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GRAVITATIONAL WAVES EFFORTS TO DETECT GRAVITATIONAL WAVES USING LASER INTERFEROMETERS Mark Coles

IVth RECONTRES DU VIETNAM Physics at extreme energies Physics and Astrophysics. GRAVITATIONAL WAVES EFFORTS TO DETECT GRAVITATIONAL WAVES USING LASER INTERFEROMETERS Mark Coles LIGO Livingston Observatory California Institute of Technology. Gravitational Waves.

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GRAVITATIONAL WAVES EFFORTS TO DETECT GRAVITATIONAL WAVES USING LASER INTERFEROMETERS Mark Coles

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  1. IVth RECONTRES DU VIETNAM Physics at extreme energies Physics and Astrophysics GRAVITATIONAL WAVESEFFORTS TO DETECT GRAVITATIONAL WAVES USING LASER INTERFEROMETERS Mark Coles LIGO Livingston Observatory California Institute of Technology IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  2. Gravitational Waves • A new vantage point to study the universe • Gravitational radiation predicted in 1916 by Einstein as a consequence of general relativity. • Experimental searches to directly detect gravitational waves using resonant bars began in 1960 (Joseph Weber at U of Maryland) • First laser interferometer search began in 1972 (Robert Forward at Hughes Research Laboratories) • LIGO is the most ambitious attempt so far to directly observe gravitational waves IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  3. Gravitational Waves • Gravitational radiation is analogous to electromagnetic radiation: • Electromagnetic: • Gravitational: IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  4. EM vs Gravitational Waves IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  5. Some History... • Electromagnetic Observation - photons • Visible radiation: • atoms near surface of stars, • surrounding gas clouds • reflected radiation from planets and moons • Other frequencies: radio, x-ray, gamma ray • Particle astrophysics • cosmic rays • neutrinos (solar neutrinos, SN1987 A) IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  6. Electromagnetic Radiation In an inertial reference frame: Positive and negative charge allows dipole radiation - - - + + + IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  7. - - - + + + + + + - - - Only positive mass exists, so dipole displacements are not allowed by conservation of momentum so quadrupole radiation is lowest order radiation multipole Gravitational source from quadrupole deformation of a sphere IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  8. Polarization of gravitational waves IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  9. Sources • Frequency set by dynamics of radiating body • types of sources • Coalescence of compact binaries: • Neutron stars, black holes, and combinations • Type II Supernovae • Asymmetric neutron stars • Rotational instabilities in neutron stars • Black hole collapse • Stochastic background sources: • primordial radiation, phase transitions, cosmic strings IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  10. Strong GW Source Big Quadrupole Moment Weak GW Source Near spherical expansion IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  11. Waveforms indicate physical processes IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  12. Detection • Strain h is very small • for coalescing binary neutron star system, amplitude of strain is of order: t= time before coalescence R= 15 Mpc is mean distance to Virgo Cluster IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  13. Indirect Detection • Indirect evidence of the phenomena exists (observation by Hulse and Taylor of the orbital decay of PSR 1913+16) • Rate of decrease of orbital period measured to ~3 ppm • 10 sec decrease observed over 15 years • Consistent with predictions of damping effect of gravitational radiation to ~0.4% IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  14. IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  15. Gravitational Wave Antenna quadrupole strain sensitivity Initial position of freely suspended test mass Displaced test mass position IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  16. Enhanced sensitivity: Michelson interferometer with Fabry-Perot arm cavities IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  17. Further Enhancement: Recycling Recycling mirror IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  18. IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  19. Interferometersthe noise floor • Interferometry is limited by three fundamental noise sources • seismic noise at the lowest frequencies • thermal noise at intermediate frequencies • shot noise at high frequencies • Many other noise sources lurk underneath and must be controlled as the instrument is improved Sensitive region IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  20. Noise Spectrum of 40 Meter Prototype Laser Interferometer Displacement spectral density in meters/sqrt(hz) IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  21. IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  22. Interferometersastrophysical sources Binary inspiral ‘chirp’ signal Sensitivity to coalescing binaries 2002 2007 Compact binary mergers future IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  23. IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  24. Astrophysics Sourcesfrequency range Space Ground-based Audio band • EM waves are studied over ~20 orders of magnitude • (ULF radio -> HE  rays) • Gravitational Waves over ~8 orders of magnitude • (terrestrial + space) IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  25. International network of gravitational wave interferometers now under construction Virgo GEO LIGO TAMA Coincident detection to enhance detection confidence source location decompose the polarization of gravitational waves AIGO IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  26. Related Ground-based Projects Now Underway • VIRGO (French/Italian) - near Pisa • 3 KM interferometer • similar optical configuration, sensitivity and detection bandwidth • near Pisa, Italy • GEO (German/British) - near Hanover • 600 meter interferometer • optical configuration different from LIGO, but similar sensitivity over narrow detectionband • TAMA (Japan) - Tokyo • 300 meter interferometer, lesser sensitivity • ACIGA (Australia) • proposed IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  27. Interferometers international network LIGO (Washington) LIGO (Louisiana) IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  28. Interferometers international network GEO 600 (Germany) Virgo (Italy) IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  29. Interferometers international network AIGO (Australia) TAMA 300 (Japan) IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  30. LIGO Locations • Two well separated observatory sites to minimize correlated noise: • Tri-cities area of Eastern Washington • Between Baton Rouge and New Orleans, Louisiana • . IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  31. Coincidence strategy: two LIGO sites • three interferometers • +/- 10 mSec time window for coincidences between Washington and Lousiana • require half length interferometer - half amplitude signal • first pass data analysis at each site using LINUX cluster • offline analysis at Caltech and further analysis at collaborating • interchange of data with VIRGO, GEO, TAMA to further refine searches IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  32. Design Features of LIGO • Basically a very large Michelson interferometer • Design features: • 10 Watt Nd:YAG Laser - 1.06m • Power recycling - Approximately 10 KW circulating optical power in Fabry-Perot arm cavities • 2 interferometers - each with 4km Fabry-Perot arms, at Hanford and Livingston • 1 interferometer with 2km Fabry-Perot arms at Hanford (shares same vacuum as 4 km interferometer) • Passive seismic isolation - 4 layers of damped springs • Single pendulum suspension of test masses and beam splitter IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  33. LIGO Hanford Observatory has 2 interferometers sharing common vacuum space IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  34. Seismic isolation stacks Damped springs Air bearing Scissors table Laser beam direction Seismic pier IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  35. Vacuum Chamberstest masses, optics LIGO chambers TAMA chambers IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  36. Seismic Isolation Virgo • “Long Suspensions” • inverted pendulum • five intermediate filters Suspension vertical transfer function measured and simulated (prototype) IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  37. Long Suspensions Virgo installation at the site Beam Splitter and North Input mirror All four long suspensions for the entire central interferometer will be complete by October 2000. IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  38. SuspensionsGEO triple pendulum IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  39. Seismic isolation system IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  40. Suspended Optics Mass 10.7 kg Mirror diameter 25 cm Mirror material Fused silica Mirror internal Q per mode >106 Mirror internal adsorption ~5 ppm Mirror loss 50 ppm Single Wire Loop Suspension Pendulum material Steel wire, Q=200,000 Pendulum frequency 1 Hz IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  41. Interferometer features arm length suspension topology fc (hz) LIGO 2,4 km (x2) single pendulum power recycled 60 FP arms VIRGO 3 km 6 stage pend PR + FP 10 GEO 0.6 km 3 stage pend + signal recycled 50 reaction mass TAMA 0.3 km FP arms 100 IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  42. Interferometers sensitivity curves TAMA 300 Virgo LIGO GEO 600 IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  43. Status • LIGO • Commissioning work underway at both sites • “Engineering” data run in 2001 • “Science” data beginning in 2002 • Plans developing for significant future upgrades >2005 • VIRGO & GEO • Similar schedule to LIGO • TAMA • “Engineering” data studies underway • Plans in development for KM scale interferometer • ACIGA • Construction of short Michelson underway • Proposal for KM scale construction IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  44. Conclusions • a new generation of long baseline suspended mass interferometers are being completed with h ~ 10-21 • commissioning, testing and characterization of the interferometers is underway • data analysis schemes are being developed, including tests with real data from the 40 m prototype and TAMA • science data taking to begin within two years • plans and agreements being made for exchange of data for coincidences between detectors • significant improvements in sensitivity (h ~ 10-22) are anticipated about 2007+ IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  45. Recycling mirror Beam Splitter Input Test Masses LASER Optics Installation - Livingston Installed End Test Mass To Be Installed Mode Cleaner End Test Mass IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  46. IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  47. Future Plans • Plan to collect approximately one year of integrated coincident data during 2002-2004 • Developing plans and proposals to install a major upgrade at both sites beginning in 2005 • Increase sensitivity by x10 • Increase event rate by x103 IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  48. Damped springs • Seismic isolation system uses passively damped stages • 1/f2 isolation for each stage of masses and damped springs • helicoil spring with high damping (~2%). • internally damped so that Q < ~5. • Large optics supported by 4 layers of spring/mass assemblies, so 1/f8 roll off in seismic noise IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  49. IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

  50. TAMA 300 optical configuration IVth RECONTRES DU VIETNAM July 19 – July 25, 2000 Hanoi, Vietnam

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