A compact neutron Ramsey resonance apparatus for polarised neutron radiography

A compact apparatus to perform polarised neutron radiography on macroscopic objects is presented. Its working principle, based on Ramsey's resonance technique, allows to observe interactions between neutron spins and magnetic fields. Despite its shortness of only 480 mm, the magnetic field homogeneity allows for large beam cross-sections of up to 20×20 mm2. The applied magnetic field at the sample position is variable and can be tuned from about 4 to almost 32 mT without violating the Ramsey resonance condition. The performance of the apparatus is demonstrated in systematic tests, which show a phase stability of 1 degree and a sensitivity of about 7.5×10−8 Tm.