Einstein gravitational wave Telescope Which optical topologies are suitable for ET? Andreas Freise for the ET WG3 working group MG12 Paris

A. FreiseA Freise MG12 15/07/2009Slide 2  How will ET look like?  How many interferometers per site?  What type of interferometer do we need?  Investigating new topologies  Practical considerations Overview The working group WP3 must select an interferometer topology for ET, we will present examples from the ongoing research:

A. FreiseA Freise MG12 15/07/2009Slide 3 What will be the shape of ET?

A. FreiseA Freise MG12 15/07/2009Slide 4 L L 45° Fully resolve polarizations 5 end caverns 4×L long tunnels 45° stream generated by virtual interferometry Null stream Redundancy 7 end caverns 6×L long tunnels 60° L’=L/sin(60°)=1.15×L Fully resolve polarizations by virtual interferometry Null stream Redundancy 3 end caverns 3.45×L long tunnels L Equivale nt to [Ruediger et al (1985), Freise et al, Class. Quantum Grav. 26 (2009)]

A. FreiseA Freise MG12 15/07/2009Slide 5 Multiple Interferometers: the Triangle Both solutions have an integrated tunnel length of 30 km, they can resolve both GW polarisations, feature redundant interferometers and have equivalent sensitivity. The triangle reduces the number of end stations and the enclosed area! [P Jaranowski et al, Phys Rev D ]

A. FreiseA Freise MG12 15/07/2009Slide 6 Today's Michelsons in a Triangle [S Hild]

A. FreiseA Freise MG12 15/07/2009Slide 7 How Many Interferometers Arms per Tunnel? Picture by Jason Bacon used under a Creative Commons License Rüdiger, Aspen 2007

A. FreiseA Freise MG12 15/07/2009Slide 8 Multiple Interferometers: a Xylophone Low power (no thermal effects), cooled, long suspensions High power, squeezing, LG modes, room temperature, `normal' suspensions Maybe we can reach the target sensitivity easier by splitting the frequency range? [S Hild et al, arXiv: ]

A. FreiseA Freise MG12 15/07/2009Slide 9 Reduction of Quantum Noise [S. Hild et al, arxiv: ]arxiv:

A. FreiseA Freise MG12 15/07/2009Slide 10 Quantum Noise Reduction Optimised SR [H. Rehbein und H. Mueller-Ebhardt, ET note ET ] [S Chelkowski]

A. FreiseA Freise MG12 15/07/2009Slide 11 Quantum Noise Reduction 10dB frequency-dependent squeezing [H. Rehbein und H. Mueller-Ebhardt, ET note ET ] [S Chelkowski]

A. FreiseA Freise MG12 15/07/2009Slide 12 Quantum Noise Reduction Variational output and 10 dB squeezing [H. Rehbein und H. Mueller-Ebhardt, ET note ET ]

A. FreiseA Freise MG12 15/07/2009Slide 13 Quantum Noise Reduction Sagnac with SR, variational output and 10dB squeezing [H. Rehbein und H. Mueller-Ebhardt, ET note ET ] [S Chelkowski]

A. FreiseA Freise MG12 15/07/2009Slide 14 Several QND topologies seem feasible:  Micheslon with SR, variational output, squeezing  Sagnac or Mach Zehnder Interferometer with SR, …  Optical bars, optical levers, double optical spring, … All can be build using the L-shape form factor! QND Topologies Optical Lever

A. FreiseA Freise MG12 15/07/2009Slide 15 Additional noise couplings: For Example: The Sagnac topology Non-zero area SagnacNear-zero area Sagnac

A. FreiseA Freise MG12 15/07/2009Slide 16 Sagnac effect in ET Analysis involves two effects 1.Static effects due to Earth’s rotation  Much more sensitive than current Laser gyros 2.Noise couplings Frequency noise Seismic noise Beam jitter noise [S. Chelkowski, talk at WP3 meeting 01/2009]

A. FreiseA Freise MG12 15/07/2009Slide 17 Example: Seismic noise Non-zero area Sagnac requirements on lateral mirror motion: Zero area Sagnac requirements: [S. Chelkowski, talk at WP3 meeting 01/2009]

A. FreiseA Freise MG12 15/07/2009Slide 18 Practical Considerations: Example, Beam Size

A. FreiseA Freise MG12 15/07/2009Slide 19  Interferometer topology selection will be driven by the quantum noise reduction scheme  All topologies can be build as an L-shape  We can assemble 3 L-shapes efficiently as a triangle  Multiple interferometers per site are beneficial for the sensitivity, yield redundancy and robust data analysis methods (null streams)  Technical details and noise couplings need to be investigated further before a topology can be selected Conclusion

A. FreiseA Freise MG12 15/07/2009Slide 20 …end