Off-Axis Space-Charge Limit for a Bunched Electron Beam in a Coaxial Conducting Structure

Hess, Mark

doi:10.1109/tps.2008.917163

Cited by 6 publications

(6 citation statements)

References 12 publications

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“…In general, the dynamics of the beams is influenced by multiple effects, including the mismatched envelope (rms radius of the beam) [50-52, 140, 171], movement outside the axis of symmetry [172][173][174][175][176][177], nonuniformities in the beam distribution [145,[178][179][180], and the image forces due to the surrounding conducting walls [181][182][183]. Of all these, the study of parametric resonances resulting from the transverse beam oscillations has attracted the most attention.…”

Section: Non-neutral Plasmasmentioning

confidence: 99%

Nonequilibrium statistical mechanics of systems with long-range interactions

et al. 2014

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Systems with long-range (LR) forces, for which the interaction potential decays with the interparticle distance with an exponent smaller than the dimensionality of the embedding space, remain an outstanding challenge to statistical physics. The internal energy of such systems lacks extensivity and additivity. Although the extensivity can be restored by scaling the interaction potential with the number of particles, the non-additivity still remains. Lack of additivity leads to inequivalence of statistical ensembles. Before relaxing to thermodynamic equilibrium, isolated systems with LR forces become trapped in out-of-equilibrium quasi-stationary state (qSS), the lifetime of which diverges with the number of particles. Therefore, in thermodynamic limit LR systems will not relax to equilibrium. The qSSs are attained through the process of collisionless relaxation. Density oscillations lead to particle-wave interactions and excitation of parametric resonances. The resonant particles escape from the main cluster to form a tenuous halo. Simultaneously, this cools down the core of the distribution and dampens out the oscillations. When all the oscillations die out the ergodicity is broken and a qSS is born. In this report, we will review a theory which allows us to quantitatively predict the particle distribution in the qSS. The theory is applied to various LR interacting systems, ranging from plasmas to self-gravitating clusters and kinetic spin models.

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Section: Non-neutral Plasmasmentioning

confidence: 99%

Nonequilibrium statistical mechanics of systems with long-range interactions

et al. 2014

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“…Unlike the thermodynamic equilibrium of short range interacting systems, the stationary state of the beam will depend explicitly on the initial particle distribution. In this respect, different phenomena, such as, envelope mismatch, [6][7][8][9][10][11][12][13][14][15][16][17] off-axis motion, 13,[18][19][20][21][22] beam distribution nonuniformities, [23][24][25][26][27][28][29][30] and forces due to the surrounding conductors, [31][32][33] have been investigated as the precursors of the beam relaxation. Among these phenomena, the one that has attracted most attention is the envelope mismatch, which arises from the unbalance between the external focusing force and the defocussing space-charge repulsion.…”

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confidence: 99%

Halo formation and emittance growth in the transport of spherically symmetric mismatched bunched beams

et al. 2015

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The effect of an initial envelope mismatch on the transport of bunched spherically symmetric beams is investigated. A particle-core model is used to estimate the maximum radius that halo particles can reach. The theory is used to obtain an empirical formula that provides the halo size as a function of system parameters. Taking into account, the incompressibility property of the Vlasov dynamics and the resulting Landau damping, an explicit form for the final stationary distribution attained by the beam is proposed. The distribution is fully self-consistent, presenting no free fitting parameters. The theory is used to predict the relevant beam transport properties, such as the final particle density distribution, the emittance growth, and the fraction of particles that will be expelled to form halo. The theoretical results are compared to the explicit N-particle dynamics simulations, showing a good agreement.

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“…In general, injected beams may deviate from the equilibrium state because of various effects, such as envelope mismatches [3][4][5][6][7][8][9], off-axis motion [8,[10][11][12][13], nonuniformities in the beam distribution [14][15][16][17][18][19][20], and forces due to the surrounding conductors [21][22][23]. Among all these effects, the one that has attracted most of the attention is the envelope mismatch because it is believed to be a major cause of emittance growth and halo formation.…”

Section: Introductionmentioning

confidence: 99%

“…Using Eqs (12),(13),(15),. and (19), we obtain TARCISIO N. TELES, RENATO PAKTER, AND YAN LEVIN Phys.…”

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confidence: 99%

Emittance growth and halo formation in the relaxation of mismatched beams

Teles

Pakter

Levin

2010

Phys. Rev. ST Accel. Beams

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In this paper, a simplified theoretical model that allows prediction of the final stationary state attained by an initially mismatched beam is presented. The proposed stationary state has a core-halo distribution. Based on the incompressibility of the Vlasov phase-space dynamics, the core behaves as a completely degenerate Fermi gas, where the particles occupy the lowest possible energy states accessible to them. On the other hand, the halo is given by a tenuous uniform distribution that extends up to a maximum energy determined by the core-particle resonance. This leads to a self-consistent model in which the beam density and self-fields can be determined analytically. The theory allows one to estimate the emittance growth and the fraction of particles that evaporate to the halo in the relaxation process. Self-consistent N-particle simulation results are also presented and are used to verify the theory.

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Off-Axis Space-Charge Limit for a Bunched Electron Beam in a Coaxial Conducting Structure

Cited by 6 publications

References 12 publications

Nonequilibrium statistical mechanics of systems with long-range interactions

Nonequilibrium statistical mechanics of systems with long-range interactions

Halo formation and emittance growth in the transport of spherically symmetric mismatched bunched beams

Emittance growth and halo formation in the relaxation of mismatched beams

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