SNS Linac: Revised configuration

The SNS Linac is required to provide a pulsed 1-GeV 1-mA-average beam of H{sup {minus}} ions to a storage/compressor ring which then delivers it to a neutron production target with high reliability and availability. Nominal rep rate is 60 Hz with a linac pulse length of 1 ms. The entire Linac is required to support a 2-mA operation; thus a facility upgrade to 2 MW merely requires doubling the injected beam current and providing the additional needed rf power. (The design basis for the Linac upgrade to a 4-MW level is a 20-MeV beam funnel.) In order to permit hands-on maintenance, the beam losses in the Linac must be less than 1 nA/m at 1 GeV. Based primarily on value engineering considerations relating to Linac support stands, ease of the placement, alignment, and possible replacements of the quadrupole magnets and diagnostic components, and other constraints such as adequate gaps between the accelerating segments for electromagnetic quadrupoles and diagnostics, the authors propose a revised Linac configuration. It should be noted that this revised configurations represents only a small change; the basic Linac architecture consisting of the three types of accelerating structures, DTL, CCDTL, and CCL, has not changed. In this brief note the authors present the overall physics and engineering design considerations and the revised linac configuration