Development of HOM damper for B-factory (KEKB) superconducting cavities

Abstract

Higher order mode (HOM) power excited in superconducting cavities can be on the order of kW in the B-factory due to high current. To extract this power, cavities are designed so that HOM can travel out through beam pipes and be absorbed in a lossy material. Ferrite has been investigated as a candidate material for the absorber. Due to its low tensile strength, bonding of tiles has been a problem. To solve this problem, we started R and D on the sinter-bonding of ferrite powder directly on the inner surface of a copper pipe using hot isostatic pressing. In this paper, we describe the manufacturing process, low power test, high power test and outgassing rate measurement of the manufactured dampers.