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  Coating Ring-down Measurement Lab elog, Page 4 of 18  Not logged in ELOG logo
ID Date Author Type Category Subjectup
  291   Mon Feb 6 11:19:13 2017 GabrieleOpticsDaily ProgressLaser swap

The Thorlabs laser has been misbehaving for the whole weekend. Even after many days being continuosly on, the wandering line is still moving all over the frequencies.

So this morning I swapped in a JDSU 1125P borrowed from the 40m lab, which provides about 6.8 mW of power. I tested it over the weekend on a separate test table, and after one day or so of operation the power looks reasonably stable. Now it's been on for a few hours: there is still a line moving around, but it's slowing down and hopefully setting down in a good place.

I started a series of test measurements on the samples that were already installed.

  • Quiet time before excitation: 1170443490
    Excitation (broad band) at 1170443523 (60 s)
    Quiet time after excitation: 1170443586


  295   Tue Feb 7 16:16:37 2017 GabrieleOpticsDaily ProgressLasers

The high power lasers I tested so far (the Thorlabs 21mW and the JDSU 1125P) are noisy: they both have wandering lines that from time to time are alised down into the base band, destroing the measurement. 

I have three JDSU 1103P units: two of them dlived about 2.5 mW, the third one delivers about 1.4 mW. One of the 2.5mW was installed in the test setup. I swapped it out with the 1.4 mW, so now I have two good 2.5 mW laser. My plan is to modify the new setup to use those two lasers in parallel, splitting each one in two, for a total of four beams of about 1.2 mW each.

The new optical layout is atttached.

Attachment 1: crime_v3.pdf
  64   Wed Jul 27 10:19:36 2016 GabrieleElectronicsConfigurationLast finding in the signal jump saga

This plot shows a signal which is generated purely digitally inside a code that I was testing.

Jumps are present even in this case.

Another addition: I was testing some simple code I was writing. Forget about OUT1 and OUT2, but OUT3 and OUT4 should be simple counters. Here's what I get by running the code on cymac3:

Since it didn't make any sense, I ran the same code on cymac2. Here's the (correct) result:

So there's something wrong even when all-digital signals are generated.

  703   Tue May 28 15:48:42 2019 AlenaGeneralVacuumLow pressure gauge exchange

After venting the vacum chamber (CR14) a few times, checking for leaks and trying to tune settings to the gauges controller, I gave up. I removed the low pressure gauge from the newer vaccum system (CR14). Inspection did now show any obviouse depositions around the electrode (due to some burns). I will pack the gauge ans send it to the manufacture for an RMA. Took the same gause from the older vaccum system (CR0) and installed it on CR14. Started pumping down. The low pressure gause turned on just fine. Will check the preassure in an our before starting a measurement.

  19   Fri May 27 02:09:37 2016 GabrieleMechanicsCharacterizationLowest usable mode of fused silica disks

I did some FEA simulation of fused silica disks, to identify the lowest usable eigenmode. By usable I mean a mode that has zero elastic energy stored in the center. 

Diameter Thickness Frequency
75 mm 1 mm 2500 Hz
100 mm 0.4 mm 564 Hz
200 mm 0.4 mm 141 Hz
75 mm 0.12 mm 293 Hz

In the attached figures, the dfisk deformation is shown exaggerated, and the color map shows the elastic energy density. All results are obtained with COMSOL/MATLAB, the disk are constrained at a point corresponding to the center of the lower surface. No gravity.

Attachment 1: disk_75mm_0.12mm.png
Attachment 2: disk_75mm_1mm.png
Attachment 3: disk_100mm_0.4mm.png
Attachment 4: disk_200mm_0.4mm.png
  173   Thu Nov 10 14:13:34 2016 gabrieleElectronicsConfigurationMATLAB code to control Thorlabs stages

To be used to automate the laser polishing.

Attachment 1: move_complete.m
function move_complete(varargin)
    global moving;
    moving = false;
Attachment 2: throlabs_activex.m
%% init the controllers
f1 = figure();
f2 = figure();
tstage = actxcontrol('MGMOTOR.MGMotorCtrl.1', [20 20 600 400], f1);
rstage = actxcontrol('MGMOTOR.MGMotorCtrl.1', [20 20 600 400], f2);
set(tstage, 'HWSerialNum', 27001029);
set(rstage, 'HWSerialNum', 27501183);

... 119 more lines ...
Attachment 3: animation.m
% try a sequence of movements


% laser position
a0 = acos(36/(75/2));  
laser = [-75/2*sin(a0), 75/2*cos(a0)];

% initial position
t = 0;
... 59 more lines ...
Attachment 4: draw_wafer.m
function draw_wafer(translation, angle, laser)
    d = 75; % diameter
    f = 36; % distance of flat from center
    a = acos(f/(d/2));  % half angle opening of the flat
    % build wafer in reference position and orientation
    phi = [linspace(a, pi-a, 100), linspace(pi+a, 2*pi-a, 100)];
    coordinates = [-d/2*cos(phi); d/2*sin(phi)]';
    coordinates(end+1,:) = coordinates(1,:);
... 25 more lines ...
  223   Fri Dec 2 14:05:47 2016 GabrieleGeneralGeneralMIT bare disk losses reproduced with edge and surface losses

The measured losses of the MIT bare disk show a remarkable split into families. The plot belo shows the measured total loss angles (error bars comes from dispersion of multiple measurements)

Using a COMSOL model, and tuning some parameters (E = 73.2 GPa, nu = 0.164, rho = 2202 kg/m^3, thickness = 0.511 mm) I can roughly reproduce the measured mode frequencies, within some tens of Hz:

There is still some splitting into families, so my guess is that the Poisson ratio is not quite right. But this is good enough for now. From this simulation, I can extract the various energies (bulk and shear) in different domains. In particular I'm focusing on the edge and surface energies. The following plot shows the ratio of shear/bulk edge energies over the total energy, as an example.

Now I used the edge shear energy ratio and the surface bulk energy ratio, and that's enough to reproduce the distribution of the measured loss angles:

The measured losses are well described by the following equation:

loss = 4.8e-6 * E_surface_bulk / E_tot + 1.2e-3 * E_edge_shear

The energy ratios here are not dimensionless, since they are the result of a surface integral over a volume integral. So to extract the real loss angles of the surface/edge defects we have to estimate the thickness of the surface/edge lossy area.

Attachment 4: losses_fit.png
  334   Wed Mar 29 11:57:09 2017 GabrieleGeneralMeasurementsMIT sample


  • 11:47am, in chamber CR0, balanced
  • 11:48am roughing pump on
  • 12:00pm, turbo pump on
  • Excitations:
    • Quiet time before excitation: 1174976553
      Excitation broadband: 1174976585
      Quiet time after excitation: 1174976607

    • Quiet time before excitation: 1174977837
      Excitation broadband: 1174977869
      Quiet time after excitation: 1174977891

    • Quiet time before excitation: 1174979121
      Excitation broadband: 1174979153
      Quiet time after excitation: 1174979175

    • Quiet time before excitation: 1174980405
      Excitation broadband: 1174980437
      Quiet time after excitation: 1174980459

    • Quiet time before excitation: 1174981689
      Excitation broadband: 1174981721
      Quiet time after excitation: 1174981743

    • Quiet time before excitation: 1174982973
      Excitation broadband: 1174983006
      Quiet time after excitation: 1174983028

    • Quiet time before excitation: 1174984258
      Excitation broadband: 1174984291
      Quiet time after excitation: 1174984313

    • Quiet time before excitation: 1174985543
      Excitation broadband: 1174985575
      Quiet time after excitation: 1174985597

  212   Mon Nov 28 15:06:09 2016 GabrieleGeneralMeasurementsMIT sample 1 (bare disk)


  • 3:00pm: removed the retaining ring and the alignment pins
  • 3:05pm, 100mm/0.5mm disk installed, balanced
  • 3:06pm, roughing pump on
  • 3:19pm, turbo pump on
  • Excitations:
    • quiet time before 1164414276
      band pass 100-3000 Hz, amplitude 3 x 2 kV, 60 seconds
      quiet time after 1164414439
    • Quiet time before excitation: 1164426582
      Excitation (broad band) at 1164426615 (60 s)
      Quiet time after excitation: 1164426677

    • Quiet time before excitation: 1164437507
      Excitation (broad band) at 1164437539 (60 s)
      Quiet time after excitation: 1164437601

    • Quiet time before excitation: 1164448433
      Excitation (broad band) at 1164448465 (60 s)
      Quiet time after excitation: 1164448527


  • 10:02am, pumps off


2016-11-28 A

% Freq        Q1                Q2
315.9         2.8096e+06        2.8096e+06
726.7         1.8635e+06        1.8635e+06
1265.9        1.4194e+06        1.4029e+06
1930.4        1.1427e+06        1.1427e+06
1945.3        3.8068e+06        3.8068e+06
2717.9        9.7820e+05        9.6825e+05
2937.1        2.9339e+06        2.8810e+06
3626.4        8.4222e+05        8.4139e+05
4082.7        2.4345e+06        2.3090e+06
4638.8        5.2362e+06        5.1759e+06
4654.2        7.4042e+05        7.4042e+05
5374.9        1.9928e+06        1.9928e+06
5800.3        6.7081e+05        6.6269e+05
6164.3        4.0627e+06        3.8329e+06
6808.9        1.8131e+06        1.7073e+06
7063.0        6.2208e+05        6.2066e+05
7849.1        3.0518e+06        3.0518e+06
8381.5        1.6107e+06        1.6105e+06
10089.4        1.3860e+06        1.3793e+06
10476.0        4.6551e+06        4.6551e+06
12692.5        3.7473e+06        3.7473e+06

2016-11-28 B

% Freq        Q1                Q2
316.2         2.9559e+06        2.9559e+06
726.7         1.9471e+06        1.9471e+06
1265.9        1.4767e+06        1.4596e+06
1324.0        1.7317e+06        1.7317e+06
1930.3        1.1866e+06        1.1826e+06
1945.2        3.8606e+06        3.8606e+06
2247.0        1.2821e+06        1.2442e+06
2717.8        1.0111e+06        9.8894e+05
2936.9        2.9926e+06        2.9494e+06
3626.2        8.6881e+05        8.6809e+05
4082.4        2.4804e+06        2.3513e+06
4638.7        5.2732e+06        5.1865e+06
4654.1        7.6228e+05        7.6228e+05
5374.6        2.0240e+06        2.0240e+06
5800.0        6.8894e+05        6.7200e+05
6164.1        3.9378e+06        3.9270e+06
6808.7        1.8616e+06        1.7343e+06
7062.7        6.2617e+05        6.2617e+05
7849.0        3.1323e+06        3.1323e+06
8381.2        1.6487e+06        1.5110e+06
8419.4        6.2761e+06        6.0088e+06
9687.4        2.6263e+06        2.6263e+06
10088.7        1.4209e+06        1.4209e+06
10475.5        4.5819e+06        3.9452e+06
11929.4        2.0706e+06        8.4521e+05
13900.0        1.1087e+06        1.1087e+06

2016-11-29 C

% Freq        Q1                Q2
316.1         3.0133e+06        3.0133e+06
726.7         1.9621e+06        1.9621e+06
1265.8        1.4754e+06        1.4754e+06
1324.0        1.5486e+06        1.5486e+06
1930.3        1.1968e+06        1.1968e+06
1945.2        3.8326e+06        3.8326e+06
2717.8        1.0236e+06        9.9498e+05
2937.0        3.0102e+06        2.9815e+06
3626.2        8.7624e+05        8.7624e+05
4082.3        2.4965e+06        2.3709e+06
4638.6        5.2551e+06        5.2551e+06
4654.0        7.6848e+05        7.6176e+05
5374.4        2.0713e+06        2.0713e+06
6164.0        4.6657e+06        4.6657e+06
6808.7        1.8860e+06        1.7018e+06
8381.1        1.6553e+06        1.6553e+06
8419.0        6.3696e+06        6.3696e+06




  214   Tue Nov 29 11:26:46 2016 GabrieleGeneralMeasurementsMIT sample 2 (disk with 4 1"/0.1mm glued blanks)


  • 11:24am, in chamber, balanced. Installed with the four glued blanks facing down
  • 11:25am, roughing pump on
  • 11:35am, turbo pump on
  • Excitations
    • Quiet time before excitation: 1164492579
      Excitation (broad band) at 1164492611 (60 s) NOTE:stopped short of planned end time
      Quiet time after excitation: 1164492673

  • ~2:40pm, Roughing pump off

    • Quiet time before excitation: 1164494418
      Excitation (broad band) at 1164494450 (60 s)
      Quiet time after excitation: 1164494512

  • Reduced excitation amplitude by a factor 2

    • Quiet time before excitation: 1164496302
      Excitation (broad band) at 1164496334 (60 s)
      Quiet time after excitation: 1164496396

  • Increased excitation back to original value

    • Quiet time before excitation: 1164497423
      Excitation (broad band) at 1164497455 (60 s)
      Quiet time after excitation: 1164497517

    • Quiet time before excitation: 1164498267
      Excitation (broad band) at 1164498300 (60 s)
      Quiet time after excitation: 1164498362

    • Quiet time before excitation: 1164499112
      Excitation (broad band) at 1164499144 (60 s)
      Quiet time after excitation: 1164499206

  • 4:01pm, turbo pump off


2016-11-28 B

% Freq       Q1                Q2
329.0        8.4824e+04        8.4824e+04
335.7        1.4025e+05        1.4025e+05
440.4        9.8646e+03        9.8646e+03
497.0        9.0449e+03        9.0449e+03
776.2        9.3536e+04        9.3536e+04
1112.1        7.1969e+03        7.1969e+03
1350.2        8.7756e+04        8.7756e+04
1358.5        7.4121e+04        7.4121e+04
1552.4        1.8858e+04        1.8858e+04
1609.0        3.3215e+04        3.3215e+04
1784.0        1.1629e+04        1.1629e+04
1798.6        2.0767e+04        2.0767e+04
1888.4        1.7837e+04        1.7837e+04
1945.0        3.3859e+04        3.3859e+04
2030.0        1.0957e+04        1.0957e+04
2050.5        7.5373e+04        7.5373e+04
2080.0        8.8890e+04        8.8890e+04
2134.5        1.1641e+04        1.1641e+04
2416.0        2.1993e+04        2.1993e+04
2470.5        2.7733e+04        2.7733e+04
2520.0        2.2354e+04        2.2354e+04
2527.0        4.5688e+04        4.5688e+04
2856.0        2.0405e+04        2.0405e+04
2874.4        5.1657e+04        5.1657e+04
3192.0        4.0038e+04        4.0038e+04
3438.0        2.4531e+04        2.4531e+04
3528.0        4.3625e+04        4.3625e+04
3810.3        8.4299e+04        8.4299e+04
3812.7        8.4331e+04        8.4331e+04
4214.0        4.5810e+04        4.5810e+04
4379.8        1.2693e+05        1.2693e+05
4550.5        4.2404e+04        4.2404e+04
4867.4        8.2873e+04        8.2873e+04
4870.5        7.8134e+04        7.8134e+04


2016-11-28 D

% Freq        Q1                Q2
335.6         1.4056e+05        1.4056e+05
672.0         1.5677e+05        1.5677e+05
777.6         9.2059e+04        9.2059e+04
1112.7        1.0553e+05        1.0553e+05
1203.1        5.5487e+04        5.5487e+04
1350.1        8.4536e+04        8.4536e+04
1358.4        7.1777e+04        7.1777e+04
1714.6        7.2616e+04        7.2616e+04
2050.5        7.6493e+04        7.6493e+04
2080.0        8.7699e+04        8.7699e+04
2098.0        9.7959e+04        9.7959e+04
2416.0        1.0540e+05        1.0540e+05
2874.4        5.6525e+04        5.6525e+04
3128.9        2.3520e+04        2.3520e+04
3134.3        2.0219e+04        2.0219e+04
3810.5        8.7060e+04        8.7060e+04
3812.5        8.7089e+04        8.7089e+04
4323.4        5.2924e+04        5.2924e+04
4379.8        1.2308e+05        1.2308e+05
4867.1        8.1170e+04        8.1170e+04
4870.4        8.9835e+04        8.9835e+04
5704.3        6.9120e+04        6.9120e+04
5728.4        6.6924e+04        6.6924e+04
6033.9        7.5637e+04        7.5637e+04
6036.0        8.0112e+04        8.0112e+04
7204.0        1.0233e+05        1.0233e+05
8625.9        1.4731e+05        1.4731e+05


Attachment 2: 2016-11-29_11.17.13.jpg
Attachment 6: results_2016_11_28b.png
Attachment 10: results_2016_11_28d.png
  215   Tue Nov 29 16:42:51 2016 GabrieleGeneralMeasurementsMIT sample 3 (disk with 4 0.5"/0.125" glued blanks)


  • 4:40pm, in chamber, blanks facing down
  • 4:41pm, roughing pump on
  • 4:53pm, turbo pump on
  • Injections:
    • Quiet time before excitation: 1164516798
      Excitation (broad band) at 1164516830 (60 s)
      Quiet time after excitation: 1164516892

    • Quiet time before excitation: 1164518722
      Excitation (broad band) at 1164518754 (60 s)
      Quiet time after excitation: 1164518816

    • Quiet time before excitation: 1164520646
      Excitation (broad band) at 1164520678 (60 s)
      Quiet time after excitation: 1164520740

    • Quiet time before excitation: 1164522570
      Excitation (broad band) at 1164522602 (60 s)
      Quiet time after excitation: 1164522664

    • Quiet time before excitation: 1164524494
      Excitation (broad band) at 1164524526 (60 s)
      Quiet time after excitation: 1164524588

    • Quiet time before excitation: 1164526419
      Excitation (broad band) at 1164526451 (60 s)
      Quiet time after excitation: 1164526513


  • 9:05am, pumps off


2016-11-29 A

% Freq       Q1                Q2
251.9        2.8630e+04        2.8630e+04
270.6        4.3984e+04        4.3984e+04
329.0        5.2792e+04        5.2792e+04
387.4        6.4408e+04        6.4408e+04
692.9        2.1202e+04        2.1202e+04
705.5        2.7294e+04        2.7294e+04
1121.5        1.9490e+04        1.9490e+04
1127.2        2.3102e+04        2.3102e+04
1242.2        1.6168e+04        1.6168e+04
1318.1        2.5395e+04        2.5395e+04
1800.6        2.3235e+04        2.3235e+04
2124.1        1.8960e+04        1.8960e+04
2797.5        9.8183e+03        9.8183e+03
2841.8        1.1002e+04        1.1002e+04
2921.3        1.2820e+04        1.2820e+04
2959.7        7.8878e+03        7.8878e+03
3701.0        8.0007e+03        8.0007e+03
3839.4        1.3538e+04        1.3538e+04
4692.3        3.4420e+04        3.4420e+04

2016-11-29 B

% Freq        Q1                Q2
251.9         2.6513e+04        2.6513e+04
329.0         5.4964e+04        5.4964e+04
387.0         5.9983e+04        5.9983e+04
692.9         2.4150e+04        2.4150e+04
705.4         2.7301e+04        2.7301e+04
1127.3        1.8674e+04        1.8674e+04
1242.1        1.2792e+04        1.2792e+04
1318.1        2.4187e+04        2.4187e+04
1800.7        2.2498e+04        2.2498e+04
2124.2        1.8534e+04        1.8534e+04
2797.5        9.8734e+03        9.8734e+03
2841.6        1.2921e+04        1.2921e+04
2959.8        1.0940e+04        1.0940e+04
3400.4        1.5128e+04        1.5128e+04
3700.7        1.0732e+04        1.0732e+04
4692.2        4.3243e+04        4.3243e+04

2016-11-29 C

% Freq        Q1                Q2
251.6         2.8079e+04        2.8079e+04
271.0         4.1437e+04        4.1437e+04
329.0         5.4328e+04        5.4328e+04
387.4         5.8614e+04        5.8614e+04
692.8         2.2689e+04        2.2689e+04
705.5         2.8442e+04        2.8442e+04
1127.2        1.8216e+04        1.8216e+04
1242.0        1.8455e+04        1.8455e+04
1317.8        2.3628e+04        2.3628e+04
1800.6        2.2896e+04        2.2896e+04
2124.2        1.8450e+04        1.8450e+04
2797.7        1.0904e+04        1.0904e+04
2841.8        1.4721e+04        1.4721e+04
2921.4        1.0612e+04        1.0612e+04
2959.8        1.0875e+04        1.0875e+04
3700.7        1.1009e+04        1.1009e+04
3705.3        1.0344e+04        1.0344e+04
3839.3        1.3205e+04        1.3205e+04
4110.4        1.3077e+04        1.3077e+04
4692.3        4.8605e+04        4.8605e+04




Attachment 5: results_2016_11_29a.png
Attachment 9: results_2016_11_29b.png
  234   Wed Dec 7 09:59:59 2016 GabrieleGeneralMeasurementsMIT sample 3 (disk with 4 0.5"/0.125" glued blanks) second round


  • Removed retaining ring and pins, aligned optical setup to horizontal reference
  • 9:59am, in chamber, balanced
  • 10:00am, roughing pump on
  • 10:12am, turbo pump on

As visible in th second picture, the distance between the disk and the ESD is about 1.5 mm

  • Excitations:
    • Quiet time before excitation: 1165178719
      Excitation (broad band) at 1165178751 (60 s)
      Quiet time after excitation: 1165178813

    • Quiet time before excitation: 1165180007
      Excitation (broad band) at 1165180039 (60 s)
      Quiet time after excitation: 1165180101

    • Quiet time before excitation: 1165181331
      Excitation (broad band) at 1165181363 (60 s)
      Quiet time after excitation: 1165181425

  • 2:39pm, pumps off



2016-12-07 A

% Freq        Q               Q (C.I. 95%)        Q (C.I. 95%)
251.8        2.9528e+04        2.9325e+04        2.9732e+04
323.4        6.9039e+04        6.5071e+04        7.3509e+04
328.7        5.5337e+04        5.5222e+04        5.5453e+04
692.8        2.4543e+04        2.4515e+04        2.4571e+04
705.5        2.7474e+04        2.7356e+04        2.7592e+04
1128.5        2.1332e+04        2.1268e+04        2.1395e+04
1242.4        1.2258e+04        1.2079e+04        1.2442e+04
1318.0        2.4548e+04        2.4419e+04        2.4678e+04
1800.7        2.6692e+04        2.6451e+04        2.6937e+04
1933.3        9.2002e+03        8.9167e+03        9.5022e+03
1937.7        8.5766e+03        8.5339e+03        8.6198e+03
2124.0        2.4927e+04        2.4872e+04        2.4982e+04
2799.2        8.1222e+03        7.9880e+03        8.2609e+03
2924.5        8.1070e+03        8.0349e+03        8.1804e+03
2964.4        8.2661e+03        8.1772e+03        8.3570e+03
4692.7        4.5716e+04        4.4885e+04        4.6578e+04

2016-12-07 B

% Freq        Q                Q (C.I. 95%)        Q (C.I. 95%)
251.7        2.8324e+04        2.8084e+04        2.8567e+04
329.0        5.4343e+04        5.4182e+04        5.4504e+04
692.7        2.4556e+04        2.4524e+04        2.4588e+04
705.5        2.7344e+04        2.7229e+04        2.7461e+04
1128.3        2.0844e+04        2.0548e+04        2.1148e+04
1242.1        1.2091e+04        1.1999e+04        1.2185e+04
1317.8        2.4709e+04        2.4659e+04        2.4760e+04
1322.0        2.8932e+04        2.6985e+04        3.1179e+04
1800.6        2.6879e+04        2.6691e+04        2.7069e+04
2123.6        2.4719e+04        2.4619e+04        2.4820e+04
2798.1        9.5908e+03        9.2072e+03        1.0008e+04
2841.0        1.1254e+04        1.0614e+04        1.1976e+04
2924.0        1.1666e+04        1.0395e+04        1.3291e+04
2963.1        9.7910e+03        9.3703e+03        1.0251e+04
3427.6        8.7265e+03        8.2911e+03        9.2102e+03
3700.2        1.4646e+04        1.3418e+04        1.6120e+04
4691.8        5.0056e+04        4.7715e+04        5.2638e+04

2016-12-07 C

% Freq        Q               Q (C.I. 95%)        Q (C.I. 95%)
251.8        2.8868e+04        2.8741e+04        2.8997e+04
313.8        4.8299e+04        4.4161e+04        5.3275e+04
658.0        4.5409e+04        4.4859e+04        4.5971e+04
692.6        2.4089e+04        2.3929e+04        2.4251e+04
705.4        2.7821e+04        2.7639e+04        2.8006e+04
1128.2        2.1583e+04        2.1087e+04        2.2103e+04
1242.1        1.2540e+04        1.2303e+04        1.2786e+04
1317.9        2.4663e+04        2.4626e+04        2.4700e+04
1571.0        1.4941e+04        1.4265e+04        1.5685e+04
1800.4        2.8559e+04        2.8113e+04        2.9019e+04
2123.4        2.7042e+04        2.6498e+04        2.7608e+04
2452.3        2.9667e+04        2.8231e+04        3.1256e+04
2797.4        8.7540e+03        8.0589e+03        9.5802e+03
2840.2        1.3484e+04        1.2967e+04        1.4043e+04
3706.5        1.0864e+04        1.0328e+04        1.1457e+04
4107.6        1.5757e+04        1.5573e+04        1.5946e+04
4690.7        4.8903e+04        4.7899e+04        4.9949e+04

2016-12-07 D

% Freq        Q               Q (C.I. 95%)        Q (C.I. 95%)
251.8        2.9311e+04        2.9189e+04        2.9434e+04
323.2        2.7246e+04        2.4352e+04        3.0908e+04
692.6        2.4309e+04        2.4226e+04        2.4392e+04
698.0        1.7009e+04        1.5425e+04        1.8954e+04
702.0        2.7209e+04        2.6645e+04        2.7796e+04
705.5        3.0025e+04        2.9300e+04        3.0785e+04
1127.6        2.0285e+04        1.9811e+04        2.0781e+04
1317.3        2.5325e+04        2.5209e+04        2.5442e+04
1800.3        3.2511e+04        3.1223e+04        3.3909e+04
1935.2        6.5014e+03        4.9517e+03        9.4607e+03
2122.5        2.8808e+04        2.7758e+04        2.9940e+04
2795.4        1.0237e+04        8.7193e+03        1.2393e+04
4688.8        4.9909e+04        4.1120e+04        6.3475e+04
6847.5        7.9848e+03        7.7352e+03        8.2510e+03




  218   Wed Nov 30 10:02:20 2016 GabrieleGeneralMeasurementsMIT sample 4 (disk with 3 1"/0.1mm glued blanks)


  • 9:57am, in chamber, balanced, glued balnks facing down
  • 9:59am, roughing pump on
  • 10:09am, turbo pump on
  • Excitations
    • Quiet time before excitation: 1164570059
      Excitation (broad band) at 1164570091 (60 s)
      Quiet time after excitation: 1164570153

    • Quiet time before excitation: 1164571983
      Excitation (broad band) at 1164572015 (60 s)
      Quiet time after excitation: 1164572077

    • Quiet time before excitation: 1164573907
      Excitation (broad band) at 1164573939 (60 s)
      Quiet time after excitation: 1164574001

    • Quiet time before excitation: 1164575831
      Excitation (broad band) at 1164575863 (60 s)
      Quiet time after excitation: 1164575925

  • 3:34pm, pumps off


2016-11-30 A

% Freq        Q1                Q2
329.0         8.3663e+04        8.3663e+04
764.8         6.6913e+04        6.6913e+04
1093.6        7.4978e+04        7.4978e+04
1173.2        4.7789e+04        4.7789e+04
1333.5        5.8904e+04        5.8904e+04
1529.0        6.9659e+04        6.9659e+04
1597.4        1.0552e+05        1.0552e+05
1748.0        4.8237e+04        4.8237e+04
2007.8        3.8014e+04        3.8014e+04
2017.3        6.4686e+04        6.4686e+04
2066.8        4.6047e+04        4.6047e+04
2077.3        5.7698e+04        5.7698e+04
2832.1        4.1680e+04        4.1680e+04
2850.9        6.3764e+04        6.3764e+04
3101.5        2.6027e+04        2.6027e+04
3468.7        1.9827e+04        1.9827e+04
3784.7        3.5492e+04        3.5492e+04
4301.1        3.6826e+04        3.6826e+04
4822.6        6.6123e+04        6.6123e+04
4834.9        4.6789e+04        4.6789e+04
6014.6        6.6507e+04        6.6507e+04

2016-11-30 B

% Freq        Q
328.8         8.5064e+04
764.6         6.7065e+04
1093.6        6.4289e+04
1173.2        4.7921e+04
1333.5        5.8311e+04
1529.0        6.4720e+04
1597.4        1.5015e+05
1748.4        4.2924e+04
2007.7        4.1694e+04
2017.4        6.3609e+04
2067.0        4.6240e+04
2077.2        5.8395e+04
2406.0        4.5908e+04
2832.1        4.5323e+04
2851.0        6.4089e+04
3101.5        2.9677e+04
3468.7        1.6697e+04
3784.5        2.1703e+04
4299.7        3.7688e+04
4835.1        4.6841e+04
5659.7        3.4913e+04

2016-11-30 C

% Freq        Q
329.1         8.3839e+04
658.0         8.6457e+04
764.6         6.6619e+04
1093.7        7.3246e+04
1163.3        2.7214e+04
1172.5        4.1708e+04
1333.7        5.9429e+04
1597.4        1.4036e+05
1748.0        2.8271e+04
2007.8        4.7532e+04
2017.4        6.5563e+04
2067.0        4.5528e+04
2077.2        5.8753e+04
2346.0        3.4762e+04
2832.1        3.9431e+04
2851.1        6.4498e+04
3101.5        3.0334e+04
3469.0        1.6427e+04
3784.7        5.0161e+04
4299.8        4.0081e+04
4835.2        5.3962e+04
4860.0        5.4326e+04
5659.8        3.5224e+04
6015.4        4.6382e+04
8739.5        4.7841e+04



Attachment 2: 2016-11-30_09.57.45.jpg
  255   Fri Jan 6 11:23:10 2017 GabrieleGeneralMeasurementsMark Optics 4

This is one of the samples we got from the first batch, no flats, edge not polished


  • 11:10am, in chamber, balanced
  • 11:11am, roughing pump on
  • 11:23am, turbo pump on
  • Excitations:
    • Quiet time after excitation 1167770663
    • Quiet time before excitation: 1167781499
      Excitation (broad band) at 1167781532 (60 s)
      Quiet time after excitation: 1167781594

    • Quiet time before excitation: 1167792424
      Excitation (broad band) at 1167792457 (60 s)
      Quiet time after excitation: 1167792519

    • Quiet time before excitation: 1167803349
      Excitation (broad band) at 1167803381 (60 s)
      Quiet time after excitation: 1167803443

    • Quiet time before excitation: 1167814274
      Excitation (broad band) at 1167814306 (60 s)
      Quiet time after excitation: 1167814368


  • 10:15am pumps stopped






  360   Fri Jun 30 11:02:18 2017 ZachElectronicsModelingMatching Forces


  • I adjusted the plot parameters slightly so that it only showed the actual force profile on the sample in the direction perpendicular to the sample surface. Additionally I compared the two methods of computing the force, as \vec{F} = -(\vec{P}\cdot \nabla)\vec{E} and as \vec{F} =- \chi_e \epsilon_0 \nabla \vec{E}^2. The profile of the force in both instances appear equal, but they differ in magnitude by exactly a factor of 2, I plotted the force computed with the explicit polarization doubled and the force magnitudes matched exactly. I'm still not entirely sure where this factor of two could be coming from.

  371   Thu Jul 20 11:37:01 2017 ZachElectronicsModelingMatlab Script


  • I believe my MATLAB script successfully calculates the force distribution into each of the modes specified by the parameters. My previous error was caused by my neglecting the proportionality factor of \frac{1}{2}\chi_e\epsilon_0. Now the force order of magnitude is on the order of 103. I am currently unclear how to think about the units of the mode shapes from the disk_frequencies script, but I will pick it apart more carefully and try to figure that out. Then it will be a matter of converting units so that it matches with the N/m^3 from the COMSOL script and then comparing with real lab results. It seems to me that the error in force distribution should be inversely proportional to the number of modes calculated, in which case it would be useful to determine an appropriate number of modes to calculate. 
Attachment 1: forces.m
par.a = 75e-3/2;    % radius [m]
par.h = 1.004e-3;   % thickness [m]
par.E = 73.2e9;     % Young's modulus [Pa]
par.nu = 0.155;     % Poisson's ratio
par.rho = 2202;     % density [kg/m^3]

%Calculate fundamental modes of the disk
[freqs, modes, shapes, x, y] = disk_frequencies(par, 10000, 1, 'shapes', 0.5e-3);

%Now we extract the force profile from the COMSOL model
... 27 more lines ...
  104   Tue Aug 23 09:44:11 2016 GabrieleGeneralGeneralMeasurements on MO-02

Two good ring-downs measurements were performed on MO-02. The first one was already reported in a previous elog entry. I performed another measurement, and refined the mode identification. I think I had misidentified some modes in my previous analysis. The following plot shows the difference between the modes as predicted by COMSOL and as measured. A clean quadratic trend is visible and fitted:

Here's the spectrum with all the modes:

And the updated Q measurement plot:

A second ring down was measured on Monday morning . Here are the relevant plots:

This is the same disk as before, but almost all Q values are systematically higher. Here's a direct comparison:

I'm not sure what changed between the two measurements, except for a re-alignment of the QPD. The disk might have moved a bit...

Attachment 4: spectrum_with_modes_12_01pm.png
  210   Wed Nov 23 14:16:59 2016 AlenaGeneralGeneralMicroscope inspection

Microscope inspection of samples:

S1600487  https://dcc.ligo.org/S1600487-v7

S1600438 https://dcc.ligo.org/S1600438



  204   Mon Nov 21 11:46:57 2016 GabrieleGeneralGeneralMicroscope inspection of 439 and 487


This is the sample that was CO2 polished (198) and measured after polishing (197, 199). Unfortunately it got damaged during annealing:

I looked at the edge under the microscope. The first image is taken with light from above, and it shows a bit of residual defects in the center of the edge:

The images below are taken with light from below (which seems always the best choice) and they show some residual defects on the edge. Also, there is some "stuff" on the borders, like some fibers of some contamination. The first image is taken in correspondence of the damage, which is barely visible on the left edge. No clean problem is visible here.


This is a sample as received from Mark Optics. I will measure its Q values, laser polish it, measure again and then anneal it. Here are some images of the edges for future reference. The last one in particular shows the transition from the round part to the flats. The surface quality is clearly different.

  201   Fri Nov 18 15:48:09 2016 GabrieleGeneralMeasurementsMicroscope inspection of CO2 polished samples


For reference, this sample has not been CO2 polished, but it has been annealed and measured. It has quite low Q values. Here are some images of the edges. The first two are taken with light from above. In the second one there some clear red residual, which is also visible as a coloration with the naked eye. The microroughness and some larger defect are well visible.

The following images instead are taken with light from below. The red residual is even more evident, and some traces probably due to the machining are clearly visible.


This sample has been laser polished with a double pass (first at 0.5 mm/s, second at 0.25 mm/s). The first two images are taken with light from above: they are not very clear because of the specular reflection of the lamps. This already indicates that the surface is much smoother. Some defects (bubbles?) are visible close to the main surfaces.

The surface quality is more apparent in the following pictures, taken with light from below. The second one is taken where there is a chip in the main surface, and indeed one can see the shading due to the light distortion iduced by the chip. Also a cluster of "bubbles" is clearly visible there.


This was our first polishing test. It is interesting because the laser tripped during the procedure, so we have a neat transition from the original surface to the polished one. First image taken with light from above, second with light from below

Attachment 9: S1600462_3.png
  412   Wed Aug 16 11:36:13 2017 ZachElectronicsModelingMiddle ESD


  • I created a model with a drive offset in the middle. It improved one of the modes by a factor of 14 or so, but overall, it diminished the vast majority of the modes by as much as a factor of 100. 

Attachment 2: overlay23.jpg
  403   Thu Aug 10 11:32:09 2017 GabrieleGeneralMeasurementsMode peak amplitudes with reference ESD

The uncoated, annealed and CO2 polished substrate S1600541 is installed in chamber CR0. This morning I performed a quick excitation: 1.6kV peak, broadband noise (500Hz - 32768 Hz), duration 20s. I measured the peak amplitude right after the excitation. The first plot below shows the SNR for all the detected 19 modes, as a function of frequency. The second plot shows the peak amplitude in physical units (radians/rHz of disk surface tilt) for all modes. The calibration of the surface motion should be reasonably good, better than a factor 2 of uncertaint. The attached TXT file contains the numerical data.

Attachment 3: peaks.txt
   1.1299461e+03   4.1911883e-06   3.7890494e+03
   2.5911635e+03   3.7687909e-06   2.9654534e+03
   4.5081875e+03   7.0826275e-07   3.4932225e+03
   6.8666454e+03   1.8347384e-06   3.7284735e+03
   6.8998265e+03   7.2550890e-08   1.4606621e+02
   9.6542682e+03   9.2541866e-07   4.2092492e+03
   1.0397923e+04   1.3057807e-07   7.8362131e+02
   1.2860601e+04   1.9470780e-07   1.4041656e+03
   1.4422018e+04   1.0362112e-07   6.3149271e+02
   1.6384301e+04   3.2555068e-08   2.0573770e+02
... 10 more lines ...
  367   Wed Jul 12 15:08:59 2017 ZachElectronicsModelingModel of actuator and sample


  • I am attaching the first fully functioning model of the actuator and sample. I cleared both meshes and solutions to make the file a reasonable size, but they can quickly be built/solved again. 
Attachment 1: Force_Model.mph
  59   Mon Jul 25 12:24:06 2016 GabrieleElectronicsConfigurationMore on the signal jumps

Here are two more tests I did this morning

  • removed the DAC card from the cymac and the models, and restarted everything: signal jumps are still there
  • move the cymac2 from the crackling noise lab to the CRIME lab, ans set it up with all the same hardware I was using with the cymac3: there are no jumps, signals look perfect (see plots at the end)

So in conclusion: the problem is in the cymac3 computer, either software or hardware. I tend to excluse an I/O hardware problem, since I used two different ADCs and removed the DAC, without improving the situation.

  73   Tue Aug 2 16:00:32 2016 GabrieleElectronicsCharacterizationMore on the signal jumps

So I’m sending a 1.123 Hz sinusoid into the ADC, and generating 3.123 Hz sines and cosines in the model. Frequencies are reasonably incommensurable with one second.

The plots below shows all three signals. In the top panels, I just separate the two segments in each second: the “normal” segment in blue, and the “jumped” segment in orange.
In the bottom panels, I took the jumped segments (orange) and shifted them “in the future” by exactly one second. The signals are perfect!
I think we could explain this if the order of the samples in each second is scrambled, like we have a circular buffer but we point to the wrong starting point…
  126   Mon Sep 26 15:54:01 2016 GabrieleFacilityConfigurationMoved vacuum controllers

I moved the turbo pump controller out of the clean room. Also, I installed the gauge controller on the Cymac rack.

  42   Thu Jul 14 17:06:47 2016 GabrieleElectronicsConfigurationNetworking

The laboratory workstation is coatings.ligo.caltech.edu

The RTS is cymac3.ligo.caltech.edu

I set up a ssh-mount of the /opt/rtcds/userapps folder in the workstation. I also created shared ssh keys for the controls user, so we can ssh into the cymac3 without password

  338   Fri Apr 7 16:19:03 2017 GabrieleOpticsDaily ProgressNew 1103P laser installed

This afternoon I installed the new Lumentum (former JDSU) HeNe laser, model 1103P in CR0.

Realigned everything.

I installed a sample in the chamber to reflect a beam back inot the QPD. Checking the QPD signals over a hour and more did not show any sign of excess noise or instability.

  323   Tue Feb 28 14:20:50 2017 GabrieleGeneralMeasurementsNew MIT sample #1


  • 2:19pm, installed in CR0, balanced, with 1/2" inserts facing down
    • It looks dusty and there is a fingerprint on the edge. I didn't clean it
  • 2:21pm, roughing pump on
  • 2:35pm, turbo pump on
  • Excitations:
    • Quiet time before excitation: 1172377933
      Excitation broadband: 1172377965
      Quiet time after excitation: 1172378027

    • Quiet time before excitation: 1172381657
      Excitation broadband: 1172381689
      Quiet time after excitation: 1172381751

    • Quiet time before excitation: 1172385381
      Excitation broadband: 1172385414
      Quiet time after excitation: 1172385476

    • Quiet time before excitation: 1172389106
      Excitation broadband: 1172389138
      Quiet time after excitation: 1172389200

    • Quiet time before excitation: 1172392830
      Excitation broadband: 1172392863
      Quiet time after excitation: 1172392925

    • Quiet time before excitation: 1172396555
      Excitation broadband: 1172396587
      Quiet time after excitation: 1172396649



  • 9:36am, pumps stopped


  • 9:00am. The laser beam was probably hitting one of the glued inserts. Checked that te disk is not touching, moved the ESD a bit lower
  • 9:04am, roughing pump on
  • 9:17am, turbo pump on
  • 1:50pm, pumps off
  328   Fri Mar 3 13:01:59 2017 GabrieleGeneralMeasurementsNew MIT sample #2


  • 1:00pm, in chamber, realigned optical lever to get as close as possible to the edge of the disk
  • 1:02pm, roughing pump on
  • 1:14pm, turbo pump on
  • Excite
    • Quiet time before excitation: 1172633160
      Excitation broadband: 1172633192
      Quiet time after excitation: 1172633224

    • Quiet time before excitation: 1172634454
      Excitation broadband: 1172634486
      Quiet time after excitation: 1172634518

    • Quiet time before excitation: 1172635748
      Excitation broadband: 1172635781
      Quiet time after excitation: 1172635813

    • Quiet time before excitation: 1172637043
      Excitation broadband: 1172637075
      Quiet time after excitation: 1172637107

    • Quiet time before excitation: 1172638337
      Excitation broadband: 1172638369
      Quiet time after excitation: 1172638401

    • Quiet time before excitation: 1172639631
      Excitation broadband: 1172639663
      Quiet time after excitation: 1172639695


  • 10:18am, pumps off


  330   Tue Mar 7 11:09:33 2017 GabrieleGeneralMeasurementsNew MIT sample #3


  • 11:08am, in chamber CR0
  • 11:09am, roughing pump on
  • 11:23am turbo pump on
  • 3:37pm, pumps stopped, the turbo is saturating CR1


  • 8:00am pumps restarted
  • Excitations
    • Quiet time before excitation: 1173048953
      Excitation broadband: 1173048986
      Quiet time after excitation: 1173049018

    • Quiet time before excitation: 1173050248
      Excitation broadband: 1173050280
      Quiet time after excitation: 1173050312

    • Quiet time before excitation: 1173051542
      Excitation broadband: 1173051574
      Quiet time after excitation: 1173051606

    • Quiet time before excitation: 1173052836
      Excitation broadband: 1173052868
      Quiet time after excitation: 1173052900

    • Quiet time before excitation: 1173054130
      Excitation broadband: 1173054163
      Quiet time after excitation: 1173054195

    • Quiet time before excitation: 1173055425
      Excitation broadband: 1173055457
      Quiet time after excitation: 1173055489


  • 10:10am, pumps off
  112   Thu Sep 15 08:27:57 2016 GabrieleGeneralGeneralNew band-limited excitation

Same as in elog #110, but now the amplitude is proportional to frequency squared:

ampl = (x/x[0])**2
xx = multi_band_noise(bands, ampl, T=20, fs=65536)
n = AWGNoiseStream(4e-4*xx, channel='X3:CR1-ESD_EXC', rate=65536)

Noise stopped at 8:27:40am LT.

Turbo pump off and spinning down at 9:37am LT. Pumo completely stopped at 11:15am LT

Openend the chamber and removed the sample at ~11:20am LT

  264   Thu Jan 19 07:32:33 2017 AlenaGeneralVacuumNew chamber first pimp down

The new chamber was build. The first attempt to pump down was unsuccessful because of dislocated lid. After the lit was placed properly, the chamber was pumped down to 0.1 torr within 8 min. In future a sky hook will be used to help placing the lid properly. The clamps should not be placed on the lid before the roughing pump turned on.

The turbo pump controller failed. Error code 698 – call the vendor.

  266   Thu Jan 19 14:16:53 2017 GabrieleMechanicsDesignNew concept for retaining ring motion

Since my experiment with coil and magnets didn't work out very well, here's a new concept for the motion of the four retaining rings (all together) using a translation stage and a picomotor. This follows the same idea put forward by Steve Penn. The translation stage is a Newport 9066-COM-V and the picomotor (which we already have) is a Newport 8301-V. Both stage and picomotor are vacuum compatible (rated at 1e-6 Torr) and tested down to 1e-8 Torr by Steve.

Here's the jig integrated in the full system:


  94   Sun Aug 21 08:51:22 2016 GabrieleGeneralDaily ProgressNew disk installed

Vented the chamber. Installed a new disk (MO 03). The one I measured yesterday is now named MO 02 and it is the one with the "burnt mark" from the previous experiment (due to the electrostatic drive).

Startep roughing pump at 8:50am. Started turbo pump at 9.00am.

Excited the disk at 9:50:30am with white noise, amplitude 10 V. Pumps are still running, pressure is about 2e-6 Torr

At 11:10am I stopped the roughing pump, pressure is 1.4e-6 Torr. Exciting again the disk at 11:10:45am. At 12:25am I checked again the situation, since both measurements look quite weird, especially for the first couple of modes.

I think the reflection from the balck glass is interfering with the reflection from the disk. Probably I wasn't careful enough when I aligned the disk. At about 12:35 I stopped the turbo pump. I'm going to open the chamber and realign everything again.

  554   Thu Jul 26 15:33:00 2018 AlenaGeneralGeneralNew laser instaled for the old chanber cr0

Installed a new HeNe laser for the old chamber cr0. No major alignement was required. The laser mount restored the alinement. Will run a test measurement now.

Attachment 1: 20180726_152508.jpg
Attachment 2: 20180726_152521.jpg
Attachment 3: 20180726_152530.jpg
Attachment 4: 20180726_154138.jpg
  106   Sun Sep 11 10:05:33 2016 GabrieleGeneralDaily ProgressNew substrate in the chamber

I installed one of the new substrates (with flats) into the chamber, and started the pumpdown at about 9:45am LT.

Before that, I removed the retaining ring: tomorrow I'm going to glue the magnet to it.

  96   Sun Aug 21 15:36:16 2016 GabrieleGeneralDaily ProgressNew test

Roughing pump stopped at about 3:30:30pm. HV amplifier on at 3:33:30pm, excitation at 3:35:30pm. Recentered QPD at 3:36pm

  98   Sun Aug 21 17:41:34 2016 GabrieleGeneralDaily ProgressNew test

I checked the status at about 5:20pm, the turbo pump was in error and spinning down, since the roughing pump has been off for about 1.5 hours.

I let the pump switch off.


Roughing pump stopped at about 3:30:30pm. HV amplifier on at 3:33:30pm, excitation at 3:35:30pm. Recentered QPD at 3:36pm


  99   Mon Aug 22 08:29:24 2016 GabrieleGeneralDaily ProgressNew test

Restarted roughing and turbo pump at about 8:10am.


I checked the status at about 5:20pm, the turbo pump was in error and spinning down, since the roughing pump has been off for about 1.5 hours.

I let the pump switch off.


Roughing pump stopped at about 3:30:30pm. HV amplifier on at 3:33:30pm, excitation at 3:35:30pm. Recentered QPD at 3:36pm



  133   Mon Oct 17 10:50:50 2016 GabrieleGeneralVacuumNo sign of problems in the electrostatic drive

I opened the chamber and took the etched disk out. Inspection of the electrostatic drive does not show any sign of burn or damage.

So it seems that the problem we had previously was due to contamination of the chamber (in the first case) or of the ESD (in the second case)

  170   Wed Nov 9 15:32:11 2016 GabrieleGeneralNoise huntingNoise below 2 kHz is not due to the roughing pump, but to the clean air filters

The two spectra below show basically no difference (blue roughing pump on, red, roughing pump off)

Instead, below is another comparison: blue same as before, standard condition, red with one of the two clean air filters momentarily off. There is some clear improvement. The second filter is too hard to switch off!

  181   Sun Nov 13 10:11:19 2016 GabrieleGeneralNoise huntingNoise due to air

The plot below compares the QPD signal spectra in different configurations (roughing pump on/off, air on/off).

The noise below ~<2kHz is making very hard to measure the Q of the first mode at 1100 Hz

The main source of noise are the clean air filters. I switched them to minimum for the moment being.

  394   Mon Aug 7 13:19:48 2017 ZachElectronicsModelingNormalized data


  • I included the modal mass factors in the code and renormalized my data. The normalization has a noticeable impact, but does not change the general trends of the data
  • In fact the impact is not even significant enough to warrant a change in the ideal parameters I picked for the rectangular ESD in my interim report

Attachment 1: Arm_gap.pdf
Attachment 2: Arm_width.pdf
Attachment 3: Offset.pdf
Attachment 4: Sample_Gap.pdf
  383   Thu Jul 27 16:56:03 2017 ZachElectronicsModelingOffset Sweep


  • I ran a low resolution sweep of the offset in the arms of the ESD, the space between the end of the arm and base of the opposite combs. The trends are much more subtle and are not coherent across as many of the modes. The lower frequency modes decrease slightly, while the force in the higher frequency modes increase more drastically. This is an interesting parameter, I will definitely run another sweep once I have written code that accounts for the mode pairs. Assuming the apparent trends are physically accurate, this could be a useful parameter because a greater offset gives a greater relative increase to the higher order modes while still leaving a substantial force on the lower order modes that are excited more easily anyway.

Attachment 1: Offset.jpg
  37   Mon Jul 11 15:21:12 2016 GabrieleGeneralDaily ProgressOne disk installed into the chamber

[Alena, Gabriele]

We attached one of the silicon lenses to a 1" optical post using some kapton tape, and installed it into the vacuum chamber. We built a simple periscope using standard optical component, and managed to send the optical level beam into the disk and back out.

To set a reference for the horizontal position of the disk we used the LMA method: we put a small container with water in place of the disk, and mark on a reference where the reflected beam hits out of the chamber:

We then put back the disk, and aligned it to have the beam hitting the same position. During pumdown we couldn't see any shift of the disk, judging from the position of the optical lever beam.

  14   Thu May 19 11:33:44 2016 GabrieleElectronicsDesignOptical lever electronics design

The circuit design sent out for fabrication is available in the DCC: D1600196

  280   Fri Jan 27 14:56:55 2017 GabrieleOpticsDaily ProgressOptical lever setup completed

The four optical levers are completely installed and aligned to a horizontal reference.

  16   Fri May 20 15:18:58 2016 GabrieleOpticsDesignOptical levers layout

Attached a first layout of the optical lever systems. The beam spot radius on the QPD is about 0.8 mm, and the lever arm length is of the orer of 1.4-1.5 m for all four beams.


Attachment 1: crime_v1.pdf
  17   Sun May 22 23:40:45 2016 GabrieleOpticsDesignOptical levers layout

An improved design is attached. I modified the input telescope to avoid using shor focal length lenses, to make it less critical, and to reduce the beam spot radius at the QPD to 0.5 mm.


Attached a first layout of the optical lever systems. The beam spot radius on the QPD is about 0.8 mm, and the lever arm length is of the orer of 1.4-1.5 m for all four beams.



Attachment 1: crime_v1.pdf
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