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ID Date Authorup Type Category Subject
  3395   Tue Aug 10 22:40:55 2010 KojiSummaryPEMAccelerometer located on and below the PSL table

Result of the accelerometer measurement


We wanted to characterize the PSL table before the work before its lifting up.
We put a set of three-axis Wilcoxon accelerometers on the ground and another set on the PSL table through the weekend.


- The data at 9th Aug 00:00(UTC) is used. This was Sunday 5PM in the local time.
- The freq resolution was 0.01Hz. The # of avg was 50.

- The accelerometer signals were calibrated by the value 1.2e-7 V/(m/s^2). We use this absolute value of the spectrum for the comparison purpose.

- The accelerometers were aligned to North(X), East(Y), and Up(Z). There was the coherence observed from 2~20Hz.
  The transfer functions are valid only this frequency region although we still can set the lower bound of them.

- The transfer functions in the horizontal directions show huge peaks at around 20Hz. The Q of the peaks are ~30 to ~100.
  The vertical transfer function shows somewhat lower peak at around 50Hz with Q of ~10.

Some thoughts

- The low resonant freq and the high Q of the horizontal mode comes from the heaviness of the table.

- We are going to raise the table. This will usually mean that we get the lower resonant freq. This is not nice.

- So, the decision to use 6 tripods rather than 4 was right.
- The steel tripods are expected to give both more rigidity and more damping than the chep-looking hollow Newport legs.
- Concrete grouting of the tripods will also lower the effective height and will benefit for us.


Attachment 1: PEM_100809.pdf
  3403   Wed Aug 11 16:56:00 2010 KojiSummaryEnvironmentCovering of the IFO

Katharine, Sharmila, Gopal, Kiwamu, Jenne, Aidan, Steve, and Koji

A guy from the carpenter shop has done the drilling work in the morning.

In the afternoon we wrapped the central part of the interferometer with plastic sheets in order to avoid the dusts from the tile ripping that will happen tomorrow.

Attachment 1: IMG_2732.jpg
  3412   Thu Aug 12 17:10:07 2010 KojiUpdatePhase CameraSideband power measurement (updated)

This sounds very relieving although this could be a lower bound of the number.
Why didn't you use the output on the PD which just give us the direct observation of your so-called SCR.

Ed: I meant time series of the PD output


So the SCR is calculated by the ratio of the FFT'd DC and the 5 Hz signal. Using the CCD, I obtained the SCR to be 0.075 ± 0.01. Previously, we expected our SCR to be 0.09 as in the previous e-log entry. 


  3487   Mon Aug 30 13:57:25 2010 KojiSummaryPSLPSL table vibrational performance after the upgrade

Jenne and Koji

Last week Jenne has put the accelerometers on and under the PSL table immediately after the plastic sheets were removed.

So I took the same measurement as I did on 9th Aug.

Here is the comparison of the vibrational performance of the table before and after the modification.

Basically the table is now stiffer and more damped than it was before.
We don't find any eminent structure below (at least) 70Hz.

This result is obtained despite elevating of the table.

1) Attachment 1

For the horizontal comparison (top),  it is clearly seen that the large resonant peak at 20Hz was eliminated.
At least the new resonances went up to 70-90Hz region. Y is basically equivalent to X.

For the vertical comparison (bottom), it is clearly seen that the resonant peaks at around 50 & 70Hz were eliminated. 
At least no new resonance is seen.

2) Attachment 2

All-in-one plot for the measurement --- spectra, coherences, transfer functions --- after the upgrade. I put the same plot for the one before the upgrade.

Attachment 1: PEM_100830_SPE.pdf
Attachment 2: PEM_100830.pdf
PEM_100830.pdf PEM_100830.pdf
  3502   Wed Sep 1 08:28:43 2010 KojiUpdatePSLPSL upgrade update

  1. We got the lenses from CVI for the mode matching, but not the metric screws for the laser mounting. I am tempted to tap holes in the laser base.

I am feeling that it is ok to carefully make new holes and threads as far as the holes do not penetrate the plate.
The thickness of the plate can be measured by the four holes at the corners.


  3503   Wed Sep 1 08:36:59 2010 KojiHowToPSL2W NPRO Mount designed with emachineshop.com software

1. I can not see whether the attaching surface is flat or not.
It should have ~1mm step to avoid "the legs" of the laser at the four corners.
Otherwise we will have ~0.5mm space between the block and the laser
and will squish this gap by the screws => cause the deformation of the block and the laser.

2. The countersinks for the M4 screws can be much deeper so that we can use the existing M4 screws.
In any case, the long M4 screws are not rigid and also not common.


To test out this website - emachineshop.com, Jenne and I are designing some of the mounts for the new beam height.


It took me a few hours to figure out how to do it, but the software is easy enough for simple stuff. This is a brass mount with M4 clearance holes which are countersunk and a lip so that it can be dogged down to the table.


  3522   Fri Sep 3 13:04:30 2010 KojiFrogsElectronicsCable cutting tools

Yeah, this looks nice.

And I also like to have something I have attached. This is "HOZAN P-90", but we should investigate American ones
so that we can cut the wires classified by AWG.


I found this very interesting German maker of cool cable cutting tools. It's called Jokari.

We should keep it as a reference for the future if we want to buy something like that, ie RF coax cable cutting knives.



Attachment 1: P90.jpg
  3527   Mon Sep 6 20:38:58 2010 KojiUpdateCDSSusension model reviewed

I have reviewed the suspension model of C1SUS and refined it.

It is comaptible to the current one but has minor additions.

Attachment 1: suspension_model.pdf
  3575   Wed Sep 15 03:08:26 2010 KojiUpdatePSLFSS locking

Brilliant! This is the VERY way how the things are to be conquered!


The RefCav is locked and aligned. I changed the fast gain sign by changing the jumper setting on the TTFSS board. The RefCav visibility is 70%. The FSS loop ugf is about 80 kHz (plot attached)  with FSS common gain max out at 30 dB. There is about 50 mW coming out of the laser and a few mW going to RefCav out of the back of the PMC. So the ugf can be made higher at full power. I have not made any changes to account for the PMC pole (the FSS is after the PMC now). The FSS fast gain was also maxed out at 30 dB to account for the factor of 5 smaller PZT actuation coefficient - it used to be 16 dB according to the (previous) snap shot. The RefCav TRANS PD and camera are aligned. I tuned up the phase of the error signal by putting cables in the LO and PD paths. The maximum response of the mixer output to the fast actuator sweep of the fringe was with about 2 feet of extra cable in the PD leg.

I am leaving the FSS unlocked for the night in case it will start oscillating as the phase margin is not good at this ugf.


  3581   Fri Sep 17 03:06:06 2010 KojiUpdateSUSSOS sent for baking

Two SOS suspensions for the ETMs were disassembled and packed for cleaning and baking by Bob.

These suspensions have been stored on the X end flow bench long years, and looked quite old.

They have some differences to the modern SOSs.

- The top suspension block is made of aluminum and had dog clamps to fix the wires.
- The side bars are not symmetric: the side OSEM can only be fixed at the right bar (left side in the picture).
- EQ stops were made of Viton.
- One of the tower bases seems to have finger prints (of Mike Zucker?).

I found that the OSEM plates had no play. We know that the arrangement of the OSEMs gets quite difficult
in this situation. Therefore the holes of the screws were drilled with the larger drill.

We decided to replace all of the screws to the new ones as all of the screws are Ag plated and got corroded
by silver sulfide (Ag2S). I checked our stock in the clean room. We have enough screws.

Important note: Use stainless screws in aluminum / Silver-plated screws in stainless
There exists some study about galling: LIGO-G020394-00-D

Attachment 1: IMG_3596.jpg
Attachment 2: IMG_3597.jpg
  3582   Fri Sep 17 03:32:11 2010 KojiUpdateSUSArrangement of the SUS towers

The day before yesterday, I was cleaning a flow bench in the clean room.

I found that one SOS was standing there. It is the SRM suspension.

I thought of the nice idea:

- The installed PRM is actually the SRM (SRMU04). It is 2nd best SRM but not so diiferent form the best one.
==> Use this as the final SRM

- The SRM tower at the clean room
==> Use this as the final PRM tower.
==> The mirror (SRMU03) will be stored in a cabinet.

- The two SOS towers will be baked soon
==> Use them for the ETMs

This reduces the unnecessary maneuver of the suspension towers.

  3595   Wed Sep 22 22:22:12 2010 KojiConfigurationComputersNetgear Network Switch fan broken.

Net switch mumbo-jumbo:

Although Rana is going to buy a replacement for the Netgear Switch for martian, I opened the lid of the Netgear as the fan already have stopped working.
Also the lid of the other network switch for GC (Black one) was opened as it has a broken fan and a noisy half-broken fan.

I have asked Steve to buy replacement fans. These would also be the replacement of the replacement.

During the work, it seemed that I accidentally toggled the power supply of linux1. It lead lengthy fsck of the storage.
This is why all of the machines which rely on linux1 got freezed. linux1 is back and the machines looked happy now.

If you find any machine disconnected from the network, please consult with me.


The Netgear Network Switch in the top shelf of Nodus' rack has a broken fan. It is the one interfaced to the Martian network.

The fan must have broken and it is has now started to produce a loud noise. It's like a truck was parked in the room with the engine running.

Also the other network switch, just below the Netgear, has one of its two fans broken. It is the one interfaced with the General Computer Side.

I tried to knock them to make the noise stop, but nothing happened.

We should consider trying to fix them. Although that would mean disconnecting all the computers.


  3597   Thu Sep 23 02:45:30 2010 KojiSummaryComputersnodus gracefully rebooted

Zach> Nodus seemed to be working fine again, and I was browsing the elog with no
Zach> problem. I tried making an entry, but when I started uploading a file it
Zach> became unresponsive. Tried SSHing, but I get no prompt after the welcome
Zach> blurb. ^C gives me some kind of tcsh prompt (">"), which only really
Zach> responds to ^D (logout). Don't know what else to do, but I assume someone
Zach> knows what's going on.

By gracefully rebooting nodus, the problem was solved.

It (">") actually was the tcsh prompt, but any commands with the shared or dynamic link libraries looked unfunctional.

I could use
    cd /.../...
    echo *
to browse the directory tree. The main mounted file systems like /, /usr, /var, /cvs/cds/caltech looked fine.
I was afraid that the important library files were damaged.

I tried
in order to flush the file systems.
These should run even without the libraries as mount must properly work even before /usr is mounted.

They indeed did something to the system. Once I re-launch a new login shell, the prompt was still ">"
but now I could use most of the commands.

I have rebooted by usual sudo-ing and now the services on nodus are back to the functional state again.

# nodus was working in the evening at around 9pm. I even made an e-log entry about that.
# So I like to assume this is not directly related to the linux1 incident. Something else could have happened.

  3599   Thu Sep 23 11:15:20 2010 KojiFrogsComputersnodus gracefully rebooted

svn is back after starting apache on nodus.



SVN down

mafalda down

I am guessing that the NFS file system hangup may have caused some machines to get into an awkward state. We may be best off doing a controlled power cycle of everything...


  3601   Thu Sep 23 13:16:57 2010 KojiFrogsComputersnodus gracefully rebooted

mafalda is up now.

I found that the cable for mafalda (the sole red cable) had a broken latch.
The cable was about falling off from the switch. As a first-aid, I used this technique to put a new latch, and put it into the switch.

Now I can logged in it. I did not rebooted it.


SVN down

mafalda down

I am guessing that the NFS file system hangup may have caused some machines to get into an awkward state. We may be best off doing a controlled power cycle of everything...


  3608   Sat Sep 25 19:01:13 2010 KojiUpdateElectronicstesting TTFSS

How much current do you need for each voltages?

GE-82 was the only PNP transister I could find in the lab. It's too old but we just like to confirm any other components are still functioning.

Similarly, we can confirm the functionality of the other components by skipping those current boost transisters,
if we don't need more than 30mA.


  3669   Thu Oct 7 15:05:46 2010 KojiUpdatePSLmeasured PMC's laser power-output relation

It was a bit difficult to comprehend the result.
Is it good? or bad? Have you seen the thermal effect? or not?

- Put linear lines to show the visibility of the cavity.

- Calibrate the incident power and make another plot to show the visibility (%) vs the incident power (W).


(Rana, Yuta)


 We wanted to see thermal effects on the PMC.

What I did yesterday:
 Changed the current of the NPRO from 2A to 0.8A and measured the power of the reflected/transmitted light from the PMC when locked.
 I also measured the power of the reflected light when PMC is not locked (It supposed to be proportional to the output power of the laser).

 Attached. Hmmmm......
 At several points of the laser current, I could'nt lock the PMC very well. The power of the reflected/transmitted light depend on the offset voltage of the PZT.
 When the laser power was weak(~<0.9A), the power of reflected/transmitted light changed periodically(~ several minutes).


  3671   Thu Oct 7 16:21:02 2010 KojiOmnistructureCDSBig 3

Both Rolf and Alex (at least his elbow) together visited the 40m to talk with Joe for the CDS.

40m is the true front line of the CDS development!!!

Attachment 1: IMG_3642.jpg
  3683   Sun Oct 10 16:44:59 2010 KojiOmnistructurePhotosKepco Tube HV supply
Attachment 1: IMG_3637.jpg
Attachment 2: IMG_3640.jpg
  3684   Sun Oct 10 16:59:20 2010 KojiOmnistructureCOCPRM phase map measurement at Downs SB 014

[Kiwamu, Yuta, Koji]

We went to the new metrology lab at Downs subbasement (Rm014) in order to measure the phase map of the delivered PRMs.

It's brand-new. So we had to measure the reference phase map, calibration as well as the phase map of our mirrors (3 PRMs and 1 spare SRM). It took a whole day...

Attachment 1: IMG_3646.jpg
Attachment 2: IMG_3647.jpg
  3685   Sun Oct 10 18:09:02 2010 KojiSummaryCOCPhase map interferometer calibration for the data on Oct 8th, 2010


Calibration of the phase map interferometer was calculated for the data on Oct 8th, 2010.
The calibration value is 0.1905 mm/pixel.

This is slightly smaller than the assumed value in the machine that is 0.192mm/pixel.
This means that the measured radii of curvature must be scaled down with this ratio.
(i.e. RoC(new) = RoC(old) / 0.1922 * 0.19052)


Our tagets of the phasemap measurement are:

1. Measure the figure errors of the mirrors
2. Measure the curvature of the mirrors

The depth of the mirror figure is calibrated by the wavelength of the laser (1064nm).
However, the lateral scale of the image is not calibrated.
Although Zygo provides the initial calibration as 0.192 mm/pixel, we should measure the calibration by ourselves.


We found an aperture mask with a grid of holes with 2mm diameter and 3mm spacing (center-to-center).
Take the picture of this aperture and calibrate the pixel size. The aperture is made of stainless and makes not interference
with the reference beam. Thus we put a dummy mirror behind the aperture. (UPPER LEFT plot)

As the holes are aligned as a grid, the FFT of the aperture image shows peaks at the corresponding pitches. (UPPER MIDDLE plot)
As the aperture was slightly rotated, the grids of the peaks are also slanted.

We can obtain the spacing of the peak grids. How can we can that values precisely? I decided to make an artificial mask image.
The artificial mask (LOWER LEFT plot) has the similar FFT pattern (LOWER MIDDLE plot). The inner product of the two
FFT results (i.e. Sum[abs(fft1) x abs(fft2)]), quite a large value is obtained if the grid pitch and the aperture angle agrees between those images.
Note that the phase information was discarded. The estimated grid spacing of the artificial mask can be mathematically obtained.


The grid pitch and the angle were manually set as initial values. Then the parameters to give the local maximum was obtained by fminsearch of Matlab.
UPPER RIGHT and LOWER RIGHT plots show the scan of the evaluation function by changing the angle and the pitch. They behave quite normal.

The obtained values are

Grid pitch: 15.74 pixel
Angle: 1.935 deg

As the grid pitch is 3mm, the calibration is

3 mm / 15.74 pixel = 0.1905 mm/pixel


A spherical surface can be expressed as the following formula:

z = R - R Sqrt(1-r2/R2)      (note: this can be expanded as r2/(2 R)+O(r3) )

Here R is the RoC and r is the distance from the center. This means that the calibration of r quadratically changes the curvature.
We have measured the RoC of the spare SRM. We can compare the RoCs measured by this new metrology IFO and the old one,
as well as the one by Coastline optics. 


Attachment 1: calibration.pdf
  3724   Thu Oct 14 22:26:38 2010 KojiUpdateComputersNew Netgear Switch

The network cables for the Martian network were moved to the new Netgear switch from the old one which had the broken fan.
The martian machines look happy so far.

Above the new switch we have the GC network switch. The two fans of it were also broken. The fans were replaced.

They are now quiet and I am quite satisfied.


I removed some old equipment from the rack outside the control room and stacked them next to the filing cabinets in the control room. I also mounted the new Netgear switch in the rack.


  3726   Fri Oct 15 00:15:52 2010 KojiUpdateIOO2W NPRO laser output power versus temperature

From the plot, you observed the reduction of the output power only by 1% between 25deg to 45deg.
This does not agree with the reduction from 2.1W to 1.6W.
Is there any cause of this discrepancy?





The measurement was made by attenuating the roughly 2W laser beam by a stack of two Neutral Density filfers and then measuring the transmitted light with the PDA36A photodetector.  This was because both the power meters used in the past were found to have linear drifts in excess of 30% and fluctuations at the 10% level. 


  3737   Mon Oct 18 18:00:36 2010 KojiUpdateSUSOld PRM, SRM stored, new PRM drag wiped

- Steve is working on the storage shelf for those optics.

- PRMU002 was chosen as it has the best RoC among the three.


[Jenne, Suresh]

We've put the old PRM and SRM (which were living in a foil house on the cleanroom optical table) into Steve's nifty storage containers.  Also, we removed the SRM which was suspended, and stored it in a nifty container.  All 3 of these optics are currently sitting on one of the cleanroom optical tables.  This is fine for temporary storage, but we will need to find another place for them to live permanently.  The etched names of the 3 optics are facing out, so that you can read them without picking them up.  I forgot to note the serial numbers of the optics we've got stored, but the old optics are labeled XRM ###, whereas the new optics are labeled XRMU ###. 

Koji chose for us PRMU 002, out of the set which we recently received from ATF, to be the new PRM.  Suresh and I drag wiped both sides with Acetone and Iso, and it is currently sitting on one of the rings, in the foil house on the cleanroom optical table.

We are now ready to begin the guiderod gluing process (later tonight or tomorrow).


  3738   Mon Oct 18 18:33:46 2010 KojiSummaryCOCSummary of the main mirrors & their phasemap measurement

I have made a summary web page for the 40m upgrade optics.


I made a bunch of RoC calculations along with the phase maps we measured.
Those are also accommodated under this directory structure.

Probably.... I should have used the wiki and copy/paste the resultant HTML?

  3743   Tue Oct 19 22:37:28 2010 KojiUpdatePSLPSL table cleaning up

I cleaned up the scattered tools, optics, and mounts of the PSL table. I gathered those stuffs at the two coners.

At the end of the work I scanned the table with an IR viewer. (This is mandatory)
I put some beam block plates to kill weak stray beams.

One thing I like to call the attention is:

I found that some beam blocks were missing at around the PBSs just after the laser source.
Those PBSs tend to reject quite a lot of beam power
--- no matter how the HWPs/QWPs are arranged.

--- even at the backward side.
(remember that we have a faraday there.)

Particularly, there was no beam block at the forward rejection side of the first PBS where we dump the high power beam.

Be careful. 

  3753   Thu Oct 21 13:05:19 2010 KojiSummaryComputerselog change and rossa tex

This is cool though the projector is flashing the blue screen alternately.

I gave the dual head video card (ATI RADEON something) to Yuta a month ago.
It is on the top of Zita. This would make the things more fun.


Yuta has also successfully set up zita to run the projector, so we should clear our some of the boxes and bookshelves in that area so that the projection can be larger.


  3755   Thu Oct 21 18:45:50 2010 KojiUpdatePSLFound the beat at 1064nm

[Koji Suresh]

We found the beat at 1064nm. T(PSL)=26.59deg, T(X-end)=31.15deg.

The X-end laser was moved to the PSL table.

The beating setup was quickly constructed with mode matching based on beam profile measurements by the IR cards.
We used the 1GHz BW PD, Newfocus #1611-FS-AC.

As soon as we swept the Xtal temp of the X-end laser, we found the strong beating.

  3759   Fri Oct 22 01:23:13 2010 KojiUpdatePSLFound the beat at 1064nm

[Koji / Suresh]

We worked on the 1064 beating a bit more.

- First of all, FSS and FSS SLOW servo were disabled not to have variating Xtal temp for the PSL.

- The PSL Xtal temp (T_PSL) was scanned from 22deg-45deg while we search the Xtal temp (T_Xend) for the Xend laser to have the beat freq well low (f<30MHz).
The pumping current for each laser was I_PSL = 2.101 [A] and I_Xend = 2.000 [A]

For a certain T_PSL, we found multiple T_Xend because the freq of the laser is not a monotonic function of the Xtal temperature. (see the innolight manual).

T_Xend to give us the beating was categorized in the three sets as shown in the figure. The set on "curve2" is the steadiest one. (Use this!)
The trends were quite linear but the slope was slightly off from the unity.

- T_PSL was scanned to see the trend of the PMC output.

The PMC was sometimes locked to the mode with lower transmission (V_PMCT ~ 3.0V).
When T_PSL ~ 31deg we consistently locked the PMC at higer transmission (V_PMCT ~ 5.3V).

At the moment we decided the operating point of T_PSL = 32.25 deg, V_PMCT = 5.34, where we found the beat at T_Xend=38.28deg.

- We cleaned up the PSL table more than how it was. Returned the tools to their original places.
The X-end laser was shut down and was left on the PSL table.

Kiwamu can move the X-end laser to the Xend and realign it.
Then we should be able to see the green beating quite easily.

Attachment 1: 101021_beat.pdf
  3774   Mon Oct 25 02:14:38 2010 KojiSummaryLockingsetup for green beat

- What is the actual photocurrent for the beam1 and beam2? We don't care how much power do you have before the BS, but care how much current do you have on the PD.

- How much is the visibility? There is mismatching of the beams. i.e. The beam diameter looked quite different. Also the beams are not TEM00 but have fringes probably comes from the TT mirrors. You maybe able to measure the visibility by the DC output, making the beat freq go through df=0 slowly.

- What is the measured gain of the RF amp? Does it include the voltage division by the output/input impedance?


 The signal level of the observed peak was -48dBm.

However I was expecting it is like -28dBm with some ideal assumptions.

There may be a 20dB unknown loss which sounds big to me.

I was assuming the parameters are like:

           A = 0.39 [A/W]   (assuming 90% quantum efficiency at 532nm)

           Z = 240 [V/A]  

           P1 = 17 uW  (measured by Newport power meter)

           P2 = 30 uW (measured by Newport power meter)

           G_RF = 23 dB

  3775   Mon Oct 25 02:23:47 2010 KojiConfigurationelogELOG 2.8.0
When I push the reply button, the raw html shows up in the edit window and have to use HTML to write the entry.
Does this happen only to me???

I stopped the ELOG and restarted us on 2.8.0.

To make sure nothing got lost, I killed the old process, copied over the logbooks/, themes/, and elogd.cfg to the new 2.8.0/ directory before starting the new Daemon.

I encountered the same Administrator bug as Joe had before. I delete all the old Admin passwords to bypass the issue.

To restart the ELOGD on NODUS, you now type '/cvs/cds/caltech/elog/start-elog.csh'.
I also added ELOG to the man pages in /usr/local/man/ on nodus by putting the *.1 files in man1/ and the *.8 files into man8/.
  3776   Mon Oct 25 02:25:21 2010 KojiUpdatePSLQuarter Wave Plate Measurements

Q1. Suppose the laser beam has a certain (i.e. arbitrary) polarization state but contains only TEM00. Also suppose the PSB is perfect (reflect all S and transmit all P). What results do you expect from your expereiment?

Q2. Suppose the above condition but the PBS is not perfect (i.e. reflects most of S but also small leakage of P to the reflection port.) How are the expected results modified?

Q3. In reality, the laser may also contain some thing dirty (e.g. deporarization in the laser Xtal, higher order modes in a certain polarization but different from the TEM00's one, etc). What actually is the cause of 170mW rejection from the PBS? Can we improve the transmitted power through the PBS?

Q4. Why is the visibility for the lambda/4 with 330deg better than the one with 326deg? Yes, as I already explained to Kevin, I suppose it was caused by the lack of the data points in the wider angle ranges.


I measured the reflected power from the PBS as a function of half wave plate rotation for five different quarter wave plate rotations.

The optimum angles that minimize the reflected power are 330° for the quarter wave plate and 268° for the half wave plate.

The following data was taken with 2.102 A laser current and 32.25° C crystal temperature.

For each of five quarter wave plate settings around the optimum value, I measured the reflected power from the PBS with an Ophir power meter. I measured the power as a function of half wave plate angle five times for each angle and averaged these values to calculate the mean and uncertainty for each of these angles. The Ophir started to drift when trying to measure relatively large amounts of power. (With approximately 1W reflected from the PBS, the power reading rapidly increased by several hundred mW.) So I could only take data near the minimum reflection accurately.

The data was fit to P = P0 + P1*sin^2(2pi/180*(t-t0)) with the angle t measured in degrees with the following results:

lambda/4 angle (°) t0 (°) P0 (mW) P1 (mW) chi^2/ndf V
318 261.56 ± 0.02 224.9 ± 0.5 2016 ± 5 0.98 0.900 ± 0.001
326 266.07 ± 0.01 178.5 ± 0.4 1998 ± 5 16.00 0.918 ± 0.001
330 268.00 ± 0.01 168.2 ± 0.3 2119 ± 5 1.33 0.926 ± 0.001
334 270.07 ± 0.02 174.5 ± 0.4 2083 ± 5 1.53 0.923 ± 0.001
342 273.49 ± 0.02 226.8 ± 0.5 1966 ± 5 1.41 0.897 ± 0.001

where V is the visibility V = 1- P_max/P_min. These fits are shown in attachment 1. We would like to understand better why we can only reduce the reflected light to ~150 mW. Ideally, we would have V = 1. I will redo these measurements with a different power meter that can measure up to 2 W and take data over a full period of the reflected power.


  3779   Mon Oct 25 23:10:06 2010 KojiUpdateIOOMC is now flashing

[Suresh / Koji]

The MC mirrors are aligned. Now the flashing of the resonances are visible on the MC2 CCD

although the modematching seemed pretty poor.

- The incident power was adjusted to be ~20mW by rotating HWP after the laser source.
The power before the window of the chamber was ~450mW. Where are those missing 1.5W?

- We checked the spot on the last two steering mirrors and the incident beam on MC1.
The beam was too much off from the center of the 1st steering mirror. It was also hitting 1cm north of the MC1.
We adjusted the steering mirrors such that the incident and reflected beams are symmetrically visible at the MC1 tower.

- The MC mirrors are aligned. We first tried to use only MC2 and MC3. And then we used MC1 too as the spot on the MC2 was too high.

- We saw some TEM00 flashes but with many other modes flashing. We checked the beam diameter on the PSL table and on the MC REFL.
The latter one looked twice large as the former one. We concluded the beam is diverging.

- We closed the tank and decided to work on the mode matching tomorrow.

  3780   Mon Oct 25 23:59:37 2010 KojiConfigurationelogELOG 2.8.0 -> ELOG 2.7.5

ELOG reverted to 2.7.5 due to editing difficulties

- /cvs/cds/caltech/elog/start-elog.csh reconfigured to launch 2.7.5

- /cvs/cds/caltech/elog/elog is linked to ./elog-2.7.5

- logbook dir of 2.8.0 was copied in the dir of 2.7.5. The old and obsolete 2.7.5 was discarded.

  3784   Tue Oct 26 10:50:08 2010 KojiConfigurationelogELOG 2.8.0 -> ELOG 2.7.5 -> ELOG 2.8.0

ELOG restarted with 2.8.0 again.

- moved elog-2.8.0/script dir to elog-2.8.0/script.orig

- copied elog-2.7.5/script to elog-2.8.0/script

- /cvs/cds/caltech/elog/start-elog.csh reconfigured to launch 2.8.0

- /cvs/cds/caltech/elog/elog is linked to ./elog-2.8.0

- logbooks on 25th and 26th were copied from 2.7.5 to 2.8.0.


  3809   Thu Oct 28 11:54:31 2010 KojiUpdateGreen Lockingchecked frequency counter SR620

ZHL-32A is a high power (well..., actually middle power) amplifier with the max output power of +29dBm (~1W!).
It seems to be overkill.
Your signal is so small so you don't need ZHL-32A, but can use small amp which we may have somewhere in the lab.

And the description:
"RF amplifier ZHL-32A has around +28dBm gain at 80MHz"
The unit is wrong.


(Kiwamu, Yuta)

  For green locking, we are planning to feedback frequency differential signal to ETM suspension for the final configuration.
  We don't have ETM suspension control system right now, so we are going to feedback the signal to X-end laser frequency for a test.
  We have two loops for the servo;
    1. coarse locking using frequency counter, feeding back to the laser temperature
    2. using VCO, feeding back to the laser PZT
  Today, we checked frequency counter SR620 and see how to get the small beat note signal(-48dBm; see elog #3771).

What we did:
  1. Using Marconi(RF signal generator), put RF signals to SR620 and see how small signal SR620 can see.
    It depends on the frequency. For 80MHz signal, you need more than about -9dBm.
       60MHz  >-12dBm
       70MHz  >-10dBm
       80MHz  >-9dBm
       90MHz  >-8dBm
      100MHz  >-7dBm

Since we are going to lock the frequency difference between X-end and PSL to 80MHz, we need at least +40dBm amp before putting the signal into SR620.

RF amplifier ZHL-32A has around +28dBm gain at 80MHz, so we need 2 of them.

  2. Marconi -> ZHL-32A -> ZHL-32A -> SR620 and see how small 80MHz signal SR620 can see.
    Around -68dBm. This should be enough.

  3. SR620 has "STRIP CHART" output on the rear panel. The output voltage is proportional to the mean frequency of the input.
    The output range is 0-8V. So in order to get 4V for 80MHz, set SCALE to 20MHz.

 - find green beat again and see if SR620 can see it with double ZHL-32A configuration


  3816   Fri Oct 29 01:18:03 2010 KojiSummarySUSPRM standoff glued

[Suresh Koji]

The standoff glued. The incandescent lamp set for curing the epoxy.

Jenne and Suresh did the balancing job. The next job was to glue it.

They ran out of the clear epoxy, and tried to use the grey epoxy which we used on the other suspensions for the upgrade.
They found that the solution A with grey color one was dried out and grainy.

We made a test piece of the grey epoxy (mixed with the solution B) in order to see the glue is still usable or not.
After the PMA party, we found that the glue was not stiffening but brittle. We judged that the grey epoxy is no longer useful.

Steve found a pack of Vac Seal in the chemical fridge. We decided to use this one for the gluing of the standoff.

After the gluing, we set an incandescent lamp to make the glue warm. 

Finally, we wrapped the suspension tower with Al foils and turned the HEPA fans again.

Attachment 1: IMG_3674.jpg
  3817   Fri Oct 29 04:24:34 2010 KojiUpdateIOOPMC output increased: need attention

[Kevin Koji]

- The PBS alignment increased the transmitted power

- The first faraday and the PMC EOM were realigned.

- The transmission of the PMC increased from ~5.4V to ~6.5V.

Thus we need to pay attention to the incident beam power on to the MC
so that it does not exceed the power of 20-40mW.

Kevin will give us the detail of the work.

  3830   Sat Oct 30 14:35:43 2010 KojiSummaryCDSCDS time delay measurement


Neglecting the digital anti-imaging filter makes the discrepancy. You must take into account your digital filter twice.

I attached the slides I made during my visit for March LVC '09. P.5 would be useful.


  [time delay of the CDS]  (left, middle)
    The time delay gets larger with frequency. The time delay seems to be -175 usec at DC.
    However, the gain seems a little different from my expectation(feCoeff4x). So, there are maybe other filters I don't know.
    I neglected TF of upsampling this time.


Attachment 1: CDS_system_investigation_090323.pdf
CDS_system_investigation_090323.pdf CDS_system_investigation_090323.pdf CDS_system_investigation_090323.pdf CDS_system_investigation_090323.pdf CDS_system_investigation_090323.pdf CDS_system_investigation_090323.pdf CDS_system_investigation_090323.pdf CDS_system_investigation_090323.pdf
  3839   Mon Nov 1 16:43:24 2010 KojiSummaryCDSCDS time delay measurement

Um, Beautiful.

Actually, 123.5usec is almost exactly twice of 1/16384Hz.
Because of the loop, we have 1/16384Hz delay. I wonder where we do have the delay.

In order to understand the behaviour of the system can I ask you to test the following things?

1) What are the delay without IOPs with fsampl of 16k, 32k, 64k?

2) What are the delay with IOP with fsampl of 32k, 64k?


  TF agreed well with 2-time feCoeff4x and CDS time delay was -123.5 usec.


  3847   Tue Nov 2 16:24:07 2010 KojiUpdateAuxiliary lockingAlignment for the green in the X trans table

[Kiwamu Koji]

Today we found the green beam from the end was totally missing at the vertex.

- What we found was very weak green beam at the end. Unhappy.

- We removed the PBS. We should obtain the beam for the fiber from the rejection of the (sort of) dichroic separator although the given space is not large.

- The temperature controller was off. We turned it on again.

- We found everything was still misaligned. Aligned the crystal, aligned the Faraday for the green.

- Aligned the last two steering mirrors such that we hit the approximate center of the ETMX and the center of the ITMX.

- Made the fine alignment to have the green beam at the PSL table.

The green beam emerged from the chamber looks not so round as there is a clipping at an in-vac steering.
We will make the thorough realignment before closing the tank.

  3851   Wed Nov 3 03:00:47 2010 KojiSummaryGreen Lockingcoarse locked green beat frequency

Wow! Great guys!!

Can I expect to see the spectra of the frequency counter output with and without the servo?

RA: I think the SBP-70 is a bad idea. It limits the capture range. So does the SHP-25. You should instead just use a DC-block; the SR620 should work from 1-200 MHz with no problems.

Also, we have to figure out a better solution for the DAC at the ends: we cannot steal the QPD gain slider in the long run and the 4116 DAC at the ends has all 8 channels used up. Should we get the purple box for testing or should we try to use the fast DAC in the EX IO chassis as the actuator?

  3874   Sat Nov 6 00:49:04 2010 KojiUpdateIOOIMC table work

[Suresh, Koji]

- Removed MCT optics in the IMC chamber

- Rotated MC1 and MC3 in clock-wise to debias the YAW bias offsets (-5V and -8V to -1.5V and -0.5V).

- Adjusted insertion of the MC1 OSEMs so as to have the outputs of about 1.0V.

- Locked to TEM00. Trying to get the beams at the center of the mirror using Yuta's A2L.

  3878   Mon Nov 8 10:37:14 2010 KojiUpdateIOOThe 10% pick-off for MCREFL was replaced to a HR mirror

As MC2 Trans mon QPD is temporary removed for fixing, we needed a reference for the MC alignment.

I replaced the 10% pick-off in the MCREFL path to the HR mirror.
Now the MCREFL DC with MC unlock is ~2.2, while it is ~0.29 in lock.
i.e. The visibility is 87%.

This means that the MCWFS were disabled for the moment.

  3885   Wed Nov 10 11:46:19 2010 KojiSummaryIOOlimitation of current MC aligning

It didn't make sense in several points.

1. Is the Faraday aperture really 3mm? The beam has the gaussian radius of ~1.5mm. How can it be possible to go through the 3mm aperture?

2. Why the MC3-FT distance is the matter? We have the steering mirror after MC3. So we can hit the center of the Faraday.
But if we have VERTICAL TILT of the beam, we can not hit the center of the Faraday entrance and exit at the same time.
That would yield the requirement.

3. If each coil has 5% variance in the response, variance of the nodal point (measured in % of the coil imbalance) by those four coils will be somewhat better than 5%, isn't it?

  3887   Wed Nov 10 14:28:33 2010 KojiSummaryIOOlimitation of current MC aligning

1. Look at the Faraday.

2. Look at the wiki. There is the optical layout in PNG and PDF.

3. 5% (0.8mm) and 2.5%(0.4mm) sounds a big difference for the difficulty, but if you say so, it is not so different.

Actualy, if you can get to the 5% level, it is easy to get to the 1-2% level as I did last time.
The problem is we are at the 15-20% level and can not improve it.

  3895   Thu Nov 11 11:51:30 2010 KojiSummaryCDSfound poor contact of DAC cable, previous A2L results were wrong

The cause is apparent! The connectors on the cables are wrong!
Currently only 50% of the pin length goes into the connector!


(Koji, Jenne, Yuta)

We found one of DAC cables had a poor contact.
That probably caused our too much "tilt" of the beam into MC.

  It was because one of the DAC cables(labeled CAB_1Y4_88) had a poor contact.
  If I push it really hard, it is ok. But maybe we'd better replace the cable.

What caused a poor connection?:
  I don't know.
  A month ago, we checked that they are connected, but things change.


  3901   Thu Nov 11 23:35:23 2010 KojiSummaryCDSfound poor contact of DAC cable, previous A2L results were wrong

[Koji / Yuta]

There were the guys who used the PENTEK 40pin connectors into the IDC 40pin connectors.
Those connectors are not compatible at all.

==> We replaced the connectors on the cables from DAC to IDC adapters to the dewhitening board for the vertex SUSs.

In addition, I found one of the Binary OUT IDC50pin connector has no clamp.

==> We put the IDC50pin clamp on it.


PENTEK connectors were inserted. The latches are not working!


the vertical pitch is different between PENTEK and IDC!

Wow! Where is the clamp???



The cause is apparent! The connectors on the cables are wrong!
Currently only 50% of the pin length goes into the connector!


(Koji, Jenne, Yuta)

We found one of DAC cables had a poor contact.
That probably caused our too much "tilt" of the beam into MC.

  It was because one of the DAC cables(labeled CAB_1Y4_88) had a poor contact.
  If I push it really hard, it is ok. But maybe we'd better replace the cable.

What caused a poor connection?:
  I don't know.
  A month ago, we checked that they are connected, but things change.



  3910   Fri Nov 12 19:24:56 2010 KojiUpdateCDSTest of ADC noise

[Koji Yuta]

We found one of the ADC cables were left unconnected. This left the MC suspensions uncontrollable through the whole afternoon.
Please keep the status updated and don't forget to revert the configuration...



Look at the effects of the ADC voltage range on the ADC noise floor.

ADC input was terminated with 50 ohms.  We then looked at the channel with DTT. This was at +/- 10 V range.  We used C1:SUS-PRM_SDSEN_IN1 as the test channel.

The map.c file (in /opt/rtcds/caltech/c1/core/advLigoRTS/src/fe/ ) then had two lines added at line 766.

//JCB temporary 2.5V test, remove me
  adcPtr[devNum]->BCR &= 0x84240;

This hard coded the 2.5 V range (we default to the 10 V range at the moment).

We then rebuilt the c1x02 model and reran the test.

Finally, we reverted the code change to map.c and rebuilt c1x02.

I've attached the DTT output of the two tests.

It appears the ADC is limited by 1.6 uV/rtHz.  Hence the increase in noise in counts by a factor of 4 when we drop to +/- 2.5 V from +/- 10 V.


  3921   Mon Nov 15 14:36:37 2010 KojiUpdatePSLC1PSL rebooted?

Has C1PSL rebooted? Has burtrestore been forgotten? Even without elog?

We found some settings are wrong and the PMC has pretty low gain.

ELOG V3.1.3-