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Brief of the May 2006 LIGO Charging Event LSC-Virgo Charging Workshop M.I.T. 7/27/2007

Brief of the May 2006 LIGO Charging Event LSC-Virgo Charging Workshop M.I.T. 7/27/2007 G070572-00-R Rupal S. Amin Louisiana State University LIGO Livingston Observatory. Outline. LIGO Overview Suspensions Charging Noise Prediction/Observed Reason for Charging

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Brief of the May 2006 LIGO Charging Event LSC-Virgo Charging Workshop M.I.T. 7/27/2007

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  1. Brief of the May 2006 LIGO Charging Event LSC-Virgo Charging Workshop M.I.T. 7/27/2007 G070572-00-R Rupal S. Amin Louisiana State University LIGO Livingston Observatory LIGO Scientific Collaboration

  2. Outline • LIGO Overview • Suspensions • Charging Noise Prediction/Observed • Reason for Charging • Possible Means of Monitoring/Discharging • Summary LIGO Scientific Collaboration

  3. Layout Power Recycled Michelson Laser Fields Blue = Non-Resonant Sidebands Green = Resonant Sidebands Red = Carrier Mirrors mounted on seismometer-type mounts. LIGO Scientific Collaboration

  4. LIGODisplacement Sensitivity Displacement Sensitivity of LIGO Livingston and Hanford Observatories. Best sensitivity at ~150 Hz of ~10-19 m/sqrt(Hz) LIGO Scientific Collaboration

  5. Suspensions BSC Chamber Isometric drawing of external suspension Mirror goes here LIGO Scientific Collaboration Credit: Oddvar Spjeld

  6. Suspensions Pendulum suspension Steel Piano Wires Steel Cage Earthquake Stops 1/2x13 stainless steel silverplated SHCS screws with viton ends Demonstation piece in LLO multipupose room LIGO Scientific Collaboration

  7. Suspensions Earthquake Stops • Current Earthquake stops have viton tips • Heterogeneous materials  charge transfer • Stops set ~1 mm away from optic LIGO Scientific Collaboration

  8. Suspensions Earthquake Stops Contacted ITMy earthquake stop Upper left stops Credit: G. Traylor May 5, 2006 LIGO Scientific Collaboration

  9. Charge Induced Noise • From a note from R. Weiss May 10, 2006 i-log • Charging noise trend follows f-3 • Possible to transfer charge to a test mass by contacting earthquake stops, friction, cosmic rays, dust/residual gas • Personal communique from G.Traylor • ITMy most likely was contacting viton stops following HEPI spring adjustment. (friction/work function charging?) • http://ilog.ligo-la.caltech.edu/ilog/pub/ilog.cgi?group=detector&date_to_view=05/10/2006&anchor_to_scroll_to=2006:05:10:09:41:18-RaiW LIGO Scientific Collaboration

  10. DARM spectrumBefore/After May 2006 Vent DARM Error spectrum plotted prior to ITMy sticking and following the vent to free ITMy Difference visible between ~40 and 100 Hz April 2, 2007 LLO i-log entry LIGO Scientific Collaboration

  11. DARM spectrumBefore/After May 2006 Vent DARM Error spectrum plotted prior to ITMy sticking and following the vent to free ITMy Difference visible between ~40 and 100 Hz Zoom and plot LIGO Scientific Collaboration

  12. DARM SpectrumFit between 40 and 110 Hz Basic fitting model yields powers -2.8 to -3.1 LIGO Scientific Collaboration

  13. Possible means of monitoring (big) charging? ITMY OSEM spectra Qualitative change in spectrum of a free swinging optic Data on right taken by B. O’Reilly May 2, 2006 ITMX LIGO Scientific Collaboration

  14. Future EffortsEnhanced LIGO/Advanced LIGO • Switch from viton tipped to glass tipped earthquake stops to mitigate contact charge transfer Metal screw body Flourel/Silica Tip Credit: Pradeep Sarin, M. Zucker, R. Weiss and others LIGO Scientific Collaboration

  15. Future EffortsEnhanced LIGO/Advanced LIGO • Test UV irradiation and alternate means for charge removal • See Ke Xun’s talk LIGO Scientific Collaboration

  16. Summary • Determined that 40-110 Hz region followed noise due to a charged optic • Determined the most likely reason due to charging was due to ITMy contacting earthquake stops • Use OSEM spectra of freely swinging pendula can qualitatively indicate whether an optic is charged • Charging group continues to search for non-venting means to neutralize mirrors • Future earthquake stops will be modified to reduce likelihood of contact charging LIGO Scientific Collaboration

  17. Done LIGO Scientific Collaboration

  18. f Credit: NASA/WMAP Science Team NASA/CXC/ASU/J. Hester et al. J. Hester ASU/NASA Hubble LIGO Overview • Einstein 1916 paper • Changing Mass Distributions • No net motion, only strain h = DL/L • Sources: • Periodic (Pulsars) • Chirp (Binary Neutron Star Inspiral) • Burst (Asymmetric Supernova) • Stochastic (Big bang) LIGO Scientific Collaboration

  19. IntroductionLIGO 3 detectors 2/4 km arms 3000 km separation Hanford, WA LIGO Scientific Collaboration Livingston, LA

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