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New entries since:Wed Dec 31 16:00:00 1969
ID Date Author Type Category Subjectdown
  67   Thu Jul 28 13:58:48 2016 Alena, GabrieleCleanDaily ProgressThe old chamber is now being cleaned and baked

Cleaned the chamber in the washing machine at 40m and started 48 baking at 120 C

Attachment 1: 20160728_092350.jpg
  100   Mon Aug 22 12:01:52 2016 GabrieleGeneralGeneralTests of the day

Disk excited at 12:01pm. Exited the room at 12:03pm.

Opened the chamber at about 2:30pm, got the disk out for edge polishing, installed it back at 3:30pm, pumping down at 3:40pm.

Stopped the roughing pump at 4:44:00pm (+60 seconds clean data, GPS 1155944657). Switched on the HV amplifier, excitation at 4:47:30pm. Recentered QPD, clean data from 4:48:30pm (GPS 1155944927)

After a first look at the data, it seems that something went wrong. I restearted the roughing pump and will pump overnight.  I found the QPD miscentered, so I centered it again.

Excited again at about 5:46:35pm. Clean data from 1155948460

  124   Fri Sep 23 08:11:48 2016 GabrieleMechanicsDaily ProgressTest of the disk retaining ring motion

In brief, it doesn't work. The magnets and coils are strong enough to push up the ring with a sample inside, but the friction with the three alignment pins is too large and random, so when the current to the coils is increased slowly, the ring doesn't move up smoothly (see first attached video). On the other hand, if the current is switched on abruptly, the ring shoot to the top and stays there. However, if a disk is placed on the support, it is ejected out (see second video). When the current is cut (smoothly or abruptly) the ring doesn't alway comes back to the bottom, but sometimes it stays stuck inclinded.

On the positive side, we probably don't need such a complicated system:

  1. in all the pump down I've done so far (ten or more), the disk never moved
  2. the ring is very useful, even when used manually, to find the initial centering of the disk: if we machine three small aluminum wedges that can be put under the ring to keep it raised (or three set screws), it can be used to place down the sample in a roughly centered position, that has always been good enough to get the beam almost back into the QPD.

Links to the two videos:
Video1 Video2

  176   Thu Nov 10 17:04:05 2016 GabrieleGeneralNoise huntingTemporary second QPD

This morning I installed temporarily a second QPD to monitor the input beam. The goal was to understand where the vibrations at frequencies below 2kHz couple from. As shown in the photo, the second QPD was close to the first one.

The signals in the two QPDs were quite different, and the coherence between them wasn't great. So I concluded that the main coupling path is not through input beam of QPD vibration, but more likely real motion of the disk.

I removed the additional QPD and restored the setup to its nominal configuration. The readout infrastructure is still in the model.

  456   Tue Jan 30 15:56:36 2018 Gabriele, CraigElectronicsConfigurationTemporary data acqusition for PSL lab beat note and accelerometers

We set up the model x3tst to acquire at 65kHz four signals coming from the PSL lab:

  • X3:TST-BEAT_OUT_DQ: beat note
  • X3:TST-ACC_X_OUT_DQ: accelerometer X
  • X3:TST-ACC_Y_OUT_DQ: accelerometer Y
  • X3:TST-ACC_Z_OUT_DQ: accelerometer Z
  9   Mon May 2 11:46:45 2016 GabrieleFacilityDaily ProgressTable and vacuum chambers in the lab

Elogs for the new Coatin RIng-down MEasurement lab had to start somewhere, so here is a couple of pictures of the optical table with shorter legs and of one of the two vacuum chambers that have been moved in.

  10   Tue May 3 11:57:47 2016 GabrieleFacilityDaily ProgressTable and vacuum chambers in the lab

We discovered a couple of days ago that the table was sitting on three legs only and the fourth one was dangling. I managed to adjust the height of the fourth leg using the large screw on the leg support. Now the table is properly supported by all four legs.


Elogs for the new Coatin RIng-down MEasurement lab had to start somewhere, so here is a couple of pictures of the optical table with shorter legs and of one of the two vacuum chambers that have been moved in.


  195   Thu Nov 17 12:06:39 2016 GabrieleGeneralVacuumSwitching on the IGM moves the disk

Here's a trend of the QPD signals when the IGM was turned on:

Turning it off does not bring the disk back.

  379   Wed Jul 26 09:27:40 2017 ZachElectronicsModelingSweeping the space between ESD and sample


  • I ran a sweep of the gap between the ESD and the sample, first from .5 mm to 1 mm. That sweep suggested that there is a significant jump in force across almost all of the modes at 1 mm. To confirm this I double checked the geometry and it appears that COMSOL is building everything as expected when changing the spacing parameter. Then I ran a finer sweep in .02 mm increments for the spacing between .9 and 1.1 mm. Once again it appears there is a large jump as the gap approaches 1 mm, but the behavior does not seem to be symmetric about that point, the force appears to diminish linearly as the gap increases beyond 1 mm. I will run a sweep of the ESD arm spacing along with the vertical gap to confirm that the jump occurs when the gap between the ESD and the sample is equivalent to the spacings between the ESD arms.

Attachment 1: Gap_near_one.jpg
  311   Fri Feb 17 13:44:47 2017 GabrieleOpticsDaily ProgressSwapped picomotor and re-alignment

Since I had recurrent problems with the picomotors used for QPD3, I swapped them with another Newport motorized mirror that was previously used in the Crackle1 experiment. This is the same model used for the other three QPD centering. Everything looks to be working fine now.

I also realigned all optical levers and swapped out an iris with a smaller one, to avoid beam clipping. All beam paths look clear now.

  336   Thu Mar 30 15:23:44 2017 GabrieleOpticsGeneralSwapped HeNe laser in CR0

The JDSU HeNe laser 1103P that I was using is dead. I swapped it with a JDSU 1125P borrowed from the 40m.

  216   Tue Nov 29 17:02:06 2016 GabrieleFacilityNoise huntingSuspending the roughing pump

I suspended the roughing pump with four springs. The reduction of the 58 Hz peak is similar to what I got when the pump was sitting on a box. So most of the coupling is due to acousting noise.

Attachment 1: 2016-11-29_11.08.17.jpg
  308   Thu Feb 16 09:47:29 2017 GabrieleGeneralMeasurementsSummary of coating runs carried out at Montreal
Substrate temperature Serial numbers
room temperature 457 458 490 492
150 C 489 491
250 C 447 456
400 C 459 461
480 C 448 453


  444   Wed Dec 6 07:53:47 2017 GabrieleGeneralMeasurementsSubstrates from University Wafers


Four fused silica substrates from University Wafers, 76.2mm diameter / 0.5 mm thickness installed in chamber

  • 7:50am in chamber
  • 7:54am roughing pump on
  • 8:03am turbo pump on
  80   Fri Aug 12 10:33:14 2016 GabrieleElectronicsConfigurationStorage added to cymac3

Installed two new 2TB disks into the cymac3. Also, the main disk has a 1TB partition with the operating system, so I created a new 1TB partition. I created a logic volume that spans the three partitions, for a total of about 5TB. This partition is mounted in /mnt/data and linked to the /frames folder. Frames are written to this new logic volume.

  242   Tue Dec 13 11:42:52 2016 GabrieleGeneralGeneralSteve Penn's model of loss angle

The plot below shows the best loss angle we expect foer our samples, based on Steve Penn's model of surface and volume losses (Phys. Lett. A 352, 3). That paper contains data only for Suprasil 2 and Suprasil 312, so it might be a bit wrong for our Corning 7980. The two experimental data sets are for samples that have been laser polished.

  48   Mon Jul 18 14:29:07 2016 GabrieleGeneralDaily ProgressStatus of the test setup

I checked that the QPD electronics works as expected, and that I can acquire the signals using the ADCs. A new model (x3cr1) is up and running. It acquires the four quadrants, convert them from counts to volts, and compensate for the analog whitening filter. The four quadrant signals are X3:CR1-Q1_OUT, X3:CR1-Q2_OUT, X3:CR1-Q3_OUT, X3:CR1-Q4_OUT.

A matrix is used to compute the X and Y signals, defined as X = (Q1+Q4-Q2-Q3) and Y = (Q2+Q4-Q1-Q3). The SUM signal is also computed as SUM = (Q1+Q2+Q3+Q4).

Finally, the X and Y signals are normalized with the sum to produce X3:CR1-X_NORM_OUT and X3:CR2-Y_NORM_OUT.

A filter bank (ESD) is connected to the DAC channel #0 to produce the excitation that will be sent to the high voltage amplifier. I checked that the DAC is working properly (adding offsets). The input to the ESD filter bank is in volts.

The normalized X and Y signals, the sum of all four quadrants and the output of the ESD driver filter bank are saved to frames. The model runs at 65kHz.

  50   Mon Jul 18 17:48:58 2016 GabrieleElectronicsConfigurationStatus of real time system and workstation

[EricQ, Gabriele]

The real time system seems to be working properly, except for the excitations: we can't activate any excitation using awggui or diaggui

Eric rebuilt the workstation from scratch installing Debian 8.5. All CDS software seem to be working. We setup a ssh-key for ssh'ing into cymac3 and configured the automatic mount of the remote /opt/rtcds.

  103   Tue Aug 23 09:21:25 2016 GabrieleGeneralGeneralStatus of Mark Optics disks

We initially received 20 disks (75 mm diameter, 1 mm thickness) from Mark Optics. Here's their status as of today

  • MO-01 was annelaed and measured at LMA. It was then taken back to Mark Optics by Julie Houser at the time of her visit
  • MO-02 was initially used to test the "dirty" measurement apparatus, then it was installed into the new chamber and measured on Saturday August 20th
    Then this disk was used as a guinea pig for the laser edge polishing, and it's now in a pretty bad shape
  • MO-03 was installed into the new chamber and measured a couple of times on Sunday and Monday. Then we laser polished the edges, with good results, although there are small damages on the surface. It has been installed back into the chamber and a couple of rind-down measurement carried out on Monday and Tuesday.
  • MO-04 is still untouched

All the other disks have been sent back to Mark Optics to grind out flats. 

  81   Sat Aug 13 11:17:17 2016 GabrieleFacilityDaily ProgressSpot the differences

  305   Tue Feb 14 10:55:13 2017 GabrieleGeneralDaily ProgressSomething fishy with bay 4 of the new setup

I did two set of measurements with the new coated samples from Montreal. I reshuffled the position in the two measurements. In both cases, the measurement being performed in bay 4 was bad, in the sense that it was very hard to see excited modes. Since the two measurements were carried out with two different disks, it's clear it is a problem with that setup.

SOLVED: there was a connection problem for the DAC output signal controlling the switch

REALLY SOLVED: it was not a cabling issue. The power supply for the switching box had the current limiter on: when all four switches are closed, the box drain about 270mA, which is more than the limit of 250mA. Therefore the power supply voltage dropped and only three switches were actually closed. I switched the power supply to 500mA range and maxed the current limit. Now all four switches are working properly

  83   Sun Aug 14 11:40:29 2016 GabrieleElectronicsDaily ProgressSome python code

Today I wrote some auxiliary functions that will be useful for the measurement system:

  • noise.py: set of functions to generate band-limited noise (using inverse FFT) and multiple band noise. Using the awg python interface I can also start and stop the noise injection. Some examples of the result:

  • readdata.py: read data online, compute a spectrum, and additionally a function that find peaks in a whitened spectrum. All peaks above a minimum SNR are returned: the central frequency is computed by an average of the bin SNR:

  • diskmodel.py: reads a list of mode frequencies from txt files. In each file, the first row is the disk diameter in mm, the second is the disk thickness in mm, all other rows are the modes are computed by COMSOL. I also produced a whole bunch of such files, with diameters within 75 +- 0.1 mm and thickness within 1 +- 0.1 mm
  277   Wed Jan 25 16:12:05 2017 GabrieleGeneralDaily ProgressSome assembly
  • assembled the four in-vacuum periscopes (no mirrors yet)
  • soldered kapton wires to the four ESD board; the vacuum side HV connectors are installed
  • installed the picomotor into the traslation stage, and soldered the two picomotor wires to a twisted kapton pair. Note: the white wire is connected to the kapton wire which is twisted on the other side.
  314   Wed Feb 22 13:56:15 2017 GabrieleElectronicsConfigurationSoftware improvements
  1. created a single interface to move the picomotors in front of QPD1 ... QPD4
    • the command qpdcenter will open an interactive python shell to control the picomotors
  2. two scripts for automatic excitations are saved in /opt/rtcds/userapps/CyMAC/src/auto_excite*.py
    • they must run on the cymac. But they can be started from the control station using the commands autoexcite0 and autoexcite14
    • before starting the commands, set the parameters in the file. The two commands edit_autoexcite0 and edit_autoexcite14 will open the correct files
    • a log file of the excitation times will be saved
    • the scripts will check if there is an excitation going
  3. the two commands noise0 and noise14 can be used to start awggui to inject the correct noise
  4. updated the autocentering scripts, so that only one instance can run at a time.
    • launch them with the commands autocenter0 and autocenter14
  265   Thu Jan 19 12:49:17 2017 GabrieleFacilityVacuumSkyhook installed

The SkyHook has been put in place and bolted down to the floor.

Attachment 1: IMG_4241.JPG
Attachment 2: IMG_4241.JPG
Attachment 3: IMG_4241.JPG
  72   Tue Aug 2 15:58:12 2016 GabrieleElectronicsDaily ProgressSix QPD functional and tested

I finished populating the new four QPD boards, and fixed the first one I populated weeks ago. I tested all five new boards: the output of the transimpendance respond correctly to the ambient light; the output of the whitening also respond correctly and has increased high frequency noise; the differential driver stages are all functional and balanced.

In summary, we have six QPD circuits ready: serial 02 is installed into the box and it has been used for the previous tests. Serial number 01, 03, 04, 05, 06 are not yet into a box, but fully functional. Boxes are ready.

For testing purposed, I also built another ADC interface board: it's complete with the exception of the connector that goes to the ADC.

  154   Mon Oct 31 12:51:13 2016 GabrieleGeneralMeasurementsSimulation of dilution factor and measured loss angles

I made a COMSOL simulation of our wafer (75 mm with flats, 1 mm thick) with a 1 micron thick coating (Tantala), and computed the dilution factor (E_coating / E_total). The result is shown in the plot below:

The dilution factor is slighly mode dependent, around a value of 5.7e-3.

The Q we measured on the latest two annealed wafers are in the range of 5e6 - 10e6 for the good modes, meaning that the total loss angle (subtrate, surface and edge combined) is 1e-7 - 2e-7.

Assuming an undoped tantala coating with loss angle of 4e-4 (http://authors.library.caltech.edu/55765/2/1501.06371.pdf), the disk loss angle after coating will be 2.2e-6, a factor 5 to 10 higher than our uncoated and annealed wafers.

So we can use the wafers as they are for our measurements.


  238   Fri Dec 9 13:13:32 2016 GabrieleGeneralMeasurementsSilicon sample

Silicon wafer from WRS materials, diameter 3", thickness 356-406 microns.


  • 1:00pm, retaining ring and pins installed back, optical system realigned to horizontal reference
  • 1:08pm, in chamber, balanced. Since silicon reflection is higher than silica, installed a ND0.3 to avoid QPD saturation
  • 1:10pm, roughing pump on
  • 1:23pm, turbo pump on
  • Excitations
    • Quiet time before excitation: 1165359305
      Excitation (broad band) at 1165359337 (60 s)
      Quiet time after excitation: 1165359399


  • Excitation:
    • Quiet time before excitation: 1165611248
      Broadband excitation
      Quiet time after excitation: 1165611382
    • Quiet time before excitation: 1165611540
      100-1000 Hz excitation
      Quiet time after excitation: 1165611619
  • 2:05pm, pumps stopped


% Freq        Q                Q (C.I. 95%)        Q (C.I. 95%)
2043.9        6.5333e+03        6.5061e+03        6.5607e+03
2307.9        1.6958e+04        1.6895e+04        1.7022e+04
3671.0        2.7458e+04        2.7324e+04        2.7595e+04
4909.0        4.1605e+04        4.1322e+04        4.1892e+04
5268.1        2.5236e+04        2.5186e+04        2.5286e+04
6079.0        2.6835e+04        2.6311e+04        2.7382e+04
7317.4        5.1946e+04        5.1799e+04        5.2095e+04
7391.0        1.3702e+04        1.3441e+04        1.3973e+04
8586.6        5.3491e+04        5.2271e+04        5.4769e+04
8719.9        5.4501e+04        5.3904e+04        5.5111e+04
9600.4        6.6514e+04        6.6390e+04        6.6639e+04
9622.1        3.0667e+04        3.0505e+04        3.0830e+04
10507.0        8.1040e+04        8.0965e+04        8.1115e+04
11053.9        6.0651e+04        5.9853e+04        6.1471e+04
11397.5        5.2873e+04        5.2242e+04        5.3520e+04
11950.0        3.2045e+04        3.1514e+04        3.2593e+04
12083.0        8.8181e+04        8.7571e+04        8.8800e+04
12330.6        4.9761e+04        4.8997e+04        5.0549e+04
13799.0        4.8752e+04        4.7609e+04        4.9951e+04
14911.9        8.7301e+04        8.6550e+04        8.8066e+04
15849.6        3.7500e+04        3.6882e+04        3.8139e+04
17381.4        7.5930e+04        7.4582e+04        7.7328e+04
17585.0        9.7947e+04        9.6811e+04        9.9110e+04
17597.0        2.8465e+04        2.7318e+04        2.9712e+04
18310.4        9.0019e+04        8.9175e+04        9.0879e+04
18542.1        6.8287e+04        6.7506e+04        6.9088e+04
18547.5        1.4131e+05        1.4017e+05        1.4248e+05
18774.9        1.0588e+05        1.0490e+05        1.0687e+05
19066.6        8.0216e+04        7.8924e+04        8.1551e+04
20253.5        9.6914e+04        9.4540e+04        9.9411e+04
20463.0        1.0020e+05        9.9323e+04        1.0109e+05
21188.2        1.1931e+05        1.1851e+05        1.2012e+05
21828.5        1.4420e+05        1.4290e+05        1.4552e+05
21837.5        1.5768e+05        1.5639e+05        1.5899e+05
22976.0        5.6472e+04        5.6229e+04        5.6717e+04
23356.5        1.2871e+05        1.2729e+05        1.3017e+05
23398.5        1.4698e+05        1.4422e+05        1.4984e+05
23455.0        1.1209e+05        1.0950e+05        1.1479e+05
23457.7        1.0716e+05        1.0509e+05        1.0932e+05
23496.0        1.4477e+05        1.4295e+05        1.4665e+05
23703.5        1.5954e+05        1.5695e+05        1.6222e+05
23993.0        1.3344e+05        1.3183e+05        1.3510e+05
24758.2        1.4752e+05        1.4655e+05        1.4850e+05
24952.6        1.3025e+05        1.2972e+05        1.3077e+05
25139.0        3.3941e+04        3.3575e+04        3.4316e+04
25298.5        1.0825e+05        1.0603e+05        1.1056e+05
25387.1        1.3101e+05        1.3055e+05        1.3148e+05
25391.7        1.2021e+05        1.2011e+05        1.2032e+05
26752.9        1.0624e+05        1.0595e+05        1.0653e+05
26762.0        1.8838e+05        1.8490e+05        1.9200e+05
26838.0        6.9555e+04        6.7066e+04        7.2237e+04
27147.7        1.0675e+05        1.0571e+05        1.0780e+05
27698.0        8.3204e+04        8.1975e+04        8.4471e+04
28101.4        1.7792e+05        1.7748e+05        1.7836e+05
28109.4        8.9486e+04        8.8527e+04        9.0466e+04
28480.6        1.1985e+05        1.1934e+05        1.2037e+05
28972.0        4.5087e+04        4.3490e+04        4.6806e+04
28979.3        1.3823e+05        1.3750e+05        1.3897e+05
29044.6        1.7261e+05        1.7177e+05        1.7347e+05
29166.4        1.7820e+05        1.7785e+05        1.7855e+05
29222.0        1.8986e+05        1.8640e+05        1.9345e+05
29451.0        3.4557e+04        3.3927e+04        3.5211e+04
30284.4        1.9755e+05        1.9701e+05        1.9810e+05
30691.3        9.7139e+04        9.6728e+04        9.7553e+04
31228.6        1.2060e+05        1.2028e+05        1.2092e+05
32159.5        2.0041e+05        1.9800e+05        2.0288e+05
32226.8        7.3880e+04        7.3119e+04        7.4658e+04
32366.0        2.0220e+05        2.0185e+05        2.0255e+05


  369   Tue Jul 18 09:13:08 2017 GabrieleGeneralMeasurementsShear and bulk losses in tantala

S1600525 has been coated in Fort Collins with 480nm of pure tantala. I used the emasured loss angles (after deposition, before annealing) to estimate the shear and bulk loss angles.


First, my COMSOL simulation shows that even if I don’t include the drum-like modes, I still have a significant scatter of shear/bulk energy ratio. The top panel shows indeed the ratio shear/bulk for all the modes I can measure, and the variation is quite large. So, contrary to my expectation, there is some room for fitting here. The bottom panel just shows the usual dilution factors.

Then I tried to fit the total losses in my sample (the substrate is negligible) using four different models:
1) one single loss angle for both bulk and shear, constant in frequency
2) one single loss angle for both bulk and shear, linear in frequency
3) separate bulk and shear loss angles, constant
4) separate bulk and shear loss angels, linear in frequency 
Instead of using Gregg harry's technique (taking pairs of losses together), I simply fit the whole datasets with the assumptions above. I derived the 95% confidence intervals for all parameters. I also weighed each data point with the experimental uncertainty. I’m not sure yet how to compare the performance of the various models and decide which is the best one, since clearly the more parameters I plug into the model, the better the fit gets.
If I use two different loss angles, but constant, I get numbers similar to what Gregg presented at the last Amaldi conference (G1701225), but inverted in bulk and shear. I cross checked that I didn’t do any mistake. Instead, if I allow linear dependency on frequency of bulk and shear, I get a trend similar to the one in Gregg's slides.
My plan is to have this sample annealed today or tomorrow and measure it again before the end of the week. 


One loss angle - constant

\phi = (6.99 \pm 0.05) \times 10^{-4} \mbox{ rad}

One loss angle - linear in frequency

\phi = (6.91 \pm 0.07) \times 10^{-4} +\frac{f-1 \mbox{ kHz}}{1 \mbox{ kHz}} \cdot (3.3 \pm 2.2) \times 10^{-6} \mbox{ rad}

Bulk and shear - constant

\begin{matrix} \phi_{shear} = (6.79 \pm 0.12) \times 10^{-4} \mbox{ rad} \\ \phi_{bulk} = (8.54 \pm 0.98) \times 10^{-4} \mbox{ rad} \end{matrix}

Bulk and shear - linear in frequency

\begin{matrix} \phi_{shear} = (6.9 \pm 0.4) \times 10^{-4} +\frac{f-1 \mbox{ kHz}}{1 \mbox{ kHz}} \cdot (9.9 \pm 7.4) \times 10^{-6} \mbox{ rad} \\ \phi_{bulk} = (6.4 \pm 3.7) \times 10^{-4} +\frac{f-1 \mbox{ kHz}}{1 \mbox{ kHz}} \cdot (-14 \pm 39) \times 10^{-6} \mbox{ rad} \end{matrix}

  370   Wed Jul 19 21:19:14 2017 GabrieleGeneralMeasurementsShear and bulk losses in tantala

To quantify which of the fit below is the most significant, I did a Bayesian analysis (thanks Rory for the help!).

In brief, I compute the Bayes factors for each of the models considered below. As always in any Bayesian analysis, I had to assume some prior distribution for the fit parameters. I used uniform distributions, between 0 and 20e-4 for the loss angles, and between -100e-6 and 100e-6 for the slope. I checked that the intervals I choose for the priors have only a small influence on the results.

The model that has the highest probability is the one that considers different bulk and shear frequency depent loss angles. The others have the following relative probabilities

One loss angle constant:                       1/13e+13
One loss angle linear in frequency:      1/5.5
Bulk/shear angles constant:                  1/48784
Bulk/shear angles linear in frequency: 1/1

So the constant loss angle models are excluded with large significance. The single frequency dependent loss angle is less probable that the bulk/shear frequency dependent model, but only by a factor of 5.5. According to the literature, this is considered a substantial evidence in favor of frequency dependent bulk/shear loss angles.



One loss angle - constant

\phi = (6.99 \pm 0.05) \times 10^{-4} \mbox{ rad}

One loss angle - linear in frequency

\phi = (6.91 \pm 0.07) \times 10^{-4} +\frac{f-1 \mbox{ kHz}}{1 \mbox{ kHz}} \cdot (3.3 \pm 2.2) \times 10^{-6} \mbox{ rad}

Bulk and shear - constant

\begin{matrix} \phi_{shear} = (6.79 \pm 0.12) \times 10^{-4} \mbox{ rad} \\ \phi_{bulk} = (8.54 \pm 0.98) \times 10^{-4} \mbox{ rad} \end{matrix}

Bulk and shear - linear in frequency

\begin{matrix} \phi_{shear} = (6.9 \pm 0.4) \times 10^{-4} +\frac{f-1 \mbox{ kHz}}{1 \mbox{ kHz}} \cdot (9.9 \pm 7.4) \times 10^{-6} \mbox{ rad} \\ \phi_{bulk} = (6.4 \pm 3.7) \times 10^{-4} +\frac{f-1 \mbox{ kHz}}{1 \mbox{ kHz}} \cdot (-14 \pm 39) \times 10^{-6} \mbox{ rad} \end{matrix}


  373   Fri Jul 21 14:55:02 2017 GabrieleGeneralMeasurementsShear and bulk losses in annealed tantala

I repeated the analysis for bulk and shear losses described in an early elog entry, with the same coating, but after annealing at 500C for 9 hours. 

The COMSOL model is the same as before, so the dilution factors are the same, except that this time I could measure a few more modes at high frequency:

As in the previous analysis, I fitted four different models:
1) one single loss angle for both bulk and shear, constant in frequency
2) one single loss angle for both bulk and shear, linear in frequency
3) separate bulk and shear loss angles, constant
4) separate bulk and shear loss angles, linear in frequency 

The data strongly favor the last model: two loss angles for shear and bulk, linearly dependent on frequency (Bayes factor -22.7 for the second best model, which is the frequency dependent single loss angle).

The results are below. 

Single constant loss angle

\phi = (3.95 \pm 0.08) \times 10^{-4} \mbox{ rad}

Single loss angle, linearly dependent on frequency

\phi = (3.69 \pm 0.17) \times 10^{-4} + \frac{f-1 kHz}{1 kHz} (4.6 \pm 0.3)\times 10^{-6} \mbox{ rad}

Bulk and shear loss angles, constant

\begin{array}{l} \phi_{shear} = (3.4 \pm 0.5) \times 10^{-4} \mbox{ rad} \\ \phi_{bulk} = (7.3 \pm 3.3) \times 10^{-4} \mbox{ rad} \\ \end{array}

Bulk and shear loss angles, linearly dependent on frequency

\begin{array}{l} \phi_{shear} = (3.58 \pm 0.15) \times 10^{-4} + \frac{f - 1 kHz}{1 kHz} (6.1 \pm 2.4) \times 10^{-6} \mbox{ rad} \\ \phi_{bulk} = (4.5 \pm 1.2) \times 10^{-4} + \frac{f - 1 kHz}{1 kHz} (-7 \pm 16) \times 10^{-6} \mbox{ rad} \\ \end{array}


Attachment 7: postannealing_linear_bulk_shear.png
  459   Tue Feb 13 16:28:49 2018 GabrieleOpticsConfigurationSetup resigned for 75mm disks
  454   Tue Jan 30 09:19:09 2018 GabrieleOpticsConfigurationSetup for 50mm disks

I realigned all optical levers to measure the 50mm disks. In brief, I moved the input 2" mirrors, the in-vacuum 2" mirrors and the PZT mirrors so that the beam hits the 50mm sample and gets back into the QPD. Re-aligned everything to the horizontal reference using water.

  120   Wed Sep 21 14:42:47 2016 GabrieleGeneralGeneralSerialized (etched) disk installed

Just for fun, I installed the disk thas has been etched in the center with "1234". I figured out that the ESD PCB was probably too close to the disk, so I moved it a bit up.

Pump down started at about 2:38pm LT.

  256   Fri Jan 6 12:19:22 2017 Alena, Bob, Stephen and CalumGeneralDaily ProgressSecond vacuum chamber

Cleaning and baking (200 C air foe SS and 120 for Al) parts for the new vacuum chamber

  139   Thu Oct 20 11:04:03 2016 GabrieleGeneralMeasurementsSample with flame polished edges

Sample with edges flame polished in Glasgow


  • into the chamber and balanced at 11am. Pump down started at 11:00am.
  • it looks like the turbo pump shaked the sample too much and moved it significantly. At 11:44am I had to tweak a bit the input steering periscope to avoid the outgoing beam to be clipped on the pickoff mirror
  • roughing pump off at 2:27pm
  • excitation at 2:36pm (2000 V, 30 s)


% Freq        First Q of pair   Second Q of pair
1117.4        2.3392e+07        2.3392e+07
2555.9        1.8650e+07        1.8650e+07
4441.1        1.3003e+07        1.3003e+07
6759.2        1.6003e+07        1.5656e+07
6781.8        1.4795e+07        1.4795e+07
9499.2        5.6765e+06        5.6765e+06
10219.5       1.3148e+07        2.7060e+06
10222.3       1.3909e+07        4.2609e+04
11444.0       2.0756e+06        6.5364e+05
12649.4       1.0264e+07        8.7228e+06
12650.7       8.6808e+06        8.6808e+06
14176.3       1.0290e+07        1.0290e+07
14177.5       1.0185e+07        1.0185e+07
16113.7       1.0856e+07        9.7535e+06
16202.5       8.6733e+06        5.0176e+06
18619.0       1.3113e+07        1.3113e+07
18622.1       1.4864e+07        1.4864e+07
20149.0       1.4047e+06        1.4047e+06
21348.8       6.9944e+06        6.9944e+06
21353.3       8.0679e+06        3.1734e+05
23529.5       1.3076e+07        1.3076e+07
24482.3       9.6841e+06        9.6841e+06
24669.1       4.8629e+06        4.8629e+06
24670.5       6.3609e+06        6.3609e+06
25499.2       5.2216e+06        5.2216e+06
25828.0       3.3780e+06        3.3780e+06
27101.0       1.4934e+07        1.4934e+07
27103.5       1.4956e+07        1.4956e+07
28883.5       1.2076e+07        1.2076e+07
29068.6       1.1494e+07        1.1494e+07
29072.0       9.7555e+06        9.7555e+06
29190.0       5.9610e+06        5.9610e+06
29193.2       7.9280e+06        7.9280e+06
29502.2       7.8254e+06        7.8254e+06
30867.0       6.3681e+06        6.3681e+06
31267.0       1.6836e+06        1.4541e+05
32194.4       5.3275e+06        5.3275e+06
32200.0       5.9215e+06        2.6587e+06

The following plot compares the Q measured on this sample yesterday here at Caltech with the GeNS system, with the measurement perfomed by Raymond Robie in Glasgow.

- blue dots: measurements on the flame polished sample here at Caltech
- orange crosses and yellow triangles: Raymond’s measurements on the flame polished sample at in Glasgow (after annealing)
- purple crosses: typical Q values measured on disk samples (not annealed nor flame polished) here at Caltech

Flame polishing of the edges did not change significantly the Q we measure with the GeNS system. However, the GeNS system rovide systematically higher Q values for basically all measurable modes.


Attachment 7: ringdown_raw_data_2016_10_20.m
%% Parameters
prefix = '2016_10_20';  % name of the folder where result will be saved
gps0 = 1161034552;      % GPS time of clean data before excitation
gps1 = 1161034619;      % GPS time right after excitation
dt = 30;                % how much data to be used to search peaks

minsnr = 6;             % minimum peak SNR
minfr = 1000;           % minimum peak frequency
Dt = 3600;              % total amount of time for the ringdown measurement

... 303 more lines ...
  135   Tue Oct 18 16:52:16 2016 GabrieleGeneralMeasurementsSample inspections from annealing run 10/10/2016


  • S1600432 shows some residual on face, close to the edge, probably from first contact
  • S1600433 looks ok
  • S1600434 shows a small residual on the face, the edge, probably from first contact, and a back spot, probably a residual of the contamination
  • S1600435 shows a large halo on the face, like what you get when solvents dry on the surface leaving some traces
  • S1600436 has some red residual on the edge, likely first contact
  • S1600437 the surface looks ok but the edge has a clear reddish color
  419   Fri Aug 18 14:15:47 2017 ZachElectronicsModelingSame Voltage ESD Sweep


  • I ran a sweep of the central position in the two ESD setup with both set at the same voltage. There were two designs that maximized excitation by different metrics, the design with a 3 mm shift from the original design maximized excitation overall, but the 20 kHz mode was worse by a bout a factor of 5. The design with a -2 mm shift maximized the high frequency modes, particularly the modes most affected by the shift.
  • MATLAB crashed shortly after the sweep so I will have to recreate the RMS plots of the dynamic modes later.


Attachment 1: two_positive_ratio_sweep.pdf
Attachment 2: -2mm_two_positive.jpg
  828   Fri Jan 17 09:16:45 2020 Seth LinkerGeneralMeasurementsS2000093, S2000094


  • 9:16 am in chamber
    • S2000093 in CR1
    • S2000094 in CR2
  • 9:17 am roughing pump on
  • 9:26 am turbo pump on
  826   Tue Jan 14 10:10:25 2020 Seth LinkerGeneralMeasurementsS2000089, S2000090, S2000091, S2000092


  • 10:10 am in chamber
    • S2000089 in CR1
    • S2000090 in CR2
    • S2000091 in CR3
    • S2000092 in CR4
  • 10:16 am roughing pump on
  • 10:26 am turbo pump on
  825   Mon Jan 13 12:40:56 2020 GabrieleGeneralMeasurementsS2000085 S2000086 S2000087 S2000088


  • 12:40pm in chamber
    • S2000085 in CR1
    • S2000086 in CR2
    • S2000087 in CR3
    • S2000088 in CR4
  • 12:41pm roughing pump on
  • 12:51pm turbo pump on
  655   Tue Apr 9 09:19:39 2019 GabrieleGeneralMeasurementsS1900198 S1900199 S1900200 S1900201


  • 9:18 am in chamber
    • S1900198 in CR1
    • S1900199 in CR2
    • S1900200 in CR3
    • S1900201 in CR4
  • 9:19am roughing pump on
  • 9:27am turbo pump on
  643   Mon Mar 25 08:27:19 2019 GabrieleGeneralMeasurementsS1900195


  • 8:20am in chamber CR0
  • 8:22am roughing pump on
  • 8:50am turbo pump on
  647   Fri Mar 29 16:26:22 2019 GabrieleGeneralMeasurementsS1900195


  • 4:20pm in chamber CR0
  • 4:23pm roughing pump on
  • 4:45pm turbo pump on
  637   Mon Mar 11 16:24:02 2019 GabrieleGeneralMeasurementsS1900072 S1900071


  • 4:23pm in chamber
    • S1900072 in CR1
    • S1900071 in CR2
  • 4:25pm roughing pump on
  • 4:35pm turbo pump on
  640   Wed Mar 20 13:10:01 2019 AlenaGeneralMeasurementsS1900071 S1900072


  • 1:20 pm in chamber
    • S1900071 in CR1
    • S1900072 in CR2
  • 1:36 pm roughing pump on
  • 1:47 pm turbo pump on
  625   Wed Feb 20 09:08:57 2019 GabrieleGeneralMeasurementsS1900046, S1900047, S1900048, S1900049


  • 09:05 am in chamber
    • S1900046 in CR1
    • S1900047 in CR2
    • S1900048 in CR3
    • S1900049 in CR4
  • 09:07am roughing pump on
  • 09:15am turbo pump on
  620   Tue Feb 12 08:23:00 2019 AlenaGeneralMeasurementsS1900046, S1900047, S1900048, S1900049


  • 08:45 am in chamber
    • S1900046 in CR1
    • S1900047 in CR2
    • S1900048 in CR3
    • S1900049 in CR4
  • 08:57am roughing pump on
  • 09:10am turbo pump on
  651   Thu Apr 4 10:24:55 2019 GabrieleGeneralMeasurementsS1900046, S1900047, S1900048, S1900049


  • 10:24 am in chamber
    • S1900046 in CR1
    • S1900047 in CR2
    • S1900048 in CR3
    • S1900049 in CR4
  • 10:26am roughing pump on
  • 10:35am turbo pump on
  616   Wed Jan 30 10:00:34 2019 GabrieleGeneralMeasurementsS1812072


  • 9:58am in chamber
    • S1812072 in CR0
  • 10:00am roughing pump on
  • 10:25am turbo pump on
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