I installed a dielectric laser line filter (Thorlabs FLH05633-5, center wavelength 633 nm, FWHM 5 nm) in front of the QPD. In this way we are no more affected by the room light. In the plot below blue is without filter, red with filter. A lot of peaks at high frequency are eliminated by the filter.

The plot below shows the QPD signal quadrant signals in a few different configurations: blue with the room light on and laser off, red with the room light off and laser off, green with the laser on. With the filter installed, when the laser is on we are dominated by its intensity noise, which shows a lot of peaks at high frequency. Those peaks are not completely eliminated by the difference of the quadrants.

Today I started programming part of the user interface that will be used to perform the measurements. Not much implemented so far, but you can get an idea of the look:

Buttons on the left sidebar will allow the user to perform some basic tasks. The main panel has a plot (which will show spectra or ring down measurements) and a log section.

Here's how I imagine the mode search to proceed:

1. the user select the list of nominal frequencies and the frequency range for the search
2. the automation creates an excitation which is a sum of band-limited white noise, centered around each of the modes, with the desired bandwidth. The excitation is normalized to match a reasonable fraction of the DAC range
3. the excitation is injected for a given amount of time and each band is searched for the mode. In each band, if a mode is found, the frequency is estimated together with the maximum SNR obtained and the results are saved
4. if some modes are not found, the automation will try to improve the noise, by scaling all band amplitudes in such a way to have the same resulting SNR for the modes. In this way we should get more dynamical range and could increase the excitation for the modes that were not found
5. if some modes are still unidentified, then the user will be asked to choose between a few options:
   1. skip the mode
   2. try to excite it with an excitation focused on that band only
   3. increase the bandwidth for the search
   4. maintain the same bandwidth but move the band to adjacent frequencies
6. At the end all identified modes will be stored in memory and saved to a file defined by the user

Everything is working pretty well. This morning the pressure was about 1.2e-6 Torr. I connected the high voltage amplifier and I could drive the disk without problems.

I measured the beam shape and size at the QPD. We have about 50 uW, we see a TEM01-like mode due to the interference of the two disk surfaces (this is normal). The beam is about 3 mm in diameter. using this information and the estimated optical lever length of 1.2 m, I calbrated the QPD NORM signals in units of angular motion of the disk surface. The computation posted in CRIME_Lab/60 is actually wrong. I'll post the correct one later.

Injecting broadband white noise I could excite all the modes that are visible up to about 30kHz. I tuned the COMSOL model, by changing the thickess of the disk to 1.017 mm, to fit the frequency of the first few modes. Here are the modes I could measure:

Take a look at the attached PDF file for the shape of all the modes, including all that are not visible. We see all the modes we expect to be able to excite with the central suspension of the disk.

The roughing pump is making a lot of non stationary low frequency noise. I turned it off, and the pressure stayed constant at 1.2e-6 Torr over about 1.5 hours. Here's the difference in the QPD spectrum:

It turned out that I have enough excitation authority to knock the disk out of the right place. So I had to vent to recover the situation. I'll open the chamber tomorrow and see what happened.

Here's a first bird eye look at the ring downs. We see beating of the two almost denegerate modes in some cases. Fits will follow, using the procedure I used for the LMA measurements.

Using the first ring down of the day (GPS 1155754513 + 3600 seconds), I computed the amplitude of each of the modes already identified, using a short FFT spectrogram (each FFT is 1 second long, overlap of 0.5 s).

Then I used the same code I developed at LMA to fit the ring down, including the beat between the unresolved mode pairs. The fit is versy sensitive to the initial conditions, so I had to fine tune them for each of the 20 modes. Still, all fits were successful with 30 minutes of work.

Here are all the fits:

And in summary all the measured Qs, which turned out to be larger than what I was expecting, considering that the disk is not annealed.

The analysis code in MATLAB is attached.

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

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

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

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

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

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

After fixing the setup, the measurement with the new disk looks great. After more than one hour the first two modes are still ringing down, meaning that the Q's are larger than 10 millions.

Here's the comparison of the spectrum before and after the excitation, with the identified modes:

I used about 4200 s of data to fit the ring downs. Most fits are good. In a couple of cases the peak splitting is large and the algorithm fails to fit the beats:

In summary, here are the Q values for all modes. Despite not being annealed, this disk shows very large Q's

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

I let the pump switch off.

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

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

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

Ring down after:

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

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. 

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...

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.

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.

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

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

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)
n.start()

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.

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)
n.start()

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

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.

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

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.

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.

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

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.

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

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

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.

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).

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)

S1600433, annealing run 10/10/2016

Installation 

• 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.

Measurements

2016-10-18

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​

2016-10-19

• 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

2016-10-19

• 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

LIGO-T1600466

• 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

S1600438, not annealed, as received from Mark Optics

Installation

• 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

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

S1600439, not annealed, as received from Mark Optics

Installation

• 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

Measurements

2016_10_19

• 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

2016_10_20

• 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

• 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.

Sample with edges flame polished in Glasgow

Installation

• 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)

Results

% 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.

Sample S1600447, as received from Mark Optics, second batch

Measurements

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

2016-10-21

• 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

2016-10-23

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

Results

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

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.

S1600439, post annealing

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

Installation

• 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

Measurements

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

All Q values are increased with respect to pre-annealing

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.

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

Summary

Measured Q values are low.

2016-10-24

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

2016-10-25

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

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

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

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

Installation

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.

Measurements

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.

Results

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

2016-10-29

• 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.

2016-10-30

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)

2016-11-01

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

Results

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

The plot above compares the measured Q for #447 (second batch, flat machined during production), before and after annealing. The annealing improves significantly all Q's.

The plot above compares the measured Q for #448 (second batch, flat machined during production), before and after annealing. The annealing improves significantly all Q's.