DRIFT TUBE LINAC DESIGN AND PROTOTYPING FOR THE CERN LINAC4

The Drift Tube Linac (DTL) for the new linear accelera- tor Linac4 at CERN will accelerate H--ion beams of up to 40 mA average pulse current from 3 to 50 MeV. It is de- signed to operate at 352.2 MHz and at duty cycles of up to 10 %, if required by future physics programmes. The accelerating field is 3.2 MV/m over the entire length. Per- manent magnet quadrupoles (PMQs) are used as focusing elements. The 3 DTL cavities consist of 2, 4 and 4 sec- tion of about 1.8 m each, are equipped with 35, 41 and 29 drift tubes respectively, and are stabilized with post- couplers. Several new features have been incorporated in the basic design. The electro-magnetic design has been re- fined in order to reduce peak field levels in critical areas. The mechanical design aims at reducing the complexity of the mechanical structure and of the adjustment procedure. Drift tubes and holders on the tanks that are machined to tight tolerances do not require adjustment mechanisms like screws or bellows for drift tube positioning. A scaled cold model, an assembly model and a full-scale prototype of the first half section have been constructed to validate the de- sign principles. The results of metrological and RF tests are presented.