Speaker
Description
The precise determination of the Newtonian gravitational constant, G, remains one of the most challenging problems in experimental physics, with existing measurements showing significant discrepancies despite continual improvements in accuracy. This work aims to develop a high-precision torsion balance apparatus designed to measure G with a target relative uncertainty of approximately 2 ppm. The experiment design should consist of two independent measurement techniques within the same system—angular acceleration feedback and time-of-swing analysis—allowing systematic effects associated with each method to be investigated and compared directly. The apparatus consists of a rotating outer turntable, attractor masses, and a torsion pendulum, with comprehensive modeling performed to predict the expected gravitational signal and optimize measurement sensitivity. Preliminary studies using a prototype pendulum demonstrate the presence of thermal drift effects, indicating that heat treatment of the suspension fiber can significantly improve signal stability. Several design features have been implemented to minimize uncertainty, including monolithic silicon test masses, increased apparatus dimensions to reduce geometric errors, interferometric position sensing for real-time mass tracking, and the use of a common apparatus for both measurement techniques. By combining multiple methodologies within a single experimental framework, this study aims to provide an improved and internally consistent determination of the gravitational constant and contribute to resolving the long-standing discrepancies among existing measurements of G.
Preliminary measurements using a prototype torsion pendulum revealed significant angular drift. Initial studies indicate that heat treatment of the suspension fiber can improve signal stability and help mitigate drift-related systematic effects.
