Antiproton Decelerator

Antiproton Decelerator. The Antiproton Decelerator is a unique storage ring at the CERN laboratory designed to produce and slow down low-energy antiprotons for precision experiments. It serves as the world's primary source of low-energy antimatter, enabling groundbreaking studies in fundamental symmetry tests and the properties of antihydrogen. This facility is central to CERN's antimatter physics program, supporting collaborations like the ALPHA, ASACUSA, and ATRAP experiments.

Overview

The primary function of the Antiproton Decelerator is to take antiprotons produced at high energies and decelerate them to speeds manageable for detailed study. Located at the CERN complex near Geneva, it succeeded the earlier Low Energy Antiproton Ring (LEAR). The machine cools and stores antiprotons at energies as low as 100 keV, which are then extracted and delivered to various connected experiments. This capability is essential for creating and trapping neutral antimatter atoms, such as antihydrogen, and for conducting high-precision comparisons between matter and antimatter.

History and Development

The development of the Antiproton Decelerator was driven by the scientific legacy of the Low Energy Antiproton Ring, which operated until 1996 and conducted pioneering work like the PS210 experiment that first produced atoms of antihydrogen. Following the closure of LEAR, CERN approved the construction of this dedicated, lower-cost decelerator to continue and expand low-energy antimatter research. The machine was built in the same tunnel as the former Initial Cooling Experiment (ICE) and began operations in the year 2000. Its commissioning marked a new era, consolidating CERN's antimatter program under a single, efficient facility supported by the CERN Research Board.

Technical Design and Operation

The Antiproton Decelerator is a circular vacuum chamber with a circumference of 182 meters, utilizing a combination of magnetic and electric fields to control particle beams. Antiprotons are initially produced by directing a high-energy proton beam from the Proton Synchrotron onto a metal target, such as iridium. The resulting antiprotons, with an energy of 3.57 GeV, are injected into the decelerator ring. Over approximately one minute, the machine uses radio frequency systems to reduce their energy down to 5.3 MeV, while techniques like stochastic cooling and electron cooling are applied to shrink and cool the beam. Finally, the antiprotons are further decelerated to just 100 keV before being ejected in short pulses to the experimental zones.

Scientific Research and Experiments

Research at the Antiproton Decelerator focuses on precision tests of fundamental physics, primarily through the creation and study of antihydrogen. The flagship ALPHA experiment successfully trapped antihydrogen atoms and has performed detailed spectroscopy to compare their properties with those of ordinary hydrogen, testing CPT symmetry. The ASACUSA collaboration has developed techniques to produce beams of antihydrogen for hyperfine structure measurements. The ATRAP experiment also studies antihydrogen formation and spectroscopy. Other experiments, like BASE, use trapped antiprotons for ultra-precise measurements of the antiproton magnetic moment and the antiproton-to-proton charge-to-mass ratio, providing stringent tests of the Standard Model.

Future Developments and Upgrades

The future of the facility is closely tied to the new ELENA (Extra Low ENergy Antiproton) ring, which began operation in 2021. ELENA further decelerates antiprotons from the Antiproton Decelerator to just 100 keV, significantly improving trapping efficiency for experiments. This upgrade, along with ongoing improvements to beam instrumentation and cooling techniques, will enhance the precision of existing experiments like ALPHA and GBAR. These developments support the long-term goal of conducting gravity measurements on antimatter and performing ever-more sensitive tests of fundamental symmetries, potentially revealing physics beyond the Standard Model.

Category:Particle accelerators Category:Antimatter Category:CERN