OMC black glass shroud and beam diverter move update

Daniel H, Matt H (and help at various times from Hugh, Greg G, Kiwamu, Sheila, others)

 

Todays events

So a  quick summary of todays work as too tired to write a detailed one sorry.

The in-vacuum cables were connected back onto the OMC and we confirmed we had signals etc. Also had a go at roughly moving the beam diverter to the position Keita/Dan hoped they could sqeeze it so as to not to have to move optics/SEI balance masses. We also had a look at trying to strain relieve the cables on the OMC that touch the OMC black glass shroud. But it looks like these are very touchy and altering these alter the balance.

 

Decided to analyse more with a laser beam.

 

Had troubles locking the mode cleaner. Apparently it was chased down to some whitening problem (something that last appeared around May 2014 I think I overheard). Once input mode cleaner locked and Dan had it set in a single bounce configuration,  The "M8" mirror (near the tiptilt and OMC shroud) was replaced (as was the additional black glass beam dump we had to remove for the OMC shroud install). The septum viewport protector was removed.  Dan was estatic (okay maybe he wasnt estatic but he was happy) that immediately saw signals. Looking at the OMC glass shroud and the beams though it looks like they go through very close to the center. Well done to Eddie Sanchez and the SYS team for all their hard work with the design to make sure they did.

 

We played more with the cables but in the end I decided to pull the trigger on removing the two upper black glass plates that r the cables that go to the glass bench are touching (it pained me to do so after all the hard work putting it in). Playing with the cables more we were able to get it to a point that Dan was "happy" with....(he would like it better if could but we decided we were at the point that perfection was the evil of good enough).

Note: we have it so that no offsets on the OMC like used to have

 

Then checked beam aligment out of OMC. As M8 didnt go back exaclty in the same spot, some of the optics had to be tweaked to re-establish the alignment. Also had to move a beam splitter as part of the beam diverter move. We chacked that both beam diverters still work in air. They did.

 

Also turned down purge air and did some TF's and they all passed (see attached).

 

Below is Dans much more succint summary......

 

Beam diverter was moved succesfully
90-10 BS was moved upstream of the second OMCR pico mirror; power on the QPDs has not changed (when the diverter is open)
Beam dump for 90-10 splitter was moved next to OMC SUS, should be out of the way

Alignment of OMCR path is good
Tested both beam diverters
Alignment into / out of OMC is excellent
Flashed OMC and saw the OMC TRANS beam out of the vacuum

OMC SUS TFs are good!

Purge air is on and OMC PZT HV is off.

 

Going forward tomorrow and still trying to get two bit of black glass back in

However not yet ready to hand over to Hugh for balancing. We are still actively investigating at how we can try to get both plates back in. After talking to Calum tonight he wants me to try putting at least one of the plates back in and taking some measurements to see how we might be able to modify the plates (ie maybe score and snap a bit off.......)

Also we should take TF's of tip tilts at some stage (after doors are on probably though).

 

Oh particle counts were basically all 0 in all locations (if not zero then had a reading of 10). Sorry am usually better at recording these details.

 

Pics:

2403...before pic of the OMC before shroud work started

2426...OMC black glass shroud installed

2424..the two cables on the OMC that interfere with the OMC black glass

2435...The OMC glass shroud with the two upper glass plates removed. It doesnt look as impressive :-(

2431 & 2434..how close the cables are to the peek support with glass removed.

2410 & 2412....beam diverter, V glass beam dumps (both), and beam splitter before move of beam diverter

2441 & 2442....playing wiht cables on OMC and checking alignment of beams into and out of OMC shroud

2445, 2449, 2451 & 2453.....the beam diverter, V balck glass dumps (ne for beam diverter and one for beam splitter) and beam splitter after beam diverter move

2454 & 2455...the "holes" in the OMC black glass shroud that the beams go in and out of

2457, 2460, 2461...the OMC black glass shroud from a different angle (with the two glass panels missing)

High acoustic coupling likely due to HAM6 ISI blade spring and suspension wire resonances; wire damping demonstrated

Summary: Frequencies excited by tapping HAM6 ISI flexures while it was vented match frequencies excited in DARM by external acoustic and shaker injections.  A prototype damping clamp damped the wire resonances. We suggest development of a permanent damping clamp for the ISI suspension wires and tuned dampers for the blade springs in the 350-450 and 850-1000 Hz bands.

Ambient acoustic sound produces noise in DARM that is only a factor of 2 below our current sensitivity in the 850-1000 Hz band and not much lower in the 350-450 Hz band and several higher frequency bands (Link).  We got a chance to study HAM6 during the vent that started last week.  It turned out to be difficult to excite and monitor the resonances that dominate in vacuum when we were vented. I believe that this is because the dominant vibration coupling path to the ISI table surface during a vent is acoustic and not through the flexures, as it is in vacuum.  External shakers did not produce peaks in the geophone signals that matched the peaks in DARM. I ended up attaching a small shaker magnetically to one of the blade springs, and monitored the frequency with an accelerometer mounted close to where the flexure attached to stage 2 (see photos in Figure1).

I thought at the outset that the high-acoustic coupling bands were likely associated with modes of the ISI flexure because they lined up with ISI resonance bands characteristic of all ISIs, and all external vibration would have to be funneled through these flexures to shake the table. Figure 2 shows that I excited a number of peaks in my in-vacuum accelerometer spectra by flicking one of the 3 ISI suspension wires (number 3). The evidence that it was the wire resonances and not some other resonances that I excited by flicking the wire is strengthened by the fact that these peaks were not evident when I damped the wire by clamping a piece of Viton to it. Since flicking amplitude is not well controlled, Figure 2 shows that I went back and forth several times between clamp-on and clamp-off states. Figure 3 shows that the lowest of the excited wire resonances, 753 Hz, matches the frequency of a peak in DARM that is excited by shaking HAM6 with a shaker. Note that the peak at this frequency is not the largest feature in DARM in this region, the feature between 850-100 Hz is larger, but, resonances of the wires do seem to account for the coupling at higher frequencies.  Figure 4, for example, shows that at least two of the high frequency resonances excited by flicking the wire line up with peaks in DARM that were excited acoustically. 

Figure 5 shows that tapping on the blade spring rather than the wire produces peaks that line up with acoustically excited peaks in DARM, including the largest acoustically excited peaks in the 850-1000 Hz band. I tried clamping a small piece of Viton to the blade spring and it was not nearly as successful as the wire damping (a factor of 2 at most). Possibly a larger piece would help, but I am inclined to suggest a tuned damper like the one for the low frequency blade spring mode.

Thus I would suggest that we develop a wire clamp damper like the prototype that I made to damp the wire modes, and that we develop tuned dampers for the 350-450 Hz band and, most importantly, for the 850-1000 Hz band.

Robert S., Hugh R., Katie Banowetz, Nutsinee K.

just adding the SEI tag so I don't loose the entry.

Magnetic coupling at ITMX

I was able to make a couple of PEM injections during ER7, not enough to get a full picture, but because it is of interest, we superimposed magnetic noise prediction points for the ITMX injection onto the plot for coupling at ETMY (figure). The predicted level for ITMX is flatter in frequency (some cable coupling?) but the coupling level near 10 Hz, where the prediction is closest to the DARM noise floor, is lower than for ETMY.

Robert S., Katie Banowetz

ITM RH heating/measurement attempt

Elli, Greg, Nutsinee

The ITMY HWS return SLED beam is slightly clipped at the moment so we are testing to see whether or not the HWS sees the similar result to alog14698 before we move on to do CO2Y alignment work. Elli turned on the ITMY HWS camera yesterday morning to let it warm up. We ran the HWS script this afternoon before and after turning on the ITMY ring heater for >30 mins (the ring heater was turned on at 21:42:18 UTC). We didn't see any significant changes in spherical power, prism X, or prism Y. We also tried to run the script on ITMX HWS to see if we could get any result but the return beam was so dim that the script crashed after taking 50 sample of centriods ("Not enough unique sample points specified"). We turned everything off and called it a day. Hopefully we can work on ITMY HWS optics alignment tomorrow.

end Y chassis 3 updated

Filiberto, Patrick

I didn't realized it had been removed, and except for communication errors with the missing chassis, the PLCs ran on without apparent incident.

Filiberto made the same modifications as to the one at end X and reinstalled it. I updated the system manager accordingly, checked it into svn and activated it.

This time I didn't restart the PLCs, but I still had to restart the EPICS IOC. I burtrestored to 6:10 this morning.

Both End Station Controls Chassis 3 were updated to wiring diagram E1400317-v2.

The following beckhoff modules were installed:
QTY 6 : EL3104 Analog Input Terminals
QTY 1: EL9410 Power Supply Terminal for E-Bus

New modules inferface with ALS WFS Demodulators and MCL PZTs.

Ops DAY Summary

Day's Activities

• Noticed SR3's Guardian was in ERROR, Guidance was to Load, so I Load-ed it.
• 8:20:  Christina cleaning at HAM6
• 8:35:  EY Beckhoff going down for ethercat vacuum guage work (Patrick/Richard)
• 8:50:  Starting ETMx charge measurements (Leonid)
• 8:55:  Pulling EX EtherCAT chassis (Filiberto/Ivan)
• 10-11:  TMDS piping work (Bubba)
• 11:00:  Ops Training
• 11:20:  HAM6 Closeout work (Matt/Dan)
• 12:26:  Stefan out to end station for timing work
• 12:45:  Nutsinee taking parts to LVEA
• 1:00:  Mike out to talk to HAM6 crew
• 1:10:  LVEA transitioned to Laser HAZARD
• 1:53:  TCS work for ITMy (Greg, Nutsinee)
• 2:15:  HAM6 Closeout work continuing again (Matt, Dan, Hugh, Greg)
• 3:55:  EY Beckhoff going down (Patrick)
• 4:01:  Checking racks for as-built (Dave)

RX FF on ST1 BSC-ISI's

After my work on the HAMS on Wednesday, I thought I would try working on BSC feedforward some more. So far I've just gotten RX FF working on ITMY (I was then promptly distracted by other stuff). First attached plot shows the improvement I've gotten between 10 and 30 hz, red and blue are the FF on and off Y ground, magenta and cyan are the T240 RX with FF on and off. Second plot shows that I managed to not spoily the Y direction anywhere (same color scheme, red/cyan FF on, blue/magenta FF off). Last plot shows my design, blue is the X/Y FF we are currently using, red is the ideal filter, green is the filter I've installed. Black was supposed to be an estimate of the performance, but I haven't quite figured that out yet, I'll post when I've fixed it. It is supposed to be something like 1 - (filter installed) / (ideal filter), but all I get is ~1, which means no subtraction.

OPLEV Charge measurements

Leonid.Prokhorov, Jeffrey.Kissel

We measured ETMY and ETMX charge using optical levers. At both TM the charges are much lower than it was before discharging. Plots of the day and long-term are attached.

Note, that for ETMY we see the other sign of pitch and yaw response than it was in measurements of June, 12. We have not find the reason. We did the couple of measurements with Low-voltage driver instead the Hi-voltage. Sign of respose for Hi and Low voltage drivers agrees even if correlation of measured points for low voltage is very low. Dependencies of pitch and yaw on bias voltage are in attachment. 
Just in case: for all ETMX measurements signs are the same as June, 12. For ETMY the previous measurements of charge was in Jan and it gives us the 3rd combination of signs. 

PSL Weekly Report - Past 10 day Trends

One year data also indicates EY tilts twice as much as EX along the beam line.

We studied one year data taken from May 01, 2014 to April 30, 2015. The results agree with the earlier findings from 4-months data (here), i.e., EY tilts twice as much as EX along the beam line. Figure shows 1 year of the 0.03 to 0.08 Hz beamline seismic band at EX and EY plotted against wind speed measured at EX. The full study is documented here.

Dipongkar Talukder & Robert Schofield

Jitter tuning improvement stable during ER7

During ER7, the alignment of the IMC was adjusted to minimize the jitter peaks in DARM around 312 and 347 Hz (Link). We examine the stability of the tuning here. The top two traces in the figure are BLRMS bands centered on the peaks, and the tuning is the sharp drop at the left of the plot. The dashed horizontal lines on the plots show the pre-tuning and post-tuning level.  

The tuning seems to have been fairly stable, the peak height at the end of the run was about what it was right after tuning. The peak height increased during the period when the power was increased to 24 W, which is indicated on the plot by a yellow background. This was expected because the alignment was not retuned for this power. But when the power was returned to about 17W (cyan background) the tuning returned to its good state. 

The main drawback that we found was that the peak height started high after each lock and drifted down to the tuned level over tens of minutes.

Dipongkar Talukder & Robert Schofield

Moved BPG402-SE at end X to output of photodiode chassis, chassis 3 removed

Filiberto, Patrick

Filiberto moved the cable for the gauge and I made the update to the system manger, committed it into svn, and activated it.

Filiberto then removed chassis 3 for his work on it. I disabled that chassis and the one following it in the target system manager, activated and ran that configuration. I have not restarted the PLCs because I am not sure they will run without the missing chassis. The gauge appears to still be operating however, as it does not need a PLC program.

So the end X Beckhoff PLCs are not running while Filiberto works on the chassis.

Filiberto reinstalled the modified chassis. I updated the system manager accordingly, committed the change to svn and activated it. I had to reboot the computer in order to get PLC2 to run. I burtrestored to 6:10 this morning.

It is back up and running again.

Added BPG402-SE to end Y Beckhoff

Richard, Patrick

Did essentially the same work as yesterday (https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=19310), except the gauge was connected at the end of the photodiode chassis.

Omc black glass shroud installed

Kate, Matt and a wee bit of help from Calum Omc black glass shroud is installed. More to follow ... To do list 1) balance mass 2) beam dump 3) beam diverter 4) laser beam check 5) cables. Please note should look at cable from omc bench. Dan and Matt are going to look at this in am.

Ops Morning Update:

From Ed's summary yesterday, assumed to be the same, since no emails about changing to Laser Hazard:

We are currently LASER SAFE in the corner and the ends. PSL is shuttered, CO2 LASERs are OFF. End station Viewports and tables are closed and locked. Not sure about the on/off statues of the ALS.

• Dust - all monitors, except optics lab and bakeout, are green, i.e. low counts.
• CDS overview - some red
• CDS DAQ - all GPS readbacks updating

Timeline - Last night:

• 6:38PM - HAM6 people out of LVEA

Timeline - This morning:

• 7:40AM - MattH into LVEA
• 7:48AM - Karen and Christine in LVEA
• 7:58AM - MattH out of LVEA
• 8:10AM - MattH into LVEA
• 8:15AM - Corey to Squeezer Bay - and back
• 8:35AM - Hugh to EX
• 8:47AM - Patrick/Daniel, WP5298
• 8:55AM - FilibertoC/PeterK/RichardM - WP5299 & WP 5300
• 9:06AM - Jason/Ed - EX Oplev
• 9:11AM - JoeD - Mids and End Stations to check fire extinguishers / lights

1PPS Time Offset Histograms for EY/EX/MSR Time Code Generators and MSR Trimble GPS Clock

Data extracted for the three week period of ER7 (since the timing system would nominally be running steadily the entire time). The histograms show:

- Tight grouping of the minute trends in the data; min and max values for each minute end up in discrete bands. 
- The Time Code Generators show nearly identical histograms for their mean minute trends.
- The mean minute trends of the GPS clock are much more tightly grouped with a width of roughly 20ns; with minimum and maximum offsets included, the width roughly doubles.

Issues:

- There was a single second during which the MSR Time Code Generator was off from the timing system by approximately 0.4 seconds. The issue self-rectified before the start of the next second. Second-trend data was not available through dataview (or at least I couldn't get any out of it). This did not happen in the EY and EX time code generators. It did not happen again in the MSR time code generator. The anomaly happened at GPS time 1117315540.

I've attached histograms as well as screenshots of data taken from Grace.

Conclusion: The timing system is internally consistent and doesn't drift much relative to the atomic clock.

We should look at this again once we hook up the Master's 1PPS input to the Symmetricom's 1PPS output; right now it's getting its 1PPS frpm the Master's built in GPS clock, which isn't as accurate as the Symmetricom's signal. 


The time code generator in MSR is connected to an atomic clock, which we'd expect to provide more accurate short-term timing, though GPS beats it in the long-run. So we're interested in short-term deviations from the atomic clock time, not the overall linear trend, which won't be flat unless the atomic clock itself is perfectly calibrated. For this reason, it's not surprising that the timeseries for the TCG and TCT show linear drift. The relevant metric (variation about the linear trend) is actually smaller than the above histograms would suggest, which is good. Even the naive measurement presented in these histograms shows variance of less than 100 ns.

DARM glitches produced with beam tube taps causing accelerations of roughly 1 m/s^2 peaking at ~1000 Hz

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.