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  • LIGO Hanford Observatory News
    extensive experience with major science facilities was on site to review our operations and the proposed funding of operations for the next five years Then the ground shook startling some but escaping the notice of others who had been focused on their tasks But very quickly it dawned on people that the interferometer had been shaken up We knew this was not good One of the first questions often asked of serious accident victims is Can you wiggle your toes Stan Whitcomb the leader of the commissioning effort at Hanford went to the control room shortly after the shaker passed and tried wiggling mirrors one by one It quickly became obvious that some of the mirrors had sustained damage and repairs would be needed Immediately we began to mobilize efforts to enter the vacuum chambers and start inspections of the mirrors Since much of the development of LIGO s suspended mirrors was done at Caltech in the midst of California s earthquake country we were not unfamiliar to the damage earthquakes can do to suspended mirrors The LIGO prototype 40 meter interferometer at Caltech was typically jolted about once a year by shakers during the 90 s and we learned to incorporate earthquake safety into our designs In the photo at left above those shiny screws aimed at the periphery of the purplish optic are called Earthquake Stops and their job is to catch the mirror as gently as possible when a jolt comes Earthquake stops are also incorporated into the optical tables and vibration isolation systems to limit their motions We have enough confidence in these stops to know that the mirror substrates surfaces and coatings would do just fine even in a fairly large local earthquake Still the Achilles heel of the design is the set of attachments glued onto the mirrors By design the mirrors are supposed to float as freely in space as possible so that they are free to follow the currents of space induced by gravitational waves That means the attachments between the mirror and the rest of the world have been made as tenuous as possible There are two sets of attachments a suspension fiber and guide rod assembly and the magnet standoff assembly These are shown in the photo on the right The 25 pound mirror is balanced on a single loop of thin 0 01 inch steel wire to an accuracy of about 1 100th of a degree This is done with the guide rod that has a small groove to locate the wire Balancing requires getting the guide rod in the right place and the wire properly seated in the groove to an accuracy thousands of times smaller than the wire diameter Not surprisingly a good shaking changes the balance and this needs to be trimmed up by hand This alignment trimming is not a difficult procedure but it does require a person to enter the vacuum chamber to tweak it up Much more worrisome is the magnet standoff assembly

    Original URL path: http://www.ligo.caltech.edu/LIGO_web/0103news/0103han.html (2015-06-02)
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  • LIGO Livingston Observatory News
    the groups have targeted the beginning of the summer for initial software tests Document Mole Surfaces at LSC Contributed by Linda Turner This March I made my first pilgrimage to the LIGO Scientific Collaboration and experienced first hand the bubbling energy and enthusiasm generated by the intellectual stimulation noteworthy accomplishments and collective problem solving of over 100 scientists and engineers Whether in complete assembly or smaller working groups one sensed a vibrancy in the air an expectancy and promise for the discoveries anticipated by LIGO And what was I doing there My task was to bring a satellite Document Control Center DCC to the conference and assist in the submission and processing of all the speakers presentations so that these could be expeditiously posted on the web And as a fringe benefit I also looked forward to meeting many of the people whose names and voices I was familiar with from dealings in email or over the phone but whom I had never before had the pleasure of meeting face to face Ordinarily creating a mini DCC at the Livingston site would be a fairly straightforward affair But this meeting convened at the charming tranquil and decidedly un high tech White Oak Plantation at left above creating a few challenges for us technically My office at right was reminiscent of one of those hasty MASH field encampments I sat in the middle of an outside patio with a canopy overhead surrounded by a color printer my computer hanging electrical wires cables and a single 26k modem line a pretty amazing setup Still with only these bare bone rudiments of technology available and the single internet phone line it meant a hundred other bodies were left incommunicado One person asked in disbelief how they could all be reduced to use of a solitary payphone Unheard of Others exhibited similar withdrawal symptoms over their detachment from email and global communication But gorgeous garden surroundings delightful rooms and gracious Southern hospitality offset whatever was lacking in modern electronic conveniences By the end of the conference I had collected and processed over half of the presentations all ready to be turned over for web posting But more importantly I came back having made new friends time spent with old friends and the DCC perhaps a black hole for all things paper became more personal to LIGO s collaborators Personally I was fascinated by the variety of expertise scientific disciplines education and cultures comprising the LIGO collaboration Upon returning home I asked some of my familiar colleagues as well as those I had met for the first time to share some of their perspectives on the week long event Here s what a few of them had to say What did you anticipate most from your attendance at the LSC What benefits did you derive The LSC meeting is a good way to keep in touch with the international community and stay informed of broader aspects of the LIGO project than the narrow aspect I

    Original URL path: http://www.ligo.caltech.edu/LIGO_web/0103news/0103liv.html (2015-06-02)
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  • LIGO Livingston Observatory News
    data Special thanks too to Mark Coles pictured at left below head of the Livingston Observatory who found time despite his many duties to treat us to his excellent lunches below right a bounty we all thoroughly enjoyed Of course the run was just the beginning of the fun Now it s time to look at the data You can follow our progress on the E3 homepage where you can find the data from and results of the investigations As a little sneak preview the two graphs at left and right below show some preliminary results from the run Above At left tidal effects on the common mode control signal The red curve shows the raw control signal while the blue segments show the reconstructed tidal variation using multiple lock stretches Each red segment corresponds to a long locked period while the end of each segment signals a lock loss often due to tidal shifts Then at right timing delay between the second tic of the GPS clock and the time stamp of the recorded data We observed small timing jumps associated with DAQ reboots The graph also shows that the timing difference was less than 100µs between the two observatories during the run The relative delay can be easily corrected by using this timing data A Journey Through Light Contributed by Bonnie Wascom Three participants from LIGO Bonnie Wascom and Rusyl Wooley from the LIGO Livingston Observatory and Dr Rainer Weiss from MIT LIGO joined a host of other guest speakers in leading the children of St Bernard School in A Journey Through Light which was the theme of this year s Annual Science Symposium The children began their journey with educational field trips to various locations the week before the symposium Each field trip centered around a location in which light plays a key role in the operation of that particular facility The 5th and 6th graders visited the LIGO Livingston Observatory and their tour concentrated on the use of laser light in the study of gravitational waves To commemorate their visit the children painted light houses like the one erected in front of their school as well as light bulbs on our tunnel of fame Pictured Above 1 Fifth Grade snapshots 2 Light house painting 3 Actual light house in front of school 4 Light bulbs painted on the tunnel of fame The symposium dawned with a boat ride for honorees down the bayou that runs along side the school followed by a blessing of the event for the parochial school Honorees included the sheriff the mothers who coordinated the symposium and Dr Rainer Weiss the keynote speaker Halos glowed with mischief and faces shinned with curiosity as the children entered the gym to hear Dr Weiss speak After being shown that it was not possible to squeeze light by looking through squeezed fingers and then observing that the largest amount of light from a bulb is not visible Dr Weiss produced a strange apparatus which made

    Original URL path: http://www.ligo.caltech.edu/LIGO_web/0103news/0103livtwo.html (2015-06-02)
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  • LIGO Caltech News
    the TAMA SAS already in production He quickly produced a fresh proposal to redesign new suspensions and have them built together with the SAS with only a small cost in schedule delay Akiteru s plan was approved by the TAMA collaboration and by September 2000 the new mechanical suspension redesign was completed and ready for production At right A schematic overview of the TAMA SAS towers The SAS towers are based on the LIGO developed Monolithic Geometric Anti Spring Filters MGASF each capable of 60 dB attenuation The TAMA SAS towers also incorporated the Virgo inertial damping of the attenuation chain resonant modes as well as the advanced accelerometers designed as part of the PhD thesis of Alessandro Bertolini and provided in part by the Univesita di Pisa The new SAS SUS system is expected to deliver a few tens of nanometers of r m s mirror motion below the observation frequency range In addition it provides passively attenuated residual seismic noise crossing the thermal noise level at or below 10 Hz The control electronics are adapted from the Virgo DSP system The new suspensions fully compatible with the SAS isolation towers were based on a double pendulum with recoil mass mirror controls first developed by Virgo along with the multiple pendulum passive mode damping developed and tested by TAMA scientists in addition to the Caltech developed MGAS springs for low frequency vertical resonances Shown below 1 The TAMA SAS assembly lab 2 A top view of one of the towers 3 An inner view The suspension production contract was awarded in October to Italy s Galli and Morelli who were already finishing the SAS towers In December 2000 Riccardo Alessandro and Akiteru took delivery in Lucca Italy from Galli and Morelli of the completed SAS SUS mechanics The SAS

    Original URL path: http://www.ligo.caltech.edu/LIGO_web/0103news/0103cit.html (2015-06-02)
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  • LIGO MIT News
    with dual hoist bridge cranes and cleanroom air conditioning was carved out of MIT s Building NW 17 to house the system back in 1997 Above The LASTI vacuum envelope shortly after installation in the MIT high bay lab One of the arms with its two Horizontal Access Module type chambers is shown the second arm extends 16 meters left of the vertical Beam Splitter type BSC chamber shown in the background For scale this chamber stands about 18 feet high and is 9 feet across Last fall we successfully commissioned the vacuum envelope certifying the machine was leak free and clean to ultrahigh vacuum standards This winter we installed softwall cleanrooms over two of the chambers and with help from LIGO Hanford experts Hugh Radkins and Corey Gray installed the basic seismic isolation support systems which are identical to those at the observatories and will be shared by the Advanced LIGO retrofit We also installed a current LIGO model isolation stack in one of the chambers to support a test cavity which will be used to commission our laser system this summer Below Hanford s Corey Gray gloats over successful installation of the HAM seismic isolation stack in the midpoint chamber on LASTI s south arm Our next step will be to mount the seismic supports and isolation bellows in the remaining BSC type chamber at the vertex Experts from LIGO Livingston will fly up to help us with this phase of the installation later this month We re also awaiting arrival of a custom cleanroom for the BSC designed by LASTI chief engineer Ken Mason This cleanroom is designed to fit our lab which is of course much tighter than the observatory vacuum equipment areas and will have an integrated work platform on its roof rather than the

    Original URL path: http://www.ligo.caltech.edu/LIGO_web/0103news/0103mit.html (2015-06-02)
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  • LIGO Hanford Observatory News
    et al They found it could cause newborn neutron stars to emit most of their rotational energy as gravitational waves within the first year after their birth This was a far larger effect than predicted for any other mode of neutron star vibration making it possible that gravitational waves from the r modes could be detected by the proposed enhanced version of LIGO One crucial factor that will determine whether gravitational waves from the r mode instability can be detected by LIGO is the critical angular velocity the spin rate for the onset of the instability Copious amounts of gravitational radiation are emitted from the r modes only while the star spins faster than this critical rate However Bildsten and Ushomirsky showed that viscous dissipation that occurs at the crust core interface of a neutron star with a solid crust and fluid core will completely suppress the instability except for very rapid spin rates Their results were later extended by Andersson et al Rieutord Levin and Ushomirsky Lindblom Owen and Ushomirsky To understand why this is so consider the situation illustrated in Figure 2 below Here the red arrows represent the flow of an oscillating unbound fluid at one moment in time In this example this flow is spatially uniform However if the fluid is bounded by a solid wall then an additional flow must develop represented by the blue arrows that cancels the original flow at the boundary A viscous fluid cannot slip at a perfectly rigid solid boundary The additional flow is large only near the boundary and falls off exponentially in the case the fluid is oscillating as one moves away from the boundary Thus elements of the fluid experience a large shear near the boundary forming what is called a viscous boundary layer VBL The large shear in the VBL leads to a large amount of viscous dissipation which damps the oscillation of the fluid For example consider the fluid element shown The difference in the gradient of the flow on either side of the fluid element in the x direction produces a net shear force on the fluid in the y direction This force damps the oscillation of the fluid and the energy of the oscillation is converted to heat by the rubbing that occurs between the sheared layers of the fluid Figure 2 A viscous fluid cannot slip past a perfectly rigid boundary This causes a large shear flow to develop blue arrows in an oscillating fluid near a boundary The effect of viscous dissipation in a VBL on the r modes seemed bad news for the detection of the r modes by LIGO since a newborn neutron star with a hot fluid crust would only spin briefly above the critical value needed to make the mode unstable before the star cooled and a solid crust formed This happens within minutes after its birth To make matters seemingly worse it has recently been shown that a neutron star s magnetic field enhances the viscous

    Original URL path: http://www.ligo.caltech.edu/LIGO_web/0104news/0104han.html (2015-06-02)
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  • LIGO Livingston Observatory News
    slightly cocked suspended optic It then hits the Beamsplitter shown at right which lets half of the light continue west towards the X Arm and sends the other half south towards the Y Arm Each of these arms consists of a slightly three percent transmitting mirror in the corner station and a highly reflecting mirror four kilometer or two and a half miles away in the end stations Shown at right Close up of the Beamsplitter If all goes well the light bounces up and down the arm a couple hundred times constructively interfering with the fresh laser light still coming out of the laser This keeps building up and up until like a rain gutter in a storm it levels off and spills out as much through the corner station mirror as it gets coming in from that direction For such an unlikely set of events to actually occur the distance between these 11 kg cylinders of glass which are suspended by a single loop of steel guitar string high E has to be held constant to within less than a nanometer close to one hundred millionth of an inch Plus the beams spilling out of the X and Y arms must interfere in such a way as to constructively add up in the direction pointing back at the laser and just exactly cancel out at the appropriately named dark port which is on the north side of the Beamsplitter Since its first lock the interferometer has gone from locking for tens of seconds to tens of minutes We are currently attacking it on several fronts to extend this duration into the few hours regime Unfortunately due mainly to the violent ground quaking induced by the construction activity for the new building we are forced to lie in wait

    Original URL path: http://www.ligo.caltech.edu/LIGO_web/0104news/0104liv.html (2015-06-02)
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  • LIGO Caltech News
    Yes but whoever said this prize would be won easily And separate formats No we had the foresight to adopt a common data format years ago That last point especially shows sound judgement It shows we were prescient enough not to make this correlation harder than it needs be So we have realized for some years that this opportunity would arrive It was fine to work separately while we were each constructing But the data is not too far over the horizon And a few years from now all the interferometers will be operating And the biggest of them LIGO and Virgo will arrive separately at roughly comparable sensitivity And the next step will be A couple of years ago in this newsletter we described a meeting of the Gravitational Wave International Committee GWIC in which project leaders from all the teams agreed to form a working group to study the technical issues involved in combined data analysis Virgo chief Giazotto has since organized two working group meetings and progress has been made The teams have also engaged more broadly in research and development of technical improvements to the interferometers anticipating the time when more sensitive instruments can be fielded There has been considerable inter project collaboration in these endeavors GEO and LIGO have collaborated in detector R D and in proposing the Advanced LIGO detector These two teams have also drafted an agreement and formed joint teams in which GEO and LIGO members work together on data analysis for LIGO engineering runs later this year We hope the GEO instrument will also run in coincidence with our upcoming fourth engineering run this autumn Additionally Virgo and LIGO over the last several months have discussed moving toward a closer collaboration in detector R D and in data sharing and joint analysis Meetings have been held in Lyon France and here in Pasadena to discuss these topics A particular R D focus is the development of fine mirror coating technology in Lyon by the SMA IPNL Laboratory coating the Virgo mirrors The development is needed for Advanced LIGO and would be useful in a next generation European detector as well On Easter Sunday I found myself at the Los Angeles airport bound for Pisa and the nearby suburb of Cascina where the Virgo instrument is rousing to life David Shoemaker of the MIT LIGO group and a leader of our R D program joined me on this trip to conclude a coating development agreement Armed with a technical plan and the draft agreement from an earlier Caltech meeting with Jean Marie Mackowski of the Lyon laboratory David and I were traveling to work out any fine details and to proceed to draft the first text of an agreement on joint Virgo LIGO data sharing and combined data analysis Clearly the time was right for this arrangement A good omen peered out at me from a magazine on the news rack in Rome s Leonardo da Vinci Airport A great scientist that

    Original URL path: http://www.ligo.caltech.edu/LIGO_web/0104news/0104cit.html (2015-06-02)
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