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Search for gravitational waves Jo van den Brand

Search for gravitational waves Jo van den Brand. Introduction. Einstein gravity : Gravity as a geometry Space and time are physical objects. Gravitational waves Dynamical part of gravitation, all space is filled Very large energy, almost no interaction

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Search for gravitational waves Jo van den Brand

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  1. Search for gravitational waves Jo van den Brand

  2. Introduction Einstein gravity : Gravity as a geometry Space and time are physical objects • Gravitational waves • Dynamical part of gravitation, all space is filled • Very large energy, almost no interaction • Ideal information carrier, almost no scattering or attenuation • The entire universe has been transparent for GWs, all the way back to the Big Bang

  3. Proper distance between xm and xm +dxm Define Wave equation Plane GW propagating in z-direction Gravitational waves `squeeze’ space: small effects

  4. GW L- D L L+ D L time • GW produced by mass acceleration • d = source distance • Q = quadrupole moment • Small coupling factor → astrophysical sources Gravitational waves • Predicted by general relativity • GW = space-time metric wave • Distance variation • Strain amplitude h: Earth-sun: 313 W L=20 m, d = 2 m, 27 rad/s

  5. Evidence for gravitational waves • PSR 1913+16 • R. Hulse, J. Taylor (1974) • Binary pulsar (T = 7.75 hr) • 1 pulsar (17 rev/s) → get the orbital parameters • Orbital period decreases • Energy loss due to GW emission (~3 x 1024 W) • Good agreement with GR • Inspiral lifetime about 300 Myears (3.5 m/yr) • Expected strain, h~10-26 m

  6. GW source: coalescing binary • End of the life of compact binary systems • Neutron stars, systems have been observed • Rare events • ~ 0.1 event/year (@20Mpc) ±1 order of magnitude • Typical amplitude (NS-NS): h ~ 10-22 @ 20 Mpc • “Known” waveform • Search with matched filtering • General relativity tests • Standard candles: get the distance from the waveform • Coincidence with short gamma ray burst?

  7. Collision of two black holes Numerical solution of Einstein equations required Problem solution started 40 years ago (1963 Hahn & Lindquist, IBM 7090) Wave forms critical for gravitational wave detectors A PetaFLOPS-class grand challenge Two body problem in general relativity

  8. Numerical relativity First merger of three black holes simulated on a supercomputer ScienceDaily (Apr. 12, 2008) Manuela Campanelli, Carlos Lousto and YosefZlochower—Rochester Institute of Technology Center for Computational Relativity and Gravitation Triple quasar (10.8 Gly) S. G. Djorgovski et al., Caltech, EPFL (Jan. 2007)

  9. VIRGO (French-Italian) Cascina, Italy AIGO (Australia), Wallingup Plain, 85km north of Perth Interferometric detectors: an international dream GEO600 (British-German) Hanover, Germany LIGO (USA) Hanford, WA and Livingston, LA TAMA300 (Japan)Mitaka

  10. Virgo: science case • First (?) direct observation of gravity waves • Better understanding of gravity • GW produced in high density area • Strong field • Tests GR • Open a new window on the universe • GW very weakly absorbed • Standard candle: Hubble constant • GW + Gamma Ray Bursts? • Supernova understanding? • Neutron stars/black hole physics? • Early universe picture?? • Pushing interferometer techniques to their limits

  11. Suspended mirror Suspended mirror Beam splitter Light Detection LASER Interferometer as GW detector • Principle: Measure distances between free test masses • Michelson interferometer • Test masses = Interferometer mirrors • Sensitivity: h = DL/L • We need large interferometer • For Virgo L = 3 km Virgo: CNRS+INFN (ESPCI-Paris, INFN-Firenze/Urbino, INFN-Napoli, INFN-Perugia, INFN-Pisa, INFN-Roma,LAL-Orsay, LAPP-Annecy, LMA-Lyon, OCA-Nice) + NIKHEF joined 2007 First science run: May – September 2007

  12. As a wave passes, the arm lengths change in different ways…. Interferometer Concept …causing the interference pattern to change at the photodiode Suspended Masses

  13. Input mode cleaner • Mode cleaner cavity: filterslaser noise, select TEM00 mode Input Mode Cleaner (144 m) 3 km long Fabry-Perot Cavities Laser 20 W Power Recycling Output Mode Cleaner (4 cm)

  14. Installation in IMC end tower Each switch has been tested in open and closed position. The mirror and RM are moved 55 mm for- and backwards.

  15. Eric Hennes Nikhef: redesign and replace dihedron Zorg dat je erbij komt… Optronica Marinebedrijf Den Helder

  16. W N EOM Nikhef: Linear alignment of VIRGO • Phase modulation of input beam • Demodulation of photodiode signals at different output beams • => longitudinal error signals • Quadrant diodes in output beams • => Alignment information • (differential wavefront sensing) • Anderson-Giordano technique • 2 quadrant diodes after arm cavities + Han Voet

  17. Linear alignment setup

  18. Crab pulsar LIGO: <10% of energy in GW GW source: pulsars • Rotating asymmetric neutron star • GW Amplitude function of the unknown asymmetry • ε = star asymmetry = ?? • Upper limit set by the pulsar spin down • A few pulsars around a few 100 Hz • Only 800 pulsars plotted out of 109 in the galaxy • Weak signal but could be integrated for months • But a complex problem due to the Doppler effect • CPU issues N f (Hz)

  19. Periodic Sources – all sky search – Roma / NIKHEF • Doppler shifts • Frequency modulation: due to Earth’s motion • Amplitude modulation: due to the detector’s antenna pattern. • Assumeoriginal frequency is 100 Hz and the maximum variation fraction is of the order of 0.0001 • Note the daily variations • After FFT: energy not in a single bin, so the SNR is highly reduced • Bin in galactic coordinates • Re-sampling • Short FFTs • Hough maps • Include binary systems ALL SKY SEARCH enormous computing challenge (Sipho van der Putten, Henk Jan Bulten, Sander Klous)

  20. GWs from binaries • Frequency changes a lot due to Doppler: df/f~10-3 Hulse-Taylor: Grid-based analysis Extension of LIGO – Virgo CW analysis Calibration systems for LISA

  21. Virgo sensitivity compared to LIGO and GEO600 May 2 Inspiral range 6.5 Mpc • The horizon (best orientation) for a binary system of two 10 solar mass black holes is 63 Mpc

  22. Discovery potential first event • Hypothesis: • Finesse = 150 (now : 50) • Same losses & power recycling as today • Horizon (Virgo+) • BNS: 150 Mpc (optimal orientation) • BBH: 750 Mpc (optimal orientation) • BNS Rates: (most likely and 95% interval) • Initial Virgo (30Mpc) 1/100yr (1/500 -1/25 yr) • Enhanced LIGO (60Mpc) 1/10yr (1/50- 1/2.5yr) • Virgo+ limit (150Mpc) 1.2/yr (1/4yr-5/yr) • Advanced detectors (350Mpc) 40/yr (8-160/yr) • Kalogera et al; astro-ph/0312101; Model 6 • BBH and other sources rates are more difficult to predict

  23. LIGO and VIRGO: scientific evolution • At present hundreds of galaxies in range for 1.4 Mo NS-NS binaries • Enhanced program • In 2009 about 10 times more galaxies in range • Advanced detectors • About 1000 times more galaxies in range • In 2014 expect 1 signal per day or week • Start of gravitational astrophysics • Numerical relativity will provide templates for interpreting signals

  24. Advanced Virgo: vacuum – cryo links Pressure mbar Start pressure Gas load from mirror 10-4 mbar l/s Intermediate Final pressure Element number 985 6885

  25. Advanced Virgo: vacuum – cryo links LN2 GN2 Reinforce rib Fixed 300 K Vacuum + super isolation Isolation vacuum Tie rod 3.2 mm/m LN2 3.2 mm/m Forces Beam vacuum

  26. Advanced Virgo: superattenuator FEA: Frans Mul Corijn

  27. Other activities in GW program • Einstein Telescope – conceptual design study • Approved in May 2008 • Funded for 3 years • Nikhef responsible for Working Group 1 on site selection Design Study Proposal approved by EU within FP7 Large part of the European GW community involved EGO, INFN, MPI, CNRS, NIKHEF, Univ. Birmingham, Cardiff, Glasgow Recommended in Aspera / Appec roadmap

  28. GRB050509B 1ST GENERATION 2ND GENERATION 3RD GENERATION INTERFEROMETER NS - NS INSPIRAL RANGE Credit G.Cagnoli

  29. LOI to ESA – LISA analysis Nikhef, VU, RUN and SRON Netherlands: Bulten/Nelemans Virgo

  30. Beyond Einstein is the umbrella program for a series of NASA/ESA missions linked by powerful new technologies and common science goals to answer the questions: • What powered the Big Bang? • What happens at the edge of a Black Hole? • What is the mysterious Dark Energy pulling the Universe apart? Gravitational Waves Can Escape from Earliest Moments of the Big Bang Inflation (Big Bang plus 10-34 Seconds) We do not know what 95% of the universe is made of! light Chandra - Each point of x-ray light is a Black Hole! Big Bang plus 300,000 Years Now Is Einstein’s theory still right in these conditions of extreme gravity? Or is new physics awaiting us? gravitational waves Big Bang plus 14 Billion Years Dark energy and matter interact through gravity September 6, 2007: Committee on NASA's Einstein Program: AnArchitecture for Implementation, National ResearchCouncil Finding 4. LISA is an extraordinarily original and technically bold mission concept. LISA will openup an entirely new way of observing the universe, with immense potential to enlarge ourunderstanding of physics and astronomy in unforeseen ways. LISA, in the committee’s view,should be the flagship mission of a long-term program addressing Beyond Einstein goals. Finding 8. The present NASA Beyond Einstein funding wedge alone is inadequate to develop anycandidate Beyond Einstein mission on its nominal schedule. However, both JDEM and LISA couldbe carried out with the currently forecasted NASA contribution if DOE's contribution that benefitsJDEM is taken into account and if LISA's development schedule is extended and funding from ESAis assumed.

  31. Summary • Gravitational wave physics • Component of our Astroparticle Physics initiative • Exciting new physics program • Important questions are addressed • Program with a long-term scientific perspective • VIRGO • Sensitivity is improving fast • First science run underway • Data sharing and analysis between LIGO and Virgo • NIKHEF commitment • Modest at this moment • Expand to FOM research program in 2009 / 2010

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