PRM SRM. Grav. Wave ReadOut

Transcription

1 Nov. 6-9,2 The 22nd Advanced ICFA Beam Dynamics Workshop on Ground Motion in Future Accelerators November 6-9, 2 SLAC Passive Ground Motion Attenuation and Inertial Damping in Gravitational Wave Detectors Presented by: V. Sannibale, A. Bertolini, G. Cella, S. Marka, R. de Salvo, A. Takamori, LI project California Institute of Technology, USA Universitá di Pisa, Italy University of Tokyo, Japan LI-G324--R

2 Nov. 6-9,2 Interferometer Topology ETMY Input Mode cleaner 4/2 ITMY 2 4/2 Laser units: m PRM SRM BS ITMX ETMX LI II Output Mode cleaner Grav. Wave ReadOut ITFs Comparison. LI I LI II Laser Power : W 8W Recycling Factor : 5 Arm Finesse : 5 2 Arm Power : ο 5kW ο 8kW Mirror Substrate : Fused Silica (Q ο 7 ) Sapphire (Q ο 8 ) Suspension Wires : steel Fused Silica LI-G324--R

3 Nov. 6-9,2 LI Sites: (Hanford and Livingston) LI-G324--R

4 Nov. 6-9,2 LI II sensitivity Curve ffl Inspiral NS/NS binaries : 2Mpc LII, 45 Mpc LI II ffl Inspiral NS/BH binaries : 4Mpc LII, Mpc LI II ffl Inspiral BH/BH binaries : Mpc LII, 2 Mpc LI II ffl Inspiral BH/BH merge Mpc Mfi/Mfi : S/N=.5 LII, S/N=LIII ffl Spinning NS,f ο 2 Hz, Galactic Core : ffl > 5 5 LII,ffl > 2 6 LIII LIII could reach a sensitivity able to allow a quantitative comparison with astrophysical models LI-G324--R

5 Nov. 6-9,2 Seismic Attenuation System (SAS): Principle Typical Linear Mechanical Oscillator Transfer Function Rigid Body Mode Resonance Detector Sensitivity Band Transmissibility Flat Response /f^2 Roll off Inertia of the Distributed Mass Internal Resonances. 5mHz Hz Hz 6Hz General Recipe to Improve Passive Seismic Isolation ffl Move down in frequency, lower as possible the rigid body modes ffl Move up in frequency, higher as possible the internal modes. ffl Damp the internal modes. ffl attenuate all the DOF (Crosstalk/Coupling Issues). ffl Active Control to damp the rigid body modes. LI-G324--R

6 Nov. 6-9,2 SAS : Performances/Goals 6 Horizontal Spectral density (m/sqrt(hz)) Mirror Thermal Noise Pendulum Thermal Noise Thermal Noise Long SAS Seismic Noise Short SAS Seismc Noise 2... Frequency (Hz) ffi ~x(ν ' 6 Hz) ο 8 p m Hz ffix rms ' 7 m rms High Reliability and robustness => uninterrupt running time of the order of months LI-G324--R

7 Nov. 6-9,2 Monolithic Geometric Anti-Spring : (Principle/ Advantages) Frame Wire Monolithic Blades Wire Side View Frame Monolithic Blades Top/Bottom View Blade Clamp F x F y mg ffl Very Low Vertical Frequency Resonance (hard task to get very low res. freq. on the vertical DOF for heavy payloads and high internal mode frequency, in a reasonable space). ffl Mechanical Stable System ffl Good Thermal Stability ffl Simple, Compact, Relatively Low Cost. LI-G324--R

8 Nov. 6-9,2 Monolithic Geometric Anti-Spring : (Design) LI-G324--R

9 Nov. 6-9,2 Monolithic Geometric Anti-Spring : (Prototype) LI-G324--R

10 Nov. 6-9,2 Monolithic Geometric Anti-Spring : (Vertical Transfer Function) 2 Vertical Mode (~35mHz) Magnitude 2 2 /f Slope Internal Blade Mode 3 Simple Pendulum Transfer Function Frequency (Hz) LI-G324--R

11 Nov. 6-9,2 Monolithic Geometric Anti-Spring : (Working Point/Thermal Stability).8.6 Resonant Frequency(Hz) Blade Compression Initial position -2.mm -4.5mm -6.mm Fitted Curve Working Point(mm) Displacement (mm).5.2. Sensitivity :.42mm/C Temperature (Degree Celsius) LI-G324--R

12 Nov. 6-9,2 Monolithic Geometric Anti-Spring : (Transfer Function/Quality Factor) 4 Rotation of Load 2 Isolation Ratio[dB] -2-4 Main GASF f=.236 (Hz) Q=4 Pitch of Load Monolithic GASF -6 Unidentified -8 st. Internal. Frequency[Hz]..5 Measured Fitted Output Signal [a.u.] Main GASF f=.236(hz) Q= Time(sec) 8 2 LI-G324--R

13 Nov. 6-9,2 Inverted Pendulum (IP): (Principle/ Advantages) dx M g l Leg Table Flexural Joint Restoring Torque of the Flex. Joint Balanced by the Torque of the Gravit. Field ν = vut k g 2ß M l ; M < kl g ffl Very Low Horizontal Frequency Resonance (ν ' 2 mhz) ffl Large Dynamic Range in the 2 Horizontal Degrees of Freedom ffl Ideal for Applying an Active Control System in 3 D.O.F. ffl Small Forces Required to offset (by dx ) the table with very large payload M (F = M! 2 dx) LI-G324--R

14 Nov. 6-9,2 Inverted Pendulum Prototype: (Design) LI-G324--R

15 Nov. 6-9,2 Inverted Pendulum : (Working Point) Frequency (Hz) ω k g ( M L M Load Load + + m m LegEff 3 LegEff 2 ) Load (kg) Minimum Resonant Frequency Achieved : ν ' mhz (Horiz. DOF) LI-G324--R

16 Nov. 6-9,2 Inverted Pendulum : (Horizontal Transfer Function) 2 Translational Mode 2 /f Slope Internal Modes Magnitude Frequency (Hz) Simple Undim. Model LI-G324--R

17 Nov. 6-9,2 Control Requirements ffl Mirrors RMS Local Positioning System to Provide a Coarse and Fine Alignment System. ffl Mirrors RMS Velocity Reduction to allow the ITF Locking. ffl Mirrors RMS Displacement Reduction to assure ITF Long Term Stability. => Inertial Damping and DC Relative Positioning Control Main Related Issues ffl Rigid Body Modes Main Source of Residual Displacement and Residual Velocity. ffl Crosstalk and Coupling of the Degrees of freedom ffl Actuators/Sensors Dynamic Range and Sensitivity. LI-G324--R

18 Nov. 6-9,2 Position Sensor : (LVDT) Linear Variable Differential Transformer (Logic Scheme) Modulation Secondary Winding Primary Winding + - Mixer Amplifier Lowpass Filter Sensitivity LVDT # 3 : Sensitivity Spectral Density (um/sqrt(hz)) 2 3 Low Pass Filter Cutoff Probable Internal Resonance of the Measurement Setup Frequency (Hz) LI-G324--R

19 Nov. 6-9,2 Inertial Sensor: (Folded Pendulum Accelerometer) l g F M m F L! = s ( M l m l +2fl) g m + M LI-G324--R

20 Nov. 6-9,2 Inertial Sensor: (Folded Pendulum Accelerometer) (Sensitivity) 5 5 Amplitude (V) -5 - Sensitivity : 5 mv/ug Acceleration (ug) Acceleration Spectral Density (ugrms/sqrt(hz)) BC Geophone Position Sensor Noise Actuator Noise Folded Pendulum Acc Frequency (Hz) LI-G324--R

21 Nov. 6-9,2 SAS-SUS Longitudinal Control Diagram Digital Control System ELECTROSTATIC DRIVER LSC:Error Signal DAC DAC COIL DRIVER SAS-SUS SUS LI II Four Stage GASF CHAIN (Passive) IP TABLE COIL DRIVER STEPPER MOTOR DRIVER SAS LVDT DRIVER ACCELER. DRIVER DAC Nonlinear feedback (Threshold Actuation) ADC DAC f=hz f=2hz f=2hz f=hz ELECTROSTATIC DRIVER Suspension f=-4mhz f=2hz VOICECOILS,2,3 ACCELEROM.,2,3 STEPPER MOTORS,2,3 LVDT,2,3 + + DAC DAC DC f=-4mhz ADC LSC:Error Signal -4mHz 4-6Hz Digital Signal Analog Signal Digital Control System Timing Board LI-G324--R

22 Nov. 6-9,2 LI-SAS Prototype Chain (Side View) LI-G324--R

23 Nov. 6-9,2 LI-SAS Prototype Chain (Top View) LI-G324--R

24 Nov. 6-9,2 LI-SAS Prototype Chain (Bottom View) LI-G324--R

25 Nov. 6-9,2 LI-SAS Prototype Chain (Actuators LVDT's) LI-G324--R

26 Nov. 6-9,2 SAS IP Sensor Actuator Map (X; Y and y ) y z x θ y Acceleration Sensor Position Sensor Voice Coil Accutator LEG3 LEG LEG2 LVDT LVDT3 LVDT2 ACT ACT2 ACT3 LI-G324--R

27 Nov. 6-9,2 Multiple Input Multiple Output System Diagonalization G(s) ^ _p D^ _v H(s) ^ u_ S^ q ffl ^H(s) Mechanical System with n eigenmodes. ffl u Sensor vector with n components. ffl v Actuators vector with n components. u = ^H(s) v Idea: Find two matrices ^S, ^D which diagonalize ^H(s) q = ^S ^H(s) ^D p ffl q Sensor vector each one sensitive to just one eigenmode. ffl p Actuators vector each one acting on just one eigenmode. ffl ^G(s) = ^S ^H(s) ^D Diagonalized System. LI-G324--R

28 Nov. 6-9,2 LVDT Sensors Diagonalization (Direct Transfer Functions) 2 LI SAS: LVDT Rotational Mode (theta) Magnitude 2 3 Two Translational Modes (x, y) Frequency (Hz) LI-G324--R

29 Nov. 6-9,2 LVDT Sensors Diagonalization (Diagonalized Transfer Functions) LI SAS: LVDT Diagonalization 2 Magnitude Two Translational Modes (x. y) Rotational Mode (theta) Frequency (Hz) LI-G324--R

30 Nov. 6-9,2 Normal Mode Ring-Down (Yaw Mode) Amplitude (A.U.) LVTP IP Diagonalization (Yaw Mode Ring Down) f =242.mHz Q = Fit Data time(s) LI-G324--R

31 Nov. 6-9,2 Normal Mode Ring-Down (Y Mode) 3 LVTP IP Diagonalization (Y Mode Ring Down) Amplitude (A.U.) Fit Data.4.2. f =47.8mHz Q = time(s) LI-G324--R

32 Nov. 6-9,2 Normal Mode Ring-Down (X Mode) LVTP IP Diagonalization (X Mode Ring Down) Amplitude (A.U.) Fit Data..8.6 f =45.6mHz Q = time(s) LI-G324--R

33 Nov. 6-9,2 SAS Control : (Recent Results) ffl Position Sensor Diagonalization working ffl Actuator Diagonalization Working ffl Closed the Loops in the 3 DOF Example: Residual Seismic Noise Spectral Density DOF : y (Very Preliminary Result) Relative Seismic Noise Spec. Dens (Vrms/Sqrt(Hz)) Gain too high 3 2 Frequency (Hz) LI-G324--R