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  • Special Report on Virgo
    bench unit Owing to lingering problems with that unit s optics the central interferometer is currently being fed by an auxiliary laser and injection telescope which had been built to test the detection bench mode cleaner The entire inner interferometer is mounted on the passive superattenuator chains the bigger brothers of the LIGO designed TAMA SAS chains recently reported on in this newsletter which effectively isolates the mirrors from all external disturbances Above At left assemlby of the injection bench Next close up view of the Virgo injection bench The structure seen at center is a ULE reference cavity All around the bench are the control coils of the actuators Third the top of a superattenuator chain with filter and inertial damping instrumentation Last an eagle s eye view of a superattenuator tower The most satisfying thing to witness is the almost preposterous ease with which the interferometer catches lock After the system is artificially excited you just wait a little watching the amplitude oscillations of the light in the dark port on a monitor After a few minutes only one to a few fringes per second pass by At this point you simply switch on the mirror and marionetta feedback and the interferometer snaps into lock The entire operation requires the pressure of a button I am told that if you do not artificially excite the towers or if you wait longer than a few minutes the inertial damping of the superattenuator rigid body oscillations is so effective that the interferometer stays on a fringe for substantial times completely uncontrolled People keep milling around doing their business while the interferometer control people do their engineering runs Nobody minds the eighteen wheelers passing by the building outside hauling pipe sections to the arms nor the earthmovers digging the foundation of the second office building in the adjoining lot But climbing on the tower metal structures does disturb the lock and causes loud complaints from the operators Using the overhead crane for more than a couple of minutes progressively feeds vibrations into the superattenuators exciting its slow oscillations to growing amplitudes eventually larger than the marionetta dynamic range Once the mirror controls are overwhelmed the lock is lost At Work in the Control Room Above First at left the control room during an inner interferometer development run The middle TV screen shows the beam spot while the centermost monitor shows the control actuator currents and the mirror residual motion Pictured here are l r M A Bizouard F Bellachia D Garrot M Barsuglia L Holloway and R Passaquieti Note the well deserved champagne bottle on the shelf Next in the center photo we see Matteo Barsuglia tuning the mode cleaner and injection bench Then at right a view of half of the Virgo control electronics Below Left The 6 meter tall vacuum chambers housing the beam splitter and west inner mirror superattenuator towers Next pictured in the control room are from foreground to background G Losurdo L Holloway M A Bizouard

    Original URL path: http://www.ligo.caltech.edu/LIGO_web/0106news/0106spr.html (2015-06-02)
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  • LIGO Livingston Observatory News
    100 mW instead of a few wattts so that the scattered light power measured at the OSEM photodiode was much smaller than the light from the LED within the OSEM The downside of this is that the signal output of the interferometer was reduced The sensitivity of the interferometer which should be dominated at frequencies above a few hundred Hz by the amount of light circulating in the interferometer was instead dominated by the electronic noise in the measurement apparatus Now that the OSEM s have been replaced with a revised version which solves the problem this important signal noise ratio will be substantially improved The new OSEM s solved the problem by utilizing shorter wavelength light in the shadow sensor so that it will be less sensitive to the scattered light from the main beam Further enhancements will be implemented later this year when electronics will be added to synchronously modulate the light source and the photodiode to reject the main laser beam scattered light Summer Programs at LLO Contributed by Mark Coles This summer the LIGO Livingston Observatory was host to seven participants of Caltech s Summer Undergraduate Research Fellowship program or SURF More information on SURF can be found at http www ligo caltech edu LIGO web students undergrads html This year the student participants came from Caltech Sean Hardesky Xavier University of New Orleans Misty Watson the University of Texas at Austin Lonique Coots Southern University of Baton Rouge Keisha Williams Florida Tech Hareem Tariq New College of Florida Homer Wolfe and the University of Michigan David Leibrandt We also had one undergraduate student from MIT Antimony Gearhardt two undergraduates from LaTech University Clay Westbrook and Nathan Scott one undergraduate student from LSU Matt Weitz one student from SLU Jeremy Day and four students from the

    Original URL path: http://www.ligo.caltech.edu/LIGO_web/0107news/0107liv.html (2015-06-02)
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  • LIGO MIT News
    was designed at Glasgow where Norna Robertson and Calum Torrie played the main design roles with the rest of the Glasgow group and Caltech visitor Phil Willems helping Once the parts kit was complete it was shipped to MIT for the first assembly and characterization Norna and Calum came along for a month visit to sometimes lovely Cambridge Massachusetts Many people from the MIT group chipped in to help assemble the system as shown in Photos 1 and 2 above Myron MacInnis was central to getting the pieces to fit together and making missing parts Other visitors and helpers during this phase included Janeen Romie and Virginio Sannibale from Caltech Above Working on the Advanced LIGO suspension The design is a quadruple suspension as seen in Figure 1 at left below Four masses are suspended in series the upper two being more or less rectangular pieces of metal and in the final design the penultimate mass is of a heavy glass and the final mass of sapphire There are two chains of pendulums for some of the suspensions allowing forces to be exerted on the test and other masses from a similarly quiet reference platform Vertical compliance is supplied by trapezoidal leaf springs as developed for the Virgo isolation system The whole system sits in an octagonal frame as shown in Figure 2 at right below Above At left an illustration of the suspension s quadruple design at right the system s octagonal frame This all metal system is intended to check mechanical clearances allow the modal frequencies to be measured and the damping of modes observed and tuned up Then the group at MIT Rich Mittleman and Peter Fritschel are particularly active on this phase along with visitors from Caltech and Glasgow will look at detailed questions of actuator

    Original URL path: http://www.ligo.caltech.edu/LIGO_web/0107news/0107mit.html (2015-06-02)
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  • LIGO Caltech News
    by shot noise and in the mid range tens of Hertz to a few hundred Hertz by thermal noise in the mirrors themselves This thermal noise is due to the motions of the atoms inside the mirrors caused by heat and limits our sensitivity right in the frequency range where we would like to look for gravitational waves It is clearly worthwhile for us to examine ways of reducing the thermal noise at these frequencies and one way is to use very high quality materials in our mirrors Current generation LIGO mirrors are made from high grade synthetic fused silica and when the instrument is completed they are expected to exhibit some of the lowest levels of thermal noise ever observed in an interferometer Still current astrophysical models predict that even at this sensitivity level a large class of interesting gravitational wave events will go unobserved lost in the noise of the instrument At some point we will want to upgrade our instrument and catch these events One candidate material that might have better noise performance than fused silica is sapphire There exists an established industry for growing synthetic sapphire mostly for military applications and a number of people are looking into the possibility of using high grade synthetic sapphire test masses to reduce the thermal noise in an advanced LIGO The Thermal Noise Interferometer is a small test bed instrument on Caltech s campus designed to evaluate the noise performance of sapphire in an environment similar to that of a gravitational wave observatory The instrument is currently under construction much like the main interferometers at Hanford and Livingston and on Thursday July 5 2001 we achieved first lock The Thermal Noise Interferometer was not very reliable initially The first lock lasted only 15 seconds But we have made considerable

    Original URL path: http://www.ligo.caltech.edu/LIGO_web/0107news/0107cit.html (2015-06-02)
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  • LIGO Hanford Observatory News
    infant universe emerged in the 1990 s from a satellite mission the Cosmic Background Explorer COBE These images captured the look of our 15 billion year old universe at the tender age of about 300 000 years In the first 300 000 years space expanded rapidly and the material of our existence gradually froze out as the expansion cooled the universe First came exotic particles Later more familiar forms of matter like protons and electrons formed But these particles were dispersed throughout the universe in a plasma with no atoms in sight A plasma is a gas of charged particles and these free charges strongly absorb and emit light basically confining the light within the plasma Visualize what it is like trying to drive at night through a deep fog and you pretty much have the picture Light from distant objects is scrambled while light emitted from your headlights comes back at you as much as it penetrates forward You may not even be able to see the road At about 300 000 years the expansion had cooled the universe enough that protons and electrons could freeze into stable hydrogen atoms Hydrogen atoms only absorb light in a very narrow band of wavelength in the ultraviolet so the universe went from a fogged state to clarity as the atoms formed Photons of light carrying the properties of the early universe could now transverse the space and time of the universe And about 15 billion years later COBE scientists captured some of these photons now chilled down to radio wavelengths and assembled them into a fuzzy portrait of the early universe These fuzzy COBE pictures show the sky as extremely uniform in temperature hovering at about 3 degrees Kelvin very close to absolute zero But there were small blotchy patches where the temperature was higher or lower by about 10 millionths of a degree The accompanying density fluctuations would be the seeds of structure stars galaxies clusters of galaxies etc in our modern universe Scientists scrambled to prepare new experiments to probe the cosmic background with higher resolution instruments And the clearer pictures started to roll out in the late 1990 s These better defined images made possible a measurement of the geometry of the universe A flat universe would follow the same rules of geometry we learn in high school math The interior angles of a triangle would add up to 180 degrees and parallel lines would keep a constant separation In a universe with positive geometry sheets of space would follow rules similar to rules of navigation on the curved surface of the earth You can find a triangle on a globe whose base is on the equator with right angles in South America Africa and at the North Pole a total of 270 degrees and parallel lines running North South from the equator will intersect at the North and South Poles Sheets of space in a universe with negative curvature would have properties similar to the surface of

    Original URL path: http://www.ligo.caltech.edu/LIGO_web/0109news/0109han.html (2015-06-02)
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  • LIGO Livingston Observatory News
    suspended test masses are evacuated we carefully monitor the residual gas within the vacuum space to be connected to the arms The gate valves are only opened when the rate of water influx into the beam tube arms from the test mass chambers at the end and corner stations is acceptably small This takes about one month of continuous pumping after initial button up Below A view through the end mirror into the transmitted light telescope the large lens seen behind and below center This is a view down the telescope tube shown in the lower right corner of the photo above The front faces of the actuators are visible through the suspended mirror Note the parallel white strips within the central aperture of each actuator These are the light sources and photodiodes which sense the end position of small cylindrical magnets glued around the circumference of each mirror and at one place along the cylindrical side surface of the mirror The strips closest to the mirror edge are the light sources while those closest to the sensor are the photodiodes The circular objects between the white strips are positioning magnets The three inch long hex bolts located around the circumference are earthquake stops Soft Teflon tips on the hex bolt ends limit the mirror motion should excessive ground motion occur So after a lot of waiting to find out if the test masses at the vertex and the end stations had been properly oriented with respect to each other we finally got our first opportunity near the end of August to open the gate valves and take a peek We were very pleased to find that the light beams were right on the money It required only a few minutes to orient the laser spots so that they were well centered on each of the end test masses and then to tweak the end test mass alignments slightly so that their reflections were well centered on the input test masses By month s end we had succeeded in once again locking the interferometer arms individually as Fabry Perot cavities at input laser powers of more than one watt IRET Program at LLO Contributed by Mark Coles This summer for the first time the LIGO Livingston Observatory LLO was host to two high school teachers participating in a pilot program aimed at providing research experiences for teachers The program dubbed IRET is modeled on a National Science Foundation NSF sponsored program that seeks to strengthen the relationship between NSF funded research and teachers involved in K 12 education Our enthusiastic trailblazers during this summer were Mr John Thacker a physics teacher for the last two years at Springfield High School in Livingston Parish and next year at Covington High School in St Tammany Parish and Mr Wilson Doucette a long time teacher at Istrouma High School in East Baton Rouge Parish John Thacker shown in the photo at left below holds a Master s Degree in Physics from the Naval

    Original URL path: http://www.ligo.caltech.edu/LIGO_web/0109news/0109liv.html (2015-06-02)
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  • LIGO MIT News
    a lead responsibility for searches for a Stochastic Background Laura Cadonati will join us as a postdoc in January 2002 but will be by from time to time in the interim Laura will also work on data analysis issues Her undergraduate degree is from the University in Milan and her PhD is from Princeton where she is presently a postdoc She comes from the field of particle astrophysics and was involved in just about every aspect of Borexino a solar neutrino detector at the Gran Sasso National Laboratory in Italy from nuts and bolts to Montecarlo and data analysis to inflating and doing stress models of big nylon balloons Keisuke Goda is a graduate student at MIT and a current member of the MIT LIGO group Before coming to MIT he graduated summa cum laude with his BS from University of California Berkeley where his research work was on the theoretical part of KamLAND Kamioka Liquid Scintillator Anti Neutrino Detector and the possibility of CP violation in neutrino oscillation experiments Keisuke has interests in the detection of gravitational radiation and a specific interest in LIGO optics and lasers as well as thermal noise Joseph Betzwieser received his B A in Physics from Cornell University last year and is starting the physics PhD program here at MIT He is planning to focus in Astrophysics At Cornell he worked at the Wilson Synchrotron both doing upgrades in the form of positional beam detectors for the electron storage ring and more recently doing experiments with the processing of niobium superconducting cavities Stefan Ballmer joins the MIT LIGO group as a graduate student He received his Master of Science Degree in Theoretical Physics from the ETH Zurich in Switzerland He studied Vorticity Perturbations in a Friedmann Universe in the framework of Cosmological Perturbation Theory

    Original URL path: http://www.ligo.caltech.edu/LIGO_web/0109news/0109mit.html (2015-06-02)
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  • LIGO Hanford Observatory News
    the monthly ad hoc tours held on the second Saturday of every month at 1 30 pm These are called ad hoc because anyone who shows up gets a tour tailored to whomever shows up That s all Month to month we are never quite sure what will happen except that someone from LIGO will give a tour The tours are never the same Attendance ranges from 6 to 60 people Anyone old enough to talk can ask whatever they want so we have wide ranging discussions of science There is often quite a mix of backgrounds People come from Kennewick Washington from Portland Oregon from Vancouver British Columbia even from Logan Utah A typical day s tourists might include preschoolers someone from a National Lab and a retired teacher Occasionally we get a few surprises We have had people come out who worked at B Reactor during the Manhattan Project Their stories provide great entertainment for the tour givers The Science teachers shown in the photo above brought John Dobson the pioneer of large aperture telescopes for everyday folks along on their tour Guests like that will keep a tour guide on his toes You never know who you will meet at LIGO What do we talk about Well first we ask the audience where they have come from and what they would like to know by the time they leave Then we get down to it What does a gravitational wave sound like We have simulations sound and waveforms of inspiralling black holes and neutron stars to show How do we know gravity waves exist We discuss the latest data from pulsar measurements kindly updated by the astronomers in the midst of the action What is an interferometer We have a kid proof hands on model that can

    Original URL path: http://www.ligo.caltech.edu/LIGO_web/0110news/0110han.html (2015-06-02)
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