arXiv subjects

Stephan I. Tzenov

Publications and source records attributed to Stephan I. Tzenov.

33 records · Page 2Linked to original sources

arXiv2003

Soliton Gas in Space-Charge Dominated Beams

Based on the Vlasov-Maxwell equations describing the self-consistent nonlinear beam dynamics and collective processes, the evolution of an intense sheet beam propagating through a periodic focusing field has been studied. It has been shown that in the case of a beam with uniform phase space density the Vlasov-Maxwell equations can be replaced exactly by the hydrodynamic equations with a triple adiabatic pressure law coupled to the Maxwell equations. We further demonstrate that starting from the system of hydrodynamic and Maxwell equations a set of coupled nonlinear Schrodinger equations for the slowly varying amplitudes of density waves can be derived. In the case where a parametric resonance between a certain mode of density waves and the external focusing occurs, the slow evolution of the resonant amplitudes in the cold-beam limit is shown to be governed by a system of coupled Gross-Pitaevskii equations. Properties of the nonlinear Schrodinger equation as well as properties of the Gross-Pitaevskii equation are discussed, together with soliton and condensate formation in intense particle beams.

nlin.PS↗

arXiv2003

Renormalization Group Reduction of the Henon Map and Application to the Transverse Betatron Motion in Cyclic Accelerators

The renormalization group method is applied to the study of discrete dynamical systems. As a particular example, the Henon map is considered as applied to describe the transverse betatron oscillations in a cyclic accelerator or storage ring possessing a FODO-cell structure with a single thin sextupole. A powerful renormalization group method is developed that is valid correct to fourth order in the perturbation amplitude, and a technique for resolving the resonance structure of the Henon map is also presented. This calculation represents the first successful application of a renormalization group method to the study of discrete dynamical system in a unified manner capable of reducing the dynamics of the system both far from and close to resonances, thus preserving the symplectic symmetry of the original map.

nlin.SI↗

arXiv2002

Solitary Waves in an Intense Beam Propagating Through a Smooth Focusing Field

Based on the Vlasov-Maxwell equations describing the self-consistent nonlinear beam dynamics and collective processes, the evolution of an intense sheet beam propagating through a periodic focusing field has been studied. In an earlier paper [1] it has been shown that in the case of a beam with uniform phase space density the Vlasov-Maxwell equations can be replaced exactly by the macroscopic warm fluid-Maxwell equations with a triple adiabatic pressure law. In this paper we demonstrate that starting from the macroscopic fluid-Maxwell equations a nonlinear Schroedinger equation for the slowly varying wave amplitude (or a set of coupled nonlinear Schroedinger equations for the wave amplitudes in the case of multi-wave interactions) can be derived. Properties of the nonlinear Schroedinger equation are discussed, together with soliton formation in intense particle beams.

physics.acc-ph↗

arXiv2001

Hamiltonian Formalism for Solving the Vlasov-Poisson Equations and Its Applications to Periodic Focusing Systems and the Coherent Beam-Beam Interaction

A Hamiltonian approach to the solution of the Vlasov-Poisson equations has been developed. Based on a nonlinear canonical transformation, the rapidly oscillating terms in the original Hamiltonian are transformed away, yielding a new Hamiltonian that contains slowly varying terms only. The formalism has been applied to the dynamics of an intense beam propagating through a periodic focusing lattice, and to the coherent beam-beam interaction. A stationary solution to the transformed Vlasov equation has been obtained.

physics.acc-ph↗

arXiv2001

Renormalization Group Reduction of Non Integrable Hamiltonian Systems

Based on the Renormalization Group method, a reduction of non integrable multi-dimensional hamiltonian systems has been performed. The evolution equations for the slowly varying part of the angle-averaged phase space density, and for the amplitudes of the angular modes have been derived. It has been shown that these equations are precisely the Renormalization Group equations. As an application of the approach developed, the modulational diffusion in one-and-a-half degree of freedom dynamical system has been studied in detail.

physics.acc-ph↗

arXiv2001

Renormalization Group Approach to the Beam-Beam Interaction in Circular Colliders

Building on the Renormalization Group (RG) method the beam-beam interaction in circular colliders is studied. A regularized symplectic RG beam-beam map, that describes successfully the long-time asymptotic behavior of the original system has been obtained. The integral of motion possessed by the regularized RG map has been used to construct the invariant phase space density (stationary distribution function), and a coupled set of nonlinear integral equations for the distributions of the two colliding beams has been derived.

physics.acc-ph↗

arXiv2001

Hamiltonian Formalism for Solving the Vlasov-Poisson Equations and Its Application to the Coherent Beam-Beam Interaction

A Hamiltonian approach to the solution of the Vlasov-Poisson equations has been developed. Based on a nonlinear canonical transformation, the rapidly oscillating terms in the original Hamiltonian are transformed away, yielding a new Hamiltonian that contains slowly varying terms only. The formalism has been applied to the coherent beam-beam interaction, and a stationary solution to the transformed Vlasov equation has been obtained.

physics.acc-ph↗

arXiv2001

Macroscopic Fluid Approach to the Coherent Beam-Beam Interaction

Building on the Radon transform of the Vlasov-Poisson equations, a macroscopic fluid model for the coherent beam-beam interaction has been developed. It is shown that the Vlasov equation, expressed in action-angle variables, can be reduced to a closed set of hydrodynamic (fluid) equations for the beam density and current velocity. The linearized one dimensional equations have been analysed, and explicit expressions for the coherent beam-beam tuneshifts are presented.

physics.acc-ph↗

arXiv2000

Nonlinear $δf$ Method for Beam-Beam Simulation

We have developed an efficacious algorithm for simulation of the beam-beam interaction in synchrotron colliders based on the nonlinear $δf$ method, where $δf$ is the much smaller deviation of the beam distribution from the slowly evolving main distribution $f_0$. In the presence of damping and quantum fluctuations of synchrotron radiation it has been shown that the slowly evolving part of the distribution function satisfies a Fokker-Planck equation. Its solution has been obtained in terms of a beam envelope function and an amplitude of the distribution, which satisfy a coupled system of ordinary differential equations. A numerical algorithm suited for direct code implementation of the evolving distributions for both $δf$ and $f_0$ has been developed. Explicit expressions for the dynamical weights of macro-particles for $δf$ as well as an expression for the slowly changing $f_0$ have been obtained.

physics.acc-ph↗

arXiv2000

Simulation of the Beam-Beam Effects in $e^+e^-$ Storage Rings with a Method of Reducing the Region of Mesh

A highly accurate self-consistent particle code to simulate the beam-beam collision in $e^+e^-$ storage rings has been developed. It adopts a method of solving the Poisson equation with an open boundary. The method consists of two steps: assigning the potential on a finite boundary using the Green's function, and then solving the potential inside the boundary with a fast Poisson solver. Since the solution of the Poisson's equation is unique, our solution is exactly the same as the one obtained by simply using the Green's function. The method allows us to select much smaller region of mesh and therefore increase the resolution of the solver. The better resolution makes more accurate the calculation of the dynamics in the core of the beams. The luminosity simulated with this method agrees quantitatively with the measurement for the PEP-II B-factory ring in the linear and nonlinear beam current regimes, demonstrating its predictive capability in detail.

physics.acc-ph↗

arXiv2000

Formation of Patterns in Intense Hadron Beams. The Amplitude Equation Approach

We study the longitudinal motion of beam particles under the action of a single resonator wave induced by the beam itself. Based on the method of multiple scales we derive a system of coupled amplitude equations for the slowly varying part of the longitudinal distribution function and for the resonator wave envelope, corresponding to an arbitrary wave number. The equation governing the slow evolution of the voltage envelope is show to be of Ginzburg-Landau type.

physics.acc-ph↗

arXiv1999

Random Beam Propagation in Accelerators and Storage Rings

A kinetic equation for the joint probability distribution for fixed values of the classical action, momentum and density has been derived. Further, the hydrodynamic equations of continuity and balance of momentum density have been transformed into a Schroedinger-like equation, describing particle motion in an effective electro-magnetic field and an expression for the gauge potentials has been obtained.

physics.acc-ph↗

arXiv1999

Nonlinear Longitudinal Waves in High Energy Stored Beams

We solve the Vlasov equation for the longitudinal distribution function and find stationary wave patterns when the distribution in the energy error is Maxwellian. In the long wavelength limit a stability criterion for linear waves has been obtained, and a Korteweg-de Vries-Burgers equation for the relevant hydrodynamic quantities has been derived.

physics.acc-ph↗

arXiv1998

Collision Integrals and the Generalized Kinetic Equation for Charged Particle Beams

In the present paper we study the role of particle interactions on the evolution of a high energy beam. The interparticle forces taken into account are due to space charge alone. We derive the collision integral for a charged particle beam in the form of Balescu-Lenard and Landau and consider its further simplifications. Finally, the transition to the generalized kinetic equation has been accomplished by using the method of adiabatic elimination of fast variables.

physics.acc-ph↗

arXiv1998

Formation of Patterns and Coherent Structures in Charged Particle Beams

In the present paper we study the long wavelength and slow time scale behavior of a coasting beam in a resonator adopting a broad-band impedance model. Based on the renormalization group approach we derive a set of coupled evolution equations for the beam envelope distribution function and the resonator voltage amplitude. The equation for the resonator voltage amplitude is further transformed into a generalized Ginzburg-Landau equation.

physics.acc-ph↗