Gamma Camera - advantages and limits identifying sources over a broad energy range

Radioactive or nuclear material could fall into the wrong hands and pose a serious threat to society. If it is suspected that this type of radioactive or nuclear material is present in an area, it is necessary to locate it and identify any material found. Especially in the case of nuclear material involved there is an urgent need to identify and classify the material. To do this simultaneously and within the shortest possible time, gamma cameras are used. It is of great interest to investigate the limits and characteristics of this kind of non-destructive technology. This paper presents the results of tests carried out with NUVIA’s NuVISION, a mobile spectrometric gamma imaging system equipped with a cadmium zinc telluride (CZT) detector. It comprises a high-resolution capability using a coded mask and a 360° field of view (FOV) using Compton imaging. The fast signal processing enables real-time display of the measurement results. The orientation of the measurement system can be controlled remotely by rotation of the detection head in three axes.
The sensitivity of CZT detectors is relatively low at higher energies, therefore the detection of 60Co with energies of 1173 keV and 1332 keV is of particular interest. The difference in performance for radioactive materials covering the energy range from 241Am to 60Co is investigated. Moreover, the spatial distribution is analyzed in order to investigate the geometric sensitivity from the Compton imaging. The influence of different shielding material on the performance of the gamma camera is also studied. In addition, the dependence of the measurement time on the quality of the measurement results is investigated.