I analyzed the spherical power measured by HWSY from last night's lock and compared it to the estimated thermal lens from the SIM model. Once the HWS and SIM models were all put into the same single-pass scale (HWS data measures a double-pass of the test mass thermal lens and the SIM data estimates the single-pass thermal lens), I could see that the SIM model was underestimating the thermal lens by about 25%. 

The old absorption value was 280ppb. The new absorption value (required to fit the SIM model estimate to the HWS data) is 360ppb.

TITLE: 05/31 Day Shift: 15:00-23:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Engineering
OUTGOING OPERATOR: N/A
CURRENT ENVIRONMENT:

Winds calm, primary and secondary uSeiem are calm
QUICK SUMMARY: ops lazy script isn't doing transition (-t).

[Vaishali, Patrick, Sheila, Jenne]

A few other locking notes from today, although nothing ground-breaking.

* I asked Vaishali to write a note "Xarm green weirdo - adjusting fiber polarization fixed it", thinking to myself that of course I'd remember exactly what I meant by weirdo.  I think (esp. from the attached screenshot) that I thought adjusting the fiber polarization fixed the drifting of the Xend laser power, since that stopped for about 2 hours, although obviously it didn't actually fix it.  Anyhow, Vaishali can comment here if she remembers more than I do....

* We really, really struggled with ALS DIFF while the wind was high earlier this afternoon.  For a long while the whole wind trend plot was above the 20 mph line, gusting to above 40 mph.  We weren't having trouble before that (it started pretty suddenly), and we were fine again after it died down and was averaging closer to 10 mph.  The seismic config was in "Windy" the whole time, per the table on the config medm screen.  We tried going through DIFF by hand several times, but I think the real key was just to wait until the wind was more calm.

* I saw that the power recycling gain dropped when we increased power. I tried re-setting the SOFT offsets, and in the end it turns out that the QPD offsets that Sheila had found were being overwritten in the ISC_LOCK guardian - a remnant of a time when we had 2 states for those that we liked - so we have reverted them to Sheila's offsets (since mine were nearly identical), and removed the hard-coded offsets from the guardian. 

* I measured DHARD yaw just after increasing the PSL power to 30W (was actually closer to 27W during the measurement), and everything looked fine for going through with the Lownoise_ASC state.  I did so by hand, and then again through at least one more lock letting guardian run through the state, and I had no problems.  We aren't sure what this is, but it's not due to the SOFT offsets, since Sheila had been re-setting them by hand each lock at that time.

* On our final successful lock from this evening, I did the reduction of 45MHz modulation depth, skipped reducing the 9MHz modulation depth, and skipped the SRC ASC high power state, but otherwise was able to complete Noise_tunings, which basically puts us at NomLowNoise.  After a while the CSOFT / dP/dTheta instability showed up, and we lost lock.  I had increased the CSOFT pit gain from 0.6 to 0.8, but we lost lock while that was ramping, so I don't know if it would have helped or not.  If all the oplevs were functional, we'd like to try oplev damping again.  Alternatively, perhaps we'll try using the ISS 3rd loop again.

* After this, we've been unable to hold ALS_COMM locked, and we're suspicious of both the CARM / IMC loop (see the thread that starts with alog 36546), and the new ALSX laser (see alog 36550).

In conclusion, lots of measurements and testing, but no fundamental progress beyond the pre-ALS-laser-fiasco situation.  Hopefully someone has inspiration for us in the morning regarding the ALSX laser power fluctuations, and we'll be able to keep moving forward.

[Patrick, Sheila, Jenne]

We are perplexed by the behavior of the new ALSX laser.  In the first attached screenshot, for most of the time after -30min (except a bit arouhnd -10min), we were sitting in Locking_arms_green, so the green lasers were locked to the arms, but nothing else was going on locking-wise (this was concurrent with some IMC diagnostics). 

We see that the green power transmitted through the arm drifts a lot.  It doesn't seem to be exactly following the IR output of the laser (as measured by the FIBR_A_LF_OUTPUT, which should be a combo of IR from the vertex and IR from the end station laser but dominated by the end station laser), although it does sometimes.  During these large drifts the arm was locked on TEM00 of the green beam, as seen on the transmission camera.  The drifts are mirrored by the LASER_GR_LF_OUTPUT, which is a measure of the green power pretty soon after the doubling crystal.  So, this is something that is really happening to the amount of green light going into the arm cavity. 

Also note that in the second attached screenshot, it looks like the output of the new laser is more noisy than the old one. We tried toggling the noise eater switch for the laser remotely from the screen but that didn't seem to affect the behavior. 

It doesn't really look like what I think of as mode hopping of the laser, since it's slow drifts and not fast jumps.  At this point we're pretty confused, and not able to hold ALS COMM lock for very long, so we're hoping that someone can take a look in the morning and help us out. 

TITLE: 05/30 Eve Shift: 23:00-07:00 UTC (16:00-00:00 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY:
LOG: Sheila, Jenne, Jeff K. and Vaishali working on relocking. Ran into possible changes in IMC/CARM loop UGF and the green power output from the end X ALS laser.

23:29 UTC Kyle and Chandra to mid Y
~23:43 UTC Jenne, Vaishali and I adjusted the fiber polarization in the MSR
01:42 UTC Sheila and Jeff to LVEA to measure CARM open loop gain
01:46 UTC Chandra and Kyle back
01:56 UTC Sheila and Jeff back
02:39 UTC Jeff to LVEA to measure IMC loop
02:51 UTC Gave Aidan remote access to take HWS measurement
Sheila to LVEA to measure IMC loop

J. Kissel, S. Dwyer

Looking into why we have such high frequency noise coupling about a few kHz, we re-measured the CARM UGF (with and without IMC Boost Filter that comes on before nominal low noise) and IMC UGF (with the boost OFF), and found both loops with a factor of 2 less gain than we expect, at 7 kHz and 26 kHz respectively.

See attached transfer functions.

For reference, 
- just a few days ago, Kiwamu suggests that the IMC loop gain was at it's normally high ~50 kHz in LHO aLOG 36354.
- I expect the current design similar from when Chris Whittle fully characterized the loop LHO aLOG 29735.
- The only difference we expect is this "new" boost, which we started using in Oct 2016; see LHO aLOG 30549.

The investigation continues...
 

Following today's minor adjustment of HWSX alignment to clear the ETMX reflection, I reran the HWS plotting code on the lock from this evening. The point absorber is still very obvious. Here are three images from periods during the first 8 minutes.

The colored contour scale is truncated at -80nm, where everything lower than -80nm is white.

After 169s:

After 229s:

After 471s

You can see the thermal diffusion taking place here - the gradient is increasing in the areas surrounding the point source. As can be seen here, the optical path distortion from the point source is 80nm over roughly about 25mm diameter.

After talking with Dave B. and Patrick T. about the set point values I gave them for CP3,4 auto overfills, I discovered that CP3 stops overfilling when thermocouples see < -30C. CP4 is set to -60C. I cannot reason why I would have set them differently, but now I know -30C is too high, and I'm concerned that last Friday's overfill never actually overfilled. Attached is a plot of Sunday night's manual fill right at the pump, where I stood for 50 minutes and verified LN2 coming out of exhaust (the final dip you see in plot). For most of those 50 minutes, the exhaust was just cold gas reading below -50C.

Also attached are the fill plots from last Wed. and Fri. You can see the usual shallow slope in Wed. plot followed by the LN2 finale. Friday's fill fell immediately to something less than -30C which could have just been cold gas.

We will change the set point to -100C for both CP3,4.

Kyle and I spent some time at CP3 sensing line this evening. We increased GN2 flow by removing the 0-5 LPM rotameter and applying up to 30 psi - anymore than this causes >10 psi exhaust pressure and we didn't feel comfortable going above that. We also applied vacuum to the sensing line using a diaphragm pump. We saw the % full read back at 100% on occasion when applying pressure. BTW, the transducer is rated for 2000 psi. We toggled between pressure and vacuum until the GN2 bottle ran out and connected a new bottle for overnight. Reinstalled the rotameter and left flow at 5 LPM overnight. 

After these activities I overfilled CP3 from control room. It took 3 minutes by applying 50% open on valve. Set back to 20% open.

I needed to work on some code on the test stand and found that x1ldasgw1 had restarted last Friday ~23:48 localtime.  So I had to remount the frame directories for x1nds1 and x1fw1.

S. Dwyer, J. Kissel

We found that the Beckhoff error handling system was reporting an intermittent error on ALS Y WFS A Demod Local Oscillator (LO) Power (H1:ALS-Y_WFS_A_DEMOD_LOMON) having surpassed its threshold (H1:ALS-Y_WFS_A_DEMOD_LONOM). 

Trending reveals that
 (a) The error bit has been green since the Beckhoff ADC was replace on Sept 22nd 2016 (see LHO aLOG 29848) 
 (b) the LO's power has been slowly increasing over time, and was now on the hairy edge of the threshold.

After consulting Sheila, she suggests "it's probably fine," so I increased the threshold from 21 [dBm?] to 22.5 [dBm], and accepted the new threshold in both safe and OBSERVE.snaps in the SDF system. (I'm not confident that this monitor is actually calibrated into physical units, but 21 [dBm] doesn't sound crazy so I put confidence in the designer of the system to have done so.)

Hopefully this doesn't turn out to be a canary for the demodulator like the diode laser power was to the now replaced ALSX laser...

Temp A: 24.4 ºC
Temp B: 21.6 ºC
Diode: 1.80A
Laser Crystal Temp: 29.60 ºC
Doubler Temp: 33.62 ºC

We had a potentially scary situation tonight at mid-Y and through crazy coincidence managed to fix it before it became a serious problem. Sheila contacted me around 10 pm local time about a verbal pressure alarm that was going off in control room for BSC7 (gauge PT-170). I checked the MEDM screen from home and didn't see anything abnormal - except that the pressure is a bit high since the vent (7e-8 Torr). Most likely it's alarming because of set point setting.

This alarm made me look at our site pressure trend (48 hr trend here) and noticed that PT-210 at mid-Y was quickly drifting up starting around 7pm. Suspected CP3 and/or CP4 were warming up due to very hot temperatures we've had this weekend. Gerardo was unable to remotely log into CDS to initiate a remote overfill even though we were supposed to have permission until June 1. I drove out to the site to manually overfill both cryopumps at the skid by opening the bypass valve 1/2 turn (just like the good ole days). Filled CP3 first and observed an almost immediate drop in pressure. Took 50 min. to overfill (verified by watching LN2 pour out of exhaust). As soon as I started the fill, the exhaust flow increased to turbulent. CP4 didn't exhibit the same turbulent behavior, and took 30 minutes to overfill. Conclusion is CP3's valve actuator setting from Friday was too low at 15% open. I reset to 18%. Also increased CP4 from 37% to 39% open. Tomorrow is supposed to be 98F!

Need to learn what the current pressure alarms are set to; I propose we tighten these just for mid-Y so vacuum staff is alerted quickly when pressure starts to rise. I also suggest we try to maintain seconds vs. minutes of overfill time as we approach a hot summer.