Our best balances are limited by the thermal noise (Brownian motion) in the torsion fiber. To achieve improved performance, we have built a new balance which is cooled to ~5 K by a pulse tube refrigerator and housed in multiple layers of magnetic and thermal shielding, including a layer of superconducting lead. Further development of noise reduction is ongoing.
Cryogenic balances may allow improved tests of short-range gravitational interaction and new spin dependent interactions, in addition to future Equivalence Principle measurements.
"A Cryogenic Torsion Balance Using a Liquid-Cryogen Free, Ultra-Low Vibration Cryostat," S. M. Fleischer, M. P. Ross, K. Venkateswara, C. A. Hagedorn, E. A. Shaw, E. Swanson, B. R.Heckel, J. H. Gundlach. Review of Scientific Instruments (2022)