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ID Date Authorup Type Category Subject
  2035   Thu Oct 1 13:12:41 2009 KojiUpdateMZMZ Work from 13:00-

I will investigate the MZ board. I will unlock MZ (and MC).

  2038   Thu Oct 1 19:04:05 2009 KojiUpdateMZMZ work done (Re: MZ Work from 13:00-)

MZ work has been done. I did not change anything on the circuit.

Recently we observed that the MZ PZT output was sticking at a certain voltage. I found the reason.
Shortly to say "we must return the PZT Ramp offset to 0, after the lock"

I am going to write a MZ auto lock script someday, to do it automatically.

According to the resister values used in the circuit, the PZT HV output voltage is determined by the following formula:

V_PZT = 150 - 12 V_ctrl - 24 Vramp

Here the ramp voltage Vramp moves from -10V to +10V, the feedback control voltage V_ctrl moves from -13V to +13V.
The baseline offset of 150V is provided in the circuit board.

When V_ramp is 0, V_PZT runs from 0 to 300. This is just enough for the full scale of the actual V_PZT range,
that is 0V~280V.

If any Vramp offset is given, V_PZT rails at either side of the edges. This limits the actual range of the PZT out.

This is not nice, but is what happened recently.


I will investigate the MZ board. I will unlock MZ (and MC).


  2039   Thu Oct 1 19:18:24 2009 KojiUpdateSUSall suspensions undamped

Ops. I restored the damping of the suspensions at around 16:30.




 The EQ did not change the input beam pointing. All back to normal, except MC2 wachdogs tripped again.

 Round 3 for the day of MC2 watchdogs tripping.

 I've watchdogged all the suspensions while I mess around with computers.  If no one else is using the IFO, we can leave them undamped for a couple of hours to check the resonant frequencies, as long as I don't interrupt data streams with my computer hatcheting.


  2050   Mon Oct 5 10:41:31 2009 KojiUpdatePSLPSL laser accidentally turned off

The PSL output looks smaller than the incident. Try to FSS Slow actuator adj of -5.6 (nominal), instead of -3.5.


Alberto, Steve,

While I was moving a cart near by the PSL table I pushed the red emergency button that turns off the PSL laser. We had to unlock the button and then power cycle the laser driver to turn the laser back on.

I relocked MZ, FSS, PMC and I'm now waiting for the power to finish ramping up back to the previous value.


  2055   Mon Oct 5 19:39:26 2009 KojiUpdatePSLPSL laser accidentally turned off

I set the FSS slow actuator adj to -5.6 at the lunch time. It gave a little help at that time. Now max of the MC Trans is comming back somehow. I hope the MC Trans level is as good as before, if the HEPA is slowed down.


The PSL output looks smaller than the incident. Try to FSS Slow actuator adj of -5.6 (nominal), instead of -3.5.


Alberto, Steve,

While I was moving a cart near by the PSL table I pushed the red emergency button that turns off the PSL laser. We had to unlock the button and then power cycle the laser driver to turn the laser back on.

I relocked MZ, FSS, PMC and I'm now waiting for the power to finish ramping up back to the previous value.



  2060   Tue Oct 6 23:39:54 2009 KojiOmnistructureEnvironmentRF area is clean!


I propose that anyone who tries to do this kind of thoroughgoing cleaning should make an e-mail to call everyone available to join just for some hours
because every member has a responsibility to keep the lab organized.

And we have the list of things to do: Electronics (now it is halfway) / Cables / Optics / Screws / Tools ...


I spent part of the afternoon cleaning up the area next to the Mode Cleaner where we keep all of our RF stuff:  Attenuators, BNC/SMA/LEMO adapters, Mini-Circuits items, and all sorts of other things which are useful while looking at our electronics/RF stuff.

We got another set of "Lyon" drawers, which aided in the organization process....Bob ordered 2, so we now have a 'spare' drawer set if anyone can think of something else to organize (unless this was premeditated for optics or something else?).

As you can see in the picture, (1) it's no longer a total disaster over there, and (2) some of the drawers have sub-divisions to make it faster and easier to find what you're looking for.  Please help out by putting things away in their proper place, and adding more labels or dividers to the drawers if there's something else which needs a 'spot'.


  2070   Thu Oct 8 20:18:56 2009 KojiSummaryGeneralArm cavity loss

Last night (Oct 07), I ran armLoss script in order to obtain the latest numbers for the arm cavity loss.
Here is the summary

<<X arm>>
Measured arm reflectivity R_cav:
0.875 +/- 0.005
Estimated round trip loss L_RT: 157ppm +/- 8ppm
Estimated finesse F: 1213+/-2
Data Points: 34

<<Y arm>>
Measured arm reflectivity R_cav:
0.869 +/- 0.006
Estimated round trip loss L_RT: 166ppm +/- 8ppm
Estimated finesse F: 1211+/-2
Data Points: 26








TE=10ppm, LE=L_RT/2, RE=1-TE-LE
tE=Sqrt(TE), rE=Sqrt(RE)

TF=0.005, LF=L_RT/2, RF=1-TF-LF
tF=Sqrt(TF), rF=Sqrt(RF)

rcav = -rF +(tF^2 rE)/(1-rF rE)
R_cav = rcav^2

F = pi Sqrt(rF rE)/(1-rF rE)


  2071   Thu Oct 8 21:32:59 2009 KojiSummaryGeneralRecycling cavity loss

I looked at the data of the day before yesterday (Oct 06) to know how much is the recycling gain.

X arm: (TRX_PRecycled) / (TRX_PRMmisaligned) * T_PRM = 83.1/0.943*0.07 = 6.17
Y arm: (TRX_PRecycled) / (TRX_PRMmisaligned) * T_PRM = 99.2/1.017*0.07 = 6.83

==> G_PR = 6.5 +/- 0.5     (oh...this estimation is so bad...)

From the recycling gain and the arm cavity reflectance, one can get the loss in the recycling cavity.

G_PR = T_PRM  / (1-Sqrt(R_PRM * (1-L_PRC)*R_cav))^2

==> loss in the recycling cavity L_PRC: 0.009+/-0.009
       (About 1% loss is likely in the recycling cavity)


<<X arm>>
Measured arm reflectivity R_cav: 0.875 +/- 0.005
Estimated round trip loss L_RT: 157ppm +/- 8ppm
Estimated finesse F: 1213+/-2

<<Y arm>>
Measured arm reflectivity R_cav:
0.869 +/- 0.006
Estimated round trip loss L_RT: 166ppm +/- 8ppm
Estimated finesse F: 1211+/-2


  2082   Mon Oct 12 17:27:20 2009 KojiConfigurationSAFETYStray beam blocking

Steve, Kiwamu, and Koji

We went through the PSL table to make sure any strong beam did not hit the wall.

We found that the reflection of Stephanie's OSA returned its path down to the beamsplitter.
This BS reflect that beam to the wall. That was fixed.

The surprising was that the relatively strong beam (~1mW?) went through the steering mirror
just before the PMC. We put thorlabs razor blades. I am still thinking what this indicates...
because the beam had been blocked if it was such from long time before.

During the work we found some stray optics such as a cube BS, a flipper mirror, and so on.
We can see them in the photo as those enclosed with yellow circles.
One of the beams was obtained from the reflection of the ND filter (...almost illeagal), and 
was even hittting a metal fixture for the BS cube.

If someone uses these components for useful purposes,
please let me(Koji) know. Otherwise, they are removed next week.

The other thing we found was the bright scatter from the EOM for the PMC.
As this scatter is so blight, I am going to align it.

  2085   Mon Oct 12 19:53:44 2009 KojiConfigurationSAFETYStray beam blocking
I aligned the EOM and the beam to the PMC.
The beam is still hitting the bottom of the EOM aperture,
but the further lowering the EOM reduces the PMC transmission.
So I put my compromise.

The work restored the PMC transmission to over 2.4.

Finally I centered the beams on to the MC WFSs.
As a result, the MC Trans recovered 7.5.
  2087   Mon Oct 12 20:01:13 2009 KojiConfigurationSAFETYStray beam blocking

OK! I saw the optics are redundant and some of the components are not in a right place.
I will talk with you when you are back such that we can keep the usefulness of the setup.


 These components are from when Rana and I used the StochMon PD to do the RFAM tuning, documented in elog 1926.  This was a very handy measurement, but I'm not sure if whether or not we need it often enough to keep the optics there.


  2103   Fri Oct 16 12:40:59 2009 KojiConfigurationGeneralSome questions

Some questions came arise to me:

A. How the green injection system should be? How the handing off between 532 and 1064 should be?

This is not new, though. It would be worth reminding.

B. Do we still need PMC if we use 2W innolight?

Innolight has low intensity noise at the detection freq. Also the spacial mode is clean.

C. Do we still need frequency prestabilization by RC?

Is the stabilization of the laser freq by the MC not enough?
What is the relationship with the green?

  2104   Fri Oct 16 13:25:18 2009 KojiSummaryLSCfunny timing setup on the LSC

Could be this.



We should be able to diagnose timing noise between the OMC and the LSC by putting in a signal in the OMC and looking at the signal on the LSC side. Should be a matlab script that we can run whenever we are suspicious of this. This is an excellent task for a new visiting grad student to help learn how to debug the digital control system.


  2113   Sun Oct 18 23:02:03 2009 KojiUpdateLSCLSC timing issue

You yourself told me that tdsdata uses some downconversion from 32k to 16k!

So, how does the downconversion appears in the measurement?
How does the difference of the sampling rate appears in the measurement?
If you like to understand the delay, you have to dig into the downconversion
issue until you get the EXACT mechanism including the filter coefficients.

AND, is the transfer function the matter now?

As far as the LSC and OMC have some firm relationship, whichever this is phase delay or advance or any kind of filering,
this will not introduce any noise. If so, this is just OK.

In my understanding, the additional noise caused by the clock jitter is the essential problem.
So, did you observe any noise from the data?


*preliminary result

The measured data are shown in attached fig.1 and 2.

In the fig.1 it looks like they are the same signal.

However in fig.2 which is just magnified plot of fig.1, it shows a time-delay apparently between them.

The delay time is roughly ~50 micro sec.

The surprising is that the LSC signal is going beyond the OMC signal, although the OMC signal drives the LSC !!

We can say it is "negative delay"...

Anyway we can guess that the time stamp or something is wrong.


*next plan

Tomorrow I'm going to measure the transfer-function between them to see the delay more clearly.

( And I would like to fix the delay. )


  2128   Wed Oct 21 13:07:54 2009 KojiUpdateWIKI-40M UpdatePSL Table Diagram wiki entry


Thanks. I love this. Could you also put the original file that is editable for future modification by anyone?


 I made a wiki entry for the PSL table diagram under the PSL directory on the 40mHomePage. I tried to use the ImageLink macro to use a resized (smaller) version of the diagram as a link to the full image, which it is designed to do if there is no target given, but it didn't seem to work. Instead, I had to create a second page that had the full-sized diagram, and I used ImageLink with a smaller version to link to that page.

The inventory that is shown is clearly incomplete. Part of this is due to the fact that many labels were either missing or impossible to read without touching stuff. For those components with labels missing, I tried to infer what they were to the best of my knowledge, but I wasn't able to for all of them. In true wiki spirit, everyone is encouraged to fill in any additional information they might have on these components. 


  2135   Thu Oct 22 21:58:26 2009 KojiUpdateWIKI-40M UpdatePSL Table Diagram wiki entry

Diagram. I don't want to say PNG is an editable format for this purpose...
You have the PPT, PDF or any drawing format to create this diagram.



Thanks. I love this. Could you also put the original file that is editable for future modification by anyone?

 Do you mean the diagram or the inventory? The diagrams are online as attachments (small versions on the main "PSL Table Diagram" page and large versions on the linked pages). The inventory is easily editable on the wiki itself. It's just rendered in table form using the CSV parse utility for "comma-separeted values" (though you actually need to use semicolons, for reasons unknown).


  2147   Mon Oct 26 23:14:08 2009 KojiUpdatePSLlaser power is down

I adjusted the steerings to the PMC and gained 7%. Now the MC_TRANS 7.0 has been recovered.

Actually I need another 7% to get MC_TRANS 7.5.
But I couldn't find how I can recover 126MOPA-AMPMON to 2.8ish.


The laser power is down 5-6%


  2149   Tue Oct 27 15:55:04 2009 KojiUpdateGeneralISS injection work / HEPA is on

I was working on the ISS excitation to take TFs.

I used ISS IL excitation, stealing from a small box on the floor for the OMC.

All the configuration was restored except that the HEPA is on.

  2158   Thu Oct 29 13:48:32 2009 KojiUpdatePSLNPRO LTMP lowered 9.5deg

13:00 Found MC TRANS less than 7.
13:50 Go into the PSL table.
14:20 Work done. Now I am running SLOWscan script.
15:10 SLOWscan finished. It was not satisfactory. I go into the table again.
15:15 Running SLOWscan again.
16:00 SLOWscan done. Lock PMC. Adjust NPRO current so as to maximize PMC TRANS.
16:10 Lock RC, PMC, MZ, MC. Align PMC / MZ on the table. Align MC WFS beams on the QPDs.
16:30 Work done.

New FSS-SLOWDC nominal is -4.0

Now MC TRANS is 7.9. This is +12% increase. ENJOY!
HEPA is on at 90%. Light is off.


NPRO TEMP trimmer adjustment
o PSL NPRO TEMP trimmer at the back of the laser head was turned 6.5 times in CW.
o It reduced NPRO crystal temp by 9.5deg. (43.5deg -> 34.0deg for FSS_SLOWDC -5.5)

To revert the previous setting, refer to the former measurement
c.f. http://nodus.ligo.caltech.edu:8080/40m/2008

NPRO Thermal scan
o 2 scans are performed.
o I selected the colder side of the second scan. i.e. SLOWDC=-4.0

NPRO Current adjustment
o Tweaked C1:PSL-126MOPA_126CURADJ while looking at PMC TRANS.
o CURADJ was changed from -2.25 to -1.9. This corresponds to change of C1:PSL-126MOPA_CURMON from 2.503A to 2.547A.

  2161   Thu Oct 29 20:21:14 2009 KojiUpdatePSLNPRO LTMP lowered 9.5deg

Here is the plots for the powers. MC TRANS is still rising.

What I noticed was that C1:PSL-FSS_PCDRIVE nolonger hit the yellow alert.
The mean reduced from 0.4 to 0.3. This is good, at least for now.

  2168   Mon Nov 2 13:00:55 2009 KojiUpdateIOOPMC aligned, MC WFS aligned

The beam to PMC aligned. The beam to MC WFS cameras aligned.
PMC Trans increased from 2.73 to 2.75 (+1%).
MC Trans increased from 7.80 to 7.87 (+1%).

  2173   Tue Nov 3 12:47:01 2009 KojiConfigurationCDS1Y9 Rack configuration update

For the CDS upgrade preparation I put and moved those stuff at the rack 1Y9:

Placed 1Y9-12 ADC to DB44/37 Adapter LIGO D080397

Placed 1Y9-14 DAC to IDC Adapter LIGO D080303

Moved the ethernet switch from 1Y9-16 to 1Y9-24

Wiki has also been updated.

  2181   Thu Nov 5 16:24:59 2009 KojiUpdateCDSETMY CDS test stuff

Joe, Peter, Jay, Koji, Rana

We put the new CDS stuff at Y end 1Y9 rack.


  • megatron
  • wireless router
  • IO chasis (black)
  • Extention cable (between megatron & IO chasis)
  • 1 ADC card
  • 1 DAC card
  • 1 BIO card
  • The adapter box for ADC
  • The adapter box for DAC
  • The adapter box for BIO
  • 2x IDC-DB37 cable for the ADC box - AA chasis
  • 1x IDC cable for the DAC box - Pentek
  • 1x DB cable for the BIO box
  • 1x +/-15V cable for the BIO box
  2216   Mon Nov 9 15:08:29 2009 KojiOmnistructureEnvironmentTidying up BNC cables rack around the lab


This would be a good trial once you put the label "BNC only" on the wall.


We have thousands of miles of BNC cables in the lab but we still don't find one when we need it. I decided to solve the problem.

This morning I tried to tidy up the several cable rack the we have in the lab.

i tried to dedicate each rack to a speecific type of cables: special cables, hand made cables, BNCs, LEMOs, etc.

In particular I tryed to concentrate BNC cable of several lengths on the rack near by the ITMX chamber.

People are invited to preserve the organization.



Done! Check it out.

  2241   Wed Nov 11 17:33:54 2009 KojiUpdateABSLWorking on the AP table

Yes it did.

For long time, the crystal temperature C1:PSL-126MOPA_LTMP was 43~46deg. Now it is 34deg. Try ~10deg lower temperature.


I wonder if the all the tinkering on the PSL laser done recently to revive the power have changed the PSL NPRO temperature and so its frequency. That could also explain why the beat doesn't show up at the same temperature of the NPRO as I used to operate it. Although I scanned the NPRO temperature +/- 2 deg and didn't see the beat.


  2251   Thu Nov 12 11:19:10 2009 KojiUpdatePSLAbandoned Frequency Generator

Last night there was an activity for a calibratuon work, which I helped. I can take care of the FG.


This morning I found a frequency generator connected to something on the PSL table sitting on the blue step next to the sliding doors.

Is anyone using it? Has it been forgotten there? If that's the case, can the interested person please take care of removing it?


  2258   Thu Nov 12 17:15:43 2009 KojiUpdatePSLMC Trans Offset

OK. I have been keeping my eyes on the MC transmission. In deed, the MC trans has been well kept at around 7.7 since the last PSL work.
Even it was over the 8 today!


On Rana's suggestion I checked the MC transmission QPD (C1:IOO-MC_TRANS_SUM). I found that the readout is almost zero when the MC is unlocked.

I unlocked the Mode Cleaner turning off the LSC control and disabling the autolocker. The QPD reads 0.014. It seems that there is no offset.

I also checked with the IR card around the photodetector and I didn't see any stray beam.


  2260   Thu Nov 12 17:42:04 2009 KojiUpdatePSLMC Trans Offset

PC_DRIVE is also improving after the last PSL work!


OK. I have been keeping my eyes on the MC transmission. In deed, the MC trans has been well kept at around 7.7 since the last PSL work.
Even it was over the 8 today!


  2269   Fri Nov 13 22:01:54 2009 KojiUpdateComputersUpdated wiki with RCG instructions/tips

I continued on the STAND ALONE debugging of the megatron codes.

- I succeeded to run c1aaa with ADC/DAC. (c1aaa is a play ground for debugging.)

  The trick was "copy DAC block from sam.mdl to aaa.mdl".
  I don't understand why this works. But it worked.
  I still have the problem of the matrices. Their medm screens are always blank. Needs more works.

- Also I don't understand why I can not run the build of c1tst when I copy the working aaa.mdl to tst.mdl.

- The problem Joe reported: "# of channels to be daqed" was solved by

make uninstall-daq-aaa
make install-daq-aaa

  This command is also useful.


- Now I am in the stable development loop with those commands

make uninstall-daq-aaa
make aaa
make install-aaa
make install-daq-aaa
make install-screens-aaa

  I have made "go_build" script under /home/controls/cds/advLigo

./go_build aaa

- Note for myself: frequently visited directories

/home/controls/cds/advLigo/src/epics/simLink (for model)
(to build)
(realtime code log)
/cvs/cds/caltech/target/c1aaaepics (ioc log)
/cvs/cds/caltech/medm/c1/aaa (medm screens)
(filter coeffs)
/cvs/cds/caltech/chans/daq (daq settings)

  2270   Sat Nov 14 06:46:48 2009 KojiUpdateComputersUpdated wiki with RCG instructions/tips

I am still working on the c1aaa code. Now it seems that C1AAA is working reasonably (...so far).

1) At a certain point I wanted clean up the system status. I have visited /etc/rc.local to add c1aaa for realtime to non-realtime task

/usr/bin/setup_shmem.rtl mdp mdc tst&
/usr/bin/setup_shmem.rtl mdp mdc tst aaa&

   I rebooted the system several times.

sudo /sbin/reboot

2) I found that gabage medm screens accumulated in ~/cds/advLigo/build/aaaepics/medm after many trials with several simulink models.
This directory is always copied to /cvs/cds/caltech/medm/c1/aaa at every make install-screens-aaa
This caused very confusing MEDM screens in the medm dir like C1AAA_ETMX_IN_MATRX.adl (NOT ETMY!)

I did

cd ~/cds/advLigo
make clean-aaa

to refresh aaaepics dir. The current development procedure is

make clean-aaa
make uninstall-daq-aaa
make aaa
make install-aaa
make install-daq-aaa
make install-screens-aaa

3) Sometimes startaaa does not start the task properly. If the task does not work, don't abandon.
Try restart the task. This may help. 

(deep breathing several times)

What to do next:

- MEDM works

* make more convenient custom MEDM screens so that we can easily access to the filters and switches
* retrofit the conventional SUS MEDM to the new system

- once again put/confirm the filter coeffs and the matrix elements

- configure DAQ setting so that we can observe suspension motion by dataviewer / dtt

- connect the suspension to megatron again

- test the control loop

  2278   Tue Nov 17 00:42:12 2009 KojiUpdateComputersUpdated wiki with RCG instructions/tips

Dmass, Joe, Koji

A puzzle has been solved: Dmass gave us a great tip

"The RGC code does not work unless the name of the mdl file (simulink model) matches to the model name "

The model name is written in the second line. This is automatically modified if the mdl file is saved from simulink.
But we copied the model by using "cp" command. This prevent from the TST model working!

megatron:simLink>head tst.mdl
Model {
  Name                    "tst"
  Version                 7.3
  MdlSubVersion           0


This explained why the AAA model worked when the DAC block has been copied from the other model.
This was not because of the ADC block but the saving model fixed the model name mismatch!

Now our current working model is "C1TST". Most of the functionalities have been implemented now:

  • The simulink model has been modified so that some of the functionalities can be accomodated, such as LSC/ASC PIT/ASC YAW.
  • Some filter names are fixed so as to inherit the previous naming conventions.
  • The SUS-ETMY epics screen was modified to fit to the new channel names, the filter topologies, and the matrices.
  • The chans file was constructed so that the conventional filter coefficients are inherited.
  • All of the gains, filter SWs, matrix elements have been set accordingly to the current ETMY settings.
  • burt snapshot has been taken: /cvs/cds/caltech/target/c1tstepics/controls_1091117_024223_0.snap
    burtrb -f /cvs/cds/caltech/target/c1tstepics/autoBurt.req -o controls_1091117_024223_0.snap -l /tmp/controls_1091117_024215_0.read.log -v

What to do next:

  • Revisit Oplev model so that it accomodates a power normalization functionality.
  • ETMY QPD model is also missing!
  • Clean up mdl file using subsystem grouping
  • Check consistency of the whitening/dewhitening switches.
  • Connect ADC/DAC to megatron
  • Test of the controllability
  • BTW, what is happened to BIO?
  • Implementation of the RFM card

Directories and the files:

  • The .mdl file is backed up as

  • The default screens built by "make" is installed in
    They are continuously overridden by the further building of the models.

  • The custom-built medm screens are stored in

    The backup is

  • The custom-built chans file is

    The backup is

  • burt snap shot file
  2280   Tue Nov 17 11:09:43 2009 KojiConfigurationSUSETMY suspension conencted to megatron ADC/DAC

I have connected ETMY sus electronics to megatron ADC/DAC.
We continue this state until 15:00 of today. (Restored 13:00)

  2281   Tue Nov 17 13:39:37 2009 KojiConfigurationSUSETMY suspension conencted to megatron ADC/DAC

0) Now the connection for the ETMY suspension was restored in a usual state. It damps well.

1) I thought it would be nice to have dataviewer and DTT working.
   So far, I could not figure out how to run daqd and tpman.
   - I tried to configure
(via daqconfig)

   - I also looked at
   but I don't understand how it works. The entries have dcuids of 13 and 14 although C1TST has dcuid of 10.
   The file is unmodified.

   I will try it later when I got a help of the experts.

2) Anyway, I went ahead. I tried to excite suspension by putting some offset.

It seems to have no DAC output. I checked the timing signal. It seems that looks wrong clock.

   I looked at DAC output by putting 5000,10000,15000,20000,25000cnt to UL/UR/LR/LL/SD coils.
   I could not find any voltage out of the DAC in any channels.

   Then, I checked the timing signal. This clock seems to have wrong frequency.
   What we are using now is a clock with +/-4V@4MHz. (Differential)
   Maybe 4194304Hz (=2^22Hz)?

   I went to 1Y3 and checked the timing signal for 16K. This was +/-4V@16kHz. (Diffrential)

   The possible solution would be
   - bring a function generator at the end and try to input a single end 4V clock.
   - stretch a cable from 1Y3 to 1Y9. (2pin lemo)


I have connected ETMY sus electronics to megatron ADC/DAC.
We continue this state until 15:00 of today.


  2282   Tue Nov 17 15:23:06 2009 KojiConfigurationSUSETMY suspension conencted to megatron ADC/DAC

OK. Now, Timing/ADC/DAC are working. It's almost there.

1) As a temporaly clock, I put a function generator at the back side of the ETMY.
Set it to the rectangular +/-4V@16384Hz. Connect it to D060064 PCIX Timing Interface Board in the IO Chasis.
That is a line receiver to feed the TTL signal into ADCs/DACs.

I confirmed the actual sampling clock is supplied to the ADC/DAC boards by looking at the SMB output of the D060064.

2) Restarted the realtime code.

3) I looked at DAC output by putting 5000,10000,15000,20000,25000cnt to UL/UR/LR/LL/SD coils again.
Yes! I could see the DAC channels are putting DC voltages.

4) Then I connected DAC CH0 to ADC CH0 using SCSI breaking up boards.
Yes! I could see the coil output switching change the ADC counts!

Now, we are ready to see the suspension damped. Check it out.

  2285   Tue Nov 17 21:10:30 2009 KojiConfigurationSUSETMY suspension conencted to megatron ADC/DAC

Koji, Rana

The megatron DAC was temporaly connected to the suspension electronics for the DAC test. We went down to ETMY as we could not excite the mirror.

The DAC is putting correct voltages to the channels. However, the anti imaging filter test output does not show any signal.
This means something wrong is there in the DAC I/F box or the cables to the AI circuit. We will check those things tomorrow.

The ETMY was restored to the usual configuration.

  2295   Wed Nov 18 22:38:17 2009 KojiUpdateElectronicsmulti-resonant EOM --- EOM characterization ---

How can I get those values from the figure?


But indeed it has lead inductance of 12nH, resistance of 0.74[Ohm], and parasitic capacitance of 5.5pF. 


  2318   Mon Nov 23 21:36:38 2009 KojiUpdateIOOAligned PMC/RC

I aligned the beam goes to PMC. It increased the MC Trans from 8.25 to 8.30.

I also aligned the beam goes to RC.
When I touched the FSS box (wrong: this was the VCO driver) that was close to one of the steering mirror, suddenly the RC trans increased.
It is now 9.8. I am afraid that it gets saturated. I could not reproduce the phenomenon. This could be caused by a bad contact?
Note that I didn't see there is any loose optic.

  2320   Tue Nov 24 10:36:21 2009 KojiUpdateLSCMeasured MC length

What I meant was the VCO driver, not the FSS box.

As for the frequency, all written numbers were the Marconi displays.
The number on the frequency counter was also recorded, and so will be added to the previous entry shortly... 


I propose that from now on, we indicate in the elog what frequencies we're referring to. In this case, I guess its the front panel readback and not the frequency counter -- what is the frequency counter readback? And is everything still locked to the 10 MHz from the GPS locked Rubidium clock?

Plus, what FSS Box? The TTFSS servo box? Or the VCO driver? As far as I know, the RC trans PD doesn't go through the FSS boxes, and so its a real change. I guess that a bad contact in the FSS could have made a huge locking offset.


  2336   Wed Nov 25 16:44:52 2009 KojiUpdatePSLMeasured MC length--FSS trend

I checked C1:PSL-FSS_VCODETPWR. The attached is the 4 months trend of the FSS RCTRANS / RFPDDC(=FSS REFL) / VCODETPWR / VCOMODLEVEL.

Although VCO modulation level setting was mostly constnt, VCODETPWR, which presumably represents the RF level, changes time by time.
It coincides with the recent reduction of the RCTRANS/RFPDDC. Actually, my touch restored the VCO to the previous more stable state.
One can see that this is not only a single occation, but it happened before too. (In the middle of Aug.)

This could be explained by the bad contact of some cable or connector.

Nevertheless we need more careful investigation:

1. Understand what VCODETPWR is exactly.
2. Investigate relationship between VCOMODLEVEL / VCODETPWR / AOM deflection efficiency / RCTRANSPD
3. Confirm the frequency matching between the VCO and AOM.


but the increase in both the RCtrans and the RCrefl is consistent with my theory that the power going to the RC has increased ; its not just an increase in the visibility.

We should scan the AOM/VCO to make sure the frequency is matched to the resonance to within 0.5 dB.


  2341   Thu Nov 26 02:08:34 2009 KojiUpdateElectronicsMulti-resonant EOM --- Q-factor ----

The key point of the story is:
"The recipe to exploit maximum benefit from a resonant EOM"
- Make a resonant EOM circuit. Measure the impedance Z at the resonance.
- This Z determines the optimum turn ratio n of the step-up transformer.
(n2 = Z/Rin where Rin is 50Ohm in our case.)
- This n gives the maximum gain Gmax (= n/2) that can be obtained with the step up transformer.
  And, the impedance matching is also satisfied in this condition.

OK: The larger Z, the better. The higher Q, the Z larger, thus the better.
(Although the relationship between Z and Q were not described in the original post.)

So, how can we make the Q higher? What is the recipe for the resonant circuit?
=> Choose the components with smaller loss (resistance). The details will be provided by Kiwamu soon??? 

When I was young (3 months ago), I thought...

  • Hey! Let's increase the Q of an EOM! It will increase the modulation!
  • Hey! Let's use the step-up transformer with n as high as possible! It will increase the modulation!
  • Hey! Take the impedance matching! It will increase the modulation!

I was just too thoughtless. In reality, they are closely related each other.

A high Q resonant circuit has a high residual resistance at the resonant frequency. As far as the impedance is higher than the equivalent output impedance of the driving circuit (i.e. Z>Rin n2), we get the benefit of increasing the turn ratio of the transformer. In other words, "the performance of the resonant EOM is limited by the turn ratio of the transformer." (give us more turns!)

OK. So can we increase the turn ratio infinitely? No. Once Rin n2 gets larger than Z, you no longer get the benefit of the impedance transforming. The output impedance of the signal source yields too much voltage drop.

There is an optimum point for n. That is the above recipe. 

So, a low Q resonant EOM has a destiny to be useless. But high Q EOM still needs to be optimized. As far as we use a transformer with a low turn ratio, it only shows ordinary performance.



  2343   Sat Nov 28 20:27:12 2009 KojiUpdatePSLFSS oscillation: Total gain reduced

I stopped by the 40m for some reason and found that the MC trans was 7.5.
This was caused by an oscillation of FSS, which seemed to be started by itself.

The oscillation stopped by reducing the FSS total gain to +9dB (from +11dB).
This is not a permanent fix (i.e. autolocker will restore the gain).
If it seems necessary to reduce the FSS gain always, we change the MC autolocker script.

  2354   Sat Dec 5 01:40:11 2009 KojiUpdateoplevsOplevs centered, IP_POS and IP_ANG centered

We restarted daqd and it did restored the problem
Then restart the 'daqd' process:'telnet fb40m 8087', type "shutdown" at the prompt. The framebuilder will restart itself in ~20s.


It did not related to the problem, but we also cleaned the processes related to dtt, dataviewer by pkill

After that the alignment scripts started to work again. As a result, we got some misalignment of the oplevs.
I am going to come on Sunday
- Align the optics
- Align the oplevs again
- Take snapshots for the suspensions
- Align the IP_POS, IP_ANG
- Align the aux laser for the absolute length
- Align PSL table QPDs, and MCT QPD

  2358   Sat Dec 5 18:23:48 2009 KojiUpdateoplevsOplevs centered, IP_POS and IP_ANG centered

NOTE: HEPA is on at its full.

[[[OK]]] Align the suspended optics (by Rob)
Align the oplevs again
[[[OK]]] Take snapshots for the suspensions/QPDs/IO QPDs/PZT strain gauges
[[[OK]]] Align the IP_POS, IP_ANG
[[[OK]]] Align the PSL table QPDs, the MC WFS QPDs, and the MCT QPD
[[[OK]]] Align the aux laser for the absolute length 

Alignment of the aux laser

o Go to only ITMX mode:
Save the alignment of the mirrors. Activate X-arm mode. Misalign ITMY and ETMX.

o Inject the aux beam:
Open the shutter of the aux NPRO. Turn the injection flipper on.

o Look at the faraday output:
There are several spots but only one was the right one. Confirm the alignment to the thorlabs PD. Connect the oscilloscope to the PD out with a 50Ohm termination.
Thanks to the Alberto's adjustment, the beat was already there at around 10MHz. After the PD adjustment, the DC was about 600mV, the beat amplitude was about 50mVpp.

o Adjust the aux beam alignment:
Adjust the alignment of the aux beam by the steering mirrors before the farady isolator. These only change the alignment of the aux beam independently from the IFO beam.
After the alignment, the beat amplitude of 100mVpp was obtained.

o Closing
Close the shutter of the NPRO. Turn off the flipper mirror. Restore the full alignment of the IFO.

  2360   Mon Dec 7 09:38:05 2009 KojiUpdateVACVent started

Steve, Jenne, Koji

The PSL was blocked by the shutter and the manual block.
We started venting
at 9:30

09:30  25 torr
10:30 180 torr
11:00 230 torr

12:00 380 torr

13:00 520 torr
14:30 680 torr - Finish. It is already over pressured.

  2366   Tue Dec 8 13:03:26 2009 KojiUpdateCOCETMY drag wiped

Jenne, Kiwamu, Alberto, Steve, Bob, Koji

We wiped ETMY after recovery of the computer system. We take the lunch and resume at 14:00 for ITMX.
Detailed reports will follow.

  2369   Wed Dec 9 00:23:28 2009 KojiUpdateSUSfree swinging spectra of ETMY and ITMX

Where is the plot for the trend?
It can be either something very important or just a daydream of you.
We can't say anything before we see the data.

We like to see it if you think this is interesting.

... Just a naive guess: Is it just because the seismic level got quiet in the night?



You looks consistently confused some words like damping, Q, and peak height.

  • Q is defined by the transfer function of the system (= pendulum).
  • Damping (either active or passive) makes the Q lower.
  • The peak height of the resonance in the spectrum dy is determined by the disturbance dx and the transfer function H (=y/x).

dy = H dx

As the damping makes the Q lower, the peak height also gets lowered by the damping.
But if the disturbance gets smaller, the peak height can become small even without any change of the damping and the Q.


By the way I found a trend, which can be seen in all of the data taken today and yesterday.

The resonances of pitch and yaw around 0.5Hz look like being damped, because their height from the floor become lower than the past.

I don't know what goes on, but it is interesting because you can see the trend in all of the data.


  2373   Wed Dec 9 18:01:06 2009 KojiUpdateCOCWiping finished

[Kiwamu, Jenne, Alberto, Steve, Bob, Koji]

We finished wiping of four test masses without any trouble. ITMY looked little bit dusty, but not as much as ITMX did.
We confirmed the surface of the ITMX again as we worked at vertex a lot today. It still looked clean.

We closed the light doors. The suspensions are left free tonight in order to check their behavior.
Tomorrow morning from 9AM, we will replace the door to the heavy ones.

  2375   Thu Dec 10 00:46:15 2009 KojiUpdateSUSRe: free swinging spectra of ETMY and ITMX

Well, I get the point now. It could be either seismic or change in the suspension Q.

The pendulum memorizes its own state for a period of ~ Q T_pend. (T_pend is the period of the pendulum)
If the pendulum Q is very high (>104), once the pendulum is excited, the effect of the excitation can last many hours.

On the other hand, in our current case, we turned on the damping once, and then turned off the damping.
Again it takes ~Q T_pend to be excited. 

In those cases, the peak height is not yet before in equilibrium, and can be higher or lower than expected. 

So, my suggestion is:
Track the peak height along the long time scale (~10hrs) and compare between the previous one and the current one.
This may indicate whether it is equilibrium or not, and where the equilibrium is.


If such variation of the peak heights is cased by the seismic activity, it means the seismic level change by several 10 times. It sounds large to me.


  2381   Thu Dec 10 09:56:32 2009 KojiUpdatePSLRCPID settings not saved

Note: The set point C1:PSL-FSS_RCPID_SETPOINT is 37.0 on C1PSL_FSS_RCPID.adl.

Now the temp is recovering with its full speed. At some point we have to restore the value of the FSS SLOW DC as the temp change drag it up.


Koji, Jenne, Rob

We found that the RCPID servo "setpoint" was not in the relevant saverestore.req file, and so when c1psl got rebooted earlier this week, this setting was left at zero.  Thus, the RC got a bit chilly over the last few days.  This channel has been added. 

Also, RCPID channels have been added (manually) to conlog_channels. 


  2395   Fri Dec 11 09:30:09 2009 KojiConfigurationLSC166 LO Disconnected

They must not be dBm, must be dB



I temporarily disconnected the Heliax cable that brings the 166MHz LO to the LSC rack.

I'm doing a couple of measurement and I'll put it back in as soon as I'm done.

 These are the losses I measured on a RG-174 cable for the two frequencies that we're planning to use in the Upgrade:

@11MHz Loss=0.22dBm/meter

@55MHz Loss=0.41dBm/meter

(The cable was 2.07m long. The input signal was +10dBm and the output voltages at the oscilloscope where: Vpk-pk(11MHz)=1.90V, Vpk-pk(11MHz)=1.82V )


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