Progress in the Design of LINAC4, the SPL Normal-Conducting Front-End (<180 MeV)

The SPL is a high-power superconducting H linac de- signed to cover the needs of future experimental programs at CERN. Its normal conducting front-end comprises an RFQ, followed by a low-energy beam chopper, an Alvarez Drift Tube Linac (DTL), a Coupled Cavity DTL (CCDTL), and a Side Coupled Linac (SCL) and can be built in a first stage as Linac4. The design is based on achieving smooth transitions between the different sections and on avoiding emittance exchange via space charge resonances. Follow- ing a collaboration agreement for the construction of a pro- totype DTL tank the original design was changed in order to reduce costs and to increase efficiency. This paper out- lines the design approach for the normal conducting SPL front-end and reports on the recent changes in the reference design.