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  Coating Ring-down Measurement Lab elog, Page 3 of 18  Not logged in ELOG logo
IDup Date Author Type Category Subject
  102   Tue Aug 23 08:46:04 2016 GabrieleGeneralDaily ProgressDaily tests

MO03 - edge polished:

Turbo off, QPD centered, before excitation (60 seconds)

PDT: 2016-08-23 08:42:54.514987
PDT UTC: 2016-08-23 15:42:54.514987
UTC GPS: 1156002191.514987

Excitation (white uniform noise, amplitude 5 V)

PDT: 2016-08-23 08:45:01.007626 PDT
UTC: 2016-08-23 15:45:01.007626 UTC
GPS: 1156002318.007626

Clean data for ring-down

PDT: 2016-08-23 08:45:46.448949 PDT
UTC: 2016-08-23 15:45:46.448949 UTC
GPS: 1156002363.448949

Restarted roughing pump, QPD got misaligned

PDT: 2016-08-23 10:00:29.259345 PDT
UTC: 2016-08-23 17:00:29.259345 UTC
GPS: 1156006846.259345

MO03 - edge polished:

Band-limited noise, +-10Hz around eahc nominal frequency, amplitude scaled based on the inverse of the peak height obtained with white noise. See attached code and plot

from numpy import *
from noise import *

x = loadtxt('/home/controls/Measurements/2016_08_23/mo_02_laserpolished_frequencies.txt')

freqs = x[:,0]
ampl = x[:,1]

bw = 10

bands = map(lambda x: [x - bw, x + bw], freqs)
a = 1 / (ampl/max(ampl))
a[a>50] = 50.

x = multi_band_noise(bands, a, 10, fs=65536)
x = x / 30

Ring down after:

PDT: 2016-08-23 11:07:02.661145 PDT
UTC: 2016-08-23 18:07:02.661145 UTC
GPS: 1156010839.661145


  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. 

  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
  105   Thu Sep 1 02:13:33 2016 GabrieleOpticsCharacterizationExpected frequencies for the 75 mm disks with flats

Here are the nominal parameters of the disk with flats

Parameter Value
Diameter (nominal) 75.0 mm
Thickness (nominal) 1.00 mm
Distance of flats from center of disk
(as measured by MO)
36.05 mm
Young's modulus (from G1601850) 72.3 GPa
Poisson's ratio (from G1601850) 0.164
Density 2202 kg/m^3

A COMSOL simulation gives the frequencies and mode shapes shown in the attached PDF file. Following the list of frequencies and a classification of the mode family (numer of radial nodes, number of azimuthal nodes in a half turn):

Frequency [Hz] Radial Azimuthal
1089.7 0 2
1109.1 0 2
1661.1 1 0
2501.3 0 3
2542.3 0 3
3837.7 1 1
3909.8 1 1
4359.9 0 4
4421.2 0 4
6656 0 5
6665.3 1 2
6732.7 0 5
6780 1 2
7283.9 2 0
9381.5 0 6
9470.6 0 6
10054.1 1 3
10210.2 1 3
11244.2 2 1
11414.2 2 1
12528.4 0 7
12655.4 0 7
13970.1 1 4
14148.9 1 4
15854.8 2 2
15856.8 2 2
16101.1 0 8
16227.8 3 0
16853.9 3 0
18387.2 1 5
18562.6 1 5
19984.9 0 9
20045.8 0 9
21067.2 2 3
21358.1 2 3
22300.9 3 1
22848.8 3 1
23270.5 1 6
23419.4 1 6
24374.1 0 10
24425.2 0 10
26793.8 2 4
27083.9 2 4
28533.5 1 7
28637.8 1 7
28692 3 2
28998.5 4 0
29228.3 0 11
29271.9 0 11
29870.1 4 0
33040 2 5
33301.4 2 5
33949.1 0 12
33986.5 0 12
Attachment 1: allmodes_aggregated.pdf
allmodes_aggregated.pdf allmodes_aggregated.pdf allmodes_aggregated.pdf allmodes_aggregated.pdf allmodes_aggregated.pdf allmodes_aggregated.pdf
  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.

  107   Mon Sep 12 16:00:06 2016 GabrieleGeneralDaily ProgressFirst fully automated measurements of ring down

I finished the first version of the automation software to measure the ring down of the disk modes. I tested it with the new substrate that was installed yesterday. Here are some screenshots and a brief explanation of how it works.

It is based on a Python/Tk GUI, that can be launched on the workstation with the command ~/CRIME/crime.py

The main screen is similar to the following. Once a baseline spectrum is acquired, it is shown in the main panel:

The user should specify the folder and prefix of the result files, and other parameters related to the excitation. The when the "Excite and ring down..." button is pressed, here's what happens

  1. If a baseline spectrum (before excitation) is not available, one is acquired with the specified parameters
  2. A broadband white excitation is applied with the selected amplitude and duration

  1. Another spectrum is taken. This is then whitened by dividing it with the baseline. This could be used directly to select the modes that have been excited. However, some parts of the noise floor are non stationary, so a second whitening is performed: the noise background is estimated by removing all lines, and it is then again divided out from the spectrum.
  2. All lines above a SNR threshold are then selected and shown in the main window together with the whitened spectrum: 

At this point the amplitude of the peaks are continuosly monitored (every second) and thei amplitude shown in a new window. The user can select a subset of the modes for the plotting.

There are some wandering peaks in the spectrum, so some of the peaks aren't actually modes that get excited. This is easily fixed in the post processing of the results. 

All peak amplitudes are saved to files in real time, so if you stop the GUI you'll have some partial results.

  108   Tue Sep 13 10:33:35 2016 GabrieleGeneralGeneralDisk excited

Disk excited with white uniform noise, amplitude 5 V, for some tens of seconds.

Excitation off at

PDT: 2016-09-13 10:32:23.887615 PDT
UTC: 2016-09-13 17:32:23.887615 UTC
GPS: 1157823160.887615


  109   Wed Sep 14 13:08:05 2016 GabrieleGeneralGeneralRingdown with roughing pump off

At 1:05pm LT I stopped the roughing pump and started a ring-down measurement. Pump restarted at 2:18pm LT.

  110   Wed Sep 14 20:17:33 2016 GabrieleGeneralGeneralBand-limited excitation

Excitation started at 20:15:30LT, 20 seconds long. The excitation is band-limited (10 Hz) centered around each of the predicted mode frequencies. Amplitude inversely proportional to the mode frequency.  The system was quiet before the excitation for many minutes.

For reference, here's the code used for the excitation:

from noise import *
from numpy import *
x = loadtxt('predicted_modes.txt')
bands = map(lambda x: [x-5,x+5], x)
ampl = x/x[0]
xx = multi_band_noise(bands, ampl, T=20, fs=65536)

n = AWGNoiseStream(1e-2*xx, channel='X3:CR1-ESD_EXC', rate=65536)


  111   Thu Sep 15 08:13:20 2016 GabrieleGeneralGeneralPump had no effect on ring down measurements

The plot below shows three measurements of the Q of the same disk: during the first two the roughing pump was on, while during the third it was off. No significant difference is visible in the Q values.

  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

  113   Thu Sep 15 11:23:13 2016 GabrieleFacilityGeneralChamber open

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

  114   Thu Sep 15 15:15:10 2016 GabrieleGeneralGeneralEdge effect on losses

I made a COMSOL model that can compute the distribution of elastic energy for each mode, dividing it into:

  • bulk and shear energies (integrated over the entire volume)
  • edge energy (integrated over the edge surface only)
  • surface energy (integrated over the top and bottom surfaces)

Then I used the measured Q values for the MO_101 disk and tried to see if I could reproduce it with the energy distribution. The first plot here shows that the loss angle of the disk (inverse of the Q) has a trend that is already quite well reproduced by the ratio on edge energy over total energy:

In particular the edge energy distribution is enough to explain the splitting of the modes in families. This fit is obtained assuming that the edge losses are uniform along the entire edge, and frequency independent. If we assume a "thickness" of the edge of the order of 1 micron, the loss angle is about 3.5e-3, which seems resonable to me since the edge is not polished.

Then I tried to improve the fit by adding also bulk, shear and surface losses. It turns out that shear is not very important, while bulk and surface are almost degenerate. The following plot shows a fit using only edge and surface losses:


The result is improved, expecially for the modes with lower loss angle. Again, assuming a surface thickness of 1 micron, the main surfaces have a loss angle of 1.3e-5, while the edge is 2.3e-3.

Including all possible losses gives a fit which is basically as good as the one above:

However, the parameters I got are a bit differentL: the surface losses are reduced to zero, while bulk dominates with a loss angle of 1.4e-4, and shear is not relevant. 

In conclusion, I think the only clear message is that the Q of our disks are indeed limited by the edge. The remaining differences are difficult to ascribe to a paritcular source. Since th disks are thin, I tend to ascribe them to the surface, which would imply that we are far from being able to see the bulk/shear losses. If I use only edge and surface losses, I found as expected that the polished main surfaces have much lower loss angle by a factor 200 or so.


  115   Fri Sep 16 14:06:43 2016 GabrieleGeneralGeneralPump had no effect on ring down measurements

Same plot as below, but this time with estimated 95% confidence intervals for the Q values, as obtained from the fit only.


The plot below shows three measurements of the Q of the same disk: during the first two the roughing pump was on, while during the third it was off. No significant difference is visible in the Q values.



  116   Tue Sep 20 15:34:00 2016 GabrieleOpticsDaily ProgressImproved optical lever layout


Improve the optical setup, by increasing the response of the QPD to disk motion.

The old configuration

In all my previous measurement the optical lever was as simple as possible: no lenses were used, and therefore the beam was free to expand over all its path. The estimated arm lever from the disk to the QPD was 1030 mm.

QPD response to disk angular motion

The response of the QPD can be characterized with its optical gain in 1/rad, which is how much the normalized signal (difference / sum) changes for one radians of motion of the disk. This is the product of two parts:

  1. the gain from angular motion of the disk to beam spot motion on the QPD. In the simple case of free propagation this is 2L, where L is the distance from the disk to the QPD, and the factor 2 is due to the fact that the beam deflection is the double of the disk angular motion. If there is a telescope in between the disk and the QPD, it is easy to compute the total ray transfer matrix:
    \begin{pmatrix} x_{QPD}\\ \theta_{QPD} \end{pmatrix}= \begin{bmatrix} A & B\\ C & D \end{bmatrix} \begin{pmatrix} 0\\ 2\theta_{disk} \end{pmatrix}
    Then the gain is simply the B element of the matrix.
  2. the response of the QPD normalized signal to beam motion. This depends only on the beam spot radius w on the QPD. It can be computed by simple gaussian integration, and in the approximation of small beam motion, it is given by the following expression:
    g = \frac{2}{w}\sqrt{\frac{2}{\pi}}

In the case of the old configuration, the beam spot size on the QPD was measured to be about 1.5 mm in radius, so the optical gain is of the order of 1900 /rad.

Laser beam profiling

Since I wanted to improve the optical setup, I first needed to measure the beam coming out of the HeNe laser. I used the WinCam beam profile and a Newport rail to measure the beam X and Y sizes at different positions.

The measurements are not the best ever, but I can still get a fit for the evolution of the gaussian beam, as shown in the plot below. The beam waist is 254 um, located 340 mm behind the laser output (inside the laser tube).

Design of the improved setup

I decided to try a brute force algorithmic optimization for the optical gain. I allow two lenses between the laser and the disk and two lenses between the disk and the QPD. I wrote a MATLAB script that picks the four lenses from a list of all those available (I have a Thorlabs LSB02-A lens kit). For each combination of lenses, MATLAB moves them around into pre-defined ranges, and try to find the maximum value of the QPD total optical gain, which is the product of the factor g above and of the B element of the ray tracing matrix.

It turned out that the best optical gains could almost always be obtained by making the beam huge on the disk (5-10 mm radius) and tiny on the QPD (tens of microns). This is not a good solution. So I decided that the beam on the disk must be smaller than 2mm in radius and the beam on the QPD must be larger than 200 microns. I enforced those limits into the optimization code by weighting the gain with a function which is one in the allowed range, and then quickly drops to zero when either of the beam sizes fall out of the allowed range.

The script ran for about half hour and gave me a lot of possible options. After some inspections, I decided to use the following one, which uses only one lens between laser and disk, and two between the disk and the QPD. Distances and focal lengths are shown below. Note that the first distance (laser to first lens) is from the laser beam waist to the lens, so the actual distance must take into account that the waist is estimated to be 340mm into the laser.

With this configuration the optical gain is computed to be 17000 /rad, or about 9 times larger than the original setup. The beam radius on the disk is 1 mm and on the QPD is 0.23 mm.


First of all I measured some distances:

  • from the inner side of the viewport to the disk: 420 mm
  • viewport thickness: 12 mm, which is about 18 mm optical length considering n~1.5
  • so from the input to the chamber to the disk: 438 mm
  • from the viewport to the upper external periscope mirror center: 110 mm
  • distance between the periscope mirror centers: 275 mm

Using these distanced I build the designed optical setup. Some remarks on the procedure

  • I first aligned the laser beam to be horizontal, then added the first lens and centered it by ensuring no beam shift far away from the lens
  • I first aligned the periscope to get the beam roughly centered on the inner 45 degrees mirror, and then roughly centered on the black glass
  • Then I put a small container with water inside the chamber, on top of the black glass. I aligned the inner mirror and the periscope so that the beam coming back from the horizontal water surface was perfectly overlapped with the input beam. I used an iris on the input beam path
  • Then I removed the water container and installed a test disk. I moved the disk around until I got the same beam position in output. This tells me that the disk is horizontal
  • Finally I moved the upper periscope mirror to separate horizontally the beam coming back, at the level of the table. The separation is large enough to allow me to pick up the outgoing beam with a mirror.

Here's a picture of the setup, with the optical path highlighted. 


  117   Tue Sep 20 16:12:09 2016 GabrieleGeneralGeneralPump down

As a test, I installed MO1 (the disk with the burn mark, used for the first edge laser polishing test) and started pumping down. Roughing pump on at 3:05pm, turbo pump on at 3:16pm.

  118   Tue Sep 20 16:43:58 2016 GabrieleGeneralGeneralExcitation and ring down

The pressure is at abour 3e-6 Torr. I centered the QPD and started an excitation. The HV amplifier manual states that the driver can source both positive and negative voltage, so this time I didn't add any offset, but simply drove with 1000 V peak to peak. After the excitation the QPD was slightly miscentered in X and I had to manually recenter it.

Good data starting from

PDT: 2016-09-20 16:38:09.330642 PDT
UTC: 2016-09-20 23:38:09.330642 UTC
GPS: 1158449906.330642

NOTE: it's a good idea to take a look at both the X and Y signals for each mode. Some of them look stronger in Y than in X. So far I only used X.

  119   Wed Sep 21 08:12:13 2016 GabrieleGeneralGeneralExcitation and ring down

New excitation (2000V) at about 8:06am. Had to recenter the QPD again after the excitation.

Engaged the 500Hz high pass filter on the ESD filter bank. New excitation ended at 8:11am. Amplitude 1000 V. Recentered the QPD at 8:11:35am

  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.

  121   Thu Sep 22 09:49:21 2016 GabrieleGeneralGeneralRing-down of etched disk

QPD centerd, quiet data, light off, one minute from

PDT: 2016-09-22 09:46:29.393609 PDT
UTC: 2016-09-22 16:46:29.393609 UTC
GPS: 1158598006.393609

Excitation (2kV) stopped at

PDT: 2016-09-22 09:49:03.784165 PDT
UTC: 2016-09-22 16:49:03.784165 UTC
GPS: 1158598160.784165


  122   Thu Sep 22 13:39:40 2016 GabrieleOpticsConfigurationUpdated design for the new C.Ri.Me. setup

Today I measured the amount of space available on the table for the new (4-fold) C.Ri.Me. setup. It's 1050 x 1220 mm, with the table hole in it. 

So I updated the optical layout to fit into this space, and optimized the telescope to have a beam spot on the QPD of the order of 350 um. The average lever arm length is 1.5 m, so the optical gain will be about 7000 /rad.


Attachment 1: crime_v2.pdf
  123   Thu Sep 22 15:00:49 2016 GabrieleElectronicsConfigurationEpics values now saved to frames

I was looking at some past trend data and discovered that EPICS values were not written to the frames. I added the following two lines to /opt/rtcds/tst/x3/target/fb/master to fix this:

  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

  125   Fri Sep 23 08:33:39 2016 GabrieleElectronicsConfigurationEpics values now saved to frames

Now EPICS values are saved to frames, but they are all zero! I noticed that we always had the same problems with the cymac2 too.

So for the moment being I set up daqd to save X_NORM_IN1 and Y_NORM_IN1 at 32 Hz. In this way I can monitor the QPD centering.


I was looking at some past trend data and discovered that EPICS values were not written to the frames. I added the following two lines to /opt/rtcds/tst/x3/target/fb/master to fix this:



  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.

  127   Mon Sep 26 15:59:09 2016 GabrieleOpticsDaily ProgressQPD auto centering

We have a few motorized mounts (with New Focus picomotors) and one controller (an old New Focus 8753, six axis total) that I connected with a makeshift null modem cable to the laboratory workstation (better cabling and power supply coming soon).

I wrote a couple of python scripts that can be used to continuosly read out the QPD values and move the picomotors if needed. It's wortking quite well, so we should be able to use it in the future to keep the QPD centered during the measurement. 

The scripts are in the ~/CRIME directory. Launch the function center() in the autocenter.py script.

  128   Tue Sep 27 08:53:46 2016 GabrieleGeneralVacuumEtched disk installed

Installed the etched disk: using manually the centering ring allowed me to get the beam on the QPD. A couple of taps to the disk were enough to get the beam centered.

Pump down started at 8:52am

  129   Tue Sep 27 14:54:53 2016 GabrieleElectronicsConfigurationEpics values now saved to frames

Apparently, there was a mismatch in the configuration, and DAQD was adding a wonderful 16 Hz comb all over the spectrum.

I stopped the processes, but couldn't restart x3cr1. It turned out that I can't save a channel to frames with a sampling frequency lower than 256 Hz. I changed the model, recompiled and restarted. Now the 16 Hz is gone.


Now EPICS values are saved to frames, but they are all zero! I noticed that we always had the same problems with the cymac2 too.

So for the moment being I set up daqd to save X_NORM_IN1 and Y_NORM_IN1 at 32 Hz. In this way I can monitor the QPD centering.


I was looking at some past trend data and discovered that EPICS values were not written to the frames. I added the following two lines to /opt/rtcds/tst/x3/target/fb/master to fix this:




  130   Tue Sep 27 15:10:59 2016 GabrieleGeneralMeasurementsRing-down of etched disk

Quiet (roughing pump off, lights off): 60 seconds from
PDT: 2016-09-27 15:05:30.805667 PDT
UTC: 2016-09-27 22:05:30.805667 UTC
GPS: 1159049147.805667
Follows excitation and ring-down with QPD autocentering (10 seconds interval). Centering is good starting 215 seconds after the time above.

There is a drift in X, corrected by the picomotor.

The spectrum of both QPD normalized signals looks quite bad. Maybe there's some scattered light issue.

  131   Wed Sep 28 10:26:58 2016 ranaGeneralGeneralreferences on ideal glasses

Some easy to read reviews on thin films and ideal glass for people getting started in this Q measuring game.

  1. M. D. Ediger, in PNAS  (2014), pp. 11232–11233.

  2. A. J. Leggett and D. C. Vural, arXiv cond-mat.dis-nn, arXiv:1310.3387 (2013).

  3. L. Berthier and M. D. Ediger, arXiv cond-mat.mtrl-sci, 40 (2015). Phys. Today.

  4. G. Parisi and F. Sciortino, Nature Materials 12, 94 (2013).

  5. S. Singh, M. D. Ediger, and J. J. de Pablo, Nature Materials 12, 139 (2013).

  132   Thu Sep 29 15:40:45 2016 GabrieleOpticsDesignBeam profile of new 21mW HeNe laser and tweak of optical lever design

I measured the beam profile of the new Thorlabs HeNe (21.8 mW measured). The beam waist is 355 microns, very close to the laser output port.

Using those numbers and the optical gain optimization algorithm, I tweaked the optical lever design. The simplest solution uses two lenses right after the laser to focus the beam down to about 300 microns on the QPD. The arm lever length is about 1.6 m, corresponding to an optical gain of about 18000/rad. I updated the DCC drawing in D1600213

  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)

  134   Tue Oct 18 16:29:37 2016 GabrieleGeneralMeasurementsS1600433

S1600433, annealing run 10/10/2016


  • Installed in the measurement system, chamber closed
  • pump down started at 4:27pm LT
  • turbo pump started at 4:38pm
  • manually recentered the QPD at 4:39pm
  • HV amplifer turned on at 4:41pm.

NOTE: initally I opened the roughing pump valve just a bit, to avoid shaking the disk too much. The reflected beam was moving quite a lot, but after the pressure went below roughly 1/3 atm there was no visible motion anymore and I opened up the valve completely.

Attached a trend of the QPD signals during the pump down. The time of incresed noise was at the beginning of the pump down.



At 8:10pm, used the autocenter.py script to fine center the QPD. Cleaned the script log and started it again after the excitation.

Used the GUI to excite (amplitude 2000 V, duration 20s) and measure the ring downs at about 8:18pm. Results saved in ~/Measurements/S16004123/2016_10_18/ringdown_8pm_*

Clean reference time: 1160882205 + 30 s
Start of ringdown: 1160882395

The automated procedure did not identify many modes, I'll look at the result offline tomorrow.

Ringdown analyzed offline using the attached MATLAB script (ringdown_rawdata_2016_10_18.m). Some plots with the results:

The following plot shows the Q values, all quite low:

% Freq        Q
1111.8        3.4136e+06
2223.5        3.4789e+06
2550.2        1.9117e+06
2592.8        5.2546e+05
4442.2        1.3452e+06
6778.0        1.1197e+06
6789.2        5.4743e+06
6858.5        7.3921e+05
9548.2        7.9478e+05
10233.4       3.3426e+06
14209.2       3.6032e+06
16132.8       3.1556e+06
21414.5       4.9099e+06
27209.0       3.0791e+06
29136.6       5.4256e+06​


  • Stopped autocentering at 7:45am
  • Excitation at 7:50am, ampltiude 1500 V, duration 30 s
  • Autocentering on right after the excitation
  • Measurement running, results saved in ~/Measurements/S16004123/2016_10_19/ringdown_8am_*

Ringdown analyzed offline using the attached MATLAB script (ringdown_rawdata_2016_10_19.m). Some plots with the results:

The following plot shows the Q values, all quite low:

% Freq        Q
1111.8        3.4159e+06
2550.2        1.9062e+06
2592.9        5.7773e+05
4442.3        1.3729e+06
6778.1        1.1435e+06
6789.5        5.8159e+06
6858.7        7.5672e+05
9548.4        8.9519e+05
10233.6       1.4926e+06
12744.3       7.9721e+05
14209.5       3.7492e+06
16123.8       1.0493e+06
16133.1       3.7737e+06
18686.6       1.7828e+06
21414.9       4.6938e+06
27209.6       3.5298e+06
29137.3       5.5508e+06
32020.0       1.8031e+06


  • Excitation at 11:04am, ampltiude 2000 V, duration 30 s
  • Autocentering on during and after the excitation
  • Measurement running, results saved in ~/Measurements/S16004123/2016_10_19b/ringdown_11am_*
  • At 11:42am stopped the turbo pump

Ringdown analyzed offline using the attached MATLAB script (ringdown_rawdata_2016_10_19b.m). Some plots with the results:

The following plot shows the Q values, all quite low. Error bars are 95% confidence level from the fit.

% Freq        Q                 Qlow (C.I. 95%)   Qhi (C.I. 95%)
1111.7        3.4733e+06        3.4663e+06        3.4804e+06
2550.2        1.9189e+06        1.9141e+06        1.9238e+06
4442.2        1.3786e+06        1.3780e+06        1.3791e+06
4513.2        2.1947e+05        2.1809e+05        2.2087e+05
6778.1        1.1472e+06        1.1464e+06        1.1480e+06
6789.4        5.4143e+06        5.4015e+06        5.4272e+06
6858.7        7.9172e+05        7.8822e+05        7.9525e+05
9548.6        8.9155e+05        8.9070e+05        8.9240e+05
10233.8       1.4482e+06        1.4315e+06        1.4653e+06
12744.6       7.9081e+05        7.8886e+05        7.9276e+05
14209.6       3.7604e+06        3.7566e+06        3.7643e+06
16124.0       1.0353e+06        1.0331e+06        1.0374e+06
16133.3       3.8920e+06        3.8822e+06        3.9019e+06
16369.5       6.7332e+05        6.4937e+05        6.9910e+05
18687.0       2.0033e+06        1.9663e+06        2.0417e+06
20301.5       3.5757e+05        3.4389e+05        3.7239e+05
20366.0       5.7647e+05        5.6413e+05        5.8936e+05
23792.6       2.8356e+05        2.7808e+05        2.8927e+05
24798.0       4.9861e+05        4.9135e+05        5.0610e+05
27209.9       3.5452e+06        3.5176e+06        3.5732e+06
28945.0       1.3041e+06        1.2593e+06        1.3522e+06
29053.6       9.7020e+05        9.4791e+05        9.9356e+05
29137.7       5.4244e+06        5.3788e+06        5.4708e+06
31134.5       5.7329e+05        5.5971e+05        5.8754e+05
32019.6       1.9805e+06        1.9167e+06        2.0487e+06
Attachment 15: ringdown_rawdata_2016_10_18.m
%% Parameters
prefix = '2016_10_18';  % name of the folder where result will be saved
gps0 = 1160882205;      % GPS time of clean data before excitation
gps1 = 1160882395;      % 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

... 273 more lines ...
Attachment 16: ringdown_rawdata_2016_10_19.m
%% Parameters
prefix = '2016_10_19';  % name of the folder where result will be saved
gps0 = 1160923727;      % GPS time of clean data before excitation
gps1 = 1160923832;      % GPS time right after excitation
dt = 30;                % how much data to be used to search peaks

minsnr = 2;             % minimum peak SNR
minfr = 1000;           % minimum peak frequency
Dt = 3600;              % total amount of time for the ringdown measurement

... 275 more lines ...
Attachment 17: ringdown_rawdata_2016_10_19b.m
%% Parameters
prefix = '2016_10_19b';  % name of the folder where result will be saved
gps0 = 1160935440;      % GPS time of clean data before excitation
gps1 = 1160935526;      % GPS time right after excitation
dt = 30;                % how much data to be used to search peaks

minsnr = 5;             % minimum peak SNR
minfr = 1000;           % minimum peak frequency
Dt = 3600;              % total amount of time for the ringdown measurement

... 276 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
  136   Wed Oct 19 13:35:23 2016 GabrieleGeneralMeasurementsS1600438

S1600438, not annealed, as received from Mark Optics


  • Turbo pump switched off at 11:42am (2016-10-19)
  • Turbo pumpo stopped (finally) at 1:11pm
  • Chamber vented and opened at 1:13pm
  • Sample installed and balanced at 1:18pm
  • Chamber closed, roughing pump on at 1:20pm, turbo pump on at 1:35pm
  • At 2:40pm pressure is about 2e-6 Torr
  • Excited at 2:54pm, results are being saved in ~/Measurements/S1600438/2016_10_19/ringdown_3pm_*
  • Roughing pump off at 3:57pm, turbo pump switched off
  • at 4:27pm the pump spins at 120 Hz, opening the venting valve slowly, the turbo pump went down to 0 Hz in a couple of minutes
  • at 4:35pm the sample was removed
Clean data: 1160949234 + 30s
Right after excitation: 1160949284 + 30s

Data have been analyzed with the attached MATLAB script ringdown_rawdata_2016_10_19.m

Results are shown below:

% Freq        Q                 Qlow (C.I. 95%)   Qhi (C.I. 95%)
1114.5        8.6842e+06        8.6163e+06        8.7530e+06
2600.0        1.5373e+06        1.5354e+06        1.5392e+06
4454.9        4.4458e+06        4.4439e+06        4.4476e+06
4526.4        3.1306e+05        3.1197e+05        3.1416e+05
6797.6        3.5778e+06        3.5758e+06        3.5799e+06
6809.8        9.1530e+06        9.1447e+06        9.1614e+06
6878.6        1.3829e+06        1.3784e+06        1.3873e+06
9576.6        3.0186e+06        3.0135e+06        3.0237e+06
10264.5       8.1674e+06        8.1534e+06        8.1815e+06
12782.6       2.5469e+06        2.5399e+06        2.5539e+06
14251.6       7.8253e+06        7.7982e+06        7.8525e+06
16171.7       3.3591e+06        3.3541e+06        3.3641e+06
16181.9       7.9905e+06        7.9842e+06        7.9969e+06
18743.0       5.4436e+06        5.3455e+06        5.5453e+06
20427.0       1.6445e+06        1.6275e+06        1.6618e+06
21479.0       3.0290e+06        2.9492e+06        3.1132e+06
21778.0       3.2835e+06        3.1820e+06        3.3918e+06
23700.5       3.6209e+06        3.5827e+06        3.6598e+06
27289.6       7.7802e+06        7.7398e+06        7.8211e+06
29031.4       4.5482e+06        4.5277e+06        4.5688e+06
29140.5       3.2060e+06        3.1774e+06        3.2352e+06
29225.4       8.4552e+06        8.3776e+06        8.5342e+06
29736.5       1.3035e+06        1.2968e+06        1.3103e+06
29786.7       1.7871e+06        1.7611e+06        1.8139e+06
31031.2       2.1918e+06        2.1512e+06        2.2338e+06
31920.7       6.5775e+06        6.5404e+06        6.6151e+06



Attachment 5: ringdown_rawdata_2016_10_19.m
%% Parameters
prefix = '2016_10_19';  % name of the folder where result will be saved
gps0 = 1160949234;      % GPS time of clean data before excitation
gps1 = 1160949284;      % 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

... 274 more lines ...
  137   Wed Oct 19 16:40:24 2016 sults:GeneralMeasurementsS1600349

S1600439, not annealed, as received from Mark Optics


  • installed and balanced, pump down started at 4:38pm (roughing pump), turbo started at 4:51pm
  • removed from the chamber on 10/20 at about 11:00am



  • QPD centered at 9:25pm, excited (2000 V, 10 s) at 9:27pm, measurement ongoing.

The spectrum was noise than usual due to the roughing pump. I already found out in the past that I can reduce the noise by tweaking the position of the pump. This time however I wasn't successful.

Here are the results:

% Freq        Q                 Qlow (C.I. 95%)   Qhi (C.I. 95%)
1111.5        6.0958e+06        6.0641e+06        6.1279e+06
2549.6        3.6416e+06        3.6305e+06        3.6528e+06
4441.7        2.6916e+06        2.6879e+06        2.6953e+06
4512.9        2.1090e+05        2.0993e+05        2.1188e+05
6777.5        1.1797e+06        1.1790e+06        1.1803e+06
6790.9        3.8621e+06        3.8540e+06        3.8701e+06
6858.4        1.2434e+06        1.2295e+06        1.2577e+06
9548.0        1.2177e+05        1.1878e+05        1.2491e+05
10234.6       3.9934e+05        3.9351e+05        4.0535e+05
10399.0       2.8135e+05        2.7455e+05        2.8849e+05
12744.2       1.3145e+06        1.3115e+06        1.3174e+06
14211.3       3.8414e+06        3.8136e+06        3.8696e+06
16123.3       2.0276e+06        2.0181e+06        2.0372e+06
16135.8       5.2811e+06        5.2770e+06        5.2852e+06
16370.0       1.4976e+06        1.4922e+06        1.5031e+06
18689.3       4.2954e+06        4.2738e+06        4.3172e+06
23632.0       2.2796e+06        2.2528e+06        2.3070e+06
24797.4       8.7545e+05        8.5819e+05        8.9341e+05
27214.5       1.2566e+06        1.2374e+06        1.2764e+06
28947.5       1.7367e+06        1.7130e+06        1.7611e+06
29144.0       3.2148e+06        3.1213e+06        3.3142e+06



  • Roughing pump was creating too much noise, switched it off at 8:30am
  • Excitation at 8:35am (2000 V, 30 s)

Here are the results:

And the measured Q values:

% Freq        Q                 Qlow (C.I. 95%)   Qhi (C.I. 95%)
1111.4        6.2206e+06        6.2061e+06        6.2351e+06
2549.6        4.1538e+06        4.1498e+06        4.1579e+06
2592.9        1.0952e+06        1.0887e+06        1.1017e+06
4441.7        2.8521e+06        2.8513e+06        2.8529e+06
4513.0        2.0592e+05        2.0455e+05        2.0730e+05
6777.5        1.1013e+06        1.1006e+06        1.1020e+06
6790.9        3.9913e+06        3.9879e+06        3.9947e+06
6858.2        1.3100e+06        1.3078e+06        1.3122e+06
9547.8        1.2492e+06        1.2469e+06        1.2514e+06
10234.7       3.4336e+06        3.4209e+06        3.4463e+06
10398.7       4.3217e+05        3.2860e+05        6.3104e+05
12744.2       4.5274e+05        4.5177e+05        4.5371e+05
14211.3       2.0254e+06        2.0081e+06        2.0430e+06
16123.0       2.1225e+06        2.1173e+06        2.1276e+06
16135.8       4.6547e+06        4.6529e+06        4.6564e+06
16370.3       1.4781e+06        1.4762e+06        1.4800e+06
18689.2       4.5978e+06        4.5891e+06        4.6064e+06
20299.5       4.1859e+05        4.1375e+05        4.2353e+05
20364.6       1.1099e+06        1.0630e+06        1.1612e+06
21418.2       4.5814e+06        4.5718e+06        4.5911e+06
23631.9       2.8907e+06        2.8700e+06        2.9116e+06
24797.4       1.1241e+06        1.1121e+06        1.1363e+06
27214.5       2.1015e+06        2.0752e+06        2.1285e+06
28947.3       2.1285e+06        2.1162e+06        2.1410e+06
29054.7       1.4873e+06        1.4631e+06        1.5124e+06
29143.8       4.1250e+06        4.1050e+06        4.1453e+06
29647.5       4.5456e+05        4.4215e+05        4.6768e+05
31135.4       7.5136e+05        7.3331e+05        7.7033e+05
32013.4       1.1846e+06        1.1565e+06        1.2140e+06
Attachment 9: ringdown_rawdata_2016_10_19.m
%% Parameters
prefix = '2016_10_19';  % name of the folder where result will be saved
gps0 = 1160972805;      % GPS time of clean data before excitation
gps1 = 1160972852;      % 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

... 274 more lines ...
Attachment 10: ringdown_rawdata_2016_10_20.m
%% Parameters
prefix = '2016_10_20';  % name of the folder where result will be saved
gps0 = 1161012900;      % GPS time of clean data before excitation
gps1 = 1161012972;      % 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

... 274 more lines ...
  138   Wed Oct 19 17:08:47 2016 GabrieleGeneralMeasurementsS1600433 vs S1600438
  • S1600433 has been annealed, was contaminated by the iron oxide, and it was cleaned using first contact. No residual were visible on the surface during a simple eye inspection (no flash light)
  • S1600438 is as received from Mark Optics. Some particules are visible on the surfaces with a flash light

The plot below compares the Q values measured today for the two disks. The disk that was annealed and cleaned clearly shows lower Q's for almost all modes.

  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 ...
  140   Thu Oct 20 14:38:24 2016 GabrieleCleanDaily ProgressCleaning of S1600433 and S1600438

Samples #433 (annealed and cleaned) and #438 (as received from Mark Optics) are now with GariLynn for deep cleaning.

Sample #438 was broken during annealing.

  141   Fri Oct 21 13:45:21 2016 GabrieleGeneralMeasurementsS1600447

Sample S1600447, as received from Mark Optics, second batch


  • Installed into the chamber, pumping down started at ~1:10pm


  • Excited at 3:38pm, amplitude 2kV, duration 30 s
  • Excited at 5:01:30pm, amplitude 3kV, duration 30 s
  • Excited at 9:11:30pm, amplitude 3kV, duration 30 s


  • Excited at 9:34:38am, amplitude 3kV duration 30 s


All measured Q values are very low. Details below, here's a summary of all four measurements:

2016-10-21 3:38pm

2016-10-21 5:01pm

2016-10-21 9:11pm

  142   Fri Oct 21 14:03:17 2016 GabrieleGeneralVacuumRoughing pump moved

I moved the roughing pump out of the clean room, adding an extension hose.


This reduced a lot the vibrations induced by the pump. In the past when the pump was running we often saw very large noise, see the red trace in the figure below. Now, in the same conditions, we get the blue trace, which is much better.

The plot below shows a comparison of different configurations:

  • blue: what I sometimes manage to get tewking the pump position and keeping it on top of a plastic box
  • red: now, with the pump far away
  • green: with the pump off

We are quite close to the pump off condition.

  143   Fri Oct 21 15:27:15 2016 GabrieleElectronicsConfigurationRemoved low pass filter in SUM

I removed the low pass filter in the QPD SUM signal, used for normalization. This reduced a lot the bump at ~20kHz due to laser intensity noise.

I also switched off the 500 Hz high pass filters in the X_NORM and Y_NORM signals.

  144   Mon Oct 24 10:26:30 2016 GabrieleGeneralMeasurementsS1600439

S1600439, post annealing

Measurements before annealing reported in elog 137. Details on the annealing run here: T1600476


  • at 10:15am turbo pump switched off
  • installed at 11:15am, pumping down
  • pumps stopped at 2:49pm
  • sample out of the chamber at 4:25pm


  • excited at 1:05:40pm, amplitude 3kV, duration 30 s

All Q values are increased with respect to pre-annealing

  145   Mon Oct 24 14:33:46 2016 GabrieleGeneralMeasurementsEffect of annealing: Q increases

S1600439 has been measured as received (before annealing, elog 137) and after annealing (elog 144). 

Q values are significantly increased for almost all modes, see the plot below for a comparison. Only modes with low Q are not improved.

  146   Mon Oct 24 16:32:01 2016 GabrieleGeneralMeasurementsS1600448

Sample S1600447, as received from Mark Optics, second batch

  • in chamber, pumping down at 4:30pm (2016-10-24)
  • pumps stopped at 9:18am (2016-10-25)
  • vented, sample of the chamber at 10:00aa


Measured Q values are low.


  • excited at 8:38:48pm, amplitude 3 kV, duration 30s


  • excited at 8:05:20am, amplitude 3kV, duration 30s

  147   Tue Oct 25 09:12:31 2016 GabrieleGeneralMeasurementsComparison of first and second batch

The plot below compares a sample from the first batch and two samples from the second batch. All samples are as received from Mark Optics, no annealing or any other treatment.

Both samples in the second batch show consistently and significantly lower Q values.

GariLynn and I inspected the two samples under the microscope. Surprisingly, the edges and the flats look much better than the samples from the first batch. See elog 148 for an image of a sample from the first batch

Link to IMG_3158.JPG

Link to IMG_3157.JPG

Link to IMG_3156.JPG

Link to IMG_3155.JPG

Attachment 2: IMG_3155.JPG
Attachment 3: IMG_3158.JPG
Attachment 4: IMG_3157.JPG
Attachment 5: IMG_3156.JPG
Attachment 6: IMG_3155.JPG
  148   Tue Oct 25 11:10:37 2016 GabrieleGeneralMeasurementsImage of S1600433

This is an image of the sample S1600433 under the microscope, courtesy of GariLynn:

Link to IMG_3150.JPG

The scale in the image is 20 microns per divison, 2 mm full scale

Attachment 1: IMG_3150.JPG
  149   Thu Oct 27 14:02:38 2016 AlenaGeneralGeneralAnnealing

Annealing run (447-448) on 3" wafers - Crime 10/27/2016 https://dcc.ligo.org/T1600485-v1


  150   Fri Oct 28 21:20:48 2016 GabrieleGeneralMeasurementsS1600447 post annealing


I had some problems in installing the wafer. I balanced it and started the pump down a couple of times, and the wafer moved so that the beam coming out of the chamber was clipping.

I decided to re-align the optical setup again. As before, I used a small container with water to have the horizontal reference, and aligned the output optics to center on the QPD. I also added a iris before the mirror with the picomotors, as additional reference.

During pump down I noticed a few sudden jumps of the QPD signals. The output beam moved a lot again, so my realignment didn't help. I even tried to slow down the pump, but this didn't help either. To recover the beam on the pick-off mirror, I had to move a bit the upper periscope mirror. So my horizontal reference is no more good.

It's not clear what's going on, but I'll keep pumping down.

  • installed on 10/28 at 9:00pm, pumping down. Turbo started at 9:09pm, The beam is slowly drifting but nothing to be worried about. Pressure is 5.9e-6 Tor at 9:20pm.
  • autocentering script on at 9:18pm
  • started a set of measurements at 9:20pm. Three excitations (3 kV, 30s). The first one will start in 2h, then the others will follow with an interval of three hours between them. A python script (auto_excite.py) is running on the workstation
  • stopped pumps at 9:30 am 10/29

I noticed another strange thing: when I switchec the IGM vacuum gauge on, the QPD signal changed, as if the beam moved. See figure below.


Excitation at 1161757257 (30 s)
Excitation at 1161757309 (30 s)
Excitation at 1161757361 (30 s)

Something went wrog with the script (some python issue I still don't understand) so the three excitations were executed in sequence. In summary, only one ring-down measurement.


Here are the plots from the ringdown measurement:

And the fitted Q factors:

% Freq        Q                 Q (C.I. 95%)      Q (C.I. 95%)
1115.3        1.2185e+07        1.2167e+07        1.2202e+07
2558.9        4.1466e+06        4.1430e+06        4.1501e+06
4456.9        2.5958e+06        2.5927e+06        2.5989e+06
4523.6        9.6000e+04        9.5990e+04        9.6011e+04
6798.5        1.9687e+06        1.9596e+06        1.9777e+06
6813.2        7.7644e+06        7.7608e+06        7.7680e+06
6876.3        1.0955e+06        1.0947e+06        1.0963e+06
9575.1        2.5100e+06        2.5061e+06        2.5139e+06
10270.5       8.1293e+06        8.0671e+06        8.1925e+06
12904.0       2.8481e+05        2.8480e+05        2.8482e+05
14259.5       4.9009e+06        4.8836e+06        4.9184e+06
16176.3       1.6116e+06        1.6097e+06        1.6135e+06
16187.8       5.7721e+06        5.7689e+06        5.7753e+06
16406.5       1.8723e+06        1.8676e+06        1.8769e+06
18751.4       1.0901e+06        1.0900e+06        1.0901e+06
20410.0       5.4342e+05        5.4341e+05        5.4343e+05
21485.0       7.3955e+06        7.3284e+06        7.4639e+06
23709.9       5.1619e+06        5.1426e+06        5.1813e+06
24845.0       1.3831e+06        1.3787e+06        1.3876e+06
29140.4       2.1742e+06        2.1742e+06        2.1742e+06
29231.0       6.8560e+06        6.8559e+06        6.8562e+06



Attachment 5: Qs.png
  151   Sat Oct 29 10:12:39 2016 GabrieleGeneralMeasurementsS1600448 post annealing


  • venting at 10:00am 10/29
  • sample installed, pumping down started at 10:12am, turbo pump on at 10:29am
  • Started automatic excitation at 10:46am. The first excitation will go off in 2 hours, then more at intervals of three hours. Amplitude 3kV, duration 30s

As with #447, the wafer moved during pum down. I clearly saw that the beam was moving as if the disk got kicked and rang down. Not sure what's going on, I've never seen such a behavior in past pump downs

Excitation at 1161805607 (30 s)
Excitation at 1161820052 (30 s)

There is something strange happening at frequencies below a few kHz. I tried stopping the autocenter, but that's not what is causing the problem. It looks like some king of saturations.


I tried to move the beam, but I still see the same behavior in the spectrum. I think the disk has shift and it now touching the ESD. Stopped all pumps at 11:58am.

Chamber open at 12:50pm. I realigned all the optical setup to the horizontal reference, and moved the ESD a bit up. The sample was installed and leveled at 1:10pm, started again pumping down at ~1:12pm. Turbo pump started at ~1:19pm.

When the frequency of the turbo pump gets to ~150-200 Hz, the wafer gets highly excited. Apart from that and the slow drift of the QPD signals that is almost always present, everything looks ok.

Started autocentering at 1:27pm. Started a set of automatic excitations: initial wait is 2 hours, then three excitation intervalled by 3 hours wait, each 30s long at 3kV.

I noticed once again that switching on the IGM vacuum gauge moved the disk.

List of excitation times:

  • Excitation at 1161901681 (30 s)
  • Excitation at 1161912526 (30 s)
  • Excitation at 1161923370 (30 s)


Excited at 7:56pm, duration 60s, amplitude 3kV


Excitation at 1161901681 (30 s)

% Freq        Q                 Q (C.I. 95%)      Q (C.I. 95%)
1111.6        8.3731e+06        8.3256e+06        8.4210e+06
2591.0        8.2131e+05        8.0451e+05        8.3882e+05
4440.0        4.2299e+06        4.2263e+06        4.2335e+06
6773.1        3.2093e+06        3.2065e+06        3.2121e+06
6851.1        2.3048e+06        2.2687e+06        2.3421e+06
9538.3        2.5313e+06        2.5159e+06        2.5469e+06
14207.1       8.7731e+06        8.7408e+06        8.8057e+06
16115.0       2.6277e+06        2.6276e+06        2.6278e+06
16131.2       1.0409e+07        1.0379e+07        1.0439e+07
16344.5       2.1568e+06        2.1496e+06        2.1640e+06
18681.9       5.9537e+06        5.9390e+06        5.9685e+06
21409.8       7.7496e+06        7.7163e+06        7.7832e+06
23619.8       4.7146e+06        4.6909e+06        4.7386e+06
24106.0       1.7430e+06        1.7430e+06        1.7430e+06
24750.5       1.3804e+06        1.3804e+06        1.3804e+06
27200.5       5.4690e+06        5.4689e+06        5.4691e+06
28928.5       3.1942e+06        3.1941e+06        3.1942e+06
29029.0       2.2298e+06        2.2298e+06        2.2299e+06
29638.0       1.5518e+06        1.5518e+06        1.5518e+06
30320.6       1.9414e+06        1.9413e+06        1.9414e+06
31178.0       8.7520e+05        8.7519e+05        8.7522e+05

Results from the measurement on 11/01

% Freq        Q                 Q (C.I. 95%)      Q (C.I. 95%)
1112.0        9.3290e+06        9.3025e+06        9.3556e+06
2549.7        6.1599e+06        6.1549e+06        6.1648e+06
2591.0        1.0033e+06        9.9970e+05        1.0070e+06
4440.3        4.3031e+06        4.3021e+06        4.3041e+06
4508.3        1.7553e+05        1.7503e+05        1.7602e+05
6773.0        3.3336e+06        3.3331e+06        3.3341e+06
6789.2        4.1646e+06        4.1566e+06        4.1727e+06
6851.2        2.4309e+06        2.4265e+06        2.4353e+06
9538.7        2.5711e+06        2.5677e+06        2.5745e+06
10233.2       3.5483e+05        3.5481e+05        3.5485e+05
10390.0       1.3584e+06        1.3537e+06        1.3632e+06
12728.4       1.8895e+06        1.8895e+06        1.8896e+06
14207.0       8.8861e+06        8.8676e+06        8.9047e+06
16115.5       2.7365e+06        2.7200e+06        2.7533e+06
16131.5       1.0602e+07        1.0564e+07        1.0640e+07
16344.7       2.2292e+06        2.2184e+06        2.2401e+06
18682.0       6.7655e+06        6.7553e+06        6.7756e+06
20331.9       1.6072e+06        1.6011e+06        1.6134e+06
23620.0       5.5499e+06        5.5263e+06        5.5736e+06
24750.6       1.5454e+06        1.5453e+06        1.5454e+06
27201.0       6.6957e+06        6.6956e+06        6.6958e+06
28929.0       2.6420e+06        2.6419e+06        2.6420e+06
29029.4       1.7762e+06        1.7762e+06        1.7763e+06
29133.8       9.1385e+06        9.0987e+06        9.1787e+06
29406.0       9.3479e+06        9.3477e+06        9.3480e+06
29601.0       5.6104e+05        5.6103e+05        5.6105e+05
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