Development of a hybrid collimator bonding tantalum and carbon-fiber-composite for SuperKEKB

Abstract

Collimators are required to reduce beam-induced backgrounds in the experiments in the SuperKEKB. Sudden beam losses that are not fully understood cause frequent beam impacts on collimators. SuperKEKB was operated with several collimator types and suffered from damage induced by sudden beam losses and from blow-up of the vertical beam size due to the collimator impedance. To address these issues, this study developed a new type of “hybrid collimator” for improved performance.Collimator damage events increase beam background (BG) noise. To address this limitation, we developed a hybrid collimator by bonding tantalum with a carbon-fiber-composite to form the collimator head that is less likely to have an adverse effect on the BG when the beam hits it.This hybrid collimator exhibited a low impedance and high durability. Particle-tracking simulations, and beam irradiation simulations were conducted, and subsequently, the hybrid collimator was installed in the SuperKEKB main ring. The designed hybrid collimator reduced the beam background noise and facilitated a low impedance and continuous stable operation.