In order to fix ELOG search, I have started running ELOG v2.9.2 on Nodus.

Sadly, due to changes in the software, we can no longer use one global write password. Instead, we must now operate with registered users.

Based on recent elog users, I'll be creating user accounts with the following names, using the same old ELOG write password. (These will be valid across all logbooks)

• ericq
• rana
• koji
• diego
• jenne
• manasa
• Steve
• Kate
• Zach
• Evan
• Aidan
• Chris
• Dmass
• nicolas
• Gabriele
• xiaoyue

All of these users will be "Admins" as well, meaning they can add new users and change settings, using the "Config" link.

Let me know if I neglected to add someone, and sorry for the inconvenience.

RXA: What Eric means to say, is that "upgrading" from Solaris to Linux broke the search and made us get a new elog software that;s worse than what we had.

Since we will not be doing any major locking, I am taking this chance to move things on the X end table and install the fiber coupler.

The first steering mirror shown in the earlier elog will be a Y1 (HR mirror) and the second one will be a beam sampler (similar to the one installed at the Y endtable for the fiber setup). 

Configuration:

Doubler --> Y1 ---> Lens (f=12.5cm) ---> Beam sampler --->Fiber coupler

The fiber coupler mount will be installed in the green region to the right of the TRX camera. 

This work will involve moving around the TRX camera and the optic that brings the trans image on it.

Let me know if this work should not be done tomorrow morning for any reason.

Today we were looking at the MC TFs and pulled out the FSS box to measure it. We took photos and removed a capacitor with only one leg.

Still, we were unable to see the weird, flat TF from 0.1-1 MHz and the bump around 1 MHz. Its not in the FSS box or the IMC servo card. So we looked around for a rogue Pomona box and found one sneakily located between the IMC and FSS box, underneath some cables next to the Thorlabs HV driver for the NPRO.

It was meant to be a 14k:140k lead filter (with a high frequency gain of unity) to give us more phase margin (see elog 4366; its been there for 3.5 years).

From the comparison below, you can see what the effect of the filter was. Neither the red nor purple TFs are what we want, but at least we've tracked down where the bump comes from. Now we have to figure out why and what to do about it.

* all of the stuff above ~1-2 MHz seems to be some kind of pickup stuff.

** notice how the elog is able to make thumbnails of PDFs now that its not Solaris!

Some TFs of the TTFSS box

I was working around the X endtable and PSL table today.

1. Y1 mirror, beam sampler and the fiber coupler have been installed.

2. Removed TRX camera temporarily. The camera will be put back on the table once we have the filter for 532nm that can go with it.

3. Removed an old fiber mount that was not being used from the table. 

4. Lowered the current for X end NPRO while working and put it back up at 2A before closing.

5. The fibers running from the X end to the PSL table are connected at an FC/APC connector on the PSL table. 

6. Found the HEPA left on high (probably from yesterday's work around the PSL table). I have brought it back down and left it that way.

I have not installed the coupling lens as yet owing to the space restrictions - not enough space for footprint of the lens. I have to revisit the telescope design again.

 Steve and I switched chiara over to the UPS we bought for it, after ensuring the vacuum system was in a safe state. Everything went without a hitch. 

Also, Diego and I have been working on getting some of the new computers up and running. Zita (the striptool projecting machine) has been replaced. One think pad laptop is missing an HD and battery, but the other one is fine. Diego has been working on a dell laptop, too. I was having problems editing the MAC address rules on the martian wifi router, but the working thinkpad's MAC was already listed. 

 Turns out that, as the martian wifi router is quite old, it doesn't like Chrome; using Firefox worked like a charm and now also giada (the Dell laptop) is on 40MARS.

 EricQ and Steve,

Steve preset the vacuum for safe-reboot mode with C1vac1 and C1vac2 running normal: closed valves as shown, stopped Maglev & disconnected valves V1 plus valves with moving labels.

(The position indicator of the valves changes to " moving " when its cable disconnected )

Eric shut down Chiara, installed APC's UPS Pro 1000 and restarted it.

All went well. Nothing unexpected happened. So we can conclude that the vacuum system with running C1vac1 and C1vac2 is not effected by Chiara's losing AC power.

 TP3 dry pump  replaced at 540 mT as TP3 50K_rpm 0.3A with annulos load. It's top seal life time was 11,252 hrs

 So, despite having registered users, it turns out that the "Author" field is still open for editing when making posts. I.e. we don't really need to make new accounts for everyone. 

Thus, I've made a user named "elog" with the old write password that can write to all ELOGs. 

(Also, I've added a user called "jamie")

In the plot it is shown the behaviour of the PSL-FSS_SLOWDC signal during the last week; the blue rectangle marks an approximate estimate of the time when the scripts were moved to megatron. Apart from the bad things that happened on Friday during the big crash, and the work ongoing since yesterday, it seems that something is not working well. The scripts on megatron are actually running, but I'll try and have a look at it.

Today we decided to continue to modify the TTFSS board.

The modified schematic can be found here: https://dcc.ligo.org/D1400426-v1 as part of the 40m electronics DCC Tree.

What we did

1) Modify input elliptic filter (L1, C3, C4, C5) to give zero and pole at 30 kHz and 300 kHz, respectively. L1 was replaced with a 1 kOhm resistor.  C3 was replaced with 5600 pF. C4 and C5 were removed. So the expected locations of the zero and pole were at 28.4 kHz and 256 kHz, respectively. This lead filter replaces the Pomona box, and does so without causing the terrible resonance around 1 MHz.

2) Removed the notch filters for the PC and fast path. This was done by removing L2, L3, and C52.

At this point we tested the MC locking and measured the transfer function. We successfully turned up the UGF to 170kHz and two super-boosts on.

3) Now a peak at 1.7MHz was visible and probably causing noise. We decided to revert L2 and adjusted C50 to tune the notch filter in the PC path to suppress this possible PC resonance. Again the TF was measured. We confirmed that the peak at 1.7MHz is at -7dB and not causing an oscillation. The suppression of the peak is limited by the Q of the notch. Since its in a weird feedback loop, we're not sure how to make it deeper at the moment.

4) The connection from the MC board output now goes in through the switchable Test1 input, rather than the fixed 'IN1'. The high frequency gain of this input is now ~4x higher than it was. I'm not sure that the AD829 in the MC board can drive such a small load (125 Ohms + the ~20 Ohms ON resistance of the MAX333A) very well, so perhaps we ought to up the output resistor to ~100-200 Ohms?

Also, we modified the MC Servo board: mainly changed the corner frequencies of the Super Boost stages and some random cleanup and photo taking. I lost the connecting cable from the CM to the AO input (unlabeled).

1.  The first two Super Boost stages were changed from 20k:1k to 10k:500 to give us back some phase margin and keep the same low freq gain. I don't really know what the gain requirement is for this servo here at the 40m. The poles and zeros were chosen for iLIGO so as to have the frequency noise be 10x less than the SRD at 7 kHz.
2. The third Super Boost (which we never used) was changed from 10k:500 to ~3k:150 (?) just in case we want a little more low freq gain.
3. There was some purple vestigial wiring on the back side of the board with a flying resistor; I think this was a way to put a DC offset in to the output of the board, but its not needed anymore so I removed it.

We run out of N2 for the vacuum system. The pressure peaked at 1.3 mTorr with MC locked. V1 did not closed because the N2 pressure sensor failed.

We are back to vac normal. I will be here tomorrow to check on things.

I reset the threshold to +6666 counts (the aligned MC transmission is ~16000 for the  TEM00 mode) so that it only turns on when we're in a good locked state.

 ITMX damping restored.

1. Control room is at +66 F. Brrrr.
2. Alignment of input beam into the IMC was wacky; locked on HOM.
3. Re-aligned beam into the PMC first.
4. Restarted mxstream for c1sus.
5. Power cycled Martian router; all laptops were lost. Now better.
6. Aligned launch beam from PSL to get onto the MCWFS better, MC is locking OK now. Moved MC SUS a little to get back to OSEM values from 6 days ago.
7. Fixed LOCK_MC screen quad displays to be cooler.
8. changed many of the ezcawrite calls in the mcup / mcdown to be 'caput -l' for more robustness. Still need ezcawrite for the binbary calls.
9.  I didn't touch the mirrors on the MC REFL path, so we can still use that as a reference once the temperature returns to normal; the PSL room temp is down to 20C from 22 C a couple days ago.
10. TRX values coming in to the LSC were frozen and the TRY_OUT16 was going to huge values even though camera flashes were reasonable. Tried restarting c1lsc model. No luck.
11. Also tried shutdown -r now on c1lsc. No luck. Probably needs a RFM boot.
12. Increased the FSS SLOW servo threshold to 9999 counts to avoid it running on some misaligned TEM01 mode locks. Increased the PID's I gain from 0.05 to 0.356 by tuning on some step responses as usual.
13. By midnight the control room temperature is back around 71 F.

Koji and I noticed that there was a comb* of peaks in the MC and FSS at harmonics of ~37 kHz. Today I saw that this shows up (at a much reduced level) even when the input to the MC board is disconnected.

It also shows up in the PMC. At nominal gains, there is just the 37 kHz peak. After tweaking up the phase shifter settings, I was able to get PMC servo to oscillate; it then makes a comb, but the actual oscillation fundamental is 1/3 of 37 kHz (some info on Jenne from elog 978 back in 2008).

Not sure what, if anything, we do about this. It is curious that the peak shows up in the MC with a different harmonic ratio than in the PMC. Any theories?

Anyway, after some screwing around with phase and amplitude of the RF modulation for the PMC from the phase shifter screen**, I think the gain is higher in the loop and it looks like the comb is gone from the MC spectrum.

Another clue I notice is that the PCDRIVE mad times often are coincident with DC shifts in the SLOWDC. Does this mean that its a flakiness with the laser? While watching the PCDRIVE output from the TTFSS interface board on a scope, I also looked at MIXER mon. It looks like many of the high noise events are associated with a broadband noise increase from ~50-140 kHz, rather than some specific lines. Don't know if this is characteristic of all of the noisy times though.

* this 'comb' had several peaks, but seem not be precise harmonics of each other: (f3 - 3*f1)/f3 ~ 0.1%

** I think we never optimized this after changing the ERA-5 this summer, so we'd better do it next.

 *** UPDATE: the second plot show the comparison between the new quiet and noisy states. Its just a broad bump.

I wonder if the variable bump around 100 kHz can be something about the NPRO and if the bump we see is the closed loop response due to the Noise Eater.

This plot (from the Mephisto manual) shows the effect of the NE on the RIN, but not the frequency noise. I assume its similar since the laser frequency noise above 10 kHz probably just comes from the pump diode noise.

I went out to the PSL and turned off the NE at ~4:53 PM local time today to see what happened. Although the overall PCDRIVE signal looks more ratty, there is no difference in the spectra of ON/OFF when the PCDRIVE is low. When its noisy, I see a tiny peak around 1 MHz with NE OFF. Turned it back on after a few hours.

All suspensions were tripped. Damping were restored. No obvious sign of damage. BS OSEM-UR may be sticking ?

 * PMC + MC were unlocked when I came in.

* I fiddled around some more with the mcup/down scripts to make locking snappier. The locking was breaking the PMC lock often, so I re-enabled the MC servo board output limiter during acquisition. It is disabled in the MC UP script.

* Re-measured the MC OLG. Still OK.

* Measured the PZT / EOM crossover (aka the FAST / PC crossover) using the connectors on Koji's summing box. With the FAST gain at 18 dB, the crossover is ~10 kHz. Looks way to shallow. Plots to follow.

* I finally discovered today that the PMC PZT stroke is what's causing the main mis-alignment of the beam going to the IMC. By relocking at a few positions, I could see that the IOO QPDs have steps when the PMC relocks. So the IO beam wander is NOT due to temperature effects on the optics mounts of the PSL table. I wonder if we have a large amount of length to angle coupling or if this is the same as the OMC PZTs ?

P.S. I found that someone is using a temporary bench power supply to power the summing box between the TTFSS and the Thorlabs HV driver...whoever did this has ~48 hours to hook up the power in the right way or else Koji is going to find out and lose it and then you have to wear the Mickey Mouse hat.

http://www.arroyoinstruments.com/files/Arroyo-UsingBenchPowerSupplies_11Apr.pdf

The first attachment shows the OLG measurements with 2 different values of the fast gain (our nominal FG is 18 dB). You can see that the higher gains produce some crossover instability; when tuning the gain we notice this as an increase in the PCDRIVE rms channel.

The second attachment shows the measurement of the 'crossover'. Its really just the direct measurement of the IN1 / IN2 from the FAST summing box, so its the crossover measurement where the OLG is high.

The BS was showing some excess motion. I think I've fixed it. Order of operations:

• The DC PIT bias from previous ASS runs was at ~500, I zeroed this and aligned the BS to be centered on its oplev QPD with DC alignment sliders
• I squished the gold box cables. This changed the alignment slightly, and brought the UR voltage back to a normal value. Excess motion still existed
• I found that the the C1:SUS-BS_LRSEN filter had HOLD OUTPUT enabled. I turned it off. All seems well. 

I'm not sure how this might have gotten switched on...

Rana noted last week that TRX's value was stuck, not getting to the lsc from iscex.  I tried restarting the individual models scx, lsc and even scy (since scy had an extra red rfm light), to no avail.  I then did sudo shutdown -r now on iscex, and when it came back, the problem was gone.  Also, I then did a diag reset which cleared all of the unusual red rfm lights.

Things seem fine now, ready to lock all the things.

 This afternoon, I labelled both ends of this cable, and reconnected it to the MC servo board. 

 [Jenne, Rana, EricQ, Diego]

Tonight we worked on getting the IFO back in a working status after the break, and then tried some locking.

• the MC is behaving better, it could stay in a stable condition for hours, even if a couple of times it lost lock, and one of them persisted for a little time;
• we managed to get to arm power of 20ish, before losing lock (this happened a couple of times);
• the main thing seems to be that we have only ~ 20 degrees of phase margin at UGF for DARM, which is evidently too little;
• one hypothesis is that DARM may change sign due to some weird length/angular interaction, and that this messes up the actuation causing the lockloss;
• one other possibility is that maybe, when arm power rises, there are some weird flashes that go back to the MC and then cause the locklosses, but this has to be verified;
• attached there is a plot of the last lockloss (and a zoom of it), which seems to point at DARM as the culprit;

We left the IFO uncontrolled and in a "flashy" state so that tomorrow we can look into the "back-flashing to the MC" hypothesis.

Two plots from tonight:

Lock loss. Based on the fact that it looked like the DARM servo was running away, Rana posited an effective sign flip in the DARM loop, perhaps due to a parasitic angular feedback mechanism.

While Jenne was probing the IFO at lower powers, we noticed a sudden jump in ASDC. Found the GPS time and fed it to the lockloss plotter. Seems fairly evident that some sudden ETMX motion was to blame. (~2urad kick in yaw)

One of the things that we had talked about last night was the totally tiny amount of phase margin that we have in the CARM and DARM loops.  DARM seemed to be the most obnoxious loop last night, so I focused on that today, although the CARM and DARM loops are pretty much identical.

(Q tells me via email that the phase budget has the same ~14 degree discrepancy between what we expect and what we measure as his estimate last night.  However, the Caltech network issues prevented his posting an elog.)

So, we definitely need to figure out where this 14 deg is going, but for now, I wanted to see if I could recover a couple of extra degrees just by modifying the filters.

The original filters do seem to eat a lot of phase:

The short version of the story is that I didn't leave the filters changed at all.  I reverted back to the last version of the filter file from Monday night, so currently everything is as it was.

I tried increasing the Q of the zeros on the cyan and brown filters, which would sacrifice some gain at ~20 Hz, but hopefully win us 10+ degrees of phase.  This gave me a dip of about a factor of 2 between the new and old filters (all servo filters combined added up to this factor of 2 in magnitude) between ~20Hz - 70Hz. 

When we were locked using DARM for just the Yarm (for the UGF servo commissioning), I took a spectra of the error signal (which was POY) as a reference, then loaded in my new filters.  For the most part, the spectra didn't change (which is good, since the magnitude of the filter didn't change much.).  The spectra was bigger though between 50-70Hz, in kind of a sharp bandpass-looking shape that I wasn't expecting.    I don't know exactly why that's happening.

Anyhow, we tried the new filters once or twice with the full IFO, but kept losing lock.  Since I clearly haven't put in enough thought yet for these (particularly, how much suppression do we really need? what are our requirements???), I reverted back to the filter file from last night.  We continued locking, and checking out the new UGF servo that Diego is elogging about.

 [Jenne, Diego]

Today we began implementing the UGF Servos. Things we did:

• we updated the LSC model with both DARM and CARM servos, and moved them from after the control system to before it, at the level of the error signal;
• we updated the medm screens; new buttons are located in the main LSC screen;
• we started commissioning the DARM servo, at first using DARM for the lock of the single Y arm, then we moved on to the PRFPMI lock and the usual transition from ALS to Transmission;
• although we had several lock losses during the night, we managed to tweak the parameters of the DARM UGF servo (phases, excitation, gains), which now seems to work sufficiently fine;
• the filters added to the I and Q filter banks are a single lowpass in each, while the only filter in the main servio is a standard integrator;
• we don't have a step response at the moment, but we can say that the settling time of the servo is in the range of 10 seconds;
• we updated the ALSdown.py and ALSwatch.py scripts with a call to a new UGFdown.py script; this script, located in the scripts/PRFPMI folder, takes care of disabling the servos and putting the excitation to zero in case of a lock loss; re-enablement of such things must be done manually;

[Jenne, Diego, Rana]

This is a note about work done last night. 

We were starting to lock, and saw glitches in the Thorlabs TRY PD about once every 1/60th of a second.  It is not a sine wave, so it is not 60Hz line noise directly.  It looks like this:

Rana pointed out that this looks like it could be from a power supply that is converting AC to DC. 

We went down to the Yend, and noticed some weird symptoms.  So far, we do not know where the noise is coming from.  Rather, we are just using the QPD for locking.

* The noise comes and goes, particularly if someone is moving around at the end station.

* Moving the Thorlabs power supply farther from the HeNe power supply didn't do much.  Turning off and disconnecting the HeNe supply didn't make the noise go away, so we conclude that it is not the HeNe's fault.

* We suspected the loops of excess cable that were sitting on top of iscey, but moving the coils away from the computer did not make the noise go away.

* We removed a few disconnected BNC cables that were near or touching the end table, but that didn't fix things.

* We disconnected the PD's signal cable and pulled it out of the table enclosure, and then put it back.  Noise was gone when cable was disconnected (good), but it was back after plugging the cable back in.

* The noise still comes and goes, but we don't have to use the Thorlabs PD for locking, so we leave it for another day.

RXA: also moved the Thorlabs power supply to a different power strip and tried putting it closer/farther to the Uniblitz shutter controller. Another suspect is that its some PWM type noise from the doubler crystal temperature driver. Need to try turning off the heater and the Raspberry PI to if it effects the noise.

As a warm-up after the holidays, before the real locking began, I installed 1064nm bandpass filters in front of the transmission QPDs to eliminate the stray green light that is there.

The Yend had threads epoxied to it, so that end should be good.  Steve is going to repeat that for the Xend QPD at some point.  Right now, the filter is just on a lens mount about 2cm away from the PD box aperture, since that's as close as I could get it.

Also, while I was at the Xend, I noticed that the transmission camera is gone.  I assume that it was in the way of Manasa's fiber work, and that it'll get put back somehow, sometime.  She elogged that she had removed it, but I mistakenly thought that it was already replaced.  We don't use that camera much, so I'm not worried.

As Jenne mentioned, I created a model of the DARM OLG to see why we have so little phase margin. However, it turns out I can explain the phase after all.

Chris sent me his work for the aLIGO DARM phase budget, which I adapted for our situation. Here's a stacked-area plot that shows the contributions of various filters and delays on our phase margin, and a real measurement from a few days ago . 

This isn't so great! Informed by Chris's model, the digital delays look like: (Here I'm only listing pure delays, not phase lags from filters)

• 64k cycle (End IOP)
• 16k cycle (End isce[x/y])
• 16k cycle x 2 (end to LSC through RFM) [See ELOG 10811]
• 16k cycle (LSC)
• 16k cycle (LSC to SUS through dolphin) [See ELOG 9881]
• 16k cycle (SUS)
• 16k cycle x2 (SUS to end through RFM)
• 16k cycle (End isce[x/y])
• 64k cycle (SUS IOP)
• DAC zero order hold

This adds up to about 570usec, 20.5 degrees at 100Hz, largely due to the sheer number of computer hops the transmission loops involve. 

As a check, I divided the measured OLG by my model OLG, to see if there is any shape to the residual, that my model doesn't explain. It looks like it fits pretty well. Plot:

So, unless we undertake a bunch of computer work, we can only improve our transmission loops through our control filter design. 

Everything I used to generate these plots is attached. 

C1:SUS-ETMX_QPD is removed and internal SM1 thread adapter epoxied into position as it is at the Y end

This adapter will take FL1064-10 line filter holder

Line filter is attached and qpd needs alignment.

I was working around the PSL table this morning.

1. I have fibers running from the Y end and the PSL table to the Optical Fiber Module for Frequency Offset Locking. 

Y+PSL out power is ~200uW. From the transimpedance and responsivity specs of the RFPD (ThorLabs FPD310), we expect ~100uW or -10dBm RF power. I have not hooked up the RF output to a spectrum analyser to confirm this as yet.

2. Also, Steve and I ran RF cables (LMR-195A) from the PSL table to the FC module on the IOO rack.

I think the dolphin and RFM transit times are double-counted in this budget. As I understand it, all IPC transit times are already built in to the cycle time of the sending model. That is, the sending model is required to finish its computational work a little bit early, so there's time left to transmit data to the receivers before the start of the next cycle. Otherwise you get IPC errors. (This is why the LSC models at the sites can't use the last ~20 usec of their cycle without triggering IPC errors. They have to allow that much time for the RFM to get their control signals down the arms to the end stations.)

For instance, the delay measurement in elog 9881 (c1als to c1lsc via dolphin) shows only the c1lsc model's own 61 usec delay. If the dolphin transfer really took an additional cycle, you would expect 122 usec.

And in elog 10811 (c1scx to c1rfm to c1ass), the delay is 122 usec, not because the RFM itself adds delay, but because an extra model is traversed.

Bottom line: there may still be some DARM phase unaccounted for. And it would definitely help to bypass the c1rfm model, as suggested in 9881.

Now that both end transmission QPDs have the line filters, I aligned them.

I locked and aligned the IR using the ASS, then went to each end table and put the beam in the center of the QPD.

The SUS Drift Monitor screen has been updated:

• removed the old dead channels from the MEDM screen;
• updated the SUS models with new 'mute' channels where the expected values should be put;
• updated the MEDM screen with the new channels
• values are still 0 since I don't know what these expected values should be, at this time

Missing filter found. Labeled drawer OPHIR in control room - behind soldering station-  with spare battery and filter

I have added another block to the LSC screen (and made the corresponding sub-screen) to expose the analog settings for the DC photodiodes. 

Note that we have 2 open channels there, which are still called something like "PD2" and "PD3" from olden times.

If we ever chose to use those, we will probably want to change their names, in /cvs/cds/caltech/target/c1iscaux2/LSC_aux2.db and /cvs/cds/caltech/target/c1iscaux/LSC_aux.db

I have attached a photo of the ETMX table. The path of the 1064nm light rejected after the doubler and the green light are indicated for reference.

The fiber mount can only be mounted in the green space shown in the picture.

Calculating lens solutions for coupling the 1064nm light rejected after the doubler into the fiber, a lens of f=12.5cm should be placed at z=15.31cm (measured from the waist in the doubler crystal) gives the best ~80% coupling. This falls in the blue region where there is not enough space to mount a lens. 

The region marked in orange has enough room for a lens; but the lens solutions give a coupling <10% which means there will be light scattering everywhere.

I am open to any suggestions on how to go about this.

 We never, ever want to use ezcaservo to do this. IN fact, we twice have already deleted scripts where people have implemented these (sometimes) unstable servos. Also, since this change had never been committed to the SVN, I just deleted it and updated from the SVN to get back the script that doesn't use any servos.

I'm going to periodically delete locking scripts that are not committed to the SVN since anyone who is too lazy to use the SVN probably can't write code worth using.

I added UGF servos for the DRMI DoFs, after creating a library block for the servos. I also deleted the FMs before the phase rotation, since we can just do it afterwards in other existing FMs. I've only added the MICH and PRCL buttons to the LSC screen because in the end, I feel like a dropdown is better, but I just wanted to get it running quickly tonight. The LSC model and the UGF block have been committed to the svn. 

We were able to use the PRCL UGF servo successfully, as Jenne was exploring MICH offset space. 

[Jenne, EricQ, Rana]

Tonight we started prepping for an attempt at variable finesse locking. 

The idea is to put in a MICH offset and hold the lock with ASDC/POPDC (so that the offset can be larger than if we were just using RF signals).  This reduces the PRC buildup, which reduces / removes the double cavity resonance problems while reducing the CARM offset. 

• So.  Today, I pulled out the POP22 razor blade so that we can use the Thorlabs PD as POPDC, without the yaw coupling.  Our other option is to use the POP QPD SUM, but that would require some model changes and more importantly it's not a particularly low noise readout path.

• We re-set the analog whitening gains for ASDC and POPDC.
  • For ASDC, we want the half-fringe in the PRMI case to be not saturating.  We chose 18dB (it had been the default 0dB).
  • For POPDC, Rana and I saw that it was saturating all the time with the 33dB that it had when the carrier became resonant.  This was never really a problem in the past, but if we use it for normalization, we get glitches that knock us out of lock every time POPDC saturated.  So, now POPDC is at 0dB.  It still occasionally saturates when the PRMI is flashing, but we can't get lower than 0dB without going and putting an ND filter on the PD.
• We turned off the analog whitening filters and digital unwhitening for both ASDC and POPDC.  We can consider turning them back on later after we have acquired lock if we need them, but we need them off for acquisition.
• Locked MICH with ASDC/POPDC.  Good.  Stays locked even if PRM is flashing.
• Locked PRMI with PRCL on REFL33I and MICH on ASDC/POPDC.
• Locked arms, held off resonance with ALS, lock MICH with ASDC/POPDC. 
• Failed to lock PRMI with arms held off resonance, using the new scheme (no transition, trying to directly acquire)
• Locked PRMI on REFL33 I&Q with the arms held off resonance, and tried to transition MICH over to ASDC/POPDC, failed.
• Confusion about the relative phase between REFL33Q and ASDC.  It looks like it is ~45deg at 100 Hz, or ~90 deg at 375 Hz.  Why isn't it 0 or 180?
• Went back to PRMI-only, tried to map out fringe by changing MICH offset (tried while MICH was on both REFL33 and ASDC/POPDC).  Not really sure where we are on the fringe.

MICH locked on ASDC normalized by POPDC, PRM and ETMs (and SRM) all misaligned.

MICH offset of -20

MICH input = -0.04*ASDC normalized by 0.1*POPDC.

MICH gain = +5

MICH always triggered on (no triggering for DoF), but FM8 (CLP400) triggered to come on after lock (didn't write down the values).

PRMI locked with MICH on ASDC normalized by POPDC, PRCL on REFL33I, ETMs and SRM misaligned.

MICH offset of -10

MICH input = -0.04*ASDC normalized by 0.1*POPDC.

PRCL input = 1*REFL33I

MICH gain = +5

PRCL gain = -0.4 (factor ten times the regular value)

MICH always on, PRCL triggered on POP22.  MICH FM8 and PRCL FM1,2,6,9 triggered on.

Gives POPDC of about 20 counts, POP22 of about 12 counts, ASDC of about 500 counts.

Arms held at 3nm, MICH locked on ASDC/POPDC, PRM and SRM misaligned.

MICH offset of -10

MICH input = -0.04*ASDC normalized by 0.1*POPDC.

MICH gain = +5

MICH always on, PRCL triggered on POP22.  MICH FM8 and PRCL FM1,2,6,9 triggered on.

Arms held at 3nm, attempt at PRMI lock with MICH on ASDC/POPDC.

Failed.  Tried mostly same MICH gains as arms+mich, and PRCL at 10* normal gain.

Arms held at 3nm, PRMI locked with REFL 33 I&Q, attempt at transition to MICH on ASDC/POPDC.

Failed.  At first, I was putting in the TF line at ~375Hz, but we looked at the full transfer function between 100Hz and 1kHz, and there was a weird dip near 300Hz from PRCL-MICH loop coupling.  Here we were seeing that the phase between REFL33Q and ASDC was ~90 degrees.  What?

Tried putting the TF line at ~100 Hz (since MICH UGF is in the few tens of Hz anyway, so 100 is still above that), but still get weird relative phase.  Here it seems to be about 45 degrees when I inject a single line, although it didn't seem like a weird phase when we did the full swept sine earlier.  Maybe I was just not doing something right at that point??

Anyhow, no matter what values I tried to put into the input matrix (starting with REFL33I&Q, trying to get MICH to ASDC/POPDC), I kept losing lock.  This included trying to ramp up the MICH offset simultaneously with the matrix changing, which was meant to help with the PRCL gain change.  Q has since given us MICH and PRCL UGF servos.

Tomorrow:

• Why is there some weirdo phase between REFL33Q and ASDC at 100Hz?  Was I just being a spaz?
• With PRMI-only, figure out how to transition from REFL33 I&Q over to MICH on ASDC/POPDC.
• Then hold the arms off resonance, and do the same transition.  (First make sure we're at a good place on the fringe)
• Lower the CARM and DARM offsets, transition them to RF, engage CARM AO path.
• Reduce MICH offset, transition to RF.
• Celebrate (maybe).

I've installed the very fresh ELOG 3.0, for nothing else than the new built in text editor which has a LATEX capable equation editor built right in. 

Check out this sweet limerick: 

The restored offset script used old tdsavg calls that our workstations can't do, and didn't include things like the transmon QPDs. I've written yet another offset script that uses cdsutils averaging to do the thing, and committed to the svn. 

The MEDM screen has been updated: the new buttons, one for each optic, call the scripts/general/SUS_DRIFTMON_update_reference.py script, which measures (and averages) for 30s the current values of the POS/PIT/YAW drifts, and then sets the average as the new reference value.

100 and 10 days trends of ETMX and ETMY_SUSPIT.  One can see clearly the earthquaks of Dec.30 and 31 on the 10 day plot. You can not see the two shakes  M3.0 & M4.3 of Jan. 3 

The long term plot looks OK , but   the 10 day plot show the problem of ETMX as it was shaken 4 times.

I worked around the PSL table today.

The Y+PSL output from the optical fiber module for FOL was fed to the input of the Thorlabs FPD310. 
200uW of incident light on the RFPD gave an RF signal of -70dBm as measured on a spectrum analyzer.

I swapped the beam splitter along the PSL path so that the incident power on the RFPD is ~1.5mW (Maximum incident power that the PD can tolerate is ~2mW).
This RF signal generated was - 43dBm which is still small for the input to the frequency counter module.

I checked this with a function generator and found that the frequency counter requires around -25 to -30 dBm at the input.

I plan to use the Minicircuits ZFL-1000ln that is on the IOO rack but not being used (This was used for green beatnote amplification but is not required/used anymore) to amplify the RF signal to the frequency counter.
If anyone has any objections to using this amplifier for the frequency counter, let me know.

Before starting to move things around the PSL table, I measured the ALS out of loop noise for reference. The noise spectrum showed excess noise around 30Hz.  The traces in blue were taken before I went in and those in red were taken after my work.

I also looked at the power spectrum of LSC-TRY_OUT to see if the noise is from the IR lock itself and there was nothing suspicious with it. 

Since the green transmission was 50% lower than the usual, I touched the steering mirrors for green at the Y end table to get a better transmission and beat signal. The noise still hasn't disappeared. 

I am not sure if this could be from our neigbors who have been running rock experiments since morning. We should check back to see if this noise disappears once they shut down.

DTT xml files are available in directory /users/manasa/data/150109/

A few hours ago I tweaked up the alignment to the PMC.  It was really bad in pitch, and the transmission was down to about 0.711.