Collaborative Development of a New Neutron Imaging Beamline at the Zero-Power CROCUS Reactor

The steady decline of neutron imaging (NI) facilities—driven in part by the shutdown of several research reactors—has increased the need to maximize the use of existing infrastructure. In this context, a collaborative effort between PSI-CNM, PSI-NES, and EPFL-LRS has led to the development of a neutron imaging capability at the CROCUS zero-power reactor at EPFL. Zero-power research reactors offer a cost-effective and flexible platform for education, materials research, and proof-of-concept studies that can support larger neutron facilities.

To enable neutron imaging at CROCUS, an air-filled aluminum channel was inserted into the water reflector to enhance neutron leakage, while aluminum flight tubes were implemented to minimize neutron transport losses. Neutron flux measurements were carried out using gold foil activation, and a helium-based position-sensitive detector was employed to map the two-dimensional flux distribution. A neutron imaging detector system—comprising a scintillator screen coupled to a CCD camera—was installed and used for initial experiments. These experiments successfully produced (i) neutron radiographs of static objects and (ii) time-resolved radiographic sequences of slow dynamic processes, confirming the feasibility of neutron imaging at CROCUS.

The results establish a foundation for a permanent neutron imaging facility at EPFL, complementing the existing infrastructure of SINQ at PSI and n_TOF at CERN. Having emerged from a researcher-driven, bottom-up collaboration between the participating institutions, this initiative increases the number of NI operational sites in Switzerland by fifty per cent, hence significantly strengthening Switzerland’s neutron imaging landscape.