Polyhedral cavity structure for linac colliders

A polyhedral superconducting cavity is being developed for possible use in linac colliders. The side view of the cavity has the ellipsoidal contour of a Tesla-type multi- cell string, yet the end view has the shape of a dodecahedron. Each of the twelve copper wedges has the TESLA contour cut out by EDM. The copper segments have refrigeration channels gun bored through them and the solid structure eliminates Lorentz detuning. A niobium foil is bonded to the inner surface of the wedge and then the twelve are assembled to create the superconducting cavity. There are no welds, and the seams between adjacent segments do not affect the high Q of the accelerating mode but at the same time block the azimuthal currents of deflecting modes. The power coupled into deflecting modes can be slot-coupled at the seams into waveguides integrated in the copper segments and conveyed to a warm termination. This open geometry makes each seg ment readily available for cleaning, polishing, inspection, and characterization. The accessibility to the surface accommodates advanced superconductors that may allow for higher gradients. The performance of these materials can be tested in a superconducting test cavity.