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ID Date Author Type Categorydown Subject
  2435   Sun Dec 20 23:42:44 2009 JenneUpdateIOONew Input Mode Matching Telescope

I've got most of the new Mode Matching Telescope figured out.  The scripts and an example result are at: MMT09 wiki  (Rather, the scripts are in the svn: MMT svn)

Issues still to be resolved: 

* We're getting pretty iffy 'angles' between tilt and translation when using the mode matching mirrors for steering.

* I haven't taken into account the astigmatism which occurs when you tilt the mode matching mirrors. 

The nifty thing about these scripts is that they take a look at the mode matching overlap:  For each possible mode matching solution it adds noise to all of the distances and radii of curvature during ~10,000 iterations and plots a histogram of the overlap so that we can see which solutions have a better chance of giving us the optimal overlap, even if we place the optics in slightly the wrong place.

 

I'd like to update the overlap part of the script with the astigmatism business:  do we lose goodness of overlap if we tilt the mirrors by a bit?  I think this will require redoing the overlap part with the X and Y directions separate.  Koji has done this in the past.  My current code assumes that the beam is always symmetric in X and Y. 

  2444   Tue Dec 22 11:23:51 2009 kiwamu, SteveUpdateIOOMC relocked

In this morning I found MC unlocked.

Steve restored the watchdogs before I found that.

Then I relocked MC and now MC is locked and working well.

The reflected DC power is ~0.38, which is usual number.

 

  2448   Wed Dec 23 16:34:25 2009 KojiUpdateIOOMCT QPD/MC REFL QPD disabled

For a certain investigation of the sum/diff module for MCT QPD/MC REFL QPD, I removed it from the system.

 

  2451   Thu Dec 24 19:13:29 2009 KojiUpdateIOOMCT QPD investigation

I found that MCT QPD has a dependence of the total output on the position of the spot. Since the QPD needs the supply and bias voltages from the sum/diff amp, I could not separate the problems of the QPD itself and the sum/diff amplifier by the investigation on Tuesday. On Wednesday, I investigated a generic quad photodiode interface module D990692.

...I was so disappointed. This circuit was left uninvestigated and used so long time with the following sorrowful conditions.
- This circuit has 4 unbuffered inputs with input impedance of 300~400 Ohm. It's way too low!
- Moreover, those channels have different input impedances. Ahhhh.
- Even worse, the QPD circuit D990272 has output impedance of 50 Ohm.
- The PCB of this circuit has four layers. It is quite difficult to make modifications of the signal route.
- It is a headache: this circuit is "generic" and used in many places.

D990692 has 4 channel inputs that are not buffered. Each channel has two high impedance buffers but they are used only for the monitors. The signal paths have no buffer.

The differential amplifier is formed by R=1k Ohm. The inverted side of the input has 1kOhm impedance. The non-inverted side has 1.5kOhm impedance.

CH1: 10K // 1.5k // 1.5k // 1k = 411 Ohm
CH2: 10K // 1.5k // 1k // 1k = 361 Ohm
CH3: 10K // 1k // 1k // 1k = 323 Ohm
CH4: 10K // 1k // 1.5k // 1k = 361 Ohm

Considering the output impedance of 50Ohm for the QPD, those too low input impedances result in the following effect:
- Because of the voltage division, we suffer absolute errors of 10.8~13.4%. This is huge.
- Because of the input impedance differences, we suffer a relative error of 1.5%~3%. This is also huge.

Unfortunately, the circuit has no room to modify; the signal paths are embedded in the internal layer.

I decided to replace the resistors of the sum/diff amps from 1k to 10k. Also the input impedance of the buffer was removed as the input is terminated by the sum/diff amps in any case.This changes the input inpedance to the followings:

CH1: 15k // 15k // 10k = 4286 Ohm
CH2: 15k // 10k // 10k = 3750 Ohm
CH3: 10k // 10k // 10k = 3333 Ohm
CH4: 10K // 15k // 10k = 3750 Ohm

These yield the absolute error of 1.2-1.5%. The relative error is now 0.3%. I can accept these numbers, but later I should put additional terminating resistors to compensate the differencies.

So far I have modified the resistors for the MCT as the modification for a QPD needs 17 10k resistors.
Next thing I have to check is the dependence of the QPD outputs on the spot positions.

-----------------------------------------------

Edit: Feb 11, 2010

I talked with Frank and he pointed out that the impedances are not the matter but the gains of the each channels are the matters (after considering the output impedance of the QPD channels).
If we assume the ideal voltage sources at the QPD and the symmetric output impedances of 50Ohm, the gain of the each circuit are affected but the change should be symmetric.

He found that several things:
- The analog switch (MAX333) used in the QPD unit adds more output impedance (somewhat randomly!).
- The resistance of the sum/diff circuits may vary each other unless we use 0.1% resistors.

 

Attachment 1: D990692.png
D990692.png
  2473   Mon Jan 4 17:21:30 2010 JenneConfigurationIOOElusive Mode Matching Solution found!

I think I have finally found a Mode Matching solution for our new Input Mode Matching Telescope!  And after looking at the layout diagram with Koji and Raffaele, it seems like all of the optics will fit into the chambers / onto the tables (not true as of last week). 

3. RoCMMT1 is -5m
   RoCMMT2 is 8m,
   with the MMTs 1.89m apart.
   This is a 1.6x telescope.
   MMT2 is 2.2641m from the PRM
   MMT1 is 2m from MC3.
   The Condition Number for this optical chain is 89219047.5781.

This layout is very similar to the one that Koji posted on the wiki yesterday:  Upgrade09/Optical Layout.  The difference is that I want to move MMT1 ~20cm closer to the MC13 table, so just on the other side of the main red beam that goes directly to PRM.  There is plenty of space there, so it should be all good.  The tricky bit is that the flat steering mirrors fit into things now while they are piezos, but they will be trickier to fit if we make them into Tip Tilts.  But I have full faith in Koji's amazing optical table layout skills, that he can make it happen. 

Unless there are major objections, I think this is the MMT that we're going to go with. (So speak now or forever hold your peace.)  The angle between tilt and translation isn't quite what we'd like it to be (at ~18deg), but it's not too terrible.  And we still have 99.5% overlap which is very important.

Attachment 1: Awesome_MM_Solution.png
Awesome_MM_Solution.png
  2481   Wed Jan 6 03:44:41 2010 KojiConfigurationIOOElusive Mode Matching Solution found!

I am in the way to get a reasonable optical layout.
Please calculate the final results with the following conditions.

"Result" =
- mode overlapping with astigmatism
- alignment matrix (m/rad, rad/rad) for Pitch and Yaw
- alignment orthogonality
- sensitivity of the mode overlapping to the perturbations
  * histgram
  * individual scan of the optic positions

Optics chain: MC3 - SM1(flat) - MMT1(f=-5m) - MMT2(f=+8m) - SM2(flat) - PRM

Incident angles: SM1 24deg, MMT1 3deg, MMT2 1deg, SM2 44.5deg

Distances:
MC3 HR - SM1: 884mm
SM1 - MMT1: 1058.2mm
MMT1 - MMT2: 1890mm
MMT2 - SM2: 2007.9mm
SM2 - PRM HR: 495.6mm

It has ~200mm deviation from the solution. I can move only MMT1 for final optimization.
Give us the numbers if it can improve the performance.
Note that this move changes SM1-MMT1 and MMT1-MMT2 simultaneously.

Quote:

I think I have finally found a Mode Matching solution for our new Input Mode Matching Telescope!  And after looking at the layout diagram with Koji and Raffaele, it seems like all of the optics will fit into the chambers / onto the tables (not true as of last week). 

3. RoCMMT1 is -5m
   RoCMMT2 is 8m,
   with the MMTs 1.89m apart.
   This is a 1.6x telescope.
   MMT2 is 2.2641m from the PRM
   MMT1 is 2m from MC3.
   The Condition Number for this optical chain is 89219047.5781.

This layout is very similar to the one that Koji posted on the wiki yesterday:  Upgrade09/Optical Layout.  The difference is that I want to move MMT1 ~20cm closer to the MC13 table, so just on the other side of the main red beam that goes directly to PRM.  There is plenty of space there, so it should be all good.  The tricky bit is that the flat steering mirrors fit into things now while they are piezos, but they will be trickier to fit if we make them into Tip Tilts.  But I have full faith in Koji's amazing optical table layout skills, that he can make it happen. 

Unless there are major objections, I think this is the MMT that we're going to go with. (So speak now or forever hold your peace.)  The angle between tilt and translation isn't quite what we'd like it to be (at ~18deg), but it's not too terrible.  And we still have 99.5% overlap which is very important.

 

  2535   Thu Jan 21 10:09:27 2010 KojiSummaryIOOPhotos of the optical tables

I made a wiki page dedicated for the photos of the optical tables.
The current layouts were uploaded.

http://lhocds.ligo-wa.caltech.edu:8000/40m/Optical_Tables

  2559   Tue Feb 2 13:14:09 2010 KojiHowToIOOAnatomy of New Focus Resonant EOM

Joe let me use the resonant EOM for GigE phase camera for a while.
Then, I immediately started to open it :)

it uses the MiniCIrcuits T5-1T transformer and a TOKO RCL variable inductor.

The photos are on the Picasa 40m album.

http://lhocds.ligo-wa.caltech.edu:8000/40m/40m_Pictures

  2584   Tue Feb 9 17:51:48 2010 JenneSummaryIOOInput Mode Matching Telescope design is complete

The upgrade's input mode matching telescope design is complete.  A summary document is on the MMT wiki page, as are the final distances between the optics in the chain from the mode cleaner to the ITMs.  Unless we all failed kindergarden and can't use rulers, we should be able to get very good mode matching overlap.  We seem to be able (in Matlab simulation land) to achieve better than 99.9% overlap even if we are wrong on the optics' placement by ~5mm.  Everything is checked in to the svn, and is ready for output mode matching when we get there.

  2698   Tue Mar 23 00:31:51 2010 KojiUpdateIOOMC realigned

This is the first touch to the MC mirrors after the earthquake on 16th.

  • I made an aluminum access connector so that we can work on the MC even the door is open. We still can be able to open the aluminum tube. The photos are attached. Steve, could you please look it at a glance whether the seal is enough or not.
  • MC resonances were flashing. Align MC2 and MC3 so that we have many TEM00s.
  • Found c1vmesus2 gone mad. Restarted remotely according to the wiki entry. 
  • Reset the MC coil output matrix to 1. (Previously, balance was adjusted so that A2L was minimized.)
  • Excite MC2 Pitch/Yaw at 8 and 9 Hz, looking at the peaks in the MC-MCL output. Move MC2 Pitch/Yaw so that the peak
    is reduced. (*)
  • MC1/MC3 were aligned so that we get the maximum transmission (or minimum reflection). (**)
  • Repeat (*) and (**)

So far, I have aligned in Yaw such that the yaw peak is minimized.

Attachment 1: IMG_2346.jpg
IMG_2346.jpg
Attachment 2: IMG_2347.jpg
IMG_2347.jpg
  2699   Tue Mar 23 09:37:36 2010 steveUpdateIOOvac envelope has to be sealed as antproof for overnight

Quote:

This is the first touch to the MC mirrors after the earthquake on 16th.

  • I made an aluminum access connector so that we can work on the MC even the door is open. We still can be able to open the aluminum tube. The photos are attached. Steve, could you please look it at a glance whether the seal is enough or not.
  • MC resonances were flashing. Align MC2 and MC3 so that we have many TEM00s.
  • Found c1vmesus2 gone mad. Restarted remotely according to the wiki entry. 
  • Reset the MC coil output matrix to 1. (Previously, balance was adjusted so that A2L was minimized.)
  • Excite MC2 Pitch/Yaw at 8 and 9 Hz, looking at the peaks in the MC-MCL output. Move MC2 Pitch/Yaw so that the peak
    is reduced. (*)
  • MC1/MC3 were aligned so that we get the maximum transmission (or minimum reflection). (**)
  • Repeat (*) and (**)

So far, I have aligned in Yaw such that the yaw peak is minimized.

 This seal is good for daily use- operation only. The IFO has to be sealed  with light metal doors every night so ants and other bugs can not find their way in.

Our janitor Kevin is mopping the hole IFO room floor area with 5%  ant killing solution in water in order to discourage bugs getting close to our openings of the vented chamber.

You may be sensitive to this chemical too.  Do not open chamber till after lunch.

Attachment 1: pc3.JPG
pc3.JPG
Attachment 2: pc4.JPG
pc4.JPG
  2700   Tue Mar 23 09:55:20 2010 KojiUpdateIOOvac envelope has to be sealed as antproof for overnight

Roger.

Quote:

 This seal is good for daily use- operation only. The IFO has to be sealed  with light metal doors every night so ants and other bugs can not find their way in.

 

  2705   Wed Mar 24 02:06:24 2010 KojiUpdateIOOvac envelope has to be sealed as antproof for overnight

Matt and Koji:

We closed the light doors of the chambers.

Quote:

Roger.

Quote:

 This seal is good for daily use- operation only. The IFO has to be sealed  with light metal doors every night so ants and other bugs can not find their way in.

 

 

  2827   Wed Apr 21 21:46:53 2010 KojiUpdateIOOMC spot diagnosis

Zach and Koji

We measured uncalibrated angle-to-length coupling using tdssine and tdsdmd.
We made a simple shell script to measure the a2l coupling.

Details:

- Opened the IMC/OMC light door.

- Saw the large misalignment mostly in pitch. Aligned using MC2 and MC3.

- Locked the MC in the low power mode. (script/MC/mcloopson AND MC length gain 0.3->1.0)

- Further aligned MC2/3. We got the transmission of 0.16, reflection of 0.2

- Tried to detect angle-to-length coupling so that we get the diagnosis of the spot positions.

- Tried to use ezcademod. Failed. They seems excite the mirror  but returned NaN.

- We used tdssine and tdsdmd instead. Succeeded.

- We made simple shell script to measure the a2l coupling. It is so far located users/koji/100421/MCspot

- We blocked the beam on the PSL table. We closed the chamber and left.

 

  2852   Tue Apr 27 22:28:58 2010 ZachUpdateIOOMC alignment

Beginning last week, I have been helping Koji with some of the IO work that must be done for the 40m upgrade. The first thing he asked me to do is to help with the alignment of the MC.

As I understand, it became apparent that the IFO beam was not centered on all (or any) of the MC mirrors, which is disadvantageous for obvious reasons. We are trying to correct this, using the following strategy:

  1. Adjust the MC mirrors into rough alignment, isolate a strong TEM00, and lock the cavity
  2. Fine-tune the alignment by minimizing the REFL power when locked (in these first two steps, we adjusted only MC2 & MC3, assuming that the REFL beam was centered on the PD, and wanting to keep it that way). At this point, the cavity is resonating some asymmetric mode, looking something like (not to scale---for illustration only):MC_misaligned.png
  3. Shake all three mirrors (in succession) in pitch and yaw, each time demodulating the error signal at the frequency used for the excitation and recording the magnitude and phase of the response.
  4. Move one mirror's DC orientation, repeat step 3, and then restore the mirror to its original position
  5. Repeat step 4 for both angular degrees of freedom of each mirror

Using the results of these measurements, it is possible to evaluate the components of a block-diagonal matrix M which relates the tilt-to-displacement coupling of each DOF to each mirror's misalignment in that degree, i.e.,

a = M x

with a a 6-dimensional vector containing the coupling of each degree of freedom to the length of the cavity and x a 6-dimensional vector containing the angular misalignments of each. Due to orthogonality of pitch and yaw, M will take the form of a 6x6 matrix with two non-zero 3x3 blocks along the diagonal and zero matrices on the off-diagonal blocks.

The idea is to isolate components of M by moving one mirror at a time, solve for them, then find the inverse M-1 that should give us the required angular adjustments to obtain the beam-centered ideal cavity mode.

In theory, this need only be done once; in practice, our measurement error will compound and M will not be accurate enough to get the beams exactly centered, so we will have to iterate.

NOTE: The fact that we are adjusting the three cavity mirrors to obtain the ideal mode means that we will necessarily tarnish our coupling into the cavity. Once we have adjusted the mirrors once, we will need to re-steer the input beam and center it on the REFL diode. 

Status: This process has been completed once through step 5. I am in the process of trying to construct the matrix for the first adjustment.

 

  2855   Wed Apr 28 12:05:44 2010 ZachUpdateIOOMC alignment

I have worked out the first set of adjustments to make on the MC mirrors (all angle figures are in units of the increments on the control screen)

Using the method described in the previous post, I obtained the following matrix relating the angle-to-length coupling and the angular deviations. In the following matrix, Mij corresponds to the contribution of the jth degree of freedom to the ith A-to-L coupling, with the state vector defined as xi = (MC1P, MC2P, MC3P, MC1Y, MC2Y, MC3Y), where each element is understood as the angular deviation of the specific mirror in the specific direction from the ideal position, such that x = 0 when the cavity eigenmode is the correct one and the beams are centered on the mirrors (thus giving no A-to-L coupling regardless of the components of M).

 

M =

   1.0e+03 *

   -0.2843   -0.4279   -0.1254         0         0         0

   -0.8903   -0.4820   -0.6623         0         0         0

    0.5024    0.0484   -0.0099         0         0         0

         0         0         0         0.1145   -0.1941   -0.3407

         0         0         0         0.0265    1.5601    0.2115

         0         0         0         0.1015    0.1805   -0.0103,

giving an inverse

M-1 =  

    0.0003   -0.0001    0.0020         0         0         0

   -0.0031    0.0006   -0.0007         0         0         0

    0.0018   -0.0018   -0.0022         0         0         0

         0         0         0        -0.0013   -0.0015    0.0117

         0         0         0         0.0005    0.0008   -0.0008

         0         0         0        -0.0037   -0.0010    0.0044

The initial coupling vector is then acted on with this inverse matrix to give an approximate state vector x containing the angular misalignments of each mirror in pitch and yaw. The results are below:

x

   1P:  0.0223

   2P: -0.0733

   3P:  0.3010

  1Y:  -0.1372

  2Y:   0.0194

  3Y:  -0.0681

 

  2856   Wed Apr 28 14:15:58 2010 AlbertoUpdateIOOMC alignment

 

 That's interesting.

Would it be possible to write about the technique on a wiki page as you get measurements and results?

  2858   Wed Apr 28 14:42:55 2010 ZachUpdateIOOMC alignment

Sure. I figured I would put up a How-To if it works. 

Quote:

 

 That's interesting.

Would it be possible to write about the technique on a wiki page as you get measurements and results?

 

  2864   Sun May 2 15:28:25 2010 KojiUpdateIOOSpot Positions of MC1/MC3

Summary

The spot positions on the MC mirrors were measured with coil balance gains.
The estimated spot positions from the center of the MC1 and MC3 are as followings:

MC1H = +0.29 mm
MC1V = -0.43 mm
MC3H = +1.16 mm
MC3V = -0.68 mm

The cordinates are described in the figure

Method

As far as the cavity mirrors are aligned to the incident beam, spots on the MC1 and MC3 tell us the geometry of the incident beam.
Note that spot position on the MC2 is determined by the alignment of the MC1 and MC3, so it does not a big issue now.
The calibration between the coil balance and the spot position are described in the previous entry.

  1. Lock the MC. Align it with MC2/MC3
  2. Run A2L scripts. script/A2L/A2L_MC1 and so on.
    • The scripts run only on the solaris machines. They require "expect" in stalled some specific place which does not exist on the linux machines.
    • Excitation amplitude, excitation freq, readback channels were modified

Result

Beam powers
MC Trans: 0.18
MC Refl: 0.12-0.13

Alignment biases
MC1P 3.2531
MC1Y -1.0827
MC2P 3.4534
MC2Y -1.1747
MC3P -0.9054
MC3Y -3.1393

Coil balances
MC1H 1.02682
MC1V 0.959605
MC3H 0.936519
MC3V 1.10755

(subtract 1, then multiply 10.8mm => spot position.)

Attachment 1: spot_position.png
spot_position.png
  2880   Wed May 5 01:19:05 2010 KojiUpdateIOOMC spot centering cont"d

Koji and Zach

We improved the beam axis rotaion on the MC. We still have 3mrad to be corrected.
So far we lost the MC Trans spot on CCD as the beam is now hitting the flange of the window. We need to move the steering mirror.

To do next:

- MC2 spot is too much off. Adjust it.

- Rotate axis for 3mrad more.

- MC2 spot is too much off. Adjust it.

- Adjust Vertical spot position as a final touch.


Monday

- Incident beam had 7mrad rotation.

- Tried to rotate in-vac steering mirror (IM1) in CCW

- After the long struggle the beam from PSL table started to hit north-east side of IM1 mount.

- Moved the IM1. All of the beam (input beam, MC Trans, MC Refl) got moved. Chaotic.

- Recovered TEM00 resonance. MC Trans CCD image missing. The beam axis rotation was 8.5mrad.
  Even worse. Disappointed.

Tuesday

- We made a strategic plan after some deliberation.

- We returned to the initial alignment of Saturday only for yaw.
  Not at once, such that we don't miss the resonance.

- Adjusted SM2Y and IM1Y to get reasonable resonance. Then adjusted MC2/3 to have TEM00 lock.

- Measured the spot positions. The axis rotation was 4.8mrad.

- Moved the spot on IM1 by 7mm by rotating SM2Y in CCW - ((A) in the figure)

- Compensated the misalignment by IM1Y CCW. ((B) in the figure)
  Used a large sensor card with puch holes to see the spot distribution between the MC1 and MC3.

- Fine alignment by MC2/MC3. Lock to TEM00. The beam axis rotation was 3mrad.The beam axis translation was 3mm.

- This 3mm can be Compensated by IM1Y. But this can easily let the resonance lost.
  Put the sensor card between MC1/MC3 and compensated the misalignment by MC3 and MC1.

Note: You match the returned spot from the MC2 to the incident beam by moving the spot deviation by MC3,
the spot returns to the good position on MC1. But the angle of the returned beam is totally bad.
This angle deviation can be adjusted by MC1.

Note2: This step should be done for max 2mm (2mrad) at once. As 2mrad deviation induces the spot move on the MC2 by an inch.

- After all, what we get is

MC1H = -0.15 mm
MC1V = -0.33 mm
MC3H = +0.97 mm
MC3V = -0.33 mm

This corresponds to the axis rotation of 3mrad and the beam axis translation of 0.8mm (to north).

Attachment 1: steering.png
steering.png
  2884   Thu May 6 01:06:16 2010 KojiUpdateIOOMC spot centering cont'd (Triumph)

Zach and Koji,

We finally aligned the incident beam enough close to the center of the all MC mirrors! Uraaaaah!

MC1H = -0.12mm
MC1V =
-0.13mm
MC2H = -0.15mm

MC2V = +0.14mm
MC3H = -0.14mm
MC3V = -0.11mm

The aperture right before the vacuum window has been adjusted to the beam position. This will  ensure that any misalignment on the PSL table can have the correct angle to the mode cleaner as far as it does resonate to the cavity. (This is effectively true as the small angle change produces the large displacement on the PSL table.)

If we put an aperture at the reflection, it will be perfect.

Now we can remove the MZ setup and realign the beam to the mode cleaner!


 

Method:

- The beam axis rotation has been adjusted by the method that was used yesterday.

Differential: SM2Y and IM1Y

Common: SM2Y only

- We developped scripts to shift the MC2 spot without degrading the alignment.

/cvs/cds/caltech/users/zach/MCalign/MC2_spot/MC2_spot_up
/cvs/cds/caltech/users/zach/MCalign/MC2_spot/MC2_spot_down
/cvs/cds/caltech/users/zach/MCalign/MC2_spot/MC2_spot_left
/cvs/cds/caltech/users/zach/MCalign/MC2_spot/MC2_spot_right

These scripts must be upgraded to the slow servo by the SURF students.

- These are the record of the alignment and the actuator balances

C1:SUS-MC1_PIT_COMM   =  2.4005
C1:SUS-MC1_YAW_COMM   = -4.6246
C1:SUS-MC2_PIT_COMM   =  3.4603
C1:SUS-MC2_YAW_COMM   = -1.302
C1:SUS-MC3_PIT_COMM   = -0.8094
C1:SUS-MC3_YAW_COMM   = -6.7545
C1:SUS-MC1_ULPIT_GAIN =  0.989187
C1:SUS-MC1_ULYAW_GAIN =  0.987766
C1:SUS-MC2_ULPIT_GAIN =  0.985762
C1:SUS-MC2_ULYAW_GAIN =  1.01311
C1:SUS-MC3_ULPIT_GAIN =  0.986771
C1:SUS-MC3_ULYAW_GAIN =  0.990253

  2899   Sat May 8 02:38:08 2010 KojiSummaryIOOMC incident power

As per Steve's request I checked the MC incident power as a function of time.

The output is negative: the lower voltage, the higher power.

Before I put the attenuator the incident power was 1.1W. It appear as -5V.

Now the output is -0.1V. This corresponds to 22mW.

 

Attachment 1: MC_input.png
MC_input.png
  2900   Sat May 8 03:09:15 2010 KojiUpdateIOOSteering around MC

After the MZ-removal work:

- I found that the input steering (IM1) was right handed. This was different from the CAD layout. This was the main reason why the MC trans was kicked by the mount.
- Removed the mount from the post and converted it to a keft handed.
- Align IM1 so that we can get TEM00 lock. Align IM1 further.

- After the IM1 was optimized for the TEM00, move the periscope mirrors to have best alignment.

- Checked the beam spot positions. They looks quite good (MC2 is not the matter now).

C1:SUS-MC1_ULPIT_GAIN = 0.998053
C1:SUS-MC1_ULYAW_GAIN = 0.992942
C1:SUS-MC2_ULPIT_GAIN = 1.00856
C1:SUS-MC2_ULYAW_GAIN = 1.04443
C1:SUS-MC3_ULPIT_GAIN = 0.99868
C1:SUS-MC3_ULYAW_GAIN = 1.00041

  2918   Wed May 12 03:56:54 2010 KojiUpdateIOOFaraday aligned

Zach and Koji

The old small MMT was removed and wrapped by Al foils.

The steering mirror IM2-IM4 were displaced and aligned.

The Faraday isolator block is moved and aligned.

The MC is realigned and resonatng TEM-00.

Now the MC has slightly miscentered beam on the mirrors owing to change of the stack leveling.
OSEMs are also in a strange state. We should check this later.

  2928   Thu May 13 23:59:46 2010 ZachSummaryIOOMC table leveled

 After the recent removal of the old IMMT and the relocation of the Faraday isolator, the MC table was tilted a bit (southward and slightly westward---as of when I opened the chamber this afternoon). I re-leveled it by putting an extra two rectangular ballast blocks on the stack that was already hanging off the NNE edge of the table (there are a total of 4 in the stack now). I also screwed down the circular block that Koji and I put between the Faraday and SM1 on Tuesday, and re-mounted the two wire harness towers onto the table.

Needless to say, this threw the MC way out of alignment. I spent the rest of the afternoon reacquiring alignment and getting it to lock robustly. Here is a summary:

  • I adjusted MC3 until I got the 2nd, 3rd+ pass beams to overlap with the input beam between MC1&3, then I adjusted MC2&1 semi-methodically until I got something flashing at the transmitted end. This took some time.
  • I went back into the control room, engaged the loops and acquired lock on the TEM00 mode, whereupon I found that the beam spot was WAY off center on MC2 (due to my meddling with all the mirrors to get resonance flashes). I began using the MC2_spot_up (etc) scripts we wrote the other day to re-center it.
  • After a few iterations, the lock became weak, and eventually gave out. This is because the REFL beam was falling off the RFPD (and being clipped by the iris on the AP table), so I moved the iris and re-centered the beam on the diode.
  • With that, I was able to get the MC2 spot more or less centered, but then I noticed that---though the lock was clearly strong as evidenced both by the REFL power dip and visually via the camera on MC2---it looked like crap on the CCD. It seemed like there was some higher order mode structure sloshing around on top of the 00 spot, which didn't make any sense, until I realized that it was just a diffraction pattern from the TRANS beam getting clipped somewhere on the way out of the vacuum system.
  • I went back to the AP table, where I noticed that the TRANS beam was hitting near the edges of several of the mirrors on the way back to the PSL table, including the first one out of the viewport, so I turned IM4 to center the beam on this mirror, then proceeded to center the beam on each mirror downstream and then onto the CCD.
  • After getting a clear picture of the transmission on the CCD, centering the spot even better on MC2, then fine-tuning MC2&3 to strengthen the lock, I went back to the MC table to check that the transmitted beam was still passing through the center of the Faraday, which, by none other than an act of God, it was.
  • Having done the necessary work in the tank, I ran the A2L_MC2 script to fine-tune the centering of the spot on MC2. It needed a couple steps up and to the side, but after that the actuator gains for pitch and yaw were both balanced again to within ~2%, which is only slightly above the measurement error. We will probably need to adjust this continually, especially during the upgrade, so I didn't bother with getting it better than that.

After that, I shut off the loops, blocked the beam, and put the light doors back on the tanks. Then I went to the parking lot, then I got in my car, etc, etc, etc.

  2929   Fri May 14 03:30:45 2010 KojiSummaryIOOMC table leveled

Thanks Zach.This was a great job.

It was not mentioned but: was the Faraday clamped down on the table?

 

  2931   Fri May 14 10:33:01 2010 ZachSummaryIOOMC table leveled

Ah... no, I didn't. That explains why there were loose dogclamps on the table. I wrapped them in foil and put them on the clean cart. Can this wait until the next time we open the tank (i.e. to measure the beam profile), or should I go over there and clamp it down today?

 

  2935   Sat May 15 04:13:33 2010 KojiSummaryIOOMC table leveled

Fixing at the next time is absolutely OK.

Quote:

Ah... no, I didn't. That explains why there were loose dogclamps on the table. I wrapped them in foil and put them on the clean cart. Can this wait until the next time we open the tank (i.e. to measure the beam profile), or should I go over there and clamp it down today? 

 

  2938   Mon May 17 02:10:10 2010 KojiConfigurationIOOHow to lock / align the MC

Let me remind you how to lock and align the IMC

To lock

1. Open the doors for the IMC/OMC chambers. Open the manual shutter of the PSL just in front of the optical window

2. Run scripts/MC/mcloopson

3. Set the MC length path gain 0.3 / Set the MC total gain "+20"

4. If you want to avoid excitation of the mirrors by air turbulence, put a big plastic film and put three posters on the top and both the sides on the floor to block the wind go into the chamber.

To shut down

1. Run scripts/MC/mcloopsoff

2. Close the manual shutter, Remove the wind blockers, and the light door of the chambers

To align the MC

1. Tweak MC2 and MC3 to get maximum transmittion and/or minimum reflection.

  2941   Mon May 17 19:42:11 2010 JenneUpdateIOOFirst steps toward MC mode measuring

[Jenne, Kevin, Steve]

We made some progress toward getting the MC's beam profile measured.  In the end, no changes were made to anything today, but we're more prepared to go for tomorrow.

What we did:

* Grabbed the scanning slit beam scan from the PSL lab.  It's the same kind as we had here at the 40m, so Kevin was able to hook it up to the computer, and confirmed that it works.

* Opened the IOO and OMC chamber doors, and locked the MC.  Unfortunately the MC mode was awful in Yaw.  Awful like TEM(0,10+). But it still locked.  

* Confirmed that the beam went through the Faraday.  I looked at the beam before and after the Faraday on a card, and it was the same nasty beam both before and after.  So it looks like Zach did a good job aligning the Faraday and everything else.  I was going to clamp the Faraday, but I didn't yet, since I wanted to see the nice happy TEM00 mode go through without clipping before risking moving the Faraday during clamping (I don't know how heavy it is, so I'm not sure how much it might potentially move during clamping.)

* Noticed that there is a whole lot of crap on both the OMC and BS tables that's going to have to move.  In particular, one of the weights leveling the OMC table is right where I need to put MMT2.  Steve suggested putting the optic there, in its approximate place, before doing too much other stuff, since it could potentially affect the leveling of the table, and thus the input pointing to the MC.  Unfortunately, to do that I'll need to move the weight, which is definitely going to change things.  Sad face.  Moving the weight will likely be one of the first things I do tomorrow, so that all 3 profile measurements have the same configuration. 

* Before closing up, I tried to align the MC, to get back to TEM00, to no avail.  I got as far as achieving TEM11 flashing, along with a bunch of other crappy modes, but didn't get 00.  That's also on the to-do list.

What we're going to do:

* Open the chambers, and align the MC to TEM00 (using the sliders on the MC align screen).

* Check with an IR card that the beam goes through the Faraday.

* Clamp the Faraday, reconfirm.

* Remove the weight on the OMC table.

* Place MMT2 on the OMC table in it's approximate final location.

* Realign the MC, and make sure the beam goes through the Faraday.  If this doesn't happen smoothly, I may need more instruction since I've never dealt with aligning the Faraday before.  What are the appropriate mirrors to adjust? 

* Move the PZT flat steering mirror from the BS table to the IOO table.  (Thoughts on this?  This will change the table leveling, and also includes the trickiness of needing to move the connectors for the PZT.)

* Place a flat mirror on the BS table to route the MC beam out to the BS/PRM/SRM oplev table. 

* Measure the mode using the beam scan: on the BS oplev table, on the POX table, and then perhaps by shooting the beam through the beamtube on the ETMY (new convention) table.

* Place MMT1 on the BS table, use flat mirrors to get it out of the chambers, repeat measurements.

* Place MMT2 in the correct position, use flat mirrors to get it out of the chambers, repeat measurements.

All of this may require some serious cleaning-up of the BS table, which is going to be ugly, but it has to happen sometime. Hopefully I can get away with only moving a minimal number of things, in order to get these measurements done.

 

Another note: Don't trust the PSL shutter and the switch on the MEDM screens! Always use a manual block in addition!!! We discovered upon closeup that hitting the "Closed" button, while it reads back as if the shutter is closed (with the red box around the buttons), does not in fact close the shutter.  The shutter is still wide open.  This must be fixed.

  2942   Tue May 18 01:40:56 2010 KojiUpdateIOOFirst steps toward MC mode measuring

OK. Don't worry. This is just an initial confusion which we also had for the suspensions a while ago.

The faraday must be clamped. It shakes the table terribly but it is fine. The leveling may change a bit but should be small enough. Otherwise, just tweak the weights. In fact, the faraday has enough large apertures and we hope we don't need to move it again, as far as the MC incident beam is not moved. But if necessary, we don't move the mirrors but move the faraday itself.

Usually the alignment of the MC is taken by MC2/MC3 such that we don't  move the refl. But if you think what have moved is the MC1/MC3 (i.e. activity in the IMC chamber), take the alignment of the MC1/MC3.

It is just a matter of time to get TEM00. If you get TEM11, it is already close. If you align for TEM11, it is enough aligned to lock TEM10 or TEM01. Once you got better mode, align for it again. Eventually you will get TEM00.

The leveling may change by moving the optics and the weight again. But once the leveling is recovered by arranging the weights somewhere else,
the pointing must be fine again. If necessary, You can remove two optics for squeezing injection (strange motorized rotating mirror and a mount sticking out from the table to south.)

Yes, we need to move the PZT mirror. For the connection, only Steve can give us the right way to do it. If it is too much hussle, just move only the mirror and ignore the wiring for now.

I will update how the mirrors should be migrated from the table to the table.

 

  2945   Tue May 18 12:04:13 2010 robUpdateIOOFirst steps toward MC mode measuring

Quote:

Another note: Don't trust the PSL shutter and the switch on the MEDM screens! Always use a manual block in addition!!! We discovered upon closeup that hitting the "Closed" button, while it reads back as if the shutter is closed (with the red box around the buttons), does not in fact close the shutter.  The shutter is still wide open.  This must be fixed.

 Has anyone tried pushing the "reset" button on the Uniblitz driver?

  2949   Tue May 18 16:44:35 2010 KojiUpdateIOOFirst steps toward MC mode measuring

Here is the upadted list http://lhocds.ligo-wa.caltech.edu:8000/40m/Upgrade_09/Optics

Quote:

I will update how the mirrors should be migrated from the table to the table. 

 

  2950   Tue May 18 23:03:08 2010 JenneUpdateIOONo real progress....

[Jenne, Kevin]

No real progress today.  We opened the chambers and again tried to lock the MC.  Gave up after ~2.5 hours (and closed up the chambers with light doors, replaced manual beam block, etc...).  With Koji's helpful coaching, hopefully we'll finally get it done tomorrow.  Then we can move forward with the actual to-do list. 

 

  2952   Wed May 19 16:00:18 2010 JenneUpdateIOOHooray! We locked the MC! (and some other stuff)

[Jenne, Kevin]

We opened up the MC chambers again, and successfully got the MC locked today!  Hooray!  This meant that we could start doing other stuff....

First, we clamped the Faraday.  I used the dog clamps that Zach left wrapped in foil on the clean cart.  I checked with a card, and we were still getting the 00 mode through, and I couldn't see any clipping.  2 thumbs up to that.

Then we removed the weight that was on the OMC table, in the way of where MMT2 needs to go.  We checked the alignment of the MC, and it still locks on TEM00, but the spot looks pretty high on MC2 (looking at the TV view). We're going to have to relevel the table when we've got the MMT2 optic in the correct place.

We were going to start moving the PZT steering mirror from the BS table to the IOO table, place MMT2 on the OMC table, and put in a flat mirror on the BS table to get the beam out to the BS oplev table, but Steve kicked us out of the chambers because the particle count got crazy high.  It was ~25,000 which is way too high to be working in the chambers (according to Steve).  So we closed up for the day, and we'll carry on tomorrow. 

 

Photos of the weight before we removed it from the OMC table, and a few pictures of the PZT connectors are on Picasa

  2954   Wed May 19 22:28:05 2010 KojiUpdateIOOHooray! We locked the MC! (and some other stuff)

Good! What was the key?

The MC2 spot looks very high, but don't believe the TV image. Believe the result of script/A2L/A2L_MC2. What you are looking at is the comparison of the spot at the front surface and the OSEMs behind the mirror.

Quote:

[Jenne, Kevin]

We opened up the MC chambers again, and successfully got the MC locked today!  Hooray!  This meant that we could start doing other stuff....

First, we clamped the Faraday.  I used the dog clamps that Zach left wrapped in foil on the clean cart.  I checked with a card, and we were still getting the 00 mode through, and I couldn't see any clipping.  2 thumbs up to that.

Then we removed the weight that was on the OMC table, in the way of where MMT2 needs to go.  We checked the alignment of the MC, and it still locks on TEM00, but the spot looks pretty high on MC2 (looking at the TV view). We're going to have to relevel the table when we've got the MMT2 optic in the correct place.

We were going to start moving the PZT steering mirror from the BS table to the IOO table, place MMT2 on the OMC table, and put in a flat mirror on the BS table to get the beam out to the BS oplev table, but Steve kicked us out of the chambers because the particle count got crazy high.  It was ~25,000 which is way too high to be working in the chambers (according to Steve).  So we closed up for the day, and we'll carry on tomorrow.  

Photos of the weight before we removed it from the OMC table, and a few pictures of the PZT connectors are on Picasa

 

  2964   Fri May 21 00:51:06 2010 JenneUpdateIOOFirst MC mode measuring (hopefully) done

[Jenne, Kiwamu, Steve]

Round 1 of measuring the MC mode is pretty much done.  Yay.

Earlier today, Steve and I launched the MC beam off the flat mirror just after the Faraday, and sent it down toward ETMY(new convention). We ended up not being able to see it all the way at the ETM because we were hitting the beam tube, but at the ITM chamber we could see that the beam looked nice and circle-y, so wasn't being clipped in the Faraday or anywhere else.  To do this we removed 2 1inch oplev optics.  One was removed from the BS table, and wrapped in foil and put in a plastic box.  The other was just layed on its' side on the BS table. 

I then took the beam out of the BS chamber, in order to begin measuring the mode.  I left the flat fixed mirror in the place of what will be PZT SM1, and instead used the PZT mirror to turn the beam and get it out the BS chamber door.  (Thoughts of getting the beam to the BS oplev table were abandoned since this was way easier, since Kiwamu and Steve had made the nifty table leg things.)  Kiwamu and I borrowed an 2inch 45P Y1 optic from the collection on Koji's desk (since we have ZERO 2inch optics on the random-optic-shelf....no good), to shoot the beam down the hallway of the Yarm (new convention).  We used the beam scan on a rolling cart to measure the beam at various distances.  I made some sweet impromptu plum bobs to help make our distance measurements a bit more accurate.

We stopped at ~25 feet from the BS chamber, since the spot was getting too big for the beam scanner.  If it turns out that I can't get a good fit with the points I have, I'll keep everything in-chamber the same, and do the farther distances using the good ol' razor blade technique.

I have measurements for the distances between the beam scan head and the opening of the BS chamber.  Tomorrow, or very soon after, I need to measure the distances in-chamber between the MC and the BS chamber opening.  Plots etc will come after I have those distances.

Next on the to-do list:

1.  Measure distances in-chamber for first mode scan.

2.  Plot spot size vs. distance, see if we need more points. Take more points if needed.

3.  Put in MMT1, repeat measurements.

4.  Put in MMT2, rinse and repeat.

5.  Move the PZT mirror to its new place as SM1, and figure out how to connect it.  Right now the little wires are hooked up on the BS table, but we're going to need to make / find a connector to the outside world from the IOO table. This is potentially a pretty big pain, if we don't by happenstance have open connectors on the IOO table.

  2977   Tue May 25 00:10:24 2010 ZachUpdateIOOIMC table leveled again

The IMC table had to be leveled again, for two reasons: 1) It was un-leveled when Jenne and Kiwamu removed an extra beam dump when they took the beam profile measurements, and 2) the stack of weights I had put there before was too tall to allow the beam to pass (I didn't realize that the BS chamber is offset a bit to the north, so the beam passes right over the NE edge of the IMC table).

First of all, I was wrong before when I said that the stack of weights was 4 blocks tall; it was 6 blocks tall. I re-leveled the table this afternoon by removing the top three blocks and placing them immediately south of the bottom three in the original stack, while also moving the circular weight north of its previous position. The table is now balanced roughly to within the tolerance of the bubble level I was using.

After the leveling, I tried to re-lock the modecleaner. Upon removing the beam block on the PSL table, I got some sort of resonance flashes on the MC TRANS monitor. With some minor adjustments to MC2&3, I was able to get a decent TEM00 mode to hit. The cavity wouldn't lock, so I went to the AP table and checked to make sure that the REFL beam was hitting the PD. It was, but the beam was very close to the edge of the focusing lens, so I moved the steering mirror slightly to make the situation a little better.

I then went to the control room to finish the by-now-mundane task of fine-tuning the MC lock, but today's was a worthier opponent. For some reason, the thing didn't want to lock for more than a few seconds at a time. I saw that the spot on MC2 was quite a bit off-center, so I ran the MC2_spot_xxx scripts to get it visually in place, then revisited the AP table to ensure that the REFL beam was still on the PD. No dice.

I don't know what was different. I had Ameristat over the opening between the tanks, with posters on top and on the sides (as usual), and I checked to ensure that the servo gains were at the appropriate levels. Joe pointed out that IOO VME was not responding, but we didn't seem to think that this was the problem (based on nothing I can put in words or stick figure cartoons), and the "alive" indicator on the Auto-Lock control in the MEDM screen was not blinking, as it usually is, but I don't know what bearing this has on anything.

I will try to lock again tomorrow.

 

  2985   Tue May 25 17:09:22 2010 KojiUpdateIOOBeam Profile After Mode Cleaner

Very nice as usual. Can you add the curve to show the ideal mode of the MC on the profile plot?

Quote:

I fit the data from the beam profile that Jenne measured on 5/21/2010. The distances are measured from halfway between MC1 and MC3 to the beam scanner. The fits give the following where w0 is the waist size and z0 is the distance from the waist to halfway between MC1 and MC3.

For the horizontal profile:

reduced chi^2 = 0.88

z0 = (1 ± 29) mm

w0 = (1.51 ± 0.01) mm

For the vertical profile:

reduced chi^2 = 0.94

z0 = (673 ± 28) mm

w0 = (1.59 ± 0.01) mm

I calculated the radius of curvature of MC2 using these values of w0:

horizontal: (16.89 ± 0.06) m

vertical:   (17.66 ± 0.07) m

For this calculation, I used the value of (13.546 ± .0005) m for the length of the mode cleaner measured on 6/10/2009. The specification for the radius of curvature of MC2 is (18.4 ± 0.1) m.

 

  2986   Tue May 25 17:22:56 2010 KevinUpdateIOOBeam Profile After Mode Cleaner

Quote:

Very nice as usual. Can you add the curve to show the ideal mode of the MC on the profile plot?

Quote:

I fit the data from the beam profile that Jenne measured on 5/21/2010. The distances are measured from halfway between MC1 and MC3 to the beam scanner. The fits give the following where w0 is the waist size and z0 is the distance from the waist to halfway between MC1 and MC3.

For the horizontal profile:

reduced chi^2 = 0.88

z0 = (1 ± 29) mm

w0 = (1.51 ± 0.01) mm

For the vertical profile:

reduced chi^2 = 0.94

z0 = (673 ± 28) mm

w0 = (1.59 ± 0.01) mm

I calculated the radius of curvature of MC2 using these values of w0:

horizontal: (16.89 ± 0.06) m

vertical:   (17.66 ± 0.07) m

For this calculation, I used the value of (13.546 ± .0005) m for the length of the mode cleaner measured on 6/10/2009. The specification for the radius of curvature of MC2 is (18.4 ± 0.1) m.

Here is the plot with the ideal mode of the mode cleaner shown in brown. The ideal mode was plotted with the radius of curvature of 18.4. The blue curve is the fit to the vertical beam radius, the purple curve is the fit to the horizontal beam radius, * denotes a data point from the vertical data, and + denotes a data point from the horizontal data.

Attachment 1: mcfit.png
mcfit.png
  2987   Wed May 26 00:50:16 2010 JenneUpdateIOOMirrors moved in prep for round 2 of MC mode measuring

[Jenne, Kevin, Kiwamu]

We moved some optics in preparation for measuring the MC mode after the first MMT curved optic, RoC -5m. 

Kevin and I found the box of DLC (sp?) mounts with the 2" Y1-45P optics in the clean tupperware boxes.  We removed one of the Y1-45P's, and replaced it with the MMT1 -5m optic, which was baked several weeks ago.  We left the Y1-45P on the cleanroom table next to where the MMT optics are.  We placed this MMT mirror in the place it belongs, according to Koji's table layout of the BS table. 

We drag wiped one of the other Y1-45P's that was in the box since it was dirty, and then placed the optic on the IOO table, on the edge closest to the BS table, with the HR side facing the BS table, so that the beam reflected off the curved mirror is reflected back in the direction of the BS table.  This was aligned so the beam hits the same PZT mirror we were using last time, to get the beam out of the BS chamber door.  We left a razor dump on the edge of the BS table, by the door, which will need to be removed before actual measurements can take place. 

Rana pointed out that the anticipated mode calculation should be modified to include the index of refraction of the crystals in the Faraday, and the polarizers in the Faraday.  This may affect where we should put MMT1, and so this should be completed before round 2 measurements are taken, so that we can move MMT1.

Also, the optics are in place now, and the beam is going out the BS chamber door, but we have not yet measured distances (design distances quoted on the MMT wiki page), and confirmed that everything is in the right place.  So there is a bit more work required before beginning to measure round 2.

 

Note:  While I was poking around on the BS table, I had to move several optics so that we could fit MMT1 in the correct place.  When preparing to move these optics, I found 2 or 3 that were totally unclamped. This seems really bad, especially for tall skinny things which can fall over if we have an earthquake.  Even if something is in place temporarily, please clamp it down.

  2991   Wed May 26 14:28:01 2010 KojiUpdateIOOMirrors moved in prep for round 2 of MC mode measuring

That's true. But I thought that you measured the mode after those optics and the effect of them is already included.

So:

  • We need to model the transmissive optics in order to understand the measured mode which is different from the MC mode slightly.
  • We just can calculate the modes based on the measurement in order to figure out the realistic positions of the MMT1 and MMT2.

Quote:

Rana pointed out that the anticipated mode calculation should be modified to include the index of refraction of the crystals in the Faraday, and the polarizers in the Faraday.  This may affect where we should put MMT1, and so this should be completed before round 2 measurements are taken, so that we can move MMT1.

 

  2993   Wed May 26 15:34:00 2010 JenneUpdateIOOMirrors moved in prep for round 2 of MC mode measuring

Quote:

That's true. But I thought that you measured the mode after those optics and the effect of them is already included.

So:

  • We need to model the transmissive optics in order to understand the measured mode which is different from the MC mode slightly.
  • We just can calculate the modes based on the measurement in order to figure out the realistic positions of the MMT1 and MMT2.

Quote:

Rana pointed out that the anticipated mode calculation should be modified to include the index of refraction of the crystals in the Faraday, and the polarizers in the Faraday.  This may affect where we should put MMT1, and so this should be completed before round 2 measurements are taken, so that we can move MMT1.

 

 Yes, the measured mode takes all of this into account.  But in Kevin's plot, where he compares 'measured' to 'expected', the expected doesn't take the Faraday optics into account.  So I should recalculate things to check how far off our measurement was from what we should expect, if I take the Faraday into account.  But for moving forward with things, I can just use the mode that we measured, to adjust (if necessary) the positions of MMT1 and MMT2.  All of the other transmissive optics (that I'm aware of) have already been included, such as the PRM and the BS.  This included already the air-glass curved interface on the PRM, etc.

  3013   Fri May 28 23:21:52 2010 KojiUpdateIOOMC alignment

Hm... You touched the optics between the MC and the Faraday... This will lead us to the painful work.

I am afraid that the beam is already walking off from the center of MC1/MC3 after the work on the PSL table.
This may result in the shift of the spot on those MC mirrors. So I recommend that:

- Lock the cavity
- Check the A2L for MC1/3
- Adjust it by the periscope
- If it is fine, adjust the optics after the MC (steering, Faraday, etc)

Off-centering of the MC2 spot is no problem. We can move it easily using Zach's scripts.
Tell me when the work is planed on Sunday as I might be able to join the work if it is in the evening.

Quote:

[Alberto, Kiwamu, Kevin, Rana]

Today we tried to measured the beam shape after the MC MMT1 that Jenne installed on the BS table.

The beam scan showed a clipped spot. We tracked it down to the Farady and the MCT pickoff mirror.

The beam was getting clipped at the exit of the Faraday. But it was also clipping the edge of the MCT pick-off mirror. I moved the mirror.

Also the beam looked off-center on MC2.

We're coming back on Sunday to keep working on this.

Now things are bad.

 

  3015   Sun May 30 15:33:21 2010 AlbertoConfigurationIOOmode cleaner and air conditioning

The mode cleaner is locked and the air conditioning is full on. So the the air conditioning doesn't seem to be so important for the lock to hold.

  3019   Mon May 31 00:10:18 2010 kiwamuUpdateIOOMC alignment

  [Alberto, Kiwamu]

The MC alignment is getting better by steering the axis of the incident beam into the MC.

We found the beam spot on MC1 and MC3 were quite off-centered in the beginning of today's work. It had the coil gain ratio of 0.6:1.4 after running the A2L script.

In order to let the beam hit the center of the MC1 and MC3, we steered the bottom mirror attached on the periscope on the PSL table to the yaw direction.

And then we got better numbers for the coil gain ratio (see the numbers listed at the bottom).

For the pitch direction, there still are some rooms to improve because we didn't do anything with the pitch. It is going to be improved tomorrow or later.

 

Here are the amounts of off-centering on MC1 and MC3 after steering the axis. 

 C1:SUS- MC1_ULPIT_GAIN =  0.900445

C1:SUS-MC1_ULYAW_GAIN =  0.981212

C1:SUS-MC3_ULPIT_GAIN =  0.86398

C1:SUS-MC3_ULYAW_GAIN =   1.03221

  3020   Mon May 31 03:38:48 2010 KojiUpdateIOOMC alignment

Remember that you only can introduce the axis translations from the PSL table.
It is quite difficult to adjust the axis rotation.

The calibration factor from A2L results to the beam position is dx = (A2L_result - 1) *10.8mm

If I believer the result below, the spot positions on the mirrors are

MC1 Pitch      -1.1mm
MC1 Yaw        -0.20mm
MC3 Pitch      -1.5mm
MC3 Yaw        +0.35mm

This means that the beam is 1.3mm too high and 0.28mm too much in north

This corresponds to tilting SM2 by
0.33mrad in pitch (23deg in CW)
and
0.10mrad in yaw (7deg in CW).

Quote:

C1:SUS-MC1_ULPIT_GAIN =  0.900445
C1:SUS-MC1_ULYAW_GAIN =  0.981212
C1:SUS-MC3_ULPIT_GAIN =  0.86398

C1:SUS-MC3_ULYAW_GAIN =  1.03221  

 

Attachment 1: MC_spot_centering.png
MC_spot_centering.png
  3021   Mon May 31 17:47:34 2010 kiwamuUpdateIOOtoday's plan : MC alignment

[Alberto, Kiwamu]

0. have a coffee and then dress up the clean coat.

1. level the MC table

2. lock and align MC 

3. run A2L script to see how much off-centering of the spots

4. steer the periscope mirror <--- We are here

5. move the pick off mirror which is used for monitoring of MCT CCD

6. check the leveling and move some weights if it's necessary

7. shut down

  3026   Tue Jun 1 16:29:51 2010 AlbertoUpdateIOOMC transmitted beam aligned to the Faraday; next things to do

We moved the MC-trans pick-off mirror (= the beam splitter between the input of the Faraday and the steering mirror located right after MC3). Now the beam goes through the Farady without getting clipped.

This is the list of the things that have to be done next:

  1. take pictures of the beam spot just before and after the Faraday
  2. lock down to the table the MCTrans pickoff mirror with its screws
  3. measure the beam profile after the first MC telescope mirror (MMT1)
  4. remove Jenne's extra steering mirror from the MC table
  5. re-level the MC table with the bubble level
  6. align the MC-trans beam to its photodiode on the PSL table
  7. align the REFL beam to its photodiode on the AP table
  3029   Wed Jun 2 01:47:28 2010 Alberto, KiwamuUpdateIOOmode measurement of new input optics

The mode profile of the new input optics was measured.

Although the distance between each optic was not exactly the same as the design because of narrow space,

we measured the profile after the curved mirror (MMT1) that Jenne and Kevin put in the last week.

 


(interference from MMT1)

Below is a sketch of the current optical path inside of the chamber.

inside_vac_2.png

 

In the beginning of this measurement, the angle between the incident and the reflection on MMT1 (denoted as theta on the sketch) was relatively big (~40deg) although MMT1 was actually made for 0deg incident.

At that time we found a spatially large interference imposed on the Gaussian beam at the beam scan. This is not good for mode measurement

This bad interference can be caused by an extra reflection from the back surface of MMT1 because the interference completely vanished by removing MMT1  .

In order to reduce the interference we decreased the angle theta as small as possible. Actually we made it less than 10deg which was our best due to narrow space. 

Now the interference got less and the spot looks better.

The picture below shows an example of the beam shape taken by using the beam scan.

Top panel represents the horizontal mode and bottom panel represents the vertical mode.

You can see some bumps caused by the interference on the horizontal mode, these bumps may lead to overestimation of the horizontal spot size .

 

beam_profile.png

 

(result)

 afterMMT1.png

 The above plot shows the result of the mode measurement.

 Here are the parameter obtained by fitting. The data is also attached as attachment:4

waist size for vertical  w0v [mm]  0.509 +/-0.0237
waist size for horizontal

w0h  [mm]

 0.537  +/- 0.0150
waist position from MMT1 for vertical  xv[m]  -2.91 +/- 0.214
waist position from MMT1 for horizontal xh[m]   -2.90 +/-  0.127


Attachment 3: MMT1_.dat.zip
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