Design Issues of the Proton Source for the Ess Facility

The European Spallation Source facility will be one of the fundamental instruments for science and engineering of the future. A 2.5 GeV proton accelerator is to be built for the neutron production. INFN-LNS is involved in the Design Update for the proton source and Low Energy Beam Transport (LEBT) line. The proton source is required to produce a low emittance 90 mA beam, 2.86 ms pulsed with a repetition rate of 14 Hz. Microwave Discharge Ion Sources (MDIS) enable us to produce such high intensity proton beams characterized by very low emittance (< 0.2 .mm.mrad). The source design is based on a flexible magnetic system which can be adapted to electrostatic Bernstein waves heating mechanism; this will permit a strong increase in the electron density with an expected boost of the output current. The main features of the source design, including the microwave injection system and beam extraction, will be described hereinafter.