LIGO-G W "Colliding Black Holes" Credit: National Center for Supercomputing Applications (NCSA) Searching for Gravitational Waves with LIGO Reported on behalf of LIGO Scientific Collaboration by Fred Raab, LIGO Hanford Observatory

LIGO-G W Raab: Overview of LIGO Instrumentation2 Outline What is LIGO? What is the gravitational-wave signature? What strength are expected signals, noise and background? What do detectors look like? How well do detectors work? What observations have been done? What comes next?

LIGO-G W Raab: Overview of LIGO Instrumentation3 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: Overview of LIGO Instrumentation4 Part of Future International Detector 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: Overview of LIGO Instrumentation5 John Wheeler’s Schematic of General Relativity Theory

LIGO-G W Raab: Overview of LIGO Instrumentation6 GR Statics: Warping of a 2-D Sheet of Space Like a flat sheet of paper Like surface of a globe

LIGO-G W Raab: Overview of LIGO Instrumentation7 GR with Accelerating Sources: 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: Overview of LIGO Instrumentation8 Basic Signature of Gravitational Waves for All Detectors

LIGO-G W Raab: Overview of LIGO Instrumentation9 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: Overview of LIGO Instrumentation10 Spacetime is Stiff! => Wave can carry huge energy with miniscule amplitude! h ~ (G/c 4 ) (E NS /r) 

LIGO-G W Raab: Overview of LIGO Instrumentation11 Detection of Energy Loss Caused By Gravitational Radiation In 1974, J. Taylor and R. Hulse discovered a pulsar orbiting a companion neutron star. This “binary pulsar” provides some of the best tests of General Relativity. Theory predicts the orbital period of 8 hours should change as energy is carried away by gravitational waves. Taylor and Hulse were awarded the 1993 Nobel Prize for Physics for this work.

LIGO-G W Raab: Overview of LIGO Instrumentation12 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: Overview of LIGO Instrumentation13 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: Overview of LIGO Instrumentation14 Vacuum Chambers Provide Quiet Homes for Mirrors View inside Corner Station Standing at vertex beam splitter

LIGO-G W Raab: Overview of LIGO Instrumentation15 Evacuated Beam Tubes Provide Clear Path for Light Vacuum required: <10 -9 Torr

LIGO-G W Raab: Overview of LIGO Instrumentation16 Vibration Isolation Systems »Reduce in-band seismic motion by orders of magnitude »Little or no attenuation below 10Hz; control system counteracts vibration »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: Overview of LIGO Instrumentation17 Seismic Isolation – Springs and Masses damped spring cross section

LIGO-G W Raab: Overview of LIGO Instrumentation18 Frequency Stabilization of the Light Employs Three Stages IO 10-Watt Laser PSL Interferometer 15m 4 km Pre-stabilized laser “Mode-cleaner” cavity cleans up laser light Common-mode signal stabilizes frequency Differential signal carries GW info

LIGO-G W Raab: Overview of LIGO Instrumentation19 All-Solid-State Nd:YAG Laser 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

LIGO-G W Raab: Overview of LIGO Instrumentation20 Pre-Stabilized Laser Subsystem

LIGO-G W Raab: Overview of LIGO Instrumentation21 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: Overview of LIGO Instrumentation22 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: Overview of LIGO Instrumentation23 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: Overview of LIGO Instrumentation24 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 + BS)  (pit, yaw) = 4 loops

LIGO-G W Raab: Overview of LIGO Instrumentation25 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: Overview of LIGO Instrumentation26 LIGO Science Runs S2 2 nd Science Run Feb - Apr 03 (59 days) S1 1 st Science Run Sept 02 (17 days) S3 3 rd Science Run Nov 03 – Jan 04 (70 days) LIGO Target Sensitivity S3 Duty Cycle Hanford 4km 69% Hanford 2km 63% Livingston 4 km 22%*

LIGO-G W Raab: Overview of LIGO Instrumentation27 Improvements to H1 Sensitivity in Last Two Years of Commissioning

LIGO-G W Raab: Overview of LIGO Instrumentation28 Limiting Noise Sources for H1 on 1Sep04

LIGO-G W Raab: Overview of LIGO Instrumentation29 Science Analyses Searches for periodic sources, such as spinning neutron stars »Known radio pulsars, x-ray binaries »Unknown sources Searches for compact-binary inspirals, e.g., neutron stars (NS), black holes (BH), MACHOs »Waveforms well characterized: use optimal-filter template searches »Template space manageable for NS, large for spinning BHs or light MACHOs Searches for burst sources »Waveforms may be unknown or poorly known »Non-triggered search »Triggered search(e.g., supernova or GRB triggers) Stochastic waves of cosmological or astrophysical origin »Cross-correlation of multiple detectors

LIGO-G W Raab: Overview of LIGO Instrumentation30 S1 Analysis Papers in Print Detector Description and Performance for the First Coincidence Observations Between LIGO and GEO; B. Abbott et al. (LSC), Nucl. Instrum. Meth., A517 (2004) First Upper Limits from LIGO on GW Bursts; B. Abbott et al. (LSC), Phys. Rev. D 69 (2004) Setting Upper Limits on the Strength of Periodic GW from PSR J Using the First Science Data from the GEO600 and LIGO Detectors; B. Abbott et al. (LSC), Phys. Rev. D 69 (2004) Analysis of LIGO Data for GW from Binary Neutron Stars; B. Abbott et al. (LSC), Phys. Rev. D 69 (2004) Analysis of LIGO Data for Stochastic GW; B. Abbott et al. (LSC), Phys. Rev. D 69 (2004)

LIGO-G W Raab: Overview of LIGO Instrumentation31 Analysis Example: Searching for Signals from Neutron Stars

LIGO-G W Raab: Overview of LIGO Instrumentation32 Time Domain Bayesian Analysis

LIGO-G W Raab: Overview of LIGO Instrumentation33 S2 G-W Search Over Known Radio Pulsars* * 10 of 38 known radio pulsars had poorly known timing and were not used.

LIGO-G W Raab: Overview of LIGO Instrumentation34 Direct Upper Limits on Neutron-Star Ellipticity from S2 Known Pulsar Search

LIGO-G W Raab: Overview of LIGO Instrumentation35 Other Periodic Analyses Planned on Data “In the can” All sky searches for unknown periodic sources »Coherent techniques – optimal, but strongly limited by processing power »Incoherent techniques – less than optimal, but more processor efficient and more forgiving of noisy models Targeted-sky searches for unknown periodic sources »Galactic center »Sco-X1 S3 data set from LIGO and GEO

LIGO-G W Raab: Overview of LIGO Instrumentation36 Binary Neutron Stars: Initial LIGO Target Range Image: R. Powell S2 Range

LIGO-G W Raab: Overview of LIGO Instrumentation37 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: Overview of LIGO Instrumentation38 Binary Neutron Stars: AdLIGO Range Image: R. Powell LIGO Range

LIGO-G W The End