I brought one CPU (Dell T3500) and one 28" monitor from Mike Pedraza's office in Downs to the 40m. It is on Steve's desk right now, pending setup. The machine already has Solidworks and Altium installed on it, so we can set it up at our leisure. The login credentials are pasted on the CPU with a post-it should anyone wish to set it up.

[yehonathan, gautam]

• we placed a PDA520 photodiode in the AS beampath, so AS110 and AS55 no longer see any light.
• ITMX and ETMX were misaligned (since the plan is to measure the Y arm loss).
• The PDA520 and MC2 transmission are currently going to the Y arm ALS beat channels in the DAQ system. Unfortunately, we have no control over the whitening gains for these channels because of the c1iscaux2 situation.

1. IMC would not lock. c1psl EPICS channels were unresponsive. I keyed the crate and went through the usual burtrestore/PMC-relocking dance.
2. While at 1X2, I decided to take this opportunity to clean up the AG4395 setup that has been setup there unused for several weeks now.
   • Unplugged the active probe connected via BNC-T connector to the mixer IF output.
   • Noticed that the active probe (S/N 2850J01450) did not have it's power connection connected. According to the manual, this is bad. I don't know if the probe is damaged or not.
   • Moved the AG4395 cart out of the way so that there is a little more room around 1X1/1X2.

Summary:

We need to determine the geometry (= round-trip length and RoC of curved mirrors) of the OMC cavities for the 40m BHD experiment. Sticking to the aLIGO design of a 4 mirror bowite cavity with 2 flat mirrors and 2 curved mirrors, with a ~4deg angle of incidence, we need to modify the parameters for the 40m slightly on account of our different modulation frequencies. I've setup some infrastructure to do this analytically - even if we end up doing this with Finesse, it is useful to have an analytic calculation to validate against (also not sure if Finesse can calculate HOMs up to order 20 in a reasonable time, I've only seen maxtem 8). 

Attachment #1: Heatmap of the OMC transmission for the following fields:

• Carrier TEM00 is excluded, but HOMs up to m+n=20 included for both the horizontal and vertical modes of the cavity.
• f1 and f2 upper and lower sidebands, up to m+n=20 HOMs for both the horizontal and vertical modes of the cavity, including TEM00.
• Power law decay assumed for the HoM content incident on the OMC - this will need to be refined
• The white region is where the cavity isn't geometrically stable.
• Green dashed line indicates a possible operating point, white dashed line indicates the aLIGO OMC operating point. On the basis of this modeling, we would benefit from choosing a better operating point than the aLIGO OMC geometric parameters.

Algorithm:

1. Compute the round-trip Gouy phase, , for the cavity.
2. With the carrier TEM00 mode resonant, compute the round-trip propagation phase, , and the round-trip Gouy phase,  for the  mode of the field, with  specifying the offset from the carrier frequency (positive for the upper sideband, negative for the lower sideband). For the aLIGO cavity geometry, the 40m modulation sidebands acquire ~20% more propagation phase than the aLIGO modulation sidebands.
3. Compute the OMC transmission for this round-trip phase (propagation + Gouy).
4. Multiply the incident mode power (depending on the power law model assumed) by the cavity transmission.
5. Sum all the fields.

Next steps:

1. Refine the incident mode content (and power) assumption. Right now, I have not accounted for the fact that the f2 sideband is resonant inside the SRC while the f1 sideband is not. Can we somehow measure this for the 40m? I don't see an easy way as it's probably power dependent?
2. Make plots for the projection along the slices indicated by the dashed lines - which HOMs are close to resonating? Might give us some insight.
3. What is the requriement on transmitted power w.r.t. shot noise? i.e. the colorbar needs to be translated to dBVac.
4. If we were being really fancy, we could simultaneously also optimize for the cavity finesse and angle of incidence as well.
5. Question for Koji: how is the aLIGO OMC angle of incidence of ~4 degrees chosen? Presumably we want it to be as small as possible to minimize astigmatism, and also, we want the geometric layout on the OMC breadboard to be easy to work with, but was there a quantitative metric? Koji points out that the backscatter is also expected to get worse with smaller angles of incidence.

The code used for the ABCD matrix calcs have been uploaded to the BHD modeling GIT (but not the one for making this plot, yet, I need to clean it up a bit). Some design considerations have also been added to our laundry list on the 40m wiki.

Chub brought the replacement Supermicro we ordered to the 40m today. I stored it at the SW entrance to the VEA, along with the other Supermicro. At the time of writing, we have, in hand, two (unused) Supermicro machines. One is meant for EY and the other is meant for c1psl/c1iool0. DDR3 RAM and 120 GB SSD drives have also been ordered, but have not yet arrived (I think, Chub, please correct me if I'm wrong).

Update 20190802: The DDR3 RAM and 120 GB SSD drives arrived, and are stored in the FE hardware cabinet along the east arm. So at the time of writing, we have 2 sets of (Supermicro + 120GB HD + 4GB RAM).

Summary:

I'd like to confirm that the IR ALS scheme will work for locking. The X-arm performance so far has been encouraging. I want to repeat the characterization for the Y arm. So I inspected the layout on the EY table, and made a list of characterization tasks. The current EY beam routing is difficult to work with, and it will definitely benefit from a re-do. However, I don't know how much time I want to spend re-doing it, so for a start, I will just try and couple some amount of light into a fiber and bring it to the PSL table, and see what noise performance I get.

Details:

Attachment #1: Photo of the current beam layout. The powers indicated were measured with the Ophir power meter.

• I measure an SHG conversion efficiency of 0.87 %/W, which is considerably lower than the ~3.7%/W that is theoretically expected, and 1.5%/W that is realized at EX.
• Of the 0.5 mW of green light that is generated, I measure ~0.375 mW at the viewport into the EY chamber. So there is ~25 % loss in the green beam path on the EY table. Seems high to me.
• The previous solution of coupling IR light into the fiber realized at EY was to use the SHG leakage IR beam. While there isn't a measurement showing that this dirty beam is noisier than a cleaner pickoff, I'd like to adopt the solution used at EX, which is to use the leakage beam from the first steering mirror in the NPRO beam path. This will allow better mode-matching and polarization control of the beam being coupled into the fiber, which at least in principle, translates to less phase noise.
• However - the beam layout at the EY table offers much less freedom to work with this idea than EX. A constraint is the clamp that secures the enclosure to the optical table, labelled in the photo. Further behind it, the green steering optics occupy all available space. A more comprehensive photo of the EY table can be found here.
• Off the top of my head, I don't see any other good open spots on the EY table where we could couple IR light into the fiber. 
• One other change I'd like to make is to replace the first steering mirror after the NPRO head, which is currently a Y1 HR mirror, with a R=99% BS. This will make it easier to control the amount of power coupled into the fiber, which is something we'd like.

Attachment #2: A candidate mode-matching solution, given the constraints outlined above. It isn't great, with only 85% modematching even theoretically possible. The lenses required are also pretty fast lenses. But I think it's the best possible without a complete overhaul of the EY layout. I'm still waiting for the lens kit to arrive, but as soon as they get here, I will start this work.

Characterization tasks:

• Characterize SHG at EY [done 7/28]
• Characterize gPDH at EY (loop TFs, improve MM, PDH discriminant, check the polarization)
• Couple IR light into fiber with good MM at EY [done with 36% MM 8/9]
• Clean fiber at EY, and at the PSL table [done 8/9]
• Make the PSL + Y IR beat [done 8/9]
• Noise budget

1. Unresponsive c1psl, c1iool0, c1auxey and c1iscaux VME crates were keyed.
2. c1psl channels were burt-restored, did a burtrestore, and re-locked the PMC. Tweaked the pointing into the PMC on the PSL table to increase the PMC transmission from ~0.69 to ~0.71.
3. Re-locked IMC. Ran WFS offset script to relieve the ~100 DAC counts (~10 urad) DC offset from the WFS servos to the IMC suspensions (a serious calibration of this into physical units should be made part of the planned 40m WFS activity). Now that I think about it, since we change the IMC alignment to match the input beam alignment, some post-IMC clipping could modulate the power incident on the ITMs, which is a source of error for the arm cavity loss determination using DC reflection. We need a better normalizing data stream than the IMC transmission.
4. The IFO_OVEREVIEW medm screen was modified such that the threshold for the PMC transmitted beam to be visible was lowered from 0.7 to 0.6, so that now there is a continuous beam line from the NPRO to the PRM when the IMC is locked even when the PMC transmission degrades by 5% due to thermally driven pointing drifts on the PSL table.
5. The wmctrl utility on pianosa wasn't working so well, I wasn't able to use my usual locking MEDM autoconfig scripts. Turned out to be due to a zombie MEDM window which I killed with xkill, now it is working okay again.
6. The misaligned XARM was re-aligned and the loss measuring PDA520 at the AS port was removed from the beam path (mainly to avoid ADC saturations the fringing Michelson will cause).
7. I noticed that the ETMX Oplev HeNe SUM level has degraded to ~50% of its power level from 200 days ago [Attachment #1], may need a new HeNe here soon. @Chub, do we have spare HeNes in stock?

I want to collect some data with the arms locked to investigate the possibility/usefullness of having seismic feedforward implemented for the arms (it is already known to help the IMC length and PRC angular stability at low frequencies). To facilitate diagnostics I modified the file /users/Templates/Seismic/Seismic_vs_TRXTRYandMC.xml to have the correct channel names in light of Lydia's channel name changes in 2016. Looking at the coherence data, the alignment of the cartesian coordinate system of the Seismometers at the ends and the global interferometer coordinate system can be improved.

I don't know if for the MISO filter design if there is any difference in using TRX/TRY as the target, or the arm length control signal.

Data collection started at 1249018179. I've setup a script running in a tmux shell to turn off the LSC enable in 2 hours.

The VEA laptop asia was configured to be able to connect to too many WiFi networks - it was getting conflicted in its default position at the vertex and trying to hop between networks, for some reason trying to connect to networks that had poor signal strength. I deleted all options from the known networks except 40MARS. Now the network connection seems much more stable and reliable.

ML2013 is unable to open Simulink on any of the workstations. We decided to make the default version of Matlab R2015b (the default of the version of RCG we are using).

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.

Currently the branch and tag are protected - once we verify that everything works as expected post migration, I will open it up. I changed the directory structure of the models, need to confirm that the rtcds compilers don't have any hardcoded paths which may break due to my change.

The symlink to Matlab R2013 was deleted and a new symlink to R2015b was made. I activated the license using the Caltech campus license. Now running matlab from shell starts up R2015b . Simulink even works 😲 .

Summary:

The requirement on the phase noise on the direct backscatter from the OMC back into the SRM is that it be less than  @ 100 Hz, for a safety factor (arbitrarily chosen) of 10 (= 20dB below unsqueezed vacuum). Assuming 5 optics between the OMC and SRM which contribute incoherently for a factor of sqrt(5), and assuming a total of 1 ppm of the LO power to be backscattered, we need the suspensions to be moving  @ 100 Hz. This seems possible to realize with single stage suspensions - I assume we get f^4 filtering from the pendulum at 100 Hz, and that there is an additional 80 dB attenuation (from the stack) of the assumed 1 micron/rtHz motion at 100 Hz, for an overall 160 dB attenutaiton, yielding 10^-14 m/rtHz at 100 Hz.

Details:

This is the same calculation as I had posted a couple of months ago (see elog that this is a reply to), except that Koji pointed out that the LO power is expected to dominate the (carrier) power incident on the OMC cavity(ies). So the more meaningful comparison to make is to have the x-axes of the plots denote the backscatter fraction,  rather than the LO power. One subtlety is that because the phase of the scattered field is random, the displacement-noise induced phase noise could show up in the amplitude quadrature. I think that in these quadrature field amplitude units, the RIN and phase noise are directly comparable but I might have missed a factor of 2*pi. But in the worst case, if all the phase noise shows up in the amplitude quadrature, we end up being only ~10dB below unsqueezed vacuum (for 1 ppm backscatter). 

For the requirement on the noise in the intensity quadrature - I think this is automatically satisfied because the RIN requirement on the incident LO field is in the mid 10^-9 1/rtHz regime.

• Removed power monitoring PD (It was off anyways)
• Installed Steering mirror and collimator in K6XS mount (fast axis = p-pol to best effort by eye)
• Installed lens mounts in approx position
• Cleaned fiber at EY and connected to the collimator
• Coupled EY--->PSL and spare PSL-->EY fibers together at the PSL table to facilitate coupling.
• tbc tomorrow...

At ~1am PDT today, all the MC1 shadow sensor readbacks (fast CDS channels and Slow Acromag channels, latter not shown here) went to negative values. Of course a negative value makes no sense. After ~3 hours, they came back to positive values again. But since then, the shadow sensor RMS noise has been significantly higher in the >20 Hz band, and there are frequent glitches which kick the suspension. The IMC has been having trouble staying locked. I claim that this has to do with the Satellite box.

No action being taken now while I work on the ALS. In the past the problem has fixed itself.

[chub, gautam]

We scoped out the 1Y3 rack this morning to figure out what needs to be done hardware wise. We did not think about how to power the Acromag crate - the LSC rack electronics are all powered by linear supplies and not Sorensens, and the linear supplies are operating at pretty close to their maximum current-drive. The Acromag box draws ~3A of current from the 20 V supply, not sure what the current draw will be from the 15 V supply. Options:

1. Since there are sorensens in 1Y2 and 1Y1, do we really care about installing another pair of switching supplies (+20 V DC and +15 V DC) in 1Y3?
   • Contingent on us having two spare Sorensens available in the lab. Chub has already located one.
2. Use the Sorensens installed already in 1Y1. 
   • Probably the easiest and fastest option.
   • +15 V already available, we'd have to install a +20 V one (or if the +/-5 V or +12 V is unused, reconfigure for +20 V DC).
   • Can argue that "this doesn't make the situation any worse than it already is"
   • Will require the running of some long (~3 m) long cabling to bring the DC power to 1Y3 where it is required. 
3. Get new linear supplies, and hook them up in parallel with the existing.
   • Need to wait for new linear supply to arrive
   • Probably expensive
   • Questionable benefit to electronics noise given the uncharacterized RF pickup situation at 1Y2

I'm going with option #2 unless anyone has strong objections.

Summary:

1. 220 uW / 600 uW (~36 % mode-matching) of IR light coupled into fiber at EY.
2. Re-connected the RF chain from the beat mouth output on the PSL table to the DFD setup at 1Y2.
3. A beat note was found between the PSL and EY beams using the BeatMouth.

Motivation:

We want to know that we can lock the interferometer with the ALS beat note being generated by beating IR pickoffs (rather than the vertex green transmission). The hope is also to make the ALS system good enough that we can transition the CARM offset directly to 0 after the DRMI is locked with arms held off resonance.

Details:

Attachment #1: Shows the layout. The realized MM is ~36 %. c.f. the 85% predicted by a la mode. It is difficult to optimize much more given the tight layout, and the fact that these fast lenses require the beam to be well centered on them. They are reasonably well aligned, but I don't want to futz around with the pointing into the doubling crystal. Consequently, I don't have much control over the pointing.

Attachment #2: Shows pictures of the fiber tips at both ends before/after cleaning. The tips are now much cleaner.

The BeatMouth NF1611 DC monitor reports ~580 mV with only the EY light incident on it. This corresponds to ~60 uW of light making it to the photodiode, which is only 25% of what we send in. This is commensurate with the BS loss + mating sleeve losses.

To find the beat between PSL and EY beams, I had to change the temperature control MEDM slider for the EY laser to -8355 cts (it was 225 cts). Need to check where this lies in the mode-hop scan by actually looking at the X-tal temperature on the front panel of the EY NPRO controller - we want to be at ~39.3 C on the EY X-tal, given the PSL X-tal temp of ~30.61 C. Just checked it, front panel reports 39.2C, so I think we're good.

Next steps:

• Fix the IMC suspension
• Measure the ALS noise for the Y arm
• Determine if improvements need to be made to the IR beat setup (e.g. more power? better MM? etc etc).

EY enclosure was closed up and ETMY Oplev was re-enabled after my work. Some cleanup/stray beam dumping remains to be done, I will enlist Chub's help on Monday.

I bench tested the functionality of all the c1iscaux Acromag crate channels. Summary: we are not ready for a Monday install, much debugging remains.

1. DAC channels were tested using 4 ch oscilloscope and stepping the whitening gain sliders through their 15 gain settings
   • Response was satisfactory - the output changes between 0 - 5 V DC in 15 steps.
   • This analog voltage is converted to binary representation by an on-board ADC on the whitening boards. So we may have to tune the offset voltage and range to avoid accidental bit flipping due to the analog voltage of a particualr step falling close to the bit-flipping edge of the on-board ADC. This will require an in-situ test.
   • Test passed
2. BIO output channels were tested using a DMM, and monitoring the resistance between the BIO pin and the RTN pin. In the "ON" state, the expected resistance is ~5 Mohm, and in the off state, it is ~3 ohms.
   • The AA filter switches on BIO1 unit do not show the expected behavior - @ Chub, please check the wiring.
   • All others (except the mbboDirect bits, see next bullet) were okay, including those for the CM board that are NOT part of the mbboDirect groups.
   • Test failed
3. ADC channels were tested by driving a ~2Vpp 300mHz sine wave with a function generator, and looking at the corresponding EPICS channel with StripTool.
   • I found that all the ADC channels don't function as expected.
   • Part of the problem is due to incorrect formatting of the EPICS records in the db files, but I think the ADCs also need to be calibrated with the precision voltage source.
   • Why only ADCs require calibration and not the DACs????
   • Test failed
4. mbboDirect BIO output test - I made a little LED breadboard tester kit to simultaneously monitor the status of these groups of binary outputs.
   • The LSB is toggled as expected when moving the gain slider along.
   • However, the other bits in the group are not toggled correctly.
   • I believe this is a problem with either (i) the way the EPICS record is configured to address the bits or (ii) the incorrect modbus datatype is used to initialize the ioc.
   • It will be helpful if someone can look into this and get the mbboDirect bits working, I don't really want to spend more time on this.
   • Test failed

I am leaving the crate powered (by bench supplies) in the office area so I have the option to work remotely on this.

[chub, gautam]

With Chub's help, most of the problems have been resolved. Summary: I judge that we are good to go ahead with an install tomorrow.

1. The problem with the BIO channels was a mis-wiring internal to the chassis - Chub fixed this and now all 32 AA enable/disable switches seem to work as advertised. Of course we will need to do the in-situ test to make sure.
2. The problem with the ADC channels were multiple:
   • On the software end, I had gotten some addressing wrong - this was fixed.
   • On the hardware side - even though the inputs of the Acromag are "differential", I found that the readback was extremely noisy (~0.5 V RMS for a 3 V DC signal from the handheld calibrator unit 😲 ). Looking through the manual, I found a recommendation (pg10) that the "IN-" terminal of the Acromag ADC units be tied to the "RTN" pins on the same units. I don't know if this preserves the differential receiving capability of the Acromag ADCs - anyways, after Chub implemented this change, all the Analog Input channels behave as expected (I tested with a DC voltage and also a 200 mHz sine wave from a function generator).
   • Note that most of the Eurocard electronics we use are single-ended sending anyways.
   • What does this mean for the other Acromag ADCs (e.g. OSEM Shadow Sensor monitors) we have installed????? I saw no documentation in the elog/wiki.
3. Binary input channel:
   • This is used by the "CM LIMIT" channel.
   • I found that I had to initialize a separate alias for the BIO3 unit, which acquires this signal, to use the modbus function "4" corresponding to "Read Input Registers" - c.f. the binary output modbus function 6, which is to "Write Single Register".
   • The fix for the mbbo channels is also likely to be along this lines - but I don't have the energy for that endavor right now.
4. Testing of the physical mbboDirect bit channels using the Acromag Window utility
   • I can't get the mbboDirect EPICS record to work as expected, so I decided to use the native Acromag utility to test the functionality
   • First I released control of the acromags from the supermicro (stopped modbus)
   • There were several wiring errors - Chub had left for the day so I just fixed it myself.
   • The LED tester kit was used to check that the correct bits were flipped - they were.
5. At the time of writing, the non-functional channels (in EPICS) are all related to the CM board:
   • C1:LSC-CM_LIMIT (binary input) tested later in the day, works okay...
   • C1:LSC-CM_REFL1_BITS (mbboDirect)
   • C1:LSC-CM_REFL2_BITS (mbboDirect)
   • C1:LSC-CM_AO_BITS (mbboDirect)
   • C1:LSC-CM_BOOST2_BITS (mbboDirect)

Since we don't immediately need the CM board, I say we push ahead with the install - at least that will restore the ability to lock PRMI / DRMI. Then we can debug these issues in situ - I'm certain the issue is related to the EPICS/Modbus setup and not the hardware because I verified the physical channel map using the Acromag windows utility.

Remaining Tasks:

1. Install power supply cables at 1Y3
2. Install supermicro and Acromag crates in 1Y3
3. Migrate existing P1 connectors to P2 where applicable (Whitening boards)
4. Connect Dsub-->P1 / P2 adaptors
5. Run in-situ tests

Repair plan:

1. Get "spare" satellite box working --- Chub
   • According to elog14441, this box has flaky connectors which probably need to be remade
2. Re-make the 64-pin IDC crimped connection on the cable from the coil driver board to sat. box, at the Satellite box end --- Chub and gautam

Any other ideas? The problem persists and it's annoying that the IMC cannot be locked.

This morning, I wanted to move the existing cables going to the P1 connectors of the iLIGO whitening boards to the P2 connector, to test the modifications made to allow whitening stage switching. Unfortunately, I found that the shrouds werent installed. Where can I find these?

As it turns out, only one extra shroud needed to be installed - I did this and migrated the cables for the 4 whitening boards from the P1 to P2 connectors. So until the new Acromag box is installed, we have no control over the whitening gains (slow channels), but do still have control over the whitening filter enable/disable (controlled by fast BIO). I am thinking about the easiest way to test the latter - I think the ambient PD dark noise level is too low to be seen above ADC noise even with the whitening enabled, and setting up drive signals to individual channels is too painful - maybe with +45dB of whitening gain, the (z,p) whitening filter shape can be seen with just PD/demod chain electroncis noise.

Summary:

I came aross an interesting suggestion by Yutaro that KAGRA's low-frequency ALS noise could be limited by the fact that the IMC comes between the point where the frequencies of the PSL and AUX lasers are sensed (i.e. the ALS beat note), and the point where we want them to be equal (i.e. the input of the arm cavity). I wanted to see if the same effect could be at play in the 40m ALS system. A first estimate suggests to me that the numbers are definitely in the ballpark. If this is true, we may benefit from lower noise ALS by picking off the PSL beam for the ALS beat note after the IMC.

Details:

Even though the KAGRA phase lock scheme is different from the 40m scheme, the algebra holds. I needed an estimate of how much the arm cavity moves, I used data from a POX lock to estimate this. The estimate is probably not very accurate (since the arm cavity length is more stable than the IMC length, and the measured ALS noise, e.g. this elog, is actually better than what this calculation would have me believe), but should be the right order of magnitude. From this crude estimate, it does look like for f<10 Hz, this effect could be significant. I assumed an IMC pole of 3.8 kHz for this calculation.

I've indicated a "target" ALS performance where the ALS noise would be less than the CARM linewidth, which would hopefully make the locking much easier. Seems like realizing this target will be touch-and-go. But if we can implement length feedforward control for the arm cavities using seismometers, the low frequency motion of the optics should go down. It would be interesting to see if the ALS noise gets better at low frequencies with length feedforward engaged.

* Some updates were made to the plot:

1. Took data from Kiwamu's paper for the seismic noise
2. Overlaid measured ALS noise

[chub, gautam]

Installation: The following equipment were installed in 1Y3, see Attachment #1:

1. Supermicro server, which is the new c1iscaux machine, with IP Address 192.168.113.83.
2. 6U Acromag chassis which contains all the ADCs, DACs and BIO units.
3. 2 Sorensen DC power supplies to provide +24 V DC and +15 V DC to the Acromags.
4. Fusable DIN rail power blocks were installed on the North side of the 1Y3 rack - I placed 2 banks of 5 connectors each for +15 V DC and +24 V DC.

Removal: The following equipment was removed from 1Y3:

1. VME crates that were the old c1iscaux and c1iscaux2 machines.
2. Spare VME crate that used to be c1susaux, which Chub and I brought over to 1Y3 in an attempt to revive the broken c1iscaux2.
3. Approximately 30 twisted ribbon cables that were going to the cross connects. For now, we have not done a full cleanup and they are just piled along the east arm (see Attachment #2), beware if you are walking there!

Software: 

1. I connected the c1iscaux machine to the martian network.
2. Then I edited the relevant files on chiara to free up the IP addresses previously used by c1iscaux (192.168.113.81) and c1iscaux2 (192.168.113.82), and re-assigned the IP address used for c1iscaux to be 192.168.113.83.
3. I also changed the hostname of the c1iscaux machine (it was temporarily called c1iscaux3 to allow bench testing).
4. I moved the old /cvs/cds/caltech/target/c1iscaux and /cvs/cds/caltech/target/c1iscaux2 directories to /cvs/cds/caltech/target/preAcromag_oldVME/c1iscaux and /cvs/cds/caltech/target/preAcromag_oldVME/c1iscaux2 respectively.
5. I moved the temporarily named /cvs/cds/caltech/target/c1iscaux3 directory, from which I was running all the tests, to /cvs/cds/caltech/target/c1iscaux.
6. I edited all references to c1iscaux3 in the systemd files so that we can run the approriate systemd services.

Next steps: 

1. We did not get around to running the DB37 cables between the Acromag chassis and the 1Y2 Eurocrates today - this operation itself took the whole day as we also needed to lay out some support struts etc on the rack to support the Sorensens and the Acromag chassis.
2. Once the Acromags are connected to the Eurocrates, we have to run in-situ tests to make sure the appropriate functionality has been restored.
3. We must have bumped something in the c1lsc expansion chassis - the CDS FE overview screen is reporting some errors (see Attachment #3). I will fix this.
4. General tidiness, strain-relief etc.

Work done today:

1. All ribbon cable connections to the backplane of the 1Y2 Eurocrates were removed. The cables themselves were cleared for more space to work with.
2. 20x 15ft DB37 Cables were run between 1Y2 and 1Y3 via overhead cable tray.
3. Backplane interface boards were installed for 1Y2 Eurocrate boards.
4. Connections were made between the Acromag chassis and the eurocrate electronics modules.

Testing of functionality:

1. Fast BIO switching was verified to work for the following photodiodes:
   • AS55, AS110, REFL11, REFL33, REFL55, REFL165, POX11, POY11, POP22, POP110.
   • No light was incident on the PDs.
   • Test was done by increasing the whitening gain to +45 dB, and then looking at the ASD of the electronics noise between 50 Hz and 500 Hz with the whitening enabled/disabled. We expect x10 difference between the two states. This was seen.
2. "DetMon" channels were verified to work - see Attachment #1
   • Y-axis units is volts
   • Test was done by toggling the output of the 11 MHz Marconi, and looking for a change.
   • As seen in the attachment, all 5 monitor channels show a change.
   • This needs to be calibrated into some sensible units - I don't know why the different modulation frequencies have such different readbacks from supposedly identical Demod Board monitor points.
   • Not sure if the ~10 V reported by the REFL165 monitor point is real or saturated.
   • These channels are installed to signal/help debug the infamous ERA-5 decay problem, but maybe already some are decayed?
3. QPD interface channels were verified to work - see Attachment #2. 
   • Test was done by shining a green laser pointer on QPD quadrants.

Much testing remains to be done, but I defer further testing till Monday - the main functionality to be verified in the short run is the whitening gain stepping. The strain-relief of cables and general cleanup will be undertaken by Chub. Current state of affairs is in Attachment #3, leaves much to be desired in terms of cleanliness.

I will also setup the autoburt for the new machine on Monday. We will also need to add some channels to C0EDCU.ini if we want to trend them over some years (e.g. RF signal powers for monitoring ERA-5 health).

* c1lsc FE was rebooted using the usual script, and everything seems to be healthy in CDS-land again, see Attachment #4.

Here is what is left to do:

1. Strain relief of all cabling. Chub will take care of this in the coming days. I have said he can connect and disconnect cables as he pleases, but after this work, we may require a hard reboot of the Acromag chassis before restoring functionality to the channels, as it is known that the Acromags can sometimes get "stuck" by a sudden connection of voltage.
2. Installation of DB15 cable to the P2 connector of the CM board and a DB9 cable to the ALS demod unit (LO and RF power monitors). These will arrive in the next couple of days and Chub will take care of the install.
3. Design, manufacture and install of a custom version of the backplane P1 adaptor board with only 1 D37 connector - for some of the PD DC signals, a custom adaptor board, part number D010005 for which I can't find any schematics is already installed on the P2 connector, and makes the DC monitor signals available to 4 LEMO connectors. These signals are then digitized by the fast CDS system, presumably for PDH signal normalization. The footprint of this P2--->LEMO adaptor is such that we cannot simply install our P1---> 2xDB37 adaptor boards, because of space constraints. Fortunately, there is a simple fix to reduce the footprint of the board: remove the bottom DB37 connector, which is unused in the c1iscaux system except for the CM board. I recommend getting ~10 pcs of such boards, as it is also useful in a few other places, where the power cabling to the eurocrates are a space constraint. See Attachment #1 for a picture explaining this situation. Anyone want to volunteer to take care of this?
4. In-situ testing. This is easiest done with some light available in the interferometer. Which in turn requires IMC to be locked. Which in turn requires satellite box fixing. Anyone want to volunteer to take care of this?
5. Modify C0EDCU.ini to trend the new slow channels we may want long-term monitoring of (e.g. LO power levels to the Demod boards). Anyone want to volunteer to take care of this?
6. Decide what to do about the CM latch logic. There are some contraints with the way the acromag register addressing works, that I've had to change the way the mbboDirect bits are controlled. Unfortunately, this seems to sometimes and unpredictably cause the bits to flip in a non-robust way, which is the whole point of having the latch in the first place. Either the latch logic needs to be improved, or we need to implement the latch logic in the fast CDS system, not the slow.

Today I set up the autoburt.req file for the c1iscaux channels, and confirmed that the snapshots are getting recorded. There were a lot of channels in the old autoburt.req file which I thought were un-necessary (and several which no longer exist), so now the only channels that are burt-ed are the whitening gains and states of the AA filters. If someone feels we need more channels to be snapshot recorded, you can add them to the file.

In the old target directory, there were also various versions of a "saverestore.req" file - why do we need this in addition to an autoburt? I guess it is possible they are used by the IFOconfigure scripts to setup some whitening gains etc...

Summary:

I did some more investigation of what the appropriate cavity geometry would be for the OMC. Unsurprisingly, depending on the incident mode content, the preferred operating point changes. So how do we choose what the "correct" model is? Is it accurate to model the output beam HOM content from NPROs (is this purely determined by the geometry of the lasing cavity?), which we can then propagate through the PMC, IMC, and CARM cavities? This modeling will be written up in the design document shortly.

*Colorbar label errata - instead of 1 W on BS, it should read 1 W on PRM. The heatmaps take a while to generate, so I'll fix that in a bit.

Update 230pm PDT: I realize there are some problems with these plots. The critically coupled f2 sideband getting transmitted through the T=10% SRM should have significantly more power than the transmission through a T=100ppm optic. For similar modulation depth (which we have), I think it is indeed true that there will be x1000 more f2 power than f1 power for both the IFO AS beam and the LO pickoff through the PRC. But if the LO is picked off elsewhere, we have to do the numbers again.

Details:

Attachment #1: Two candidate models. The first follows the power law assumption of G1201111, while in the second, I preserved the same scaling, but for the f1 sideband, I set the DC level by assuming a PRG of 45, modulation depth of 0.18, and 100 ppm pickoff from the PRC such that we get 50 mW of carrier light (to act as a local oscillator) for 10 W incident on the back of PRM. Is this a reasonable assumption?

Attachment #2: Heatmaps of the OMC transmission, assuming (i) 0 contrast defect light in the carrier TEM00 mode, (ii) PRG=45 and (iii) 1 W incident on the back of PRM. The color bar limits are preserved for both plots, so the "dark" areas of the plot, which indicate candidate operating points, are darker in the left-hand plot. Obviously, when there is more f1 power incident on the OMC, more of it is transmitted. But my point is that the "best operating point(s)" in both plots are different.

Why is this model refinement necessary? In the aLIGO OMC design, an assumption was made that the light level of the f1 sideband is 1/1000th that of the f2 sideband in the interferometer AS beam. This is justified as the RC lengths are chosen such that the f2 sideband is critically coupled to the AS port, but the f1 is not (it is not quite anti-resonant either). For the BHD application, this assumption is no longer true, as long as the LO beam is picked off after the RF sidebands are applied. There will be significant f1 content as well, and so the mode content of the f1 field is critical in determining the OMC filtering performance.

There were a bunch of useless / degenerate channels added - e.g. whitening gains which are alreay burt-snapshot. Maybe there are many more useless channels being trended, but no need to add more.

Copy-pasting wasn't done correctly - the first 4 added channels were duplicates. There are in fact 5 LO power mons, one for each of the frequencies 11, 33, 55, 110 and 165 MHz. 

I cleaned up. Basically only the detect-mon channels, and the ALS channels, are new in the setup now. I will review if any extra channels are required later. While checking that the daqd is happy, I noticed c1lsc FEs are in their stuck state, see Attachment #1. I guess a cable was bumped when the strain relief operation was underway. I'm not attempting a remote resuscitation.

Chub wanted to get the correct part number for the replacement UPS batteries which necessitated opening up the UPS. To be cautious, all the workstations were shutdown at ~9:30am while the unit is pulled out and inspected. While looking at the UPS, we found that the insulation on the main power cord is damaged at both ends. Chub will post photos.

However, despite these precautions, rossa reports some error on boot up (not the same xdisp junk that happened before). pianosa and donatella came back up just fine. It is remotely accessible (ssh-able) though so maybe we can recover it...

I installed 6 of these in 1Y2. Three were for PD INTF #1-3, and I used three more for the AS110, REFL11, and REFL33 Demod board FEs, where the strain-reflief of the DC power cables to the Eurocrate was becoming a problem. So now there are only 4 units available as spares.

Once the strain-relieving of the Dsub cabling to 1Y3 is done, we can move ahead with testing. I'd like to put this to bed this week if possible.

1. Jordan (new Engineer) and Chub neatened out the cabling at 1Y2/1Y3 today. After their work, I plugged in all the Dsubs to the rear Eurocrate DB37->DIN96 adaptors. Jordan nicely fixed up the labels on the cable with some extra sellotape for a more durable label.
2. As part of the war on cross-connects, Chub removed some cables that were piping BIO signals from the fast CDS system to the whitening boards.
   • There is a SCSI to DB37 custom ribbon cable going from the BIO card in the expansion chassis to a 1U chassis box at the very bottom of 1Y2.
   • This 1U box, with DCC number D080478 (but no schematic exists on the DCC or any of the usual secret hidey-holes) breaks out the 32 BIO channels to 16+16.
   • Each set of 16 channels was supposed to get broken out to 8+8 via some cross connects and then goto the whitening boards. This is the part that got distrubed.
   • Koji and I discussed options - if Chub cannot resotre this easily, we will make a D37--> 4*D15 breakout board, and pipe the signals via the backplane P2 connectors. This will mean ~10 more days before the LSC system can be tested.
   • Some cabling to the TT DACs and an ADC were also disturbed, but these are easily restored.
3. From the hardware standpoint, some cross-struts for strain relief on the back of 1Y2 need to be installed --> Chub.

Let's not worry about C1LSC until the c1iscaux upgrade is done.

For some reason, the daqd_fw service was dead on FB. This meant that no frames were being written since Aug 23, which probably coincides with when the c1lsc frontend crashed. Sad 😢 😭 🙁 . Simply restarting the fw service does not work, it crashes again after ~20 seconds. The problem may have to do with the indeterminate state of the c1lsc expansion chassis. However, this is not something that can immediately be fixed, as Chub is still working on the wiring there. So in summary, no frame data will be available until we fix this problem (it is still unclear what exactly the problem is). Team WFS can still work by getting online data.

Why were the CDS overview DC indicators not red???

Unrelated to this work: I had to key the c1psl crate to get the IMC autolocker functioning again. However, I found that the key 🔑 turns continuously - as opposed to having two well defined states, ON and OFF. Be careful while handling this.

Came across this while looking up the BIO situation at 1Y2. For reference, the fix Koji mentions can be seen in the attached screenshot (one example, the other BIO cards also have a similar fix). The 16th bit of the BIO is grounded, and some bit-shifting magic is used to implement the desired output.

Summary:

1. Frames seem to be written again.Slowly but surely, we are converging to an operable state...
2. No frames are available for the period 23 Aug to 17 September 2019
3. Don't edit the C0EDCU.ini file unless you know what you're doing.
4. If you make some changes to the RT system/channel list or reboot FEs, please make sure all the dependent systems are back up and running. There shouldn't be a need to willy-nilly reboot things.
5. Tomorrow I will prepare the map of BIO channels for Chub to restore the whitening switching capability. Then we can try locking some cavities.

Details:

1. First, I checked to make sure the /frames partition wasn't full. It wasn't.
2. Next, I looked into the C0EDCU.ini file.
   • The last date for which frames are available, 23 Aug, coincided with the date when this file was modified.
   • It is a known problem that the daqd_fw service can crash if one of the channels in this file is reporting an unusually large number.
   • Several channels were added to this file - in the end, only 9 new ones were required, 5x "DetectMon" channels for each of the RF demodulation frequencies, and 4 for the new ALS LO and RF signal power monitor channels.
   • It is highly likely that one of the other channels was what caused the daqd_fw service to crash - though I can't say for sure, because I did not exhaustively search through the ~100 un-necessary channels that were in this file to see what values they were reporting.
3. For good measure, I ran the reboot script, and brought the c1lsc models back online.
   • I want to do the mapping of the BIO channels to the pin-out of the BIO adaptor unit, which requires c1lsc to run.
   • Reboot script ran smoothly.
4. Then I went into fb and restarted all the daqd services. This time, they all seem to run without crashing, at least in the ~10min window it took me to type out this elog.

Unrelated to this work: c1auxey was keyed.

INCORRECT INFO IN THIS ELOG HAS BEEN REMOVED. SEE THIS ELOG FOR THE UPDATED INFO.

Summary:

With the help of a tester board, I verified the mapping between fast BIO DB37 pins, and pins on the IDC50 connectors that are to be broken out to the whitening boards. I will enlist Chub to implement this mapping in hardware later today.

Details:

1. The LSC PD demodulated signals are optionally whitened before acquisition by our RTCDS ADCs.
2. The switching of each channel's whitening (enable/disable) is done by a single bit from the fast (a.k.a. RTCDS) system's BIO cards.
3. The whitening boards live inside Eurocrates.
4. The aforementioned switching signal needs to be sent to the whitening boards via the backplane of the Eurocrate.
5. This requires some cross-connect based cable splicing between the BIO card outputs and the P2 connectors of the whitening boards in the Eurocrates.
6. This connection was accidentally destroyed during the war on cross-connects at 1Y2. I couldn't find a wiring diagram anywhere.
7. Today, with the help of a tester board, I verified the mapping by toggling the appropriate channels on the MEDM screen, and verifying the correct LEDs on the tester board were toggled.
8. Map will be posted here after the meeting... Also now on the wiki.

Update 2019 Sep 19 1730: The pin numbers of the IDC 50 connector are all off by 1. i.e. 3-->4 and so on. I will fix this shortly. The problem was because of me looking at the pinout for the wrong gender of IDC50 connectors.

Summary:

The custom ribbon cables piping the coil driver board outputs to the eLIGO (?) TTs (a.k.a. TT1 and TT2) are damaged. They need to be re-made. I can't find any pin-mapping for them.

Details:

While waiting for the LSC photodiode whitening switching cross-connect work to be done, I thought I'd re-align the IFO a bit. However, I was unable to find any beam making it to the REFL/AS ports despite some TT steering. I remembered that Chub had undone the TT connections at 1Y2 as well, and thought I'd check the cabling to make sure all was in order. On going to the rack, however, I found that these connections were damaged at the coil-driver end (see Attachment #1), presumably during the cable extraction. These need to be re-made...😔 

While debugging this problem, c1lsc models crashed. I ran the reboot script this morning to bring the models back. There was a 0x4000 error on the DC indicators for the c1lsc models (mx_stream error which couldn't be fixed by restarting the mx service) the first time I ran the script so I did it again, now the indicator lights are in their nominal state.

False alarm - the mistake was mine. Looking at the schematic diagram, the AI/Dewhite board, D000316, accepts the inputs from the DAC on the P2 connector. While restoring the connections at 1Y2, I had plugged the outputs of the DAC interface board into the P1 connectors of the AI boards. Having rectified this problem, I am now able to move the beam on the AS camera in both PIT and YAW using TT1 or TT2. So to zero-th order, this subsystem appears to work. A more in-depth analysis of the angular stability of the TTs can only be done once we re-align the arms and lock some cavities.

[KA, GV]

Summary:

1. New cross connect system for splicing the fast BIO signals for whitening switching to the P2 connectors was installed and tested at 1Y2.
2. It passed a first round of tests. 😁 
3. As of now, I believe all the necessary electrical connections have been made at 1Y2/1Y3, and we are ready for testing the c1iscaux system.

Details:

1. We did some testing in the office area, and found several wiring mistakes. These were all rectified. Attachment #1 is an accurate reflection of the implemented wiring scheme (softcopy in the 40m google sheets area). Be aware that the IDC 50 pin connector pin-out is tricky, and you have to be aware of the difference between male/female connector when looking for this pin-out on the internet.
2. In order to facilitate further testing, we re-routed the ADC0 SCSI cable that was unplugged on the overhead cable tray, and plugged it back into the c1lsc expansion chassis. This action necessitated a reboot of the vertex FEs, but everything came back alright.
3. Did some general neatenign and strain relieving. Removed a few existing cross-connects to make space for our new terminal blocks.
4. Attachment #2 shows the layout of the terminal blocks. Note the unusual (vertical) order of the orange terminal blocks.
5. The final integrated CDS test done was the following:
   • Set whitening gain for channel under test to 45dB, so that the dark noise level is boosted to a measurable level such that a change can be seen with the whitening enabled/disabled.
   • Compare the ASD of the signal between 30-100 Hz with the whitening engaged/disengaged.
   • Example result shown in Attachment #3.I believe the whitening is 15:150 (z:p) 

Tomorrow:

1. Recover POX/POY locking,.
2. ...

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.

I was hoping that the dark / electronics noise level on the LSC photodiodes would be sufficient for me to test the whitening gain switching on the iLIGO Pentek whitening boards. However, this does not seem to be the case. I guess to be thorough, we have to do this kind of test. It's a bit annoying to have to undo and redo the SMA connections, but I can't think of any obvious easier way to test this functionality. More annoyingly, the sensing matrix infrastructure necessary to do the kind of test described in the linked elog is only available for some PDs. I don't really want to modify the c1cal model and go through another mass reboot cycle.

While I was at it, I was also thinking about the tests we want to do. Here is a quick first pass - if you can think of other tests we ought to do, please add them to the list!

1. Whitening gain switching on the D990694 boards.
   • Need to inject some signal to do this in a clean way. 
   • With some signal injected, we need to switch the whitening gain through the 15 available levels and confirm that we see a +3dB gain for each step.
   • An example script to do this operation and make a diagnostic plot is at /cvs/cds/caltech/target/c1iscaux/testScripts/testWhtGain.py.
2. AA enable/disable on the D000076 boards. Do we really need this functionality? Can't we permanently enable the AA, as was done for WF2?
   • Need to measure the TF with an SR785 or drive a high-freq line and confirm that the aliased peak height is attenuated as expected in DTT.
3. LO Det Mon channel check
   • Zeroth level test can be done by turning Marconi OFF/ON, and confirming we see a change in the corresponding monitor channel, like I did here.
   • A more rigorous diagnostic would require these channels to be calibrated to dBm of LO power.
4. PD INTF board check
   • Zeroth level check can be done by shining light onto PDs one at a time and confirming that the correct channel shows a response.
   • A more rigorous diagnostic would require these channels to be calibrated to mW of optical power incident on the PDs.
5. QPD INTF board check
   • This is the IP-POS QPD readback.
   • Need to confirm the quadrant mapping, and that Pitch is really Pitch, Yaw is really Yaw.
   • A more rigorous diagnostic would require these channels to be calibrated to mm of position shift.
6. CM Board
   • Need to determine what tests need to be done.
   • 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.
7. ALS INTF board
   • This board isn't actually connected yet, pending strain relief of cabling at 1Y2.
   • The calibration of the board output volts to dBm is known, so we can easily check this functionality.

I tried to lock the Y arm cavity length to the PSL frequency using POY11_I as an error signal. Even though I think the cavity alignment is good (I see TRY flashes ~0.8), I am unable to achieve a lock. I checked the signal conditioning, and as far as I can tell, all the settings are correct, but there may be some settings that have not been re-assigned correct values. The other possibility is that something is not quite right with the new c1iscaux. The PDH error signal and arm cavity flashes all seem good though (see Attachment #1), so I'm not sure what obvious thing I'm missing.

To be continued...

I reset the normalization for both arms on Jul 9 2019.

Summary:

There is no visible PDH error signal on the POX11 channels. As a result, I am unable to lock the XARM length to the laser frequency. See Attachment #1 - the Y arm length is locked to the PSL frequency, and control is disabled for the XARM servo.

Details:

Now that several of the c1iscaux functionality tests have been completed, I wanted to push ahead with some locking. However, I was foiled at this early stage, for reasons as yet unknown. One possibility is that the

• I am able to see TRX cavity flashes >0.8, which suggest to me that the cavity is well aligned.
• Moreover, I am able to lock some (admittedly high TEM order) mode of the green laser, which further supports the above hypothesis.
• However, there are no visible PDH-like features in the POX11_I or POX11_Q channels.
• I checked that the cables from the output of the POX11 demod board are in fact going to the correct channels on WF1 (#5 and #6 respectively), and that the whitening gain for this channel is set to the nominal +30 dB.
• Next, I went to the POX table and looked for the POX IR beam. I couldn't see anything, but this beam is expected to be weak (of the order of 1 W * T_PRM * R_AR_ITM ~ 30 uW), which is probably not so easily visible.

Next steps:

• Look for the POX beam with an IR viewer.
• Confirm that everything is order on the LSC Demod board for POX 11 - maybe the LO isn't connected (somehow)?

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.

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.

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. 

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.

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.

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).

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.

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.