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ID Date Author Type Category Subject
5123   Fri Aug 5 13:51:51 2011 steveUpdateSUScross coupling

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

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

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

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

 Quote from #5123 We need a plan how to minimize cross coupling in the OSEMs now

5138   Mon Aug 8 12:08:05 2011 ranaUpdateSUSsus at atm

A plot showing that the daily variation in the OLs is sometimes almost as much as the full scale readout (-1 to +1).

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

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

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

The inspection is still ongoing.

(Review : How wrong ?)

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

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

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

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

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

(Status update : Noise spectra)

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

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

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

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

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

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

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

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

from the one measured in vacuum.

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

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

5145   Mon Aug 8 22:12:58 2011 NicoleSummarySUSDaily Summary

Today I balanced the mirror, finished putting together the second photosensor, and finished my photosensor circuit box!

Upon Jamie's suggestion, I have used a translation stage to obtain calibration data points (voltage outputs relative to displacement) for the new photosensor and for the first photosensor.

I will plot these tomorrow morning (too hungry now > < )

Here is a photo of the inside of my circuit box! It is finally done! It is now enclosed in a nice aluminum casing ^ ^

Attachment 1: frontview.jpg
5146   Tue Aug 9 01:35:45 2011 SureshUpdateSUSETMX Side Sensor slow channel down for a long time

The slow signal from the side sensor on ETMX was last seen in action sometime in May 2010!  And then the frame builder has no data for a while on this channel.  After that the channel shows some bistability starting Sept 2010 but has not been working.  The fast channel of this sensor  (C1:SUS-ETMX_SDSEN_OUTPUT) does work so the sensor is working.  Probably is a loose contact... needs to be fixed.

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

[Rana / Jenne / Kiwamu]

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

The adjustment of the OSEMs is ongoing.

(What we did)

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

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

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

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

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

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

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

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

+ Trying to minimize the cross couplings

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

5150   Tue Aug 9 02:44:32 2011 SureshUpdateSUSETMX free swinging data

I switched off damping to the ETMX and used a reduced version of freeswing-all.csh script (called freeswing-ETMX.csh) to set it swinging.    After about an hour I used the saved template ETMX/2008.08.06.xml to obtain the following plot.

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

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

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

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

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

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

 Quote from #5150 There is something defintely wrong with the side sensor.  It might be the electronics as it also has this problem with it slow channel readings (my previous elog today).

5154   Tue Aug 9 13:34:40 2011 NicoleSummarySUSNew Calibration Plots for Photosensors

Here are the new calibration plots for my photosensors. These calibrations were done using a translation stage.

The linear region for the first photosensor appears to be between 15.2mm and 30 mm

The linear region for the second photosensor appears to be between 12.7mm and 22.9mm

The slope for both is -0.32 V/mm  (more precisely, -0.3201 V/mm for PS 1 and -0.3195 V/mm for PS 2)

5160   Tue Aug 9 19:53:56 2011 NicoleSummarySUSWeekly Summary

This week, I have finished assembling everything I need to begin shaking. I built an intermediary mounting stage to mount the TT suspension base to the horizontal sliding platform, finished assembling the second photodiode, finished assembling the photosensor circuit box, and calibrated the two photosensors. Today I built a platform/stage to mount the photodiodes so that they are located close enough to the mirror/suspension that they can operate in the linear range.  Below is an image of the set-up.

The amplifer that Koji fixed is acting a bit strange again...It is sometimes shutting off (Apparently, it can only manage to do short runs ~ 1minute? That should be enough time?).

The set-up is ready to begin taking measurements.

5161   Wed Aug 10 00:11:39 2011 jamieUpdateSUScheck of input diagnolization of ETMX after OSEM tweaking

Suresh and I tweaked the OSEM angles in ETMX yesterday.  Last night the ETMs were left free swinging, and today I ran Rana's peakFit scripts on ETMX to check the input diagnolization:

It's well inverted, but the matrix elements are not great:

       pit       yaw       pos       side      butt
UL    0.3466    0.4685    1.6092    0.3107    1.0428
UR    0.2630   -1.5315    1.7894   -0.0706   -1.1859
LR   -1.7370   -1.5681    0.3908   -0.0964    0.9392
LL   -1.6534    0.4319    0.2106    0.2849   -0.8320
SD    1.0834   -2.6676   -0.9920    1.0000   -0.1101


The magnets are all pretty well centered in the OSEMS, and we worked at rotating the OSEMS such that the bounce mode was minimized.

Rana and Koji are working on ETMY now.  Maybe they'll come up with a better procedure.

5163   Wed Aug 10 01:40:40 2011 KojiUpdateSUSETMY exploration

[Rana Koji Jenne Jamie]

- The situation of the ETMY suspension is improved.
- The damping servos except for Pitch are now functional.
- We intentionally turned off the damping servos for the matrix measurements.

- Opened the light door of the ETMY chamber.

- We set up the CDS SUS lockin:

Excite UL/UR/LL/LR equally [by setting the output matrix (1, 1, 1, 1, 0)] at 3.12Hz with 2000 cnts
Put the OSEM PD outputs into lockin one by one. For the image rejection, 0.1Hz 4th order LPF has been used though we like to use a faster settling LPF.

- Found only UL was responding to the excitation. After fitzing with the cables and connectors, it was found that the DAC card was loose from the bus.
By pushing the card the responses have been back. [Note we had the reboot of c1iscey almost at the same time.]

- Checked the response in the I channel of the lockin.
UL -8ish / UR +7ish / LR +5ish / LL +2ish

- Tweaked LL sensor to get better response ==> in vain. Decided to move the lower OSEM plate for the better positioning of the LR/LL.
- Got reasonable (+5ish) response for LL.

- Confirmed that the POS/YAW/SIDE damping works with positive gains. PITCH did not work with the negative gain (but that could be a good sign.)

- Let the suspension freely swinging for a while (~30min). Checked the side/pos separation. They are not perfect but seemed diagonalizable.

- Closed the light door.

- Jenne will make a better kick/free-swing test later.

5164   Wed Aug 10 02:29:38 2011 JenneUpdateSUSETMY exploration

 Quote: - Jenne will make a better kick/free-swing test later.

02:27am, ran the new freeswinging-ifo.csh script.  It's just a copy of freeswinging-all.csh, but it doesn't include the MC mirrors, since Suresh and Kiwamu are still working.

Now we have copies of the script for -all, -mc, -ifo to cover the various sections of the suspended interferometer.

5166   Wed Aug 10 07:59:33 2011 steveUpdateSUSthis is too dam nice

 Quote: Suresh and I tweaked the OSEM angles in ETMX yesterday.  Last night the ETMs were left free swinging, and today I ran Rana's peakFit scripts on ETMX to check the input diagnolization: It's well inverted, but the matrix elements are not great:  pit yaw pos side butt UL 0.3466 0.4685 1.6092 0.3107 1.0428 UR 0.2630 -1.5315 1.7894 -0.0706 -1.1859 LR -1.7370 -1.5681 0.3908 -0.0964 0.9392 LL -1.6534 0.4319 0.2106 0.2849 -0.8320 SD 1.0834 -2.6676 -0.9920 1.0000 -0.1101  The magnets are all pretty well centered in the OSEMS, and we worked at rotating the OSEMS such that the bounce mode was minimized. Rana and Koji are working on ETMY now.  Maybe they'll come up with a better procedure.

5169   Wed Aug 10 12:32:09 2011 NicoleSummarySUSWeekly Summary Update

Last night, I attached a metal plate to the Vout faceplate of my photosensor circuit box because the BNC connection terminals were loose. This was Jamie's suggestion to establish a more secure connection (I had originally drilled holes for the BNCs that were much too large).

I have also fixed the mechancial set-up of my shaking experiment so that the horizontal sliding platform does not interfere with the photodiode mounting stage. Koji pointed out last night that in the full range of motion, the photodiode mounting stage interferes with the movement of the sliding platform when the platform is at its full range.

I have began shaking. I am getting a problem, as my voltage outputs are just appearing a high-frequency noise.

5176   Wed Aug 10 15:39:33 2011 jamieUpdateSUScurrent SUS input diagonalization overview

Below is the overview of all the core IFO suspension input diagonalizatidons.

### UPDATE:

I had originally put the condition number of the calculated input matrix (M) in the last column.  However, after some discussion we decided that this is not in fact what we want to look at.  The condition number of a matrix is unity if the matrix is completely diagonal.  However, even our ideal input matrix is not diagonal, so the "best" condition number for the input matrix is unclear.

What instead we do know is that the matrix, B, that describes the difference between the calculated input matrix, M, and the ideal input matrix, M0: should be diagonal (identity, in fact):

M = M0 B

B should be diagonal (identity, in fact), and it's condition number should ideally be 1.  So now we calculate B-1, since it can be calculated from the pre-inverted input matrix:

B-1 = M-1 * M0

From that we calculate cond(B) == cond(B-1).

cond(B) is our new measure of the "badness" of the OSEMS.

### new summary: ITMY, PRM, BS are really bad (in that order) and are our top priorities.

 TM INPUT MATRIX (M) cond(M) cond(B) PRM       pit     yaw     pos     side    butt UL   -2.000  -2.000  -2.000  -0.345   2.097  UR   -0.375  -0.227  -0.312  -0.060   0.247  LR    1.060   1.075   0.971   0.143  -0.984  LL   -0.565  -0.698  -0.717  -0.141   0.672  SD    1.513   1.485   1.498   1.000  -1.590  75.569 106.756 SRM       pit     yaw     pos     side    butt UL    0.791   1.060   1.114  -0.133   1.026  UR    1.022  -0.940   1.052  -0.061  -1.027  LR   -0.978  -0.987   0.886  -0.031   0.903  LL   -1.209   1.013   0.948  -0.103  -1.043  SD    0.286   0.105   1.249   1.000   0.030  2.6501 3.90776 BS       pit     yaw     pos     side    butt UL    1.420   0.818  -0.069   0.352   1.038  UR    0.276  -1.182   1.931  -0.217  -0.905  LR   -1.724  -0.274   1.940  -0.254   0.862  LL   -0.580   1.726  -0.060   0.315  -1.194  SD    0.560   0.171  -3.535   1.000   0.075   9.8152 7.28516 ITMX       pit     yaw     pos     side    butt UL    0.437   1.015   1.050  -0.065   0.714  UR    0.827  -0.985   1.129  -0.221  -0.957  LR   -1.173  -1.205   0.950  -0.281   1.245  LL   -1.563   0.795   0.871  -0.125  -1.084  SD   -0.581  -0.851   2.573   1.000  -0.171   4.08172 4.69811 ITMY       pit     yaw     pos     side    butt UL    0.905  -0.884  -0.873   0.197   0.891  UR   -1.095   1.088   1.127  -0.252  -1.115  LR   -0.012  -0.028   0.002   0.001   0.030  LL    1.988  -2.000  -1.998   0.451   1.964  SD    4.542  -4.608  -4.621   1.000   4.517   801.453 774.901 ETMX       pit     yaw     pos     side    butt UL    0.344   0.475   1.601   0.314   1.043  UR    0.283  -1.525   1.786  -0.071  -1.181  LR   -1.717  -1.569   0.399  -0.102   0.938  LL   -1.656   0.431   0.214   0.283  -0.837  SD    0.995  -2.632  -0.999   1.000  -0.110   4.26181 4.33518 ETMY       pit     yaw     pos     side    butt UL   -0.212   1.272   1.401  -0.127   0.941  UR    0.835  -0.728   1.534  -0.101  -1.054  LR   -0.953  -1.183   0.599  -0.066   0.827  LL   -2.000   0.817   0.466  -0.092  -1.177  SD   -0.172   0.438   2.238   1.000  -0.008   4.04847 4.33725

5177   Wed Aug 10 18:25:45 2011 JenneUpdateSUSETMY mini-update

[Jenne, Jamie]

ETMY is now in its new nominal position, according to the rails that Kiwamu put in the other day.  OSEM voltages are all centered, and the magnets looked pretty well centered in the OSEM bores.  We're taking data for some free swinging spectra, to check the decoupling.

Next up: Align Y-green to the arm, then move on to fixing the other optics that Jamie pointed out.

5178   Wed Aug 10 19:18:26 2011 NicoleSummarySUSFixed Reflective Photosensors; Recalibrated Photosensor 2

Thanks to Koji's help, the second photosensor, which was not working, has been fixed. I have re-calibrated the photosensor after fixing a problem with the circuit.  I have determined the new linear region to lie between 7.6 mm and 19.8mm. The slope defining the linear region is -0.26 V/mm (no longer the same as the first photosensor, which is -0.32 V/mm).

Here is the calibration plot.

5183   Thu Aug 11 06:45:14 2011 NicoleSummarySUSShaking Testing

Koji and I have finished shaking the table for the first round of measurements (horizontal shaking). We have cleaned up the lab space used.

The FFT Analyzer has been put back to its position at the back side of the rack (near the seismometers).

I will calibrate the photosensor for the suspension frame and piece together/analyze/produce graphs of the data today. If everything is fine (the measurements are fine) and if there is a chance, we hope to shake the TT suspension vertically.

5188   Thu Aug 11 12:31:39 2011 NicoleSummarySUSPhotosensor Head Calibration Curve for TT Frame

I have re-calibrated the photosensor I used to measure the displacements of the TT frame (what I call "Photosensor 2").

As before, the linear region is about 15.2mm to 25.4mm. It is characterized by the slope -0.0996 V/mm (-0.1 V/mm). Recall that photosensor 1 (used to measure mirror displacements) has a calibration slope of -3.2V/mm. The ratio of the two slopes (3.2/0.1 = 32). We should thus expect the DC coupling level to be 32? This is not what we have for the DC coupling levels in our data (2.5 for flexibly-supported, fully-assembled TT (with EDC, with bar), 4.2 for EDC without bar, 3.2 for rigid EDC without bar, 3.2 for no EDC, with bar, 3.2 for no EDC without bar) . I think I may need to do my calibration plot for the photosensor at the frame?

5191   Thu Aug 11 14:22:00 2011 NicoleSummarySUSPhotosensor Head Calibration Curve for TT Frame

 Quote: I have re-calibrated the photosensor I used to measure the displacements of the TT frame (what I call "Photosensor 2"). As before, the linear region is about 15.2mm to 25.4mm. It is characterized by the slope -0.0996 V/mm (-0.1 V/mm). Recall that photosensor 1 (used to measure mirror displacements) has a calibration slope of -3.2V/mm. The ratio of the two slopes (3.2/0.1 = 32). We should thus expect the DC coupling level to be 32? This is not what we have for the DC coupling levels in our data (2.5 for flexibly-supported, fully-assembled TT (with EDC, with bar), 4.2 for EDC without bar, 3.2 for rigid EDC without bar, 3.2 for no EDC, with bar, 3.2 for no EDC without bar) . I think I may need to do my calibration plot for the photosensor at the frame?

I have redone the voltage versus displacement measurements for calibrating "Photosensor 2" (the photosensor measuring the motions of the TT frame). This time, I calibrated the photosensor in the exact position it was in during the experimental excitation ( with respect to the frame ). I have determined the linear region to be 15.2mm to 22.9mm (in my earlier post today, when I calibrated the photosensor for another location on the frame, I determined the linear region to be 15.2mm to 25.4mm). This time, the slope was -0.92 V/mm (instead of -0.1 V/mm).

This means that the calibration ratio for photosensor 1 (measuring mirror displacements) and photoensor 2 (measuring frame displacements) is 34.86.

Since this "unity" value should be 34.86 for my transfer function magnitude plots (instead of the ~3 value I have), do I need to scale my data? It is strange that it differs by an order of magnitude...

5192   Thu Aug 11 14:32:12 2011 KojiSummarySUSPhotosensor Head Calibration Curve for TT Frame

The entry was quite confusing owing to many misleading wordings.

- The PS2 should be calibrated "as is". (i.e. should be calibrated with the frame)

- The previous calibrations with the highly reflective surface were 0.32V/mm and 0.26V/mm, respectively.
This time you have 0.10V/mm (with an undescribed surface). The ratio is not 32 but 3.2.

- The DC output of PS2 on the shaking setup was 2.5V. The DC output seen in the plot is 3.5V-ish.
This suggests the possibiliteies:
1) The surface has slightly higher reflectivity than the frame
2) The estimation of the distance between the frame and the PS2 during the TF measurement was not accurate.

- The word "DC coupling level" is misleading. I guess you mean the DC value of the vbration isolation transfer function
of the suspension.

 Quote: I have re-calibrated the photosensor I used to measure the displacements of the TT frame (what I call "Photosensor 2"). As before, the linear region is about 15.2mm to 25.4mm. It is characterized by the slope -0.0996 V/mm (-0.1 V/mm). Recall that photosensor 1 (used to measure mirror displacements) has a calibration slope of -3.2V/mm. The ratio of the two slopes (3.2/0.1 = 32). We should thus expect the DC coupling level to be 32? This is not what we have for the DC coupling levels in our data (2.5 for flexibly-supported, fully-assembled TT (with EDC, with bar), 4.2 for EDC without bar, 3.2 for rigid EDC without bar, 3.2 for no EDC, with bar, 3.2 for no EDC without bar) . I think I may need to do my calibration plot for the photosensor at the frame?

5194   Thu Aug 11 16:07:37 2011 steveUpdateSUSETMY rack cables strain releived
Attachment 1: P1080159.JPG
Attachment 2: P1080160.JPG
5195   Thu Aug 11 16:09:05 2011 NicoleSummarySUSBode Plot for TT Suspension

All of my plots have already taken into account the calibration of the photosensor (V/mm ratio)

Here is a bode plot generated for the transfer function measurements we obtained last night/this morning. This is a bode plot for the fully-assembled T.T. (with flexibly-supported dampers and bottom bar). I will continue to upload bode plots (editing this post) as I finish them but for now I will go to sleep and come back later on today.

Here is a bode plot comparing the no eddy-current damper case with and without the bar that we suspected to induce some non-uniform damping. We have limited data on the NO EDC, no bar measurements (sine swept data from 7 Hz to 50 Hz) and FFT data from 0 Hz to 12.5 Hz because we did not want to induce too much movement in the mirror (didn't want to break the mirror).  This plot shows that there is not much difference in the transfer functions of the TT (no EDC) with and without the bar.

From FFT measurements of  the no eddy-current damper case without the bar (800 data points, integrated 10 times) we can define the resonance peak of the TT mirror (although there are still damping effects from the cantilever blades).

The largest resonance peak occurs at about 1.94 Hz. The response (magnitude) is 230.

The second-largest resonance peak occurs at about 1.67 Hz. The response (magnitude) is 153. This second resonance peak may be due to pitch motion coupling (this is caused by the fact that the clamping attaching the mirror to the wires occurs above the mirror's center of mass, leading to inevitable linear and pitch coupling).

Here is a bode plot of the EDC without the bar. It seems very similar to the bode plot with the bar

Here is a bode plot of the rigidly-supported EDC, without bar. I need to do a comparison plot of the rigid and flexibly-supported EDCs (without bar)

Attachment 1: flexwithbase.jpg
Attachment 3: stage1.jpg

[Jamie, Koji]

ITMX OSEMs were adjusted so as to have the right DC numbers and the more uniform response to POS excitation.

It is waiting for the free-swinging test.

- ITMX was moved from its position to the north side of the table.

- The table was rebalanced.

- We found that the output of the LR OSEM has an excess noise compared with the other OSEMs.
We tried to swap the LR and SD OSEMs, but the SD OSEM (placed at the LR magnet) showed
the same excess noise at around 10-50Hz.

- We found that one of the EQ stops was touching the mirror. By removing this friction, all of the OSEMs
come to show similar power spectra. Good!

- Then we started to use LOCKIN technique to measure the sensitivity of the OSEMs to the POS excitation.

Originally the response of the OSEMs was as follows
UL 3.4 UR 4.3
LL 0    LR 2.5

After the adjustment of the DC values, final values became as follows
UL 3.9 UR 4.4
LL 3.9  LR 3.2

- We decided to close the light door.

5199   Thu Aug 11 19:01:45 2011 SureshUpdateSUSITMX given a kick to start it freeswing' but to no avail.

We started an ITMX freeswing run at this time

Thu Aug 11 18:58:59 PDT 2011
997149554

But the optic did not repond to the kick.  It is possible that the earthquake stops are close to the face and/or rear of the optic and prevent it from oscillating.  We will check again and see what is up in a few hours.

[Suresh / Kiwamu]

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

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

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

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

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

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

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

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

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

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

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

- - -

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

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

Excited all optics - -
Fri Aug 12 03:34:12 PDT 2011
997180467

5205   Fri Aug 12 11:07:50 2011 NicoleSummarySUSMore TT Shaking Completed This Morning

This morning (about 10am to 11am), I have collected additional transfer function measurements for the T.T. suspension. I have finished taking my measurements. The SR785 has been returned to its place next the the seismometer racks.

The data has been backed up onto the cit40m computer

5206   Fri Aug 12 14:15:07 2011 NicoleSummarySUSBode Plot for TT Suspension

Here is my bode plot comparing the flexibly-supported and rigidly-supported EDCs (both with no bar)

It seems as if the rigidly-supported EDC has better isolation below 10 Hz (the mathematically-determined Matlab model predicted this...that for the same magnet strength, the rigid system would have a lower Q than the flexible system). Above 10 Hz (the resonance for the flexibly-supported EDCs seem to be at 9.8 Hz) , we can see that the flexibly-supported EDC has slightly better isolation? I may need to take additional measurements of the transfer function of the flexibly-supported EDC (20 Hz to 100 Hz?)  to hopefully get a less-noisy transfer function at higher frequencies. The isolation does not appear to be that much better in the noisy region (above 20Hz). This may be because of the noise (possibly from the electromagnetic field from the shaker interfering with the magnets in the TT?). There is a 3rd resonance peak at about 22 Hz. I'm not sure what causes this peak...I want to confirm it with an FFT measurement of the flexibly-supported EDC (20 Hz to 40 Hz?)

5207   Fri Aug 12 15:16:56 2011 jamieUpdateSUStoday's SUS overview

Here's an update of the suspensions, after yesterdays in-vacuum work and OSEM tweaking:

• PRM and ETMY are completely messed up.  The spectra are so bad that I'm not going to bother posting anything.   ETMY has extreme sensor voltages that indicate that it's maybe stuck to one of the OSEMS.  PRM voltages look nominal, so I have no idea what's going on there.
• ITMY is much improved, but it could still use some work
• SRM is a little worse than what it was yesterday, but we've done a lot of work on the ITMY table, such as moving ITMY suspension and rebalancing the table.
• BS looks for some reason slightly better than it did yesterday
 TM M cond(B) SRM       pit     yaw     pos     side    butt UL    0.828   1.041   1.142  -0.135   1.057  UR    1.061  -0.959   1.081  -0.063  -1.058  LR   -0.939  -0.956   0.858  -0.036   0.849  LL   -1.172   1.044   0.919  -0.108  -1.035  SD    0.196  -0.024   1.861   1.000   0.043  4.20951 ITMY       pit     yaw     pos     side    butt UL    1.141   0.177   1.193  -0.058   0.922  UR    0.052  -1.823   0.766  -0.031  -0.974  LR   -1.948  -0.082   0.807  -0.013   1.147  LL   -0.859   1.918   1.234  -0.040  -0.957  SD   -1.916   2.178   3.558   1.000   0.635   7.70705 BS       pit     yaw     pos     side    butt UL    1.589   0.694   0.182   0.302   1.042  UR    0.157  -1.306   1.842  -0.176  -0.963  LR   -1.843  -0.322   1.818  -0.213   0.957  LL   -0.411   1.678   0.158   0.265  -1.038  SD    0.754   0.298  -3.142   1.000   0.053  6.12779

5208   Fri Aug 12 15:34:16 2011 NicoleSummarySUSBode Plot for TT Suspension

 Quote: Here is my bode plot comparing the flexibly-supported and rigidly-supported EDCs (both with no bar) It seems as if the rigidly-supported EDC has better isolation below 10 Hz (the mathematically-determined Matlab model predicted this...that for the same magnet strength, the rigid system would have a lower Q than the flexible system). Above 10 Hz (the resonance for the flexibly-supported EDCs seem to be at 9.8 Hz) , we can see that the flexibly-supported EDC has slightly better isolation? I may need to take additional measurements of the transfer function of the flexibly-supported EDC (20 Hz to 100 Hz?)  to hopefully get a less-noisy transfer function at higher frequencies. The isolation does not appear to be that much better in the noisy region (above 20Hz). This may be because of the noise (possibly from the electromagnetic field from the shaker interfering with the magnets in the TT?). There is a 3rd resonance peak at about 22 Hz. I'm not sure what causes this peak...I want to confirm it with an FFT measurement of the flexibly-supported EDC (20 Hz to 40 Hz?)

Since the last post, I have found from the Characterization of TT data (from Jenne) that the resonant frequency of the cantilever springs for TT #4 (the model I am using) have a resonant frequency at 22 Hz. They are in fact inducing the 3rd resonance peak.

Here is a bode plot (CORRECTLY SCALED) comparing the rigidly-supported EDCs (model and experimental transfer functions)

Here is a bode plot comparing the flexibly-supported EDCs (model and experimental transfer functions). I have been working on this graph for FOREVER and with the set parameters, this is is close as I can get it (I've been mixing and matching parameters for well over an hour > <). I think that experimentally, the TTs have better isolation than the model because they have additional damping properties (i.e. cantilever blades that cause resonance peak at 22 Hz). Also, there may be a slight deviation because my model assumes that all four EDCs are a single EDC.

5209   Fri Aug 12 15:46:51 2011 JenneUpdateSUSEarthquake stop procedure

According to Rana, the following is the "new" (should always have been used, but now we're going to enforce it) earthquake stop backing-off procedure:

1. Back all EQ stops away from the optic, so that it is fully free-swinging.

2. Confirm on dataviewer that the optic is truely free-swinging.

3. One at a time, slowly move the EQ stop in until it barely touches the optic.  Watch dataviewer during this procedure - as soon as the time series of the OSEMs gets a 'kink', you've just barely touched the optic.

4. Back the EQ stop off by the calculated number of turns.  No inspections, no creativity, just math.  Each EQ stop should be between 1.5m and 2.0mm away from the optic.

5. Repeat steps 3 and 4 for each EQ stop.

Note: The amount that you need to turn the screws depends on what the threads are.

FACE and TOP stops are all 1/4-20, so 1.5 turns is 1.90mm

BOTTOM stops are either #4-40 or #6-32 (depending on the suspension tower).  If #4-40, 3 turns is 1.90mm.  If #6-32, 2.5 turns is 1.98mm

5215   Fri Aug 12 17:37:11 2011 JenneUpdateSUSETMY hopefully good again

[Jamie, Jenne]

We went in to have a look-see at ETMY since it looked stuck-ish.  Jamie noticed that the side magnet was pretty close to the teflon plates of the OSEM.  We rotated it a bit, and now its all better.  We also adjusted the OSEMs until their mid-ranges were happy.  The U's were a little low, and the L's were a little high, as if the optic were a bit pitched backward.  Anyhow, we checked that the table is level, and tweaked the OSEMs.  We're starting the free-swinging test now...

Excited all optics

Fri Aug 12 17:38:53 PDT 2011
997231148

5216   Fri Aug 12 20:28:13 2011 JenneUpdateSUSETMY hopefully good again

 Quote: [Jamie, Jenne] We went in to have a look-see at ETMY since it looked stuck-ish.  Jamie noticed that the side magnet was pretty close to the teflon plates of the OSEM.  We rotated it a bit, and now its all better.  We also adjusted the OSEMs until their mid-ranges were happy.  The U's were a little low, and the L's were a little high, as if the optic were a bit pitched backward.  Anyhow, we checked that the table is level, and tweaked the OSEMs.  We're starting the free-swinging test now... Excited all optics Fri Aug 12 17:38:53 PDT 2011 997231148

Hmmm.  I'm no longer convinced that ETMY is healthy.  I think that when I gave it a kick, it's bouncing against something.  I can't fit the peaks to get the input matrix.  I guess step 1 is to try giving it a smaller kick for the free swinging spectra.  But if the owl shift folk feel like it, they might have a look-see.

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

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

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

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

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

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

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

(POS sensitivity check)

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

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

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

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

So PRM used be in an extremely bad situation.

After the adjustment, the plot became much better.

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

 Quote from #5203 We tried adjusting the OSEMs on PRM, but we didn't complete it due to a malfunction on the coils. The UL and LL coils are not working correctly, the forces are weak.

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

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

--
Excited all optics
Sat Aug 13 02:08:07 PDT 2011
997261703
--

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

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

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

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

 Quote from #5216 I'm no longer convinced that ETMY is healthy. I can't fit the peaks to get the input matrix.

5222   Sat Aug 13 15:40:38 2011 NicoleSummarySUSTT Shaking Today and Hopefully More?

As reported in my  previous entry of TT supsension bode plots, I found that my experimental data had what appears to be very noise peaks above 20 Hz (as mentioned earlier, the peak at 22 Hz is likely due to vertical coupling, as 22 Hz is the resonant frequency of the cantilever blades). This is very unusual and needs to be explored further. I would like to vertically-shake the TTs to obtain more data on possible coupling. However, I am leaving on Monday and will not return until Thursday (day of SURF talks). I am leaving campus Friday afternoon or so. I would may need some help coming up with an assembly plan/assembling set-up for vertical shaking (if it is possible to do so in such a limited time frame).

Today I wanted to see if the "noisy peaks" above 30 Hz were due to EM noise coupling. I tested this hypothesis today, seeing if EM fields generated by the coil at higher frequencies were injecting noise into my transfer function measurements. I found that the "noisy peaks" above 30 Hz are NOT DUE TO EM NOISE COUPLING. I am very curious as to what is causing the high peaks (possibly coupling from other degrees of freedom)?

5223   Sat Aug 13 15:47:47 2011 NicoleSummarySUSTT Optimization Curves

Using my Matlab model of the flexibly-supported eddy current damping system, I have changed parameters to see if/how the TTs can be optimized in isolation. As I found earlier, posted in my bode plot entry, there is only a limited region where the flexibly-supported system provides better isolation than the rigidly-supported system.

Here is what I have found, where \gamma is the scale factor of the magnetic strength (proportional to magnetic strength), \beta is the scale factor of the current damper mass (estimated by attempting to fit my model to the experimental data), and \alpha is the scale factor of the current resonant frequency of the dampers.

Here are my commentaries on these plots. If you have any commentaries, it would be very helpful, as I would like to incorporate this information in my powerpoint presentation.

It seems as if the TT suspensions are already optimized?

It may be difficult to lower the resonant frequency of the dampers because that would mean changing the lengths of the EDC suspensions). Also, it appears that a rather drastic reduction (at most 0.6*current EDC resonant frequency --> reduction from about 10 Hz to 6 Hz or less) is required . Using the calculation that the resonant frequency is sqrt(g/length), for my single-suspended EDC model, this means increasing the wire length to nearly 3 x its current value. I'm not sure how this would translate to four EDCs...

The amplification at resonance caused by increasing the magnet strength almost offsets the isolation benefits of increasing magnet strength. From my modeling, it appears that the magnet strength may be very close (if not already at) isolation optimization.

Lowering the mass to 0.2 the current mass may be impractical. It seems as if the benefits of lowering the mass only occur when the mass is reduced by a factor of 0.2 (maybe 0.4)

5224   Sat Aug 13 19:08:01 2011 KojiSummarySUSTT Optimization Curves

What are the parameters you are using? As you have the drawings of the components, you can calculate the masses of the objects.

Reducing the ECD resonance from 10Hz->6Hz looks nice.

The resonant freq of the ECDs are not (fully) determined by the gravitational energy but have the contribution of the elastic energy of the wire.

Q1: How much is the res freq of the ECDs if the freq is completely determined by the grav energy? (i.e. the case of using much thinner wires)

Q2: How thin should the wires be?

5225   Sat Aug 13 21:15:47 2011 NicoleSummarySUSTT Optimization Curves

 Quote: What are the parameters you are using? As you have the drawings of the components, you can calculate the masses of the objects.   Reducing the ECD resonance from 10Hz->6Hz looks nice. The resonant freq of the ECDs are not (fully) determined by the gravitational energy but have the contribution of the elastic energy of the wire. Q1: How much is the res freq of the ECDs if the freq is completely determined by the grav energy? (i.e. the case of using much thinner wires) Q2: How thin should the wires be?

The drawings do not have the masses of the objects.

For the resonant frequency:

Instead of sqrt (g/l) would the numerator in the square root be[ g + (energy stored in wire)/(mass of damper)] ?

5226   Sat Aug 13 21:48:17 2011 KojiSummarySUSTT Optimization Curves

1) Drawing has the dimensions => You can calculate the volume => You can calculate the mass
Complicated structure can be ignored. We need a rough estimation.

2) Your restoring force can have two terms:
- one comes from the spring constant k
- the other from the gravity

5227   Sun Aug 14 00:26:51 2011 NicoleSummarySUSTT Optimization Curves

 Quote: 1) Drawing has the dimensions => You can calculate the volume => You can calculate the mass Complicated structure can be ignored. We need a rough estimation. 2) Your restoring force can have two terms: - one comes from the spring constant k - the other from the gravity

Thank you.

The wire used to suspend the EDCs is tungsten?

To verify, for my model, the EDC will be the mass of all four dampers or a single damper? The length of the wire used to suspend the EDC will be the combined length of 4 wires or length of  a single wire?

Taking into account the densities for each material (specific material of each component was listed, so I looked up the densities), and trying my best to approximate the volumes of each component, I have determined

the mass of the mirror + mirror holder to be ~100 g and the mass of a single EDC to be ~19 g

5229   Sun Aug 14 13:57:52 2011 NicoleSummarySUSTT Optimization Curves

Quote:

 Quote: 1) Drawing has the dimensions => You can calculate the volume => You can calculate the mass Complicated structure can be ignored. We need a rough estimation. 2) Your restoring force can have two terms: - one comes from the spring constant k - the other from the gravity

Thank you.

The wire used to suspend the EDCs is tungsten?

To verify, for my model, the EDC will be the mass of all four dampers or a single damper? The length of the wire used to suspend the EDC will be the combined length of 4 wires or length of  a single wire?

Taking into account the densities for each material (specific material of each component was listed, so I looked up the densities), and trying my best to approximate the volumes of each component, I have determined

the mass of the mirror + mirror holder to be ~100 g and the mass of a single EDC to be ~19 g

I am thinking that perhaps my mass estimations were off? The model that I have used fits the data better than the model that I have made (changing the masses to fit my estimations of the values)

5231   Sun Aug 14 17:47:39 2011 NicoleSummarySUSTT Shaking Today and Hopefully More?

 Quote: As reported in my  previous entry of TT supsension bode plots, I found that my experimental data had what appears to be very noise peaks above 20 Hz (as mentioned earlier, the peak at 22 Hz is likely due to vertical coupling, as 22 Hz is the resonant frequency of the cantilever blades). This is very unusual and needs to be explored further. I would like to vertically-shake the TTs to obtain more data on possible coupling. However, I am leaving on Monday and will not return until Thursday (day of SURF talks). I am leaving campus Friday afternoon or so. I would may need some help coming up with an assembly plan/assembling set-up for vertical shaking (if it is possible to do so in such a limited time frame).   Today I wanted to see if the "noisy peaks" above 30 Hz were due to EM noise coupling. I tested this hypothesis today, seeing if EM fields generated by the coil at higher frequencies were injecting noise into my transfer function measurements. I found that the "noisy peaks" above 30 Hz are NOT DUE TO EM NOISE COUPLING. I am very curious as to what is causing the high peaks (possibly coupling from other degrees of freedom)?

I have been redoing the noise test multiple times today. Here is the best plot that I got

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

Excited all optics
Sun Aug 14 20:22:33 PDT 2011
997413768

[Suresh / Kiwamu]

Adjustment of the OSEMs on BS has been done.

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

5237   Mon Aug 15 13:16:50 2011 JenneUpdateSUSRe: ETMY hopefully good again

Quote:

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

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

 Quote from #5216 I'm no longer convinced that ETMY is healthy. I can't fit the peaks to get the input matrix.

Turns out I was missing a critical step in the process...running makeSUSspectra.m  After I do that, everything is back under control, and ETMY looks fine.

I'm almost done doing the peak-fitting and matrix inversion for all optics.

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