The mankind increasingly spends effort and resources on fighting against drug traffic, international terrorism and illegal explosives and weapon transportation. Special attention is paid to technical ways of hazardous substance detection and control at critical strategic sites, in mass crowds, at air- and ground transport.
In the current technical facilities, the precision of drug and explosives detection facilities for nondestructive inspection of transported cargo and luggage has reached 30% to 40%. Distinct increase in probability of identification of prohibited and smuggled substances and goods was enabled by the zinc selenide semiconducting monocrystal synthesized by the specialists of the Scientific-Technological Concern “Institute of Monocrystals” (National Academy of Sciences of Ukraine) in Kharkov. The introscope equipped with X-radiation sensors, based on the monocrystal, is capable of recognizing 95% of the luggage contents without error.
Attendees of the International specialized “Security-2006” exhibition could observe the new introscope at work. The content of each suitcase or a bag is highlighted on the monitor screen as a colouful picture: different substances are painted by different colors. For example, organic matter is colored by tints of orange, and nonorganic substances – by dark-blue. Certainly, if necessary, the suspicious luggage is checked further, however, the extent of manual inspection has now significantly decreased. As traffic streams are constantly growing, one more advantage of new introscopes based on the Kharkov detectors is important – speed of operation. Within an hour, each of them can process by dozens of times more than the previous 200 units of luggage. The well-known German corporation Smiths Heimann GmbH now equips the largest airports of the world with batch-produced introscopes based on the Kharkov crystals.
The Kharkov researchers believe that it would be even more advantageous to use semiconducting zinc selenide monocrystals in the sphere of medical diagnostics. The intention is clear – there are about a thousand big airports operating in the world, but each modern clinic should be equipped with a medical tomographic scanner. The point is that the crystals based on zinc selenide possess optimal sensitivity for transmission of a human organism. With its help, a physician can get the diagnostic “picture” quicker than previously, without exposing the patient to unnecessary irradiation, and the picture will be of a higher quality - brighter, more contrasting and with the maximum possible resolving capacity. A specialist will be able to see the nidus of pathology of less than a millimeter in size. Specialists of the ELECTROPHYSICS Scientific-Production Association in Russia have already established a pre-production model of medical fluorograph based on the Kharkov crystals, the model showing excellent results.
What is the secret of these semiconducting crystals? It is in their unique ability to transform external action, for example, radiation, directly into light or electricity. That is, in fact, the processor function is initially imbedded in them. Taking into account rather universal design schemes of contemporary devices, this ability turned out to be very important.
Interest to these semiconducting crystals arose long ago, forty years back, however at that time researchers failed to get zinc selenide samples with stable characteristics due to its surprising unexpectedness. Once the growth conditions are slightly changed, the crystal might change so drastically that it could hardly be recognized. For example, while remaining the same zinc selenide from the chemical point of view, it could change the color and specific resistance. The effect is even more striking upon introduction of the third component on top of selenium and zinc, for example tellurium – every time, there appeared a crystal with different properties.
The achievement of Ukrainian researchers and technologists is that they are the first and still the sole in the world who managed to “tame” the capricious material and to design the facilities that allow to introduce admixture and to change semiconductor crystal growth conditions with complete confidence in the final result. Besides such areas of application as nondestructive inspection and medical diagnostics, the Kharkov specialists are planning to use the materials based on zinc selenide for monitoring of ionizing radiation in the environment, in technological and medical lasers.
Out of hundreds of semiconducting materials known to science, few of them (but for classical germanium and silicon) are applied in contemporary engineering. It is not because they are not good, but because of complexity of search for optimal utilization area of a certain compound. To this end, it is necessary not only to give detailed response to a long chain of physical, chemical and technological questions, but to offer specific practical implementation of these developments.
The Scientific-Technological Concern “Institute of Monocrystals” (National Academy of Sciences of Ukraine) has already created more than thirty crystals for utilization in various spheres of science, engineering and medicine. The experimental-industrial plant operates based on the Scientific-Technological Concern, the plant being certified in compliance with international standards. The Kharkov researchers are able not only to fully meet the demand of the instrument-making industry in the Ukraine for semiconducting crystals and articles made of them, but also to sell them at the international science intensive production market.
(The photograph is available)
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