Abstract
The particle-core model for a continuous cylindrical beam is used to describe the motion of single particles oscillating in a uniform linear focusing channel. Using a random variation of the focusing forces, the model is deployed as proof of principle for the occurrence of large single particle radii without the presence of initial mismatch of the beam core. Multiparticle simulations of a periodic 3D transport channel are then used to qualify and quantify the effects in a realistic accelerator lattice.
Highlights
In high-intensity hadron linacs, parametric 2:1 resonances between coherent oscillations of a mismatched beam core and single particle oscillations are regarded as one of the major sources of beam halo
Using a simple particle-core model one can show that statistical errors can excite oscillations of the beam core which can via parametric resonances, transfer energy to single particles. 3D simulations for a periodic transport channel show that this mechanism results in rms emittance growth and initiates the development of a low-density beam halo surrounding the core
The process scales more or less linearly with the error amplitude and the length of the transport channel but seems to be almost insensitive to the type of particle distribution that is chosen in 3D simulations
Summary
In high-intensity hadron linacs, parametric 2:1 resonances between coherent oscillations of a mismatched beam core and single particle oscillations are regarded as one of the major sources of beam halo. Energy transfer from the core to the single particle oscillations [3,4] can drive core particles to large amplitude radii and create a low-density halo surrounding the core This energy transfer can be studied with a simple particle-core model, where single test particles interact with the space charge forces of the core and the external focusing forces of a continuous focusing channel. In the following this approach is used to introduce the workings of initial mismatch and the development of parametric beam halo. The mechanism of halo development due to statistical errors can be especially important for the understanding of halo in ring systems where the effects of initial or distributed mismatch are generally not taken into account
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