The Mainz Microtron MAMI

The Mainz Microtron MAMI is an accelerator for electron beams run by the Institute for Nuclear Physics of the University of Mainz used for hadron physics experiments. The operation principles including the first levels of operation were developed by Prof. Dr. Helmut Herminghaus in cooperation with Dr. Karl-Heinz Kaiser. It is setup as a multilevel racetrack microtron with a normal conducting linear accelerator. Since 1979 the accelerator has been available for experiments and has continuously undergone further development. With MAMI-C, the latest stage of development, polarised electron beams (polarisation degree typical 80%) of more than 20 µA beam current and unpolarised elecron beams of up to 100 µA can be accelerated to relativistic energies up to 1,5 GeV.

MAMI is a so-called continuous wave accelerator. Thus, the electron beam is not macroscopically clustered in bunches as it is the case for most accelerators; on the contrary, the time structure of the beam is too small to be registered by the experiment’s detectors so that the beam seems like a continuous current. This has the great advantage that the amount of accumulated experimental data is distributed equally rather than being concentrated on short pulses. The accelerator generates a well-defined beam: the beam diameter is few 0.1 mm leaving the energy uncertainty at less than 13 keV. Thus the energy of the elctrons in the beam scatters around the setpoint by approximately 100,000th. The position of the beam is also maintained at a constant position at less than 200 µm via a complex control mechanism.

This device is hence particularly well suited to conduct precision tests on the structure of matter. Research at the Institute especially concentrates on the investigation of subatomic entities which are combined of many particles with strong interaction. To this day, four experimental collaborations with cooperation partners from more than 10 countries have become established at the Institute to run the accelerator.