For decades, improved theory and experiment of the n=2 3 P fine structure of helium have allowed for increasingly-precise tests of quantum electrodynamics, determinations of the fine-structure constant α, and limitations on possible beyond-the-Standard-Model physics. Here we use the new frequency-offset separated-oscillatory-fields (FOSOF) technique to measure the 2 3 P2→ 2 3 P1 interval. Our result of 2 291 176 590(25) Hz represents a major step forward in precision for helium fine-structure measurements.

Four billion positrons (e +) are accumulated in a Penning-Ioffe trap apparatus at 1.2 K and <6×10 −17 Torr. This is the largest number of positrons ever held in a Penning trap. The e + are cooled by collisions with trapped electrons (e −) in this first demonstration of using e − for efficient loading of e + into a Penning trap. The combined low temperature and vacuum pressure provide an environment suitable for antihydrogen (H) production, and long antimatter storage times, sufficient for high-precision tests of antimatter gravity and of CPT.

We present a Lyman-α laser developed for cooling trapped antihydrogen. The system is based on a pulsed Ti:sapphire laser operating at 729 nm that is frequency doubled using an LBO crystal and then frequency tripled in a Kr/Ar gas cell. After frequency conversion, this system produces up to 5.7 μW of average power at the Lyman-α wavelength. This laser is part of the ATRAP experiment at the antiproton decelerator in CERN.