Revomed the PEM_WIND test. After talking with Dave it doesnt seem too useful when we have other tools in the control room to show wind. Plus the connections to the weather stations seem to be unreliable and we dont want to stop the DIAG_MAIN from showing notificaitons just because of a connection error at a weather station, especially in an observing run.

Since lowering this gain we haven't had any more of the locklosses shortly after switching to analog carm. 

This trip has just happened again.  But, this time we aren't able to fix it.  Sheila went to the CER to look, and all the lights on the coil driver chassis are green.  No overtemps are on, and fuse status is green.  We're calling Hugh right now, but if anyone sees this and knows how to fix it, please give the control room a call.

We tracked down the BS ISI trip to a single bit flip in the h1seib2 DIO_0 card, corresponding to the BS ISI ST1 V3 coil driver:

H1:ISI-BS_BIO_IN_CD_ST1_V3_STATUS

This bit being true was causing the ST1 watchdog to be permanentaly tripped.

We tried without success to clear the problem with the following:

• power cycling the relevant BIO chassis
• power cycling the relevant coil driver chassis
• power cycling the entire h1seib2 IO chassis, which involved:
  • shutting down all h1seib2 models
  • taking h1seib2 FE out of Dolphin
  • power FE down
  • power IO down
  • power AI down (to protect again DAC high output on restart)
  • power IO up
  • power FE up
  • power AI up

None of that cleared the bad bit.  Eventually Sheila checked the binary output from the coil driver and determined that everything looked good.  This gets the coil driver off the hook, narrowing the problem down to the BIO chassis or the BIO card itself in the IO chassis.

Given that we determined there was no actual problem with the coil driver, we decided to just bypass the problem by using the H1:ISI-BS_BIO_IN_BIO_IN_TEST EPICS channel to add in a value to the BIO input that would flip the single bad bit back to the desired value.  This solves the problem for the time being

Once the BIO chassis/card is fixed, the H1:ISI-BS_BIO_IN_BIO_IN_TEST channel will need to be set back to zero (0).  See the "BIO" screen from the ISI BS overview screen.

Unfortunately this bad bit is actually periodically flipping, and not staying flipped, so our test sum-in hack solution is not working.  We've had maybe two more locklosses caused by these bit flips.

Today, we locked the ISS at 2.1 W and measured the low end of the transfer function. Everything as expected.

This task is in the Ops checklist. Did not realize Patrick had already posted these data via a FAMIS task. 

Couple of notes:

• Low diffracted power:
  • The new normal for the ISS diffracted power is 3%-4%.  The script should be updated to reflect this.
• PMC reflcted power high:
  • After Saturday's power glitch the power meter that measures the PMC reflected power is misbehaving.  It is constantly reading 174+ watts, even though it's not seeing that much ligh; we're getting about 119W transmitted so at most we should be seeing ~31W reflected.  There's a couple things I'm going to try tomorrow, but if those fail the power meter will need replacing.  Until this gets resolved the Reflected Power and Power Sum for the PMC will be incorrect.

This is a result of the alignment dither loop railing the OMC suspension actuators.  This should not be happening, especially after Sheila offloaded some of the alignment to the OMs (alog 29377).  We'll look into it. 

In the attached screenshot, note that the first lock at 50W does not rail the actuators, but we do pretty immediately for the second lock.  H1:FEC-46_DAC_OUTPUT_0_6 is the T3 actuator on the OMC suspension.

We have angle to length feedforward for the OMC which was put in place to prevent scattering due to the angular dirves 19691.  In the second attachment to the alog Jenne linked you can see that the offloading helped us to not rail the suspensions, but most of the problem was due to the change as we power up not the miscentering when we first lock, so offloading with the pico motors could only help a litle bit.  I don't know why there seems to be a difference between the alignment of the carrier (which the OMC follows using the alignment dither loops) and the sidebands at the AS port, whoes alignment should be fixed by the AS_C and AS WFS centering servos.  

Durring the last few minutes of the 50W lock, the DC PDs were saturating due to PI, which could have confused the dither servo. 

If this continues to happen, we can try retuning the angular feedforward for the OMC.  It is possible both this and the confusing noise are related to the PIs being rung up.

Andy, Josh

This doesn't seem like fringe wrapping. We're looking mostly at the time from 2:50 to 3:30 UTC (actually Sep 12 in UTC day), after the IFO has settled a little from the transition from 50 down to 35 Watts, and before the power changes again. We find no optics moving enough longitudinally to make a scattering shelf, though it could be something moving in angle. But also, this doesn't really seem to have the time structure of a scattering shelf.

The first attachment has spectra starting at 2:50 and stepping every 10 minutes. It's very confusing, and things are moving in different directions. But focusing on the feature between 20 and 40 Hz, it's hard to get a sense of what it actually is. The next two attachments are 15-minute spectrograms that show a wide band of noise slowly walking down in frequency. But an Omega scan shows bursts of noise - they don't look like scattering. They also don't look big enough to account for all of this noise, so maybe there's a glitchy bit and a background of Gaussian noise.

The next two plots are coherences with MICH/PRC/SRC at the beginning and end of the period. The coherence is significant with all, and it goes up at the low frequencies toward the end (when the excess noise has moved down in frequency). So maybe it's just because of changing coupling to some auxiliary degrees of freedom.

I'll quickly mention that there's a lot of other things going on. The last attachment is a spectrogram showing a huge moving comb around 300 Hz. We also saw clear RF beatnote whistles. We'll look into all of these more.

The PI difficulties are probably my fault. The phases may not have been set properly after the power glitch.

After damping PIs (Terra is writing about this) we tried to take the IFO back to 50 W, but lost lock within a few minutes.  I'm not sure why we lost lock, it didn't seem to be PI or the usual sidebands tanking problem, there was a glitch in CHARD and DHARD a second before lockloss (1st attachment). 

We spent some time relocking and found that we had some problems durring the latter CARM offset reduction steps which were similar to what we had last night.  We measured the DARM loop at RF DARM and at the state CARM 15 pm, it seems fine (2nd attachment).  

It is possible that our relocking difficulties were due to bad alignment, or the new TCS.  As we were about to try to relock the 3rd time, we got hit by an EQ so we stopped for tonight. 

Here is some analysis of the sideband imbalance.

Synopsis -- Overall, adjustment of the CO2 lasers I did at 50 W improved the sideband imbalance at the AS port

However, the resulting CO2 setting does not match what we expected from the previous test (29585). We expected the final CO2 settings to be [CO2X, CO2Y] = [100 mW , 0 mW], but we ended up with [400 mW, 0 mW].

The 45 MHz seems to prefer a high CO2 contrast of roughly 400 mW (CO2X minus CO2Y) regardless of the ring heater settings so far, and this prevents us from further reducing the common lens.

[The sideband evolution as seen by the OSA]

The below shows a plot of the OSA raw output. I plotted several scans from different times, each of them is separated almost by 10 minutes in time.

Also, here is a rough time line of what I have done in this lock.

• 17:36 The interferometer reached 50 W
  • CO2X and CO2Y were simultaneously reduced to 100 mW and 0 W respectively.
• 18:00 I started increasing CO2X because the sideband imbalance was becoming worse.
• 18:53 I kept increasing CO2X and eventually set CO2X to 400 mW
• 19:24 PSL power was decreased to low power to combat the PIs.

Here is another plot showing how the sideband amplitude evolved as a function of time.

It is evident that increasing CO2X helped reducing the imbalance. Before I started changing CO2X, there was a slow trend in which the imbalance kept decreasing.

Here is another trend plot.

The carrier recycling gain stayed at 29 at 50 W. The sideband build up or ASAIR90 seemed to have reached some kind of equilibrium after approximately 1 hour or so. Also, looking at ASAIR RF 45 Q, I don't see any change in the DARM offset point -- hopefully this is an indication of a stable optical gain. The Pcal line at 331.9 Hz was too small that it was burried below intensity noise. So I could not directly check the DARM optical gain.

The intensity noise coupling changed as a function of time at 50 W. Here is a plot showing several coupling transfer functions from different time.

The measurement time were set to identical to the ones showed in above or 29637. Here is a plot of the transfer coefficient at 400 Hz as a function of time.

As you can see, the coupling became worse at the beginning for about 20 minutes or so. Then it came back to a value as small as the very begining. Although high frequency above 100 Hz seems to have settled to a small coupling, the low frequency part looked worse at the end. See the first attachment.

As for the HWS signals, while the HWSX signal seems reasonable, the HWSY reports a twice large self heating.

Here are some conclusions from comparison of the predicted ITM lensing (outputs from TCS-SIM) and HWS outputs.

• HWSX
  • It looks that we are overestimating the defocus by the self heating in the ITM substrate by 15% or so. This could be due to an inaccurate calibration of the arm power in the TCS simulator.
  • The CO2 actuator coefficient needs to be updated to 25 uD/W (28799). Because we use a high value for the CO2 actuation coefficient, the simulator overestimates the effect by 24 %.
• HWSY
  • The below assumes an accurate readout of the HWSY.
  • The predicted self heat seems to be too low by almost a factor of two.
  • The predicted CO2 defocus is too high by 24% or so. This means the actuation coefficient should be 47 uD/W in the TCS simulator.
  • However, a 47 uD/W is not consistent with what we have measured (28799) -- the past measurement suggested that it should be about 25 uD/W.
• Questions
  • Why does the CO2 X now have a smaller actuator coefficient? In the past it was 62.3 uD/W (T1400685).
  • Why is the CO2 Y coefficient different from a calibration measurement (28799)? The measurement suggested it was 25 uD/W and now it seems more like 47 uD/W.
  • Why the ITMY self heating increased by a factor of two?

The below shows a comparison between the single-pass defocus measured by HWSX and that predicted by simulator (with some coefficient fitting similarly to 27330):

I added a constant offset to the simulated defocus in order to plot it on top of the measured defocus. I removed the ring heater component that was unfortunately in the middle of settling to the equilibrium in the simulator due to the unscheduled model restart (29592).

The below is a same plot, but for the ITMY substrate defocus.

As noted in the legend, the component from the self heat needed to be increased by a factor of two.

The stability of AS90 was apparently better with the combination of the new ring heater setting and dynamically-decreased CO2s.

The below plot shows a comparison of this lock stretch (Sep. 12) and two lock stretches (Sep. 09) from a day before we started changing the ring heater setting.

The two lock stretches from Sep. 09 both showed AS90 decreasing monotonically as a function of time. This was something we have been suffering from (29486) and has been an issue since the begining of this month (29457) at which we considerably changed the interferometer alignment.

In contrast, AS90 settled to a value pf 600 counts on a time scale of 30 minutes or so in the new lock stretch. This lock was stable until PI modes started ringing up. The carrier recycling gain was slightly lower than the previous two stretches. I don't know if this due to misalignment or new ring heater setting.

Here are the evolution of the wavefront gradient as a function of time as seen by the Hartman sensors.

The starting time is set to Sep 12 2016 00:30:30 UTC at which the interferometer was in the middle of powering up to 50 W. The gradients are initilized such that the gradients are zero at dt = 0.

The output filters for both the reflected power and power sum report what look like the correct
values.  For the reflected power signal, the ADC seems fine so it must be the power meter.

Filed FRS #6194 for the apparent power meter failure.