800e-6 / 0.225^2 = 0.016

=> 1.6%/W

I thought Kiwamu had roughtly 2%/W.

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

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

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

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

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

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

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

Pasadena reported the Sunday night event as a power transient caused by the trip of a power transmission line. This affected the entire city. Once the loss was detected, the system automatically switches to an alternate source. It was about one second for the system to recover.

2W Innolight, both Lightwaves at the ends, PSL HEPA, Ref Cavity and 3 AC units  turned on.

The 40m vacuum did not trip. It is vacuum normal.

The Jetstore computer is indicating power failer.

Chiara reports an uptime of >195 days, so its UPS is working fine 

FB, megatron, optimus booted via front panel button.

Jetstor RAID array (where the frames live) was beeping, since its UPS failed as well. The beep was silenced by clicking on "View Events/Mute Beeper" at 192.168.113.119 in a browser on a martian computer. I've started a data consistency check via the web interface, as well. According to the log, this was last done in July 2015, and took ~19 hrs.

Frontends powered up; models don't start automatically at boot anymore, so I ran rtcds start all on each of them. 

All frontends except c1ioo had a very wrong datetime, so I ran sudo ntpdate -b -s -u pool.ntp.org on all of them, and restarted the models (just updating the time isn't enough). There is an /etc/ntp.conf in the frontend filesystem that points to nodus, which is set up as an NTP server, but I guess this isn't working.

PMC locking was hindered by sticky sliders. I burtrestored the c1psl.snap from Friday, and the PMC locked up fine. (One may be fooled by the unchanged HV mon when moving the offset slider into thinking the HV KEPCO power supplies need to be brought down and up again, but it's just the sliders)

Mode cleaner manually locked and somewhat aligned. Based on my memory of PMC camera/transmission, the pointing changed; the WFS need a round of MC alignment and WFS offset setting, but the current state is fine for operation without all that. 

 I was able to realign the arms, lock them, and have run the dither align to maximize IR transmission - looks like things are back to normal now. For the Y-end, I used the green beam initially to do some coarse alignment of the ITM and ETM, till I was able to see IR flashes in the control room monitors. I then tweaked the alignment of the tip-tilts till I saw TEM00 flashes, and then enabled LSC. Once the arm was locked, I ran the dither align. I then tweaked ITMX alignment till I saw IR flashes in the X arm as well, and was able to lock it with minimal tweaking of ETMX. The LSC actuation was set to ETMX when the models were restarted - I changed this to ITMX actuation, and now both arms are locked with nominal IR transmissions. I will center all the Oplev spots tomorrow before I start work on getting the X green back - I've left the ETM Oplev servos on for now.

While I was working, I noticed that frame builder was periodically crashing. I had to run mxstream restart a few times in order to get CDS back to the nominal state. I wonder if this is a persistent effect of the date/time issues we were seeing earlier today?

TP3 drypump replaced after 10,344 hrs at 750 mTorr foreline pressure.

The foreline pressure is 13 mTorr after 8 hrs of running, TP3: 50K rpm, 0.14 Amp with all annuloses pumped.

The annulos pressures are 0.3 - 5 mtorr

************************

Frame builder just crashed again

daqd has indeed continued to be unstable. I found system times had drifted apart again... I think something weird happened in the booting of the frontends. The monit processes were not running on any of the frontends. I ntpdate'd again, and manually started monit on each fronted via sudo /etc/init.d/monit start. 

I manually aligned the IMC. Spot positions are all < 1.5mm. PMC trans of ~0.74, MC2 Trans of ~15400, MC Refl ~0.4, which is better than its been for some time now.

Somehow the WFS DC offsets were off, which made it look like it was impossible to center the beam on WFS2. The script for setting these wasn't working so I fixed it, ran it. WFS and MC2 trans offsets were set, WFS are back on and have been holding MC REFL nice and low for ~3 hours.

Arms were dither aligned, wrote the offsets to SDF files. Oplevs need centering. No further daqd crashes.

Eric and I spent some time yesterday night trying to recover the green in the arm after the laser swap. The problem essentially was that though I was getting ~800uW of green out of the doubling oven, the mode wasn't clean, and hence, the beam profile looked really messed up just before entering the arm cavity.We got to a point where we thought we were getting a good mode out of the doubling oven (as judged by propagating this beam onto the wall with the help of a mirror). But we were only getting ~400uW of green power. I tried tweaking the alignment of the oven on the 4 axis stage for a while, but was not able to improve the situation much. So I decided to start from scratch:

• First, I made sure that the IR beam from the laser was hitting the first steering mirror approximately at the center (see here for the optical layout). 
• Then I used the two steering mirrors immediately after the laser to make sure that the IR beam was hitting the first lens and the HWP before the IR faraday roughly at their center. 
• Next, I propagated the beam through the IR Faraday, again using SM1 and SM2 to do the steering - initial alignment through the Faraday was done by eye, and I did  some fine adjustment by maximizing the power coming out of the Faraday. We have 252mW of IR going into the IR Faraday, and 225mW coming out. I judged that these numbers were reasonable, and compared favourably to what we had with the Innolight.
• Keeping the downstream alignment, I used SM1 and SM2 to hit the second lens roughly at its center. I then re-measured the distance from this lens to the center of the doubling oven, and tweaked this slightly to match my mode-matching calculation. 
• I then tried to carefully play with this lens and the alignment of the doubling oven using the four axis stage. After (many) iterations, and with some luck, I managed to find what I judged to be a good alignment. Using the mirror-on-a-stick to reflect the green beam out of the doubler onto the wall nearby (see Attachment #1, all photos taken using my phone camera), the mode looks reasonably clean. I was also able to get 1mW of green power out of the doubler, an efficiency of ~2%/W. The doorknob should give some sense of scale, but at this point, the mode looks pretty clean (this was not the case previously).
• I then aligned the post doubler optics to send the beam through the green Faraday (~0.85mW of green out of the green Faraday) and through the two irides I had put in before swapping the lasers. As the beam propagates, however, some ellipticity in it becomes more and more apparent - especially after the f=-100mm lens between the two piezo mirrors. Attachment #2 shows the beam immediately after this lens, while Attachment #3 shows the beam on the iris just before it is sent into the arm cavity. 

I am beginning to wonder if this ellipticity is inherent from the IR beam from the laser? My beamscan results suggest that the beam is more divergent in the "P direction" as compared to the "S direction", which is borne out by these photographs. And if this is indeed the case, do we need to add cylindrical lenses to correct this?

Unrelated to this work: The ITMX Oplev seems to have wandered off so the X arm won't lock. I am not realigning the Oplev for now, but am turning the ITMX Oplev servo off for the night. 

Perhaps related to my work on the endtable: The ETMX oplev MEDM readings seemed to be frozen, though there was red light on the QPD on the endtable. Checking the CDS overview screen, I saw that all models on c1iscex had crashed. I sshed into c1iscex and restarted all the models, but the IOP block remained red. I checked the datetime, and found that this was wrong - so I followed the instructions here, but the "Diag Word" block remains red. I am shutting down the watchdog for ETMX and leaving this as is for now... This seems to have happened before...

Local EQ4.3

kicks ITMX-UL magnet into stuck position.

Hopefully it is only sticking.

I tried aligning the green beam, elliptical as it is, to the arm by using the various steering mirrors after the doubling oven. The following was done:

1. Eric and I aligned the beam through the green Faraday - we levelled the beam using an iris to check the beam height immediately after the Faraday and a little further along the beam propagation direction.
2. We checked that the beam is reasonably centered on all the lenses. We changed the lens holder for one of the lenses from a Thorlabs model to a Newport model, so as to get the lens to the correct height such that the green beam was roughly centered on it. 
3. I then tweaked the alignment of the steering mirrors until the reflected beam from the ETM roughly coincided with the input beam. The return beam is getting clipped slightly on the way back through the green Faraday, so some more alignment needs to be done. However, given the ITMX situation, I can't align the arm to IR, so I'm holding off on further alignment for now...

Taking inspiration from J. Lewis et. al, ITMX has been freed. 

Even better, I'm now seeing Green flashes in the X arm.  

Good job Q! Give us more details please or  play Rachmaninoff Piano Concernto #2

Atm2,  EQ 3.5 and 4.1 

          confirming ITMX is really free

Looks like another EQ 4.8 took out all the watchdogs, I've restored them, everything looks alright and doesn't look like any magnets got stuck this time... 

Given that we were seeing green flashes in the arms, I tried to see if I could get the green locked to the arm in a nice mode. For a start, I tried hooking up the PDH box and LO using the same settings as was being used previously. However, this did not work. I suppose we will have to do the whole AM/PM measurement for the Lightwave as well before we can determine what would be a suitable frequency for the LO. The AM measurement was relatively straightforward, I just repeated the same steps as detailed here. The two attachments show the AM response (one from 10kHz to 5MHz, the other for a narrower range of 100kHz to 1MHz, both with an excitation amplitude of 0dBm). To see if I could guess some sweetspot for operation, I tried setting the LO frequency to the two marked notch frequencies but was unsuccessful in getting the PDH lock going. At the moment, the alignment for the optics that picks off the IR after the doubler and routes it to the fiber are ccompletely misaligned, I will align these and do the PM measurement tomorrow and then we should conclusively be able to say what the appropriate frequency is to actuate on the PZT.

Unrelated to this work: the KEPCO high voltage power supply that drives the green steering mirror PZTs was switched off - I suppose this has been the case since the power outage last week. I turned it back on and reset it to the nominal settings: Vout = 100V, and Imax_out = 10mA, the driver board is currently drawing ~7mA which I judged to be consistent with the values labelled on the unit.

 Celebration

Safety audit went smothly.

Crane inspection is scheduled for March 4

Safety glasses will be measured before April 1

After the discussion at the meeting today, I decided to try and lock the green by sweeping through PZT dither frequencies in the vicinity of 200kHz without worrying about the AM/PM ratio for now. I was able to lock the PDH loop relatively quickly, at an empirically determined PZT dither frequency of 213.873kHz, 2Vpp (the amplitude was copied from the value at the Y-end). For today's efforts, I borrowed the sum+HPF pomona box from the Y-end, I will make a replica given that we are using Lightwave lasers at both ends now. After adjusting the PZT sliders and lenses on the translational stages at the endtable to maximize the green transmission as best as I could, I was able to get GTRX up to about 0.07 - this is far off from the value of ~0.25-0.3 I seem to remember us having with the old setup, even though we have more green light into the arm cavity. I will take a measurement of the loop transfer function to see what sort of bandwidth we have...

10:15 power glitch today. ETMX Lightwave and air conditions turned back on

The CDS situation was not as catastrophic as the last time, it was sufficient for me to ssh into all the frontends and restart all the models. I also checked that monit was running on all the FEs and that there was no date/time issues like we saw last week. Everything looks to be back to normal now, except that the ntpd process being monitored on c1iscex says "execution failed". I tried restarting the process a couple of times, but each time it returns the same status after a few minutes.

I spent some more time today trying to optimize the modulation frequency and amplitude for the X end PDH, and the alignment/mode-matching of the green to the arm. Some notes:

1. After my best efforts to tweak the alignment and mode-matching into the arm by using the two lenses on translational stages, I was able to get the green TRX up to about 0.06. As mentioned in a previous elog, this is much lower than what we had with the old setup, even though we have more green power going into the arm now. However, the mode looks pretty bright and clean on the monitors. Could the large ellipticity in the beam is the limiting factor now?
2. I measured the transfer function (attachment #1) of the PDH loop once I had settled on a modulation frequency and amplitude that I judged to be optimal (indicated on the plot). The UGF is ~7kHz. The PDH error signal as viewed on the oscilloscope is comparable to what we had with the Innolight. All this optimization was done empirically, I have yet to do the PM measurement. I can't seem to get more than 0.2 mW of IR arriving at the fiber coupler, the number I found in some older elogs is 2mW with the old setup.
3. I did some alignment of the PSL green and the X arm green onto the beat PD on the PSL table. After the power glitches, the doubling ovens do not automatically turn on, I had turned on the end ovens earlier, and today I turned on the PSL oven. I noticed some strange behaviour initially - though the setpoint was 36.9 deg C, when I enabled the heater, there was a large overshoot (it went to almost 50deg C). I disabled the heating at this point, and re-enabled it once the oven had cooled down to ~35 deg C. I didn't observe anything like this while turning on the end ovens. But the PID parameters at the PSL table are very different, so perhaps this large overshoot and ringing is to be expected. In any case, I managed to get this working. But I was not able to find a beatnote tonight. 

To do:

1. Verify that the two beams are aligned on the beat PD - I think I've done this carefully by checking the near and far-field, but I will double check.
2. Find the beat note and look at the ALS noise performance with this new setup to see if it is usable even though GTRX is only 20% of what it used to be..
3. Fix the coupling of the IR pickoff into the fiber at the endtable. Once this is done, I can do the PM measurement, and finding a beatnote may be easier given the IR beat PDs have a much wider bandwidth...

I continued the hunt for a green beatnote today - I decided to take the output from the RF amplifiers sitting on the PSL table and directly connect it to the analyzer in the control room while I swept the temperature of the end laser 10,000 counts on either side of a temperature at which I had taken this measurement - so I expect the beatnote should be found somewhere in this neighbourhood. But I did not see any peaks throughout the sweep. I re-checked that the mode overlap onto the BBPD is reasonable. We have considerably less transmitted green power from the arm now than we did before the laser swap (by a factor of ~3) but I still expected to see some sort of beat signal.

It would be handy to have the IR beat set up as well for this process, but as mentioned in a previous elog, I was getting only ~0.1 mW of IR power incident on the coupler at the end table last week. As I had suspected, tweaking the alignment of the steering optics for the pick-off IR beam after the doubler improved the situation somewhat, and I am now getting about 1mW of IR power incident on the coupler at the end table. But I've not been able to adjust the alignment into the fiber at the end such that I get any IR light at the PSL table.  

Amstron batteries replaced after 11 months with SP-12-5.5HR,  2 years warranty from replaceUPSbattery.com

Note: the replace battery LED did not go out ( well pasted 24 hrs ) till the self test bottom was hold down for 2-3 sec

The crane inspection is scheduled for this coming Friday from 8-12

[Koji, Johannes, gautam]

With Koji's and Johannes' help, I managed to resolve the coupling the pick-off IR beam into the fiber at the X end. I will put up a more detailed elog about how this was done - but in summary, we have about 31% coupling efficiency into the fiber, which isn't stellar, but I felt this was adequate to find a beatnote. Koji also pointed out that the collimation telescope attached to the fiber at the X-end is poorly mounted - this is something to fix when we swap endtables, but this was not addressed right now because if we were to adjust this, we would also have to adjust the mode matching into the fiber.

I then attempted to tune the temperature to find the IR beatnote. While doing so, I noticed some strange features of the controller - there are essentially two display modes relevant to laser crystal temperature, one which allows us to change the setpoint and one which is an actual readback of the temperature (this one can't be adjusted). While tuning the temperature, I noticed that the latter display ("LT") did not change in value. On a hunch, I disconnected the "SLOW" control BNC on the front panel, and voila, I was able to tune the setpoint and observe the measured temperature shift accordingly. I was thus able to find a reasonably strong IR beatnote (-9dBm) at T ~ 44.6 deg C (the beat PD was set to 0dB attenuation, i.e. high gain mode). However, the moment I reconnected the SLOW control BNC, the beatnote vanished (it gradually shifted out of range of the HP network analyzer), and the same thing happens if I terminate the SLOW control BNC connector! I don't understand this behaviour, as the manual says that the range of voltages accepted to this input is +/-10V, so I would assume 0V means do nothing, but clearly this isn't the case, as the beatnote is being shifted in frequency by > 1GHz, and the tuning coefficient is listed as 5GHz/V in the manual. This situation needs further investigation.

Since I had a reasonable IR beatnote setup, I returned the HP analyzer to the control room and tried to see if a green beatnote was present as well - I first ran ASS, then maximized the green transmission using the PZT mirrors, but no beatnote is evident. The contrast isn't great, the ratio of AUX power to PSL power on the green beat PD is something like 5:1, so this probably requires some tuning as well. I will update this elog after today evening's activities...

[ericq, gautam]

Summary of work done tonight:

• The PDH setup at the Y-end has been restored after I had pulled the whole thing apart some weeks ago to see that nothing was obviously wrong with the uPDH box
• Adjusted the temperature of the Y-end laser such that a beatnote was obtained - I did this using the IR beat (the end laser temp wasn't updated after the PSL temp was changed recently)
• The Y green beatnote was found easily, there was no alignment on the PSL table necessary, though there is room to improve this situation (beatnote amplitude was ~ -35dBm though we are used to more like -25dBm)
• The X green beat remains elusive - I played around with the alignment onto the green beat PD at the PSL table for some time, and the two beams are aligned as far as I can tell given the constrained area available in that area. It may be that I have to clear some optics, do a rigorous near-field/far-field alignment of the two beams and then try again
• Since we had two strong (-5dBm for Y, -9dBm for X) IR beatnotes, we decided to take the ALS noise spectra for these. So as to not overload the amplifiers, a -10dB attenuator (-6dB) was placed directlty after the Y (X) IR beat PDs, before routing these signals through the usual green beat signal chain. Attached is the measured spectrum. The new values of the temperature sliders at which beatnotes can be found are : 1700 for X and -5990 for Y (spectra taken at these values).

To do:

• For both ends, find the three temperatures at which we have beatnotes, and choose the middle one
• PM characterization of AUX X laser - it may be that the excess noise in the X spectrum is due to sub-optimal PDH
• Align the Y green better at the endtable, also take an OLTF measurement for the Y PDH loop
• Re-check the alignment onto the green beat PD for the X beat

Remarks:

• The Lightwave laser controllers differ from the Innolight ones in that it is not possible to directly set the signal to the SLOW control BNC to 0, and have that as the new reference point. Rather, there seems to be some setpoint which is saved as a reference, and the moment any signal is applied to the SLOW control BNC, it adjusts the actual temperature w.r.t. this saved setpoint. I believe it is possible to update this setpoint (it is also possible to update the calibration of the power readout, this is an additional issue at the X end), but since this wasn't critical, I've left it as is for the moment...
• The ALS nosie spectrum for the Y arm IR beat is surprisingly good!

Bob cleaned the safety glasses. They were sonicated in warm 2% Liquinox  water for 10 minutes.  Steve checked them by transmission measurement of 1064 nm at 150 mW

The good news: both green beatnotes have now been found. The problem was alignment on the green beat PD on the PSL table which I fixed. They are about -40dBm in amplitude (compare to -25dBm we used to see). But looking at the phase tracker Q output seems to suggest that there is adequate signal...

The bad news: the ALS noise still looks bad (see attachment)- I think the IR beat for the Y was perhaps marginally better. The beat amplitude for the X beat was optimized on the PSL table with the help of the oscilloscope. There may be some headroom for improvement with the Y beat.

I also did the AM/PM measurement for the replaced lightwave, chose an LO frequency based on this, and took the loop OLTF, plots to follow...

To do: 

• Check Y-end PDH loop OLTF
• Optimize beat note amplitude of Y beat
• Align Y-green better to the arm using steering mirrors on the endtable.
• Double check calibration of PM/AM measurement and that I've picked the correct LO frequency/ I don't have any other ideas for improving the situation with the X beat though

All 3 cranes inspected by professional and load tested with 450 lbs at max reach.

PSL Table doors were open, and the laser shutter was closed.

Doors have been closed, laser has been opened. 

Sorry, that was me; taking some photos of the PSL and EX mirrors.

I've been a little behind on my elogs so here is an update of the end laser situation.

IR beat for X-end recovered

• The issue was optimizing the alignment into the fiber at the end table.
• Using Fluke fiber illuminator helped in aligning IR pickoff into mount. Useful note: there is an unused fiber running between the X-end and the PSL table, by connecting these at the PSL table, I was able to monitor the coupled power while remaining at the X-end.
• Another major issue was that one of the steering mirrors (marked "Y1" in Attachment #1) was mounted with AR coated side facing the beam. This was fixed by simply rotating the post, the mirror was not removed from its mount. I can only assume that this mirror is in this kind of mount because of space constraints.
• The fiber has a collimating telescope attached to the end of it. In principle, this gives us more angular acceptance while coupling the beam into the fiber, but as I found out, the acceptance is still tiny (I don't have a number to quantify it). Furthermore, the Fluke visual fault locator revealed that the lens in the collimating telescope is not set up great - when re-doing the X end table, we should fix this situation so as to have a fairly large collimated beam coming out of the fiber when illuminated from the other end, this would make the mode matching much easier.
• Bottom line: we have ~1.2 mW of IR light incident on the coupler at the end table, and ~400uW of IR power at the PSL table => coupling efficiency is ~30%, not stellar, but sufficient for now I guess. After the various splitters etc, there is about 160uW of EX IR light and ~300uW of PSL IR light incident on the beat PD, and the beat amplitude is about -9dBm.

AM/PM characterization of newly installed Lightwave

• Having recovered the IR beat, I set out to do the PM characterization for the end laser.
• Attachment #2 shows the electrical setup. The IR beat was piped to the X-end via an existing long cable that runs between the vertex and the endtable. Not shown in the diagram, but I used a 20dB coupler to keep track of the beat frequency on the HP spectrum analyzer while doing this measurement.
• I restricted myself to the range between 100kHz and 500kHz to do the scan, because it takes quite a while to do the scan with fine resolution (IF bandwidth = 10Hz).
• To calibrate the magnitude response to rad/V, I divided the output of the network analyzer (converting dB to absolute magnitude first) by the amplitude of the signal seen on the monitoring oscilloscope while the PLL is unlocked. This number was 96mV/rad.
• To confirm that the error signal spectrum is indeed a good approximation of the "plant" transfer function (i.e that 100kHz >> UGF of loop transfer function of the PLL), I measured the loop TF of the PLL - Attachment #3 suggests a UGF of ~ 16kHz, which means the assumption is reasonable.
• Excitation amplitude was -25dBm (which gave reasonable SNR), and 3 averages were taken.
• The AM measurement was done using the same procedure as detailed here - the DC block was used. The DC level of the PD output was 2.72 V. The excitation amplitude was 0dBm.
• Attachment #4 shows the AM response, PM response and PM/AM ratio
• The peak in the PM/AM ratio at 256620 Hz is compelling because it is not too sharp (and so we can be reasonably confident we are at a good operating point) and the PM response of 23.83 rad/V is also acceptable. 
• As a consistency check, the PM response of ~30rad/V at 100kHz => PZT actuator gain is ~3MHz/V, which is in the region we expect it to be...

Next steps in recovering ALS and trying to lock again

• Having set the PDH modulation frequency to 256.62kHz, I took the spectrum of ALS noise using the IR beat (i.e. by piping the IR beat signal through the electronics the green beats usually go through - 6dB and 10dB attenuators were placed immediately after the beat PDs for the X and Y arms respectively, to make the signal levels compatible with the electronics), Attachment #5 unfortunately suggests that the noise performance is still poor, and I suspect the situation will be similar using the green beat (though I have not measured this yet).
• The modulation depth could be sub-optimal for the X-end PDH, I have to measure this and check that it is at an acceptable level. This will also tell me if I need to change the sum+HPF pomona box used to send the PDH control signal + piezo dither signal to the laser PZT. In order to do this, I need to know what the input impedance to the FAST control BNC is - the manual isn't very helpful, it just says the piezo has a capacitance less than 10,000pF. I suppose I will have to actually measure this.
• PDH loop OLTFs have to be re-measured for both ends to check that the servo gain's are appropriately placed.
• We know that the mode-matching into the arm for the X end is poor (I have yet to quantify this) - I suspect that the beam ellipticity is the main culprit. However, the DC transmitted power levels at the PSL table are comparable to (even slightly better than) the Y arm numbers, and so this cannot be the sole reason why the X-arm ALS noise is so much worse... I will continue my investigations next week...

I came in to check the status of the nitrogen and noticed that the striptool panels in the control room were all blank.

• PMC was unlocked but I was able to relock it using the usual procedure
• FB seems to be down: I was unable to ssh into it (or any of the FEs for that matter). I checked the lights on the RAID array, they are all green. I am holding off on doing a hard reboot of FB in case there is some other debugging that can be done first
• None of the watchdogs were tripped, but judging by the green spots on the mirrors, all of them are moving quite a bit. I've shutdown the watchdogs on all the optics except the MC mirrors, but the ITMs and ETMs still seem to be moving quite a bit.

I am leaving things in this state for now. It is unclear why this should have happened, it doesn't seem like there was a power glitch?

We went and looked at the monitor plugged into FB. All kinds of messages were being spammed to the screen (maybe RAM errors), and nothing could be done to interrupt. Sadly, a hard reboot of FB was neccesary.

Video of error messages: https://youtu.be/7rea_kokhPY

After the reboot, it just took a couple of model restarts to get the CDS screen happy.

Attachment #1

Since I could not determine how many volts at the LO input of the pomona box input corresponds to how many volts at the laser PZT, I measured the transfer function between these points using the Agilent network analyzer. The measured TF suggests that for a function generator output of 2Vpp, we get approximately 75mrad of phase modulation, which compares reasonably well with the value of 120mrad reported here. I did not attempt to further increase the LO output signal to push this number closer to 120mrad, as with 2Vpp from the function generator we get +7dBm at the mixer, which is what it wants - so I wanted to avoid any attenuators etc...

Attachments #2 and #3

After ensuring that we have appreciable phase modulation, I set out to measure the PDH OLTFs and adjust the gain on the uPDH boxes accordingly. The X end gain is at 6.0, and the Y end gain is at 4.0. Before measuring the Y-end OLTF, I adjusted the steering mirrors to increase GTRY to ~0.45. GTRX remains a paltry 0.05... But the UGFs seem satisfactory..

Attachment #4

Finally, I took the ALS noise spectrum for the green beats. The beat note amplitudes on the network analyzer in the control room are still puny compared to what we had, -40dBm for Y and -45dBm for X. But the phase tracker Q values are ~1000 and ~3000 for X and Y respectively, which are pretty close to what these were if memory serves me right. There may still be some room for optimization of the PDH loop gains etc, and we could perhaps look at lowering the gain of the REFL PD at the X end? I also have yet to do the sweep for the 3 temperatures at which we can find a beatnote and park at the middle one...

These spectra suggest we could even possibly try locking? We are approximately a factor of 3 above the reference for X and on par with the reference for Y....

Unrelated to this work: I also realinged the PMC, PMC transmission is now 0.730V up from ~0.65V.

Why is the transmission of X green so low? Perhaps you can phase lock the IR and then scan the X frequency, using the X arm as the analyzer. i.e. put a slow ramp into MC2 to pull the PSL frquency and thus the green frequency. You can record a movie of the scan using the framegrabber and record the green transmission peaks to see how big the mode match is exactly (which modes are so big)

[ericq, Gautam]

We worked on getting the DRFPMI back up and running, hoping the ALS performance was good enough. 

We did succeed in bringing in enough of the AO path to stabilize arm powers > 100, but failed at the full RF DARM handoff. 

REFL165 angle was adjusted to -86 to minimize PRCL in the Q signal. 

The AS110 signals are mysteriously huger than they used to be. Whitening gain reduced to 15dB from 27dB. Old trigger thresholds are still fine.

The new AUX X laser has a different sign for the temperature-> frequency coupling, so our usual convention of "beatnote goes up when temp slider goes up" meant the ALSX input matrix elements had to change sign.

We think the POPDC PD (which I think is the POP2F PD) may be miscentered, since in PRMI configuration, its maximum does not coincide with the REFLDC minimum, and leaves a sizeable TEM10 lobe on the REFL camera. This was a pain. 

I did a quick sweep of the lab to find out what hardware has already been acquired for the X-end table upgrade. The attached PDF is an inventory check in the spirit of this elog.

Some things we have to decide:

• Are we okay with using the old green coloured faraday mount for the IR faraday? I have in hand a piece identical to the one used at the Y-end for the green faraday, that is red in colour, so I guess we can switch this out.
• The way in which the doubling oven is currently mounted at the X-end is using some posts cobbled together. The Y-end looks to have a custom mount machined for it (see Attachment #2). Do we want to go ahead and get something like this done?
• I suppose it is okay to reuse all the old optics (mirrors, lenses, harmonic separators) and PDs? It may be that we need to order som extra mirrors/lenses/posts (this will become clear once I do the layout)

I have not gotten around to planning the layout or doing drawings. I will try and first work through a mode-matching solution to make sure we have all the required lenses. It may be that we need some 1" or 2" mirrors as well. The beam from the lightwave NPRO is quite elliptical, but we have a number of cylindrical lenses in hand already if we decide we want to use these, so I guess we don't have to worry about this...

This is quite a preliminary list, and I will add/update over the coming days as I do more detailed planning, but have I missed out anything obvious?

Its not a good idea to use green mounts with green lasers. Steve should be able to get another copy of the EY doubler mount made up if we really don't have another one sitting in the Manasa end table box which Koji mentioned.

Johannes found dripping water at the vac rack. It is safe. It is not catching anything. Actual precipitation was only 0.62"

I located the second doubler mount, it was sitting inside a cabinet along the Y-arm. So this will not have to be machined. The doubling oven mount is black in colour.

So as things stand now, the only thing that needs to be machined is a non-green mount for the IR faraday (IO-5-1064-HP) - is it possible to just coat the existing mount with a different color? I've got a drawing for this part ready, but it seems unnecessary to machine the whole thing from scratch when only the color is an issue. Steve was talking about dipping this in some sort of solution and taking the green off. But if this isn't possible, I'll send Steve the drawings tomorrow so that he can place the order with the machine shop...

I will work on the mode-matching calculations over the next couple of days to make sure we have all the mirrors and lenses we need.

It's may be the janitor's doing.

I noticed that the HEPA filers were off. They are turned on at 20%
 

Ruby wire standoff 1 mm od. with V-groove test cut. SOS sus wire 0.0017" od. is in the background.
 

It looks almost OK, but we need a bit sharper picture for both the groove and thw wire.

Kate Dooley picked up this item today.

The enclosure top piece in the middle is still in the machine shop.

The carpenter who helps in the built just left for one week vacation.

The unit will be ready  on April 1

I'd prefer doing the installation with the enclosure on the new table.

It's the only way to minimize the resonances of the enclosure with shimming.

Diagnoses from Glasglow:

“So far we have analyzed the laser. The pump diode is degraded. Next we would replace it with a new diode. We would realign the diode output beam into the laser crystal. We check all the relevant laser parameters over the whole tuning range. Parameters include single direction operation of the ring resonator, single frequency operation, beam profile and others. If one of them is out of spec, then we would take actions accordingly. We would also monitor the output power stability over one night. Then we repackage and ship the laser.”

The 2W Innolight was turned on.

The alignment of the PMC adjusted on the PSL table: Trans 0.737->0.749

The alignment of the IMC adjusrted on the sliders: Trans 14300->15300

WFS offset has been reset by /opt/rtcds/caltech/c1/scripts/MC/WFS/WFSoffsets