LIGO-G W "Colliding Black Holes" Credit: National Center for Supercomputing Applications (NCSA) The Status of Gravitational-Wave Detectors, Especially LIGO Reported on behalf of LIGO colleagues by Fred Raab, LIGO Hanford Observatory

LIGO-G W Raab: Status of GW Detectors, Especially LIGO2 LIGO’s Mission is to Open a New Portal on the Universe In 1609 Galileo viewed the sky through a 20X telescope and gave birth to modern astronomy LIGO’s quest is to create a radically new way to perceive the universe, by directly listening to the vibrations of space itself LIGO consists of large, earth-based, detectors that will act like huge microphones, listening for “spacequakes” from the most violent events in the universe

LIGO-G W Raab: Status of GW Detectors, Especially LIGO3 Big Questions for 21 st Century Science Images of light from Big Bang imply 95% of the universe is composed of dark matter and dark energy. What is this stuff? The expansion of the universe is speeding up. Is it blowing apart? There are immense black holes at the centers of galaxies. How did they form? What was it like at the birth of space and time? WMAP Image of Relic Light from Big Bang Hubble Ultra-Deep Field

LIGO-G W Raab: Status of GW Detectors, Especially LIGO4 John Wheeler’s Picture of General Relativity Theory

LIGO-G W Raab: Status of GW Detectors, Especially LIGO5 General Relativity: A Picture Worth a Thousand Words

LIGO-G W Raab: Status of GW Detectors, Especially LIGO6 The New Wrinkle on Equivalence Not only the path of matter, but even the path of light is affected by gravity from massive objects Einstein Cross Photo credit: NASA and ESA A massive object shifts apparent position of a star

LIGO-G W Raab: Status of GW Detectors, Especially LIGO7 Gravitational Waves Gravitational waves are ripples in space when it is stirred up by rapid motions of large concentrations of matter or energy Rendering of space stirred by two orbiting black holes:

LIGO-G W Raab: Status of GW Detectors, Especially LIGO8 Different Frequency Bands of Detectors and Sources l EM waves are studied over ~20 orders of magnitude »(ULF radio  HE  rays) l Gravitational Wave coverage planned to cover ~8 orders of magnitude » (terrestrial + space) Audio band spaceterrestrial

LIGO-G W Raab: Status of GW Detectors, Especially LIGO9 Gravitational Collapse and Its Outcomes Present LIGO Opportunities f GW > few Hz accessible from earth f GW < several kHz interesting for compact objects

LIGO-G W Raab: Status of GW Detectors, Especially LIGO10 Catching Waves From Orbiting Black Holes and Neutron Stars Sketches courtesy of Kip Thorne

LIGO-G W Raab: Status of GW Detectors, Especially LIGO11 Gravitational Waves the evidence Neutron Binary System – Hulse & Taylor PSR Timing of pulsars   17 / sec Neutron Binary System separated by 10 6 miles m 1 = 1.4m  ; m 2 = 1.36m  ;  = Prediction from general relativity spiral in by 3 mm/orbit rate of change orbital period ~ 8 hr Emission of gravitational waves

LIGO-G W How does LIGO detect spacetime vibrations? Leonardo da Vinci’s Vitruvian man

LIGO-G W Raab: Status of GW Detectors, Especially LIGO13 Basic Signature of Gravitational Waves for All Detectors

LIGO-G W Raab: Status of GW Detectors, Especially LIGO14 Transducer Electronics wiring support LHe4 vessel Al2081 holder Main Attenuator Compression Spring Thermal Shield Sensitive bar AURIGA II Resonant Bar Detector Original Terrestrial Detectors (Continue to be Improved) Efforts to broaden frequency range and reduce noise Size limited by sound speed Courtesy M. Cerdonnio

LIGO-G W Raab: Status of GW Detectors, Especially LIGO15 New Generation of “Free- Mass” Detectors Now Online suspended mirrors mark inertial frames antisymmetric port carries GW signal Symmetric port carries common-mode info Intrinsically broad band and size-limited by speed of light.

LIGO-G W Raab: Status of GW Detectors, Especially LIGO16 The International Interferometer Network LIGO Simultaneously detect signal (within msec) detection confidence locate the sources decompose the polarization of gravitational waves GEO Virgo TAMA AIGO

LIGO-G W Raab: Status of GW Detectors, Especially LIGO17 LIGO (Washington) (4-km and 2km) LIGO (Louisiana) (4-km) The Laser Interferometer Gravitational-Wave Observatory Funded by the National Science Foundation; operated by Caltech and MIT; the research focus for more than 500 LIGO Scientific Collaboration members worldwide.

LIGO-G W Raab: Status of GW Detectors, Especially LIGO18 GEO 600 (Germany) (600-m) Virgo (Italy) 3-km Interferometers in Europe

LIGO-G W Raab: Status of GW Detectors, Especially LIGO19 TAMA 300 (Japan) (300-m) AIGO (Australia) (80-m, but 3-km site Interferometers in Asia, Australia

LIGO-G W Raab: Status of GW Detectors, Especially LIGO20 Bar Network: Int’l Gravitational Event Collaboration Network of the 5 bar detectors almost parallel ALLEGRO NFS-LSUhttp://gravity.phys.lsu.edu AURIGA INFN-LNLhttp:// NIOBE ARC-UWAhttp:// EXPLORER INFN-CERN NAUTILUS INFN-LNF

LIGO-G W Raab: Status of GW Detectors, Especially LIGO21 Spacetime is Stiff! => Wave can carry huge energy with miniscule amplitude! h ~ (G/c 4 ) (E NS /r)

LIGO-G W Raab: Status of GW Detectors, Especially LIGO22 Some of the Technical Challenges Typical Strains < at Earth ~ 1 hair’s width at 4 light years Understand displacement fluctuations of 4-km arms at the millifermi level (1/1000 th of a proton diameter) Control arm lengths to meters RMS Detect optical phase changes of ~ radians Hold mirror alignments to radians Engineer structures to mitigate recoil from atomic vibrations in suspended mirrors

LIGO-G W Raab: Status of GW Detectors, Especially LIGO23 What Limits Sensitivity of Interferometers? Seismic noise & vibration limit at low frequencies Atomic vibrations (Thermal Noise) inside components limit at mid frequencies Quantum nature of light (Shot Noise) limits at high frequencies Myriad details of the lasers, electronics, etc., can make problems above these levels

LIGO-G W Raab: Status of GW Detectors, Especially LIGO24 Commissioning Time Line Now Inauguration E1 Engineering E2E3E4E5E6E7E8E9 S1 Science S2S3 First Lock Full Lock all IFO's strain noise 200 Hz [Hz -1/2 ] Runs E

LIGO-G W Raab: Status of GW Detectors, Especially LIGO25 Despite a few difficulties, science runs started in 2002.

LIGO-G W Raab: Status of GW Detectors, Especially LIGO26 Vibration Isolation Systems »Reduce in-band seismic motion by orders of magnitude »Little or no attenuation below 10Hz »Large range actuation for initial alignment and drift compensation »Quiet actuation to correct for Earth tides and microseism at 0.15 Hz during observation HAM Chamber BSC Chamber

LIGO-G W Raab: Status of GW Detectors, Especially LIGO27 Seismic Isolation – Springs and Masses damped spring cross section

LIGO-G W Raab: Status of GW Detectors, Especially LIGO28 Seismic System Performance Horizontal Vertical HAM stack in air BSC stack in vacuum

LIGO-G W Raab: Status of GW Detectors, Especially LIGO29 Core Optics Substrates: SiO 2 »25 cm Diameter, 10 cm thick »Homogeneity < 5 x »Internal mode Q’s > 2 x 10 6 Polishing »Surface uniformity < 1 nm rms »Radii of curvature matched < 3% Coating »Scatter < 50 ppm »Absorption < 2 ppm »Uniformity <10 -3 Production involved 6 companies, NIST, and LIGO

LIGO-G W Raab: Status of GW Detectors, Especially LIGO30 Core Optics Suspension and Control Shadow sensors & voice-coil actuators provide damping and control forces Mirror is balanced on 30 micron diameter wire to 1/100 th degree of arc Optics suspended as simple pendulums

LIGO-G W Raab: Status of GW Detectors, Especially LIGO31 Feedback & Control for Mirrors and Light Damp suspended mirrors to vibration-isolated tables »14 mirrors  (pos, pit, yaw, side) = 56 loops Damp mirror angles to lab floor using optical levers »7 mirrors  (pit, yaw) = 14 loops Pre-stabilized laser »(frequency, intensity, pre-mode-cleaner) = 3 loops Cavity length control »(mode-cleaner, common-mode frequency, common-arm, differential arm, michelson, power-recycling) = 6 loops Wave-front sensing/control »7 mirrors  (pit, yaw) = 14 loops Beam-centering control »2 arms  (pit, yaw) = 4 loops

LIGO-G W Raab: Status of GW Detectors, Especially LIGO32 Suspended Mirror Approximates a Free Mass Above Resonance Data taken using shadow sensors & voice coil actuators Blue: suspended mirror XF Cyan: free mass XF

LIGO-G W Raab: Status of GW Detectors, Especially LIGO33 Background Forces in GW Band = Thermal Noise ~ k B T/mode Strategy: Compress energy into narrow resonance outside band of interest  require high mechanical Q, low friction x rms  m f < 1 Hz x rms  2  m f ~ 350 Hz x rms  5  m f  10 kHz

LIGO-G W Raab: Status of GW Detectors, Especially LIGO34 Thermal Noise Observed in 1 st Violins on H2, L1 During S1 ~ 20 millifermi RMS for each free wire segment

LIGO-G W Raab: Status of GW Detectors, Especially LIGO35 LIGO Science Run S1 17 days in Aug-Sep LIGO interferometers in coincidence with GEO600 and ~2 days with TAMA300 Joint analyses with GEO reported at Spring APS meeting, papers appearing soon in Phys. Rev. D Remember: All performance data for all detectors are snapshots that reflect work in progress, not ultimate detector capability.

LIGO-G W Raab: Status of GW Detectors, Especially LIGO36 Binary Neutron Stars: S1 Range Image: R. Powell

LIGO-G W Raab: Status of GW Detectors, Especially LIGO37 LIGO Science Run S2 Feb 14 – Apr 14, LIGO interferometers in coincidence with TAMA300; GEO600 not available for science running

LIGO-G W Raab: Status of GW Detectors, Especially LIGO38 Binary Neutron Stars: S2 Range Image: R. Powell S1 Range

LIGO-G W Raab: Status of GW Detectors, Especially LIGO39 LIGO Science Run S3 Oct 31, 2003 – Jan 9, LIGO interferometers in coincidence with periods of operation of TAMA300, GEO600 and Auriga

LIGO-G W Raab: Status of GW Detectors, Especially LIGO40

LIGO-G W Raab: Status of GW Detectors, Especially LIGO41 Binary Neutron Stars: Initial LIGO Target Range Image: R. Powell S2 Range

LIGO-G W Raab: Status of GW Detectors, Especially LIGO42 Future Plans for Terrestrial Detectors Improve reach of initial LIGO to run 1 yr at design sensitivity Virgo has made steady progress commissioning components in vertex, now commissioning long arms and due to come on line in ~ 1 year GEO600, TAMA300, striving for design sensitivity IGEC expects to network with interferometers for future runs Advanced LIGO technology under development with intent to install by 2009

LIGO-G W Raab: Status of GW Detectors, Especially LIGO43 What’s next? Advanced LIGO… Major technological differences between LIGO and Advanced LIGO Initial Interferometers Advanced Interferometers Open up wider band Reshape Noise Quadruple pendulum Sapphire optics Silica suspension fibers Advanced interferometry Signal recycling Active vibration isolation systems High power laser (180W) 40kg

LIGO-G W Raab: Status of GW Detectors, Especially LIGO44 Binary Neutron Stars: AdLIGO Range Image: R. Powell LIGO Range

LIGO-G W Raab: Status of GW Detectors, Especially LIGO45 …and opening a new channel with a detector in space. Planning underway for space-based detector, LISA, to open up a lower frequency band ~ 2011-ish

LIGO-G W Raab: Status of GW Detectors, Especially LIGO46 Summary We are currently experiencing a rapid advance in the sensitivity of searches for gravitational waves Elements of world-wide networks of interferometers and bars have been exercised The near future will see the confrontation of theory with many fine observational results