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ID Date Author Type Categoryup Subject
  816   Fri Aug 8 13:29:54 2008 YoichiUpdateSUSNo groove in the stand-off ... wait, it is not even a stand-off !
Yoichi, Steve, Seiji

We took magnified pictures of the stand-offs of the PRM.
Attm1: North side stand-off.
Attm2: South side stand-off.
Attm3: Zipped file of the full pictures.

We found no groove in the south side stand-off.
After some discussion, we concluded that it is actually a guide rod. You can see it from the size difference (the magnification is the same for the two pictures).
The stand off on the south side is missing (fell off, ran away, evaporated or whatever ...).
Also we noticed that the guide rod on the north side is missing.

We have to find a stand-off and place it on the south side.
Seiji suggested that it is better to put a guide rod next to the north side stand-off, otherwise the stand-off itself is too weak to hold the load.
He also said that the PRM was installed after he left, so it was not his fault.
Attachment 1: north-standoff-preview.jpg
north-standoff-preview.jpg
Attachment 2: south-standoff-preview.jpg
south-standoff-preview.jpg
Attachment 3: No-groove.zip
  817   Fri Aug 8 15:10:35 2008 YoichiUpdateSUSNo groove in the stand-off ... wait, it is not even a stand-off !
I tried to find the missing stand-off and the guide rod in the BS chamber, but I couldn't.
  818   Fri Aug 8 17:54:52 2008 JenneUpdateSUSStandoffs and Guide Rods
After closer inspection of other small optics, it is clear that the guide rods should be above the standoffs on our small optics. Yoichi took a picture of the SRM that shows this clearly. This makes sense since the tension of the wire will make the standoff 'want' to go up during pre-epoxy adjustment, so the guide rod prevents the standoff from popping up and out.

Looking at the side of the PRM without the groove, it looks like there is lots of space between the guide rod and the alignment etch in the glass, so we can just place a standoff directly under the guide rod that is present.

A spare standoff is being shipped tomorrow morning, so we should have it by Monday for installation on the PRM.
Attachment 1: SRM_Standoff_and_guide.JPG
SRM_Standoff_and_guide.JPG
  831   Wed Aug 13 17:00:59 2008 steveConfigurationSUSBS sat amp removed
The PRM sat amp is broken. Ben is working on it.
The BS sat amp was removed from the BS sus and it is used with the PRM in
order to damp it for wire stand-off alignment.
  832   Wed Aug 13 20:13:35 2008 YoichiUpdateSUSPRM stand-off is glued
Steve, Janne, Rob, Bob, Koji, Yoichi

We finally managed to balance the PRM and the stand-off is now glued.

The whole procedure was something like this:

(1) Measure the levelness of the optical table. It was done by a bubble level claiming that
the sensitivity is 60 arcsec (roughly 0.3 mrad).
There was no noticeable tilt along the longitudinal direction of the table.

(2) We put a He-Ne laser on one end of the table. Mounted a QPD on a X-Y-Z stage. Put the QPD very
close to the laser and centered it by moving the QPD.
Then we moved the QPD far away from the laser and centered the beam spot in vertical direction
by changing the tilt of the laser mount.
We then moved the QPD close to the laser again and adjusted the height to center it. By repeating
the centering at two locations (near and far) several times, we aligned the laser beam parallel to
the table.

(3) The PRM suspension tower was put on the other end of the optical table, i.e. far from the laser.
The QPD was moved next to the laser to form an optical lever. The height of the QPD is preserved from
the previous step.


(4) A stand-off was picked by a pair of tweezers. By gently lifting the mirror by the bottom earthquake stops,
the tension of the wire was relieved. Then the stand off was slid in below the guide rod.

(5) Using the microscope, it was confirmed that the wire is in the grooves on both sides.

(6) Without damping, it was too much pain to balance the mirror. So we put spare OSEMs in the suspension and
pulled a long cable from the suspension rack to the clean room with a satellite amp.

(7) It turned out that the pinout of the cable is flipped because of the vacuum feed through. So we asked Ben for help.
He made conversion cables. We also found UR OSEM was not responding. Ben opened the satellite box, and we found an op-amp was burnt.
Probably it was because we connected OSEMs wrongly at first and the LED current driver was shorted. We switched the satellite box
from the PRM one to the BS one. Ben will fix the PRM box.
Bob cleaned up some D-Sub converters for the interface with the clean OSEM pigtails.

(8) While waiting for Ben, we also tried to short the OSEM coils for inductive damping. We saw no noticeable change in the Q.

(9) After the OSEMs were connected to the digital control system, Rob tweaked the damping gains a bit to make it work efficiently.

(10) I pushed the stand-off back and forth to make the reflected beam spot centered on the QPD. I used the PZT buzzer to gently move the stand-off.
For fine tune, just touching it is enough. I found it useful to touch it without clamping the mirror, because if it is clamped, we can easily push
it too hard. When the mirror is freely hanging, once the tip of the buzzer touches the stand-off, the mirror escapes immediately. If the mirror
swings wildly by your touch, you pushed it too hard.

(11) After about an hour of struggle, I was able to level the mirror. We used about 1.5m optical lever arm. A rough calibration tells us that the
beam spot is within 0.6mm of the center of the QPD. So the reflected light is deflected by 0.4mrad. That means the mirror
is rotated by 0.2mrad. The OSEMs should have about 30mrad of actuation range. So this should be fine.

(12) We mixed the Vac Seal epoxy and put it under vacuum for 15min to remove bubbles. Actually 15min was not enough for removing bubbles completely. But
stopped there because we did not want the epoxy to be too stiff.
I dipped a thin copper wire into the epoxy and applied it on the top of the stand-off. I found the epoxy is already not fluid enough, so Steve made
another Vac Seal mixture. This time we put it under vacuum for only 3 min.
I also applied the epoxy to the sides of the stand-off.
While working on this, I accidentally touched the side of the PRM. Now there is a drop of epoxy sitting there (upper left of the attached picture).
We decided not to wipe it out because we did not want to screw up the levelness.

(13) We put an incandescent light about 1m away from the suspension to gently warm up the epoxy but not too much. We will leave it overnight to cure the
epoxy.
Attachment 1: img1.jpg
img1.jpg
  833   Thu Aug 14 10:26:45 2008 steveHowToSUSsus cable pin cheater for out of vac damping
The 40m D25 vacuum feed troughs give you a mirror image pin count.

Sus damping outside of the vacuum envelope require this cheater cable where
on the male D pin 1 is connected to female D 13 and so on
and male D pin 14 is connected to female D 25 and so on
Attachment 1: suscabmin.png
suscabmin.png
  836   Thu Aug 14 19:08:14 2008 YoichiConfigurationSUSFree swing measurement going on
I started free swinging spectra measurement of all the suspensions now Aug 14 19:05 (PDT).
The watch dogs are all shutdown. Please do not turn them back on until tomorrow morning.
  842   Fri Aug 15 17:38:41 2008 YoichiUpdateSUSOSEM free swinging spectra before the pump down
I ran an overnight measurement of the free swinging OSEM spectra.
The attm1 shows the results. Everything look ok except for the ITMY UL OSEM.
The time series from that OSEM was very noisy and had many spikes.
We suspected the cable from the satellite box to the computer rack because we disconnected the cable
when we tested a spare cable which was used to connect the spare OSEMs to the PRM suspension in the clean room.
Janne remembered when she put the cable back, she trusted the latch on the connector and did not push it in too hard.
However, Rob suggested the latch does not work well. So she pushed the connector again. Then the signal from
the ITMY UL OSEM got back to normal.
The second attachment shows the ITMY spectra after the cable push.
We decided to pump down after confirming this.

There are still a lot of extra peaks especially in the suspensions in the BS chamber.
These may be inter modulations (by the non-linearities of the OSEMs) of the modes of the multiple
suspensions sitting on the same stack.
Attachment 1: 2008-8-15.pdf
2008-8-15.pdf 2008-8-15.pdf 2008-8-15.pdf 2008-8-15.pdf 2008-8-15.pdf 2008-8-15.pdf 2008-8-15.pdf 2008-8-15.pdf
Attachment 2: ITMY2.pdf
ITMY2.pdf
  844   Mon Aug 18 08:07:10 2008 YoichiConfigurationSUSSuspension free swinging
I've started a free swinging measurement of OSEM spectra now. Please leave the watchdogs untouched.
  846   Mon Aug 18 11:50:29 2008 YoichiUpdateSUSIn vacuum free swinging results
The first attachment is the results of the free swinging spectra measurement performed in vacuum this morning.
They are freely swinging, but the suspensions in the BS chamber got even more extra peaks.
Especially, the SRM spectrum looks like a forest.
If those extra peaks are inter-modulations of the primary suspension modes, the heights of them should be
enhanced (compared to the in-the-air case) by the increased quality factors of the primary modes (due to the less air friction).
This might explain the observed increase in the extra peaks.

While doing the free swinging, we had two big spikes in the OSEM signals of the ETMs and only in ETMs.
Those spikes screwed up the spectra of the ETMs. So the ETM spectra were calculated using the time series
after the spikes.
The second attachment shows one of those spikes. It looks like a computer glitch.
Attachment 1: 2008-8-18.pdf
2008-8-18.pdf 2008-8-18.pdf 2008-8-18.pdf 2008-8-18.pdf 2008-8-18.pdf 2008-8-18.pdf 2008-8-18.pdf 2008-8-18.pdf
Attachment 2: spike.pdf
spike.pdf
  851   Tue Aug 19 13:12:55 2008 JenneUpdateSUSDiagonalized PRM Input Matrix
NOTE: Use the values in elog #860 instead (20Aug2008)

Using the method described in LIGO-T040054-03-R (Shihori's "Diagonalization of the Input Matrix of the Suspension System"), I have diagonalized the input matrices for the PRM.

Notes about the method in the document:
  • Must define the peak-to-peak voltage (measured via DataViewer) to be NEGATIVE for PitLR, PitLL, YawUR, YawLR, and POSITIVE for all others
  • As Osamu noted in his 3 Aug 2005 elog entry, all of the negative signs in equations 4-9 should all be plus.

New PRM Input Matrices:

POSPITYAW
UL1.0001.0001.000
UR1.18771.0075 -1.0135
LR0.8439 -0.9425 -0.9653
LL0.9684 -1.05001.0216
  860   Wed Aug 20 12:04:47 2008 JenneUpdateSUSBetter diagonalization of PRM input matrix
The values here should replace those in entry #851 from yesterday.

After checking the results of the input matrix diagonalization, I have determined that Sonia's method (described in LIGO-T070168) is more effective at isolating the eigenmodes than Shihori's method (LIGO-T040054).

So, the actual new PRM input matrices are as follows:

POSPITYAW
UL0.96781.0000.7321
UR1.0000.8025 -0.9993
LR0.7235 -1.1230 -1.0129
LL0.6648 -1.04521.0000


Attached are plots of the spectra of the eigenmodes, using both Shihori's and Sonia's methods. Note that there isn't a good way to get the side peak out of the eigenmodes.

I've put these into the SUS-PRM MEDM screen.
Attachment 1: PRM_Eigmodes_shihori.png
PRM_Eigmodes_shihori.png
Attachment 2: PRM_Eigmodes_sonia.png
PRM_Eigmodes_sonia.png
  869   Fri Aug 22 10:39:41 2008 JenneUpdateSUSTaking Free Swinging spectra of PRM, SRM, ITMX, BS
I'm taking free swinging spectra of PRM, SRM, ITMX and BS, so I've turned off their watchdogs for now. I should be done around 11:15am, so I'll turn them back on then.
  970   Fri Sep 19 01:55:41 2008 ranaSummarySUSSUS Drift Screen Updated
I wrote 2 matlab scripts to update the SUS DRIFT screen:
- setsval.m   uses mDV to get the minute trend from some specified start time
              and duration in the past. It then writes that 'good' value to the
              .SVAL field of the SUSPOS, SUSPIT, and SUSYAW records for all the
              optics

- setHILO.m   reads the .SVAL field and then sets the alarm levels and severity
              for the same records given a "sigma" as an argument. i.e. 1 sigma = HIGH,
              2 sigma = HIHI.

Attached is the new screen. WE can now use this to judge when the optics have moved alot.

If someone will edit the BURT .req file to have these subfields
(.HIHI .HIGH .LOW .LOLO .HHSV .HSV .LSV .LLSV) then they will come back after a reboot as well.

Below I'm also attaching the matlab code for people at the observatories who don't have
access to the SVN here.
Attachment 1: infection-3.png
infection-3.png
Attachment 2: setsvals.m
function varargout = setsvals(varargin)
% SETSVALS
% sets the SVAL records for the SUS

debug = 0;


if nargin < 2
  error('Needs 2 arguments.')
elseif nargin > 2
... 56 more lines ...
Attachment 3: setHILO.m
function setHILO(varargin)
%  SETHILO 
%  Ex.  setHILO(1000);
%      this sets the SUS alarm levels to be 1000 counts
%      from the nominal

% 1 for debugging
debug_flag = 0;

if nargin == 1
... 62 more lines ...
  975   Mon Sep 22 12:06:58 2008 robUpdateSUSITMY UL OSEM


Last week I found the ITMY UL OSEM dead. I went around and checked the connections on the various flat ribbon cables
in the suspension control chain; pushing hard on the rack end of the long cable that goes from the sus electronics rack to the
ITMY sat amplifier fixed the problem. It's been fine since then.

NB: A visual inspection of the cable connection would not have revealed a problem. You just can't trust those flat
ribbon connectors with the hook latches.
  996   Fri Sep 26 09:05:47 2008 steveUpdateSUSMC2 damping restored
The MC2 sus damping was restored.
  1021   Thu Oct 2 18:56:19 2008 ranaSummarySUSResistivity of Suspension Wire
Bob and Steve measured the resistance of the suspension wire today:
OD     = 0.0036" =  0.091 mm
Length = 46"     = 1168.4 mm
Resistance     =   33.3 Ohms

resistivity = R * pi * (OD/2)^2
              ----------------- = 1.85e-7 Ohm-meters
                  Length 


This was a batch of California Fine Wire from 2001 (same as used at LHO and LLO).

By comparison the standard tabulated resistivity for steels is (http://hypertextbook.com/facts/2006/UmranUgur.shtml):
                  resistivity (Ohm-meter x 10^-7)
-------------     ----------------
304 Stainless       7.2
316 Stainless       7.4
Cast Steel          1.6

This is all to see whether or not the 60 Hz fields produce forces on the suspension wires via coupling with the Earth's DC field.

TBD
  1103   Fri Oct 31 08:52:19 2008 steveUpdateSUSETMY damping restored
ETMY watchdogs were tripped yesterday morning also. This is a problem that existed some months ago.(?)
Our seimo channels are inactive.
Attachment 1: etmy2d.jpg
etmy2d.jpg
  1188   Mon Dec 8 17:50:21 2008 YoichiUpdateSUSITMY drift
The suspension drift monitor shows that the ITMY alignment was shifted after the earthquake.
Looks like only the UL sensor had a step at the earthquake (see the attachment 1).
So it is probably an electronics problem.
I pushed in the cable between the rack and the ITMY satellite amplifier, but no change observed.
Actually, the ITMY-UL sensor looks like it has been dead before the earthquake.
The second attachment shows a long-term trend of the UL sensor.
The sensor output had been around zero since Nov. 17th.
When I disabled the output of the UL sensor, the sus-drift-mon fields turned green.
So I think the drift-mon's reference values are wrong, and currently the ITMY is in a good alignment.

I also attached the free-swing measurements of the ITMY taken on Aug. 18th and today.
There is no notable change in the resonant frequencies.
Attachment 1: ITMY-OSEMs.png
ITMY-OSEMs.png
Attachment 2: ITMY-UL.png
ITMY-UL.png
Attachment 3: ITMY-08-18.pdf
ITMY-08-18.pdf
Attachment 4: ITMY-12-08.pdf
ITMY-12-08.pdf
  1192   Thu Dec 18 12:52:00 2008 AlbertoConfigurationSUSMode Cleaner Cavity Alignment
This morning I found the MC locked to the 10 mode. When I locked it on the 00 mode, it was unstable and eventually it always got locked to the wrong mode.

I looked at the Drift Mon MEDM screen, which shows a reference record for position, pitch and yaw of each mirror, and I found that the MC optics were in a different status. Moving the sliders of the mirrors' actuators, I brought them back to the reference position. Then the lock got engaged and it was stable, although the MC reflection from the photodiode, with the wave front sensors (WFS) off, was about 2V. That's higher than the 0.5V the it could get when we aligned the cavity and the input periscope last time.

With the WFS on, the reflection dropped to 0.3V and, so far, the the cavity has been stably locked.
  1193   Thu Dec 18 19:15:54 2008 Alberto, YoichiConfigurationSUSMode Cleaner Cavity Alignment

Quote:
This morning I found the MC locked to the 10 mode. When I locked it on the 00 mode, it was unstable and eventually it always got locked to the wrong mode.

I looked at the Drift Mon MEDM screen, which shows a reference record for position, pitch and yaw of each mirror, and I found that the MC optics were in a different status. Moving the sliders of the mirrors' actuators, I brought them back to the reference position. Then the lock got engaged and it was stable, although the MC reflection from the photodiode, with the wave front sensors (WFS) off, was about 2V. That's higher than the 0.5V the it could get when we aligned the cavity and the input periscope last time.

With the WFS on, the reflection dropped to 0.3V and, so far, the the cavity has been stably locked.


This evening the mode cleaner was again locking on a higher mode so we tweaked the mirrors' actuators by their sliders on the MEDM screen until we improved the reflection to 0.3V.

Then we went inside and, on the AS table, we centered the beam on the wave front sensors.

Now the mode cleaner is locked, the reflection is less than 0.3V and the transmission about 3V, tha is it is in ideal conditions. We'll see if it holds.
  1234   Fri Jan 16 18:29:08 2009 YoichiUpdateSUSOplevs QPDs centered
Kakeru centered ITMX and BS optical levers with the help of Jenne on the walkie-talkie.
  1314   Mon Feb 16 22:58:51 2009 rana, yoichiConfigurationSUSHysteresis in SUS from Misalignments
WE wondered if there was some hysteresis in the SUS alignments. When we leave the optics misaligned for a
long time it seems to take awhile for the optic to settle down. Possibly, this is the slow deformation of
the wires or the clamps.

The attached PNG shows the plot of the bias sliders for a few days. You can see that we misalign some of the
optics much more than the others. This must be stopped.

Kakeru is going to use his nearly complete optical lever calibrations to quatify this by stepping the optics
around and measuring the effect in the optical lever. Of course, the misalignment steps will be too large to
catch on the OL, but he can calibrate the align-sliders into radians to handle this.
Attachment 1: a.png
a.png
  1420   Tue Mar 24 09:04:02 2009 steveUpdateSUS4.8 mag earthquake

SRM, ITMX, ETMX, ITMY and ETMY lost damping at 4:55am this morning from 4.8 magnitude earthquake.

Their damping were restored.

C1:SUS-ITMX_URSEN_OUTPUT swich was found in off position. It was turned on.

MZehnder  and MC were locked.

The WFS qpd spot needs recentering

  1422   Tue Mar 24 13:54:49 2009 JenneUpdateSUSOp Levs Centered

ITMX, ITMY, BS, SRM, PRM op levs were all recentered.  ETM's looked okay enough to leave as-is. 

  1439   Sun Mar 29 13:44:27 2009 steveUpdateSUSETMY sus damping restored

ETMY sus damping was found to be tripped.

It was retored.

All fluorecent light were turned off. Please try to conserve some energy.

  1440   Sun Mar 29 17:54:41 2009 YoichiUpdateSUSMC1 drift investigation continued
The attached plots show the trend of the MC OSEM signals along with the voltages across the output resistors of the bias current buffers.
The channel assignments are:
MC_TMP1 = LL coil
MC_DRUM1 = UL coil
OSA_APTEMP = UR coil
OSA_SPTEMP = LR coil

Although the amplitude of the drift of MC1 is much larger than that of MC2 and MC3, the shape of the drift looks like a daily cycle (temperature ?).
This time, I reduced the MC1 bias currents to avoid saturation of the ADCs for the channels measuring the voltages across the output resistors.
This may be the reason the MC1 has been non-glitchy for the last day.

OSA_APTEMP (UR Coil) shows a step function like behavior, although it did not show up in the OSEM signals.
This, of course, should not happen.

Today, I went to the MC1 satellite box and found that the 64-pin IDE like connector was broken.
The connector is supposed to sandwich the ribbon cable, but the top piece was loose.
The connector is on the cable connecting the satellite box and the SUS rack.
I replaced the broken connector with a new one. I also swapped the MC1 and MC3 satellite boxes to see if the glitches show up in the MC3.

I restored the bias currents of the MC1 to the original values.

The probes to monitor the voltages across the output resistors are still there. For OSA_SPTEMP, which was saturating the ADC, I put a voltage divider before the ADC. Other channels were very close to saturation but still within the ADC range.

Please leave the MC unlocked at least until the Monday morning.
Also please do not touch the Pomona box hanging in front of the IOO rack. It is the voltage divider. The case is connected to the coil side of the output resistor. If you touch it, the MC1 bias current will change.

Attachment 1: Drift1.pdf
Drift1.pdf
  1441   Mon Mar 30 09:07:22 2009 ranaUpdateSUSMC1 drift investigation continued
Maybe we can temporarily just disconnect the bias and just use the SUS sliders for bias if there's enough range?
  1444   Mon Mar 30 13:29:40 2009 YoichiUpdateSUSMC1 drift investigation continued

Quote:
Maybe we can temporarily just disconnect the bias and just use the SUS sliders for bias if there's enough range?


We could do this, but I'm suspicious of the cables between the coil driver and the coils (including the satellite box). In this case, disabling the bias won't help.
Since the MC1 has been quiet recently, I will just lock the MC and resume the locking.
  1583   Wed May 13 21:15:04 2009 ranaSummarySUSChannel Hopping: That ancient enemy (MC problems)
The MC side problem could also be the side tramp unit problem. Set the tramp to 0 and see if that helps.
  1584   Thu May 14 00:15:39 2009 robSummarySUSChannel Hopping: That ancient enemy (MC problems)

Quote:
The MC side problem could also be the side tramp unit problem. Set the tramp to 0 and see if that helps.


This started around April 23, around the time that TP1 failed and we switched to the cryopump, and also when there was a mag 4 earthquake in LA. My money's on the EQ. But I don't know how.
Attachment 1: sidemon.png
sidemon.png
  1586   Thu May 14 15:28:28 2009 steveSummarySUSApril 24 earthquake effect on MC2

Quote:

Quote:
The MC side problem could also be the side tramp unit problem. Set the tramp to 0 and see if that helps.


This started around April 23, around the time that TP1 failed and we switched to the cryopump, and also when there was a mag 4 earthquake in LA. My money's on the EQ. But I don't know how.



Only MC2 moved in this earth quake. Was the MC alignment touched up since than?
Have you guys swapped satellite amp of MC3 yet?
Attachment 1: eq042409.jpg
eq042409.jpg
  1587   Thu May 14 16:07:20 2009 peteSummarySUSChannel Hopping: That ancient enemy (MC problems)

Quote:

Quote:
The MC side problem could also be the side tramp unit problem. Set the tramp to 0 and see if that helps.


This started around April 23, around the time that TP1 failed and we switched to the cryopump, and also when there was a mag 4 earthquake in LA. My money's on the EQ. But I don't know how.


I wonder if this is still a problem. It has been quiet for a day now. I've attached a day-long trend. Let's see what happens.
Attachment 1: mc3_5days.jpg
mc3_5days.jpg
  1588   Fri May 15 00:02:34 2009 peteUpdateSUSETMX coils look OK

I checked the four rear coils on ETMX by exciting XXCOIL_EXC channel in DTT with amplitude 1000@ 500 Hz and observing the oplev PERROR and YERROR channels.  Each coil showed a clear signal in PERROR, about 2e-6 cts.  Anyway, the coils passed this test.

 

  1603   Mon May 18 21:34:18 2009 ranaConfigurationSUSETMY f2pRatio script run
Now that the ETMY optical lever is not so bad, I ran the f2pRatio script and it seems to have worked.

I cleaned up the script a little also. Updated in the SVN.

ETMY's A2L scripts have to be run to reduce the A2L noise once the arm is locked again. Might also need
to set the OL UGF too.
  1605   Tue May 19 12:30:41 2009 robConfigurationSUSETMY f2pRatio script run

Quote:
Now that the ETMY optical lever is not so bad, I ran the f2pRatio script and it seems to have worked.

I cleaned up the script a little also. Updated in the SVN.

ETMY's A2L scripts have to be run to reduce the A2L noise once the arm is locked again. Might also need
to set the OL UGF too.


Just to show, in part, what the script does.

The F2A filters are turned on at 12:21, and the oplev no longer responds to large LSC drives in ETMY.
Attachment 1: f2ademo.png
f2ademo.png
  1616   Thu May 21 18:05:03 2009 peteUpdateSUSETMX coils look OK

Quote:

I checked the four rear coils on ETMX by exciting XXCOIL_EXC channel in DTT with amplitude 1000@ 500 Hz and observing the oplev PERROR and YERROR channels.  Each coil showed a clear signal in PERROR, about 2e-6 cts.  Anyway, the coils passed this test.

 

 I also made xfer fctns of the 4 piston coils on ETMY and ETMX with OL_PIT.  (I looked at all 4 even though the attached plot only shows three.)  So it looks ike the coils are OK.

Attachment 1: etmx_etmy_coils.pdf
etmx_etmy_coils.pdf
  1620   Fri May 22 01:27:14 2009 peteUpdateSUS200 days of MC3 side

Looks like something went nuts in late April.  We have yet to try a hard reboot.

Attachment 1: mc3_side_200days.png
mc3_side_200days.png
  1796   Mon Jul 27 14:12:14 2009 ranaSummarySUSTM Coil Noise Spectra
Rob noticed that the ITMY DAC channels were saturating occassionally. Looking at the spectrum we can see why.
With an RMS of 10000 cts, the peak excursions sometimes cause saturations.

There's a lot of mechanical noise which is showing up on the ITM oplevs and then going to the mirror via
the oplev servo. We need to reduce the mechanical noise and/or modify the filters to compensate. The ITM
COIL_OUT RMS needs to be less than ~3000.
Attachment 1: Coils.pdf
Coils.pdf
  2024   Tue Sep 29 23:43:46 2009 robUpdateSUSITMY UL OSEM

We had a redo of elog entry 975 tonight.  The noisy OSEM was fixed by jiggling the rack end of the long cable.  Don't know exactly where--I also poked around the OSEM PD interface board.

In the attached PDF the reference trace is the noisy one.

Attachment 1: ITMYosemBAD.pdf
ITMYosemBAD.pdf
  2031   Thu Oct 1 08:37:43 2009 steveUpdateSUSsuspention damping restored and MZ HV stuck

Earthquake  of magnitude 5.0  shakes ETMY loose.

MC2 lost it's damping later.

Attachment 1: eq5oct1.jpg
eq5oct1.jpg
  2034   Thu Oct 1 11:39:47 2009 JenneUpdateSUSMC2 damping restored again

Quote:

 The EQ did not change the input beam pointing. All back to normal, except MC2 wachdogs tripped again.

 Round 3 for the day of MC2 watchdogs tripping.

  2036   Thu Oct 1 14:22:28 2009 robUpdateSUSall suspensions undamped

Quote:

Quote:

 The EQ did not change the input beam pointing. All back to normal, except MC2 wachdogs tripped again.

 Round 3 for the day of MC2 watchdogs tripping.

 I've watchdogged all the suspensions while I mess around with computers.  If no one else is using the IFO, we can leave them undamped for a couple of hours to check the resonant frequencies, as long as I don't interrupt data streams with my computer hatcheting.

  2039   Thu Oct 1 19:18:24 2009 KojiUpdateSUSall suspensions undamped

Ops. I restored the damping of the suspensions at around 16:30.

Quote:

Quote:

Quote:

 The EQ did not change the input beam pointing. All back to normal, except MC2 wachdogs tripped again.

 Round 3 for the day of MC2 watchdogs tripping.

 I've watchdogged all the suspensions while I mess around with computers.  If no one else is using the IFO, we can leave them undamped for a couple of hours to check the resonant frequencies, as long as I don't interrupt data streams with my computer hatcheting.

 

  2193   Fri Nov 6 12:56:30 2009 HaixingUpdateSUSMagnet has been levitated

  In this experiment, we used a feedback control to create a stable trap for a NdFeB permanent magnet. The block diagram is the following:

block_diagram.PNG

 

 

The displacement of the magnet is sensed by the Hall-effect sensor, whose output voltage is proportional to the magnetic flux produced

by the permanent magnet. It has a flat response within the frequencies we are interested in. It is driven by a 5 V power supplier and its

output has a DC voltagle of 2.5 V. We subtracted the DC voltage and used the resulting signal as the error signal. This was

simply achieved by using two channels "A" and "B". The output is "A-B" with a gain equal to one. We then put the error

signal into another  SR560 as a low-pass filter with a gain of 100 above 30 Hz. We used the "DC" coupling modes in both

preamplifers. The output is then used to drive a coil. The coil has a dimension of 1.5 inch in diameter and 2 inch in length.

The inductance of the coil is around 0.5 H and the resistance is 4.7 Om. Therefore, it has a corner frequency aournd 10/2pi Hz.

The coil has a iron core inside to enhance the DC force to the permanent magnet. The low-frequency 1/f response of the magnet is produced

by the eddy current damping of the aluminum plane that is below the magnet. This 1/f response is essential for a stable configuration. In the

next stage, we will remove the aluminum plane, and instead we will use a filter to create similar transfer function. At high-frequencies, it behaves as 

a free-mass and has a 1/f^2 response. Finally, the magnet is stably levitated.

 

Attachment 1: DSC_0964.JPG
DSC_0964.JPG
  2204   Sun Nov 8 14:18:25 2009 AlbertoUpdateSUSETMY Watchdogs tripped

This afternoon I re-enabled the ETMY coils after I found that the watchdogs for the mirror had tripped last night at 2:06am.

  2207   Mon Nov 9 08:43:16 2009 steveUpdateSUSMC2 damping restored

MC2 damping restored,  MZ locked and the arms are flashing now.

  2246   Thu Nov 12 01:18:34 2009 haixingUpdateSUSopen-loop transfer function of mag levi system (comparison between simulink and measurement)

I built a Simulink model of the magnetic levitation system and try to explain the dip in the open-loop transfer function that was observed.

One can download the model in the svn. The corresponding block diagram is shown by the figure below.

 

block_diagram.png

Here "Magnet" is equal to inverse of the magnet mass. Integrator "1/s" gives the velocity of the magnet. A further integrator gives the displacement of the magnet.

 

Different from the free-mass response, the response of the magnet is modified due to the existence of the Eddy-current damping  and negative spring in the vertical

direction, as indicated by the feedback loops after two integrals respectively. The motion of the magnet will change the magnetic field strength which in turn will pick

up by the Hall-effect sensor. Unlike the usual case, here the Hall sensor also picks up the magnetic field created by the coil as indicated by the loop below the mechanical

part. This is actually the origin of the dip in the open-loop transfer function. In the figure below, we show the open-loop transfer function and its phase contributed by both

the mechanical motion of the magnet and the Hall sensor with the black curve "Total". The contribution from the mechanical motion alone is shown by the magenta curve

"Mech" which is obtained by disconnecting the Hall sensor loop (I rescale the total gain to fit the measurement data due to uncertainties in those gains indicated in the figure). 

The contribution from the Hall sensor alone is indicated by the blue curve "Hall" which  is obtained by disconnecting the mechanical motion loop. Those two contributions

have the different sign as shown by the phase plot, and they destructively interfere with each other and create the dip in the open-loop transfer function.

contribution_plot.png

In the following figure, we show the close-loop response function of the mechanical motion of the magnet.

 

mech_resp_plot.png

As we can see, even though the entire close loop of the circuit is stable, the mechanical motion is unstable around 10 Hz. This simply comes from the fact that

around this frequency, the Hall sensor almost has no response to the mechanical motion due to destructive interference as mentioned.

 

In the future, we will replace the Hall sensor with an optical one to get rid of this undesired destructive interference.

 

 

  2274   Mon Nov 16 15:18:10 2009 haixingUpdateSUSStable magnetic levitation without eddy-current damping

By including a differentiator from 10 Hz to 50 Hz, we increase the phase margin and the resulting

magnetic levitation system is stable even without the help of eddy-current damping.

The new block diagram for the system is the following:

 block_diagram_new.png

Here the eddy-current damping component is removed and we add an additional differential

circuit with an operational amplifier OP27G.

In addition, we place the Hall sensor below the magnet to minimize the coupling between

the coil and the Hall sensor.

The resulting levitation system is shown by the figure below:

mag_levi_new.jpg

  2280   Tue Nov 17 11:09:43 2009 KojiConfigurationSUSETMY suspension conencted to megatron ADC/DAC

I have connected ETMY sus electronics to megatron ADC/DAC.
We continue this state until 15:00 of today. (Restored 13:00)

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