It seems that what has been typical noise in the 15Hz-35Hz range has settled down to the preferred reference. That being said there seems to be a new feature (at least to me) that is occuring from approx 70Hz to around 200Hz. I took a snapshot of the DARM spectrum. I'm not certain when this began to look like this but judging by the downward trend in the BNS range it looks to be on the order of the last couple of hours. Range at this moment is 46Mpc.
10:04:30UTC
Insection Guardian is, and has been,set to INJECT_KILL.
H1 is in Observe Intent
1 hour stand down time is being initiated.
forgot to mention that I spoke with LLO to confirm the alert was heard by them as well.
1 hour stand down expired.
Nothing noteworthy to report. Plots show normal consistencies between humidity fluctuations and front end diode powers. Incursions for FSS alignment are evident in environmental plots.
Looking back I believe the task number is a typo. It's supposed to read 6130. uups.
TITLE: 01/13 Eve Shift: 00:00-08:00 UTC (16:00-00:00 PST), all times posted in UTC
STATE of H1: Observing at 58.0094Mpc
INCOMING OPERATOR: Ed
SHIFT SUMMARY:
It's another cold night where our Temperature Sensors hit 0degF (& then go to 6553degF!). H1 in OBSERVING the majority of the shift.
LOG:
Have heard noises from within the Control Room. Not sure what they can be. We have piles of snow on the roof. I have gone out after most of the noises to see if a pile of snow or ice has fallen, but have not found anything obvious. As noted below, some of these bumps corresponded with a glitch seen on H1's DARM. Here are some of the times I noticed hearing these bumps in the night:
Over halfway into my shift I happen to glance up at the PI StripTools and noticed something amiss: Mode27 was flat & elevated!
Sure enough on VERBAL_ALARM, this mode rung up at 2:16utc & I didn't catch it until 5:13utc. I immediately flipped the sign on its phase and this brought it down. While it was elevated a few channels looked odd (Mode 24 was flat and lower for instance). Attached is how these Modes & H1 Range look over this time.
Surprised H1 stayed locked over this time. Surprised to see range approach 70Mpc toward end of elevated MODE27 ring up.
All quiet & cold (below 5degF) tonight. Feared some EQ might rumble us a bit, but they didn't pan out here. H1 at NLN for 5hrs with a range of 60-65Mpc.
It was noted by Stuart Anderson that applying the kappas has a drastic effect on h(t) around the cal line frequencies, as seen from ASD ratio plots of h(t) with and without kappas applied (see attached plots). It turns out that this is due to the fact that the DARM line is injected into the DARM loop right after the digital filters, affecting its phase in the residual and control chains in a way that causes them to partially cancel when added. See the subway map: https://dcc.ligo.org/DocDB/0122/G1501518/014/darmschematics-v14.pdf Applying the kappas affects the degree of cancellation, as they multiply the residual chain and the tst and pum/uim stages of the actuation separately. To see quantitive analysis of the data that produced the plots below, refer to the pdf attachment.
Please see LLO alog 30874.
Robert, Valera, Anamaria
A few further points, using the same methods as in the link above:
1) If H1 had the same jitter noise but the L1 coupling, things would be kind of alright for the current noise/power - see first plot.
2) Comparing to O1 couplings there are some interesting things... We did two tests, one in the beginning and one at the end, after Robert's work. The couplings and, as such, the DARM contributions, are vastly different, see second plot comparing the two injections. Something reduced the coupling between these two points, perhaps Robert's adjustment of IMC WFS offsets. Then it got big again in O2... If we could get to the coupling at the end of O1, life would be grand in psljitterland.
The third plot compares all three "states", beginning of O1, end of O1 and O2 in terms of ambient jitter as seen by IMC WFS A DC (in lock) and the coupling functions. Notice that there was something strange going on in the beginning of O1 with these signals, they show ridiculous 60 Hz harmonics - perhaps some grounding/wiring problem that was later fixed.
The fourth plot does the same comparison, but with the periscope motion (for completeness).
As far as L1 is concerned, we have the same coupling and approximately the same noise as in O1, so I'm not adding those plots here.
I suppose it's possible that H1 has always had jitter issues but they were not obvious (I definitely didn't appreciate the scale) ... until the noise was exacerbated by the HPO and the detector noise at higher power was low enough to see it.
One difference between O1 and O2 for H1 is the laser power. We are currently running with 30W input, whereas it was 22W for O1. One observation we made during the last commissioning period was that the coupling seemed strongly dependent on the initial alignment.
Topped Crystal Chiller with 175mL. Diode chiller was green/OK. This closes FAMIS 6505.
TITLE: 01/13 Eve Shift: 00:00-08:00 UTC (16:00-00:00 PST), all times posted in UTC
STATE of H1: Observing at 61.1842Mpc
OUTGOING OPERATOR: Patrick
CURRENT ENVIRONMENT:
Wind: 4mph Gusts, 3mph 5min avg
Primary useism: 0.02 μm/s
Secondary useism: 0.20 μm/s
Clear skies out, but it is chilly (under 10degF) & luckily winds are minimal.
QUICK SUMMARY:
After some OMC work Patrick took H1 to OBSERVING.
Group of us ventured out to see the sunset (since we've not had the sun last few days) from the roof observation deck. We have some big snow drifts on the roof & also ice in spots as well.
This morning we sat in nominal low noise without going to observing from 19:21 to 19:51 UTC (Jan 9th) in a configuration that should be much better for the 1084Hz glitches. (WP6420)
On Friday we noticed that the 1084Hz feature is due to OMC length fluctuations, and that the glitch problem started on Oct 11th when the dither line amplitude was decreased (alog 30380 ). This morning I noticed that the digital gain change described in alog 30380 that was intended to compensate for the reduced dither amplitude didn't make it into any guardian, so that we have had a UGF that was a factor of 8 lower than what I used when projecting OMC length noise to DARM: 30510 The first attachment shows open loop gain measurements from the 3 configurations: before oct 11th (high dither amplitude), after october 11th (lower dither amplitude, uncompensated) and the test configuration (lower dither amplitude, compensated).
We ran with the servo gain set to 24 (to give us the nominal 6Hz ugf) and the lowered dither line amplitude from 19:21 UTC to 19:51 UTC Jan 9th. You can see the spectrum durring this stretch in the second attached screenshot, in the test configuration the peak around 1083Hz is gone, with just the pcal line visible, and the OMC length dither at 4100Hz is reduced by more than an order of magnitude. You can also compare the glitches from this lock stretch with one from yesterday to see that the glitches at 1084 Hz seem to be gone. This is probably the configuration we would like to run with for now, but we may try one more test with increased dither line amplitude.
Other notes because we don't have an operator today due to weather:
This morning all 4 test mass ISIs were tripped probably from the Earthquake last night that brought the EQ BLRMS to 10 um/second around midnight UTC. ITMY tripped again while it was re-isolating, no problem on the second try.
Richard topped added 400mL to the TCSY chiller around 10:15 or 10:30 local time, since we were getting low flow alarms. The flow alarms came back a few minutes before 11am local time.
I went through inital alingment witout problems and got to DC_readout transition. Then I measured the UGF of the OMC length loop in preparation for increasing the dither line height From that measurement and trends it became clear that when the OMC dither amplitude was reduced, the compensation of the OMC digital gain described in didn't make it into the guardian. This means we have been operating with a UGF in the OMC length loop that was a factor of 8 too low since mid october.
We arrived in low noise at 19:21 UTC with the OMC ugf increased to 6Hz. After about a half hour PI modes 27 and 28 rang up, and I wasn't fast enough to get them under control so we lost lock.
Here's a graphical version of what Sheila wrote, showing the time on Oct 11 when the 1083 Hz glitches started. The dither amplitude was reduced at 3:20 UTC, but the servo gain was increased to compensate. There are no 1083 Hz glitches at this time. Severe RF45 noise starts an hour later and lasts until the end of the lock. The 1083 Hz glitches are evident from the beginning of the next lock, and persist in every lock until the recent fix. The dither amplitude stayed low in the second lock, but the servo gain was reset back to its low value. Apparently, both need to be low to produce the glitches.
Keita tells me that people are concerned about making this change because of the increased noise below 25 Hz in the screenshot attached to the original post. We did not run the A2L decoupling durring this lock strech, and it was not well tuned. The shape of the HARD loop cut off at 25Hz is visible in the spectrum, which is one way of identifying bad ASC noise. The high coherence between CHARD P and DARM at this time is another way of seeing that this is angular noise (attachment).
So I think that this is unrelated to the OMC gain change and not really a problem.
1080Hz removal OMC gain/line conditions, does it make more low frequency noise?
Josh, Andy, TJ, Beverly
Conclusion: For two on/off times each for the two OMC gain tests (total 8 times) it looks like the high gain / low line configuration that takes away 1080 Hz (and also takes away some bumps around 6280Hz) coincides with a bit more noise below 25Hz.
Request: We hope this connection with noise below 25Hz is chance (It might have just been drift and we chose times unluckily) and we would like debunk/confirm it. We could do that with a couple cycles of on/off, (e.g. 5 minutes each, with the current configuration vs high gain / low dither configuration).
See the attached PDF. The pages are:
Also: There is no coherence above 10Hz between STRAIN and OMC LSC SERVO/I for any of these test times. So coupling must be non-linear.
Also: When the 1080Hz bumps disappear we also see a bump around 6280Hz disappear (attached image, sorry no x-axis label but its 6280Hz)
Our post crossed with Sheila's. If possible, we'd still like to see a quick on/off test with the A2L tuned. Could we have five minutes with the gain high and then ramp it down? Maybe with one repeat. Since this is a non-linear effect, we'd like to make sure there's no funny coupling with the CHARD noise. We're not too worried by excess noise below 25 Hz now, but it might be important when we're able to push lower.
While LLO was down I attempted to do a test by increasing the OMC length gain while in lock, which unlocked the IFO. So on/off tests aren't possible. Edit: I broke the lock by changing the gain after the integrator (which had been OK when not on DC readout), we can change the gain upstream instead without unlocking.
For now I put the new gain into the guardian so the next lock will be with the increased gain, and hopefully see that the low frequency noise is fine.
Now we have relocked, Patrick ran a2l, and Jeff, Evan, Krishna and I did an on off test by ramping H1:OMC-LSC_I_GAIN:
The attached screen shot using the same color scheme as in the presentation above shows that there is not a difference at low frequency between high gain and low gain.
We are back in observing in the low gain configuration, but the gain is set in an unusual way (and accepted in SDF so that we can go to obsevering). Keita would like us to hear confirmation from detchar before making this permanent.
Thank you Sheila, this looks really good. No change at low frequency. 1080Hz gone. The 6280Hz just varies on its own timescale. From our end we're happy with the configuration change since it only does good. Sorry for the red herring about low frequencies.
16:29 Fil , J. Batch ad John Worden out to LDAS.
16:42 Jim. Johm and Fil back from LDAS. Electrical panels are tripped. Electrician is on his way to investigate. Still not sure what order things went down.
16:46 Lockloss EQ
16:50 Switched ISI config for Large EQ in Northern California.
17:04 Switch ISI config back to Windy after quick decay of EQ
17:20 GRB alert. H1 not locked
17:34 H1 locked and observing. Monitoring f1 violin modes which are slightly rung up.
19:14 Fil reports that the LDAS power panel trips were due to the room, first, overheating. Queries into remote monitoring of LDAS room temps are being made.
19:17 filed FRS ticket for noisy ops station computer fan.
20:12 lockloss HAM5 and 6 ISI tripped
20:20 HAM5 CPS glitching. Jim out to power cycle chassis in CER.
20:34 Jim and Fil out to LVEA to physically "exercise" CPS connections.
21:30 Recieved Hanford Release advisory. Decided that I should get my non-snow ready vehicle home. TJ is there as well as Patrick who is the evening shift operator.
Assuming Ed meant to mark this entry for 12/14.
Assuming Ed meant to mark this entry for 12/14.