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

2. 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)

3. Signal recycling: optimization at 1 kHz
(*) = mirror 1kHz

4. 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

5. 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

6. 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”

7. 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

8. 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

9. 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

10. 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 prototype: the closest to the optical scheme of an advanced Virgo (~ 2004)  collaboration with Caltech

11. 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

12. 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

13. 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