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Rizzato, F. B.

Paper Title Page
THPMN002 Nonlinear Dynamics of Electromagnetic Pulses in Cold Relativistic Plasmas 2707
  • A. Bonatto, R. Pakter, F. B. Rizzato
    IF-UFRGS, Porto Alegre
  Funding: CNPq, Brasil

In the present analysis we study the self consistent propagation of nonlinear electromagnetic pulses in a one dimensional relativistic electron-ion plasma, from the perspective of nonlinear dynamics. We show how a series of Hamiltonian bifurcations give rise to the electric fields which are of relevance in the subject of particle acceleration. Nonlinear coupling of plasma waves and electromagnetic pulses triggers strong chaotic dynamics which may detrap the plasma wave from the electromagnetic pulse, leading to wave breaking. Connections with results of earlier analysis are discussed.

THPAN002 A Self-Consistent Model for Emittance Growth of Mismatched Charged Particle Beams in Linear Accelerators 3220
  • R. P. Nunes, R. Pakter, F. B. Rizzato
    IF-UFRGS, Porto Alegre
  Funding: CNPq, Brazil

The goal of this work is to analyze the envelope dynamics of magnetically focused and high-intensity charged particle beams. As known, beams with mismatched envelopes decay into its equilibrium state with a simultaneous increasing of emittance. This emittance growth implies that, in the stationary regime, the transverse phase-space of the beam is characterized by a tenuous population of hot particles around a dense population of cold particles. To describe this emittance growth, it was used the test-particle approach for the development of a simplified self-consistent macroscopic model, whose self-consistency is a result of the inclusion of the emittance growth into the envelope equation. The model is then compared with full N-particle beam simulations and the agreement is shown to be quite reasonable. The model revealed to be useful to understand the physical aspects of the problem and is computationally faster when compared with full simulations.

THPAN003 Image Effects on the Transport of Intense Beams 3223
  • R. Pakter, Y. Levin, F. B. Rizzato
    IF-UFRGS, Porto Alegre
  Funding: CNPq and FAPERGS, Brazil, and U. S. AFOSR Grant No. FA9550-06-1-0345.

We start by analyzing the image effects of a cylindrical conducting pipe on a continuous beam with elliptical symmetry. In particular, we derive an exact expression for the self-field potential of the beam inside the pipe without using any sort of multipole expansion. By means of a variational method, the potential for beams with varying density profiles along an elliptical shape is used to search for equilibrium solutions for intense beams. For that, we assume a uniform focusing in the smooth-focusing approximation. A curious result is that the product of the rms sizes along the ellipsis semi-axis stays constant as the pipe radius is varied. Finally, we prove that despite the nonlinear forces imposed by the image charges of an arbitrary shape conducting pipe, intense beams in uniform focusing fields preserve a uniform density in the equilibrium.

FRPMN007 Image Charge Effects in Dynamics of Intense Off-Axis Beams 3880
  • K. Fiuza, R. Pakter, F. B. Rizzato
    IF-UFRGS, Porto Alegre
  Funding: CNPq, Brasil.

This paper analyzes the combined envelope-centroid dynamics of magnetically focused high-intensity charged beams surrounded by conducting walls. Similarly to the case were conducting walls are absent, we show that the envelope and centroid dynamics decouples from each other. Mismatched envelopes still decay into equilibrium with simultaneous emittance growth, but the centroid keeps oscillating with no appreciable energy loss. Some estimates are performed to analytically obtain some characteristics of halo formation seen in the full simulations.

FRPMN008 Wave Breaking and Particle Jets in Inhomogeneous Beams 3886
  • R. P. Nunes, Y. Levin, R. Pakter, F. B. Rizzato
    IF-UFRGS, Porto Alegre
  Funding: CNPq, Brasil and AFOSR under grant FA9550-06-1-0345.

We analyze the dynamics of inhomogeneous, magnetically focused high-intensity beams of charged particles. While for homogeneous beams the whole system oscillates with a single frequency, any inhomogeneity leads to propagating transverse density waves which eventually result in a singular density build up, causing wave breaking and jet formation. The theory presented in this paper allows to analytically calculate the time at which the wave breaking takes place. It also gives a good estimate of the time necessary for the beam to relax into the final stationary state consisting of a cold core surrounded by a halo of highly energetic particles.