Model of Electron Cloud Instability In Fermilab Recycler

TL;DR

This paper presents an analytical model of electron cloud-induced instability in Fermilab Recycler, explaining recent experimental observations and aiding future intensity upgrade planning.

Contribution

The paper introduces a new analytical model for electron cloud instability in combined function dipoles, aligning with experimental data and simulations.

Findings

Instability growth rate of about 30 revolutions.

Model matches experimental observations.

Provides estimates for future intensity upgrades.

Abstract

An electron cloud instability might limit the intensity in the Fermilab Recycler after the PIP-II upgrade. A multibunch instability typically develops in the horizontal plane within a hundred turns and, in certain conditions, leads to beam loss. Recent studies have indicated that the instability is caused by an electron cloud, trapped in the Recycler index dipole magnets. We developed an analytical model of an electron cloud driven instability with the electrons trapped in combined function dipoles. The resulting instability growth rate of about 30 revolutions is consistent with experimental observations and qualitatively agrees with the simulation in the PEI code. The model allows an estimation of the instability rate for the future intensity upgrades.