Detector Watch 3

Mike Hewson
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Topic 192070

This is a continuation of this thread.

Plus thunderstorms, winds, rain at Livingstone.

Cheers, Mike.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Mike Hewson
Mike Hewson
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Detector Watch 3

Alas Livingstone isn't even plotting data at the moment:

and here's why:

which seems about as bad as it can get, preventing any IFO lock at all. The Kamchatcha/Kuril quake was re-assigned as 8.3, and others of similiar magnitude + aftershocks are occuring!! The IFO's are not in the P-wave shadow zone:

which is between 103 and 140 degrees away from the epicentre of the quake area ( marked by the thicker black lines on the above plot from USGS ). This is the region, on the spherical Earth, that relatively little energy from the quakes propagate ( by pressure waves ) through the deep substance of Earth's interior.

Storms, trains, and coastal waves pounding the shoreline have done the rest.

Mind you they are taking the opportunity to poke about and inspect/test a few things given that lock can't be obtained at the moment.

Cheers, Mike.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Chipper Q
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Still some problems with the

Still some problems with the winds at Hanford, but they've still been able to maintain lock a little over half the time:

S5 Run Statistics, Daily Locked Statistics (Nov 15) for H1 was 52.8%, and for H2 was 54.3%

There was an informative entry regarding calibration studies for H1 and H2:

Quote:
On late Tuesday afternoon, we began calibration investigations on both machines. The goal is to make a final round of measurements and produce an S5 V3 calibration for the first calendar year of the run (Nov 4 05 - Nov 14 06). This final round of measurements are required i) to close out the calibration for the final epoch of S5, as the machines may have changed calibration subtly owing to recent commissioning efforts, and ii) to understand some structure seen in the ITM/AS_Q Michelson transfer functions, first noted in the summer.
...


Also more tumbleweed baling: '...The winds of last night have added to our initial crop... ' Thanks, BTW, for the pictures of Hanford up close. I had confused the location of Hanford with the parts of Oregon and Washington with a famous history for logging (it was a way of life for a lot of folks who live in the Pacific Northwest). East of that region, past the Columbia River Gorge area, the land is more like desert (well, it is desert) than what I'm familiar with, which looks like this:

Hanford is off in the distance (not visible), on the left side of the river... I didn't realize it was as far east as that... definitely not a single tree in sight at Hanford! :)

Of course, the difficulties (in addition to logging) at Livingston are obvious, from the Figures of Merit in the Hanford elog, and even in the local news here on the West Coast, about the terrible weather back east... :(

Chipper Q
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When watching the detectors,

When watching the detectors, it helps to know what such things as DARM, AS, PO, WFS, REF, and GDS mean, with respect to the detection of gravitational waves. These are seen frequently in both elogs, but don't appear in this (more general) list of acronyms.

They are all related to the Length Sensing and Control (LSC) and Alignment Sensing and Control (ASC) systems, and sensing and controlling overall alignment of all the many optical elements in the interferometer is critical to measuring changes in length of the arms that would be due, apart from the many types of noise, specifically to a passing gravity wave. The LSC and the ASC are both part of the Interferometer Sensing and Control (ISC) system.

I found a 3-page (pdf) paper that's not too difficult to understand, on the The LIGO Interferometer Sensing and Control System, where these acronyms (and others) are more clearly explained (than what I could do, if I tried to summarize it). Fascinating to learn that it takes 13 microseconds for a control signal from a CPU located at the vertex of the interferometer, to travel to a servo located at one of the end stations (in a 4 kilometer arm), and of course this must be taken into account when the servos are designed...
- - - -
S5 Run Statistics, Daily Locked Statistics (11/16) for H1 was 71.8%, and for H2 was 47.2%

Some trouble with the End Test Mass in H2's Y-arm again, still looking closely for possible causes, and it's looking like it happens at roughly weekly intervals...

Also the most recent (end of Day Shift) 'Figure of Merit 1' showed that H1 and H2 at Hanford, and L1 at Livingston, for the last few hours, are finally getting some coincident data locked in Science Mode. :)

Chipper Q
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The S5 Run Statistics have

The S5 Run Statistics have been posted for Nov 18, and Hanford's Daily Locked Statistics were 85.2% for H1, and 85.1% for H2, and Livingston's L1 Science Data Statistics were 82.2%

There were several earthquakes mentioned:
Mt. St. Helens at 20:21 PST on Hanford's evening shift summary for the 18th, so 04:21 UTC on the 19th
Mag 5.7 near Colima, Mexico, happened at 06:57:13 UTC on the 19th
Lockloss for L1 at 19:11 UTC on the 19th, from an earthquake
Mag 5.2 in the East Pacific at 18:57 UTC on the 19th
L1 lockloss at 13:02 UTC on the 19th, due to earthquake

This was a bit difficult to sort out looking by at the State Vector, Seismic, NS/NS Inspiral Range, and Cal Lines plots (which together make up Figure of Merit 1 --samples of FOM1 & explanations here), and so I checked Hanford's previous elog entries for the day before, and I was thrilled to see the following brilliant proof of concept, using the seismic data from all the sensors, combined with the fact that they're conveniently located in two, long, 4-kilometer rows that form a 90-deg angle at the vertex of the rows. What can you do with this arrangement (in addition to isolating the optics from much of the Earth's vibrations)? Well, when there is an earthquake (or some other possibly mysterious, unidentified source for a seismic event), you can use the data to determine the direction of the source - - you can literally (and quite accurately) point to the source of the disturbance! Here's what Tobin Fricke (at Hanford, using the recent Mt. St. Helens event data) worked out so far, with accompanying figure:

Quote:

[pre] time-delay of arrival for seismic events - proof of concept[/pre]I wrote a Matlab program that does a coherent "time delay of arrival" analysis on the seismic channels (currently only considering the Z direction). In examining the waveforms from the Mt. St. Helens event, the analysis gives a bearing to the source of 261.9 degrees. Computing a bearing using the published epicenter of the earthquake and the LHO location using the WGS84 earth model gives an actual bearing to the published epicenter of 263.9 degrees, a difference of 2 degrees. At the distance of Mt. St. Helens this corresponds to a distance of 7.5 km.

The figure at left [below] shows the waveforms from the six seismometers at this time, after filtering with an elliptical bandpass filter with a pass band of 1-5 Hz, and decimation by a factor of ten. I estimated (using Google Maps) the location of the seismic vault in "LIGO coordinates" to be X=1040m, y=186m. The figure at right shows the "power" (not well-defined) associated with various wavevectors; the X axis gives "east slowness" and the Y axis gives "north slowness," in seconds per kilometer. The circle indicates a velocity of 5000 m/s, the approximate velocity of P-waves in rock. The seismometer locations are superimposed for directional reference only.

I am interested in whether this could be used to image local seismic noise.

Performing this analysis on the microphones might be another way to find airplanes.


[img]http://groups.msn.com/_Secure/0TQDiAvEXFr2GZGeyCB33ghxOXJGVxWfWnurIRSCXUad25RHJUUsJ59*p!T6CA8dVwcD7EL3UcNpGOeFzFBXpdNPvcdFM*WY6MElWQTqfVNYwC5tgQiungw/FrickeSeismicPOC.jpg?dc=4675598555859732442[/img]
The science within the science is amazing! :)

tullio
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A very foolish idea: why not

A very foolish idea: why not using the whole Earth as a resonant bar detector? The deformations caused by a GW could be detected by horizontal pendulums such as those placed in the Grotta Gigante geophysical observatory near Trieste (google) which can detect not only seismic waves but also Earth tides caused by the Moon. The observatory was founded by prof. Antonio Marussi of the University of Trieste who was one of my teachers and also the scientist of the Italian team which conquered K2 in 1954. Please don't shoot the pianist, he does what he can!
Tullio

RenaudKener
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RE: A very foolish idea:

Message 50947 in response to message 50946

Quote:
A very foolish idea: why not using the whole Earth as a resonant bar detector? The deformations caused by a GW could be detected by horizontal pendulums such as those placed in the Grotta Gigante geophysical observatory near Trieste (google) which can detect not only seismic waves but also Earth tides caused by the Moon. The observatory was founded by prof. Antonio Marussi of the University of Trieste who was one of my teachers and also the scientist of the Italian team which conquered K2 in 1954. Please don't shoot the pianist, he does what he can!
Tullio


Even the new european GPS system "Galileo" hasn't enough accuracy to measure deformations alongs 3 orthogonal axis... now.
But, maybe in a decade or two.

"Entia non sunt multiplicandam praeter necessitatem"
(OKHAM)

Chipper Q
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The numbers for the 19th are

The numbers for the 19th are in, and they look pretty good for triple coincidence. S5 Run Statistics, Daily Locked Statistics were 99.2% for H1, and 84.9% for H2. The Livingston L1 Science Data Statistics were 77.2%.

Quote:
why not using the whole Earth as a resonant bar detector?


The resonant bar detectors continue to be improved in their sensitivity. This table is from the Gravitational Wave Detection A3 / 4 Seminar Report (J. Robert Taylor, Oct. '02) [29-page pdf doc, the table is linked to it]
[img]http://groups.msn.com/_Secure/0VAAAALsax53Z9YShIKzWtcPbRGVP5yUmHoUQlxjXlnaJYIsgF!X*Z*qkF9YM8FcgfkX0K8wftnXifauJJLGq5S1vM1xjcLSytmdOf1IajanSE8!XNQdHQzYhucy0RLU9/ResonantBarDetectors_02.jpg?dc=4675598691990057100[/img]

In the report it was pointed out that there are a couple drawbacks with the resonant bar detectors. One is that the detector will only be sensitive to gravitational waves whose frequencies are resonant with the bar. The other drawback (and I think this has to do with your question, Tullio) is that the material used for the bar will, of course, be sensitive to temperature - - any temperature whatsoever. The thermal motion of atoms overpowers any gravitational wave signals. And when you cool the detectors and use something as sensitive as SQUIDs to measure the position of the bar, you get an unpredictable quantum mechanical 'kick' from the detector in terms of being certain about bar's velocity. This is known as the Standard Quantum Limit (SQL).

The best prospects for more sensitive detectors are the interferometers. And some of the best IFOs around, the ones we're watching, are due shortly to get even better :)

I'll try to highlight some of the various upcoming improvements that will be made to the H1/H2 and L1 LIGOs, during the next few days, and wish for everyone a happy and safe Thanksgiving holiday!

tullio
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Thanks Chipper for bringing

Thanks Chipper for bringing my attention to the article by J.Robert Taylor. I have just printed it on my old HP 710C printer. In 1970 I published Fig.2 in an article by prof. Peter G.Bergmann, a coworker of Einstein, titled "Researches on general relativity" in Mondadori's Yearbook of Science and Technology. The photo was kindly provided by prof. Weber. The article was not exactly applauded by Italian elementary particle physicists but I think it drew the attention of prof. Edoardo Amaldi on an up to then neglected field of research. So, maybe, mine work as a science editor gave a small contribution to the progress of science.
Tullio

Chipper Q
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The National Science

The National Science Foundation has produced an excellent documentary called "Einstein's Messengers" (streamed by LIGO Laboratory). The only thing that disappointed me about it, was it's only twenty minutes long :)

@Tullio: I've seen that photo of Weber quite a few times, prominent in most accounts of early gravitational wave research; well spotted, to recognize the significance back in '70! By the way, data from the S4 Science Run from Livingston's L1 is being checked for coincidence with data from the ALLEGRO resonant bar detector. The results were still under internal review (as of 9/06)...

tullio
tullio
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RE: The National Science

Message 50951 in response to message 50950

Quote:

The National Science Foundation has produced an excellent documentary called "Einstein's Messengers" (streamed by LIGO Laboratory). The only thing that disappointed me about it, was it's only twenty minutes long :)


I disagree. 20 minutes is the right time to keep up the attention. If a sermon is longer than that every faithful yawns. Very cool, very professional. Is the film director related to George Lucas?
Tullio

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