Dynamics of uncaught foil-stripped electrons in the Oak Ridge Spallation Neutron Source accumulator ring

S Cousineau,W Lu,M A Plum,J A Holmes

doi:10.1103/physrevstab.14.064001

Abstract

The Spallation Neutron Source accelerator utilizes ${\mathrm{H}}^{\ensuremath{-}}$ charge exchange injection to merge a 1 GeV, 1 MW beam from a linac into an accumulator ring. The design calls for the 545 keV foil-stripped electrons to be absorbed by an electron catcher located below the foil. However, multiple observations of hardware damage caused by stripped electrons indicate that at least a fraction of the electrons are reflected back into the vacuum chamber. This paper presents the results of a 3D computational model employed to simulate the dynamics of foil-stripped electrons, including a surface interaction model for the catcher. Simulation results are compared with experimental observations, and the implications for high power beam operations are discussed.

Highlights

Many high power hadron accelerators utilize HÀ charge exchange injection to transfer beams from one section of the accelerator to the often from a linac into a ring [1]
This paper presents the results of a study to investigate this hypothesis
Given the observations of black marks on the catcher surface, and the fact that the catcher has never been located within the design position acceptance, it can be reasoned that most of the electrons are impacting the top surface of the catcher

Summary

Introduction

Many high power hadron accelerators utilize HÀ charge exchange injection to transfer beams from one section of the accelerator to the often from a linac into a ring [1]. This method of injection is ideal for high intensity beam accumulation because it minimizes emittance blowup. Less effort has been dedicated to understanding the dynamics of the foil-stripped electrons, especially in operational machines. The electrons constitute only a fraction of the beam power contained in the parent ion beam, for high power beams this fraction is sufficient to cause damage to machine hardware, unless properly handled

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Conclusion