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Progress Report on ILIAS-GW Interferometer Improvements

Detailed progress report on the annual general meeting regarding the ILIAS-GW interferometer upgrades, noise reduction strategies, thermal effects, lock acquisitions, sensitivity improvements, and future actions.

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Progress Report on ILIAS-GW Interferometer Improvements

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  1. VIRGO Commissioning progressJ. Marque (EGO) 3rd ILIAS-GW annual general meeting

  2. Status one year ago Run C7 duty cycle 64% 14 h lock Run C6 duty cycle 90% 40 h lock C7 C6 3rd ILIAS-GW annual general meeting

  3. C7 noise budget • Interferometer working with a reduced input power ~ 0.8 W (25 W on the beam splitter) • High frequency sensitivity limited by shot noise • Necessity to increase the stored power (input power and recycling factor ) 3rd ILIAS-GW annual general meeting

  4. Laser Frequency Noise (Hz) Absence of optical isolation Power recycling aligned Power recycling misaligned • Short term solution : attenuate the input beam • Long term: install a Faraday isolator 3rd ILIAS-GW annual general meeting

  5. New Input Bench: optical layout To interferometer Parabolic output telescope Faraday isolator Input Mode cleaner Attenuation no more neededinput power = 10W From laser 3rd ILIAS-GW annual general meeting

  6. New injection bench • September 2006Spring 2007 • Installation and commissioning of the new injection bench • Mode-cleaner restart • Cavities re-lock • New power recycling mirror • Lock acquisition with high power and new power recycling mirror (higher reflectivity) 3rd ILIAS-GW annual general meeting

  7. Lock acquisition and thermal effects • Interferometer locked with ~10 W input power and 300 W on the beam splitter (more than 10 times C7) • Lock acquisition much more complicated than expected • long work to improve locking robustness during the thermal transient • Thermal lensing discovered • Absorption input mirror 4-10 times higher than expected Thermal transient 3rd ILIAS-GW annual general meeting

  8. Automatic alignment • 14 degrees of freedom controlled • 7 full bandwidth (3Hz), no local controls • 7 with low bandwith (10 mHz), local controls 3rd ILIAS-GW annual general meeting

  9. WSR-1: september 2006 Interferometer internal power Inspiral range for NS-NS optimally oriented • Science mode: 88% • 6 data taking segments, 10h average • inspiral range for NS-NS optimally oriented ~ 2 Mpc (0.8 Mpc averaged) 3rd ILIAS-GW annual general meeting

  10. Sensitivity 3rd ILIAS-GW annual general meeting

  11. Noise budget Longitudinal noises (PR, BS) Actuators noise Frequency noise shot noise 3rd ILIAS-GW annual general meeting

  12. Next steps/1: robustness Red curve: 2.7 Mpc -(wind+sea) ~ sea activity ~ wind One mechanism: Seismic noise  alignment fluctuations horizon decrease and unlocks Ideas to decrease the reintroduction of the seismic noise  better superattenuator control 3rd ILIAS-GW annual general meeting

  13. Next steps/2: noise • Several hardware actions already performed after WSR1 • Optimization of optical isolation of the Faraday isolator (x10) • Acoustic enclosure laser laboratory • Reduction of actuators noise • Increase of the aperture of optical vacuum window • Now post-intervention recovering • Next sensitivity expected in a few weeks 3rd ILIAS-GW annual general meeting

  14. Conclusions • New injection bench commissioned (x10 input power) • Now interferometer works with 300 W of stored power (500 W design) • Thermal lensing discovered, lock acquisition more complex, no thermal compensation needed so far • New sensitivity curve: high-mid frequency improvements, 2.5 Mpc peak • WSR-1 (56hours): 90% duty cycle and inspiral range ~ 2 Mpc • Several actions in progress to improve the noise and the sensitivity to weather conditions 3rd ILIAS-GW annual general meeting

  15. 3rd ILIAS-GW annual general meeting

  16. End End 3rd ILIAS-GW annual general meeting

  17. Commisioning progress (1/2) Sept05 Oct05 Nov05 Dec05 Jan06 Feb06 Mar06 Full ITFrelockFull ITFautomatic alignmentInertial dampingupgradeInput Bench +Input Mode Cleaner automatic alignmentReference Cavity alignmentand locking Injection sytem realignmentLocal controlsretuningInput Mode CleanerrelockInput Mode Cleanerautomatic alignmentReference Cavityalignment ITFalignmentInput Beam Control IntegrationInput Mode Cleaner matchingReference Cavity alignment Commissioning New injection sytem integration(input power * 10,Faraday isolation,ParabolicInput telescope)PR mirrorchange RunC7 3rd ILIAS-GW annual general meeting

  18. Commisioning progress (2/2) Apr06 May06 Jun06 Jul06 Aug06 Sep06 Oct06 WSR1 WSR2 WSR3 WSR4 Full ITF Locking / Output Mode Cleaner locking(Fabry Perrot input mirrors thermal lensing issue)Full ITF Automatic AlignmentFull automationWires heating compensation / Local controls optimizationBeam centering on ITF core optics optimization /Input telescope tuning / matching Input Bench + Input Mode Cleaner Automatic AlignmentDetection Bench seismic isolation upgrade Coil drivers optimizationFaraday IsolatoroptimizationInput telescopefine tuningLaser Acoustic enclosure installationDetection BrewsterWindow change Locking,LocalControlsandAlignmentloops fine tuningNoiseHunting 3rd ILIAS-GW annual general meeting

  19. 350 mm 120 mm R=4100 mm New Power Recycling Mirror • Old PR mirror: • non-monolithic • curved (part of beam matching telescope) • R=95% Old PR mirror mounting • New PR mirror: • monolithic: no nore internal resonance in the control band • flat: no more lens effect, larger beam coming out of input bench, need for a parabolic telescope on input bench • R=98%: recycling gain increased by 30% - Old - New PR mirror transfer function 3rd ILIAS-GW annual general meeting

  20. New injection bench (above) 3rd ILIAS-GW annual general meeting

  21. Reference cavity New injection bench (below) 3rd ILIAS-GW annual general meeting

  22. Laser Frequency Noise Faraday isolator performance Issue: Input Mode Cleaner diodes polluted by fringes between ITF reflection and backscattered light in IMC => laser frequency noise and alignment loops are affected, need for a Faraday isolator. Hz Power Recyclingmirror misalignedPower Recyclingmirror aligned Time The attenuation of the Faraday has been measured to be 1000. => Does not limit the ITF performance anymore. BeforeNowLight transmitted by IMC 3rd ILIAS-GW annual general meeting

  23. New input system alignment scheme control 3rd ILIAS-GW annual general meeting

  24. Mode matching and mirror centering Tuning of parabolic input telescope:o Mode matching of the FP cavities (97%)o Beam positionning in ITF (clipping issue) TEM01 TEM02 2 techniques for mirror centering:o Direct imaging where possible (BS)o Mirror shaking at natural resonance=> alignment/locking coupling minimization. Power transmitted by FP swinging cavity All optics centered with 5mm accuracy. Before AfterBS mirror centering 3rd ILIAS-GW annual general meeting

  25. Suspension control upgrade Mirror excitation with bad weather => Changed suspension top stage controlNoise introduced by DAC on the mirror=> Rearrange forces going to suspension, Switch to low noise coil driver Emphasis-deemphasis filtering 3rd ILIAS-GW annual general meeting

  26. Locking acquisition suffers from thermal lensing transient Lock acquisition is delicate => Thermal lensing studyo Compensation for gain change thermal drift, o Installed scanning Fabry Perrot to measure sidebands unbalanceo Setup a mirror temperature monitoring (mirror drum modes frequency is shifting with temperature increase)o Started optical simulation efforto Phase camera preparation=> Mirror coating absorption is 4 to 10 times higher than expected Sidebands evolution over 15mn 3rd ILIAS-GW annual general meeting

  27. Automatic alignment 14 degrees of freedom controledo 7 full bandwith (3Hz)o 7 low bandwith integrator (10mHz) + Local Controls 3rd ILIAS-GW annual general meeting

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