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

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.