COCAE

Cooperation across Europe for Cd(Zn)Te based Security Instruments

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 Obiettivo del progetto (Objective)

'The proposal concerns the technology development for instruments with the following capabilities: (a) To make spectroscopic measurements with efficiency equivalent to that of NaI detectors and energy resolution close to that of HPGe devices but without using cryogenic systems. (b) To find the direction and the distance of the radioactive source. (c) To localize the source into a cargo and estimate the radioactive source activity taking information about the source environment (shielding, absorption in the surrounding materials) (d) To work at a wide range of absorbed dose rates by adjusting the effective volume of the detector. The above capabilities will improve the quality of the data gathered by the customs officers during the routine inspections at the boarders and will assist the first responders in case of a radiological or nuclear emergency to estimate the exact situation. Basic tasks of the project will be: (a) The growth of high purity, detector grade Cd(Zn)Te crystals. Their performance will be optimized by material purification, selection of right dopants and post-growth processing to obtain high resistivity, high transport properties and homogeneous distribution of these material properties in the grown crystals. The growth of crystals with a diameter up to 75 mm will be performed. (b) The fabrication of pixel detectors having structure of p-n and Schottky diodes. This will permit the application of bias voltage high enough to collect all the induced charge by both electrons and holes. (c) The design of pixel electronics capable for simultaneous imaging and spectroscopy. The electronics will be bump bonded to the pixel detectors. This is essential for the localization and the identification of the radioactive source. (d) The construction of a portable instrument having a stack of detecting elements. This will allow to exploit the Compton Effect for the localization of the radioactive source and also to have variable detection efficiency.'

Introduzione (Teaser)

The technology needed to build portable state-of-the-art radiation detectors has been developed, encouraging innovative companies to commercialise new systems in the field.

Descrizione progetto (Article)

Japan's Fukushima Daiichi nuclear disaster showed the world how important it is to assess hazards rapidly and respond to situations where radiation could be an issue. One effective response system requires radiation detectors that rely on a compound of cadmium, zinc and tellurium (Cd(Zn)Te). With this in mind, the EU-funded project 'Cooperation across Europe for Cd(Zn)Te based security instruments' (COCAE) worked on developing a portable instrument that can accurately pinpoint radiation type and source.

To overcome current detector technology that is expensive and prone to errors, the project team employed principles that are inspired by high-energy astrophysics. It focused on cultivating high-grade Cd(Zn)Te crystals in Europe and exploiting advanced pixel electronics to achieve highly accurate radioactive source localisation and identification within a few metres.

Project members also envisaged the inclusion of a camera system to identify and map radioisotopes in different situations. This is useful for monitoring security near border areas, recycling plants and nuclear waste facilities, as well as for decommissioning nuclear installations or facilitating emergency responses. Technological advances in this respect were based on the Compton imaging technique and efficient crystal growth, in addition to advanced diode detectors and semiconductor technology to process information.

COCAE produced valuable research in this domain and made tremendous progress in developing the technology required to produce cutting-edge portable radiation detectors. It disseminated the project results through leading journals, the project website and key events such as conferences and symposia. This is an important step for commercialising a Cd(Zn)Te Compton camera system, whose technology could also benefit other industries such as the dental and medical ones.

Overall, the project's results pave the way for perfecting and exploiting this important European-based technology that enhances safety and security with positive effects relating to science and technology. This presents many opportunities for smaller enterprises that want to invest in the technology.