Mechanism of electron cloud clearing in the accumulator ring of the Spallation Neutron Source

Abstract

We describe a mechanism using clearing electrodes and solenoids to remove the electron cloud in the Spallation Neutron Source's accumulator ring. Simulation indicates that strong multipacting could happen at median clearing fields. A similar phenomenon was reported in an experimental study at Los Alamos Laboratory's Proton Storage Ring. A weak solenoid is proven to be a good remedy for suppressing multipacting by confining electrons near the chamber wall's surfaces. We investigated the clearing mechanism using both electrodes and solenoids.

Recent studies on photoelectron and secondary electron yields of TiN and NEG coatings using the KEKB positron ring

“…However, if the SEY spectrum is different, the estimated d max can be different. For example, the following formula has also been frequently used for SEY studies [51][52][53][54][55]:…”

Demonstration of electron clearing effect by means of a clearing electrode in high-intensity positron ring

“…Another direct and efficient method involves the installation of a clearing electrode in the beam pipe. This electrode is used to attract or repel electrons through a static electric field [9,[27][28][29][30][31][32][33][34]. This method can be applied even inside magnets, unlike the method employing a solenoid field.…”

Suppression of secondary emission in a magnetic field using triangular and rectangular surfaces

“…The detailed model of secondary electron emission of CLOUDLAND is described in Refs. [33,34]. Two series of secondary parameters are considered here: d max ¼ 1.40, E max ¼ 190 eV and d max ¼ 1.74, E max ¼ 330 eV which are typical of a copper or coated aluminum vacuum chamber.…”