NIST Builds Neutron Camera That Can Penetrate Surfaces
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ABSTRACT We experimentally demonstrate that electrically neutral particles, neutrons, can be used to directly visualize the electrostatic field inside a target volume that can be physically isolated or occupied. Electric field images are obtained using a spin-polarized neutron beam with a recently developed polarimetry method for polychromatic beams that permits detection of a small angular change in spin orientation. This Letter may enable a new diagnostic technique sensitive to the structure of electric potential, electric polarization, charge distribution, and dielectric constant by imaging spatially dependent electric fields in objects that cannot be accessed by other probes.

Yuan-Yu Jau, Daniel S. Hussey, Thomas R. Gentile, and Wangchun Chen Phys. Rev. Lett. 125, 110801 Published 10 September 2020

See the paper at APS Physical Review Letters.

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Neutrons (blue), which can penetrate solid objects (like a gray steel wall), have no electric charge. However, the magnetic spins of moving neutrons are affected by an electric field (green), experiencing a slight tweak to their spin direction as they pass through the field. This spin direction change (red angle) can be measured by polarimetry (using a neutron spin filter and solenoid, represented by the coil), offering a potential method for inspecting electrical devices that cannot be observed directly.