On a Vlasov-Fokker-Planck equation for stored electron beams

TL;DR

This paper analyzes a Vlasov-Fokker-Planck model for electron beams in storage rings, proving existence, uniqueness, and stability of solutions, and exploring the long-term behavior and steady states of the system.

Contribution

It establishes mathematical foundations for the equation's solutions, including existence, uniqueness, and stability, and connects the model to physical derivations.

Findings

Existence and uniqueness of global classical solutions.

Existence and characterization of steady states (Haissinski solutions).

Stability of solutions for small beam currents.

Abstract

In this paper we study a self-consistent Vlasov-Fokker-Planck equations which describes the longitudinal dynamics of an electron bunch in the storage ring of a synchrotron particle accelerator. We show existence and uniqueness of global classical solutions under physical hypotheses on the initial data. The proof relies on a mild formulation of the equation and hypoelliptic regularization estimates. We also address the problem of the long-time behavior of solutions. We prove the existence of steady states, called Haissinski solutions, given implicitly by a nonlinear integral equation. When the beam current (i.e. the nonlinearity) is small enough, we show uniqueness of steady state and local asymptotic nonlinear stability of solutions in appropriate weighted Lebesgue spaces. The proof is based on hypocoercivity estimates. Finally, we discuss the physical derivation of the equation and its particular asymmetric interaction potential.