1. Torsion Pendulum Dual Oscillator (TorPeDO) David McManus, Min Jet Yap, Robert Ward, Bram Slagmolen, Daniel Shaddock, David McClelland

2. TorPeDO system: A Low Frequency Gravitational Force Sensor Why? Measuring Newtonian noise Early earthquake detection Measuring Quantum Radiation Pressure Noise Testing semi-classical gravity Measurements of big G 2 Based on the TOBA (M.Ando, et al. 2010) Changes in gravitational force cause a differential rotation between the bars Frequency and COM are matched for common mode cancellation

3. 3 Controls Prototype COM

4. Measurement Systems 4 Optical Lever Higher range, Higher noise Damping and large motion sensing BOSEMs Actuation through coils Lower range, Lower noise Cavity Read-out Main science measurement

5. Measurement Systems 5 Optical Lever Higher range, Higher noise Damping and large motion sensing BOSEMs Actuation through coils Lower range, Lower noise Cavity Read-out Main science measurement

6. Measurement Systems 6 Optical Lever Higher range, Higher noise Damping and large motion sensing BOSEMs Actuation through coils Lower range, Lower noise Cavity Read-out Main science measurement

7. Transfer functions 7 White noise transfer function Driving through coils, measuring through optical lever

8. Resonance Tuning 8

9. 9

10. Next stages for Prototype 10 Damping and Locking / Optical Read-out Move system into vacuum Sensitivity improvements (next slide) Test common mode rejection

11. 11 - Tungsten Susp Wires - Passive 0.5Hz seismic

12. 12 - Fused Silica Susp Wires - Active multi-stage suspension

13. Future Focus Long Term Vision Quantum Radiation Pressure Noise experiment with smaller silicon bars Cryogenic Cooling 13 Potential Problems Magnetic Field Coupling Actuation w.r.t ground Improving suspension

14. Thanks for Listening 14