1. Katrin Dahl for the AEI 10 m Prototype team March 2010 – DPG Hannover Q29.1 http://10m-prototype.aei.uni-hannover.de Stabilising the distance of 10 m separated optical tables to 100 pm/sqrt(Hz) optical tables to 100 pm/sqrt(Hz) AEI 10m Prototype

2. 2 Prototype hall 11.65 m

3. 3 Residual table motion

4. 4 Longitudinal motion stabilised

5. 5 Relative table motion stabilised

6. Why distance stabilisation of tables? The AEI 10 m Prototype will provide ultra-low displacement noise testing environment To probe at (and later go beyond) the standard quantum limit Entanglement of macroscopic test masses For GRACE follow-on and LISA related experiments... 6

7. (Homodyne) Mach-Zehnder interferometry 7

8. Heterodyne Mach-Zehnder interferometry No specific lock point  Enables to track table motion over more than one wavelength Control bandwidth 100 Hz  heterodyne frequency of about 19 kHz Use of in-house knowledge (LISA Pathfinder technology) 8

9. Optical layout 9 Heterodyne Mach- Zehnder IFOs with unequal arm lengths (by 23m) Stable laser required to reach design sensitivity of 100 pm/sqrt(Hz)@10 mHz – iodine stabilized Nd:YAG

10. Optical layout 10 Thermal drifting requires components to be bonded onto a Clearceram (CTE=0.4*10 -7 /K) baseplate by hydroxide-catalysis bonding technique. Beam height 45 mm Use of quadrant photodiodes

11. 11 4 Interferometers

12. 12 Monitoring of power fluctuations beam pointing Power monitor

13. 13 Reference IFO

14. 14 Diagnostic IFO

15. 15 West IFO

16. 16 South IFO

17. Test setup 17

18. Optical layout 18

19. Longitudinal displacement 19

20. Pitch 20

21. Yaw 21

22. Blind test 22

23. 23 Thank you for your attention http://10m-prototype.aei.uni-hannover.de

24. Phase determination Phase is extracted from heterodyne signal by use of an hardware Phasemeter 1 based on FPGA chips 1.Preamplifier and A/D conversion – Photocurrent converted to voltage – Digitising signals –  results in time series 2.Single bin discrete Fourier transform – Fourier transform at only one frequency –  complex amplitude of PD signal at f het 3.Signal combination of each QPD quadrant leads to phase, DC, Differential Wavefront Sensing (DWS) and contrast information 24 Illustration of DWS 1 developed for LISA Pathfinder, Heinzel G et al. 2004 Class Quantum Grav 21 581

25. Signal processing 25 Transfer rate from phasemeter EPP to microcontroller ethernet around 1.9 kHz with 16 channels

26. Why distance stabilisation of tables? 26 1 http://www.physics.gla.ac.uk/igr/index.php?L1=igr_public&L2=phd In gravitational-wave detectors mirrors need to be isolated from environmental noise sources. Ease lock acquisition of cavities by reducing residual motion of the suspended mirrors Reduction of burden to actuators on the mirrors 1 Schematic layout of a gravitational-wave detector GEO600 300 m to 4 km