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ID Date Author Type Category Subjectup
  4876   Fri Jun 24 07:40:23 2011 steveUpdateSUSPRM damping restored

The PRM sus damping restored. C1:SUS-PRM_SDPD_VAR is still 20-30mV and going up.  Side gain  turned on. This pulled it down to 5-8 mV

Why is the side osem sensing voltage 4.4V ? It can not be higher than ~2.4V.......something is rotten in the state of Denmark?

Edit by KI:

 It's because Valera increased the transimpedance gain of the PRM SIDE OSEM to match the signal level to the new ADC range (#3913 ).

  4938   Tue Jul 5 13:35:56 2011 steveUpdateSUSPRM damping restored

The PRM sus damping was restored. It's side rms motion came down from 35 to 4 mV immediately.      Lab   air quality is back to normal.

 

  4987   Tue Jul 19 09:19:14 2011 steveUpdateSUSPRM damping restored

The PRM watchdogs were tripped. The side was kicked up to 180mV Damping was restored.

  5403   Wed Sep 14 07:51:20 2011 steveUpdateSUSPRM damping restored

The PRM damping was restored at side sensor var 1050

  5415   Thu Sep 15 07:28:08 2011 steveUpdateSUSPRM damping restored

Quote:

The PRM damping was restored at side sensor var 1050

 The PRM sus damping restored.

  5909   Wed Nov 16 10:25:57 2011 steveUpdateSUSPRM damping restored

The  PRM lost damping about a day ago. It was restored.

  7333   Tue Sep 4 10:29:41 2012 SteveUpdateSUSPRM damping restored
  7544   Mon Oct 15 08:08:33 2012 steveUpdateSUSPRM damping restored

Quote:

Quote:

Quote:

Quote:

Yuta claims he fixed the PRM oplev by centering it the other day, but no one has left it on and watched it for a long while, to make sure it's okay.  We watched it now for ~2 min, and it was good, but we're leaving the oplevs off anyway for the night.  Tomorrow we should restore PRM (it's currently restored), turn on the oplevs, and let it sit to make sure it doesn't go crazy.

 

 PRM oplev servo was turned on with PITgain 0.5  and YAWgain  -0.7

Note: gain settings were PIT  1.0  and  YAW --0.5   on Jun 1, 2012 that I measured Feb 23, 2012

 It is still oscillating. Gains turned down to zero.

 Earthquake test our suspensions            PRM damping restored.             Oplev servo gains turned to zero.

 The PRM damping restored. Oplev  PIT gain  0.15 and YAW  gain   -0.3 turned to zero.

  7781   Tue Dec 4 10:51:10 2012 SteveUpdateSUSPRM damping restored

PRM oplev gains set to zero from PIT 0.15 and YAW -0.3 and damping restored

  7903   Wed Jan 16 08:29:45 2013 SteveUpdateSUSPRM damping restored

PRM oplev servo turned off.  OLPIT servo gain 0.15 and OLYAW  -0.3 set to ZERO.  PRM damping restored

  10466   Mon Sep 8 07:50:40 2014 SteveUpdateSUSPRM damping restored
  10506   Mon Sep 15 15:52:44 2014 SteveUpdateSUSPRM damping restored

 The PRM side was kicked up

  11339   Mon Jun 1 08:32:14 2015 SteveUpdateSUSPRM damping restored

Local earthquake 3.8 Mag tripped only PRM

Vac monitor is not communicating.

PSL HEPA turned on
 

Attachment 1: indio3.8Meq.png
indio3.8Meq.png
  11948   Mon Jan 25 08:36:46 2016 SteveUpdateSUSPRM damping restored

PRM suspension damping restored after 4.1 Mag Ludlow earthquake.

 

Attachment 1: EQ4.1mLudlow.png
EQ4.1mLudlow.png
Attachment 2: EQ7.1mAlaska_4.1mLudlow.png
EQ7.1mAlaska_4.1mLudlow.png
Attachment 3: 7.1_4.1.png
7.1_4.1.png
  12050   Mon Mar 28 08:30:09 2016 SteveUpdateSUSPRM damping restored

Recent  EQ 4.8 mag San Felipe, Mexico trips PRM sus damping.

PRM damping restored. PMC locked.

Attachment 1: shaking.png
shaking.png
  12541   Mon Oct 10 09:31:25 2016 SteveUpdateSUSPRM damping restored

Local earth quake 3.7 mag  trips PRM

ETMY_UL glitch

What about the MC?

 

Attachment 1: 3.7mLomaLinda.png
3.7mLomaLinda.png
Attachment 2: ETMY_UL_glitch.png
ETMY_UL_glitch.png
Attachment 3: MC_glitcing?.png
MC_glitcing?.png
  6764   Wed Jun 6 09:27:09 2012 steveUpdateSUSPRM damping restored

Quote:

What not to do:

The PRM oplev servo was left on and it was driving this oscillation overnight.

 Oplev servo turned off and sus damping restored. What is kicking up the PRM?

Attachment 1: PRMwhat.png
PRMwhat.png
  9140   Thu Sep 19 10:24:58 2013 SteveUpdatePEMPRM damping restored after earth quake

Local m3.8 eq shakes PRM lose.

Attachment 1: eq3.8mLaVerne.png
eq3.8mLaVerne.png
  837   Thu Aug 14 19:35:54 2008 JenneSummaryIOOPRM in the chamber, ready to pump!
Rob, Yoichi, Jenne, Steve

Summary: Everything is back in the chamber, we just need to put on the big doors, and start pumping in the morning.

After letting the PRM's standoff epoxy cure overnight, it was time to put the optic back in the BS Chamber. Rob put the optic cage back in the chamber, as close to the guide points that Rana had placed as possible. A handy technique was discovered for pushing the cage into place: put a long screw into the table, leaving an inch or so above the table, then use that as a push-off point so that you can push the base of the cage with your thumb. According to Rob, this is probably just about as effective as using a pusher-screw.

The guides were helpful in getting the PRM back to its original position, but one of them was placed in such a way that it could move when pushed against. The clamp that was used as a guide point was placed with one of the screws half on the edge of a hole, so that when the cage was pushed against the guide point, that screw could wiggle around, causing the clamp to rotate thus no longer being a definite guide point.

Just after putting the PRM in place, Rob found the standoff that had gone missing. (see elog #835)

Once the PRM was back in place, we put the OSEMs back, and reinstalled the satellite boxes that had been removed (PRM's, which Ben has fixed - an op-amp was blown, and BS's, which we used over in the clean room with the spare OSEMs). We found a problem with the LR PRM OSEM reading on Dataviewer. It was saturating when the OSEM was just sitting on the table, with nothing between the LED and the sensor. We measured the output from the satellite box with the octopus cables, and measured 2.3 volts, which is too much for the DAQ. It seems fine when we install it in the cage, and the magnet is blocking part of the light. We should investigate the gain of the satellite box when convenient. This is not something that needs to be done prior to pump-down. Also, when we put an allen wrench to block the light while checking which OSEM was which, we noticed that the Dataviewer reading would go down to -2V, then come back to 0V when the light was completely blocked. This may be some incorrect compensation for some whitening. Again, we should look into this, but it is not terribly time-sensitive.

Once the OSEMs were centered, we tried to turn on the damping for the PRM. This was successful, so we are confident that we have put all of the OSEMs back in their correct places.

We found that we were easily able to get the PRM's oplev back on the QPD, so we ~centered the oplev, and then centered all of the PRM's OSEMs. This assumes that the oplev was in a good place, but I think we've determined that this is the case.

We did the same thing for the SRM and the BS, to check the OSEM values before we close up for good. We found that some of the SRM OSEMs were reading low (magnet too far in), and that all of the BS OSEMs were low, perhaps as if the table were tilted a tiny bit after removing and replacing the weight of the PRM. We recentered all of the OSEMs for both of these optics.

We checked that all of the pigtails for the PRM OSEMs were anchored to the PRM cage using some copper wire as tie-downs.

We checked that all of the earthquake stops were within 1mm or so of each of the 3 optics in the BS chamber. The SRM's earthquake stops were fairly far out. One of the bottom ones was far enough that when Yoichi turned it the wrong way (accidentally), it fell out. He put it back in, and adjusted all of the earthquake stops appropriately. This 1mm distance comes from Seji, and the specs for the optics' cages.

We did a look-through of the chamber, and took out all of the tools, and other things that were not bolted down to the table.

We have left the damping of the PRM off for the night.

To do: put the doors back on, and start the pump down.
  6629   Wed May 9 04:47:20 2012 JenneUpdateLockingPRM is really moving when PRMI locked

A few things tonight.  Locked both arms simultaneously (IR only).  Locked MICH, Locked PRMI, although it doesn't like staying locked for more than a minute or so, and not always that long.

Locking PRCL was possible by getting rid of the power normalization.  We need to get some triggering going on for the power norm.  I think it's a good idea for after the cavity is locked, but when PRCL is not locked, POP22 is ~0, so Refl33/Pop22 is ~inf.  The PRCL loop kept railing at the Limit that was set.  Getting rid of the power normalization fixed this railing. 

I took some spectra of PRM's oplev, while PRMI was locked, and unlocked.  The PRM is definitely moving more when the cavity is locked.  I'm not sure yet what to do about this, but the result was repeatable many times (~6 or 7 over an hour or so).  The OpLev spectra when PRMI was locked didn't depend too strongly on the PRM's alignment, although I think that's partly because I wasn't able to really get the PRM to optimal alignment.  I think POP22I is supposed to get to 7 or so...last week with Koji it was at least flashing that high.  But tonight I couldn't get POP22I above 4, and most of the time it wouldn't go above 3.  As I was aligning PRM and the circulating SB power increased, POP22I fluctuations increased significantly, then the cavity unlocked.  So maybe this is because as I get closer, PRM gets more wiggly.  I tried playing 'chicken' with it, and took spectra as I was aligning PRM (align, get some improvement, stop to take spectra, then align more, stop to take spectra....) but usually it would fall out of lock after 1-2 iterations of this incremental alignment and I'd have to start over.  When it relocked, it usually wouldn't come back to the same level of POP22I, which was kind of disappointing. 

In the PDF attached, pink and light blue are when the PRMI is locked, and red and dark blue are no PRCL feedback.  The effect is more pronounced with Pitch, but it's there for both Pitch and Yaw.

Also, I need to relook at my new restore/misalign scripts.  They were acting funny tonight, so I'm taking back my "they're awesome, use them without thinking about it" certification.

Attachment 1: PRM_louder_when_aligned.pdf
PRM_louder_when_aligned.pdf
  6631   Wed May 9 09:19:22 2012 KojiUpdateLockingPRM is really moving when PRMI locked

Is this enhancement of spectrum caused by the lock? Or by the actuation?

If this is also seen with approximately same amount of actuation to PRM POS,
this is just a suspension problem.

If this is only seen with the PRM locked, this is somehow related to the opt-mechanical coupling.

  6781   Thu Jun 7 08:12:20 2012 steveUpdateSUSPRM is still oscillating

Quote:

Quote:

What not to do:

The PRM oplev servo was left on and it was driving this oscillation overnight.

 Oplev servo turned off and sus damping restored. What is kicking up the PRM?

 The PRM oscillation stopped by turnig off oplev servo.

Do not turn Oplev Servo on when PRM is missaligned !

 

Attachment 1: PRMoscil.png
PRMoscil.png
  6785   Thu Jun 7 13:18:42 2012 ranaUpdateSUSPRM is still oscillating

  Set the PRM OL servo gains to zero until someone can take care of this. Turning off the buttons doesn't help anything if people run the alignment scripts.

  6786   Thu Jun 7 13:25:37 2012 KojiUpdateSUSPRM is still oscillating

Done.

C1:SUS-PRM_OLPIT_GAIN 1.0 -> 0
C1:SUS-PRM_OLYAW_GAIN -0.7 -> 0
 

Quote:

  Set the PRM OL servo gains to zero until someone can take care of this. Turning off the buttons doesn't help anything if people run the alignment scripts.

 

  9371   Wed Nov 13 01:35:40 2013 JenneUpdateLSCPRM motion causing trouble?

Quote:

* Still need to finish calculating what could be causing our big arm power fluctuations (Test mass angular motion?  PRM angular motion? ALS noise?) (Calculation)

 I think that our problem of seeing significant arm power fluctuations while we bring the arms into resonance during PRMI+arms tests is coming from PRM motion. I've done 3 calculations, so I will describe below why I think the first two are not the culprit, and then why I think the PRM motion is our dominant problem.

===============================================================

ALS length fluctuations

Arm length fluctuations seem not to be a huge problem for us right now, in terms of what is causing our arm power fluctuations.

What I have done is to calculate the derivative of the power in the arm cavity, using the power buildup that optickle gives me. The interferometer configuration I'm using is PRFPMI, and I'm doing a CARM sweep. Then, I look at the power in one arm cavity. The derivative gives me Watts buildup per meter CARM motion, at various CARM offsets. Then, I multiply the derivative by 60 nm, which is my memory of the latest good rms motion of the ALS system here at the 40m. I finally divide by the carrier buildup in the arm at each offset, to give me an approximation of the RIN at any CARM offset.

I don't know exactly what the calibration is for our ALS offset counts, but since we are not seeing maximum arm cavity buildup yet, we aren't very close to zero CARM offset. 

From this plot, I conclude that we have to be quite close to zero offset for arm length fluctuations to explain the large arm power fluctuations we have been seeing.

 xarmRIN_vs_CARM.png

=======================================================================

AS port contrast defect from ETM motion

For this calculation, I considered how much AS port contrast defect we might expect to see given some ETM motion. From that, I considered what the effect would be on the power recycling buildup. 

Rather than doing the integrals out, I ended up doing a numerical analysis. I created 2 Gaussian beams, subtracted the fields, then calculated the total power left. I did this for several separations of the beams to get a plot of contrast defect vs. separation. My simulated Gaussian beams have a FWHM of 1 unit, so the x-axis of the plot below is in units of spot motion normalized by spot size. 

Unfortunately, my normalization isn't perfect, so 2 perfectly constructively interfering beams have a total power of 0.3, so my y-axis should all be divided by 0.3. 

The actual beam separation that we might expect at the AS port from some ETM motion (of order 1e-6 radians) causing some beam axis shift is of the order 1e-5 meters, while the beam spot size is of the order 1e-3 meters. So, in normalized units, that's about 1e-2. I probably should change the x-axis to log as well, but you can see that the contrast defect for that size beam separation is very small. To make a significant difference in the power recycling cavity gain, the contrast defect, which is the Michelson transmission, should be close to the transmission of the PRM. Since that's not true, I conclude that ETM angular motion leading to PRC losses is not an issue. 

I still haven't calculated the effect of ITM motion, nor have I calculated either test mass' angular effect directly on arm cavity power loss, so those are yet to be done, although I suspect that they aren't our problem either. 

ASportOverlap_moveGaussianBeams.png

========================================================================

PRM motion

 

I think that the PRM moving around, thus causing a loss in recycling gain, is our major problem. 

First, how do I conclude that, then some thoughts on why the PRM is moving at all. 

=========

theta = 12e-6 radians (ref: oplev plot from elog 9338 last week)

L = 6.781 meters

g = 0.94

a = theta * L /(1-g) = 0.0014 meters axis displacement

w0 = 3e-3 meters = spot size at ITM

a^2/w0^2 = 0.204 ==>> 20% power loss into higher order modes due to PRM motion.

That means 20% less power circulating, hitting the ITMs, so less power going into the arm cavities, so less power buildup. This isn't 50%, but it is fairly substantial, using angular fluctuation numbers that we saw during our PRMI+arms test last week. If you look at the oplev plot from that test, you will notice that when the arm power is high (as is POP), the PRM moves significantly more than when the carrier buildup in the cavities was low. The rms motion is not 12 urad, but the peak-to-peak motion can occasionally be that large. 

So, why is that? Rana and I had a look, and it is clear that there is a difference in PRM motion when the IFO is aligned and flashing, versus aligned, but PSL shutter is closed. Written the cavities flash, the PRM gets a kick. Our current theory is that some scattered light in the PRC or the BS chamber is getting into the PRM's OSEMs, causing a spike in their error signal, and this causes the damping loops to push on the optic. 

We should think a little more on why the PRM is moving so much more that any other optic while the power is building up, and if there is anything we can do about the situation without venting. If we have to, we should consider putting aluminum foil beam blocks to protect the PRM's OSEMs. 

  9373   Wed Nov 13 09:31:15 2013 GabrieleUpdateLSCPRM motion causing trouble?

Interesting results. When you compute the effect of ETM motion, you maybe should also consider that moving around the arm cavity axis changes the matching of the input beam with the cavity, and thus the coupling between PRC and arms. But I believe this effect is of the same order of the one you computed, so maybe there is only one or two factors of two to add. This do not change significantly the conclusion.

Instead, the numbers you're giving for PRM motion are interesting. Since I almost never believe computations before I see that an experiment agrees with them, I suggest that you try to prove experimentally your statement. The simplest way is to use a scatter plot as I suggested the past week: you plot the carrier arm power vs PRM optical lever signals in a scatter plot. If there is no correlation between the two motions, you should see a round fuzzy ball in the plot. Otherwise, you will se some non trivial shape. Here is an example: https://tds.ego-gw.it/itf/osl_virgo/index.php?callRep=18918

 

  9378   Wed Nov 13 19:22:58 2013 JenneUpdateLSCPRM motion correlated to intracavity power

[Gabriele, Jenne]

Nic and Evan put the ISS together (elog 9376), and we used an injection into the error point (?) to modulate the laser power before the PMC (The AOM had a bias offset, but there is no loop).  This gives us some RIN, that we can try to correlate with the PRM OSEM sensors. 

We injected several lines, around 100, 200, 500 and 800 Hz.  For 100, 200 and 800 Hz lines, we see a ratio between POPDC and the OSEM sensors of 1e-4, but at 500 Hz, the ratio was more like 1e-3. We're not sure why this ratio difference exists, but it does.  These ratios were true for the 4 face OSEMs.  The side OSEM saw a slightly smaller signal.  

For these measurements, the PRMI was sideband locked, and we were driving the AOM with an amplitude of 10,000 counts (I don't know what the calibration is between counts and actual drive, which is why we're looking at the POPDC to sensor *ratio*).  

To get a more precise number, we may want to consider locking the PRMI on carrier, so we have more power in the cavity, and so more signal in the OSEMs.  

These ratios look, by eye, similar to the ratios we see from the time back on 30 Oct when we were doing the PRMI+2arms test, and the arms were resonating about 50 units.  So, that is nice to see some consistency.

AOMmodulated_POPDC_OSEM.pdf

This time series is from 1067163395 + 27 seconds, from 30 Oct 2013 when we did the PRMI+2arms.

POPDC_sensors_30oct2013.png

 


Ideas to go forward:

We should think about chopping the OSEM LEDs, and demodulating the PD sensors. 

We should also take a look in the chamber with a camera from the viewport on the north side of the BS chamber, to see if we see any flashes in the chamber that could be going into the OSEMs, to see where we should maybe put aluminum foil shields.

  9383   Thu Nov 14 02:55:26 2013 ranaUpdateSUSPRM motion correlated to intracavity power

 

Some more words about the ISS -> OSEM measurement:

The calibration of the OSEMs have been done so that these channels are each in units of microns. The SIDE channel has the lower noise floor because Valera increased the analog gain by 5x some time ago and compensated with lower digital gain.

The peak heights in the plot are:

UL   0.85

LL   0.78

UR   0.61

LR   0.45

S    0.27

So that tells us that the coupling is not uniform, but mostly coming in from the left side (which side is the the SIDE OSEM on?).

Jenne and I discussed what to do to mitigate this in the loops. Before we vent to fix the scattering (by putting some covers around the OSEMs perhaps), we want to try to tailor the OSEM damping loops to reduce their strength and increase the strength of the OL loops at the frequencies where we saw the bulk of the instability last time.

Jenne is optimizing OL loops now, and I'm working on OSEM tweaking. My aim is to lower the overall loop gains by ~3-5x and compensate that by putting in some low Q, resonant gain at the pendulum modes as we did for eLIGO. We did it here at the 40m several years ago, but had some troubles due to some resulting instability in the MC WFS loops.

 

In parallel, Steve is brainstorming some OSEM shields and I am asking around LIGO for some AC OSEM Satellite modules.

  4599   Mon May 2 17:10:55 2011 steveUpdateSUSPRM oplev

The returning spot diameter on the qpd ~10 mm. In order to reduce the spot size I moved the f 1145 mm lens toward the PRM ~ 25 cm. The spot size was reduced to ~8 mm, 3200 counts.

I'll try to find an other lens tomorrow.

  7915   Thu Jan 17 19:33:53 2013 ManasaUpdateAlignmentPRM oplev

 We had to work on redesigning the oplev layout in BSC when I found that the positions of the mirrors were clipping IPPOS and the green beam while updating the CAD layout.  

To avoid any clipping, the prm oplev beam is steered into the vacuum by an oplev mirror and out of vacuum through 3 steering mirrors. The table weights had to be moved to allow room for the oplev mirrors. Hence table had to be re-leveled. I will update the CAD drawing with the current position of the mirrors and will reconfirm that the new mirrors are not in the way of any of the beams. In-vac photos are updated in picasa.

  6788   Thu Jun 7 18:46:13 2012 yutaUpdateSUSPRM oplev centered

PRM oplev beam was not hitting on the QPD since Jun 1, so I centered it. I reverted the oplev servo gains and now oplev servo looks fine.

C1:SUS-PRM_OLPIT_GAIN = 1.0
C1:SUS-PRM_OLYAW_GAIN = -0.7

There's SIDE to UL/UR/LL/LR coil element in PRM TO_COIL matrix. They were 0 until Mar 31, 2012, but someone changed them to -0.160. I couldn't find elog about it.
Same thing happened to BS on Mar 13, 2012 (see elog #6409), so I think somebody did the same thing to PRM.

  11256   Sun Apr 26 15:34:34 2015 JenneUpdateSUSPRM oplev centered

After last week's work on the BS/PRM oplev table, I think the PRM oplev got centered while the PRM was misaligned.  With the PRM aligned, the oplev spot was not on the QPD.  It has been centered.

  9616   Mon Feb 10 16:02:12 2014 JenneUpdateGeneralPRM oplev clipped in vacuum

The PRC (locked on carrier so far today), is pretty wobbly.  It'll stay locked on carrier, but it's wobbling.  The ASC was over-ridden during the vent.  While I was looking around for that, I noticed that the PRM oplev sum is very low. 

I went into the lab, and turned off / blocked all oplev beams except the PRM beam.  I can't tell what it's clipping on, but there is definitely some red glow in the BS chamber (not as much as the stuff that's coming from the ITMY or SRM oplev hitting a tip tilt suspension - that giant spot went away when I turned off the ITMY/SRM oplev laser).  The beam going into the vacuum is nice and strong, but the beam coming out is very weak, and has a horizontal line of scatter through it, like it's clipped somewhere in pitch.  The PRM oplev sum is currently ~150 cts, when it should be closer to 2,000.

Screenshot-Untitled_Window-1.png

So far, this seems to be livable, but it's definitely disappointing. 

  7838   Mon Dec 17 14:13:55 2012 JenneUpdateSUSPRM oplev gains restored

Quote:

PRM oplev gains set to zero from PIT 0.15 and YAW -0.3 and damping restored

 Put them back to normal.

  9382   Thu Nov 14 02:50:43 2013 JenneUpdateLSCPRM oplev measured and modeled TF

In the process of figuring out what we can do to fix our PRM motion problem, I am looking at the PRM oplev. 

Eventually (as in, tomorrow), I'd like to be able to simulate some optic motion as a result of an impulse, and see what the oplev loops do to that motion.  (For starters, I'll take the impulse response of the OSEM loop as my time series that the oplev loop sees).

One thing that I have done is look at the oplev model that Rana put together, which is now in the noisebudget svn: /ligo/svncommon/NbSVN/aligonoisebudget/trunk/OpLev/C1

This script plots the open loop gain of the modeled oplev:

PRM_OL_TF_model.png

This should be compared to the pitch and yaw measured transfer functions:

 PRM_OLPIT_TF.pdf

PRM_OLYAW_TF.pdf

In the YAW plot, there are 2 transfer functions.  The first time around, the UGF was ~2.5Hz, which is too low, so I increased the gain in the C1:SUS-PRM_OLYAW filter bank from -3 to -9. 

The shapes of the measured and modeled transfer functions look reasonably similar, but I haven't done a plot overlay.  I suspect that the reason I don't see the same height peak as in the model is just that I'm not taking a huge number of points.  However, if the other parts of the TF line up, I'll assume that that's okay.

I want to make sure that the modeled transfer function matches the measured ones, so that I know I can trust the model.  Then, I'll figure out how to use the time series data with the simulated loop.  Ideally, I'd like to see that the oplev loop can fully squish the motion from the OSEM kicks.  Once I get something that looks good (by hand-tweaking the filter shape), I'll give it a try in the actual system.  We should, as soon as I get the optimal stuff working, redo this in a more optimal way.  Both now, and after I get an optimal design, I'll look at the actual step and impulse responses of the loop, to make sure there aren't any hidden instabilities.

Other thoughts for the night:

Rana suggests increasing the gain in some of the oplev QPD heads (including PRM), so that we're getting more than a few hundred counts of power on each quadrant.  Since our ADCs go to 32,000 counts, a few hundred is very small, and keeping us close to our noise limits.

Also, just an observation, but when I watch the REFL camera along with POP and AS, it's clear that the PRM is getting kicked, and I don't have the ETMs aligned right now, so this is just PRMI flashes.  There is also a lot of glow in the BS chamber during flashes (as seen on the PRM face video camera).

  9401   Mon Nov 18 21:02:54 2013 JenneUpdateLSCPRM oplev measured and modeled TF

I have created a new filter for the PRM oplev damping loops.  The biggest change is an increase in the gain between 0.4 - 7 Hz.

Here is a plot of the old, and my new modelled open loop gain:

PRM_OLG_NewOld.png

When I look at my step and impulse response time series, the notches for the bounce and roll were causing some ringing, so for now they are turned off, both in the model and in the real time system.  Also, the "OLG orig" trace has a 4th order elliptic lowpass at 75 Hz, but the real system had a 4th order elliptic low pass at 35 Hz.  When we use 35 Hz in the model, we get lots of ringing.  So, we have moved both model and real system to 55 Hz 4th order elliptic low passes.  Also, also, we haven't been using the 3.3 Hz resonant gain, so I removed that from the modelled loop.

I have put the "boost" for the .4-7 Hz emphasis into FM 7 of the PRM oplev filters.  I also removed several old filters that are never used.  So, for now, the PRM oplevs should have engaged:  FM 1, 7, 9. Pitch gain is +5, yaw gain is -9.  We can consider re-implementing the bounce-roll notches, and the stack resgain if it looks like those are getting rung up, and causing trouble.

Here is a set of spectra, showing the improvement.  It's unclear why yaw is worse than pitch below 4Hz, and why pitch is so much worse than yaw between 4-15 Hz, however for each of pitch and yaw, the before (reference pink and cyan traces) is higher than the improved (dark red, dark blue traces) between a few tenths of a Hz up to 3ish Hz.  And, we're not causing more noise elsewhere.  We do want to monitor to make sure we're not ringing up the bounce and roll modes, but for now they seem fine.

PRM_oplev_improvement.pdf

  9404   Mon Nov 18 21:40:24 2013 KojiUpdateLSCPRM oplev measured and modeled TF

I forgot how we could turn on the PRM oplev servo and the PRM ASC servo at the same time without conflict.
It seems that this new oplev servo covers 0.04 to 8Hz. It's pretty broadband. Do we inject the ASC signal to the oplev error?

  9410   Tue Nov 19 14:47:44 2013 JenneUpdateLSCPRM oplev measured and modeled TF

Quote:

I forgot how we could turn on the PRM oplev servo and the PRM ASC servo at the same time without conflict.
It seems that this new oplev servo covers 0.04 to 8Hz. It's pretty broadband. Do we inject the ASC signal to the oplev error?

 Right now all 3 servos that control PRM angle (OSEM damping, Oplev, and ASC) run in parallel, and they're all AC coupled. 

  6952   Tue Jul 10 17:47:55 2012 yutaUpdateSUSPRM oplevs fixed

I centetered PRM oplev, lowered gain and PRM oplev servo is not oscillating any more.
It is OK for more than a softball practice.

C1:SUS-PRM_OLPIT_GAIN = 0.15  (was 0.5)
C1:SUS-PRM_OLYAW_GAIN = -0.3  (was 0.7)

Openloop transfer function:
  Oplev Pitch: gain ~ 12 at 0.69 Hz resonance
  Oplev Yaw: gain ~ 18 at 0.83 Hz resonance
PRMoplevpitOLTF.pngPRMoplevyawOLTF.png

  I adjusted the gain so that oplev damps resonance as much as possible, but not introduce additional noise. I did no calculation, but just measured OSEM spectra (SUSPIT and SUSYAW). Below, you can see the noise reduces at resonance when oplev servo is on, and not increasing at other frequencies. It was introducing noise before. Someone should do more systematic adjustment of oplev servos for all the optics.

PRMOplevSpectra20120710.png
 

  6799   Tue Jun 12 02:07:42 2012 JenneUpdateSUSPRM oplevs left off

Yuta claims he fixed the PRM oplev by centering it the other day, but no one has left it on and watched it for a long while, to make sure it's okay.  We watched it now for ~2 min, and it was good, but we're leaving the oplevs off anyway for the night.  Tomorrow we should restore PRM (it's currently restored), turn on the oplevs, and let it sit to make sure it doesn't go crazy.

 

  6804   Tue Jun 12 16:33:32 2012 steveUpdateSUSPRM oplevs servo ON for confirmation

Quote:

Yuta claims he fixed the PRM oplev by centering it the other day, but no one has left it on and watched it for a long while, to make sure it's okay.  We watched it now for ~2 min, and it was good, but we're leaving the oplevs off anyway for the night.  Tomorrow we should restore PRM (it's currently restored), turn on the oplevs, and let it sit to make sure it doesn't go crazy.

 

 PRM oplev servo was turned on with PITgain 0.5  and YAWgain  -0.7

Note: gain settings were PIT  1.0  and  YAW --0.5   on Jun 1, 2012 that I measured Feb 23, 2012

  7098   Mon Aug 6 23:05:22 2012 JenneUpdateSUSPRM oplevs servo is fine

The PRM was pointing totally the wrong way, so there was no light on the oplev PD.  I restored the PRM, turned the gains back to (0.15, -0.3) as per Yuta's elog 6952, and it seems just fine to me.

I want to check the data from last night / the weekend to see when the mispointing happened, but dataviewer can't connect to the fb, since Jamie is still working his magic.  I'm pretty sure I restored all of the optics after Eric finished playing with MICH Friday night, but it's possible that I forgot one, I suppose.  If it wasn't me, then I'm curious when it happened.

  6805   Tue Jun 12 17:04:55 2012 steveUpdateSUSPRM oplevs servo is still bad

Quote:

Quote:

Yuta claims he fixed the PRM oplev by centering it the other day, but no one has left it on and watched it for a long while, to make sure it's okay.  We watched it now for ~2 min, and it was good, but we're leaving the oplevs off anyway for the night.  Tomorrow we should restore PRM (it's currently restored), turn on the oplevs, and let it sit to make sure it doesn't go crazy.

 

 PRM oplev servo was turned on with PITgain 0.5  and YAWgain  -0.7

Note: gain settings were PIT  1.0  and  YAW --0.5   on Jun 1, 2012 that I measured Feb 23, 2012

 It is still oscillating. Gains turned down to zero.

Attachment 1: PRMolvstillosc.png
PRMolvstillosc.png
  7087   Mon Aug 6 07:59:33 2012 steveUpdateSUSPRM oplevs servo is still bad

Quote:

Quote:

Quote:

Yuta claims he fixed the PRM oplev by centering it the other day, but no one has left it on and watched it for a long while, to make sure it's okay.  We watched it now for ~2 min, and it was good, but we're leaving the oplevs off anyway for the night.  Tomorrow we should restore PRM (it's currently restored), turn on the oplevs, and let it sit to make sure it doesn't go crazy.

 

 PRM oplev servo was turned on with PITgain 0.5  and YAWgain  -0.7

Note: gain settings were PIT  1.0  and  YAW --0.5   on Jun 1, 2012 that I measured Feb 23, 2012

 It is still oscillating. Gains turned down to zero.

 Earthquake test our suspensions            PRM damping restored.             Oplev servo gains turned to zero.

Attachment 1: PRMeq.png
PRMeq.png
  6752   Tue Jun 5 09:32:12 2012 steveUpdateSUSPRM oscillation

What not to do:

The PRM oplev servo was left on and it was driving this oscillation overnight.

Attachment 1: PRMosc.png
PRMosc.png
  3684   Sun Oct 10 16:59:20 2010 KojiOmnistructureCOCPRM phase map measurement at Downs SB 014

[Kiwamu, Yuta, Koji]

We went to the new metrology lab at Downs subbasement (Rm014) in order to measure the phase map of the delivered PRMs.

It's brand-new. So we had to measure the reference phase map, calibration as well as the phase map of our mirrors (3 PRMs and 1 spare SRM). It took a whole day...

Attachment 1: IMG_3646.jpg
IMG_3646.jpg
Attachment 2: IMG_3647.jpg
IMG_3647.jpg
  759   Tue Jul 29 19:53:19 2008 KojiUpdateSUSPRM photos from the south window
Steve and Koji

We took some photos of PRM from the south window.
You can see one of the side magnets, a wire stand-off, and the wire itself from the round hole.
So, the wire looks OK.

For the coils, we could see only one coil. The magnet is apparently too high.
Attachment 1: PRM_from_South_Window1.jpg
PRM_from_South_Window1.jpg
Attachment 2: PRM_from_South_Window2.jpg
PRM_from_South_Window2.jpg
  9398   Mon Nov 18 16:39:38 2013 SteveUpdateSUSPRM pictures

PRM is aligned. IFO is not locked. It is just flashing, including arms. Olympus SP570UZ camera used without IR blocker. Note: PRM side OSEM does not show IR effect.

I will take more pictures with IOO IR blocked and HeNe oplev blocked  tomorrow morning.

Attachment 1: PRM1.JPG
PRM1.JPG
Attachment 2: PRMsurface.JPG
PRMsurface.JPG
Attachment 3: PRM2.JPG
PRM2.JPG
  9399   Mon Nov 18 17:00:20 2013 JenneUpdateSUSPRM pictures

It crossed my mind that, from these pictures, it could be glow from the oplev scattered light that is causing the problem.  However, that seems not possible, since the power fluctuations that we see depend on the presence of the IR light - if it were the oplev light, then when I close the PSL shutter, I should see the same amount of kick, which I don't.  Also, the amount of fluctuation increases with increased stored power in the cavities.  Also, also, Steve reminds me that some of the MC mirrors see similar kicks in their OSEM signals, but they don't have oplevs.

So, I don't believe that the oplev light is causing the problem, but I wanted to write down why I don't think that's it. 

Investigations into OSEM and oplev loops to get rid of the kicks are continuing.

  9400   Mon Nov 18 19:45:42 2013 RANAUpdateSUSPRM pictures

Nice camera work Steve! I will use these for publicity photos.

Now we need to get one of the video cameras hooked into the MUX so that we can see the flashing and do some image subtraction.

ELOG V3.1.3-