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Emerald Group Publishing Limited
Copyright © 2002, MCB UP Limited
Diamond detectorsKeywords: Sensors, Radiation
Diamond has an extremely high resilience to radiation – three orders of magnitude higher than silicon – making it an ideal material for detectors that monitor radioactivity inside nuclear energy plants. But because of the high price of real diamond, synthetic diamond is needed. The latest developments in making and improving synthetic diamond were presented by Dr Bergonzo of CEA Saclay (the French Atomic Energy Commissariat) at the Institute of Physics Congress 2002 (8 April 2002).
Diamond has many enviable properties that make it desirable to reproduce synthetically. As well as being highly resilient to radiation, unlike other semiconductors it hardly reacts with any chemicals, particularly acids. As radioactive waste is reprocessed by separating the constituents using acids, diamond radiation monitoring devices would be the perfect detectors.
But the problem with synthetic diamond is that it is a long way from the quality of the real thing, so researchers are concentrating their efforts on finding uses for this imperfect substitute. Dr Bergonzo and colleagues are currently tailoring the synthetic diamond so that it is ideal for monitoring radiation in the core of a nuclear reactor. Such measurements are usually performed using large and bulky devices known as gaseous ionisation chambers, because solidstate devices cannot withstand the high radioactivity levels. Smaller devices based on synthetic diamonds would be much better.
"Of course the ultimate goal is to improve the quality of synthetic diamond, but unlike silicon, its quality can't be improved by melting it – when diamond is heated it turns into graphite – its ugly brother. It is consequently very difficult to make good quality synthetic diamond with current technology", said Dr Bergonzo. "Until we have the technology to make really good quality synthetic diamond, it is important that we find and develop ways of using what we've got".
Diamond devices could be used to measure the amount of radioactivity a cancerous tumour receives during radiotherapy. Because both the diamond detector and the human body are carbon-based, the dose received by the detector can be compared directly to that received by the tumour, without the need for complicated calculations.