Suppression of electron cloud using copper thermal spray coating in SuperKEKB

Abstract

The electron cloud effect (ECE) has posed serious challenges in recent high-intensity proton and positron rings. An aluminum beam pipe coated with copper thermal spray film (T.S. coating), which had a low secondary electron yield (SEY), was developed to suppress electron clouds in accelerators. After 72 h conditioning, the lowest δmax (the maximum SEY within scanning) reached ∼0.7. In addition, to check the applicability of T.S. coating in accelerators, its outgassing rate and surface resistance were measured as a reference. Finally, an aluminum beam pipe with a T.S. coating was produced and installed in the positron ring of SuperKEKB to measure the electron density. The results show that the electron density in the finished beam pipe was comparable with that of the TiN-coated beam pipe; however, the relatively high surface resistance of T.S. coating must be considered when applied to accelerators.