Marcel Grossman 12, Paris, July 13th 2009

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Plans for Advanced VirgoRaffaele 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

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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

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Virgo noise budget

Noise budget well understood Sensitivity close to fundamental noises Large improvements need large hardware modifications: Advanced Virgo

SHOT

Mirror thermal

Suspension thermal

ActuationEddy currentsMagneticScattered light

Marcel Grossman 12, Paris, July 13th 2009

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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 generationdetector 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

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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

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Advanced Virgo design

Marcel Grossman 12, Paris, July 13th 2009

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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

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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

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Laser

Main driver 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

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Input optics Main drivers

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

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Thermal compensation Main driver

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

Compensation plates shined with CO2 laser will correct thermal effects in the PRC

Shielded heating rings will compensate HR surface deformations

Marcel Grossman 12, Paris, July 13th 2009

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Mirrors

Main drivers 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

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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

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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

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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

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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

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Advanced Virgo performance

Marcel Grossman 12, Paris, July 13th 2009

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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

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Timeline

08

09

10

11

12

13

14

15

16

Virgo+ installation

Advanced Virg

o

Virgo+

Virgo+ commissioning

Installation of new mirrors and monolithic suspensions

Advanced Virgo installation

Advanced Virgo commissioning

AdV Science Run 1

6.5 Virgo Science Run 2

8

150AdV goal

BNS INSPIRAL R

ANGE (Mpc)

Marcel Grossman 12, Paris, July 13th 2009

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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