Radiography with fast neutrons

Neutrons are excellent probes for non-destructive material investigations. Neutrons can reveal properties and material compositions which x-rays cannot or only with insufficient resolution. Radio-graphy and tomography with slow (thermal) neutrons are already widespread methods to measure the distribution of substances containing hydrogen in samples – predominantly at stationary facilities such as research reactors and spallation sources. Contrarily, high energy neutrons, like those produced at the PTB accelerator, so far have been scarcely deployed. Due to their specific interactions with the atomic nuclei of matter and their high penetration power, however, they are particularly suited for investigating voluminous objects such as travel luggage, containers, heavy machine parts or minerals. Until nowadays though the complexity of facilities to produce neutrons and a less well-developed status of image-producing detection systems prevent a wider employment of this method.

At PTB efficient high-resolution cameras for energy-resolved radiography with 2 MeV to 10 MeV neutrons are developed in cooperation with the University of Frankfurt and the Weizmann Institute in Rehovot/Israel. To date several prototypes of such cameras, based on two different functional principles, have been developed and investigated at PTB’s neutron facility. Combined with intense pulsed neutron sources these cameras will enable measuring light elements such as C, N, and O in closed containers, for instance to identify explosives or drugs.

For practical applications at airports, border installations or in industry, however, in addition to efficient imaging procedures compact high power facilities to produce neutrons are needed. Therefore, in a new project together with the University of Jena PTB will investigate if high power neutron sources, driven by high power lasers, can be built for these applications.