1. Einstein gravitational wave Telescope Next steps: from technology reviews to detector design Andreas Freise for the ET WG3 working group 15.10.2009, 2nd general ET workshop, Erice

2. A. FreiseA Freise, 2nd general ET workshop 15/10/2009 Slide 2  What will ET look like?  How many interferometers per site?  Quantum noise reduction  Alternative topologies  Practical considerations  Sensitivity Studies  List of reviews/reports  Discussion of trade-off study Overview In the ET design study we are soon reaching the milestones `Evaluation of XXX technique’ and then start the trade-off activity.

3. A. FreiseA Freise, 2nd general ET workshop 15/10/2009 Slide 3 Detector Geometry What will be the shape of ET?

4. A. FreiseA Freise, 2nd general ET workshop 15/10/2009 Slide 4 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 58 1998]

5. A. FreiseA Freise, 2nd general ET workshop 15/10/2009 Slide 5 Geometry/Topology How Many Interferometers Arms per Tunnel? Picture by Jason Bacon used under a Creative Commons License Rüdiger, Aspen 2007

6. A. FreiseA Freise, 2nd general ET workshop 15/10/2009 Slide 6 Today's Michelsons in a Triangle [S Hild]

7. A. FreiseA Freise, 2nd general ET workshop 15/10/2009 Slide 7 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:0906.2655]

8. A. FreiseA Freise, 2nd general ET workshop 15/10/2009 Slide 8 Topology Main Driver: Reduction of Quantum Noise [S. Hild et al, arxiv:0810.0604]arxiv:0810.0604

9. A. FreiseA Freise, 2nd general ET workshop 15/10/2009 Slide 9 Quantum Noise Reduction Optimised SR [H. Rehbein und H. Mueller-Ebhardt, ET note ET-010-09 2009] [S Chelkowski]

10. A. FreiseA Freise, 2nd general ET workshop 15/10/2009 Slide 10 Quantum Noise Reduction 10dB frequency-dependent squeezing [H. Rehbein und H. Mueller-Ebhardt, ET note ET-010-09 2009] [S Chelkowski]

11. A. FreiseA Freise, 2nd general ET workshop 15/10/2009 Slide 11 Quantum Noise Reduction Variational output and 10 dB squeezing [H. Rehbein und H. Mueller-Ebhardt, ET note ET-010-09 2009] [S Chelkowski]

12. A. FreiseA Freise, 2nd general ET workshop 15/10/2009 Slide 12 Quantum Noise Reduction Sagnac with SR, variational output and 10dB squeezing [H. Rehbein und H. Mueller-Ebhardt, ET note ET-010-09 2009] [S Chelkowski]

13. A. FreiseA Freise, 2nd general ET workshop 15/10/2009 Slide 13 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

14. A. FreiseA Freise, 2nd general ET workshop 15/10/2009 Slide 14 Practical considerations New technologies introduce new technical noises which might not be thought of in the first conceptual designs and have to be studied carefully. Two examples …

15. A. FreiseA Freise, 2nd general ET workshop 15/10/2009 Slide 15 Additional noise couplings: For Example: The Sagnac topology Non-zero area SagnacNear-zero area Sagnac

16. A. FreiseA Freise, 2nd general ET workshop 15/10/2009 Slide 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]

17. A. FreiseA Freise, 2nd general ET workshop 15/10/2009 Slide 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]

18. A. FreiseA Freise, 2nd general ET workshop 15/10/2009 Slide 18 Practical Considerations: Example, Beam Size

19. A. FreiseA Freise, 2nd general ET workshop 15/10/2009 Slide 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 Summary of the overview

20. A. FreiseA Freise, 2nd general ET workshop 15/10/2009 Slide 20 Sensitivity Studies  One of the WG3 tasks is to provide official sensitivity curves  See main ET webpage  Please use these for your studies and ask (email) if you have questions!

21. A. FreiseA Freise, 2nd general ET workshop 15/10/2009 Slide 21 Sensitivity Studies  The available data (currently internal to ET science team but should be opened):  Plot as pdf file  Data as.txt and.mat file  Polynomial fit (coming soon)  These sensitivities are:  Documented, version controlled, centrally stored data  Generally discussed and accepted sensitivity examples for activities such as trade-off studies  These sensitivities are NOT:  Representing proposed ET detector options  Always achievable using known technologies  Taking into account detector geometry (triangle, network effects,…)

22. A. FreiseA Freise, 2nd general ET workshop 15/10/2009 Slide 22 Technology review  Technology review documented in internal notes and papers:  Quantum noise reduction  Detector geometry and topology  High power lasers  Parametric instabilities  Diffractive interferometers  Squeezed light  Displacement noise free interferometry

23. A. FreiseA Freise, 2nd general ET workshop 15/10/2009 Slide 23 Trade-off studies  Problem:  New technology ideas are cheap, we have to stop evaluating those at some point  Everything depends on everything (e.g. thermal noise on beam size, on free aperture, on tunnel size on available money): it is difficult to do trade-off studies with too many options  Proposal:  Identify parameters/problems which can be separated, such as the triangular shape from the QND topology  For the rest, agree on one (maybe two) complete design as reference and compute sensitivity, noise models, costs Discussion now. Kick-off of dedicated activities in next WG3 meeting

24. A. FreiseA Freise, 2nd general ET workshop 15/10/2009 Slide 24 …end

25. A. FreiseA Freise, 2nd general ET workshop 15/10/2009 Slide 25 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)]