Signal recycling R&D at LAL: Influence in Virgo Matteo Barsuglia CNRS/IN2P3 - LAL Orsay ILIAS, Padova January 28th 2005

SR: influence on the sensitivity curve Virgo Sensitivity (/Hz1/2) AdvVirgo (M.Punturo) AdvVirgo with SR Arm finesse = 600 fsr = 800 Hz rsr = 0.95 Frequency (Hz)

Signal recycling: optimization at 1 kHz (*) = mirror TN @ 1kHz

Signal recycling at high frequency Sensitivity optimized at different frequencies Why HF sensitivity ? HF periodic sources (?) HF bursts (?) Black Hole Ringdowns Virgo and Virgo FS factor 10 Virgo + SR 10 Mo BH with maximal rotation  rings at about 3 kHz 3 Mo Schwarzschild BH  rings at about 4 kHz Virgo FS + SR

SR: influence in Virgo sensitivity Impact in an advanced Virgo detector SR has to be first compared with other shot-noise reduction (laser power, recycling factor, finesse) The influence depends widely from the thermal noise reduction Need and overall design for an advanced Virgo

Virgo central area Laser beam Space for signal recycling suspension Power recycling West input Beam splitter North input Laser beam Space for signal recycling suspension ITF output “dark port”

Why not? Control problems longitudinal: 5 dof instead 4) autoalignment more complex R&D needed demonstrate lock acquisition and linear control demonstrate autoalignment Extra hardware second,third phase modulation / second beam / low finesse locks… control system more poweful and faster

What R&D does it mean for SR? propose locking/autoalignment strategies test-them with simulation (frequency domain and time domain) Build a prototype – acquire experience

SR in the world Table top interferometers with dual rec and FP in the arms (Australia, Caltech, Florida): principle, first control tests GEO600, Hannover: dual recycling, no FP in the arms locked, noise hunting in progress 40m, Caltech 5 dof controlled (not in the final configuration) as close as possible to advanced LIGO

Which prototype? Suspended prototype at LAL was studied initially and excluded (~ 2002) Attention given to the Glasgow group (~ 2003) dual rec FP ITF project delayed/cancelled GEO: great experience (contact: ILIAS-WG1) Attention to 40m@Caltech prototype: the closest to the optical scheme of an advanced Virgo (~ 2004)  collaboration with Caltech

Collaboration LAL- 40m@Caltech Founded by EGO travels post-doc ( M.Varvella, 2Y post-doc, during 2005 based in Caltech) Goal of the collaboration: Collaboration on the 40m/Adv LIGO simulation  Have a simulation package for Virgo/SR Follow the 40m commissioning  transfer the experience and ideas to Virgo

2005 activity Participation to the LIGO-40m simulation group e2e simulation of 40m/adv LIGO Improvement of the speed: re-summation cavity Start a signal recycling package for Virgo/SR

Future Configurations and scientific impact: Prepare an overall design for Virgo/SR (Virgo white paper) Control and simulation: Follow the locking ideas used in the 40m and GEO Use the simulation packages and ideas developed in the 40m/Adv LIGO to prepare the Virgo/SR control scheme