GSI, Darmstadt
The FAIR accelerator project at GSI should increase the intensity of primary proton and heavy ion beams by up to two orders of magnitude, relative to the existing GSI facility. In addition to the design of the new synchrotrons and storage rings, the intensity upgrade of the existing UNILAC linac and SIS-18 synchrotron plays a key role for the FAIR project. In order to reach the FAIR design beam parameters several challenges related to operation with high brightness, high current beams in SIS-18 and in the new SIS-100 have to mastered. Important issues are
- the minimization of beam loss caused by space charge induced resonance crossing and the identification of appropriate working points.
- The control of coherent beam instabilities in the presence of space charge, image currents and different ring impedance sources.
- Beam quality conservation during the rf cycle.
- The control of dynamic vacuum pressure during operation with medium charge state heavy ions.
GSI, Darmstadt
The head-tail instability is a well known intensity limitation for hadron bunches in synchrotrons. The instability has been observed in several synchrotrons and storage rings. Also for the FAIR synchrotrons the head-tail instability represents a potential intensity limitation. In the SIS-18 and SIS-100 synchrotrons space charge effects together with image currents play an important role for the determination of the instability threshold. In this work we study head-tail modes using 3D particle simulations for SIS100 beam parameters. The unstable modes are driven by the resistive wall impedance. Space-charge and image currents are taken into account. The possibility to include space charge into long-term simulations, which are necessary for head-tail instability studies, is investigated using the HEADTAIL code and the PATRIC code, developed at GSI. Potential instability cures will be discussed.