A Conceptual Description of the ESS-Bilbao Accelerator

The ESS-Bilbao (ESSB) light ion linear accelerator is conceived as a multi-purpose machine that will serve as a driving force for the construction of the European Spallation Source (ESS). The first part of the ESSB injector comprises a proton source of the Electron Cyclotron Resonance (ECR) kind. The low energy beam is transported along a two solenoid Low Energy Transport System (LEBT) that will couple the ion source to the 352.2 MHz Radio Frequency Quadrupole (RFQ). This RFQ –based on a modular design where the vane sections are held in place by bolts, and the welds only serve to make the structure vacuum tight, aims to accelerate a 75 mA beam from 45 keV up to 3 MeV, while keeping the beam both transversely and longitudinally focused together with minimum emittance growth. Once the RF timing structure is set to the beam, it is conveniently matched through the Medium Energy Beam Transport (MEBT) to the Drift Tube Linac (DTL), which will take this 3 MeV beam up to the required energy by the designed Be rotating target (50 MeV).