1. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Linear Alignment System for the VIRGO Interferometer M. Mantovani, A. Freise, J. Marque, G. Vajente

2. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover N W Input beam Mode Cleaner Michelson interferometer with 3km long Fabry-Perot cavities Main output port The Virgo Detector Layout

3. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover The Virgo Mirror Suspension Main mirrors are suspended for seismic isolation. Active control is necessary to keep the mirrors at their operating point: Inertial damping Local damping Local control, i.e. steering of the mirrors Angular Fluctuation ~ 1  rad RMS

4. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover The Virgo Mirror Suspension Main mirrors are suspended for seismic isolation. Active control is necessary to keep the mirrors at their operating point: Inertial damping Local damping Local control, i.e. steering of the mirrors Alignment precision requests: 10 -7 rad RMS for the recycling mirror 2·10 -8 rad RMS for the cavity input mirrors 3·10 -9 rad RMS for the cavity end mirrors Angular Fluctuation ~ 1  rad RMS Shot noise: 10 -13 rad/sqrt(Hz) @10Hz

5. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover The Virgo Mirror Suspension Main mirrors are suspended for seismic isolation. Active control is necessary to keep the mirrors at their operating point: Inertial damping Local damping Local control, i.e. steering of the mirrors A more precise alignment system is needed

6. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover The purpose of the linear alignment system is to keep the beams and mirrors at their set position, in order to: allow a stable interferometer operation over long periods, i.e. perform a control for low frequencies, where the SA does not suppress motions. minimise the coupling of noise into the dark fringe signal In other words: the automatic alignment control should not actively suppress motion in the measurement band (>10Hz) the linear alignment should allow to switch of „noisy“ local controls. Linear Alignment System

7. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Linear Alignment System Overview

8. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Recombined Mode 4 Quadrant Photodiodes (→ 8 signals for each degree of freedom tx or ty) Linear Alignment System

9. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Linear Alignment System Recombined Mode 4 Mirrors to control 4 Quadrant Photodiodes (→ 8 signals for each degree of freedom tx or ty)

10. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Quadrant Photo-Detector Specification photodiode sensitivity = 0.45 A/W maximum DC power = 3 mW transmittivity = 2 k  Bias voltage = 180 V Shot Noise ~ 4 nV/sqrt(Hz)

11. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Recombined Mode Linear Alignment System

12. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Feedback Feedback is applied to the Marionette via the four coil-magnet actuators used also for the local control.

13. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Linear Alignment System Recycled Mode 8 Quadrant Photodiodes (→ 16 signals for each degree of freedom tx or ty )

14. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Linear Alignment System Recycled Mode 8 Quadrant Photodiodes (→ 16 signals for each degree of freedom tx or ty ) 5 Mirrors to control

15. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Linear Alignment System Recycled Mode

16. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Linear Alignment System Recycled Mode

17. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Reconstruction Algorithm The reconstructed signals are computed by using a χ 2 algorithm starting from the optical matrix. The optical matrix is measured by injecting frequency lines, at the level of the reference mass of the mirrors or at the level of the marionette, and then it is computed by calculating the transfer function, at the lines frequencies, and the quadrants signals (Matlab script)

18. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Reconstruction Algorithm function [Matrix]=Mmeasure(TxTy,GPSb,GPSe,fres,ave,filename,lines,checkpast) Loads the ffl file starting from the GPS time Computes the fft of the mirror signals and quadrant signals Searches the lines frequencies by using the nominal frequency values Computes the transfer functions between the mirror signals and the quadrant signals at the line frequencies Makes a coherence analysis in order to estimate the measurement noise Prints the signal to noise ratio matrix in order to control the amplitude of the frequency lines Prints the optical matrix

19. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover PRBSNINEWIWE B2_q1_ACp B2_q1_ACq B2_q2_ACp B2_q2_ACq B5_q1_ACp B5_q1_ACq B5_q2_ACp B5_q2_ACq B7_q1_ACp B7_q1_ACq B7_q2_ACp B7_q2_ACq B8_q1_ACp B8_q1_ACq B8_q2_ACp B8_q2_ACq Optical Matrix Reconstruction Algorithm

20. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Matrix Measurements Method Measure the matrix coefficients evolution as a function of the demodulation phases of the quadrants in order to: o Understand the behavior of the matrix o Tune the demodulation phase Each measurement point takes 3 minutes => 18 minutes for the whole evolution measurement (180 sec for 15 FFT averages)

21. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Matrix Measurements Method Measure the matrix coefficients evolution as a function of the demodulation phases of the quadrants in order to: o Understand the behavior of the matrix o Tune the demodulation phase

22. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Demodulation Phases Tuning for the Recombined Mode In this situation we have decided to minimize one signal respect to the other Fine tuning for the demodulation phases

23. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Experimental Progress

24. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Characterising the Optical System Studied the evolution behavior for the matrix coefficients depending on the fringe offset Checked the repeatability of the phase tuning measurement the repeatability of the matrix measurement Tried to work at 0.2 offset from the dark fringe in order to benefit from the higher stability of the lock in this state Discovered some, not understood, problems at 20% of the dark fringe which obliged us to work at 0.08 fringe offset Found some anomalies of the optical matrix measured in the recycled mode by using a set of frequency lines injected at the level of the reference mass of the mirrors Measured the optical matrix by injecting the frequency lines at the level of the marionette

25. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Optical Matrix measurement for different fringe offsets The amplitudes of the matrix coefficients are very different for the 0.1 fringe offset with respect to the dark fringe We can not measure the optical matrix at 0.1 fringe offset 0.1 fringe offsetdark fringe

26. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Optical Matrix measurement for different fringe offsets The matrix coefficients at the 0.05 fringe offset and at the dark fringe match well 0.05 fringe offset dark fringe

27. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Repeatability of the Matrix Measurement The Matrix measurement done at the dark fringe in successfully repeatable

28. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Matrix Measurement at 0.2 Fringe offset We do not understand the reason of this behavior, we decided to work at 0.08 of fringe offset.

29. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Reference Mass Line Injecting Point In the Recycled configuration we observed a strange behavior of the measured optical matrix (even if the sine behavior of the matrix as a function of the demodulation phase was verified) We have measured the optical matrix of the system by injecting high frequency lines (from 20 to 50 Hz) at the level of the reference mass in the Recombined Mode (in which we did not have any problem) and in Recycled Mode.

30. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover PRBSNINEWIWE B2_q1_ACp-0.1750-3.024-0.643 2.174 -0.318 B2_q1_ACq-0.20202.282-0.484 1.476-0.234 B2_q2_ACp-0.0970-1.238-0.250.831-0.118 B2_q2_ACq001.136-0.2510.821-0.13 B5_q1_ACp 1.61700000.432 B5_q1_ACq 6.3980-33.5337.5-21.3352.298 B5_q2_ACp 4.270018.8454.79-12.7641.071 B5_q1_ACq-2.5060-19.8843.665 -10.9261.533 B7_q1_ACp-0.9450-4.018-0.498 2.612-0.888 B7_q1_ACq-0.6580 7.2061.5354.457-1.225 B7_q2_ACp 0.7670 4.943-0.933 2.897-0.269 B7_q2_ACp 0.5660 2.621001.04 B2_q1_ACp0.9660-7.053-1.263 4.109-0.48 B2_q1_ACp-0.9150 6.6751.1204.512-1.601 B2_q1_ACp0.83340-9.802.175-6.7180.60 B2_q1_ACp-1.6620-12.459-2.377 6.913-0.998 PRBSNINEWIWE B2_q1_ACp-0.1840-3.445-0.75 2.639 -0.289 B2_q1_ACq0.31303.236-0.624 2.11-0.253 B2_q2_ACp-0.10-1.515-0.3131.058-0.113 B2_q2_ACq0.12401.1338-0.80.963-0.119 B5_q1_ACp 1.17900000.65 B5_q1_ACq 5.0380-27.6725.9810.5391.199 B5_q2_ACp 3.866015.8433.98-6.050 B5_q1_ACq-1.9730-15.8973.031 -6.960.915 B7_q1_ACp-0.8840-4.322-0.501 1.367-0.78 B7_q1_ACq0.750 7.6271.5794.655-1.157 B7_q2_ACp 0.7570 4.315-0.533 2.4840.147 B7_q2_ACp 0.5040 2.33-0.45101.03 B2_q1_ACp-0.6380-6.61-1.18 3.270.48 B2_q1_ACp-0.670 6.3380.833.79-1.556 B2_q1_ACp-0.760-9.802.05-6.1690.371 B2_q1_ACp-1.60-12.93-2.5725.72-0.767 Excessively high coefficient values Reference Mass Line Injecting Point

31. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover PRBSNINEWIWE B2_q1_ACp-0.1750-3.024-0.643 2.174 -0.318 B2_q1_ACq-0.20202.282-0.484 1.476-0.234 B2_q2_ACp-0.0970-1.238-0.250.831-0.118 B2_q2_ACq001.136-0.2510.821-0.13 B5_q1_ACp 1.61700000.432 B5_q1_ACq 6.3980-33.5337.5-21.3352.298 B5_q2_ACp 4.270018.8454.79-12.7641.071 B5_q1_ACq-2.5060-19.8843.665 -10.9261.533 B7_q1_ACp-0.9450-4.018-0.498 2.612-0.888 B7_q1_ACq-0.6580 7.2061.5354.457-1.225 B7_q2_ACp 0.7670 4.943-0.933 2.897-0.269 B7_q2_ACp 0.5660 2.621001.04 B2_q1_ACp0.9660-7.053-1.263 4.109-0.48 B2_q1_ACp-0.9150 6.6751.1204.512-1.601 B2_q1_ACp0.83340-9.802.175-6.7180.60 B2_q1_ACp-1.6620-12.459-2.377 6.913-0.998 Sign Flips PRBSNINEWIWE B2_q1_ACp-0.1840-3.445-0.75 2.639 -0.289 B2_q1_ACq0.31303.236-0.624 2.11-0.253 B2_q2_ACp-0.10-1.515-0.3131.058-0.113 B2_q2_ACq0.12401.1338-0.80.963-0.119 B5_q1_ACp 1.17900000.65 B5_q1_ACq 5.0380-27.6725.9810.5391.199 B5_q2_ACp 3.866015.8433.98-6.050 B5_q1_ACq-1.9730-15.8973.031 -6.960.915 B7_q1_ACp-0.8840-4.322-0.501 1.367-0.78 B7_q1_ACq0.750 7.6271.5794.655-1.157 B7_q2_ACp 0.7570 4.315-0.533 2.4840.147 B7_q2_ACp 0.5040 2.33-0.45101.03 B2_q1_ACp-0.6380-6.61-1.18 3.270.48 B2_q1_ACp-0.670 6.3380.833.79-1.556 B2_q1_ACp-0.760-9.802.05-6.1690.371 B2_q1_ACp-1.60-12.93-2.5725.72-0.767 Reference Mass Line Injecting Point

32. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Marionette line injecting point We decided to measure the optical matrix by injecting the lines at the level of the marionette (going to low frequency 5 to 9 Hz) The strangely high amplitude of the coefficients is disappeared There are not sign flip anymore The matrix measurements seem to be nicely repeatable

33. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Offline Validation of the Linear Alignment Loops

34. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Offline Data Analysis The error signals are constructed, in an offline analysis, starting from the measured quadrant signals and then applying the reconstruction matrix In this way we can easily check the quality of our reconstruction taking the decoupling of the injected signals as a measure Reconstructing Matrix Optical Matrix Reconstructed Correction Signals

35. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Offline Data Analysis PRNINE WIWE

36. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Further Matrix Quality Analysis PRNINEWIWE B2q1p0.107-0.0960.0133-0.02850.0224 B2q1q0.588-0.2960.00867-0.3060 B2q2p0.573-0.3080-0.2780.0107 B2q2q0.317-0.126-0.0136-0.191-0.0238 B5q1p0-0.01470.04520.0117-0.0248 B5q1q0.307-0.1660.0601-0.149-0.052 B5q2p0.311-0.1770.0296-0.142-0.0231 B5q2q0-0.00233-0.01360.00557-0.00633 B7q1p0.0155-0.01070.022-0.00535-0.0199 B7q1q-0.004050.01020.000141-0.006070 B7q2p0.0284-0.02270.00156-0.00636-0.00194 B7q2q0.00283-0.002830.01940-0.0192 B8q1p0.01130-0.0165-0.0120.0182 B8q1q0.00585-0.00698-0.01050.0006440.012 B8q2p0.0264-0.006190-0.0209-0.00019 B8q2q0.009030.0011-0.0191-0.009490.0194 Optical matrix computed with SIESTA simulation (G.Giordano)

37. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Suspended bench External bench PRNINEWIWE PR07.171.25.774.1 NI7.1067.912.875.1 NE71.267.9074.140.4 WI5.712.874.1073.9 WE74.175.140.473.90 Angle between column vectors: Minimum angle: 6 deg (matrix subset: 30 deg) Conditioning of the system: 300  2 noise distribution: PRNINEWIWE 3.53.413.61 Further Matrix Quality Analysis

38. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Latest Results

39. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Closing the Tx Loops

40. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover Conclusions and Next Steps Closed the Tx loops in a stable state for 5 min We will continue following the same strategy We have to analyze the data to understand the different behavior from the theory But before we want to close the Ty loops to have more precise data

41. M. Mantovani, ILIAS Meeting 7 April 2005 Hannover

42. Offline Data Analysis In order to have an evaluation of the goodness of the algorithm, used to reconstruct the mirror angular positions, we have injected lines on the mirrors and measured the quadrant signals