40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
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ID Date Author Type Categoryup Subject
  13236   Mon Aug 21 21:26:41 2017 gautamSummaryGeneralLoss measurements plan

In case you want to use it, I had profiled the Lightwave NPRO sometime back, and we were even using it as the AUX X laser for a short period of time. 

As for using the AS laser for mode spectroscopy: don't we want to match the beam into the cavity as best as possible, and then use some technique to disturb the input mode (like the dental tooth scraper technique from Chris Mueller's thesis)? 

Johannes and I did an arm scan of the X arm today (arm controlled with ALS, monitoring IR transmission) - only 2 IR FSRs were scanned, but there should be sufficient information in there to extract the modulation depth and mode matching - can we use Kaustubh's/Naomi's code?. The Y arm ALS needs to be touched up so I don't have a Y arm scan yet. Note that to get a good arm scan measurement, the High Gain Thorlabs PD should be used as the transmission PD.

Quote:
 

Week Aug 21 - Aug 27:

  • Update mode-overlap estimates
  • Obtain current DC refl estimates
  • Spatial profile of auxiliary NPRO
  • Fiber setup concept; purchasing
  • CCD software prep work

 

  13241   Tue Aug 22 16:56:54 2017 johannesSummaryGeneralAS laser existing components inventory

I surveyed the lab today to see what we may need to buy for the AS laser setup.

We have:

NPRO 200 mW + Driver

Faraday Isolator from cabinet

ISOMET Model 1201E: This is a free space AOM I found in the modulator cabinet. It needs to be driven at 40MHz (to be confirmed) with ~6W of electrical power. For a 500 micron beam it can allegedly achieve rise times of '93' [units not specified, could this be nanoseconds?]. I did not find a dedicated driver for it, however there was a 5W minicircuits amplifier ZHL-5W-1 in the RF cabinet and a switch ZSDR-230, which has a typical switch time of 2 microseconds, however I'm not sure how this translates to rise/fall times of the deflected power. It seems we have everything to set this up, so we'll by the end of the week if we can use a combination of these things or if we need to buy additional driver electronics.

New Focus model 4004 broadband phase modulator which is labeled as dusty, and in fact quite dirty when looking through. We should attempt to clean this thing and maybe we can use it here or at the ends.

Probably all the optics we need for the PSL table setup.

 

We need:

Beat PD: How about one of these: EOT ET-3000A? I didn't find a broadband PD for the beat with the PSL

Fiber Stuff: coupler & polarization maintaining fiber 20m & collimator. There are a couple options here, which we can discuss in the meeting.

Faraday Isolator: If we want to inject P-polarization. If S is okay we can use a polarizing plate beamsplitter instead.

Possibly some large lenses for mode-matching to IFO (TBD)

 

 

  13253   Fri Aug 25 11:11:26 2017 gautamUpdateGeneralMC1 kicked again

Looks like MC1 got another big kick just under 4 hours ago. None of the other optics show any evidence of a glitch so it seems unlikely that this was some sort of global event. It's been well behaved for ~2weeks now. IMC was unlocked. I manually re-aligned MC1, at which point the autolocker was able to lock the IMC.

Looking at this plot, it seems that LR and UL coils seem to have the largest kicks. UR barely saw it. Not sure what (if anything) to make of this - apparently the optic moved by ~20urad with the UR magnet approximately the pivot.

Attachment 1: MC1_glitch.png
MC1_glitch.png
  13275   Wed Aug 30 15:00:06 2017 gautamUpdateGeneralEdgeswitch fiber swap

A couple of minutes ago, Larry W swapped the fibers to our 40m Edgeswitch (BROCADE FWS 648G) to a faster connection. This is the switch to which our gateway machine, NODUS, is connected. The actual swap itself happened at the core router in Bridge, and took only a few seconds. After the switch, I double checked that I was able to ssh into nodus from my laptop, and Larry informed me that everything is working as expected on his end.

Larry also tells us that the other edgeswitch at the 40m (Foundry Networks), to which most of our GC network machines are connected, is a 100MBPS switch, and so we should re-route the connections from this switch to the BROCADE switch at our convenience to take advantage of the faster connection.

  13283   Thu Aug 31 21:40:24 2017 gautamUpdateGeneralMC1 kicked again

There was a pretty large glitch in MC1 about an hour ago. The misalignment was so large that the autolocker wasn't able to lock the IMC. I manually re-aligned MC1 using the bias sliders, and now IMC locks fine. Attached is a 90 second plot of 2K data from the OSEMs showing the glitch. Judging from the wall StripTool, the IMC was well behaved for ~4 hours before this glitch - there is no evidence of any sort of misalignment building up, judging from the WFS control signals.

Attachment 1: MC1_glitch.png
MC1_glitch.png
  13305   Mon Sep 11 09:47:53 2017 SteveUpdateGeneralWIMA caps refilled

Instock WIMA caps refilled to a minimum 50 pieces each.

Attachment 1: WIMA.png
WIMA.png
  13308   Mon Sep 11 15:58:02 2017 SteveUpdateGeneralNPRO for repair

This NPRO has a tripping power output******

 

" Hi Eric,

I checked with the Engineer as Vincent is travelling.

“The lasers have serial number below 2000 which we cannot repair them, we only can repair NPRO laser has serial number 2000 or later.”

Thanks,

Betty-Ann Watt

Customer Service Professional
Global Customer Service/Communication & Commercial Optical Products "

www.lumentum.com

 

 

Attachment 1: NPRO_tripping.jpg
NPRO_tripping.jpg
  13393   Wed Oct 18 19:17:42 2017 gautamUpdateGeneralPRC angular feedforward

Last night, I collected ~30mins of data for the vertex seismometer channels and the POP QPD PIT/YAW signals with the PRMI locked on carrier (angular FF OFF). The ITM Oplev loops weren't DC coupled, as they are in the full IFO locking sequence, but I feel like the angular FF filters can be improved - there are frequent sharp dives in the AS110 signal level which are correlated with large amplitude motion of the POP spot on the control room CCD monitor.

Repeating the frequency domain multicoherence analysis using BS_X and BS_Y seismometer channels as witnesses suggest that we can win significantly (see Attachment #1).

I've never really implemented feedforward filters - I was planning on using ericq's latest entry on this subject as a guide. From what I gather, the procedure is as follows:

  1. Pre-filter the target (POP QPD PIT or YAW) and witness (BS_X, BS_Y) channels
    • Downsample the 2k target data and 256Hz witness data to 32 Hz (how to choose this?)
    • Detrend (linear?)
    • Apply elliptic low pass filter (previously, a 3rd order Elliptic Low pass with 3dB ripple, 40dB stopband attenuation, corner at 5Hz was used).
  2. Filter the target signal (i.e. POP QPD PIT/YAW) by the inverse actuator TF.
    • This "actuator TF" is a measurement of how actuating on the angular DoFs of the PRM affects the POP QPD spot.
    • So by pre-filtering the target signal through the inverse actuator TF, we get a measure of how much the PRM angular motion is.
    • The reason we want to do this is to give the FIR filter that produces optic motion (output) given ground motion sensed by the seismometer (input) fewer poles/zeros to fit (?).
    • The actual actuator TF has to be measured using DTT, and fit - is there anything critical about this fitting? Seems like this should be just a simple pendulum transfer function so a pair of complex poles should be sufficient?
  3. The actual Wiener filter is calculated by the function miso_firlev.m. There are many versions of this floating around from what I can gather.
    • This function requires 3 input parameters.
      • Order of filter to be fit
      • Witness channels (can be multiple)
      • Target channel (has to be single, hence the "miso" in the function name).
    • Today, at the meeting, we talked about weighting the cost function that the optimal Wiener filter calculator minimizes.
    • The canonical wiener filter minimizes the mean squared error between the output of the filter and the desired signal profile (which for this particular problem is the angular motion of the PRM, calculated by dividing the target signal by the actuator TF, knowing which we can cancel it out).
    • But as seen in Attachment #1, the main reduction in RMS comes below f=5Hz.
    • So can we weight the cost function more heavily at lower frequencies? From what I can find in previous calculations, it looks like this weighting happens in the pre-filtering stage, which is not the same thing as including the frequency dependent weighting in the calculation of the Weiner filter? The PSD and acf are F.T. pairs per the Wiener-Khinchin theorem so intuitively I would think that weighting in the frequency domain corresponds to weighting on the lags at which the acf is calculated, but I need to think about this.
    • What kind of low-pass filter do we use to prevent noise injection at higher frequencies? Does the optimal filter calculation automatically roll-off the filter response at high frequencies?
  4. As I write this, seems like there is another level of optimization of "meta-parameters" possible in this whole process - e.g. what is the optimal order of filter to fit? what is the optimal pre-filtering of training data? Not sure how much we can gain from this though.

Some notes from Rana from some years ago: https://nodus.ligo.caltech.edu:8081/40m/11519

If anyone has pointers / other considerations I should take into account, please post here.

Attachment 1: pop_feedforward_potential.pdf
pop_feedforward_potential.pdf
  13418   Wed Nov 8 14:28:35 2017 gautamUpdateGeneralMC1 glitches return

There hasn't been a big glitch that misaligns MC1 by so much that the autolocker can't lock for at least 3 months, seems like there was one ~an hour ago.

I disabled autolocker and feedback to the PSL, manually aligned MC1 till the MC_REFL spot looked right on the CCD to me, and then re-engaged the autolocker, all seems to have gone smoothly.

 

Attachment 1: MC1_glitchy.png
MC1_glitchy.png
Attachment 2: 6AFDA67D-79B1-469C-A58A-9EC5F8F01D32.jpeg
6AFDA67D-79B1-469C-A58A-9EC5F8F01D32.jpeg
  13460   Fri Dec 1 17:09:29 2017 Udit KhandelwalSummaryGeneral 

Current objectives and statuses:

  • CAD Model of 40m lab (facility, chambers, invacuum components etc)
    • Status: On hold since I'm unable to acquire general dimensions of 
  13472   Wed Dec 13 17:46:08 2017 Udit KhandelwalSummaryGeneralSummary of Current Tasks

40m Lab CAD

1. 40m_bldg.dwg has 2D drawing of the 40m building

  • After importing file as a 2D sketch into solidworks, make sure to retrace all the lines before performing any 3D extrusion stuff.
  • Made walls 3m high

2. 40m_VE.dwg has the Vaccuum Envelope.

  • Divided the file into individual sketches for the tubes, test mass, and beam splitter chambers (so they can be individually modified later if required).

3. 40melev.dwg has the relative positioning between (1) and (2).

  • Using this file to position objects inside building cad.

4. All files can be found in Dropbox folder [40m SOS Modeling], which should be renamed to [40m CAD].

5. Next step would be to add the optical table, mirrors.

Tip-Tilt Suspension

1. Current objective: (refer to D070172) - Increase the length of the side arms (so it matches the dimensions of D960001), while keeping the test mass subassembly at the same height.
2. Future objective: Resonant frequency FEM of the frame (sans the test mass), and then change height to get the desired frequency.

Past Work

  • Completed solidworks model of SOS (D960001). I understand this is not the focus right now so this is for reference that the model is ready to be used.

Comments

  • I will be in India from 16th December until 6th January so this is my final visit for this year. I have enough material to work from home, and will correspond with Koji over email regarding Lab CAD and tip-tilt suspension.
  13475   Thu Dec 14 08:59:17 2017 SteveUpdateGeneralwe are here
Attachment 1: 8_days.png
8_days.png
  13489   Wed Dec 20 00:43:58 2017 KevinSummaryGeneralDAC noise contribution to squeezing noise budget

Gautam and I looked into the DAC noise contribution to the noise budget for homodyne detection at the 40m. DAC noise is currently the most likely limiting source of technical noise.

Several of us have previously looked into the optimal SRC detuning and homodyne angle to observe pondermotive squeezing at the 40m. The first attachment summarizes these investigations and shows the amount of squeezing below vacuum obtainable as a function of homodyne angle for an optimal SRC detuning including fundamental classical sources of noise (seismic, CTN, and suspension thermal). These calculations are done with an Optickle model. According to the calculations, it's possible to see 6 dBvac of squeezing around 100 Hz.

The second attachment shows the amount of squeezing obtainable including DAC noise as a function of current noise in the DAC electronics. These calculations are done at the optimal -0.45 deg SRC detuning and 97 deg homodyne angle. Estimates of this noise are computed as is done in elog 13146 and include de-whitening. It is not possible to observe squeezing with the current 400 Ω series resistor which corresponds to 30 pA/rtHz current noise at 100 Hz. We can get to 0 dBvac for current noise of around 10 pA/rtHz (1.2 kΩ series resistor) and can see 3 dBvac of squeezing with current noise of about 5 pA/rtHz at 100 Hz (2.5 kΩ series resistor). At this point it will be difficult to control the optics however.

So it seems reasonable to reduce the DAC noise to sufficient levels to observe squeezing, but we will need to think about the controls problem more.

Attachment 1: 40m_squeezing.pdf
40m_squeezing.pdf
Attachment 2: 40mDAC_squeezing.pdf
40mDAC_squeezing.pdf
  13490   Thu Dec 21 19:25:48 2017 KevinSummaryGeneralDAC noise contribution to squeezing noise budget

Gautam and I redid our calculations, and the updated plot of squeezing as a function of DAC current noise per coil is shown in the attachment. The current noise is calculated as the maximum of the filtered DAC noise and the Johnson noise of the series resistor. The total noise is for four optics with four coils each.

The numbers are worse than we quoted before: according to these calculations we can get to 0 dBvac for current noise per coil of about 2.4 pA/rtHz at 100 Hz.

Quote:

Gautam and I looked into the DAC noise contribution to the noise budget for homodyne detection at the 40m. DAC noise is currently the most likely limiting source of technical noise.

Several of us have previously looked into the optimal SRC detuning and homodyne angle to observe pondermotive squeezing at the 40m. The first attachment summarizes these investigations and shows the amount of squeezing below vacuum obtainable as a function of homodyne angle for an optimal SRC detuning including fundamental classical sources of noise (seismic, CTN, and suspension thermal). These calculations are done with an Optickle model. According to the calculations, it's possible to see 6 dBvac of squeezing around 100 Hz.

The second attachment shows the amount of squeezing obtainable including DAC noise as a function of current noise in the DAC electronics. These calculations are done at the optimal -0.45 deg SRC detuning and 97 deg homodyne angle. Estimates of this noise are computed as is done in elog 13146 and include de-whitening. It is not possible to observe squeezing with the current 400 Ω series resistor which corresponds to 30 pA/rtHz current noise at 100 Hz. We can get to 0 dBvac for current noise of around 10 pA/rtHz (1.2 kΩ series resistor) and can see 3 dBvac of squeezing with current noise of about 5 pA/rtHz at 100 Hz (2.5 kΩ series resistor). At this point it will be difficult to control the optics however.

So it seems reasonable to reduce the DAC noise to sufficient levels to observe squeezing, but we will need to think about the controls problem more.

 

Attachment 1: 40mDAC_squeezing.pdf
40mDAC_squeezing.pdf
  13491   Fri Dec 22 09:40:19 2017 ranaSummaryGeneralDAC noise contribution to squeezing noise budget
  1. Should not count the ITMs. On those we can use big resistors / filters to cut out the noise.
  2. For the initial LIGO, we used 7 K resistors and the mass was 10 kg. But...the output driver went +/- 150 V.

So we had a max F/m = (20 mA * 0.064 N/A)/(10 kg) = 0.0001. For the 40m, to get the same thing, we would need 40x less current (~0.5 mA). At the moment we have (12 V / 400 Ohm) = 30 mA.

We need to get a spectrum and times series of the required coil current for acquiring and holding the DRMI, and also the single arm. Then we can see where to make noise reductions to allow this drastic force reduction. 

Coil Driver Upgrade wiki here.

  13492   Tue Dec 26 17:24:24 2017 SteveUpdateGeneralpower outage

There was a power outage.

The IFO pressure is 12.8 mTorr-it and it is not pumped. V1 is still closed. TP1 is not running. The Rga is not powered.

The PSL output shutter is still closed. 2W Innolight turned on and manual beam block placed in its beampath.

3 AC units turned on at room temp 84F

Attachment 1: powerOutage.png
powerOutage.png
  13493   Thu Dec 28 17:22:02 2017 gautamUpdateGeneralpower outage - CDS recovery
  1. I had to manually reboot c1lsc, c1sus and c1ioo.
  2. I edited the line in /etc/rt.sh (specifically, on FB /diskless/root.jessie/etc/rt.sh) that lists models running on a given frontend, to exclude c1dnn and c1oaf, as these are the models that have been giving us most trouble on startup. After this, I was able to bring back all models on these three machines using rtcds restart --all. The original line in this file has just been commented out, and can be restored whenever we wish to do so.
  3. mx_stream processes are showing failed status on all the frontends. As a result, the daqd processes are still not working. Usual debugging methods didn't work.
  4. Restored all sus dampings.
  5. Slow computers all seem to be responsive, so no action was required there.
  6. Burtrestored c1psl to solve the "sticky slider" problem, relocked PMC. I didn't do anything further on the PSL table w.r.t. the manual beam block Steve has placed there till the vacuum situation returns to normal.

@Steve: I noticed that we are down to our final bottle of N2, not sure if it will last till 2 Jan which is presumably when the next delivery will come in. Since V1 is closed and the PSL beam is blocked, perhaps this doesn't matter.

from Steve: there are spare full N2 bottles at the south end outside and inside. I replaced the N2 on Sunday night. So the system should be Ok as is.

I also hard-rebooted megatron and optimus as these were unresponsive to ping.

*Seems like the mx_stream errors were due to the mx process not being started on FB. I could fix this by running sudo systemctl start mx on FB. After which I ran sudo systemctl restart daqd_*. But the DC errors persist - not sure how to fix this. Elogging suggests that "0x4000" errors are connected to timing problems on FB, but restarting the ntp service on FB (which is the suggested fix in said elogs) didn't fix it. Also unsure if mx process is supposed to automatically start on FB at startup.

Attachment 1: 28.png
28.png
  13499   Wed Jan 3 15:13:55 2018 SteveUpdateGeneralprojector light bulb replaced

Bulb  is replaced.

Quote:

I noticed this behaviour since ~Dec 20th, before the power failure. The bulb itself seems to work fine, but the projector turns itself off after <1 minute after being manually turned on by the power button. AFAIK, there was no changes made to the projector/Zita. Perhaps this is some kind of in-built mechanism that is signalling that the bulb is at the end of its lifetime? It has been ~4.5 months (3240 hours) since the last bulb replacement (according to the little sticker on the back which says the last bulb replacement was on 15 Aug 2017

 

  13503   Thu Jan 4 14:39:50 2018 gautamUpdateGeneralpower outage - timing error

As mentioned in my previous elog, the CDS overview screen "DC" indicators are all RED (everything else is green). Opening up the displays for individual CPUs, the error message shown is "0x4000", which is indicative of some sort of timing error. Indeed, it seems to me that on the FB machine, the gpstime command shows a gps time that is ~1 second ahead of the times on other FE machines.

Running gpstime on other FE machines throws up an error, saying that it cannot connect to the network to update leap second data. Not sure what this is about...

I double checked the GPS timing module, we had some issues with this in the recent past. But judging by its front panel display, everything seems to be in order...

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/bin/gpstime", line 9, in <module>
    load_entry_point('gpstime==0.2', 'console_scripts', 'gpstime')()
  File "/usr/lib/python3/dist-packages/pkg_resources.py", line 356, in load_entry_point
    return get_distribution(dist).load_entry_point(group, name)
  File "/usr/lib/python3/dist-packages/pkg_resources.py", line 2476, in load_entry_point
    return ep.load()
  File "/usr/lib/python3/dist-packages/pkg_resources.py", line 2190, in load
    ['__name__'])
  File "/usr/lib/python3/dist-packages/gpstime/__init__.py", line 41, in <module>
    LEAPDATA = ietf_leap_seconds.load_leapdata(notify=True)
  File "/usr/lib/python3/dist-packages/ietf_leap_seconds.py", line 158, in load_leapdata
    fetch_leapfile(leapfile)
  File "/usr/lib/python3/dist-packages/ietf_leap_seconds.py", line 115, in fetch_leapfile
    r = requests.get(LEAPFILE_IETF)
  File "/usr/lib/python3/dist-packages/requests/api.py", line 60, in get
    return request('get', url, **kwargs)
  File "/usr/lib/python3/dist-packages/requests/api.py", line 49, in request
    return session.request(method=method, url=url, **kwargs)
  File "/usr/lib/python3/dist-packages/requests/sessions.py", line 457, in request
    resp = self.send(prep, **send_kwargs)
  File "/usr/lib/python3/dist-packages/requests/sessions.py", line 569, in send
    r = adapter.send(request, **kwargs)
  File "/usr/lib/python3/dist-packages/requests/adapters.py", line 407, in send
    raise ConnectionError(err, request=request)
requests.exceptions.ConnectionError: ('Connection aborted.', OSError(101, 'Network is unreachable'))

 

 

  13506   Fri Jan 5 21:54:28 2018 ranaUpdateGeneralpower outage - timing error

Rolf came here in the morning, but not sure what he did or if Jamie remotely did something. But the screen is green.

Attachment 1: huh.png
huh.png
  13507   Fri Jan 5 22:19:53 2018 gautamUpdateGeneralpower outage - timing error

Just putting the relevant line from email from Rolf which at least identifies the problem here:

Looks like FB time is actually off by 1 year, as your timing system does not get year info.

There still seems to be something funky with the X arm transmission PDs - I can't seem to get the triggering to switch between the QPD and the Thorlabs PD, and the QPD signal seems to be wildly fluctuating by several orders of magnitude from 0.01-100. The c1iscex FE was pulled out, and it seemed to me like someone was doing some cable re-arrangement at the X end.

I will look into this tomorrow. 

Quote:

Rolf came here in the morning, but not sure what he did or if Jamie remotely did something. But the screen is green.

 

  13510   Sat Jan 6 18:27:37 2018 gautamUpdateGeneralpower outage - IFO recovery

Mostly back to nominal operating conditions now.

  1. EX TransMon QPD is not giving any sensible output. Seems like only one quadrant is problematic, see Attachment #1. I blame team EX_Acromag for bumping some cabling somewhere. In any case, I've disabled output of the QPD, and forced the LSC servo to always use the Thorlabs "High Gain" PD for now. Dither alignment servo for X arm does not work so well with this configuration - to be investigated.
  2. BS Seismometer (Trillium) is still not giving any sensible output.
    • I looked under the can, the little spirit level on the seismometer is well centered.
    • I jiggled all the cabling to rule out any obvious loose connections - found none at the seismometer, or at the interface unit (labelled D1002694 on the front panel) in 1X5/1X6.
    • All 3 axes are giving outputs with DC values of a few hundred - I guess there could've been some big earthquake in early December which screwed the internal alignment of the sensing mass in the seismometer. I don't know how to fix this.
    • Attachment #2 = spectra for the 3 channels. Can't say they look very seismicy frown. I've assumed the units are in um/sec.
    • This is mainly bothering me in the short term because I can't use the angular feedforward on PRC alignment, which is usually quite helpful in DRMI locking.
    • But I think the PRM Oplev loop is actually poorly tuned, in which case perhaps the feedforward won't really be necessary once I touch that up.

What I did today (may have missed some minor stuff but I think this is all of it):

  1. At EX:
    • Toggled power to Thorlabs trans monitoring PD, checked that it was actually powered, squished some cables in the e- rack.
    • Removed PDA55 in the green path (put there for EX laser AM/PM measurement). So green beam can now enter the X arm cavity.
    • Re-connected ALS cabling.
    • Turned on HV supply for EX Green PZT steering mirrors (this has to be done every time there is a power failure).
  2. At ITMY table:
    • Removed temporary HeNe RIN/ Oplev sensing noise measurement setup. HeNe + 1" vis-coated steering mirror moved to SP table.
    • Turned on ITMY/SRM Oplev HeNe.
    • Undid changes on ITMY Oplev QPD and returned it to its original position.
    • Centered ITMY reflected beam on this QPD.
  3. At vertex area
    • Looked under Trillium seismometer can - I've left the clamps undone for now while we debug this problem.
    • Power-cycled Trillium interface box.
    • Touched up PMC alignment.
  4. Control room
    • Recover IFO alignment using combination of IR and Green beams.
    • Single arm locking recovered, dither alignment servos run to maximize arm transmission. Single arm locks holding for hours, that's good.
    • The X arm dither alignment isn't working so well, the transmission never quite hits 1 and it undergoes some low frequency (T~30secs) oscillations once the transmission reaches its peak value.
    • Had to do the usual ipcrm thing to get dataviewer to run on pianosa.

Next order of business:

  1. Recover ALS:
    • aim is to replace the vertex area ALS signals derived from 532nm with their 1064nm counterparts.
    • Need to touch up end PDH servos, alignment/MM into arms, and into Fibers at ends etc.
    • Control the arms (with RMs misaligned) in the CARM/DARM basis using the revised ALS setup.
    • Make a noise budget - specifically, we are interested in how much actuation range is required to maintain DARM control in this config.
  2. Recover DRMI locking
    • Continue NBing.
    • Do a statistical study of actuation range required for acquiring and maintaining DRMI locking.
Attachment 1: EX_QPD_Quad1_Faulty.pdf
EX_QPD_Quad1_Faulty.pdf
Attachment 2: Trillium_faulty.pdf
Trillium_faulty.pdf
  13541   Fri Jan 12 18:08:55 2018 gautamUpdateGeneralpip installed on nodus

After much googling, I figured out how to install pip on SL7:

sudo easy_install pip

Next, I installed git:

sudo yum install git A

Turns out, actually, pip can be installed via yum using

sudo yum install python-pip
  13544   Fri Jan 12 20:35:34 2018 Udit KhandelwalSummaryGeneral2018/01/12 Summary
  1. 40m Lab CAD
    1. Worked further on positioning vacuum tubes and chambers in the building.
    2. Next step would be to find some drawings for optical table positions and vibration isolation stack. Need help with this! 
  2. Tip Tilt Suspension (D070172)
    1. Increased the length of side arms. The overall height of D070172 assembly matches that of D960001.
    2. The files are present in dropbox in [40mShare] > [40m_cad_models] > [TT - Tip Tilt Suspension]
  13555   Wed Jan 17 23:36:12 2018 johannesConfigurationGeneralAS port laser injection

Status of the AS-port auxiliary laser injection

  • Auxiliary laser with AOM setup exists, first order diffracted beam is coupled into fiber that leads to the AS table.
  • There is a post-PMC picked-off beam available that is currently just dumped (see picture). I want to use it for a beat note with the auxiliary laser pre-AOM so we can phaselock the lasers and then fast-switch the phaselocked light on and off.
  • I was going to use the ET3010 PD for the beat note unless someone else has plans for it.
  • I obtained a fixed triple-aspheric-lens collimator which is supposed to have a very small M^2 value for the collimation on the AS table. I still have the PSL-lab beam profiler and will measure its output mode.
  • Second attached picture shows the space on the AS table that we have for mode-matching into the IFO. Need to figure out the desired mode and how to merge the beams best.
Attachment 1: PSLbeat.svg.png
PSLbeat.svg.png
Attachment 2: ASpath.svg.png
ASpath.svg.png
  13560   Fri Jan 19 15:22:19 2018 Udit KhandelwalSummaryGeneral40m CAD update 2018/01/19

40m CAD Project

  1. All parts will be now named according to the numbering system in this excel sheet: LIGO 40m Parts List in dropbox folder [40mShare] > [40m_cad_models] > [40m Lab CAD]
  2. I've placed optical tables in the chambers at 34.82" from the bottom for now. This was chosen by aligning the centre of test mass of SOS assembly (D960001) with that of vacuum tube (Steve however pointed out last week they might not necessarily be concentric).

  13561   Fri Jan 19 20:59:07 2018 Udit KhandelwalUpdateGeneralSolidworks Rendering

Rendered the SOS assembly (D960001) with correct materials and all and it looks very nice. Will extend this to the building cad later.

  13566   Mon Jan 22 12:48:48 2018 KojiSummaryGeneralBeat setup for aLIGO EOM test

I'm planning to construct a beat setup between the PSL and AUX beams. I am going to make it in the area shown in a blue square in the attached photo. This does not disturb Johannes' and PSL setups. The beams are obtained from the PBS reflection of the PSL and the dumped beam of the aux path (0th or 1st order beam of the AOM).

Attachment 1: IMG_3048.JPG
IMG_3048.JPG
  13567   Mon Jan 22 20:54:58 2018 KojiSummaryGeneralAUX-PSL beat setup

The beat setup has been made on the PSL table. The BS and the PD were setup. The beat was found at 29.42degC and 50.58degC for the PSL and AUX crystal temperatures, respectively.
We are ready for the EOM test. I have instruments stacked around the PSL table. Please leave them as they are for a while. If you need to move them, please contact with me. Thanks.


A picked-off PSL after the main modulator was used as the PSL beam. This was already introduced close to the setup thanks to the previous 3f cancellation test ELOG 11029. The AUX beam was obtained from the transmission of 90% mirror. Both paths have S polarization. The beams are combined with a S-pol 50% BS. The combined beam is detected by a new focus 1GHz PD.

The PSL crystal temp (actual) was 50.58degC. The AUX crystal temp was swept upward and the string beat was found at 50.58degC. After a bit of alignment, the beat strength was -18dBm (at 700V/A RF transimpedance of NF1611) .

Attachment 1: IMG_3051.JPG
IMG_3051.JPG
  13601   Fri Feb 2 21:12:46 2018 Udit KhandelwalSummaryGeneralSummary - 2018/02/02

Tip-Tilt Suspension CAD:
Discussed with Koji about motivation to simplify the design of this assembly, which has many unnecessary over-constraints. I have started to cad alternate parts with the aim of removing these over-constraints.

40m Lab CAD:
Acquired a stack of original engineering drawings of the vacuum chambers from Steve which I will take home, get scanned, and then use as reference for the cad i'm working on.

Other:
Started paperwork at west bridge office to get paid as an "occasional employee". Hopefully I receive old money.

  13602   Fri Feb 2 22:47:00 2018 KojiSummaryGeneralAP1053: Packaging & Performance

I've packaged an AP1053 in a Thorlabs box. The gain and the input noise level were measured. It has the gain of ~10 and the input noise of ~0.6nV/rtHz@50MHz~200MHz.

Details

AP1053 was soldered on Thorlabs' PCB EEAPB1 (forgot to take a picture). The corresponding chassis is Thorlabs' EEA17. There is a 0.1uF high-K ceramic cap between DC and GND pins. The power is supplied via a DC feedthru capacitor (Newark / Power Line Filter / 90F2268 / 5500pF) found in the WB EE shop. The power cable has a connector to make the long side of the wires detachable. Because I did not want to leave the RF signal path just mechanically touched, the SMA connectors were soldered to the PCB. As the housing has no access hole, I had to make it at one of the sides.

The gain of the unit was measured using the setup shown in the upper figure of Attachment 2. When the unit was energized, it drew the current of about 0.1A. The measued gain was compensated by the pick off ratio of the coupler (20dB). The gain was measured with the input power of -20, -10, 0, 10, and 15dBm. The measurement  result is shown in Attachment 3. The small signal gain was actually 10dB and showed slight degradation above 100MHz. At the input of 10dB some compression of the gain is already visible. It looks consistent with the specification of +26.0dBm output for 1dB compression above 50MHz and +24.0dBm output below 50MHz.

The noise level was characterized with the setup shown in the bottom figure of Attachment 3. The noise figure of the amplifier is supposed to be 1.5dB above 200MHz and 3.5dB below 200MHz. This is quite low and the output noise of AP1053 can not be measured directly by the analyzer. So, another LN amplifier (ZFL-500HLN) was stacked. The total gain of the system was measured in the same way as above. The measured noise level was ~0.7nV/rtHz between 50MHz and 200MHz. Considering the measurement noise level of the system, it is consistent with the input referred noise of 0.6nV/rtHz. I could not confirm the advertized noise figure of 1.5dB above 200MHz. The noise goes up below 50MHz. But still 2nV/rtHz at 3MHz. I'd say this is a very good performance.

Attachment 1: AP1053.JPG
AP1053.JPG
Attachment 2: AP1053_measurement.pdf
AP1053_measurement.pdf
Attachment 3: AP1053_gain.pdf
AP1053_gain.pdf
Attachment 4: AP1053_noise.pdf
AP1053_noise.pdf
  13638   Fri Feb 16 21:03:17 2018 Udit KhandelwalSummaryGeneralSummary 2018/02/16

40m Lab Cad:
Updated the dimensions of and fleshed out the chambers in greater detail, by referring to the engineering drawings that Steve gave to me. I have scanned and uploaded most of these drawings to Dropbox in [40mShare]>[40m_cad_models]>[Vacuum Chamber Drawing Scans]. The excel file "LIGO 40m Parts List" in the [40m Lab CAD] folder also lists the Steve drawings I referenced for dimensions of each part.


Next steps:
1. Finish details of all chambers.
2. Start placing representative blocks on the optical table.

  13639   Fri Feb 16 22:15:30 2018 gautamUpdateGeneralc1mcs model restarted

c1mcs had died for some reason. Looking at dmesg, I see:

[769312.996875] c1mcsepics[1140]: segfault at 7f5000000012 ip 00007f50ea8ded8f sp 00007f50e9f53a10 error 4 in libc-2.19.so[7f50ea865000+1a1000]

None of the other EPICS processes died. Not sure what to make of this. I was at the PSL table working, and had closed the PSL shutter to avoid MC autolocker trying to keep the MC locked while I was mucking about, but this shouldn't have had any effect on an EPICS process?

Anyway, I just logged into c1sus, stopped and restarted the model. IMC locks fine now.

  13640   Fri Feb 16 22:19:07 2018 gautamUpdateGeneralFibel ALS input polarization tuning

After discussing with Koji, I decided to try and align the input beam polarization at the PSL fiber coupler to one of the special axes of the PM fiber. The motivation is to try and narrow down the source of the large RF beatnote amplitude drift I noticed and reported last night.

The setup for doing so is shown in Attachment #1 - essentially, I setup one of the newly purchased couplers in a mount, set up a PBS, and placed two photodiodes at the S and P ports of the PBS. The idea is to rotate the input coupler in its mount, thereby maximizing the PER (monitored on two Thorlabs PDA520s - I didn't check the gain balance of them). 

I spent ~30mins doing some preliminary trials just now, and, I was able to achieve a PER of ~1/20. But I think much better numbers were reported in this SURF project (although I'm not entirely sure I understand that measurement). I will spend a little more time tweaking the alignment. The procedure is tricky as at some point, simply rotating the mount reduces the mode-matching efficiency into the fiber so much that it is not possible to get a meaningful PER measurement from the photodiodes. I'm adjouring for now, more to follow...

Attachment 1: PER_setup.JPG
PER_setup.JPG
  13641   Mon Feb 19 14:27:25 2018 gautamUpdateGeneralFibel ALS input polarization tuning

Summary:

Current configuration of PSL free-space to fiber coupling is:

  • 3.25 mW / 4.55mW (~71%) coupling efficiency, both numbers measured with Ophir power meter, Filter OFF
  • \mathrm{PER} \doteq \frac{\mathrm{P_{fast}}}{\mathrm{P_{slow}}} (I choose to define it in this way as opposed to the reciprocal) of 75 (~19dB). The uncertainty in this number is large (see discussion), but I am confident that we have >10dB, which while isn't as good as can be, is sufficient for the main motivation behind this work.

Motivation:

I had noticed that the RF beat amplitude was fluctuating by up to 20dBm as viewed on the control room analyzer. As detailed in my earlier elog, I suspected this to be because of random polarization drift between the PSL and EX fields incident on the Fiber coupled PDs. Since I am confident the problem is optical (as opposed to something funny in the electronics), we'd like to be able to isolate which of the many fiber segments is dominating the contribution to this random polarization drift.

Some useful references:

  1. General writeup about how PM fibers work and PER. Gives maximum achievable PERs for a given misalignment of incident beam relative to one of the two birefringent axes.
  2. Another similar writeup. This one put me onto the usefulness of the alignment keys on the fibers.
  3. Thorlabs PM980 specs - this tells us about the orientation of the two axes for the kind of fibers we use.

Procedure and details:

  • The principle of operation behind polarization maintaining (PM) fibers is that intentional birefringence is introduced along two perpendicular axes in the fiber.
  • As a result of which light propagates with different phase velocity along these axes.
  • For an arbitrary incident field with E-field components along both axes, it is almost impossible to predict the output polarization as we do not know the length of propagation along each axis to sufficient precision (it is also uncontrolled w.r.t. environmental fluctuations). So even if you launch linear polarization into the fiber, it is most likely that the output polarization state will be elliptical.
  • But if we align the incident, linear polarization along one of the two axes, then we can accurately predict the polarizaiton at the output, to the extent that the fiber doesn't couple power in the two axes during propagation. I cant find a spec for the isolation between axes for the fiber we use, but the specs I could find for other fiber manufacturers suggest that this number is >30dB, so I think the assumption is a fair one.
  • A useful piece of information is that the alignment key on the fibers gives us information about the orientation of the birefringent axes inside the fiber. For the Thorlabs fibers, it seems that the alignment key lines up with the stress-inducing rods inside the fiber (i.e. the slow axis). I confirmed this by looking at the fiber with the fiber scope.
  • The PSL pickoff beam I am using for this setup is from the transmission of the PBS after the Faraday. So this field should have relatively pure P-polarization.
  • The way I have set up the fiber on the PSL table, the fast axis of the fiber corresponds to P-polarization (i.e. E field oscillates parallel to the plane of the optical table). Actually, it was this alignment that I tweaked in this work.
  • Using the information about the alignment key defining polarization axes on the fiber, I also set up the output fiber coupler such that the fast axis lined up as near parallel to the plane of the optical table as possible. In this way, the beam incident on the PBS at the output of my setup should be pure P-polarizaiton if I setup my input alignment into the fiber well.
  • I tweaked the rotation of the Fiber mount at the input coupler to maximize the ratio of P_p / P_s, as measured by the pair of PDs at the output. 
  • As #1 of my listed references details, you need to align the incident linear polarization to one of the two birefringent axes to closer than 6 degrees to achieve a PER of >20dB. While this sounds like a pretty relaxed requirement, in practise, it is about as good as we can hope to achieve with the mounts we have, as there is no feature that allows us to lock the rotational degree of freedom once we have optimized the alignment. Any kind of makeshift arrangement like taping the rotating part to the mount is also flaky, as during the taping, we may ruin the alignment.
  • Attachment #1 shows the result of my alignment optimization - the ratio P_p / P_s is about 75.
  • The uncertainty on the above number is large. Possible sources of error:
    • Output coupler is not really aligned such that fast axis corresponds to P-polarizaiton for the output PBS.
    • The two photodiodes' gain balance was not checked.
    • The polarization content of the input beam was not checked.
    • The PBS at the output could be slightly misaligned relative to the S/P polarization directions defined by the tabletop.
    • The PBS extinction ratio was not checked.
  • But anyways, this is a definite improvement on the situation before. And despite the large uncertainty, I am confident that P_p / P_s is better than 10dB.
  • Moreover, Steve and I installed protective tubing on the lengths of fiber that were unprotected on the PSL table, this should help in reducing stress induced polarization drifts in the fiber, at least in these sections of fiber.
  • So I think the next step is to monitor the stability of the RF beatnote amplitude after these improvements. At some point, we need to repeat this procedure for the EX and EY fibers as well.
  • If the large drifts are still seen, the only thing we can exclude as a result of this work is the section of fiber from the PSL light coupler to the beat mouth.
Attachment 1: IMG_6900.JPG
IMG_6900.JPG
  13642   Tue Feb 20 13:59:30 2018 KojiUpdateGeneralModulation depth measurement for an aLIGO EOM

Last night I worked at the PSL table for the modulation depth measurement for an aLIGO EOM. Let me know if the IFO behavior is unusual.

What I did was:

  • Cranked up the HEPA speed to 100
  • Placed an aLIGO EOM in the AUX beat path (south side of the PSL laser). (It is still on the PSL table as of Feb 20, 2018)
  • Closed the PSL shutter
  • Turned off the main Marconi forr 11MHz. The freq and output power of this marconi have not been touched.
  • Turned off the freq generation unit
     
  • Worked on my measurement with the spectrum and network analyzers + aux marconi.
     
  • Turned down the HEPA speed to 30
  • Turned on the freq generation unit
  • Turned on the main Marconi
  • Opened the PSL shutter => IMC locked
  13650   Thu Feb 22 16:11:14 2018 KojiUpdateGeneralaLIGO EOM crystal replacement

aLIGO EOM crystal replacement

  • The entire operation has been performed at the south flow bench @40m.
  • We knew that the original crystal in the aLIGO EOM we are testing has some problem. This was replaced with a spare RTP crystal.
  • Once the housing was removed, it was obvious that the crystal has a crack (Attachment 1).
    It seemed that it was produced by either a mechanical stress or a thermally induced stress (e.g. soldering).
  • I wanted to make sure the new crystal is properly aligned interms of the crystal axis.
    The original crystal has the pencil marking at the top saying "Z" "12". The new (spare) crystal has "Z" and "11".
    So the new crystal was aligned in the same way as the original one. (Attachment 2)
  • I took an opportunity to measure the distribution of the electrode lengths (Attachment 3). The lengths are 14, 5, and 14mm, respectively.
Attachment 1: IMG_3421.JPG
IMG_3421.JPG
Attachment 2: IMG_3426.JPG
IMG_3426.JPG
Attachment 3: IMG_3427.JPG
IMG_3427.JPG
  13652   Thu Feb 22 17:19:47 2018 KojiUpdateGeneralModulation depth measurement for an aLIGO EOM

aLIGO EOM test: Setup

  • The modulation signal was supplied from an aux Marconi.
  • Between the Marconi and the EOM, a 20dB coupler (ZFDC-20-5) was inserted. There the Marconi was connected to the output port, while the EOM was to the input port. This way, we can observe how much of the RF power is reflected back to Marconi.
  • The beat setup (40m ELOG 13567) was used for the measurement. The EOM was placed in the beam path of the beat setup in the PSL side.
  • To eliminate the modulation sidebands of 11MHz and 55MHz, the 40m Marconi and the freq generator were turned off (in this order).
  • The nominal amplitude of the carrier beat note was -15dBm ~ -16dBm.
  • The cable from the source to the EOM was ~3m. And the loss of this cable was ~0.4dB.

Measurement

  • The EOM had three input ports. 
  1. 9MHz input - In reality, there was no matching circuit.
  2. Center port - matched at 24.1MHz and 118.3MHz. 24.1MHz port has no amplification (just matching), and 118.3MHz is resonant.
  3. 45.5MHz port - resonantly matched at 45.5MHz
  • The Marconi output power was set to be +13dBm. For the 45MHz measurement, 20dB attenuator is inserted right next to the Marconi so that the VSWR seen from the Marconi was improbed. (Marconi did not like the full reflection of unmatched circuit and shutdown due to the protection function.)
  • The amplitude ratios between the sidebands and the carrier were multiplied by a factor of 2, to obtain the modulaiton depths. ( BesselJ(1,m)/BesselJ(0,m) ~ m/2 )
     
  • The result is found in Attachment 2.
    • The center port showed the modulation response of 0.7mrad/V and 15mrad/V for 24.1MHz and 118.3MHz, respectively. This suggests that the amplification factor for 118.3MHz is ~x21.
    • The VSWR of the center port is below 1.5 at the target frequencies. That's as tuned in Downs and has not been changed by the crystal replace.
    • The 45MHz port has the modulation response of 0.034mrad/V. This later tuned out that the amplification of ~x19. The circuit is well matched at the resonant frequency.
       
  • The linearity was checked with the 45MHz port (Attachment 3). The input power (idrectly connected to the EOM without 20dB attn) was varied between -17dBm to +13dBm. There was no sign of non linearity.
     
  • The modulation response at 24MHz was compared at various input ports. (Attachment 4)
    • The input signal was amplified tobe 23dBm by ZHL-3A for better sideband visibility. The actual amplifier output was ~30dBm, and a 6dB ATTN was used to improve the VSWR to protect the amplifier.
    • The 9MHz port showed 3.6mrad/V and 1.8mrad/V with the port unterminated and terminated, respectively. This factor of two difference is as expected.
      This 1.8mrad/V is roughly x2.6 higher compared to the one of the matched 24/118MHz port. This is close number to the ratio of the plate sizes (14mm/5mm = 2.8).
    • With the current condition, the 9MHz (unterminated), 9MHz (terminated), 24/118MHz, and 45MHz ports requires 22dBm, 27dBm, 36dBm, and 21dBm to realize the current modulation depth of 0.014 at 24MHz.
    • Comparing this matched 9MHz performance, the amplification of the 45MHz port at 45MHz was determined to be ~x19.
       
  • Considering these results, the modulation response of the center port at 24MHz seems too low. We don't want to supply 36dBm for the 0.014rad modulation (nominal number for H1).
    Here are some thoughts:
    • Use the 45MHz or 9MHz port for 24MHz modulation. Probably the unit is unmatched but, we can come up with the idea to improve the VSWR at 24MHz somehow?
    • Redistribute the plate length to have better modulation at 24MHz. Can we achieve sufficient modulation capability with the frequency of the long and short ports swapped? We hope that we don't need to start over the matching of the 24/118MHz again because the capacitances of the ports are almost the same.
Attachment 1: IMG_3436.JPG
IMG_3436.JPG
Attachment 2: modulation_depth.pdf
modulation_depth.pdf
Attachment 3: modulation_linearity.pdf
modulation_linearity.pdf
Attachment 4: modulation_24MHz.pdf
modulation_24MHz.pdf
  13654   Fri Feb 23 20:46:04 2018 Udit KhandelwalSummaryGeneralCAD Summary 2018/02/23

I have more or less finished cadding the test mass chamber by referring to the drawings Steve gave me. Finer details like lugs and bolts and window flaps can be left for later. Here's a quick render:

  13669   Thu Mar 8 01:10:22 2018 gautamUpdateGeneralCDS recovery after work at LSC rack

This required multiple hard reboots, but seems like all the RT models are back for now. The only indicator I can't explain is the red DC field on c1oaf. Also, the SUS model seems to be overclocking more frequently than usual, though I can't be sure. The "timing" field of this model's state word is RED, while the other models all seem fine. Not sure what could be going on.

Will debug further tomorrow, when I probably will have to do all this again as I'll need to recompile c1lsc for the ALS electronics test with the new ADC card from the differential AA board.

Attachment 1: CDS-recovery.png
CDS-recovery.png
  13670   Thu Mar 8 14:41:25 2018 gautamUpdateGeneralCDS recovery after work at LSC rack

As I had found before, restarting the c1oaf model fixed the DC error. There is however still a pesky red indicator light on the "ADC0" in c1oaf. Trying to open up the ADC MEDM screen to investigate this further leads to the blank screen on the bottom right of Attachment #1. Probably has something to do with the fact that the model has an ADC block (because every model needs one?) but no signals are actually being piped to the model directly from the ADC.

Another observation, though I don't have any hypothesis as to why this was happening: on the c1sus machine, the c1sus model would frequently overclock, and then eventually, crash. I observed this behaviour at least 3 times between last night and now. The other models seemed fine though, in fact, IMC stayed locked. Why should this have been the case? It remains to be seen if this was somehow connected to the red DC indicator on c1oaf, though why should this be the case? Isn't the DC just concerned with writing data to frames? Any sort of IPC should be independent? Attachment #2 shows that there's been a definite increase in the maximum time on c1sus clock-cycle since yesterday (it's a 10 day minute trend plot of the model clock cycle timing and also the maximum time). Why? Koji and I did switch off all the Sorensens at the LSC rack for about 30mins, but why should this affect anything at 1X6? There are no red lights in either the c1lsc or c1sus expansion chassis. Curiously, the PRM also seems to be glitchy - as I'm sitting in the control room, I see a spot flashing across vertically on the REFL CRT monitor sporadically. Note that nominally, with PRM misaligned, the REFL CRT should be dark. dmesg on c1sus doesn't shed any light on the issue.

Seems like some high level voodoo indecision.


Edit 330pm: The model just crashed again. dmesg rather unhelpfully just says "ADC timeout". Unclear how to debug further. See Attachment #3.

Quote:

This required multiple hard reboots, but seems like all the RT models are back for now. The only indicator I can't explain is the red DC field on c1oaf. Also, the SUS model seems to be overclocking more frequently than usual, though I can't be sure. The "timing" field of this model's state word is RED, while the other models all seem fine. Not sure what could be going on.

Will debug further tomorrow, when I probably will have to do all this again as I'll need to recompile c1lsc for the ALS electronics test with the new ADC card from the differential AA board.

Attachment 1: CDS-recovery.png
CDS-recovery.png
Attachment 2: c1sus_timing.png
c1sus_timing.png
Attachment 3: c1sus_crashed.png
c1sus_crashed.png
  13672   Thu Mar 8 18:15:42 2018 gautamUpdateGeneralCDS recovery after work at LSC rack

I was forced into a simultaneous power-cycle rebooting of the three vertex FEs just now. I took the opportunity to completely disconnect the c1sus expansion chassis from all power and then restart it.

Everything is back up right now, and the weird timing issues I noticed in the sus model seem to be gone now (I'll need a longer baseline to be sure and I'll post a trend of the CPU timing tomorrow). It's disconcerting that apparently the only way to get everything back up and running is the nuclear option of power-cycling all FE related electronics. I was considering borrowing an ADC adapter card from the Y end and measuring the calibrated IR ALS noise with the digital system, but if I'm going to have to go through this whole dance each time I do a model recompile on c1lsc (which I'm going to have to in order to get the extra ADC recognized), I'm wondering if it's just better to wait till we get the new adapter cards we ordered. I think I'm going to work on tuning the input coupling into the fiber at EX in the next couple of days instead.

Quote:
 

Seems like some high level voodoo indecision.


Edit 330pm: The model just crashed again. dmesg rather unhelpfully just says "ADC timeout". Unclear how to debug further. See Attachment #3.

 

  13677   Fri Mar 9 20:35:41 2018 Udit KhandelwalSummaryGeneralSummary 2018/03/09

1. Optical Table Layout 

I had discussed with Koji a way to record coordinates of optical table equipments in a text file, and load to solidworks. The goal is to make it easier to move things around on the table in the CAD. While I have succeeded in importing coordinates through txt files, there is still a lot of tediousness in converting these points into sketches. Furthermore, the task has to be redone everytime a coordinate is added to or changed in the txt file. Koji and I think that this can all be automated through solidworks macros, so I will explore that option for the next two weeks.

2. Vacuum Chamber CADs 

Steve will help find manufacturing drawings of the BS chamber. I have completed the ETM chambers, while the ITM ones are identical to them so I will reuse parts for the CAD. 

  13678   Mon Mar 12 13:58:37 2018 gautamUpdateGeneralprojector light bulb blown

Bulb went out ~10am today. Looks like the lifetime of this bulb was <100 days.

Steve: bulb is arriving next week

Quote:

Bulb  is replaced.

  13695   Wed Mar 21 10:00:35 2018 steveUpdateGeneralprojector light bulb replaced

Light bulb replaced.

Quote:

Bulb went out ~10am today. Looks like the lifetime of this bulb was <100 days.

Steve: bulb is arriving next week

 

  13707   Mon Mar 26 23:49:27 2018 gautamUpdateGeneralNew ADC Adaptor Board installed in C1LSC expansion chassis

Todd informed me that the ADC Timing adaptor boards we had ordered arrived today. I had to solder on the components and connectors as per the schematic, though the main labor was in soldering the high density connectors. I then proceeded to shut down all models on c1lsc (and then the FE itself). Then classic problem of all vertex machines crashing when unloading models on c1lsc happened (actually Koji noticed that this was happening even on c1ioo). Anyways this was nothing new so I decided to push ahead. 

I had to get a cable from Downs that connects the actual GS ADC card to this adaptor board. I powered off the expansion chassis, installed the adaptor board, connected it to the ADC card and restarted the expansion chassis and also the FE. I also reconnected the SCSI cable from the AA board to the adaptor card. It was a bit of a struggle to get all the models back up and running again, but everything eventually came back(after a few rounds of hard rebooting). I then edited the c1x04 and c1lsc simulink models to reflect the new path for the X arm ALS error signals. Seems to work alright.

At some point in the afternoon, I noticed a burning smell concentrated near the PSL table. Koji traced the smell down to the c1lsc expansion chassis. We immediately powered the chassis off. But Steve later informed me that he had already noticed an odd burning smell in the morning, before I had done any work at the LSC rack. Looking at the newly installed adaptor card, there wasn't any visual evidence of burning. So I decided to push ahead and try and reboot all models. Everything came back up normally eventually, see Attachment #1. Particle count in the lab seems a little higher than usual (actually, according to my midnight measurement, they are ~factor of 10 lower than Steve's 8am measurements), but Steve didn't seem to think we should read too much into this. Let's monitor the situation over the coming days, Steve should comment on the large variance seen in the particle counter output which seems to span 2 orders of magnitude depending on the time of the day the measurement is made... Also note that there is a BIO card in the C1LSC expansion chassis that is powered by a lab power supply unit. It draws 0 current, even though the label on it says otherwise. I a not sure if the observed current draw is in line with expectations.


The spare (unstuffed) adaptor cards we ordered, along with the necessary hardware to stuff them, are in the Digital FE hardware cabinet along the east arm.

Steve:  particle count in the 40m is following outside count, wind direction, weather condition .....etc. The lab particle count is NOT logged ! This is bad practice.

Attachment 1: CDS_20180326.png
CDS_20180326.png
  13713   Wed Mar 28 16:44:27 2018 SteveUpdateGeneralAP table today

MCRefl is absent, it is under investigation. I removed a bunch of hardware and note all spare optics along the edges.

 

Attachment 1: AP_Table_20180328.png
AP_Table_20180328.png
  13717   Thu Mar 29 12:03:37 2018 Jon RichardsonSummaryGeneralProof-of-Concept SRC Gouy Phase Measurement

I've been developing an idea for making a direct measurement of the SRC Gouy phase at RF. It's a very different approach from what has been tried before. Prior to attempting this at the sites, I'm interested in making a proof-of-concept measurement demonstrating the technique on the 40m. The finesse of the 40m SRC will be slightly higher than at the sites due to its lower-transmission SRM. Thus if this technique does not work at the 40m, it almost certainly will not work at the sites.

The idea is, with the IFO locked in a signal-recycled Michelson configuration (PRM and both ETMs misaligned), to inject an auxiliary laser from the AS port and measure its reflection from the SRC using one of the pre-OMC pickoff RFPDs. At the sites, this auxiliary beam is provided by the newly-installed squeezer laser. Prior to injection, an AM sideband is imprinted on the auxiliary beam using an AOM and polarizer. The sinusoidal AOM drive signal is provided by a network analyzer, which sweeps in frequency across the MHz band and demodulates the PD signal in-phase to make an RF transfer function measurement. At the FSR, there will be a AM transmission resonance (reflection minimum). If HOMs are also present (created by either partially occluding or misaligning the injection beam), they too will generate transmission resonances, but at a frequency shift proportional to the Gouy phase. For the theoretical 19 deg one-way Gouy phase at the sites, this mode spacing is approximately 300 kHz. If the transmission resonances of two or more modes can be simultaneously measured, their frequency separation will provide a direct measurement of the SRC Gouy phase.

The above figure illustrates this measurement configuration. An attached PDF gives more detail and the expected response based on Finesse modeling of this IFO configuration.

Attachment 1: src_gouy_phase_v3.pdf
src_gouy_phase_v3.pdf src_gouy_phase_v3.pdf src_gouy_phase_v3.pdf src_gouy_phase_v3.pdf
  13720   Fri Mar 30 03:23:50 2018 KojiUpdateGeneralaLIGO EOM work

I have been working on the aux beat setup on the PSL table between 9PM-3AM.

This work involved:

- Turning off the main marconi
- Turning off the freq generation unit (incl IMC modulation)
- Closing the PSL shutter

After the work, these were reverted and the IMC and both arms have been locked.

  13725   Mon Apr 2 15:14:21 2018 KojiUpdateGeneralModulation depth measurement for an aLIGO EOM

The new matching circuit was tested.

Results:

f_nominal  f_actual  response    required mod.  drivng power
 [MHz]      [MHz]    [mrad/V]     [rad]         needed [dBm]
  9.1       9.1        55         0.22      =>   22
118.3     118.2        16         0.01      =>    6

 45.5      45.4        45         0.28      =>   25
 24.1       N/A         2.1       0.014     =>   27

Comments:

- 9.1MHz and 118.3MHz: They are just fine.

- 24.1MHz: Definitely better (>x3) than the previous trial to combine 118MHz & 24MHz.
  We got about the same modulation with the 50Ohm terminated bare crystal (for the port1).
  So, this is sort of the best we can do for the 24.1MHz with the current approach.
  The driving power of 27dBm is required at 24.1MHz

- About the 45MHz
  - The driving power of 27dBm is required at 24.1MHz
  - The maximum driving power with the AM stabilized driver is 23dBm, nominally to say.
  - I wonder how we can reduce resistance (and capacitance) of the 45MHz further...?
  - I also wonder if the IFO can be locked with reduced modulation (0.28 rad->0.2 rad)
  - Can the driver max power be boosted a bit? (i.e. adding an attenuator in the RF power detection path)

 

Attachment 1: modulation_depth.pdf
modulation_depth.pdf
Attachment 2: impedance_eom.pdf
impedance_eom.pdf
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