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  Coating Ring-down Measurement Lab elog, Page 3 of 18  Not logged in ELOG logo
ID Date Authorup Type Category Subject
  699   Wed May 22 07:41:23 2019 AlenaGeneralMeasurementsS1600542 S1600664 S1600680 S1600678


  • 08:00 am in chamber
    • S1600542 in CR1
    • S1600664 in CR2
    • S1600678 in CR3
    • S1600680 in CR4
  • 08:19 am roughing pump on
  • 08:30 am turbo pump on

Correct samples placement:

  • S1600542 in CR1
  • S1600664 in CR2
  • S1600680 in CR3
  • S1600678 in CR4
  700   Thu May 23 09:59:09 2019 AlenaGeneralMeasurementsS1600649 S1600650 S1600651 S1600652


  • 09:50 am in chamber
    • S1600649 in CR1
    • S1600650 in CR2
    • S1600651 in CR3
    • S1600652 in CR4
  • 10:09 am roughing pump on
  • 10:15 am turbo pump on
  701   Thu May 23 18:16:11 2019 AlenaGeneralMeasurementsS1600709 S1600710 S1600711 S1600712


  • 18:00 in chamber
    • S1600709 in CR1
    • S1600710 in CR2
    • S1600711in CR3
    • S1600712 in CR4
  • 18:15 roughing pump on
  • 18:26 turbo pump on
  703   Tue May 28 15:48:42 2019 AlenaGeneralVacuumLow pressure gauge exchange

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

  704   Wed May 29 08:36:07 2019 AlenaGeneralMeasurementsS1600713 S1600714 S1600715 S1600716


  • 15:00 in chamber
    • S1600713 in CR1
    • S1600714 in CR2
    • S1600715in CR3
    • S1600716 in CR4


  • 16:00 roughing pump on
  • 16:10 turbo pump on


restarted the measuterment

  705   Thu May 30 13:53:03 2019 AlenaGeneralMeasurementsS1600717 S1600718 S1600719 S1600720


  • 14:30 in chamber
    • S1600717 in CR1
    • S1600718 in CR2
    • S1600719in CR3
    • S1600720 in CR
  • 14:40 roughing pump on
  • 14:53 turbo pump on
  706   Tue Jun 4 15:07:55 2019 AlenaGeneralMeasurementsS1600542 S1600664 S1600678 S1600680


  • 15:10 in chamber
    • S1600542 in CR1
    • S1600664 in CR2
    • S1600678 in CR3
    • S1600680 in CR4
  • 15:18 roughing pump on
  • 15:31 turbo pump on
  707   Fri Jun 7 07:32:51 2019 AlenaGeneralMeasurementsS1600542 S1600664 S1600678 S1600680


  • 15:40 in chamber
    • S1600542 in CR1
    • S1600664 in CR2
    • S1600678 in CR3
    • S1600680 in CR4
  • 15:48 roughing pump on
  • 15:57 turbo pump on

The mesuremet started next morning 2019-06-07 at 7:30 AM

  854   Tue Mar 31 13:12:21 2020 AlenaGeneralMeasurementsS1600784 S1600785 S1600789 S1600791


  • 1:00 pm in chamber
    • S1600784in CR1
    • S1600785 in CR2
    • S1600789 in CR3
    • S1600791 in CR4
  • 1:05 pm roughing pump on
  • 1:14 pm turbo pump on
  256   Fri Jan 6 12:19:22 2017 Alena, Bob, Stephen and CalumGeneralDaily ProgressSecond vacuum chamber

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

  155   Tue Nov 1 15:34:49 2016 Alena, CalumGeneral Annealing run

Annealing run (449-453) on 3" wafers - Crime 11/01/2016 https://dcc.ligo.org/T1600507

  174   Thu Nov 10 16:07:13 2016 Alena, CalumGeneralGeneralAnnealing run

Annealing run (466-471) on 3" wafers - Crime 11/10/2016


  184   Mon Nov 14 08:54:49 2016 Alena, CalumGeneralGeneralAnnealing run

Annealing run (472-477) on 3" wafers - Crime 11/11/2016 https://dcc.ligo.org/T1600527

  90   Fri Aug 19 13:46:55 2016 Alena, Calum, Jon, Liz, Steve, GabrieleFacilityDaily ProgressClean room and vacuum complete

This morning we installed the clean room curtains and washed them. It turns out that the air filters are supposed to be powered at 277V (?) instead of 115V. So right now the flux is quite low. We are looking into the problem: either replace them with 115V modules or install a small transformer.

We also installed the vacuum chamber on the table and connected all the pumps and gauges. There are no leaks and we could pump down easily the empty chamber. We left for lunch when the pressure was at a few 1e-6 Tor and still going down.

  67   Thu Jul 28 13:58:48 2016 Alena, GabrieleCleanDaily ProgressThe old chamber is now being cleaned and baked

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

Attachment 1: 20160728_092350.jpg
  86   Tue Aug 16 11:53:30 2016 Alena, GabrieleCleanDaily ProgressClean room progress

Some progress on the cleam room: bar fixed to the wall, some more structure built, filters in place. We had to (literally) work around a corner of the low ceiling that we haven't noticed before. More contruction will follow tomorrow. We also had to order some additional parts (more extrusions, brackets, screws, etc...) 

  337   Fri Apr 7 14:12:52 2017 Eric, GabrieleGeneralGeneralS1600525 S1600526 S1600527 S1600528


  • 2:12pm in chamber, pumps on
    • S1600525 in CR1
    • S1600526 in CR2
    • S1600527 in CR3
    • S1500528 in CR4
  • Excitations
    • Quiet time before excitation: 1175653360
      Excitation broadband: 1175653395
      Quiet time after excitation: 1175653460

    • Quiet time before excitation: 1175660690
      Excitation broadband: 1175660725
      Quiet time after excitation: 1175660790

    • Quiet time before excitation: 1175668021
      Excitation broadband: 1175668056
      Quiet time after excitation: 1175668121

    • Quiet time before excitation: 1175675351
      Excitation broadband: 1175675386
      Quiet time after excitation: 1175675451

    • Quiet time before excitation: 1175682681
      Excitation broadband: 1175682717
      Quiet time after excitation: 1175682782

    • Quiet time before excitation: 1175690012
      Excitation broadband: 1175690047
      Quiet time after excitation: 1175690112

    • Quiet time before excitation: 1175697342
      Excitation broadband: 1175697377
      Quiet time after excitation: 1175697442

    • Quiet time before excitation: 1175704672
      Excitation broadband: 1175704707
      Quiet time after excitation: 1175704772


  • 11:19am, valve closed, pumps off
  9   Mon May 2 11:46:45 2016 GabrieleFacilityDaily ProgressTable and vacuum chambers in the lab

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

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

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


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


  11   Fri May 6 14:20:43 2016 GabrieleElectronicsDesignDesign of optical lever electronics

For the optical levers we are going to use the same QPD that are used in aLIGO optical levers (see T1600085 and D1100290): Hamamatsu S5981

Based on the aLIGO design, I put together a design fof the QPD boards, see the first attached PDF file. Some comments:

  • I'm using a quad opamp to implement the transimpendance and a doubel stage of whitening for the readout of each quadrant. I haven't decided yet which is the right whitening
  • The bias to the QPD is just coming from the +15V with a capacitor to ground, as in the aLIGO setup. However, I allowed the possibility of supplying a lower noise bias if needed, by removing R0 and connecting an external circuit
  • There is no sum or difference computation, each quadrant is sent directly to the ADC with a differential driver (DRV135)
  • Each board hosts one QPD, and it is interfaced with a 14 pin header (we're going to use twisted cables for the signals)

The stable power supply will be provided by an additional board, which will also interface 8 QPD boards to the ADC connector, see the second attached PDF. The ADC signal grounds can be connected directly to the power supply ground, left floating, or connected with a RC filter, depending on what we find to be the best solution.

Total cost estimated for PCB manufacturing and components, including the QPDs is less than 3k$, for a total of 12 boards (we need 8, plus some spares)

Attachment 1: qpd.PDF
qpd.PDF qpd.PDF
Attachment 2: Breakout.PDF
Breakout.PDF Breakout.PDF
  13   Tue May 10 13:32:17 2016 GabrieleElectronicsDesignDesign of optical lever electronics

After a very useful discussion with Rich this morning, I think the circuit based on aLIGO optical levers design should be good for our applications.

It uses a LT1125 as input stage, which has

  • (maximum) current noise of 1e-12 A/rHz @ 100 Hz and 0.4e-12 A/rHz @ 1 kHz
  • (maximum) voltage noise of 4e-9 V/rHz @ >100 Hz

We expect to send about 5 mW into the disk, getting back a 4% reflection, which would correspond to 200 uW on the QPD. Let's say we lose half of this power in reflections through viewports and such, so we have a total of 100 uW on the QPD, or 25 uW on each quadrant. From the QPD datasheet the repsonse is about 0.4 A/W, so we have a photocurrent of 10 uA. The corresponding shot noise limit is about 1.8e-12 A/rHz.

Using a transimpendace of 200k, the noise at the output of the transimpendance is

  • shot noise = 3.6e-7 V/rHz
  • voltage noise = 4e-9 V/rHz
  • current noise = 2e-7 V/rHz @ 100 Hz, 0.8e-7 V/rHz @ 1 kHz

So in the worst case the current noise will be about half of the shot noise. This seems good enough.


Koji, Rich, and I recently came up with a new QPD design which is better for general lab use than the aLIGO ones (which have a high-noise preamp copied from iLIGO). 


This page has the mechanical drawing only, but perhaps Rich can tell us if he's ready to make the first version for you or not. I think you can get by with the old design, but this new one should be lower noise for low light levels.


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

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

  15   Thu May 19 11:36:04 2016 GabrieleMechanicsDesignA first design of the disk assembly

Here are some screenshots of the disk assembly and a look at how four of them will sit into the vacuum chamber. The Solidworks models are available here: D1600197

Attachment 3: Screen_Shot_2016-05-18_at_3.41.25_PM.png
  16   Fri May 20 15:18:58 2016 GabrieleOpticsDesignOptical levers layout

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


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

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


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



Attachment 1: crime_v1.pdf
  18   Thu May 26 02:51:27 2016 GabrieleElectronicsDesignESD design

A preliminary design of the ESD board is available on the DCC: D1600214

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

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

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

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

Attachment 1: disk_75mm_0.12mm.png
Attachment 2: disk_75mm_1mm.png
Attachment 3: disk_100mm_0.4mm.png
Attachment 4: disk_200mm_0.4mm.png
  20   Mon Jun 6 13:35:36 2016 GabrieleElectronicsGeneralComponents

The PCBs for the QPD circuit and ADC interface are here and look ok. All electronics components are also here (except for the ADC connector which should be ordered separately from Mouser, after confirming that the ADC we're going to use have the same cable as the one we use in the Crackling Noise experiment). The QPD will be shipped on 06/17.

  21   Tue Jun 7 14:07:55 2016 GabrieleFacilityGeneralRack and workstation

I moved the unused rack from the Crackling Noise lab to the C.Ri.Me lab. It will be used for the new cymac. I also started putting the new workstation together, but I'm missing some adaptors for the monitors.

  22   Fri Jun 10 13:44:06 2016 GabrieleElectronicsConfigurationHow to setup a workstation

Instructions on how to setup a workstation are available here:


I'll copy them here and integrate once I got the C.Ri.Me. workstation up and running


** libmotif4 >> libxm4 : sudo apt-get install libxm4

** all .sh files in etc must be modified to point to the correct version of the downloaded software

** add the following line to the end of the ligoapps-userv-end.sh file to get medm and striptool working


** to fix diaggui problem, create a symbolic link in /usr/lib/x86_64-linux-gnu/

sudo ln -s libtiff.so.5 libtiff.so.4

  23   Thu Jun 16 00:47:42 2016 GabrieleOpticsDaily ProgressQuality factor measurement of a Mark Optics disk at LMA

[Massimo Granata (LMA), Quentin Cassar (LMA), Gabriele] 

This week I'm visiting LMA to learn how their Gentle Nodal Suspension system works and to measure the quality factors (Q) of one of Mark Optics disks. First of all we annealed the disk for 9 hours at 900 degrees (plus 9 hours warm up and 9 hours cool down).

Then we installed the disk into the measurement system and started by searching for all the resonances.

My COMSOL simulation proved to be good enough to give us the frequencies, especiallty after a small fine tuning of the disk thickness (within specs). We identifies a total of 32 modes of different families, and measured the ring down of all of them. Since our disk has no flats, each mode is actually a doublet with very small frequency separation. The analysis software has a bandwith of 1 Hz to find the peak amplitude, so it can't resolve the two modes. When both are excited to a significant amplitude by the electrostatic actuator, we see a clear beat in the ring-down. I had to write a new fitting code to take this into account. More details will follow in a DCC document. However, here I can say that the fit works remarkably well for all modes. 

A couple of examples:


Here is a summary plot of the quality factor and loss angle for all modes. We measured Q as high as 10e6, in line with other LMA samples (2") we tested in these days. In conclusion, the Mark Optics disks, as they are, are good enough for our coating tests.


  24   Fri Jun 24 17:03:47 2016 GabrieleElectronicsDaily ProgressQPD electronics

Between yesterday and today I populated one QPD board (based on D1600196), and started testing it. The transimpedance stages seems to work fine (they show about 5-6 V in ambient light). However the whitening stages show a large ~100 kHz oscillation. While trying to fix it I probably burnt one of the output drivers.

I'll continue the investigations and debugging on Monday.

  25   Tue Jun 28 10:17:28 2016 GabrieleElectronicsDaily ProgressQPD electronics

Transimpendance and whitening are working properly. I can't get useful signal out of the differential stages yet. I replaced the channel 1 DRV134 that was burnt (very hot when powered on). But the new one got hot too after powring on, so there might be something else wrong there. I'm also wondering if it's ok to use an oscilloscope to look at the differential stage output. The scope will ground one of the two outputs: according to the DRV134 datasheet this should be ok, but I'll check better later on.


Between yesterday and today I populated one QPD board (based on D1600196), and started testing it. The transimpedance stages seems to work fine (they show about 5-6 V in ambient light). However the whitening stages show a large ~100 kHz oscillation. While trying to fix it I probably burnt one of the output drivers.


  26   Wed Jun 29 16:44:17 2016 GabrieleGeneralConfigurationFirst disk eigenfrequency

The following table shows the lowest eigenfrequency (Hz) for different sizes of disks

Diameter \ Thickness [mm] 0.125 0.250 0.500 1.000
75 137 273 545 1090
100 77 154 307 613
150 34 68 136 272
200 19 38 77 153

  27   Thu Jun 30 16:18:28 2016 GabrieleElectronicsDaily ProgressQPD electronics is working

Today I gave up trying to fix the first board I populated, and built a second one. The good news is that it's working as expected.

With 27.5 uW incident on each quadrant, I measure about 4.5 V, which is in line with the transimpedance of 200k, a responsivity of about 0.4 A/W and ad additional gain of two coming from the differential driver.

I also measured the noise with a SR785 (it wasn't connected to a GPIB interface and I couldn't find any, so all I have are the following numbers and the attached screenshots). 

Frequency [kHz] Noise [uV/rHz] Equivalent beam motion [m/rHz]
1 1.3 5.7e-14
5 2.2 9.6e-14
10 3.3 14e-14
30 2.4 10e-14
60 1.2 5.2e-14

At low frequency we are dominated by 60 Hz harmonics (probably coming from the laser). At high frequency there are some large peaks of unknown origin. I can't acquire digitally the signals to compute the difference, so I don't know if the noise we see is, for example, laser intensity noise. As soon as the cymac is up and running, I'll run some more tests.


  28   Thu Jun 30 17:23:54 2016 GabrieleElectronicsDaily ProgressCymac

I got two new ADC and DAC boards from Rolf, with the correct PCIe interface. I installed them into the cymac and checked that the system could boot. The cymac is now sitting in the rack. As requested by Jamie I installed Debian 8.5

  29   Fri Jul 1 15:12:12 2016 GabrieleElectronicsDaily ProgressQPD electronics noise


I turned out that all the noise I was seeing in the QPD spectrum was due to ambient light. I covered the QPD with a box and switched off all the light. As shown in the following plot the noise is lower.

Considering that in the final setup we'll have a beam spot radius of 0.5mm, the sensitivity to beam motion on the QPD will be 23e6 V/m. The following plot shows the resulting beam motion sensitivity, if limited by electroninc noise:

It's at a level of 6e-15 m/rHz at all frequencies above 120 Hz.

  31   Thu Jul 7 17:44:11 2016 GabrieleFacilityDaily ProgressVacuum chamber tests

[Alena, Gabriele]

This afternoon we opened the tall belljar vacuum chamber, and took everything out of it. All the stuff that was inside the chamber is "temporarily" stored on the floor beside the optical table.

We installed a "spacer" into the chamber, made from one of the optical table legs that were sitting in the hallway. We installed one of the aluminum base plates on top of it, so that the optical components will be at the level of the viewport. Another leg and a thinner base plate are installed out of the chamber, at a similar level.

After this we closed the chamber with one of the flats used for the old chamber, and a rubber o-ring. We started the roughing pump, quickly reached a pressure below 1 mTorr and switched on the turbo pump. Unfortunately, it seems that the low pressure gauge is not working properly, so we don't know what's the pressure right now. We'll check the gauge and controller tomorrow morning and swap it out if needed.

  34   Fri Jul 8 16:49:11 2016 GabrieleElectronicsConfigurationCyMAC

In the last days Jamie installed the patched kernel to run the real time system (RTS) on the new CyMAC. Today (with Jamie's remote advices) I managed to get a IOP (input output process) model compiled and running. There is still no timing input (to be fixed at the beginning of the netx week, I'm presently missing a connector which is on order).

Running the x1iop model gives:

controls@cymac3:/opt/rtcds/tst/x1/scripts$ ./startx1iop 

x1iopepics: no process found

Number of ADC cards on bus = 1

Number of DAC16 cards on bus = 1

Number of DAC18 cards on bus = 0

Specified filename iocX1.log does not exist.

x1iopepics X1 IOC Server started


controls@cymac3:/opt/rtcds/tst/x1/scripts$ awg_server Version $Id: awg_server.c 2917 2012-05-22 22:33:39Z alexander.ivanov@LIGO.ORG $

channel_client Version $Id: gdschannel.c 4170 2016-04-05 21:24:46Z jonathan.hanks@LIGO.ORG $

testpoint_server Version $Id: testpoint_server.c 3303 2013-03-05 23:33:45Z alexander.ivanov@LIGO.ORG $

/opt/rtcds/tst/x1/target/gds/bin/awgtpman -s x1iop -4 -l /opt/rtcds/tst/x1/target/gds/awgtpman_logs/x1iop.log started on host cymac3 hostid ffffffffd783d97b 

awgtpman Version $Id: awgtpman.c 4170 2016-04-05 21:24:46Z jonathan.hanks@LIGO.ORG $

which seems reasonable. Also, the GDT TP medm screen shows something running:
Here's what I had to do to get the models to compile and run:

1) install MATLAB and add to startup.m the following line



2) copied from cymac2 the file /opt/rtcds/rtcds-user-env.sh and changed the content to match the right folders


3) installed readline library which was missing: apt-get install 

sudo apt-get install libreadline-dev


4) installed linux headers sudo apt-get install linux-headers-3.2.0-rts-amd64


5) created symbolic link to linux headers:

sudo ln -s /usr/src/linux-headers-3.2.0-rts-common /usr/src/linux


6) changed host name to cymac3

sudo vi hostname


7) created symbolic link to lspci 

sudo ln -s /usr/bin/lspci /usr/sbin/lspci


8) created a symbolic link to awgtpman

ln -s /usr/bin/awgtpman /opt/rtcds/tst/x1/target/gds/bin/awgtpman

  35   Mon Jul 11 08:49:25 2016 GabrieleElectronicsConfigurationCymac RTS configuration

I copy here parts of an email from Jamie with instructions on how to run the RTS on the cymac:

I had to change the site/ifo to be "caltech/x3" to avoid EPICS
collisions with other cymacs.  You'll need to update your models to
reflect this change (change names, site/ifo parameters in the model,
etc.).  So for instance, change x1iop -> x3iop, and update the params
block inside.

daqd is installed and running, although I haven't really stress tested
it yet (no models/channels/etc).  It's running under systemd, which is
the Debian service management system.  You can control daqd with the
following commands:

# systemctl restart daqd
# systemctl stop daqd
# systemctl start daqd
# systemctl status daqd
# journalctl --unit=daqd

controls@cymac3:~ 0$ systemctl status daqd
● daqd.service - Advanced LIGO RTS daqd service
  Loaded: loaded (/etc/systemd/system/daqd.service; enabled)
  Active: active (running) since Sat 2016-07-09 11:22:38 PDT; 23h ago
Main PID: 20827 (daqd-standiop)
  CGroup: /system.slice/daqd.service
          └─20827 /usr/bin/daqd-standiop -c /etc/advligorts/daqdrc
controls@cymac3:~ 0$ sudo journalctl --unit=daqd

Remember to restart daqd ("systemctl restart daqd") after you add/change

I've gotten all the RCG components working, but not without some small
kinks.  The RCG currently expects a specific EPICS install, different
than the system install we're using right now.  I've hacked a way to
make this work seemlessly for model builds, but it requires sourcing the
following file before *starting* models:


So in the mean time, you can start/stop models via the following:

$ . /opt/rtapps/epics/etc/epics-user-env.sh
$ /opt/rtcds/caltech/x3/scripts/startx1iop


  37   Mon Jul 11 15:21:12 2016 GabrieleGeneralDaily ProgressOne disk installed into the chamber

[Alena, Gabriele]

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

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

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

  39   Tue Jul 12 17:19:07 2016 GabrieleElectronicsDaily ProgressADC and DAC cabling

This afternoon I completed the assembly of the electronics boards to interface the ADC and DAC. The ADC is interfaced with a new custom board, which accepts up to eight QPD inputs, the syncronization signal, and it's connected to the ADC:

For the DAC I used one spare board from the Crackle experiment. However, that board had a wrong pinout for the DAC side connector, so I had to implemented again the same hack I did for the crackling noise experiment. 

All boards are connected to the ADC and DACs, and to the syncronization signal generated with a SR DS345. No boxes for the moment being, I'll figure out a better organization of the boards in the future if needed. I still haven't tested if the real time system is able to communicate properly with the new interfaces.

  42   Thu Jul 14 17:06:47 2016 GabrieleElectronicsConfigurationNetworking

The laboratory workstation is coatings.ligo.caltech.edu

The RTS is cymac3.ligo.caltech.edu

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

  43   Fri Jul 15 16:05:07 2016 GabrieleElectronicsDaily ProgressElectrostatic actuator installed

Using the already installed high voltage feedthrough, I cabled one of the electrostatic actuators (1mm gap between electrodes) and installed it into the chamber. One of the electrodes is connected to the feedthrough cenral pin, the other is grounded on the bottom of the chamber.

The electrostatic actuator is mounted at about 1 mm above the disk, see pictures.

As a preliminary test, I checked that switching the HV amplifier on and off with about 1.5kV produces a visible motion (~2-3 mm) of the optical lever beam. So the actuator is working.

  44   Fri Jul 15 17:56:50 2016 GabrieleGeneralDaily ProgressQPD connected to digital system

I connected the QPD to the ADC interface with a temporary cable running on the floor.

I could get signals. I still have a problem with the digital system: I can't access test points with dataviewer, but I get them with DTT. This will have to be fixed.


  45   Sat Jul 16 14:15:44 2016 GabrieleFacilityDaily ProgressPump down started

Following Alena's procedure, at about 1:30pm LT I started the chamber pump down. At 14:15pm LT the pressure was still 240 mTorr

At 6:20pm the pressure was about 70 mTorr, so I started the turbo pump.

  46   Mon Jul 18 13:39:45 2016 GabrieleFacilityDaily ProgressPump down started

Today at 1:40pm pressure is 8.5e-7 Torr


Following Alena's procedure, at about 1:30pm LT I started the chamber pump down. At 14:15pm LT the pressure was still 240 mTorr

At 6:20pm the pressure was about 70 mTorr, so I started the turbo pump.


  47   Mon Jul 18 13:42:46 2016 GabrieleElectronicsCharacterizationQPD signal convention

The QPD quadrants are wired accoridng to the following convention

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

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

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

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

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

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

  49   Mon Jul 18 17:46:04 2016 GabrieleGeneralDaily ProgressFirst look at QPD signals

Here's the first spectrum of the QPD X and Y signals, acquired with the digital system. Roughing and turbo pumps are still on.

The noise floor seems quite non stationary. To be investigated.

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