any of the other lockins the resulting output would not have the correct phase
(relative to the 1st lockin output). As a result unless we can reset the phase of all the lockins
simultaneously, we cannot demodulate multiple signals at the same time. (Joe/Jamie, Is it possible to
reset/reinitialise the phase of the CLK signals of the lockings? )


To get around this problem Koji suggested that I use just one lockin and determine all the 36 elements of the transfer matrix with it one at a
time rather than six at a time. When I did that, I got results consistent with the previoulsly determined outmatrix. It, of course, takes six times longer.

The matrix I first got is this one

 

(Mag, Phase) WFS1P WFS2P MC_T_P WFS1Y WFS2Y MC_T_Y
MC1P 0.332 0.518 0.316 0.019 0.066 0.000
  5.832 1.892 8.180 38.285 8.807 0.000
             
MC2P 0.355 1.798 0.342 0.023 0.144 0.000
  72.977 76.683 76.804 -16.364 77.451 71.579
             
MC3P 0.352 0.394 0.254 0.036 0.023 0.000
  2.005 3.249 6.249 5.712 26.349 NAN
             
MC1Y 0.051 0.055 0.058 0.788 1.024 0.001
  15.979 -4.487 -9.707 2.642 1.276 0.000
             
MC2Y 0.142 0.044 0.130 1.966 0.579 0.017
  70.044 83.818 76.397 74.283 76.134 77.269
             
MC3Y 0.044 0.052 0.022 0.080 0.948 0.194
  22.932 14.227 -45.924 9.677 1.125 1.124
             
Which can be  recast as below          
             
             
Magnitude WFS1P WFS2P MC_T_P WFS1Y WFS2Y MC_T_Y
MC1P 0.332 0.518 0.316 0.02 0.07 0
MC2P 0.355 1.798 0.342 0.02 0.14 0
MC3P 0.352 0.394 0.254 0.04 0.02 0
MC1Y 0.05 0.05 0.06 0.788 1.024 0.001
MC2Y 0.14 0.04 0.13 1.966 0.579 0.017
MC3Y 0.04 0.05 0.02 0.080 0.948 0.194

Phase WFS1P WFS2P MC_T_P WFS1Y WFS2Y MC_T_Y
MC1P 5.8 1.9 8.2 38.3 8.8 0.0
MC2P 73.0 76.7 76.8 -16.4 77.5 71.6
MC3P 2.0 3.2 6.2 5.7 26.3 NA
MC1Y 16.0 -4.5 -9.7 2.6 1.3 0.0
MC2Y 70.0 83.8 76.4 74.3 76.1 77.3
MC3Y 22.9 14.2 -45.9 9.7 1.1 1.1

 

Note that when MC2 is excited all the sensors showed a response about 75 deg out of phase with the reference (MC1 --> WFS1_PIT ) This was traced to the fact that while there is a 28Hz Elliptic LP filter on

both MC1 and MC3, while it is absent on MC2.  The Transfer functions  below show the difference in the phase of their response

WFS1P_RespTo_MC1andMC2.pdf

 

Since the MC2 POS is used in servos involving MCL we cannot afford to install a 28 Hz LP filter into the MC2 coil drivers.  However a module with the 28 Hz ELP was switched on, in each of the

 MC2 PIT and YAW filter banks.   I then checked to see if this has affected the relative phase of variour sensors.  The Phase angle between I and Q on each sensor channel was checked and corrected. 

Below are the spectra with the "before" and "after" correction of phases.

Before:

 WFS1_IQphase20111015_1.pdf        WFS2_IQphase20111015_1.pdf

 

Obviously this needed adjustment to reduce Q phase.   

  After twealkng the angle "R":

WFS1_IQphase20111015_2.pdf      WFS2_IQphase20111015_2.pdf

 

And again determined the transfer matrix (below). 

( I , Q ) WFS1P WFS2P MC_T_P WFS1Y WFS2Y MC_T_Y
MC1P 0.236 -0.300 0.229 0.049 -0.008 0.000
  0.015 -0.004 -0.027 0.011 -0.019 0.000
             
MC2P -0.125 -0.962 -0.135 0.114 0.028 0.000
  0.007 -0.052 -0.028 -0.004 -0.002 0.000
             
MC3P -0.225 -0.254 -0.255 -0.026 -0.010 0.000
  0.004 -0.012 -0.010 0.009 0.002 0.000
             
MC1Y -0.059 -0.023 -0.040 0.460 0.705 0.001
  0.004 0.003 0.009 0.009 0.017 0.000
             
MC2Y 0.030 0.190 0.040 -1.144 -0.296 0.015
  0.007 0.006 -0.009 -0.038 -0.009 0.001
             
MC3Y 0.018 -0.108 -0.018 0.134 -0.832 -0.001
  0.017 0.005 0.001 0.006 -0.016 0.000
 

Magnitude WFS1P WFS2P MC_T_P WFS1Y WFS2Y MC_T_Y
MC1P 0.236 0.300 0.231 0.05 0.02 0
MC2P 0.125 0.964 0.138 0.11 0.03 0
MC3P 0.225 0.254 0.255 0.03 0.01 0
MC1Y 0.06 0.02 0.04 0.460 0.705 0.001
MC2Y 0.03 0.01 0.19 1.145 0.296 0.015
MC3Y 0.02 0.11 0.02 0.134 0.832 0.001

Phase WFS1P WFS2P MC_T_P WFS1Y WFS2Y MC_T_Y
MC1P 3.694 0.784 -6.778 13.1 66.67 #DIV/0!
MC2P -3.214 3.100 11.557 -2.05 -4.48 0
MC3P -1.020 2.665 2.158 -19.1 -10.76 NA
MC1Y -3.96 -6.45 -12.14 1.085 1.357 0.000
MC2Y 13.22 41.08 -2.6 1.887 1.706 4.987
MC3Y 42.69 -2.56 -3.73 2.652 1.068 0.000

 

This time the signals are all nearly in the same phase and in agreement with the  outmatrix estimate made earlier.

 

I plugged these TFCs into the matrix inversion code: wfsmatrix2.m.   And get the following inverse:

 

  WFS1P_Act WFS2P_Act MC_Trans_P_Act WFS1Y_Act WFS2Y_Act MC_TRANS_Y_Act
MC1P 1 -0.64        
MC2P -0.27 -1        
MC3P 0.98 -0.65        
MC1Y       -0.26 -1  
MC2Y       1 0.12  
MC3Y       0.16 0.07  

 

I have ignored the MC2_Trans_P and Y sensors for now.

  5669   Sat Oct 15 10:58:32 2011 ranaUpdateIOOMC WFS Output Matrix determination

In order to save time and sanity, you should not measure the pitch ->yaw and yaw-> pitch. It makes things too complicated and so far is just not significant. In the past we do not use these for the matrix work.

i.e. there should just be a 3x3 pitch matrix and a 3x3 yaw matrix. Once the loops are working we could investigate these things, but its really a very fine tweak at the end. There are quite a few other, more significant effects to handle before then.

To make things faster, I think we can just make a LOCKIN which has 3 inputs: it would have one oscillator, but 6 mixers. Should be simple to make.

  5904   Wed Nov 16 08:57:08 2011 SureshUpdateIOOMC WFS Servo OLG data and fits

I measured the Transfer Functions between from IN2 to IN1 on the WFS1PIT, WFS2PIT, WFS1YAW and WFS2YAW servo loops. 

Then I used the foton filter profiles of the servo filters in the loop and added another one to simulate the pendulum to generate a reasonable fit to the data.  Only the pendulum filter was hand tweaked since the PIT and YAW pendula have different resonant frequencies.

The filter modules included are:

1) Integrator: zpk([0.8],[0],0.8,"n")

2) Phase lead: zpk([0.8],[100,100],1,"n")

3) 45 deg filter: zpk([1:10],[3,30],1,"n")

4) ELP28: ellip("LowPass",5,1,50,28)

5)Pendulum: zpk([ ],0.03+i*0.82;0.03+i*0.82;],1,"n"  (for YAW)

5)Pendulum: zpk([ ],0.05+i*0.68;0.05+i*0.68;],1,"n"  (for PIT)

The data and fits are below.   The UGF is around 2 to 3 Hz and there is no servo bump at this gain setting.  The fits are poor at and below the resonance because the coherence was poor at these frequencies.  I will have to do a swept sine measurement for these low frequencies.

WFS1PITservo.png  WFS2PITservo.pngWFS1YAWservo.png  WFS2YAWservo.png

  5883   Sat Nov 12 03:46:55 2011 SureshUpdateIOOMC WFS Servo: Open loop gain

[Mirko, Suresh]

I closed the WFS loops and measured the transfer function from IN2 to IN1 testpoints on the WFS1_PIT filterbank. 

We looked at the filter shape consisting of

1) Integrator: zpk([0.8],[0],0.8,"n")

2) zpk([0.8],[100,100],1,"n")

3) zpk([1:10],[3,30],1,"n")

The combined filter shape (along with an added pendulum filter, zpk([ ],0.8,1,"n")  ) is given below

WFS1_PIT_servo_filtershape_20111111_1.png

 

The OL Transfer function measured for WFS1_PIT loop is

WFS1_PIT_servo_OLG_20111111_1.png

 The blue reference is a measurement  without the third "45 deg" filter in the list above.  Without it the UGF is around 1.5Hz and increasing the gain results in additional noise from the servo bump seen in the earlier elog .  With it the UGF is around 3Hz.

The supression of the error signal is shown here

 Error_signal_WFS1_PIT_20111111_1.png

The other WFS loops are expected to have a similar behaviour with the exception of the MC2 QPD channels.  I will measure their OLTF shortly and then proceed with the inclusion of the QPD sensors into the WFS system.

 

 

  5884   Sat Nov 12 08:09:47 2011 ranaUpdateIOOMC WFS Servo: Open loop gain

Somehow, I generically don't like the idea of lead filters for the WFS loops. We don't really need so much bandwidth. I think you should include with the servo measurements, a servo model ( on the same plot ) that matches the loop shape.

For example, this means including the 28 Hz ELP in the MC1/3 hardware and MC2 ASCPIT/YAW digital filter banks. BY comparing the model v. measurement we can determine if the cross-coupling due to imperfect output matrix is very serious or not.

In the measurements, the loop with the most low frequency gain looks the most promising.

  5892   Tue Nov 15 01:44:36 2011 SureshUpdateIOOMC WFS Servo: Open loop gain

Quote:

Somehow, I generically don't like the idea of lead filters for the WFS loops. We don't really need so much bandwidth. I think you should include with the servo measurements, a servo model ( on the same plot ) that matches the loop shape.

For example, this means including the 28 Hz ELP in the MC1/3 hardware and MC2 ASCPIT/YAW digital filter banks. BY comparing the model v. measurement we can determine if the cross-coupling due to imperfect output matrix is very serious or not.

In the measurements, the loop with the most low frequency gain looks the most promising.

WFS1_PIT servo replotted with foton data overlaid:

I included the following filters in foton:

1) Integrator: zpk([0.8],[0],0.8,"n")

2) zpk([0.8],[100,100],1,"n")

3) zpk([1:10],[3,30],1,"n")

4) ELP28

I have unwound the phase by adding or subtracting 180 to portions of the phase data.

And here is the plot for WFS1_PIT.  I will repeat this process for the other three WFS loops tomorrow.

WFS1PIT_OL_gain.png

 

  5840   Tue Nov 8 12:07:08 2011 SureshUpdateIOOMC WFS Servo: suppression of WFS error signals below 3Hz

I switched on the WFS servos with the output matrix (open loop) determined last Friday.  Only the WFS1Pit, WFS2Pit, WFS1Yaw and WFS2Yaw servo filters are now on.   I then adjusted the gains to obtain maximum suppresson of error signals without oscillations in the loops

I now proceed to determine the output matrix again.

WFS_servo-20111108.png

  455   Sun Apr 27 05:09:30 2008 ranaConfigurationIOOMC WFS Whitening turned on
I hardwired on the MC WFS whitening filters.

The MAX333A switches which choose between whitening and bypass on that board were in the bypass position
because the Xycom220 connections are not there. So the control switch gets +15V but there is no pull
down to set it to the whitened mode.

The least invasive (easiest) change I could do was to tie all of those inputs to ground. This pulls a few mA
through the pull-down resistors but is otherwise innocuous. All of these control lines come in on the A-row
of the P1 connector, so I was able to solder a single wire across all of them to ground them all.

The WFS2 board had a blown electrolytic capacitor on the -15 V line and so there was probably some extra noise
getting in that way. I couldn't find any extra SMD to replace it so I cut the legs off of a 22 uF polarized
tantalum and stuck it in there. Its even close to being the same color. I checked out the other caps, and they were all
close to 68 uF as spec'd. This one had luckily blown open and so didn't suck down the Sorensen and destroy everything.

Plugged everything back in switched the WFS servos back on. Looks good. Took before and after spectra.

In the plot:

GREEN: Open loop dark noise before changes
RED: Open loop bright (MC locked but MCWFS off)
BLUE: Closed loop, MC locked

BLACK: Dark noise after whitening
ORANGE:Closed loop after whitening

The cursor is at 16.25 Hz, the SOS bounce mode.

The I ran the new setMCWFSgains script which uses pzgain to set the UGFs of the 4 loops to 4.01 Hz.
We have in the past had problems with high WFS gains causing instabilities with the CM servo around 10-30 Hz. If this happens we should
just lower the gain by a factor of ~5.
Attachment 1: mcnoise.png
mcnoise.png
  10424   Fri Aug 22 15:11:55 2014 andres, nicolasSummaryIOOMC WFS activity

1. Before doing anything, we centered the IOO QPDs.
2. With the WFS enabled, we offloaded the control signals onto the bias sliders. Then we saved the slider values. The MC LSC diode had a DC value of ~0.5
3. Turned down power with half wave plate before PMC.  Power injected to vacuum ~ 100mW.
4. We did a beam scan of MC REFL, it looks smaller than what Andres predicted based on the MC eigenmode by 10-20%.
5. We made many changes on the table, pictures to be added by Andres.
6. We didn't have the 80% reflector we wanted to increase the WFS power, so it's still a 98%.
6. Beams were aligned on MC REFL PL, camera, beam dumps, WFSs.
7. Clean up
8. PSL power increased to 1.2W, MC locked right away.
9 We didn't change the IOO WFS output matrix, but we changed some signs and gains to make everything stable. MC autolocker brings it back from cold just fine.
10. All time bombs that we've left will be E.Q.'s to clean up. Sorry.\
11. Yay

  10425   Fri Aug 22 15:58:02 2014 SteveSummaryIOOMC WFS activity

 

 

Attachment 1: GoyphaseSet.png
GoyphaseSet.png
  7452   Fri Sep 28 21:17:41 2012 KojiUpdateIOOMC WFS adjustment

MC WFS was fixed. Now it is running constantly with the autolocker.

Found a bug in the IOO screen: All of the 6 WFS signal indicators is liked to the same info (C1:IOO-MC1_PIT_OUTPUT).
Fix this, Jenne! Baaaaagghhhhh! 


What I did:

1. C1:IOO-MC_RFPD_DCMON indicator was saturating. "HOPR" of this entry was  set to 5 by running the following command:

ezcawrite C1:IOO-MC_RFPD_DCMON.HOPR 5

2. Scan MC2 spot position by using /opt/rtcds/caltech/c1/scripts/MC/moveMC2 scripts.
or the adjustment, C1:SUS-MC2_ASCPIT_EXC and C1:SUS-MC2_ASCYAW_EXC were excited with 300cnt at 12Hz and 10Hz, respectively.
The corresponding peaks (i.e. ANgle to length coupling) in C1:IOO-MC_F were monitored on DTT and adjusted so that the peaks are approximately nulled.

3. moveMC2 scripts are not perect to keep the maximum of the transmission. So, the alignment was adjusted with MC1 and MC3.

4. Repeated 2 and 3 until the alignment converges.

5. Once I got satisfied with the MC2 spot position, I went to the MC2 table and aligned the steering mirror before the QPD.

6. As these actions above moves the REFL beam, I went to the MC REFL path and adjusted the MC REFL PD position and the MC WFS spot positions.

7. Checked if the alignment is still good. The MC REFL is 0.50~0.51. Pretty good.

8. Run /opt/rtcds/caltech/c1/scripts/MC/WFS/WFS_FilterBank_offsets to register the current WFS offset etc.

9. At this point, MC WFS started working fine. I also confirmed the autolocker worked with this setting.

--------

Checked how the things are going in the morning. There were several unlocks. But the autolocker and WFS kept the cavity lcoked again.
Very good.

Some power fluctuation of ~1% is observed in the MC trans. I checked the PMC trans and found it is also fluctuating by 1% in a coherent way.
So I judge the WFS itself is fine. (See attached)

 

 

Attachment 1: MC_WFS_12h.png
MC_WFS_12h.png
  7455   Mon Oct 1 11:08:25 2012 JenneUpdateIOOMC WFS adjustment

Quote:

Found a bug in the IOO screen: All of the 6 WFS signal indicators is liked to the same info (C1:IOO-MC1_PIT_OUTPUT).
Fix this, Jenne! Baaaaagghhhhh! 

 My bad.  As it turns out, you can't copy and paste between MEDM instances.  It is now fixed.

  1196   Fri Dec 19 14:35:58 2008 Yoichi AlbertoUpdateIOOMC WFS and IOO-POS QPD re-centering
For the past two days, the MC alignment has kept drifting.
This morning, the MC alignment was so bad that it wouldn't lock to the TEM00 mode.
We aligned the MC mirrors manually until the reflection looks like a nice bull's-eye (the WFSs were off at this moment).
Then we un-locked the MC and centered the beams on the WFS QPDs.
Since the QPDs were saturated with the full laser power falling on them, I reduced the PSL power by turning the HWP after the MOPA.
After this, we turned on the WFSs and everything looks normal now.
We will see the trend of the MC related channels to monitor the drift.

Although unlikely, it might be caused by the drift of the input beam to the MC.
We found that the IOO-POS QPD was mis-centered and saturating.
We replaced the BS picking up the beam for the QPD from 33% reflection to 10% one. The QPD was still saturated.
So we put the 33% BS in the beam path to the QPD to further reduce the power. The beam kicked by the 33% BS
is dumped to a black aluminum plate. We should use a better beam dump later.
Now the IOO-POS QPD should tell us some information about the beam pointing of the PSL, though it has no sensitivity
to the relative motion of the PSL table to the vacuum chambers.
  8534   Tue May 7 03:25:28 2013 JenneUpdateIOOMC WFS drifting??

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

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

  9806   Mon Apr 14 11:19:55 2014 JenneUpdateLSCMC WFS found off

I'm not sure why, but the WFS were turned off when I came in this morning.  The MC was not staying locked, and even during brief locks, the FSS FAST out was railed at 10. 

Aligning the MC mirrors to maximize the transmission, and then engaging the WFS seems to have made things better.

  10704   Wed Nov 12 20:11:41 2014 KojiUpdateIOOMC WFS gain reduced again

MC WFS was oscillative at 1Hz. I've reduced the servo gain further (x1, x1, x10, x1, x1, and x10).

The MC mirrors were realigned, and the WFS offsets were reset.

  8843   Sun Jul 14 17:47:28 2013 KojiUpdateIOOMC WFS maintenance

Annalisa notified me that the MC autolocker could not keep the MC locked.

I found the initial alignment was not good and the MC was too much excited when the WFS kicked in.

There might have been the WFS offset issue due to the miscentering of the spots on the WFS diodes.

I used the usual procedure of the maintenance and it looked OK if I followed the switching procedure the mc autolocker suppoed to do.
http://nodus.ligo.caltech.edu:8080/40m/7452

I still could not get the autolocker running smoothly. I opened mcup script and compared what was the difference
between my manual sequence and what the script did. The only difference was the lines related to MCL.
It was still turning on the filter module. I checked the MCL path and found that the gain was not zero but 1.0.
So now the MCL gain is set to zero. This solved all the remaining issue.

  6767   Wed Jun 6 15:16:00 2012 yutaUpdateIOOMC WFS offsets adjusted

MC reflection (C1:IOO-MC_RFPD_INMON) got worse when WFS servos were on. After aligning MC optics, it will be ~0.5 but if I turned on WFS, it became ~0.8.
I measured the beam spot positions on MC optics. They seemed like the same from the measurement yesterday.

# filename      MC1pit  MC2pit  MC3pit  MC1yaw  MC2yaw  MC3yaw  (spot positions in mm)
./dataMCdecenter/MCdecenter201206052111.dat     3.234388        4.234564        2.654212        -6.656221       -0.677541       4.506170       
./dataMCdecenter/MCdecenter201206061420.dat     3.300867        4.567555        2.692971        -6.484464       -1.705443       4.423250

So, I ran /opt/rtcds/caltech/c1/scripts/MC/WFS/WFS_FilterBank_offsets to adjust the WFS offsets.

C1:IOO-MC_RFPD_INMON is now ~ 0.5 and  C1:IOO-MC_TRANS_SUM is now ~ 2.7e3 with WFS on.

  7741   Sat Nov 24 23:50:35 2012 KojiUpdateIOOMC WFS refusing to work

Today I found the IMC was misaligned significantly by WFS feedback.
Once the feedback was cleared, it locks with nice visibility.
But WFS misaligns it again as soon as the intergrators are engaged.
I checked the beam on the table, but found nothing really wrong.
The offsets of the error signals were nulled at the input filter modules of the WFS segments.
They did not fix the problem.

The instability started about 48hour ago, that means my work on the AP table did not 
made immediate trouble. But it does not mean anything.

For now, the WFS outputs are off. More work is needed to find what's wrong.

 

  6015   Sat Nov 26 07:18:11 2011 SureshUpdateIOOMC WFS related changes to c1ioo model

What I did:

    I have changed the c1ioo model such that the signals which are demodulated in the WFS lockin (the SIG inputs) are now picked up just after the input matrix.  This permits us to put a notch filter at the excitation frequency into the WFS servo filterbanks and thus prevent the excitation of all the actuators when we wish to excite just one of them. 

 

The Problem:

    I had followed the procedure of determining the TF coefs between actuators (MC1,2,3 P and Y ) and sensors (WFS1, 2 and MC2Trans P and Y)  and found the output matrix by inverting this TF coef matrix. However these matrices, once substituted for the heuristically determined matrices were always unsuccessful in keeping the WFS servo lock.  The reason appeared to be that when the loops are closed the exitation of one actuator led to the excitation of all actuators through the cross couplings in the output matrix.    In order to prevent this we need a notch filter in the servo filter banks.   But then we will not be able to see the sensor response after the servo filters since the response at 10Hz would be blocked from reaching the lockins.  So I shifted the point at which we sample the sensor response to a point before the WFS servo filters. 

The solution:

a) shift the point where the lockin input signals are picked up in the c1ioo model.

b) retune the lockin servo phases to minimise Q phase

c) edit the WFS lockin scripts to ensure that the 10Hz notch is turned on

d) measure the TF coefs and compute the -1*inverse

e) plug it into the output matrix and tweak the gains to ensure a stable lock

f) examine cross talk by comparing the expected TF in each loop with the expected loop TF.

 

Current state:

  I have completed steps a to e above.  The loops are stable and the error signal is suppressed (see attached pdf files)

To be done:

  The open loop transfer function has to be compared with expected OLTF to be sure we have minimised cross talk.

 

Attachment 1: WFS_err_20111127.png
WFS_err_20111127.png
Attachment 2: cioo_20111127.png
cioo_20111127.png
  11583   Tue Sep 8 20:30:44 2015 ranaUpdateIOOMC WFS relief re-commissioned

I converted our MC WFS relief from CSH to BASH today. I also added 'wait' commands and 'echo' commands so that all DoFs run in parallel nicely. It can be accessed from the MC WFS screen.

I increased the overall MC WFS gain input slider from 0.02 to 0.1 (its in the mcwfson script). The MC Trans loops now have a time constant of ~30 seconds. The relief script relieves ~90% of the MC WFS control signals in the 2 minutes that its allowed to run.

On the next upgrade, we should make it python and have it kill the relief process if the MC loses lock before relief is applied via the alignment sliders.

Attachment 1: WFSrelief.png
WFSrelief.png
  10078   Fri Jun 20 09:46:49 2014 manasaUpdateIOOMC WFS servo turned ON

The IMC stayed locked last night, but with  a high REFL ~3.0. I found the WFS servo OFF; so went ahead and enabled it. (Did somebody disable it for reasons not elog'd?)

MC returned to a happy state. But the WFS offsets are quite large. So I tweaked the alignment and got MC REFL down to ~0.45 and MC TRANS SUM to ~16500 counts. MC WFS offsets also dropped significantly after this without any need to touch the alignment to the WFS PDs.

  8718   Tue Jun 18 18:24:07 2013 ManasaUpdateIOOMC WFS turned OFF

[Jenne, Jamie, Manasa]

Jamie was working on the MC guardian today (I think he will elog about this soon).

After this, I received the MC locked in TEM00 with MC_REFL at ~2.5 counts from Jamie. Usually the WFS would do their job in this case to bring MC to a good locking condition and since this did not happen, I figured out that something was wrong with the MC_WFS.

What we did:

1. The WFS were turned off. 

2. As a first step, we wanted to run the WFS_OFFSET script (Koji's elog) which requires MC to be locked with MC_REFL<0.5 and spot positions centered. The autolocker was disabled and MC locked manually to MC_REFL<0.5. 

3. While running the WFS_OFFSETS script, Jamie pointed out that the inputs to the WFS servo had been turned off. After the WFS_OFFSET script finished running we turned ON the WFS inputs. 

4. Following this, the MC was relocked manually and MC spot positions were measured (all spot positions were decentered by < 2 mm). 

5. We ran the WFS_OFFSET script again and turned the WFS back ON. But this would still kick the MC out of lock. 
 

Status: MC is locked with WFS turned OFF. Jamie will be looking through what changes he had made earlier today to fix this problem. 

 

  451   Fri Apr 25 20:53:02 2008 ranaConfigurationIOOMC WFS with more gain
Quick update: we found that the reason for the MC WFS instability was that the digital anti-whitening was one but not the analog whitening.

We turned off the digital filters and were able to increase the gain by a factor of ~30. It is left like this, but if it hampers IFO locking then best to just turn it back down to an overall gain of 0.1 or 0.05.
  7761   Thu Nov 29 00:15:13 2012 Den, KojiUpdateIOOMC WFS work

Quote:

The instability started about 48hour ago, that means my work on the AP table did not 
made immediate trouble. But it does not mean anything.

For now, the WFS outputs are off. More work is needed to find what's wrong.

 

 The problem was caused by low reflectivity of the mirror that splits MC reflected beam into two: first goes to trash, second - to WFS. Power before the mirror was 100mW, reflected beam that goes to WFS was 0.3mW. Using dataviewer we learnt that the beam intensity was ~5 times more in the past.

This happened because the mirror position was adjusted a few days ago. Its reflection depends on the angle of incidence and amount of light to WFS was significantly reduced. We could either increase the angle of incidence or use two mirrors with high reflectivity instead of this with high transmission.

We've chosen the second variant not to confuse anyone in future with non-45 degrees angles. We are now using one mirror with reflectivity 98% to direct most power to the trash while other 2% are directed using the second mirror to WFS path. We now have 0.7 mW on WFS1 and 1.3 mW on WFS2.

Then we adjusted WFS 

  • blocked the beam and run scripts/MC/WFS/WFS_FilterBank_offsets to calculate offsets in the WFS servo
  • aligned MC and centered beams on WFS 1 and 2
  • provided excitation to MC1 at 5 Hz (400 counts) and adjusted I&Q phase rotation
  • adjusted the gain and changed it in MC autolocker (reduced from 0.25 to 0.15 as we now have more power of WFS as before)

We were able to close the loops. The phase margin is too low though, we need to improve feedback filters.

DSC_4942.JPG

Attachment 1: wfs_fb.pdf
wfs_fb.pdf wfs_fb.pdf wfs_fb.pdf wfs_fb.pdf wfs_fb.pdf wfs_fb.pdf
  1924   Tue Aug 18 15:16:15 2009 robUpdateIOOMC WFS working again

Rob, Yoichi

 

The MC WFS have apparently been bad for a few days, causing the MC alignment to drift away at DC.  We tried a few things to fix it, including jiggling some EPICS settings in the WFS head & demod screens.  This seemed to work for WFS1 but not WFS2.  Confused, we decided to go stare at the rack 1Y2.  While doing that, we noticed that the top two Sorensens in 1Y1 (these are directly below the Guralp box) were at different voltages from nominal.  The 5V had dropped to 4.2V and the 24V was at 24.6V.  We adjusted the knobs until these were set correctly.  After this, the MC WFS appear to work again.

 

When working in a rack, you must be as careful about accidentally touching things as when working on an optical table.

  6575   Thu Apr 26 18:17:56 2012 SureshUpdateIOOMC WFS: Tweaked the WFS offsets

[Jamie, Suresh]

Yesterday Den and Koji reported that the WFS loops were causing the MC to become unlocked.  They had aligned the PMC.   The input beam into the MC seems to be well aligned.  MCREFL DC close to minimum it gets while MC is locked (~0.45 V).

I checked and saw that the WFS heads and the MC2_TRANS_QPD had picked up DC offsets.  To reset them I turned off the MC_autolocker and closed the PSL shutter.

The ADC offsets were set using this script /cvs/cds/rtcds/caltech/c1/scripts/MC/WFS/WFS_QPD_offsets.  (Jamie fixed the paths to ezcaservo to get this script to work)

The WFS sensor head offsets were manually set to adjust the Q and I signals from the sensor head to zero.  (This operation is supposed to be done by a script which is available, but I will check it out before I direct people to it).

Then we noticed that the ASC outputs were turned off.  (Presumably Koji turned them off yesterday, when the MC was repeatedly unlocking due to the WFS loops).

We turned on the ASC outputs and the MC stayed locked with reasonable outputs on the WFS output channels.  (+/-100)

However, engaging the WFS servo increases the MCREFL DC signal to 0.7 V from the 0.45 V value when the servo is not engaged.  This could be because of DC offsets in the WFS servo filters.   I will adjust these offsets to maintain good MC transmission when the WFS servo is engaged.

 

 

 

  5857   Wed Nov 9 21:21:30 2011 SureshUpdateIOOMC WFS: Output matrix determined with loops closed.

With the loops closed I ran the $SCRIPTS/MC/WFS/senseWFSoutMATRX script and analysed the lockin outputs with $SCRIPTS/MC/WFS/matlab/wfsmatrix3.m.  I had to edit both the setupWFSlockins and the sensWFSoutMATRX scripts because in the past we used to switch on / off the ASC filter bank GAINs on the MC suspensions to start / stop the lockin excitation.  We cannot do this any more since these the WFS feedback signals have to get through these filters while the WFS loops are closed.  So the current, more sensible, scheme is to set the appropriate elements to 1 / 0 in the C1IOO_LKIN_OUT_MTRX.

Note:  The senseMCdecenter script will also have to be ammended in the same manner.

The lockin outputs measured are (reduceddata):

             wfs1P    wfs2P       mc2tP        wfs1Y     wfs2Y       mc2tY

MC1P  -10.3694    7.0642  -10.2133   -0.1025    0.4653   -0.0000
MC2P    8.2838   21.5141    8.4102   -0.2215    0.0734    0.0000
MC3P    9.4804    6.0835    9.6346   -0.0080    0.0366   -0.0000
MC1Y   -0.7339   -1.4498   -0.6175  -11.7502  -13.0480    0.0004
MC2Y    0.9004    0.6645    1.0554   25.6083    7.3399   -0.0046
MC3Y   -0.2914    2.1573   -0.1829   -2.1130   14.3038   -0.0000
 

After inverting and normalising a subset of the above matrix ( done in the wfsmatrix3.m )  we obtain the following output matrix coefs:

  WFS1P WFS2P
MC1P -1.0 0.82
MC2P 0.15 1.0
MC3P 0.62 0.02

 

  WFS1Y WFS2Y
MC1Y -0.11 -0.56
MC2Y 1.00 -0.17
MC3Y -0.62 1.00

 

Apart from a negative sign (introduced by the negative gains in the WFS servo filters ) these values are quite close to the actuation vectors determined in open loop.

I have plugged these values into the WFS output matrix.  Will determine the open loop gain later when there arent so many people stomping around the MC.

 


 

  11595   Mon Sep 14 21:42:00 2015 ranaUpdateIOOMC Wiener + Summary

I turned on the MCF FF in the OAF today (we need to fix the labeling of the 'ON' buttons on the RHS of the screen). The performance is still good; before / after attached.

Not only is the 1 Hz performance in the MC still good, but the X & Y arm noise reduction is ~1 order of magnitude. Good to know that the filters aren't changing much with time.

Can we just leave this on all the time now? Seems to be OK and there's no visible increase in the arm noise with this on.

Also did some updates to the summary pages and added a CDS FEC tab for CPU times.

Please take a look at the summary pages and bring a list of demands to the Wednesday meeting.

Attachment 1: mcf.pdf
mcf.pdf
  8647   Tue May 28 11:11:37 2013 ManasaUpdateIOOMC aligned

[Jenne, Manasa]

Fixed crappy alignment of MC by moving MC mirrors. MC REFL PD measured 0.5 after alignment. Spot positions were measured using msassMCdecenter. Plot for the same is attached.

Attachment 1: MC_0528.png
MC_0528.png
  9320   Wed Oct 30 16:46:17 2013 manasaUpdateIOOMC aligned

MC has not been very happy since last night. 

What I did to fix this:

1. Disabled autolocker and WFS and aligned the MC to bring MC REFL down to <0.50

2. When I re-enabled autolocker, MC was losing lock everytime WFS turned ON.

3. I relocked MC, measured the spot positions and moved MC spot positions by running /opt/rtcds/caltech/c1/scripts/ASS/MC/mcassMCdecenter 
and 
/opt/rtcds/caltech/c1/scripts/MC/moveMC2/

4. I reset the WFS offsets by running /opt/rtcds/caltech/c1/scripts/MC/WFS/WFS_FilterBank_offsets

5. MC is locked and looks happy right now with REFL DCMON at ~0.5

 

  9527   Tue Jan 7 17:16:04 2014 manasaUpdateIOOMC aligned

Quote:

Edit, JCD:  What this really means is that our DC MC pointing is bad, and we need to move the MC suspensions to offload the WFS.  (All of the WFS output numbers for MC1 and 3 were around 100, which is pretty big for those numbers).  We should resurrect the WFS offloading scripts so that we can do this more regularly, and not have to do it by hand.

 Aligned MC to offload the WFS

1. Turned OFF the WFS feedback servo.

2. Aligned the MC suspensions by moving the pit and yaw sliders. MC trans sum brought from ~11000 counts to ~15000 counts. MC RFPD DCMON reads 0.45 counts.

3. Turned ON the WFS servo. The WFS output now reads in the order of 0 to +/-15.

4. Measured the MC spot positions. The spot positions look like they moved for the better compared to what they were yesterday.

 

Attachment 1: MCspots.png
MCspots.png
  9528   Tue Jan 7 20:57:41 2014 JenneUpdateIOOMC aligned

[Rana, Jenne]

We turned off the WFS servos, and looked at the MC REFL DC, and saw that it was still good, so we said that since the MC spots are pretty good, that we'll keep this alignment for now. 

Rana put the beam back on the center of the IOO QPDs on the PSL table.

We switched a steering mirror in the WFS path that was the wrong handed-ness to be the correct handed-ness, then put the beam on the centers of the WFS.  We turned on the WFS, and everything seems good.

While we were out on the table, we also changed the anodized aluminum dump for a razor dump, to catch the reflection from the 2inch lens that is the first thing the MC refl path sees out of vac.

There were no major drifts in the WFS error signals while we were gone for dinner, so the MC seems okay for now.

  9532   Tue Jan 7 23:09:10 2014 manasaUpdateIOOMC aligned

Quote:

[Rana, Jenne]

We turned off the WFS servos, and looked at the MC REFL DC, and saw that it was still good, so we said that since the MC spots are pretty good, that we'll keep this alignment for now. 

Rana put the beam back on the center of the IOO QPDs on the PSL table.

We switched a steering mirror in the WFS path that was the wrong handed-ness to be the correct handed-ness, then put the beam on the centers of the WFS.  We turned on the WFS, and everything seems good. 

There were no major drifts in the WFS error signals while we were gone for dinner, so the MC seems okay for now.

 The last 4 hour trend for WFS error signals show some amount of drift. We should still look at the long term trend to solve the issue.

Attachment 1: WFSdrift.png
WFSdrift.png
  3905   Fri Nov 12 06:10:24 2010 yutaUpdateIOOMC aligned (without coil balancing)

Background:
  Last night, we found that one of DAC channels are poorly connected, so we fixed the connectors.
  Rana and Koji used their incredible eyeballs to roughly align MC.
  Next thing to do is to balance the coils, but it takes some time for the setup.
  So, we decided to do A2L anyway.

What I did:
  Using the last steering mirror at PSL table and IM1, changed the incident beam direction to align MC.

Result:
MCalignCALIB.png
 
  I was amazed by their eyeballs.
  I turned the nobs of SM@PSL and IM1 in small increments, so I never lost TEM00.

Is it enough?:
  The length of the whole faraday is about 20cm and aperture diameter is about 12mm. (I couldn't measure the aperture size of the core)
  The beam is about 9mm diameter at 6w.
  So, if the beam is vertically tilted at more than ~3/200rad, it(6w) cannot go through.
  3/200 rad is about 20% difference in position at MC1 and MC3.
  So, the result meets the requirement.

  Also, assuming that coils have 5% imbalance, the beam position I measured have ~3% error.
  So, to do more precise beam centering, we need to balance the coils.

  5490   Tue Sep 20 21:13:39 2011 SureshUpdateIOOMC aligned and PSL beam into MC readjusted

This morning after Kiwamu maximised the PSL beam coupling into the MC we noticed that the MC2 face camera showed the spot position had moved away from the center by about a diameter.  So I checked the beam spot positions with MCASS and indeed found that the spot on MC2 had moved to about 6mm away from the center in yaw and about 3mm in pitch.  I adjusted the MC2 (and only MC2) to recenter the spots on all the three mirrors.  The new spot positions are given below

spot positions in mm (MC1,2,3 pit MC1,2,3 yaw):
    1.3337   -0.2660    0.6641   -1.0973    0.0468   -1.7130

The PSL beam into MC has been readjusted for maximal coupling into MC.

 

  8794   Wed Jul 3 10:39:25 2013 manasaUpdateIOOMC aligned and WFS enabled

I found WFS had been left disabled from sometime yesterday. I don't see anyone mentioning  when and why they had turned OFF the WFS servo.

I aligned MC and turned ON the WFS servo. MC is back.

  1396   Thu Mar 12 18:48:37 2009 YoichiUpdateIOOMC aligned but ...
After the MZ alignment, I aligned the MC with the periscope mirrors.
It looked like the MC mis-alignment was mainly caused by the input beam change.
So I left the MC mirrors as they were to keep the output beam pointing.
However, after I finished the alignment, the MC output beam was too low on the Faraday.
Also the X-arm did not lock to TEM00 mode. So the MC mirrors must have also shifted to a weird alignment state.
I should have restored the MC mirror alignment to a good state using the OSEM DC signals.

Rana came in and restored the MC mirror alignment using the SUS drift mon.
He and Kakeru is now working on the periscope to align the beam into the MC.
  3883   Tue Nov 9 05:40:12 2010 yutaSummaryIOOMC aligning going on

(Suresh, Yuta)

Background:
  Last week, we reduced the common mode displacement of the beam through MC1 to MC3. 
  Next work is to tilt the beam and center it.

What we did:
  1. Changed the offset going into 1201 Low Noise Amplifier(1201 is for adding +5V offset so that the feedback signal will be in the range of 0-10V)
  2. Using the last steering mirror(SM@PSL) and IM1, tilted the beam
  3. As the beam height changed alot(~0.5cm higher at IM1), MC1 reflection could not reach MCREFL PD. So, we tilted the mirror just after MC1, too.

Result:
MCalignNov9.png

Plan:

  - continue to tilt IM1 in small increments in order to reduce PIT/YAW to length coupling
      If large increments, it takes so much time re-aligning MC to get flashing!

By the way:

    The signal we kept saying "MCL" was not the error signal itself. It was a feed back signal(output of the mode cleaner servo board). The cable labeled "MC REFL" is the error signal. Compare MEDM screen C1IOO_MC_SERVO.adl and the mode cleaner servo board at 1X2. You will be enlightened.

Quote (from elog #3857):

4. Disconnected the cable labeled "MC OUT1" at 1X2 (which is MCL signal to ADC) and put MC2_ULCOIL output directly using long BNC cable.

 

  1386   Wed Mar 11 14:51:01 2009 Kakeru, Joe, RobUpdateIOOMC alignment

This morning, MC alignment was gone and MC wasn't lock.

We checked old value of pitch, yaw, and position offset of each MC mirror, and found they were jumped.

We don't know the reason of this jump, but we restore each offset value and MC backed to lock.

  2852   Tue Apr 27 22:28:58 2010 ZachUpdateIOOMC alignment

Beginning last week, I have been helping Koji with some of the IO work that must be done for the 40m upgrade. The first thing he asked me to do is to help with the alignment of the MC.

As I understand, it became apparent that the IFO beam was not centered on all (or any) of the MC mirrors, which is disadvantageous for obvious reasons. We are trying to correct this, using the following strategy:

  1. Adjust the MC mirrors into rough alignment, isolate a strong TEM00, and lock the cavity
  2. Fine-tune the alignment by minimizing the REFL power when locked (in these first two steps, we adjusted only MC2 & MC3, assuming that the REFL beam was centered on the PD, and wanting to keep it that way). At this point, the cavity is resonating some asymmetric mode, looking something like (not to scale---for illustration only):MC_misaligned.png
  3. Shake all three mirrors (in succession) in pitch and yaw, each time demodulating the error signal at the frequency used for the excitation and recording the magnitude and phase of the response.
  4. Move one mirror's DC orientation, repeat step 3, and then restore the mirror to its original position
  5. Repeat step 4 for both angular degrees of freedom of each mirror

Using the results of these measurements, it is possible to evaluate the components of a block-diagonal matrix M which relates the tilt-to-displacement coupling of each DOF to each mirror's misalignment in that degree, i.e.,

a = M x

with a a 6-dimensional vector containing the coupling of each degree of freedom to the length of the cavity and x a 6-dimensional vector containing the angular misalignments of each. Due to orthogonality of pitch and yaw, M will take the form of a 6x6 matrix with two non-zero 3x3 blocks along the diagonal and zero matrices on the off-diagonal blocks.

The idea is to isolate components of M by moving one mirror at a time, solve for them, then find the inverse M-1 that should give us the required angular adjustments to obtain the beam-centered ideal cavity mode.

In theory, this need only be done once; in practice, our measurement error will compound and M will not be accurate enough to get the beams exactly centered, so we will have to iterate.

NOTE: The fact that we are adjusting the three cavity mirrors to obtain the ideal mode means that we will necessarily tarnish our coupling into the cavity. Once we have adjusted the mirrors once, we will need to re-steer the input beam and center it on the REFL diode. 

Status: This process has been completed once through step 5. I am in the process of trying to construct the matrix for the first adjustment.

 

  2855   Wed Apr 28 12:05:44 2010 ZachUpdateIOOMC alignment

I have worked out the first set of adjustments to make on the MC mirrors (all angle figures are in units of the increments on the control screen)

Using the method described in the previous post, I obtained the following matrix relating the angle-to-length coupling and the angular deviations. In the following matrix, Mij corresponds to the contribution of the jth degree of freedom to the ith A-to-L coupling, with the state vector defined as xi = (MC1P, MC2P, MC3P, MC1Y, MC2Y, MC3Y), where each element is understood as the angular deviation of the specific mirror in the specific direction from the ideal position, such that x = 0 when the cavity eigenmode is the correct one and the beams are centered on the mirrors (thus giving no A-to-L coupling regardless of the components of M).

 

M =

   1.0e+03 *

   -0.2843   -0.4279   -0.1254         0         0         0

   -0.8903   -0.4820   -0.6623         0         0         0

    0.5024    0.0484   -0.0099         0         0         0

         0         0         0         0.1145   -0.1941   -0.3407

         0         0         0         0.0265    1.5601    0.2115

         0         0         0         0.1015    0.1805   -0.0103,

giving an inverse

M-1 =  

    0.0003   -0.0001    0.0020         0         0         0

   -0.0031    0.0006   -0.0007         0         0         0

    0.0018   -0.0018   -0.0022         0         0         0

         0         0         0        -0.0013   -0.0015    0.0117

         0         0         0         0.0005    0.0008   -0.0008

         0         0         0        -0.0037   -0.0010    0.0044

The initial coupling vector is then acted on with this inverse matrix to give an approximate state vector x containing the angular misalignments of each mirror in pitch and yaw. The results are below:

x

   1P:  0.0223

   2P: -0.0733

   3P:  0.3010

  1Y:  -0.1372

  2Y:   0.0194

  3Y:  -0.0681

 

  2856   Wed Apr 28 14:15:58 2010 AlbertoUpdateIOOMC alignment

 

 That's interesting.

Would it be possible to write about the technique on a wiki page as you get measurements and results?

  2858   Wed Apr 28 14:42:55 2010 ZachUpdateIOOMC alignment

Sure. I figured I would put up a How-To if it works. 

Quote:

 

 That's interesting.

Would it be possible to write about the technique on a wiki page as you get measurements and results?

 

  3012   Fri May 28 21:32:32 2010 AlbertoUpdate40m UpgradingMC alignment

[Alberto, Kiwamu, Kevin, Rana]

Today we tried to measured the beam shape after the MC MMT1 that Jenne installed on the BS table.

The beam scan showed a clipped spot. We tracked it down to the Farady and the MCT pickoff mirror.

The beam was getting clipped at the exit of the Faraday. But it was also clipping the edge of the MCT pick-off mirror. I moved the mirror.

Also the beam looked off-center on MC2.

We're coming back on Sunday to keep working on this.

Now things are bad.

  3013   Fri May 28 23:21:52 2010 KojiUpdateIOOMC alignment

Hm... You touched the optics between the MC and the Faraday... This will lead us to the painful work.

I am afraid that the beam is already walking off from the center of MC1/MC3 after the work on the PSL table.
This may result in the shift of the spot on those MC mirrors. So I recommend that:

- Lock the cavity
- Check the A2L for MC1/3
- Adjust it by the periscope
- If it is fine, adjust the optics after the MC (steering, Faraday, etc)

Off-centering of the MC2 spot is no problem. We can move it easily using Zach's scripts.
Tell me when the work is planed on Sunday as I might be able to join the work if it is in the evening.

Quote:

[Alberto, Kiwamu, Kevin, Rana]

Today we tried to measured the beam shape after the MC MMT1 that Jenne installed on the BS table.

The beam scan showed a clipped spot. We tracked it down to the Farady and the MCT pickoff mirror.

The beam was getting clipped at the exit of the Faraday. But it was also clipping the edge of the MCT pick-off mirror. I moved the mirror.

Also the beam looked off-center on MC2.

We're coming back on Sunday to keep working on this.

Now things are bad.

 

  3019   Mon May 31 00:10:18 2010 kiwamuUpdateIOOMC alignment

  [Alberto, Kiwamu]

The MC alignment is getting better by steering the axis of the incident beam into the MC.

We found the beam spot on MC1 and MC3 were quite off-centered in the beginning of today's work. It had the coil gain ratio of 0.6:1.4 after running the A2L script.

In order to let the beam hit the center of the MC1 and MC3, we steered the bottom mirror attached on the periscope on the PSL table to the yaw direction.

And then we got better numbers for the coil gain ratio (see the numbers listed at the bottom).

For the pitch direction, there still are some rooms to improve because we didn't do anything with the pitch. It is going to be improved tomorrow or later.

 

Here are the amounts of off-centering on MC1 and MC3 after steering the axis. 

 C1:SUS- MC1_ULPIT_GAIN =  0.900445

C1:SUS-MC1_ULYAW_GAIN =  0.981212

C1:SUS-MC3_ULPIT_GAIN =  0.86398

C1:SUS-MC3_ULYAW_GAIN =   1.03221

  3020   Mon May 31 03:38:48 2010 KojiUpdateIOOMC alignment

Remember that you only can introduce the axis translations from the PSL table.
It is quite difficult to adjust the axis rotation.

The calibration factor from A2L results to the beam position is dx = (A2L_result - 1) *10.8mm

If I believer the result below, the spot positions on the mirrors are

MC1 Pitch      -1.1mm
MC1 Yaw        -0.20mm
MC3 Pitch      -1.5mm
MC3 Yaw        +0.35mm

This means that the beam is 1.3mm too high and 0.28mm too much in north

This corresponds to tilting SM2 by
0.33mrad in pitch (23deg in CW)
and
0.10mrad in yaw (7deg in CW).

Quote:

C1:SUS-MC1_ULPIT_GAIN =  0.900445
C1:SUS-MC1_ULYAW_GAIN =  0.981212
C1:SUS-MC3_ULPIT_GAIN =  0.86398

C1:SUS-MC3_ULYAW_GAIN =  1.03221  

 

Attachment 1: MC_spot_centering.png
MC_spot_centering.png
  3903   Fri Nov 12 00:42:11 2010 rana, kojiUpdateIOOMC alignment

We decided to ignore the computer script outputs for the beam positions and use instead the eyeball method to get the beam into the MC:

  1. Adjust PSL launch beam to get the beam centered on IM1.
  2. Eyeball the beam to hit the center of MC1. We can get this pretty good by using the brackets to get the vertical and using the centering of the input/refl beams to center it horizontally.
  3. Use MC3 suspension to hit the center of MC2. We did this by hitting each of the 3 EQ stop screw heads and triangulating the MC3 bias settings.
  4. Use MC2 bias to hit the center of MC1.
  5. Use MC1 to get good flashes.
  6. Use all 3 MC sus biases to maximize the transmitted light and minimize the REFL DC.

With this rough alignment in place, we leave it to Yuta to finish the coil balancing and the A2L. We will have an aligned MC in the morning and will start the BS chamber alignment.

  6115   Wed Dec 14 01:35:06 2011 KojiUpdateIOOMC alignment craziness

~11PM I came to the 40m and found the MC is repeating "LOCK->WFS ON->UNLOCK" sequence for ~2hours.

I checked the WFS spots on the QPDs and aligned them. No luck. I suspected the clipping of the beam in the chamber.

After I checked the trends of MC SUS OSEM values and IPPOS, I concluded that the input beam was aligned to somewhat misaligned MC.

The most noticable thing was that IPPOS (X, Y) indicated about (-0.5, 0) although the recent trend shows (-1, -0.5) is nominal.
In fact, the beam was about dropping from the diode. In addition, I found that the MC2 suspension showed a jump in the morning at around 8.30AM.|
This is consistent with what Jenne described.

This was a difficult situation as everything was moved.
I used the OSEM values to come back to the previous alignment of the suspensions, and started touching Zig-Zag before the MC.
After the alignment I ended up more clipping of the MC REFL. Also the spot on the IPPOS QPD was more dropping.

So, I have empirically used MC3 to misalign in Yaw to have better spot position on IPPOS. Then, the Zig Zag was aligned.
Then the spot on MC2 was adjusted while MCTRANS was kept maximized.

This helped the things back in the normal state.

Now the WFS servo is happily controlling the alignment.
MC REFL is 4.8 and 0.47 for unlocked and locked. (MCREFL_UNLOCK was 4.6 before my touch)
MCTRANS is 27000, which is close to the nominal.
IPPOS total, x, and y are 0.36, -0.97, and -0.47, respectively. They are about the nominal.

~1AM done

HOWEVER, we still don't know the position of the spot on MC1/MC3, and ITMY and ETMY.
I should consult with Kiwamu to check the spot positions tomorrow.

General lessons:
- If you find any reduction of MC transmission, check the suspensions to see if there is any slip.
- Before touching the input optics to recover the MC alignment, we should think what was moved.
- Before touching EOM alignment you must check the MC alignment WITHOUT WFS, so that you can recover the misalignment of EOM by the Zig-Zag steering.
- WFS is sensitive to clipping of the beam.
- We need a nifty indicator to tell how the MC transmitted beam is good.

Attachment 1: Untitled.png
Untitled.png
ELOG V3.1.3-