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ID Date Author Type Category Subjectup
  9827   Thu Apr 17 17:27:32 2014 ericqUpdateLSCSome reference Plots

Jenne made some suggestions for some plots that would be useful on our CARM offset reduction adventures, so I made some with my MIST model. 

First, here's a plot showing the transfer function of CARM to TRX, with logarithmically spaced offsets out to 3nm. While not a control signal, it shows us where the optical plant resonance stuff is happening. The peaks in this TF correspond to peaks in REFL11, REFL55, AS11, etc., as in the close-to-resonance TFs in ELOG 9785


[more to come, had a MATLAB issue]


Attachment 2: carmSignalLevels.pdf
  5409   Wed Sep 14 20:30:36 2011 ranaUpdateSUSSome screens are still bad

I've found that a few of the screens still have Whited-Out fields due to naming changes (OL SUM and ALS-> TM OFFSET). I attach a screen shot of it.

The OL screens have the wrong SUM names and the IFO ALIGN screen is pointing to the wrong SUS screens.


  5439   Fri Sep 16 17:46:13 2011 kiwamuUpdateSUSSome screens fixed

The bad medm screens have been fixed. There are no blank fields and all the links are correct.

Quote from #5409

I've found that a few of the screens still have Whited-Out fields due to naming changes (OL SUM and ALS-> TM OFFSET). I attach a screen shot of it.

The OL screens have the wrong SUM names and the IFO ALIGN screen is pointing to the wrong SUS screens.


  5466   Mon Sep 19 17:45:39 2011 ranaUpdateSUSSome screens fixed


Kiwamu:       The bad medm screens have been fixed. There are no blank fields and all the links are correct.

Quote from #5409

I've found that a few of the screens still have Whited-Out fields due to naming changes (OL SUM and ALS-> TM OFFSET). I attach a screen shot of it.

The OL screens have the wrong SUM names and the IFO ALIGN screen is pointing to the wrong SUS screens.


 Really? I found this one with ~15 seconds of clicking around.


  15195   Fri Feb 7 02:24:24 2020 gautamUpdateLSCSome short notes

[koji, gautam] 

Plots + interpretation tomorrow.

  • CM_Slow path can be used to stabilize the arm powers somewhat but the AO crossover remains out of reach.
  • The REFL11 (=CARM_B) path offset has to be manually determined - we found that it can change by ~20% depending on the alignment, which maybe isn't surprising given that the mode shapes seen at POP, REFL and AS look like Rorschach inkblots.
  • We saw TRX/TRY regularly hit ~150, and at times even 200 (= recycling gain of ~10). Though any conclusive statement about the PRG can only be made once the lock is stabilized.
  • I was able to take a few CARM loop TFs with an SR785 hooked up at 1Y2. Despite ramping up the AO gain, we saw no effect at high frequencies in the TF shape (the phase bubble continued to roll off at ~100 Hz and there was no visible phase lead even as the AO gain was increased). It has to be estimated what the expected crossover gain is from the experiment with the high BW POY locking (taking into account the net difference in optical gain between POY for single arm and REFL for the full IFO).
  • The fact that I was able to hold the high BW POY lock makes me think that the IMC servo board's IN2 input (and indeed the rest of the IMC locking loop) is functioning as expected. But maybe this board will benefit from a detailed checkout like Koji did for the CM board.

Getting closer... To facilitate this work, I made some convenience scripts that can be run from the CM MEDM screen.

  11212   Fri Apr 10 03:44:51 2015 JenneUpdateLSCSome small progress, may have DAC problem?

Small steps tonight, but all in the forward direction.

On one of my better locks, I saw a kind of weird phenomenon with the PRMI sideband powers versus the carrier powers:

For the last 100 seconds of this plot, I'm all 1f.  Alignment is being handled mostly by Q's DC coupled ITM oplevs, and the transmission QPD ASC loops, although I was trying to adjust the offsets in the ASC loops to improve transmission for a bit.

At the very end, the last 10 seconds or so, the POP110 power goes down, and sits at about half it's maximum value.  POP22 isn't quite as bad, in that it still touches the max, but the RIN is about 50%.  The carrier DC signals (TRX, TRY, POPDC) don't see this huge jump.  I don't think I was touching anything the last few tens of seconds.  I'm not sure yet how I can so significantly lose sideband power, without losing a similar amount of carrier power. 

The ring-ups at about -70sec in the CARM and DARM outs are the bounce mode. 

I tried looking at 2D histograms of different combinations of channels, for the time around -30 seconds where things looked pretty clean.  It looks like the offsets that Q put in last night (+1 for MICH_B and -3 for PRCL_B) are still about right.  The PRCL_IN1 and MICH_IN1 were centered around zero at the maximum power points.  CARM and DARM had small offsets, which I put into the DARM_B and CARM_B filter banks (0.0066 for DARM_B, and 0.027 for CARM_B), although these are small enough that I don't know that they really do anything.

As a break from locking for a little while, I tried to see if I could get the TT3 and TT4 DAC channels to work for me.  I had hoped it would be a quick and easy task, but I'm not seeing signal out.  Since it wasn't working, I decided to go back to locking for the night, and look into the DAC in the daytime.  I want to use one channel as the IN2 input of the CM board, and another as the external modulation input to the Marconi for transfer functions, so I need them to work. 

As a side note on the input to the Marconi situation, it occurred to me that instead of laying a new cable, I can borrow the POP55 heliax.  We don't have a POP55 diode right now, and the other end comes out across the hall from the Marconi, so it would be pretty easy to have a medium-length cable go from ITMX table to the Marconi.  Objections to this? 

Attachment 1: PRMI_sb_powers_9Apr2015.png
  11213   Fri Apr 10 12:09:19 2015 ericqUpdateLSCSome small progress, may have DAC problem?

At the very end, the last 10 seconds or so, the POP110 power goes down, and sits at about half it's maximum value.  POP22 isn't quite as bad, in that it still touches the max, but the RIN is about 50%.  The carrier DC signals (TRX, TRY, POPDC) don't see this huge jump.  I don't think I was touching anything the last few tens of seconds.  I'm not sure yet how I can so significantly lose sideband power, without losing a similar amount of carrier power. 

I saw this same kind of behavior in my locklosses on Wednesday night; we should check out the 165 data, and see if the 3f PRCL error signal shows some drift away from zero.

Also, it's odd that CARM_IN1 and REFL11_I_ERR have different low frequency behavior in the plot you posted. I guess they have some difference in demodulation phase.  REFL11_I's bump at -40sec coincides with the dip in arm power and a rise in REFLDC, but ASDC seems pretty smooth, so maybe it is a real CARM fluctuation.

I set the REFL11 analog demodulation angle (via cable length) about a year ago (ELOG 9850), with some assumption about PRCL having the same demod angle as CARM, but this was probably set with the arms misaligned. We should recheck this; maybe we're coupling some other junk into CARM. 

  2310   Fri Nov 20 17:44:38 2009 JenneUpdateAdaptive FilteringSome svn shenanigans

[Sanjit, Jenne]

Sanjit and I are trying to put names to some signals which exist in SimuLink land, but which don't (yet) exist in EPICS land.  The deelio is that for each of the chosen SEIS signals in the ASS_TOP_PEM screen, the signal is split.  One part of the signal is used to decide how the adaptive filter should look, and the other part is actually used when doing the on-line subtraction.  Previously only the part of the signal which is used to decide on the Adaptive Filter could be seen on the screens, and had names. 

Before touching anything on the Simulink ASS.mdl, I did an svn check in, which put things at revision 36639. 

To try to make the desired signals exist, I put cdsFilt boxes (to create filter modules for each of these signals), and gave each of them a name (kind of like the Neverending Story....once they have a name, they'll exist).  My new names are C1:ASS-TOP_PEM_#_APPLY, which correspond to the previously-existing C1:ASS-TOP_PEM_#_ADPT (these are the ones that are along the top of the ASS_TOP_PEM matrix screen).  This version of the simulink model was checked in, and the svn is now at revision 36640.

We then did some "make clean", "make ass" and "make install-ass" action, and burt restored c1assepics, but nothing seems to be happening.  The screen doesn't have white boxes all over the place, and we didn't get any errors when we did the makes, and I'm sure we burt restored correctly (made sure the ASS GDS screen had a 1 in the lower left box etc), but all the values on the screen are still zero.  

When we ran the ass front end in terminal on the c1ass machine, we did see an error: "Invalid chan num found 2 = 30624" "DAQ init failed -- exiting".  I think this means that we need to have told some file somewhere that I was going to be adding 8 new channels. (maybe an .ini file?) Hopefully the Joe & Peter team can help us out with this, since they've been doing this kind of thing for the new system.

Moral of the story is, the new (non-working) simulink file has been svn checked in as revision 36640, and we're reverting to revision 36639, which was before I touched anything today.

  15682   Wed Nov 18 22:49:06 2020 gautamUpdateASCSome thoughts about AS WFS electronics

Where do we want to install the interface and readout electronics for the AS port WFS? Options are:

  • 1Y1 / 1Y3  (i.e. adjacent to the LSC rack) - advantage is that 55 MHz RF signal is readily available for demodulation. But space is limited (1Y2, where the RF signal is, is too full so at the very least, we'd have to run a short cable to an adjacent rack), and we'd have a whole bunch of IPC channels between c1lsc and c1ioo models.
  • 1X1/1X2. There's much more space and we can directly digitize into the c1ioo model, but we'd have to route the 55 MHz signal back to this rack (kind of lame since the signal generation is happening here). I'm leaning towards this option though - thinking we can just open up the freq generation box and take a pickoff of the 55 MHz signal...

There isn't much difference in terms of cable length that will be required - I believe the AS WFS is going to go on the AP table even in the new optical layout and not on the ITMY in-air oplev table? 

The project requires a large number of new electronics modules. Here is a short update and some questions I had:

  1. WFS head and housing. Need to finalize the RF transimpedance gain (i.e. the LC resonant part), and also decide which notches we want to stuff. Rich's advise was to not stuff any more than is absolutely necessary, so perhaps we can have at first just the 2f notch and add others as we deem necessary once we look at the spectrum with the interferometer locked. Need to also figure out a neat connector solution to get the signals from the SMP connectors on the circuit board to the housing - I'm thinking of using Front-Panel-Express to design a little patch board that we can use for this purpose, I'll post a more detailed note about the design once I have it.
  2. WFS interface board + soft-start board (the latter provides a smooth ramp up of the PD bias voltage). These go in a chassis, the assembly is almost complete, just waiting on the soft-start board from JLCPCB. One question is how to power this board - Sorensens or linear? If we choose to install in 1X1/1X2, I guess Sorensen is the only option, unless we have a couple of linear power supplies lying around spare.
  3. Demod board (quad chassis). Assembly is almost complete, need to install the 4 way RF splitter, some insulating shoulder washers. (to ensure the RF ground is isolated from the chassis), and better nuts for the D-sub connectors. A related question is how we want to supply the electrical LO signal for demodulation. The "nominal" level each demod board wants is 10 dBm. This signal will be sourced inside the chassis from a 4-way RF splitter (~7 dB insertion loss). So we'd need 17dBm going into the splitter. This is a little too high for a compact amplifier like the ZHL-500-HLN to drive (1dB compression point is 16 dBm), and the signal level available at the LSC rack is only ~2 dBm. So do we want a beefy amplifier outside the chassis amplifying the signal to this level? Or do we want to use the ZHL-500-HLN, and amplify the signal to, say 13 dBm, and drive each board with ~6 dBm LO? The Peregrine mixer on these boards (PE4140) are supposed to be pretty forgiving in terms of the LO level they want... In either case, I think we should avoid having an amplifier also inside the chassis, it is rather full in there with 4 demod boards, regulator board, all the cabling, and an RF splitter. It may be that heat dissipation becomes an issue if we stick an RF amplifier in there too...
  4. Whitening chassis. Waiting for front panels to arrive, PCBs and interface board are in hand, stuffed and ready to go. A question here is how we want to control the whitening - it's going to be rather difficult to have fast switchable whitening. I think we can just fix the whitening state. Another option would be to control the whitening using Acromag BIO channels.
  5. AI chassis - will go between whitening and ADC.
  6. Large number of cables to interconnect all the above pieces. I've asked Chub to order the usual "Deluxe" shielded Dsub cables, and we will get some long SMA-SMA cables to transmit the RF signals from head to demod board from Pasternack (or similar), do we need to use Heliax or the Times Microwave alternative for this purpose? What about the LO signal? Do we want to use any special cable to route it from the LSC rack to the IOO rack, if we end up going that way? 

Approximately half of the assembly of the various electronics is now complete. The basic electrical testing of the interface chassis and demod chassis are also done (i.e. they get power, the LEDs light up, and are stable for a few minutes). Detailed noise and TF characterization will have to be done.

  15690   Wed Nov 25 18:30:23 2020 gautamUpdateASCSome thoughts about AS WFS electronics

An 8 channel whitening chassis was prepared and tested. I measured:

  1. TF from input to output - there are 7 switchable stages (3 dB, 6 dB, 12 dB and 24 dB flat whitening gain, and 3 stages of 15:150 Hz z:p whitening). I enabled one at a time and measured the TF. 
  2. Noise with input terminated.

In summary,

  1. All the TFs look good (I will post the plots later), except that the 3rd stage of whitening on both boards don't show the expected transfer function. The fact that it's there on both boards makes me suspect that the switching isn't happening correctly (I'm using a little breakout board). I'm inclined to not debug this because it's unlikely we will ever use 3 stages of 15:150 whitening for the AS WFS. 
  2. The noise measurement displayed huge (x1000 above the surrounding broadband noise floor) 60 Hz harmonics out to several kHz. My hypothesis is that this has to do with some bad grounding. I found that the circuit ground is shorted to the chassis via the shell of the 9pin and 15pin Dsub connectors (but the two D37 connector shields are isolated). This seems very wierd, idk what to make of this. Is this expected? Looking at the schematic, it would appear that the shields of the connectors are shorted to ground which seems like a bad idea. afaik, we are using the same connectors as on the chassis at the sites - is this a problem there too? Any thoughts

Whitening chassis. Waiting for front panels to arrive, PCBs and interface board are in hand, stuffed and ready to go. A question here is how we want to control the whitening - it's going to be rather difficult to have fast switchable whitening. I think we can just fix the whitening state. Another option would be to control the whitening using Acromag BIO channels.

  15418   Fri Jun 19 16:30:09 2020 gautamUpdateASCSome thoughts about ASC


In ELOG 15368, I had claimed that the POP QPD based feedback servo actuating on the PRM stabilized the lock. I now believe this scheme of sensing using the POP QPD and feeding back to the PRM is not a good topology for stabilizing the PRC angular motion.


  • I was never able to get a measurement of the OLTF of this loop that made sense 
    • the loop was initally commissioned with the PRMI locked on the carrier, and the settings hence inferred to give a ~5 Hz UGF loop were used in the PRFPMI lock.
    • In the PRFPMI configuration, however, the loop gain seemed way too low when I measured using the usual IN1/IN2 method.
    • So it is critical for the lock stability that the angular feedforward works well, which it kind of does now (not that I have changed anything, but the glitches in the seismometer have not resurfaced recently).
    • Hopefully, this becomes less of an issue once we replace the TTs with SOS and OSEM based damping.
  • To get some more insight, I did some finesse modeling
    • Attachment #1 shows the sensing response at the QPDs we have available currently (POP and TR). 
    • I included the telescopes (propagation distances, in-air lenses) to these QPDs as best as I could.
    • A simplified model (3 mirror coupled cavity) is used, so there isn't really a common/differential mode in this picture, but we still get some insight I think.
    • Specifically, once the full lock is realized, the PRC optic motion isn't sensed well with our QPDs, and so it was some fluke that turning on these PRC angular feedback loops worked. 
    • Attachment #2 shows the same info as Attachment #1, but with the pendulum transfer functions (and radiation pressure effects) included. The SOS suspensions are modelled as f0=0.7/0.8 Hz (for P/Y), Q=5, while the tip-tilts have f0~5 Hz, Q~10. The high frequency phase is 0 degrees and not 180 as expected because of the pendulum complex pole pair because of the way the quantity is computed in Finesse.
  • The current scheme I use is:
    • DC couple the ITM oplevs, using their individual Oplev QPDs.
    • Use the TR QPDs, mixed to actuate on the ETMs in a common/differential way.
    • I think the system is under-determined with the sensors we currently have - we wan't to sense the 10 angular modes - PIT and YAW for the PRC, Csoft, Chard, Dsoft and Dhard (using the terminology from Kate's thesis), but we only have 6 sensors of the same field (POP, TRX and TRY QPDs, PIT and YAW from each).
    • So we need more sensors?
  • One thing that can easily be improved I think is to make the ASS system work at high power. 
    • think this should be as simple as scaling the gain for the loops to work for the high power.
    • Then we can counteract the input pointing drift at least.
    • But the ITM Oplev DC coupling would need to be turned OFF and then ON again, I'm not sure if this will introduce some transient that will destroy the lock...

I would also like to bring up the topic of implementing some WFS for the interferometer fields again, there doesn't seem to be any mention of this in the procurement/planning for the BHD. It is not obvious to me yet that we need WFS and not just DC QPDs from a noise point of view, but at least we should discuss this.

Attachment 1: sensingResponse.pdf
Attachment 2: sensingResponse_torque.pdf
  14324   Thu Nov 29 17:46:43 2018 gautamUpdateGeneralSome to-dos

[koji, gautam, jon, steve]

  • We suspect analog voltage from N2 pressure gauge is connected to interfacing Omega controller with the 'wrong' polarity (i.e pressure is rising over ~4 days and then rapidly falling instead of the other way around). This should be fixed.
  • N2 check script logic doesn't seem robust. Indeed, it has not been sending out warning emails (threshold is set to 60 psi, it has certainly gone below this threshold even with the "wrong" polarity pressure gauge hookup). Probably the 40m list is rejecting the email because controls isn't a part of the 40m group.
  • Old frames have to be re-integrated from JETSTOR to the new FB in order to have long timescale lookback.
  • N2 cylinder pressure gauges (at the cylinder end) need a power supply - @ Steve, has this been purchased? If not, perhaps @ Chub can order it.
  • MEDM vacuum screen should be updated to have gate valves be a different color to the spring-loaded valves. Manual valve between TP1 and V1 should also be added.
  • P2, P3 and P4 aren't returning sensible values (they should all be reading ~760torr as is P1). @ Steve, any idea if these gauges are broken?
  • Hornet gauges (CC and Pirani) should be hooked up to the new vacuum system.
  • add slow channels of   foreline pressures of TP2 & 3   and    C1:Vac-IG1_status_pressure
  4834   Fri Jun 17 23:20:05 2011 KojiUpdateLSCSome updates of the LSC screen

Some updates of the LSC screen

- Signal amplitude monitor for the PD signals (--> glows red for more than 1000)

- Kissel Buttons for the main matrices

- Trigger display at the output of the DOF filters

- Signal amplitude monitor for the SUS LSC output (--> glows red for more than 10000)


ADC Over flow monitor is showing some unknown numbers (as ADCs are handled by IOPs).
I asked Joe for the investigation (and consideration for the policies)

Attachment 1: screen.png
  5914   Wed Nov 16 17:29:46 2011 kiwamuUpdateGreen LockingSome updates on the Y end green PDH
Quote from #5894

 (Things to be done)

   [DONE]   1.1 Measurement of the arm fluctuation => to allow re-designing the servo shape
   [DONE]   1.2 temporary SR560 servo
   [ONGOING]1.3 Sanity checks on the modulation depth, reflectivity, PD dark noise and etc.,
   [DONE]  1.4 Make the servo more robust
   [DONE]  1.5 Some modifications on the medm screens
   [NOTYET]   1.6 Activation of the temperature feedback through the realtime digital control

Some updates on the Y end green PDH lock

(Measurement of the Y arm fluctuation)

In order to design the PDH box's servo shape we wanted to measure the Y arm fluctuation.
Here is the spectrum taken by looking at the control signal before the laser PZT.
 The scale of the Y axis is calibrated by using the PZT response of 5 MHz/V.
Above 10 Hz the spectrum shows 1/f noise which I believe the laser frequency noise.

(Temporary servo setup)

 We have found that the servo shape was not enough (#5890) to well-suppress the fluctuation shown above.
 Since the Newfocus fast servo box only makes 1/f shape, the error signal wasn't suppressed within the linear range.
So I have added an SR560 in the other input of the Newfocus servo box to make the filter shape 1/f^2.
Then the lock became more solid and the reflected DC light in time series is now much flat if the alignments are good.
I will post the servo shape and diagram later.

(Sanity checks)

 I looked at the reflected DC light when the laser was kept locked.
The reflectivity of the Y arm cavity went down to about 30% and this is good because it is supposed to be 27.5% when it is locked according the spec.
This means the mode-matching is not so bad.
  14152   Fri Aug 10 01:10:56 2018 gautamUpdateLSCSome vertex locking restored

For the first time after the whirlwind vent, I managed to lock the PRMI.

  • First, I did POX/POY locking, dither aligned the arms to maximize TRX and TRY.
  • Next, I misaligned the ETM and tested the Michelson locking
    • Since we've lost ~70% of power on the AS55 PD, I set the whitening gain for AS55 I and Q channels to +6dB (old value was 0dB).
    • worked alright. In this new config, the peak-to-peak Michelson fringe count is ~80 cts, while I reported ~60cts-pp a couple of months ago, so all seems good on that front.
    • But the config script in the IFOconfigure MEDM screen somehow doesn't set the AS55_Q ----> MICH_A element in the LSC input matrix anymore.
    • I edited the .snap file for this configuration to set the relevant matrix element EPICS channel to +1.0.
    • I also edited the overall loop gain for this configuration from +30 to +2 (for bright fringe, use -2 for dark fringe).
  • Feeling adventerous, I decided to try PRMI in the carrier resonant tuning (to be clear, PRCL on REFL11_I, MICH on AS55_Q).
    • Finding the REFL spot on the camera took a while since the PRM has been macroscopically misaligned for the mode-scanning
    • Went out to the table and centered the REFL beam onto REFL11 and REFL55 PDs - didn't need much tweaking, which is a good sign, since we shouldn't have screwed anything up on the symmetric side by any of the vent activities.
    • Restored PRMI locking using the IFOconfigure MEDM screen - lock caught almost immediately.
    • Ran the dither alignment servos for MICH and PRCL - BS needed a bit of encouragement to make the dark spot dark, but POP has been pretty stable over ~15mins.
    • I didn't take any loop transfer functions, to do.

I don't have the energy to make a DRMI attempt tonight - but the signs are encouraging. I'd like to use the IFO in the next few days to try and recover DRMI locking. The main concern is that the optical path on the AS beam has changed by ~0.3m I estimate. So the demod phase for AS55 may need to be adjusted, but the change due to optical path length only should be ~10degrees so the DRMI locking with the old settings should still work. Perhaps we also want to scan the PRC and SRC with the phase information from the Trans/Refl transfer functions as well.

Don't want to jinx it, but the c1lsc FE models have been stable. Tomorrow, I'd like to re-enable c1cal, since it has some useful channels for NBing. Could c1daf/c1oaf which have significant amounts of custom C code be the culprits?

Attachment 1: PRMIcarrier.png
  14602   Fri May 10 15:18:04 2019 gautamUpdatePSLSome work on/around PSL table
  1. In anticipation of installing the new fan on the PSL, I disconencted the old fan and finally removed the bench power supply from the top shelf.
  2. Moved said bench supply to under the south-west corner of the PSL table.
  3. Installed temporary Acromag crate, now with two ADC cards, under the PSL table and hooked it up to the bench suppy (+15 VDC). Also ran an ethernet cable from 1X3 to the box on over head cable tray and connected it.
  4. Brought other end of 25-pin D-sub cable used to monitor the NPRO diagnostics channels from 1X4/1X5 to the PSL table. Rolled the excess length up and cable tied it, the excess is sitting on top of the PSL enclosure. Key parts of the setup are shown in Attachments #1-3. This is not an ideal setup and is only meant to get us through to the install of the new c1psl/c1ioo Acromag crate.
  5. Edited the modbus config file at /cvs/cds/caltech/target/c1psl2/npro_config.cmd to add Jon's new ADC card to the list.
  6. Edited EPICS database file at /cvs/cds/caltech/target/c1psl2/psl.db to add entries for the C1:PSL-FSS_RMTEMP and C1:PSL-PMC_PMCTRANSPD channels.
  7. Hooked up said channels to the physical ADC inputs via a DB15 cable and breakout board on the PSL table.
    CH0 --- FSS_RMTEMP (Pins 5/18 of the DB25 connector on the interface box to pins 1/9 of the Acromag DB15 connector)
    CH1 --- PMC TRANS (BNC cable from PD to pomona minigrabber to pins 2/10 of the Acromag DB15 connector)
    CH2-6 are unsued currently and are available via the DB15 breakout board shown in Attachment #3. CH7 is not connected at the time of writing
    The pin-out for the temperature sensor interface box may be found here. Restarted the modbus process. The channels are now being recorded, see Attachment #4, although checking the status of the modbus process, I get some error message, not sure what that's about.

So now we can monitor both the temperature of the enclosure (as reported by the sensor on the PSL table) and the NPRO diagnostics channels. The new fan for the controller has not been installed yet, due to us not having a good mounting solution for the new fans, all of which have a bigger footprint than the installed fan. But since the laser isn't running right now, this is probably okay.

modbusPSL.service - ModbusIOC Service via procServ
   Loaded: loaded (/etc/systemd/system/modbusPSL.service; disabled)
active (running) since Fri 2019-05-10 13:17:54 PDT; 2h 13min ago
  Process: 8824 ExecStop=/bin/kill -9 ` cat /run/modbusPSL.pid`
(code=exited, status=1/FAILURE)
 Main PID: 8841 (procServ)
   CGroup: /system.slice/modbusPSL.service
           ├─8841 /usr/bin/procServ -f -L /home/controls/modbusPSL.log -p /run/modbusPSL.pid 8009 /cvs/cds/rtapps/epics-
           ├─8842 /cvs/cds/rtapps/epics- /cvs/cds/caltech/target/c1psl2/npro_config.c...
           └─8870 caRepeater

May 10 13:17:54 c1auxex systemd[1]: Started ModbusIOC Service via procServ.

Attachment 1: IMG_7427.JPG
Attachment 2: IMG_7428.JPG
Attachment 3: IMG_7429.JPG
Attachment 4: newPSLAcro.png
  14604   Sat May 11 11:48:54 2019 JonUpdatePSLSome work on/around PSL table

I took a look at the error being encountered by the modbusPSL service. The problem is that the /run/modbusPSL.pid file is not being generated by procServ, even though the -p flag controlling this is correctly set. I don't know the reason for this, but it was also a problem on c1vac and c1susaux. The solution is to remove the custom kill command (ExecStop=...) and just allow systemd to stop it via its default internal kill method.

modbusPSL.service - ModbusIOC Service via procServ
   Loaded: loaded (/etc/systemd/system/modbusPSL.service; disabled)
active (running) since Fri 2019-05-10 13:17:54 PDT; 2h 13min ago
  Process: 8824 ExecStop=/bin/kill -9 ` cat /run/modbusPSL.pid`
(code=exited, status=1/FAILURE)
 Main PID: 8841 (procServ)
   CGroup: /system.slice/modbusPSL.service
           ├─8841 /usr/bin/procServ -f -L /home/controls/modbusPSL.log -p /run/modbusPSL.pid 8009 /cvs/cds/rtapps/epics-
           ├─8842 /cvs/cds/rtapps/epics- /cvs/cds/caltech/target/c1psl2/npro_config.c...
           └─8870 caRepeater

May 10 13:17:54 c1auxex systemd[1]: Started ModbusIOC Service via procServ.

  666   Mon Jul 14 10:57:00 2008 KojiFrogsEnvironmentSomeone at 40M sent LHO water of life
Someone at the 40m sent Mike@LHO a pound of peets coffee with the name of Koji Arai.
It was a good surprise! Thanks, we will enjoy it!
I will return to Pasadena next week. See you then.
  11990   Mon Feb 15 12:28:03 2016 gautamUpdateGeneralSomething has gone wrong - was there a power outage?

I came into the 40m a few minutes ago, and noticed the following (approximately in this order):

  • The striptool plots projected onto the wall were gone, even though the projector seemed to be working fine
  • There was no light at all in the IFO 
  • There was an incessnt beeping noise coming from inside the lab.

To investigate further, I checked today's summary pages, and whatever caused this, happened around 730am today morning (approx 5 hours ago). I also saw that all the watchdogs were tripped, except MC3, BS and SRM. 

I then tracked down the beeping - I believe that it is coming from Megatron.(in fact, it is coming from the Jetstor..) 

I also found that the PSL is OFF, and the Marconi, though ON, has the display parameters set to values that I normally see when it is first turned ON (i.e. the carrier frequency is 1200MHz, the output is -140dBm etc - this is what led me to suspect that somehow the power connection was interrupted? As far as the workstation computers are concerned, I don't think ROSSA was affected, but pianosa is frozen and donatella is at the login screen. The CDS overview MEDM screen refuses to load correctly (though some of the other MEDM screens are working fine). I'm not entirely sure how to go about fixing all of this, so for now, I'm leaving the PSL off and I've shutdown the remaining watchdogs.

It just occurred to me to check the status of the vacuum - the MEDM screen seems to suggest everything is fine (see Attachment #1). I went down to the X end to do a quick check on the status of the turbo pumps and everything looks normal there...

Attachment 1: Vac_15Feb2016.png
  11991   Mon Feb 15 13:09:33 2016 KojiUpdateGeneralSomething has gone wrong - was there a power outage?

Looks like that's the case. LIGO GC also sent an e-mail that there was a popwer glitch.

  224   Thu Jan 3 12:38:49 2008 robBureaucracyTMISore throat


I did not feel anything wrong yesterday, but unfortunately I have a very much sore throat today. I need to drink warm milk with honey and rinse my throat often today. So far I do not have other illness symptomes (no fever), so I hope that this small disease will not last for a long time, but I feel that it is better for me to cure my sore throat today at home (and probably it is safer for others in 40-m).

I took yesterday the book "Digital Signal Processing", so I have it for reading at home.

Hope to see you tomorrow.

I've added a new category--TMI--for entries along these lines.
  8402   Wed Apr 3 15:00:24 2013 JamieSummaryElectronicsSorensen supplies in LSC rack (1Y2)

I investigated the situation of the two Sorensen supplies in the LSC rack (1Y2).  They are there solely to supply power to the LSC LO RF distribution box.  One is +18 V and the other is +28 V.  All we need to do is make a new longer cable with the appropriate plug on one end (see below), long enough to go from the bottom of the 1Y3 rack to the top of 1Y2, and we could move them over quickly.  Some sort of non-standard circular socket connector is used on the distribution box:


It could probably use thicker conduction wire as well.

If someone else makes the cable I'll move everything over.

  12814   Thu Feb 9 11:22:56 2017 gautamUpdateGeneralSorensens and DIN connections at 1X1

I'd like to fix a few things at 1X1 when we plug in the new amplifier for the 29.5MHz modulation signal. 

  1. Split off separate +24 and ground wires to the green BBPD RF amplifiers and the AOM driver (they are sharing a single fuse at the moment)
  2. Tap a new +24 GND -24V set for the FSS Fast summing box - this is currently running with a bench power supply underneath the PSL table set to +/-18V, but I checked the 7815/7915 datasheets and they accept up to 35V input for a 15V output, so it should be fine to use 24V
  3. Hook up the ZHL-2A for the IMC modulation.

Steve has ordered rolls of pre-twisted wire to run from 1X1 to the PSL table, so that part can be handled later.

But at 1X1, we need to tap new paths from +/- 24V to the DIN connectors. I think it's probably fine to turn off the two Sorensens, do the wiring, and then turn them back on, but is there any procedure for how this should be done? 

Attachment 1: Screen_Shot_2017-02-10_at_9.01.46_AM.png
  341   Tue Feb 26 20:24:04 2008 AndreySummaryTMISorrow
As for that plot of three-dimensional surface, I indeed was wrong with the axis "Q_ETMX-Q_ITMX" (I put there wrong string "Q_ITMX-Q_ETMX"). On Friday plot there were values 10^(-12) on the z-axis, and that should be really meters, but the point that as I realized on Monday, I have never calibrated experimental measurement results from counts to meters , that's why it is this difference between 10^(-6) and 10^(-12). I still did not find the way to compare experim. and theoretical plots, because even if I leave "counts" on both plots, so that I have scale 10^(-6) on both plots, then the change in theoretical plot is just 0.02*10^(-6) for the range of Q-factors change, while the change in experimental measurements is an order of magnitude more 0.4*10^(-6), so the surface for theretical plot would be almost flat in the same axes as experimental results.
  16026   Wed Apr 14 13:12:13 2021 AnchalUpdateGeneralSorry, it was me

Sorry about that. It must be me. I'll make sure it doesn't happen again. I was careless to not check back, no further explanation.indecision

  16029   Wed Apr 14 15:30:29 2021 ranaUpdateGeneralSorry, it was me

Maybe tighten the tensioner on the door closer so that it closes by itself even in the low velocity case. Or maybe just use the front door like everyone else?

  7751   Tue Nov 27 01:03:42 2012 AyakaUpdateWienerFilteringSound on PSL

 Last Thursday, I put the speaker and my laptop in the PSL table, and make triangular wave sound with the basic frequency of 40Hz, and Gaussian distributed sound.
(I create the sounds from my laptop using the software 'NHC Tone Generator' because I could not find the connector from BNC to speaker plug.)
And I measured the acoustic coupling in MCF signal. The all the 6 microphones were set in PSL table around PMC and PSL output optics. 

The performance of the offline noise cancellation with wiener filter is below.
(The target signal is MCF and the witness signals are 6 microphones.)

  • With Gaussian sound (Sorry for wrong labeling 'XARM' and no calibration)
  • With 40Hz Triangular sound (Sorry for no calibration again)

I can see some effects on MCF due to the sound on PSL table. Though I can subtract some acoustic signal and there are no coherence between MCF signal and mic signals, still some acoustic noise remains.
This is maybe because of some non-linearity effects or maybe because we have other effective places for acoustic coupling measurement. More investigations are needed.

Also, I compared the wiener filter and the transfer function from microphones signal to MCF signal. They should be the same ideally.

(Left: Wiener filter, Right: Transfer function estimated by the spectrum. They are measured when the Gaussian sound is on.)

These are different especially lower frequencies than 50 Hz. The wiener filter is bigger at lower frequencies. I guess this adds extra noise on the MCF signal. (see the 1st figure.)
The wiener filter can be improved by filterings. But if so, I want to know how can we determine the filters. It is interesting if we have some algorithms to determine the filters and taps and so on.
The more investigations are also needed.

  7760   Wed Nov 28 23:55:13 2012 AyakaUpdateWienerFilteringSound on PSL

 I have been searching for the way we can subtract signal better since I could see the acoustic coupling signal remains in the target signal even though there are no coherence between them.

I changed the training time which is used to decide wiener filter.
I have total 10 minutes data, and the wiener filter was decided using the whole data before.

(Right: the performance with the data when the triangular sound was created. Left: the performance with the data when the gaussian sound was created.)

I found that the acoustic signal can be fully subtracted above 40 Hz when the training time is short. This means the transfer functions between the acoustic signals and MCF signal change.
However, if the wiener filter is decided with short-time training, the performances at lower frequencies get worse. This is because wiener filter do not have enough low-frequency information.

So, I would like to find the way to combine the short-time training merit and long-time training merit. It should be useful to subtract the broad-band coupling noise.

  14148   Thu Aug 9 02:12:13 2018 gautamUpdateCOCSouth East or West?


For operating the SRC in the "Signal-Recycled" tuning, the SRC macroscopic length needs to be ~4.04m (compared to the current value of ~5.399m), assuming we don't do anything fancy like change the modulation frequencies and not transmit through the IMC. We're putting together a notebook with all the calculations, but today I was thinking about what the signal extraction path should be, specifically which chamber the SRM should be in. Just noting down the thoughts I had here while they're fresh in my head, all this has to be fleshed out, maybe I'm making this out to be more of a problem than it actually is.


  • For the current modulation frequencies, if we want the reosnance conditions such that the f2 sideband is resonant in the SRC (but not f1, i.e. small Schnupp asymmetry regime) while the carrier is resonant in the arms (required for good sensing of the SRC length), the macroscopic length of the SRC needs to be changed to ~4.04m.
  • Practically, this means that the folded SRC would only have one folding mirror (SR2).
  • There is a shorter SRC length of ~1.something metres which would work, but that would involve changing the relative position between ITMs and BS (currently ~2.3m) so I reject that option for now.
  • So the SR2 would be roughly where it is right now, ~20cm from the BS.
  • The question then becomes, where do we direct the reflection from the SR2? We need an optical path length of ~1.5m from SR2. So options are 
    • ITMY table (East)
    • ITMX table (South)
    • IMC table (West)
  • Moreover, after the SRM, we have to accommodate:
    • Some kind of pickoff for in-air PDs.
    • OFI.
    • OMC MMT.
    • OMC.
  • Some kind of CBA (as of now I think going to the ITMY table is the best option):
Option Advantages Disadvantages
  • Easy to direct beam from BS/PRM chamber to the ITMY table (i.e. we don't have to worry too much about avoiding other optics in the path etc).
  • Ease of access to chamber, ease of working in there.
  • ITMY table probably has the most room to work out an OFI + OMC MMT + OMC solution.
  • AS beam extraction to air will be more complicated, possibly have to do it on ITMY optical table.
  • Not sure if the ITMY table can accommodate all of the output optics subsystems I listed above.
  • Routing the LO beam to this table would be tricky I guess.
  • Routing the LO beam for homodyne detection is probably easiest in this chamber.
  • Allows for small AoI on folding mirror, reducing the impact of astigmatism.
  • Pain to work in this chamber because of IMC tube.
  • Steering beam from SR2 to ITMX table means threading the needle between PRM and PR3 possibly.
  • Probably allows the use of (almost) the entire existing OMC chamber for the output optics (OFI, OMC MMT, OMC).
  • IMC table is crowded (2 SOS towers, several steering optics for the input beam, input faraday).
  • Not sure what is the performance of the seismic isolation stacks on these tables vs the larger optical tables.
  • Painful to work in these smaller chambers.
  15624   Tue Oct 13 21:22:29 2020 gautamUpdateGeneralSpace cleared in 1Y1 for new FEs

[JV, GV]

We cleared up some space in the 1Y1 electronics rack to install the 3 new FE machines. I removed the current driver and laser from 1Y1, they are now stored in the E10 cabinet. I will upload some photos to gPhotos soon.

  1. I think it's good to have all these FEs in one rack (at least the new ones) - we should then hook it up to an ethernet power source, so that we can remotely power cycle them. I think we have long enough cables to interface to expansion chasses / dolphin switches, but if not, I think it's still a good idea to have these machines in 1Y1 as it is the least sensitive area in terms of immunity to bumping some cable during setup work and disturbing the rest of the IFO.
  2. We found that the rails that the Supermicros shipped with the servers seem to be just a little too narrow - we mounted these in the rack, but had considerable difficulty sliding the server units in. Once they are in, they don't slide smoothly. Is there some special trick to installing these? 
  3. I spent a few minutes trying to get Debian 8 installed on these machines, so that the rest of the setup work could be done remotely - however, there appear to be some firmware issues and so I'm not gonna dive into this.
    • I couldn't find a disk image for Debian 8.5 which is what the KT wikl recommends, so the OS I tried to install was Debian 8.11.
    • The error that comes up is related to a "stalled CPU" - apparently this is related to some graphics driver issue (there's another forum page that suggests upgrading the BIOS, but I don't think that's the problem here).
    • Anyways, this part of the process is only to install some drivers and do the initial setup - these machines will eventually run a diskless boot from the image on FB, so who knows if there will be some other driver issues/hardware-software incompatibilities there 😱 .
    • We should also make an effort to set these machines up with IPMI, but I think we first need to install an OS and a CLI to setup the IPMI. My cursory browsing of the manual suggests that the initial setup maybe can be done without installing an OS, and then subsequent work, including OS install, can be done remotely. If someone reads more in detail and can provide me a step-by-step, I can follow those instructions (if they aren't available to come into the lab). See here for some brief documentation of how to access the IPMI.
  15168   Tue Jan 28 19:12:30 2020 JonConfigurationPSLSpare channels added to c1psl chassis

After some discussion with Gautam, I decided to build more spare channels into the new c1psl machine. This is anticipation of adding new laser and ISS channels in the near future, to avoid having to disconnect the installed chassis and pull it out of the rack. The spare channels will be wired to DB37M feedthroughs on the front side of the chassis, with enough wire length to be able to pull the breakout boards out of the front to reconfigure their wiring as needed (e.g., split off channels onto a separate connector).

To have enough overhead, this will require installing 1 additional ADC unit (XT1221) and 1 additional DAC (XT1541). We have enough spare BIO channels among the existing units (both sinking and sourcing). This will give us:

  • 13 spare ADC channels
  • 14 spare DAC channels
  • 16 spare sinking BIO channels
  • 12 spare sourcing BIO channels

The updated c1psl chassis wiring assignments are attached. It adds 4 new DB37M connectors for the spare channels (highlighted in yellow) and fixes one typo Jordan found while wiring today. The most current spreadsheet is available here.

Attachment 1: c1psl_feedthrough_wiring_v2.pdf
c1psl_feedthrough_wiring_v2.pdf c1psl_feedthrough_wiring_v2.pdf c1psl_feedthrough_wiring_v2.pdf c1psl_feedthrough_wiring_v2.pdf c1psl_feedthrough_wiring_v2.pdf
  15615   Tue Oct 6 14:35:16 2020 JordanUpdateVACSpare forepumps

I have placed 3 new in box, IDP 7 forepumps along the x arm of the interferometer. These are to be used as spares for both the 40m and Clean and Bake.

  12158   Wed Jun 8 13:50:39 2016 jamieConfigurationCDSSpectracom IRIG-B card installed on fb1

[EDIT: corrected name of installed card]

We just installed a Spectracom TSyc-PCIe timing card on fb1.  The hope is that this will help with the GPS timeing syncronization issues we've been seeing in the new daqd on fb1, hopefully elliminating some of the potential failure channels.

The driver, called "symmetricom" in the advLigoRTS source (name of product from competing vendor), was built/installed (from DCC T1500227):

controls@fb1:~/rtscore/tests/advLigoRTS-40m 0$ cd src/drv/symmetricom/
controls@fb1:~/rtscore/tests/advLigoRTS-40m/src/drv/symmetricom 0$ ls
Makefile  stest.c  symmetricom.c  symmetricom.h
controls@fb1:~/rtscore/tests/advLigoRTS-40m/src/drv/symmetricom 0$ make
make -C /lib/modules/3.2.0-4-amd64/build SUBDIRS=/home/controls/rtscore/tests/advLigoRTS-40m/src/drv/symmetricom modules
make[1]: Entering directory `/usr/src/linux-headers-3.2.0-4-amd64'
  CC [M]  /home/controls/rtscore/tests/advLigoRTS-40m/src/drv/symmetricom/symmetricom.o
/home/controls/rtscore/tests/advLigoRTS-40m/src/drv/symmetricom/symmetricom.c:59:9: warning: initialization from incompatible pointer type [enabled by default]
/home/controls/rtscore/tests/advLigoRTS-40m/src/drv/symmetricom/symmetricom.c:59:9: warning: (near initialization for ‘symmetricom_fops.unlocked_ioctl’) [enabled by default]
/home/controls/rtscore/tests/advLigoRTS-40m/src/drv/symmetricom/symmetricom.c: In function ‘get_cur_time’:
/home/controls/rtscore/tests/advLigoRTS-40m/src/drv/symmetricom/symmetricom.c:89:2: warning: ISO C90 forbids mixed declarations and code [-Wdeclaration-after-statement]
/home/controls/rtscore/tests/advLigoRTS-40m/src/drv/symmetricom/symmetricom.c: In function ‘symmetricom_init’:
/home/controls/rtscore/tests/advLigoRTS-40m/src/drv/symmetricom/symmetricom.c:188:2: warning: ISO C90 forbids mixed declarations and code [-Wdeclaration-after-statement]
/home/controls/rtscore/tests/advLigoRTS-40m/src/drv/symmetricom/symmetricom.c:222:3: warning: label ‘out_remove_proc_entry’ defined but not used [-Wunused-label]
/home/controls/rtscore/tests/advLigoRTS-40m/src/drv/symmetricom/symmetricom.c:158:22: warning: unused variable ‘pci_io_addr’ [-Wunused-variable]
/home/controls/rtscore/tests/advLigoRTS-40m/src/drv/symmetricom/symmetricom.c:156:6: warning: unused variable ‘i’ [-Wunused-variable]
  Building modules, stage 2.
  MODPOST 1 modules
  CC      /home/controls/rtscore/tests/advLigoRTS-40m/src/drv/symmetricom/symmetricom.mod.o
  LD [M]  /home/controls/rtscore/tests/advLigoRTS-40m/src/drv/symmetricom/symmetricom.ko
make[1]: Leaving directory `/usr/src/linux-headers-3.2.0-4-amd64'
controls@fb1:~/rtscore/tests/advLigoRTS-40m/src/drv/symmetricom 0$ sudo make install
#remove all old versions of the driver
find /lib/modules/3.2.0-4-amd64 -name symmetricom.ko -exec rm -f {} \; || true
find /lib/modules/3.2.0-4-amd64 -name symmetricom.ko.gz -exec rm -f {} \; || true
# Install new driver
install -D -m 644 symmetricom.ko /lib/modules/3.2.0-4-amd64/extra/symmetricom.ko
/sbin/depmod -a || true
/sbin/modprobe symmetricom
if [ -e /dev/symmetricom ] ; then \
        rm -f /dev/symmetricom ; \
mknod /dev/symmetricom c `grep symmetricom /proc/devices|awk '{print $1}'` 0
chown controls /dev/symmetricom
controls@fb1:~/rtscore/tests/advLigoRTS-40m/src/drv/symmetricom 0$ ls /dev/symmetricom
controls@fb1:~/rtscore/tests/advLigoRTS-40m/src/drv/symmetricom 0$ ls -al /dev/symmetricom
crw-r--r-- 1 controls root 250, 0 Jun  8 13:42 /dev/symmetricom
controls@fb1:~/rtscore/tests/advLigoRTS-40m/src/drv/symmetricom 0$ 
  12161   Thu Jun 9 13:28:07 2016 jamieConfigurationCDSSpectracom IRIG-B card installed on fb1

Something is wrong with the timing we're getting out of the symmetricom driver, associated with the new spectracom card.

controls@fb1:~/rtscore/tests/advLigoRTS-40m/src/drv/symmetricom 127$ lalapps_tconvert 
controls@fb1:~/rtscore/tests/advLigoRTS-40m/src/drv/symmetricom 0$ cat /proc/gps 
controls@fb1:~/rtscore/tests/advLigoRTS-40m/src/drv/symmetricom 0$ 

The GPS time is way off, and it's counting up at something like 900 seconds/second.  Something is misconfigured, but I haven't figured out what yet.

The timing distribution module we're using is spitting out what appears to be an IRIG B122 signal (amplitude moduled 1 kHz carrier), which I think is what we expect.  This is being fed into the "AM IRIG input" connector on the card.

Not sure why the driver is spinning so fast, though, with the wrong baseline time.  Reboot of the machine didn't help.

  15608   Fri Oct 2 12:52:22 2020 gautamUpdateGeneralSpectroscopic grade Isopropanol delivered

2x500 ml bottles of spectroscopic grade isopropanol were delivered. I marked them with today's date and placed them in the solvent cabinet. In the process, my shoulder bumped the laser interlock switch by the door to the VEA in the drill press area, which turned the PSL NPRO off. I turned it back on just now. The other NPROs are not connected to the interlock and so were unaffected.

  15898   Wed Mar 10 17:35:47 2021 gautamUpdateSUSSpooky action at a distance

As I am sitting in the control room, the PRM suspension watchdog tripped again. This time, there is clearly no seismic activity. Yet, the BS suspension also shows a slight disturbance at the same time as the PRM. ITMY shows no perturbation though. My best hypothesis here is that the problem is electrical. In Attachment #1, you can see that all of the Sensors go to -6000 cts (whut?) for ~30 seconds. Zooming in to that segment in Attachment #2, it would appear that the light detected by the LED changed dramatically (went dark?) on all 5 coils. The 4 face coils have the same time constant but the side has a different one, but in any case, this level of light change in half a second is clearly not physical. Then the watchdog trips because this huge apparent motion elicits a kick from the damping loops.

The plots I attach are for the DQed sensor channels, so there is some digital filtering involved. But I confirmed that the signal doesn't go negative if I disable the input to the filter module. So it would seem that the voltage input to the ADC really chanegd polarity, seems unphysical. Could be Satellite Box or whitening electronics I suppose - I think we can exclude bad cabling, as that would just lead to the signals going to 0, whereas it would appear here that they did really change sign (confirmed by looking at the ULPDmon channel, which is digitized by Acromag, which reports -10 V at the time of glitch). But why should the BS care about the PRM electronics going wonky?

In addition to an exorcist, we need functioning electronics!

This optic has been hampering my locking attempts all evening. I switched the PRM and SRM satellite boxes, but then I remembered PRM has the Al foil "hats" to attenuate scattered light. of course the Al foil is conducting and can short the OSEM leads. I put some kapton pieces in between OSEM and foil to try and mitigate this issue but I suppose over time it could have slipped, and is making some intermittent contact, shorting PD anode and cathode (that would explain the PD reporting -10 V instead of some physical value).

If this is the problem we would need a vent to address it. In the daytime I'll measure L and R of the coils to see if the actuator imbalance I reported is also due to the same problem...

Attachment 1: PRMtrip.png
Attachment 2: PRMtrip_zoom.png
  14531   Wed Apr 10 22:59:22 2019 gautamUpdateIOOSpooled fiber

Steve had showed me some stock of long fibers a while back - they are from Oz Optics, and are 50m long, and are already spooled - so barring objections, we will try the MZ setup with the spooled fiber and see if there is any improvement in the fringing rate of the MZ. Then we can evaluate what additional stabilization of the fiber length is required. Anjali will upload a photo of the spooled fiber.

  14534   Thu Apr 11 09:05:06 2019 AnjaliUpdateIOOSpooled fiber
  • Attchment #1,2,3 and 4 shows the results with frequency modulation of 32 Hz, 140 Hz , 300 Hz and without frequency modulation. I am trying to understand these results better.
  • A lot of fringing is there even when no modulation is applied. We hope to improve this by spooling the fiber and then encasing it in a box. 
  • As mentioned by Gautam, we have got a 50 m spooled fiber. Attachment #5 shows the photo of the same

Steve had showed me some stock of long fibers a while back - they are from Oz Optics, and are 50m long, and are already spooled - so barring objections, we will try the MZ setup with the spooled fiber and see if there is any improvement in the fringing rate of the MZ. Then we can evaluate what additional stabilization of the fiber length is required. Anjali will upload a photo of the spooled fiber.

Attachment 1: Frequecy_modulation_32_Hz.pdf
Attachment 2: Frequecy_modulation_140_Hz.pdf
Attachment 3: Frequecy_modulation_300_Hz.pdf
Attachment 4: Without_modulation.pdf
Attachment 5: New_fiber_spool.JPG
  2864   Sun May 2 15:28:25 2010 KojiUpdateIOOSpot Positions of MC1/MC3


The spot positions on the MC mirrors were measured with coil balance gains.
The estimated spot positions from the center of the MC1 and MC3 are as followings:

MC1H = +0.29 mm
MC1V = -0.43 mm
MC3H = +1.16 mm
MC3V = -0.68 mm

The cordinates are described in the figure


As far as the cavity mirrors are aligned to the incident beam, spots on the MC1 and MC3 tell us the geometry of the incident beam.
Note that spot position on the MC2 is determined by the alignment of the MC1 and MC3, so it does not a big issue now.
The calibration between the coil balance and the spot position are described in the previous entry.

  1. Lock the MC. Align it with MC2/MC3
  2. Run A2L scripts. script/A2L/A2L_MC1 and so on.
    • The scripts run only on the solaris machines. They require "expect" in stalled some specific place which does not exist on the linux machines.
    • Excitation amplitude, excitation freq, readback channels were modified


Beam powers
MC Trans: 0.18
MC Refl: 0.12-0.13

Alignment biases
MC1P 3.2531
MC1Y -1.0827
MC2P 3.4534
MC2Y -1.1747
MC3P -0.9054
MC3Y -3.1393

Coil balances
MC1H 1.02682
MC1V 0.959605
MC3H 0.936519
MC3V 1.10755

(subtract 1, then multiply 10.8mm => spot position.)

Attachment 1: spot_position.png
  7413   Wed Sep 19 19:38:37 2012 JenneUpdateGeneralSpot centered on BS, ETMY, ETMX

[Unni, Manasa, Jenne]

It turned out that the beam was a teeny bit high in the corner, so we touched PZT1 and PZT2 knobs to translate the beam down a bit.

Now the beam is centered on the BS (using the 45 degree non-iris target), centered on ETMY (using Steve's latest target, which worked perfectly), and then BS was aligned a tiny bit (really, it didn't need much) to get the beam centered on ETMX.

After dinner I'll align ITMX and ITMY such that their beams retroreflect and I get MICH fringes.  I'll also align SRM and PRM to retroreflect.  Check no clipping on AS path, get REFL path out, center IPPOS and IPANG, check POX, POY and POP.  Then, I think we might be almost done.

  15967   Thu Mar 25 17:39:28 2021 gautamUpdateComputer Scripts / ProgramsSpot position measurement scripts "modernized"

I want to measure the spot positions on the IMC mirrors. We know that they can't be too far off centerBasically I did the bare minimum to get these scripts in /opt/rtcds/caltech/c1/scripts/ASS/MC/ running on rossa (python3 mainly). I confirmed that I get some kind of spot measurement from this, but not sure of the data quality / calibration to convert the demodulated response into mm of decentering on the MC mirrors. Perhaps it's something the MC suspension team can look into - seems implausible to me that we are off by 5mm in PIT and YAW on MC2? The spot positions I get are (in mm from the center):

MC1 P          MC2P           MC3P           MC1Y          MC2Y           MC3Y

0.640515    -5.149050    0.476649    -0.279035    5.715120    -2.901459

A future iteration of the script should also truncate the number of significant figures per a reasonable statistical error estimation.

Attachment 1: MCdecenter202103251735_mcmirror0.pdf
Attachment 2: MCdecenter202103251735_mcdecenter0.pdf
  14225   Tue Oct 2 23:57:16 2018 gautamUpdatePonderSqueezeSqueezing scenarios

[kevin, gautam]

We have been working on double checking the noise budget calculations. We wanted to evaluate the amount of squeezing for a few different scenarios that vary in cost and time. Here are the findings:

Squeezing scenarios

Sqz [dBvac] fmin [Hz] PPRM [W] PBS [W] TPRM [%] TSRM [%]
-0.41 215 0.8 40 5.637 9.903
-0.58 230 1.7 80 5.637 9.903
-1.05 250 1.7 150 1 17
-2.26 340 10 900 1 17

All calculations done with

  • 4.5kohm series resistance on ETMs, 15kohms on ITMs, 25kohm on slow path on all four TMs.
  • Detuning of SRC = -0.01 deg.
  • Homodyne angle = 89.5 deg.
  • Homodyne QE = 0.9. 
  • Arm losses is 20ppm RT.
  • LO beam assumed to be extracted from PR2 transmission, and is ~20ppm of circulating power in PRC.


  1. Existing setup, new RC folding mirrors for PRG of ~45.
  2. Existing setup, send Innolight (Edwin) for repair (= diode replacement?) and hope we get 1.7 W on back of PRM.
  3. Repair Innolight, new PRM and SRM, former for higher PRG, latter for higher DARM pole.
  4. Same as #3, but with 10 W input power on back of PRM (i.e. assuming we get a fiber amp).


  • The errors on the small dB numbers is large - 1% change in model parameters (e.g. arm losses, PRG, coil driver noise etc) can mean no observable squeezing. 
  • Actually, this entire discussion is moot unless we can get the RIN of the light incident on the PRM lower than the current level (estimated from MC2 transmission, filtered by CARM pole and ARM zero) by a factor of 60dB.
    • This is because even if we have 1mW contrast defect light leaking through the OMC, the beating of this field (in the amplitude quadrature) with the 20mW LO RIN (also almost entirely in the amplitude quad) yields significant noise contribution at 100 Hz (see Attachment #1).
    • Actually, we could have much more contrast defect leakage, as we have not accounted for asymmetries like arm loss imbalance.
    • So we need an ISS that has 60dB of gain at 100 Hz. 
    • The requirement on LO RIN is consistent with Eq 12 of this paper.
  • There is probably room to optimize SRC detuning and homodyne angle for each of these scenarios - for now, we just took the optimized combo for scenario #1 for evaluating all four scenarios.
  • OMC displacement noise seems to only be at the level of 1e-22 m/rtHz, assuming that the detuning for s-pol and p-pol is ~30 kHz if we were to lock at the middle of the two resonances
    • This assumes 0.02 deg difference in amplitude reflectivity b/w polarizations per optic, other parameters taken from aLIGO OMC design numbers.
    • We took OMC displacement noise from here.

Main unbudgeted noises:

  • Scattered light.
  • Angular control noise reinjection (not sure about the RP angular dynamics for the higher power yet).
  • Shot noise due to vacuum leaking from sym port (= DC contrast defect), but we expect this to not be significant at the level of the other noises in Atm #1.
  • Osc amp / phase.
  • AUX DoF cross coupling into DARM readout.
  • Laser frequency noise (although we should be immune to this because of our homodyne angle choice).

Threat matrix has been updated.

Attachment 1: PonderSqueeze_NB_LORIN.pdf
  13841   Mon May 14 18:58:32 2018 KevinUpdatePonderSqueezeSqueezing with no SRM

Note that for Signal Recycling, which is what Kevin tells us we need to do, there is a DARM pole at ~150 Hz.

To be quantitative, since we are looking at smaller squeezing levels and considering the possibility of using 5 W input power, it is possible to see a small amount of squeezing below vacuum with no SRM.

Attachment 1 shows the amount of squeezing below vacuum obtainable as a function of homodyne angle with no SRM and 5 W incident on the back of PRM. The optimum homodyne angle at 210 Hz is 89.2 deg which gives -0.38 dBvac of squeezing. Figure 2 is the displacement noise at this optimal homodyne angle and attachment 3 is the same noise budget shown as the ratio of the various noise sources to the unsqueezed vacuum.

The other parameters used for these calculations are:

  • 4.5 kΩ series resistance for the ETM coils; 15 kΩ for the ITM coils
  • 100 ppm transmissivity on the folding mirrors giving a PRC gain of 40
  • PD quantum efficiency of 0.88

So maybe it's worth considering going for less squeezing with no SRM if that makes it technically more feasible.

Attachment 1: homodyne_heatmap.pdf
Attachment 2: displacement_noise.pdf
Attachment 3: noise_budget.pdf
  9116   Fri Sep 6 23:01:08 2013 KojiUpdateLSCStable DRMI lock was recovered from the impact on the RF system modification


Stable DRMI lock was recovered. The AS110 phase was adjusted. PRCL and MICH were locked with REFL33I and REFL165Q.
Still SRCL is controlled with REFL55Q.

PRMI sensing matrix

Thursday night, Jenne and I found DRMI can not be locked at all. Also the PRMI lock with REFL55 showed change in the optical gain.

In order to investigate what is happening, the PRMI sensing matrix was measured and compared with the previous one taken in the night of 8/26.


It shows that some signals are unchanged, some are partial change, and some are completely different.
My intuition saids something is wierd with the sensing matrix measurement.
Right now I can't trust these plots.

- Jenne and I have adjusted REFL55 demod angle so that REFL55Q has no PRCL. And I have confirmed with DTT that this is still true.
  However, the radar chart shows that REFL55Q is almost correct phase for PRCL instead of MICH.

- REFL11 shows the same amplitude and angle as before. But POX11/POY11 shows different MICH angle.

- I have rotated REFL55 demod phase and remearsured the sensing matrix. Evrything else looked same but REFL55.
  Since REFL55I&Q were not used for the control for this measurement, what we expect is to see no change of the sensing matrix and
  only see the angle of "I"&"Q" rotates. But the result was different from the expectation.

DRMI locking

Since no real info was obtained from the sensing matrix, I had to make a fight without any weapon.
After sevral hours of work, stable DRMI lock was recovered.

Basically I gave larger gains to REFL55 signals: REFL55I for SRCL was 100 instead of 1, and REFL55Q for MICH was 2 instead of 0.1.
This was enough to get a second locking. Using this short sections, I have optimized the FM triggers and the gain boosts (i.e. FM1)
as well as the mirror alignment.

Then, PRM ASS was left running during the lock. This actually stabilized the lock a lot.
This made thee lock indefinite.

The demod phase of AS110I was adjusted so that AS110Q fluctuates around zero.
In this condition, the nominal AS110I was 7300 with the whitening gain of 30dB.

Note that the AS110I&Q were also measured with PRMI. With the same phase and gains, AS110I and Q were -35,  -170, respectively.
Do we expect to have this phase shift? If I believe these numbers, the aplitude of 110MHz at the optimal phase is 173,
The ratio of AS110 between DRMI and PRMI is 7300/173 = 42. This corresponds to the ratio of the 110MHz sideband power at the AS port.
According to the wiki, this ratio shoud be ~160.

AS110I was in fact glitchy as you can see in the StripTool chart. I wonder this signal is suitable for the normalization or not.

=== SENSING ===

REFL11 -67deg / whitening gain 0dB
REFL33 -20deg / whitening gain 30dB
REFL55 45deg / whitening gain 6dB
REFL165 96deg / whitening gain 45dB

POP110 69deg whitening on / 15dB
POP22 102.2deg whitening on / 21dB
AS110 145deg whitening off / 30dB (seems to be related to AS11 whitening setting)


REFL11I x -0.125 => PRCL (REFL33I x 2.5 was also OK)
REFL55I x 100 => SRCL
REFL55Q x 2 => MICH (REFL165Q x 0.1 was also OK)


No normalization

Trigger settings


MICH x -0.8 FM4/5 ON, no limitter
FM Trigger: delay 2sec, FM1 (modified from 6dB to 20dB), FM2, FM3

PRCL x +0.035 FM4/5 ON, no limitter
FM Trigger: delay 0.5sec, FM2/3/6

SRCL x -0.1 FM4/5 ON, no limitter
FM Trigger: delay 5sec, FM1, FM2


MICH => PRM -0.267 / BS +0.5

PRCL => PRM +1.0

SRCL => SRM +1.0


delay 1sec: FM1/FM2/FM3/FM6

=== ASC/ASS ===

PITCH&YAW: FM1/9 (ALWAYS ON) + FM2/3 (turned on by the up-script)

PRM ASS left turned on for slow tracking

Attachment 1: DRMI.png
  2274   Mon Nov 16 15:18:10 2009 haixingUpdateSUSStable magnetic levitation without eddy-current damping

By including a differentiator from 10 Hz to 50 Hz, we increase the phase margin and the resulting

magnetic levitation system is stable even without the help of eddy-current damping.

The new block diagram for the system is the following:


Here the eddy-current damping component is removed and we add an additional differential

circuit with an operational amplifier OP27G.

In addition, we place the Hall sensor below the magnet to minimize the coupling between

the coil and the Hall sensor.

The resulting levitation system is shown by the figure below:


  560   Tue Jun 24 22:43:23 2008 ranaSummarySEIStack TF
Attachment 1: Screenshot.png
  3252   Tue Jul 20 17:38:16 2010 GopalConfigurationOptic StacksStack Type Clarifications

Some clarification is warranted regarding the different shapes of stacks. Corrections are appreciated:

1) The single-leg stack that I just completed should function as a working model for the IO, OO, and MC1/3. Rana commented, however, that the current dimensions are slightly off for MC1/3 (which makes sense since I could only find drawings for the IOC). If anyone knows the whereabouts of similar drawings for MC1/3, I'd much appreciate it.

2) A triple-leg stack can model the BS, ITMX, and ITMY chambers. I don't have exact dimensions for these, but I can make decent approximations from to-scale stack drawings. I'll probably work on a model for this style next, since at least I have some information regarding this version.

3) The MC2 chamber has its own stack model, about which I haven't found any drawings in the binders. I can't start on MC2C at all until I find such drawings.

  13821   Mon May 7 15:27:28 2018 gautamUpdateSUSStack measurement expectation


We tried to estimate what the load cell measurement should yield. Here is the weight breakdown (fudge factor for Al table is to try and account for tapped holes):


Diameter [m]

Height [m]

Density [kg/m^3]

Mass [kg]

Number or fudge factor

Dim in inches

Table 1.22 0.08 2700.00 240.07 0.85 Dia=48", thickness=3"
Stack leg 0.36 0.13 8000.00 100.85 9 Dia=14", thickness=5"
Base plate 1.37 0.05 8000.00 600.18 1 Dia=60",thickness=2"
Base rods 0.10 1.83 8000.00 118.55 2 Dia=4", length=6ft
Stuff on table       100.00    
Blue beams       100.00    
Total [kg]       2149.01    
Total [lbs]       4835.28  


  • Steve pointed out that there is some material removed from the stack legs for stability (hollows into which the viton springs fit). These countersinks have dimensions of diameter=2", height=1.75". So if we assume each leg has 10% less mass, the total weight becomes ~4600lbs.
  • I think we will need to use one more load cell (i.e. total 4) for this measurement (we have more load cells, just need to setup one more controller).
  • Steve is looking into acquiring some low profile jacks to deal with the fact that we only have limited travel range on the overall stack height because of the bellows.
  • A useful document, from which we pulled some numbers (which also look reasonable using estimated dimensions and density calculations): P952005
Attachment 1: 40m_TMstack.JPG
  13815   Fri May 4 18:59:39 2018 gautamUpdateSUSStack measurement ongoing


The stack weight measurement is going on at EX. ETMX watchdog is shutdown. Area is off limits over the weekend until the test is finished.

Not related to this work, but the dog clamps used on the EX table have to be re-positioned such that the clamping force is better distributed. The 2" beam splitter mount used to pick off a portion of the EX NPRO beam to the fiber has to be rotated. Also, there was a M6.9 EQ in Hawaii while we were doing this work it seems..

  13846   Tue May 15 21:56:57 2018 gautamUpdateGeneralStack measurement setup decommissioned


Since we think we already know the stack mass to ~25% (i.e. 5000 +/- 1000 lbs), we decided to restore the ETMX stack. Procedure followed was:

  • Take photos of all dial indicators and spirit level. We were at ~-22 mils on all 3 indicators, with 0 being the level before we touched the stack two Fridays ago, i.e. May4.
  • Raised all four jacks installed underneat blue crossbeams in 5mil increments until we were at +25mils on all of them. At this point, there was negligible load on the load cells on top of the STACIS legs, and we could easily slide the load cells out.
  • Rotated all jack screws clockwise (i.e. moving jack screws downwards) by 270 degrees. The southeast jackscrew was rotated by an additional 360 degrees. This was to undo all the jack-screw raising we did on Friday, May 4.
  • Re-installed jacks which were present originally on the STACIS legs, taking care to center the jack as best as we could by eye on the STACIS leg, per Dennis Coyne's suggestion not to impose shear strain on STACIS legs. There were supposedly never carrying any load, and are according to Steve, are there more for safety purposes.
  • Lowered all four jacks in 5 mil steps until dial indicators read ~0. The Northwest jack resting on the STACIS leg was somehow ~0.5cm (!!) below the blue crossbeam even though the corresponding dial gauge read 0, so we raised the jack until it was barely grazing the bottom of the blue crossbeam (confirmed by looking at the point where the dial indicator started going up again). Not sure why this should have been, best hypothesis we have is that someone (one of us) changed the level of this jack while it was removed from the setup.
  • Checked that jack screws could not be turned by hand. At this point, all the load has to be resting on the jack screws, as the jacks we had installed to raise the blue crossbeams could be slid out from underneath the blue beams and hence were carrying no load.
  • Took photographs of all dial indicators, spirit level. We were satisfied that we had recovered the "nominal" stack alignment as best as we could judge with the available indicators.
  • ETMX Oplev spot had returned to the PD. ETMX watchdog was re-engaged, optic was re-aligned using SLOW bias sliders to center Oplev spot.
  • EX NPRO was turned back on, and the green beam was readily locked to a cavity TEM00 mode yes.

I will upload the photos to the PICASA page and post the link here later.


In this case, we only need a mass estimate of the end chamber contents with an accuracy of ~25%. If we think we have that already, we don't need to keep doing the jacks-strain gauge adventure.


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