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ID Date Author Typeup Category Subject
  14911   Sun Sep 29 16:08:25 2019 gautamUpdateOptical LeversETMX Oplev HeNe replaced

To facilitate POX locking investigations, I replaced this HeNe today with one of the spares Chub/Steve had acquired some time ago. Details:

  • Part number: Lumentum 22037130 (1103P)
  • Serial number: PA00836
  • Manufacture date: 01/2019
  • Power output: ~2.64 mW (Measured with Ophir power meter in the 632nm setting)
  • Power received on QPD: ~0.37 mW = ~18700 cts (Measured with Ophir power meter in the 632nm setting)

The RIN of the sum channel with the Oplev servo engaged, along with that for the other core FPMI optics, in shown in Attachment #1. The ETMX HeNe RIN is compatible with the other HeNes in the lab (the high-frequency behaviour of the BS Oplev is different from the other four because the QPD whitening electronics are different).

Not sure what to make of the ETMY RIN profile being so different from the others, seems like some kind of glitchy behaviour, I could see the mean level of the ASD moving up and down as I was taking the averages in DTT. Needs further investigation.

The old / broken HeNe is placed i(nside the packaging of the abovementioned replacement HeNe) on Steve's old desk for disposal in the proper way.

*It looked like Steve had hooked up a thermocouple to be able to monitor the temperature of the HeNe head. I removed this feature as I figured if we don't have this hooked up to the DAQ, it isn't a really useful diagnostic. If we want, we can restore this in a more useful way.

Quote:

While working on recovering interferometer alignment, I noticed that the ETMX Oplev SUM channel reported 0 counts. Attachment #1 shows the 200 day trend - despite the missing data, the accelerating downward decay is evident. I confirmed that there is no light coming out of the HeNe by walking down to EX. The label on the HeNe says it was installed in March 2017, so the lifetime was ~30 months. Seems a little short? I may replace this later today.

Attachment 1: OLRIN_20190929.pdf
OLRIN_20190929.pdf
  14912   Mon Sep 30 11:20:43 2019 gautamUpdateCDSc1iscaux testing - CM board code updated

DATED, SEE ELOG14941 for the most up-to-date info on latch.py.

I modified /cvs/cds/caltech/target/c1iscaux/latch.py and /cvs/cds/caltech/target/c1iscaux/C1_ISC-AUX_CM.db to set up the mbbo logic for the other three channels on the CM board, namely REFL2 Gain, AO Gain, and the Super boosts. The systemctl processes were restarted on c1iscaux. We are now ready to perform systematic checks on the CM board functionality.

Remarks:

The addressing of the Acromag BIO registers is done in a way that is kind of inconvenient to use the EPICS mbboDirect protocol

  • The control word going to the Acromag is 16 bits in length
  • However, only the 4 least significant bits actually correspond to physical channels - the remaining 12 bits are "unused".
  • Because each Acromag BIO unit has 16 BIO channels, this means that they are grouped into four "banks" of 4 bits each.
  • The mbboDirect EPICS/modbus protocol is used to control multiple physical BIO channels using a single input, which is exactly what we want for the gain sliders on the CM board. However, one caveat is that the bits need to be consecutive.
  • This means that we have to break up the 6 bits used for the gain sliders (and in fact also the 2 bits used for the super boosts) into a least-significant-bits (LSB) group and a most-significant-bits (MSB) group.
  • What's more annoying is that our physical wiring scheme means that we can't uniformly decide on how this division into LSBs and MSBs work for all the channels - e.g. for REFL1 Gain, the LSB is the 4 least significant bits, while the MSB is the 2 most significant ones, while for REFL2 Gain, the roles are reversed.
  • In hindsight, the "clever" way to do the wiring assignment would have been to factor this in - but the problem is (sort of) easily fixed in software, and so I recommend we stick with the existing wiring scheme.

I tested the new latch.py script by toggling the various sliders (one at a time) between two values and monitoring the states of the various soft and "*_BITS" channels, see Attachment #1. The behavior seems consistent to me, but to be sure, we have to use Koji's LED tester board and confirm that the physical bits are being toggled correctly. The StripTool templates live in /cvs/cds/caltech/target/c1iscaux/CMdiag.

Quote:

I have not yet implemented the fix for the MBBO gain channels for all the gains - only REFL1_GAIN is set up correctly now. Need to look at the hardware for the correct addressing of bits

Attachment 1: CMsoftTest.png
CMsoftTest.png
  14913   Mon Sep 30 11:42:36 2019 aaronUpdateComputerscontrol rm wkstns shutdown

I booted Rossa in rescue mode; though I see no errors on bootup, I still see the same error ("a problem has occurred") after boot, and a prompt to logout. I powered rossa off/on (single short press of power button), no change.

Booting in debug mode, I see that the error occurs when mounting /cvs/cds, with the error

[FAILED] Failed to mount /cvs/cds.
See `systemctl status cvs-cds.mount` for details.
[DEPEND] Dependency failed for Remote File System

Which is odd, because when I boot in recovery mode, is mounts /cvs/cds successfully. 

I booted in emergency mode by adding to the boot command

systemd.unit=emergency.target

but didn't have the appropriate root password to troubleshoot further (the usual two didn't work).

  14914   Mon Sep 30 13:20:55 2019 aaronUpdateIOOshot noise measurement

I wanted to measure the RF transimpedance of the WFS heads, as outlined above.

Summary: Measurement is not done.

Details:

  • closed the PSL shutter
  • taped over the WFS 2 opening with frosted scotch tape
  • illuminated the QPD with an incandescent flashlight.
    • All of the D batteries were close to dead, so it seemed dimmer than usual
  • Observed the WFS2 segment 1 RF spectrum on the Agilent, but saw no difference between the spectrum with and without the flashlight. Must need a brighter light, and possibly also better alignment.
  • Needed to skype someone and pass off the IFO to gautam, so I untaped the QPD, returned the appropriate LEMO connector, and opened the PSL shutter.
  14915   Mon Sep 30 14:16:43 2019 gautamUpdateLSCPOX PD checkout - solved

I confirmed that there is light incident on the POX photodiode. So the problem must lie downstream in the demod / whitening / AA electronics. With the PRM aligned (i.e. PRFPMI config with all DoFs uncontrolled), I could see the flashing beam on an IR card. I could also see the spikes in DC power incident on the photodiode using the "DC Monitor" port on the photodiode head and an oscilloscope.

Update 245 pm: I confirmed that I could see a 11 MHz sine wave by connecting the POX11 RFPD output cable at the 1Y2 end to an oscilloscope. The amplitude of this signal was also changing, corresponding to the cavity fringing in and out of resonance. I couldn't, however, see any signal on the RFPDmon port, or the I/Q demodulated output ports. So as of now, the culprit seems to be something on the Demod board. Further investigations underway...

Update 315pm: I did the following checks:

  1. Checked the LO signal level into a 50ohm input scope - it was ~720 mVpp, which was compatible with the LO level into the POY Demod board, so the LO signal level couldn't be to blame.
  2. Connected an RF funcgen to the PD input of the demod board. Drove it at 11.066210 MHz, 50 mVpp, and saw a signal 400 cts-pp in the CDS system - so the demod + digitizaiton electronics also seemed fine.
  3. #2, coupled with the fact I could see no signal at the RF-mon port of the demod board (even though there was a signal visible at the cable coming to 1Y2) suggested that the cable routing the POX11 PD output from the Heliax-breakout in 1Y2 to the demod board was busted - indeed this was the case!
  4. Koji replaced the cable without changing its length, and now the XARM locks readily 👏 . I ran ASS and got TRX ~ 0.95. See Attachment #1
Quote:

Look for the POX beam with an IR viewer.

  14916   Mon Sep 30 15:51:59 2019 gautamUpdateCDSc1iscaux - some admin

I did the following:

  1. symlinked /cvs/cds/rtcds to /opt/rtcds.
  2. Added a line to /etc/systemd/system/modbusIOC.service that executes a burt-restore of the latest c1iscaux.snap file so that whitening gains etc are restored to their last saved value in the event of a service restart.
  14917   Mon Sep 30 17:04:30 2019 gautamUpdateCDSSome path changes

I made some model changes to c1lsc. To propagate the changes, I tried the usual rtcds make sequence. But I got an error about the model file not being in the path. This is down to my re-organization of the paths to cleanly get everything under git version control. So I had to run the following path modification. Where is this variable set and how can I add the new paths to it? The model compilation, installation and restart all went smooth after I made this change. 

For smooth reboot of the models, I used the reboot script. I had to restart the daqd processes on FB, but now all the CDS indicator lights are green.

export RCG_LIB_PATH=/opt/rtcds/userapps/release/isc/c1/models/isc/:/opt/rtcds/userapps/release/isc/c1/models/cds/:/opt/rtcds/userapps/release/isc/c1/models/sus/:$RCG_LIB_PATH
Quote:

I commenced the procedure of the migration, starting with making a tagged commit of the current running simulink models. A local backup was also made, plus we have the usual chiara-based backup so I think we're in good hands.

  14918   Mon Sep 30 18:20:26 2019 gautamUpdateALSALS OOL noise - a first look

Attachment #1 shows a first look at the IR ALS noise after my re-coupling of the IR light into the fiber at EY. 

Measurement configuration: 

  • Each arm length was individually stabilized to the PSL frequency using POX/POY locking.
  • The respective AUX laser frequencies were locked to the arm cavity length using the AUX PDH loops.
  • GTRX ~0.3 (usually I can get ~0.5) and GTRY ~ 0.2 (the mode-matching to the arm cavities is pretty horrible as suggested by the multitude of bullseye modes seen when toggling the shutter).
  • The control signal to the AUX PZT had the DC part offloaded by the slow temperature control servos to the AUX laser crystal temperature.

CDS model changes:

  • The c1lsc model was modified to route the input signals to the Y phase tracker servo from ADC1_2 and ADC1_3 (originally, they were ADC0_20 and ADC0_21).
  • This change was necessary because the DFD output is sent differentially to the ADC1 card in the c1lsc expansion chassis (bypassing the iLIGO whitening and AA electronics, for now just going through an aLIGO AA board with no whitening available yet).
  • I chose to use the differential receiving (as opposed to using the front-panel single ended BNC connectors) as in principle, it is capable of delivering better noise performance.
  • After making the model changes, I compiled and restarted the model. Apart from the missing path issue, the compile/restart went smoothly.

Next steps:

  • Get the easy fixes done (better GTRX, GTRY).
  • Test the noise with POX and POY as the OOL sensors, and the arms controlled using the ALS error signal - this is the relevant metric for how ALS will be used in locking.
  • Noise budget. Need to double-check the DFD output calibration into Hz.
  • For the general interferometer recovery, I think I will push ahead with trying to lock some other configurations like the PRMI (should be easy to recover), DRMI (potentially more difficult to find the right settings), and the FPMI (I'd like to use this config to get an estimate for how much contrast defect we have in the interferometer, but I think it'll be pretty challenging to lock in this configuration).
Attachment 1: ALS_OOL_20190930.pdf
ALS_OOL_20190930.pdf
  14919   Tue Oct 1 18:35:12 2019 gautamUpdateGeneralBeam centering campaign
  1. With TRX and TRY maximized using ASS, I centered the Oplev spots on the respective QPDs for the four test masses and the BS. I also centered the spot onto the IPPOS QPD by moving the available steering mirror.
  2. At EX, I tweaked the input pointing of the green beam into the arm by manually twiddling with the PZT mirrors. I was able to get GTRX~0.4.
  3. On the AS table - Koji and I found that there was a steering mirror placed in the AS beam path such that there was no light reaching the AS110 or AS55 PDs. Please - when you are done with your measurement, return the optical configuration to the state it was in before so that the usual locking activity isn't disturbed by a needless few hours troubleshooting electronics.

Once Koji is done with his checkout of the whitening electronics, I will try and lock the PRMI.

  14920   Tue Oct 1 21:19:51 2019 gautamUpdateLSCPRMI locked on carrier

Summary:

The PRMI was locked with the carrier field resonant in the PRC 🙌. The lock is pretty stable (I only let it stay locked for ~10mins and then deliberately unlocked to see if I could readily re-lock, but it has stayed locked for the last ~20mins while I typed this up). See Attachment #1 for the DC power monitor StripTool for a short section of lock.

Details:

  • This is the opposite of the config we'd want usually for locking the IFO, but it is a useful configuration for setting the alignment of the vertex optics, and also to train angular feedforward filters, so I decided to try it out.
  • Some patient alignment work was required. I started with the single arm locks, maximized TRX/TRY with ASS, and then misaligned the ETMs and brought the PRM into alignment.
  • The PRM Oplev spot was roughly centerd on its QPD once I judged I was getting decent PRMI cavity flashes on the POP camera. The PRMI Oplev servo needs some tuning, it is currently susceptible to oscillations in Pitch.
  • The error signals used were: REFL11_I ---> PRCL and AS55_Q ---> MICH.
  • The whitening gains were: REFL11 --> +18 dB, AS55 ---> +6 dB.
  • Triggering was done using POPDC, this worked better for me than any of the RF signals (e.g. POP22/POP110). Trigger ON --> 200cts, Trigger OFF --> 100 cts.
  • The DCPD whitening gains may not be set correctly - I think I remember POPDC being ~4000 cts in this configuration, but it may also be that we are not well centered on the POP photodiode.
  • The dominant cause of the POP circulating power seems to be the usual angular instability ascribed to the TTs. The OAF model wasn't running tonight (and I didn't want to try starting it and have to do a full vertex FE reboot tonight) so I didn't get a chance to engage the angular FF.

Next (for LSC activities):

  • PRMI locking with the sidebands resonant in the PRC.
  • DRMI locking

I'm leaving the LSC mode off for tonight, but with the PRMI optics aligned and ETMs misaligned.

Attachment 1: PRMIlocked.png
PRMIlocked.png
  14921   Wed Oct 2 01:11:40 2019 KojiUpdateCDSc1iscaux testing

I worked on more troubleshooting of the whitening filters Tuesday afternoon

== Test Status ==

[done] Whitening gain switching test => Remaining issues ASDC overall behavior
[done] AA enable/disable switching
[0th order] LO Det Mon channel check
[none] PD I/F board check
[done] QPD I/F board check
[none] CM Board
[none] ALS I/F board


Issue 1: POP110Q did not show any gain switching [Resolved]

A DB37 breakout board was connected to the acromag front panel. I found that Ch6 (POP110Q) did not show any differential DC output. I searched around the other pins and found that the corresponding signal showed up on PIn36  instead of Pin35. Opening the front panel revealed that the internal wiring was wrong (Attachment 1). The wire which should have gone to Pin 35 was connected to Pin 36. By correcting the wiring, POP110Q started to show identical behavior to POP110I. (Attachment 2)

Issue 2: LSC reboot [Resolved]

A rough activity around the acromag chassis crashed c1lsc realtime processes (as usual). I ran usual rebooting script /opt/rtcds/caltech/c1/scripts/cds/rebootC1LSC.sh. This successfully restored the status of the vertex RT processes.

Issue 3: REFL33 different behavior between I and Q [Resolved]

REFL33I and Q consistently showed a difference (Attachment 3). The whitening board was pulled out and powered with an extension card. The raw outputs were checked with a function generator and an oscilloscope connected. The outputs for 33I and Q were identical (Attachment 4). So I concluded that the observed difference was an artifact of the checking script.

Issue 4: Whitening 3_8 did not switch at all [Resolved]

To switch the gain stages, each channel of the whitening board takes a DAC output from acromag and convert it into 4bit digital signals. For CH8 of the WF#3, this signal did not reach the instrumentation amplifier AD620. After tracing the signal on the electronics bench, it was found that the CH8 gain input to the DIN96 connector is not conducive to the input of the AD620. As there were no exposed pads between the DIN96 connector and the AD620 input (pin2), a wire was additionally soldered (forgot to take a photo). This solved the gain switching issue as the test result indicates (Attachment 5). The noisiness came from the whitening filter which can not be turned off right now. For this reason, the test of the whitening part is pending too.

The StripTool plot during the overall WF#3 test is shown in Attachment 6.

Issue 5: ASDC behavior [Unresolved]

First of all, at this test, I found that WF#4 was not responding to the gain change at all. This issue was restored by power cycling the acromag chassis (as usual).

The whitening filter #4 was pulled, and the behavior of CH5,6,7,8 (CH8=ASDC) was compared. It was found that the analog outputs were identical and the problem lies further downstream.

Issue 6: Illeagal REFL11 LO cable [Unresolved]

This is a newly found issue. The cable between the LO distributor and the REFL11 demodulator is not the legit solder soaked RG402 coax, but flexible coax (Attachment 7). This cable needs to be replaced in the end. But for today, it was not so that we can have a consistent configuratin as before.

Issue 7: Signature of a damaged POPDC cable [Resolved]

The cable for POPDC cale indicated some damage at the WF#4 side. It was not a complete damage, and therefore the solder coating was added (Attachment 8).

Attachment 1: WF3_wiring.png
WF3_wiring.png
Attachment 2: POP110.pdf
POP110.pdf
Attachment 3: REFL33.pdf
REFL33.pdf
Attachment 4: P_20191001_174548_vHDR_On.jpg
P_20191001_174548_vHDR_On.jpg
Attachment 5: Whitening3_8.pdf
Whitening3_8.pdf
Attachment 6: Screenshot_WF3_191001.png
Screenshot_WF3_191001.png
Attachment 7: P_20191001_181052_vHDR_On.jpg
P_20191001_181052_vHDR_On.jpg
Attachment 8: POPDCcable.png
POPDCcable.png
  14922   Wed Oct 2 10:40:07 2019 gautamUpdateCDSc1oaf model restarted

This morning, I restarted the c1oaf model on the c1lsc machine, so as to have the option of enabling some feedforward action. Unsurprisingly, the "DC" indicator is red, citing a "0x2bad". In the past, I've been able to correct this by simply restarting the model. But given the fragility of the c1lsc machine, I think I'll live with not having the OAF model signals in frames. Medium-term, I'd like to pare down the c1oaf model a bit - I think it has way too many options/matrices right now, and is an un-necessarily bloated and heavy model. Unless there are serious objections, I will do this work when I next feel like it.

Attachment 1: c1oafRestart.png
c1oafRestart.png
  14923   Wed Oct 2 10:50:20 2019 gautamUpdateCDSAnaconda updated

The anaconda distribution used by the control room workstations is actually installed on the shared drive (/cvs/cds/ligo/apps/anaconda/) for consistency reasons. The version was 4.5.11. I ran the following commands to update it today. Now it is version 4.7.12.

conda update conda
conda update anaconda

The second command takes a while to resolve conflicts, so I've left it running inside a tmux session for now.

Recall that the bash alias for using the anaconda managed python is "apython". I recommend everyone set up a virtual environment when trying out new package installs, to avoid destroying the locking scripts.

  14924   Wed Oct 2 11:52:16 2019 gautamUpdateLSCPRMI Oplev loop checkout

I measured the OLTF of both the PRM Oplev loops. Nothing odd sticks out as odd to me in this measurement - there seems to be ~40 degrees of phase margin and >10 dB gain margin for both loops, see Attachment #1. I didn't measure down to the second UGF at ~0.2 Hz (the Oplev loops are AC coupled), so there could be something funky going on there. The problem still persists - if I misalign and realign the PRM using the ifoalign scripts, the automatic engagement of Oplev loops causes the loop to oscillate. Could be that the script doesn't wait for long enough for the alignment transient to die out.

Update 1230pm: Indeed, this was due to the integrator transient. It dies away after a couple of seconds.

Quote:

The PRMI Oplev servo needs some tuning, it is currently susceptible to oscillations in Pitch.

Attachment 1: PRM_OLTF.pdf
PRM_OLTF.pdf
  14925   Wed Oct 2 20:45:18 2019 ranaUpdateComputersrossa revival

Formatted and re-installing OS on rossa for the 3rd or 4th time this year. I suggest that whoever is installing software and adjusting video settings please stop.

If you feel you need to tinker deeply, use ottavia or zita and then be prepared to show up and fix it.

While I was moving the UPS around, the network lights went out for Rossa, so I may have damaged the network interface or cable. Debugging continues.

  14926   Wed Oct 2 23:15:02 2019 gautamUpdateLSCFPMI locking

Summary:

I was able to lock the FPMI. The lock was quite stable. However, the fluctuations in the ASDC power suggest that it will be difficult to make a DC measurement of the contrast defect in this configuration. This problem can be circumvented in part by some electronics tuning. However, the alignment jitter couples some HOM light which is an independent effect. Can this be a good testbed for the proposed AS WFS system? 

Details:

  • First, the arm cavities were locked and TRX/TRY were maximized using ASS.
  • Next, AS55_Q-->MICH_A (MICH-->BS) matrix element was set to 1 in the LSC input (output) matrix. The trigger was set to always on.
  • AS55 digital demod phase was -37 degrees.
  • I was then able to increase the gain on the MICH servo and turn on some integrators without any problem.
  • Some guesswork had to be done to get the correct sign. Final servo gain used was -0.8. 

I didn't do any serious budgeting yet - need to think about / do some modeling on how this configuration can be made useful.

Attachment 1: FPMIlocked.png
FPMIlocked.png
  14927   Wed Oct 2 23:23:02 2019 gautamUpdateCDSc1oaf DC indicator needs to be green

Today, I found out that this type of "0x2bad" DC error is connected to the 1e+20 cts output. The solution was to bite the bullet and stop/start the c1oaf model (at the risk of crashing the vertex FEs). Today, I was lucky and the model came back online with all CDS indicators green. At which point I was able to engage length feedforward to MC2 (with some admittedly old filter). Some subtraction is happening, see Attachment #1. This was just meant to test whether the signal routing is happening - the feedforward signal goes to the "ALTPOS" input of the suspension CDS block, which AFAIK does not have a corresponding MEDM EPICS indicator. So I couldn't figure out whether the feedforward control signal was in fact making it to the suspension. On the evidence of the suppression of MCL in the 1-3 Hz band, I would conclude that it is. Useful to be able to engage these FF filters for better lockability.

Quote:

Attachment #1 - the vertex seismometer input produces 1e+20 cts at the output of the feedforward filter. Attachment #2 shows the shape of the feedforward filters - doesn't explain the saturation. Since this is a feedforward loop, a runaway loop can't be the explanation either.

Attachment 1: MCL_FF_Test.pdf
MCL_FF_Test.pdf
  14928   Thu Oct 3 11:01:18 2019 ranaUpdateLSC(PR)FPMI locking

wonder if its possible to do variable finesse locking

Gabriele mentioned that Virgo used arm trans PDH for this, but I guess we could possibly use POX/POY to start and bring in the PRM with 50% MICH trans

  14929   Thu Oct 3 11:38:35 2019 aaronUpdateIOOWFS measurements

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

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

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

  14930   Thu Oct 3 12:08:47 2019 gautamUpdateGeneralMake the Jenne-laser setup fiber-coupled

I propose the following re-organization of the PDFR measurement breadboard. We have all the parts on hand, just needs ~30mins of setup work and some characterization afterwards. The fiber beamsplitter will not be PM, but for this measurement, I don't think that matters (the patch fiber from the diode laser head isn't PM anyways). We have one spare 1 GHz BW NF1611 that is fiber coupled (used to live on the ITMY in-air table, and is (conveniently) labelled "REF DET", but I'm not sure what the function of this was). In any case, we have at least 1 free-space NF1611 photodiode available as well. I suggest confirming that the FC version works as expected by calibrating against the free space PD first.

Update 245pm: Implemented, see Attachment #2. Aaron is testing it now, and will post the characterization results.

Attachment 1: PDFR_tabletop.pdf
PDFR_tabletop.pdf
Attachment 2: IMG_8014.JPG
IMG_8014.JPG
  14931   Thu Oct 3 14:32:37 2019 ranaUpdateGeneralMake the Jenne-laser setup fiber-coupled

I'm curious to see if we really need the 1611, or if we can calibrate the diode laser vs. the 1611 one time and then just use that calibration to get the absolute cal for the DUT.

  14932   Thu Oct 3 14:54:33 2019 KojiUpdateGeneralMake the Jenne-laser setup fiber-coupled

I'm afraid that the RF modualtion of the laser is nonlinear and the electrical and optical resoponse is dependent on the LD pumping current and RF input power. So I feel safe if we keep the reference PD. Of course, this is my feeling and it should be quantitatively tested.

  14933   Thu Oct 3 19:40:18 2019 gautamUpdateLSCPOX/POY imbalance

Summary:

There is an imbalance between the POX and POY detector outputs reported in the CDS system. Possibilities are (i) the POX PD has a uncoated glass window whereas POY does not or (ii) there is some problem in the elctronics.

Details:

  1. Nominally, we run the POX/POY locking with +18dB whitening gain on POY and +30 dB on POX. This is a factor of 4 difference.
  2. The DC levels reported in C1:LSC-POXDC_OUT and C1:LSC-POYDC_OUT differ by a factor of 10 (24 cts for POY vs 2.4 cts for POX with 0dB whitening gain). These channels come from the P2 connector on the back of the PD Interface board into the fast CDS system.
  3. The levels reported by the Acromag system (which come out of the P1 connector) are 60mV for POY  vs 15 mV for POX.
  4. I confirmed that this imbalance is not due to clipping on the POX photodiode - I tweaked the steering mirror and observed the plateau (I did not, however, look at the beam on the PD active area with an IR viewew which would be a more conclusive test).
  5. I measured the power incident on either PD (using Ophir power meter, filter OFF). They were both ~10uW, as expected since the beam extraction for POY and POX are identical - a single HR mirror and the vacuum viewport.

Update 820pm: 

  1. I checked that there is no glass window on the PD.
  2. It is hard to see the beam on a viewer - but with the PRM aligned, I think I convinced myself that the beam is pretty well centered on the PD. 

So increasingly, it looks like the electronics are the source of the problem.

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

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

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

Attachment 1: PD_response.pdf
PD_response.pdf
  14935   Thu Oct 3 21:50:22 2019 ranaUpdateComputersrossa revival

Got the network to work again just by unplugging the power cord and letting it sit for awhile. But corrupted OS by trying to install Nvidia drivers.

https://www.advancedclustering.com/act_kb/installing-nvidia-drivers-rhel-centos-7/

  14936   Thu Oct 3 23:15:39 2019 KojiUpdateGeneralMake the Jenne-laser setup fiber-coupled

The 1GHz PD has a bit more flat response, but the laser and the driving network have more frequency dependence as you saw.

  14937   Fri Oct 4 00:30:31 2019 gautamUpdateGeneralMake the Jenne-laser setup fiber-coupled

I think the metric of interest here is the consistency of the AC transimpedance of the proposed new "Reference PD" (= fiber coupled NF1611) vs the old reference (free space NF1611), since everything will be calibrated against that.

Quote:

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

  14938   Fri Oct 4 00:32:24 2019 gautamUpdateALSMore locking updates

Summary:

I managed to achieve a few transitions of control of the XARM length using the ALS error signal. The lock is sort of stable, but there are frequent "glitches" in the TRX level. Needs more noise hunting, but if the YARM ALS is also "good enough", I think we'd be well placed to try PRMI/DRMI locking with the arms held off resonance (while variable finesse remains an alternative).

Details:

Attachment #1One example of a lock stretch. 

Attachment #2ASD of the frequency noise witnessed by POX with the arm controlled by ALS. The observed RMS of ~30pm is ~3-4 times higher than the best performance I have seen, which makes me question if the calibration is off. To be checked...

Attachment 1: ALS_singleArm.png
ALS_singleArm.png
Attachment 2: ALS_OOL_20191003.pdf
ALS_OOL_20191003.pdf
  14939   Fri Oct 4 01:57:09 2019 KojiUpdateCDSc1iscaux testing

The AA filter for ASDC was fixed.

== Test Status ==

[done] Whitening gain switching test
[done] AA enable/disable switching
[0th order] LO Det Mon channel check
[none] PD I/F board check
[done] QPD I/F board check
[none] CM Board
[none] ALS I/F board


The AA filter for the 4th section of the LSC analog electronics bank (D000076) was pulled out for the test. On the workbench, questionable CH8 was checked. It tuned out that the filter amplifier module for the 8th-order elliptic filter at 7.5kHz was not properly working and exhibited unusual attenuation. This filter module (Frequency Devices Inc D68L8E-7.50kHz) was desoldered and replaced with a module from a spare board. Note that Gautam and I had tried to use this spare board instead of the current one, but it didn't give us any signal for an unknown reason. Since the desoldering required a lot of force and had a risk of damaging the PCB, a socket was made from an IC socket (see Attached 1). This change made CH8 functioning equally to the other channels do.


I took this opportunity to ckech the performance of the AA filters. For each channel, the input signal was injected from J3 using a pomona clip. The output was taken from pin 1, 5, 9, ... of J2. This is the + side of the differential output. The - side just has the equivalent performance but the signal polarity. The digital signals for the AA bypass switches were not connected. Fortunately, this was just fine as it made the anti-aliasing filters engaged.

Attachment 2 shows the transfer functions of all the channels. All the channels showed an identical response (at least visually). The transfer function for CH1 was fitted by LISO. The ZPK values are listed here:

pole 5.2860544577k 503.1473053928m
pole 5.9752193716k 1.0543411596
pole 8.9271953580k 3.5384364788
pole 8.2181747850k 3.4220607928
pole 182.1403534923k 1.1187869426 # This has almost no effect
zero 13.5305051680k 423.6130434049M
zero 15.5318357741k 747.6895990654k
zero 23.1746351749k 1.5412966100M


factor 989.1003181564m
delay 24.4846075283n

Attachment 3 shows the ASD of the output voltage noise measurement. Note the input was shorted for this measurement. The nominal output voltage was found to be 0.1 uV/rtHz and the 1/f noise corner freq was about 100Hz. Only CH3 showed a deviation from the typical values. It looks like this is neither an artifact nor transient noise. Fortunately, nothing is connected to this channel right now.

Attachment 1: P_20191003_172956_vHDR_On.jpg
P_20191003_172956_vHDR_On.jpg
Attachment 2: TF.pdf
TF.pdf
Attachment 3: PSD.pdf
PSD.pdf
Attachment 4: 191003_AA_Filter.zip
  14940   Fri Oct 4 14:25:59 2019 aaronUpdateGeneralMake the Jenne-laser setup fiber-coupled

Summary:

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

Details

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

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

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

I didn't find Agilent's manual very helpful for learning about the available calibration schemes, and didn't find a resource online that I liked -- is there a good one?
I think I want to characterize the WFS heads treating the DUT as a three-port device (AM in, ref PD, WFS segment PD).
Attachment 1: PD_norm.pdf
PD_norm.pdf
Attachment 2: PD_AB.pdf
PD_AB.pdf
Attachment 3: JenneAM_fiberPD_cals.pdf
JenneAM_fiberPD_cals.pdf
  14941   Fri Oct 4 22:22:03 2019 gautamUpdateCDSFinal incarnation of latch.py

[KA, GV]

This elog is meant to be a summary of some of the many subtleties on the CM board. The latest schematic of the version used at the 40m can be found at D1500308 .

Latch logic:

  • There are several Binary Outputs and one Binary Input to the CM board.
  • The outputs control ENABLE/DISABLE switches and gains of amplifier stages, while the input reports whenever the limiter has been reached.
  • The variable gain feature is implemented by enabling/bypassing several cascaded fixed gain stages. So in order to change the gain of a single composite amplifier stage, multiple individual amplifier stages have to be switched.
  • This is implemented by the user interacting with the hardware via a "control word", consisting of a number of bits depending on the number of cascaded stages that have to be switched. 
  • This control word is sent to the device via modbus EPICS, which is an asynchronous communication protocol. Hence, it may be that the individual bits composing the control word get switched asynchronously. This would be disastrous, as there can be transient glitches in the gain of the stage being controlled. 
  • To protect against such problems, there is a latch IC in the hardware between the Binary Inputs to the board (= Binary Outputs from Acromags), and the actual switches (= MAX333) that enable/bypass the cascaded gain stages. The latch IC used is a SN74ALS573. This device acts as a bus, which transmits/blocks changes for multiple bits (= our control word) from propagating, depending on the state of a single bit (= the LATCH ENABLE bit). Thus, by controlling a single bit, we can guarantee that multiple bits get switched synchronously
  • In order to use this latch capability, we need some software logic that sets/disables the LATCH ENABLE bit. For our system, this logic is implemented in the form of a continuously running python 🐍 script, located at /cvs/cds/caltech/target/c1iscaux/latch.py. It is implemented as a systemctl service on the c1iscaux Supermicro. The logic implemented in this script is shown in Attachment #1. While the channels referred to in that attachment are for REFL1_GAIN, the same logic is implemented for REFL2_GAIN, AO_GAIN, and the SuperBoosts.
  • Some FAQ:
    1. Q: Why do we need the soft channels C1:LSC-REFL1_SET_LSB and C1:LSC-REFL1_SET_MSB?
      A: These soft channels are what is physically linked to the Acromag Binary Outputs. In order for our latch logic to be effective, we need to detect when the user asks for a change, and then disable the LATCH ENABLE bit (which is on by default, see FAQ #3) before changing the physical acromag channels. The soft channels form the protective layer between the user and the hardware, allowing latch.py to function.
    2. Q: Why is there an "_MSB" and "_LSB" soft channel? 
      A: This has to do with the mbboDirect EPICS channel type, which is used to control the multiple bits in our control word using a single input (= an MEDM gain slider). The mbboDirect data-type requires the bits it controls to have consecutive hardware addresses. However, the Acromag hardware addressing scheme is not always compatible with this requirement (see pg 33 of the manual for why this is the case). Hence, we have to artifically break up the control word into two separate control words compatible with the Acromag addressing scheme. This functionality is implemented in latch.py.
    3. Q: Why is the default state of LATCH ENABLE set to ON? 
      A: This has to do with the fact that all Binary Inputs, not just the multi-bit ones, to the CM board are propagated to the control hardware via a latch IC. For the single-bit channels, there is no requirement that the switching be synchronous. Hence, rather than setting up ~10 more single-bit soft channels and detecting changes before propagating them, we decided to leave the LATCH ENABLE ON by default, and only disable it when changing the multi-bit gain channels. This is the same way the logic was implemented in the VME state code, and we think that there are no logic reasons why it would fail. But if someone comes up with something, we can change the logic.

Acromag BIO testing:

During my bench testing of the Acromag chassis, I had not yet figured out mbboDirect and the latch logic, so I did not fully verify the channel mapping (= wiring inside the Acromag box), and whether the sitching behavior was consistent with what we expect. Koji and I verified (using the LED tester breakout board) that all the channels have the expected behavior 👏. Note that this is only a certification at the front-panel DB37 connectors of the Acromag chassis  testing of the integrated electronics chain including the CM board is in progress...

Attachment 1: LatchLogic.pdf
LatchLogic.pdf
  14942   Sat Oct 5 00:03:21 2019 KojiUpdateCDSc1iscaux testing

[Gautam, Koji]

Input gain part of the CM servo board D1500308 was tested. A couple of problems were detected. One still remains.

== Test Status ==

[done] Whitening gain switching test
[done] AA enable/disable switching
[0th order] LO Det Mon channel check
[none] PD I/F board check
[done] QPD I/F board check
[in progress] CM Board
[none] ALS I/F board


We started to test the CM Servo board from the input stages. Initially, DC offsets were provided to IN1 and IN2 to check the gain on the oscilloscope or a StripTool plot. However, the results were confusing, AC measurements with SR785 was carried out in the end. It turned out that both IN1 and IN2 had some issues. IN1 showed an increment of the gain by 2dB every two gain steps, having suggested that the 1dB gain stage had a problem. IN2 showed sudden drop of the signal at the gain +8~+15dB and +24~+31dB, having suggested that a particular 8dB stage had a problem. The board was exposed with the extender and started tracing the signals.

CH1: The digital signal to switch the 1dB stage reached Pin 1A of the DIN96 connector. However, the latch logic (U47 74ALS573) does not spit out the corresponding level for this bit. Note that the next bit was properly working. We concluded that this 74ALS573 had failed and need to be replaced. We have no spare of this wide SOIC-20 chip, but Downs seems to have some spares (see Todd's spare parts list). We will try to get the chip on Monday.

CH2: The stage only used between +8dB and +15dB and between +24dB and +31dB is the +8dB stage (U9 and U2A). I found that the amped output signal did not reach the FET switch U2A (MAX333A). Therefore it was concluded that the opamp U9 (AD829) has an issue. In fact, the amp itself was working, but the output pin was not properly soldered to the pad.  Resoldering this chip made the issue gone. Note that this particular channel has some OP27s soldered instead of AD829. Gautam mentioned that there was some action on the board a few years back to deal with the offset issue. Next time when the board is polled out, I'll take the photos of the board.


Using SR785, the swept sine measurements between 100 and 100kHz were taken for all the gain settings for each channel. Between -31dB and -11dB, the input signal amplitude of 300mV was used. Between -10dB and +10dB, it was reduced to 100mV. For the rest, the amplitude was 10mV. Note that the data for +11dB for CH1 and +2dB for CH2 are missing presumably due to a data transfer issue.

The results are shown in Attachments 1~4.

Attachments 1 and 3 show the gain at each slider value. The measured gain was represented by the average between 1kHz and 10kHz. The missing 1dB every two slide values are seen for CH1. The phase delay at 100kHz is show in the lower plot. There is some delay and delay variation seen but it is in fact less than 1deg at 10kHz (see later) so it's effectfor CM servo (IMC AO path) is minimum. The gain for CH2 tracks the slider value nicely. The phase delay is larger than that of CH1, as expected because of OP27.

Attachments 2 and 4 show the transfer functions. The slider value was subtracted from the measured gain magnitude to indicate the deviation between them. The missing 1dB is obviously visible for CH1 in addition to the overall gain offset of ~0.2dB. CH2 also shows the gain offset of 0.1dB~0.2dB. The phase delay comes into the play around 20kHz particularly at higher gains where the UGF of the AO path is.


gautam: Here is the elog thread for IN2 opAmps going AD829-->OP27. Also, I guess Attachment #1 and #3 x-axes should be "Gain [dB]" rather than "Frequency [Hz]".

Attachment 1: REFL1_GAIN1.pdf
REFL1_GAIN1.pdf
Attachment 2: REFL1_GAIN2.pdf
REFL1_GAIN2.pdf
Attachment 3: REFL2_GAIN1.pdf
REFL2_GAIN1.pdf
Attachment 4: REFL2_GAIN2.pdf
REFL2_GAIN2.pdf
  14943   Sat Oct 5 21:26:34 2019 gautamUpdateALSY-end green alignment tweaked

Summary:

I improved the alignment of the green beam into the Y arm cavity.

  • GTRY went from ~0.2 to ~0.25, see Attachment #1.
  • This resulted in improvement of the Y arm ALS noise above 💯Hz by a factor of ~5, see Attachment #2.
  • I tried controlling the two arm cavities in the CARM/DARM basis using ALS error signals - but didn't manage to successfully execute this transition today - this will be the commissioning goal for the upcoming week.

Details:

  • I had to do the alignment by tweaking the steering mirrors at EY - the PZTs didn't give me anywhere near enough range.
  • While I was at EY, I tried moving the two MM lenses mounted on translation stages to try and improve the mode-matching into the arm cavity - wasn't successful, still see a bunch of bullseye modes when I toggle the shutter.
  • They EY green layout would benefit from a do-over (basically just copy the EX layout), but this isn't the priority right now, the ALS noise RMS is dominated by low frequency noise (as usual). 
  • There is a ~5% leakage of the GTRX beam onto the GTRY photodiode.
  • One thing to try would be to revive the MCL loop to reduce the <1 Hz laser frequency noise and see if that helps - basically testing this hypothesis.
  • I had done some careful noise-budgeting of the EX green PDH system, the EY system would benefit from the same, but not critical.
  • The improvement of the high-frequency noise is clear, and now we are consistent with the "known good reference" level from the time the DRFPMI locking was working back in early 2016.

Other changes made today:

  1. /opt/rtcds/caltech/c1/scripts/general/videoscripts/videoswitch was modified to be python3 compatible - for some reason, there were many syntax errors being thrown (even though I was using python2.7) and I wasn't able to change the displays in the VEA using the MEDM screen, but now it works again 👍.
  2. The LSC overview and several daughter MEDM screens were edited to remove references to channels that no longer exist. All screens I edited have a backup stored in the MEDM directory with today's date as a suffix.
  3. Input pointing into the PMC was tweaked.
  4. Noted that some pump is noisy at pumpspool - also noted that the annuli are no longer pumped. Some event seems to have triggered an interlock condition that closed off the annular volume from TP3, needs investigation...
Attachment 1: ALSY_alignment.png
ALSY_alignment.png
Attachment 2: ALSY_OOL.pdf
ALSY_OOL.pdf
  14944   Sun Oct 6 15:23:27 2019 gautamUpdateALSArm control using error signals achieved

Summary:

I managed to execute the first few transitions of locking the arm lengths to the laser frequency in the CARM/DARM basis using the IR ALS system 🎉 🎊 . The performance is not quite optimized yet, but at the very least, we are back where we were in the green days.

Details:

  1. Locking laser frequency to Y arm cavity length using MC2 as a frequency actuator
    • This is the usual diagnostic done to check the single-arm ALS noise using POY as an out of loop sensor.
    • The procedure is now scripted - I had to guess the sign and optimize the gains a few times, but this works deterministically now. 
    • Script lives at /opt/rtcds/caltech/c1/scripts/YARM/Lock_ALS_YARM.py.
    • Attachment #1 shows the result. If we believe the POY sensor calibration, the RMS displacement noise is ~6 pm
  2. Encouraged by the good performance of the Y arm, I decided to try the overall transition from the POX/POY basis to the CARM/DARM basis using ALS error signals.
    • The procedure starts with the arm cavities locked with POX/POY, and the respective green frequencies locked to the arm cavity length by the end PDH servos.
    • The DFD outputs serve as the ALS error signals - the PSL frequency is adjusted to the average value of DFD_X_OUT and DFD_Y_OUT.
    • I changed the LSC output matrix element for DARM-->ETMX from -1 to -5, to make it symmetric in actuation force w.r.t. ETMY (since the series resistane on ETMX is x5 that on ETMY).
    • After some guesswork, I fould the right signs for the gains. After enabling the boosts etc, I was able to keep both arms (approximately) on resonance for several minutes. See Attachment #2 for the time series of the transition process - the whole thing takes ~ 1 minute. 
    • A script to automate this procedure lives at /opt/rtcds/caltech/c1/scripts/ALS/Transition_IR_ALS.py.
    • The transition isn't entirely robust when executed by script - the main problem seems to be that in the few seconds between ramping off the IR servos and enabling the CARM/DARM integrators/boosts, the DARM error-point offset can become rather large. Consequently, when the integrator is engaged, ETMX/ETMY get a large kick that misalign the cavity substantially, degrade the green lock, and destroy the CARM lock as well. The problem doesn't seem to exist for the CARM loop. 
    • Anyways, I think this is easily fixed, just need to optimize sleep times and handoff gains etc a bit. For now, I just engage the DARM boosts by hand, putting in a DARM offset if necessary to avoid any kicking of the optic.
    • Attachment #3 shows the length noise witnessed by POX/POY when the arm cavities are under ALS control. If we believe the sensor calibration, the RMS displacement noise is ~15 (20) pm for the Y (X) arm.
    • This is rather larger than I was hoping would be the case, and the RMS is dominated by the <1 Hz "mystery noise".
    • Nevertheless, for a first pass, it's good to know that we can achieve this sort of ALS performance with the new IR ALS system.

Over the week, I'll try some noise budgeting, to improve the performance. The next step in the larger scheme of things is to see if we can lock the PRMI/DRMI with CARM detuned off resonance.

Attachment 1: ALSY_20191006.pdf
ALSY_20191006.pdf
Attachment 2: transitionIRALS.png
transitionIRALS.png
Attachment 3: arms_ALS.pdf
arms_ALS.pdf
  14945   Mon Oct 7 14:51:20 2019 aaronUpdateElectronicsWFS head RF measurements

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

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

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

 

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

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

Attachment 1: WFShead_response.pdf
WFShead_response.pdf
  14946   Mon Oct 7 19:50:33 2019 gautamUpdateIOOIMC locking not working after this work

See trend. This is NOT symptomatic of some frozen slow machine - if I disable the WFS servo inputs, the lock holds just fine.

Turns out that the beam was almost completely missing the WFS2 QPD. WTF 😤. I re-aligned the beam using the steering mirror immediately before the WFS2 QPD, and re-set the dark offsets for good measure. Now the IMC remains stably locked. 

Please - after you work on the interferometer, return it to the state it was in. Locking is hard enough without me having to hunt down randomly misaligned/blocked beams or unplugged cables.


I took this opportunity to do some WFS offset updates.

  • First I let the WFS servo settle to some operating point, and then offloaded the DC offsets to the IMC suspensions.
  • Then I disabled the WFS servo.
  • I hand-tweaked MC1 and MC3 PIT/YAW (while leaving MC2 untouched) to minimize IMC REFL (a more sensitive indicator of the optimal cavity alignment than the transmission).
  • Once I felt the IMC REFL was minimized (~1-2% improvement), I set the RF offsets for the WFS while the IMC remained locked. I chose this way of setting the RF offsets as opposed to unlocking the cavity and having the high-power TEM00 mode incident on the WFS QPDs.
  • Overnight, I'm going to run the MC2 spot position scanning code (in a tmux session on pianosa, started ~945pm) to see if we can find a place where the transmission is higher, looking at Kruthi's code now to see it makes sense...
  • The convergence time of the MC2 spot position loop is pretty slow, so the scan is expected to take a while... Should be done by tomorrow morning though, and I expect no work with the IFO tonight.
  • Does this loop have to be so slow? Why can't the gain be higher?
Attachment 1: IMCflaky.png
IMCflaky.png
Attachment 2: IMG_8015.JPG
IMG_8015.JPG
  14947   Tue Oct 8 03:19:14 2019 KojiUpdateCDSFinal incarnation of latch.py

Now with the CM board tested with the signal injected, it turned out that the latch logic was flipped. As the default state locked the digital levels, the buttons other than the mbbo channels were inactive.

By giving 0 to C1:LSC-CM_LATCH_ENABLE, the modification of the digital state is enabled. And with the value of 1, the digital bits on the board is locked.

In order to reflect this, latch.py was modified and now the controls are all activated.

  14948   Tue Oct 8 03:32:42 2019 KojiUpdateCDSCM servo board testing

[Koji]

The logic chips 74ALS573 were replaced. And now the gain sliders are working properly.

== Test Status ==

[done] Whitening gain switching test
[done] AA enable/disable switching
[0th order] LO Det Mon channel check
[none] PD I/F board check
[done] QPD I/F board check
[done] CM Board
[none] ALS I/F board


Last week we found that the logic chip for the REFL1 gain switching was not transmitting the input logic. I went to Downs and obtained the chips. After some inspection some other latch chips were suspicious. Therefore U46, U47, and U48 (#1, #3, and #4 from the top) were replaced. After the replacement, the gain measurements were repeated. This time the test for the AO gain was also performed. Now all three slideres show the gain as expected except for the consistent -0.2dB deficit.

Note that the transfer functions for the REFL gains were measured with the input at IN1 or IN2 and the output at TESTA1. The TFs for the AO gain was measured with the excitation at EXC B, the input at TESTB2 and the output at the SERVO output. The gain and phase variantions for the AO gain at low frequency is the effect of AC coupling existing between the excitation and the servo output.

[Update on Oct 14, 2019]

The measured transfer functions show the phase delay determined by the opamps involved. The phase delay well below the pole frequencies can be represented well by a simple time delay (a phase delay linear to the frequency). Attachment 7 shows the time delay estimated by LISO for each gain setting of each gain stage. REFL2 has particularly large phase delay because of the use of OP27s. The delay is even larger when the gain is high presunmably because of the limited GBW.

Attachment 1: REFL1_2_GAIN1.pdf
REFL1_2_GAIN1.pdf
Attachment 2: REFL1_2_GAIN2.pdf
REFL1_2_GAIN2.pdf
Attachment 3: REFL2_2_GAIN1.pdf
REFL2_2_GAIN1.pdf
Attachment 4: REFL2_2_GAIN2.pdf
REFL2_2_GAIN2.pdf
Attachment 5: AO_GAIN1.pdf
AO_GAIN1.pdf
Attachment 6: AO_GAIN2.pdf
AO_GAIN2.pdf
Attachment 7: delay.pdf
delay.pdf
  14949   Tue Oct 8 08:08:18 2019 gautamUpdatePEMPEM BLRMS anomaly

Yesterday, Koji and I noticed (from the wall StripTool traces) that the vertex seismometer RMS between 0.1-0.3 Hz in the X-direction increased abruptly around 6pm PDT. This morning, when I came in, I noticed that the level had settled back to the normal level. Trending the BLRMS channels over the last 24 hours, I  see that the 0.3-1 Hz band in the Z direction shows some anomalous behaviour almost in the exact same time-band. Hard to believe that any physical noise was so well aligned to the seismometer axes, I'm inclined to think this is indicative of some electronics issues with the Trillium interface unit, which has been known to be flaky in the past.

Attachment 1: PEManomaly.png
PEManomaly.png
  14950   Tue Oct 8 10:29:19 2019 gautamUpdateIOOMC Transmission scan

Summary:

There is ~ 7% variation in the power seen by the MC2 trans QPD, depending on the WFS offsets applied to the MC2 PIT/YAW loops. Some more interpretation is required however, before attributing this to spot-position-dependent loss variation inside the IMC cavity.

Analysis:

Attachment #1This shows a scatter plot of the MC2 transmission and IMC REFL average values after the WFS loops have converged to the set offset positions. The size of the points are proportional to the normalized variance of the quantity. The purpose of this plot is to show that there is significant variation of the transmission, much more than the variance of an individual datapoint during the course of the averaging (again, the size of the circles is only meant to be indicative, the actual variance in counts is much smaller and wouldn't be visible on this plot scale). For a critically coupled cavity, I would have expected that the TRANS/REFL to be perfectly anti-correlated, but in fact, they are, if anything, correleated. So maybe the WFS loops aren't exactly converging to optimize the inoput pointing for a given offset? 

Attachment #2Maps of the transmission/reflection as a function of the (YAW, PIT) offset applied. The radial coordinate does not yet mean anything physical - I have to figure out the calibration from offset counts to spot position motion on the optic in mm, to get an idea for how much we scanned the surface of the optic relative to the beam size. The gray circles indicate the datapoints, while the colormaps are scipy-based interpolation. 

Attachment #3After talking with Koji, I explicitly show the correlation structure between the IMC REFL DCMON and MC2 TRANS. The shaded ellipses indicate the 1, 2 and 3-sigma bounds for the 2D dataset going radially outwards. The correlation coefficient for this dataset is 0.46, which implies moderate positive correlation. 🤔 

Scan algorithm:

The following was implemented in a python scipt:

  1. Choose 2 independent random numbers from the uniform distribution in the interval [-0.5, 0.5] (in uncalibrated counts).
  2. One of these numebrs is set as the error point offset for the QPD spot-centering PITCH WFS loop, while the other is the YAW offset.
  3. Wait for 600 seconds - this long wait is required because the step-response time for these loops is long. 
  4. If there is an MC unlock event - wait till the MC relocks, and then another 600 seconds, to give the WFS loops sufficient time to converge.
  5. Once the WFS loops have converged, average a few data channels (MC TRANS, REFL, WFS loop error points etc) for 10 seconds, and write these to a file.

I am now setting the offsets to the WFS QPD loop to the place where there was maximum transmission, to see if this is repeatable. In fact it was. Looking at the QPD segment outputs, I noticed that the MC2 transmission spot was rather off-center on the photodiode. So I went to the MC2 in-air optical table and centered the beam till the output on the 4 segments were more balanced, see Attachment #4. Then I re-set the MC2 QPD offsets and re-enabled the WFS servos. The transmission is now a little lower at ~14,500 counts (but still higher than the ~14200 counts we had before), presumably because we have more of the brightest part of the beam falling on the gap between quadrants. For a more reliable measurement, we should use a single-element photodiode for the MC2 transmission.

Quote:
  • Overnight, I'm going to run the MC2 spot position scanning code (in a tmux session on pianosa, started ~945pm) to see if we can find a place where the transmission is higher,
Attachment 1: MC2_transmission_scatter.pdf
MC2_transmission_scatter.pdf
Attachment 2: transmissionMaps.pdf
transmissionMaps.pdf
Attachment 3: correlStructure.pdf
correlStructure.pdf
  14951   Tue Oct 8 16:00:06 2019 aaronUpdateElectronicsWFS head RF measurements

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

Removing the DC readout chain from the circuit does not affect the AC response.
Perhaps something to do with the (currently unmodeled) capacitance of the diode? I think this forms a necessary part of the resonant circuit. The gain is also suspiciously low.
Edit: Indeed, simply adding the 'typical' shunt capacitance (9pF) and a small series resistor (10 Ohm) gives the right qualitative response
The python notebook is in /users/aaron/WFS/electronics.
The DC response flattens off at ~20dB by ~mHz, which also seems longer than the timescales I saw while measuring; I'm not sure I have some of the AD827 parameters correct (eg 'delay')
 
I came across this nice note on photodiodes.
 
 
Attachment 1: WFS_ACresponse.pdf
WFS_ACresponse.pdf
Attachment 2: WFS_DCresponse.pdf
WFS_DCresponse.pdf
  14952   Tue Oct 8 16:54:56 2019 ranaUpdateIOOIMC locking not working after this work

I think this offset setting thing is not so good. People do this every few years, but putting offsets in servos means that you cannot maintain a stable alignment when there are changes in the laser power, PMC trans, etc. The better thing is to do the centering of the WFS spots with the unlcoked beam after the control offsets have been offloaded to the suspensions.

  14953   Tue Oct 8 17:59:29 2019 KojiUpdateCDSCM servo board testing (portal)

== Test Status ==

[done] Whitening gain switching test
[done] AA enable/disable switching
[0th order] LO Det Mon channel check
[none] PD I/F board check
[done] QPD I/F board check
[done] CM Board
[none] ALS I/F board


The photos of the latest board can be found as Attachments 3/4

With some input signals, the functionarities of the CM servo switches were tested.

  • Latch logic works. But latch alive signal is missing.
  • IN1 enable/disable, IN2 enable/disable are properly working
  • OUT2 toggle switch for REFL1/REFL2 mon is wokring
  • Boost / Super Boosts are working
  • EXC A enable/disable, EXC B enable/disable switches are working
  • Option 1 and Option 2 now isolate the input when either is enabled (as there is no option board)
  • 79Hz-1.6kHz pole zero pair works fine
  • OUT1 works fine
  • Disable/Enable switch for the fast path works
  • Polarity switch works
  • AO Gain property changes the gain
  • Limitter switch works (Attachments 4/5). The limitter clipps the output at 4~4.5V. The Limitter indicator also works.

After the tests the LSC cables were reconnected (Attachment 6)

Attachment 1: Screen_Shot_2019-10-08_at_18.36.04.png
Screen_Shot_2019-10-08_at_18.36.04.png
Attachment 2: CM_Board_asof_191007_1.jpeg
CM_Board_asof_191007_1.jpeg
Attachment 3: CM_Board_asof_191007_2.jpeg
CM_Board_asof_191007_2.jpeg
Attachment 4: no_limitter.jpg
no_limitter.jpg
Attachment 5: with_limitter.jpg
with_limitter.jpg
Attachment 6: P_20191008_012442_vHDR_On.jpg
P_20191008_012442_vHDR_On.jpg
  14954   Tue Oct 8 18:35:09 2019 gautamUpdateLSCLocking prep

In preparation for some locking work tonight, I did the following at the POP in air table with the PRMI locked on carrier:

  1. Raised the POP camera by ~5mm. The POP spot is now well centered on the CCD view.
  2. Tweaked alignment onto the PDA10CF photodiode that serves as (i) POP22, (ii) POP110, and (iii) POP DC. In lock the POPDC level went from ~800 cts to ~1200 cts.
  3. Moved the QPD that witnesses part of the POP beam such that the spot was centered on the photodiode. This may be useful for collecting some FF data or if we want to try feedback to stabilize the PRMI.

TBC...

  14955   Tue Oct 8 18:42:39 2019 KojiUpdateCDSCM servo board testing

The boost filters of the CM servo board were tested. Their ZPK models were made.


The transfer functions of the boost filters were measured with the SG output of a SR785 connected to IN1. The IN1 gain was set to be 0dB. The transfer function was taken between the IN1 input and the TEST1A output.
With no boost and normal boost, the input signal amplitude was fixed to 20mVpk. For the other boosts, however, I could expect large gain variation through a single sweep. Therefore automatic SG amplitude tracking was used. The target was to have the output to be 1V with maximum amplitude of 100mV.

Attachment 1 shows the measured transfer functions.

The pole and zero frequencies of the boosts were estimated using LISO. Here the TFs were normalized by the TF of 'no boost' to cancel the delay of the other stages including that of the monitor channel.

 

ZPK model of Normal Boost:

pole 44.0597566447
zero 4.3927650910k

factor 98.8275377818

 

ZPK model of Super Boost (State1):

pole 878.5368382789
zero 17.5107366335k
factor 20.0840668188

 

ZPK model of Super Boost (State2):

pole 714.8112014271
pole 1.0147609373k
zero 13.2470941080k
zero 22.2259701828k

factor 404.5411036031
 

ZPK model of Super Boost (State3):

pole 886.3650348470
pole 420.4089305781
pole 887.8490768202
zero 8.3635166134k
zero 15.7953592754k
zero 20.5144907279k

factor 8.2051379423k

 

Attachment 1: boosts.pdf
boosts.pdf
  14956   Tue Oct 8 20:23:03 2019 gautamUpdateCDSc1iscaux testing

Looking at the old latch.st code, looks like this is just a heartbeat signal to indicate the code is alive. I'll implement this. Aesthetically, it'd be also nice to have the hex representation of the "*_SET" channels visible on the MEDM screen.

 

Quote:

Latch logic works. But latch alive signal is missing.

  14957   Tue Oct 8 20:39:42 2019 aaronUpdateIOOWFS loop measurements

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

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

I installed nds2 again, this time successfully with

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

 

  14959   Wed Oct 9 12:15:05 2019 ranaUpdateElectronicsWFS head RF measurements

It would be good if you and Shruti can look at how to change the parameters in Zero so as to do a fit to the measured data. Usually, in scipy.optimize we give it a function with some changeable params, so maybe there's a way to pass params to a zero object in that way. I think Ian and Anchal are doing something similar to their FSS Pockel's cell simulator.

  14960   Wed Oct 9 18:15:26 2019 gautamUpdateLSCPRMI 3f locking

After making sure the beams were hitting the 3f photodiodes on the "AP" table, I was able to lock the PRMI with the sidebands resonant inside the RC using 3f error signals. This would be the config we run in when trying to lock some more complicated configuration, such as the PRFPMI (i.e. start with the arms controlled by ALS, held off resonance). Tonight, I will try this (even though obviously I am not ready for the CARM transition step). The 3f lock is pretty robust, I was able to stay locked for minutes at a time and re-acquisition was also pretty quick. See Attachment #1. Not sure how significant it is, but I set the offsets to the 3f paths by averaging the REFL33_I and REFL33_Q signals when the PRMI was locked with the 1f error signals.

As usual, there's a lot of angular motion of the POP spot on the CCD monitor, but the lock seems to be able to ride it out.

Lock-settings (I modified the .snap file accordingly):

REFL33_I --> PRCL, loop gain = -0.019, Trigger on POP22, ON @ 20cts, OFF@0.5cts.

REFL33_Q --> MICH, loop gain = +1.4, Trigger on POP22, ON @ 20cts, OFF@0.5 cts.

Attachment 1: PRMI_1f.png
PRMI_1f.png
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