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ID Date Authorup Type Category Subject
  5089   Tue Aug 2 02:35:23 2011 kiwamuUpdateGeneralpreparation of the vent : status and plan

The vent will take place on Wednesday.

Plan for Tuesday :

  (Morning) Preparation of necessary items for the low power MC (Steve / Jamie)

  (Daytime) Measurement of the MC spot positions (Suresh)

  (Daytime) Arm length measurement (Jenne)

  (Nighttime) Locking of the low power MC (Kiwamu / Volunteers)


Plan for Wednesday :

  (Early morning) Final checks on the beam axis, all alignments and green light (Steve / Kiwamu / Volunteers )

  (Morning) Start the vent (Steve)

  (daytime-nighttime) Taking care of the Air/Nitrogen cylinders (Everybody !!)


Status of the vent preparation :


  (not yet) Low power MC

  (ongoing) Measurement of the arm lengths

  (ongoing) Measurement of the MC spot positions

  (80% done) Estimation of the tolerance of the arm length (#5076)

  (done) Alignment of the Y green beam (#5084)

  (done) Preparation of beam dumps (#5047)

  (done) Health check of shadow sensors and the OSEM damping gain adjustment (#5061)

  (done) Alignment of the incident beam axis (#5073)

  (done) Loss measurement of the arm cavities (#5077)

  5092   Tue Aug 2 11:52:44 2011 kiwamuSummaryGeneralSchedule

I have updated the 40m public calender.

Main change :

  + The vent starts from 3rd of August

  + Keiko and Anamaria (LSU) come from 13th of August

  5093   Tue Aug 2 15:41:06 2011 kiwamuUpdateIOOMeasurement of MC spot positions : done

[Suresh / Kiwamu]

 The measurement of the spot positions on the MC mirrors are DONE.

Surprisingly the spot positions are not so different from the ones measured on May.

    Feb 26 2011      May 08 2011 (New !) Aug 2 2011
MC1 pit [mm]   1.6   1.9  1.93
MC2 pit [mm]   6.4   9.0 9.03
MC3 pit [mm]   1.4   2.0 2.01
MC1 yaw [mm]   -1.5   -1.7 -1.72
MC2 yaw [mm]   1.0   0.2 0.178
MC3 yaw [mm]   -1.3   -1.9 -1.87


(some notes)
We used Valera's script senseMCdecenter to estimate the spot positions ( see his entry).

It returns so many EPICS error messages and sometime some measured values were missing. So we had to throw away some of the measurements.

Anyways we gave the resultant ASCII file to Valera's matlab file sensmcass.m to get the actual amount of off-centering in milli-meter.

The attached file is the resultant plot from his matlab code.

Attachment 1: MCdecenter.png
  5097   Tue Aug 2 19:05:13 2011 kiwamuUpdateIOOpeparation for low power MC : HWP+PBS installed

[Steve / Kiwamu]

  An attenuator, consisting of two HWPs and a PBS, has been installed on the PSL table for the MC low power state.

Those items allow us to reduce the amount of the incident power going into the MC.

We haven't decreased the power yet because we still have to measure the arm lengths.

After we finish the measurement we will go to the low power state.

We have adjusted the polarization after the last HWP using another PBS. Now it is S-polarizing beam.

After the installation of the attenuator the beam axis has changed although we were immediately able to lock the MC with TEM00 mode.

I touched two steering mirrors on the PSL table to get the transmitted power of MC higher. At the moment the transmitted power in MC_TRANS is at about 30000 cnts.


The attached picture is the setup of the attenuator on the PSL table.

Attachment 1: attenuator.png
  5103   Wed Aug 3 04:29:48 2011 kiwamuUpdateIOOpeparation for low power MC : HWP+PBS installed

[Suresh / Kiwamu]

 The incident beam power going into MC was decreased down to 20 mW by rotating the HWP that we set yesterday.

A 10% beam splitter which was sitting before MCREFL_PD was replaced by a perfect reflector so that all the power goes into the PD.

And we confirmed that MC can be still locked by increasing C1IOO-MC_REFL_GAIN. Some modifications in the Autolocker script need to be done later.

Also we opened the aperture of the MC2F camera to clearly see the low power beam spot.



Power after the EOM = 1.27 W

Power after the HWPs and PBS = 20.2 mW

Power on MCREFL = 20 mW (MC unlocked)

MCREFL_DC = 0.66 V (with MC locked)



After we finish the measurement we will go to the low power state.


  5105   Wed Aug 3 11:34:59 2011 kiwamuUpdateVACRe: vent

An important rule during the in-vac work :

   Do not change the incident axis of the X and Y green beams.

Because of the air flows and unusual pressure in the chambers, the DC alignment of the suspensions become less reliable in terms of the beam pointing reference.

The green beams will be considered as references during the vent.


The vacuum system is coming up to atm. The vent was started with slow N2 flow.

  5110   Wed Aug 3 14:40:32 2011 kiwamuSummaryGeneralminutes of 40m meeting : plan tomorrow

Tomorrow's main goal is : let the both X and Y green light come out from the chambers.


Plan of the in-vac work for tomorrow :

    - Removal of the access connector and the BS north door, starting from 9:00 AM. (requires 6 people)

   - If necessary, align ITMs and ETMs to get the green light nicely flashing / locked.

   - Take pictures of the BS and IOO table before installing / repositioning some optics.

   - Repositioning of the green periscope in the BS chamber to let the Y green light go through it.

   - Steer some green mirrors on the IOO table to let the Y green light come out from the chamber.

   - Steer some green mirrors on the BS table to let the X green light come out from the chamber.

   - Put some beam traps on the BS table

   - Leveling of the BS table. (Do we need to level the IOO table ? it will change the spot positions on the MC mirrors somewhat)

   - Take pictures again.

   - Extra jobs : if we still have some more times, lock MC and check the beam clearance at the Faraday. Also check some possible beam clippings for the IR beam.

   - Close the chamber with the light doors.

   - Softball game at 6:30 PM.

  5120   Fri Aug 5 02:00:09 2011 kiwamuSummaryGeneralsummary of today's invac work

[Jamie, Jenne, Suresh, Steve, Koji, Kiwamu]

We got two green beams coming out from the chambers !


Summary of today's invac work :

    - removed the access connector and the BS north door

    - realigned the X and Y arm to the green beams.

    - installed a HWP on the ETMY table to rotate the polarization of the green beam to P.

    - repositioned the first periscope on the BS table.

    - repositioned the second periscope on the IOO table.

    - steered some green mirrors on the IOO and OMC chamber to let the Y green beam come out to the PSL table.

    - installed a PBS in front of the first periscope to spatially overwrap two green beams.

    - adjusted the incident angle of the PBS to maximize the power of the Y green beam, which is transmitted through it.

   - steer two mirrors on the BS table to align the X green beam

   - installed two beam dumps, one is near the PBS to eliminate a ghost in the X green beam, and the other is on the back side of IPPOS/ANG pick off window.

   - closed the doors.


Some Notes:

 When steering the final green mirror on the OMC table, accidentally we changed the alignment of the MC incident mirror.

So the alignment of the incident beam going into MC has changed, and we haven't re-aligned it yet.

 During we were installing the PBS on the BS table, we found that the allowable incident angle for the Y beam is about ~ 55 deg, which maximizes the amount of the transmitted Y green.

Since the PBS had been considered to be 45 deg incident in our optical layout, this required several modifications in the green mirrors.

To have a clear X green beam path going into the PBS, we had to slide the PBS and periscope to the West.

The periscope is now sitting on the very edge of the BS table, and in fact ~ 20% of the bottom plate of the periscope is already sticking out.

Also since 30% of the area of the PBS's post is on a hole, which is somehow for the stack, we had to use three dog clamps instead of a folk clamps to make the contact tight.

  5122   Fri Aug 5 08:08:42 2011 kiwamuSummaryGeneralplan today

Today's main mission is : adjustment of the arm length


   + Open the ETMX(Y) door, starting from 9:00 AM

   + Secure the ETMX(Y) test mass by tightening the earthquake stops.

   + Move the ETMX(Y) suspension closer to the door side

   + Inspect the OSEMs and take pictures before and after touching the OSEMs.

   + Level the table

   + Adjust the OSEM positions

   + Move the ETMX(Y) suspension to have designed X(Y)arm length

   + Level the table again

   + Align the ETMX(Y) such that the green beam resonate

  5125   Fri Aug 5 15:11:24 2011 kiwamuUpdateSUSRe: cross coupling

There is a page on the 40m wiki explaining the procedure.



Additionally there are several old elogs about the cross-coupling minimization, which can be useful for us:

[1] "SUS ranking from measured data", iLog by Osamy (Aug.22 2005)

[2] "TF from position to sensors for ETMX ", iLog by Osamu (Aug.25 2005)

[3] "Further OSEM tweaking", iLog by Rana (Oct.3 2006)

Quote from #5123

We need a plan how to minimize cross coupling in the OSEMs now


  5129   Fri Aug 5 22:54:29 2011 kiwamuMetaphysicsTreasureCrane crew here Monday morning

Also, according to Steve, there will be some crane guys for fixing the Y end crane issue (#5124) Monday morning.

Quote from #5128

 a film crew will be here Monday morning. They are slated to be here from 8am to 12:30pm or so. 

  5133   Sun Aug 7 14:01:58 2011 kiwamuUpdateGreen LockingX green beam re-aligned

[Jenne / Kiwamu]

 The X green beam has been realigned to compensate the effect of the ETMX repositioning.

After the alignment we became able to lock the 00 mode with the X green beam.


For the alignment:

  spot position on the ETMX mirror = within ~ 1 cm. This number is strictly constrained by a homemade aluminum iris that Jamie put last Friday.

  spot position on the ITMX mirror = unknown, but looks pretty good on the CCD camera.

  spot position on the PSL table = ~ 1 mm downward from what it used to be. The horizontal alignment is perfect.

Conclusions :

  The X green beam again became a reference of the beam axis.

  The ETMX suspension tower is in a good place.

Quote from #5127

Kiwamu will work on the green alignment over the weekend.  Assuming everything works out, we'll try the same procedure on ETMY on Monday.


  5141   Mon Aug 8 15:20:49 2011 kiwamuUpdateSUSinspection on ETMY (round 1)

Since ETMY have been showing some strange behaviors we deeply inspect the ETMY suspension.

Here is a brief review of the ETMY suspension and a brief status update of the inspection so far.

The inspection is still ongoing.


(Review : How wrong ?)

First of all, let us summarize what were the observed phenomena on the ETMY suspension :

   1. unknown low frequency noise covering frequency range from 0.1 to 3 Hz in all of four face sensors (#5025, #5029).

   2. LR sensor showed a very broad bounce peak at ~ 17 Hz (#5025).

   3. The sign of some of the sensors are flipped.

   4. The control gains had to be higher than those of ETMX by 10-100 (#5025).


(Status update : Noise spectra)

Currently the ETMY suspension is sitting on the north side of the table for the inspection.

We took dark noise of the OSEMs when the OSEMs were taken off from the tower and put on the table.

The plot below is an example of the LR sensor spectra. Note that the whitening filters have been always ON.


The black curve is the dark noise when the sensor was off from the tower.

The blue curve is the free swinging spectrum newly taken today.

The red curve is the free swinging spectrum (damped spectrum ?) on 25th of July, this was still in vacuum.


The dark noise is below the free swinging spectrum from 0.2 - 30 Hz, which looks reasonable

The most interesting thing is that the free swinging spectrum became better in low frequency (below 3 Hz)

from the one measured in vacuum.

It needs more investigation to answer the reason why it happened.

Note that before we moved the tower to the current position, we looked at the OSEM-magnets relations, and found nothing was touching.


  5147   Tue Aug 9 02:03:16 2011 kiwamuSummarySUSsummary of today's work on ETMY

[Rana / Jenne / Kiwamu]

The ETMY suspension tower is currently sitting on the north side of the table for some inspections.

The adjustment of the OSEMs is ongoing.


(What we did)

  + Taken out two oplev mirrors, Jamie's windmill and a lemo patch panel.

  + Put some pieces of metal as makers for the original place

  + Put some makers on the distance of  dLY = -25.49 cm = -10.04 inch from the original place (see the 40m wiki).

     The minus sign means it will move away from the vertex.

  + Brought the ETMY suspension tower to the north side to do some inspections

  + Did some inspections by taking the noise spectra (#5141)

  + Adjusted the OSEM range and brought the magnets on the center of the OSEM holders by rotating and translating the OSEMs

  + During the work we found the proper PIT and YAW gains were about -5, which are the opposite sign from what they used to be.

  + Trying to minimize the cross couplings

JD: There is still some funny business going on, like perhaps the LR magnet isn't quite in the OSEM beam.  We leave the optic free swinging, and will continue to investigate in the morning.

  5151   Tue Aug 9 03:05:05 2011 kiwamuSummaryGeneralweekly report

Summary of the week ending Aug 8th.  Number of elog entries = 56

 + The vent started Wednesday morning
 + Repositioning of the green periscopes and associated mirrors are done.
 + Got both of the green beams coming out from  the chambers
 + Moved the ETMX suspension tower by -8.09 inch (away from vertex)
 + Fixed the alignment of the ETMX CCD mirrors
 + Recovered the X green beam axis for the latest ETMX position

 + oplev centered prior to the vent

 + ETMY_TRANS_QPD didn't respond at all, needs to be fixed
 + Old MZ PD (InGaAs 2mm, @29.5MHz) has been modified for REFL33.
  The 11MHz notch circuit is at the amp side instead of the diode side. This is ready for the installation
 + REFL165 PD has been made from the old 166MHz PD.

 + IPPOS has been sick since 19th of July, 2011
 + IPANG is clipped on a pick-up mirror on the ETMY table. QPD itself is healthy.
 + The spot positions on the MC mirrors were measured prior to the vent.
   The results are almost the same as before within a few percent difference expect for the MC2 yaw.
 + An attenuator, consisting of two HWPs and a PBS, has been installed on the PSL table for the MC low power state.
 + a 10% BS in front of the MCREFL_RFPD was replaced by a perfect reflector for the low power mode.
 + The incident power for MC was decreased to 20 mW
 + The beam axis going to MC was misalgned due to the attenutor.
    Then the beam was aligned by touching two steering mirrors on the PSL table
 + MC is able to be locked in air. The reflection DC goes from 1.4 to 0.13 V when the MC is locked.

 + With the mass-kicking technique, the arm lengths were measured.
   Xarm =  37.5918 m, Yarm = 37.5425 m.

- Green locking
 + Y green beam is aligned to the Y arm
 + Locking of the Y green is not robust, it needs to be revisited

 + Wiener Filtering was applied on the data collected from the X-arm for a duration of 1500 seconds.

- Misc.
 + The hazardous waste people are moving chemicals around outside our door, and have roped off our regular front door.
 + The horizontal trolley drive of the east end crane stopped working. It will be fixed.

  5152   Tue Aug 9 10:15:25 2011 kiwamuUpdateGeneralin-vac work plan today

We will move on to the vertex region today.

The goal of the vertex region work is to get the pick-off beams out the chambers, including POX/Y and POP.

The work will be in parallel to the ETM woks.

The first step will be : lock and align MC with the IR beam.

  5153   Tue Aug 9 11:33:33 2011 kiwamuUpdateSUSRe: ETMX free swinging data

I believe that the 17 Hz broad structure on SIDE is just because of a bad rotational angle of the SIDE OSEM.

The same structure had been observed on the EMTY_UR, and the structure became narrower after we repositioned/rotated the OSEM yesterday.

My guess is that the SIDE OSEM is now in a place where the OSEM is quite sensitive to the bounce mode

and creating the broad structure due to a bi-linear coupling between the bounce mode and low frequency signals.

Quote from #5150

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

  5173   Wed Aug 10 14:30:55 2011 kiwamuUpdateIOORe: MC A2L alignment

I modified a set of the automated MC locking scripts which are dedicated for the low power MC.

Currently there are three scripts like the usual MC locking scripts:

(1)mcup_low_power, (2) mcdown_low_power and (3) autolockMCmain40_low_power.

I ran those scripts on op340m as usual and so far they are running very well. The lock acquisition is quite repeatable.

I hope theses scripts always bring the lock condition to the same one and hence the LOCKIN signals don't change by every lock.


- To run the script

  log into op340m and run autolockMCmain40m_low_power

Quote from #5167

And the MC settles into a new position when the MC-PSL servo loop was disturbed by random denizens in the lab.  Requiring us to start over again.


  5189   Thu Aug 11 12:54:06 2011 kiwamuUpdateIOOMC spot positions

The spot positions on the MC mirrors were adjusted by steering the MC mirrors, resulting in 1 mm off-centering on each optic.



(Requirement cleared)

One of the requirements in aligning the MC mirrors is the differential spot positions in MC1 and MC3.

It determines the beam angle after the beam exists from MC, and if it's bigger than 3 mm then the beam will be possibly clipped by the Faraday (#4674).

The measured differential spot positions on MC1 and MC3 are : PIT = 0.17 mm and YAW = 1.9 mm, so they are fine.


(Measurement and Results)

 Suresh and I aligned the MC cavity's eigen axis by using MCASS and steering the MC mirrors.

Most of the alignment was done manually by changing the DC biases

because we failed to invert the output matrix and hence unable to activate the MCASS servo (#5167).

Then I ran Valera's script to measure the amount of the off-centering (#4355), but it gave me many error messages associated with EPICS.

So a new script newsensedecenter.csh, which is based on tdsavg instead of ezcaread, was made to avoid these error messages.


The resultant plot is attached. The y-axis is calibrated into the amount of the off-centering in mm.

In the plot each curve experiences one bump, which is due to the intentional coil imbalance to calibrate the data from cnts to mm (#4355).

The dashed lines are the estimated amount of off-centering.

For the definition of the signs, I followed Koji's coordinate (#2864) where the UL OSEM is always in minus side.

    Feb 26 2011      May 08 2011 Aug 2 2011 [NEW!!] Aug 10 2011 (in air)
MC1 pit [mm]   1.6   1.9  1.93 -0.858
MC2 pit [mm]   6.4   9.0 9.03 -0.844
MC3 pit [mm]   1.4   2.0 2.01 -1.03
MC1 yaw [mm]   -1.5   -1.7 -1.72 -0.847
MC2 yaw [mm]   1.0   0.2 0.178 0.582
MC3 yaw [mm]   -1.3   -1.9 -1.87 -1.06


Quote from #5182

After the beam spots on MC1 and MC3 were close to the actuation nodes (<1mm away)

Attachment 1: MCoffcenter.png
  5203   Fri Aug 12 03:52:51 2011 kiwamuUpdateSUSPRM OSEM adjustment

[Suresh / Kiwamu]

 We tried adjusting the OSEMs on PRM, but we didn't complete it due to a malfunction on the coils.

The UL and LL coils are not working correctly, the forces are weak.

Tomorrow we will look into the satellite box, which is one of the suspects.


 During the adjustment we found that the POS excitation force was unequal in each sensor.

At the beginning we thought it's because of the difference of the sensitivity in each OSEM due to the bad OSEM orientations.

However it turned out that it comes from the actual force imbalance on each coil.

We checked the force of each coil by putting an offset (-2000 cnts) in each output digital filter and looked at the OSEM signals in time series.

The UL and LL coils are too weak and the responses are almost buried in the noise of the OSEMs in time series.

We briefly checked some analog electronics and found the DAC, AI board and deWhitening board were healthy.

We were able to see the right amount of voltage from the monitor pin on the front panel of the coil driver.

So something downstream are suspicious, including the satellite box, feedthrough and coils.

- - -

Although the coil issue, it could be worth trying to check the input matrix.

  5204   Fri Aug 12 04:11:13 2011 kiwamuUpdateSUSfree swinging

Excited all optics - -
Fri Aug 12 03:34:12 PDT 2011

  5219   Sat Aug 13 01:54:18 2011 kiwamuUpdateSUSPRM OSEM adjustment part II

Adjustment of the PRM OSEMs are done. The coils turned out to be healthy.

The malfunction was fixed. It was because the UL OSEM was too deeply inserted and barely touching the AR surface of the mirror.


(OSEM adjustment)

 + Excited POS at 6.5 Hz with an amplitude of 3000 cnts by the LOCKIN oscillator.

 + Looked at the signal of each sensor in frequency domain.

 + Maximized the excitation peak for each of the four face OSEMs by rotating them.

 + Minimized the excitation peak in the SIDE signal by rotating it.

 + Adjusted the OSEM translational position so that they are in the midpoint of the OSEM range.


(POS sensitivity check)

From the view point of the matrix inversion, one thing we want to have is the equally sensitive face sensors and insensitive SIDE OSEM to the POS motion.

To check the success level of today's PRM adjusment, I ran swept sine measurements to take the transfer function from POS to each sensor.

The plots below are the results.  The first figure is the one measured before the adjustment and the second plot is the one after the adjustment.

As shown in the plot, before the adjustment the sensitivity of OSEMs were very different and the SIDE OSEM is quite sensitive to the POS motion.

So PRM used be in an extremely bad situation.

After the adjustment, the plot became much better.

The four face sensors have almost the same sensitivity (within factor of 3) and the SIDE is quite insensitive to the POS motion.

before.png after.png

Quote from #5203

 We tried adjusting the OSEMs on PRM, but we didn't complete it due to a malfunction on the coils.

The UL and LL coils are not working correctly, the forces are weak.

  5220   Sat Aug 13 02:11:33 2011 kiwamuUpdateSUSfree swinging again

I am leaving all of the suspensions free swinging. They will automatically recover after 5 hours from now.

Excited all optics
Sat Aug 13 02:08:07 PDT 2011

FYI : I ran a combination of two scripts:   ./freeswing && ./opticshutdown

  5221   Sat Aug 13 02:31:42 2011 kiwamuUpdateSUSRe: ETMY hopefully good again

I guess the ETMY suspension is still fine. Their OSEM DC voltage and the free swinging spectra look healthy.

It could be a failure in the initial guess for fitting.

Quote from #5216

I'm no longer convinced that ETMY is healthy. I can't fit the peaks to get the input matrix.

  5234   Sun Aug 14 22:48:37 2011 kiwamuUpdateSUSfree swinging again

Excited all optics
Sun Aug 14 20:22:33 PDT 2011

  5235   Mon Aug 15 10:02:27 2011 kiwamuUpdateSUSBS OSEM adjustment done

[Suresh / Kiwamu]

 Adjustment of the OSEMs on BS has been done.

All the bad suspensions (#5176) has been adjusted. They are waiting for the matrix inversion test.

  5236   Mon Aug 15 10:58:52 2011 kiwamuUpdateIOOMC misaligned a lot

This morning Steve and I opened the doors on the IOO and OMC chamber to let the IR beam go to MC.

And found the MC flashing is way far from TEM00, there were very higher order modes.

The MC suspensions were realigned based on an assumption that the incident beam didn't change recently.

Anyways we should check the leveling of the IOO table and the spot positions on the MC mirrors again to make sure.

  5238   Mon Aug 15 14:07:39 2011 kiwamuUpdateIOORe: MC misaligned a lot

The leveling was still okay. The MC mirrors were realigned and now they all are fine.

We will go ahead for the vertex alignment and extraction of the pick-off beams.


Here is a summary of the spot measurement.

    Feb 26 2011      May 08 2011 Aug 2 2011  Aug 10 2011 (in air) [NEW!!] Aug 14 2011 (in air)
MC1 pit [mm]   1.6   1.9  1.93 -0.858 -0.2
MC2 pit [mm]   6.4   9.0 9.03 -0.844 -0.8
MC3 pit [mm]   1.4   2.0 2.01 -1.03 -0.1
MC1 yaw [mm]   -1.5   -1.7 -1.72 -0.847 -1.1
MC2 yaw [mm]   1.0   0.2 0.178 0.582 0.6
MC3 yaw [mm]   -1.3   -1.9 -1.87 -1.06 -1.1


Quote from #5236

Anyways we should check the leveling of the IOO table and the spot positions on the MC mirrors again to make sure.


  5245   Tue Aug 16 04:28:09 2011 kiwamuUpdateGeneraltoday's work to do

The main goal of today is to extract the pick-off beams

Today's menu :

  + If necessary steer ETMs and ITMs to make the X and Y green beam flashing.

  + Open the IOO and OMC chamber and lock MC.

       => cover the place of the access connector by a large piece of aluminum foil. It will give a robust lock of MC.

  + Check the beam pointing down to Y arm by looking at the ETMY face camera.

        => If it's necessary align PZT1 and PZT2 from EPICS to make the IR beam flashing in the X arm.

  + Align BS and let the beam hit the center of ETMX to make the X arm flashing.

        => These alignment procedure will automatically gives us the MICH fringes on the AS CCD camera.

  + Rotate the SRM tower to get the SRMI fringes on the AS CCD camera.

        => This is because the required amount of the YAW correction on SRM is currently beyond the range of the DC bias.

  + Align PRM to get the PRMI fringes on AS CCD camera. Also make sure the beam comes back to the REFL CCD camera.

  + Lock the PRC to make POP/POX/POY bright enough.

     => Probably the REFL11 RFPD needs more power. To increase the power, just rotate the HWP, which is sitting before the RFPDs on the AS table.

     => If the signal on AS55 is too small, we can use REFL11_Q or REFL55 for the MICH lock.

  + OR inject and align the ABSL laser to make those pick-off beams bright enough.

     => This case we don't have to make the DRMI exactly on the resonance, what we need is just the DRMI flashing.

  + Align necessary optics for those pick-off beams.

     => In our definition (aLIGO definition) POP is the beam propagating from BS to PRM. Don't be confused by another one, which propagates from PRM to BS.

  + Steer two mirrors on the ETMY table for aligning IPANG. Also, steer some mirrors on the BS table for IPPOS.

    => IPANG has already reached the ETMY table, so ideally we don't have to steer a mirror on the BS table.

    => IPPOS/ANG are very visible with a sensor card.

  + Align some oplevs.

     => This work is relatively independent from the other tasks. Steve can take care of it.

  + Adjust the OSEM to their mid-range.

     => This work can be done anytime, but everytime we have to recover the alignment of the interferometer.

  5246   Tue Aug 16 04:50:17 2011 kiwamuUpdateSUSfree swinging again

 Since Suresh and I changed the DC biases on most of the suspension, the free swingning spectra will be different from the past.

- -


Tue Aug 16 04:48:02 PDT 2011

  5251   Wed Aug 17 02:48:56 2011 kiwamuUpdateRF SystemRe: AM in the PM

[Keiko / Suresh / Anamaria / Kiwamu]

 The AM components do exist also on the beam after the EOM.

The peaks were found at 11, 29 and 55 MHz, where the PM are supposed to be imposed.

Suresh and Keiko minimized them by rotating the HWP, which is in front of the EOM.

Also Anamaria and I tried minimizing them by adjusting the EOM crystal alignment.

However everytime after we minimized the AM peaks, they grew back in a time scale of ~ 1 min.

Potentially it could be a problem of the HWP and/or EOM alignment.

Since we wanted to proceed the in-vac work anyways, we stopped investigating it and decided to postpone it for tomorrow.

We again adjusted the incident power to 20 mW.


-- P.S.

 The incident power going to MC went down to 7 mW for some reasons. This was found after ~ 6 hours from our works on the PSL table.

We haven't touched anything on the PSL table since the daytime work.

Possibly the angle of the HWP is drifting (why?) and changed the amount of the P-polarizing beam power.

Suresh locked the angles of two HWPs, which are the one just after the EOM and the one after the attenuation PBS.

Quote from #5249

So first check is beam out of PSL EOM, to make sure the input beam is aligned to the crystal axis and is not giving AM modulation in adition to PM.


  5252   Wed Aug 17 03:10:06 2011 kiwamuUpdateGeneralcurrent status of in-vac work

[Jamie / Suresh / Kiwamu] 

The in-vac work is ongoing.

Before we run out our energy we are posting this entry to briefly report the current status.

- (done) BS earthquake stop adjustment.

- (done) PRM earthquake stop adjustment

- (done) MC spot position check => They are almost the same within 10 %.

- (done) Injection and alignment of the ABSL laser to make the beam brighter in the vertex region.

- (done) POY => We repositioned an in-vac steering mirror to get the POY beam hitting the center of the steering mirror.

                           It's now coming out from the chamber.

(done)  IPANG => realigned two mirrors on the ETMY table to get the IPANG out from the chamber. Now it's reaching the ETMY optical table.

                             It needs a final touch before we pump down.  We revisited it later in the night after realigning the IFO and it is well aligned now.

- (done)  POP => We have aligned the ABSL laser injected from the AS port to reach the REFL camera.  We turned it up to max power of 300mW and used it as a substitute for the PRC beam.

                         Even this was not enough to see anything in the POP beam path after the PR2 (tip-tilt).  So we used a green beam from the Y-arm as a guide of the POP beam path because the ABSL (POP) beam was too dim to work with.

                         We placed a lens and a CCD camera to detect the green and then blocked the Y-green.  It was then possible to see the ABSL-POP beam in the CCD camera.  The lens and the CCD are markers for this beam. 

                         Do not remove these markers unless absolutely necessary.

-(done) POX => We located the ABSL (mimicking POX) beam on the POXM1 mirror and adjusted the mirror to ensure that the beam exits at the right height and a convenient location on the POX table. 

- (0%) OSEM mid-range adjustment

- (0%) IPPOS

- (0%) oplev re-alignment

  5253   Wed Aug 17 06:42:38 2011 kiwamuUpdateGeneralin-vac work : the end is near

We will pump down the chambers on Thursday morning.

Today will be a day of the OSEM and oplev party.


 -- to do list for today --

 + OSEM mid-range adjustment

 + oplev realignment

 + placement of beam traps

 + extraction of IPPOS

 + table leveling

 + interferometer alignment

 + AM-PM mystery

 + preparation for drag and wipe

  5275   Mon Aug 22 02:43:28 2011 kiwamuUpdateGeneralin-vac work

[Kieko / Kiwamu]

 The AS beam shows a little bit of clipping and right now this is the only concern for the alignment of the interferometer.

Other than that everything is okay including :

  + Beam centering on all the suspended optics

  + Arm cavity alignments. The Fabry-Perot fringes from both arm cavity were found on the AS camera.

  + POX/POY/POP, they are still successfully coming out from the chambers


  + Alignment of the green beams and the associated optics. Both green are reaching to the PSL table


We need to check/fix the AS beam clipping and once it's done we will readjust the OSEM mid range and the oplevs.

Then it will be ready for the drag/wipe and door closing.

  5279   Mon Aug 22 21:32:10 2011 kiwamuUpdateGeneralmore in-vac work : AS clipping fixed and OSEM/oplev adjustment

[Keiko / Jenne / Jamie / Kiwamu]

 We did the following things today :

  + fixed the AS clipping issue

  + realigned all the oplevs

  + checked and adjusted the all OSEM DC values, including PRM, SRM, BS, ITMs, ETMs, MC1 and MC3


Since we touched the OSEMs the alignment has changed somewhat.

Right now Jenne, Suresh and I are working on the "confirmation alignment".

Once we find the alignment is still good (steerable by the PZTs and the DC coil bias), tomorrow we will do the drag&wipe and door closing.

Quote from #5275

We need to check/fix the AS beam clipping and once it's done we will readjust the OSEM mid range and the oplevs.


  5282   Tue Aug 23 01:09:44 2011 kiwamuUpdateSUSfree swinging test

excited all the optics ---

Tue Aug 23 01:08:00 PDT 2011

  5285   Tue Aug 23 09:40:37 2011 kiwamuUpdateGeneralRe: AS clipping fixed

Indeed it was suspenseful.

We tried finding where the clipping happened, but we couldn't find any obvious clippings.

So we checked centering of the beams on all the optics associated with the AS path, starting from BS, SR3,... to the AS optical bench.

And during the work some of them were recentered.

At the end we found no clipping. To make sure we tested the available range (no clipping range) by exciting the angular motion of BS with AWG (f ~ 1Hz, a ~ 1000).

The beam looked successfully coming out at the most of the angular oscillation point.

Quote from #5284

Where was the AS clipping?! Ah, the suspense...


  5287   Tue Aug 23 11:57:22 2011 kiwamuUpdateSUSfree swinging test during lunch time

excited all the optics. (with ITMY WTF OFF)

Tue Aug 23 11:52:52 PDT 2011

  5290   Tue Aug 23 17:21:45 2011 kiwamuUpdateSUSfree swinging test for ETMY


Excited ETMY

Tue Aug 23 17:20:45 PDT 2011


  5298   Wed Aug 24 16:13:36 2011 kiwamuUpdateSUSbroke UL magnet on ITMX

I broke the UL magnet on ITMX

The ITMX tower was shipped into the Bob's clean room to put the magnet back on.


 Since we found that all the magnets were relatively high (#5296) in the shadow sensors, we decided to slide the OSEM holder bar upward.

During the work, I haven't made the OSEMs far enough from the magnets.

So the magnets and OSEMs touched as I moved the holder.

Then the UL magnets were broken off and fell into the UL coil.


  5316   Mon Aug 29 00:49:00 2011 kiwamuUpdateCDSRe : fb down

Fb is in a bad situation. It needs a MANUAL fsck to fix the file system.

HELP US, Jamieeeeeeeeeeee !!!


When Suresh and I connected a display and tried to see what was going on, the fb computer was in a file system check.

This was because Suresh did a hardware reboot by pressing a power button on the front panel.

Since the file checking took so long time and didn't proceed fast, we pressed the reset button and again the power button.

Actually the reset button didn't work (maybe ?) it just made some light indicators flashing.

After the second reboot the reboot message said that it needs a manual fsck to fix the file system. This maybe because we interrupted the file checking.

We are leaving it to Jamie because the fsck command would do something bad if unfamiliar persons, like us, do it.


In addition to it, the boot message was also saying that line 37 in /etc/fstab was bad.

We logged into the machine with a safe mode, then found there was an empty line in 37th line of fstab.

We tried erasing this empty line, but failed for some reasons. We were able to edit it by using vi, but wasn't able to save it.

  5326   Tue Aug 30 14:44:06 2011 kiwamuUpdateSUSITMY released without opening chambers

The ITMY mirror was released. The OSEM readouts became healthy.


To see what is going on, I changed the PIT DC bias slider on ITMY from 0.8 to -1 or so, and then the optic started showing a free swinging behavior.

If there were no responses to the DC bias, I was going to let people to open the chamber to look at it closer, but fortunately it released the optic.

Then I brought the slider back to 0.8, and it looked still free swinging. Possibly the optic had been stacked on some of the OSEMS as Jamie expected.

Quote from #5320

ITMY, which is supposed to be fully free-swinging at the moment, is displaying the tell-tale signs of  being stuck to one of it's OSEMs. 

Do we have a procedure for remotely getting it unstuck?  If not, we need to open up ITMYC and unstick it before we pump.


  5329   Wed Aug 31 14:50:18 2011 kiwamuUpdatePhotospictures of OSEMs

The pictures that we took are now on the Picasa web site. Check it out.

Quote from #5280

Also, we took photos (to be posted on Picasa in a day or two) of all the main IFO magnet-in-OSEM centering, as best we could.  SRM, BS, PRM all caused trouble, due to their tight optical layouts.  We got what we could.

  5335   Fri Sep 2 13:12:08 2011 kiwamuUpdateIOOtriple resonant box : ready to install

The triple resonant box was checked again. Each resonant frequency was tuned and the box is ready to go.

Before the actual installation I want to hear opinions about RF reflections because the RF reflection at 29 MHz isn't negligible.

It might be a problem since the reflection will go back to the RF generation box and would damage the amplifiers.


(Frequency adjustment and resultant reflection coefficient)

In order to tune the resonant frequencies the RF reflection was continuously monitored while the variable inductors were tweaked.

The plot below shows the reflection coefficient of the box after the frequency adjustment. 


In the upper plot, where the amplitude of the reflection coefficient of the box is plotted, there are three notches at 11, 29.5 and 55 MHz.

A notch means an RF power, which is applied to the resonant box, is successfully absorbed and consequently the EOM obtains some voltage at this frequency.

These power absorptions take place at the resonant frequencies as we designed so.

A good thing by monitoring this reflection coefficient is that one can easily tune the resonant frequency by looking at the positions of the notches.

Note that :

If amplitude is  0dB ( =1),  it means all of the signal is reflected.

If a circuit under test is impedance matched to 50 Ohm the amplitude will be ideally zero (= -infinity dB).


Reflections :

at 11 MHz = -15 dB (3% of RF power is reflected)

at 29.5 MHz = -2 dB (63% of RF power is reflected)

at 55 MHz = -8 dB (15% of RF power is reflected)

  5337   Fri Sep 2 17:52:16 2011 kiwamuUpdateSUSITMX realigned

The new ITMX was aligned by changing the DC biases.

The resultant DC biases are reasonably small.

C1:SUS-ITMX_PIT_COMM = -0.2909

C1:SUS-ITMX_YAW_COMM = -0.0617


The alignment was done by trying to resonate the green light in the X arm cavity.

The spot position of the green light on the ITMX mirror looked good. This was confirmed by inserting a sensor card.

I did the OSEM mid-range adjustment and the rotation adjustment but at the end the OSEM DC voltage has changed due to the DC bias operation.

The OSEM rotation was approximately optimized so that all the face shadow sensors are sensitive to the POS motion but the SIDE shadow sensor is insensitive to the POS motion.

It needs a free swinging diagnosis.

  5338   Fri Sep 2 17:57:18 2011 kiwamuUpdateSUSRe: ITMY released without opening chambers

It stacked again . We should take a closer look at it.

Quote from #5326

The ITMY mirror was released. The OSEM readouts became healthy.


  5339   Sat Sep 3 14:47:50 2011 kiwamuUpdateIOOtriple resonant box : brief estimations about reflections and mode. depths

(RF reflections)

The reflected RF power going back to the RF generation box will be :

    Power at 11MHz =  2 dBm

   Power at 29.5 MHz = 3 dBm

   Power at 55 MHz = 9dBm

Assuming the input power at 11 and 55 MHz are at 27 dBm (40m wiki page). And 15 dBm for 29.5 MHz.

Since there is an RF combiner in between the generation box and the resonant box, it reduces the reflections by an additional factor of 10 dB (#4517)

In the estimation above, the reduction due to the RF combiner was taken into account.


(Modulation depths)

Besides the reflection issue, the circuit meets a rough requirement of 200 mrad at 11 and 55 MHz.

For the 29.5 MHz modulation, the depth will be reduced approximately by a factor of 2, which I don't think it's a significant issue.

So the modulation depths should be okay.

Assuming the performance of the resonant circuit remains the same (#2586), the modulation depths will be :

      Mod. depth at 11 MHz =  280 mrad

      Mod. depth at 29.5 MHz = 4 mrad (This is about half of the current modulation depth)

      Mod. depth at 55 MHz = 250 mrad


Quote from #5336

What are the reflected RF powers for those frequencies? 
Is the 29.5MHz more problem than the 55MHz, considering the required modulation depth?


  5345   Tue Sep 6 17:48:57 2011 kiwamuUpdateSUSfree swinging test on ITMY

Tue Sep  6 17:48:02 PDT 2011

  5359   Wed Sep 7 16:21:35 2011 kiwamuUpdateLSCarm loss measurement : resluts

Here are the results of the arm loss measurements, which I have done before the vent.

I ran the existing matlab script, called 'armLoss.m', to estimate the loss. The script resides in /scripts/LSC.

(Y arm)

 Round trip loss =  154.668624 +/- 11.343204 ppm


The figure above is a time series of the measurement.

In the lower plot the power in the ASDC_PD are plotted. The green dotted-curve is the power when the Y arm is unlocked.

The blue dotted-curve is the one when the Y arm is locked.

In the upper plot the estimated loss from each combination of locked/unlocked power are plotted.


(X arm)

Round trip loss = ????? 50 ppm ?????

The obtained time series looked wired because difference in the ASDC power when the arm was locked/unlocked were small.

This small difference results in such a small loss.

To see what was going on I will look at the trend data.


Quote from #5077

I did the measurement of the arm loss on both X and Y arm by running the armLoss script.

The results will be posted later.


  5360   Wed Sep 7 17:28:41 2011 kiwamuUpdateLSCX arm loss measurement : not good

The measurement itself wasn't good.

I looked at the full 2 kHz data which was taken during the time when I was running the arm loss script on the X arm.

The plot below shows the raw data. The X arm was locked and unlocked sequentially several times.

The ASDC power didn't show a significant difference between the state where it is locked and unlocked.

I am not sure why, but It could be because of a misalginment or some kind of mode-mismatching, which can decrease the coupling efficiency of light going into the cavity.




(some notes)

The raw data were analyzed.

I split the ASDC data into two data, (1) low power state, when the cavity is locked (2) high power state, when the cavity is unlocked.

Then each state was averaged to estimate the averaged ASDC power in each case.

The number I obtained are :

    ASDC when X arm was locked = 54.77755 cnts

    ASDC when X arm was unlocked = 55.45830 cnts

Those numbers correspond to a round trip loss of  78.780778 ppm, which sounds too small for me.

Quote from #5359

To see what was going on I will look at the trend data.


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