Scott L. Ed P.

6/15/15
Cleaned 33 meters ending at HNW-4-076. Removed lights and move to next section north. Test results posted here.

6/16/15
Rehang lights, vacuum support tubes, spray heavily soiled floor areas with water/bleach solution and begin cleaning beam tube. Cleaned 19 meters ending at HNW-4-077.

6/17/15
Cleaned 60.6 meters ending at HNW-4-080.

A total of 3603 meters of tube have been cleaned to date.

Hugh, Bubba, Andres, Jeff B.

   After removing the HAM6 south & east doors, we rolled two cleanrooms and a garb room around the south and east sides of the HAM5/6 big cleanroom. The fans are on. There will be a cleaning of these cleanrooms in the morning. 

NOTE: The south corridor from just before HAM5 to the north side of the HAM5/6 big cleanroom is blocked. Access to the north side of the output arm will be from the long way around.    

Will run the Aux cleanrroms overnight before using.  Thxs to Andrias Jim Bubba JeffB

Dan Hoak gave us a clue on page 19067 and then Bas Swinkels ran Excavator and found that the channel H1:SUS-OMC_M1_DAMP_L_IN1_DQ had the highest correlation with the fringes. Andy Lundgren pointed me to equation 3 from “Noise from scattered light in Virgo's second science run data” which predicts the fringe frequency from a moving scatterer as f_fringe = 2*v_sc/lambda. Using the time from Dan and the channel from excavator and the fringe prediction, I wrote the attached m-file. Fig 1 shows the motion, velocity, and predicted frequency from OMC M1 longitudinal. Figure 2 shows the predicted frequency overlayed with the fringes in DELTAL. Math works.

PS. Thanks to Jeff and the SUS team for calibrating these channels and letting me know they are in um. Thanks to Gabriele for pointing out an error in an earlier draft of the derivative calculation.

Calibration Team

Sign of h(t):

The gravitational wave strain h(t) is given by  h(t) = Delta L/L where Delta L  is is computed using

                         Delta L = ± (Lx - Ly)

The sign of Delta L can be determined using Pcal actuation on the test mass. Pcal only introduces a push force  so pcal readout signal (truly pcal excitation) is minimum when the testmass is away from the corner station (closer to pcal laser). From the first plot the phase between DARM/PCAL is ~ -180 degrees (DARM lags PCAL) which suggests that DARM signal from ETMX will be maximum when pcal is minimum (ETMX further away from corner station). Similarly, from second plot, since DARM and PCAL have a phase difference of ~-360 degrees (essentially 0 degrees), the  DARM signal from ETMY is minimum when the pcal is minimum. This shows that the sign convention for the Delta L is '+'

Time Delay between Pcal and DARM:

Also the slope of the curve gives the time delay between Pcal and DARM signal chain. The time delay is about 125±20 us. This time delay can be accounted for, within the uncertainity, from the difference in signal readout chain outlined in Figure 3 attached.

Refer to LLO alog #18406 for the detailed explanation behind this  conclusion.

Following up an earlier report on narrow lines in early ER7 data ("ER7A"), attached are spectra and a longer list of lines found in the 5-2000 Hz band
from examining an inverse-noise-weighted average spectrum over 149 hours of full-ER7 DC-readout data, using 30-minute Hann-windowed FScan SFTs.

The overall spectrum is similar to before, but the additional data reveals more structure. Here are highlights and lowlight of apparent changes:

 The bounce modes are better suppressed in the latter part of the run.
 A comb with 0.1698-Hz spacing is now visible in its 41st through 59th harmonics
 There is a newly apparent comb-on-comb structure with a fine spacing of 0.0884 Hz attached to a comb of 
76.9426-Hz lines. Only the clusters up to the 3rd harmonic of 76.94 Hz are labeled on the spectra, but one
can still see indications of the comb-on-comb up to at least the 12th harmonic at 923 Hz.
 Something I overlooked before is that the OMC dither lines at 1675.1, 1700.1, 1725.1 and 1750.1 Hz are prominent on 
top of their induced up-conversion. This is in contrast to what I usually see in L1 data, where the dither lines
themselves are servoed to near zero and are barely visible in the up-conversion they create.
 In addition to the previously noted combs of 16 Hz and 64 Hz harmonics, one can now see a very sporadic
set of 8-Hz lines. The more prominent ones are marked on the spectra and include 376, 552, 808, 1064, 1096,
1112, 1144, 1176, 1192, 1416, 1544, 1608, 1624, 1672, 1704, 1784, 1800, 1816, 1832, 1880 and 1896 Hz. 


Figure 1 - Spectrum 0-2000 Hz with labeled lines

Attachments: 
1 - Line list
2 - zip file with 27 sub-band spectra

As of COB today, we are on-schedule for the 4 day EX and EY vents.  So far no major surprises or issues.  Further dust monitor data to be posted later.

As per the schedule:

- The ISI's have been locked on both ETMx and ETMy.

- 2 CC witness samples have been pulled from each BSC9 and BSC10.

- The VE port work has finished at ETMy.

- The TMS work has finished at both stations.

- The ETMx debiasing has been completed (removed ~440 uRad of pitch mechanically at the suspension using the optical lever as the monitor.)  Bias is now at zero.  This is where commissioners should start looking for beams in a few weeks.  Yaw bias remains unchanged (and non-zero).

- Local charge measurements taken on ETMx with in-chamber equipment in prep for discharge procedures. 

- ESD feedthru swap has started.  Filiberto and Gerardo have pulled the flange and have it out and ready to reterminate with the new connector.

- Quick P and V TFs of ETMx show healthy suspension - Arnaud launched matlab overnight TFs of SUS-ETMx for further check.

First up tomorrow:

- Finish ETMx ESD feedthru work.

- Finish VE port work at ETMy.

- Move equipment to ETMy and Discharge ETMy.

- Close ETMy chamber.

I modified and restarted the BSC-ISI models to close ECR E1500245, E1500253 and E1500270. The changes are listed below, and described in details in the attached pdf.

* removed sts blrms calculation from the sensor correction of stage 1. The calculation is now done at the top level. A list of the new channel names is provided in the attached text files 

* Added a pick off of stage 1 CPS X and Y signals to feed the LSC model through PCIE senders on BS ITMX and ITMY

* Added a path from sus to the error point of the stage 1 controls to use for tidal feedback (mainly for LLO). 

18:02 PDT: DAQ restarted to sync with new INI files for BSC-ISI and OAF.

ISI was locked by Jim in the morning.

Before doing anything, EY alignment slider [PIT, YAW] = [142.0, -75.1], TMSY = [116.6, -20.0], EY OPLEV=[-39, -15]-ish.

Transitioned to laser hazard, moved EY such that the green return beam hits the center of the relf PD: EY [PIT, YAW]=[207.4, -75.1]

- Krytox on beam diverter in situ: Good.

Everything went well as per yesterday.

- QPD strain relief: Good-ish.

Unlike TMSX, it turns out that all QPDs were already equipped with a make-shift strain relief using stainless steel cable clamps, the same clamps used for fixing the cables on the TMS ISC table, but the cables were without kapton tubes. We decided to install the right strain relief anyway.

In the end, we were able to install the right ones on three out of four QPDs. As for the remaining one (Green QPDB), we weren't able to install it as the 1/4-20 Allen key to attach the PEEK strain relief to the QPD base would have interfered with the YAW knob of one of the QPD sled mirror holders (M102 in D1201458).  The stainless steel strain relief was left as is.

After this work, we checked if QPDs still work and they did (used green beam for the green QPDs and a flashlight for IR QPDs).

- TMS balancing: Good.

After the work, we checked the balace of the TMS table with the green light injected to the chamber. The vertical alignment was found to be already good and therefore we did not make any mechanical adjustment. Similarly, the horizontal was also good and giving an extra digital bias of +13 urad (resulting in -7.0 urad in OPTICALIGN_OFFSET) made the return beam well-centered on ALS-REFL_PD. So the balance is good.

After everything was done: EY slider [PIT, YAW] = [142.0, -75.1] (back to the original), TMSY = [116.6, -7.0], EY OPLEV=[-24, -31]-ish.

Seems like EY moves around by 15urad-ish both in  PIT and YAW, so TMS alignment could be only as good as 15urad-ish.

Corey, Keita, Kiwamu,

We conituned working on the remaining tasks for the TMSX in chamber (see alog 19157 from yesterday).

[Strain Relief for QPDs]

This morning we installed the strain reliefs for the two QPDs in which we had a difficulty inserting a screw due to bad threading. Today, we brought 10-32 screws so that the screw can go all the way through to the back without any interference from the bad threads. We put combination of a nut and washer on the other side to hold the 10-32 screw and the strain relief parts. We did this on the two QPDs. So now all four QPDs have the strain reflef parts installed.

[Balancing of the table]

We then balanced the table such that the green light is retro-reflected off of ETMY. The table seemed to have pitched by some amount. We decided to move the counter mass at the bottom of the table. The adjustement went very smooth and we were able to get the beam retrao-reflected all the way back to the PD on the ISCTEX table. Touching the TMS digital bias suggested that the pitch angle is good with a precision of about 4 urad. While pitch is good, yaw seemed to be slightly off. So we moved the digital bias in yaw as well and confirmed that adding an additional +40 urad (resulting in a bias of ) in the digital bias can give us a decent alignment on the reflection PD. So we are good in yaw too.

[Addendum]

After initial balancing we were concerned that we did not use vented washers for the two QPDs which required the screw/nut workaround.  Keita found that one QPD did NOT have a vented washer, so a vented washer was installed.  This required a re-balance.  We were a little off in pitch, so a counterweight (1/4-20 screw) was added to pitch the TMS.

Photos of this work from Mon afternoon & Tues morning is on ResourceSpace here.

EX is now Laser Safe.

(And ready for the SUS crew to take over.)

(times in PST)

0:04 - Locked @ LSC_FF, started PCAL swept line measurement

0:29 - PCAL measurment done, started DARM OLGTF measurement

0:50 - Both measurements done and no more for now it seems, Intention Bit set to Undisturbed

There were eight separate locks during this shift, with typical inspiral ranges of 60 - 70 Mpc. Total observation time was 28.2 hours, with the longest continuous stretch 06:15 - 20:00 UTC on June 11. Lock losses were typically deliberate or due to maintenance activities.

The following features were investigated:

1 – Very loud (SNR > 200) glitches
Omicron picks up roughly 5-10 of these per day, coinciding with drops in range to 10 - 30 Mpc. They were not caught by Hveto and appear to all have a common origin due to their characteristic OmegaScan appearance and PCAT classification. Peak frequencies vary typically between 100 - 300 Hz (some up to 1 kHz), but two lines at 183.5 and 225.34 Hz are particularly strong. These glitches were previously thought to be due to beam tube cleaning, and this is supported by the coincidence of cleaning activities and glitches on June 11 at 16:30 UTC. However, they are also occurring in the middle of the night, when there should be no beam cleaning going on. Tentative conclusion: they all have a common origin that is somehow exacerbated by the cleaning team's activities.

2 – Quasi-periodic 60 Hz glitch every 75 min
Omicron picks up an SNR ~ 20 - 30 glitch at 60Hz which seems to happen periodically every 70 - 80 min. Hveto finds that SUS-ETMY_L2_WIT_L_DQ is an extremely efficient (use percentage 80-100%) veto, and that SUS-ETMY_L2_WIT_P_DQ and PEM-EY-MAG-EBAY-SEIRACK-X_DQ are also correlated. This effect is discussed in an alog post from June 6 (link): "the end-Y magnetometers witness EM glitches once every 75 minutes VERY strongly and that these couple into DARM".  Due to their regular appearance, it should be possible to predict a good time to visit EY to search for a cause. Robert Schofield is investigating.

3 – Non-stationary noise at 20 - 30Hz
This is visible as a cluster of SNR 10 - 30 glitches at 20 - 30 Hz, which became denser on June 11 and started showing up as short vertical lines in the spectrograms as well. The glitches are not caught by Hveto. Interestingly, they were absent completely from the first lock stretch on June 10, from 00:00 – 05:00 UTC. Daniel Hoak has concluded that this is scattering noise, likely from alignment drives sent to OMC suspension, and plans to reduce the OMC alignment gain by a factor of two to stop this (link to alog).

4 – Broadband spectrogram lines at 310 and 340 Hz
A pair of lines at 310 and 340 Hz are visible in the normalized spectrograms, strongest at the beginning of a lock and decaying over a timescale of ~1 hr as the locked interferometer settles into the nominal alignment state. According to Robert Schofield, these are resonances of the optic support on the PSL periscope. The coupling to DARM changes as the alignment drifts in time (peaks decay beacuse the alignment was tuned to minimize the peaks when the IFO is settled.) Alogs about this: link, link, link.

There are lines of Omicron triggers at these frequencies too, which interestingly are weakest when the spectrogram lines are strongest (probably due to a 'whitening' effect that washes them out when the surrounding noise rises). Robert suspects that the glitches are produced by variations in alignment of the interferometer (changes in coupling to the interferometer making the peaks suddenly bigger or smaller).

5 – Wandering 430 Hz line
Visible in the spectrograms as a thin and noisy line, seen to wander slightly in Fscan. It weakened over the course of the long (14h) lock on June 11. Origin unknown.

6 – h(t) calibration
Especially noisy throughout the shift, with the ASD ratio showing unusually high variance. May be related to odd broadband behavior visible in the spectrogram. Jeff Kissel and calibration group report that nothing changed in the GDS calibration at this time. Cause unknown.

Attached PDF shows some relevant plots.

More details can be found at the DQ shift wiki page.

Richard, Evan

Summary

It appears that the EY ESD bias was stuck at −430 V ever since the installation of the low-voltage driver in May. It became unstuck on 11 June, when Richard reset the driver.

Since we have always requested a positive bias for EY in the digital system (using SUS-ETMY_L3_LOCK_BIAS), this means that the reset on 11 June flipped the sign of the EY ESD actuation, causing the transition of DARM from EX to EY to fail (as TJ found).

To fix the transition, the EY bias is now requested to be negative in the digital system, thereby restoring the sign (but not the magnitude) of the true analog bias that we have had since 22 May. Of course, if the magnitude of the L3 actuation has changed, this will affect the accuracy of the calibration in the region dominated by the control signal.

Details

First, let us enumerate some of the mysteries surrounding the EY ESD:

1. After the low-voltage driver was installed (i.e., after 2015-05-22), we found that we had to flip the sign of the L3 actuation from positive to negative. This is despite the fact that both the low-voltage driver and the high-range driver supposedly have positive polarity at dc (so we should not expect to have to compensate for an analog sign flip).
2. After the low-voltage driver was installed, we found that the dc actuation strength of EY L3 was 50 times weaker than EX L3. We expect only a factor of 20×1.25 = 25. The factor of 20 comes from the difference in dc gain between the high-range driver and the low-noise driver (40 V/V versus 2 V/V). The factor of 1.25 is what Kiwamu had previously found necessary to match the dc strengths of EX L3 and EY L3 when they were both driven by the high-range drivers.
3. After the low-voltage driver was installed, the analog readbacks for the high-range driver (bias line and 4 quadrants) were stuck at −15000 ct.
4. After Richard reset the high-range EY driver for the charge measurements (2015-06-11, circa 21:00:00 UTC), there has not been a successful transition of DARM from EX to EY (although there have been only four trials, according to the summary pages).

We hypothesize that mysteries (1), (3), and (4) are explained by the EY ESD bias being stuck at −430 V between 2015-05-22 and 2015-06-11, and the driver's readbacks being nonresponsive. Mystery 2 is still unsolved.

When Richard went to EY on the 11th, he found the high-range driver putting out −430 V on all five lines, and the driver's analog readbacks were frozen at −15000 ct or so. According to him, this is a known failure mode of the driver's microcontroller. After he reset the driver, the analog readbacks became functional again.

The attached plot shows a trend of the analog readback of the EY ESD bias. It is stuck at about −15000 ct from 2015-05-22 (when the low-voltage driver installation was finished) to 2016-06-11 21:00:00ish UTC (when Richard reset the driver). The natural conclusion from this is that the EY ESD bias has been railed at −430 V between these two dates (even though we thought we were giving +380 V of bias).

I flipped the requested bias so that it is now (I think) −380 V, which is the most negative bias that can be requested from the driver when it is operating properly. I was able to transition control of DARM from EX to EY by hand following the steps in the guardian.