E. Calloni – MG12 – July 13 2009 Paris 1

Status of the Virgo interferometer

Enrico CalloniFederico II Univ. - Naples

on behalf of the Virgo collaborationMG12, July 13 2009, Paris

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Commissioning timeline May '07 - Sep '07 First Virgo Science Run (VSR1) Oct '07 - May '08 Commissioning

Scattered light mitigation: replaced brewster window by cryotrap TCS installation, mirror magnets strength reduction

9 May '08 Vacuum viewport failure May - Oct '08 Virgo+ shutdown

Injection system, infrastructure and electronics upgrade NE payload recovery, replacement of all viewports

Oct '08 – July ‘09 Commissioning Remaining electronics upgrade Commissioning with more input power and TCS New Global Control

7 Jul '09 Start Second Virgo Science Run (VSR2) 2010 Monolithic suspension upgrade?

This talk

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Incident recovery

Caused by weak design of view-port, identified and tested safer model Replaced about 90 view-ports throughout whole interferometer Cleaned and tested North-End tower New payload at North-End: coating of already polished spare mirror

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Virgo+ upgrade: infrastructure Replaced complete wiring

of main power and grounding in central building

Replaced and doubled UPS Replaced 15 kV transformer New hot water pipes Lowered speed of air-

conditioning

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Virgo+ upgrade: injection system New laser amplifier: up to 50 W (25 W at interferometer input) New pre-mode-cleaner Remotely tunable in-vacuum Faraday Isolator Heavier input-mode-cleaner end-mirror

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Virgo+ upgrade: electronics

Replaced real-time fiber links: more flexible signal routing Replaced old RIOs by real-time PC: much more computing power New ADCs: from 16 to 18 bit New quadrants read-out electronics for alignment

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Interferometer restart

Interferometer no longer showed bi-stability during lock acquisition Different working point: modulation frequency changed by 700 Hz Maybe caused by slightly different radius of curvature of new mirror

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Thermal Compensation System

Annulus and central spot from CO2 laser on both input mirrors Essential for compensating thermal lensing in input mirrors when

working with high input powers Not yet stabilized in amplitude, some evidence for introduced noise

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Phase camera

Beam scanned on pinhole detector, signal demodulated to separate carrier and sidebands

Located on dark fringe before output-mode-cleaner (B1p) Extensively used, but more as 'amplitude camera'

TCS fine alignment, 'cold interferometer' experiments Mirror cool-down experiments to measure coating absorption

field amplitude

phase between fields

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High power operation Power increased in steps from 8 W (VSR1) to 17 W now

limited by thermal aberrations of input mode cleaner No major problems with interferometer stability Some alignments loops more critical Quadrature signals (B1_ACq or B5_ACq) kept close to zero using slow

servos on TCS power Currently about 1.5 W on both mirrors: interferometer similar to 8W 'Cold interferometer' with about 2x 6W

More optical gain, ideal frequency stabilization TF, but TCS too noisy

without TCS with TCS

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Sensitivity

May 2007: ~3 MpcJuly 2009: ~8 Mpc

Sensitivity at VSR1 start (black) and VSR2 start (red)

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Noise budget Low frequency

Some environmental Some scattering Laser bench

resonances Actuator noise No control noise!

Medium frequency Mirror thermal noise Shot noise Detection bench

resonances TCS radiation pressure?

High frequency Shot noise

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Robustness

Locking duty cycle : 97.4%(update at July 12 )

Science Mode duty cycle: 94.9%

Interventions in “adjusting mode”are visible

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Future work During the run (commissioning breaks)

Damp external bench resonance (sorbothane) TCS power stabilization? Replace detection output window, with AR

coating? More noise hunting

Long term Monolithically suspended mirrors, finesse 50 ->

150

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Concluding Robust interferometer

95% Science Mode duty cycle Good sensitivity

Stable horizon: 8-8.5 Mpc (1.4-1.4 Ns-Ns) - averaged 42-44 Mpc (10-10 BH-BH) - averaged

fluctuating with input mirror etalon effect Low glitch rate: factor 10 lower than VSR1 Preparing for installation of monolithic suspensions

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End