A high intense reactor based positron source

An intense source of monoenergetic, low energy positrons is presented. The positrons are produced by pair production from high energy γ-rays after the capture of thermal neutrons in cadmium. The pair production itself takes place in a stack of layers, each consisting of two concentric rings made of tungsten foils. The source is placed in a beam tube at the Research Reactor Munich at Garching. From first experimental data, we can extrapolate an intensity of 2 × 108 slow positrons per second and a spot size of less than 26 mm.