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  40m Log, Page 101 of 341  Not logged in ELOG logo
ID Date Authorup Type Category Subject
  6887   Thu Jun 28 01:44:57 2012 KojiUpdateLockingPRMI work started, commissioning plan

To be fair, this is Kiwamu's idea. And nothing is reasonable before it is confirmed quantitatively.


Koji's idea of flipped-PRM seems reasonable, so I think we should better measure something to prove this.

  6939   Sun Jul 8 00:58:08 2012 KojiSummaryLockingcalibrating phase tracking mode scan data


FSR for X/Y arm are 3.97 +/- 0.03 MHz and 3.96 +/- 0.02 MHz respectively. This means X/Y arm lengths are 37.6 +/- 0.3 m and 37.9 +/- 0.2 m respectively.

These aren't so bad. (Look at this entry)

And interestingly the ETM curvatures are closer to ATF measurements than Coastline's measurement. (Look at wiki)

  6949   Tue Jul 10 01:52:47 2012 KojiUpdateLSCPRMI got more stable a bit

The phase margins looks still too small.

Do You need such high gain at LF? This is not a high finesse cavity so can we sacrifice
some DC gain while gaining more phase around UGFs?

Otherwise, the gain fluctuation should be nicely compensated (i.e. fancy normalization).

  7009   Mon Jul 23 19:00:26 2012 KojiUpdateGreen LockingALS_END.mdl model added for end station green ALS channels

This is a good modification. We just need to check how the ALS scripts are affected.


The end sus models (c1scx and c1scy) both contain some ALS stuff.  This stuff could maybe be moved to their own models, but whatever.

The stuff at X and Y were identical, but were code copies (BAD!).  I made a new library part for the ALS end controls: ${userapps}/isc/c1/model/ALS_END.mdl

It contains just some filter modules for the ALS end laser control, and a monitor of the ALS end REFL PD DC.  I also added a DQ block for the recorded channels (see screen shot).

When I added this new part to c1scx and c1scy I made it so the channel names would be more sensible.  Instead of "GCX" and "GCY", they are now "ALS-X" and "ALS-Y".  They will now all show up under the ALS subsystem.


  7033   Wed Jul 25 22:16:36 2012 KojiUpdateLSCringdown measurement

Is this the step response of the single pole low pass???
It should have an exponential decay, shouldn't it? So it should be easier to comprehend the result with a log scale for vertical axis...

I think you need a fast shutter. It is not necessary to be an actual shutter but you can use faster thing
which can shut the light. Like PMC or IMC actuators.

Another point is that you may like to have a witness channel like the MC transmission to subtract other effect.

  7061   Tue Jul 31 19:34:55 2012 KojiUpdateSTACISOpen loop gains and block diagram

With your definition of the open loop gain, G=+1 is the condition to have singularity in a closed loop transfer function 1/(1-G).

But this is not the sole criteria of the loop stability.
Basically, the closed loop transfer function should not have "unphysical" pole.
For more about loop instability, you should refer stability criteria in literature such as Nyquist's stability criterion.

Both of the X and Z loops look unstable with the current gain.

  7120   Wed Aug 8 13:37:46 2012 KojiUpdateComputer Scripts / ProgramsWeek 8/Summary Pages update

Hey, the pages got significantly nicer than before. I will continue to give you comments if I find anything.

So far: There are many 10^-100 in logarithmic plots. Once they are removed, we should be able to see the seismic excitation during these recent earth quakes?

Incidentally, where the script is located? "./" isn't the absolute path description.


Over the past week, I have been working on my progress report and finalizing the summary pages.  I have a few more things to address in the pages (such as starting at 6 AM, including spectrograms where necessary and generating plots for the days more than ~a week ago) but they are mostly finalized.  I added all of the existing acoustic and seismic channels so the PEM page is up to date.  The microphone plots include information about the transfer factor that I found on their information sheet (http://www.primomic.com/).  If there are any plots that are missing or need editing, please let me know!

I also modified the c1_summary_page.sh script to run either the daily plots or current updating plots by taking in an argument in the command line.  It can be run ./c1_summary_page.sh 2012/07/27
 or ./c1_summary_page.sh now to generate the current day's pages.  (Essentially, I combined the two scripts I had been running separately.)  I have been commenting my code so it is more easily understandable and have been working on writing a file that explains how to run the code and the main alterations I made.  The most exciting thing that has taken place this week is that  the script went from taking ~6 hours to run to taking less than 5 minutes.  This was done by using minute trends for all of the channels and limiting the spectrum plot data.

The summary pages for each day now contain only the most essential plots that give a good overview of the state of the interferometer and its environment instead of every plot that is created for that day.

I am waiting for Duncan to send me some spectrogram updates he has made that downsample the timeseries data before plotting the spectrogram.  This will make it run much more quickly and introduce a more viable spectrogram option.


Today's Summary Pages can be accessed by the link on the wiki page or at:



  7124   Wed Aug 8 20:50:39 2012 KojiUpdateASSTrouble measuring sensing matrix

From the log, I couldn't understand what has been done.

The procedure we should perform is

  1. Dither total 4 dofs of the two mirrors with different frequencies. Some fluctuation of TRY is even visible in dataviewer.
  2. The cavity is aligned at the beginning. These 4 peaks in TRY in DTT is small or invisible. Some 2nd harmonics are visible.
  3. Misalign one of the dofs. Some peaks get bigger.
  4. Correspoding lockin output becomes bigger.

Then you can start measuring the sensing matrix. At which part did the attempt fail?


I turned on the ASS, without closing the loops, to try to measure the sensing matrix. 

The Yarm was locked (Eric did a nice job earlier - he'll ELOG ABOUT IT before he goes home!), and I used an LO CLKGAIN of 300 on all of the TRY Lockins.  Then I put on and took away a 10% offset in pitch, but it's almost impossible to see the difference. 

The attached is a truly awful screenshot, but you can kind of see what's going on.  The big steps are me increasing the LO gain, but around "0" on the x-axis I changed the pitch offset from 10% away to nominal.  Since there are such big oscillations, the change is basically non-existent.  Grrrr. I'll look at it again tomorrow, since I have an exiting bike ride home ahead of me....


  7131   Thu Aug 9 01:26:03 2012 KojiUpdateASSTrouble measuring sensing matrix

That's a good point, but I suspect that you end up with the in-phase (0deg) as the response of the IFO is immediate compared with the dithering frequency
as long as the whitening/dewhitening are properly compensated in the digital realm.


 Okay, so this is a little stream-of-consciousness-y, and you're going to think I'm really dumb, but I just realized that I haven't set the phase of the lockin demodulators yet.  So I think I need to dither the optics, and go through each of the sensors, and adjust the phase until the peak in TRY in DTT is maximized for the I phase, and minimized for the Q phase (since we use the I-output).  Bah.  Bad Jenne.


  7155   Sun Aug 12 10:34:45 2012 KojiUpdateSAFETYexit door left unlocked

I unlocked the door on Tuesday in order to move the red cart.
After that I confirmed that the door was locked.


Caltech security called me at 1am Sunday. Control room emergency exit door was found unlocked!

It is your responsibility to lock door if you unlocked it ! 


  7158   Mon Aug 13 09:59:05 2012 KojiUpdateGeneralMysterious banging on emergency door

You mean 5000?


Probably, security. You can call 5555 and ask them. Otherwise you can ask them to come and check everything.


  7216   Fri Aug 17 09:34:27 2012 KojiUpdateCamerasvideo cameras in the dark
I used the LED illuminations at ETMX and BS yesterday for a tour.
I am afraid that I left them on.
  7264   Thu Aug 23 22:41:04 2012 KojiUpdateIOOMC Autolocker update

[Koji Rana]

MC Autolocker was updated. (i.e. mcup and mcdown were updated)


  • Turn on the MCL input and output switches
  • Change the MCL gain from 0 to -300 with nominal ramp time of 5sec
  • Turn on FM2, FM5, MF7 after a sleep of 5sec. Note: FM1 FM8 FM9 are always on.
  • Set the offset of 42 counts
  • Turn on the offset

# Turn on MCL servo loop
echo mcup: Turning on MCL servo loop...
ezcawrite C1:SUS-MC2_MCL_GAIN -300
sleep 5
ezcaswitch C1:SUS-MC2_MCL FM2 FM5 FM7 ON
# Offset to take off the ADC offset of MC_F
ezcawrite C1:SUS-MC2_MCL_OFFSET 42
ezcaswitch C1:SUS-MC2_MCL OFFSET ON

This offset of 42 count is applied in order to compensate the ADC offset of MC_F channel.
The MCL servo squishes the MC_F signal. i.e. The DC component of MC_F goes to zero.
However, if the ADC of MC_F has an offset, the actual analog MC_F signal, which is fed to FSS BOX,
still keep some offset. This analog offset causes deviation from the operating point of the FSS (i.e. 5V).


  • Basically the revese process of mcup.
  • This script keeps FM1 FM8 FM9 turned on.

# Turn off MCL servo loop
echo mcdown: Turning off MCL servo loop...
ezcawrite C1:SUS-MC2_MCL_GAIN 0
# Remove Offset to take off the ADC offset of MC_F
ezcawrite C1:SUS-MC2_MCL_OFFSET 0

  7265   Thu Aug 23 22:44:32 2012 KojiUpdatePSLFSS Slow DC servo is turned off (not temporary)

[Koji Rana]

The FSS Slow DC servo was turned off.

As MCL stabilizes the MC_F (Fast PZT), we no longer need to use the laser temp to do so.

In other word, if you like to turn off the MCL servo for some reason, we need to turn it on in order to keep the MC locked.

  7273   Fri Aug 24 20:48:10 2012 KojiUpdatePSLPMC aligned

as usual.

  7274   Fri Aug 24 21:00:40 2012 KojiUpdateLSCX end green investigation

I checked and fixed the X end green situation. Now the X green beam is locked with TEM00.

There are various reasons it did not lock nicely.

  • The IR beam axis was changed by Yoichi and Rana (ELOG #7169). So the green axis also had to be changed.
  • The end green optics is really "BS". Anytime I see it, I feel disgusted. Because of 3D steering mirrors, cross couplings
    between yaw and pitch are big. This makes the alignment hard.
  • Even with acceptable alignment, the lock was only momentarily. I found the slow control was on. This pushed the frequency
    too much and made the lock unstable.
  • The slow control screen was broken as Jamie changed the model names but did not fix the slow screens.
    • Jamie saids (ELOG #7011): Fix the c1sc{x,y}/master/C1SC{X,Y}_GC{X,Y}_SLOW.adl screens. 
      I need to figure out a more consistent place for those screens.

Now some action items are left:

- IR TRX is not aligned.
- X end green needs precise alignment.
- PSL GR TRX is not aligned.

These will be checked on Sunday.

- End green setup is horrible. => Manasa and I should work on this together.

  7279   Sun Aug 26 21:47:50 2012 KojiUpdateCDSC1LSC ooze

I came in to the lab in the evening and found c1lsc had "red" for FB connection.
I restarted c1lsc models and it kept hung the machine everytime.

I decided to kill all of the model during the startup sequence right after the reboot.
Then run only c1x04 and c1lsc. It seems that c1oaf was the cause, but it wasn't clear.

  7283   Mon Aug 27 10:49:03 2012 KojiUpdateSUSEQ damage

After shaking ITMX by the alignment bias in yaw, it came back.

As ETMX seems to be largely misaligned yaw (and did not come back with the alignment impact),
the condition of the magnets are not clear. Only the side OSEM is responding nicely.


  It looks like we may lost 1 (or 3 )  magnets? Do not panic, it's not for sure


  7284   Mon Aug 27 12:03:54 2012 KojiUpdateIOOMC spot position - callin' it quits

The MC REFL path was checked. ==> Some clippings were fixed. MC WFS is working now.

- MC was aligned manually

- The steering mirror for the WFS and camera was clipping the beam. => FIxed

- The WFS spots were realigned.

- There was small clipping on the MC REFL RFPD. ==> Fixed

  7302   Tue Aug 28 19:06:32 2012 KojiMetaphysicsRingdownripples

Isn't it just a ringing of the intracavity power as you shifted the laser frequency abruptly?


Let's see if the ripples observed in the MC ringdown can be due to tilt motion of the mirrors.

The time it takes to produce a phase shift corresponding to N multiples of 2*pi is given by:

t = sqrt(2*N*lambda/(L*omega_T^2*(alpha_1+alpha_2)))

L is the length of the MC (something like 13m), and alpha_1, alpha_2 are the DC tilt angles of the two mirrors "shooting into the long arms of the MC" produced by the MC control with respect to the mechanical equilibrium position. omega_T is the tilt eigenfrequency of the three mirrors (assumed to be identical). lambda = 1.064e-6m;

The time it takes from N=1 to N=2 (the first observable ripple) is given by: tau1 = 0.6/omega_T*sqrt(lambda/L/(alpha_1+alpha_2))

The time it takes from N=2 to N=3 is given by: tau2 = 0.77*tau1


First, we also see in the measurement that later ripples are shorter than early ripples consistent with some accelerated effect. The predicted ripple durations tau seem to be a bit too high though. The measurements show something like a first 14us and a late 8us ripple. It depends somewhat on the initial tilt angles that I don't know really.

In any case, the short ripple times could also be explained if the tilt motions start a little earlier than the ringdown, or the tilt motion starts with some small initial velocity. The next step will be to program a little ringdown simulation that includes mirror tilts and see what kind of tilt motion would produce the ripples exactly as we observe them (or maybe tilt motion cannot produce ripples as observed).


  7304   Tue Aug 28 20:23:54 2012 KojiMetaphysicsRingdownripples

Laser frequency shift = longitudinal motion of the mirrors

Ringing: http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-20-24-2463


Hmm. I don't know what ringing really is. Ok, let's assume it has to do with the pump... I don't see how the pump laser could produce these ripples. They have large amplitudes and so I always suspected something happening to the intracavity field. Therefore I was looking for effects that would change resonance conditions of the intracavity field during ringdown. Tilt motion seemed to be one explanation to me, but it may be a bit too slow (not sure yet). Longitudinal mirror motion is certainly too slow. What else could there be?


  7310   Wed Aug 29 17:35:34 2012 KojiUpdatePSLPower reduced!

The biggest reason why we could not lock the MC was that the beam was not properly hitting the MC REFL diode.

Now the MC REFL DC is about ~0.1 and 1.2 when the MC is and is not locked.

We increased the power according to the quantitative analysis of the intracavity power in this earlier entry

Autolocker script for the low power MC was modified so that the initial VCO gain is 3 in stead of 10.
The 2 steps of super boost were also enabled again.

  7312   Wed Aug 29 20:43:23 2012 KojiUpdateIOOSetup for a cavity scan or the input mode cleaner

The technique is based on detection of the beating between the resonant carrier and a resonant higher order mode.
This means that the beat signal is cancelled out if the transmitted beam is integrated over the entire beam.
Thus, you may want to introduce intentional clipping (or cutting a half of the beam with a razor blade). 

Ref: LIGO DCC G080467: Precise Measurements on Longitudinal and Transverse Mode Spacings of an Optical Cavity using an Auxiliary Laser

I am quite curious on the measurement as I am going to do the same measurement for the aLIGO OMC.
I am interested in seeing the statistical evaluation on the precision of the measurement.

  7332   Fri Aug 31 18:32:47 2012 KojiUpdateIOOCorrecting improper termination of the 55MHz input to the EOM


The power switch of the frequency source was mechanically broken. I replace it with the spare in Kiwamu's treasure box.
I think this replaced new one also had the same problem before, we basically have to find an alternative switch.
The problem is too much friction between the metal housing and the plastic button. I have lubricated the button with
bicycle oil.

I have checked that the 55MHz output still have the output of 25dBm after a 5m BNC cable. (nominal: 27dBm)

I could not test it with the MC as the chambers have already been closed with the light doors.

  7347   Thu Sep 6 02:51:47 2012 KojiUpdateGeneralGreen beam roughtly aligned (Re: Yarm aligned to IR incident beam)

The Y-End green beam was roughly aligned by the steering mirrors for the green beam.

I couldn't understand the Y-End green setup as the PD was turned off and the sign of the servo was flipped. Once they are fixed, I could lock the cavity with the green beams.

After a long alignment session, TEM00 was found. The alignment of the green beam has not been optimized.

Looking at the spot position at ETMY OSEM holders (not by the ccd image), it seems that the cavity mode is not at the center of the mirrors.


[EricQ, Jenne, brains of other people]

Get green spots co-located with IR spots on ETMs, ITMs, check path of leakage through the arms, make sure both greens get out to PSL table


Attachment 1: green_y.png
  7360   Fri Sep 7 12:28:09 2012 KojiUpdateLSC11&55MHz modulations turned off

11MHz modulation source was turned off (disabled) at Marconi at 12:00.

  7450   Thu Sep 27 20:05:57 2012 KojiUpdate40m UpgradingNew ETMX layout - Version 1.0

1. I wonder how the mode profiling/matching was considered in the new layout.

I can see the distances between the components and lenses are largely different from the old ones.

This is OK if you plan to go through a new mode matching solution with new lenses.
But it takes
 a certain amount of time.

Note that we don't care the distance after the last lens as the Rayleigh range there is supposed
to be long enough to allow this kind of change.

2. The huge frustration of the green alignment in the old setup was caused by the 3D beam steering
at the last two 2" mirrors. i.e. the beam elevation on the table does not match with the beam elevation of the cavity.
In order to avoid this, I suggest you to use three 45 deg 2" mirrors instead of two. In fact these mirrors are supposed to be used at 45deg incidence!

3. The incident green beam and the transmitted IR beam should share a same path as they
 share a same cavity mode.
This means that you should use a harmonic separator for the transmitted light pick-off.

4. Use the harmonic separator for the fiber path too. Get the mirror spec from Jamie.

5. Since the optical window on the chamber has a wedge angle, the beam paths are not straightforward.
The cavity beams can't be moved as they are constrained by the arm cavity.
Probably there is almost no freedom to move even for the oplev beams.
It would be safe just to follow the old positions and angles on the window.
Make sure the beam on the drawing is realistic. The angles of the oplev beams in the old setup look strange.

Is there a possibility to replace the optical window so that it has an AR for 532 and 1064 at least???

6. I wonder if the rejected beam by the Farady have a realistic angle or not. Check it with the old setup.
It is definitely better to have a steering mirrror and a lens before the refl PD.

7. The IR QPD and trans PD are intended to be used for the low and high power detection.
I forgot which is which. So check the range of them and think about the power distribution.

8. We should have separated CCDs for IR Trans and Green Refl.
We had a terrible ghost green beam on the IR trans CCD.
Thus, think about the amount of ghost reflection and consider filtering if necessary.

  7452   Fri Sep 28 21:17:41 2012 KojiUpdateIOOMC WFS adjustment

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

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

What I did:

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


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

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

4. Repeated 2 and 3 until the alignment converges.

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

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

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

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

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


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

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



Attachment 1: MC_WFS_12h.png
  7473   Wed Oct 3 23:24:05 2012 KojiUpdateSUS MC2 sus damping restored


This is the third morning in a row that the MC2 was tripped.  Would you look at it Koji?

This may be cause by the impact of crazy WFS signal after the lock loss.
The auto locker is not fast enough to shut the WFS down before the mirrors are kicked.

Jenne and I discussed the issue and agreed that this can be solved by implementing
the same triggering algorithm as the LSC triggers.

Give us a bit more time to work on this.

  7474   Wed Oct 3 23:36:54 2012 KojiConfigurationPSLAOM installation

After the AOM work the beam wasn't well aligned to the PMC. The PMC REFL CCD shows large misalignment in yaw.

Attachment 1: PMCTRANS.png
  7482   Thu Oct 4 22:16:28 2012 KojiConfigurationPSLAOM installation

Do more investigation to understand what is causing the power reduction.

Is the alignment inadequate? Check the in-lock ccd image.

Is the incident power reduced? (by what?) Use dataviewer.

Is the AOM doing something? Is it active? Then how much power is it eating?

BY THE WAY, how the deflected beam is dumped?
If you don't have anything for blocking the 1st order beam, you have to expect Steve coming to you.

  7484   Thu Oct 4 22:27:54 2012 KojiUpdateSUSHow about the slow machines?

One terrible concern of mine is that the slow machines were rebooted at the power interruption.
Based on the elog entries, I assume they have not been burtrestored...

If this is true, they may cause some weird behaviors of the PSL/IOO electronics.


  7536   Fri Oct 12 14:01:33 2012 KojiUpdateSUSTT PITCH damping


 We can only decide the need of pitch damping when the coils are activated.

Could you tell us why? Are you thinking about induced current damping?

  7555   Tue Oct 16 02:34:38 2012 KojiUpdateLSCPOP lens placed on POX table, 2 PRMI movies

How can you lock the PRMI without the REFL beams? c.f. this entry by Kiwamu
Which signals are you using for the locking?

I think the first priority is to find the fringes of the arms and lock them with POX/POY.

As for the POP, make sure the beam is not clipped because the in-vac steering mirrors
have been supposed to be too narrow to accommodate these two beams.

  7570   Wed Oct 17 19:35:58 2012 KojiUpdateComputersRe: Lots of new White :(

Solved. The power code of c1iscaux was loose.
Has anyone worked around the back side of 1Y3?

I looked into the problem. I went around the channel lists for each slow machines and found the variables are supported by c1iscaux

controls@pianosa:/cvs/cds/caltech/target/c1iscaux 0$ cd /cvs/cds/caltech/target/c1iscaux
controls@pianosa:/cvs/cds/caltech/target/c1iscaux 0$ grep C1:IF *

It seemed that the machine was not responding to ping. I went to 1Y3 and found the crate was off. Actually this is not correct.
The key was on but the power was off. I looked at the back and found the power code was loose from its inlet.
Once the code was pushed in and the crate was keyed, the white boxes got back online.

Just in case I burtrestored these slow channels by the snapshot at 6:07am on Sunday.

  7604   Wed Oct 24 01:02:10 2012 KojiUpdateSUS PITCH damping needed

Wow... This is even more complicated than the original "Y" design...

  7616   Thu Oct 25 02:01:15 2012 KojiUpdateComputer Scripts / ProgramsPhase map summary of LaserOptik mirrors

Previous phasemap data and analysis for the new 40m COC are summarized on the following page


(Use traditional LVC authentication (not albert.einstein))

The actual instance of the files can also be found on nodus below the following directory:


The programs for the analysis are found in


The main program is RunThis.m

Basically this program takes ascii files converted from opd by Vision32.
(i.e. You need to go to Downs)
Then the matlab program takes care of the plots and curvature analyses.

  7617   Thu Oct 25 02:10:22 2012 KojiUpdate my assesment of the folding mirror (passive tip-tilt) situation

The thinner wire has a history that it did not improve the hysteresis (ask Jenne). Nevertheless, it's worth to try.

If you flip the clamp upside-down, you can lift the clamping point up. This will make the gravity restoring torque stronger.
(i.e. Equivalent effect to increasing the mass)

Luckily (or unluckily) the clamp has no defined location for the wire as we have no wire fixture.
Therefore the clamp will grab the wire firmly even without milling.

  7618   Thu Oct 25 06:49:49 2012 KojiUpdate my assesment of the folding mirror (passive tip-tilt) situation


My big question right now is: is the plan to install new dichroics in PR2 and SR2 as well, or just in PR3 and SR3, where the green beams are extracted?  I think the answer is no, we only want to install new dichroics in {P,S}R3.

 Why not? The new dichroic mirrors have more transmission of 1064nm than G&H. Thus it will give us more POP beam and will help locking.

  7648   Wed Oct 31 17:33:39 2012 KojiUpdateAlignmentTransmitance Measurements on LaserOptik mirror

...Looks like the coating is out of spec at any angle for 1064nm. E11200219-v2

  7706   Tue Nov 13 20:13:07 2012 KojiConfiguration40m UpgradingEndtable upgrade for auxiliary green laser : Circularize the 1W NPRO beam profile

These fs are too short.


I propose to use lenses with focal lengths f1 = 22.2 mm and f2 = 25 mm. The beam diameter after the lenses will be dx = 164.05 um and dy = 163.19 um.


  7717   Fri Nov 16 00:08:36 2012 KojiUpdateSUSMC2 woes

People complained about the MC instability: If we aligned the MC, it locked nicely for a while.
Then suddenly you find that it got totally misaligned with the order of 0.2 with the alignment slider.
This misalignment usually happens for MC2, but it happend on MC3 once.

Surprisingly to me, this instability happened even without MCL and WFS, not only once but at least three times.
This suggests that the suspensions are the cause of the trouble.

I played with the MC2 suspension for a while in the afternoon. It seems that it has a hysteresis (or say, bistablity).
And the nominal alignment of MC2 seems close to the point where the transition happens. (Dunno why)

I further played with MC2 and found that a step of POS actuation by +/-10000 induces this transition go and back.
When the POS kick is in the negative direction (-10000), the MC2 seems to return to the preferrable
position. Therefore, I applied DC position force of -5000 to pull the mirror a bit from the nominal position.

I let the MC locked for ~4hours without MCL and WFS, it kept good alignment and the lock was stable
except for unlocks because of the activties by Den and Ayaka.

All of them has been done without previous monitor data as the tools were available.

The MC2 situation is not conclusive but we should check how we can prevent the bistable transition
by restricting MCL/WFS.

  7722   Sat Nov 17 22:50:17 2012 KojiUpdateAlignmentred in arms

You have constraints for the IR beams (i.e. one PZT and one BS for 8 dofs), so now you need to align the arms for the input IR beams.
The PZT and BS should be aligned so that you have the beam spots as center as possible with the above restrictions.

Then realign end greens for the given arm alignment. You can replace the mounts if necessary to align the end green.
Even if you lose the coarse alignment of the green, realignment is not difficult as you know now



POY11 does not go out of the vacuum

 It does but slighty low and does not get on mirrors. We need to change optic mounts to adjust the height. Red is flashing in yarm at 00 and 10 modes. TRY is ~0.4-0.5.

I've adjusted BS angle, camera and TRX PD at ETMX table so I can see red flashing at 03 mode while green is locked to 00 and its transmission is maximized. I thought that by adjusting BS angle, I will be able to align red to 00 not disturbing green, but this was not the case. Maximum TRX I could get was 0.1. I've adjusted POX to get into PD and I can see PDH signal though I can't lock as cavity is still misaligned for red.


  7728   Mon Nov 19 22:42:14 2012 KojiConfiguration40m UpgradingEndtable upgrade for auxiliary green laser : ETMX layout on new table
  • I don't like the idea to place the cylindrical lenses right in front of the laser.
    This design requires the CLs to be tilted to avoid direct reflections going into the laser.
    It is also required that they are made of UV fused silica to avoid thermal lensing.

  • Instead, move the CLs after the farday while we keep L1, HWP, QWP after the laser.
    L1 should be UV fused silica lens. I should be placed with slight tilt.
    It is preferrable to place CLs after the faraday at somewhere the beam is not too small.
  • The HWP before the SHG can be moved to downstream of the steering mirrors as they can change the poralization.
    (Probably I am too paranoic.)
  • Why don't you use the harmonic separator right after the SHG crystal in stead of relying on an arbitrary transmission of the 532nm mirrors?
  • I am not confident about such a "nice" separation angle of the returning beam from the green faraday.
    Confirm the separation angle on the actual setup.

    The beams split in the polarizer rather than in the air like in your diagram.
    Then because of this small angle separation, the pick-off mirror may have a bit more critical distance than you indicated.
    (I could be wrong.)
  • I don't think the green faraday is IO-5-532-HP. It should be IO-?-532-LP.
    Rotate the tilt aligner 180deg so that we can easily access to the adjusting screws
  • The green PDA36A path needs more length and probably a focusing lens too.
  • After the PLCX lens, the beam is big (w=3mm) everywhere. Don't you want to use 2" mirrors and mounts?
  • We eventually will install steering PZTs for the green.
    On which mirrors do you want to install the PZTs?
    Do you have enough spare space for them?
  • The mount indicated "HS" is one of the trickiest mounts on the table as the big beam goes through the mirror.
    Probably you want to use 2" suprema mount with correct chirality.
  • How is the power budget of the IR trans path? Which is the low power PD and which is the high power PD?
    What's the transimpedance of them? Where is the crossover?
    How much power does go into the CCD? Is it a reasonable amount?

  • The IR transmon beam is even larger than the green beam (w=5mm)
    You definitely need a lens to shrink the beam. But we don't want to have the QPD and the CDD at the focus.
  • As Jenne pointed out, having a steering mirror for the IR PDA36A is a good idea.
    But do you really want to use the Si PD for the IR tmonitor?
  • I feel I don't want to have the pair of steering mirrors in the oplev incident path. One is enough.
    We should be able to accommodate optional mode-matching lenses in the incident path.
    We definitely don't want to have any lens in the returning path of the oplev.
  7735   Tue Nov 20 20:37:51 2012 KojiUpdateIOOMC autolocker

Last night I found that the MC autolocker has not been updated since the chamber was closed.
i.e. The low power version had been used.

I logged into op340m and modified crontab via "crontab -e" so that the normal power version is spawned.

  7737   Wed Nov 21 01:36:36 2012 KojiUpdateIOOMCL disabled / WFS clear history restored

As MCL is disturbing arm locking by injecting a lot of noise, I have modified 'mcup'  to disable MCL

As MC WFS keeps failing to start up when it is locked, the lines in 'mcwfsoff' to clear WFS filter history were restored.

  7740   Sat Nov 24 22:14:08 2012 KojiUpdateGeneralAP table cleaning up

On Wednesday (21st) night, I checked the AP table as I wanted to try PRMI locking. 
It was difficult to work with the table as there were so many unnecessary components on it.
Also the beams went through complicated paths as they have funny angles. 

So I decided to clean up of IMC REFl WFS, IFO REFL, and IFO AS paths.
I found that the AS beam was highly astigmatic as the beam went through a (too-much-) tilted lens.
I made several blocked optical paths for REFL and AS for future extension of the detection system.

The current status of the table was uploaded below.

The optical spectrum analyzers and the aux NPRO were left untouched but they should be moved
somewhere (either on the table or outside) which does not disturb the other optical paths.

After the cleaning, I started locking PRMI. I could lock PRMI stably. But I could not figure out how
the intra-cavity mode looked like as I did not have the POP camera. The power recycling
gain was not quantitatively evaluated as I did not have POP and I wasn't sure how the beam was aligned at POX/POY.

We need to know:

- Quantitative evaluation of the beam shape in the PRC

- Quantitative evaluation of the power recycling gain

Some obvious things to be fixed

- The POX whitening filters seem not switching. This issue should be checked at the circuit module itself and at the BIO.

- The POX beam is not well focused on the PD. This was particularly clear when PRMI was locked with carrier.

- The POP beam is going nowhere. We need POP55 and POP CCD for diagnoses.

I haven't checked ITMY table.

Attachment 1: APTable121124.pdf
Attachment 2: APTable121124.graffle.zip
  7741   Sat Nov 24 23:50:35 2012 KojiUpdateIOOMC WFS refusing to work

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

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

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


  7767   Fri Nov 30 11:49:24 2012 KojiUpdateAdaptive FilteringYARM

This is interesting. I suppose you are acting on the ETMY.
Can you construct the compensation filter with actuation on the MC length?
Also can you see how the X arm is stabilized?

This may stabilize or even unstabilize the MC length, but we don't care as the MC locking is easy.

If we can help to reduce the arm motion with the MCL feedforward trained with an arm sometime before,
this means the lock acquisition will become easier. And this may still be compatible with the ALS.

Why did you notched out the 16Hz peak? It is the dominant component for the RMS and we want to eliminate it.

  7785   Tue Dec 4 20:13:55 2012 KojiUpdateSUSTTs are ready

Please leave here what was the instruction by Bran and Suresh so that the other people can redo it sometime later!

ELOG V3.1.3-