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ID Date Authorup Type Category Subject
  5150   Tue Aug 9 02:44:32 2011 SureshUpdateSUSETMX free swinging data

I switched off damping to the ETMX and used a reduced version of freeswing-all.csh script (called freeswing-ETMX.csh) to set it swinging.    After about an hour I used the saved template ETMX/2008.08.06.xml to obtain the following plot.



There is something defintely wrong with the side sensor.  It might be the electronics as it also has this problem with it slow channel readings (my previous elog today).



  5167   Wed Aug 10 11:22:55 2011 SureshUpdateIOOMC A2L alignment

[Kiwamu, Suresh]

We attempted to minimise the A2L coupling in the MC mirrors (centering the beam spot on the actuation node on each optic).  While it was easy to minimise the coupling in the pitch for all the three optics and yaw of MC2, the yaw alignment of MC1 and MC3 proved to be difficult.  For one the adjustment required was quite large, so much so that PSL alignment into the MC is often lost during this adujstment.  We had to align the PSL coupling several times in order to proceed.   And the MC settles into a new position when the MC-PSL servo loop was disturbed by random denizens in the lab.  Requiring us to start over again.

Kiwamu wrote a script to measure the MC(optic)(Pitch/yaw) -> Lockin(#1 to #6) matrix.  Inverting this matrix gave us the linear combination of the offsets to put on the MC# PIT/YAW  inorder to minimise a specific Lockin output.  However the cross couplings were not completely eliminated.  This made it very hard to predict what a given set of offsets were going to do to the Lockin outputs.

Net result:  the spots are centered in vertical direction (pitch) but not in the horizontal (yaw)

Day time tasks have started so I am quitting now.

  5182   Thu Aug 11 04:45:07 2011 SureshUpdateIOOAligning the 1064nm beam with the in-vacuum pzt's

[Kiwamu, Suresh]

We worked on the beam path from MC to BS this evening. 

After the beam spots on MC1 and MC3 were close to the actuation nodes (<1mm away) we checked the beam position on the Faraday Isolator (FI) to make sure that it is passing through both the input and output apertures without clipping.  The beam is slightly displaced (by about half a beam diameter) downwards at the input of the FI.  The picture below is a screen shot from the MC1 monitor while Kiwamu held an IR card in front of the FI.



We then proceeded to check the beam position on various optical elements downstream.  But first we levelled the BS table and checked to see if the reflection from PJ1 (1st Piezo) is landing on the MMT1 properly.  It was and we did not make any adjustment to PJ1.  However the reflection from MMT1 was not centered on MMT2.  We adjusted the MMT1 to center the beam on it.  We then adjusted MMT2 to center the beam on PJ2.  At this point we noticed that the spot on IPPO (pick off window)  was off towards the right edge.  When we centered the beam on this it missed the center of the PRM.  In order to decide what needs to be moved, we adjusted PJ2 such that the beam hits the PR2, bounces back to PR3, and becomes co-incident with the green beam from X-arm on the BS.  Under this condition the beam is not in the center of PRM and nor is it centered on IPPO.  In fact it is being clipped at the edge of the IPPO. 

It is clear that both IPPO and the PRM need to be moved.  To be sure that the beam is centered on PR2 we plan to open the ITMX chamber tomorrow.

  5199   Thu Aug 11 19:01:45 2011 SureshUpdateSUSITMX given a kick to start it freeswing' but to no avail.

We started an ITMX freeswing run at this time

Thu Aug 11 18:58:59 PDT 2011

 But the optic did not repond to the kick.  It is possible that the earthquake stops are close to the face and/or rear of the optic and prevent it from oscillating.  We will check again and see what is up in a few hours.



  5266   Fri Aug 19 01:15:22 2011 SureshUpdateSUSFreeSwing all optics

I ran "freeswing all" at Fri Aug 19 01:09:28 PDT 2011 (997776583)  and "opticshutdown"  as well.


  5267   Fri Aug 19 01:46:06 2011 SureshUpdateGeneralIFO alignment

[Keiko, Jamie, Kiwamu, Anamaria,

We followed the procedure that we laid-out in our elog of yesterday.  We completed the first six steps and we now have the y-arm well aligned to the green beam which passes through the center of of both ETMY and ITMY. 

The IR beam was steered with the PZTs to coincide with the green beam.  The BS was adjusted to see IR beam scatter on a target placed near the center of the ETMX.  And then the AS IR beam was steered to the AS camera by adjusting several components along OM path ( we touched OM1, OM2, OM3, OM4, OM5, OMPO and OM6).  We then looked for IR fringes in the AS port from the Y-arm. But no luck there.  We need to realign the IR beam into the Y-arm cavity axis using the pzts.

We aligned ITMX and PRM to get power recycled Michelson fringes at the AS.


  5277   Mon Aug 22 16:28:44 2011 SureshUpdateGeneralSRM tower shifted on Friday

[Kiwamu, Suresh]   This is a belated elog entry from last Friday night + Saturday morning! 

    We shifted the SRM tower across the beam and away from the door by about 5mm. 

                  After the input beam from MC was aligned to the Y-arm,  Kiwamu noticed that the AS beam was being clipped and that the correction had to start from SRM onwards as the beam had become offcentered on the SRM.  So we shifted the SRM tower by about 5mm away from the door and transverse to the beam and rotated it by a few degrees to center the OSEM offsets.  After this we aligned all optics along the AS beam path to extract the AS beam from the chamber.    We then aligned each optic in the vertex so that their beams overlap at the AS port with the reflection from ITMY.  Then we aligned BS to center the beam on ETMX and then looked for flashes from the Y arm.

      At this point Kiwamu checked and found that the input beam from the MC had shifted.  It was landing on the ITMY about 5mm below the center.  And (inexplicably) it was still centered on ETMY!  The Y- green which traced the cavity axis (since this was still flashing) was not coincident with the IR beam.   So all the work we did in aligning the AS beam and the vertex optics work was lost..... and had to be done again.



  5283   Tue Aug 23 02:03:04 2011 SureshUpdateIOOMC realigned and spot positions recentered

After the MC1 and MC3 OSEMs were  repositioned  MC had to be realigned and the beam spots had to be recentered on the actuation nodes.  

To do that I had to change the input beam direction into the MC  and the coil offsets.   

I also measured the resultant spot positions

spot positions in mm (MC1,2,3 pit MC1,2,3 yaw):
    0.1354   -0.2522   -0.1383   -1.0893    0.7122   -1.5587



The MC1 and MC3 yaw can be improved further after the chambers are closed and evacuated.  The PZT adjustments needed to realign the input beam pointing are quite small and should not pose a problem.



  5305   Thu Aug 25 17:57:35 2011 SureshUpdateSUSBroken UL magnet on ITMX


Dmass just reminded me that the usual procedure is to bake the optics after the last gluing, before putting them into the chambers.  Does anyone have opinions on this? 

On the one hand, it's probably safer to do a vacuum bake, just to be sure.  On the other hand, even if we could use one of the ovens immediately, it's a 48 hour bake, plus cool down time.  But they're working on aLIGO cables, and might not have an oven for us for a while.  Thoughts?

I think we should follow the established procedure in full, even though it will cost us a few more days.  I dont think we should consider the vacuum bake as something "optional".  If the glue has any volatile components they could be deposited on the optic resulting in a change in the coating and consequently optical loss in the arm cavity.



  5313   Sat Aug 27 20:38:17 2011 SureshUpdateIOOLight is back on WFS

[Valera, Suresh]

   We wanted to continue the work with WFS servo loops.  As the current optical paths on the AP table do not send any light to the WFS, I changed a mirror to a 98% window and a window to a mirror to send about 0.25mW of light towards the WFS.   The MC locking is unaffected by this change.   The autolocker works fine.

   When the power to the MC is increased, these will have to be replaced or else the WFS will burn.

  5315   Sun Aug 28 22:49:40 2011 SureshUpdateCDSfb down

I recompiled c1ioo after making some changes and restarted fb. (about 9:45 - 10PM PDT)  But it failed to restart.  It responds to ping, but does not allow a ssh or telnet. The screen output is:

allegra:~>ssh fb
ssh: connect to host fb port 22: Connection refused
allegra:~>telnet fb 8087
telnet: connect to address Connection refused
telnet: Unable to connect to remote host: Connection refused

Nor am I able to connect to c1ioo either....



  5321   Mon Aug 29 19:14:31 2011 SureshUpdateIOOWFS phase adjustments

[Valera, Suresh]

1) To see if there are significant dark-offsets on the WFS sensors we closed the PSL shutter and found that the offsets are in the 1% range.  We decided to ignore them for now.

2) To center the MC_REFL beam on the WFS we opened the PSL shutter, unlocked the MC and then centered the DC_PIT and DC_YAW signals in the C1IOO_WFS_QPD screen.

3) We then looked at the power spectrum of the I and Q signals from WFS1 to see if the spectrum looked okay and found that some of the quadrants looked very different from others.  The reason was traced to incorrect Comb60 filters.   After correcting these filters we adjusted the R phase angle in the WFS1_SETTINGS screen to suppress the 1Hz natural oscillation signal in the Q channels of all the four quadrants.  We repeated this process for WFS2

4) To see if the relative phase of all four quadrants was correct we first drove the MC_length and tried to check the phase of the response on each quadrant.  However the response was very weak as the signal was suppressed by the MC servo.  Increasing the drive made the PMC lock unstable.  So we introduced a 6Hz, 50mVpp signal from an SR785 into the MC_servo (Input2) and with this we were able to excite a significant response in the WFS without affecting the PMC servo.    By looking at the time series of the signals from the quadrants we set the R phase angle in WFS_Settings such that all the quadrants showed the same phase response to the MC_length modulation. 

     Using the larger response were were able to further tweak the R angle to supress the Q channels to about 1% of the I phase signals.

5)  I then edited the c1ioo.mdl so that we can use the six lockins just as they are used in MC_ASS.  However we can now set elements of the SEN_DMD_MATRX (sensor demod matrix) to select any of the MCL, WFS PIT and YAW channels (or a linear combination of them) for demodulation.  The change is shown below.  While compiling and model on C1IOO FE machine there were problems which eventually led to the FB crash.




  5327   Tue Aug 30 17:31:55 2011 SureshUpdateIOOC1IOO model reverted and fb restarted

I reverted the C1IOO model to the last working version and restarted the fb at this time..Tue Aug 30 17:28:38 PDT 2011

  5344   Tue Sep 6 17:43:01 2011 SureshUpdateIOOFree Swing ITMY started

Free swing of ITMY started at

Tue Sep  6 17:41:43 PDT 2011


  5351   Wed Sep 7 00:01:23 2011 SureshUpdateIOOITMY chamber ready for heavy doors

[Jenne, Suresh]

We did the following things in the ITMY chamber today:

1) We tried to get the ITMY stuck again by adjusting the coil gains so that it goes into the orientation where it used to get stuck.  We (reassuringly) failed to get it stuck again.  This, as we came to know later, is because kiwamu had rotated the side OSEM such that the optic does not get stuck . However the OSEM beam is at about 30 deg to the vertical and the SD is sensitive to POS motion now resulting in the poorer separation of modes as noted by Jenne earlier (5439)

2) We checked the earthquake stops and repositioned two at the bottom (towards the AR side of the optic)  which we had backed out earlier.

3) We took pics of all the OSEMS.

4) Checked to see if there are any stray beams with an IR card.  There were none.

5) I obtained the max values of the OSEMS by misaligning the optic with the coil offsets.  These values are in good agreement with those on the wiki

OSEM     UL     UR     LR     LL      SD

Max      1.80    1.53   1.68   1.96    2.10

Current  0.97   0.79    0.83   0.97   1.02


We can close the heavy doors tomorrow morning.

  5362   Wed Sep 7 20:44:11 2011 SureshUpdateelogrestarted

Elog crashed / dormant for long time.  A look at the log file indicated that it was busy generating png thumbnails for pdf files.

Restarted at Wed Sep  7 20:41:13 PDT 2011


  5390   Mon Sep 12 23:45:14 2011 SureshConfigurationComputer Scripts / ProgramsStripTool does not scale properly on Pianosa

When I run StripTool on Pianosa, I get the following message

==== StripTool Xt Warning Handler ====
warning:         Axis: minVal is greater than or equal to maxVal


And the y-axis scale reverts to 0 -100 regardless of what ever I set in the controls panel

I ssh'ed into rosalba and ran striptool from there and did not face this problem.  So I think pianosa has a problem with Striptool.

  5393   Tue Sep 13 09:16:00 2011 SureshUpdateIOOMC spots recentered and input beam aligned

The shift of MC2 which Rana noted caused the beam spots on the MC mirrors to decenter. I used the mcassUp and mcassOn scripts and checked the output of the C1IOO lockins to get the spot positions.  I first tried to realign just the MC2 to recenter the spots.  But this was not sufficient.  I then worked on the pitch of all three optics since it is easier to align.   By the time this was done the offset in yaw also reduced, probably due to cross coupling between pitch and yaw in the coils.  At the end of the process I obtained all decentering around 1.5mm or less, then I went over to adjust the MC2TransQPD beam path so that we center the spot on the QPD.  This action shifted the stack,  I had to iterate this two more times before the successive corrections grew sufficiently small.  I think it may shift again if we touch the chamber (the image of MC2Face is still inverted).

The new spot positions in mm (MC1,2,3 pit MC1,2,3 yaw):
    1.3212   -0.8415    0.6795   -1.4292   -0.3574   -1.5208


 mcdecenter20110912_1.png    mcdecenter20110912_2.png      


- Further improvement of beam centering can be done but first I would like to be sure that the MC is stable.  The MC2Trans light is centered on the QPD as a reference.


  5396   Tue Sep 13 19:04:58 2011 SureshUpdateComputer Scripts / ProgramsRestarted Frame builder several times while compiling c1ioo, c1mcs and c1rfm

I restarted the frame builder at the following times


Tue Sep 13 14:53:49 PDT 2011


Tue Sep 13 16:46:32 PDT 2011


Tue Sep 13 17:24:16 PDT 2011

  5397   Tue Sep 13 19:12:53 2011 SureshUpdateComputer Scripts / Programschanges to the c1ioo, c1mcs and c1rfm

[Suresh, Jamie]

The new versions of these three models have been committed to the svn.  I copy below the svn log I wrote over there.

I edited three models,namely c1ioo, c1mcs and c1rfm to bring four channels from C1MCS model into the
 C1IOO model through the RFM.

We plan to use the MC2-Trans-QPD as a third sensor in addition to the WFS1 and WFS2 in the ASC system so that we can sense all the six degrees of freedom of the MC.  However the MC2-Trans_QPD is a new incarnation of the old MC2 Oplev QPD and its four segments are are picked up in the c1mcs model running on the C1SUS machine.  Since we need these    in the C1IOO machine we    had to port these signals via the RFM.  The    changes    I made to these    models are described below:
1) c1rfm.mdl -->  I added several cds parts to carry these four    channels from c1mcs to c1ioo via c1rfm

2) c1mcs.adl -->  In the MC2 block of c1mcs I cut out the structure which converts the four segments of the  QPD in the pitch, yaw and sum signals and copied it to the c1ioo model.     In the    c1mcs I  grounded the input of the oplev signals just as they are in    the MC1    and MC2    suspension blocks. I then routed the ADC channels associated with the oplev QPD signals to the rfm model.

3) c1ioo.mdl --> I have made extensive changes to the c1ioo model to include the third sensor in the WFS feedback loop.  The six lockins in the model are used to excite the MC mirrors and the signals from WFS and QPD can be demodulated to determine the input or output matrices in the WFS feedback.  A sensor_demod_array permits us to select the signals we wish to demodulate. The MCL signal, used in the MC_ASS and A2L measurements, is retained as one of the signals.  The MC_TRANS_SUM was used several in  scripts and to preserve the continuity with this channel name we inserted three EPICS parts to generate a slow channel by the same name from this model.

Since the MC_TRANS_SUM is used in the MC-autolocker script we checked to make sure that the script is running after we recompiled all the three models and restarted them.  It is all fine.

  5416   Thu Sep 15 11:37:24 2011 SureshUpdateComputer Scripts / Programsfb restarted at Thu Sep 15 11:30:30 PDT 2011

I changed a filter bank name (C1IOO-WFS1_PIT) in c1ioo model reverting it to its earlier name.  Had to restart c1ioo model and the fb

  5433   Fri Sep 16 14:43:43 2011 SureshUpdateComputer Scripts / ProgramsChanged c1ioo model and restarted fb

I had to change the c1ioo model and restart the fb since the paths allowing us to select various signals to demodulate using the lockins were not correct. The signal selection vector was not flexible enough to permit us to select the signals to demod.

fb was restarted twice at following times.  The changes have been commited to the svn.

Fri Sep 16 13:35:47 PDT 2011

Fri Sep 16 14:36:21 PDT 2011


  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.


  5505   Wed Sep 21 19:20:41 2011 SureshUpdateIOOPSL beam into MC was off in Pitch. Readjusted.

I found the PSL beam into the MC off in pitch by large amount.  I readusted the PSL beam for optimal coupling.

The beam had shifted on the WFS as well.  So I recentered the DC signal on the WFS with the MC unlocked.  However both the DC and RF signals on the WFS shift when we lock the MC.  This ought to indicate sub-optimal coupling of PSL into MC.  But instead, if we were to reduce these offsets on the WFS by adjusting the MC axis it leads to higher reflected power from the MC.

The current plan is to retain these RF offsets and lock the WFS with a DC offset in the servo filters.

  5524   Thu Sep 22 22:53:06 2011 SureshUpdateComputer Scripts / ProgramsActivated DAQ channels in C1IOO model and restared fb

To look at the WFS servo signals I was using test points in the servo filter banks.  This is not recommended for regular operation since acquiring the testpoint data at 16k loads the fb. Instead, I ran the daqconfig script from the scripts directory and activated the IN1_DQ, IN2_DQ and OUT_DQ channels in all the six servo filter banks (at 2048 Hz sampling rate) and then restarted the fb.   However the c1ioo Sun machine stopped responding after this.  Koji and I went in to see what was going on and the machine was not reponding to a keyboard plugged directly into the machine.  The screen display showed no reponse to our key press.  So we did a hardware reboot with the tiny switch in front of the machine.  It came up okay and all the c1ioo models were back in action.

I then checked with the dataviewer to make sure that I can see the trends on the newly activated DQ channels.  They were all fine.

  5526   Thu Sep 22 23:02:15 2011 SureshUpdateIOOno light on WFS2. Realigned input onto both WFS

Rana noticed that the sum on WFS2 was about 10 times smaller than that on WFS1. Though the beam appeared centered on the DC QPD screens it was not really true.  When I went and checked the actual beam position it was landing on the metal enclosure of the WFS2 sensor and scattering back on to the diode. 

I also checked the power levels of light landing on the sensors  It was about 0.25mW in both cases.  This needs further investigation since the power split at the beam spitter is like 0.25mW onto WFS1 and 0.45 towards WFS2. The lost 0,20 mW has to be traced and we have to be sure that it is not scattered around on the table.


  5527   Thu Sep 22 23:10:07 2011 SureshUpdateIOOproposed modifications to the C1IOO model

Rana advised that we put in a lockin-output matrix which will allow us to excite any combination of MC mirrors so that we can excite pure translations or rotations of the MC beam axis.  This would require us to direct a lockin output into all the three mirrors simultaneously with a +1 or -1 as needed in the matrix..

  5533   Fri Sep 23 18:00:54 2011 SureshUpdateIOOPSL beam realigned to MC

I noticed that the beam centering on the WFS had changed over night and the MC_TRANS_SUM was about 40k counts.  When well aligned this SUM is around 50-55k counts. So PSL coupling into MC was suboptimal. It was not clear whether the MC shifted or the PSL beam shifted. So I looked at the PSL ANG and POS QPDs. 


The plots above show the gradual drift of the PSL beam in vertical direction during the last 8hrs or so. But the last bit shows the adjustments I had to make to reobtain optimal alignment.  And these adjustments are not undoing the drift!  This would indicate that the MC axis has also shifted during the same time period. 

  5555   Tue Sep 27 09:47:52 2011 SureshUpdateAdaptive FilteringPlan for making MC_F



For the acquisition of the MC_F channel, I suggest taking the FAST_MON BNC output from the blue FSS interface card in the Eurocard crate in the PSL rack. This can then be piped into the 2-pin LEMO plug (Ch. 1) of the Generic Pentek DAQ card which used to acquire the MC_L signal from the MC Servo Board.

 [Jenne, Den]

Suresh tells us that he already has this channel physically plugged in.  Probably as a result of Valera's MCASS work.  Neat.  We just have to make the channel.  Right now the signal goes straight into some lockin stuff, so there is no actual "C1:IOO-MC_F" channel.

We don't want to make the new channel right now, since it is nighttime, and Kiwamu and Suresh are working on things.  So.  Tomorrow.  In the morning:

We will add a fast test point to the C1IOO model, and call it "C1:IOO-MC_F".  We will also route this signal via memory stuff over to the OAF model so that we can do adaptive filtering on the MC.  Then we will compile all the things.  Or at least all the things that we touched.  This will go hand-in-hand with the compling of Mirko's sweet new OAF model, which we were planning on compiling in the morning anyway.  Neat.

Things to compile tomorrow:  c1ioo and c1rfm, because of channel routing.  c1oaf because of all the new stuff.  That should be all.


Is it okay to have two names for the same signal?  We would have both MCS_MCL and MC_F referring to MC length signal.  This signal is picked up from the MC-Servo (analog) and brought into the CDS through the adc_0_0 channel in C1IOO.   Then this signal is sent from C1IOO to C1MCS model without going through the c1rfm model.  This seems to break the current protocol that signals passed between machines have to go through the c1rfm model.  It should be sufficient to send this signal to c1rfm once and from there redirect to MCS and OAF from there, with an appropriate name.

  5566   Wed Sep 28 15:33:58 2011 SureshUpdateComputer Scripts / Programsediting database files for medm screens and restarting the slow c1psl machine

I changed the names on a switch(SW1) in the C1:PSL-FSS screen.  To do this I had to edit the psl.db database file in the directory /cvs/cds/caltech/target/c1psl.  After this change, when I executed this screen, all fields in the C1PSL_FSS screen went blank.  As the change to database file takes effect only after we restart the C1PSL machine (slow machine) I went ahead and reset the c1psl machine.  I then used the burttoday to locate the most recent snapshot files and then used burtgooey to restore all the values in the c1psl.snap file.

Everything back to normal now.


  5581   Fri Sep 30 03:36:19 2011 SureshUpdateComputer Scripts / ProgramsCIOO modified, but not yet compiled

I have added a switch in series with the WFS_GAIN. And I have also added a LKIN_OUT_MATRX between the lockin-outputs and the MC suspensions.  This will enable us to drive the MC mirrors in any combination so that we can (in principle) attain pure translations and rotations of the MC axis.

I will compile the model later during the day.  This is just in case anyone one else were to compile c1ioo.mdl before then.


  5606   Mon Oct 3 20:02:59 2011 SureshUpdatePSLAM / PM ratio

[Koji, Suresh]

In the previous measurement, the PDA 255 had most probably saturated at DC, since the maximum ouput voltage of PDA255 is 5V when it is driving a 50 Ohm load.  It has a bandwidth of 0 to 50MHz and so can be reliably used to measure only the 11 MHz AM peak.  In this band it has a conversion efficiency of 7000 V per Watt (optical power at 1064nm).  [Conversion efficiency:  From the data sheet we get 0.7 A/W of photo-current at 1064nm and 10^4 V/A of transimpedance]  The transimpedance at 55 MHz is not given in the data sheet.  Even if PDA255 is driving a high impedance load, at high incident power levels the bandwidth will be reduced due to finite gain x bandwidth product of the opamps involved, so the conversion efficiency at 11 MHz would not be equal to that at DC.

So Koji repeated the measurement with a lower incident light level:


V_DC = 1.07 V  with 50 Ohm termination on the multimeter.

Peak height at 11 MHz on the spectrum analyzer (50 Ohm input termination) = -48.54 dBm



a) RF_Power at 11 MHz :  -48.45 dBm = 1.4 x 10^(-8) W

b) RF_Power = [(V_rms)^2] / 50_ohm  ==> V_rms = 8.4 x 10^(-4) V

c) Optical Power at 11 MHz: [V_rms / 7000] = 1.2 x 10^(-7) W

d) Optical Power at DC =  [V_DC / 7000] = 1.46 x 10^(-4) W

e) Intensity ratio:  I_AM / I_c = 7.9 x 10^(-4) . AM:Carrier amplitude ratio is half of the intensity ratio = 4.0 x 10^(-4)

f) PM amplitude ratio from Mirko's measurement is 0.2

g) The PM to AM amplitude ratio is 506


As the AM peak is highly dependent upon the drifting EOM position in yaw, it is quite likely that a higher PM/AM ratio could occur.  But this measurement shows how small it could get if the current situation is allowed to continue.



[Mirko / Kiwamu]

 We have reviewed the AM issue and confirmed the ratio of AM vs. PM had been about 6 x103.

The ratio sounds reasonably big, but in reality we still have some amount of offsets in the LSC demod signals.

Next week, Mirko will estimate the effect from a mismatch in the MC absolute length and the modulation frequency.



 Please correct us if something is wrong in the calculations.

 According to the measurement done by Keiko (#5502):

        DC = 5.2 V

        AM @ 11 and 55 MHz = - 56 dBm = 0.35 mV (in 50 Ohm system)

Therefore the intensity modulation is 0.35 mV / 5.2 V = 6.7 x 10-5

Since the AM index is half of the intensity modulation index, our AM index is now about 3.4 x 10-5

According to Mirko's OSA measurement, the PM index have been about 0.2.

As a result,  PM/AM = 6 x 103

Quote from #5502

Measured values;

* DC power = 5.2V which is assumed to be 0.74mW according to the PDA255 manual.

*AM_f1 and AM_f2 power = -55.9 dBm = 2.5 * 10^(-9) W.



  5614   Tue Oct 4 15:57:30 2011 SureshUpdateIOOMC Trans channels are digital 0

I thought this problem might be arising because the MC2_TRANS QPD signals are not being passed from the c1mcs to c1ioo models over the rfm.   But there was no way to check if there is any data being picked up in c1mcs model.  So I copied the MCTRANS block from the c1ioo model into the c1mcs.  This block takes the four segments of the MC2_TRANS QPD and computes the pitch, yaw and sum signals from that.   It also exports these into epics channels.  I then recompiled and started the c1ioo c1mcs and c1rfm models. 

Restared fb at

Tue Oct  4 15:19:10 PDT 2011

Koji then noted that the MC2_TRANS filter banks in c1rfm and in c1ioo were showing nonzero values.   So the signals were infact reaching the c1ioo model.  They were being blocked by the INMATRIX (which the autoburt had not restored) of the MC_TRANS block, because all its elements were zero.  We burtrestored the c1iooepics to about 30hrs ago and then MC_TRANS signals were back in the LOCK_MC screen.


  5615   Tue Oct 4 16:10:45 2011 SureshUpdateComputer Scripts / ProgramsMC was not damping

The MC was not damping earlier this morning around 11:45AM.  The reason was that the INMATRIX on all the three MC1, 2 and 3 were zero.   This was seen earlier when autoburt did not restore this.

This got fixed when I Burt-Restored c1mcsepics.snap

In the afternoon we had to restore c1mcs again to restore the MC_TRANS channels because its INMATRIX was also zero.

Can we do something to make sure this gets done in the autoburt properly?

  5616   Tue Oct 4 16:58:45 2011 SureshUpdatePSLAM / PM ratio

Correction: Koji noted that Mirko actually reports a PM modulation index of 0.17 for the 11 MHz sideband (elog: http://nodus.ligo.caltech.edu:8080/40m/5462. This means

f) the amplitude ratio of the PM side-band to carrier is half of that = 0.084

g)  the PM to AM amplitude ratio as 0.084 / [4.0 x 10^(-4)]  = 209.

  5632   Fri Oct 7 19:06:46 2011 SureshUpdateIOOMC spot positions: checked and corrected.

Koji and Kiwamu had adjusted the MC beam axis slightly such that we can couple the MC output into the Y-arm without exceeding the current range of adjustability on PZT1.  This changed the centering of beam spots on MC mirrors.  I checked the mc-decentering make sure we have not made too big a compromise.  And since we can move MC2 spot position while maintaining the current positions on MC1 and MC3 decentering, we can atleast eliminate the A2L coupling on that mirror.  I used the scripts in $scripts$/MC/moveMC2/ to adjust the MC2 spot position.

Spot positions in mm (MC1,2,3 pit MC1,2,3 yaw) before adjustment:
    1.4674   -0.3548    1.0199   -1.5519    1.9834   -1.5971

After correcting MC2:

    1.4528    0.1431    0.9958   -1.2147    0.3823   -2.0163

After correcting MC1:

    1.3745    0.0669    0.8899   -1.5269    0.0296   -1.7314


The spot positions on MC1 and MC3 are very nearly (+/- 0.06 mm) same as before, while the MC2  decentering has been reduced close to zero.

A slight adjustment of the PZTs may be required to reset the beam pointing.

  5635   Fri Oct 7 22:48:26 2011 SureshUpdateIOOMC2 Trans QPD spot size and incident power decreased

After centering the spot on the MC2, I started to adjust the spot position on MC_TRANS_QPD to center the beam on it.  I noticed that the spot size was about 3 to 4mm dia. because the 200mm lens was too close to the QPD.  I moved it back and decreased the spot size to about 1mm and the sensitivity to spot position increased.  However, Koji noted that the QPD sectors were near saturation, so I put in a ND=0.3 filter to reduce the incident power on the QPD.

At optimal alignment the current QPD_SUM is around 25k to 26k counts (factor of 2 down). Eventually the gain of the QPD ckts have to be reduced to prevent saturation, for the moment this is temporary fix.

The MC_TRANS_SUM trigger for MC autolocker is working fine no further change was required.

  5647   Tue Oct 11 00:59:55 2011 SureshUpdateIOOPreliminary locking of WFS loops

[Kiwamu, Koji, Suresh]

After correcting several errors in the WFS loops, we turned them on today and saw them working!

A while back (last week actually) I noticed that the WFS1 and WFS2  QPD segments were numbered in a different order but that their input matrices did not reflect this change.  As result the WFS pitch and yaw definitions were pretty much mixed up.  However even after clearing this up the signals still showed significant amount of cross couplings. 

This problem was finally traced to the relative phase between I and Q channels of the WFS segments.  Koji suggested that I check the relative phase between all the segments to be sure.  I then repeated the procedure that Valera and I followed in our earlier elog # 5321 , and found that the phases indeed required to be adjusted.  The excitation of MCL was at 6Hz, 100mVpp, as before.   The WFS response after this was much improved i.e.  the pitch yaw cross couplings were not visible when we misalign the MC with sliders in MC_ALIGN.  And the magnitude of the response also increased since the signal was transferred from the Q to I channels.  The the phases were tweaked by hand till Q< 1% of I.  However when I repeated this measurement an hour later (I wanted to save the plots) I found that the phases had changed by a few percent! 

Koji noticed that the MC_REFL camera image showed significant intensity fluctuations and advised that we try a higher frequency and lower amplitude to avoid nonlinear effects in the WFS and in the MCL to PSL lock.  So we repeated the process at 20Hz and 20mVpp, introduced at the IN2 of the MC_Servo.  The fig below shows the level to which we reduced the signal in Q.

WFS1_IQphase20111010.pdf    WFS2_IQphase20111010.pdf

We then checked the relative phase between various quadrants by looking at the time series in dataviewer.  WFS2 Seg4 phase had to be flipped to bring it into phase with all the rest. 



After this I tried to see the WFS response to moving the MC1 and MC3 with the sliders and determined the following relations:

Pitch WFS1 WFS2
MC1 + -
MC2 - -
MC3 + +


MC1 + +
MC2 - -
MC3 + -


Disregarding the MC2 for now and assuming arbitrary gains of 1 for all elements we inverted these matrices inserted them into the WFS_servo_outmatrix.  We then found that the with a sign flip on all elements the loops were stable.  In the servo filters we had turned on only the filter modules 3 and 4.  There was no low frequency boost.   We gradually increased gain till we saw a significant suppression of the error signal at low frequencies as shown below.  There was also an associated suppression of Intensity noise at REFL_DC after a single bounce from PRM.

 WFS_error_signal_Oct10.pdf        WFS_reduction_intensity_noise_Oct10.png


To see if the locks can actually realign the MC if it were manually misaligned, we turned the loops off and misaligned MC by moving MC3 pitch by 0.05 (slider position), and then turned on the loops.  The locks were reengaged successfully and the MC regained alignment as seen on the StripTool below:



We can now proceed with the fine tuning the servo filters and understand the system better:

Q1:    Does the WFS (I to Q) phase drift rapidly?  How can we prevent it?

Q2:   How is that we do not see any bounce or roll resonances on the WFS error signals?

Q3:  How do we include the MC2 QPD into the WFS Servo?

I will proceed with determination of the actual transfer coefs between the MC DoF and the WFS sensors. 



  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


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          
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

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



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.


 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). 

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

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

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.

  5683   Mon Oct 17 23:56:34 2011 SureshUpdateIOOMC WFS Integrators switched on and WFS_MASTER screen updated

[Rana, Suresh]

     To see if the loops will stay locked when the Integrators in the servo are switched on, we stayed with the same simple output matrix (just 1 or -1 elements) and switched on the FM1 on all WFS servo filter banks.  We monitored the time domain error signals to see if engaging the locks made the error signals go to zero.  Most of the error signals did go to zero even when an intentional offset was introduced into the MC pitch of the suspension.

      We need to include TestPoints just before the Input Servo Matrix so that we can monitor the error signals without being affected by the gain changes in the WFS_GAIN slider.   These are currently not present in the C1IOO model and the position of the WFS_GAIN also has to be shifted to the other side of the Input matrix.

      The C1IOO_WFS_MASTER screen has been changed to the new one.  This incorporates filter banks for the MC_TRANS_P and _Y channels.  The screen is not yet fully functional but I am working on it and I it will continue to improve it.


  5687   Tue Oct 18 20:50:19 2011 SureshUpdateIOOC1IOO and WFS associated screens

In keeping with the current protocol,  I have started to move all the user-built medm screens associated with C1IOO into the $screens$/c1ioo/master/ directory. 

I then edited the menu button in the sitemap.adl to point to the screens in the ..c1ioo/master/ directory.  All the screens in $screens$/c1ioo/ directory have been backed up into bak/.  I plan to edit the c1ioo model soon and at that time I will delete all the screens in the $screens$/c1ioo directory and let only the automatically regenerated screens  stay there.   If there are broken links to user-built screens associated with c1ioo, please copy the relevant screen to the master/ directory and edit the path in the menus.


  5689   Tue Oct 18 22:47:09 2011 SureshConfigurationIOOMC autolocker script edited to shutdown and restart WFS loops


I found that the MC WFS had large offset control signals going to the MC SUS. Even though the input switch was off, the integrators were holding the offset.

I have disabled the ASCPIT outputs in the MC SUS. Suresh is going to fix the MC autolocker script to gracefully handle the OFF and ON and then test the script before resuming the WFS testing.

MCL data for OAF may be suspect from this morning.

 I have edited (uncommented existing commands)  the following scripts to enable WFS locking to come on when the MC is locked.

1) $scripts$/MC/autolockMCmain40m*

2) $scripts$/MC/mcup

3) $scripts$/MC/mcdown

4) $scripts$/MC/WFS/mcwfson

5) $scripts$/MC/WFS/mcwfsoff.

I have checked that the autolocker script switches off the mcwfs when mc loses lock and then switches it on after re-obtaining lock.


  5696   Wed Oct 19 12:25:58 2011 SureshUpdate40m UpgradingActive Tiptilts from LLO moved to clean shelf along X arm

I have moved the active tip tilts that we brought over from LLO to the Clean Bureau along the X arm (closest to the ETMX). There are two tip tilts and a pack of spare parts.

  5697   Wed Oct 19 13:45:11 2011 SureshUpdate40m UpgradingActive Tiptilts from LLO moved to clean shelf along X arm

I have moved the active tip tilts that we brought over from LLO to the Clean Bureau along the X arm (closest to the ETMX). There are two tip tilts and a pack of spare parts.  I am sure that the tip tilts are clean, packed in the clean room at LLO.  I am not sure whether the spares are clean.  I have kept them together for now.

We need to open one of the Tip tilt packages to be sure what we have got.

  5706   Wed Oct 19 18:18:03 2011 SureshUpdateElectronicsStochMon : Filters installed


To get to the bottom of the RFAM mystery, we've got to resurrect the StochMon to trend the RFAM after the IMC.

We will put an 1811 on the MC_TRANS or IP_POS beam (the 1811 has an input noise of 2.5 pW/rHz).

Then the Stochmon has an input pre-amp, some crappy filters, and then Wenzel RMS->DC converters. We will replace the hand-made filters with the following ones from Mini-Circuits which happen to match our modulation frequencies perfectly:

11 MHz     SBP-10.7+

55 MHz     SBP-60+

29.5 MHz   SBP-30+


The Stochmon had a four-way splitter, four hand-made filters and four mini-circuits ZX47-60-S+ Power Detectors.

Using the filters from our stock I have replaced the hand-made filters with the ones mentioned in Rana's elog.   The power supply solders to the ZX47-60-S+ Power Detectors were weak and came off during reassembly. And some of the handmade short SMA cables broke off at the neck.  So I changed the power supply cables and replaced all the short SMA cables with elbows.  I also removed one of the Power Detectors since there were four in the box and we need only three now.

The power supply connector on the box is illegal.  The current lab standard for  {+15, 0 , -15}  uses that connector.  So we are going to change it as soon as possible.  We need to identify a good {0, 5} lab standard and stock them.

The following were removed from the box:



The box now looks like this:



Steps remaining in installation of Stochmon:

1) Install the Newfocus 1811 PD at the IPPOS by diverting some of the power in that path

2) Connect the outputs of the Stochmon to ADC inputs in 1X2 rack.

  5716   Thu Oct 20 18:57:35 2011 SureshSummarySUSMC2 Misaligned 2:27PM on Wednesday


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



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



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.



ELOG V3.1.3-