FAIR (Facility for Antiproton and Ion Research in Europe)

The existing GSI accelerator facilities as well as the planned facilities within the FAIR project are the focus of the department's activities. Furthermore, there is close cooperation with the major European research facility CERN and with Brookhaven National Laboratory (USA).

Picture: I. Karpov
Filamentation of a beam injected into a circular machine with an error in position with respect to the design orbit
Distribution of longitudinal momentum deviation over time for laser cooling process of Li-like Sn-ions

Collective effects in ion beams

Important performance parameters of modern accelerator facilities are primarily the intensity and quality of the accelerated ion beam. These are mainly limited by collective effects, which are caused by the electromagnetic interaction of the beam ions with each other (space charge), with the accelerator environment (impedances) and with secondary electrons (electron clouds).

Electron cloud pinch in the field of an offcentered bunch
Animation of the dipolar electric field at constant frequency f=100MHz in a cross-section of a SIS100 kicker magnet (U. Niedermayer)

Resistive wall impedance is the main cause of instabilities in synchrotrons and storage rings. The real part of the dipolar transverse coupling impedance can drive transverse beam instabilities. For SIS18 as well as in the planned SIS100, the resistive part of the transverse Koppel impedance is dominated by the beam tube at low frequencies.

To reduce eddy current effects during the magnetic ramp, the SIS100 beamline will be very thin. Due to mechanical and vacuum reasons, the SIS100 beamline will be built with stabilising struts and cooling tubes. For such complicated structures, the coupling impedance can no longer be determined analytically, but must be calculated with numerical 3D electromagnetic frequency-domain simulations. For calculating the coupling impedance of accelerator elements, the software CST Particle Studio can be used, for example. However, the department also develops its own tools for calculating beam coupling impedances in the frequency domain. We will be happy to provide you with some of these tools; please contact us personally!