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

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:

• Pcal showed an OK agreement in terms of a DARM optical response with our model (i.e. the one used for generating GDS and CAL-CS).
• Roughly speaking, Pcal agreed with our model with descrepancy of 20 % level in magnitude above 10 Hz.
  • Pcal X seemed to have a larger systematic of 20-ish% in the overall scale factor. Not sure why. Needs to repeat the measurement.
  • Pcal Y agrees with the model with several % at one time.
• The measured phase agree with the model within +/- 10 deg uncertainty below 1 kHz.
• Another sweep measurement on a different lock stretch showed a 20 % reduction in the optical gain.
  • presumably due to a different DARM offset and maybe different alignment (see alog 19014).
• For some reason, the measured magnitude descreases as it goes to lower frequencies below 10 Hz.
  • This somehow does not change the phase. I don't understand.

-----

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,

• Pcal X sweep (13/6/2015 23:40:53 UTC)
• Pcal Y sweep (13/6/2015 23:56:21 UTC)
• Pcal Y sweep (14/6/2015 07:03:59 UTC)

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:

• aligocalibration/trunk/Runs/ER7/H1/Scripts/PCAL_TRENDS/2015-06-13_optgain_estimation.ipynb
• aligocalibration/trunk/Runs/ER7/H1/Results/PCAL_TRENDS/ *png
• aligocalibration/trunk/Runs/ER7/H1/Measurements/PCAL_TRENDS/ * txt

[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. 

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

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.

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

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). 

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.