Development of alumina ceramics vacuum duct for the 3 GeV-RCS of the J-PARC project

An alumina ceramics vacuum duct has been developed for the 3 GeV-RCS of J-PARC project at JAERI. There are two types of alumina ceramics vacuum ducts needed, one being 1.5 m long with a circular cross-section for use in the quadrupole magnet, the other being 3.5 m long with a 15°, bend with a race-track cross-section for use in the dipole magnet. These ducts could be manufactured by joining several duct segments of 0.5-0.8 m in length by brazing. The alumina ceramic ducts have copper stripes on the outside surface to reduce the duct impedance. One of the ends of each stripe is connected to a titanium flange by way of a capacitor so to interrupt an eddy current circuit. The copper stripes are produced by an electroforming method in which a stripe pattern formed by Mo-Mn metallization is first sintered on the exterior surface and then overlaid by PR-electroformed copper (periodic current reversal electroforming method). In order to reduce emission of secondary electrons when protons or electrons strike the surface, TiN film is coated on the inside surface of the ducts.