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21.
The problems presented in different security areas are varied but the solutions that have been offered are generally based upon the same principles. Employing radiation to locate and identify explosives or contraband has been most obvious at airports but other locations are now receiving equal attention. Neutron and X-ray interrogation are the systems most frequently employed. However, the more recently developed approaches such as multi-view dual-energy imaging and the use of high-speed diffraction measurements are the most likely systems to become widely available. This review looks briefly at the neutron and X-ray based systems that have been developed indicating their mode of operation and their advantages and disadvantages. It then summarizes the current state-of-the-art. The paper finishes by looking in some detail at one of the most promising areas of development—in-line diffraction measurements. 相似文献
22.
White beam neutron diffraction by time-of-flight (TOF) technique has been studied over a number of years as it is believed
to be the most convenient method to investigate solids in a fixed geometry. This technique needs a pulsed neutron source and
a suitable multichannel, analysing system. The entire system is in general, mechanically quite intricate and expensive.
We have investigated an alternative technique to achieve the end result of a constant geometry around the diffracting sample.
This involves the use of a single crystal as an analyser to study diffraction pattern from the sample bathed in a white beam
and diffracting at any fixed scattering angle. In this paper we report the results of our investigations and have compared
this technique with other diffraction techniques. Taking Si, KCl and KNO3 as typical specimens we have illus. trated the results of our technique and we find that the results are comparable to those
obtained by conventional neutron diffraction and TOF diffraction. The technique is simple in mechanical design and data acquisition.
It can be easily adapted for high pressure diffraction which is being attempted. 相似文献
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