ELENA

ELENA. The Extra Low Energy Antiproton ring is a unique decelerator installed at the CERN research complex. It is designed to receive antiprotons from the Antiproton Decelerator and cool them to even lower energies, significantly increasing the number of particles available for trapping and study. This facility enables a new generation of high-precision experiments in the field of antimatter physics, allowing scientists to probe fundamental symmetries of the universe with unprecedented accuracy.

Overview

ELENA operates as a specialized storage ring that slows down and cools antiprotons delivered by its predecessor, the Antiproton Decelerator. The machine reduces the kinetic energy of the antiproton beams from 5.3 MeV to just 0.1 MeV upon injection, and further down to a mere 13 keV before extraction. This drastic reduction in energy is crucial for experiments conducted by collaborations such as ALPHA, ASACUSA, ATRAP, and BASE, which require slow-moving antiparticles for efficient trapping. The construction of ELENA was a key upgrade to the CERN Antiproton Decelerator facility, enhancing its scientific output and supporting the research programs of the CERN Physics Department.

Technical Design

The technical design of ELENA centers on a compact, 30.4-meter circumference ring that utilizes sophisticated beam cooling and deceleration techniques. Key components include an electron cooler to reduce the beam's transverse and longitudinal emittance, ensuring a dense and mono-energetic beam, and a system of magnetic septum and electrostatic deflectors for efficient extraction. The ring's lattice is optimized for low-energy operation, incorporating precise dipole magnets and quadrupole magnets for beam steering and focusing. The entire system is housed in the same experimental hall as the Antiproton Decelerator in the CERN Meyrin site, requiring intricate integration with existing beamlines and the ultra-high vacuum systems essential for antimatter research.

Scientific Goals and Applications

The primary scientific goal of ELENA is to facilitate stringent tests of the CPT symmetry by enabling ultra-precise comparisons between the properties of antihydrogen and ordinary hydrogen. Experiments like those conducted by the ALPHA collaboration aim to measure the spectral lines of antihydrogen using techniques such as laser spectroscopy, while the ASACUSA experiment focuses on measuring the hyperfine structure of antiprotonic helium. Other research includes precision measurements of the magnetic moment of the antiproton by the BASE collaboration and studies of gravitational interaction of antimatter. These investigations probe the validity of the Standard Model and seek to understand the matter-antimatter asymmetry observed in the cosmos.

Development and Timeline

The development of ELENA was approved by the CERN Research Board in 2011, following extensive design studies and a successful prototype test of its electron cooler. Major construction took place between 2013 and 2016, involving an international consortium of institutes including the University of Liverpool, the University of Tokyo, and the Max Planck Institute for Nuclear Physics. The first decelerated beam was achieved in 2016, marking a critical commissioning milestone. After a period of technical runs and optimization, the machine was officially inaugurated and began delivering beams to experiments in 2018. The project was managed under the auspices of the CERN Accelerator and Technology Sector.

Operational History

Since commencing routine operation, ELENA has dramatically increased the efficiency of antiproton delivery to its connected experiments, often by orders of magnitude. Its first physics runs supplied beams to the ALPHA experiment for antihydrogen trapping and spectroscopy studies. Subsequent operational periods have supported the BASE experiment's record-precision measurements and the ASACUSA experiment's beamline studies. The facility undergoes regular shutdowns for maintenance and upgrades, synchronized with the broader CERN Long Shutdown schedules, to improve its performance and reliability. Data from ELENA-supported experiments continue to be analyzed and published in leading journals like Physical Review Letters and Nature.

Category:Particle accelerators Category:CERN Category:Antimatter