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LIGO The Bumpy Road from Construction to Science

Explore the journey from LIGO construction to scientific discoveries, highlighting seismic, thermal, and quantum noise challenges and advanced technologies enhancing sensitivity. Witness the evolution of LIGO's infrastructure, interferometer limits, test masses, and subsystem integrations.

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LIGO The Bumpy Road from Construction to Science

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  1. LIGOThe Bumpy Road from Construction to Science Barry C Barish Caltech 14-August-2018

  2. My Goalstoday • v 1) Integration and Commissioning – Lessons learned from LIGO experience 2) Introduce AMCL and myself to the LSST community

  3. Gravitational Waves • Ripples of spacetimethat stretch and compress spacetime itself • The amplitude of the wave is h ≈ 10-21 • Change the distance between masses that are free to move by ΔL = h x L • Spacetime is “stiff” so changes in distance are very small L ΔL

  4. Suspended Mass Interferometry ~ ~

  5. Siting LIGO LIGO Sites Project Approved 1994

  6. LIGO Construction Began in 1994 Evolution over 22 years to Advanced LIGO

  7. LIGOLIGO Infrastructure beam tube

  8. LIGO Interferometer Infrastructure Queen's University Colloquium

  9. Hanford, WA LIGO Interferometers Livingston, LA

  10. Seismic Noise Quantum Noise Radiation pressure Residual gas scattering "Shot" noise Wavelength & amplitude fluctuations Thermal (Brownian) Noise Interferometer Noise Limits test mass (mirror) LASER Beam splitter photodiode

  11. What Limits LIGO Sensitivity? • Seismic noise limits low frequencies • Thermal Noise limits middle frequencies • Quantum nature of light (Shot Noise) limits high frequencies • Technical issues - alignment, electronics, acoustics, etc limit us before we reach these design goals Queen's University Colloquium

  12. Evolution of LIGO Sensitivity

  13. Initial LIGO Performance (Final)

  14. Advanced LIGO GOALS Better seismic isolation Higher power laser Better test masses and suspension

  15. How to obtain a x10 sensitivity improvement? Laser EOM

  16. 200W Nd:YAGLaser • Stabilized in power and frequency • Uses a monolithic master oscillator followed by injection-locked rod amplifier

  17. Mirror / Test Masses • Mechanical requirements: bulk and coating thermal noise, high resonant frequency • Optical requirements: figure, scatter, homogeneity, bulk and coating absorption 40 kg Test Masses: 34cm  x 20cm Round-trip optical loss: 75 ppm max 40 kg Compensation plates: 34cm  x 10cm BS: 37cm  x 6cm ITM T = 1.4%

  18. Optics Table Interface (Seismic Isolation System) Damping Controls Hierarchical Global Controls Electrostatic Actuation Test Mass Quadruple Pendulum Suspension Final elements All Fused silica

  19. Seismic IsolationPassive / Active Multi-Stage Queen's University Colloquium

  20. Subsystem Installation at LIGO Sites2012 Snapshot Each subsystem installation led by subsystem leader and on-site subsystem manager, plus coordination with system engineering and commissioning teams

  21. Subsystem Integration at LIGO Sites2013 Snapshot Each subsystem integrated and tested

  22. Input Optics: Subsytem Tests –> Integrated Tests2014 Snapshot

  23. Full Commissioning begins Sept 2014Sept 2014 March 2015

  24. Sensitivity for Advanced LIGO Broadband, Factor ~3 improvement At ~40 Hz, Factor ~100 improvement Initial LIGO O1 aLIGO Design aLIGO

  25. Finding a weak signal in noise • “Matched filtering” lets us find a weak signal submerged in noise. • For calculated signal waveforms, multiply the waveform by the data • Find signal from cumulative signal/noise PHYS. REV. X 6,041015 (2016)

  26. hg Observed Signals – Sept 14, 2015 September 14, 2015 Queen's University Colloquium

  27. Gravitational Wave EventGW150914 Data bandpass filtered between 35 Hz and 350 Hz Time difference 6.9 ms with Livingston first Second row – calculated GW strain using Numerical Relativity Waveforms for quoted parameters compared to reconstructed waveforms (Shaded) Third Row –residuals bottom row – time frequency plot showing frequency increases with time (chirp) Phys. Rev. Lett. 116, 061102 (2016) Queen's University Colloquium

  28. Construction to Science • Hardware • Equipment construction and Intallation; • Integration into subsystems; • Commissioning subsystems; • Overall Commissioning • Data Handling • Data Quality (glitches, etc) • Calibrations (sensitivity, etc) • Data Pipelines (unmodeled, templates, etc) • Data Analysis • Numerical Relativity • Parameter Estimation

  29. Thanks!

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