1. LIGO-G040004-00-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

2. LIGO-G040004-00-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

3. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO3 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

4. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO4 Gravitational Collapse and Its Outcomes Present LIGO Opportunities f GW > few Hz accessible from earth f GW < several kHz interesting for compact objects

5. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO5 Catching Waves From Orbiting Black Holes and Neutron Stars Sketches courtesy of Kip Thorne

6. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO6 Gravitational Waves the evidence Neutron Binary System – Hulse & Taylor PSR 1913 + 16 -- Timing of pulsars   17 / sec Neutron Binary System separated by 10 6 miles m 1 = 1.4m  ; m 2 = 1.36m  ;  = 0.617 Prediction from general relativity spiral in by 3 mm/orbit rate of change orbital period ~ 8 hr Emission of gravitational waves

7. LIGO-G040004-00-W How does LIGO detect spacetime vibrations? Leonardo da Vinci’s Vitruvian man

8. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO8 Basic Signature of Gravitational Waves for All Detectors

9. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO9 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

10. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO10 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.

11. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO11 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

12. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO12 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.

13. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO13 GEO 600 (Germany) (600-m) Virgo (Italy) 3-km Interferometers in Europe

14. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO14 TAMA 300 (Japan) (300-m) AIGO (Australia) (80-m, but 3-km site Interferometers in Asia, Australia

15. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO15 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://www.auriga.lnl.infn.it NIOBE ARC-UWAhttp://www.gravity.pd.uwa.edu.au EXPLORER INFN-CERN http://www.roma1.infn.it/rog/rogmain.html NAUTILUS INFN-LNF

16. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO16 Spacetime is Stiff! => Wave can carry huge energy with miniscule amplitude! h ~ (G/c 4 ) (E NS /r)

17. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO17 Some of the Technical Challenges Typical Strains < 10 -21 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 10 -13 meters RMS Detect optical phase changes of ~ 10 -10 radians Hold mirror alignments to 10 -8 radians Engineer structures to mitigate recoil from atomic vibrations in suspended mirrors

18. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO18 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

19. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO19 Time Line Now First Science Data Inauguration 1999 3Q 4Q 2000 1Q 2Q 3Q 4Q 2001 1Q 2Q 3Q 4Q 2002 1Q 2Q 3Q 4Q 2003 1Q 2Q 3Q 4Q E1 Engineering E2E3E4E5E6E7E8E9 S1 Science S2S3 First LockFull Lock all IFO's 10 -17 10 -18 10 -19 10 -20 strain noise density @ 200 Hz [Hz -1/2 ] 10 -21 Runs 10 -22 E10

20. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO20 Despite a few difficulties, science runs started in 2002.

21. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO21 Vibration Isolation Systems »Reduce in-band seismic motion by 4 - 6 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

22. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO22 Seismic Isolation – Springs and Masses damped spring cross section

23. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO23 Seismic System Performance 10 2 10 0 10 - 2 10 - 4 10 - 6 10 - 8 10 -10 Horizontal Vertical 10 -6 HAM stack in air BSC stack in vacuum

24. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO24 Core Optics Substrates: SiO 2 »25 cm Diameter, 10 cm thick »Homogeneity < 5 x 10 -7 »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

25. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO25 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

26. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO26 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

27. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO27 Suspended Mirror Approximates a Free Mass Above Resonance Data taken using shadow sensors & voice coil actuators Blue: suspended mirror XF Cyan: free mass XF

28. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO28 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  10 -11 m f < 1 Hz x rms  2  10 -17 m f ~ 350 Hz x rms  5  10 -16 m f  10 kHz

29. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO29 IO Frequency Stabilization of the Light Employs Three Stages Pre-stabilized laser delivers light to the long mode cleaner Start with high-quality, custom-built Nd:YAG laser Improve frequency, amplitude and spatial purity of beam Actuator inputs provide for further laser stabilization Wideband Tidal 10-Watt Laser PSL Interferometer 15m 4 km

30. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO30 Pre-stabilized Laser (PSL) Custom-built 10 W Nd:YAG Laser, joint development with Lightwave Electronics (now commercial product) Frequency reference cavity (inside oven) Cavity for defining beam geometry, joint development with Stanford

31. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO31 Digital Interferometer Sensing & Control System

32. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO32 Digital Controls screen example Analog In Analog Out Digital calibration input

33. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO33 Why is Locking Difficult? One meter Human hair, about 100 microns Wavelength of light, about 1 micron LIGO sensitivity, 10 -18 meter Nuclear diameter, 10 -15 meter Atomic diameter, 10 -10 meter Earthtides, about 100 microns Microseismic motion, about 1 micron Precision required to lock, about 10 -10 meter

34. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO34 Tidal Compensation Data Tidal evaluation on 21-hour locked section of S1 data Residual signal on voice coils Predicted tides Residual signal on laser Feedforward Feedback

35. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO35 Microseism Trended data (courtesy of Gladstone High School) shows large variability of microseism, on several-day- and annual- cycles Reduction by feed-forward derived from seismometers Microseism at 0.12 Hz dominates ground velocity

36. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO36 LIGO Science Run S1 17 days in Aug-Sep 2002 3 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.

37. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO37 Thermal Noise Observed in 1 st Violins on H2, L1 During S1 ~ 20 millifermi RMS for each free wire segment

38. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO38 Binary Neutron Stars: S1 Range Image: R. Powell

39. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO39 LIGO Science Run S2 Feb 14 – Apr 14, 2003 3 LIGO interferometers in coincidence with TAMA300; GEO600 not available for science running

40. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO40 Binary Neutron Stars: S2 Range Image: R. Powell S1 Range

41. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO41 LIGO Science Run S3 Oct 31, 2003 – Jan 9, 2004 3 LIGO interferometers in coincidence with periods of operation of TAMA300, GEO600 and Auriga

42. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO42

43. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO43 Binary Neutron Stars: Initial LIGO Target Range Image: R. Powell S2 Range

44. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO44 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

45. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO45 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

46. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO46 Binary Neutron Stars: AdLIGO Range Image: R. Powell LIGO Range

47. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO47 …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

48. LIGO-G040004-00-W Raab: Status of GW Detectors, Especially LIGO48 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