Continuing study on electron-cloud clearing techniques in high-intensity positron ring: Mitigation by using groove surface in vertical magnetic field

Abstract: Beam instability caused by an electron cloud is one of the limiting factors in the performance of future advanced positron and proton storage rings. At a wiggler section in the positron ring of the KEK B-factory (KEKB), we installed a test beam chamber with a replaceable insertion and investigated different techniques for the mitigation of electron-cloud effect in a high magnetic field. All techniques were investigated under identical conditions. In this study, the insertions with an isosceles-triangular groove surface and a flat surface were investigated and compared. The groove insertion was composed of grooves running longitudinally along the beam orbit in order to reduce the beam impedance. In this experiment, a large reduction of almost one order of magnitude in the measured electron-cloud current was observed when the groove surface was used instead of the flat one. This is the first experimental demonstration of the concept of the groove surface in a magnetic field. The results are also compared with those obtained in a previous experiment in which a clearing electrode insertion was used. [Copyright &y& Elsevier]