[Sudarshan, Gabriele]
We tried to better dump the beams on IOT2R with a piece of black glass (and dumping the glass reflections with the razor blades).
The PRM was aligned, but to avoid disturbing too much the locking activities, we left the two arms and the BS aligned as well. The PRC flashes made very difficult to get any conclusive result. We think that the 18 Hz bump was not there anymore, but at the end we were not completely sure, since there was too much more noise due to the flashes. We'll try again tomorrow morning, with only PRM aligned.
For the moment we put back the upper mirror and dumped the beams with two razor blade dumps just before the two bottom mirrors. The situation is back as before.
In the meanwhile, we noticed that the periscope was not propely clamped to the table, and we accidentaly moved it. This shouldn't be important. Now we clamped it securely.
The first plot compares intensity noise as measured on the ISS (in and out of loop) signals, on IM4_TRANS and on MC2_TRANS:
The conclusion is that the noise added by the PRM reflection is still there, even though it's not as bad as before. However, in the present configuration, closing the second loop does not give us good performance, since for example on MC2_TRANS we can measure intensity noise as large as 8e-6, worse than when the second loop is open at some frequencies (18 Hz).
To better understand the origin of this noise, I aligned the PRM, misaligned the BS to avoid any IFO fringes, and closed the second loop. The attached figures 2 to 4 shows the out-of-loop ISS signal (SUM58) and another measurement of intensity noise using MC2_TRANS (both calibrated in units of RIN, but MC2 is sensor noise limited at 1e-7 /rHz level).
In conclusion, there is still a lot of scattered / backreflected light coming from this bench, likely already at the level op the upper periscope mirror. We must dump these beam properly.
In the last figure, I misaligned the PRM mirror and I stroke the bench much strongly than before. There is no visible effect. So it's the REFL beam that causes the problem. In addition, we can conclude that the noise that we normally see in the out-of-loop signal is not coming from this bench, but it's something else, still unidentified. One interesting observation from the first plot, is that hen the PRM is aligned, some of the structures visible in the out-of-loop ISS signal are not there. So maybe they are again light from the REFL beam, which is scattered in-vacuum.
Hanford hauling through the Wye barricade will occur on swing shift on Friday 11/21 starting near 2:00 PM but not on day shift, meaning that LHO 1-10Hz seismic should be quieter than usual on Friday until mid-afternoon. ERDF will operate a day shift on Friday.
no restarts reported.
conlog frequently changing channel report attached.
Nic ran Jim's script.
Earlier tonight, we had a large drift in ETMX pitch (1 urad over about 7 minutes). I turned off the sensor correction (ETMX ISI X only) for the last several hours, this seemed to help. Now I've turned it back on so we can see if this continues to happen overnight.
We are leaving the arms locked in green, and the mode cleaner locked. This should give a chance to see if the mode cleaner is really stable when there is no actuation on it.
Thanks Sheila, for reporting this.
I looked for minutes long features into the ISI CPS, at 0am and 4am, but did not find anything obvious over such low frequencies. However, I don't understand why the vertical Stage 1 CPS signal is so low. The local CPS signals should be quite larger if the platform was well isolated. I am getting inertial sensors and optical levers data to look into more details.
[Rich, Fabrice]
At 0am, the time series show a large drift in ETMX SUS top mass, not only in pitch but also in longidudinal, see first plot (the ylabel should say "nm"). According to the Stage 1 T240s (second plot), the ETMX ISI was performing as well as the other units, but this doesn't tell us anything about slow drift, so we need to get back to CPS data (maybe look at the rotations in the cartesian basis for the non-corrected CPS signals).
At 4am, ETMX SUS drift has stopped (third plot), though the sensor correction seems to be on (fourth plot).
K. Venkateswara
One thing to note is that turning sensor correction on is somewhat equivalent to blending at still lower frequencies than the normal 45 mHz. This makes it very sensitive to ambient ground tilt (caused by human activity or wind). It should not be used if there are people/activity near the ground seismometer.
Using tilt-subtraction makes sensor correction less susceptible to wind-induced tilt but unfortunately BRS is very sensitive to gravity gradients from people. So walking near the BRS when it is being used can cause very large low frequency signals to show up in the super-sensor.
Should we ask the operators to turn off the sensor correction at End X if they know someone is headed down there?
Did you and Evan go there around 6 PM? The attached plot shows a spike at ~6:20 PM
In general, yes, it would be better to turn off sensor correction along the horizontal directions during the day if there is a chance of someone being close to the ground seismometers.
Yes Sensor correction should not be on if there is any activity in the VEA.
Sensor correction is a form of feed forward so it assumes that the chamber and ground sensor are seeing the same thing. So someone walking by the ground sensor, making a large local disturbance can produce large motions in the platform
[Rich, Seb, Fabrice]
We are now looking into HEPI to see if it caused the drifts that was observed on the ETMX suspension. Sebastien is processing the data.
Please let us know if this is not anymore of interest because the cause of problem is now known (for instance related to John's comment on temmperature, or Nic's comment on suspension control).
A 1ºC temperature excursion was reported in alog 15212.
Sheila, Alexa, Dan, Nic, Evan
EX/EY:
Setting up sqrt(TRX+TRY):
Attempt at sqrt(TRX+TRY):
Guardian improvements:
Using the L1 screen as a template, I increased the number of matrix elements in the input matrix screen. I couldn't just copy the L1 screen for 2 reasons. First they don't use a ramping matrix but H1 does. Second, they have an additional signal coming into their input matrix.
Their extra signal is the so-called "TR_DARM" signal. One nasty time bomb is that their signal would need to be inserted in the matrix at position 36, in between the TR_CARM and TR_REFL9 signals, shifting those down. So this screen will change all around if that difference is incorporated from L1.
screenshot attached
Sheila, Nic, Evan
The refcav power has steadily declined over the last 10 days. Tonight it got so low that the modecleaner could not maintain lock for longer than a few minutes.
Sheila and Nic have realigned the pointing to the refcav in order to recover the power.
Sheila and Evan measured the FSS path AOM efficiency.
Power levels:
Before the AOM: 64mW
First pass through AOM: 52mW
Second pass: 38mW
First pass efficiency: 81%
Second pass efficiency: 73%
Total efficiency: 59%
here is a trend of the ref cav trans and PSL temperature, its not clear if temperature caused the problem.
This is sheila
SR3 oplev was realigned to the new SR3 angle.
We've found that this oplev had a clipping problem even before SR3 angle was changed. OPLEV SUM used to be about 30000 counts, and after we were done the SUM jumped up to about 66000 counts without changing the whitening setting. Doug thinks that this might be a bit too high a count, but ADC is not railing so we'll leave it as is.
Details:
SR3 oplev had two serious problems that are not related to SR3 angle.
After these were fixed, Doug aligned the launcher such that the return beam comes through the receiver viewport/pipe cleanly. Due to the beam angle shooting up from HAM5, in order to avoid clipping by the receiver viewport, bellows and the pipe, the beam was positioned much higher than the center of the pipe opening at the receiver box.
At this point, we recognized that the oplev sensor couldn't be moved high enough to receive the beam as the vertical stage doesn't have enough range. Actually the vertical stage has a huge range, but at least 3/4 of that range is wasted to be able to lower the sensor to the position where there is no possibility of receiving any beam with any SR3 alignment.
We removed the aluminum part on which the sensor is mounted, Doug made new holes, we remounted the sensor at a higher position (4th picture) and the translation stages were moved until the beam was roughly centered (5th picture), and we used the MEDM screen to fine tune.
A cell phone camera with selfie mode turned out to be quite useful to monitor the beam position when there's no light on the sensor, and that's what was used to take the 5th picture.
The whitening board is already on the lowest gain setting, so I think we cannot reduce the counts that way.
I have turned off the single whitening stage that was on previously (LHO#14756). This won't help if the optic makes large excusions in pitch/yaw and saturates the ADC, but we are so far above the ADC noise that I think whitening is not necessary here. (See first attachment. Blue is with whitening, red is without whitening.)
The SR3 pitch oplev damping loop appears to work fine with no modifications. (See second attachment. Blue is loop off, red is loop on.)
(Alexa, Nic, Sheila)
We measured the ALS COMM OLTF and found the UGF to be ~400 Hz, with a crossover at ~70 Hz. In September we had changed filters in MC2, and CARM as reported in alog 14214 to increase the crossover frequency. I also noticed we had changed our configuration in the LSC_REFL_SERVO CM board relative to what was in model (alog 11109). Now we have:
9:17 Fil to pick stuff up at EX, then to EY PEM cabling
9:56 Doug to LVEA for SR3 OpLev work
9:58 Jeff and Andres to LVEA staging for SUS storage
10:22 Jeff and Andres exit LVEA
10:28 Krishna and Jim to EX for BRS checkup
11:03 Mitch and Jeremy out of LVEA
11:11 Cris to EX
12:02 Sheila and Nic to ISC electronics racks in LVEA
12:04 Fil back from EY
12:32 Doug out of LVEA
15:45 Doug to SR3 for more OpLev work
There has been some concern that there might be excess cps noise in some of the channels. So i looked at 20 minutes of data at 1am sunday night/monday morning.
Looking only above 30Hz where the sensors have hit the noise floor, all of the coarse channels are similar and between 3.5-4.5E-10m/rrtHz about what we expect.
The stage 2 channels show two outliers, ITMX H2 and ITMX V1, maybe BS H2 also but that is close enough so that it could just be at a large offset (we expect the noise floor to go as the gap squared) I'll check that.
The first thing to do is for me to look at another time, and to check the cables and connections for those sensors
I looked at a second data set calling it "B" (24 hours later) ST2 ITMX H2 and ST2 ITMX V1 still show excess noise BS H2 is down to 4.5-5E-10m/rtHz which is a little bit noisy, but probably within what we are calling acceptable. I attached the data because Jeff asked to see the ADC noise on the plot
When I say large offset I mean > 10000 counts, so 1200 counts is centered for this discussion
ITMX Stage2 H2 & V1 CPS offsets are 900 & 3800 counts. While V1 is actually the largest offset of all the BSC CPSs, H2 is 21st of 30 (towards the bottom) of Stage2 CPS offsets. At 1200cts, BSC2 H2 ranks 17th of 30. So the offset maybe an issue for ITMX V1 but the others...? And, what about ITMY V1 at 3700 counts and ITMX V3 at 3200?
Attached are all the BSC medms showing the offsets.
Some additional info regarding the CPS - On the figures are plotted time series, integrated RMS, and ASD down to low frequencies. Somme comments:
- At high frequencies, not much to add on sensor noise (ITMX and BS both have two CPS untis with elvevated sensor noise on Stage 2). I looked at data of the Nov 17th, 18th and 19th, and get similar results.
- All Stage 1 CPS units are within 1um p2p, except BS horizontal that is moving 4 times more. Something to look into.
- At the microseism, the three vertical sensors are moving in sync, on all stages of all platforms. Probably normal (the platform is inertially decoupled down to the micro-seism with th 90 mHz blends)
- The low frequency motion amplification is about 100 times larger in the vertical directions than it is in the horizontal directions.
The 5 figures in the previous log are for data ten on the 17th at 3pm PT.
Results and comments are similar for the 18th and 19th, except for ETMX (attached plot) that shows different behavior at low frequencies, as expected with the sensor correction that was turned on Tuesday. It also shows features on Stage 2 at the SUS resonances, that might need to be doubled checks.
Could this be related to the trips on ITMX? (alog 15021)
this log seems to have gotten hijacked
I check the HAM-CPS and they all seem to be good at high frequency
Alexa, Dan, Nic, Sheila, Evan
Tonight we made some improvements to our automation, and we reduced the CARM offset with DRMI locked on 3F.
I have attached DRMI spectra on 1f and 3f with the arms off resonance (1kHz green COMM offset). The first plot is the DRMI 1f configuration; Kiwamu pointed out that one can see the periscope resonances that are present in ALS COMM noise appear in the DRMI signals. The second attachment is of the DRMI 3f configuration, and these noise features are less prominent.
Relevant UTC times:
Great progress! About the ASC, L1 uses REFL_B_45Q -> SRM with bandwidth of 100 mHz ( LLO 13513 ) in the first part of the locking sequence, as AS_RF36_I for SRM didn't work well ( LL0 13358 ). Here I see that you are using AS_RF36_I for SRM ASC in DRMI without arms...just checking.
Thanks for the information Lisa.
Also, for the record, here are several times that we lost the arm locks last night without a known reason (at least, we didn't think we were doing anything stupid at the time that would have caused the lock loss). All times are UTC, Nov 19, and the lock loss should be several seconds before the time I wrote down.
2:36:27, 3:06:34, 5:58:43, 6:12, 6:25:08, 6:51:07, 7:40:50
Here is the sensing matrix of DRMI3f with 7 nm (= 1000 Hzgreen) CARM offset. I extracted this using the three calibration lines that were injected during the locking period: 131.7 Hz, 6000 ct into PR2; 183.7 Hz, 1000 ct into BS; and 152.9 Hz, 6000 ct into SR2.
In the following table, the first number in each pair is the magnitude (in ct/ct), and the second is the phase.
PR2 | BS | SR2 | |
---|---|---|---|
RF27 | 7.6(1.2), 3.4(3)° | 0.29(6), 151.3(7.8)° | 0.07(3), -70(110)° |
RF135 | 12.3(2.0), 139.7(4.5)° | 0.7(3), -84(35)° | 1.6(4), 6(14)° |