I have increased the chilled water set point by 5 degrees F to 45 F on the corner station chiller.
After tweaking the alignment into the pre-modecleaner, I measured the power noise spectra
for both photodiodes PDA and PDB when either was used as the in-the-loop sensor.
The plot PDA.png is for when PDA was used as the in-the-loop sensor. PDB.png is for when
PDB is used as the in-the-loop sensor. When the ISS is off, in both cases the free-running
power noise measurements agree quite well. However the in-the-loop and out-of-the-loop spectra
disagree quite badly when PDB is used as the in-the-loop sensor. The in-the-loop noise suggests
there's enough gain in the loop in this case with the level being ~1.0E-8. The out-of-the-loop
spectrum is more than a factor of 10 higher, which suggests there's a difference in the two optical
paths (most likely beam pointing).
Not sure why at this stage. I would probably use PDA as the photodiode to be used as the
loop sensor (for now).
The BRS at EY has had a long term drift requiring periodic recentering. That drift seems to have stopped or changed sign, following the power outage on Saturday. Attached image is a 60 day trend for H1:ISI-GND_BRS_ETMY_DRIFTMON. The black streaks are from when the BRS went out of range and when it was recentered during Krishna's last visit. The little blip up to zero at the end is from the power outage, before the commissioners recovered the BRS code. Second image is the last 6 days, outage is when the signal goes to zero. Definitely looks like the drift has changed sign.
I checked the temperature ('H1:ISI-GND_BRS_ETMY_TEMPR') and it looks a bit lower than normal, so it doesn't account for the change in the drift. It may be good to go to EndY and check on the Ion pump controller and make sure that it is ON? If it didn't get turned on after the power outage, a rising pressure might be the cause for the change in drift. The Ion pump controller should have a High Voltage indicator which should be on and clicking the OK button should give you the pump current and pressure reading.
The ion pump was off. It took a couple tries to get it to come back on. Voltage was around 5200V and 9-12 mA when I left the end station, pressure was already back to ~1E-5 torr. The power supply is kind of hidden under some other stuff, under the beam tube. Gerardo tells me that the power supplies at each end station are different, the one at EX comes back on it's own, EY doesn't. I'll see about adding a note to the start up procedure in T1600103.
IP power supply status should be added to vacuum GUI in CDS so we can catch power failures right away.
Dave, Patrick Restarted all web medm screenshots on script0.
And all other driver dofs are quiet as well. Remember, Monday night 29667, this channel, H1:ISI-BS_BIO_IN_CD_ST1_V3_STATUS, was dropping to zero, indicating a thermal problem. Checks suggested the coil driver was not actually sending the bad signal and the BIO Chassis was responding appropriately to simulated state changes. The I/O computer cards were reseated and by default, all the machines were power cycled. Maybe we've seen the last of this issue for the time.
Sheila, Matt, Lisa The ISS has been oscillating a couple of times when reaching 50W in the last two locks. Sheila fixed that by turning off the AC coupling. We leave the IFO locked at 50W with the ISS AC coupling off, at Sep 15, 9.45UTC. It has been locked for about 20 minutes, powers are stable, no PIs. Matt updated SDF with the latest PI settings. We just noted that the PSL NOISE EATER is oscillating -- so please fix that in the morning.
The 50 W lock lasted for about 3 hours. It is unclear what broke it. There were two PI modes (modes 10 and 26) which rung and weren't successfully damped. See the attached.
It's possible MODE 26 broke the lock, although lockloss occured when the amplitude of the mode was much lower than the usual breaking point. We're still re-finding settings after the ETMY ring heater change that happened yesterday afternoon and probably the gain sign was wrong on this mode.
More interesting is the unusual broad noise between 14kHz and 16kHz seen the entire lock. In spectra below, orange is OMC trans showing high frequency behavior during last nights lock and a reference 'normal' lock from a few hours prior. Despite the suspicious frequency range, we don't think this noise is associated with PI (we've checked to make sure we weren't injecting, had wrong settings, etc.); even very high amplitude PI create a symmetric peak with much higher Q. Perhaps laser noise?
Below left is just after locking last night (note the cursor is sitting ~15410 Hz, an area where there's no known mechanical modes). Below right is ~5 seconds before the lockloss 3 hours later. PIs are ringing up in the latter, but amplitudes are below those that have broken locks in the past.
Below is a 'normal' spectrum from a lock earlier in the day while two PIs were ringing up to similar amplitdue.
Sheila, Lisa, trying to summarize the work of many people today * More Intensity Stabilization Science made possible to engage all of the ISS loops and lock several times at 50W; * The lock at 50W had been broken earlier today due to the inability to damp the ETMY Mode 27 (18041 Hz). This triggered the decision to turn off the EMTY ring heater (see Terra's elog ). After that we had a couple of stable locks at 50W, when Terra and Matt were able to keep all the Pis damped, and the sideband power and the recycling gain were stable. As Kiwamu already observed, it looks like the current combination of ITM ring heaters and CO2 powers is good (enough) to prevent the sideband power and the recycling gain from dropping (note: Corey and Kiwamu noticed a drop in AS90 in another 50W lock later in the evening (see Corey's entry ) and they had to deal with some PI damping, but that lock was done with no CO2 X power, instead of 400 mW, as Kiwamu was exploring CO2 tuning); * After more than 2 hours at 50W we started some low noise steps. Evan engaged the OMC whitening filters, but that didn't help at all unfortunately, as we are entirely dominated by intensity noise above 300 Hz. Looking at the noise budget from O1, a by-eye estimate tells us that the current level of intensity noise is at least ~300 times worse than during O1, even more at some frequencies. The noise is also worse than what it was during ER9 (when the HPO was operational). Sheila's entry shows indeed that the intensity noise coupling to the interferometer is about 3 times worse than it was during O1; also, the ISS out of loop sensor is about 3 times higher than previously measured, showing coherence with PSL accelerometers. If you add that the current ISS loop has a factor of 2 less gain than during O1, while the intensity noise with the HPO is 30 times higher, well..the factor of 300 worse noise than during O1 makes sense. So the bottom line is: * we are close to a stable 50W configuration, it looks like PIs can be controlled, and the sideband power can be stable; need to work on robustness from lock to lock; * the intensity noise is huge, and it dominates the noise above 300 Hz; trying to get more gain out of the current ISS loop didn't prove successful tonight, so we need a better strategy. Probably we should start by going in the PSL and realign the PMC and see if it improves the ISS out of loop PD spectrum.
Lisa, Sheila
We have had 2 more incidents of locklosses where the ISS autolocker unlocks the interferometer in response to an ISS saturation. (described last night as well)
Here is a plot very similar to last nights, showing one of these locklosses.
Sheila, Lisa, Keita, Daniel, ...
Here are a few plots ilustrating our intensity noise situation.
It seems possible that a worse alingment on the PSL table since July (ER9) is contributing to our worse intensity noise. It might be worth considering a PSL incursion to align through the PMC better to take care of some of these peaks, as seen by the first loop PDs at least.
Walked in to a locked H1 and several tests going on. After a while H1 dropped out & then Daniel/Keita ran some ISS arm power scaling tests.
After these tests I wanted to get H1 locked up at High Power. Similarly to last night DRMI & PRMI locking looked quiet. So I went & used Sheila's trick of pushing the BS (see note in her alog about this & how to end the excitation). This seemed to work in that PRMI was able to lock up...but I also tweaked the BS to bump up the PRMI flashes.
Took H1 up to INCREASE_POWER (I assumed it would take H1 to 30W, but it actually kept on going....at around 54W, I went ahead and selected 50W.). I kept H1 at 50W for some high power locking. Here are some notes from the lock thus far:
FOM/Nuc5 Note:
I tried to fix nuc5, but after reboot, the seismic DMT viewers were not getting data from correct time. Is this a kerberos ticket issue? Do we have instructions on this?
Seismic Config Note:
EX was taken to Windy NO BRS because Nutsinee was going to go in the VEA & just wanted to be safe. EX ISI was returned to Windy config after she exited the VEA. In hindsight, looks like we didn't need to do anything (her incursion wasn't seen on the STS).
We are having trouble relocking the modecleaner, with FSS oscialltions.
This could have something to do with the new ISS 2nd loop, but the ref cav alignment seems to have drifted in the last few days.
4:20pm local Went out to overfill CP3 and found that the exhaust is dripping LN2 and the exhaust pipe is frosty. I did not open the bypass LLCV, and instead lowered the LLCV value from 18% to 16% open. Picture attached.
Title: 09/14/2016, Day Shift 15:00 – 23:00 (08:00 –16:00) All times in UTC (PT) State of H1: IFO is unlocked. Commissioning: Daniel & Keita working on ISS Second Loop Outgoing Operator: N/A Activity Log: All Times in UTC (PT) 15:00 (08:00) Start of Shift 15:55 (08:55) Karen – Cleaning in the Optics Lab 16:45 (09:45) Dave – PSL ISS Model change and DAQ restart Title: 09/14/2016, Day Shift 15:00 – 23:00 (08:00 – 16:00) All times in UTC (PT) Support: Jenne Incoming Operator: Corey Shift Detail Summary: Relocked the IFO at DC_READOUT on the first attempt without running an Initial Alignment. Commissioners are working on the ISS Second Loop. After initial lock was broken, had to rerun Initial Alignment. Once complete the IFO was relocking with little operator’s intervention. The interferometer was locked for most of the day while the commissioners continued improving the system.
We turned the ETMY ring heater off (.55 W --> 0 W top and .55 W --> 0 W bottom) at 21:00 UTC.
Change was made since we seem unable to damp ETMY Mode 27 (18041 Hz).
Change seems effective. We just had ~2 hour lock during which we passed through the RH change transient peak and all PIs are dampable; we're no longer sitting over the 47kHz mechanical modes that were undampable this morning. We've been slowly changing modes over to PLL damping (as opposed to just static BP + phase filters). The potentially problematic Mode 2 (15520 Hz on ITMX) became unstable during the lock but remained damped with the PLL. We've confirmed that some too-high damping gain, even below ESD saturation values, will indeed make damping efforts ineffective; something along the way must be saturating. Damping using the PLL solves this as it outputs some fixed gain that we can keep below this 'bad' gain level (~30k cts).
Corey, Sheila
Tonight we have very low ground motion (useism band 10^-1 um/second earthquake band 10^-2um/second)
We have been using awggui to add an 8000 count sine wave at 0.1 Hz to the BS M1 LOCK L filter bank (which has a gain of 0.1). This is helping us to catch fringes more often tonight, and we are manually ramping it off once DRMI locks. This would be a good idea for operators who find themselves havign trouble locking DRMI in low ground motion.
To do this, use a terminal and type awggui. Set it up like the attached screenshot. It is a good idea to start with the gain (bottom middle) set to 0, hit set/run, then ramp the up to 8000 by hitting set in the gain box.
How does one manually ramp off this excitation? I set gain from 8000 down to 0 & the ramp time from 1 to 10 and then hit the Set button, but I wasn't sure if this did anything (the excitation was still seen on the CDS Overview for H1SUSBS).
I couldn't find instructions on killing/clearing testpoints in the wiki, but luckily Kiwamu was here and he knew the command:
> tpclear 31 *
This cleared the excitation.
Sheila let me know that I could have taken care of the excitation by taking the gain from 8000 to 0 and then EXIT-ing the awggui session. Will try this next time.
Evan H., Jenne, Matt, Kiwamu,
We locked the interferometer at 50 W with the latest ring heater setting (RHX = 0.5 W, RHY = 2.5 W, 29588). So far the interferometer has been locked at 50 W for roughly 1 hour.
P.S. we have now having difficulty damping a PI mode (mode2, 15520 ITMX) and decreased the PSL power back to 30 W.
[DRMI lock on POP sensors]
As reported yesterday (29601), we had a difficulty in switcing the sensors from the 3fs to 1fs earlier today (29603). In the end, I manually executed the sensor switch process one by one and for some reasons this was successful. I then measured the open loop transfer functions of the DRMI LSC degrees of freedom, but they looked OK. See the first attachjment. This may be due to that we did not wait for long enough time to let the new CO2 setting settle (29603) for lock acquisition ([CO2X, CO2Y] = [500 mW, 1000 mW]). Not sure.
Also, in lock acquisition, I manually kept aligning PR3 when the interferometer was at ANALOG_CARM in order to maintain the lock.
[CO2 tuning at 50 W]
This is not well tuned, but the below is an OK CO2 tuning for 50 W which gave us a 30% imbalance at the AS port OSA.
[CO2X, CO2Y ] = [300 -400 mW, 0W]
This time I did not spend time for tuning the dCO2 at 20 W or 40 W. Maybe I should have done that to collect more data points.
[PIs]
MODEs 17 and 27 needed a sign flip. Mode 27 seems tricky -- every time when it rang up we needed to flip the control sign.
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.
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.
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.
