MESA in Mainz: Progress on the next big physics adventure!

MESA in Mainz: Progress on the next big physics adventure!

The construction of the energy-recovery particle accelerator MESA (Mainz Energy-recovery Accelerator) at the Johannes Gutenberg University Mainz (JGU) is taking shape. On April 10, 2025, a vacuum chamber weighing over 3 tons was delivered, which is crucial for the ongoing research projects. This delivery follows the installation of a 21 tonne superconducting magnet in November 2024, further demonstrating the progress of the project. MESA is not only part of the Mainz Cluster of Excellence PRISMA+, but also opens up new possibilities in basic research in physics.

A central goal of MESA are the two main experiments, MAGIX and P2, which are intended to contribute to the research of the so-called “new physics”. The focus of the P2 experiment is the precise measurement of the weak mixing angle in order to clarify open questions in elementary particle physics. The new vacuum chamber has an impressive length of 7 meters and a diameter of 2.4 meters, giving a volume of 32 cubic meters. This condition is important because the chamber creates the necessary vacuum for the target cell, which must operate at extremely low temperatures of around -257 degrees Celsius.

Technological challenges and solutions

Liquid hydrogen is stored in this target cell, the volume of which is around 70 liters. The chamber's vacuum not only serves as insulation, but also ensures that the heat generated by the electron beam onto the target cell is efficiently dissipated by a helium cooler. The vacuum chamber also contains a silicon pixel detector in the rear part that measures the momentum of the electrons. A special feature is the vacuum window, made of carbon fiber reinforced epoxy resin, which is attached between the front and rear parts of the chamber.

The vacuum chamber itself is made of high-strength aluminum alloy, which is equipped with special metal seals to ensure high radiation resistance. It was designed to fit into the superconducting magnet, which means its shape must be very round.

Funding and further steps

The development work on the P2 experiment benefited from funding from the PRISMA+ Cluster of Excellence and the large-scale equipment program of the German Research Foundation (DFG). At the same time, the development of the technologies used in projects such as MESA is also being driven forward through international collaborations. One example is the International Linear Collider (ILC), which relies on superconducting accelerator technology, which offers advantages such as low power losses and high quality of the particle beams. These technologies have been developed by institutions such as DESY and the TESLA Technology Collaboration since the 1990s and provide a valuable background for current developments in Mainz.

Overall, MESA is an outstanding example of modern particle physics that is at the forefront of technological advances in recent years and enables university research at an international level.