Neutronic analyses of the European spallation source target design option META:LIC

In the framework of the design update phase of the European Spallation Source (ESS) a design for a liquid metal target, called META:LIC (MEgawatt TArget: Lead bIsmuth Cooled), is being developed at the Karlsruhe Institute of Technology (KIT) as a ''comparative target solution''. A comparative concept is required by the licensing authorities in addition to the reference target solution which for ESS is a rotating solid tungsten target called RoTHeTa. ESS aims at producing high energy spallation neutrons of high brilliance for fundamental material research analyses. The spallation process in the target is induced by a high energy (2500 MeV) proton beam with a mean current of 2 mA. The lead bismuth target and its structure are subjected to proton and/or neutron radiation and therefore will be activated and potentially damaged. In ESS the high beam power (5MW) is provided by a pulsed source with long pulses (2.86 ms) and a repetition rate of 14 Hz. With each pulse the target material is heated within a few nanoseconds. The heating is non-uniform, as the heat deposition varies strongly, i.e. it decreases exponentially with the penetration depth of the beam into the target material. The maximum heat deposition for the selected beam energy is close to the proton beam window and becomes quite low (less than 2 orders of magnitude relative to the maximum) at a penetration depth of about 600 mm. Heating is accompanied with thermal expansion of the target material and thus with thermal stresses and potentially with pressure waves propagating through the target material. In this work the conceptual design of the META:LIC target is first summarized in section 2, followed by a presentation of an analysis of the neutronic performance as well as radiation damage in section 3. A conclusion of the results is given in section 4. (orig.)