1. LIGO-G050484-00-R LIGO R&D1 Improvement of the MGAS Filter Damping Performance Alberto Stochino University of Pisa, Italy SURF Student Mentor: Dr. Riccardo De Salvo

2. LIGO-G050484-00-R LIGO R&D2 Seismic Noise Noise Budget It is the disturbance resulting from the displacement of the mirrors due to the ground motion seismic

3. LIGO-G050484-00-R LIGO R&D3 The vertical and horizontal degrees of freedom are not independent mechanical complexity non uniformity of the terrestrial gravitational field Vertical Motion of the Mirrors the motion of the mirrors in the vertical direction can change the arm length of the interferometer

4. LIGO-G050484-00-R LIGO R&D4 Vertical Attenuation ground motion ~ 10 -6 m expected GW signal ~ 10 -18 m required attenuation factor ~ 10 -12 vertical to horizontal couplings must not be limiting factors to the horizontal sensibility ~< 10e-3 Gravitational Coupling negligible respect to other couplings ~ 1%

5. LIGO-G050484-00-R LIGO R&D5 Passive Mechanical Filters Massive spring

6. LIGO-G050484-00-R LIGO R&D6 The C.O.P. Effect limitation on attenuation performance Center Of Percussion

7. LIGO-G050484-00-R LIGO R&D7 MGAS Filter Linear Model for GAS Springs

8. LIGO-G050484-00-R LIGO R&D8 GAS Filter Limit (Kenji Numata) Transfer Function COP limit

9. LIGO-G050484-00-R LIGO R&D9 Inverted Pendulum Transfer Function

10. LIGO-G050484-00-R LIGO R&D10 C.O.P. Displacement Transfer Function for the counterweighted IP

11. LIGO-G050484-00-R LIGO R&D11 Extending the Idea to the GAS Springs M noise cop What we had before What we wanted to do blade

12. LIGO-G050484-00-R LIGO R&D12 Prototype Design

13. LIGO-G050484-00-R LIGO R&D13 Making it Real

14. LIGO-G050484-00-R LIGO R&D14 Tuning of the Counterweight

15. LIGO-G050484-00-R LIGO R&D15 Experiment Setup 1) GAS blade 2) Filter body 3) Support spring 4) Voice-coil 5) Payload 6) Rigid connector 7) Accelerometer 4 3 2 5 1 1 6 7 7

16. LIGO-G050484-00-R LIGO R&D16 The Initial TF

17. LIGO-G050484-00-R LIGO R&D17 Overcompensation Three Booms No CWs

18. LIGO-G050484-00-R LIGO R&D18 Three Booms + 2x3 CWs Note the phase advance

19. LIGO-G050484-00-R LIGO R&D19 Undercompensation Two Booms No CWs

20. LIGO-G050484-00-R LIGO R&D20 Two Booms + 1 CW

21. LIGO-G050484-00-R LIGO R&D21 Two Booms + ½ CW ?

22. LIGO-G050484-00-R LIGO R&D22 Two Booms 1 CW CW positions comparison

23. LIGO-G050484-00-R LIGO R&D23 Two Booms 1 CW Inner

24. LIGO-G050484-00-R LIGO R&D24 E.M. Antispring Circuitry

25. LIGO-G050484-00-R LIGO R&D25 E.M. Antispring Two Booms 1 CW Inner

26. LIGO-G050484-00-R LIGO R&D26 Next Lower the noise at high frequencies Deepen the TF and Phase data analysis Find the optimal setup for the best compensation HAM-SAS

27. LIGO-G050484-00-R LIGO R&D27 Acknowledgments Dr. Riccardo DeSalvo Virginio Sannibale Francesco Fidecaro The LIGO-SURF Program The NSF Caltech Pasadena, California, USA