I used the sitemap to look at the code revision numbers of each timing device. All DuoTones, Master/Fanouts, and Comparators are programmed to the correct code revision (documented at https://awiki.ligo-wa.caltech.edu/aLIGO/TimingFpgaCode). The 3 issues are: 1) The C_MA_A IRIG-B in the MSR shows Rev. 0. This is a known issue and will be corrected by reprogramming the IRIG-B when possible. The IRIG-B seems to be producing the correct time code output, so we're going to test the effect of a temporary (< 15 minute) interruption to the IRIG-B signal on an IRIG-B device in the test stand to see whether we can reprogram the MSR IRIG-B without causing hiccups. 2) The other 2 IRIG-B in Y_FO_A and X_FO_A show Rev. 133. They should show Rev. 113. They are otherwise operating nominally. It is possible that the timing wiki needs to be updated, or that the revision number was entered incorrectly in the firmware source code. 3) All of the Oscillator Locking slaves in Y_FO_A, X_FO_A, and C_FO_A show Rev. 83, which is the deprecated code. They are operating nominally. Again, this could be an incorrect revision number. We need to check whether 2) and 3) are meaningful problems that need correction.
Note, as a further contamination test, we blew the N2 gun across a new 4" witness wafer for the same amount of time/distance as we did during the discharge and inspected. We blew for 30sec at 20psi 2" from the wafer. Upon inspection, we found the wafer still looked very clean, as expected.
We have been stating the witness wafers as 3" wafers, but in-fact they are 4" wafers. There are not 2 sizes on site.
Dang it - I didn't relogin - Betsy posted this, not Corey.
Today we finished up the ETMx in-chamber activities adn closed the door. Sequence of events:
Filiberto checked for TMS QPD cable grounds at the feedthru. All ok there. (Actually did this yesterday afternoon.)
Kyle and Gerardo finished the port work (that was scheduled in the original vent plan).
Fil check the ESD pinout with aid from an "inside" guy multiple times in order to make clear the understanding of the pins on the air-side of the feedthru.
Jim unlocked the ISI.
Performed the discharge procedure on ETMx as per T1500101 - again, this took around 1 hour.
Swapped the vertical witness plates (1" and 4") that were mounted on the QUAD structure. 1" optic vertical on floor is now: SN 242.
Removed all equipment and re-suspended lower masses.
Dust counts taken throughout. Counts were nomnally 30-200 counts in all sizes of particles with few bursts up to 500 in th 0.3um size once in a while when 2 or more people were moving in chambelr. Counts were zero or 30 (max when entering chamber after lunch or in morning.
Measured ETMx main and reaction chain P and V TFs. All looked healthy with purge air on and soft cover over door.
Door being put on.
Checked EQ (earthquake) stops (Note this is the same as we found/set on ETMy):
Barrels of ERM ~2mm
Barrels of ETM ~1.5-2mm
12 o'clock stop ~3+mm
PenRe barrel ~1.5-2mm
PUM barrel ~2mm
All face stops 1-1.5mm
Purge air has been valved off.
Dang it - I didn't relogin - Betsy posted this, not Corey.
Discharge of ETMx WBSC9 (in chamber)
Using the ETM / ERM Gap discharge procedure https://dcc.ligo.org/LIGO-T1500101 we discharged the optics in chamber at ETMx. As before the procedure includes a swing back of the ERM i.e. an increase in the gap between the optics. Using the electrometer https://www.trifield.com/content/ultra-stable-surface-dc-volt-meter/ mounted centrally (on an X brace) 1" from the back of the ERM (i.e. between the ERM and TMS) we measured the following voltage: -
Note: - Prior to starting we zeroed the electrometer (10:28 am) with the cap on.
1) At start (after electrometer was mounted 1" from back of ERM and prior to swing back) = 21.9 V (10:30 am)
Note: During work on pinning ESD the reading went to = 17.2 V. Then the locking of the sus took it up to = 25.9 V. More to follow.
2) During mounting of swing back tooling = 26.6 V.
3) Electrometer was moved 5mm away from the ERM to allow for space during swingback = N/R V.
Note: Jim came into chamber to un-lock ISI. The ESD was re-pinned twice at this time. At this point (for saftey) we took off electrometer.
4) (Once electrometer was back on & Jim was finished) During swingback went up to peak of = 18.9 V.
5) Once Electrometer was moved back to being 1" from optic (and in chamber team in home position) = 21.1 V.
6) At this pont we broke for lunch. Once everyone out the chamber and soft door cover on = 20.6 V.
7) When we came back from lunch (2 hour later) = 9.5 V.
8) (When Danny entered chamber just after) the soft door cover came off = 8.8 V (1:38 pm)
Note: At this point humidity was 26%.
9) After completion of ETM / ERM Gap discharge procedure (inc 5 min after home) = 4.0 V (and decaying).
10) After swing back of ERM (back to original position) and with electrometer reset to being 1" from optic = 4.9 V
Note: - At this point team started to suspend the chains and run (basic) transfer functions on both the main chain and the reaction chain. We left the electrometer in place during this time.
11) At end (prior to doors on) at pm = 3.6 V *.
12) Final number - At the end we put the cap back on the electrometer and it was now reading 1.4 V. Therefore we are calling the final number = 2.2 V (i.e. 3.6 V - 1.4 V).
Note: - The final number was not decaying as per previous on Y end. More to follow on this. Data was collected over 10+ minutes.
Note: - Humidity was 28% just before doors on. Doors were in place at around 4:03 pm.
Kate Gushwa, Gary Traylor, Danny Sellers, Travis Sadecki, Betsy Weaver and Calum Torrie
ETMX ESD 1. Continuity test was done on each pin to verify each section LR, UR, BIAS, UL, and LL. 2. The old vacuum feedthrough was removed by Gerardo 2. The in-vacuum cable was re-terminated for installation of the new UHV 5-way coaxial connector. 4. In-vacuum cable was connected to feedthrough 5. Gerardo installed new feedthrough. 6. In-air cable connected to feedthru. 7. All pins were HIPOT tested to 800V and passed. 8. Pins were rechecked, by grounding each section to ground (in chamber) and verifying at feedthrough (air side). Pin layout for ESD (@ Feedthrough) is as follows: Pin 1 - LR Pin 2 - UR Pin 3 - BIAS Pin 4 - UL Pin 5 - LL Following E1400430, Pin 1 is slightly offset in spacing from the other pins.
Removed 4" wafer from HAM6, (T1500311).
Took PET swipe from south side of chamber from base of OMC to edge of the ISI table.
Both samples have been prepared for processing at CIT.
Note: The placement of the 4" wafer was in a difficult spot to remove. One had to lean into the chamber on an off balance stance and remove the wafer from the center of a group of small optics. There were no good handholds or bracing points available. The wafer being placed flat on the ISI table had to be pushed across the table until it came up against a cable clamp before one could get the tweezers under it. There was a risk of bumping or disturbing the optics around the disk. See attached photo.
Dust counts taken during work, inside and outside the chamber were all zero or in the low 10s of counts.
We found an error in the GDS calibration filters originally generated for ER7 and discussed in LHO alog #18813. Originally, we had double compensated for the AI filter in the actuation chain and the AA filter and OMC whitening poles in the sensing chain. This was corrected on June 4, 2015 (at GPS time 1117505816) and new plots of the filters are attached. The new filters file is located in the calibration SVN: aligocalibration/trunk/Runs/ER7/GDSFilters/H1GDS_1117505690.npz.
Particle counts taken during the removal of the HAM6 south & east doors on 06/17/15. Counts were taken with an older HPPC-6, using differential mode. HAM6 South Door Time 0.3µ 0.5µ 1.0µ Sample Location 13:24 100 0 100 In cleanroom – breaking bolts 13:32 300 100 100 In cleanroom – breaking bolts 13:35 0 100 0 In cleanroom – breaking bolts 13:43 40 20 20 Top of door flange venting purge air 13:48 3050 250 40 LVEA Room air HAM6 East Door Time 0.3µ 0.5µ 1.0µ Sample Location 14:07 2530 750 320 LVEA room air 14:09 960 350 320 In cleanroom – breaking bolts 14:30 0 0 0 In cleanroom – Door coming off 14:43 20 10 0 In cleanroom - Putting on the door covers 15:00 10 0 0 In chamber – Cover on 15:39 50 20 10 In chamber – Cover on
Discharge of ETMy WBSC10 (in chamber)
Using the ETM / ERM Gap discharge procedure https://dcc.ligo.org/LIGO-T1500101 we discharged the optics in chamber at ETMy. Remember that this procedure includes a swing back of the ERM i.e. an increase in the gap between the optics. Using the electrometer https://www.trifield.com/content/ultra-stable-surface-dc-volt-meter/ mounted centrally (on an X brace) 1" from the back of the ERM (i.e. between the ERM and TMS) we measured the following voltage: -
Note:- The humidity at 10:00 am was 30%.
Note: - Prior to starting we zeroed the electrometer (11:12 am) with the cap on.
1) At start (after electrometer was mounted 1" from back of ERM and prior to swing back) = 6.8 V (this was steady over couple of minutes).
2) During mounting of swing back tooling = 6.7 V.
3) Electrometer was moved 5mm away from the ERM to allow for space during swingback = 6.4 V.
4) During swingback went up to peak of = 25.2 V.
5) Once Electrometer was moved back to being 1" from optic (and in chamber team in home position) = 24.9 V.
6) At this pont we broke for lunch. Once everyone out the chamber and soft door cover on = 23.1 V.
7) When we came back from lunch (1 hour later) = 13.7 V.
8) When the soft door cover came off = 12.2 V (with slow decay).
Note: - We had a first round failed discharge procedure. Panel was not flapping in gap. Decided to stop and start again. More details to follow.
9) After completion of ETM / ERM Gap discharge procedure (2nd time) = 3.8 V (and decaying). This was done at 2:56 pm.
10) After swing back of ERM (back to original position) and with electrometer reset to being 1" from optic = 9.3 V (and decaying). This was at around 3:04 pm.
Note: - At this point team started to suspend the chains and run transfer functions on both the main chain and the reaction chain. We left the electrometer in place during this time.
11) At end (prior to doors on) at 4:12 pm = 4.2 V * (and decaying).
12) Final number - At the end we put the cap back on the electrometer and it was now reading 1.3 V. Therefore we are calling the final number = 2.9 V (i.e. 4.2V - 1.3V).
Note:- The humidity got as high as 41% during efforts. At end before doors on it was 32%.
Note: - Doors were finally in place at around 5 pm.
Kate Gushwa, Gary Traylor, Danny Sellers, Travis Sadecki, Betsy Weaver and Calum Torrie
Last weekend I used the offset-lock methof to measure the cavity length noise of the OMC. I tried this with a single-bounce beam last fall, but the intensity noise from the IMC was too large and it contaminated the signal. Here, with the carrier light from the full IFO, the intensity noise is low enough that a good measure of the displacement noise can be made, at least below 100Hz. Here I describe how to offset-lock the OMC and how the cavity length noise is measured; also I make a projection of the OMC cavity noise contribution to DARM. Noise due to OMC length fluctuations should be >10x below the DARM noise floor, except around the ISI resonances at ~1kHz.
This result is complementary to the cavity length noise measurement that Koji & I made by PDH locking the OMC with a single-bounce beam. In comparison, this half-fringe (or "offset-locking") method is limited by intensity noise, but it's less invasive and can be performed entirely from the control room. It might be useful for, e.g., estimating the OMC cavity noise during PEM injections or remeasuring the displacement noise after we install dampeners on the HAM6 ISI (still speculative).
[Yet another method is estimating the displacement noise from the dither-locking error signal; Koji has done this in April and it agrees with the PDH result below 10Hz, but above 10Hz the dither error signal is limited by sensing noise.]
Here are the steps to lock the OMC on the half-fringe, while the full IFO is locked (and the DARM offset engaged). This is essentially the same technique as I used last fall (and is halfway coded in the OMC guardian), which was itself a copy of what Zach did at LLO.
The next steps adjust the OMC-LSC error signal path to set the offset locking at the half fringe point:
Figure 1 illustrates how the offset locking technique uses the RIN on transmission to measure the cavity length noise (delta-x). There's a theorist on my thesis committee, this is for them.
Figure 2 is the transfer function of the length servo, while locked on the half-fringe. This was used to correct for the loop suppression.
Figure 3: the top panel is a plot of the measured RIN during the half-fringe lock (red), and the same data corrected for the loop suppression (blue). The RIN has a noise floor of ~1e-7 / rt[Hz] above 100Hz. This noise is coherent between the DCPDs and is well above the shot noise + dark noise level. (To demonstrate this I plot the NULL stream, along with the DCPD dark noise; both of these were convereted to RIN-equivalent noise by dividing by the DCPD_SUM during the offset lock, 10.2mA. The shot-noise RIN for 10.2mA is in good agreement with the NULL channel.)
I think the noise floor is due to intensity noise coming from the IFO, and above 100Hz we are not measuring RIN due to cavity length fluctuations (except around 1kHz, more on this later). This 1e-7/rt[Hz] noise floor matches the noise floor of the ISS 2nd loop PDs (not plotted), but the coherence is not =1 everywhere. Why isn't it filtered by the IFO?
Figure 4 is the cavity length noise derived from the RIN measurement, red is the in-loop data, blue is the 'free-running' length noise (corrected for loop suppression). The displacement noise is calculated from the RIN using the RIN/dx relationship, derived from the cavity transmission formula. For the OMC, locked halfway up the fringe, the conversion is 2.72e-9 meters/RIN - to get this number you need to know the transmissivity of the OMC input and output mirrors, it is 8000ppm.
Figure 5 is a comparison between our measurements of the OMC displacement noise: Zach's measurement from L1 (red); Koji's result from the PDH lock of the OMC (black); and this measurement (blue). This plot is an update of LHO:16174. In general the measurements are in agreement. The PDH result has a lower noise floor above 100Hz; probably the other measurements are limited by intensity noise. The half-fringe result is lower than the others around 10Hz; Koji measured the noise from the PZT drivers in January, this may be the limiting noise source for the current measurement. (Zach says that the L1 measurement is possibly limited by laser frequency noise in the 3-40Hz band.) The peaky excess in the half-fringe result around 1Hz and 3Hz are coherent with intensity noise and are not real cavity motion, see Fig. 3.
Figure 6 is a zoom of the region around 1kHz.
Here I estimate the contribution of OMC cavity length noise to the DARM noise. Valera, Ryan, and Sam discussed this in G1100903, and I think my methods are essentially the same as what they describe.
First, the noise in the light transmitted through the OMC due to the (suppressed) cavity length noise can be calculated two ways:
For the quadratic case, we calculate the noise in the power measured by the DCPDs due to the cavity length noise as:
dP[f] = (4*F/lambda)^2 * ASD[x(t)**2]
...where F is the cavity finesse (=391), lambda is 1064nm, and the final term is the ASD of the square of the cavity length noise, x(t). This is a quadratic approximation to the peak of the Fabry-Perot transmission curve, for the OMC it is accurate for motion less than ~3e-11 meters, which is true for our data across all frequencies. [Important: you have to take the ASD of the square of the time-series, not the square of the ASD -- the Fourier transform is a linear operator but squaring is not. Thanks Sheila!]
Alternatively, the bilinear coupling is estimated as:
dP[f] = (4*F/lambda)^2 * 2 * x_rms * ASD[x(t)]
I've used x_rms = 3e-13 meters, although this could be an overestimate (see comment below).
Next, to convert dP[f] into an estimate for the DARM noise budget, I turn the crank on the DCPD_SUM --> OMC-READOUT_ERR calculation that is described here:
OMC-READOUT_ERR = DCPD_SUM * (Pref / P0) * xf**2 / (2*x0) * G
...where Pref = 1.56 (power normalization), P0 = 24.1 (input power, Watts), xf = 14 (fringe offset, picometers), x0 = 15.8 (DARM offset, picometers), and G = 8.56e-7 (overall gain factor). These are the values during the lock on Jun 7 at 00:00 UTC that Evan used for his latest noise budget. This calculation converts DCPD_SUM in mA into counts at the DARM_IN1 error point.
Finally, to convert counts of DARM_IN1 into meters of CAL-DELTAL displacement noise, I use a factor of 5e-7, a zero at 389Hz and a pole at 7kHz. The factor of 5e-7 was estimated by matching DARM_IN1 to CAL-DELTAL_EXTERNAL_DQ in DTT. This is about 3x larger than what I expected, based on the calibration of the DARM offset in counts to picometers: 1e-5 counts / 14 picometers. Not sure why there is this discrepancy.
In Figure 7 I plot the CAL-DELTAL spectrum from June 7 with estimates of the contribution from the OMC, using the quadratic and bilinear coupling results. As mentioned before, the OMC length noise projection above 10Hz is probably limited by intensity noise and is bogus, except for the peaks around 1kHz, which are about a factor of two below the noise floor. If this result is correct, it's an ongoing mystery as to why we don't see this 1kHz noise in the DARM spectrum. Robert has investigated the acoustic coupling in this band and also projects that some noise at ~900Hz should be peaking above the noise floor. Why don't we see it?
For interested NoiseBudgeters, the attached text files have the data for the red (quadratic) and blue (bilinear) traces in Fig. 7. (You shouldn't think this noise source has gone unattended in the noise budget until now: Evan says he had measured the OMC-->DARM noise coupling some time ago, using excitations into the OMC-LSC loop, and had convinced himself the OMC wasn't a source of broadband noise. No reason to think any different from this study.)
There is some uncertainty in the value of x_rms. For the half-fringe result, the in-loop RMS is ~4e-12 meters, due to the noise around 0.2Hz (Figure 4). This is certainly an overestimation of the RMS motion during DC readout, because I did not engage the low-frequency boost in the OMC-LSC loop, so the low-frequency suppression was not as large. Koji has measured the RMS from the dither error signal in full lock (LHO:18034) to be ~3e-13 meters. For the PDH measurement (LHO:16089), the RMS motion was even lower, ~4e-14 meters. (The loop gain was significantly larger during the PDH measurement and I suspect it is an underestimate compared to the current loop shape for the OMC.) To err on the side of being conservative I use the dither error signal RMS for the bilinear noise estimation. (Zach measured the L1 OMC in-loop RMS as 7e-13 meters [G1301007, slide 18], but again the loop gain for that measurement is larger than what we use now.)
(Betsy, Calum, Kate, Gary, Travis, Danny)
Since all other work at End-Y finished yesterday, today we performed the in-chamber SUS/SYS discharge procedure T150101 on ETMy and then closed the chamber.
Todays sequence of events at EY:
Jim unlocked the ISI.
Filiberto checked for grounding of the TMS QPD cables at the feedthru since Keita/crew had made adjustments to them. As well, we then rechecked the QPDs with a flashlight for response. All is well with the QPDs post the strain relieving.
Locked lower masses of ETMy and installed discharge equipment onto QUAD frame. Discharged ETMy. Removed equipment and unlocked lower masses. Numbers to follow regarding the charge measured at the ETMy before executing the procedure and after completed. The procedure took about an hour.
Swapped in fresh 1" optic and 3" wafer contam. control witness samples - 1 each on the floor of the chamber just under the QUAD and the other set on the QUAD. All in the same places as before.
Wiped the floor on the way out.
Measured ETMy main and reaction chain P, V, and L TFs. All looked healthy with purge air on and soft cover over door.
Door put on, purge valved off.
Measured particle counts a few times throughout above. Numbers to follow.
Summary: A seismometer was buried 40 m from EY to take advantage of strong attenuation of the tilt signal relative to the acceleration signal from distant sources. Seismometers located outside the buildings may be useful in reducing problems associated with tilt.
Our buildings are tilted by wind. Our seismometers do not discriminate between this tilt and acceleration (like a pendulum), so wind-induced tilt produces spurious control signals that can make it difficult to lock and maintain lock. A tilt sensor can be used to discriminate between tilt and acceleration, but we may also be able to discriminate between the two by taking advantage of source differences in the band below 0.5 Hz, where tilt generates the largest spurious acceleration signals. The tilt in this band is mainly generated locally by the wind pressure against the walls, while the acceleration signal is mainly generated by ocean waves and other distant sources.
While the seismometers are in the far field for most low frequency accelerations, they are in the near field for building-generated tilt (wavelengths at 0.1 Hz are about 50 km). To take advantage of the rapid attenuation with distance in the near-field, I buried an STS-2 seismometer in a meter deep hole I dug 40 m from EY (Figure 1). Figures 2 and 3 show a comparison of the buried seismometer to the SEI seismometer on the ground inside the EY station. During the low wind period the spectra look virtually identical below 0.5 Hz and the coherence is high because the sources are mostly distant and the wavelengths are large. During the high wind period, the buried seismometer doesn’t change that much (there is some change in the microseismic peak because high/low wind were about 24 hours apart), but the building seismometer shows a huge signal from tilt. The coherence in windy conditions is low because the tilt is highly attenuated 40 m from the building. Figure 4 shows spectra for higher wind, 15-35 MPH.
Of course the external seismometer would not detect real building accelerations due to the wind. But if the unwanted tilt signal dominates over the wanted wind acceleration signal, a seismometer outside the building may be useful, and I think that this is the case below about 0.5 Hz.
I note that I first tried this in the beam tube enclosure tens of meters from EY, but found that the wind tilts the beam tube enclosure almost as much as the building (but not coherently), supporting a hypothesis that aspect ratio is the important variable. Also, Jeff points out that, if we insulate the buried seismometer well (and I did not) we might even be able to do better than the building seismometers with their current insulation during even low-wind periods. Figure 5 is like Figure 2 except that the signal from the stage 1 Trilliums is included.
Interesting data! I'm fascinated by the observation that at 25 mph, the horz. spectra don't match at any frequency. unfortunately, this makes it seem quite problematic to try and use the data in realtime from the outside sensors, since you have to figure out at what freq. they are telling you something useful, and at what frequency they are not. Certainly at 0.5 Hz, the slab sensors are the ones to use and I suspect that at 0.05 Hz one should believe the outdoor sensor, but in between? Several years ago, in response to an (incorrect) estimate of newtonian noise from wind-eddies, various suggestions of shrouds, fairings, shorter buildings, trees, berms, etc. were floated and dismissed. any evolution of this thinking? this data seems to imply that if we put a wind block 40 m from the building, and kept the wind off the building, we'd be in better shape. Sadly, short of a giant pile of tumble-weeds, I don't see any practical way to achieve this. It certainly bolsters Krishna's assertion that the wind-tilts are local to the buildings.
Yes, but we more often have to deal with the 10-20 MPH range, and I think its clear that the burried seismometer is better for that in the 0.05-0.5 range. For higher wind speeds, I would explore the tilt-acceleration cross over by substituting a burried seismometer for building seimometers and see to what wind speed the burried seismometer is an improvement.
I set up an accelerometer on the beam tube and measured the accelerations as I simulated the tapping that I observed during cleaning, and my tapping experiment mentioned here: https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=19038. Examination of the time series indicated that accelerations during typical taps reached about 1 m/s^2. I suspect that some taps reached 1g. The figure shows spectra for metal vs. fist taps. The above link notes that I was unable to produce glitches while hitting the beam tube with my fist. The fist and metal taps both had about the same maximum acceleration of 1 m/s^2 (ambient acceleration levels are about 4 orders of magnitude lower), so the source of the difference in liberating the particles is probably not acceleration. Instead, it may be the change in curvature of the beam tube, which would be expected to be greater at higher frequencies. The responses from metal taps in figure 1 peak at about 1000 Hz while the fist taps peak at about 100 Hz. These results are consistent with a hypothesis that the metal oxide particles are liberated by fracture associated with changes in curvature rather than simple vertical acceleration.
When I was producing glitches in DARM for the link above, I noticed that we did not get glitches every metal tap but every several metal taps. I tried to quantify this by making many individual taps at several locations along the beam tube. Unfortunately, we lost lock with the first loud glitch and I did not get a chance to repeat this before the vent. Nevertheless, it would be good for DetChar to look for smaller glitches at the time of the taps given below. Allow a 1 second window centered around the times given below for my tap timing uncertainty. I tapped once every ten seconds, starting at ten seconds after the top of the minute so that there were six taps per minute.
UTC times, all on June 14
Location Y-1-8
20:37 - 20:38 every ten seconds
20:47 - 20:50 every ten seconds
Next to EY
20:55 - every ten seconds until loss of lock at 20:56:10
I don't think the IFO stayed locked for the whole time. The summary page says it lost lock at 20:48:41, and a time series of DCPD_SUM (first plot) seems to confirm that. I did a few spectrograms, and Omega scanned each 10 seconds in the second series, and the only glitch I find is a very big one at 20:48:00.5. Here is an Omega scan. The fourth tap after this one caused the lock loss. Detchar will look closer at this time to see if there are any quiet glitches. First we'll need to regenerate the Omicron triggers... they're missing around this time probably due to having too many triggers caused by the lockloss. I'm not sure why there's a discrepancy in the locked times with Robert's report.
Any chance this could be scattered light? at 1 m/s^2 and 1 kHz, it is a displacement of 25 nm, so you don't need fringe wrapping.
I think that you would expect any mechanism that does not require release of a particle to occur pretty much with every tap. These glitches dont happen with every tap.
Here I present some results from our first Pcal sweep measurement (alog 19128 and 19132) in 5-5000 Hz frequency range.
The main conclusions are:
-----
This time, our traget was the sensing function or the DARM optical plant in counts/meters. To access the sensing function, we essentially need two different measurements i.e. a TF from ETM displacement to DARM_IN1 [cnts/meters] and DARM loop suppression [cnts/cnts]. Jeff took an open-loop TF and Pcal sweep for each arm, but unfortunately the Y arm measurement did not complete (alog 19128). Approximately 8 hours later of Jeff's measurements, TJ managed to measure a sweep of Pcal Y and DARM suppression TFs (alog 19132). So in total we have three different Pcal sweep data sets as follows,
The first two measurements were from a same lock stretch, and the last from a different lock stretch. All the measurement were made with a PSL requested power of 17 W. The plots below show the main results:
The first plot shows the estimated sensing functions from all three sweep measurements. As seen in the plot, signal-to-noise ratio becomes significantly low above a few kHz. Also as the sweep goes across the fundamental and the second harmonic of the violine modes, the coherence dropped and hence a low signal-to-noise ratio. The cyan solid curve represents the model that we have used for generating GDS and CAL-CS where the DC gain is set to 1.311x-6 cnts/meters and a cavity pole frequency to 355 Hz. Additionally, I set a delay time of the model to 55 usec by eye-ball fitting without any good explanation.
The second plot shows the residual between the measrured and model transfer functions. Even though the first two measurements were from the same lock stretch, they differed by approximately 20 % from each other. I am not sure what caused the descrepancy, but it is clear that the descrepancy is mostly in the scaling factor. The last measurement, which was from a different lock stretch showed a lower optical gain by 20 %. We know that our LSC automation can cause such a variation in the optical gain (alog 19014). So I believe that this 20% reduction is real and not due to some calibration in Pcal. Also the first and third measurements showed significant drop in the magnitude below 10 Hz by more than 50 %. Since the phase does not seem to roatte below 10 Hz, this is not a simple zero-pole argument. Looking at the Pcal active intensity stablization servos, Darkhan and I cofirmed that there was no saturation when the low frequencies were measured (although Pcal Y seemed to have saturated at the beginning of the measurement, meaning higher frequencies). We have no idea.
The analysis code, measurements and figures can be found in:
[sus crew]
Following the in chamber work from today at end-Y we took quick TFs on the quad and the transmon. They look ok.
Since the pump won't happen before tomorrow I started matlab tfs for all DOF.
The measurement will be running for few hours.
More clue on the TMSX measurement showing a different TF than before the vent (cf log below 19246). I looked at the response from pitch and vertical drive to the individual osems (LF, RT) and it looks like something is funny with the RT osem which should have the same response as the LF one, cf light red curves below
EDIT : Actually, LF and RT osem response are superposed on the graphs (green LF lies under red RT), so their response is the same.
ETMY ant TMSY transfer functions were measured on thursday after the doors went on, with chamber at atmospheric pressure. They did not show signs of rubbing, cf the first two pdf attached showing good agreement with previous measurements.
Today, I remeasured the vertical dof, after the suspension sagged ~120um from the pressure drop, and it still looks fine, cf figures below.
ETMX and TMSX were measured today when pressure in chamber was about 3 Torrs, after the QUAD sagged by about 130um.
The second pdf attachment on the log above was supposed to show TMSY transfer functions. Attached is the correct pdf.
Kyle -> Soft-closed GV7 and GV5 -> Vented HAM6 Bubba, Hugh, Jim W. -> Removed HAM6 South and East doors Kyle, Gerardo -> Installed NEG and TMDS reducer nipple+valve+elbow at X-end Danny S., Gary T., Gerardo, Kyle -> Hung North door on BSC10 (NOTE: Noticed ~1 hour before hanging door on BSC10 that the purge-air drying tower had been left off since tying-in the 1" TMDS line on Monday afternoon -> Turned it back on and notified the ETMY discharge crew
Forgot to log -> Purge-air measured <-39 C just prior to venting HAM6
To test the power-up status of the SUS HWWD, I activated the SUS ITMY HWWD which is located in the CER SUS-C6 rack. The long DB-37 cables which run from the ITMY M0 OSEMS were not connected to the monitor ports of the HWWD. I found the cables on the top of the rack, and after verifying they were connected to the monitor ports of the satellite amps for ITMY M0 (located in the LVEA beer garden) I plugged them into the HWWD.
After the tests were completed, I disconnected the cables in the CER and returned them to the top of the rack.
Depreciated is ok.
IRIG-B revision 85 is reported as 133 due to a decimal-to-hex conversion error. Not enough reason to update.
The error reporting will take this into account, when the updated EtherCAT code is loaded.