Detector Watch 4

Mike Hewson
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Topic 192183

This is a continuation of a previous thread.

Ok, detector fiends, gravity detectives and number crunchers!! With all those stormy oceans it's time to speak of wave propagation.

Consider the counting of waves with respect to time. If each time a given part of a wave passes a point then we can note the time that this happens. Each instance of measurement would create a little set of linked numbers consisting of:
- a time ( some clock reading )
- a place ( some ruler mark )
- and a wave 'level' ( some quantity like voltage, or light intensity )

Like so:


[pre]Time Place Volts
---------------------------------
0.5 6 20
[/pre]If you sat for a while at some position, and collected a few of these little sets then perhaps some pattern may arise - like 'gee, every time the voltage reaches 20V then a whole second has passed since the last measurement'. You'd then define a frequency of one Hertz for that signal.


[pre]Time Place Volts
---------------------------------
0.5 6 20
1.5 6 20
2.5 6 20
3.5 6 20
4.5 6 20
5.5 6 20
...etc
[/pre]With a 'regular' wave then if the you moved back and forth a bit along some line, then when sitting at another given point for a while you'd see much the same behaviour - a one Hertz rythm.


[pre]Time Place Volts
---------------------------------
0.375 4 20
1.375 4 20
2.375 4 20
3.375 4 20
4.375 4 20
5.375 4 20
...etc
[/pre]Because of the finite speed of the wave travel, then each point you sat at would be slightly earlier or later with respect to another depending upon whether it was 'upstream' or 'downstream' of that point.

This raises an particular thing about such waves. Suppose I was real keen on 20V levels. Then If I am at 6 metres when the 20V is at the 4 metre mark like so:

then I can EITHER wait a short time for the wave to reach me OR I could ( magically/instantaneously ) shift back two metres to the left and get it now!!

This embodies the idea of a wave keeping it's shape as it moves along. Gravity waves pretty well do this over the distances we are likely to be sampling them hereabouts. They do diminish as the reciprocal of distance, but many light years from source:

1 / ( SOME_REALLY_BIG_NUMBER )

is much the same as

1 / ( SOME_REALLY_BIG_NUMBER + ONE )

For those of you more mathematically inclined, the wave can be expressed as follows
( wave propagating along in the positive x-axis direction for simplicity )

Sin( 2*PI*f*t - k*x )

where:

Sin = sine-function
x = distance co-ordinate
t = time co-ordinate
k = the wave number
PI = good old 3.14159 ... etc
f = frequency

The factor of w*t - k*x is generally called the phase. Note the negative sign within. This means I could increase the phase ( to get to my 20V level ) either by waiting ( let t increase a bit ) or by moving to the left ( let x decrease a bit )

w = 2*PI*f is called the angular frequency, for historical reasons mainly. It is the rate of change of phase with time, when distance is held constant. k is similiarly the rate of change of phase with distance when time is held constant. These are partial derivatives if you like.

[ The 2*PI factor indicates that plain trigonometric functions repeat their amplitude/values after that much phase change ]

If you're still with me, then what values do we have for the waves above?
Assuming I've instructed my young Steve ( all hail the King of Macromedia Shock Wave!! ) correctly, then you'll note a quarter cycle is 4m long, making the wavelength 16 m. It takes ( by the tables above, not from your viewing speed via your browser ) 0.125 seconds to travel the 2 metres from the 4m mark to the 6m one. So it would travel 2 / 0.125 = 16m in one second. Hmmm .... yes .... you see it? Yep

frequency * wavelength = speed ( = w / k )

Just to cap off now, recall that Mr Fourier's Transform allows us to disassemble any old wave to a bunch of sines, and it's inverse transform to assemble a bunch of sines into some final wave shape. Thus with little alteration, all of the above applies in principle to pretty much any shape of propagating wave.

( More exactly we've been discussing phase velocity, as distinct from the group velocity of a gaggle of sinusoids .... but enough for now )

Cheers, Mike.

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

Mike Hewson
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Detector Watch 4

Livingstone managed to get 55% SM on 11/12/2006, with AS_TRIGGER @ 20 ( was up to 100 the day before ). This would have to be the messiest seismic plot I've seen so far:

& they have done some maintainance.

At Hanford H2 outdid H1 at 85% to 71% for SM. Also maintainance ( being a Tuesday ) as follows:
[pre]Corey/Ray F. MX accel. relocation DONE
Dave Moved injection machines DONE
Betsy/Rick 2k MOPA PD swap DONE
Josh 2k MOPA PD power hookup DONE
Sprague On site
USB Electric. On Site - MSR work
Anamaria/Mark 4k PSL LVEA pipe layout measurements
Robert ISCT4 and ISCT10 table floatation check DONE
Robert/Richard Radio work
Oscar On site - cleanup
Rick/Evan/Mal 2k VCO measurements
Praxair CP3 fill DONE
ACE Septic Visited then left (maybe be back?)
H2 dark offsets run DONE
Dave Conlog/Stat work
Corey EX visit - pix
Michael/Eiichi 4k dark Mich. calibration work [/pre]
- four hours is allocated, and everyone rolls up their sleeves. A couple of data segments for H1 have been flagged as the timing channels were off/disconnected during maintainance and not immediately re-enabled. The significance is that signal correlation with other IFO's particularly may be difficult for those data lumps. Some problematic photodiodes were replaced on H2 to a newer/better types- these devices convert light shining on them to an electrical signal.

Also don't forget some mundane tasks which are more vital than they might at first sound:

Quote:

Before the tumbleweeds plugged up the arms OSCAR was performing routine maintenance on the two arms. This maintenance includes:

- plugging holes in the concrete covers to keep the rodent count down,
- cleaning rocks, sand, and tumbleweed remnants off the roads and away from the concrete covers,
- spraying anti germination chemical at the sides of the asphalt.

For some of this work he uses his weed trimmer and leaf blower. If he needs to run this equipment within 125m of a building he does this on Tuesday am. He will continue to use one of our tricycles for travel up the arms.


This is Oscar's team:

Robert Schofield has another excellent discussion, regarding the mounting of ISCT4 ( Interferometer Sensing and Control Table 4 ). This is at H1's Anti-Symmetric/Dark Port in the LVEA ( Laser and Vacuum Equipment Area ), ie. in the corner station. Corey Gray has this excellent shot:

It's in the white box/room which is parked against a vacuum module ( the big shiny kettle/still looking thing on the right ). Inside the table looks like this ( thanks to Corey Gray again - his site is a real goldmine ):

AS = Anti-Symmetric
WFS = Wave Front Sensor
Hamster House = ????

I'll work out the detail of this table's function one day, but for now note that it is a crucial component for extracting the relative phase delay between the laser paths on the two interferometer arms. The problem was parts of the table touching stops when it should have been floating ( on fluid ). At ISCT10 ( the equivalent arrangement for H2 ) a tiny particle was bridging a small gap where it shouldn't be.

Cheers, Mike.

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

Mike Hewson
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Moving on from propagation

Moving on from propagation now ( I'm gradually working up to resonance ), let's discuss reflection at interfaces/boundaries. In the IFO's this happens for the laser light in our IFO's, sound vibrations etc whenever there is a substantial change in material properties ( eg. near vacuum to mirror substrate ). The gravity waves themselves simply pass straight through the whole kit'n'kaboodle unaffected.

Recall our hard working standard sine wave going to the right in the positive x-direction:

with the expression: Sin( 2*PI*f*t - k*x )

There is a deep symmetry here. Let's freeze the wave in time.

Then flip it over ( or multiply the amplitude by -1 if you like ):

Now move this inverted wave back/forward by one-half cycle:

Back where we started! Another way of saying this is that a 180 degree ( or PI in radians ) phase change is equivalent to an inversion. [ Radians is simply another measure of angle - a full circle of 360 degrees is 2*PI, thus 180 degrees = 1*PI, 90 degrees = PI/2 etc. The plain trigonometirc functions repeat their values after a full circle/360 degrees/2*PI. ]

[ Generally whenever there is a symmetry it should be eagerly seized, they are the gold nuggets of physics!! ]

Well what does happen at a mirror surface say? It's roughly as follows - the wave flips over and goes back from whence it came:

If you stare at the animation for a while you'll note that it looks like the incoming wave ( coming from the left and moving to the right ) simply disappears behind the blue wall. The reflected wave ( coming from the right and moving to the left ) looks like it appears from behind the wall. This is why when you look into a mirror it seems like there is a whole universe behind it!!

Mathematically:

Sin( 2*PI*f*t - k*x )

becomes ( flip it over )

-Sin( 2*PI*f*t - k*x )

and then ( reverse it's direction )

-Sin( 2*PI*f*t + k*x ) = Sin( 2*PI*f*t + k*x + PI ) [ using the inversion rule ]

The change of the sign of k deserves further explanation. Recall that k was the rate of change of phase with distance when t is held constant ( partial derivative ). So if this rate is reversed/negated then what was an +ve change in phase ( with distance ) becomes a -ve one, and vice versa. [ Please note that we are discussing how the phase changes with distance, NOT how the amplitude ( measured along the vertical axis ) of whatever quantity we are measuring, changes with distance.]

So let's make that phase change, so that now it decreases to the right ( ie. increase to the left ):

which is a left going wave.
Also note, again, that a full cycle takes a given distance ( the wavelength ) to complete 2*PI worth of phase. [ NB Some textbooks/sources use k = 1/wavelength, I've used/implied k = 2*PI/wavelength ]

Cheers, Mike.

NB. Thanks also to Steve ( who may have the better half of my genes ) for the graphics work.

NB. I feel I ought to strongly thank Image Shack for hosting these animations/GIF's for free!!

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

Mike Hewson
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Summarizing the last few

Summarizing the last few days:
13/12/2006

Livingstone - SM @ ~87%, inspiral range at ~ 12Mpc. Faulty magnetometers +/- batteries for same ( these measure ambient magnetic field ). AS_TRIGGER initially at 150, then set to 9 and worked up to 100 - this determines the threshold for staying in SM. Two GRB notifications.

Hanford - those piezo-electric elements required an alteration to their calibration, as did photon calibrators ( convert light power to voltage ). Both ground movements and wind limiting lock.

14/12/2006

Livingstone - SM @ ~90%. trouble with the ilog server. AS_TRIGGER varied similiarly again. Trains, else quiet.

Hanford - Database trouble with aligning data segments with their proper times. Wind warnings for 40 - 60 mph. GRB alert ( hence veto of injections ) but later reported to be cosmic ray showers triggering this ( ie. not an astronomical source of interest for gravity waves ). Science mode about 50%, H1 and H2 ranges a bit below nominal. Trucks and power supply glitches a factor. Wind gusting to 109mph!!

Quote:
The winds forecast have arrived like a wall of water. We went from near calm to 70mph winds in just a few minutes. This wall washed up from the Ends to the mids and finally the corner station.


and you can clearly see when it arrived by the vibration it caused:

Also:

Quote:
A loud (prop) plane flew over at 14:54 PST.

15/12/2006

Livingstone - SM @ ~73%. The Thermal Control System, which heats areas of the mirror faces to preserve optimal shape using a laser, adjusted thus bringing inspiral range up another Mpc.

Quote:
An uneventful night with no 100+ mph wind gusts.


Quote:
"cry Havoc! and let slip the dogs of war!"

- Dan Hoak :-)

Hanford - Pacific storms literally blowing through. SM @ < 50%. This results in a large collection of tumbleweeds, cleaned up by Oscar ( pictures by Corey Gray ):

Note the embedded pines on the right, and upper/roof level residents below the external stairs!!
Similiar problems at the arms:

An interesting coupling between 500kV transmission lines, there are several, ~parallel to the Y-arm, and ( probably ) the magnets attached to the test masses. Correlates have been found between currents in those lines ( up to 2000 Amps!! ) and a 60Hz ( the standard AC supply frequency in the USA ) peak in the differential arm signal ( DARM ). Supposedly if the phase between the various lines is right it could account for about 1/3 of the magnetic fields observed - however if the phase of the lines differ by up to 3% then it can be somewhat more. Think of it like being really close to powerful radio transmitter. As mentioned this has implications for future magnet design, shielding and power line routing! Thanks again to Robert Schofield.
A Mt St Helens earthquake ( mag. 3.1 ) bumped H1 & H2 out of SM ( ~55% each).

16/12/2006

Livingstone - SM @ ~high%, laser power 8W ( quite good ) and Inspiral range @ 14MPc ( excellent ). Seismic noise relatively low. Passage of trains ( there is a line a few km to the south of the Y-arm ) excited violin modes, these subsided/decayed.

Hanford- Trucks and tumbleweed bailing. A group from Goddard Space Flight Center who have developed a transform for short burst of variable frequency data, were invited to examine upconversion of noise from lowish frequencies ( 1.7 Hz ) to 40 - 120 Hz band. Upconversion is a generic term that refers to energy in low/slow modes of vibration moving to higher/faster regions of the interferometers spectrum. As the sweet spot/band for the IFO's are centered on 200Hz, it's preferred to keep noise out of this area, so understanding upconversion is important. I have no idea what a Hilbert-Huang Transform is, but it sounds impressive!! All these types of studies help to provide knowledge to produce an end-to-end ( E2E ) model of the interformeters.

Cheers, Mike.

NB. Observing high voltage lines here DownUnder I note that the wires are grouped in fours ( with spacers ). This I think gives a quadrupolar radiation pattern, ie. rapid fallof with distance....

( edit ) Also, for those who may have had trouble with grasping the phase discussion ( last post )- one could think of it like seasons. So instead of phase going from 0 through to 2*PI, or 0 through 360 degrees, you could mentally substitute Autumn/Winter/Spring/Summer if you like! It's cyclic and analogises well enough. :-)

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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Found this from the Goddard

Found this from the Goddard Space Flight Center: Hilbert-Huang Transform Technology. Looks like HHT picks up, where Fast Fourier Transform, Discrete Fourier Transform, and Wavelet Transforms leave off, when it comes to the analysis of signals that are nonlinear or nonstationary (or where there's intra-wave modulation, and in the case of the LIGOs this would mean seismic, acoustics, and optics applications). Probably most impressive is the ease of implementation (in either software or hardware) to provide real-time signal analysis.

Mike Hewson
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Here's some links to the

Here's some links to the talks recently at AEI ( Albert Einstein Institute ) recently:

Bruce Allen: audio and Powerpoint

Brian O'Reilly: audio and Powerpoint

Bernard Schutz: audio and Powerpoint

I'd particularly highlight this duty-cycle analysis ( % of time in science mode ):

which is composed of, for Livingstone:

and for Hanford:

Check out this map to the future:

with the lovely lower blue line indicating expected LIGO II performance ( but ~ 2011 + ), noting that:

Quote:
…a year of observation with initial LIGO is equivalent to just several hours of observation with Advanced LIGO


Wouldn't this be a superb 'credit rating' ?

and lastly I must show this:

which is a beautiful graphic related to calculations of two black holes dancing prior to merger.
Top desktop/screensaver material!!

Needless to say, E@H is a healthy project all round, and hearty congratulations should be extended to all participants at all levels of involvement!! It is a terrific example of co-operation... :-)

Cheers, Mike.

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

Mike Hewson
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Another multi-day summary,

Another multi-day summary, fairly subdued overall:

17/12/2006

Livingstone SM @ ~ 92%. Trains and various earthquakes, laser power dropped to stay in SM.

Quote:
17:00 Two-engine airplane seen over the arms and corner station. Noise level on the ground similar to "a gasoline lawnmower at 30 meters".


Hanford SM 100% on H1!!, 97% H2 & good inspiral ranges. Ground and atmosphere pretty quiet, quite cold. Tumbleweed baling. Two GRB alarms. Possibility of the roll modes ( 17.4 Hz ) of the mirrors being excited, with harmonics ( 52.3 Hz ). This is when the mirror rotates/oscillates around an axis perpendicular to the centre of the mirror face

18/12/2006

Livingstone SM @ ~ 76%. Heat sbsorption levels were studied for ITMx and ITMy ( input test masses in x and y arms ).

Hanford SM ~ 95.3% on H1, ~ 88% H2 & good inspiral ranges. Fog, cold. On H2 something is upsetting it on a 50 minute cycle, being investigated, perhaps supporting equipment ( chillers, fans etc ) ?

19/12/2006

Livingstone SM quite good even with the maintenance: valves checked OK, magnetometer ( still the batteries? ) again suspect. In case you didn't know, Louisiana is close to sea level:

and the magnetometer:

is down in an underground vault ( Mike Fyffe pictured ):



Hanford SM high on both despite being maintenance day, and some baling. Good inspiral ranges. Bit warmer, winds a bit higher.

Cheers, Mike.

( edit ) Some of those lovely images from GR simulations can be found at AEI.

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

Mike Hewson
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Here's hoping all had a happy

Here's hoping all had a happy and safe Christmas. I had too much white wine, but not enough Pavlova .... :-)

20/12/2006

Livingston SM @ ~91%. Wind, trains, microseism and a loose & knocking 'wavewall' ( I think this is a demo/display in the visitors centre ). Inspiral @ ~ 12Mpc. Here's a set of TV images showing on the left: the 'bullseye' of a wavefront in reflection from the ETMY, and on the right: the ETMY itself.

Hanford SM H1 @ ~50%, H2 @ ~ 85%. Two nearby earthquakes ( 3.1 and 2.8 on the Richter ) bumped H1 & H2 out of lock, quickly regained.

21/12/2006

Livingston SM @ ~92%. Bursts of wind, rain, some lightning - but a 21 hr continuous lock despite this - attributed to the HEPI ( Hydraulic External Pre-Isolator ) and tidal servo improvements. These impressive systems attempt to isolate the IFO components from ground movements by anticipating & compensating, thus buffering/damping transmission of vibrations. One of the components looks like this:

and each is arranged around a HAM ( Horizontal Access Module - a vacuum chamber for IFO components ) like so:

Hanford SM H1 @ ~60%, H2 @ ~ 80%. High microseism ( Pacific waves 12+ metres ) and tumbleweeding [ now why not mount the baler on a HEPI? ;-) ]. Two GRB alarms. Note:

Quote:
The return air register in the optics lab was found to be connected to a dead end closet. Therefore there has been very poor air flow in this room - likely since construction of this building. The ceiling tiles in the closet have been removed so that now this register is connected correctly to the return air plenum.


and that pretty regular glitch in AS_Q, looks like this :

[ for what it's worth, I'd say that looks like what is seen on a cardiac/pulse echodoppler for valve shutting ( with pipe compliance/elasticity oscillations following ) ]
with some timings:

Quote:
[pre]next glitch, last glich, dt, number of 50 minute intervals
850607481 - 850604512 = 2969s (÷50m = 0.98967)
850610449 - 850607481 = 2968s (÷50m = 0.98933)
850613457 - 850610449 = 3008s (÷50m = 1.0027)
850616425 - 850613457 = 2968s (÷50m = 0.98933)
850619628 - 850616425 = 3203s (÷50m = 1.0677)
850622675 - 850619628 = 3047s (÷50m = 1.0157)
850625721 - 850622675 = 3046s (÷50m = 1.0153)
850631736 - 850625721 = 6015s (÷50m = 2.005)[/pre]


22/12/2006

Livingston SM @ ~75%. Inspiral range 13+ Mpc, laser @ 8.3W. A faulty blower switch in the CDS ( Control and Data Systems ) at the Y-end caused elevated temperatures. Less microseism, but an Indian earthquake ( guess when ? ):

Hanford SM H1 @ ~95%, H2 @ ~ 90%. Lower wind better range. Glitches correlates strongly with activity of the DARM servo. H2 high frequency noises again investigated.

23/12/2006

Livingston SM @ ~83%. Yesterday's chiller failure at the Y-end ( Vacuum Equipment Area ) caused some mis-alignment in pitch and yaw for ETMY. Temperature sensor there unreliable too..

Hanford SM H1 @ 99.5%, H2 @ ~ 100%. Wow!! Less microseism, low winds, and some snow.The TCS has a Wiki.

24/12/2006

Livingston SM @ ~55%. Now here's a new FOM we haven't seen before, related to the TCS ( Thermal Control System ):

A separate laser heats a given mirror in an annular or central pattern ( see middle right ) to keep the shape correct. There will be some absorption of all those photons bombarding the mirrors. But it's material properties don't lend to easy management of that ( complex ), hence deliberate extra heating ( through a side port ) to actively compensate.

Hanford SM H1 @ ~93%, H2 @ ~ 87%. Basically it's all quiet on the Western front, until....

25/12/2006

Livingston SM @ ~39%. High winds, stray dogs, earthquakes, here's Dan Hoak's view:

Quote:

James Brown, 1933-2006

0400 Locked, seg4092. The microseism between 0.2 and 0.35 Hz is increasing
rapidly. I feel good.

0430 AS trigger, more ASQ glitching. Increasing the threshold. Seg4093. Papa's
got a brand new bag.

0617 Lost lock. The upper band of the microseism is well above the 95th percentile. I don't want nobody to give me nothing.

0654 It's suddenly become very windy out - gusts are over 20mph. The NWS predicts high winds for Livingston from now until the morning of the 26th. Because of the microseism, we can't ramp down the FIRs. Ain't that a groove.

The microseism remained prohibitively high throughout the rest of the shift. No
night train!

Hanford SM H1 @ ~75%, H2 @ ~ 75%. Pacific storms arrive, but waves are coming in more directly to shore - presumably 'coupling' better to the ground, hence higher microseism.

Cheers, Mike.

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

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26/12/2006 Livingston SM @

26/12/2006

Livingston SM @ ~66%. Taiwan earthquake @ 7.1, with big aftershocks thus started maintenance early. I'm chuckling that I wasn't the only one initially confused by FOM timing displays ( see here ):

Quote:
Seemingly, the T0 mentioned on the FOM's refer to the left end of time axis which is "-12" hours of current time, rather than the right side of the ( time axis which is "0" or current time.
So, if T0 = -12 rather than 0, then the FOM's are okay.


Hanford SM H1 exactly ZERO, H2 @ ~ 55%. An overnite power outage bumped all non-UPS'ed systems down. Restarting involved a rebuild on a 2 Terabyte RAID array!! A real bootfest, with the order of same causing issues. Fire alarms beeped and required fire department attendance to check out. Laser systems alarming, along with Interferometer Signal and Control Table ( ISTC, there are several numbered versions ) upsets, and other miscreants - beam centering servo, ION pump, power supplies for photodiodes and charge coupled devices, a projector, a reset of atomic clock based timing, thermal control system, gate valve too... oh and a bucket of switches need resetting/cycling.

The various computers have lots of interesting names: King, Granite, Obsidian, Gabbro, Flint, Marble, Gneiss, Gypsum, Basalt - obviously someone has done a Geology major! It's hard sometimes when reading the logs to distinguish between the boxes and the processes ( programs ) that's running on them. A total of 192 processes required restarting!!

Now some scorched tumbleweeds were found nearby adjacent powerlines, likely wind & moisture assisted into a high voltage short circuit role. A whole new meaning to smoked weed!

H2 came back up in a few hours back to lock, however H1 was hard to get past Mode Cleaner ( MC ) stage. I'm dying to know what this means ( my emphasis ):

Quote:
May be a case of mad slider disease as seen in the past with the MC/CM servo boards, if the gains are right.

27/12/2006

Livingston SM @ ~56%. Trains, seismics, anthropogenics.

Hanford SM H1 exactly ZERO, H2 @ ~ 84%. H1 still not really up, largely flakey and failing when power is increased to function beyond the Mode Cleaner ( this essentially ensures the photons enter the IFO in phase/step with each other ). Wave Front Sensors ( WFS ) were out of line - these on on the ISTC's and help determine alignment. A vacuum pump controller was found to be actually OFF for about a month.

The Data AQuisition ( DAQ ) was giving 'helpful' error messages like:

Quote:
[pre]medmCAExceptionHandlerCb: Channel Access Exception:
Channel Name: Unavailable
Native Type: Unavailable
Native Count: 0
Access: Unavailable
IOC: Unavailable
Message: Network connection lost.....[/pre]


Now that's almost down to Microsoft standard!! :-)

Aside: Does anyone out there actually report errors to Microsoft? Or examine those stunningly informative hexadecimal codes that pop up on 'abnormal program termination'? Apple/MAC/Linux/etc users, bless your hearts & minds, need not reply.... :-)

28/12/2006

Livingston SM @ ~85%. Much the same, power dropped to 5W to hold lock better- succeeded.

Hanford SM H1 @ ~ 76, H2 @ ~ 88%. H1 finally comes into SM after much head scratching, trial and test. Certain gain settings were found to be most unusual - 'gain' generically refers to the ratio between output and input levels of some device - a factor between some stimulus and the response to it. Finally:

Quote:
A phone call from Daniel who had read my issue with DARM, and he thought a toggle of the LSC Mask switches was in order, since something with DARM didn't seem to be scaling correctly. (I could get into PWRUP by throwing DARM gain overboard.)
Sure enough, on the next lock cycle, we immediately achieved PWRUP with no loop adjustments.
Aargh.


Aside: this is somewhat reminiscent of the final few minutes of the descent of Apollo 11 onto the moon's surface. ( That's in 1969, for you young un's. ) An ultimately harmless alarm was activated due to a program overflowing the memory, ie. not enough bytes. That's bytes, not even kilobytes, I'll add. This occurred at a tense time when they were awaiting lock from a downlooking radar, which would tell them how high above the surface they were, a pretty important parameter on the day. This distracted that dear brave crew, Neil Armstrong was at the control stick and Buzz Aldrin was watching the instruments ( and watching Neil too ). Buzz simply solved the problem by 'cycling' a single switch ( the right one! ) - turning it OFF, pause, then turning it ON again ...... it was a 'toggle' type switch. Sigh .... :-)

Oh, and guess what was the first thing they did, moments after landing? Neil turned OFF the switch that enabled the joystick that controlled the craft.... a bad time to flip the lander over by inadvertently knocking the joystick ehh? Neil later admitted ( tongue in cheek ) that he would have slapped Buzz if he'd gone any where near it... :-) Buzz had the designation of 'pilot', but the 'commander' actually flew it... :-)

A gate valve caused some concerns, but came good. These gates separate the components of the vacuum system physically sealing ( aka. 'airlock' ) so that portions of the interior space of the beam tube, modules etc can be accessed without losing the considerable volume within to atmospheric pressure. The LIGO's have the record for the 'largest hole in the Earth's atmosphere', and take ages to pump down.

29/12/2006

Livingston SM @ ~24%. The wind is up, useism up, storm(s) coming... :-(
Check out this exhibit in the visitors' centre :

A big suspended slinky!! :-)
See more here.

Hanford SM H1 @ ~92%, H2 @ ~ 90%. Some adjustment to the TCS lasers on both H1 & H2, a truck, useism up thus range down, but a good 15+ hour run.

30/12/2006

Livingston SM @ ~55%. Wind, rain, thunder, nearby lightning strikes, earthquakes.

Hanford SM H1 = 100%, H2 = 100%. WOW!! North Pacific storms off the coasts of Alaska and British Columbia, so ranges down to about 12 and 6 Mpc respectively. 15 and 7.5 respectively are the 'ideal' inspiral ranges. Kuril Islands quakes, these are south of the tip of Kamchatka, one of many on the Pacific's 'Rim of Fire'. Quick re-lock though.

Cheers, Mike.

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

Mike Hewson
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Well dear readers, not only

Well dear readers, not only has server failure(s) deferred any entries here but pleasingly there has not been much to report either!

It's been a stunning run early in this New Year with lots of lovely lock ( L-cubed ) ie. high duty cycles at the IFO's. Livingstone had a record breaking 40+ hours continuous lock, also Hanford at record 65+ hours on H1 - though H2 also had long periods too. This means lots of triple co-incidence ( 3C ) periods, and excellent inspiral ranges, which is the golden target......

...... up until 05/01/07, when at Hanford high winds ( up to 60 mph ) prevented much success, which went quiet for 06/01, but returned for an encore on the 7th. It was remarked:

Quote:
I am hoping not to see tumbleweeds blocking my car door today.


There has been some examination/thought about the thermal control system and input lasers at Hanford.

Cheers, Mike.

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

Chipper Q
Chipper Q
Joined: 20 Feb 05
Posts: 1,540
Credit: 708,571
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Is this new, or is my memory

Is this new, or is my memory getting that bad? It's 1 of 4 plots from Livingston's Figure of Merit 6. The other 3 are for mid-, higher-, and highest-frequency RMS strains. This one is for the low-frequencies:

Does 'Signal' mean we're seeing what's there after all the noise sources have been removed? Is this plot similar (as in over a longer interval of time) to the one (in this previous post of Mike's) regarding the glitch in AS_Q? Is this light being detected from the dark port?

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