[en] This paper reports on an approach to investigate the dynamics of halo particles in mismatched charged-particle beams propagating through periodic-focusing channels using the particle-core model. The proposed method employs canonical transformations to minimize, in new phase-space variables, the flutter due to the periodic focusing to allow making stroboscopic plots. Applying this method, we find that in periodic-focusing systems, certain particles initially not in the halo region can be brought into resonance with the core oscillation to become halo particles. (c) 2000 The American Physical Society

[en] It is shown that there exists a new class of cold-fluid corkscrewing elliptic beam equilibria for ultrahigh-brightness, space-charge-dominated beam propagation through a linear focusing channel consisting of uniform solenoidal, periodic solenoidal, and/or alternating-gradient quadrupole focusing magnets in an arbitrary arrangement including field tapering. The equilibrium beam density and flow velocity profiles and equilibrium self-electric and self-magnetic fields are determined by solving generalized beam envelope equations. In proper limits, such cold-fluid corkscrewing elliptic beam equilibria recover many familiar beam equilibria in beam physics, including the round rigid-rotor Vlasov beam equilibria in uniform and periodic solenoidal focusing fields and the Kapchinskij-Vladimirskij beam equilibrium in an alternating-gradient quadrupole focusing field. For beams with negligibly small emittance, the equilibrium solutions are validated with self-consistent simulations. Examples and applications of the present equilibrium beam theory are discussed. As an important application of the present equilibrium beam theory, a general technique is developed and demonstrated with an example to control large-amplitude density and flow velocity fluctuations (such as beam hollowing and halo formation) often observed in ultrahigh-brightness beams. (c) 2000 The American Physical Society

[en] Ionization cooling in solenoidal channels, such as that envisioned for the future muon colliders or neutrino factories, is studied. Assuming that the interaction with the ionization material is weak, the evolution of the transverse emittance and angular momentum can be determined analytically. Simple and practical formulas are derived for a general cooling configuration as well as for periodic channels. The prediction of these formulas agrees well with those obtained from simulation codes. The method developed here should be useful to other areas of beam physics involving solenoidal focusing. (c) 2000 The American Physical Society

[en] This paper considers an intense non-neutral charged particle beam propagating in the z-direction through a periodic focusing quadrupole magnetic field with transverse focusing force, -κ_q(s)[xe_x-ye_y], on the beam particles. Here, s=β_bct is the axial coordinate, (γ_b-1)m_bc² is the directed axial kinetic energy of the beam particles, q_b and m_b are the charge and rest mass, respectively, of a beam particle, and the oscillatory lattice coefficient satisfies κ_q(s+S)=κ_q(s), where S is the axial periodicity length of the focusing field. The particle motion in the beam frame is assumed to be nonrelativistic, and the Vlasov-Maxwell equations are employed to describe the nonlinear evolution of the distribution function f_b(x,y,x^',y^',s) and the (normalized) self-field potential ψ(x,y,s)=q_bφ(x,y,s)/γ_b³m_bβ_b²c² in the transverse laboratory-frame phase space (x,y,x^',y^'), assuming a thin beam with characteristic radius r_b<< S. It is shown that collective processes and the nonlinear transverse beam dynamics can be simulated in a compact Paul trap configuration in which a long non-neutral plasma column (L>>r_p) is confined axially by applied dc voltages V=const on end cylinders at z=±L, and transverse confinement in the x-y plane is provided by segmented cylindrical electrodes (at radius r_w) with applied oscillatory voltages ±V₀(t) over 90 degree sign segments. Here, V₀(t+T)=V₀(t), where T=const is the oscillation period, and the oscillatory quadrupole focusing force on a particle with charge q and mass m near the cylinder axis is -mκ_q(t)[xe_x-ye_y], where κ_q(t)≡8qV₀(t)/πmr_w². (c) 2000 American Institute of Physics

[en] In colliding-beam facilities, the ''final-focus system'' must demagnify the beams to attain the very small spot sizes required at the interaction points. The first final-focus system with local chromatic correction was developed for the Stanford Linear Collider, where very large demagnifications were desired. This same conceptual design has been adopted by all of the future linear collider designs as well as the Superconducting Super Collider, the Stanford and KEK B Factories, and the proposed Muon Collider. In this paper, the overall layout, physics constraints, and optimization techniques relevant to the design of final-focus systems for high-energy electron-positron linear colliders are reviewed. Finally, advanced concepts to avoid some of the limitations of these systems are discussed. (c) 2000 The American Physical Society