Concept design of a new liquid metal target station for high power neutron scattering facilities

Abstract

A new liquid metal target station without a window wall for high power charged particle beams to pass through is proposed for neutron-scattering sources and/or neutron-spallation sources. The beams are irradiated directly from above into the free surface of the liquid metal in a target tube soaked vertically in a reservoir tank of the liquid metal. A large hollow chamber is located above the target tube. This chamber works as a getter pump to evacuate the system and as a heat siphon to remove the heat fed by the beams, where the liquid metal works as the working liquid for both functions. Bismuth, Bi in the liquid state at temperatures above 300 °C, is chosen as the target medium. Experimental data for a cylindrical bismuth target are used to calculate the temperature distribution along the liquid metal target column. The evaporation rate of Bi atoms due to boiling under reduced pressure is calculated under a simple assumption in order to evaluate its activity as the working medium of a getter pump and a heat siphon.