The Mainz Microtron, a four stage microtron-cascade called MAMI-C, is the central research facility at the Institute for Nuclear Physics.  It supplies an electron beam with a maximum energy of 1558 million electron-volts (MeV). MAMI‘s outstanding qualities include a beam current of up to 100µA, an energy spread of less than 10^-4, as well as excellent reliability, yielding more than 7000 beam time hours per year. 

The Mainz Energy-recovery Superconducting Accelerator (MESA) is presently under construction. Using energy-recovery and superconductivity, it will deliver a beam current more than 10 times higher than MAMI at less than 50% of the power consumption. This will enable new particle physics experiments that were hitherto not possible. 

Both the MAMI and MESA accelerators can provide a spin polarization of the beam larger than 80%, thus allowing for the observation of spin-sensitive observables at all experimental stations.

Spin-polarized electron beams are a key ingredient for experiments in hadron and particle physics since they allow for the investigation of the spin-dependence of fundamental forces. The aim of our group is the production, manipulation, and analysis of such beams. The production requires the control of special semiconductors – superlattices – in which the angular momentum of circular polarized laser light is transferred to the spin of the electrons. Extracting such electrons from the semiconductor requires the application of special methods from surface science, and forming them into a useful beam as well as manipulating the spin vector of the electrons is a challenging task for accelerator beam dynamics. Finally, to make precision experiments possible, the analysis of the ratio between “spin up” and “spin down” electrons in the beam must be as accurate as possible. This is achieved by specific electron scattering reactions such as Mott- and Möller-scattering.  All materials and methods mentioned here are subject to constant optimization and offer a multitude of subjects for bachelor’s, master’s, and doctoral theses.

The UNILAC working group is responsible for operating and further developing the UNILAC heavy-ion accelerator at GSI. In the initial FAIR Phase 0, our top priority is to ensure smooth and reliable beam operations. The team plans, organizes, and manages the required beam time and shutdown periods; during beam time, group members provide on-call support 24/7. In preparation for the planned commissioning and operational phase of the FAIR accelerator facility, various system components must be replaced or optimized—work that is likewise planned and coordinated by the group.

The working group is also responsible for development of the superconducting linear accelerator HELIAC (HElmholtz LInear ACcelerator). At the GSI Helmholtzzentrum für Schwerionenforschung, HELIAC will deliver heavy-ion beams with energies from 3.5 to 7.6 MeV/u (A/Z = 6). Thanks to superconducting radio-frequency (RF) technology, it will provide high average beam currents in continuous-wave (cw) operation. The RF resonators of the crossbar H-mode (CH) type are being developed in collaboration with the Institute for Applied Physics (IAP) at Goethe University Frankfurt. Their basic suitability for ion-beam acceleration was demonstrated in an earlier phase of the project. In the current advanced demonstrator stage, an extended beam test with the first fully equipped series cryomodule is planned at GSI. The required infrastructure has been established in recent years: in addition to a radiation-shielded area connected to the on-site 4 K helium liquefier, essential preparations were completed at the Helmholtz Institute Mainz (HIM), where the superconducting resonators were individually performance-tested and a spacious ISO Class 4 cleanroom was commissioned to enable the high-purity assembly of superconducting RF structures. This work involves close cooperation with specialist departments across the GSI accelerator division and with internal and external user communities, including partners at Johannes Gutenberg University Mainz (JGU) and HIM.