High Power Laser Science and Engineering, 2015, 3 (4): 04000001, Published Online: Jan. 7, 2016
Using LiF crystals for high-performance neutron imaging with micron-scale resolution 
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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. 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.
A. Faenov, M. Matsubayashi, T. Pikuz, Y. Fukuda, M. Kando, R. Yasuda, H. Iikura, T. Nojima, T. Sakai, M. Shiozawa, R. Kodama, Y. Kato. Using LiF crystals for high-performance neutron imaging with micron-scale resolution[J]. High Power Laser Science and Engineering, 2015, 3(4): 04000001.
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