Plans for Advanced Virgo Raffaele Flaminio LMACNRS on
- Slides: 20
Plans for Advanced Virgo Raffaele Flaminio LMA/CNRS on behalf of the Virgo Collaboration SUMMARY - Motivations - Detector design - Expected sensitivity - Status and timeline Marcel Grossman 12, Paris, July 13 th 2009
Virgo commissioning history l l Virgo just started its second science run (VSR 2) Detector close to the design sensitivity u BNS range > 8 Mpc (design is ~12 Mpc) Marcel Grossman 12, Paris, July 13 th 2009
Virgo noise budget Actuation Eddy currents Magnetic Scattered light Suspension thermal SHOT Mirror thermal l Noise budget well understood Sensitivity close to fundamental noises Large improvements Marcel Grossman 12, Paris, July need 13 th 2009 large hardware modifications: Advanced Virgo
Motivations for Advanced Virgo l Present detectors are testing upper limits of theoretical predictions l Even in the optimistic case expected rates are too low to start GW astronomy Enhanced LIGO/Virgo+ l Need to improve the sensitivity l Upgrade Virgo to a 2 nd generation detector Virgo/LIGO 108 ly u Sensitivity: 10 x better than Virgo u Detection rate: ~1000 x better l Be part of the 2 nd generation GW detectors network u Timeline: commissioning to start in 2014. u Make science with Advanced LIGO Adv. Virgo/Adv. LIGO Credit: R. Powell, B. Berger Marcel Grossman 12, Paris, July 13 th 2009
Advanced Virgo Science Case l l 1 day of Ad. Virgo data ~ 3 years of Virgo data Coalescing binaries detection rates u BNS ~ 10/yr u BBH ~ 0. 1 - 100/yr (model dependent) l Advanced Virgo in the network: u Much better event reconstruction » Source location in the sky » Reconstruction of polarization components » Reconstruction of amplitude at source and determination of source distance (BNS) u Detection probability increases: 40% more events than Advanced LIGO only u Detection confidence increase (coincidence techniques) l Multi-messenger opportunities u Collaboration with E. M. and v detectors will increase the search sensitivity or equivalently detection confidence u Advanced GW network opens new perspectives for Astroparticle Physics l The experimentalists view u After ten years of R&D, technology for a major improvement has been demonstrated Marcel Grossman 12, Paris, July 13 th 2009
Advanced Virgo design Marcel Grossman 12, Paris, July 13 th 2009
Optical configuration and readout l Main drivers u Reduce impact of quantum noise u Mitigate coating thermal noise u Allow for sensitivity tunability l Use of signal recycling u Foreseen since the beginning u Compatible with vacuum infrastructure u Mature technique l l Increase cavity finesse (~900) Enlarged spot size on test masses u From 2/5 cm to 5/6 cm l Use DC detection u New higher finesse output mode cleaner u Under vacuum photodiodes Marcel Grossman 12, Paris, July 13 th 2009
Non degenerate cavities/ Multiple payloads l Main drivers u Reduce signal loss due to scattering into higher modes u Improve interferometer control signals u Relax spec on thermal compensation system l Use non degenerate recycling cavities u Cavity length ~ 28 m u Telescope in the recycling cavity u Reduce beam size on input/output bench (~ from cm’s to mm’s) l Need for multiple payloads u Impact on couplings and mirror position control Marcel Grossman 12, Paris, July 13 th 2009
Laser l Main driver u Reduce shot noise u Improve high frequency sensitivity l Increase laser power 10 x u Reference solution: solid state amplifier developed at LZH for Advanced LIGO (can provide 180 W) u Alternative: fiber laser l Drawbacks u Radiation pressure noise u Mirror thermal lensing l Mitigation u Heavier mirrors u Improved thermal compensation Marcel Grossman 12, Paris, July 13 th 2009
Input optics l Main drivers u Manage higher power, Meet Ad. V noise requirements l Input mode cleaner u Keep 144 m suspended triangular cavity: more noise filtering, easier modulation frequency choice, existing infrastructure u Mirrors: heavier for radiation pressure mitigation, improved polishing for smaller low angle scattering l Electro-optics modulators u Low thermal lensing KTP crystals l Faraday isolator u Realized at IAP (Russia), meets Ad. V specs Marcel Grossman 12, Paris, July 13 th 2009
Thermal compensation l Main driver u Avoid degradation of interferometer performance due to thermal lensing l Main effects Shielded heating rings will compensate HR surface deformations u Wavefront distortion in PR/SR cavities u Test masses surface deformation l Thermal compensation u Combined action of a CO 2 laser and heating rings u CO 2 laser cannot act directly on test masses » Requirements on power stabilization too demanding u Project CO 2 laser on silica compensation plates l Drawback u Additional transmissive optics on the main beam l Mitigation u CP seismically isolated u Wedge on CP u Tilted to suppress impact on alignment signals Marcel Grossman 12, Paris, July 13 th 2009 Compensation plates shined with CO 2 laser will correct thermal effects in the PRC
Mirrors l Main drivers u Thermal noise reduction u Radiation pressure noise mitigation u Scattering losses reduction l Use state of the art coating in 2011 u Ti: Ta 2 O 5 reference solution u On going R&D l Larger mass u 35 cm diameter, 20 cm thick u 42 kg l l Low absorption fused silica Scattering loss reduction u Specs: flatness < 1 nm, Roughness < 1 Ǻ u Reference solution: corrective coating u Alternative: improved polishing Marcel Grossman 12, Paris, July 13 th 2009
Seismic isolation l Main drivers u Isolate test mass form seismic noise u Control mirror positions l Use present Virgo super-attenuators (SA) u Compliant with Ad. Virgo requirements l l A new SA to be built for the signal recycling mirror More isolation required for input and output optics u Due to use of non-degenerate recycling cavities l Upgrade of top stage control u Full 6 dof control; add tilt control u Help control in windy days u Foreseen since the beginning Marcel Grossman 12, Paris, July 13 th 2009
Monolithic suspensions l Main driver u Reduction of suspensions thermal noise l l Use of fused silica fibers to suspend the test masses Relevant progress during the last months u Fiber production » Geometry under control » Excellent reproducibility u Clamp design u Welding technique » Can be done far from the mirror u Assembly procedure thoroughly tested u Dummy monolithic suspension tested Marcel Grossman 12, Paris, July 13 th 2009
Vacuum envelope l Main driver u Reduction of index of refraction fluctuation noise l Reduce residual pressure in the Virgo tubes u u l Current pressure ~ 10 -7 mbar (dominated by water) Reduction 100 x required Tubes bakeout needed Need to separate tubes from towers Design solution u Cryotraps at the tubes extremes Marcel Grossman 12, Paris, July 13 th 2009
Infrastructure: ‘culture’ noise reduction l Main driver u Reduce machine noise l Virgo commissioning experience showed that infrastructure improvements allows reducing environmental noise u Replacement of old air conditioning machines and relocation out of experimental halls u Insulated rooms for noisy racks, power supplies, scroll pumps u Improvement of laser/detection acoustic isolation Marcel Grossman 12, Paris, July 13 th 2009
Advanced Virgo performance Marcel Grossman 12, Paris, July 13 th 2009
Risk reduction: Virgo+ l The Virgo+ program is helping reducing the Ad. V risk by tackling in advance some relevant issues: u Higher power laser u Use of TCS u Monolithic suspensions u Higher arm cavity finesse l The use of monolithic suspensions in Virgo+ is crucial to reduce the risks connected to the fused silica fibers Marcel Grossman 12, Paris, July 13 th 2009
Timeline 150 Ad. V goal IN S BN RA I P L go c) d p M ( E G 16 va d A N A R e nc 15 r Vi 14 Ad. V Science Run 1 Advanced Virgo commissioning 13 S 12 Advanced Virgo installation 8 r Vi 6. 5 11 + go Installation of new mirrors and monolithic suspensions 10 Virgo Science Run 2 09 Virgo+ commissioning Virgo+ installation Marcel Grossman 12, Paris, July 13 th 2009 08
Status of the project and conclusions l l Advanced Virgo baseline design and cost evaluation is completed Project reviewed by an External Review Committee (ERC, chair B. Barish) u Review started in Nov 08 and concluded in May 09 u Final report submitted to the EGO council (funding agencies) u The ERC supports Advanced Virgo as a worthwhile investment for funding l INFN set up a scientific committee (chair N. Cabibbo) to set priorities among the new proposed experiments u Advanced Virgo was top ranked l EGO council meeting on July the 2 nd u u l Virgo/EGO are allowed to place the first preparatory orders Project leader is appointed Final INFN decision expected at the end of July Extraordinary EGO council meeting called on October the 6 th for final decision Advanced Virgo is ready to go and join the 2 nd generation GW detector network in 2015 Marcel Grossman 12, Paris, July 13 th 2009
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