Compact magnetostatic cavity for polarised 3He neutron spin filter cells

We present a concept for a compact magnetostatic cavity called a “Magic box” that provides a very homogeneous magnetic environment for a polarised 3He neutron spin-filter cell in the presence of moderate magnetic stray fields. Based on this concept different systems have been built and tested. The concept is ideal for the transport or hosting of a spin-filter on a neutron beam-line.