Proton transport from the antimatter factory of CERN

Precision measurements using low-energy antiprotons, exclusively available at the antimatter factory (AMF) of CERN¹, offer stringent tests of charge-parity-time (CPT) invariance, which is a fundamental symmetry in the Standard Model of particle physics². These tests have been realized, for example, in antiprotonic helium³ and antihydrogen⁴. In our cryogenic Penning-trap experiments⁵, we measure the magnetic moments^6,7 and charge-to-mass ratios of protons and antiprotons and now provide the most precise test of CPT invariance in the baryon sector⁸. Our experiments are limited by magnetic field fluctuations imposed by the decelerators in the AMF; therefore, we are advancing the relocation of antiprotons to dedicated precision laboratories. Here we present the successful transport of a trapped proton cloud from the AMF using BASE-STEP⁹-a transportable, superconducting, autonomous and open Penning-trap system that can distribute antiprotons into other experiments. We transferred the trapped protons from our experimental area at the AMF onto a truck and transported them across the Meyrin site of CERN, demonstrating autonomous operation without external power for 4 h and loss-free proton relocation. We thereby confirm the feasibility of transferring particles into low-noise laboratories in the vicinity of the AMF and of using a power generator on the truck¹⁰ to reach laboratories throughout Europe. This marks the potential start of a new era in precision antimatter research, enabling low-noise measurements of antiprotons, the charged antimatter ions ${\overline{H}}^{+}$ ¹¹ and ${\overline{H}}_2^{-}$ (ref. ¹²), and other accelerator-produced ions, such as hydrogen-like lead or uranium ions^13,14.