A new torsion pendulum for gravitational reference sensor technology development

Area of Science:

• Physics
• Astrophysics
• Geophysics

Background:

• Ultra-precise inertial sensors are crucial for space-based gravitational wave observatories and geodesy missions.
• Existing technologies require further development to meet the sensitivity demands of these applications.

Purpose of the Study:

• To design and characterize a novel torsion pendulum for measuring the performance of ultra-precise inertial sensors.
• To explore its potential for advancing technologies in gravitational wave detection and geodesy.

Main Methods:

• A 1-meter tungsten fiber supports an aluminum crossbar with four hollow cubic test masses within a vacuum system.
• Capacitive sensors provide readout and actuation for two test masses, with controlled electrical charge via photoemission.
• A laser interferometer complements the capacitive readout for displacement measurement.

Main Results:

• The capacitive readout achieves a broadband sensitivity of 30 nm/√Hz.
• The laser interferometer offers a sensitivity of approximately 0.5 nm/√Hz.
• The pendulum exhibits a residual torque noise of ~200 fN/√Hz at 2 mHz, a factor of 20 above the fiber's thermal noise limit.

Conclusions:

• The developed torsion pendulum demonstrates high sensitivity suitable for ultra-precise inertial sensing.
• This technology is a promising development for future space-based gravitational wave observatories and geodesy missions.
• Further optimization is needed to approach the thermal noise limit of the fiber.