Mechanical engineering of a linac for the Spallation Neutron Source

The linac for the Spallation Neutron Source (SNS) Project will accelerate an average current of 1 mA of H^- ions from 20 MeV to 1 GeV for injection into an accumulator ring. The linac will be an intense source of H^- ions and as such requires advanced design techniques to meet project technical goals as well as to minimize costs. The DTL, CCDTL and CCL are 466 m long and operate at 805 MHz with a maximum H^- input current of 28 mA and 7% RF duty factor. The drift tube linac is a copper-plated steel structure using permanent magnet quadrupoles. The coupled-cavity portions are brazed Cu structures and use electromagnetic quads. RF losses in the copper are 80 MW peak, with RF power supplied by 52 klystrons. Additionally, the linac is to be upgraded to the 2and 4-MW beam power levels with no increase in duty factor. We give an overview of the linac mechanical engineering effort and discuss the special challenges and status of the effort