Beam Halo Studies Using a 3-dimensional Particle-core
نویسندگان
چکیده
In this paper we present a study of beam halo based on a three-dimensional particle-core model of an ellipsoidal bunched beam in a constant focusing channel. For an initially mismatched beam, three linear envelope modes – a high frequency mode, a low frequency mode and a quadrupole mode – are identified. Stroboscopic plots are obtained for particle motion in the three modes. With higher focusing strength ratio, a 1:2 transverse parametric resonance between the test particle and core oscillation is observed for all three modes. The particle-high mode resonance has the largest amplitude and presents potentially the most dangerous beam halo in machine design and operation. For the longitudinal dynamics of a test particle, a 1:2 resonance is observed only between the particle and high mode oscillation, which suggests that the particle-high mode resonance will also be responsible for longitudinal beam halo formation.
منابع مشابه
The Effect of Nonlinear Transport on Beam Halo Formation
Halo formation is an important issue in intense charged particle beams because the loss of halo particles can lead to radioactivation of the accelerator. In this paper, we investigate the influence of the addition of nonlinear terms to the linear focusing as a possible mechanism to control halo formation. With nonlinear focusing, the core oscillations can no longer be described by an envelope e...
متن کاملHalo Formation of Bunched Beams in Periodic Focusing Systems
A very critical design issue for high intensity proton linacs is to keep particle loss below 1 W/m at the high energy end and allow unconstrained hand on maintenance. Particle loss is caused by a small number of particles outside the dense beam core, called the beam halo. Halo formation of bunched beams in a periodic focusing channel is driven by mismatch, high space charge and temperature anis...
متن کاملSpace-charge transport limits of ion beams in periodic quadrupole focusing channels
It has been empirically observed in both experiments and particle-in-cell simulations that space-charge-dominated beams suffer strong growth in statistical phasespace area (degraded quality) and particle losses in alternating gradient quadrupole transport channels when the undepressed phase advance σ0 increases beyond about 85 per lattice period. Although this criterion has been used extensivel...
متن کاملHalo Formation and Control
In this report we suggest some approaches to very intricate problem of the halo formation process. It is known that this process leads to the formation of a sufficiently compact core and a spreading cloud halo, which surrounds the core. Our approach to this problem is based on two main objects: initial distribution functions and matrix formalism for Lie algebraic tools for time evolution of par...
متن کاملAnalysis of the beam halo in negative ion sources by using 3D3V PIC code.
The physical mechanism of the formation of the negative ion beam halo and the heat loads of the multi-stage acceleration grids are investigated with the 3D PIC (particle in cell) simulation. The following physical mechanism of the beam halo formation is verified: The beam core and the halo consist of the negative ions extracted from the center and the periphery of the meniscus, respectively. Th...
متن کامل