1 / 51

LIGO The Search for Gravitational Waves

Explore the groundbreaking research on gravitational waves and their detection through terrestrial and space-based detectors. Understand the technology, sensitivities, and challenges involved in this search for astrophysical sources and cosmological signals.

josephmarsh
Download Presentation

LIGO The Search for Gravitational Waves

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. LIGOThe Search for Gravitational Waves Barry Barish Laboratori Nazionali del Gran Sasso 28-Oct-02

  2. Einstein’s Theory of Gravitation gravitational waves Newton’s Theory “instantaneous action at a distance” Einstein’s Theory information carried by gravitational radiation at the speed of light • A necessary consequence of Special Relativity with its finite speed for information transfer • Time dependent gravitational fields come from the acceleration of masses and propagate away from their sources as a space-time warpage at the speed of light LVD, The First 10 Years

  3. Direct Detectionastrophysical sources Gravitational Wave Astrophysical Source Terrestrial detectors LIGO, TAMA, Virgo,AIGO Detectors in space LISA LVD, The First 10 Years

  4. Astrophysics Sourcesfrequency range Audio band • EM waves are studied over ~20 orders of magnitude • (ULF radio -> HE -rays) • Gravitational Waves over ~10 orders of magnitude • (terrestrial + space) Space Terrestrial LVD, The First 10 Years

  5. Astrophysical Sources the search for gravitational waves • Compact binary inspiral: “chirps” • NS-NS waveforms are well described • BH-BH need better waveforms • search technique: matched templates • Supernovae / GRBs: “bursts” • burst signals in coincidence with signals in electromagnetic radiation • prompt alarm (~ one hour) with neutrino detectors • Pulsars in our galaxy: “periodic” • search for observed neutron stars (frequency, doppler shift) • all sky search (computing challenge) • r-modes • Cosmological Signals“stochastic background” LVD, The First 10 Years

  6. Interferometers terrestrial free masses free masses International network (LIGO, Virgo, GEO, TAMA, AIGO) of suspended mass Michelson-type interferometers on earth’s surface detect distant astrophysical sources suspended test masses LVD, The First 10 Years

  7. Suspended Mass Interferometerthe concept As a wave passes, the arm lengths change in different ways…. • Arms in LIGO are 4km • Current technology then allows one to measure h = dL/L ~ 10-21which turns out to be an interesting target • An interferometric gravitational wave detector • A laser is used to measure the relative lengths of two orthogonal cavities (or arms) …causing the interference pattern to change at the photodiode LVD, The First 10 Years

  8. How Small is 10-18 Meter? One meter, about 40 inches Human hair, about 100 microns Wavelength of light, about 1 micron Atomic diameter, 10-10 meter Nuclear diameter, 10-15 meter LIGO sensitivity, 10-18 meter LVD, The First 10 Years

  9. What Limits Sensitivityof 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 LVD, The First 10 Years

  10. Noise Floor40 m prototype sensitivity demonstration • displacement sensitivity • in 40 m prototype. • comparison to predicted contributions from various noise sources LVD, The First 10 Years

  11. LIGO Observatories Hanford Observatory Livingston Observatory LVD, The First 10 Years

  12. Coincidences between Sites • Time Window • Separation ~ 3020 km (   msec) • Two Sites – Three interferometers • Single interferometer non-gaussian level ~50/hour • Local coincidence - Hanford 2K and 4K (÷~1000) ~1/day • Hanford/Livingston coincidence (uncorrelated) <0.1/yr • GEO / TAMA coincidences further reduces the false signal rate • Data (continuous time-frequency record) • Gravitational wave signal 0.2MB/sec • Total data recorded 9 MB/sec • Gravitational Wave Signal Extraction • Signal from noise (noise analysis, vetoes, coincidences, etc) LVD, The First 10 Years

  13. University of Adelaide ACIGA Australian National University ACIGA Balearic Islands University - Spain California State Dominquez Hills Caltech CACR Caltech LIGO Caltech Experimental Gravitation CEGG Caltech Theory CART University of Cardiff UK GEO Carleton College Cornell University Fermi National Laboratory University of Florida @ Gainesville Glasgow University GEO NASA-Goddard Spaceflight Center University of Hannover GEO Hobart – Williams University India-IUCAA IAP Nizhny Novgorod Iowa State University Joint Institute of Laboratory Astrophysics Salish Kootenai College LIGO Livingston LIGOLA LIGO Hanford LIGOWA Loyola New Orleans Louisiana State University Louisiana Tech University MIT LIGO Max Planck (Garching) GEO Max Planck (Potsdam) GEO University of Michigan Moscow State University NAOJ - TAMA Northwestern University University of Oregon Pennsylvania State University Southeastern Louisiana University Southern University Stanford University Syracuse University University of Texas@Brownsville Washington State University@ Pullman University of Western Australia ACIGA University of Wisconsin@Milwaukee LIGO Scientific Collaboration Oct 02 LSC Institutional Membership 44 collaborating groups > 400 collaborators International India, Russia, Germany, U.K, Japan, Spain and Australia. The international partners are involved in all aspects of the LIGO research program. LVD, The First 10 Years

  14. LIGOscheduleand plan Primary Activities 1996 Construction Underway (mostly civil) 1997 Facility Construction (vacuum system) 1998 Interferometer Construction (complete facilities) 1999 Construction Complete (interferometers in vacuum) 2000 Detector Installation (commissioning subsystems) 2001 Commission Interferometers (first coincidences) 2002 Sensitivity studies(initiate LIGO I Science Run) 2003+ LIGO I data run (one year integrated data at h ~ 10-21) 2006+ Begin ‘Advanced LIGO’ installation LVD, The First 10 Years

  15. LIGO Livingston Observatory LVD, The First 10 Years

  16. LIGO Hanford Observatory LVD, The First 10 Years

  17. Beam Pipe and Enclosure • Minimal Enclosure (no services) • Beam Pipe • 1.2m diam; 3 mm stainless • 65 ft spiral weld sections • 50 km of weld (NO LEAKS!) LVD, The First 10 Years

  18. Vacuum Chambers and Seismic Isolation Constrained Layer Damped Springs Vacuum Chambers Vacuum Chamber Gate Valve Passive Isolation LVD, The First 10 Years

  19. LIGO I Suspension and Optics fused silica Single suspension 0.31mm music wire Surface figure = /6000 • surface uniformity < 1nm rms • scatter < 50 ppm • absorption < 2 ppm • internal Q’s > 2 106 LVD, The First 10 Years

  20. Commissioning LIGO Subsystems Tidal Wideband 4 km 15m 10-Watt Laser Interferometer PSL IO stabilization 10-4 Hz/Hz1/2 10-7 Hz/Hz1/2 10-1 Hz/Hz1/2 LIGO I Goal Nd:Yag 1.064 mm Output power >8 Watt TEM00 mode LVD, The First 10 Years

  21. LIGO Prestabilized Laserdata vs simulation LVD, The First 10 Years

  22. Interferometer Configuration end test mass Requires test masses to be held in position to 10-10-10-13 meter: “Locking the interferometer” Light bounces back and forth along arms about 150 times Light is “recycled” about 50 times input test mass Laser signal LVD, The First 10 Years

  23. LIGO Facility Noise Levels • Fundamental Noise Sources • Seismic at low frequencies • Thermal at mid frequencies • Shot at high frequencies • Facility Noise Sources (example) • Residual Gas • 10-6 torr H2 unbaked • 10-9 torr H2 baked LVD, The First 10 Years

  24. Lock Acquisition Developed by Matt Evans Caltech PhD Thesis LVD, The First 10 Years

  25. Composite Video LIGO watching the interferometer lock Y Arm Laser X Arm signal LVD, The First 10 Years

  26. 2 min LIGO watching the interferometer lock Y arm X arm Y Arm Reflected light Anti-symmetricport Laser X Arm signal LVD, The First 10 Years

  27. Detecting the Earth Tides Sun and Moon LVD, The First 10 Years

  28. LIGO Lab Planning MemoAugust 2001 “…The LIGO Laboratory will carry out the E7 run before the end of the year. We anticipate that the run will take place during December and will be scheduled for two full weeks. The run is an engineering run and will be the responsibility of the LIGO Laboratory…” • PRIMARY GOAL: • Establish coincidence running between the sites • Obtain first data sample for shaking down data analysis Last LIGO Construction Project Milestone LVD, The First 10 Years

  29. LIGO + GEO InterferometersE7 Engineering Run 28 Dec 2001 - 14 Jan 2002 (402 hr) Coincidence Data All segments Segments >15min 2X: H2, L1 locked 160hrs (39%) 99hrs (24%) clean 113hrs (26%) 70hrs (16%) H2,L1 longest clean segment: 1:50 3X : L1+H1+ H2 locked 140hrs (35%) 72hrs (18%) clean 93hrs (21%) 46hrs (11%) L1+H1+ H2 : longest clean segment: 1:18 4X: L1+H1+ H2 +GEO: 77 hrs (23 %)26.1 hrs (7.81 %) 5X: ALLEGRO + … Singles data All segments Segments >15min L1 locked 284hrs (71%) 249hrs (62%) L1 clean 265hrs (61%) 231hrs (53%) L1 longest clean segment: 3:58 H1 locked 294hrs (72%) 231hrs (57%) H1 clean 267hrs (62%) 206hrs (48%) H1 longest clean segment: 4:04 H2 locked 214hrs (53%) 157hrs (39%) H2 clean 162hrs (38%) 125hrs (28%) H2 longest clean segment: 7:24 Conclusion: Large Duty Cycle is Attainable LVD, The First 10 Years

  30. LIGO Engineering Run (E7)Sensitivities Final LIGO Milestone ----------- “Coincidences Between the Sites in 2001” Engineering Run 28 Dec 01 to 14 Jan 02 LVD, The First 10 Years

  31. LVD, The First 10 Years

  32. Improvements to LHO 4k noise S1 Further low-freq improvement 2 days later 13 Oct LVD, The First 10 Years

  33. Science Runningplan • Two “upper limit” runs S1 and S2, interleaved with commissioning at publishable early sensitivity • S1 Sept 02 duration 2 weeks • S2 March 03 duration 8 weeks – sensitivity better by >x10 • First “search” run S3 will be performed in late 2003 (~ 6 months) LVD, The First 10 Years

  34. LIGO data vs. SimLIGO Triple Strain Spectra - Thu Aug 15 2002 LIGO S1 Run ----------- “First Upper Limit Run” Aug – Sept 02 Strain (1/Hz1/2) Frequency (Hz) LVD, The First 10 Years

  35. Preliminary LVD, The First 10 Years

  36. S1 Duty Cycle • Longest locked section for individual interferometer: 21 hrs (11 in “Science mode”) • Need to improve low frequency seismic isolation – protection from local anthropogenic noise LVD, The First 10 Years

  37. “Upper Limits”S1,S2 Data Analysis Groups • Compact binary inspiral: “chirps” • Supernovae / GRBs: “bursts” • Pulsars in our galaxy: “periodic” • Cosmological Signal “stochastic background” LVD, The First 10 Years

  38. Do Supernovae Produce Gravitational Waves? Puppis A • Not if stellar core collapses symmetrically (like spiraling football) • Strong waves if end-over-end rotation in collapse • Increasing evidence for non-symmetry from speeding final neutron stars • Gravitational wave amplitudes uncertain by factors of 1,000’s !! LVD, The First 10 Years

  39. Explosion of a Star supernova sequence gravitational waves n’s light LVD, The First 10 Years

  40. Model of Core Collapse Burrows et al kick sequence gravitational core collapse LVD, The First 10 Years

  41. Supernovae gravitational waves Non axisymmetric collapse ‘burst’ signal Rate 1/50 yr - our galaxy 3/yr - Virgo cluster LVD, The First 10 Years

  42. Supernovae asymmetric collapse? • pulsar proper motions • Velocities - • young SNR(pulsars?) • > 500 km/sec • Burrows et al • recoil velocity of matter and neutrinos LVD, The First 10 Years

  43. Supernovaesignatures and sensitivity LVD, The First 10 Years

  44. “Upper Limits”S1,S2 Data Analysis Groups • LSC Upper Limit Analysis Groups • Typically ~25 physicists • One experimentalist / One theorist co-lead each group ---------------------------------- • Compact binary inspiral: “chirps” • Supernovae / GRBs: “bursts” • Pulsars in our galaxy: “periodic” • Cosmological Signal “stochastic background” LVD, The First 10 Years

  45. Stochastic Background Sensitivity • Detection • Cross correlate Hanford and Livingston Interferometers • Good Sensitivity • GW wavelength  2x detector baselinef  40 Hz • Initial LIGO Sensitivity   10-5 • Advanced LIGO Sensitivity   5 10-9 LVD, The First 10 Years

  46. Stochastic BackgroundLHO/LLO coherence plots from E7 LVD, The First 10 Years

  47. S1 – Expected Sensitivities Upper limit: (90% CL, 70 hrs H2-L1 data) 0 < 30 40 Hz < f < 215 Hz NOTE: Factor of 2 x 103 improvement over E7. LVD, The First 10 Years

  48. Stochastic Background sensitivities S1 LVD, The First 10 Years

  49. Advanced LIGOsensitivity and source signals • Advanced LIGO: 2.5 hours = 1 year of Initial LIGO • Volume of sources grows with cube of sensitivity • ~15x in sensitivity; ~ 3000 in rate LVD, The First 10 Years

  50. Conclusions • LIGO construction complete • LIGO commissioning and testing ‘on track’ • Engineering test runs underway, during period when emphasis is on commissioning, detector sensitivity and reliability. (Short upper limit data runs interleaved) • First Science Search Run : first search run begin in 2003 • Significant improvements in sensitivity anticipated to begin about 2007 • Detection is likely within the next decade ! LVD, The First 10 Years

More Related