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ID Date Authorup Type Category Subject
  14929   Thu Oct 3 11:38:35 2019 aaronUpdateIOOWFS measurements

I set up the spectrum analyzer to make the WFS head RF transfer function measurement (V/W) on WFS1. I placed the Jenne laser on the AP table, along with the reference PD power supply, laptop, and laser power supply. The Agilent output AM modulates the laser; the reference PD is again NewFocus 1611, with its AC output sent to Agilent's R channel and DC output sent to an oscilloscope;

At Koji's suggestion, I've started setting up a small breadboard to hold the fiber collimator, BS, and reference PD. I haven't really used fiber optics before, I'd appreciate another set of eyes before I get too deep.
Gautam showed me the collimator and fiber BS.

I closed the PSL shutter while checking for a location to place the breadboard, and opened it while writing this. Headed back to Cryo to pick up the large incandescent bulb we'd borrowed over the summer.

  14934   Thu Oct 3 21:05:04 2019 aaronUpdateGeneralMake the Jenne-laser setup fiber-coupled

I measured the RF response of the fiber-coupled NewFocus 1611, calibrating out the cable delay. The laser current was set to 20.0 mA, and the RF power going into the splitter was -10 dBm. The DC voltage was 1.87 V, and Gautam and I measured the power from the fiber at 344uW.

Something still looks very wrong -- the PD is supposed to be flat out to 1GHz, and physical units pending, need food.

Attachment 1: PD_response.pdf
PD_response.pdf
  14940   Fri Oct 4 14:25:59 2019 aaronUpdateGeneralMake the Jenne-laser setup fiber-coupled

Summary:

The fiber-coupled PD seems to have a factor of ~1.5 difference in responsivity compared to the free-space PD. There are some differences in the two ways I made the measurement that I don't yet understand.

Details

I measured relative responsivities of the fiber and free coupled NewFocus 1611 PDs (scaled by the Jenne AM transfer function).

I made the measurement in two ways, see attachment threeIn attachment oneI show the response for separately measuring the two PDs relative to a pickoff of the source (two-port thru calibration). In attachment two I measure the relative responses directly, without picking off a reference (three-port calibration). I scaled the transfer functions by their DC voltages; both PDs have transimpedances of 700 V/A.

However, there are some clear differences in the response (overall factor of 0.5dB offset that may be explained by a miscalibrated DC level; apparent periodicity in attachment 1) that I don't yet understand.The free path of the non-fiber PD is ~5-6 inches, which accounts for the ~45 degrees of phase advance of the fiber relative to free coupled PD signal. (12.7cm / (c / 300 MHz) * 360 degrees ~ 45 degrees)

I didn't find Agilent's manual very helpful for learning about the available calibration schemes, and didn't find a resource online that I liked -- is there a good one?
I think I want to characterize the WFS heads treating the DUT as a three-port device (AM in, ref PD, WFS segment PD).
Attachment 1: PD_norm.pdf
PD_norm.pdf
Attachment 2: PD_AB.pdf
PD_AB.pdf
Attachment 3: JenneAM_fiberPD_cals.pdf
JenneAM_fiberPD_cals.pdf
  14945   Mon Oct 7 14:51:20 2019 aaronUpdateElectronicsWFS head RF measurements

Mon Oct 7 14:51:53 2019. I closed the PSL shutter to measure the WFS head responsivity.

I made a thru calibration as in this elog, treating laser, reference PD, and WFS RF output as a three-port device. The DC current supplied to the laser is 20.0 mA in all cases. The Agilent spectrum analyzer supplies a -10 dBm excitation to Jenne laser's AM port, and A/B is measured with 20dB attenuation on each input port. Results are in /users/aaron/WFS/data/191007/. The calibration had 100 averages, all other measurements 32 averages; other parameters found in the yml file, same folder as the data.

Measurement Reference PD DC (V) WFS Segment DC (V) WFS Segment DC, beam blocked (V) File Notes
WFS 1 Segment 1 1.86 0.79 -0.23
TFAG4395A_07-10-2019_154446.txt
 
WFS 1 Segment 2 1.86 0.72 -0.30 TFAG4395A_07-10-2019_155017.txt  
WFS 1 Segment 3 1.86 0.79 -0.21
TFAG4395A_07-10-2019_155645.txt
 
WFS 1 Segment 4 1.86 0.70 -0.30
TFAG4395A_07-10-2019_160334.txt
TFAG4395A_07-10-2019_160847.txt
I noticed the BS-PRM illuminator was on, and turned it off for the second measurement
WFS 2 Segment 1 1.86 0.56 -0.38 TFAG4395A_07-10-2019_162533.txt  
WFS 2 Segment 2 1.86 0.71 -0.21
TFAG4395A_07-10-2019_163402.txt
 
WFS 2 Segment 3 1.86 0.68 -0.28 TFAG4395A_07-10-2019_164152.txt  
WFS 2 Segment 4 1.86 0.57 -0.42 TFAG4395A_07-10-2019_164745.txt  

 

I normalized the result by the difference between the dark and bright DC levels of each segment.

Mon Oct 7 17:29:58 2019 opened PSL shutter.

Attachment 1: WFShead_response.pdf
WFShead_response.pdf
  14951   Tue Oct 8 16:00:06 2019 aaronUpdateElectronicsWFS head RF measurements

I simulated this circuit with zero, but haven't gotten the results to match the measurements above.

Removing the DC readout chain from the circuit does not affect the AC response.
Perhaps something to do with the (currently unmodeled) capacitance of the diode? I think this forms a necessary part of the resonant circuit. The gain is also suspiciously low.
Edit: Indeed, simply adding the 'typical' shunt capacitance (9pF) and a small series resistor (10 Ohm) gives the right qualitative response
The python notebook is in /users/aaron/WFS/electronics.
The DC response flattens off at ~20dB by ~mHz, which also seems longer than the timescales I saw while measuring; I'm not sure I have some of the AD827 parameters correct (eg 'delay')
 
I came across this nice note on photodiodes.
 
 
Attachment 1: WFS_ACresponse.pdf
WFS_ACresponse.pdf
Attachment 2: WFS_DCresponse.pdf
WFS_DCresponse.pdf
  14957   Tue Oct 8 20:39:42 2019 aaronUpdateIOOWFS loop measurements

I installed nds2 on donatello with yum, but still can't import nds2.

  14958   Wed Oct 9 09:37:28 2019 aaronUpdateIOOWFS loop measurements

I installed nds2 again, this time successfully with

conda install -c conda-forge python-nds2-client

 

  375   Thu Mar 13 12:11:58 2008 aivanovUpdateComputer Scripts / Programsrouting PEM -> ASS -> SUS_MCL

on ASS RFM 1 has PEM signals at

float at 0x100000 has c0dcu1 first ICS110B chan 1
float at 0x100004 has chan 2
etc.

ASS sends to RFM 0

float at 0x100000 goes to PRM MCL
0x100004 to BS MCL
0x100008 to IMTX MCL
0x10000c to ITMY MCL
0x100010 to SRM MCL
0x100018 to MC1 MCL
0x10001c to MC3 MCL
0x100020 to ETMX MCL
0x100024 to ETMY MCL
  376   Thu Mar 13 13:15:09 2008 aivanovUpdateComputer Scripts / Programsnew sfotware intall, backup files
New:
op440m:40m>ls -alt /cvs/cds/caltech/target/c1susvme[12]/*.o
-rw-r--r-- 1 controls staff 57920 2008-03-13 13:11 /cvs/cds/caltech/target/c1susvme2/losLinux2.o
-rw-r--r-- 1 controls staff 57976 2008-03-13 13:11 /cvs/cds/caltech/target/c1susvme1/losLinux1.o
op440m:40m>ls -alt /cvs/cds/caltech/target/c1isce[xy]/*.o
-rw-r--r-- 1 controls staff 246861 2008-03-13 13:12 /cvs/cds/caltech/target/c1iscey/losEtmy.o
-rw-r--r-- 1 controls staff 246861 2008-03-13 13:12 /cvs/cds/caltech/target/c1iscex/losEtmx.o
op440m:40m>ls -alt /cvs/cds/caltech/target/c0dcu1/*.o
-rw-r--r-- 1 controls staff 63547 2008-03-12 14:57 /cvs/cds/caltech/target/c0dcu1/dcuDma.o


Backups:
op440m:40m>ls -alt /cvs/cds/caltech/target/c1susvme[12]/*.o.13mar08
-rw-r--r-- 1 controls staff 55960 2005-06-21 13:30 /cvs/cds/caltech/target/c1susvme2/losLinux2.o.13mar08
-rw-r--r-- 1 controls staff 55960 2005-06-21 13:30 /cvs/cds/caltech/target/c1susvme1/losLinux1.o.13mar08
op440m:40m>ls -alt /cvs/cds/caltech/target/c1isce[xy]/*.o.13mar08
-rw-r--r-- 1 controls staff 229793 2007-03-08 11:09 /cvs/cds/caltech/target/c1iscex/losEtmx.o.13mar08
-rw-r--r-- 1 controls staff 229793 2007-03-08 11:09 /cvs/cds/caltech/target/c1iscey/losEtmy.o.13mar08
op440m:40m>ls -alt /cvs/cds/caltech/target/c0dcu1/*.o.12mar08
-rw-r--r-- 1 controls staff 60810 2004-09-08 08:47 /cvs/cds/caltech/target/c0dcu1/dcuDma.o.12mar08
  3   Thu Oct 18 15:03:14 2007 ajwRoutineGeneralthis is only a test

  7   Mon Oct 22 12:02:59 2007 ajwRoutineGeneralSTACIS as microseismic shaker
In case we ever want to use our Stacis systems as shakers, check this:
link
  30   Tue Oct 30 13:58:07 2007 ajwConfigurationIOOMC Ringdowns
Here's a quick fit-by-eye to the latter part of the data from tek00000.xls.

The prediction (blue) is eqn 41 of
http://www.ligo.caltech.edu/docs/P/P000017-A.pdf

T1 = T2 = 0.002. Loss1 = Loss2 = 150 ppm.
MC3 assumed perfectly reflecting.
Velocity = 320 um/s (assumed constant), 2 usec into the ringdown.

OK, there's one little fudge factor in the prediction:
I multiplied D by 2.
Attachment 1: CavityRingdown.png
CavityRingdown.png
Attachment 2: CavityRingdown.m
% CavityRingdown.m
% Eqn 41 of 
% "Doppler-induced dynamics of fields in FabryĖPerot
% cavities with suspended mirrors", Malik Rakhmanov (2000).
% http://www.ligo.caltech.edu/docs/P/P000017-A.pdf

clear all

% read in ringdown timeseries:
at = importdata('tek00000.csv');
... 121 more lines ...
  77   Wed Nov 7 10:55:21 2007 ajwConfigurationComputersbackup script restarted
Following the reboot of computers on 10/31/07, the backup script required restart (which unfortunately "can't" be automated because a password needs to be typed in). I restarted, following the instructions in /cvs/cds/caltech/scripts/backup/000README.txt and verified that it more-or-less worked last night (the rsync sometimes times out; it gets through after a couple of days of trying.)
  144   Fri Nov 30 11:22:22 2007 ajwSummaryCDSGEO DV => LIGO DV

Quote:
Martin Hewitson of GEO600 fame has modified the cool GEO DV
to work with the LIGO NDS system with some NDS advice from Rolf (who's over in Germany this week).

I've moved it onto the 40m CDS system and installed it on the AdhikariLab computer named 'django'. It worked immediately.

I modified the main .m file to include the 40m's NDS server. When you run it you have to include the path to the NDS
client written by Ben Johnson.

The attached is a screenshot of it working on a Mac; it looks as cool on Linux.

Its installed in /cvs/cds/caltech/apps/ligoDV/. In matlab you navigate to that directory and then
type addpath('/cvs/cds/caltech/apps/linux/UNIX_NDS_Client_beta2/') to add the NDS client.
On the Solaris machines, type type addpath('/cvs/cds/caltech/apps/solaris9/UNIX_NDS_Client_beta2/') instead.

Then type ligoDV to start it up. Then click away and have fun.

In the example I've selected
C1:PEM-BS_ACC_EAST_Z
and plotted its specgram.

Big grin


Download and installation instructions, as well as a few examples for use
can be found here (typical lsc username and password):

https://www.gravity.phy.syr.edu/dokuwiki/doku.php?id=ligodv:home
https://www.gravity.phy.syr.edu/dokuwiki/doku.php?id=ligodv:downloading_the_ligodv_software
  453   Sat Apr 26 11:21:15 2008 ajwOmnistructureComputersbackup of /cvs/cds restarted
The backup of /cvs/cds (which runs as a cron job on fb40m; see /cvs/cds/caltech/scripts/backup/000README.txt) 
has been down since fb40m was rebooted on March 3.
I was unable to start it because of conflicting ssh keys in /home/controls/.ssh .
With help from Dan Kozak, we got it to work with both sets of keys
( id_rsa, which allows one to ssh between computers in our 113 network without typing a password,
 and backup2PB which allows the cron job to push the backup files to the archive in Powell-Booth).

It still goes down every time one reboots fb40m, and I don't have a solution.
A simple solution is for the script to send an email whenever it can't connect via ssh keys
(requiring a restart of ssh-agent with a passphrase), but email doesn't seem to work on fb40m.
I'll see if I can get help on how to have sendmail run on fb40m.
  457   Sun Apr 27 22:57:15 2008 ajwDAQComputersbr40m?

Quote:

The testpoint manager (which runs on fb40m) crashed this afternoon. Upon re-starting it, I found there was a rogue dtt process on op440m and also a daqd daemon running on br40m. One or both of these caused the tpman to crash. br40m is the frame broadcaster, which is never used here as we don't run DMT. I killed the daqd process there.

The way to find if there is a rogue process is to watch the output to the console from the tpman when you start it:

Allocate new TP handle 56 by 131.215.113.203
Allocate new TP handle 57 by 131.215.113.203
Allocate new TP handle 58 by 131.215.113.203
Allocate new TP handle 59 by 131.215.113.203
Allocate new TP handle 60 by 131.215.113.203
Allocate new TP handle 61 by 131.215.113.203
Allocate new TP handle 62 by 131.215.113.203
Allocate new TP handle 63 by 131.215.113.203
Allocate new TP handle 64 by 131.215.113.203
Allocate new TP handle 65 by 131.215.113.203
Allocate new TP handle 66 by 131.215.113.203
Allocate new TP handle 67 by 131.215.113.203
Allocate new TP handle 68 by 131.215.113.203


If you see something like this, with a new TP handle being allocated every few seconds, you need to log in to the corresponding host and kill whatever process has run away.


I *think* Alex is responsible for the daqd daemon running on br40m (he set up some new stuff recently, a data concentrator and broadcaster); I'll make sure he sees this post.
  1854   Fri Aug 7 13:42:12 2009 ajwOmnistructureComputersbackup of frames restored

Ever since July 22, the backup script that runs on fb40m has failed to ssh to ldas-cit.ligo.caltech.edu to back up our trend frames and /cvs/cds.

This was a new failure mode which the scripts didn't catch, so I only noticed it when fb40m was rebooted a couple of days ago.

Alex fixed the problem (RAID array was configured with the wrong IP address, conflicting with the outside world), and I modified the script ( /cvs/cds/caltech/scripts/backup/rsync.backup ) to handle the new directory structure Alex made.

Now the backup is current and the automated script should keep it so, at least until the next time fb40m is rebooted...

 

  532   Thu Jun 12 15:09:33 2008 alanUpdateLockingreport
Rob: Awesome figure. As you can imagine, I have lots of questions, and hope that you will consider this figure to be the beginning, leading to ever-more detailed versions. But for now, I just want to ask whether you understand *what* is twitchy, and what the twitchiness does to prevent you from taking this further?
  661   Fri Jul 11 23:55:25 2008 alanUpdateLockingRF common mode at zero offset

Quote:
rob, john, yoichi

Last night we succeeded in reducing the CARM offset to zero.



Congratulations! Well done! I look forward to hearing the details and further progress!
  138   Thu Nov 29 10:36:47 2007 albertoConfigurationComputer Scripts / ProgramsAgilent 82357B GPIB to USB Interface Installation Procedeure
To run the Agilent Automation-Ready CD provided with the interface is only the first step of the installation. Apparently there should be also a second CD with the drivers for Windows XP but I couldn't find it. So, after Installaing the IO Libraries Suite from the CD, I had to install the drivers with an executable downloaded from the Agilent's website at:

http://www.home.agilent.com/agilent/editorial.jspx?cc=US&lc=eng&ckey=1188958&nid=-35199.0.00&id=1188958

and only then I could plug in the interface.
Anyway, I burned a cd with the file and put it together with the other one.
  164   Wed Dec 5 10:57:08 2007 albertoHowToComputersConnecting the GPIBto USB interface to the Dell laptop
The interface works only on one of the USB ports of the laptop (the one on the right, looking at the computer from the back).
  165   Wed Dec 5 13:49:08 2007 albertoUpdateElectronicsRF AM PD lines monitor
In the last weeks Iíve been working on the design of an electronic board to measure directly the power of the main spectral lines on of the RF-AM photodiode from as many independent outputs. The idea is to have eventually a monitor channel in the CDS network for the power of each line.
Looking at at the spectrum from the RF-AM PD (see attached plot), there are 5 main lines:
Frequency
3 fsr = 33 195 439 Hz
4 fsr = 66 390 878 Hz
12 fsr = 132 781 756 Hz
15 fsr = 165 977 195 Hz
18 fsr = 199 172 634 Hz

Two main approaches have been proposed for the circuit depending on the way followed to isolate the lines:
1) Filters: the frequencies are separated by narrow notch filters, then a diode bridge rectifies and a low pass filter extracts the DC component.
2) Mixers: for each frequency there is a mixer driven by a copy of the correspondent modulation frequency provided by the function generators (the Marconi). The mixers automatically give the DC component of the rectified signals.
Because of the phase lags that we should compensate if we used mixers, we would prefer the first approach, if it works.
Starting with a tolerance of about 10% between the channels, the spectrum (see attachment) sets the constraint to the filterís suppression:
Filter central frequency [MHz]******Suppression within 30 Mhz [dB]
33*********************************-7-20 = -27
66**********************************7-20 = -13
133*********************************12-20 = -8
166********************************-12-20 = -32
199*********************************10-20 = 10

So far Iíve tried two kinds of designs for the filters, Butterworth (see attachment) and LC and I'm measuring transfer functions tuning the components to match the central frequency and the bandwdth of the filters with the requirements.

The frequencies weíre dealing with are rather high and several adjustments had to be done to the measurement system in order to shield the circuit from the impedance of the input and the output line (i.e., amplifier turned out to be necessary). Also, an the mixer had to be replaced to an RF one.
It seems I'm now measuring new transfer functions (which look quite different from what I've got with no amplifiers).
To be posted soon.
Attachment 1: alberto.spectrum2.png
alberto.spectrum2.png
Attachment 2: Butterworth.PNG
Butterworth.PNG
  173   Thu Dec 6 15:21:59 2007 albertoFrogsElectronicsRF Transfer Function of Stiff Aluminum Wires
Transfer function of 3cm long Aluminum wires and of 3cm stranded wires
Attachment 1: TF_3cm_stiff_wires.amplitude.png
TF_3cm_stiff_wires.amplitude.png
Attachment 2: DSC_0225compressed.JPG
DSC_0225compressed.JPG
Attachment 3: TF_3cm_stranded_wires.amplitude.png
TF_3cm_stranded_wires.amplitude.png
  188   Wed Dec 12 16:22:22 2007 albertoOmnistructureElectronicsLC filter for the RF-AM monitor circuit
In the LC configuration (see attached schematic) the resonant frequency is tuned to one of the peak of our RF-AM monitor and it is amplified by a factor equal to the Q of the filter. As I wrote in one of the last elog entries, we would like amplifications of about 10-30 dB in order to have negligible couplings. Such values are obtained only with small capacitances (few or less pF). The drawback is relatively large inductance (uH or more) which has inevitably low Self Resonant Frequencies (SRF - the resonant frequencies of the RLC circuit usually associated with an actual inductor - ~ MHz). Even before, one limit is also the input impedance of the RF amplifier. Quality factors > 1 require megaohms, far from the 50 ohms in the MiniCircuit amplifiers Iím using now. So, if we plan to use these even for the final design of the circuit, we have to abandon the LC configuration.
For this same reason the only way I could get the expected responses from my several test boards was with a 10 megaohm input probe (see attachment for the measurement with and without probe). Assuming that impedance, I found these as the best trade-offs between the attenuation requirements and the values of the inductors for respectively the peaks at 33, 66,133, 166,199 MHz:
26uH, 6.6u, 20u, 73u, 16u
If we could find inductor with these values and high SRF the configuration should work. The problem is I couldnít find any. Above a few uH they all seem to have SRF ~ MHz.
That is why I switched to the Butterworth. This should work despite the input impedance of the amplifier and with much smaller inductances. I made a totally new test circuit, with surface mount components. I think I still have to fix some things in the measurements but (this time I got rid of the simulator I was using earlier and designed a new configuration with new values from the Horowitzís tables) it seems I have the expected peaks. More soon.
Attachment 1: TF_LC_filter_10pF_1.8uH_scope_probe.png
TF_LC_filter_10pF_1.8uH_scope_probe.png
Attachment 2: TF_LC_filter_10pF_1.8mH_no_probe.png
TF_LC_filter_10pF_1.8mH_no_probe.png
Attachment 3: LC_filter_schematic.png
LC_filter_schematic.png
  190   Thu Dec 13 12:05:36 2007 albertoOmnistructureElectronicsThe new Butterworth seems to work quite well
It works better probably because of the small inductors I'm using this time.
The peak is at 30 MHz because I didn't have the precise elements to get 33.

The bandwidth and the Q could be improved by adding one or two more order to the filter and trying to better match the low-pass' resonant frequency with the high-pass'.

Also I have to see if it could work at 166 and 199 MHz as well.
Attachment 1: TF_New_Butterworth_12-Nov-2007_TF.png
TF_New_Butterworth_12-Nov-2007_TF.png
Attachment 2: Bultervverth2.png
Bultervverth2.png
  193   Mon Dec 17 11:47:13 2007 albertoUpdateElectronicsan alternative design for the RFAM monitor's filter at 33Mhz
Since the Butterworth turned out o be rather wide-band, I tried an other configuration for the 33 MHz filter. Attached are the simulated transfer function and the measured. As one can see, the measured peak is much broader than expected.
Attachment 1: RFSim99-33MHz.png
RFSim99-33MHz.png
Attachment 2: RF99-SimmButterworthPrototype.png
RF99-SimmButterworthPrototype.png
Attachment 3: RFSim99-33MHz-TFplot.png
RFSim99-33MHz-TFplot.png
  650   Tue Jul 8 21:58:22 2008 albertoUpdateGeneralSecondaty beam aligned to the IFO beam again
Yesterday the alignment of the secondary beam to the IFO was completely lost and today I had to realign all the optics before I was able to match the two spots again. I had to reset the height of the irises and I had also to replace mirror M1 with one with a larger angular motion. Eventually I obtained the beat again. Working on the optics table I inadvertently misaligned the OSA but I didn't make in time to bring it back before the night shift people came. I'll work on that tomorrow morning.
  943   Thu Sep 11 23:28:35 2008 albertoUpdateGeneralabs cavity length experiment
The MC lost lock for some reason not related to either the FSS or the PMC I'm done with my measurement for tonight. I've shut the NPRO beam before leaving.
  1108   Mon Nov 3 19:12:27 2008 albertoUpdateGeneralTransverse mode spacing measurement for the X arm
I know a lot of expectations have been building up on these days in the scientific community at the 40m towards a conclusive elog entry about the g-factor measurement of the X arm cavity.
The reason of the delay is that the results are still under review by the author. It turned out that the measurements of the transverse mode spacing have been performed on the beat
of the TEM02/20 and TEM00 modes between the two laser beams instead of on the beat between 00 and 01/10. However, the results posted on the elog in the last weeks seem likewise correct,
in particular my plot of the HOM of the sidebands.

Anyways, lately I have been trying to repeat the measurement on the beat of TEM01/10 with 00 but, despite all the efforts and the countless configurations tried (on the locking of
the arm, on the tilt of the mirrors, on the injection of the secondary beams, on the chopping with the blade), only the beat of TEM10 has been measured - although quite clearly -
whereas that of TEM01 has so far hidden itself.

The search continues but even if it does not succeeds, a summarizing document is going to be posted soon.

Here I attach a plot that shows the kind of difficulties trying to detect TEM10. The red neat peak is the beat of TEM01 whereas the other curves are some of the resulting
resonances after trying to couple TEM10 with 00 (or vice versa, according to whether I'm locking the cavity to the 00 mode of the main laser or to that of the secondary beam).
Attachment 1: 2008-11-02_summarizingplot.png
2008-11-02_summarizingplot.png
  1830   Tue Aug 4 23:03:56 2009 albertoUpdateLockingIFO Alignment

After the mini boot fest that Jenne did today, I checked whether that fixed the overflow issues we yesterday prevented the alignemnt of the arms. 

I ran the alignment script for the arms getting 0.85 for TRX and 0.75 for TRY: low values.

After I ran the script ,C1SUSVME1 and C1SUSVME2 started having problems with the FE SYNC (counter at 16378). I rebooted those two and fix the sync problem but the transmitted powers didn't improve.

Are we still having problem due to MC misalignment?

  1833   Wed Aug 5 09:48:05 2009 albertoUpdateLockingIFO Alignment

Quote:

After the mini boot fest that Jenne did today, I checked whether that fixed the overflow issues we yesterday prevented the alignemnt of the arms. 

I ran the alignment script for the arms getting 0.85 for TRX and 0.75 for TRY: low values.

After I ran the script ,C1SUSVME1 and C1SUSVME2 started having problems with the FE SYNC (counter at 16378). I rebooted those two and fix the sync problem but the transmitted powers didn't improve.

Are we still having problem due to MC misalignment?

I also noticed that the FSS transmitted power has been constantly decaying for the last 6 months. Only in the last month tt dropped by 15%. The laser power hasn't decayed as much, so it's probably not the cause.
Maybe this is one reason why lately of less power going to the IFO.
 
We call it FSS Transmission, but I guess we mean power transmitted TO the IFO, that is it measures the power reflected from reference cavity, right?
 
Still on the front of the FSS, the reflected power has dropped from -0.5 to -1.2. Here I also wonder about the reason of negative values for that.
 

See attachments

Attachment 1: 2009-08-09_FSStransPD.png
2009-08-09_FSStransPD.png
Attachment 2: 2009-08-09_FSreflPD.png
2009-08-09_FSreflPD.png
  1842   Thu Aug 6 09:33:08 2009 albertoUpdateLockingFSS Transmitted and Reflected Power Trends

 I've now also trended the MOPA output power for the last 200 days to check a possible correlation with the FSS reflected power. See attachment.

The trend shows that the laser power has decayed but it seems that the FSS reflected power has done it even faster: 30% drop in the FSS vs 7% for the MOPA in the last 60 days (attachment n.2).

Attachment 1: 2009-08-06_PSL_trends200days.png
2009-08-06_PSL_trends200days.png
Attachment 2: 2009-08-06_PSL_trends.png
2009-08-06_PSL_trends.png
  2876   Tue May 4 06:32:58 2010 albertoConfigurationPSLRC Temperature Servo Turned OFF temporarily

Quote:

 

 My attempt to passively measure the transfer function of the foam failed fantastically.

As it turns out, the room temperature fluctuations inside the PSL box reach the 1 mK/rHz noise floor of the  AD590 (or maybe the ADC) at ~1-2 mHz. Everything at higher frequencies is noise.

So to see what the foam is doing we will have to do something smarter - we need a volunteer to disable the RC temperature servo from the EPICS screen and then cycle the PSL table lights every hour in the morning.

We'll then use our knowledge of the Laplace transform to get the TF from the step responses.

 more detailed instructions needed....

  3075   Mon Jun 14 07:57:07 2010 albertoUpdateLocking40m Upgrade Optickle Model

Quote:

 

 In my calculation of the digital filters of the optical transfer functions the carrier light is resonant in coupled cavities and the sidebands are resonant in recycling cavities (provided that macroscopic lengths are chosen correctly which I assumed).

Carrier and SB (f2) shouldn't be resonant at the same time in the SRC-arms coupled cavity. No additional filtering of the GW signal is wanted.

The SRC macroscopic length is chosen to be = c / f2 - rather than = [ (n+1/2) c / (2*f2) ] - accordingly to that purpose.

  3079   Tue Jun 15 21:28:44 2010 albertoUpdateLocking40m Upgrade Optickle Model

Quote:

Quote:

 

 In my calculation of the digital filters of the optical transfer functions the carrier light is resonant in coupled cavities and the sidebands are resonant in recycling cavities (provided that macroscopic lengths are chosen correctly which I assumed).

Carrier and SB (f2) shouldn't be resonant at the same time in the SRC-arms coupled cavity. No additional filtering of the GW signal is wanted.

The SRC macroscopic length is chosen to be = c / f2 - rather than = [ (n+1/2) c / (2*f2) ] - accordingly to that purpose.

I calculated the frequency of the double cavity pole for the 40m SRC-arm coupled cavity.

w_cc = (1 + r_srm)/(1- r_srm) * w_c

where w_c is the arm cavity pole angular frequency [w_c = w_fsr * (1-r_itm * r_etm)/sqrt(r_itm*r_etm) ]

I found the pole at about 160KHz. This number coincides with what I got earlier with my optickle model configured and tuned as I said in my previous entry. See attachments for plots of transfer functions with 0 and 10pm DARM offsets, respectively.

I think  the resonance at about 20 Hz that you can see in the case with non-zero DARM offset, is due to radiation pressure. Koji suggested that I could check the hypothesis by changing either the mirrors' masses or the input power to the interferometer. When I did it frequency and qualty factor of the resonance changed, as you would expect for a radiation pressure effect.

Independently, Jan also calculated the pole frequency of the transfer function DARM / ASQ2 as we would expect it for the SRC-coupled cavity. He also found the pole at about 160KHz. I'm attaching the plot with the transfer function he calculated.
He also said that the little bump at the pole frequency is OK considering that our signal recycling cavity is not much shorter than the arms.

This gave me more confidence about my optickle model of the 40m. This is quite comforting since I used that model other times in the past to calculate several things (i.e. effects of higher unwanted harmonics from the oscillator, or, recently, the power at the ports due to the SB resonating in the arms).

I don't know anymore what Valera said that wasn't right.
Also, as he said, he set it for the carrier to be resonant in the SRC-arms couple cavity. But that is not our case.
Attachment 1: allTransferFunctions_DARMoff_0.pdf
allTransferFunctions_DARMoff_0.pdf allTransferFunctions_DARMoff_0.pdf allTransferFunctions_DARMoff_0.pdf
Attachment 2: allTransferFunctions_DARM2AS_10pmDARMoffset.pdf
allTransferFunctions_DARM2AS_10pmDARMoffset.pdf allTransferFunctions_DARM2AS_10pmDARMoffset.pdf allTransferFunctions_DARM2AS_10pmDARMoffset.pdf
Attachment 3: Jan_DARM2AS.pdf
Jan_DARM2AS.pdf
  3009   Fri May 28 13:32:01 2010 alberto, kiwamuUpdateVACvacuum work

We started a vacuum work in this morning. And still it's going on.

 

Although the last night the green team replaced a steering mirror by an 80% reflector on the PLS table, the beam axis to the MC looks fine.

The MC refl beam successfully goes into the MCrefl PD, and we can see the MC flashing as usual.

We started measuring the distance of the optics inside the vacuum chamber, found the distance from MC3 to MMT1(curved mirror) is ~13cm shorter than the design.

We moved the positions of the flat mirror after the Faraday and the MMT1, but could not track the beam very well because we did not completely lock the MC.

Now we are trying to get the lock of the MC by steering the MC mirrors.

 

P.S.

Kevin suceeded in locking it !!

  1843   Thu Aug 6 10:32:45 2009 alberto, robUpdateLockingMore PSL trends: NPRO, MOPA, FSS, PMC and MZ

 Here we trended also the PMC and the MZ. The drop in the PMC happens at the same rate as the MOPA's.

That let us think that the FSS transmitteed power has gone down because of the reference cavity progressive misalignment to the laser beam.

We need to adjust that alignment sometime.

The drop in the NPRO output power (upper row, 3rd plot: Ch10 C1:PSL_126MOPA_126MON) accompained an increase of "fuzziness" in PMCTRANSPD and both coincided in time with the day we tempoarirly removed the flap from the laser chiller's chiller (July 14 2009).

Attachment 1: 2009-08-06_PSLtrends.png
2009-08-06_PSLtrends.png
  425   Fri Apr 18 16:02:58 2008 alexUpdateSUSend station sus front-end bug fix
installed and started new susEtmx.o and susEtmy.o to fix a problem with ETMY optical lever variables.
  17224   Thu Nov 3 16:00:58 2022 alexSummaryGeneralSensoray updates

I am currently working on getting the driver reinstalled on Donatella for the sensoray. An issue keeps arising that will not allow me to run "make" successfully in the unzipped driver folder. Will continue to remedy this.

This is why there is no light showing up on the device while plugged in. The computer does see the device, but does not show its model due to the inability for it to communicate without the driver.

 

-Alex

  17239   Mon Nov 7 21:57:42 2022 alexUpdateGeneralSensoray

I have made little progress in getting the sensoray driver installed on Donatella. I have confirmed that it is indeed the reason why none of the hardware is working. I am now working through changes on a virtual machine that is running Scientific Linux to find something that may work. If no progress is made soon, I will ensure that software for a replacement video encoder is able to be installed before requesting we order one.

  17247   Tue Nov 8 21:39:12 2022 alexSummaryGeneralSensoray & SDI Video Encoder selection

I have been looking at various replacements for the sensoray, and have found that the majority of new usb video encoders don't have drivers anymore and now just work through being embedded with video-capturing software. This means that the hardware must be used with a compatible video player such as VLC or OBS. VLC can natively be run with terminal commands, and because OBS is open source, there are packages that can be downloaded to use terminal commands to control the software as well. I am not sure to what extent the usb video encoder can then be controlled with these commands, but this seems to be the easiest method so far. I will finish picking which new unit we should purchase tomorrow, and order it through JC. 

  17267   Tue Nov 15 16:34:55 2022 alexUpdateGeneralDebian with Sensoray

I have confirmed the ability to install the sensoray drivers on Debian 11 in a virtual machine environment. I will do testing with the sensoray device on this tomorrow and if all works, begin working on code for capturing images. I will then test this out on Donatella once Tega finishes installing Debian across all computers in the coming week or so. 

Attachment 1: sensoray_debian_VM_1.png
sensoray_debian_VM_1.png
  3629   Thu Sep 30 17:11:01 2010 alex iUpdateCDSDAQ system update

The frame builder is timed from the Symmetricom GPS card now, which is getting the IRIGB timecode from the freq. distribution amplifier (from the VME GPS receiver card).

I have adjusted the GPS seconds to match the real GPS time and the DTT seems to be happy: sweeping MC2 MCL filter module produces nice plot.

Test points are working on SUS.

Excitations are working on SUS.

I am leaving the frame builder running and acquiring the data.

 

Alex

 

  15482   Wed Jul 15 17:46:05 2020 anchalSummaryALSNoise budget for ALS

I started my attempt on noise budgeting of ALS by going back to how Kiwamu did it and adding as many sources as I could find up till now. This calculation is present in ALS_Noise_Budget notebook. I intend to collect data for noise sources and all future work on ALS in the ALS repo.

The noise budget runs simulink through matlab.engine inside python and remaining calculations including the pygwinc ones are done in python. Please point out any errors that I might have done here. I still need to add noise due to DFD and the ADC after it. For the residual frequency noise of AUX laser, I have currently used an upper limit of 1kHz/rt Hz at 10 Hz free-running frequency noise of an NPRO laser.

Attachment 1: ALS_nb.pdf
ALS_nb.pdf
  15496   Mon Jul 20 19:21:16 2020 anchalSummaryALSFew proposals for Voyager ALS

I've added 4 proposed schemes for implementing ALS in voyager. Major thing to figure out is what AUX laser would be and how we would compare the different PSL and AUX lasers to create an error signal for ALS. Everywhere below, 2um would mean wavelengths near 2 um including the proposed 2128nm. Since it is not fixed, I'm using a categorical name. Same is the case for 1um which actually would mean half of whatever 2 um carries.


Higher Harmonic Generation:

  • We can follow the current system of ALS with using 1.5 times PSL frequency as AUX instead of second harmonic as 1 um is strongly absorbed in Si.
  • To generate 1.5 times PSL frequency, three stages would be required.
    • SHG: Second Harmonic Generation mode matched to convert 2um to 1um. If we are instead making 2 um from 1um to start with, this stage will not be required.
    • SFG: Sum Frequency Generation mode matched to sum 2um photon and 1um photon to give 0.65 um photon.
    • DPDC: Degenerate Parametric Down Conversion mode matched to convert 0.65 um to 1.3 um (which would be 1.5 times PSL frequency).
  • To compare, we can either convert pick-off from PSL to AUX frequency by doing the above 3 stages (Scheme II).
  • Or we can just do SHG and SFG at PSL pick-off and do another SHG at AUX end (Scheme I) to compare the AUX and PSL both converted to 0.65 um (which would be 2 times AUX and 3 times PSL frequency).
  • This method would have added noise from SHG, SFG and DPDC processes along with issues to be inefficiency of conversion.

Arbitrary AUX frequency:

  • We can get away with using some standard laser near 1.5 um region directly as AUX. Most probably this would be 1550 nm.
  • What's left is to devise a method of comparing 1.5 um and 2um frequencies. Following are two possible ways I could think of:

Using a frequency comb:

  • Good stable frequency combs covering the wavelength region from 1.5 um to 2 um are available of the shelf.
  • We would beat PSL and transmitted AUX separately with the frequency comb. The two beat note frequencies would be:
    \Delta_\text{PSL} = \nu_\text{PSL} - \nu_{CEO} - m_1 \nu_\text{Rep}
    \Delta_\text{AUX} = \nu_\text{AUX} - \nu_{CEO} - m_2 \nu_\text{Rep}
  • Here, m1 and m2 represent the nearest modes (comb teeth) of frequency comb to PSL and AUX respectively.
  • Carrier Envelope Offset frequency (\nu_{CEO}) can be easily generated by using an SHG crystal in front of the Frequency comb. This step is not really required since most of the modern frequency combs now comb with inbuilt zero \nu_{CEO} stabilization.
  • Mixing above beatnotes with \nu_{CEO} would remove \nu_{CEO} from them along with any noise associated with \nu_{CEO}.
  • Further, a Direct Digital Synthesis IC is required to multiply the AUX side RF signal by m1/m2. This finally makes the two RF signals to be:
    \nu_{A} = \nu_\text{PSL} - m_1 \nu_{Rep}
    \nu_{B} = \frac{m_1}{m_2}\nu_\text{AUX} - m_1 \nu_{Rep}
  • Which on mixing would give desired error signal for DFD as :
    \nu_\text{PSL} - \frac{m_1}{m_2}\nu_\text{AUX}
  • This method is described in Stenger et al. PRL. 88, 073601 and is useful in comparing two different optical frequencies with a frequency comb with effective cancellation of all noise due to the frequency comb itself. Only extra noise is from the DDS IC which is minimal.
  • This method, however, might be an overkill and expensive. But in case (for whatever reason) we want to send in another AUX at another frequency down the 40m cavity, this method allows the same setup to be used for multiple AUX frequencies at once.

Using a Transfer Cavity:

  • We can make another more easily controlled and higher finesse cavity with a PZT actuator on one of the mirrors.
  • In the schematic, I have imagined it has a triangular cavity with a back end mirror driven by PZT.
  • Shining PSL from one side of the transfer cavity and employing the usual PDH, we can lock the cavity to PSL.
  • This lock would require to be strong and wide bandwidth. If PZT can't provide enough bandwidth, we can also put an EOM inside the cavity! (See this poster from Simon group at UChicago)
  • Another laser at AUX frequency, called AUX2 would be sent from the other side of the cavity and usual PDH is employed to lock AUX2 to the transfer cavity.
  • So clearly, this cavity also requires coatings and coarse length such that it is resonant with both PSL and AUX frequencies simultaneously.
  • And, the FSS for AUX2 needs to be good and high bandwidth as well.
  • The transmitted AUX2 from the transfer cavity now would carry stability of PSL at the frequency of AUX and can be directly beaten with transmitted AUX from the 40m cavity to generate an error signal for DFD.
  • I believe this is a more doable and cheaper option. Even if we want to do a frequency comb scheme, this could be a precursor to it.

_________________________

EditTue Jul 21 17:24:09 2020: (Jamie's suggestion)

Using Mode Cleaner cavity as Transfer Cavity:

  • If we coat the mode cleaner cavity mirrors appropriately, we can use it to lock AUX2 laser (mentioned above).
  • This will get rid of all extra optics. The only requirement is for FSS to be good on AUX2 to transfer PSL (MC) stability to AUX frequency.
  • I've added suggested schematic for this scheme at the bottom.

 

Attachment 1: VoyagerALSSchemes.pdf
VoyagerALSSchemes.pdf VoyagerALSSchemes.pdf VoyagerALSSchemes.pdf VoyagerALSSchemes.pdf VoyagerALSSchemes.pdf
  15587   Sat Sep 19 23:59:22 2020 anchalSummaryALSALS noise budget update

Setting the record straight

I found out an error I did in copying some control model values from Kiwamu's matlab code. On fixing those, we get a considerably reduced amount of total noise. However, there was still an unstable region around the unity gain frequency because of a very small phase margin. Attachment 3 shows the noise budget, ALS open-loop transfer function, and AUX PDH open-loop transfer function with ALS disengaged. Attachment 4 is the yaml file containing all required zpk values for the control model used. Note that the noise budget shows out-of-loop residual arm length fluctuations with respect to PSL frequency. The RMS curve on this plot is integrated for the shown frequency region.


Trying to fix the unstable region

Adding two more poles at 100 Hz in the ALS digital filter seems to work in making the ALS loop stable everywhere and additionally provides a steeper roll-off after 100 Hz. Attachment 1 shows the noise budget, ALS open-loop transfer function, and AUX PDH open-loop transfer function with ALS disengaged. Attachment 2 is the yaml file containing all required zpk values for the control model used. Note that the noise budget shows out-of-loop residual arm length fluctuations with respect to PSL frequency. The RMS curve on this plot is integrated for the shown frequency region.

But is it really more stable?

  • I tried to think about it from different aspects. One thing is sure that  1+G_{OL} remains greater than 1 in all of the frequency region plotted for. This is also evident in the common-mode to residual noise transfer function which shows no oscillation peaks and is a clean mirror image of the open-loop transfer function (See Attachment 1, page 2).
  • Another way is to look for the phase margin. This is a little controversial way of checking stability. For clarity, the open-loop transfer function I'm plotting does not contain the '-1' feedback in it. So the bad phase value at unity gain frequency is -180 degrees (or 180 degrees) for us. I've taken the difference from the closest side and got 76.2 degrees of phase margin.
  • Another way I checked was by plotting a Nyquist plot for the open-loop transfer function. It is said that if the contour does not encircle the point '-1' in the real axis, then the loop would be stable even if the f_{180} < f_{UGF} where f_{180} is the frequency where phase lag becomes -180 degrees at the lowest frequency. For us, f_{180} is at 1 Hz because of the test mass actuator pole. But I have verified that the Nyquist contour of the open-loop transfer function does not encircle '-1' point. I have not uploaded the Nyquist plot as it is not straight forward to plot. Because of large dc gain, it covers a large region and one needs to zoom in and out to properly follow what the contour is really doing. I didn't get time to make insets for it.

Is this close to reality?

For that, we'll have to take present noise source estimates but Gautum vaguely confirmed that this looked more realistic now 'shape-wise'. If I remember correctly, he mentioned that we currently can achieve 8 pm of residual rms motion in the arm cavity with respect to the PSL frequency. So we might be overestimating our loop's capability or underestimating some noise source. More feedback on this welcome and required.


Additional Info:

The code used to calculate the transfer functions and plot them is in the repo 40m/ALS/noiseBudget

Attachment 5 here shows a block diagram for the control loop model used. Output port 'Res_Disp' is used for referring all the noise sources at the residual arm length fluctuation in the noise budget. The open-loop transfer function for ALS is calculated by -(ALS_DAC->ALS_Out1 / ALS_DAC->ALS_Out2) (removing the -1 negative feedback by putting in the negative sign.) While the AUX PDH open-loop transfer function is calculated by python controls package with simple series cascading of all the loop elements.

 

 

Attachment 1: ALS_nb_ExtraPoles.pdf
ALS_nb_ExtraPoles.pdf ALS_nb_ExtraPoles.pdf ALS_nb_ExtraPoles.pdf
Attachment 2: ALS_controls.yaml
# -----------------------------------------------------------------------------
# AUX
# -----------------------------------------------------------------------------
## Cavity Pole
C_AUX:
  p: 1.8883e+04
  k: 1.1865e+05

H_AUX:
  z: 0
... 109 more lines ...
Attachment 3: ALS_nb_Kiwamus_Values.pdf
ALS_nb_Kiwamus_Values.pdf ALS_nb_Kiwamus_Values.pdf ALS_nb_Kiwamus_Values.pdf
Attachment 4: ALS_controls_Kiwamus_Values.yaml
# -----------------------------------------------------------------------------
# AUX
# -----------------------------------------------------------------------------
## Cavity Pole
C_AUX:
  p: 1.8883e+04
  k: 1.1865e+05

H_AUX:
  z: 0
... 107 more lines ...
Attachment 5: ALS_simulink_model.svg
ALS_simulink_model.svg
  15593   Tue Sep 22 00:14:43 2020 anchalSummaryALSALS noise budget update

This is not a reply to comments given to the last post; Still working on incorporating those suggestions.


Trying out a better filter from scratch

Rana suggested looking first at what needs to be suppressed and then create a filter suited for the noise from scratch. So I discarded all earlier poles and zeros and just kept the resonant gains in the digital filter. With that, I found that all we need is three poles at 1 Hz and a gain of 8.1e5 gives the lowest RMS noise value I could get.

Now there can be some practical reasons unknown to me because of which this filter is not possible, but I just wanted to put it here as I'll add the actual noise spectra into this model now.


Few questions:

  • What anti-aliasing filters are used in ALS?
  • Is the digital delay fixed to a constant upper limit or is it left to change as per filters? I have already used a 470 us delay (modeled with Pade 4th order approximation).
  • I could not find a good place where channel names are listed with corresponding meaning. Where can I find them?
  • Is there a channel which keeps a record of lock status? In short, how do I find the in-lock times
Attachment 1: ALS_NoiseBudgetUpdate.pdf
ALS_NoiseBudgetUpdate.pdf ALS_NoiseBudgetUpdate.pdf ALS_NoiseBudgetUpdate.pdf
Attachment 2: ALS_controls.yaml
# -----------------------------------------------------------------------------
# AUX
# -----------------------------------------------------------------------------
## Cavity Pole
C_AUX:
  p: 1.8883e+04
  k: 1.1865e+05

H_AUX:
  z: 0
... 106 more lines ...
  15601   Wed Sep 23 11:13:49 2020 anchalSummaryALSALS noise budget update

Yes, that loop was unstable. I started using the time domain response to check for the stability of loops now. I have been able to improve the filter slightly with more suppression below 20 Hz but still poor phase margin as before. This removes the lower frequency region bump due to seismic noise. The RMS noise improved only slightly with the bump near UGF still the main contributor to the noise.


For inclusion of real spectra, time delays and the anti-aliasing filters, I still need some more information.

Few questions:

  • What anti-aliasing filters are used in ALS?
  • Is the digital delay fixed to a constant upper limit or is it left to change as per filters? I have already used a 470 us delay (modeled with Pade 4th order approximation).
  • I could not find a good place where channel names are listed with corresponding meaning. Where can I find them?
  • Is there a channel which keeps record of lock status? In short, how do I find the in-lock times

Additional Info:

The code used to calculate the transfer functions and plot them is in the repo 40m/ALS/noiseBudget

Related Elog post with more details: 40m/15587

Attachment 1: ALS_NoiseBudgetUpdate.pdf
ALS_NoiseBudgetUpdate.pdf ALS_NoiseBudgetUpdate.pdf ALS_NoiseBudgetUpdate.pdf ALS_NoiseBudgetUpdate.pdf
Attachment 2: ALS_controls.yaml
# -----------------------------------------------------------------------------
# AUX
# -----------------------------------------------------------------------------
## Cavity Pole
C_AUX:
  p: 1.8883e+04
  k: 1.1865e+05

H_AUX:
  z: 0
... 113 more lines ...
  15622   Fri Oct 9 18:32:14 2020 anchalSummaryALSALS noise budget update - Updated AUX PDH Loop values

The only two PZT Phase modulation transfer function measurements I could find are 40m/15206 and 40m/12077. Both these measurements were made to find a good modulation frequency and do not go below 50 kHz. So I don't think these will help us. We'll have to do a frequency transfer function measurement at lower frequencies.
I'm still looking for ALS PDH loop measurements to verify the model. I found this 40m/15059 but it is only near the UGF. The UGF measured here though looks very similar to the model prediction. A bit older measurement in 2017 was this 40m/13238 where I assume by ALS OLTF gautum meant the green laser PDH OLTF. It had similar UGF but the model I have has more phase lag, probably because of a 31.5 kHz pole which comes at U7 through the input low pass coupling through R28, C20 and R29 (See D1400293)

If the green laser is not being used, can I go and take some of these measurements myself?

  15626   Wed Oct 14 17:03:55 2020 anchalSummaryALSALS noise budget update - Added whitening filter for ADC

Koji recommended that I can add whitening filters to suppress ADC noise easily. I added a filter before ADC in ALS loop with 4 zeros at 1.5 Hz and 4 poles at 100 Hz and added a reversed filter in the digital filter of ALS. This did not change the performance of the loop but significantly reduced the contribution of ADC noise above 1 Hz. One can see ALS_controls.yaml for the filter description. Please let me know if this does not make sense or there is something that I have overlooked.

Now, the dominant noise source is DFD noise below 100 Hz and green laser frequency noise above that. For DFD noise, I used data dating back to Kiwamu's paper. The noise contribution from DFD in the model is lower than the latest measured ALS noise budget post on elog. I'll look further into design details and noise of DFD.


Code, data, and schematics

Attachment 1: ALS_NoiseBudgetUpdate.pdf
ALS_NoiseBudgetUpdate.pdf ALS_NoiseBudgetUpdate.pdf ALS_NoiseBudgetUpdate.pdf ALS_NoiseBudgetUpdate.pdf ALS_NoiseBudgetUpdate.pdf
ELOG V3.1.3-