A novel neutron lens based on reflection has recently been developed that could greatly benefit neutron imaging and other neutron scattering techniques.
A practical lens helps solve two of the challenges in developing neutron instrumentation: neutron sources are weak and it is inefficient to focus neutrons due to the small neutron refractive index. For instance, to obtain high resolution neutron images, one must strongly collimate the neutron beam, which sacrifices even more neutron flux. With a lens, collimation is no longer needed to achieve spatial resolution so that one can increase the usable flux by a least a factor of 100! The novel lens is a Wolter Optic similar in design to the telescope of the CHANDRA x-ray observatory. NASA has developed a new method to create a lens using nested, thin foils of nickel, so that the lens will have high neutron or x-ray throughput and focal lengths on the order of a few meters. Also, the lens can also be made to have a magnification of 10, which will improve the achievable spatial resolution of neutron imaging to 1 µm.
A collaboration between MIT, NASA and NIST has begun with the goal of creating the world’s first neutron microscope. A proof-of-principle experiment was conducted with a prototype lens that had a magnification of 4. As shown in Figure 1, the lens performed well, creating images from a divergent source just like a microscope with magnification 4. The spatial resolution of this prototype lens was about 70 µm and can be improved upon with a technique called differential deposition.
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