Compact Advanced Passive Isolation Stages

Transcription

1 Compact Advanced Passive Isolation Stages for Third Generation Gravitational Wave Detectors Li Ju, Jean-Charles Dumas, Siddartha S Verma, Chunnong Zhao, David Blair

2 Outline Requirements for 3 rd generation detectors Review of available technologies Comparison of isolation techniques New Approaches Euler LaCoste vertical stage Roberts linkage horizontal stage with internal actuation

3 Motivation 3 rd generation detectors aiming to achieve GW detection sensitivity ~1Hz ET vibration isolation concept proposed 17m - 50m super attenuator type chains Can ET isolation performance be obtained in a compact design? S. Hild et al, Class. Quantum Gravi. 27 (2010)

4 Different Ultralow Frequency Stages Vertical Geometric Anti-Spring (GAS) LaCosta Stage m #"!" $ %"! &" O' Horizontal Invert Pendulum Roberts Linkage m m Blade springs, Euler springs

5 Comparison of Different Techniques Synthetic Pendulums (horizontal) Invert Pendulum Roberts Linkage m m Technique Compressive flexure Tensile wire Stress High compressive stress Pure tension Internal modes Long rods Tensile wire violin

6 Comparison of Different Techniques Synthetic Vertical Stages GAS LaCoste (with coil springs) #" $ %" Zero length spring $ % " " m!"! O' $"!'" (" Stress Internal modes High stressed negative springs (load orthogonal to stress) Blade spring modes Stability Dislocation flows * Creep &" Pre-stressed zero length springs Coil spring normal modes *R. DeSalvo, A. DiCintio and M. Lundin, Eru. Phys. J. Plus, 126:75 (2011)

7 Concept of Zero Length Spring Force negative length spring zero length spring positive length spring -l 0 L 0 L Displacement!l =L-L 0 (positive length spring, initial length l 0 =L 0 )!l =L (zero length spring, effective initial length l 0 =0)!l=L+l (negative length spring, effective initial length l 0 =-l)

8 P Euler springs l

9 Comparison of blade springs & Euler Springs Blade Springs Euler Springs Stored energy mgδl small, mgδl 1 ~10-2 mgδl Spring mass ~kg ~grams Stress High Low Compressive stress Frequency with load Internal f of spring element Low Fixed by deflection Low High Tunable (f~l length pendulum) High

10 Can we combine benefits of Euler spring with low frequency performance of a LaCoste stage?

11 Euler Spring Module for Use in LaCoste Stage High tensile strength Maraging steel Stable Tensional Euler module Under tension Stable tensional Euler Module

12 Euler spring module performance (ring) y = x Force (N) Displacement (m)

13 Euler-LaCoste Prototype Parameters: Spring blades: length: 260mm width: 20mm thickness: 0.5mm Load: ~20kg Extended wires+ negative length Euler spring to realize zero length spring

14 Frequency tuning with x-offset Frequency (Hz) mm 290mm 280mm 270mm 260mm Δx (mm) f~0.15hz so far Expect improvement with better engineered structure Expect lower frequency with large scaled structure f (Hz) Euler-LaCoste Prototype Frequency Tuning Frequency tuning with h-offset L=432mm L=410mm L=395mm L=385mm D h (mm)

15 Large Scale Euler-LaCoste Design concept 4 Euler modules replacing the coil springs Height: 1m Maraging steel blades : 350mm x 20mm x 1.5mm thick Max stress: 30% of yield (no observable creep*) Load: 800kg Expected frequency: 50mHz *Virdone, J. Agresti, et.al., Nucl. Instr. and Meth. A, 593, (2008)

16 Roberts Linkage Horizontal Stage P moving in a shallow potential path f~50mhz

17 Improve the low frequency performance through thermal actuation Electrical current through the suspension wire DC to compensate slow drift* AC (low frequency) signal from the bottom of the chain feedback to Roberts Linkage to suppress low frequency vibration *J.C. Dumas et al. Rev. Sci. Instrum. 80, (2009)

18 Transfer function at low frequency

19 Conclusions Euler springs allow tunable vertical suspension frequencies 0.3-1Hz Euler-LaCoste allows 50mHz main suspension Robets allows 20mHz horizontal suspension low frequency (~50mHz) pre-isolation stages Elegant actuation system through resistive heating of suspension wires These stages could allow improved performance and more compact design for 3 rd generation detectors