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ID Date Author Type Category Subjectdown
  6457   Tue Mar 27 21:20:32 2012 JenneUpdateIOOBeam Profile measurement: IPPOS beam

Quote:

The moral of the story that I'm getting from this plot:  something funny is going on.

 Yup, something funny was going on.  Nic's MM code that I used, "a la mode", calls for the focal length of the optics, whereas the code that I wrote and used for ages called for the radius of curvature.  f = R/2.  Fixing that factor of 2 I get something more like:

BeamProp_usingMeas2012MMTnumbersLowRes.png

This is obviously much better, in that the beam profile goes through (within some error) both of the measured sets of points - the MC waist measured in May 2010, and after the MMT measured yesterday.

So, what does it all mean?  That I'm not sure of yet.

  6459   Tue Mar 27 23:37:35 2012 SureshUpdateIOOBeam Profile measurement: IPPOS beam

Quote:

Quote:

The moral of the story that I'm getting from this plot:  something funny is going on.

 Yup, something funny was going on.  Nic's MM code that I used, "a la mode", calls for the focal length of the optics, whereas the code that I wrote and used for ages called for the radius of curvature.  f = R/2.  Fixing that factor of 2 I get something more like:

.....

So, what does it all mean?  That I'm not sure of yet.

 In an attempt to estimate the errors on the fit parameters I upgraded my Mathematica code to use the function 'NonlinearModelFit', which allows us to define weights and also reports the errors on the fit parameters.   The plots have been upgraded to show the error bars and residuals.

Beam-Profile_IPPOS_wError.png

 

The parameters determined are given below and compared to the earlier measurements of 06/18/2010

Vertical Profile:

Parameter Estimate Standard Error 95% Confidence interval 06/18/2010 measurement
Waist (mm) 2.768 0.005 2.757 -- 2.779 2.81
Waist location from MMT2 (m) 5.85 0.12 5.625-- 6.093 5.36

 

 

Horizontal Profile:

Parameter Estimate Standard Error 95% Confidence Interval 06/18.2010 measurement
Waist (mm) 2.476 0.009 2.455 -- 2.496 2.91
Waist Location from MMT2 (m) 4.935 0.145 4.645 -- 5.225 1.96

 

There is a significant change in the beam waist location (as compared to previous report) because I corrected a mistake in the sign convention that I was using in measuring the distances to the waist from the zero-reference.
 

  6460   Wed Mar 28 01:17:29 2012 JenneUpdateIOOBeam Profile measurement: IPPOS beam

As I was a little dissatisfied with the inaccuracy in the distance numbers in Kiwamu's sketch, I went back to the 18 Dec 2010 table layout drawing for more accurate numbers.  These are now included in this round of plots.

Also, I include astigmatism due to the incident angles on MMT1 (~3.5 deg) and MMT2 (~1 deg).

First plot, IPPOS path, using the recent (fixed) measurements from Suresh to fix the beam width.  Note that the old 2010 measurements of the MC waist are consistent with this measurement.

Second plot, Main IFO path all the way to the ITM (average) position, using the 2010 MC waist measurements to fix the beam width.

Third plot, Main IFO path all the way to the ITM position, but with PRM flipped (negative RoC), using the 2010 MC measurement to fix beam width.

With the PRM correctly oriented (2nd plot), I get beam waists of (x = 2.529 mm, y = 2.646 mm), which corresponds to a mode matching to the arm cavity of (eta = 97.43%, PRM correct).

With the PRM flipped (3rd plot), I get beam waists of (x = 3.176 mm, y = 3.3 mm), which corresponds to a mode matching to the arm cavity of (eta = 99.55%, PRM flipped).

 

First plot:

BetterDistances_IPPOSLowRes.png

Second plot (this is how the MMT was designed to be, before the ETMs were moved, which made the ideal waist larger):

BetterDistances_MainIFO_PRMnormalLowRes.png

Third plot:

BetterDistances_MainIFO_PRMflippedLowRes.png

For both the 2nd and 3rd plot, we can't look at the post-MMT waist measurements, since that distance on the plots is after the PRM, which is a curved optic.  So the fact that the post-MMT measurements match the correct-PRM plot better than the flipped-PRM plot can't be taken to be meaningful.

Moral of the story:  I'm not sure how to interpret any of this to tell us if the PRM is flipped or not, since the measurements are all of the beam profile before the beam sees the PRM.  We'd have to measure the profile after the PRM somehow in order to get that information.  We have okay but not great mode matching to the arm if the PRM is correct, but I don't know that we readjusted the MMT after we moved the ETMs.  I don't remember recalculating any optimal telescope lengths after the arm length change.  If we need better mode matching, I can do that calculation, although given how much space we don't have, it would be hard in practice to move the MMT mirrors by much at all.

  6461   Wed Mar 28 18:26:47 2012 JenneUpdateIOOBeam Profile measurement: IPPOS beam

More calculations....

Game Plan:  Using MC waist measured beam as the starting point of beam propagation, move MMT mirrors around until the beam profile fits with the IPPOS measurements from Monday.

Plot 1:  Allow MMT mirrors to move as much as they want to.  Note that the Y-beam goes through the IPPOS measured point. (This implies we put the MMT in the wrong place by ~half a meter.  Unlikely)

Plot 2: Using MMT locations from plot 1, what does the beam look like at the ITMs? 

Plot 3:  Allow MMT mirrors to move as much as 2cm.  Note that the Y-beam doesn't quite go through IPPOS measured point.

Plot 4: Using MMT locations from plot 3, what does the beam look like at the ITMs?

For all of the above, I was optimizing the propagation of the Y-beam profile.  Since the X-beam profile measurement is so different, if I want to optimize to X and let the MMT mirrors move as much as they want, MMT1 ends up inside the MC.  Unlikely.  So I'm just looking at Y for now, and maybe Suresh or someone needs to rethink the error bars on their measurements or just remeasure.

Plot 1:

OptimizedMMT_halfMeterChange_IPPOSviewLowRes.png

Plot 2:

OptimizedMMT_halfMeterChange_IFOviewLowRes.png

Plot 3:

OptimizedMMT_pt2cMeterChange_IPPOSviewLowRes.png

Plot 4:

OptimizedMMT_pt2cMeterChange_IFOviewLowRes.png

  6462   Wed Mar 28 20:54:02 2012 JenneUpdateIOOBeam Profile measurement: IPPOS beam

I fitzed by hand with the numbers for the incident angles on MMT1 and MMT2, and then let the code optimize the position of MMT1 and MMT2.

Here I have set the incident angle for MMT1 = 25deg, and MMT2 = 12deg (should be 3.5deg, 1deg by design).  The length of the telescope doesn't want to change by more than 7mm, but the position of the telescope wants to change by 1.3meters.  Is it possible that the distances on the Monday IPPOS measurements aren't actually correct?

MMT_moved_by_1pt3meters_MMT1th_25_MMT2th_12_LowRes.png

Attachment 1: MMT_moved_by_1pt3meters_MMT1th_25_MMT2th_12_LowRes.png
MMT_moved_by_1pt3meters_MMT1th_25_MMT2th_12_LowRes.png
  6476   Mon Apr 2 18:58:32 2012 JenneUpdateIOOBeam Profile measurement: IPPOS beam

Suresh noted that I never wrote down the waist positions of the beam propagated through the MMT (based on where we think it is from ruler-based measurements).  This uses the MC waist measured beam as the starting point, and just propagates through the MMT, out to the IPPOS port.

Yq:

  Properties:
                    q: 2.2488 +23.8777i
               lambda: 1.0640e-06
            waistSize: 0.0028  (at z = 13.2676 meters)
               waistZ: 2.2488    (relative to z = 13.2676 meters)
      divergenceAngle: 1.1910e-04
    radiusOfCurvature: 255.7849
            beamWidth: 0.0029
        rayleighRange: 23.8777

So, to sum up, the vertical beam waist is 2.8438 mm at 11.0188 meters from the MC waist.

 

Xq:

  Properties:
                    q: 5.1953 +24.7342i
               lambda: 1.0640e-06
            waistSize: 0.0029   (at z = 13.2676 meters)
               waistZ: 5.1953    (relative to z = 13.2676 meters)
      divergenceAngle: 1.1702e-04
    radiusOfCurvature: 122.9525
            beamWidth: 0.0030
        rayleighRange: 24.7342

So, to sum up, the horizontal beam waist is 2.8943 mm at 8.0723 meters from the MC waist.

In pictorial form,

NonOptimized_propagatedWaistPlotted_LowRes.png

  2984   Tue May 25 17:04:37 2010 KevinUpdate Beam Profile After Mode Cleaner

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

For the horizontal profile:

reduced chi^2 = 0.88

z0 = (1 ± 29) mm

w0 = (1.51 ± 0.01) mm

For the vertical profile:

reduced chi^2 = 0.94

z0 = (673 ± 28) mm

w0 = (1.59 ± 0.01) mm

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

horizontal: (16.89 ± 0.06) m

vertical:   (17.66 ± 0.07) m

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

In the following plots, the blue curve is the fit to the vertical beam radius, the purple curve is the fit to the horizontal beam radius, * denotes a data point from the vertical data, and + denotes a data point from the horizontal data.

Attachment 1: mcfit.png
mcfit.png
Attachment 2: mcerrors.png
mcerrors.png
  2985   Tue May 25 17:09:22 2010 KojiUpdateIOOBeam Profile After Mode Cleaner

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

Quote:

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

For the horizontal profile:

reduced chi^2 = 0.88

z0 = (1 ± 29) mm

w0 = (1.51 ± 0.01) mm

For the vertical profile:

reduced chi^2 = 0.94

z0 = (673 ± 28) mm

w0 = (1.59 ± 0.01) mm

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

horizontal: (16.89 ± 0.06) m

vertical:   (17.66 ± 0.07) m

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

 

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

Quote:

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

Quote:

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

For the horizontal profile:

reduced chi^2 = 0.88

z0 = (1 ± 29) mm

w0 = (1.51 ± 0.01) mm

For the vertical profile:

reduced chi^2 = 0.94

z0 = (673 ± 28) mm

w0 = (1.59 ± 0.01) mm

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

horizontal: (16.89 ± 0.06) m

vertical:   (17.66 ± 0.07) m

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

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

Attachment 1: mcfit.png
mcfit.png
  7855   Wed Dec 19 11:14:25 2012 SteveUpdateSUSBeCu wire in stock

Quote:

Just in case we want to retrofit the Tip/Tils with Beryllium Copper wire, here are links to a few sources which have a supply of the right composition and temper:

http://www.lfa-wire.com/Tempered-Alloy-25_C17200.htm

http://www.alloywire.com/beryllium_copper_CB_101.html

http://www.ngk.co.jp/english/products/electronics/berylliumcopper/wire/index.html

http://www.goodfellow.com/E/Copper-Beryllium-Wire.html

 

I don't think its worth it to do something to modify them unless we get a real reduction in the hysteresis - need a benchtop test setup ASAP.

 Be Copper in the lab is from Ca Fine Wire :  alloy 10 CDA 17 in sizes .008"  &  0.002"  There are other sus wire choices in the Drever lab

  7844   Mon Dec 17 21:41:30 2012 ranaSummarySUSBeCu wire

Just in case we want to retrofit the Tip/Tils with Beryllium Copper wire, here are links to a few sources which have a supply of the right composition and temper:

http://www.lfa-wire.com/Tempered-Alloy-25_C17200.htm

http://www.alloywire.com/beryllium_copper_CB_101.html

http://www.ngk.co.jp/english/products/electronics/berylliumcopper/wire/index.html

http://www.goodfellow.com/E/Copper-Beryllium-Wire.html

 

I don't think its worth it to do something to modify them unless we get a real reduction in the hysteresis - need a benchtop test setup ASAP.

  15448   Thu Jul 2 16:51:23 2020 JordanUpdateGeneralBathroom Science

As part of an ongoing effort to improve airflow in workspaces/bathrooms on campus, I have installed an air scrubber unit in each of the bathrooms at the 40m lab.

Attachment 1: AirScrubber40m.jpg
AirScrubber40m.jpg
  12617   Tue Nov 15 20:26:35 2016 JohannesUpdateCamerasBasler GigE-Camera on Optimus (+Mafalda dead)

I powered up the existing ace100gm GigE cam with the PoE injector and tried to interface with it as described in elog 4163. After a few initial problems with IP assignment and interfacing I connected it to one of the gigabit hubs and installed the most recent pre-compiled software suite on /opt/pylon5 on optimus, after which I was able to find it with the configuration software. I named it "c1gige_bas100-1" and gave it the static IP address 192.168.113.151.

Afterwards the image acquisition worked without problems.

It may be a good idea to leave the gigecam interfacing up to a dedicated machine. I was thinking I could use Mafalda for this, and also for developing the code for framegrabbing and imager settings, but found that it was dead, burnt at the stake so to say. I guess it wasn't running anything critical, since it wasn't even connected to the network and smelled like burnt electronics. I'll get a replacement desktop for it.

Attachment 1: gige_test.png
gige_test.png
  12622   Thu Nov 17 12:14:21 2016 ranaUpdateCamerasBasler GigE-Camera on Optimus (+Mafalda dead)

Indeed. I suggest discussing with Joe B. I believe we should use a dedicated cam network to get the camera signals from the ends and corner all into one machine. Do not use the main CDS FE network for this since it might produce weird collissions. How about make a diagram, post it to elog, and send link to Joe?

It may be a good idea to leave the gigecam interfacing up to a dedicated machine.

  13348   Mon Oct 2 12:44:45 2017 johannesUpdateCamerasBasler 120gm calibration

Disclaimer: Wrong calibration factors! See https://nodus.ligo.caltech.edu:8081/40m/13391

The two acA640-120gm Basler GigE-Cams have been calibrated. I used the collimated output of a fiber that carried the auxiliary laser light from the PSL table. With a non-polarizing beam splitter some of the light was picked off onto a PD, and I modified the RF amplitude of the AOM drive signal to vary the power coming out of the fiber. The fiber output was directed at a white paper, which was placed 1.06m from the front of the lens tube assembly, which is where the focal plane is. Using the Pylon Viewer App I made sure that the entirety of the beam spot was imaged onto the CCD. Since the camera sensor is 1/4" across, I removed the camera from the lens tube and instead placed the Ophir power meter head at the position of the sensor and measured the power reported versus PD voltage, which turned out to be 1.5 V/uW.

The camera was put back in place and I used the Pypylon package Gautam had stumbled upon to sweep the exposure time from 100us to 10ms at different light power settings including no laser light at all for background subtraction, and rather than keeping the full bitmap data for O(100s) of images I recorded only the quantities

  1. Pixel Max
  2. Pixel Sum
  3. Pixel Mean
  4. Pixel Standard Deviation
  5. Pixel Median

I performed this procedure for both the 152 and 153 cameras and plotted the pixel sum and the pixel max vs the exposure time. All the exposures were taken at a gain setting of 100, which is the smallest possible setting (out of 100-600). To obtain the calibration factor I use the input power Pin=75nW in the 'safe' region 1ms to 10ms where the pixel sum looks smooth and the CCD is reportedly not saturated.

Camera IP Calibration Factor CF
192.168.113.152 8.58 W*s
192.168.113.153 7.83 W*s

The incident power can be calculated as Pin =CF*Total(Counts-DarkCounts)/ExposureTime.

Attachment 1: calib_20170930_152.pdf
calib_20170930_152.pdf
Attachment 2: calib_20170930_153.pdf
calib_20170930_153.pdf
  14568   Wed Apr 24 17:39:15 2019 YehonathanSummaryLoss MeasurementBasic analysis of loss measurement

Motivation

  • Getting myself familiar with Python.
  • Characterize statistical errors in the loss measurement.

Summary

​The precision of the measurement is excellent. We should move on to look for systematic errors. 

In Detail

According to Johannes and Gautam (see T1700117_ReflectionLoss .pdf in Attachment 1), the loss in the cavity mirror is obtained by measuring the light reflected from the cavity when it is locked and when it is misaligned. From these two measurements and by using the known transmissions of the cavity mirrors, the roundtrip loss is extracted.

I write a Python notebook (AnalyzeLossData.ipynb in Attachment 1) extracting the raw data from the measurement file (data20190216.hdf5 in Attachment 1) analyzing the statistics of the measurement and its PSD.

Attachment 2 shows the raw data. 

Attachment 3 shows the histogram of the measurement. It can be seen that the distribution is very close to being Gaussian.

The loss in the cavity pre roundtrip is measured to be 73.7+/-0.2 parts per million. The error is only due to the deviation in the PD measurement. Considering the uncertainty of the transmissions of the cavity mirrors should give a much bigger error.

Attachment 4 shows noise PSD of the PD readings. It can be seen that the noise spectrum is quite constant and there would be no big improvement by chopping the signal.

The situation might be different when the measurement is taken from the cavity lock PD where the signal is much weaker.

Attachment 1: LossMeasurementAnalysis.zip
Attachment 2: LossMeasurement_RawData.pdf
LossMeasurement_RawData.pdf
Attachment 3: LossMeasurement_Hist.pdf
LossMeasurement_Hist.pdf
Attachment 4: LossMeasurement_PSD.pdf
LossMeasurement_PSD.pdf
  13863   Fri May 18 14:18:03 2018 gautamConfigurationElectronicsBasic MEDM Control Screen setup

I setup a basic MEDM screen for remote control of the PLL.

The Slow control voltage slider allows the frequency of the laser to be moved around via the front panel slow control BNC.

The TTL signal slider provides 0/5V to allow triggering of the servo. Eventually this functionality will be transferred to the buttons (which do not work for now).

The screen can be accessed from the PSL dropdown menu in sitemap. We can make this better eventually, but this should suffice for initial setup.

Attachment 1: AUX_PLL_CTRL.png
AUX_PLL_CTRL.png
  4879   Fri Jun 24 17:04:25 2011 NicoleUpdateSUSBasic Laser Safety Training; Moved TT Mirror; Horizontal Displacement Mech Plan

Today Ishwita, Sonali, and I completed basic laser safety training with Peter King. I completed the Laser Safety Quiz and have turned in my certificate sheet.

I just need to turn in a signed copy of the Lab Safety Checklist to SFP (which I can now have signed by Koji after completing the course).

 

Steve and I have removed the TT mirror from the clean box. It is now on the small optical table in the lab that I have been working on.  Thanks to Steve, all of the mechanical components for the horizontal displacement measurement experiment are compiled and on the small optical table. Here is a photo of the small optical table with the gathered components. CompiledParts.JPG

The plan is to attach the slider and the shaker directly to the black mounting plate. On the slider, we we then place the smaller black mounting plate (with the lip). The lip will attach to the shaker. We know exactly where to drill and everything is lined up. The shaker will be placed on the smaller black mounting plate (with the lip).  The assembly will begin on Monday.

 

Here is a photo of the planned set-up for the shaker and the horizontal slider + mounting base.

 HorizontalDispMount.JPG

  13505   Fri Jan 5 19:19:25 2018 ranaConfigurationSEIBarry Controls 'air puck' instead of 'VOPO style' breadboard

We've been thinking about putting in a blade spring / wire based aluminum breadboard on top of the ETM & ITM stacks to get an extra factor of 10 in seismic attenuation.

Today Koji and I wondered about whether we could instead put something on the outside of the chambers. We have frozen the STACIS system because it produces a lot of excess noise below 1 Hz while isolating in the 5-50 Hz band.

But there is a small gap between the STACIS and the blue crossbeams that attache to the beams that go into the vacuum to support the stack. One possibility is to put in a small compliant piece in there to gives us some isolation in the 10-30 Hz band where we are using up a lot of the control range. The SLM series mounts from Barry Controls seems to do the trick. Depending on the load, we can get a 3-4 Hz resonant frequency.

Steve, can you please figure out how to measure what the vertical load is on each of the STACIS?

Attachment 1: mm_slm.jpg
mm_slm.jpg
Attachment 2: Screen_Shot_2018-01-05_at_7.25.47_PM.png
Screen_Shot_2018-01-05_at_7.25.47_PM.png
  11416   Wed Jul 15 17:05:06 2015 JessicaUpdateGeneralBandpass Pre-Filter created

I applied a bandpass filter to the accelerometer huddle data as a pre-filter. The passband was from 5 Hz to 20 Hz. I found that applying this pre-filter did very little when comparing the PSD after pre-filtering to the PSD with no pre-filtering. There was some improvement though, just not a significant amount. For some reason, it also seemed as though the second accelerometer improved the most from pre-filtering the data, while the first and third remained closer to the unfiltered noise. Also, I have not yet figured out a consistent method for choosing passband ripple and stopband attentuation, both of which determine how good the filter is. 

My next step in pre-filtering will be determining a good method for choosing passband ripple and stopband attenuation, along with implementing other pre-filtering methods to combine with the bandpass filter. 

Attachment 1: acc1.png
acc1.png
Attachment 2: acc2.png
acc2.png
Attachment 3: acc3.png
acc3.png
  337   Fri Feb 22 16:47:54 2008 robUpdateElectronicsBaloney
Well I guess Rana didn't study too hard at Professor School, either. If he'd even bothered to actually read John's entry, he might have looked at the RF Out from the HP Analyzer. As it is, this experience so far has been like taking your car to a highly respected mechanic, telling him it's having acceleration problems, and then he takes a rag and wipes some dirt off the hood and then tells you "It's running fine. That'll be 500 bucks."

I make the current score:

Snarkiness: 2
Education:  0



I did RTFM, and it doesn't mention anything about crazy behaviour on the RF Output. So, I set up the analyzer to do a sweep from 500MHz to 1MHz, with output power of 0dBm, and plugged the output directly into the 300MHz scope with the input set to 50 Ohm impedance. The swept sine output looks totally normal from 500Mhz to 150MHz (measuring ~220mVrms below 300MHz -- 0dBm), where it abruptly transitions to a distorted waveform which the scope measures as having a frequency of ~25MHz and with 450mVrms (+6dBm). It then transitions again at some other part of the sweep to a cleaner-looking 25MHz waveform with ~1.2Vrms (+15dBm). See the attached Quicktime movie. The screeching in the background is the PSL door.

With this bizarre behaviour, it's actually possible that even someone who does everything carefully and correctly could break sensitive electronics with this machine. Let's get it fixed or get a new one.

Don't use the HP4195A anymore unless you want broken electronics.


Quote:
I'm not sure where Ward and Miller went to Analyzer school, but it was probably uncredited.
I turned it on and used 2 BNC cables and a T to hook up the source to the 2 inputs and measured the always-exciting TF of cable.

Score:  HP Analyzer  1
        Rob & John   0


I have left the analyzer on in this complicated configuration. RTFM boys.


Quote:
The HP 4195A network analyser may be broken, measurements below 150MHz are not reliable. Above 150MHz everything looks normal. This may be caused by a problem with its output (the one you'd use as an excitation) which is varying in amplitude in a strange way.

Analyzer
Attachment 1: bustedHP.mov
  4178   Thu Jan 20 17:00:39 2011 AidanConfigurationLockingBallpark figures for Green Locking PLLs (Digital vs Analogue)

If we use a digital PLL for locking the frequency of the PSL and END green lasers then we can expect a UGF of around 1kHz (assuming a sampling rate of 16kHz). Let's assume a simple 1/f loop giving a loop gain of ~1000x at 1Hz. If the free-swinging ETM pendulum motion at 1Hz is of the order of 1 micron, then the residual motion at 1Hz, once we lock the digital PLL by actuating on the ETM position, will be of the order of 1nm. This is bordering on too high.

Alternatively, is we use an analogue PLL then we can expect a much higher UGF and many orders of magnitude more gain at 1Hz (see here). So we would expect the residual motion of the pendulum to be much smaller - probably limited by some other noise source somewhere in the system (I doubt it's going to be reduced by 12 orders of magnitude).

RA: I think ballpark's not good enough for this. To see what's good enough, we need to to an analysis similar to what Bram has for the ALS. Get the 40m seismic spectrum from the arm locking spectrum or the green laser feedback signal and then correct it for a realistic loop shape.

KA: For this purpose I have made the simulink model for the green locking more than a year ago, but the entire green team has consistently neglected its presence...
https://nodus.ligo.caltech.edu:30889/svn/trunk/docs/upgrade08/Green_Locking/Servo_modeling/091121/

  4182   Fri Jan 21 11:45:01 2011 AidanConfigurationLockingBallpark figures for Green Locking PLLs (Digital vs Analogue)

Quote:

If we use a digital PLL for locking the frequency of the PSL and END green lasers then we can expect a UGF of around 1kHz (assuming a sampling rate of 16kHz). Let's assume a simple 1/f loop giving a loop gain of ~1000x at 1Hz. If the free-swinging ETM pendulum motion at 1Hz is of the order of 1 micron, then the residual motion at 1Hz, once we lock the digital PLL by actuating on the ETM position, will be of the order of 1nm. This is bordering on too high.

Alternatively, is we use an analogue PLL then we can expect a much higher UGF and many orders of magnitude more gain at 1Hz (see here). So we would expect the residual motion of the pendulum to be much smaller - probably limited by some other noise source somewhere in the system (I doubt it's going to be reduced by 12 orders of magnitude).

RA: I think ballpark's not good enough for this. To see what's good enough, we need to to an analysis similar to what Bram has for the ALS. Get the 40m seismic spectrum from the arm locking spectrum or the green laser feedback signal and then correct it for a realistic loop shape.

KA: For this purpose I have made the simulink model for the green locking more than a year ago, but the entire green team has consistently neglected its presence...
https://nodus.ligo.caltech.edu:30889/svn/trunk/docs/upgrade08/Green_Locking/Servo_modeling/091121/

 Agreed. It doesn't completely rule out the digital PLL. I'll check out Kiwamu's model.

  7354   Thu Sep 6 19:21:58 2012 ManasaConfiguration40m UpgradingBaffle problem

For the current baffle (dia. 40mm) centered along the beamline place at 1.77" from the test mass, the baffle will allow ~8.6mm visibility on the camera from the center of the test mass (in case of ETMY).

*assuming the pick off mirror is placed at the edge of the tunnel

Attachment 1: bfl.png
bfl.png
  7359   Fri Sep 7 11:58:12 2012 ManasaConfiguration40m UpgradingBaffle problem

Quote:

The required diameter for the baffle if it sits on the cage at 1.77" from the test masses: the current baffle (dia. 40mm) centered along the beamline, will allow ~8.6mm visibility from the center of the test mass (in case of ETMY).

*assuming the pick off mirror is placed at the edge of the tunnel

Estimations of the visibility region (r1 on the test mass) with baffle (aperture size 40mm).

The baffle is installed on the cage at 1.125" from the test mass (distance changed from the previous elog after a double check).

The 40mm aperture is in no way going to help get clear view of the ITMs; 

Attachment 1: bfl.png
bfl.png
  7361   Fri Sep 7 13:01:53 2012 ManasaConfiguration40m UpgradingBaffle problem

Quote:

Quote:

The required diameter for the baffle if it sits on the cage at 1.77" from the test masses: the current baffle (dia. 40mm) centered along the beamline, will allow ~8.6mm visibility from the center of the test mass (in case of ETMY).

*assuming the pick off mirror is placed at the edge of the tunnel

Estimations of the visibility region (r1 on the test mass) with baffle (aperture size 40mm).

The baffle is installed on the cage at 1.125" from the test mass (distance changed from the previous elog after a double check).

The 40mm aperture is in no way going to help get clear view of the ITMs; 

Required baffle diameter to have a visibility region r1 = 3 times the beam diameter

Picture1.png

  3098   Tue Jun 22 18:56:32 2010 JenneUpdateEnvironmentBad placement of recycling bin

Someone has been moving the big blue recycling bin in front of the laser-chiller-chiller (the air conditioner in the control room).  This is unacceptable.  The chiller temp was up to 20.76C.  No good. 

You are free to move the recycling bin around so you can access drawers or the bike-exit-door in the control room, but make sure that it does not block air flow between the chiller-chiller and the chiller. 

The attached photo shows the BAD configuration.

Attachment 1: BlockingLaserChillerChiller_small.jpg
BlockingLaserChillerChiller_small.jpg
  1051   Thu Oct 16 09:44:49 2008 YoichiUpdatePSLBad cable for FSS
Yesterday arount 1:30PM, we lost the LO signal for the FSS.
I found it was caused by a bad cable connecting from the peter's RF oscillator box to the LO of the FSS.
I temporarily replaced it with a BNC cable of comparable length.
  4804   Fri Jun 10 12:04:57 2011 JenneUpdateRF SystemBad RF connections!!

I am in the process of calibrating AS55's shot noise, and I noticed that the AS55 PD input to the demod board was only finger-tight.  I then checked all of the other SMA connections in the set of RF PD demod boards, and found several more that were loose, including all of the REFL55 connections.  This is no good!!!! RF connections need to be tightened!  I went through and tightened all of the offending connections with my personal Snap-on SMA wrench. 

  3712   Thu Oct 14 00:54:12 2010 ranaHowToCDSBad PSL Quad, so I edited the SUS MEDM screens

We found today that there was some (unforgivably un-elogged) PSL-POS & PSL-ANG work today.

The wedge splitter at the end of the PSL table is so terribly dogged that it actually moves around irreversibly if you touch the post a little. Pictures have been recorded for the hall of shame. This should be replaced with a non-pedestal / fork mount.

I was so sad about the fork clamp, that I edited the SUS Master screen instead according to Joe-Yuta instructions; see attached.Untitled.png

There's clearly several broken/white links on there, but I guess that Yuta is going to find out how to fix these from Joe in the morning.

  11051   Thu Feb 19 15:45:43 2015 ericqUpdateCDSBad CDS behavior

At about 10AM, the C1LSC frontend stopped reporting any EPICS information. The arms were locked at the time, and remained so for some hours, until I noticed the totally whited-out MEDM screens. The machine would respond to pings, but did not respond to ssh, so we had to manually reboot.

Soon thereafter, we had a global 15min EPICS freeze, and have been in a weird state ever since. Epics has come back (and frozen again), but the fast frontends are still wonky, even when EPICS is not frozen. Intermittantly, the status blinkers and GPS time EPICS values will freeze for multiple seconds at a time, sporadically updating. Looking at a StripTool trace of an IOPs GPS time value shows a line with smooth portions for about 30 seconds, about 2 minutes apart. Between this is totally jagged step function behavior. C1LSC needed to be power cycled again; trying to restart the models is tough, because the EPICS slowdown makes it hard to hit the BURT button, as is needed for the model to start without crashing.

The DAQ network switch, and martian switch inside were power cycled, to little effect. I'm not sure how to diagnose network issues with the frontends. Using iperf, I am able to show hundreds of Mbit/s bandwidth betweem the control room machines and the frontends, but their EPICS is still totally wonky. 

What can we do??? indecision

  11052   Thu Feb 19 23:23:52 2015 ChrisUpdateCDSBad CDS behavior

The frontends have some paths NFS-mounted from fb. fb is on the ragged edge of being I/O bound. I'd suggest moving those mounts to chiara. I tried increasing the number of NFS threads on fb (undoing the configuration change I'd previously made here) and it seems to help with EPICS smoothness -- although there are still occasional temporal anomalies in the time channels. The daqd flakiness (which was what led me to throttle NFS on fb in the first place) may now recur as well.

 

Quote:

At about 10AM, the C1LSC frontend stopped reporting any EPICS information. The arms were locked at the time, and remained so for some hours, until I noticed the totally whited-out MEDM screens. The machine would respond to pings, but did not respond to ssh, so we had to manually reboot.

Soon thereafter, we had a global 15min EPICS freeze, and have been in a weird state ever since. Epics has come back (and frozen again), but the fast frontends are still wonky, even when EPICS is not frozen. Intermittantly, the status blinkers and GPS time EPICS values will freeze for multiple seconds at a time, sporadically updating. Looking at a StripTool trace of an IOPs GPS time value shows a line with smooth portions for about 30 seconds, about 2 minutes apart. Between this is totally jagged step function behavior. C1LSC needed to be power cycled again; trying to restart the models is tough, because the EPICS slowdown makes it hard to hit the BURT button, as is needed for the model to start without crashing.

The DAQ network switch, and martian switch inside were power cycled, to little effect. I'm not sure how to diagnose network issues with the frontends. Using iperf, I am able to show hundreds of Mbit/s bandwidth betweem the control room machines and the frontends, but their EPICS is still totally wonky. 

What can we do??? indecision

 

  11053   Fri Feb 20 12:08:10 2015 ericqUpdateCDSBad CDS behavior

I've been able to get all models running. Most optics are damped, but I'm having trouble with the ITMs, BS and PRM. 

  11055   Fri Feb 20 14:44:47 2015 ericqUpdateCDSBad CDS behavior

In an effort to ease the IO load on the framebuilder, I've cleaned up the DQ channels being written to disk. The biggest impact was seven 64kHz channels being written to disk, on ADC channels corresponding to microphones. 

The frame files have gone from 75MB to 57MB. 

  16317   Wed Sep 8 19:06:14 2021 KojiUpdateGeneralBackup situation

Tega mentioned in the meeting that it could be safer to separate some of nodus's functions from the martian file system.
That's an interesting thought. The summary pages and other web services are linked to the user dir. This has high traffic and can cause the issure of the internal network once we crash the disk.
Or if the internal system is crashed, we still want to use elogs as the source of the recovery info. Also currently we have no backup of the elog. This is dangerous.

We can save some of the risks by adding two identical 2TB disks to nodus to accomodate svn/elog/web and their daily backup.

host file system or contents condition note
nodus root none or unknown  
nodus home (svn, elog) none  
nodus web (incl summary pages) backed up linked to /cvs/cds
chiara root maybe need to check with Jon/Anchal
chiara /home/cds local copy The backup disk is smaller than the main disk.
chiara /home/cds remote copy - stalled we used to have, but stalled since 2017/11/17
fb1 root maybe need to check with Jon/Anchal
fb1 frame rsync pulled from LDAS according to Tega
       

 

  4043   Fri Dec 10 12:55:27 2010 JenneUpdateComputersBackup should be running successfully now

[Joe, Jenne]

The nightly backup of the frames and the /cvs/cds directories is back up and running.  We are free again to do crazy stuff at will, and it will all be saved for eternity.

  11463   Thu Jul 30 03:19:24 2015 ericqUpdateLSCBack towards PRFPMI

The refreshed ALS didn't look so bad today (elog forthcoming), so I decided to give PRFPMI locking a shot tonight. I was able to hold the PRMI while swinging through resonsance, but transitions to RF signals failed. Demod angles / whitening gains/ etc. etc. all need to be rechecked

Some little things here and there that got cleaned up...

  • The PRM oplev beam was being blocked. Why? I removed the block. Should recheck OLTF/spot size on QPD. 
  • ALS -> CARM, DARM signs changed, maybe because I've used the delayed beat as the RF input on the demod board, whereas I imagine it may have been the LO in the beatbox. No big deal.
  • REFL165 whitening gain and input matrix updated. Should recheck demod angles.
  • PRMI triggering settings weren't being set in the script. It's important to include arm transmission signals, since POP2F signals can momentarily dive when swinging through resonance. 
  • I should revisit phase tracker UGF normalization. I/Q amplitudes are varying quite a bit from lock to lock. 
  • PRC angular feedforward disabled for now; need to remeasure the witness/target data with DC coupled ITM oplevs
  • I think there has been a little bit of MC servo tweaking since our last locks, may need to recheck AO TF / gains. 
  3133   Tue Jun 29 11:48:17 2010 JenneConfigurationSAFETYBack in LASER HAZARD mode.

[Steve, Kiwamu, Jenne]

The 40m is now back in Laser Hazard mode.  Safety glasses are required for entry into the LVEA / IFO room.

  3135   Tue Jun 29 14:16:35 2010 KojiConfigurationSAFETYBack in LASER HAZARD mode.

The insects and the laser trouble... Strange coincidences with LHO surprised me, but now I have been relieved.

Quote:

[Steve, Kiwamu, Jenne]

The 40m is now back in Laser Hazard mode.  Safety glasses are required for entry into the LVEA / IFO room.

 

  8180   Wed Feb 27 02:52:40 2013 JenneOmnistructureSAFETYBack door unlocked

Did someone unlock the back door by the (unofficial) bike storage lately?  Out of habit, I checked the door behind me while about to leave, and it is unlocked. 

Please recall that if you leave through that door, it should automatically lock behind you (if it was locked already), however if you unlock and enter through the back door, it stays unlocked until someone locks it again.

(Obviously, I'm locking the door before I actually go).

  9454   Tue Dec 10 17:27:47 2013 JenneUpdateTreasureBaby oplev LQR designed loop

I *finally* figured out how to bend Matlab to my will, and close a very simple oplev loop using LQR technology. 

This is super, super simple, but it's a step in the right direction.  There is no noise, just a simple pendulum with a resonant frequency of 0.75Hz, and a Q of 10.  The LQR tries to keep the position of the pendulum at a minimum, and does not care at all about the velocity.  You cannot (with Matlab's LQR, at least that I can find) make it care "0" about the control output, so it cares about the control output a factor of 1e-4 as much as the position.

Here are some plots:

The first plot has the open loop system (just the pendulum, no control at all), as well as the closed loop system (the pendulum under control).

NoControlVsClosedLoop_BabyOplev.png

Plot 2 is the open loop gain of the controller that the LQR designed.

OpenLoopGain_BabyOplev.png

Plots 3 and 4 are the step and impulse responses of the open loop (pendulum with no control), and closed loop (pendulum with feedback) systems.

StepResp_BabyOplev.png

ImpResp_BabyOplev.png

The conclusion from the plots (if this were an interesting system) is that it doesn't take much to damp an ideal pendulum.  The real conclusion here is that I think I now know how to use the Matlab LQR function, and can make a loop with some noise now.

  6085   Thu Dec 8 00:18:38 2011 ranaSummaryComputer Scripts / ProgramsBURT restore problems / issues in snapshot scripts

I tried to run the seismic StripTool tonight, which seems liek a simple task. But instead I fell through the rabbit hole again...

The seismic.stp couldn't be run from zita/op340m because zita doesn't have EPICS or MEDM and because the op340m version of StripTool cannot load the new file format in which rossa/pianosa save their files.

Once I got it running by sshing in to rossa, I noticed that the BLRMS trends didn't make any sense. Correctly guessed that this was because all of the BP and LP filters were off. Why? Because of bad BURT, that's why.

As it turns out (if you look through the autoburt logs), several of our FE machines haven't been correctly saving snapshots because of some channel count mismatch between old and new SNAP files. So we are not getting the settings restored correctly for these systems when they get booted. Probably, someone has got to suss out the source of the BURT snap messages; it may be that we have to rehash the snap process after any substantial model rebuild.

For c1pemepics, I did a manual restore from the time when Mirko last ELOG'd that BLRMS was trending OK (Nov 23 @ 3 AM).

Seems like we should also get some kind of auto email warning if the BURTs fail in this way. Otherwise, we'll lose a lot of work if it goes on for weeks.

Bottom line: fix the autoburt so that it doesn't fail after model rebuilds.

  12722   Mon Jan 16 18:54:01 2017 ranaUpdateSUSBS: whitening re-engaged

Found that the BS whitening was off. Gautam says that "it has always been that way" and "there's nothing in the elog about this" and "I have no special relationship with Putin".

I looked at DV and DTT while turning the OSEM whitening back on. As expected, the sensor noise improved by 10x above 10 Hz. The time series shows no problems - its just less fuzzy now.

All OSEM spectra after the switch show on upper panel of plot. Lower panel shows comparison of BS UL before/after. To rotate the DTT PDF landscape output I typed this:

pdftk BS-white.pdf cat 1N output BSwhite.pdf

"if you see something, do something"

Attachment 1: BSwhite.pdf
BSwhite.pdf
  1563   Fri May 8 04:46:01 2009 rana, yoichiSummaryoplevsBS/PRM/SRM table bad!
We went to center the oplevs because they were far off and found that (as usual) the numbers changed
a little after we carefully centered the oplevs and came back to the control room.

To see if the table was on something soft, we tried pushing the table: no significant effect with ~10 pounds of static force.

With ~10 pounds of vertical force, however, we saw a large change: ~0.25 Oplev units. This corresponds to
~20-30 microradians of apparent optic pitch.

In the time series below you can see the effects:

2.5 s: lid replaced on table after centering.

2.5 - 11 s: various force tests on table

11 s: pre-bias by aligning beams to +0.25 in pitch and then add lid.


So there's some kind of gooey behavior in the table. It takes ~1 s to
settle after we put the lid on. Putting the laptops on the table also
has a similar effect. Please do not put anything on this table lid.
Attachment 1: a.png
a.png
  14404   Fri Jan 18 12:52:07 2019 gautamUpdateOptical LeversBS/PRM Oplev HeNe replaced

I replaced the BS/PRM Oplev HeNe with one of the heads from the SP table where Steve was setting up the OL RIN/pointing noise experiment. The old one was dead. The new one outputs 3.2 mW of power, I've labelled it with this number, serial number and date of replacement. The beam comes out of the vacuum chamber for both the BS and PRM, and the RIN spectra (Attachment #1) look alright. The calibration into urad and loop gains possibly have to be tweaked. Since the beam comes out of vacuum, I say that we shouldn't open the BS/PRM chamber for this vent - we don't have a proper plan for the in-air layout yet, so we can add this to the list of to-dos for the next vent.

I think we are down to our last spare HeNe head in the lab - @Chub, please look into ordering some more, the ITMX HeNe is going to need replacement soon.

Attachment 1: OLRIN_20190118.pdf
OLRIN_20190118.pdf
  14345   Tue Dec 11 18:20:59 2018 gautamUpdateOptical LeversBS/PRM HeNe is dead

I found that the BS/PRM OL SUM channels were reading close to 0. So I went to the optical table, and found that there was no beam from the HeNe. I tried power-cycling the controller, there was no effect. From the trend data, it looks like there was a slow decay over ~400000 seconds (~ 5 days) and then an abrupt shutoff. This is not ideal, because we would have liked to use the Oplevs as a DC alignment reference during the ventnoI plan to use the AS camera to recover some sort of good Michelson alignment, and then if we want to, we can switch out the HeNe.

*How can I export PDF from NDscope?

Attachment 1: BSOL_dead.png
BSOL_dead.png
  8393   Tue Apr 2 18:19:30 2013 JenneUpdateSUSBS, PRM oplev servos improved

 

[Gabriele, Jenne]

We have implemented 4Hz resonant gains for both PRM and BS yaw.  The filter was already in place for PRM Yaw, so we just turned it on, but we also copied the filter over to BS Yaw.  We also changed the 3.3Hz res gain and the ELP for the PRM servo to match the BS servo, since after implementing the 4Hz gain, PRM was still much noisier than BS.  Now the 2 servos match, and PRM is a little quieter.  We hope that tonight's locking might be a little more stable after this work.

PRM_servo_matches_BS.pdf

prm_bs_optical_levers_comparison.pdf

  8914   Tue Jul 23 22:55:13 2013 JenneUpdateVACBS, ITMY doors to be opened in the morning

We will open the BS and ITMY doors first thing tomorrow morning. I plan to try to be in around 9 am. The first order of business will be to flip the folding mirrors that are not currently flipped (SR2, SR3, PR3).

  8915   Wed Jul 24 10:35:41 2013 SteveUpdateVACBS, ITMY doors are removed

Quote:

We will open the BS and ITMY doors first thing tomorrow morning. I plan to try to be in around 9 am. The first order of business will be to flip the folding mirrors that are not currently flipped (SR2, SR3, PR3).

 Jenne, Annalisa & Steve

Attachment 1: beforeDoorsOff.png
beforeDoorsOff.png
Attachment 2: particlecount10d.png
particlecount10d.png
  8119   Wed Feb 20 19:48:16 2013 yutaUpdateAlignmentBS table oplev re-arranged

[Sendhil, Yuta]

After aligning IFO and putting the access connector on, we also centered IPANG/IPPOS and all oplevs (except SRM).
To avoid clipping of PRM/BS oplevs, we re-arranged oplev steering mirrors on BS table.

What we did:
  1. Checked IPANG comes out unclipped after putting on the access connector.
  2. Centered IPANG on its QPD.
  3. Checked oplevs beams for ITMX/ITMY centered on in-vac mirrors, and centered them on their QPDs.
  4. Checked IPPOS beam is centered on the mirrors inside BS chamber, and centered IPPOS on its QPD.
  5. Tweaked oplev mirrors on BS chamber to make PRM/BS oplev beam unclipped and centered on mirrors, and centered them on their QPDs. To avoid clipping of oplev beams in BS table, we re-arranged oplev steering mirrors on BS table (outside the vaccum).


Current status:
  QPD values, IFO_ALIGN/MC_ALIGN screens, OSEM values attached.

  - IR incident beam and IFO aligned
  - X/Y end green coming out to PSL table (in higher order modes)
  - IPANG/IPPOS available
  - All oplevs available
  - AS/REFL/POP cameras ready
  - access connector, ETMX/ETMY heavy doors on
  - ITMX/ITMX/BS heavy doors are not on
  - AS/REFL/POP PDs not centered
  - POX/POY/TRX/TRY not aligned
  - AS beam coming out of the OMC chamber low by ~ 1 beam diameter (my bad)


Tomorrow:
  - Align AS/REFL/POP PD and lock PRMI
  - Take pictures of ITMX/ITMY/BS stacks
  - Put heavy doors on ITMX/ITMY/BS chambers
  - Start pumping down

Attachment 1: IFOALIGN_QPDs_OSEMs.png
IFOALIGN_QPDs_OSEMs.png
ELOG V3.1.3-