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 13th 2009

Virgo commissioning history Virgo just started its second science run (VSR2) Detector close to the design sensitivity BNS range > 8 Mpc (design is ~12 Mpc) Marcel Grossman 12, Paris, July 13th 2009

Virgo noise budget Noise budget well understood Actuation Eddy currents Magnetic Scattered light Suspension thermal SHOT Mirror thermal Noise budget well understood Sensitivity close to fundamental noises Large improvements need large hardware modifications: Advanced Virgo Marcel Grossman 12, Paris, July 13th 2009

Motivations for Advanced Virgo Present detectors are testing upper limits of theoretical predictions Even in the optimistic case expected rates are too low to start GW astronomy Need to improve the sensitivity Upgrade Virgo to a 2nd generation detector Sensitivity: 10x better than Virgo Detection rate: ~1000x better Be part of the 2nd generation GW detectors network Timeline: commissioning to start in 2014. Make science with Advanced LIGO 108 ly Enhanced LIGO/Virgo+ Virgo/LIGO Credit: R.Powell, B.Berger Adv. Virgo/Adv. LIGO Marcel Grossman 12, Paris, July 13th 2009

Advanced Virgo Science Case 1 day of AdVirgo data ~ 3 years of Virgo data Coalescing binaries detection rates BNS ~ 10/yr BBH ~ 0.1 - 100/yr (model dependent) Advanced Virgo in the network: Much better event reconstruction Source location in the sky Reconstruction of polarization components Reconstruction of amplitude at source and determination of source distance (BNS) Detection probability increases: 40% more events than Advanced LIGO only Detection confidence increase (coincidence techniques) Multi-messenger opportunities Collaboration with E.M. and v detectors will increase the search sensitivity or equivalently detection confidence Advanced GW network opens new perspectives for Astroparticle Physics The experimentalists view After ten years of R&D, technology for a major improvement has been demonstrated Marcel Grossman 12, Paris, July 13th 2009

Advanced Virgo design Marcel Grossman 12, Paris, July 13th 2009

Optical configuration and readout Main drivers Reduce impact of quantum noise Mitigate coating thermal noise Allow for sensitivity tunability Use of signal recycling Foreseen since the beginning Compatible with vacuum infrastructure Mature technique Increase cavity finesse (~900) Enlarged spot size on test masses From 2/5 cm to 5/6 cm Use DC detection New higher finesse output mode cleaner Under vacuum photodiodes Marcel Grossman 12, Paris, July 13th 2009

Non degenerate cavities/ Multiple payloads Main drivers Reduce signal loss due to scattering into higher modes Improve interferometer control signals Relax spec on thermal compensation system Use non degenerate recycling cavities Cavity length ~ 28 m Telescope in the recycling cavity Reduce beam size on input/output bench (~ from cm’s to mm’s) Need for multiple payloads Impact on couplings and mirror position control Marcel Grossman 12, Paris, July 13th 2009

Laser Main driver Increase laser power 10x Drawbacks Mitigation Reduce shot noise Improve high frequency sensitivity Increase laser power 10x Reference solution: solid state amplifier developed at LZH for Advanced LIGO (can provide 180 W) Alternative: fiber laser Drawbacks Radiation pressure noise Mirror thermal lensing Mitigation Heavier mirrors Improved thermal compensation Marcel Grossman 12, Paris, July 13th 2009

Input optics Main drivers Input mode cleaner Electro-optics modulators Manage higher power, Meet AdV noise requirements Input mode cleaner Keep 144 m suspended triangular cavity: more noise filtering, easier modulation frequency choice, existing infrastructure Mirrors: heavier for radiation pressure mitigation, improved polishing for smaller low angle scattering Electro-optics modulators Low thermal lensing KTP crystals Faraday isolator Realized at IAP (Russia), meets AdV specs Marcel Grossman 12, Paris, July 13th 2009

Thermal compensation Main driver Main effects Thermal compensation Avoid degradation of interferometer performance due to thermal lensing Main effects Wavefront distortion in PR/SR cavities Test masses surface deformation Thermal compensation Combined action of a CO2 laser and heating rings CO2 laser cannot act directly on test masses Requirements on power stabilization too demanding Project CO2 laser on silica compensation plates Drawback Additional transmissive optics on the main beam Mitigation CP seismically isolated Wedge on CP Tilted to suppress impact on alignment signals Shielded heating rings will compensate HR surface deformations Compensation plates shined with CO2 laser will correct thermal effects in the PRC Marcel Grossman 12, Paris, July 13th 2009

Mirrors Main drivers Use state of the art coating in 2011 Larger mass Thermal noise reduction Radiation pressure noise mitigation Scattering losses reduction Use state of the art coating in 2011 Ti:Ta2O5 reference solution On going R&D Larger mass 35 cm diameter, 20 cm thick 42 kg Low absorption fused silica Scattering loss reduction Specs: flatness < 1 nm, Roughness < 1 Ǻ Reference solution: corrective coating Alternative: improved polishing Marcel Grossman 12, Paris, July 13th 2009

Seismic isolation Main drivers Isolate test mass form seismic noise Control mirror positions Use present Virgo super-attenuators (SA) Compliant with AdVirgo requirements A new SA to be built for the signal recycling mirror More isolation required for input and output optics Due to use of non-degenerate recycling cavities Upgrade of top stage control Full 6 dof control; add tilt control Help control in windy days Foreseen since the beginning Marcel Grossman 12, Paris, July 13th 2009

Monolithic suspensions Main driver Reduction of suspensions thermal noise Use of fused silica fibers to suspend the test masses Relevant progress during the last months Fiber production Geometry under control Excellent reproducibility Clamp design Welding technique Can be done far from the mirror Assembly procedure thoroughly tested Dummy monolithic suspension tested Marcel Grossman 12, Paris, July 13th 2009

Vacuum envelope Main driver Reduction of index of refraction fluctuation noise Reduce residual pressure in the Virgo tubes Current pressure ~ 10-7 mbar (dominated by water) Reduction 100x required Tubes bakeout needed Need to separate tubes from towers Design solution Cryotraps at the tubes extremes Marcel Grossman 12, Paris, July 13th 2009

Infrastructure: ‘culture’ noise reduction Main driver Reduce machine noise Virgo commissioning experience showed that infrastructure improvements allows reducing environmental noise Replacement of old air conditioning machines and relocation out of experimental halls Insulated rooms for noisy racks, power supplies, scroll pumps Improvement of laser/detection acoustic isolation Marcel Grossman 12, Paris, July 13th 2009

Advanced Virgo performance Marcel Grossman 12, Paris, July 13th 2009

Risk reduction: Virgo+ The Virgo+ program is helping reducing the AdV risk by tackling in advance some relevant issues: Higher power laser Use of TCS Monolithic suspensions Higher arm cavity finesse The use of monolithic suspensions in Virgo+ is crucial to reduce the risks connected to the fused silica fibers Marcel Grossman 12, Paris, July 13th 2009

BNS INSPIRAL RANGE (Mpc) Timeline 150 AdV goal AdV Science Run 1 Advanced Virgo Advanced Virgo commissioning BNS INSPIRAL RANGE (Mpc) 08 09 10 11 12 13 14 15 16 Advanced Virgo installation Virgo Science Run 2 8 Virgo+ Installation of new mirrors and monolithic suspensions 6.5 Virgo+ commissioning Marcel Grossman 12, Paris, July 13th 2009 Virgo+ installation

Status of the project and conclusions Advanced Virgo baseline design and cost evaluation is completed Project reviewed by an External Review Committee (ERC, chair B. Barish) Review started in Nov 08 and concluded in May 09 Final report submitted to the EGO council (funding agencies) The ERC supports Advanced Virgo as a worthwhile investment for funding INFN set up a scientific committee (chair N. Cabibbo) to set priorities among the new proposed experiments Advanced Virgo was top ranked EGO council meeting on July the 2nd 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 6th for final decision Advanced Virgo is ready to go and join the 2nd generation GW detector network in 2015 Marcel Grossman 12, Paris, July 13th 2009