Fig. 1. Schematic layouts for neutron radiography by LiF detector. Self-radiography of (a) large-size and (b) tiny neutron sources using a pinhole imaging approach and high-resolution LiF crystal detectors. (c) Neutron radiography of the internal structure of objects. In such a case the object is placed in close contact to the LiF crystal.

Fig. 2. Principles of neutron imaging generation in LiF crystals.

Fig. 3. In image readout, luminescence from the LiF crystal was observed with a laser scanning confocal luminescence microscope. The line of an argon laser was used for excitation and luminescence from the CCs at ^[33–36].

Fig. 4. Schematic diagrams and sizes of the line pairs produced on thickness Gd patterns coated onto the overall surface of a glass substrate and their images obtained by using the LiF crystal neutron imaging detector (top). Line-pair images obtained using the LiF single crystal detector and line profiles of the pairs with widths of ^[36] (bottom). The spatial resolution on the scale of is clearly seen.

Fig. 5. (a) Neutron image of a thick Cd plate taken with 10 s exposure time and a trace of the neutron image across the edge, which is compared with a calculation at a spatial resolution of ^[33]. (b) Neutron radiography images of a 100 mm thick Gd plate of triangular shape^[33]. Optical microscope and neutron images of the same part near the edge obviously demonstrate a high-resolution quality of the LiF neutron imaging detector comparable with optical microscopy imaging. The magnified image of a small crack in the Gd plate and the line scan of this part, shown by the blue lines, clearly manifest high contrast and spatial resolution of such images. We could see that this line scan has a best fit with a modeled curve with a width (dashed curve).

Fig. 6. (a) Comparison of the neutron images of the Au wires of 42, 95 and diameter recorded with exposure times of 10 and 30 min^[33]. (b) Comparison^[33] of the traces of the experimental intensity transmittance of neutrons through the Au wires (solid curves) with the theoretical transmittance (dashed curves) for two attenuation beam coefficients. It is clearly seen that the best coincidence between the modeling and the experimental curves is obtained for (bottom panel). Changes of of even () show a large disagreement between the theoretical and experimental curves, which testifies to the high quality and sensitivity of the LiF crystal neutron imaging detector. (c) A plot of the luminescent intensity from the CCs in LiF versus the neutron fluence on LiF^[33]. The neutron fluence was varied by the neutron exposure time and the attenuation of the neutron flux by various filters, such as Au wires, Au foils and Cd plates. The straight line is a fit to the data, showing a good linear response of the LiF to the neutron fluence.

Fig. 7. Neutron radiography of a thick Gd plate. A defect with a size of and some micron-scale changes of thickness of the hammered Gd plate edge (due to cutting the Gd plate with scissors) are clearly seen in the magnified images of different parts of the sample^[35].

Fig. 8. (a) Neutron images of a ball-point pen obtained by a tiling sequence of magnified images^[33]. A metal tube, a roller ball at the top and the ink in the metal tube with strong neutron attenuation are obviously distinguished. It is also clearly seen that a small air bubble of diameter in the ink has moved to the upper part of the pen between the first experiment with 30 min neutron exposure and the second measurement with 10 min exposure. (b) A schematic drawing of a small fuel cell and the neutron image of it^[35]. Tiny details with sizes of at least of the fuel cell structure and its inhomogeneity along and perpendicular to the anode–cathode directions are evidently resolved.