Development of collimator jaw for SuperKEKB main ring

Low-impedance beam collimators for SuperKEKB were designed to fit an antechamber scheme in the vacuum system. They were installed to suppress background noise in the particle detector named Belle II and also to protect various components from the damage due to the hitting of steered beam. Following two horizontal collimators for test in the phase-1 commissioning, four horizontal and two vertical collimators were installed in the phase-2 commissioning. They contributed the steady operations during the commissioning. We report the design process of the collimator jaw to reduce the impedance and at the same time to withstand the high heat load, and also some problems found in the commissioning. (author)