Advanced damped detuned structure development at SLAC

The first damped detuned accelerator structure, DDS 1, has been built, tested in the ASSET experiment, and installed in the NLCTA. The planning and construction of a series of further structures, incorporating some modifications, is under way. DDS 2, 3, and 4 all incorporate the same basic design as DDS 1. The manifold design for the last 5% of the downstream end of the structure has been modified to accommodate improvements in the manifold loads. Calculations based on the spectral function method indicate, on average, a factor two or better reduction in the long range wake. Modest modifications in the distribution of geometrical detuning parameters along the structure which, according to calculations based on spectral function theory, significantly improve the short range wake will be incorporated in DDS 3 and 4. The basic cell configuration will be redesigned in DDS 5 with the intention of improving shunt impedance as well as incorporating further improvements in the wake