The transverse long-range wakefield in RDDS1 for the JLC/NLC X-band linacs

The re-designed RDDS (Rounded Damped Detuned Structure) consists of 206 cells with a rounded cell profile formed by a number of circular arcs and a straight section. In the previous analyses of the present structure all cells have been assumed to be coupled to the manifold via slots cut into the cells and, a perfect match to the HOM (Higher Order Mode) couplers has been used. In the structure being fabricated, four cells on either end of the structure are decoupled to accommodate the HOM couplers and the HOM couplers have finite, frequency dependent, reflection coefficients. The wakefield is calculated incorporating both effects.