Superfluid Helium Beam Enables First Direct Gravity Test of Second-Generation Particles
Researchers at ETH Zurich and the Paul Scherrer Institute (PSI) have created a narrow, high-intensity beam of muonium atoms using superfluid helium, overcoming a major technical barrier to testing Einstein’s weak equivalence principle for second-generation particles. The beam, produced by ejecting muonium from helium cooled to 0.2 kelvin, moves at approximately 2.1 km/s with a tight velocity distribution. While no gravitational measurement has been made yet, the setup aims to achieve 1% precision in muonium’s gravitational acceleration within 100 days of future data collection.
