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VIRGO Superattenuators in next generation detectors S.Braccini, INFN-Pisa

VIRGO Superattenuators in next generation detectors S.Braccini, INFN-Pisa on behalf of the Virgo Collaboration. 1) SAT Seismic Isolation: Present & Future. 2) SAT “Passive Control”. 3) SAT Mechanical Glitch Noise. 2. Superattenuator. Magnetic Anti-Spring. 8 m. Blade Springs. 3. 2 Hz.

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VIRGO Superattenuators in next generation detectors S.Braccini, INFN-Pisa

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  1. VIRGO Superattenuators in next generation detectors S.Braccini, INFN-Pisa on behalf of the Virgo Collaboration

  2. 1) SAT Seismic Isolation: Present & Future 2) SAT “Passive Control” 3) SAT Mechanical Glitch Noise 2

  3. Superattenuator Magnetic Anti-Spring 8 m Blade Springs 3

  4. 2 Hz Ground Resonances f-2N Transmisson Frequency (Hz) Long Pendula Soft Springs Mirror 4

  5. 2 Hz Resonances f-2N Frequency (Hz) Large Inertia Thin Wires 5

  6. Stage by Stage Measurement Thermal Noise Ground Seismic Noise Mirror Residual Seismic Noise 6

  7. DirectMeasurement SA design e freccette 7

  8. TF < 1.7 x 10-12 TOP 1.2 x 10-6m Hz-1/2 MIRROR 2 x 10-18m Hz-1/2 8

  9. TF = 1.26 x 10-11 TOP MIRROR ! ! 9

  10. Upper limitHoriz Upper limit Vertical 10

  11. Upper limitHoriz Upper limit Vertical 11

  12. SA design e freccette SA design e freccette X-Excitation Experiment Bypass ? 12

  13. AdV - Seismic Isolation OK ET - Reduction of low frequency cut-off 13

  14. Stage by Stage TF Crossing expected @ 2.5-3 Hz 14

  15. Confirmed by direct measurements Horiz Vertical ET ETx Horizontal seismic noise dominant 15

  16. PRESENT CROSS-OVER ET ETx 16

  17. Change both number of filters and their distance (thus varying the total length) HORIZONTAL TF 17

  18. HORIZONTAL 5 filters - 15 m 7 filters - 16 m 6 filters - 17 m 6 filters - 14 m TF 1.8 Hz 18

  19. Upper limitHoriz Upper limit Vertical Vertical Attenuation 19

  20. 6 Filters (as now) TF FILTER @ 310 mHz

  21. CONCLUSION 3rd GENERATION: Use identical technology with cross-over below 2 Hz Present SA extension 9 17 m (1.8 Hz conservative cross-over) 21

  22. 1) Seismic Isolation: Present & Future 2) “Passive Control” 3) Mechanical Glitch Noise 22

  23. several microns mirror swing 23

  24. Accelerometers DSP DAC Actuators ADC 24

  25. Swing reduction by ID + ultra-low freq. passive attenuation 8 m 25

  26. Alignment without affecting mirror swing (Payload ad hoc design) 1) Intrinsically diagonalized (Easy control) 2) “Nothing happens” in the off-diagonal world 26

  27. “Passive strategy” in prealignment (qy) 27

  28. “Passive strategy” in prealignment (qx) 28

  29. Alignment transparent for SA 8 m 29

  30. Acquire the locking with no recoil 30

  31. Acquire the locking with negligible recoil 31

  32. Lock Acquisition transparent for SAT 8 m

  33. 1) Longitudinal swing fraction of mm/s 2) Prealign mirror (fract. of mrads) (not affecting 1) 3) Lock acquisition (not affecting 1 - 2) 8 m 4) Reallocation & Tidal Control (not affecting 1 - 2 - 3) Residual Swing LONGITUDINAL: around 100 nm pk pk ANGLES: fractions of mrad pk pk

  34. 500 nrad RESIDUAL (OPEN LOOP) DISPLACEMENTS 100 nm SMALL LOCKING & ALIGNMENT CORRECTIONS  LOW NOISE HIGH ACCURACY: 10 nrads on PR,a few nrads on test masses

  35. RM AdV Marionetta CONTROL NOISE - OK for AdV 35

  36. 1) Seismic Isolation: Present & Future 2) “Passive Control” 3) Mechanical Glitch Noise 36

  37. Self-organized criticality dynamics of dislocations induces a mechanical shot-noise force (1/f) 37

  38. Potential problem in last filter(s) of the chain 38

  39. 3 VERTICAL MODES F7 -Blades 40 Hz Marionetta 15 Hz 7 Hz Reference Mass Mirror 39

  40. MODES VISIBLE IN DARK FRINGE Displacement Strain (m Hz^-1/2) 40 Freq (Hz)

  41. TF MEASUREMENT Blades Mar RM Mir 41

  42. TF MEASUREMENT Mirror-Beam Displacement (m) / Vertical Force (N) 7 Hz 15 Hz 40 Hz Freq (Hz) 42

  43. VERTICAL FORCE UPPER LIMIT z(w) = TF(w) x Fv(w) 7 Hz 40 Hz Fv_max (w) = z(w) / TF(w) 43

  44. VERTICAL FORCE UPPER LIMIT Vertical Force (Upper Limit – N/Hz1/2) Freq (Hz) 44

  45. VERTICAL FORCE UPPER LIMIT Vertical Force (Upper Limit – N/Hz1/2) Freq (Hz) 45

  46. VERTICAL FORCE UPPER LIMIT Vertical Force (Upper Limit – N/Hz1/2) X TF Freq (Hz) 46

  47. h(f) Virgo AdV 1/f noise upper limit 47

  48. START PARENTHESIS (just for a betterunderstanding)

  49. F Vertical Force on Marionetta  MirrorDisplacementalongbeam z

  50. Closedparenthesis h(f) Virgo AdV 1/f noise upper limit

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