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  • LIGO Louisiana Site Dedication
    construction of the Laser Interferometer Gravitational Wave Observatory LIGO will take place on July 6 at 10 00 AM at Doyle High School Livingston Louisiana The sponsors of the ceremony are California Institute of Technology Massachusetts Institute of Technology National

    Original URL path: http://www.ligo.caltech.edu/LIGO_web/9495news/dedication.html (2015-06-02)
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  • LIGO Contracts for Vacuum Equipment
    1 2 meters The total pumped volume is approximately 20 000 cubic meters The operating pressures will range from 1 x 10 6 torr to 1 x 10 9 torr The completed vacuum system will consist of the beam tubes and the vacuum equipment itself Upon completion expected in 1999 the LIGO vacuum system will be one of the largest in the world PSI submitted the winning design and lowest

    Original URL path: http://www.ligo.caltech.edu/LIGO_web/9495news/psi_contract.html (2015-06-02)
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  • LIGO Plans to Change to Nd:YAG Lasers
    groups who have generally adopted solid state near infrared lasers for their detectors The process of evaluating a change was started in May 1995 with wide ranging discussion of the issues and questions which must be addressed before making such a major change to the baseline design To provide the basic data for assessing the benefits of changing lasers LIGO scientists Alex Abramovici and David Shoemaker prepared a report comparing the technical merits and uncertainties of Argon ion lasers operating at 515 nm and Nd YAG lasers operating at 1 06 um This report collected published and unpublished data on the performance of the two laser systems and summarized the experience and plans of the other laser interferometer gravitational wave groups This report was distributed in August to the LIGO science team and discussed at meeting with the project management The majority opinion was that Nd YAG lasers were nearing the performance and maturity of Argon ion lasers and that commercial lasers meeting the LIGO requirements would likely be available on a timescale compatible with the installation of the initial interferometers Furthermore many laser experts predict further advances in Nd YAG technology leading to enhancements to the initial interferometers that

    Original URL path: http://www.ligo.caltech.edu/LIGO_web/9495news/lasers.html (2015-06-02)
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  • LIGO starts beam tube fabrication
    of two detectors currently under construction in Livingston Louisiana and Hanford Washington at a total cost of 292 million Construction will be completed in 1999 LIGO was designed by a team of scientists and engineers from the California Institute of Technology and the Massachusetts Institute of Technology Each U S facility will be L shaped with two 4 kilometer long arms with buildings at the corner and at the end of each arm A vacuum system with chambers in the buildings and tubes along each arm will contain the gravitational wave detectors When completed LIGO will allow scientists to conduct a long term research program to study the nature of gravitational waves and to understand the astrophysical sources of gravitational waves including black holes neutron stars supernovae and the Big Bang The beam tube modules will be installed at the LIGO sites where each arm of the observatory will consist of four kilometers of beam tube length each with a diameter of 1 2 meters The completed vacuum system will consist of the beam tube modules and the vacuum equipment which was placed under contract this past September The ultra high vacuum environment within the beam tubes is needed to

    Original URL path: http://www.ligo.caltech.edu/LIGO_web/9495news/beamtube.html (2015-06-02)
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  • LIGO News and Highlights
    Please update your bookmark If for some reason this page does NOT redirect you in about 5 seconds then please follow this link LIGO News and Highlights If you need

    Original URL path: http://www.ligo.caltech.edu/LIGO_web/news/news.html (2015-06-02)
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  • LIGO Vocabulary
    against excessive swinging of the mirror in circumstances such as a nearby earthquake Electronic Log LIGO s official lab books If it s not in the E log it didn t happen Both the Hanford and Livingston E logs are viewable on the Web Surf to the LIGO Laboratory and click on the Electronic Log links under Observatories The Detector logs hold the most information Engineering run These occur with the interferometers in full science mode but are shake down runs that follow rounds of commissioning and that precede science runs Frequency spectrum A plot of an amplitude or power as a function of frequency Such spectra might display amplitude in vertical units of strain or displacement Gate valves Large valves that partition LIGO s vacuum enclosure into discreet sections permitting a vent in one portion of the system while the remainder is held at low pressure Gravitational wave signal A gravitational wave will change the spacetime composition of one interferometer arm relative to the other This will result in a change in the instrument s interference pattern which will register as a voltage fluctuation at the photodetector Interferometer labels H1 is the Hanford 4 km detector H2 is the Hanford 2 km detector and L1 is the Livingston 4 km detector Light year One of the common units of astronomical distance representing the distance that light will travel in a year roughly 9 5 trillion kilometers Parsecs are often used instead of light years 1 parsec is the equivalent of 3 26 light years Mirror labels LIGO refers to its mirrors as test masses The label ITMX stands for Inner Test Mass on the X Arm This is the inner mirror of the 2 5 mile X arm Fabry Perot cavity This mirror rests just outside the beam splitter 2 5 miles away from its companion ETMX the end test mass on the X arm Lock The condition in which light continues to resonate at high power in the cavities of the interferometer Disruptions to the optics can misdirect the beam destroying the resonant condition and rendering the instrument insensitive loss of lock Lock is threatened by mirror movements of as small as one atomic diameter against a cavity length of up to 4 km Noise floor LIGO defines noise as any factor other than a gravitational wave that sends a fluctuating signal to the interferometer s photodetector The noise floor of the instrument is the point at which a gravitational wave is undetectable because it doesn t rise above the other fluctuating contributions to the photodetector signal This level varies with frequency so the noise floor is usually given as a frequency spectrum Optical lever Part of the suspension subsystem Optical levers provide angular control of the mirrors An oplev consists of a small laser that undergoes an angled reflection off a LIGO mirror through a window in a vacuum chamber The reflected light then strikes a target photodiode that acts as the sensor in a feedback loop

    Original URL path: http://www.ligo.caltech.edu/~ll_news/0607a_news/LIGO_Vocabulary.htm (2015-06-02)
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  • LIGO Hanford Observatory News
    space were relative Scientists in a spaceship laboratory hurtling past Earth at near the speed of light and their colleagues in an earthbound laboratory would both agree that their experiments obeyed the laws of physics But they would tell vastly different stories of what they saw outside their windows peering into the other group s lab Clocks would slow down and rulers would shrink Everything was relative everything except the speed of light Common sense argued that this was total rubbish but experiments showed that in fact it was true Yet inside this revelation there lurked a dark secret It only worked if one ignored gravity Two and a half centuries earlier Isaac Newton had described how gravity behaved But no one had ever described how it actually worked Einstein felt compelled to do so Einstein discovered a vital clue as to how gravity could work Imagining a laboratory moving through space he realized that all the effects of gravity were equivalent to the effects of acceleration The mathematician Herman Minkowski a professor at the Swiss institute where Einstein had studied provided another crucial piece of the puzzle Einstein developed Special Relativity by following physics But Minkowski discovered a mathematical pattern in Einstein s work The relationships between space and time in Einstein s theory traced the same patterns as the mathematical description of how we see an object from different perspectives In this case the physics was telling us of a pattern of rotations in four dimensions the three familiar dimensions of space length width and heigh and an oddly defined dimension of time Einstein probed for the consequences of this newfound symmetry If Special Relativity could be explained by geometry could geometry also provide a picture uniting gravity and acceleration With singular focus Einstein eventually discovered the key to the puzzle It was the shape of space and time In General Relativity the flow of matter and energy through space and time follows from the shape of space and time This shape results from the warping of space and time caused by the matter and energy in space and time Matter energy space time and gravity are intricately braided together always and everywhere The mere presence of matter in space should cause light to move through space like it was moving through a cosmic window glass distorted by bubbles and defects These space warps should bend the light from distant stars In 1919 the bending of starlight was first observed in photographs of stars near the limb of the Sun taken during a total eclipse The news made banner headlines in newspapers across the globe Reality it seemed was not as it had appeared to be General Relativity provided the framework for the new science of cosmology the history of our universe Einstein himself wrote one of the first papers in this field and other thinkers soon followed But the emergence of quantum mechanics in the 1920s would eventually eclipse relativity and cosmology as the hot fields of

    Original URL path: http://www.ligo.caltech.edu/LIGO_web/0503news/0503han1.htm (2015-06-02)
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  • LIGO Caltech News
    of a signal mirror now stands in the way of the signal sidebands recycling them back into the interferometer at some frequencies and resonantly extracting them at others in order to shape the frequency response of the detector for optimal sensitivity to gravitational waves The signal mirror does not see the carrier laser light until a gravitational wave induces the signal sidebands but when that happens it must be precisely pre positioned microscopically in order to manipulate the signal as intended This means that the sensing and control of the signal mirror must be accomplished without the help of carrier laser light in contrast to the way all mirror positions are sensed in Initial LIGO As a result the power and signal recycled Fabry Perot Michelson optical configuration of Advanced LIGO requires a new and much more complex scheme for sensing and controlling the microscopic positions of all the mirrors The LIGO Scientific Collaboration LSC Advanced Interferometer Configurations working group established the need for this more complex configuration five years ago it is one consequence of the need for higher laser light power But it was clear that new approaches to the sensing of the mirrors were required and that thorough tests of these schemes must be performed at a full up LIGO like interferometer the 40 Meter lab was the obvious place to do this Over the last five years the 40 Meter lab has been completely rebuilt keeping only the vacuum enclosure and seismic isolation stacks in order to test lock acquisition and control schemes for the Advanced LIGO interferometers For most of the last five years the incredibly talented team of physicists and electrical mechanical and optical engineers that helped build Initial LIGO have labored to assemble the infrastructure for yet another LIGO interferometer with a pre stabilized laser ten precision optics suspended as pendula optical beamlines laid out precisely in a claustrophobic laboratory and vacuum enclosure and a full complement of servos slow controls and data acquisition systems A steady stream of Caltech undergrads NSF Research Experiences for Undergraduate summer students and scientific visitors from LSC collaborating institutions contributed to the emerging interferometer Then in the last six months efforts to lock and control the full interferometer were in full swing greatly aided by visitors from Japan Germany Scotland and Australia By Thanksgiving eve 2004 all that hard work finally paid off lock was acquired in all five length degrees of freedom of the dual recycled Fabry Perot Michelson interferometer which was kept under control for on the order of one minute despite rush hour traffic on Del Mar Avenue a block away The configuration was not the correct one for resonant signal extraction the arm cavities were locked somewhat away from resonance for technical reasons and moving to the correct configuration is the next step Meanwhile small parties celebrating crucial steps towards this milestone culminated in a particularly festive celebration that Friday Of course this means that the real work at the 40 Meter lab

    Original URL path: http://www.ligo.caltech.edu/LIGO_web/0503news/0503cit.htm (2015-06-02)
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