BASE STEP
BASE-STEP: The transportable Penning-trap system for the relocation of antiproton precision measurements.
Our Mission
Our aim is to establish the offline operation of antiproton precision measurements outside of CERN’s Antimatter Factory, to enable the next generation of antiproton precision measurements without fluctuations and noise induced by the machines and experiments operation in the antiproton decelerator complex.
We have constructed the transportable Penning trap system BASE-STEP that is capable of transporting charged particles by crane and on a truck in an autonomous operation mode, i.e. without external power supply for up to 4 hours duration.
How does it works?
The BASE-STEP system is designed to store antiprotons and other charged particles and transport them over long distances. Since antiprotons annihilate upon contact with normal matter, they must be kept in an ultra-high vacuum environment, specifically at pressures below 10⁻¹⁶ mbar. This vacuum prevents annihilation caused by collisions with residual gas molecules over periods of several months. To achieve this, the antiprotons are stored in a cryogenic vacuum chamber, where the walls are maintained at liquid helium temperature (4.2 K). At such low temperatures, any residual gas present within the chamber freezes onto the cold walls.
The antiprotons are confined within a Penning trap, an ion trap configuration that uses a combination of electric and magnetic fields to keep them suspended at the center of the chamber. A magnetic field generated by a superconducting electromagnet forces the antiprotons into circular motion around the field lines. An electric field, maintained by voltages applied to a stack of cylindrical electrodes, pulls the antiprotons back to the trap’s center along the direction of the magnetic field lines.
Project Development and Results
The design work and construction of the BASE-STEP trap system was conducted in the Institute for Physics, at Johannes Gutenberg University of Mainz (2020-2022), commissioned at CERN (2023-2024), and operated at CERN (2024) and at HHU with protons (2024-2025).
We have published the results from the design and commissioning phase in Review of Scientific Instruments: read here. Our paper was selected for the cover of the November 2023 issue (see here).
In 2024, we have trapped and transported a cloud of protons on CERN’s Meyrin site using the antiproton experiment zone of BASE-STEP as start and destination for the trip. CERN promoted this action on their news site (read here) and footage from the transport can be found here (see here). The scientific publication of this work is currently in progress.
Future work
Our next milestone is to transport antiprotons on CERN’s Meyrin site in our trap system to demonstrate the feasibility of relocating antiprotons into other laboratories near the Antimatter Factory. Following this, we will establish long distance transport by upgrading the transportable trap with a power generator on the truck to reach our laboratory at HHU with antiprotons.
Transportable antiproton traps will play a key role to establish offline precision measurements with antiprotons and contribute to improve CPT invariance tests by high-precision measurements with protons and antiprotons. The technology can also be applied to other exotic ions like accelerator produced highly charged ions, or other antimatter ions that may become accessible in the future, for example, the positive antihydrogen ion, the antideuterium ion, or the antihydrogen molecular ion.
Funding
This work is funded by an ERC starting grant (ERC StG 2019, STEP, grant no. 852818), Heinrich Heine University, Johannes Gutenberg University of Mainz, RIKEN, the Max Planck Society, CERN, and supported by the other institutes in the BASE collaboration.
