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, Evan, Sheila)
We roughly centered the EX IR QPDs; the beam is now on all four quadrants, however, more fine tuning could be done. The beam was slightly off in yaw common to both QPDs, and already fairly well aligned in pitch. I adjusted picomotor M14 by ~200 steps in yaw to bring the beam center on the QPDs. I did not have to adjust M4, which would affect the IR transmitted beam onto ISCTEX, and potentially clip the green beam. The current picomotor positions are:
M14: X = 53045, Y = -38603, M4: X = 9267, Y = 1665
The sum show about 1000 cnts on QPDA, and 700 cnts on QPDB. This is consistent with the power budget (alog 10006), so I believe this is the real beam and it is now centered enough.
I did something similar for EY. QPDA was farily well centered, with the beam on all four quadrants. QPDB was off a bit; so I adjusted M14 in both pitch and yaw, to get this beam better centered and on all four quadrants. This adjustment did not move QPDA all that much. There does not seem to be a picomotor position readback for EY ???? They are all zero. The sum show about 840 cnts on QPDA, and 760 cnts on QPDB.
J. Warner, K. Venkateswara
Jim installed Rich's SC filters to all sensor correction filter banks. This afternoon, I turned on ETMX SC to Stage 1 using the tilt-subtracted ground sensor and then for ITMX using the normal ground sensor (STS) along X. For Z, SC to HEPI was enabled for both chambers. Sheila then aligned the arms and locked them using ALS.
The aim was to observe if SC reduced arm motion between~ 50 to 500 mHz as indicated by the local sensors while keeping the low frequency motion small. The noise in this band seemed lower, but unfortunately activity at ITMX increased ground motion as measured by the seismometers which ended up re-injecting excessive noise at low frequencies. This test should be repeated later in the evening or night when activity at the corner is reduced.
For the moment, I have left tilt-subtracted SC on at ETMX and SC off at ITMX.
As per Aidan, I set all 4 of the LOWER RH RTD channel calibration gains and offste to their nominal setting. Likely these were not input after the summer vent or they were over written sometime since. Settings for all 4 should be:
LOWERRTD_GAIN = 50 (K/V)
LOWERRTD_OFFSET = -257 (C)
One arm RH calibration medm screen shot is attached.
Gabriele, Sudarshan
We were able to close and open the ISS Second Loop with attached python script.
Some details about the script:
These python script will be eventually implemented on the IMC Guardian.
Note: We tested it 10 times in a row and it never failed.
I've been asked to investigate the proper (or not so proper) operation of the SUS AUX / monitor channels. It appears that, in particular, the L1 stage of ETMY has some questionable counts in the NOISEMON (all 4), the FASTIMON (LR) and the VOLTMON (UL). I've done an excitation of 4Hz with an amplitude of 10 cts on all stages (Pitch) of ETMY and taken measurements. Below are the results.
K. Venkateswara
Attached plot shows the various temperature sensors at EX. The thermistor temperature sensors temporari;y use the PEM tiltmeter channels as described in 14825. The two left plots show the thermistors and the top right plot shows the PEM temperature sensors. The very low frequency position of the beam-balance is also a sensitive thermometer as seen in the lower right plot.
There seems to be some oscillation in the temperature control loop for the VEA seen in the last 1-2 days. May need some tuning.
Nic, Sheila, Alexa
We pulled the CM summing junction from R4 (in the ISC racks by the PSL, the one closest to HAM1). The OK light was not on and the measured transfer function was -80 when it should have been 0dB. The TF from the excitation to the output was also garbage.
To have maximum power transmitted by the IMC, I had to move the beam on WFS_A a bit out fo the center (WFS_A_DC_PIT = 0.1, WFS_A_DC_YAW = 0.23). I was not able to recover the same power with centered WFS and an offset on DOF1/2. But maybe just because I didn't have much time to try. Right now, I'm leaving the IMC angular control runnng without any offset. Intensity noise should be good enough.
In a previous report I showed that the beam can wander on the IMC WFS by something like 0.1 in QPD normalized units. To understand how much this can affect the optimality of the IMC alignment, I moved the beam on WFS using the picomotors, and tracked the change of jitter to RIN coupling.
I injected a 11 Hz pitch line on the PZT (amplitude 0.5) and a 17 Hz yaw line on the PZT (amplitude 2) and looked at the amplitude of induced RIN, both in the second loop signals and in IM4_TRANS. All signals gave consistent result, so here I'm quoting only one value.
Here are the raw results. The first four columns give the deviation of the beam position with respect to the initial one (which was not centered)
WFS A pitch | WFS A yaw | WFS B pitch | WFS B yaw | 11 Hz (pitch) RIN x1e-6 [1/rHz] | 17 Hz (yaw) RIN x1e-6 [1/rHz] |
---|---|---|---|---|---|
0 | 0 | 0 | 0 | 8 | 8 |
+0.1 | 0 | 0 | 0 | 6 | 13 |
0 | -0.1 | 0 | 0 | 10 | 8 |
0 | 0 | +0.1 | 0 | 5 | 24 |
0 | 0 | 0 | +0.1 | 8 | 8 |
The effect is not so small, in particular a pitch miscentering of the beam can increase by as much as a factor 3 the coupling of jitter to RIN.
So it seems that the normal wandering of the beam on the long period can give some IMC misalignment that will cause a significant worsening of intensity noise. One solution would be to implement the beam size modification already done at Livingston.
re 15131, attached are pdfs of spectra for the ITMY HEPI L4Cs around 1am Tuesday and Wednesday before and after I made these changes Tuesday morning. The first two pages are the individual runs and the third crowds things up and puts them on the same plot to maybe improve the comparison.
Bottom line--some places better some not as good even considering the differing ground motion. I think these controller could be more aggressive if we want.
apologies for not being more clear o which is which. The earlier time, gps 11003xxxxxx is before 11004xxxxxx is after. On the busy third plot, the first ground and first L4C races are the early time (before) and the second ground and L4C traces are at the later time, after the change.
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)° |
J. Warner, J. Kissel, K. Venkateswara
After improved modelling of sensor correction (SC), thanks to Rich M. (615, 623), we re-attempted SC along X (and along Z). X sensor correction was to stage 1 ISI, while Z was on HEPI. Unlike our previous attempt (14896), we used Rich's SC_filter described previously in 14570.
The first pdf shows the ASD from before SC for X and Z. Stage 1 T240, CPS and ground motion is shown and the coherence between them. The second shows the platform motions after SC. The third pdf shows a comparison between the configurations as measured by the T240 showing the expected 2-5 factor improvement between 0.1 to 0.5 Hz. It also shows an improvement below that which is more surprising (maybe from Z SC?). There is no visible re-injection of noise (factor of ~2 is epxected between 20-40 mHz), because we are probably dominated by pre-existing noise which is larger. More testing will be done tomorrow. The OpLevs are currently mis-aligned so I can't see the effect of SC on them.
Note that the we did not use tilt-subtraction at the moment because wind-speeds were practically zero. We will test the tilt-subtraction when winds pick up a bit.
Once again, if this appears to be adding noise instead of helping, the comissioners can turn it off from the ETMX ISI medm screen as before.
Looks like the X arm is better behaved this time. I've attached ASD of the ALS-X control signal and the Stage 1 CPSs for ETMX and ITMX from tonight's locking.
This morning, I tried using the tilt-subtracted ground super-sensor for sensor correction along X, rather than the plain ground sensor. The attached pdf shows the Ground Sensor (T240), the super-sensor, Stage 1 T240 X, BRS RY OUT * g/w^2 and the Stage 1 CPS. Please note that the CPS data is after the sensor correction (it is input to the blend filters), hence it is should be less than the ground motion above ~100 mHz.
The plot shows that in non-windy periods, the super-sensor is not much noisier than the regular ground sensor and tilt-subtracted sensor correction is therefore about the same as regular sensor correction.
A second round of testing on the all-metal 3IFO QUAD unit Q7 is attached. After we saw a few cross coupling terms and struggled with coherence in the prior measurement set, we made a few adjustments to the QUAD mechanics. However, readjusting the lacing cabling and retuning the sensor mounting tablecloth seemed to not help much. There is still L and R bleeding into P on the reaction chain. We were able to improve the coherence by building a fort around the test stand however. The main chain looks to be in pretty good shape though.
The first attachement below is of Q7 with damping on and off.
The attachment below is of the Q7 (pink traces) undamped TFs compared to the 3IFO Q6 and Q8 units.
Screenshots of damping filters for DC offset diagnosis.
Spectra for all stages of Q7 attached. Note that the L1 and L2 stage OSEMs are not aligned and centered.