Spallation Target

The present target is an array of lead rods, enclosed in zircaloy tubes and cooled in cross flow by heavy water coolant. Since it is essential to minimise neutron absorption in the region of the coolant/moderator in order to obtain a high neutron flux, the part of the target unit extending into the moderator tank is filled with heavy water, except for the rod bundle. It is about 50 cm long and located in the centre of the moderator tank.

The target and its coolant is enclosed by a double walled aluminum shell, whoose intermediate surface is also cooled by a separate heavy water circuit. The target enclosure cooling system prevents overheating and melting of the target window, where it is penetrated by the proton beam. Like all other radioactive heavy water and light water cooling systems, the target and target enclosure cooling system is equiped with filters, ion exchangers and recombinators to remove undesired products from the coolant (mainly radiolysys products and Beryllium-7) to maintain a low residual radiation level in the cooling plant when shut down.

In 2006 a liquid metal target with eutectic lead-bismut target material was tested successfully in the framework of the MEGAPIE-Project. The MEGAPIE target improved the neutron yield to about 80%, related to the beam current.