Electron Cloud Measurements in Fermilab Booster

TL;DR

This paper investigates the presence of electron clouds in Fermilab's Booster synchrotron, analyzing their effects on beam stability and exploring mitigation techniques through experimental measurements and simulations.

Contribution

It provides the first experimental evidence of electron cloud effects in the Booster using the clearing bunch technique and compares observations with PyECLOUD simulations.

Findings

Electron cloud effects cause measurable tune shifts in the Booster.

Presence of electron clouds depends on bunch train structure and intensity.

Simulation results align with experimental observations.

Abstract

Fermilab Booster synchrotron requires an intensity upgrade from 4.5x1012 to 6.5x1012 protons per pulse as a part of Fermilabs Proton Improvement Plan-II (PIP-II). One of the factors which may limit the high-intensity performance is the fast transverse instabilities caused by electron cloud effects. According to the experience in the Recycler, the electron cloud gradually builds up over multiple turns in the combined function magnets and can reach final intensities orders of magnitude greater than in a pure dipole. Since the Booster synchrotron also incorporates combined function magnets, it is essential to discover any existence of an electron cloud. And if it does, its effects on the PIP-II era Booster and its mitigating techniques. As the first step, the presence or absence of the electron cloud was investigated using the clearing bunch technique. This paper presents experimental details and observations of the bunch-by-bunch tune shifts of beams with various bunch train structures at low and high intensities and simulation results conducted using PyECLOUD.