Using DWS Optical Readout to Improve the Sensitivity of Torsion Pendulum.

Area of Science:

• Space physics
• Gravitational wave detection
• Precision measurement

Background:

• Drag-free systems are crucial for space gravitational wave detection to maintain ultralow-noise environments for test masses.
• Ground verification is essential to assess the shielding and compensation capabilities against stray force noises.

Purpose of the Study:

• To design and analyze a hybrid apparatus for ground verification of drag-free systems.
• To propose and test a differential wavefront sensing (DWS) optical readout technique for enhancing torsion pendulum sensitivity.

Main Methods:

• A hybrid apparatus combining a traditional torsion pendulum with DWS optical readout was designed and analyzed.
• Readout resolution experiments were conducted on a custom-built optical bench.

Main Results:

• The DWS optical readout achieved an angular resolution of 10 nrad/Hz^1/2 across the measurement band.
• The sensitivity of the torsion pendulum was significantly improved compared to an autocollimator.
• Expected background noise levels of 4.5 × 10^-15 Nm/Hz^1/2 at 10 mHz were projected.

Conclusions:

• The proposed DWS technique offers enhanced sensitivity for torsion pendulum systems.
• This method is suitable for ground verification of drag-free systems and potential upgrades for future missions.