1. S. ChelkowskiSlide 1ET Meeting, Hannover 01/2009

2. Overview  Introduction  ET  Sagnac topology  Sagnac effect  Consequences for ET with Sagnac topology  Static effects  Noise couplings  Frequency noise  Seismic noise  Beam jitter noise S. ChelkowskiET Meeting, Hannover 01/2009Slide 2

3. ET S. ChelkowskiET Meeting, Hannover 01/2009Slide 3

4. ET  Triangular geometry  Topology currently undefined  Michelson,Mach- Zehnder, Sagnac, etc  Configuration currently undefined S. ChelkowskiET Meeting, Hannover 01/2009Slide 4

5. Sagnac topology S. ChelkowskiET Meeting, Hannover 01/2009Slide 5 Non-zero area SagnacNear-zero area Sagnac

6. Sagnac interferometer and effect  Named after Georges Sagnac  Correctly explained only with General Relativity  Rotational induced phase shift S. ChelkowskiET Meeting, Hannover 01/2009Slide 6 Original experimental setup from 1913 Ref: [1] G. B. Malykin, "The Sagnac effect: correct and incorrect explanations", Physics-Uspekhi, Vol.43, (2000), 1229-1252 [2] G. E. Stedman, "Ring-laser tests of fundamental physics and geophysics", Reports on Progress in Physics, Vol.60, (1997), 615-688

7. Location dependency S. ChelkowskiET Meeting, Hannover 01/2009Slide 7 Earth rotation Detector location Equator

8. Sagnac effect today  Lasergyroscopes are used for geodesic measurements to determine variations in the Earth rotation rate  Also used to do seismometry  Current sensitivity: S. ChelkowskiET Meeting, Hannover 01/2009Slide 8 Images with courtesy Laser Gyro Group Wettzell, Germany

9. Sagnac effect in ET S. ChelkowskiET Meeting, Hannover 01/2009Slide 9 Non-zero area SagnacNear-zero area Sagnac AA = B - C B C

10. Sagnac effect in ET S. ChelkowskiET Meeting, Hannover 01/2009Slide 10 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

11. Static Sagnac effect S. ChelkowskiET Meeting, Hannover 01/2009Slide 11 Location Strasbourg: Arm length of 10km Simulation parameters No longer on dark fringe! 33% of laser power lost in “dark” port 10km A = B - C B C Change arm length to 10068m to achieve dark port condition again! Include Matlab figure which Shows the fringes?

12. Noise coupling analysis S. ChelkowskiET Meeting, Hannover 01/2009Slide 12 Our aim is @ 10Hz Hild et al., (2008) arXiv:0810.0604v2

13. How does strain sensitivity translates into Sagnac phase shift? S. ChelkowskiET Meeting, Hannover 01/2009Slide 13 10km Clockwise propagating beam: Counter-clockwise propagating beam

14. 10km Noise couplings – Frequency noise S. ChelkowskiET Meeting, Hannover 01/2009Slide 14 Non-zero area Sagnac

15. Noise couplings – Frequency noise S. ChelkowskiET Meeting, Hannover 01/2009Slide 15 A = B - C B C Near-zero area Sagnac

16. Noise couplings – Seismic noise S. ChelkowskiET Meeting, Hannover 01/2009Slide 16 10km Non-zero area Sagnac

17. Noise couplings – Seismic noise S. ChelkowskiET Meeting, Hannover 01/2009Slide 17 A = B - C B C Near-zero area Sagnac

18. Noise couplings – Beam jitter noise S. ChelkowskiET Meeting, Hannover 01/2009Slide 18

19. Noise couplings – Beam jitter noise S. ChelkowskiET Meeting, Hannover 01/2009Slide 19 10km Non-zero area Sagnac

20. Noise couplings – Beam jitter noise S. ChelkowskiET Meeting, Hannover 01/2009Slide 20

21. Noise couplings – Beam jitter noise S. ChelkowskiET Meeting, Hannover 01/2009Slide 21 A = B - C B C Near-zero area Sagnac

22. Conclusion  Two possible solutions for ET with Sagnac topology  Non-zero area Sagnac  Near Zero area Sagnac  Noise coupling analysis performed for both cases  Near-zero area Sagnac performs better!  Seismic noise and frequency noise coupling are fine  Only beam alignment has stringent requirement S. ChelkowskiET Meeting, Hannover 01/2009Slide 22