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ID Date Authordown Type Category Subject
  5716   Thu Oct 20 18:57:35 2011 SureshSummarySUSMC2 Misaligned 2:27PM on Wednesday

Quote:

There looks some activity at around MC2 on Wednesday afternoon.
It caused the misalignment of MC2. Misalignment was not found in MC1/3.

It seems that the incident beam on the MC was aligned in the evening.
This increased the MC transmission but it is vibible that the spot on MC2 is shifted from the center.

We need an action on this issue tomorrow in the daytime.

 

I am working on fixing this.  You might some strange stuff going on in the control room screens.  Pls ignore it till I am done.

 

  5717   Fri Oct 21 02:36:44 2011 SureshSummarySUSMC2 Misaligned 2:27PM on Wednesday : MC Realigned

Quote:

Quote:

There looks some activity at around MC2 on Wednesday afternoon.
It caused the misalignment of MC2. Misalignment was not found in MC1/3.

It seems that the incident beam on the MC was aligned in the evening.
This increased the MC transmission but it is vibible that the spot on MC2 is shifted from the center.

We need an action on this issue tomorrow in the daytime.

 

I am working on fixing this.  You might some strange stuff going on in the control room screens.  Pls ignore it till I am done.

 

 

  I have realigned the MC by recentering the spots on all the MC optics.  The current spot positions (in mm) are:

MC1P     MC2P     MC3P      MC1Y      MC2Y     MC3Y

0.2245    0.3364   -0.2801   -1.8891    0.1631   -1.744

Initially the lockins 2 and 5 showed very small outputs.  This was traced to the fact that we have recently switched on a 28Hz ELP filter module in the MC2 ASC filter bank which introduces an extra phase of about 75deg..  See this elog.

When the MC ASS lockins were initially setup, the phase was set with this filter module switched off.  Since quite some time has passed since the last calibration of these phases, I readjusted the phases to minimise the  Q_OUTPUT and I also adjusted the GAINs in the SIG filter banks  of all the six lockins so that their I_OUT's drop by the calibration value of -2.65 when an offset of 0.1 is introduced into the MC suspension output matrices.  Two short scripts in the $scripts$/ASS/ directory help in setting and removing these offsets.  They are called MCxoffsetOn and MCxoffsetOff.   They have to be edited appropriately to address each DoF of the MC.

The $scripts$/ASS/mcassUp script., which sets up everything to make the MC spot decentering measurement, has been edited to set these new phases and gains.  The old settings have been commented out.

I then centered the spots on the WFS sensors and the MC_TRANS QPD.  We are now ready to make the MC WFS output matrix transfer coef measurement again, but this time with the WFS loops closed.

 

  5718   Fri Oct 21 02:57:38 2011 SureshSummarySUSMC2 Misaligned 2:27PM on Wednesday : cause traced

Quote:

Quote:

There looks some activity at around MC2 on Wednesday afternoon.
It caused the misalignment of MC2. Misalignment was not found in MC1/3.

It seems that the incident beam on the MC was aligned in the evening.
This increased the MC transmission but it is vibible that the spot on MC2 is shifted from the center.

We need an action on this issue tomorrow in the daytime.

 

I am working on fixing this.  You might some strange stuff going on in the control room screens.  Pls ignore it till I am done.

 

While chatting with Jenne I learnt that some substantial amount of work had taken place yesterday around the MC2 chamber.  This was associated with the relocating of seismometers.  ref elog

I reiterate what is well known for quite sometime:  MC2 table is not well isolated from the ground.  And we should not approach this chamber unless absolutely necessary. I have blocked off the area around it which we should avoid.  It is a serious waste of time and effort to realign the MC each time the MC2 table decides to settle into a new position.

Steve tells me that the mild-steel frame supporting the chamber+MC2_table sits with two legs on one concrete slab while the other two legs sit on another one.   The frame is also quite weak without sufficient gussets or cross connects.  The next time we have a major shutdown we must replace this frame with a more sturdy one which sits on one slab (preferably the one on which the rest of the MC sits).

Till we improve this mounting, I suggest that we avoid that area as much as possible.

 

  5724   Fri Oct 21 15:49:35 2011 SureshUpdateIOOPMC input alignment improved

The image on the PMCR camera was quite assymetric and PMC output was at 80% .... upon improving the alignment I managed to push it up to 87%

 

  5725   Fri Oct 21 16:06:12 2011 SureshUpdateComputer Scripts / ProgramsMC input matrices empty again

The MC suspensions were not damping and the reason was traced to the empty imput matrices in the suspension controls.  This has been an issue in the past as well when the sus machine is rebooted some of the burt restore does not populate these matrices.

I ran the burtgooey and restored c1mcs.snap file.  from a couple of hours ago.

 

 

  5732   Tue Oct 25 01:14:15 2011 SureshUpdateIOOC1IOO model modified to include new WFS lockin structure

A while back we faced the problem that when we use several lockins to excite the MC degrees of freedom, their relative phase was not known.  The solution suggested was to use one oscillator and several demodulators.

I have now modified the C1IOO.mdl so that this can be implemented.  Previously we were using the MC_ASS lockins for WFS work.  I have now separated the WFS and MC_ASS structures. 

Other jobs to be done in this context are:

1) The medm screens associated with WFS lockins need to be updated with new channel names.

2) The scripts associated with both MC_ASS decentering and WFS ouput matrix determination have to be updated with the new channel names.

3) I also deleted all medm screens in the $screens$/c1ioo/ directory after copying them to $screens$/c1ioo/bak/.  After installing the new c1ioo model $screens$/c1ioo directory now contains just the automatically created screens.  All other user made screens should go into $screens$/c1ioo/master/ directory

This is a pic of the new c1ioo model:

 

 c1ioo20111025.png

 

  5733   Tue Oct 25 01:19:17 2011 SureshUpdateComputersfb restarted and c1ioo model committed to svn

When I installed the new model I restarted the fb between 1 and 1:30 AM PDT Oct 25, 2011

  5735   Tue Oct 25 16:24:58 2011 SureshUpdateIOOC1IOO model modified to include new WFS lockin structure

I forgot to mention another change I made to the C1IOO model.

The location of the WFS global switch and the WFS_GAIN have been shifted. The switch now cuts off signals just before the WFS servo filters.

I have also added some test points just before the switch and the so that we can monitor the WFS error signals which would be unaffected even if the WFS_GAIN is changed..

 

 

Quote:

A while back we faced the problem that when we use several lockins to excite the MC degrees of freedom, their relative phase was not known.  The solution suggested was to use one oscillator and several demodulators.

I have now modified the C1IOO.mdl so that this can be implemented.  Previously we were using the MC_ASS lockins for WFS work.  I have not separated the WFS and MC_ASS structures. 

Other jobs to be done in this context are:

1) The medm screens associated with WFS lockins need to be updated with new channel names.

2) The scripts associated with both MC_ASS decentering and WFS ouput matrix determination have to be updated with the new channel names.

3) I also deleted all mdem screens in the $screens$/c1ioo/ directory after copying them to $screens$/c1ioo/bak/.  After installing the new c1ioo model $screens$/c1ioo model now contains just the automatically created screens.  All other user made screens should to into $screens$/c1ioo/master/ directory

This is a pic of the new c1ioo model:

 

 c1ioo20111025.png

 

 

  5737   Tue Oct 25 18:50:22 2011 SureshUpdateIOOC1IOO model modified to include new WFS lockin structure

Some small fixes to the c1ioo model.

1) I edited the WFS lockin modules to make use of new library part called demod.

2) c1ioo model has been compiled and restarted.

3) fb was restarted at Tue Oct 25 18:43:55 PDT 2011

 

Quote:

I forgot to mention another change I made to the C1IOO model.

The location of the WFS global switch has been shifted. It now cuts off signals just before the WFS servo filters.

I have also added some test points just before the switch so that we can monitor the WFS sensor signals even if the switch is off.

 

 

Quote:

A while back we faced the problem that when we use several lockins to excite the MC degrees of freedom, their relative phase was not known.  The solution suggested was to use one oscillator and several demodulators.

I have now modified the C1IOO.mdl so that this can be implemented.  Previously we were using the MC_ASS lockins for WFS work.  I have not separated the WFS and MC_ASS structures. 

Other jobs to be done in this context are:

1) The medm screens associated with WFS lockins need to be updated with new channel names.

2) The scripts associated with both MC_ASS decentering and WFS ouput matrix determination have to be updated with the new channel names.

3) I also deleted all mdem screens in the $screens$/c1ioo/ directory after copying them to $screens$/c1ioo/bak/.  After installing the new c1ioo model $screens$/c1ioo model now contains just the automatically created screens.  All other user made screens should to into $screens$/c1ioo/master/ directory

This is a pic of the new c1ioo model:

 

 c1ioo20111025.png

 

 

 

  5750   Fri Oct 28 02:41:18 2011 SureshMetaphysicselogelog unresponsive: restarted

Elog did not respond despite running the /cvs/cds/caltech/elog/start-elog.csh  script two times.  

It worked the after the third restart. 
 

  5751   Fri Oct 28 03:12:37 2011 SureshUpdateIOOMC2 realigned to align MC to PSL

Around 6PM on the 27th, I found that the C1:IOO-MC_RFPD_DCMON had risen to about 2.5V.   I checked the trend of MC2 sensors and found that  between 2PM and 6PM, MC2 had drifted in a strange way.  And also that the alignment had grown worse over several days.   I also noticed that the spot on the MC2F camera had shifted to the left.

I attempted to correct the alignment (decrease the C1:IOO-MC_RFPD_DCMON to ~0.5V ) by just moving the MC2 and succeeded!! So it is quite likely that most of the slow MC drift is arising due to MC2 table drift.

MC2_Drift_20111027.png

 

I decided to try and close the MC2_TRANS QPD to MC2 loops separately to see if MC alignment becomes stable  But several screens needed to be fixed before we could try anything.   So I fixed C1IOO_WFS_MASTER,  C1IOO_WFS_INMATRIX and ...OUTMATRIX screens.  Deleted the older ones to avoid confusion.

In this process I noticed that the directory of $screens$/c1mcs/master contains copies of older C1SUS_MC1 , 2. and 3 screens which look very similar to the new autogenerated screens.  Some of the links in the WFS screens were pointing to the old screens.  I have redirected the links and I will delete these in a couple of days, if no one objects.

 

 

 

  5761   Sat Oct 29 02:35:39 2011 SureshUpdateIOOWFS_MASTER screen and lockin screens fixed

I have fixed the WFS_MASTER screen and several of the subscreens such as the MCASS and MC_WFS_LKIN.

Since MC_WFS_LKIN uses six demodulators and single oscillator I could not use the automatically built Lockin screens. 

I built one using the compact filter banks mentioned earlier

The phases in the WFSlockins have yet tp be set.

  5799   Thu Nov 3 17:19:54 2011 SureshUpdateIOOMC realigned to center the spots on actuation nodes

Several activities in the past week (elog1, Mirko's rough realignment of MC and adjustment of the PSL zig-zag on Monday and elog2 ), had led to an MC state where the spots were not centered on the actuation nodes.

The change in the C1IOO model part dealing with MC_ASS led to the disappearance of all MC_ASS filter definitions in the lockins.  I have fixed all that, remade the screens and scripts for making the MC Decenter measurements.

I have just completed the re-centering of the spots on the MC and this of course will lead to some change in the input pointing. 

The MC_REFL beam also was recented on the WFS and the MC2_TRANS QPD.

Will add the mc-decenter measurement in a few mins

  5803   Thu Nov 3 22:32:48 2011 SureshUpdateIOOMC realigned to center the spots on actuation nodes

Quote:

Several activities in the past week (elog1, Mirko's rough realignment of MC and adjustment of the PSL zig-zag on Monday and elog2 ), had led to an MC state where the spots were not centered on the actuation nodes.

The change in the C1IOO model part dealing with MC_ASS led to the disappearance of all MC_ASS filter definitions in the lockins.  I have fixed all that, remade the screens and scripts for making the MC Decenter measurements.

I have just completed the re-centering of the spots on the MC and this of course will lead to some change in the input pointing. 

The MC_REFL beam also was recented on the WFS and the MC2_TRANS QPD.

Will add the mc-decenter measurement in a few mins

 The current MC spot decentering is given below:

spot positions in mm:

MC1P     MC2P     MC3P      MC1Y     MC2Y     MC3Y

0.4089    0.4800   -0.1266   -1.4095    0.3808   -1.7517

 

The yaw measurement probably has the wrong scale factor in the conversion to mm.  It could be under estimated by a factor 2.65/2.00 since the 10% step in coil gains produces a 2mm offset rather than the expected 2.65mm.  See the figures below.  I will check this during the next iteration when another mode clearner alignment comes up.

As I had to redefine all the MC_ASS lockin filters it is possible that Lockin phase might have changed by a few degrees giving rise to a change in the scale factor.

20111103_1.png    20111103_2.png

  5813   Fri Nov 4 16:23:41 2011 SureshUpdateIOOMC spot decenter measured

After Kiwamu adjusted the MC2 PIT to accommodate the limited range of the PZT1 ( elog ),  I remeasured the spot positions today.  

  MC1P MC2P MC3P MC1Y MC2Y MC3Y
Yesterday 0.1354 -0.2522 -0.1383 -1.0893 0.7122 -1.5587
Today 4.0411 4.4994 3.5564 -1.4170 -0.2606 -1.7109

 

As expected there is a translation of the beam axis to one side (Up? Down?) .  

I wonder how a beam translation by 5mm solved the PZT1 angular range limitation problem (?!)

  5818   Sat Nov 5 00:24:13 2011 SureshUpdateASCASS scripts gone

Quote:

Did somebody delete all the scripts in /opt/rtcds/caltech/c1/scripts/ASS ?

 I have moved all the MC_ASS scripts to a directory called MC under ASS

 

  5819   Sat Nov 5 01:10:29 2011 SureshUpdateIOOWFS output matrix measured (open loop)

 

The scripts and screens needed to make the MC WFS ouput matrix are once again functional

I corrected the WFS lockins' phases to ensure that the Q outputs are minimised.  Since all the lockins have the same relative phase with respect to the oscillator I found that the same phase works for all of them.  About 90 deg in this case.

The scripts used to make the WFS outmatrix measurement live in /cvs/cds/rtcds/caltech/c1/scripts/MC/WFS

1) setupWFSlockins:   This script makes sure that all the ASC, WFS_ LKIN and WFS_servo filter banks used in this measurement are set up properly.  It also sets the WFS_lockin oscillator to 10 Hz.  There are filter modules in the SIG filter bank of the WFS demodulators. 

2) senseWFSoutMATRX:  This script cycles through the various MC actuators ( MC 1 2 3 : PIT and YAW ) and measures the response of the various ASC sensors (WFS and MC2_TRANS QPD).

3) The data collected by the sensWFSoutMATRX can be analysed with a matlab file called " wfsmatrix3.m " located in a subdirectory under WFS called 'matlab'.   I have added some comments in this file to make it easier to follow.   The output of this file, at the moment, gives only the " Actuation Vectors " for WFS1P, WFS2P, WFS1Y and WFS2Y.  It ignores the MC2TransQPD for now. 

4)  The lockin outputs are given below ( the 'reduceddata' )

             wfs1p      wfs2p      mc2tp      wfs1y      wfs2y     mc2ty

mc1p    0.2926   -0.4086    0.2926    0.0340    0.0064    0.0001
mc2p   -0.2830   -1.3060   -0.2833    0.0628    0.1171   -0.0003
mc3p   -0.3283   -0.3455   -0.3288   -0.0456    0.0275    0.0000
mc1y    0.0440    0.0261    0.0429    0.7204    0.9351   -0.0008
mc2y   -0.1006    0.0850   -0.1036   -1.5509   -0.3882    0.0165
mc3y     0.0150   -0.0832    0.0144    0.1114   -1.0573    0.0006

5) The actuation vectors are given below

Pitch WFS1P WFS2P
MC1 1.00 -0.86
MC2 -0.12 -1
MC3 -0.72 0.09

 

Yaw WFS1Y WFS2Y
MC1 0.16 0.59
MC2 -1.00 0.20
MC3 0.51 -1

6) This measurement was performed with the WFS servo loops open. I will try to close the loops with this matrix and run the script again to measure the output matrix in closed loop.

7) This a.vectors obtained above are significantly different from that obtained a while ago (elog 5668) before the lockin demod phases (relative to each other) were fixed.  This could also be because both are open loop measurements and we might have wandered into the nonlinear regime of the WFS sensors.

 

 

 

  5839   Tue Nov 8 10:34:42 2011 SureshUpdateIOOMC spot decenter measured

Quote:

After Kiwamu adjusted the MC2 PIT to accommodate the limited range of the PZT1 ( elog ),  I remeasured the spot positions today.  

  MC1P MC2P MC3P MC1Y MC2Y MC3Y
Yesterday 0.1354 -0.2522 -0.1383 -1.0893 0.7122 -1.5587
Today 4.0411 4.4994 3.5564 -1.4170 -0.2606 -1.7109
8Nov2011 4.7341 4.8794  4.3907 1.3542 -3.0508 -1.7167


As expected there is a translation of the beam axis to one side (Up? Down?) .  

I wonder how a beam translation by 5mm solved the PZT1 angular range limitation problem (?!)

 The MC alignment was bad and I wondered if it is because MC shifted or because the input PSL beam shifted.   So I remeasured the spot positions and find that MC2 Yaw has shifted a lot.   Todays measurements are in Cyan boxes above. The shift in MC3P is probably an associated shift due to some pit--yaw coupling.  So I am going to move MC2 and try to align the MC to the PSL.

  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

  5855   Wed Nov 9 19:08:18 2011 SureshUpdateelogrestarted elog

Elog was not responding and was restarted.

  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.

 


 

  5859   Wed Nov 9 21:48:43 2011 SureshUpdateIOOWFS Servo included into the MC_Autolocker

The WFS servo loop will come on 5 seconds after the MC is locked

 

I have uncommented the lines in the mcup script which turn on the WFS servos.  But I shifted their location to the part after the MC is locked.

  5866   Thu Nov 10 20:20:57 2011 SureshUpdateIOOMC Spot positions have shifted after accelerometer installation on MC2 chamber

[ Jenne, Suresh ]

We were tying the fix the WFS and noticed that the PSL --> MC alignment was poor.   The PMC output was also at about 0.5 instead of its optimal 0.86 .   So Jenne started by first realinging the PMC input and pushed the PMC ouput to about 0.8  

Then we decided to fix the PSL--> MC alignment by using the zigzag.  After Jenne finished that, we realised that it was probably not the best thing to do since the MC2 might have shifted after the accelerometer installation on the MC2 chamber.

So I measured the spot positions and find that the MC2Y has shifted by about 3.6mm and  MC2P has shifted by about a mm.  There is also a shift of 2mm in MC3P, but hopefully it will go away when we adjust the MC2

 

    MC1P MC2P MC3P MC1Y MC2Y MC3Y
03Nov2011   0.1354 -0.2522 -0.1383 -1.0893 0.7122 -1.5587
04Nov2011   4.0411 4.4994 3.5564 -1.4170 -0.2606 -1.7109
08Nov2011   4.7341 4.8794  4.3907 1.3542 -3.0508 -1.7167
10Nov2011 ........ 3.9944 3.7676 6.1001 -1.3058 -3.8087 -1.6418

 

I am going to adjust the MC2 to recover its nominal position as marked above in green

  5877   Fri Nov 11 21:09:30 2011 SureshUpdateSUSMC2 is being a little wild...WFS to blame

Quote:

Mirko and  Den are measuring MC_F, which they will report about later, but I noticed that MC2 is totally crazy right now.  It shouldn't matter that they are doing things (like unplugging the feedback to the PSL's PZT), because we actuate on the laser, not on the MC.  I disabled the MC autolocker before they started working. 

Anyhow, somehow MC2 got kicked up (whatever, that happens), but it won't re-damp.  I think it's the WFS.  The yaw output from the WFS is truely crazy. 

I have disabled the WFS output / ASC input on the MC SUS screens, and MC2 was then able to damp.  My disabling only the MC2 WFS input at first kicked up MC1 and 3, so I disabled all of the WFS stuff, and all 3 MC mirrors are again happy. 

SURESH: FIX ME!  (signed, The WFS)

WFSscreenshot.png

 

The Problem

Turning off the WFS servo loops usually should be done using the 'mcwfsoff' script.  The script takes care of switching off the integrators and Clears the History.  

'mcdown' and 'mcup' scripts run the 'mcwfsoff' and 'mcwfson' scripts so when the MC unlocks the WFS servos are shutdown and restarted properly.  However if the MC autolocker script is suspended by pressing the Enable/Disable switch in the LOCKMC screen and then the MC unlocks, it results in the WFS servo integrators accumulating large values.  If these values are passed through the ASC filter banks the optic will get a pretty huge kick.

The Solution

I have added some indicators which will let us know if the WFS Servo Filter outputs are larger than +/-1000.  When engaging the WFS loops the user has to take care to Clear History in the servo filter banks if these indicators are steadily Red.   before engaging the WFS Servo loops ensure that the servo filter outputs are zeroes. 

Koji and I discussed whether it would be useful to run the 'mcwfsoff' script when the Disable button is pressed in the autolocker.  His recommendation is that we should keep  the autolocker script simple and that user has to be cautious when switching on the WFS servos and when directing the ASC outputs to the suspensions.

LOCKMC_screen.png

 

  5878   Fri Nov 11 22:07:43 2011 SureshUpdateIOOTried to recover the MC alignment of 4th Nov: partial success, PSL beam clipping

I have recovered the yaw values pretty much .  As the PZT1 rails in this direction perhaps this is the more relevant of the two alignments.  The beam is translated in the vertical direction, but this can be easily corrected by changing the pitch of MC2

However note that if the WFS are switched on .. MC is going to follow the PSL beam. 

 

 

 Date  #### MC1P MC2P MC3P MC1Y MC2Y MC3Y
03Nov2011   0.1354 -0.2522 -0.1383 -1.0893 0.7122 -1.5587
04Nov2011   4.0411 4.4994 3.5564 -1.4170 -0.2606 -1.7109
08Nov2011   4.7341 4.8794  4.3907 1.3542 -3.0508 -1.7167
10Nov2011    1   3.9944 3.7676 6.1001 -1.3058 -3.8087 -1.6418
11Nov2011    1  3.8542 3.6831 3.0418 -0.8383 0.1550 -2.3841
11Nov2011    2    3.6876 2.7429 2.7830 -1.6250 -0.0386 -1.6346

 

 

  5880   Sat Nov 12 02:27:00 2011 SureshUpdateComputersC1IOO front end suddenly froze. Was restarted remotely

[Koji Suresh]

No one was messing with the c1ioo or any other machine.   The medm screens for WFS and MC alignment froze while I was working on Rossa.

There were number of red lights pertaining to c1ioo machine on the CDS_FR_STATUS screen.  So we logged into c1ioo   from Rossa and restarted it with 'sudo shutdown -r now'.  It came back up but the C1IOO_MC_TRANS_SUM, P and Y signals were not available on the C1IOO LOCKMC screen.

I saw several messages similar to the one here


Sat Nov 12 02:09:14 PST 2011

  medmCAExceptionHandlerCb: Channel Access Exception:
  Channel Name: Unavailable
  Native Type: Unavailable
  Native Count: 0
  Access: Unavailable
  IOC: Unavailable
  Message: Virtual circuit disconnect
  Context: c1ioo.martian:43553
  Requested Type: TYPENOTCONN
  Requested Count: 0
  Source File: ../cac.cpp
  Line number: 1126

 

The MC autolocker script wasnt running.  The heartbeat bit was not blinking on the MC_LOCKMC screen.  So we manually restarted the script.  Hopefully it will return to normal operation.

I restarted the fb at Sat Nov 12 02:12:19 PST 2011  in an attempt to see this resolves the problem.

It didnt.

 

  5881   Sat Nov 12 02:44:18 2011 SureshUpdateComputersC1IOO front end suddenly froze. Was restarted remotely

Quote:

[Koji Suresh]

No one was messing with the c1ioo or any other machine.   The medm screens for WFS and MC alignment froze while I was working on Rossa.

There were number of red lights pertaining to c1ioo machine on the CDS_FR_STATUS screen.  So we logged into c1ioo   from Rossa and restarted it with 'sudo shutdown -r now'.  It came back up but the C1IOO_MC_TRANS_SUM, P and Y signals were not available on the C1IOO LOCKMC screen.

I saw several messages similar to the one here


Sat Nov 12 02:09:14 PST 2011

  medmCAExceptionHandlerCb: Channel Access Exception:
  Channel Name: Unavailable
  Native Type: Unavailable
  Native Count: 0
  Access: Unavailable
  IOC: Unavailable
  Message: Virtual circuit disconnect
  Context: c1ioo.martian:43553
  Requested Type: TYPENOTCONN
  Requested Count: 0
  Source File: ../cac.cpp
  Line number: 1126

 

The MC autolocker script wasnt running.  The heartbeat bit was not blinking on the MC_LOCKMC screen.  So we manually restarted the script.  Hopefully it will return to normal operation.

I restarted the fb at Sat Nov 12 02:12:19 PST 2011  in an attempt to see this resolves the problem.

It didnt.

 

 The problem was resolved after I burtrestored (c1mcs c1ioo and c1rfm) epics snapshots.

 

  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.

 

 

  5891   Tue Nov 15 00:00:15 2011 SureshUpdateIOOMC was realigned to remove beam clipping and to accommodate PZT1 range

[Kiwamu, Suresh]

The MC was realigned to readjust the input beam direction in pitch such that the clipping of the beam at the PSL table reduced and the railing of the PZT1 is avoided.

The current spot positions are given below on the last row:

 

 Date  #### MC1P MC2P MC3P MC1Y MC2Y MC3Y
03Nov2011   0.1354 -0.2522 -0.1383 -1.0893 0.7122 -1.5587
04Nov2011   4.0411 4.4994 3.5564 -1.4170 -0.2606 -1.7109
08Nov2011   4.7341 4.8794  4.3907 1.3542 -3.0508 -1.7167
10Nov2011    1   3.9944 3.7676 6.1001 -1.3058 -3.8087 -1.6418
11Nov2011    1  3.8542 3.6831 3.0418 -0.8383 0.1550 -2.3841
11Nov2011    2    3.6876 2.7429 2.7830 -1.6250 -0.0386 -1.6346
14Nov2011    1 5.9412 2.7658 5.4806 -4.7676 0.7778 2.2053

 

We have quite a lot of decentering in the MC which we must try to remove by parallel transporting the beam in Pitch and Yaw..

At the current settings we might be clipping on the Faraday Isolator as we had estimated that we can allow atmost a 2mm offset in spot positions due to this constraint.

 

 

 

  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

 

  5899   Tue Nov 15 19:59:41 2011 SureshUpdateIOOWFS output matrix measured (open loop)

Quote:

Quote:

 The scripts used to make the WFS outmatrix measurement live in /cvs/cds/rtcds/caltech/c1/scripts/MC/WFS

 I assume you mean /opt/rtcds/caltech/c1/scripts/MC/WFS.

As I've tried to reitterate many times: we do not use /cvs/cds anymore.  Please put all new scripts into the proper location under /opt/rtcds.

 Yes the files are in /opt/rtcds/caltech/c1/scripts/MC/WFS.

I just went to wherever the 'scripts' alias takes me, found the 'pwd' and did a cp+paste of the path.   I checked to be sure that 'scripts' takes me to /opt/rtcds/caltech/c1/scripts/.

So why does the pwd show /cvs/cds.... instead of /opt/rtcds  ?

 

  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

  5905   Wed Nov 16 09:21:56 2011 SureshUpdateIOOMC2 Shifted in Pitch, corrected by adjusting the pitch bias

[Steve, Suresh]

    Steve went over to the MC2 walkway and stepped over the barrier to pick up some stuff there.  MC2 stack shifted and MC2 pitch as off.  MC unlocked and could not relock till the MC2 pitch bias was readjusted

previous MC2PIT reading: 3.6235           current MC2PIT reading:  3.9565

Without the WFS the MC to PSL alignment is poor, but it is largely due to a shift in the MC and not a shift in the PSL beam.  We know this 'coz the shift in the DC spot positions on WFS (when the MC is unlocked) is not significant nor is the shift on the C1:IOO-QPD.  When WFS loops are engaged the MC optics are turned to optimise the PSL to MC alignment, but the shift is large at the moment.

(Sorry Mirko your measurement could not be completed.  The MC unlocked in the middle)

Please Note:  If you need to access the blocked off area near MC2 stack, do not step over the barrier.  The disturbance is too great and the MC2 stack will shift.  Instead please move the barrier aside and walk as gently as possible near it, taking care not to touch the MC2 Chamber.

  5906   Wed Nov 16 10:08:17 2011 SureshUpdateIOOEffect of turning on the MC2_TRANS_PIT and YAW loops in ASC

I turned on the two remaining loops in the ASC system to see if we can lock.   I put in some ones into the WFS_OUTPUT matrix

WFS_OUTMATRIX.png

and locked the MC2_TRANS_PIT and MC2_TRANS_YAW loops.

The effect of doing so is visible in the error signals.  The black loops are with all ASC loops off, Blue traces are with the WFS1 and 2 loops locked and Red traces are with all loops locked.  I took the red traces to a lower frequency to see if the suppression of the error signals at low frequencies is disturbed by the switching on of the MC2_TRANS loops.  They seem to be working fine without adding any perturbation above the UGF.

WFS_servo_err_20111115.png

I measured the  Transfer Function coefs (at 10Hz using the WFS Lockins)  with MC2_TRANS loops locked in this rudimentary fashion

  WFS1P WFS2P MC2TP WFS1Y WFS2Y MC2TY
MC1P -23.8541 15.2501 -24.3470 -3.3166 -2.0473 -0.1202
MC2P 29.7402 54.7689 29.5102  -0.2922 -17.4226 0.0310
MC3P 34.3612 10.7279 33.9650 6.6582 -4.0892 0.2333
MC1Y 0.9510 -6.3929 0.8722 -98.2414 -82.9129 -4.2802
MC2Y 12.0673 6.1708 11.9502 237.1172 20.7970 14.6480
MC3Y -0.8498 2.8712 -1.4195 -20.6031 111.2531 -1.5234

 

The green and blue bits are the only relevant parts since we ignore the off diagonal parts.  And most of these off diagonal coefs are indeed quite small (<5% of the max).  I have marked the not-so-small ones in yellow.

I then calculated the output matrix elements in two different ways.

a) Using a null vector in the place of MC_DoF --> MC2_TRANS transfer coefs.  The output matrix we get is

 

  WFS1P WFS2P Null Vector
MC1P -1.0000 0.8271  -0.8880
MC2P 0.0962 1.0000  0.4431
MC3P 0.9306 -0.2913  -1.0000

 

  WFS1Y WFS2Y Null Vector
MC1Y -0.2340 -0.5840 1.0000
MC2Y 1.000o -0.1551  0.4714
MC3Y -0.3613 1.0000 0.6571

 

b) Without using the null vector.  i.e. using the MC_DoF --> MC2_TRANS transfer coefs and inverting the full matrix.  The output matrix we get is

 

   WFS1P WFS2P  MC2TP
 MC1P  0.1471  -0.8880  0.8655
 MC2P  1.0000  0.4431  -0.4369
 MC3P  -0.7634  -1.0000  1.0000

 

  WFS1Y WFS2Y MC2TP
MC1Y 0.1401 1.0000 -1.0000
MC2Y 0.1449 0.4714 -0.3627
MC3Y 1.0000 0.6571 -0.6775

 

I plan to try out these two output matrices and measure the OL TFs of the MC2_TRANS and see if we can include these into ASC in a useful fashion.

Attachment 1: WFS_OUTMATRIX.png
WFS_OUTMATRIX.png
  5910   Wed Nov 16 10:53:35 2011 SureshUpdateIOOMC2 Shifted in Pitch, corrected by adjusting the pitch bias

Quote:

[Steve, Suresh]

    Steve went over to the MC2 walkway and stepped over the barrier to pick up some stuff there.  MC2 stack shifted and MC2 pitch as off.  MC unlocked and could not relock till the MC2 pitch bias was readjusted

previous MC2PIT reading: 3.6235           current MC2PIT reading:  3.9565

Without the WFS the MC to PSL alignment is poor, but it is largely due to a shift in the MC and not a shift in the PSL beam.  We know this 'coz the shift in the DC spot positions on WFS (when the MC is unlocked) is not significant nor is the shift on the C1:IOO-QPD.  When WFS loops are engaged the MC optics are turned to optimise the PSL to MC alignment, but the shift is large at the moment.

(Sorry Mirko your measurement could not be completed.  The MC unlocked in the middle)

Please Note:  If you need to access the blocked off area near MC2 stack, do not step over the barrier.  The disturbance is too great and the MC2 stack will shift.  Instead please move the barrier aside and walk as gently as possible near it, taking care not to touch the MC2 Chamber.

 

Apparently the MC2 stack had not finished shifting.   The MC unlocked while Steve was working on the PSL table installing the mirror for IOO_QPD and then it could not relock.  So I moved the MC2 once again in Pitch.  The current status of the sliders is here

C1IOO_MC_ALIGN.png

 

Yesterday I fixed the yellow buttons on the MC_ALIGN and MCLOCK screens.  They use the new updatesnap script  .  Could we also add a couple of lines to this script so that eveytime we save a snap shot the various values are written(appended) to a text file?  That way we do not need to depend solely on the conlog, which is quite slow.

 

  5925   Thu Nov 17 13:58:12 2011 SureshUpdateIOOMC unlocked and misaligned.

Quote:

Quote:

Actually, do we need to reset the filter history at every lock loss of the MC?

Those DC offsets were necessary to keep the alignment good just until the MC is unlocked.
So if we keep the history, we can maintain the good alignment.

 I suspect the integrators get fed a huge wrong signal on lockloss. Clearing the history on the trans DOFs when the MC was badly aligned gets it nicely aligned again. I switched off the alignment transmission DOFs for now.

I have modified the 'mcwfson' and 'mcwfsoff' scripts to include the Clear History step for the MC2_TRANS_PIT and _YAW filters.  

These scripts can be run, by hand, from LOCKMC screen or from the WFS_MASTER screen.  Use the 'Turn WFS ON/OFF' button. 

The mcautolockmain script will now clear history on all ASC filter banks when the MC unlocks.

I have turned on ASC loops on the MC2_TRANS (= alignment transmission DOFs of the above elog) paths.

 

 

  5938   Fri Nov 18 01:12:14 2011 SureshUpdateCDSMC1 LR dead for > 1 month; now revived temporarily

[Den, Mirko, Suresh]

    We were investigating why there is no correlation between MC1 osem signals and seismic motion.   During this we noticed a recurrence of this old problem of MC1_LR sensor being dead.  I went and pressed down the chip holders where the AA filters used to sit and which now hold the jumper wire.  The board is large and flexible it is quite likely some solder joint is broken on the MC1_LR path on this board.

   The signal came back to life and is okay now. But it can break off again any time.

 

 

Quote:

 Since the MC1 LRSEN channel is not wasn't working, my input matrix diagonalization hasn't worked today wasn't working. So I decided to fix it somehow.

I went to the rack and traced the signal: first at the LEMO monitor on the whitening card, secondly at the 4-pin LEMO cable which goes into the AA chassis.

The signal existed at the input to the AA chassis but not in the screen. So I pressed the jumper wire (used to be AA filter) down for the channel corresponding to the MC1 LRSEN channel.

It now has come back and looks like the other sensors. As you can see from this plot and Joe's entry from a couple weeks ago, this channel has been dead since May 17th.

The ELOG reveals that Kiwamu caught Steve doing some (un-elogged) fooling around there. Burnt Toast -> Steve.

bt.jpg

993190663   =      free swinging ringdown restarted again

 

  5943   Fri Nov 18 08:29:35 2011 SureshUpdateIOOHEPA air-flow effect on WFS.

[Koji, Suresh]

    We investigated the effect of airflow from the HEPA filters on the PSL beam fluctuation and the resultant noise injected into the WFS loops.   The hint that the WFS are injecting PSL beam jitter into MC mirror motion lies in the MC2_TRANS_PIT and YAW signal's power spectrum shown here.  First, in the blue trace, which shows the spectrum when the WFS loops are off, we see that the WFS1 and WFS2 error signals have a different shape from that of MC2_TRANS.  Since WFS are affected by the PSL beam jitter while the MC2_TRANS_QPD is not, the WFS spectrum contain excess noise, while the MC2_TRANS signals show only the mirror motion.  Next, upon switching on the WFS1 and WFS2 loops, we notice that the MC2_TRANS  spectra acquire the same shape as the WFS spectra.  This shows that the excess noise from the beam jitter has been injected into the MC2 motion, and shows up in the MC2_TRANS spectra.

   To confirm these conclusions we repeated the above measurement with the HEPA fans at 0% (Blue trace), 20% (Red), 30% (Brown) and  100% (Green).   The plots are shown below.  We can see that there is no difference between 0 and 20% levels but beam jitter is visible at 30% HEPA level.  The WFS loops were ON during this time and we can can see the PSL noise injected in to MC2 motion (Green).

WFS_err_HEPA.png

 

The HEPA filter fans are now at 20%.  How can we be sure that they are really working at 20%, since we cannot see any difference between 0 and 20%?

Now that we have this quiet situation, we also investigated the effect (or lack thereof) of switching on the MC2_TRANS loops.  The figure below shows the spectra with all the loops turned off (Blue), with the WFS1 and WFS2  loops turned on (Green)  and with everything turned on (Red).   With the current output matrix, which is the same simple one as the one in this elog, we see some low frequency suppression.  But it also seems to add some noise into the other WFS loops.  I am not sure of this result, due the long duration of this measurement, the seimic noise level may have changed over the course of this measurement.

WFS_err_mc2t_effect.png

As they are not doing any good just now.  I have turned them off by setting the gain in MC2_TRANS PIT and YAW to zero.

 

  5958   Sat Nov 19 06:04:43 2011 SureshUpdateIOOMC_WFS Servo: The MC2_TRANS_PIT and YAW loops switched ON

Without adding significant amounts of noise to other WFS loops I have engaged the MC2_TRANS_PIT and YAW loops. 

After several attempts to measure the system response and computing the output matrix, none of which gave any useful results, I gave up on that and decided to find three orthogonal actuation vectors which enable us to close the loops.  So using the last good output matrix (below left side)  as a template, I rounded it off to the nearest set of orthogonal vectors and arrived at the following matrix (right side):

WFS_OUTMx_Lastgood.png        WFS_OUTMATRIX_20111118.png

 

I also decided that WFS1 and 2 need not drive MC2.  This is just to decouple the loops and minimise cross-talk.   This (albeit heuristic)  matrix seems to work pretty well and the real matrix is probably quite close to it.

I show below the suppressed error signals after tweaking the gains a bit.   The blue line is with no WFS, the green one with only WFS1 and 2 loops on, while the red is with all loops turned on.  The WFS1Yaw and MC2_Trans_pit loops might benefit from a more careful study to determine a better output matrix.

WFS_err_MC2T_on_OMx5_20111118.png

  5989   Wed Nov 23 16:48:39 2011 SureshUpdateGeneralcable cleanup

[Koji Suresh]

As part of the general lab clean up we removed many unused BNC cables (long and short) from around the SP table.  We removed one very long BNC cable which was connected on one side to an PEM input and not connected on the other side near the 1X2 rack..   There were several cables from an old SURF phase camera project which were still attached to a couple of RF amps on the SP tables and running towards the 1X6 rack. 

We also removed some unused power cables  plugged into a power distribution strip near Megatron.

 

  5990   Wed Nov 23 16:55:57 2011 SureshUpdateIOOMC realigned

The PSL alignment into the MC was too poor for the autolocker to engage.  So retaining the last coil slider settings on the MC_Align screen that Kiwamu wanted, I have realigned the PSL beam and recentered the beam on the WFS.

When the WFS_MASTER was burtrestored after the recent power shutdown, the values loaded into the output matrix were not optimal.  When we switch on the WFS loops now, the MC_TRANS loops seem to push the WFS into away from the best possible coupling to PSL.  So I have switched them off for now.   Will load a new optimised output matrix and measure the transfer functions to see what is going on.

 

 

  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
  6290   Thu Feb 16 21:13:07 2012 SureshUpdateElectronicsREFL165 repair: PD replaced, DC response checked with a torch light

[Koji, Suresh]

Kiwamu mentioned that REFL165 is not responding and its DC out seems saturated at 9V.  Koji and I checked to see if changing the power supply to the PD changed its behaviour. It did not.  

I then look a close look at the PD and found that the front window of the PD was not clear and transparent.  There was a liquid condensation inside the window, indicating an over heating of the PD at some point.  It could have arisen due to excessive incident power.  The pic below shows this condensation:

PC_30641_old.jpg

 

I also checked the current flowing through the reverse bias voltage line.  There was a voltage drop of 3V across R22 (DCC D980454-01-C)   indicating a 150mA of current through the PD.  This is way too much above the operating current of about 20mA.   The diode must have over heated.

I pulled out the old PD out and installed a new one from stock.  The pic below shows the clear window of a new PD.

PD_30641_new.jpg

After changing the PD I checked the DC output voltage while shining a torch light on to the PD.  It showed an output of about 30 to 40 mV.  This seemed okay because the larger 2mm photodiodes showed ~100mA DC output with the same torch.Below is the current state of the ckt board.

IMG_0548.JPG

 

I will tune the PD to 165 MHz tomorrow and measure its transimpedance.

  6333   Tue Feb 28 16:31:08 2012 SureshUpdateElectronicsREFL165 repair: Characterization

The transfer function and current noise were measured.  The location of the peak shifts with the amount of incident light power (RF or DC).  The TF was measured at an incident 1064nm light power of 0.4 mW which produced a DC output voltage of 14 mV => DC photocurrent of 0.28 mA. 

Many of the effects that Koji noted in the previous characterization are still present.

In addition I observed a shift of the peak towards lower frequencies as the RF power supplied to the AM Laser (Jenne Laser) is increased.  This could create a dependance of the demodulation phase on incident RF power.

The plots are attached below.

Attachment 1: REFL165_Characterization.pdf
REFL165_Characterization.pdf REFL165_Characterization.pdf REFL165_Characterization.pdf REFL165_Characterization.pdf
Attachment 2: REFL165_response_shift.pdf
REFL165_response_shift.pdf
  6337   Wed Feb 29 00:22:35 2012 SureshUpdateElectronicsREFL165 repair: Installed on the AS table

1) The REFL165 has been replaced onto the AS table.

2) When the PD interface cable is attached the PD shows a DC out put of 6mV and does not respond to a flash light.  I changed the PD interface port in the LSC rack by swapping the other end of the cable with an unused (Unidentified PD) interface cable,  The PD is working fine after that.   There could be a problem with some binary switch state on the PD interface where the REFL165 cable was plugged in earlier.

 

  6339   Wed Feb 29 01:14:40 2012 SureshUpdateElectronicsREFL165 repair: Characterization

Quote:

The transfer function and current noise were measured.  The location of the peak shifts with the amount of incident light power (RF or DC).  The TF was measured at an incident 1064nm light power of 0.4 mW which produced a DC output voltage of 14 mV => DC photocurrent of 0.28 mA. 

Many of the effects that Koji noted in the previous characterization are still present.

In addition I observed a shift of the peak towards lower frequencies as the RF power supplied to the AM Laser (Jenne Laser) is increased.  This could create a dependance of the demodulation phase on incident RF power.

The plots are attached below.

 [Koji, Suresh]

To determine the amount of RF power in the AM laser beam at various RF drive levels I measured the RF power out of the Newfocus 1611 PD while driving the AM laser with a Marconi.  During this measurement the DC output was 2.2V.  With the DC transimpedance of 10^4 and a sensitivity of 0.8 A/W we have carrier power as 0.275 mW (-5.6 dBm).  [Incidentally the measured carrier power with a power meter is about 0.55 mW. Why this discrepancy?]

  1 2 3 4 5 6
Marconi Output (dBm) 0 -5 -10 -15 -20 -25
AG 4395 measurement (dBm) -8.1 -13.0 -18.0 -23 -28 -33
RF/DC ratio dB -2.5 -7.4 -12.4 -17.6 -22.6 -27.6

 

Estimation of the signal strength at the REFL165 PD:

   From the 40m Sensing Matrix for DRFPMI we see that the signal strength at REFL165 in CARM is about 5x10^4 W/m.  Since we expect about 0.1nm of linear range in CARM length we expect about 0.05 mW of RF power.  If the (DC) carrier power is about 10 mW at the photodiode (18mW is about the max we can have since the max power dissipation is 100 mW in the diode)  then the RF : DC power ratio is 5x10^-3 => -23 dB

As this is lower than the power levels at which the PD transfer function was determined and where we noted the distorsion and shift of the resonance peak, it is likely that these effects may not be seen during the normal operation of the interferometer.

The shift due to the carrier power level (DC) change may still however pose a problem through a changing demodulation phase. 

 

  6402   Mon Mar 12 22:14:56 2012 SureshUpdateRF SystemCalibration of Demod Board Efficiency.

I have completed the calibration of the demod board efficiencies.  Here is the schematic of the set-up.

 Calibration_Schematic.png

The data is given below and the data-file is attached in several different formats.

 Demod_calib.png

 

Attachment 3: Demod_calib.txt
								
	Measurements			 After corrections			Efficiency= out/in	
Demod Board	mV_ampl	mV_pk-pk	mV_pk-pk	mV_ampl	mV_ampl	mV_ampl	Vout/Vin	Vout/Vin
	PD in	Q out	I out	PD in	Q out	I out	Q out	I out
REFL33	10.6	10.0	10.0	9.4	5.0	5.0	0.53	0.53
AS11	24.0	10.0	11.0	21.3	5.0	5.5	0.23	0.26
REFL11	22.5	240.0	255.0	20.0	120.0	127.5	6.00	6.38
POX11	24.0	9.2	8.5	21.3	4.6	4.3	0.22	0.20
POY11	22.4	10.5	9.0	19.9	5.3	4.5	0.26	0.23
AS55	17.6	268.0	268.0	15.6	134.0	134.0	8.57	8.57
REFL55	19.7	15.8	15.5	17.5	7.9	7.8	0.45	0.44
POP55	18.8	278.0	274.0	16.7	139.0	137.0	8.32	8.20
REFL165	21.2	16.0	16.4	18.8	8.0	8.2	0.42	0.44
POY110	23.4	14.7	14.4	20.8	7.4	7.2	0.35	0.35
POY22	17.5	11.9	9.3	15.6	6.0	4.6	0.38	0.30
Attachment 4: Demod_calib.xlsx
  6418   Wed Mar 14 16:39:02 2012 SureshUpdateGeneralREFL165 signal was not reaching demod board : Fixed

Quote:

The following tasks need to be done in the daytime tomorrow.

  • Hook up the DC output of the Y green BBPD on the PSL table to an ADC channel (Jamie / Steve)
  • Install fancy suspension matrices on PRM and ITMX [#6365] (Jenne)
  • Check if the REFL165 RFPD is healthy or not (Suresh / Koji)
    • According to a simulation the REFL165 demod signal should show similar amount of the signal to that of REFL33.
    • But right now it is showing super tiny signals [#6403]

 The REFL165 RF output was not reaching the Demod board.  The RF cable was disconnected.  I fixed that and then I put in a RF signal at 165MHz , 1.66 mVrms at the test input  (100Hz off set from the 165MHz LO) and saw that the 100 Hz demodulated signal was visible in the dataviewer. 

Test_CDS_Calibration.png

 

Will complete the Optical RF power -> CDS counts calibration tomorrow morning. 

  6423   Fri Mar 16 06:17:56 2012 SureshUpdateElectronicsREFL165 calibration : measurements

 

These are the measurements for estimating the amplitude of the signal recorded in the CDS when a known amount of modulated light is incident on the photodiode. 

I mounted the PD characterisation setup onto a small breadboard which could then be placed close AP table.  I then placed position markers for REFL165 on the AP table before moving it onto my small breadboard.  The AM laser was driven by an RF function generator (Fluke 6061A) at a frequency of 165.98866 MHz, which is 102 Hz offset from the 165MHz LO.  The power level was set at -45dBm.  This power level was chosen since anything higher would have saturated the AntiAliasing  Whitening Filters.  The counts in the CDS were converted to voltage using the ADC resolution = 20V per 2^16 counts.

  

  RF source RF power to AM laser 1611 PD 1611 PD REFL165 REFL165 CDS CDS
  power set (dBm) Actual power out (dBm) DC (V) RF out (dBm) DC (mV) RF out (dBm) Amplitude (V)   102 Hz Amplitude (V) 102 Hz
                 
1  -45  -50.6  -2.5 -58.9  10  -37.4  0.171 0.172
2  -48  -53.5  -2.5 -62.1  10  -40.3  0.122  0.121
3  -51  -56.5  -2.5 -65.0  10  -43.1  0.085  0.085

    

 When the 166MHz power is decreased by a factor of 2 the amplitude of 102Hz wave recorded in CDS goes down by sqrt(2) as expected.   The RF AM power incident on the REFL165 was estimated to be 0.011mW(rms)  (case #1 in the above table)  using the DC power ratio and using the transimpedance of the 1611 BBPD to be 700 Ohms.  This produces a 171 mV amplitude wave at 102 Hz.  I then stepped down the power by factor of 2 and repeated the measurement. 

(These numbers however are not agreeing with the power incident on REFL165 if we assume its transimpedance to be 12500.  It will take a bit more effort to make all the numbers agree.  Will try again tomorrow)

Here is a picture of the small black breadboard on which I have put together the PD characterisation setup.  It would be great if we can retain this portable set up as it is, since we keep reusing it every couple of weeks.  It would be convenient if we can fiber couple the path to the PD under test with a 2m long fiber.  Then we will not have to remove the PD from the optical table while testing it.

IMG_0552.JPG

 

  6428   Mon Mar 19 21:25:31 2012 SureshUpdateElectronicsREFL165 calibration : measurements

Quote:

 To characterize the RF V to counts we need to know the state of the whitening filter board. Was the filter on or off ? What was the value of the whitening gain slider?

 The filter was ON and the whiterning filter gain was 45dB

 

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