I calculated the MC1&3 Vs WFS1&2 Output Matrix today from the above measurements with koji's help.

the matrix can be generated from the m file at /cvs/cds/caltech/users/nancy/Align_Matrix/matrix.m

these values were put in, and the direction of control is sort of confirmed. I tried twiddling with the gains in the loop to get a 4*4 stable control, but could not succeed.

the mode cleaner is back locked now, and WFS matrix as well as gains are reverted to the old values.  (1.30 am)

The output Matrices are

Pitch

Yaw

 I realised today morning that there was a flaw in my calculations for the yaw matrix.

Correcting the values, and also making teh tables more readable.

I will test these values once our computers are back to working condition.

Upon Nancy's request, I checked the status of the suspensions.

I found that the power strip of the 1Y4 rack was turned off.
Since it has a over current breaker, I don't know whether it happened by someone or over current.

Anyway, I restarted the sus computers, and now the suspensions are damping as usual.
The MC has been aligned, the auto locker is also working.

Incidentally, I found that the WFS servos are not working. Actually since the last night
It repeated losing lock and unlock.

Probably some values of the matrix or the gain is wrong.
I left the WFS as it is because Nancy will put new values this afternoon.
I will ask her to confirm that the old values work at the end of her work.

 Yesterday , I put in the Output Matrix, and changed the gain sliders for the 4 WFS loops.

It worked and was keeping the lock for the MC.

I then tested whether the MC1 and 3 were following any change in MC2 alignment. It was indeed workinng,

Next we stepped to putting in the gains for the MC2 oplev servo.

the signs are decided on the basis of convergence, and the magnitude is kept very low, to have a very slow control for MC2.

This complete 6 * 6 model does work, and was able to keep the transmission held.

I also tried poking each mirror in pitcg and yaw, and the cavity comes back to high resonance after some time.

This time is indeed large if the poking is made for MC2, and the transmission comes back to normal after big oscillations.

I tried to measure the Open loop TFs for all these loops yesterday, but somehow could not find a correct excitation.

I will do it today.

Plan ahead :

1.  Center the spot on MC2 and the QPD

2. Optimize the gains by looking at response to noise.

3. Measure Power Spectrum Density of each error signal.

Nancy has the Mode Cleaner for her work for the night, and is going to leave the MC happy, locked, autolocker on, WFS enabled, the works, and write down in the elog the time that she's finished. After that, I'm taking MC/seismic data all weekend long.  During the weekend, if at all possible, please don't go into the IFO room, especially near the Mode Cleaner.  If you do need to go into the IFO room, please elog the time you went in, and the time you left so I can correlate it with my data.  This is actually important, so please stick a quick elog entry in if you even think about opening the doors to the IFO room. It is much appreciated. 

From how much to how much have you chnged the gain?

I like to put the credit to Aidan for teaching Nancy how to use FOTON.

This should be in this size:

This complete 6 * 6 model does work,
and was able to keep the transmission held.
Yeeeeah!

Question:

Do you like to keep the WFS turned on?

This may change the transfer functions between the ground motion to the angle time by time,
and thus change the TF between the GND and the MCL.

From how much to how much have you chnged the gain?

I changed the gains from all 4 0.01 to o.27, 0.23, 0.32 and 0.11 and the main alignment gain to be 0.8

I like to put the credit to Aidan for teaching Nancy how to use FOTON.

 Yes, I am sorry for not mentioning this.

Thanks Aidan

 E-log entry for Friday - will attach more plots to this entry on wednesday after i am back   to the 40.

Status	MC_Trans	MC_REF
New Control ON
New Control OFF
Old Control ON

The WFS and QPD servos were working. That was great.
Everything was fine except for the time series plots.

I could not get what story you are telling with the time series.
(e.g. your's are good or bad or anything)

 Well, the data is kind of not enough to be analysed in time domain,

But by far from what I analyse, I think that the new control is not worse than the old one.

I donot also find any better results, except for this one being theoritically stronger.

(Rana, Koji, Kiwamu, Suresh, Yuta)

 We attempted to lock the MC and finally got flashes of the MC, but no luck. 

Tomorrow we are going to check every components one by one to make sure if everything is okay or not.

Background:
 MC suspensions are well damped now.
 We need MC locked for the alignment of the in-vac optics.

Issues:
  These are the issues which we are going to fix.
1. DC alignment of the MC2 suspension doesn't seem to be working correctly. (see here)

  We should check the satellite box and the cable connection.

  The coils look like woking fine because we can kick MC2 by using each of the coils.

2. Incomplete modematching.

The spot size of the reflected light from MC1 looked like bigger. 

3. beam axis of the injection light to MC1

Steve measured an apparent power drop in the 2W NPRO output from 2.1W to 1.6W(elog entry no 3698) at 2.1A of diode current in the laser (elog entry:  2822).  It was later noticed that the laser temperature was set to about 45 degC while the initial calibration was done at 25 deg C.  

It was felt that the recent power drop may have something to do with the increase in the operating temperature of the laser from 25 to 45 deg C.  Therefore the laser was returned to 25 deg C and the power output was remeasured and found to be 2.1W as it was at the begining(elog entry:3709)

It was also noticed that returning the laser to 25 deg. C resulted in a loss of efficiency in coupling to the PMC.  We suspected that this might be due to multimode operating conditions in the laser at particular operating temperatures.  In order to see if this is indeed the case the laser power output was observed as a function of temperature.  We do notice a characteristic saw-tooth shape which might indicate multimode operation between 39 and 43 deg C.  It is best to verify this by observing the power fluctuations in the transmitted beam of the stabilised reference cavity.

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. 

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 power meter used in the measurements of elog entries 2822, 3698 and 3709 was the Ophir PD300-3W.  This power head has several damaged patches  and a slight movement of the laser spot changes the reading considerably.  To verify I checked the power out with another power meter (the Vector S310) and found that there is no significant variation of the power output with the temperature of the laser.  And the power at 2.1A of diode current is 2W with 10% fluctuation arising from slight repositioning of the laser head.  There are regions of the Ophir PD300 which show the laser power to be about 1.9W.

[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.

(Rana, Koji, Suresh, Yuta, Thanh, Kiwamu)

 MC was locked successfully !

 Instead of feeding back the signal to the MC length we just injected it to the NPRO pzt with a high voltage (HV) amplifier.

So now we can move on to an in-vac work which needs the main beam to align the stuff.

(mode matching to MC)

Suresh and Thanh (a visitor from ANU) improved the mode matching to the MC. 

As written in the entry #3779  the beam after the mode matching lenses were diverging.

It is supposed to converge from 1.7mm radius at the last lens to 1.6 mm radius at the middle point of MC1 and MC2.

They slided the last lens toward the MC to make it more collimated and roughly measured the beam size using a sensor card.

As a fine tuning, they looked at some higher order modes showing up in the MC2 camera, and tried reducing the higher order modes by slightly sliding the last lens.

(assuming the lens position doesn't so much change the alignment)

During the work we removed a steering mirror for green locking because it was on the way of the lens slider.

- - measured optics' distances - - 

25.5 cm  from 1st lens to the front surface of the EOM

5.5 cm  length of the EOM

24.5 cm from the front surface of the EOM to the 2nd lens (concave)

15.5 cm  from the 2nd lens to the 1st steering mirror in the zig-zag path

20.5 cm  from the steering mirror to the last lens

(preparation for locking) 

Rana, Yuta and Koji prepared an old instant amplifier which can produce +/-13V output instead of usual SR560s.

We added an offset (~5V) on the signal to make it within 0-10V which is the input range of the HV amplifier.

If we take SR560, it's probably not sufficiently wide range because they can handle handle only about +/-4V.

We strung a cable from Marconi via the RF stabilizer to the wideband EOM in order to drive the EOM at 24.5MHz.

SInce the EOM doesn't have 50 Ohm input impedance we had to put a 50 Ohm load just before the EOM in order to drive it efficiently.

From a medm screen we set the driving RF amplitude slider (C1:IOO_MCRF_AMPADJ) to 0.0, which provides the maximum RF power on it.

(locking mode cleaner)

At first we unlocked the PMC to see an offset in the error signal without any lights on the MC_REFL PD.

Then we adjusted the offset to zero on the MC servo screen.

At the beginning of the locking the PMC was not stable for some reasons during the MC was locked.

But after increasing the laser power to the MC twice bigger, it looks like the PMC and the MC are quite stable.

(Rana, Suresh, Jenne, Kiwamu, Kevin, Yuta)

Summary:
  Last night we locked MC by feeding back the signal to NPRO PZT.
  But it was not so stable.
  We wanted more gain to lower the seismic motion, but we don't need high gain in high frequency part(>~1kHz) because it may cause something bad(NRPO PZT oscilatting, PMC not able to catch up with the NPRO frequency change, etc).
  So, we put DC gain boost today.
  It successfully made MC locking stable!

What we did:
1. Lowered the main laser temperature from 32.2° C to 31.8° C.
  When we increased the laser temperature, PMC transmission get lower.  32.2° C was on the cliff, so we put it to plateau region.

2. Lowered the gain of PMC servo (2dB instead of 8dB last night), because PMC was oscillating.
  We got 5.3V OMC transmission.

3. Made 3Hz pole, 30Hz zero filter and put in NPRO PZT servo loop.
  0dB at DC, -20dB at high frequency (see Kevin's elog #3802)

4. Put more gain to NPRO PZT servo loop to compensate -20dB at high frequency.
  In a word, we put DC gain boost.
  Attachment #1 is the MEDM screen screenshot for MC servo.

5. Aligned the beam into QPD at MC2 trans.
  We put lens in front of the QPD.
  Now, we can see the actual motion of the beam, and resonance peaks(Attachment #2; not locked at the highest).
    (We added 30Hz LPF after each 4 quadrant inputs to reduce noise)

Plan:
 - optimize MC suspension alignments
 - activate OL DAQ channels
 - reduce RFAM
 - install tri-mod box
 - QPD signal at MC2 should be more high(currently, ~7counts which equals to ~4mV)
 - change temperature of X-end laser to get green beat

To get the angle to length signal before the c1ioo processor gets going, we need a length signal. We can use either the error signal or the control signal.

I recommend using the control signal since its not puny. The 4-pin LEMO inputs to the OSEM ADC that Suresh has wired are differential so we can, in principle, use either the BNC output of the SERVO plug or the 2-pin LEMO output.

The analog whitening on the OSEM Whitening board should be engaged via the SUS MEDM screen so that we get a good SNR at the A2L dither frequencies.

If the ADC saturates, then we should use a pomona box RC low pass to cut everything off above 100 Hz.

Also, a comment about Yuta's elog: we estimated that the seismic motion was ~1e-7 - 1e-6 meters. The MC linewidth ought to be ~lambda/(2*Finesse) ~ 1e-9.

So, the MC servo as it was was not giving us enough gain (1/f above 50 Hz; UGF ~5-10 kHz) to get the error signal to stay in the linear PDH region. Kevin's filter gave us ~10x more gain at the seismic frequencies (1-3 Hz) of concern.

[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.

(Suresh, Kiwamu, Yuta)

Summary:
  Lastnight, we locked the MC and tried angle to length(A2L) measurement using my new python script (see elog #3863).
  Although the amount of position script shows looks too big, the response seemed somewhat reasonable.
  Using the results of A2L measurement, we managed to reduce the displacement from the center of the MC optics, but we lost TEM00 mode after changing the incident beam direction and PMC lock got off .
  We restored the alignments and now it is 00, but the displacements got worse than the best we achieved last night.

  I think I have to rethink how to align MC. Even if I could somehow get exact position of the beam, how to align the beam to the center of the optics?

What we did:
  1. At first we tried to align by changing the direction of the incident beam. We found that A2L.py shows opposite direction(lower <-> upper). It was because of my misunderstanding and we agreed that the direction is opposite.

  2. Aligned MC optics without changing the direction of the incident beam. We could understand which directions decrease the displacements from the center, and managed to decrease them.

  3. There seemed to be a limit in aligning the MC optics without changing the incident beam direction. So, we started to change the incident beam direction again by steering mirrors at PSL table.

  4. During the change, PMC lock got off. We restored it, but we lost MC's 00 mode.

  5. We restored MC 00 mode, and measured the final A2L. The result was worse than we achieved by step #2.

Result:
  The final result from last night using my script was as follows;

  % is the length compared to the half of coil to coil length. Low / right are positive.
  We can see the beam position got better by looking at the monitor from MC2, and the A2L measurement result agrees with that.

  Here's some pictures from the measurement last night. Each plots are not taken at the same time.

   (It was painful using slow computers to make measurement. The StripTool graph shows straight lines when computers got frozen)

Plan:
 - Plan a strategy
 - The script needs self-estimation of the measurement. Now, the script fits the plot assuming every data has the same error.
 - When the beam is near the center, the signal gets smaller and the result will be unreliable. One thing I can do is to change TO_COIL gains radically so that the axis of rotation go far from the center.

We like to have the MC TRANS channels so that we can run all of our old scripts and trends on it. This is the usual BROWN

channel that's on the LockMC screen. Its also the thing that we use for thresholding to activate the MC Autolocker Daemon.

I modified the ioo.db file in the target/c1iool0/ directory so that the MC_TRANS_SUM, _P, and _Y channels are all now just

CALC records of the MC2 OL channels (where the calculation is MC_TRANS_SUM = MC2 OL_SUM + 0.001, etc.). I then

rebooted c1iool0 a few times to get the syntax right. It SEEMS to be working now. I'm sure that this won't effect anything.
I've committed the new file to the SVN repo. Once Suresh is done hacking the QPD circuit, we can set the threshold in the Autolocker.

[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.

(Koji, Suresh, Yuta)

Summary:
  We need MC to be locked and aligned well to align other in-vac optics.
  By using a new python script A2L.py(see elog #3863), we are measuring A2L coupling and centering the beam.
  Tonight's goal was to reduce common mode displacement of the beam through MC1 to MC3, and we succeeded.

Strategy of beam centering:
  We first ignore the beam position at MC2 and focus on MC1,MC3. If MC1,MC3 alignments are given, MC2 alignment is determined.

  For MC1 and MC3, we first reduce the common mode displacement using the last steering mirror at PSL table.
  The last steering mirror makes translation of the incident beam because it is far (~m) from the MC.
  So,
    1. Rotate the steering mirror nob a little
    2. Lock MC so that MC beam axis will be the same as the incident beam axis
    3. A2L measurement
    4. To 1-3 over until the beam crosses MC1 center to MC3 center axis
        The amount of vertical/horizontal displacements of the beam spot at MC1 and MC3 should be the same.
        From our convention, for vertical, MC1 and MC3 should have opposite sign. For horizontal, same sign. (see picture below)

Result:

 
  From the A2L measurement, now the beam spot is lower right at MC1 and upper right at MC3.
 

  The directions of the beam spot motion agree with the steering mirror tilts.
  Also, the amount of the motion seems reasonable.
    1 tooth rotation of the steering mirror nob makes ~1e-3 inch push which equals to ~0.5mrad rotation.
    The steering mirror to MC is like ~2m and 0.5mrad mirror tilt makes ~2mm displacement at the MC optics.
    2mm displacement is ~15% at the mirror (see Koji's elog #2863;note that coil-coil distance is 1/sqrt(2) of the mirror diameter).
    The measured vertical spot motion is ~15%/1tooth. Horizontal is sqrt(2) times bigger because of the angle of the MC1, MC3 and they are about that much, too.

Plan:
 - Use IM1 to make beam tilt and finally center the beam
 - Improve the script so that it features weighting in fitting
 - Write a script that balances actuation efficiency of the 4 coils.
     We are currently assuming that 4 coils are well balanced.
     In order to do the balancing, we need to balance OSEMs too.

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.

Increased the transimpedance gain of the MC-Trans-Mon QPD ckt

The gain of this QPD was insufficient to see the light transmitted through the MC2.  The resulting voltage output was about  10 steps of the 16-bit ADC card.  As the input power, which is currently held at about 40mW may be increased to the vicinity of 2W (total output of the NPRO) we would have 500 ADC steps.  But the dynamic range of the ADC is 64k and  increasing the gain of this QPD ckt by a factor of 50 would enable us to utilise this dynamic range effectively.  However as we do not need a response faster than 10Hz from this ckt its response time has been limited by increasing the feedback capacitance value.

The ckt diagram for the QPD ckt is D980325-Rev-C1  .  The particular unit we are dealing with has the Serial No. 110.  The resistors R1, R2, R3, R4 are now 499 kOhm.  As per the guidelines in the ckt diagram, we increased the capacitance values C3,C4,C5,C6 to 2.2 nF.  The current cut off frequency for the MC-Trans-Mon is 145 Hz (computed).

Initially, while reassembling the QPD unit, the IDC 16 connector to the ckt board was reversed by mistake and resulted in the OP497 chip over-heating.  Consequently one of the opamps on the chip was damaged and showed monotonously increasing ouput voltage.  Todd Etzel gave us a spare OP497 and I replaced the damaged chip with this new one. The chips are also available from  Newark Stock No. 19M8991 . The connector has been marked to indicate the correct orientation. The ckt was checked by temporarily connecting it in the place of the PRM Optical lever QPD.  It worked fine and has been put back in its place at the MC2 Transmission.  The QPD was wiped with a lens tissue+Methanol  to remove dust and finger prints from its surface.

It may need to be repositioned since the beam would have shifted under the MC realignment procedure.

(Suresh, Yuta)

Background:
  Last week, we reduced the common mode displacement of the beam through MC1 to MC3. 
  Next work is to tilt the beam and center it.

What we did:
  1. Changed the offset going into 1201 Low Noise Amplifier(1201 is for adding +5V offset so that the feedback signal will be in the range of 0-10V)
  2. Using the last steering mirror(SM@PSL) and IM1, tilted the beam
  3. As the beam height changed alot(~0.5cm higher at IM1), MC1 reflection could not reach MCREFL PD. So, we tilted the mirror just after MC1, too.

Result:


Plan:
  - continue to tilt IM1 in small increments in order to reduce PIT/YAW to length coupling
      If large increments, it takes so much time re-aligning MC to get flashing!

By the way:
    The signal we kept saying "MCL" was not the error signal itself. It was a feed back signal(output of the mode cleaner servo board). The cable labeled "MC REFL" is the error signal. Compare MEDM screen C1IOO_MC_SERVO.adl and the mode cleaner servo board at 1X2. You will be enlightened.

(Suresh, Yuta)

Summary:
  We need MC to be locked and aligned well to align other in-vac optics.
  We continued to align the incident beam so that the beam passes the actuation nodes of MC1 and MC3.
  From the previous measurement, we found that beam height at IM1 has to be increased by ~3cm.
  Today, we increased it by ~1cm and achieved about 1/3 of the required correction.
  But we cannot proceed doing this because the beam is hitting IM1 at the edge already.

What is the goal of this alignment?:
  If the beam doesn't hit MC optics in the center, we see angle to length coupling, which is not good for the whole interferometer.
 
  Also, if the beam is tilted so much, transmitted beam though MC3 cannot go into FI at right after MC3.
  Say, FI has an aparture of 3mm and MC3-FT distance is 300mm. The beam tilt should be smaller than 3/300 rad. MC1-MC3 distance is 200mm, so the displacement at each mirror should be smaller than ~1mm.
  1mm is about 7% (see Koji's elog #2863) TO_COIL gain imbalance in A2L measurement.
 
  We are currently assuming that each coils are identical. If they have 5% variance, it is meaningless to try to reduce the beam displacement less than ~5%.

  So, we set the goal to 7%.

What we did:
  1. Leveled the MC table.

  2. Measured the table height using DISTO D3 laser gauge.
    PSL table 0.83m (+-0.01m)
    OMC table 0.82m
    MC table  0.81m

  3. Using the last steering mirror(SM@PSL) and IM1, tilted the beam vertically

Result:


  At t=0 (this morning), the beam tilt was ~40%/(MC1-MC3 distance). Now, it is ~30%/(MC1-MC3 distance).
  30%/(MC1-MC3 distance) is ~5/200 rad.

Plan:
 We have to somehow come up with the next story. Too much vertical tilt. What is wrong? Table leveling seems OK.
 - measure in-vac beam height
 - maybe OSEMs are badly aligned. we have to check that.

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?

1. We didn't measure the aperture size last night. We have to check that.

2. We have to measure the length of FI. Or find a document on this FI.

3. Yes, 5%/sqrt(4). But I didn't think the factor of 2 is important for this kind of estimation.

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.

For Yuta's business, I intentionally misaligned the wideband EOM slightly to Yaw direction.  Good luck.

It should show a big AM component at photo detectors.

I touched only the top right knob on the EOM mount and tweaked it by exactly  2 turns in counterclockwise direction.

(Suresh, Yuta)

Background:
  Previous A2L measurement is based on the assumption that actuator efficiencies are identical for all 4 coils.
  We thought that the unbelievable "tilt" may be caused by imbalance of the coils.

Method:
  1. Setup an optical lever.
  2. Dither the optic by one coil and demodulate oplev outputs(OL_PIT or OL_YAW) in that frequency.
  3. Compare the demodulated amplitude. Ideally, the amplitude is proportional to the coil actuation efficiency.

What we did:
[MC2]
  MC2 is the least important, but the easiest.
  1. Placed a red laser pointer at MC2 trans table. During the installation, I moved the mirror just before QPD.
  2. Made a python script that measures coil actuation efficiency using the above method. I set the driving frequency to 20Hz.
  It is /cvs/cds/caltech/users/yuta/scripts/actuatorefficiency.py.
  The measurement result is as follows. Errors are estimated from the repeated measurement. (Attachment #1)

MC2_ULCOIL 1
MC2_URCOIL 0.953 ± 0.005
MC2_LRCOIL 1.011 ± 0.001
MC2_LLCOIL 0.939 ± 0.006

[MC1]
  For MC1, we can use the main laser and WFS1 QPD as an oplev.
  But we only have slow channels for QPD DC outputs(C1:IOO_WFS1_SEG#_DC).
  So, we intentionally induce RF AM by EOM(see Kiwamu's elog #3888) and use demodulated RF outputs of the WFS1 QPD(C1:IOO_WFS1_I/Q#) to see the displacement.
  1. Replaced HR mirror in the MCREFL path at AP table to BS so that we can use WFS1.(see Koji's elog #3878)
    The one we had before was labeled 10% pick-off, but it was actually an 1% pick-off.
  2. Checked LO going into WFS1 demodulator board(D980233 at 1X2).
    power: 6.4dBm, freq: 29.485MHz
  3. Turned on the hi-voltage(+100V) power supply going into the demodulator boards.
  4. Noticed that no signal is coming into c1ioo fast channels.
    It was because they were not connected to fast ADC board. We have to make a cable and put it in.

[MC3]
  Is there any place to place an oplev?

Plan:
 - prepare c1ioo channels and connections
 - I think we'd better start A2L again than do oplev and coil balancing.

We decided to ignore the computer script outputs for the beam positions and use instead the eyeball method to get the beam into the MC:

1. Adjust PSL launch beam to get the beam centered on IM1.
2. Eyeball the beam to hit the center of MC1. We can get this pretty good by using the brackets to get the vertical and using the centering of the input/refl beams to center it horizontally.
3. Use MC3 suspension to hit the center of MC2. We did this by hitting each of the 3 EQ stop screw heads and triangulating the MC3 bias settings.
4. Use MC2 bias to hit the center of MC1.
5. Use MC1 to get good flashes.
6. Use all 3 MC sus biases to maximize the transmitted light and minimize the REFL DC.

With this rough alignment in place, we leave it to Yuta to finish the coil balancing and the A2L. We will have an aligned MC in the morning and will start the BS chamber alignment.

Background:
  Last night, we found that one of DAC channels are poorly connected, so we fixed the connectors.
  Rana and Koji used their incredible eyeballs to roughly align MC.
  Next thing to do is to balance the coils, but it takes some time for the setup.
  So, we decided to do A2L anyway.

What I did:
  Using the last steering mirror at PSL table and IM1, changed the incident beam direction to align MC.

Result:

 
  I was amazed by their eyeballs.
  I turned the nobs of SM@PSL and IM1 in small increments, so I never lost TEM00.

Is it enough?:
  The length of the whole faraday is about 20cm and aperture diameter is about 12mm. (I couldn't measure the aperture size of the core)
  The beam is about 9mm diameter at 6w.
  So, if the beam is vertically tilted at more than ~3/200rad, it(6w) cannot go through.
  3/200 rad is about 20% difference in position at MC1 and MC3.
  So, the result meets the requirement.

  Also, assuming that coils have 5% imbalance, the beam position I measured have ~3% error.
  So, to do more precise beam centering, we need to balance the coils.

Since we are going to lock the MC today, I aligned it back to the default place.

(Koji, Yuta)

We aligned the Faraday after MC and we are now ready to install PRM.

Background:
  MC was roughly aligned (beam spot ~0.7mm from the actuation center).
  So, we started aligning in-vac optics.
  First thing to align was the Faraday after MC3.

What we did:
  1. Ran A2L.py for confirmation.(Second from the last measurement point on the A2L result plot)

  2. Aligned the Faraday so that MC3 trans can go through it. We moved the Faraday itself, while we didn't touch IM2.
     We turned the pitch nob of the last steering mirror at PSL table in CCW slightly in order to lower the beam at the Faraday by ~1mm.

  3. During the alignment, we found that the polarization of the incident beam was wrong. It should have been S but it was P.
     As there is the HWP right before the EOM, Rana rotated it so as to have the correct polarization of S on the EOM and the MC.
     Note that the PMC and the main interferometer are configured to have P-pol while the MC is to have S-pol.

  4. Setup the video camera to monitor the entrance aperture of the Faraday. It required 4 steering mirrors to convey the image to the CCD.

  5. Moved all of the OSEMs for MC1 and MC3 so that the sensor output can have roughly half of their maxima.

  6. Ran A2L.py. (The last measurement point on the A2L result plot)

  7. Aligned the IO optics so that the beam goes Faraday -> MMT1 -> MMT2 -> SM3.

Result:
  1. OSEM sensor outputs for MC1 and MC3 are;

  2. A2L result is;



     The beam position slightly got lower(~0.2mm), because we touched SM at PSL table.
     Alignment slider values changed because we moved MC1 and MC3 OSEMs.

  3. Now, MC_RFPD_DCMON is ~0.39 when MC unlocked and ~0.083 when locked.
     So, the visibility of MC is ~79% (for S-pol).

  4. Now the incident beam to the MC has S polarization, the cavity has higher finesse. This results the increased MC trans power.
     It was ~8e2 when the polarization was P, now it is ~4.2e3 when the MC is locked.

  5. The beam reached SM3 at BS table. The alignment of the SM2, MMT1, MMT2 were confirmed and adjusted.

  6. All pieces of the leftover pizza reached my stomach.

Plan:
  - Install PRM to the BS chamber.
  - Align PRM and get IFO reflection beam out to the AP table
 

(Kiwamu, Yuta)

Background:
  Yesterday, we aligned the Faraday and the beam reached SM2 at BS table.
  Today, we placed a new PRM tower to BS table.

What we did:
  1. Moved IPPO, IPPOSSM1, IPPOSSM3, IPANGSM1, IPANGSM2 out from the BS chamber.

  2. Moved SRM tower(at PRM's place) to the ITMX chamber.

  3. Placed the new PRM tower at the BS chamber.

  4. Adjusted positions of the OSEMs for PRM and BS so that the sensor output can have roughly half of their maximum.

  5. Checked damping servo for PRM and BS. They were working and helped us when adjusting OSEM positions.

  6. Placed IPPO back and using SM2, made the beam hit PR2 at ITMX table.

  7. Aligned the PRM so that the reflected beam path overlaps the incident beam.
     We checked it by looking at MMT1.
     For the alignment, we used IFO align sliders(C1:SUS-PRM_PIT_COMM, YAW_COMM).
        To use them, we rebooted c1susaux.

Result:
  1. The new PRM tower is placed.

  2. OSEM sensor outputs for PRM and BS are;

    We changed PRM aligning slider values, and they changed OSEM sensor outputs. We set the slider values to 0 when adjusting OSEM positions.

(Kiwamu, Yuta)

Summary:
  Yesterday, we placed the new PRM to BS chamber and the beam reached PR2 at ITMX chamber.
  Today, we lead the PRM reflected beam back to AP table.
  Also, we aligned PRs so that the beam hits ITMX and ITMY.

What we did:
  1. Aligned PR2 at ITMX chamber and PR3 at BS chamber so that the beam hits ITMY.

  2. Aligned ITMX using IFO_ALIGN sliders so that the reflected beam overlaps at BS.

  3. Aligned BS using IFO_ALIGN sliders so that the splitted beam to ITMX overlaps the green beam from the X-end.

  4. Roughly aligned ITMY using IFO_ALIGN sliders so that the reflected green goes to far x-end.

  5. From yesterdays in-vac work, the reflected beam from PRM reached the Faraday.
     Aligned 2 steering mirrors in MC chamber so that the beam reaches AP table.

  6. Found the beam is double-spotted by a steering mirror at just after the Faraday symmetric port.
      The mirror is Y1-2037-45S. The beam is hitting it in ~10deg, so we have to replace it.

Plan:
  - replace the steering mirror right next to the Faraday symmetric port.
  - recyled Michealson

Note:
  We had to use "ITMX" channels to align ITMY. We have to fix and check X-Y confusion.
  Also, damping servo for ITMs does not seem to work. We have to check this.

[Kiwamu/Koji]

- The tanks are open

Plan

[done] - Remove the PZT cable currently underlying between BS and ITMY chambers
[done] - Put this PZT cable between BS and IMC chambers. Connect it on the PZT on the IMC table (SM1)
[done]- Put the two OSEM cables between BS and ITMY chambers. Connect this cable to SRM.
  The connector for this cable at the BS side is coming from Bob's place on Wednesday. We left it disconnected for now.

- Energize all of four PZTs and check the functionality.

 [Suresh, Kiwamu]

We found that two of three PZT mirrors are at wrong place in the chambers.

Therefore we have to move these PZT mirrors together with their connections.

Here is a diagram for the current situation and the plan.

  Basically mirror (A) must be associated to the output beam coming out from the SRM, but it was incorrectly put as a part of the input optics.

Similar to that, mirror (C) must belong to the input optics, but it is incorrectly being used as a part of OMC stuff.

Therefore we have to swap the positions of mirror (A) and mirror (C) as shown in the diagram above.

In addition to the mirror immigration, we also have to move their cables as well in order to keep the right functions.

 We took a look at the length of the cables outside of the chambers in order to check if they are long enough or not.

And we found that the cables from c1asc (green line in the diagram) is not long enough, so we will put an extension D-sub cable.

This morning I opened the chambers and started some in-vac works.

As explained in this entry, I swapped pzt mirror (A) and (C) successfully.

The chambers are still open, so don't be surprised.

(today's missions for IOO)

 - cabling for the pzt mirrors

 - energizing the pzt mirrors and slide them to their midpoint.

 - locking and alignment of the MC

 - realignment of the pzt mirrors and other optics.

 - letting the beam go down to the arm cavity

As a result of the vacuum work, now the IR beam is hitting ETMX.

The spot of the transmitted beam from the cavity can be found at the end table by using an IR viewer.

  [Jenne, Koji and Kiwamu]

 We finished a coarse alignment of IP_ANG.

 The beam for IP_ANG successfully reached to the ETMY chamber and is ready for the final alignment.

 (Additionally we again tried looking for a resonance for TEM00 in the X arm, but we obtained only flashes of some higher order modes.)

--- what we did

 * installed the steering mirrors for IP_ANG and IP_POS.

 * checked PZT1 if it worked correctly or not. It was healthy.

 * neutralized and realigned PZT1.

 * flipped a window, which is standing before PRM, because the wedged side of the window was at wrong side.

 * realigned PZT2 and checked the spot positions on the TTs.

 * repositioned more carefully the TTs and aligned them to the correct angles.

 * aligned the beam to the center of both the BS and ITMY by rotating the last TT.

 * aligned the beam more precisely by tweaking PZT2 while looking at the spot at the Y end.

         The beam is still hitting the center of ETMY.

 * aligned the steering mirror for IP_ANG while looking at the spot at the Y end.

        In fact IP_ANG is visible with a card. 

 * aligned the BS by looking at the spot on ITMX.

 * covered ETMX with aluminum foil, and made a ~1cm hole on the foil as a target.

         The hole was placed on the center of ETMX.

 * more precisely aligned the BS by looking at the spot on the aluminum foil.

         The spot was clearly visible on CCD monitor.

 * aligned the ITMX by looking at a spot on the foil. The spot represented the beam reflected by ITMX back to ETMX.

 * saw flashes on the foil but couldn't make it TEM00 because it was difficult to see any flashes on the surface of either ETMX or ITMX.

        It means the flashes are visible only when the beam is hitting some scattering surface.

        The mirror surface of the test masses are less lossy than that of the old test masses ??

What else?

v: Edit on Dec 15 10PM
v: Edit on Dec 16 10PM


JD:  We should check OSEMs for all optics *after* table leveling.  Some of them (esp. BS and ITMX) are currently close to their limits right now.

KA: Check green alignment.

Take photos of the tables.

Fix the leveling weights


Location    Optics            Action
--------------------------------------------------------------
@ITMX -     v POX             alignment
            v POP1/POP2       alignment
            v Table Leveling

@ITMY -     POY               mirror replacement (45deg->0deg) / alignment
            v SR2-TT          alignment
            v SRM Tower       alignment / EQ-stop release
            v SRM             alignment
            v SRM OSEM
            vvSRM OPLEV (X2)  install (VIS)/ alignment
            v ITMY OPLEV (X2)   install (VIS)/ alignment
            v OM1/OM2         install (DLC 45deg)/ alignment       
            v Table Leveling

@BSC -      v OM3             install (DLC 45deg/ alignment)
            v OM4(PZT)          neutralize, adjustment
            IPPOS steering    alignment
            v BS OPLEV        alignment
            v PRM OPLEV(x2)     alignment
            Beam dumps
            Table Leveling

@IMC -      v REFL              mirror replacement　(45deg->0deg)

@ETMX -     Al foil removal
            Table Leveling

@ETMY -     ETMY damping
            OSEM
            OPLEV
            Al foil removal
            Table Leveling

@OMC -      v OM5(PZT)        neutralize, adjustment

@ITM/ETM -  Mirror Wiping



I helped the vacuum installation work in the evening.

- Three steering mirrors after the SRM (OM1-OM3) were installed on the table. OM1 and OM2 were aligned.
  OM3 is in-place but not aligned to the OM4 (PZT).

- The ITMY oplev setup was disintegrated. The SRM/ITMY oplev beams were prepared.

- The SRM oplev mirrors were placed on the table and aligned.

- The ITMY oplev mirrors were placed on the table but not in-place.

[Steve and Koji]

The invac OPLEV mirrros were aligned before we get to the PMA party.

The OPLEV mirrors were adjusted in accordance with the optical layout.
Surprisingly the optical layout was enough precise such that we have the healthy red beams on the optical tables.
Steve placed the apertures at the position of the returning spots while I shook the stack to check if the range of the spot motion is sufficient.

The sole thing that has been deviated from the optical layout was that the SRM returning beam had to be reroute
as the SRM has better reflectivity on the AR surface in stead of the HR one.

[Koji and Kiwamu]

We obtained two dark port beams on the AP table: OMC REFL and AS

- First, IPANG and BS were aligned so as to have the beams on the center of the ETMs.

- Then ITMX/ITMY/PRM/SRM were aligned to have fringes in a single spot anywhere.

- As we already had the dark port beam on the steering mirrors on the BS table, today the PZT mirrors were adjusted.
This work was the beam steering between the BS table to the OMC table. After some tweaking of the mirror mounts, 
the spot on the last PZT mirror was found.

As we have not touched any of the OMC optics since they were aligned well, the alignment has been adjusted by the nobs of the PZT steering mirrors.
Once the beam is on the output mode matching telescope (OMMT), the work was quite easy thanks to the beam shrinking by the OMMT.

Note that the dark port beam is slightly clipped by the green steering mirror. The steering mirror will be moved next time.

After the alignment, we indeed obtained OMC REFL and AS beams on the AP table.
The fringes were visible on the OMC REFL CCD.

We keep the dark port setup on the OMC (in-vac) and AP tables so that they can be the reference of the dark port alignment.
In principle we can align the beams onto the OMC by the two PZT mirrors.

What is left?

Our minimum success of this vent is to setup the X arm cavity which is needed for the green locking.
This setup was already realized. So we fulfilled the condition to close the tank even if the damping of
the ETMY is not achieved. (But we should try)

Tomorrow, we make a light touches to POY, Green, IPPOS, and check the table leveling, clamping, etc, in general.

JD:  We should check OSEMs for all optics *after* table leveling.  Some of them (esp. BS and ITMX) are currently close to their limits right now.

KA: Check green alignment. / Take photos of the tables. / Fix the leveling weights

Location    Optics            Action
--------------------------------------------------------------
@ITMY -     POY               mirror replacement (45deg->0deg) / alignment
@BSC -      Green steering    alignment
            IPPOS steering    alignment
            Beam dumps
            Table Leveling

@ETMX -     Al foil removal
            Table Leveling

@ETMY -     ETMY damping
            OSEM
            OPLEV
            Table Leveling

@ITM/ETM -  Mirror Wiping



 [Koji and Kiwamu]

 We did some more vacuum works today. It is getting ready to pump down.

 (what we did) 

 - alignment of the POY mirrors. Now the beam is coming out from the ITMY chamber successfully

  - leveling of the tables (except for the IOO and OMC chamber)

  - realigned the beam axis down to the Y arm because the leveling of the BS table changed the alignments.

 - installed IP_POS mirrors

 - aligned the green beam and made it overlap with IR beam path.

 - repositioned green steering mirrors since one of them are too close to the dark beam path