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ID Date Authorup Type Category Subject
  1789   Sat Jul 25 13:34:58 2009 KojiUpdateGeneralWeek 5/6 Update


The last week I've started setting up the HeNe laser on the PSL table and doing some basic measurements (Beam waist, etc) with the beam scan, shown on the graph.  Today I moved a few steering mirrors that steve showed me from at table on the NW corner to the PSL table.  The goal setup is shown below, based on the UCSD setup.  Also, I found something that confused me in the EUCLID setup, a  pair of quarter wave plates in the arm of their interferometer, so I've been working out how they organized that to get the results that they did.  I also finished calculating the shot noise levels in the basic and UCSD models, and those are also shown below (at 633nm, 4mw) where the two phase-shifted elements (green/red) are the UCSD outputs, in quadrature (the legend is difficult to read).




Some comments:

0. Probably, you are working on the SP table, not on the PSL table.

1. The profile measurement looks very nice.

2. You can simplify the optical layout if you consider the following issues
  A. The matching lenses just after the laser:
      You can make a collimated beam only with a single lens, instead of two.
      Just put a lens of f0 with distance of f0 from the waist. (Just like Geometrical Optics to make a parallel-going beam.)

      Or even you don't need any lens. In this case, whole optical setup should be smaller so that your beam
      can be accomodated by the aperture of your optics. But that's adequately possible.

  B. The steering mirrors after the laser:
      If you have a well elevated beam from the table (3~4 inches), you can omit two steering mirrors.
      If you have a laser beam whose tilte can not be corrected by the laser mount, you can add a mirror to fix it.

  C. The steering mirrors in the arms:
      You don't need the steering mirrors in the arms as all d.o.f. of the Michelson alignment can be adjusted
      by the beamsplitter and the mirror at the reflected arm. Also The arm can be much shorter (5~6 inches?)

  D. The lenses and the mirrors after the PBS:
      You can put one of the lenses before the PBS, instead of two after the lens.
      You can omit the mirror at the reflection side of the PBS as the PBS mount should have alignment adjustment.

The simpler, the faster and the easier to work with!

  1790   Sat Jul 25 13:49:28 2009 KojiUpdateGeneralMultiply Resonant EOM Update


After speaking with Rana and realizing that it would be better to use smaller inductances in the flying-component circuit (and after a lot of tinkering with the original), I rebuilt the circuit, removing all of the resistors (to simplify it) and making the necessary inductance and capacitance changes. A picture of the circuit is attached, as is a circuit diagram.

A plot of the measured and simulated transfer functions is also attached; the general shape matches between the two, and the resonant frequencies are roughly correct (they should be 11, 29.5, and 55 MHz). The gain at the 55 MHz peak is lower than the other two peaks (I'd like them all to be roughly the same). I currently have no idea what the impedance is doing, but I'm certain it is not 50 Ohms at the resonant peaks, because there are no resistors in the circuit to correct the impedance. Next, I'll have to add the resistors and see what happens.


This is a quite nice measurement. Much better than the previous one.

1) For further steps, I think now you need to connect the real EOM at the end in order to incorporate
the capacitance and the loss (=resistance) of the EOM. Then you have to measure the input impedance
of the circuit. You can measure the impedance of the device at Wilson house.
(I can come with you in order to consult with Rich, if you like)

Before that you may be able to do a preparatory measurement which can be less precise than the Wilson one,
but still useful. You can measure the transfer function of the voltage across the input of this circuit,
and can convert it to the impedance. The calibration will be needed by connecting a 50Ohm resister
on the network analyzer.

2) I wonder why the model transfer function (TF) has slow phase changes at the resonance.
Is there any implicit resistances took into account in the model?

If the circuit model is formed only by reactive devices (Cs and Ls), the whole circuit has no place to dissipate (= no loss).
This means that the impedance goes infinity and zero, at the resonance and the anti-resonance, respectively.
This leads a sharp flip of the phase at these resonances and anti-resonances.

The real circuit has small losses everywhere. So, the slow phase change is reasonable.

  1792   Sat Jul 25 19:04:01 2009 KojiUpdatePSLAligning the beam to the Faraday



When I turned them on, the control signal in Pitch from WFS2 started going up with no stop. It was like the integrator in the loop was fed with a DC bias. The effect of that was to misalign the MC cavity from the good state in which it was with the only length control on (that is, transmission ~2.7, reflection ~ 0.4).

I don't know why that is happening. To exclude that it was due to a computer problem I first burtrestored C1IOO to July the 18th, but since that did not help, I even restarted it. Also that didn't solve the problem.



At least one problem is the mis-centering of the resonant spot on MC2, which can be viewed with the video monitors.  It's very far from the center of the optic, which causes length-to-angle coupling that makes the mulitple servos which actuate on MC2 (MCL, WFS, local damping) fight each other and go unstable.

I played with the MC alignment for the beam centering. After that, I restored the alignment values.

In principle, one can select the MC2 spot as one likes, while the transmitted beam axis to the IFO is not changed
as far as you are at the best alignment. This principle is almost trivial because the beam axis matches
to the input beam axis at the best alignment.
The alignment solution is not unique for a triangle cavity if we don't fix the end spot position.

In practice, this cruising of the MC2 spot is accomplished by the following procedure:
0) Assume that you are initially at the best alignment (=max transmission).
1) Slightly tilt the MC2.
2) Adjust MC1/MC3 so that the best transmission is restored.

I started from the following initial state of the alignment sliders:


MC1 Pitch  +3.6242
MC1 Yaw  -0.8640
MC2 Pitch  3.6565
MC2 Yaw -1.1216
MC3 Pitch -0.6188
MC3 Yaw -3.1910
MC Trans 2.70

After many iterations, the spot was centered in some extent. (See the picture)

MC1 Pitch  +3.363 (-0.26)
MC1 Yaw  -1.164 (-0.3)
MC2 Pitch  3.7565 (+0.1)
MC2 Yaw -1.2800 (~ -0.16)
MC3 Pitch -0.841 (~ -0.22)
MC3 Yaw -3.482 (~ -0.29)
MC Trans 2.75  

The instability looked cured somewhat.
Further adjustment caused a high freq (10Hz at the camera) instability and the IMCR shift issue.
So I returned to the last stable setting.

Side effect:
Of course, if you move MC1, the reflected spot got shifted.
The spot has been apparently off-centered from the IMCR camera. (up and right)
At this stage, I could not determine what is the good state.
So, I restored the alignment of the MC as it was.
But now Alberto can see which mirror do we have to move in which direction and how much.

Attachment 1: MC2_Cam.jpg
  1799   Mon Jul 27 19:55:19 2009 KojiHowToIOOLens selection: plano-convex? or bi-convex?

Q. When should we use plano-convex lenses, and when should we use bi-convex?

As I had the same question from Jenne and Dmass in a month,
I just like to introduce a good summary about it.
Lens selection guide (Newport)

At a first order, they have the same function.
Abberation (= non-ideal behavior of the lens) is the matter.

  1801   Tue Jul 28 18:32:21 2009 KojiUpdateCDSRCG work

Peter and Koji,

We are constructing a setup for the new 40m CDS using Realtime Code Generator (RCG).
We are trying to put simulated suspensions and test suspension controllers on a different processors of megatron
in order to create a virtual control feedback loop. Those CDS processes are communicating
each other via a shared memory, not via a reflective memory for now.

After some struggles with tremendous helps of Alex, we succeeded to have the communication between the two processes.
Also we succeeded to make the ADC/DAC cards recognized by megatoron, using the PCI express extension card replaced by Jay.
(This card runs multi PCI-X cards on the I/O chasis.)

Next steps:
- Establish a firewall between the 40m network and megatron (Remember this)
- Make DTT and other tools available at megatron
- Try virtual feedback control loops and characterize the performance
- Enable reflective memory functionalities on megatron
- Construct a hybrid system by the old/new CDSs
- Controllability tests using an interferometer

o Each cdsIPC should have a correct shared memory address spaced by 8 bytes. (i.e. 0x1000, 0x1008, 0x1010, ...)

Note on MEDM
o At the initial state, garbage (e.g. NaN) can be running all around the feedback loops. They are invisible as MEDM shows them as  "0.0000".
To escape from this state, we needed to disconnect all the feedback, say, by turning off the filters.

Note on I/O chasis
o We needed to pull all of the power plugs from megatron and the I/O chasis once so that we can activate
the PCI-e - PCI-X extension card. When it is succeeded, all (~30) LEDs turn to green.

  1813   Thu Jul 30 19:55:23 2009 KojiUpdateGeneralMultiply Resonant EOM Update


For the past couple of days I have been trying to understand and perform Koji's method for impedance measurement using the Agilent 4395A Network Analyzer (without the impedance testing kit). I have made some headway, but I don't completely understand what's going on; here's what I've done so far.

I have made several transfer function measurements using the attached physical setup (ImpedanceTestingPhysicalSetup.png), after calibrating the setup by placing a 50 Ohm resistor in the place of the Z in the diagram. The responses of the various impedances I've measured are shown in the attached plot (ImpResponses.png). However, I'm having trouble figuring out how to convert these responses to impedances, so I tried to derive the relationship between the measured transfer function and the impedance by simplifying the diagram Koji drew on the board for me (attached, ImpedanceTestingSetup.png) to the attached circuit diagram (ImpedanceTestingCktDiagram.png), and finding the expected value of VA/VR. For the circuit diagram shown, the equation should be VA/VR = 2Z/(50+Z). 50 Ohms is good to use for calibration because the expected value of the transfer function for this impedance is 1 (0 dB).

So I used this relationship to find the expected response for the various impedances, and I also calculated the impedance from the actual measured responses. I've attached a plot of the measured (red) and expected (black) response (top) and impedance (bottom) for a 1 nF capacitor (1nF.png). The expected and measured plots don't really match up very well; if I add extra inductance (7.6 nH, plots shown in blue), the two plots match up a little better, but still don't match very well. I suspect that the difference may come from the fact that for my analysis, I treated the power splitter as if it were a simple node, and I think that's probably not very accurate.

Anyway, the point of all this is to eventually measure the impedance of the circuit I created on Friday, but I don't think I can really do that until I understand what is going on a little better.

 I checked the setup and found RF reflection at the load was the cause of the unreasonable response in the impedance measurement.
So, I have put a total 22dB attenuation (10+6+6 dB) between the power splitter and the load to be measured. See the picture.
This kind of attenuators, called as PADs, is generally used in order to improve the impedance matching, sacrificing the signal amplitude at the load.

Then, It looks the measurements got reasonable up to 100MHz (at least) and |Z|<1kOhm.
For the measurements, I just followed the procedure that Stephanie described.
Stephanie has measured the impedance of her resonant circuit.

As a test of the method, I measured impedances of various discrete devices. i.e. 50Ohm, 10-1000pF Cap, Inductances, circuit opened.

a) 50Ohm (marine-blue) was calibrated to be recognized as 50Ohm.

b) The mica capacitances (orange 10pF, yellow 100pF, green 1000pF) appeared as the impedances f^-1 in the low freq region. It's nice.
At high frequency, the impedances deviate from f^-1, which could be caused by the lead inductance. (Self Resonance)
So 1000pF mica is not capacitance at 50MHz already.

c) Open BNC connector (Red) looks have something like 5pF. (i.e. 300Ohm at 100MHz)

d) I could not get good measurements with the inductors as I had 200nH (and some C of ~5pF) for a Pomona clip (blue).
This is just because of my laziness such that I avoid soldering the Ls to an RF connector!

Attachment 1: imepedance.png
Attachment 2: impedance_meas.jpg
  1849   Thu Aug 6 20:03:10 2009 KojiUpdateGeneralWe left two carts near PSL table.

Stephanie and Koji

We left two carts near the PSL table.
We are using them for characterization of the tripple resonant EOM.

  1902   Fri Aug 14 14:19:25 2009 KojiSummaryComputersnodus rebooted

nodus was rebooted by Alex at Fri Aug 14 13:53. I launched elogd.

cd /export/elog/elog-2.7.5/
./elogd -p 8080 -c /export/elog/elog-2.7.5/elogd.cfg -D

  2003   Fri Sep 25 17:51:51 2009 KojiUpdateMOPASolved (Re: Total MOPA power is constant, but the NPRO's power has decreased after last night's activities?)

Jenne, Koji

The cause of the decrease was found and the problem was solved. We found this entry, which says

Yoich> We opened the MOPA box and installed a mirror to direct a picked off NPRO beam to the outside of the box through an unused hole.
Yoich> We set up a lens and a PD outside of the MOPA box to receive this beam. The output from the PD is connected to the 126MON cable.

We went to the PSL table and found the dc power cable for 126MOPA_AMPMON was clipping the 126MON beam.
We also made a cable stay with a pole and a cable tie.

After the work, 126MON went up to 161 which was the value we saw last night.

We also found that the cause of the AMPMON signal change by the DAQ connection, mentioned in this entry:

Jenne> 6.  We teed off of the AMPMON photodiode so that we could see the DC values on a DMM. 
Jenne> When we used a T to connect both the DMM and the regular DAQ cable, the DMM read
Jenne> a value a factor of 2 smaller than when the DMM was connected directly to the PD.

We found a 30dB attenuator is connected after the PD. It explains missing factor of 2.


[Koji, Jenne]

Steve pointed this out to me today, and Koji and I just took a look at it together:  The total power coming out of the MOPA box is constant, about 2.7W.  However, the NPRO power (as measured by 126MOPA_126MON) has decreased from where we left it last night.  It's an exponential decay, and Koji and I aren't sure what is causing it.  This may be some misalignment on the PD which actually measures 126MON or something though, because 126MOPA_LMON, which measures the NPRO power inside the NPRO box (that's how it looks on the MEDM screen at least...) has stayed constant.  I'm hesitant to be sure that it's a misalignment issue since the decay is gradual, rather than a jump. 

Koji and I are going to keep an eye on the 126MON value.  Perhaps on Monday we'll take a look at maybe aligning the beam onto this PD, and look at the impedance of both this PD, and the AMPMON PD to see why the reading on the DMM changed last night when we had the DAQ cable T-ed in, and not T-ed in. 


  2008   Sun Sep 27 14:45:45 2009 KojiUpdatePSLSLOWscan result

I ran (script dir)/PSL/FSS/SLOWscan on op440m from 11:30 to 12:30 on 27th. Although Rana and later I myself set "timed bombs" for the scan, they did not work as they have probably been ran on Linux. After the scan I relocked PMC, FSS, and MZ . MC locked automatically.


1. To keep away from the mode hop, FSS_SLOWDC is to be at around 0. The values -5 ~ -6 is the place for the power, which is my preference for now. BTW, the mode hop only appears to the PSL output (=AMPMON) is this normal?

2. The PSL output looks dependent on the NPRO wavelength. The NPRO output and the PSL output tends to be high when the FSS_SLOWDC is low (= LTMP: Laser Crystal Temp is low). Also there is a step at the LTMP where we think the mode hop is present. This may cause the daily PSL output variation which induced by the daily change of the reference cavity length.

My naive speculation is that the NPRO wavelength is too long (= hot side) for the MOPA absorption as the MOPA heads are cooled to 19deg.

3. Scanning of -10 to +10 changes the LTMP from 42-49deg. This is almost 1/10 of the NPRO capability. The manual told us that we should be able to scan the crystal temperature +/-16deg (about 30deg to 60deg).

What I like to try:
a) Change the NPRO temp to more cold side.
b) Change the MOPA head temp to a bit hot side.
c) Tweak the MOPA current (is it difficult?)

Attachment 1: SLOWscan_090927.png
Attachment 2: Pages_from_miser_126_manual.png
  2009   Sun Sep 27 15:25:58 2009 KojiUpdatePSLSLOWscan result
Oh, AMPMON dependence could be an artifact of the ND filter???
For my case, it should be real dependence on the NPRO wavelength,
as the other PDs like the PMC reflection (PMC_RFPDDC) and the RC reflection (FSS_RFPDDC) show the same dependence.
Attachment 1: power_dependence.png
  2015   Mon Sep 28 23:44:18 2009 KojiOmnistructureSAFETYCrappy power outlet

Jenne, Koji

Tonight we found that the wireless for Martian network was down.
We inspected the router and found the power was down. The power of the weather station was also down.

By touching the power outlet which they are connected, the power changes on and off.
This problematic power outlet has a label "L#17" just below the photograph of the mk I (1989).
The plug was connected to the left one.

As it was scary, we moved the power plug to the next one (L#19).
The wireless router and the weather station were powered now,
though the weather station is showing a wrong time in its clock.

  2017   Tue Sep 29 10:44:29 2009 KojiUpdateMZMZ investigation

Rana, Jenne, Koji

Last night we checked MZ. The apparent thing we found was the gain slider does not work.
The slider actually changes the voltage at the cross connection of 1Y2 (31 pin4?), the gain does not change.
The error spectrum didn't change at all even when the slider was moved.

Rana poked the flat cable at the bottom of 1Y2, we had no imporvement.

We coudn't find the VME extender board, so we just replaced AD602 (=VGA) and LT1125 (=Buffer for the ctrl voltage).
Even after the replacement, the gain slider is not working yet.

Today, I will put a lead or probe to the board to see whether the slider changes the voltage on the board or not.

Somehow the gain is sitting at a intermediate place that is not to low not to high. So I still don't know the gain slider
is the cause of the MZ instability or not.

  2018   Tue Sep 29 12:47:08 2009 KojiUpdateMZMZ unlocked

12:45 I started the work on MZ. Thus the MZ was unlocked.

Found the bad connection on the FLKM 64pin cross connection board. We need a replacement.

I went to Wilson and got the replacement, two VME extender boards, three 7815, and three 7915. Thanks, Ben!

  2020   Tue Sep 29 18:21:41 2009 KojiUpdateMZMZ work done

The MZ work completed. I replaced the bad cross connection terminal. The gain slider is working now.

I looked at the error spectrum on an FFT analyzer. I could see the lock was more tight.

Then I proceeded to the MZ epics panel.

1) C1:PSL-MZ_MZTRANSPD has no meaning (not connected). So I put  C1:PSL-ISS_INMONPD as the MZ trans monitor.

2) The EPICS setting for the MZ gain slider was totaly wrong.
    Today I learned from the circuit, the full scale of the gain slider C1:PSL-MZ_GAIN gave us +/-10V at the DAC.
    This yield +/-1V to V_ctrl of the AD602 after the internal 1/10 attenuation stage.
    This +/-1V didn't correspond to -10dB~+30dB, but does -22dB~+42dB and is beyond the spec of the chip.

    The gain of AD602 is calculated by

G [dB] = 32 V_crtl + 10,  for -0.625 [V]< V_ctrl < +0.625 [V].

    In order to fix this I used the following commands which overrode the EPICS parameters.
    The tip of EGUF/EGUL is to know how much the gain (virtually) goes for the full scale of the DAC output. 

ezcawrite C1:PSL-MZ_GAIN.EGUF 42
ezcawrite C1:PSL-MZ_GAIN.EGUL -22
ezcawrite C1:PSL-MZ_GAIN.DRVH 30
ezcawrite C1:PSL-MZ_GAIN.DRVL -10
ezcawrite C1:PSL-MZ_GAIN.HOPR 30
ezcawrite C1:PSL-MZ_GAIN.LOPR -10

   and for the permanent change I modified the db file /cvs/cds/caltech/target/c1iool0/c1iooMZservo.db
   This will be active when cliool0 is rebooted.

# This yields the output limited to -6.25V ~ +6.25V, which corresponds to -10dB ~ +30dB
# modified by Koji Arai (29-Sept-2009)
        field(DESC,"GAIN- overall pre-modecleaner servo loop gain")
        field(OUT,"#C3 S5 @")

# previous code
        field(DESC,"GAIN- overall pre-modecleaner servo loop gain")
        field(OUT,"#C3 S5 @")


12:45 I started the work on MZ. Thus the MZ was unlocked.

Fond the bad connection on the FLKM 64pin cross connection board. We need the replacement.

I went to Wilson and got the replacement, two VME extender boards, three 7815, and three 7915. Thanks, Ben!


  2022   Tue Sep 29 21:51:32 2009 KojiUpdateMZMZ work done : some noise checking

The previous "+15" was Vctrl = 0.25 [V]. Which was +18 dB.


Since we used to run with a gain slider setting of +15 dB on the MZ, I wanted to check that the new setting of +30dB was OK.


  2023   Tue Sep 29 22:51:20 2009 KojiUpdateMZPossible gain mis-calibration at other places (Re: MZ work done)

Probably there is the same mistake for the PMC gain slider. Possibly on the FSS slider, too???


2) The EPICS setting for the MZ gain slider was totaly wrong.
    Today I learned from the circuit, the full scale of the gain slider C1:PSL-MZ_GAIN gave us +/-10V at the DAC.
    This yield +/-1V to V_ctrl of the AD602 after the internal 1/10 attenuation stage.
    This +/-1V didn't correspond to -10dB~+30dB, but does -22dB~+42dB and is beyond the spec of the chip.

  2032   Thu Oct 1 09:36:09 2009 KojiUpdateMZMZ relocked (Re:suspention damping restored and MZ HV stuck)

MZ stayed unlocked. Now It was relocked.


Earthquake  of magnitude 5.0  shakes ETMY loose.

MC2 lost it's damping later.


  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).


Attachment 1: MZ_PZT.pdf
  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.

Attachment 1: PSL.png
  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%


Attachment 1: PSL091026.png
  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.

Attachment 1: 091028_PSL.png
  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.

Attachment 1: PSL_MC.png
  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.


Attachment 1: MC_TRANS.png
  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!


Attachment 1: PC_DRV.png
  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)

ELOG V3.1.3-