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eLigo Photon Calibrator investigation: long-term stability of DARM actuation

eLigo Photon Calibrator investigation: long-term stability of DARM actuation. Rick Savage Jonathan Berliner, Pablo Daveloza, Roberto Grosso, Greg Mendell, Michael Sakosky, Ryan DeRosa, Matt West. Photon Calibrator method.

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eLigo Photon Calibrator investigation: long-term stability of DARM actuation

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  1. eLigo Photon Calibrator investigation:long-term stability of DARM actuation Rick Savage Jonathan Berliner, Pablo Daveloza, Roberto Grosso,Greg Mendell, Michael Sakosky, Ryan DeRosa, Matt West LVC meeting - Arcadia, CA March 2010

  2. Photon Calibrator method Power-modulated auxiliary laser to displace the mass via the recoil of the photons (in “Science mode” configuration). E. Goetz, et al. Class. Quantum Grav. 26 (2009) LVC meeting - Arcadia, CA March 2010

  3. eLigo Pcal upgrades Integrating spheres for absolute power calibration 1047 nm Nd:YLF laser Acousto- optic modulator Improved optical layout and enclosures LVC meeting - Arcadia, CA March 2010 • Upgraded Pcals installed for S6. H1 and L1 X-arm end test masses (Matt West, Ryan DeRosa, Michael Sakosky)

  4. Calibrating DARM_CTRL_EXC with Pcal Coil – 393.1 Hz Pcal – 401.2 Hz Simultaneously drive ETM position with both Pcal and voice coil actuators with sinusoidal excitations separated by 7.1 Hz Ratio of peaks together with Pcal absolute power calibration yields on-line, continuous calibration of DARM_ERR LVC meeting - Arcadia, CA March 2010

  5. DARM_ERR lines with ~ 60-sec FFTs ASD of DARM_ERR Voice coils Pcal Excitation frequencies: H1: coils – 393.1 Hz; Pcal – 400.2 Hz L1 : coils – 396.7 Hz; Pcal – 403.8 Hz LVC meeting - Arcadia, CA March 2010

  6. Relevant LLO Pcal peaks – high BW LVC meeting - Arcadia, CA March 2010

  7. Relevant LLO Pcal peaks – Low BW LVC meeting - Arcadia, CA March 2010

  8. DARM actuation long-term trend investigation S/N ~ 200 S/N ~ 70 • C++ code running on cluster atCaltech (LHO or LLO)- level 1 RDS frames- one S6 day per core • 60 sec. data segmentsfor three channels- DARM_ERR- 2 excitation readback channels • Hann window data- all lines bin-centered • FFT using FFTW3 • Write- GPS time at start of data segment- minimum state vector value during segment- complex amplitude for four lines 2 DARM_ERR 2 excitation readbacks LVC meeting - Arcadia, CA March 2010

  9. 60-sec FFT Science Mode data: H1 Higher S/N Pcal beam spot loctions changed Violin notches removed - response function change LVC meeting - Arcadia, CA March 2010

  10. 60-sec FFT Science Mode data: L1 Swap of coil driver Shorted wire in Pcal internal power sensor LVC meeting - Arcadia, CA March 2010

  11. Characterization of data LVC meeting - Arcadia, CA March 2010 • Outliers • Glitches • Data errors • Distribution • Correlated noise due to laser speckle • etc., etc. • Focus on goal of assessing long-term stability of DARM acutation

  12. One-hour averages – Science Mode: H1 LVC meeting - Arcadia, CA March 2010 • DARM_CRTL_EXC calibration (> 8 mos of S6) • Mean 1.28 nm/ ct ; standard deviation 0.28%

  13. One-hour averages – Science Mode: L1 • DARM_CTRL_EXC calibration (> 8 mos of S6) • Mean 0.53 nm/ ct ; standard deviation 0.40% LVC meeting - Arcadia, CA March 2010

  14. Conclusions – Future work • Long-term stability of actuation • Photon calibrator calibration and DARM actuation (coil driver and voice coils) stable within fraction of a percent over ~ 8 months • Continue to monitor during remainder of S6 • Future work: • Use relative phase between DARM_ERR and Pcal readback peaks to investigate phase jumps due to computer reboots, etc. • Generate Pcal data using DMT monitor (R. Grosso) • Drive Pcal with GPS-synched aLIGO timing module for absolute phase reference (with I. Bartos, et al.) • Investigate source of outliers • Investigate if laser speckle is fundamental limit to Pcal precision using integrating spheres (J. Berliner) LVC meeting - Arcadia, CA March 2010

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