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  40m Log, Page 201 of 341  Not logged in ELOG logo
ID Date Authordown Type Category Subject
  9521   Mon Jan 6 18:32:17 2014 RANAUpdateIOOMC1/3 kicked this morning at 8:30

 The trend shows a big jolt to the MC1/3 pointing this morning at 8:30.

Was anyone working anywhere near there today? There is no elog.

If not, we will have to put a 'no janitor' sign on all of the 40m doors permanently to prevent mops misaligning our interferometer.

Attachment 1: kicked.png
  9666   Mon Feb 24 17:59:31 2014 RANAUpdateElectronicsMeasured REFL165 demod board


 Demod boards should be at 90 deg, not 82.7 or 12 or yellow or ****. We should re-inject the RF and then set the D Phase in the filter module to make the signals orthogonal. 165 is a challenging one to get right, but its worth it since the signals are close to degenerate already.

  11138   Thu Mar 12 19:54:31 2015 Q UpdateLSCHow to: PRY

Q doesn't like elogging, but he sent me this nice detailed email, so I'm copying it into the log:

I’ve locked the power recycled Y arm numerous times today, to try and find a usable AO recipe for the full locking.

Really, the “only" things that I think are different are the DC gain and pole frequency of the REFL11 CARM signal. The pole frequency can be simulated in the CM board (through the 1.4k:80 zero/pole pair), and the DC gain can be changed by changing the REFL1 gain on the CM board. 
The crossover frequency only depends on the relative gains of the digital and AO path, which is independent of these two factors, since they’re common to both. So, if we scale the common part appropriately, the same AO crossover procedure should work. I think.
So, concretely, I set up the gain in the CM_SLOW input filter so that 1x CM_SLOW_OUT -> CARM in the input matrix matched the ~120Hz UGF that we get with a gain 6 or 7 in the CARM FM. The REFL1 gain on the CM board was 0dB. 
I then normalized the signal by 1/Trmax. (i.e. I had TRY of ~3.3, so I put 0.30 in the normalization matrix), so that at full resonance, the slope should bee the same as with no normalizing. 
Then, with the Yarm locked on ALS through 1xCARM_A, PRY locked on REFL165, and at zero arm offset (TRY~3.3), I did the following
  • Transition the digital loop from 1xCARM_A (ALS) to 1xCARM_B (1xCM_SLOW_OUT)
  • Turn on CM_SLOW FM1 (whitening)
  • With CM board gains: 0db REFL1, 0dB AO, negative polarity, MC In2 gain=-32dB, turn on In2 on MC servo
  • Slowly ramp up MC In2 gain to -10dB (this starts pulling up the phase bubble of the loop)
  • Turn on the 300:80 filter in the CM_SLOW input filter (this provides a f^-2 slope around the crossover region)
  • Go from [AO,REFL1]=[-10,0] to [-4,+6] by stepping them together. (This brings you to a UGF of a few hundred Hz with tons of phase margin)
  • At this point, up the REFL1 gain to +12 or so. Turn on the :300 FM in the CM_SLOW input filter (This rolls off the digital part of the loop, makes the violin filters stop interfering with the shape)
  • UGF is now ~1kHz. Boosts can be turned on once the gain is ramped up high enough. 
The moral of the story is: if you set the REFL1 gain such that a +1.0 element in the input matrix gives you about the right UGF, then the above recipe should work, just with the REFL1 gains offset by your starting gain. (I suppose if you need a minus sign in the input matrix, that just means that the AO polarity needs to change too)
Every time the REFL1 gain is changed, the electronic offset changes, so I had to keep an eye on POY as a DC out-of-loop sensor and adjust the CM board voltage offset. For the full IFO, I think REFL55 would work for this. However, I hope that, since less REFL1 gain will be needed for the PRFPMI, the changes will be smaller….
Lastly, I think it’s good to keep the digital UGF at around 120, because the crossover steals some gain below the UGF, and you want to have some gain margin there. Turning off boosts may help with this too; I did all of this with all the normal CARM boosts on. 
Hope this made some sense!
  12220   Tue Jun 28 16:09:41 2016 PrafulUpdateGeneral40m Summary Pages

Set up gwsumm on optimus and generated summary pages from both L1 and C1 data. Still a few manual steps need to be taken during generation, not fully automated due to some network/username issues. nds2 now working from optimus after restarting nds2 server.

  12221   Tue Jun 28 16:10:49 2016 PrafulUpdateGeneralBluebird Microphones

Found 1 out of 2 bluebird microphones in the 40m.

  12222   Tue Jun 28 17:11:27 2016 PrafulUpdateGeneralEM172 Microphones

Found 60 EM172 microphones. Previous elog with details: 7777.

  12239   Fri Jul 1 17:51:28 2016 PrafulSummaryElectronicsReplacing DIMM on Optimus

There has been an ongoing memory error in optimus with the following messages:

controls@optimus|~ >
Message from syslogd@optimus at Jun 30 14:57:48 ...
 kernel:[1292439.705127] [Hardware Error]: Corrected error, no action required.

Message from syslogd@optimus at Jun 30 14:57:48 ...
 kernel:[1292439.705174] [Hardware Error]: CPU:24 (10:4:2) MC4_STATUS[Over|CE|MiscV|-|AddrV|CECC]: 0xdc04410032080a13

Message from syslogd@optimus at Jun 30 14:57:48 ...
 kernel:[1292439.705237] [Hardware Error]: MC4_ADDR: 0x0000001ad2bd06d0

Message from syslogd@optimus at Jun 30 14:57:48 ...
 kernel:[1292439.705264] [Hardware Error]: MC4 Error (node 6): DRAM ECC error detected on the NB.

Message from syslogd@optimus at Jun 30 14:57:48 ...
 kernel:[1292439.705323] [Hardware Error]: cache level: L3/GEN, mem/io: MEM, mem-tx: RD, part-proc: RES (no timeout)

Optimus is a Sun Fire X4600 M2 Split-Plane server. Based on this message, the issue seems to be in memory controller (MC) 6, chip set row (csrow) 7, channel 0. I got this same result again after installing edac-utils and running edac-util -v, which gave me:

mc6: csrow7: mc#6csrow#7channel#0: 287 Corrected Errors 

and said that all other DIMMs were working fine with 0 errors. Each MC has 4 csrows numbered 4-7. I shut off optimus and checked inside and found that it consists of 8 CPU slots lined up horizontally, each with 4 DIMMs stacked vertically and 4 empty DIMM slots beneath. I'm thinking that each of the 8 CPU slots has its own memory controller (0-7) and that the csrow corresponds to the position in the vertical stack, with csrow 7 being the topmost DIMM in the stack. This would mean that MC 6, csrow 7 would be the 7th memory controller, topmost DIMM. The channel would then correspond to which one of the DIMMs in the pair is faulty although if the DIMM was replaced, both channels 0 and 1 would be switched out. Here are some sources that I used:




I'll find the exact part needed to replace soon.

  12244   Tue Jul 5 18:44:39 2016 PrafulUpdateComputer Scripts / ProgramsWorking 40m Summary Pages

After hardware errors prevented me from using optimus, I switched my generation of summary pages back to the clusters. A day's worth of data is still too much to process using one computer, but I have successfully made summary pages for a timescales of a couple of hours on this site: https://ldas-jobs.ligo.caltech.edu/~praful.vasireddy/


Currently, I'm working on learning the current plot-generation code so that it can eventually be modified to include an interactive component (e.g., hovering over a point on a timeseries would display the GPS time). Also, the 40m summary pages have been down for the past 3 weeks but should be up and working soon as the clusters are now alive.

  12252   Wed Jul 6 11:02:41 2016 PrafulUpdateComputer Scripts / ProgramsVMon Tab on Summary Pages

I've added a new tab for VMon under the SUS parent tab. I'm still working out the scale and units, but let me know if you think this is a useful addition. Here's a link to my summary page that has this tab: https://ldas-jobs.ligo.caltech.edu/~praful.vasireddy/1151193617-1151193917/sus/vmon/

I'll have another tab with VMon BLRMS up soon.

Also, the main summary pages should be back online soon after Max fixed a bug. I'll try to add the SUS/VMon tab to the main pages as well.

  12254   Wed Jul 6 17:17:22 2016 PrafulUpdateComputer Scripts / ProgramsNew Tabs and Working Summary Pages

The main C1 summary pages are back online now thanks to Max and Duncan, with a gap in pages from June 8th to July 4th. Also, I've added my new VMon and Sensors tabs to the SUS parent tab on the main pages. These new tabs are now up and running on the July 7th summary page.

Here's a link to the main nodus pages with the new tabs: https://nodus.ligo.caltech.edu:30889/detcharsummary/day/20160707/sus/vmon/

And another to my ldas page with the tabs implemented: https://ldas-jobs.ligo.caltech.edu/~praful.vasireddy/1150848017-1150848317/sus/vmon/

Let me know if you have any suggestions or see anything wrong with these additions, I'm still working on getting the scales to be right for all graphs.

  12275   Fri Jul 8 15:44:07 2016 PrafulUpdateElectronicsReplacing DIMM on Optimus

Optimus' memory errors are back so I found the exact DIMM model needed to replace: http://www.ebay.com/itm/Lot-of-10-Samsung-4GB-2Rx4-PC2-5300P-555-12-L0-M393T5160QZA-CE6-ECC-Memory-/201604698112?hash=item2ef0939000:g:EgEAAOSwqBJXWFZh I'm not sure what website would be the best for buying new DIMMs but this is the part we need: Samsung 4GB 2Rx4 PC2-5300P-555-12-L0 M393T5160QZA-CE6.

  12277   Fri Jul 8 19:33:16 2016 PrafulUpdateComputer Scripts / ProgramsMEDM Tab on Summary Pages

A new MEDM tab has been added to the summary pages (https://nodus.ligo.caltech.edu:30889/detcharsummary/day/20160708/medm/), although some of the screens are not updated when /cvs/cds/projects/statScreen/cronjob.sh is run. In /cvs/cds/projects/statScreen/log.txt, the following error is given for those files: import: unable to read X window image `0x20011f': Resource temporarily unavailable @ error/xwindow.c/XImportImage/5027. If anyone has seen this error before or knows how to fix it, please let me know.

In the meantime, I'll be working on creating an archive of MEDM screens for every hour to be displayed on the summary pages.

  12280   Fri Jul 8 21:15:03 2016 PrafulUpdateComputer Scripts / ProgramsMEDM Tab on Summary Pages

Thanks! Yes, only the screens that are not updated when the script is executed show this error. I'll try to keep debugging over the weekend.


Very nice!

Some of the screens are up-to-date, and some are not. Are the errors associated with the screens that failed to get updated?


  12329   Mon Jul 25 10:54:55 2016 PrafulUpdateComputer Scripts / ProgramsFinished MEDM Tab on Summary Pages

The MEDM screen capture tab is now working and up on the summary pages: https://nodus.ligo.caltech.edu:30889/detcharsummary/day/20160725/medm/

Please let me know if you have any suggestions or notice any issues.

  12344   Wed Jul 27 22:42:00 2016 PrafulUpdateElectronicsEM172 Amplifier

I recreated Den's microphone amplifier circuit on a solderless breadboard to test it and make sure it does what it's supposed to. So far it seems like everything is working- I'll do some testing tomorrow to see what the amplified output is like for some test noises. Here's the circuit diagram that Den made (his elog as well https://nodus.ligo.caltech.edu:8081/40m/6651):

I'm not sure why he set up the circuit the way he did- he has pin 7 grounded and pin 4 going to +12V while in the datasheet for the opamp (http://cds.linear.com/docs/en/datasheet/1677fa.pdf), pin 7 goes to positive voltage and pin 4 goes to negative voltage. There's some other strange things about the circuit that I don't really understand, such as the motivation for using no negative voltage source, but for now I'm going to stick with Den's design and then make some modifications after I have things working and a better understanding of the problem.

Here's my current plan:

-Make sure Den's amplifier works, test it out and make changes if necessary

-Make multiple amplifier circuits on soldering breadboard

-Either make a new amplifier box or reuse Den's old box depending on how many changes I make to the original circuit

-Solder EM172s to BNC connectors, set them up around the floor suspended

-Get the amplifier box hooked up, set up some data channels for the acoustic noise

-Add new acoustic noise tab to the summary pages


Den also mentioned that he wanted me to measure the coupling of acoustic noise to DARM.

  12356   Fri Jul 29 19:37:43 2016 PrafulUpdateElectronicsMic Amplifier

I set up a test inverting amplifier circuit using the LT1677 opamp:

The input signal was a sine wave from the function generator with peak to peak amplitude of 20 mV and a frequency of 500 Hz and I received an output with an amplitude of about 670 mV and the same 500 Hz frequency, agreeing with the expected gain of -332k/10k = -33.2:

So now I know that the LT1677 works as expected with a negative supply voltage. My issue with Den's original circuit is that I was getting some clipping on the input to pin 2, which didn't seem to be due to any of the capacitors- I switched them all out. I set up a modified version of Den's circuit using a negative voltage input to see if I could fix this clipping issue:

I might reduce the input voltages to +5V and -5V- I couldn't get my inverting amp circuit to work with +12V and -12V. I'll start testing this new circuit next week and start setting up some amplifier boxes.

Attachment 1: inverting_amp.pdf
Attachment 4: inverting_amp.png
Attachment 6: new_amp_scheme.png
  12369   Wed Aug 3 18:53:46 2016 PrafulUpdateElectronicsMic Amplifier

I could not get Den's circuit to work for some reason with microphone input, so I decided to try to use another circuit I found online. I made some modifications to this circuit and made a schematic:

Using this circuit, I have been able to amplify microphone input and adjust my passband. Currently, this circuit has a high-pass at about 7 Hz and a low-pass at about 23 kHz. I tested the microphone using Audacity, an audio testing program. I produced various sine waves at different frequencies using this program and confirmed that my passband was working as intended. I also used a function generator to ensure that the gain fell off at the cutoff frequencies. Finally, I measured the frequency response of my amplifier circuit:


A text file with the parameters of my frequency response and the raw data is attached as well.

These results are encouraging but I wanted to get some feedback on this new circuit before continuing. This circuit seems to do everything that Den's circuit did but in this case I have a better understanding of the functions of the circuit elements and it is slightly simpler.

Attachment 2: ampTest_03-08-2016_180448.pdf
Attachment 3: ampTest_03-08-2016_180448.txt
# SR785 Measurement - Timestamp: Aug 03 2016 - 18:04:48
#---------- Measurement Setup ------------
# Start frequency (Hz) = 1.000000
# Stop frequency (Hz) = 102400.000000
# Number of frequency points = 800
# Excitation amplitude (mV) = 50.000000
# Settling cycles = 1
# Integration cycles = 5
#---------- Measurement Parameters ----------
# Measurement Group:  "Swept Sine" "Swept Sine"
... 820 more lines ...
Attachment 4: simple_amp.png
  12374   Thu Aug 4 17:29:17 2016 PrafulUpdateGeneralGuralp Cable

The Guralp cable has been pulled and put in the corner to the left of the water cooler:


Ben came by today before the cable had been pulled but he said he'll be back tomorrow.

  12380   Fri Aug 5 16:25:08 2016 PrafulUpdateElectronicsMic Amplifier

I took the spectrum of an EM172 connected to my amplifier inside and outside a large box filled with foam layers:

I also made a diagram with my plan for the microphone amplifier boxes. This is a bottom view:

The dimensions I got from this box: http://www.digikey.com/product-detail/en/bud-industries/CU-4472/377-1476-ND/696705

This seemed like the size I was looking for and it has a mounting flange that could make suspending it easier. Let me know if you have any suggestions.

I'll be doing a Huddle test next week to get a better idea of the noise floor and well as starting construction of the circuits to go inside the boxes and the boxes themselves.

  12387   Tue Aug 9 15:50:30 2016 PrafulUpdateGeneralGuralp Cable

The Guralp cable has been reconnected and powered after having the connector changed out.

  12395   Wed Aug 10 18:10:26 2016 PrafulUpdateElectronicsMic Amplifier

I set up 3 of my circuits in the interferometer near MC2 to do a huddle test. I have the signals from my microphones going into C1:PEM-MIC_1_IN1, C1:PEM-MIC_2_IN1, and C1:PEM-MIC_3_IN1. These are channels C17-C19. Here are some pictures of my setup:

I'll likely be collecting data from this for a couple of hours. Please don't touch it for now- it should be gone soon. There are some wires running along the floor near MC2 as well.

  12400   Thu Aug 11 11:51:38 2016 PrafulUpdateComputer Scripts / ProgramsSummary Pages

The summary pages have been updated with the new naming seismometer channel naming conventions. Here's a link to them working on my own page: https://ldas-jobs.ligo.caltech.edu/~praful.vasireddy/1154908817-1154909717/pem/seismic/

Let me know if the actual pages aren't working when they come back online or if there's something that needs to be changed.

  12402   Thu Aug 11 17:30:05 2016 PrafulUpdateElectronicsMic Amplifier

The results of my first huddle test were not so good- one of the signals did not match the other two very well- so I changed the setup so that the mics would be better oriented to receive the same signal. Pictures of the new setup are attached.

I also noticed some problems with one of my microphones so I soldered a new mic to bnc and switched it out. Just judging from Dataviewer, the signals seem to be more similar now. I'll be taking data for another few hours to confirm.

  12405   Fri Aug 12 19:13:25 2016 PrafulUpdateElectronicsMic Self Noise

I used the Wiener filtering method described by Ignacio and Jessica (https://dcc.ligo.org/DocDB/0119/T1500195/002/SURF_Final.pdf and https://dcc.ligo.org/public/0119/T1500194/001/Final_Report.pdf) and got the following results:




The channel readout has a gain of 0.0005 and the ADC is 16-bit and operates are 20V. The channel also reads the data out in Pa. I therefore had to multiply the timeseries by 1/0.0005=2000 to get it in units of counts and then by (20 Volts)/(2^16 counts) to get back to the original signal in volts. The PSDs were generated after doing this calibration. I also squared, integrated, and square rooted the PSDs to get an RMS voltage for each microphone as a sanity check:

Mic 1: 0.00036 V

Mic 2: 0.00023 V

Mic 3: 0.00028 V

These values seem reasonable given that the timeseries look like this:




Attachment 4: mic1_wiener.pdf
Attachment 5: mic2_wiener.pdf
Attachment 6: mic3_wiener.pdf
Attachment 7: timeseries_elog.pdf
  12408   Mon Aug 15 12:23:56 2016 PrafulUpdatePEMMic Self Noise

I didn't have a separate training set and data set, so I think that's why the graphs came out looking too good. The units on the graphs are also incorrect, I was interpreting PSD as ASD. I haven't been able to get my Wiener filtering code working well- I get unreasonable subtractions like the noise being larger than the unfiltered signal, so Eric showed me this frequency-dependent calculation described here: https://dcc.ligo.org/LIGO-P990002

This seems to be working well so far:




Here's all the plots on one figure:


Let me know if this looks believable.


Seems to good to be true. Maybe you're over fitting? Please put all the traces on one plot and let us know how you do the parameter setting. You should use half the data for training the filter and the second half for doing the subtraction.


Attachment 1: freq1.png
Attachment 2: freq1.pdf
Attachment 4: freq2.pdf
Attachment 6: freq3.pdf
Attachment 8: frequency_dependent.pdf
  12427   Sun Aug 21 17:21:22 2016 PrafulUpdateElectronicsProblems with PCB Circuit

For the past week, I've been trying to make a soldered amplifier circuit to use in a prototype box, However, I've been running into this same issue. The circuit, pictured below, works fine on a solderless breadboard.


When I amplify a sine wave, I get a clean looking result at the output on the solderless breadboard:

However, on my soldered circuit, if I turn up the negative voltage supply from the power supply past about -12.5V (the target is -15V), I get a strange signal that Gautam suggested looks like some kind of discharging.

At -12.3 V (soldered breadboard):

At -15.0 V (soldered breadboard):

The signal is much noisier. Zooming in on this second signal, this pattern appears:

This pattern is also showing up even when there is no input from the function generator and the circuit is just given a voltage supply of +/- 15V:

I have tried switching out both the positive and negative voltage regulators, the opamp, and remaking and resoldering the entire circuit but I'm still getting the same signal, which is absent from the solderless circuit. This output was produced with a function generator, so I have also ruled out the microphone as a source of this extra noise. The voltage dependence of this problem made me think it was the voltage regulator, but I've switched out the voltage regulator multiple times and it's still showing up. I'm not sure why this signal appears only as the negative voltage supply is increased- there is no problem with increasing the positive input voltage. Please let me know if you have any ideas as to what component or issue could be causing this.

Attachment 2: simple_amp.png
Attachment 4: clean.jpg
Attachment 5: -12.jpg
Attachment 6: -15.jpg
Attachment 7: pat1.jpg
Attachment 8: pat2.jpg
Attachment 10: bad.jpg
Attachment 11: pattern.jpg
Attachment 12: pattern2.jpg
Attachment 13: pat2.jpg
Attachment 16: patternzoomed.jpg
  12431   Mon Aug 22 18:35:16 2016 PrafulUpdatePEMthe lab temp is up

The temperature is decreasing slowly but is still above 24 C.



The IFO room temp is up a bit and it is coming down. The out side temp is not really high.


Attachment 1: temp_plot.png
Attachment 3: temp_plot.png
  12433   Tue Aug 23 17:05:20 2016 PrafulUpdateElectronicsSoldered Circuit Working

I remade another soldered circuit, adding extra 100uF electrolytic bypass capacitors at the input and output of the voltage regulator and ensuring that every grounded component now has its own path to ground rather than going through other elements. This circuit now seems to be working just like the solderless circuit. Attached is the transfer function of the soldered circuit, which matches with the result from the solderless circuit.




Here are both on the same figure- they are about overlapping but are slightly different if you zoom in enough.


I have also attached a new version of the circuit schematic to reflect the changes and to make the physical layout more clear.


My next step for these last few days this summer will be designing a PCB using Altium. I've emailed Varun about how to use Altium on the iMac but he hasn't responded. If anyone else knows how to use the software, please let me know.

Attachment 2: soldered_transfer_function.png
Attachment 3: soldered_transfer_function.png
Attachment 5: solderless_transfer_function.png
Attachment 6: both_transfer.png
Attachment 8: both_transfer.png
Attachment 10: simple_ampv2.pdf
  12436   Wed Aug 24 14:11:09 2016 PrafulUpdateElectronicsMicrophone Testing

I added an EM172 to my soldered circuit and it seems to be working so far. I have taken a spectra using the EM172 in ambient noise in the control room as well as in white noise from Audacity. My computer's speakers are not very good so the white noise results aren't great but this was mainly to confirm that the microphone is actually working.


Attachment 1: white_v_ambient.png
Attachment 2: white_v_ambient.pdf
Attachment 3: white_v_ambient.pdf
  12437   Wed Aug 24 14:44:33 2016 PrafulUpdateElectronicsDecoupling capacitor 101

Do these look good for the ceramic capacitors? We're running low.



What I suggested was:
- For most cases, power decoupling capacitors for the regulators should be ~100nF "high-K ceramic capacitors" + 47uF~100uF "electrolytic capacitors".
- For opamps, 100nF high-K ceramic should be fine, but you should consult with datasheets.
- Usually, you don't need to use tantalum capacitors for this purpose unless specified.
- Don't use film capacitors for power decoupling.

79XXs are less stable compared to 78XXs, and tend to become unstable depending on the load capacitance.
One should consult with the datasheet of each chip in order to know the proper capacitors values.
But also, you may need to tweak the capacitor value when necessary. Above recipe works most of the case.


  12439   Wed Aug 24 23:47:30 2016 PrafulUpdateElectronicsFinished Prototype Box

Gautam helped me drill holes in a metal box and I set up my circuit inside. Everything seems to be working so far. Tomorrow I'll be suspending the box near the PSL and setting up a data channel. Attached are some pictures of the box- sorry some of the angles turned out weird.

Attachment 1: out1.pdf
Attachment 2: out2.pdf
Attachment 3: out3.pdf
Attachment 4: in1.pdf
Attachment 5: in2.pdf
  12442   Thu Aug 25 19:03:56 2016 PrafulUpdateElectronicsAcoustic Tab and Amp Suspension

My box has been suspended in the PSL using surgical tubing, and it has been connected to C1:PEM-MIC_1 (C17) with a BNC. I made a braided power cable as well but it turned out to be slightly too short... Once this is fixed, everything should be ready and we can see if it's working correctly. I also set up a new tab on the summary pages for this channel:


This data is back from when I had my solderless breadboard running near MC2. I'll add this tab to the real pages once the box is working (which could be a while since I'm gone for a month). Let me know if you see any issues with either the tab or the box/cables.

  12463   Thu Sep 1 17:25:02 2016 PrafulUpdateElectronicsAcoustic Tab and Amp Suspension

I'll add a picture of the installation when I get back to campus and finish hooking up the power cable. I haven't added this channel to the actual pages yet because there's not any data right now- the box is still unpowered because my braided power cable wasn't long enough. I just changed the format of the spectrum to ASD and added spectrograms. Here's how the tab looks now: https://ldas-jobs.ligo.caltech.edu/~praful.vasireddy/1155014117-1155015017/pem/acoustic/

Let me know if there's anything else to change.

  1. add photo of installation
  2. no more secret personal pages! put channels into the actual pages that we look at
  3. make it ASD instead of PSD, same as the other channels
  4. add specgram (whitened and not)

My box has been suspended in the PSL using surgical tubing, and it has been connected to C1:PEM-MIC_1 (C17) with a BNC. I made a braided power cable as well but it turned out to be slightly too short... Once this is fixed, everything should be ready and we can see if it's working correctly. I also set up a new tab on the summary pages for this channel:


This data is back from when I had my solderless breadboard running near MC2. I'll add this tab to the real pages once the box is working (which could be a while since I'm gone for a month). Let me know if you see any issues with either the tab or the box/cables.



  12968   Wed May 3 17:16:30 2017 PrafulUpdateElectronicsNew Altium Schematic Design for Microphone Amp

I made an Altium schematic for the microphone amplifier circuit for fabrication.


Attachment 1: mic_schematicv2.pdf
  13862   Fri May 18 09:13:41 2018 PoojaUpdateSUSColored GigE image

To obtain a colored version with good contrast of the grayscale image of scattering of light by dust particles on the surface of test mass, got using GigE camera. The original and colored images are attached here.


Attachment 1: Image__2017-11-14__08-25-13_100k100g1V_colored.png
Attachment 2: Image__2017-11-14__08-25-13_100k100g1V.tiff
  13868   Fri May 18 20:03:14 2018 PoojaUpdateCamerasTelescopic lens solution for GigE

Aim: To find telescopic lens solution to image test mass onto the sensor of GigE camera.

I wrote a python code to find an appropriate combination of lenses to focus the optic onto the camera keeping in mind practical constraints like distance of GigE camera from the optic ~ 1m and distance between the lenses need to be in accordance with the Thorlab lens tubes available. We have to image both the enire optic of size 3" and beam spot of 1" using this combination of lens. The image size that efficiently utilizes the entire sensor array is 1/4". Therefore the magnification required for imaging the entire optic is 1/12 and that for the beam spot is 1/4.

I checked the website of Thorlabs to get the available focal lengths of 2" lenses (instead of 1" lenses to collect sufficient power). I have tried several combination of lenses and the ones I found close enough to what is required have been listed below along with thier colorbar plots.

a) 150mm-150mm (Attachment 2 & 3)

With this combination, object distance varies like 50cm for 1" beam spot to 105cm for 3" spot. Therefore, it posses a difficulty that there is a difference of ~48cm in the distances between the optic and camera in the two cases: imaging the entire optic and the beam spot.

b) 125mm-150mm (Attachment 4 & 5)

With this combination, object distance varies like 45cm for 1" beam spot to 95cm for 3" spot. There is a difference of ~43cm in the distances between the optic and camera in the two cases: imaging the entire optic and the beam spot.

c) 125mm-125mm (Attachment 6 & 7)

The object distance varies like 45cm for 1" beam spot to 90cm for 3" spot. There is a difference of ~39cm in the distances between the optic and camera in the two cases: imaging the entire optic and the beam spot.

Sensitivity check was also done for these combination of lenses. An error of 1cm in object distance and 5mm in the distance between the lenses gives an error in magnification <2%.

The schematic of the telescopic lens system has been given in Attachment 8.


Attachment 1: Image__2017-11-14__08-25-13_100k100g1V_colored.png
Attachment 2: plot_2018-05-18_tel-lens_150_150_1.pdf
Attachment 3: plot_2018-05-18_tel-lens_150_150_3.pdf
Attachment 4: plot_2018-05-18_tel-lens_125_150_1.pdf
Attachment 5: plot_2018-05-18_tel-lens_125_150_3.pdf
Attachment 6: plot_2018-05-18_tel-lens_125_125_1.pdf
Attachment 7: plot_2018-05-18_tel-lens_125_125_3.pdf
Attachment 8: tel_design.pdf
  227   Tue Jan 8 15:20:17 2008 PkpUpdateCamerasGigE update
[Tobin , Pinkesh]

Finally we got the camera doing something (other than giving out its attributes). The only thing that seems to work so far is a program called AAviewer, which converts the image into an ASCII format and displays it on the screen. If you want to play around with it, log into mafalda ( via rana.ligo.caltech.edu. Access /cvs/cds/caltech/target/Prosilica/bin-pc/x86/ and there should be a few programs in there, one of which is AAviewer, which requires you to get an IP address (which is for the camera right now. (You can also get the IP information via the ListCameras program). The camera is physically in the 40m near the network rack.

Other programs dont seem to be working and its probably due to the network/packetsize issues. Since linux2 can change its packetsize to a higher number, I will get it to compile on linux2 for now and then give it a shot.
  234   Thu Jan 10 13:45:52 2008 PkpUpdateCamerasGLIBC Error
So, I have tried to compile the camera files which are in /cvs/cds/caltech/target/Prosilica/examples for the past 2 days now and have been unable to get rid of the following error. (specifically ListCameras.cpp, as it doesnt have any other libraries required, which unnecessarily complicates things)

../../bin-pc/x86/libPvAPI.so: undefined reference to `__stack_chk_fail@GLIBC_2.4'
collect2: ld returned 1 exit status
make: *** [sample] Error 1

I used to get this error on mafalda too, but I had fixed it by installing the latest version of the glibc libraries. Inspite of doing so on linux2, the error still persists. I suspect it had something to do with it being a FC3 machine. My own laptop, which also runs Ubuntu works fine too. The problem with these Ubuntu machines is that they dont let me set the packet sizes to 9 kb which is required by the camera. Linux2 does.

If anyone has any idea how to resolve this issue, please let me know.

  9028   Mon Aug 19 10:16:15 2013 PicassoMetaphysicsTreasureoutsider art


  1950   Wed Aug 26 16:10:28 2009 Peter KingConfigurationPSLPSL reference cavity temperature box modifications

The 40m Lab reference cavity temperature box S/N BDL3002 was modified as per DCN D010238-00-C.

These were:

    R1, R2, R5, R6 was 10k now are 25.5k metal film

    R11, R14 was 10k now are 24.9k metal film

    R10, R15 was 10k now are 127k thick film - no metal film resistors available

    R22 was 2.00k now is 2.21k

    R27 was 10k now is 33.2k

    U5, the LM-336/2.5 was removed

    An LT1021-7, 7 V voltage reference was added.  Pin 2 to +15V, pin 4 to ground, pin 6 to U6 pin 3.

    Added an 8.87k metal film resistor between U6 pin 1 and U4 pin 6.

    Added an 8.87k metal film resistor between U6 pin 1 and U4 pin 15.

    The 10k resistor between J8 pin 1 and ground was already added in a previous modification.

In addition R3, R4, R7, R8, R12 and R13 were swapped out for metal film resistors of the same value


    The jumper connection to the VME setpoint was removed, as per Rana's verbal instructions.

This disables the ability to set the reference cavity vacuum chamber temperature by computer.




  5419   Thu Sep 15 17:00:10 2011 Paul and SteveUpdateSUSNew ITMY and SRM oplev plan

 We have made a new plan for the ITMY and SRM oplev optical path which uses as few optics as possible. This should help to reduce coupling from vibrations of optics in the oplev path back into the GW channel. To get enough room for the turning mirror into the SRM it might be necessary to move the POY optics a bit nearer to the tank. 

Attachment 1: oplev_plan1.png
  5418   Thu Sep 15 16:45:59 2011 PaulUpdateSUSITMY and SRM Oplev status

Today I worked on getting the ITMY and SRM oplevs back in working order. I aligned the SRM path back onto the QPD. I put excitations on the ITMY and SRM in pitch and yaw and observed the beam at the QPDs to check for clipping. They looked clean from clipping.

Measurements of the beam power at various points:
Straight after the laser - 7.54mW
After the BS in the SRM path - 1.59mW
After the BS in the ITMY path - 3.24mW
Incident on the SRM QPD - 0.03mW
Incident on the ITMY QPD - 0.25mW
Counts registered from the QPD sum channels:
SRM QPD SUM dark count - 1140
SRM QPD SUM bright count - 3250
ITMY QPD SUM dark count - 150
ITMY QDP SUM bright count - 12680
The power incident on the SRM QPD seems very low with respect to the ITMY QPD. Is the SRM mirror coating not very reflective for the He-Ne laser?There are some back reflections from lenses, which we should be careful of to avoid scattering.
  5422   Thu Sep 15 18:24:54 2011 PaulUpdateSUSITMY and SRM Oplev current status - comparison with ITMY

Just to find out where we are currently, I plotted the ITMY and SRM oplev spectra along with the ETMY oplev spectra. ETMY seems to be very good, so comparing with this seemed useful, so we know how much we have to improve by. The SRM power spectrum appears to be around 2 orders of magnitude higher than ETMY over pretty much the whole measurement band. The ITMY power spectrum is not so bad as the SRM above about 60Hz. Next thing to do is to check the dark noise level for the ITMY and SRM QPDs.

Attachment 1: oplev_spectra_comparison.pdf
  5423   Thu Sep 15 18:31:27 2011 PaulUpdateSUSITMY and SRM Oplev current status - comparison with ITMY


Just to find out where we are currently, I plotted the ITMY and SRM oplev spectra along with the ETMY oplev spectra. ETMY seems to be very good, so comparing with this seemed useful, so we know how much we have to improve by. The SRM power spectrum appears to be around 2 orders of magnitude higher than ETMY over pretty much the whole measurement band. The ITMY power spectrum is not so bad as the SRM above about 60Hz. Next thing to do is to check the dark noise level for the ITMY and SRM QPDs.

 The title of this post should of course have been " ... - comparison with ETMY" not " ... - comparison with ITMY"

  5427   Thu Sep 15 22:26:32 2011 PaulUpdateSUSITMY Oplev QPD dark noise PSD

 I took a dark noise measurement for the ITMY QPD, for comparison with measurements of the oplev noise later on. Initially I was plotting the data from test points after multiplication by the oplev matrix (i.e. the OLPIT_IN1 / OLYAW_IN1), but found that the dark noise level seemed higher than the bright noise level (!?). Kiwamu realised that this is because at that test point the data is already divided by QPD SUM, thus making the dark noise level appear to be greater than the bright level, since QPD SUM is much smaller for the dark measurements. The way around this was to record the direct signals from each quadrant before the division. I took a power spectrum of the dark noise from each quadrant, then added them in quadrature, then divided by QPD SUM at the end to get an uncalibrated PSD. Next I will convert these into the equivalent for pitch and yaw noise spectra. To calibrate the plots in radians per root Hz requires some specific knowledge of the oplev path, so I won't do this until I have adjusted the path.

Attachment 1: ITM_dark_QPD_PSD.pdf
  5429   Fri Sep 16 00:08:30 2011 PaulUpdateSUSITMY Oplev QPD dark and bright noise spectra

 I tried again at plotting the ITMY_QPD noise spectra in for dark and bright operation. Before we had the strange situation where the dark noise seemed higher, but Kiwamu noticed this was caused by dividing by the SUM before the testpoint I was looking at. This time I tried just multiplying by the measured SUM for bright and dark to normalise the spectra against each other. The results looks more reasonable now, the dark noise is lower than the bright noise for a start! However, the dark noise spectrum now doesn't look the same as the one I showed in my previous post.

Attachment 1: ITMY_oplev_dark_noise_vs_bright_noise.pdf
  5432   Fri Sep 16 14:03:53 2011 PaulUpdateSUSSRM oplev QPD noise measurement

 I checked the dark and bright noise of the SRM oplev QPD. The SRM QPD has a rather high dark level for SUM of 478 counts. The dark noise for the SRM QPD looked a little high in the plot against the bright noise (see first attachment), so I plotted the dark noise with the ITMY QPD dark noise (see second attachment). It seems that the SRM QPD has a much higher dark noise level than the ITMY! In case anyone is wondering, to make these traces I record the data from the pitch and yaw test points, then multiply by the SUM (to correct for the fact that the test point signal has already been divided by SUM). I will check the individual quadrants of the SRM QPD to see if one in particular is very noisy. If so, we/I should probably fix it.

Attachment 1: SRM_oplev_dark_noise_vs_bright_noise.pdf
Attachment 2: SRM_ITMY_QPD_dark_noise_comparison.pdf
  5436   Fri Sep 16 16:34:54 2011 PaulUpdateSUSITMY SRM oplev telescope plan

I've calculated a suitable collimating telescope for the ITMY/SRM oplev laser, based on the specs for the soon-to-arrive 2mW laser (model 1122/P) available here: http://www.jdsu.com/ProductLiterature/hnlh1100_ds_cl_ae.pdf

Based on the fact that the 'beam size' value and 'divergence angle' value quoted don't match up, I am assuming that the beam radius value of 315um is _not_ the waist size value, but rather the beam size at the output coupler. From the divergence angle I calculated a 155um waist, (zR = 12cm). This gives the quoted beam size of about 316um at a distance of 8.5" away from the waist. This makes me think that the output coupler is curved and the waist is at the back of the laser, or at least 8.5" from the output coupler.

The collimating telescope gives a waist of size 1142um (zR=6.47m) at a distance of 1.427m away from the original laser waist, using the following lens combo:


L1 f=-0.15 @ 0.301m

L2 f=0.3 @ 0.409m


This should be fine to get a small enough spot size (1-2mm) on the QPDs.


Attachment 1: ITMY_SRM_telescope.png
  5437   Fri Sep 16 17:09:07 2011 PaulUpdateSUSITMX oplev plan

 I just drew a basic picture of how the ITMX oplev path could be reworked to minimise the number of optics in the path. Only possible problem with this might be the turning mirror onto the ITMX getting in the way of the collimating lenses. Should be easy to solve though. Does anyone know if there is a ITMX pick off beam I should be careful to avoid?

Attachment 1: ITMX_oplev_plan.png
  5442   Fri Sep 16 22:11:21 2011 PaulUpdateSUSITMY transfer function

First of all I moved the lenses on the ITMY/SRM oplev path to get a smaller spot size on the QPDs. I couldn't get the beam analyzer to work though, so I don't know quite how successful this was. The software brought up the error "unable to connect to framegrabber" or something similar. I don't think the signal from the head was being read by the software. I will try to get the beam analyzer working soon so that we can characterize the other oplev lasers and get decent spot sizes on the QPDs. I searched the elog for posts about the analyzer, and found that it has been used recently, so maybe I'm just doing something wrong in using it. 

After this I measured the transfer function for the ITMY oplev yaw. I did a swept sine excitation of the ITMY in yaw with an amplitude of 500, and recorded the OSEM yaw values and the oplev yaw values. This should show a flat response, as both the QPD and the OSEMS should have flat frequency response in the measurement band. This measurement should therefore just yield a calibration from OSEM yaw to oplev yaw. If the OSEM yaw values were already calibrated for radians, we would then immediately have a calibration from oplev yaw values to radians. However, as far as I'm aware, there is not a calibration factor available from OSEM yaw values to radians. Anyway, the TF I measured did not appear to be very flat (see attached plot). Kiwamu suggested I should check the correlation between the OSEM measurements and the oplev QPD measurements - if the correlation is less than 1 the TF is not reliable. Indeed the coherence was poor for this measurement. This was probably because at frequencies above the pendulum frequency, the excitation amplitude of 500 was not enough to cause a measurable change in the optic angle. So, the plot attached is not very useful yet, but I learned something while making it.


Attachment 1: ITMY_osem_to_oplev_TF.pdf
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