The LIPAc beam dump

Abstract

The International Fusion Materials Irradiation Facility (IFMIF) aims to provide an accelerator-based, D-Li neutron source to produce high energy neutrons at sufficient intensity and irradiation volume for fusion materials qualification. The LIPAc is a 125 mA 9 MeV continuous wave deuteron accelerator whose components are under construction mainly in Europe, which is being installed in Rokkasho (Japan) with the purpose of validating the IFMIF accelerator design.

The beam generated by the LIPAc accelerator will be stopped by a copper cone (2.5 m long, 6.8° angle), cooled by water flowing at high velocity along its outer surface. This piece is surrounded by a shield made of iron and low Z materials for attenuating the neutron and gamma radiation originated by the interaction of the deuterons with the copper. It incorporates dedicated diagnostics for beam dump monitoring: accelerometers for detection of localized heating due to incorrect alignment of the beam and ionization chambers, which ensure that the deuteron beam footprint remains within the beam dump design limits.

A lead shutter has been designed to be inserted in the beam tube during beam-off periods to stop the gamma radiation from the activated copper cone escaping through the beam tube, allowing access inside the accelerator vault. The junction of the beam dump to the beam tube has a special design to allow its remote disconnection, enabling the end of life decommissioning operations of the facility. The design and material selection of the beam dump and neighboring elements are driven by a maintenance-free requirement after a short period of operations, as the cartridge activation precludes any maintenance activities in the beam dump and neighboring elements downstream the lead shutter.

This paper describes the design and manufacturing of the beam dump and related elements explaining the interrelations between them and the reasons behind their main features.