A nonlinear analysis of the transport of breathing beams considering nonaxisymmetric perturbations is performed. It is shown that large-amplitude breathing oscillations of an initially round beam may couple nonlinearly to quadrupole-like oscillations, such that the excess energy initially constrained to the axisymmetric breathing oscillations is allowed to flow back and forth between breathing and quadrupole-like oscillations. In this case, the beam develops an elliptical shape with a possible increase in its size along one direction as the beam is transported. This is a highly nonlinear phenomenon that occurs for large mismatch amplitudes on the order of 100% and is found to be particularly relevant for space-charge-dominated beams with K≳k0ϵ, where K is the beam perveance, k0 is the vacuum phase advance per unit axial length, and ϵ is the emittance of the beam. A simple model based on mapping techniques is used to clarify the mechanism that leads to the energy exchange between the modes and is tested against results from direct integration of the envelope equations.
New improvements on the Kansas State University cryogenic electron beam ion source, a user facility for low energy, highly charged ions Rev. Sci. Instrum. 71, 902 (2000
For the purpose of material studies for future nuclear fusion reactors, the IFMIF deuteron beams present a simultaneous combination of unprecedentedly high intensity (2 × 125 mA CW), power (2 × 5 MW) and space charge. Special considerations and new concepts have been developed in order to overcome these challenges. The global strategy for beam dynamics design of the 40 MeV IFMIF accelerators is presented, stressing on the control of micro-losses, and the possibility of online fine tuning. Start-to-end simulations without and with errors are presented for the prototype accelerator. Considerations about conflicts between halo and emittance minimization are then discussed in this very high space charge context.
This work presents an energy criterion to define the halo of homogeneous and mismatched charged particle beams. In the simulations used in this work, the beam is considered to be azimuthally symmetric, initially cold and is confined by an external constant magnetic field inside a cylindrical conducting pipe. The energy criterion is established through the analysis of the beam energy distributions with time. The obtained results are in reasonable agreement with the past results that considered the beam phase-space topology, for many values of the beam initial envelope mismatch.
For very high intensity accelerators, not only beam power but also space charge is a concern. Both aspects should be taken into consideration for any analysis of accelerators aiming at comparing their performances and pointing out the challenging sections. As high beam power is an issue from the lowest energy, careful and exhaustive beam loss predictions have to be done. High space charge implies lattice compactness making the implementation of beam diagnostics very problematic, so a clear strategy for beam diagnostic has to be defined. Beam halo is no longer negligible. Its dynamics is different from that of the core and plays a significant role in the particle loss process. Therefore, beam optimization must take the halo into account and beam characterization must be able to describe the halo part in addition to the core one. This paper presents the advanced concepts and methods for beam analysis, beam loss prediction, beam optimization, beam diagnostic, and beam characterization especially dedicated to very high intensity accelerators. Examples of application of these concepts are given in the case of the IFMIF accelerators.
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