<div>Neutron diffraction is a powerful tool for noninvasive and nondestructive
characterization of materials and can be applied even in large devices such as
internal combustion engines thanks to neutrons’ exceptional ability to penetrate
many materials. While proof-of-concept experiments have shown the ability to
measure spatially and temporally resolved lattice strains in a small aluminum
engine on a timescale of minutes over a limited spatial region, extending this
capability to timescales on the order of a crank angle degree over the full
volume of the combustion chamber requires careful design and optimization of the
engine structure to minimize attenuation of the incident and diffracted neutrons
to maximize count rates. We present the design of a “neutronic engine,” which is
analogous to an optical engine in that the materials and external geometry of a
typical automotive engine have been optimized to maximize access of the
diagnostic while maintaining the internal combustion chamber geometry and
operability of the engine. The high transparency of aluminum to neutrons makes
it the ideal window material for neutron diagnostics, which allows the neutronic
engine to be a truly all-metal engine with the same load and boundary condition
capabilities of a modern downsized passenger car engine. The neutronic engine
will enable 3D and time-resolved measurements of strain, stress, and temperature
fields as well as phase transformation, texture, and microstructure throughout
the metal components of the combustion chamber.</div>