Particle-beam behavior in the SNS linac with simulated and reconstructed beams

The Spallation Neutron Source (SNS) project is a collaborative effort between Brookhaven, Argonne, Jefferson, Lawrence Berkeley, Los Alamos and Oak Ridge National Laboratories. Los Alamos has designed the entire linac for this accelerator complex. The final design of the SNS linac is comprised of both normal- and super-conducting RF (SRF) structures. The normal-conducting linac section up to 185 MeV, consists of a 2.5-MeV RFQ, a Medium Energy Beam Transfer (MEBT) line, a 402.5-MHz DTL, followed by a 805-MHz CCL. The SRF structure accelerates the beam from a nominal energy of 185 MeV to 1000 MeV. The SRF section consists of two, a medium beta (β= 0.61), and a high beta (β= 0.81) sections. The base-line design of the linac was done with a simulated beam at the input to the DTL. In this paper, we present the behavior of particle-beams originating at different locations upstream of the DTL. Input beams include a simulated beam at the input to the RFQ and a beam reconstructed from measurements.