In the process of setting up some cabling at 1Y2, I must've bumped a cable to the c1lsc expansion chassis. Anyways, the c1lsc models crashed. I ran the reboot script around 530pm PDT. Usual locking behavior was recovered after this. The work at 1Y2 was:

• Ran a cable from X Beat power splitter ("LO" leg of the analog delay line) to variable delay line. 
• Ran cable from delay line to demodulator's LO input.
• Set up the SR785 for some CM board TF measurements.

The IN2 to CM board was already connected to I single ended output of the ALS X demodulator. The ~100 Hz UGF digital locking using the CM_SLOW path is straightforward but I didn't have any success with the AO path tonight. I wonder how high BW this lock can be made without injecting a ton of noise into the IMC loop, given that the EX uPDH only has ~ 10 kHz UGF.

Attachment #1 shows the spectra of the ALS signal 

• The two "CM Slow" traces are the digitized "SLOW" output of the common mode board, whose IN2 is connected to the demodulated I output of the analog delay line.
• The delay in the LO line of the analog delay line is adjusted to zero the DC value of this signal to best effort.
• These spectra are measured with the arm cavities POX/POY locked, and the EX laser locked to the arm cavity using the end PDH box.
• I simultaneously monitor the output of the digital phase tracker servo, and scale the CM Slow signal such that the spectra line up. The scaling factor required was to multiply the CM_SLOW signal x10 (CM board IN2 gain was set to +6dB, to account for the x2 gain in going from single ended to differential inside the ALS demodulator box).
• One puzzline feature is why switching on the ADC whitening makes the ALS spectrum noisier (even though it clearly changes the digitization noise floor). There is a peak that appears at ~ 8 kHz with the whitening on, and it may also be downconverted noise from some peak at higher frequencies I guess (if the AA isn't sharp enough). 

Attachment #2 is an OLTF measurement.

• In the blue trace, the arm length is controlled by using the CM Slow signal as an error signal, applying feedback to IMC length via MC2.
• In the red trace, I turned the digital MC2 violin notches off, and added upped the IMC IN2 gain to -12 dB (AO gain slider = 0dB).
• This was as high as I could go before the PC drive RMS began to go crazy.
• But still, there isn't any significant phase advance.
• It is possible I need to tack on a low-pass filter to prevent noise injection at higher frequencies...

[Meenakshi, Shruti]

Even though we were not able to lock the the IR beat (by enabling LSC) during the day possibly because of increased seismic activity, we tried to the measure the ALS beat frequency noise by changing the PDH side-band frequency to different values.

I tried choosing values that corresponded to the peaks in the PM/AM as found in elog:15206 but for some reason unknown to us the cavity did not lock between 700-800 kHz.

The three attachments have data for different sideband frequencies:

Attachment 1: 819.472 kHz (peak in PM/AM, measured around noon)

Attachment 2: 225.642 kHz (peak in PM/AM, measured earlier in the morning)

Attachment 3: 693.500 kHz (not a peak in PM/AM)

We don't think these plots mean much and will do the measurement at some quieter time more systematically.

While doing the experiment, the ITMY pitch actuation was changed from -2.302 to -2.3172V because it locked better.

The ITMX, ETMX alignment was also tweaked to try to lock with different sideband frequencies and then restored to the values that were found earlier in the morning.

Unlikely, the alignment was probably just not good. I restored the alignment and now the arms can be locked to IR frequency.

{Yehonathan, Meenakshi}

We measure the IMC transfer function using SR785.

We hook up the AOM driver to the SOURCE OUT, Input PD to CHANNEL ONE and the IMC transmission PD to CHANNEL TWO.

We use the frequency response measurement feature in the SR785. A swept sine from 100KHz to 100Hz is excited with an amplitude of 10mV.

Attachment 1 shows the data with a fit to a low pass filter frequency response.

IMC pole frequency is measured to be 3.795KHz, while the ringdowns predict a pole frequency 3.638KHz, a 4% difference.

The closeness of the results discourages me from calibrating the PDs' transfer functions.

I tend to believe the pole frequency measurement a bit more since it coincides with a linewidth measurement done awhile ago Gautam was telling me about.

Thoughts:

I think of trying to try another zero-order ringdown but with much smaller excitation than what used before (500mV) and than move on to the first-order beam.

Also, it seems like the reflection signal in zero-order ringdown (Attachment 2,  green trace) has only one time constant similar to the full extinction ringdown. The reason is that due to the fact the IMC is critically coupled there is no DC term in the electric field even when the extinction of light is partial. The intensity of light, therefore, has only one time constant.

Fitting this curve (Attachment 3) gives a time constant of 18us, a bit too small (gives a pole of 4.3KHz). I think a smaller extinction ringdown will give a cleaner result.

We proceeded with the trying to measure the ALS out-of-loop noise of the X arm when the X arm cavity is green-locked using different PDH sideband frequencies.

Before doing the experiment, Koji helped us with getting the arm cavities locked in IR using LSC (length) and ASC (angular).

With the arms locked in IR and green, we repeated the same measurements as before at different sideband frequencies (Refer Attachment 1 - label in Hz). We did not optimize the phase nor did we look at the PDH error signal today which is possibvly why we did not see an improvement in the noise. We will look into this possibly tomorrow.

Could you please put physical units on the Y-axis and also put labels in the legend which give a physical description of what each trace is?

It would also be good to a separate plot which has the IR locking signal and the green locking signal along with this out of loop noise, all in the same units so that w can see what the ratio is.

1. Delay line for adding extra phase (would require over 40m of cable for 90 deg phase shift)
2. Using two function generators for generating the sideband, clocked to each other, so that one can be sent to the PZT and the other to the mixer for demodulation.
3. Use a different LPF (does not seem very useful for investigating multiple possible frequencies)

Once we adjust the phase we may be able to increase the servo gain for optimal locking. Unless it may be a good idea to increase the gain without optimizing the phase?

Check out this elog: ELOG 4354

If this summing box is still used as is, it is probably giving the demod phase adjustment.

[Meenakshi, Shruti]

In order to adjust the relative phase for PDH locking, we used the Siglent SDG 1032X function generator which has two outputs whose relative phase can be adjusted.

This Siglent function generator was borrowed from Yehonathan's setup near the PSL table and can be found at the X end disconnected from our setup after our use.

Initially, we used the Siglent at 231.250 kHz and 5 Vpp from each output with zero relative phase to lock the green arm cavity. By moving the phase at intervals of 5deg and looking at the PDH error signals when the cavity was unlocked we concluded that 0deg probably looked like it had the largest linear region (~1.9 V on the yaxis. Refer elog 15218 for more information) as expected.

Then we tried the same for 225.642 kHz, 5 Vpp, and found the optimal demod phase to be -55deg, with linear region of ~3 V (Ref. Attachment 2). A 'bad' frequency 180 kHz was optimized to 10deg and linear region of ~1.5 V.

The error signals at higher frequencies appeared to be quite low (not sure why at the moment) and tuning the phase did not seem to help this much.

For the noise measurement, the IFO arms were locked to IR and green, but even after optimizing the transmission with dither, we couldn't achieve best locking (green transmission was around ~0.2). Further, the IMC went out of lock during the experiment after which Koji helped us by adjusting the gains a locking point of the PMC servo. Attachment 1 contains some noise curves for the 3 frequencies with a reference from an earlier 'good' time.

to make the comparisons meaningfully

one needs to correct for the feedback changes

faithfully

The HVAC people replaced a valve and repaired the pneumatic plumbing on the roof air handler.  Temperature has been stable during the day since Thursday.  If anyone is in the control room during the evening, please make a note of the temperature.

Chub

Seems that the GPS is out of sync on donatella. We could not get any data from diaggui...

[Yehonathan, Hang]

We did some quick DC balancing of the MC2 coil drivers to reduce the l2a coupling. We updated the gains in the C1:SUS-MC2_UL/UR/LR/LLCOIL to be 1, -0.99, 0.937,-0.933, respectively. The previous values were 1, -1, 1, -1.

The procedures are the following:

Lock IMC.

Drive UL+LR and change the gain of LR to zero pitch.

Drive UR+LL and change the gain of LL to zero pitch.

Lastly, drive all 4 coils and change UR & LR together to zero yaw. 

We used C1:SUS-MC2_LOCKIN1_OSC to create the excitations at 33 Hz w/ 30,000 cts. The angular error signals were derived from IMC WFSs.

While this time we did things by hand, in the future it should be automated as the procedure is sufficiently straightforward. 

{Yehonathan, Gautam}

In order to measure the loss in the arm cavities in reflection, we use the DC method described in T1700117.

It was not trivial to find free channels on the LSC rack. The least intrusive way we found was to disconnect the ALS signals DSUB9 (Attachment 1) and connect a DSUB breakout board instead (Attachment 2).

The names of the channels are ALS_BEATY_FINE_I_IN1_DQ for AS reflection and ALS_BEATY_FINE_Q_IN1_DQ for MC transmission. Actually, the script that downloads the data uses these channels exactly...

We misalign the Y arm (both ITM ad ETM) and start a 30 rep measurement of the X arm loss cavity using /scripts/lossmap_scripts/armLoss/measureArmLoss.py and download the data using dlData.py.

We analyze the data. Raw data is shown in attachment 3. There is some drift in the measurement, probably due to drift of the spot on the mirror. We take the data starting from t=400s when the data seems stable (green vertical line). Attachment 5 shows the histogram of the measurement

X Arm cavity RT loss calculated to be 69.4ppm.

We repeat the same procedure for the Y Arm cavity the day after. Raw data is shown in attachment 5, the histogram in attachment 6.

Y Arm cavity RT loss calculated to be 44.8ppm. The previous measurement of Y Arm was ~ 100ppm...

Loss map measurement is in order.

Today, I did the following tests (and so was touching electronics/cables at/around 1X2):

• Measured the IMC OLTF.
• Measured the TF from injection at IN2 to response at the IMC error point (T-eed the I out of the IMC demodulator as there is no longer a monitor point available).
• Measured the IMC in loop error signal with 0.25 Hz resolution from DC-2kHz.
• Confirmed that the IMC IN2 (a.k.a. AO path) gain slider performs as advertised. This is a useful test to run post Acromag switchover on Friday.

Results to follow.

After this work, I reverted the EPICS channels to the usual values. The IMC can be locked.

In the style of the KA characterization of the CM board, the AO path gain EPICS slider (IN2) of the IMC servo board was stepped by 1 dB through the full available range of -32 dB to +31 dB. For each value of the requested gain, I measured the TF from the injected signal (to IN2) to TP1A on the IMC servo board. I used the BNC connector for this test, whereas we use the LEMO connector for the AO path. The source was tee-d off at the SR785 side, with one leg going to IN2 of the IMC servo board, and the other going to CH1A of the SR785. TP1A of the IMC board was connected to CH2A of the SR785. 

Attachment #1 - Measured gain vs requested gain.

• When debugging the CM board, it was this kind of test that revealed the faulty latch ICs.
• -12 dB to -11 dB gain step looks anomalous, but overall the trend seems linear.
• I was confused by why there should be a discontinuity at this stage of the gain stepping - seems like the scanning script I use changes the SR785 excitation amplitude at this point (from 300mV to 100mV). But why should the size of the excitation signal change the magnitude of the transfer function? Is this indicative of some loading issue?
• There is an overall offset between the requested gain and measured gain of ~2-3 dB. This seems large.
• There is nothing in the schematic which would have me expect this - there is a 1/2 divider at the positive input of the differential receiving stage, but this just cancels out the non-inverting gain of x2.

Attachment #2 - Frequency dependent transfer functions

• There seem to be two families of curves - they correspond to <-12 dB and >-12 dB.
• The feature at 90 kHz is strange - need to look at the schematic to see what this could be.

The motivation here is to try and figure out why I cannot engage the AO path smoothly in the CARM handoff part of lock acquisiton. I plan to use this information to do some loop modeling and project laser frequency noise coupling in various stages of the lock acquisition process.

In 1X1, there is a box labelled "FSS REF" below a KEPCO HV supply. This box had a power cable that wasn't actually connected to any power. I removed said cable.

[many people]

in prep for the install tomorrow, we did the following:

• Install the c1psl Supermicro in the 1X2 rack (Attachment 1). To make room we removed the anti-image filter and mounted it on the OMC rack.
• Set up a local workstation (monitor+mouse+keyboard) for the Supermicro so we can do some local testing (Attachment 2).
• Clear up the immediate area around the 1X1/1X2 rack, setup a cart for the Acromag.
• Make sure there are sufficient adaptor boards cables (DB37, DB15, DB9, DB25, ethernet) etc available at the cart.
• Label cables, connect on Acromag chassis end (Attachment 3).
• Keep some large (A3) printouts of the channel mapping handy by the cart.
• made sure we have open fuse-able DIN rail connectors for +/-15 V DC and +/-24 V DC for the Acromag box (we are waiting on some thinner gauge cabling for the 24V supply, once that arrives, we will power the box from the Sorensens. For now, they are powered by bench supplies on the cart).
• made sure c1psl1 (still this name for the Supermicro) is ssh-able.

Barring objections, tomorrow (Friday 28 Feb 2020) morning I will commence the switch (I still want to work on the IFO tonight).

While my checks of the AO signal path have thrown up some unanswered questions, I don't think there's any evidence in those measurements to suggest the AO crossover can't be realized. Thinking about it today though - I was wondering if it could be that the IN1 gain slider of the CM board is configured optimally. Looking back at some data, when the ALS CARM offset is zeroed, the CM_SLOW digitized data has a peak-to-peak range of ~200 cts. This is paltry. One possibility is that as I am upping the AO path gain, I'm simply injecting the electronics noise of the CM board into the IMC error point. I'd say it is safe to up the IN2 gain by 20dB to -12 dB, in which case the peak-to-peak would be ~2000 cts, still only 10% of the ADC range. It'll be straightforward to re-scale the CARM_B loop gain to account for this. Let's see if this helps.

I'd also like to measure the spectrum of the REFL11_I signal in a few different states. I think I should be able to do this using the OUT2 of the CM servo board. These are the things to try tonight:

• Try CARM RF handoff with CM_SLOW gain starting at -12dB instead of -32dB.
• Measure spectrum of REFL11_I when it is in the linear range.

There was some UNELOGGED work at EX today. The DFD outputs were also hijacked for loss measurement. Unclear who the culprit was, but there is now a broad noise bump centered around ~180 Hz in the ALS X noise curve, which certainly wasn't there yesterday. Maybe let's keep the few working systems working, it is annoying to have to deal with these auxiliary issues every night. I'll push ahead with locking, hopefully the ALS noise is "good enough".

And so it begins.

Summary:

There are several problems evident already.

1. Several EPICS database entries were missing. WTF.
2. After fixing the missing entries, the PMC could be locked. However, the IMC could not be locked.
3. I think the FSS Interface card is not configured correctly.

For now, I've returned the old c1psl connections, the PMC and IMC are both locked. Need to do some debugging on the bench.

1. The new c1psl Acromag crate is now interfaced to the Eurocrate electronics in 1X1 (formerly VME c1psl) and 1X2 (formerly c1iool0).
2. The PMC and IMC can be locked. We will investigate stability / duty cycle over the weekend.
3. There were a few issues with the wiring - specifically, the worng kind of Acromag BIO unit (sourcing, whereas we want sinking) was used for the FSS board switches. Once Jordan fixed this issue, the IMC could be locked.
4. I began to do the detailed tests of the IMC Servo card channels - there may be some issues with the boost stages, but I ran out of time yesterday, so tbc Monday.

On Monday, we will remove the old c1psl and c1iool0 machines from the electronics rack and install the Acromag crate in a more permanent way. We will also clean up some of the old cabling and cross connects, althoug the situation seems so complicated (some cross connects are also used by the rtcds c1ioo expansion chassis) that I am inclined not to remove any cables.

The area around 1X1/1X2 has a lot of dangling cables and general detritus. Be careful if you are walking around there. We will clean up on monday.

$TARGET_DIR = /cvs/cds/caltech/target

• $TARGET_DIR/c1psl and $TARGET_DIR/c1iool0 moved to $TARGET_DIR/preAcromag_oldVME/
• $TARGET_DIR/c1psl1 moved to $TARGET_DIR/c1psl 
• $TARGET_DIR/c1psl/*.service and $TARGET_DIR/C1_PSL.cmd modified - i executed :%s/c1psl1/c1psl/g in vim.
• $TARGET_DIR/preAcromag_oldVME/c1psl/autoBurt.req and $TARGET_DIR/preAcromag_oldVME/c1iool0/autoBurt.req catenated into $TARGET_DIR/c1psl/autoBurt.req. The first snapshot at 16:19 has been verified.

It remains to (Jon is taking care of these)

• add a line to modbusIOC.service on the new c1psl machine that restores the latest burt snapshot on startup (this necessitated installation of a debian jessie libXp6 package on our debian buster machine because our shared EPICS is soooooooooooooo oooooooold)
• change the hostname from c1psl1 to c1psl
• update martian.hosts

[JV, JWR, YD, GV]

• The old c1psl VME crate, and all the ribbon cables connected to it were removed from 1X1. They are presently dumped in the office area - we will clear these in the next few days, once the c1iool0 crate also gets removed from the rack.
• The Acromag crate was capped on the top and bottom, had ears bolted on, and was installed on support rails in the newly cleared up space.
• The strange orientation of the crate (with the intended backside facing the front of the rack) is to facilitate easy access to the "spare" channels we have in this box, e.g. for a future ISS or laser amplifier.
• Remaining connections to make are (these will be done tomorrow along with the extrication of the c1iool0 VME crate):
  • PMC trans PD
  • FSS RMTEMP 
  • PSL shutter
  • 2W Mephisto diagnostic connector
  • 24 V DC from Sorensens via DIN connector (we are waiting on a new power cable to arrive).

Channel list with test status
== Test Status ==

[done] Lock PMC and IMC
[done] IMC Servo board test
[done] IMC LO Det Mon channel check
[0th order] WFS quadrant DC mon
[none] WFS I/F monitors
[0th order] WFS attenuators
[none] IOO QPD channels
[done] FSS readbacks 
[done] PMC readbacks

Some more detailed elogs about the individual tests will follow.

Basically, I have characterized the IMC Servo board in detail. The summary finding is that the IN2 (=AO gain) slider needs to be investigated. 

All other channels need to be verified in a more thorough fashion than my basic checks which were just to guarantee the core interferometer functionality, which is important to me.

Had to reboot both end machines and the c1rfm model to get the TRX and TRY signals to the LSC models. Now both arms can be locked using POX/POY respectively.

Jordan and I removed another 10 kg of cabling from 1X2. The c1iool0 crate now has all cabling to it disconnected - but it remains in the rack because I can't think of a good way to remove it without disturbing a bunch of cabling to the fast c1iool0 machine. We can remove it the next time the vertex FEs crash. Cross connects have NOT been removed - we will identify which cross connects are not connected to the fast system and trash those. 

Do we want to preserve the ability to use the PZT driver in 1X2?

I used existing BNC cables running from the PSL table to the PSL rack and reassigned them to the PSL Shutter and PMC transmission PD channels.

The PSL shutter turned out to be a sinking channel. Jordan reconnected the PSL shutter wires to a sinking BIO Acromag. Channel list is updated.

Both channels have been tested to be working as expected.

gautam add on about EPICS:

• the PSL shutter channels were previously hosted on c1aux.
• I didn't comment out the original database entries on c1aux because we changed the prefix for all these channels - i.e. C1:AUX-PSL_Shutter --> C1:PSL-PSL_Shutter.
• Modified the LSC offset script to close/open the PSL shutter by writing to the correct channel now.
• there is some EPICS logic that checks the main volume pressure and prevents the opening of the PSL shutter if the main volume pressure is between 0.003 torr and 500 torr. I preserved this capability (so there are some associated soft channels in the database as well).

P.S - there is a problem we noticed - if the modbus process is started with the local subnet not having a fixed IP address, then all the EPICS channels will not be responsive. The way to fix this is to run the following sequence of commands:

• Re-aligned and locked the arm cavities for IR and green.
• Re-set trans normalization because after the c1iscex and c1iscey reboots, these didn't come back to the old values.

Allegra had no network cable and no mouse. We found Allegra'snetwork cable (black) and connected it.

I found a dirty old school mouse and connected it.

I wiped Allegra and now I'm currently installing debian 10 on allegra following Jon's elog.

04/01 update: I forgot to mention that I tried installing cds software by following Jamie's instruction: I added the line in /etc/apt/sources.list.d/lscsoft.list: "deb http://software.ligo.org/lscsoft/debian/ stretch contrib". But this the only thing I managed to do. The next command in the instructions failed.

I realigned the input pointing into the PMC this morning. Usually, the way I do this is to minimize any discernible mode structure in the PMC reflection CCD image. Today, I noticed that making the DC reflection go down also makes the DC transmission go down. Possibilities:

• we are sampling slightly different spots inside the PMC cavity which change the buildup by ~2-3%.
• we are misaligned on the transmission/reflection photodiode.
• ??

There was some work done on the Acro crate this morning. Unclear if this is independent, but I found that the IMC servo board IN1 slider doesn't respond anymore, even though I had tested it and verified it to be working. Patient debugging showed that BIO1 (and only that acromag unit with the static IP 192.168.114.61) doesn't show up on the subnet in c1psl. Hopefully it's just a loose network cable, if not we will switch out the unit in the afternoon. 

Jon is going to make a python script which iteratively pings all devices on the subnet and we will put this info on an MEDM screen to catch this kind of silent failure.

After discussing with Koji, I removed the PZT driver and associated AI card from the Eurocrate at 1X2. The corresponding backplane connectors were also removed from the cross connects. An additional cable going from the DAC to IDC adaptor on 1X2 was removed. Finally, some cables going to the backplane P1 and P2 connectors for slots in which there were no cards were removed. 

Finally, there is the IMC WFS whitening boards. These were reconfigured in ~2016  by Koji to have (i) forever whitening, and (ii) fixed gain. So the signals from the P1 connector no longer have any influence on the operation of this board. So I removed these backplane cables as well.

Some pics attached. The only cross connect cabling remaining on the south side of 1X2 is going to the fast BIO adaptor box - I suspect these are the triggered fast whitening switching for the aforementioned WFS whitening board. If so, we could potentially remove those as well, and remove all the cross connects from 1X1 and 1X2.

Update 1720: indeed, as Attachment #2 shows, the RTCDS BIO channels were for the WFS whitening switching so I removed those cables as well. This means all the xconnects can be removed. Also, the DAC and BIO cards in c1ioo are unused.

To debug a problem with the new c1psl (later elog), we needed a Supermicro EPICS server that was using the shared EPICS/modbus/asyn binaries rather than a local install. Of those available in the lab (c1iscaux, c1vac, c1susaux being the others), this was the only one which uses the shared install. So I 

• turned the slow bias voltages to 0
• shutdown the watchdog
• disconnected the Acromag crate in 1X9 from the 192.168.114.xxx subnet at the supermicro end
• connected a test ADC to the local subnet using a different ethernet cable (leaving the original one dangling)
• ran some software tests to see if we could open up a communication line to the test ADC using modbus without any errors being thrown
• removed the test ADC and restored the ethernet connection.

At which point Jon reset the software end, I restored the slow bias voltage and re-enabled the local damping. The optic seems to have damped okay. The Oplev spot is back in ~center of the QPD and the green beam can be locked to a TEM00 mode (so the alignment is okay - the IR beam is unavailable while c1psl issues are being sorted but I judge that things are back to the nominal state now).

Jon is going to write up the details of todays adventures. But the C1PSL Acromag chassis is sitting on the floor between the IMC beamtube and the 1X1 electronics rack, and is very much a trip hazard. Be careful if youre in that area.

We are going to replace the old Sun c1ioo with a modernized supermicro. At the opportunity, remove the DAC and BIO cards to use them with the new machines. BTW I also have ~4 32ch BIO cards in my office.

I investigated the problem reported earlier today with the BIO1 channels. By logging the systemd messages generated when the IOC starts, I was immediately able to determine that the problem was not limited to BIO1. The modbus communications were failing for several other units as well.

Because some in-situ rewiring of a handful of channels had recently been done (more on this soon), I initially suspected that one of the Acromags had been damaged in the process. However, removing BIO1 (or other non-communicating modules) did not restore communications with the rest of the modules. To test whether the chassis was the source of the problem at all, we set up a fresh ADC (new out of the package) and directly connected it to the secondary Ethernet interface of c1psl. With only the one new ADC connected, the modbus IOC failed in exactly the same way.

To confirm that the new ADC did in fact work, we connected it to c1auxex in the same configuration. The unit worked fine connected to c1auxex. This established that the source of the problem was the c1psl host. After some extensive debugging, I traced the problem to a pre-execution script (part of the modbus IOC systemd service) which resets the secondary network interface (the one connected to the Acromag chassis) prior to launching the IOC. This was to ensure the secondary interface always had the correct IP address. It appears this reset was somehow creating a race condition that allowed the modbus initializations (first communications with the Acromags) to sometimes start before the network interface had actually come back up.

I still don't understand how this was happening, or why the pre script worked just fine up until yesterday, but eliminating the network interface reset fixes the problem in 100% of the trials we ran. Unfortunately we lost the entire day to debugging this problem, so the final round of testing is still to be completed. We plan to pick it back up tomorrow afternoon.

[jordan, gautam]

The C1PSL crate has now been installed in a more permanent way in the rack.

• Top and bottom covers were re-attached after work yesterday.
• +/- 24 V DC and +15 V DC power connectors were screwed on for better robustness (I had removed the fuse for the -24V supply as part of debugging yesterday, this was reconnected).
• PSL diagnostics DB 25 cable was re-run appropriately over the cable tray and connected to the unit.
• The chassis sits on some rails - these rails are mounted to the rack using rack nuts but that means the ears on the Acromag chassis no longer line up with any rack nut slots, and so the chassis is not bolted on to the rack.
• We also took this opportunity to remove the c1iool0 VME chassis from 1X2 - given that the DAC and BIO cards of c1ioo (rtcds system) are unused, I felt comfortable disconnecting them and that made the removal relatively easy. The CDS overview MEDM screen reports no errors after this work.

After this work, I disabled logging and restarted the modbus service (and copied the current version of the systemd service file to the target directory for backup). The PMC and IMC lock alright. The system is now ready to be tested in-situ. I will separately continue my IMC Servo board tests in the evening.

One thought about how to protect against this kind of silent failure - how about we always run the modbus service with logging enabled, and then send out a warning email and stop the service if the logfile size suddenly blows up (which is characteristic of when the communications process dies)? This should be done in addition to the ping-ing of the individual IPs.

Regarding the burt-restore step that the systemd service runs after starting up the IOC - this is not even that useful, at least in the way it is currently setup (restore the "latest" burt snapshot file). If the maintenance takes >1hour as it often does, the "latest" snapshot for the system under maintenance is just garbage. So either the burt-restore should be for a "known good time" (dangerous because this will require frequent updates of the systemd service every time we find a new safe state) or we should just do it manually (my preference). Then there is no need to install custom packages on the server machine. Anyway, for now, I have not commented this step out.

Jordan is going to take pictures of all the electronics racks and update the relevant wiki pages.

[Jon, Yehonathan]

Summary

With the Acromag chassis now permanently installed, we tested the C1PSL channels going over the channel list one by one, excluding the IMC channels which Gautam is taking responsibility for (the servo board itself is also in question).

The strategy is to check the response of input channels to specific output channels for expected behaviour whenever is possible.

We marked on the channel list spreadsheet the status of the channels that were tested.

In more detail

FSS

Frequency Ref

PMC Servo Card

WFSs

MC Servo

NPRO Diagnostics

I am running some tests on the IMC servo board with an extender card so the IMC will not be locking for a couple of hours.

It seems like the AO path gain stages on the IMC Servo board work just fine. The weird results I reported earlier were likely a measurement error arising from the fact that I did not disconnect the LEMO IN2 cable while measuring using the BNC IN2 connector, which probably made some parasitic path to ground that was screwing the measurement up. Today, I re-did the measurement with the signal injected at the IN2 BNC, and the TF measured being the ratio of TP3 on the board to a split-off of the SR785 source (T-eed off). Attachments #1, #2 shows the result - the gain deficit from the "expected" value is now consistent with that seen on other sliders.

Note that the signal from the CM board in the LSC rack is sent single-ended over a 2-pin LEMO cable (whose return pin is shorted to ground). But it is received differentially on the IMC Servo board. I took this chance to look for evidence of extra power line noise due to potential ground loops by looking at the IMC error point with various auxiliary cables connected to the board - but got distracted by some excess noise (next elog).

Summary:

Sometime between 1PM and 6PM on Tuesday, excess laser frequency noise shows up in MCF at around 800 Hz, as shown in Attachment #1. Sigh.

Details:

While I show the MCF spectrum here, I confirmed that this noise is not injected by the IMC loop (with the PSL shutter closed, and the IMC servo board disconnected from the feedback path to the NPRO, the PMC error and control points still show the elevated noise, see Attachment #2). I don't think the problem is from the PMC loop - see Attachment #3 which is the ALS beat out-of-loop noise with the PMC unlocked (the PSL beam doesn't see the cavity before it gets to the ALS setup, and we only actuate on the cavity length for that loop, so this wasn't even really necessary).

Was there some work on the PSL table on Tuesday afternoon that can explain this? 

I did some preliminary debugging of this, and have localized the problem to the output path (after MC slow) on the IMC Servo card. Basically, I monitored the spectrum of the ALS beat frequency fluctuations under a few different conditions: 

• With the BNC to the NPRO PZT disconnected, there is no noise. So the laser and the FSS phase correction EOM (which the ALS beat pickoff sees) are not responsible.
• With the input to the Koji summing box disconnected, still no excess - so the summing box + Thorlabs HV driver are not responsible.
• With the TTFSS output connected to the summing box, but with the input switch to the TTFSS box disabled (isolating the on-PSL table parts of the FSS system), still no excess.
• With the input to the TTFSS enabled, and the BNC output of the IMC Servo card disconnected at 1X2, still no excess.
• Finally, when I connect the BNC cable, the excess starts to show up.

Toggling C1:IOO-MC_FASTSW, which supposedly isolates the post-MC slow (a.k.a. MCL) part of the servo, I see no difference. I am also reasonably confident this switch itself works, because I can break the IMC lock by toggling it. So pending a more detailed investigation, I am forced to conclude that the problem originates in the part of the IMC servo board after the MCL pickoff. Some cabling was removed at 1X2 on Tuesday between the times when there was no excess and when it showed up, but it's hard to imagine how this could have created this particular problem.

An earthquake around 330 UTC (=730pm yesterday eve) tripped ITMX, ITMY and ETMX watchdogs. ITMX got stuck. I released the stuck optic and re-enabled the local damping loops just now.

ETMX was grossly misaligned.

I re-aligned it and the X arm now locks.

7:00PM with Koji

Both the alignment of the X and Y arms was recovered.

~>z avg 10 C1:LSC-TRX_OUT C1:LSC-TRY_OUT
C1:LSC-TRX_OUT 0.9914034307003021
C1:LSC-TRY_OUT 0.9690877735614777

We are running ass for the X arm to recover the X arm alignment.

Meanwhile, i want to block the Y arm trans PD (Thorlabs). To do it, the PD<->QPD thresholds were changed from 5.0/3.0 to 0.5/0.3.

I returned the triggering threshold to normal values (5/3).

I want to measure the transfer function of the arm cavities to extract the pole frequencies and get more insight into what is going on with the DC loss measurements.

The idea is to modulate the light using the PSL AOM. Measure the light transmitted from the arm cavities and use the light transferred from the IMC as a reference.

I tried to start measuring the X arm but the transmission PD is connected to the QPD whitening filter board with a 4 pin Lemo for which I couldn't find an adapter.

• I switch to the Y arm where the transmission PD - Thorlabs PDA520 (250KHz Bandwidth) - is BNC all the way.
• I lay an 82ft BNC cable from the Y Arm 1Y4 to 1Y1 where the BNC from the IMC Trans PD and an SR785 are found. 
• I lock the Arm cavities.
• I connect the AOM cable to the source, the TRY PD (Teed off from the QPD whitening filter) to CH1 and IMC_TRANS to CH2 and measure the transfer function using a swept sine with an offset of 300mV and amplitude of 100mV.
• I fit it to a low pass filter function - see attachment 1 - but it seems like the fit rails off at 10KHz. 

Could this be because of the PDA520 limited BWs? I tried playing with the PD gain/bandwidth switch but it seems like it was already set to high bandwidth/low gain.

In any case, the extracted pole frequency ~ 2.9kHz implies a finesse > 600 (assuming FSR = 3.9MHz) which is way above the maximal finesse (~ 450) for the arm cavities.

I disconnected the source from the AOM. But left the other two BNCs connected to the SR785. Also, TRY PD is still teed off. Long BNC cable is still on the ground.

My old scheme was flawed as I used pitch as the readback. The pitch signal could not distinguish the cross-coupling due to coil imbalance and that due to the natural suspension L2P. A new scheme based on yaw alone has been developed and will be integrated into ifo_test. For now we revert the C1:SUS-MC2_UL/UR/LR/LLCOIL gains back to 1, -1, 1, -1. 

I opened the packages send from Syracuse.

- The components are not vacuum clean. We need C&B.
- Some large parts are there, but many parts are missing to build complete SOSs.

- No OSEMs.
- Left and right panels for 6 towers
- 3 base blocks
- 1 suspension block
- 8 OSEM plates. (1 SOS needs 2 plates)

- The parts looks like old versions. The side panels needs insert pins to hold the OSEMs in place. We need to check what needs to be inserted there.

- An unrelated tower was also included.