HIGH RESOLUTION DETERMINATION OF THE SPATIAL DISTRIBUTION OF RADIOISOTOPES WITH A DIGITAL INTENSIFIED DETECTOR

Digital imaging has proven to be a valid technique to determine the spatial distribution of radioisotopes in nuclear applications. In the present work, an intensified EBCCDcamera with 80 mm photocathode and a fiber optics plate covered by a thin Gadolinium oxysulfide layer was used as a detector to obtain a digital map of the activity distribution for a variety of beta sources. The distribution map was elaborated and displayed in a 1024 · 1024 pixel format by using digital imaging techniques. The decay constant of various radioisotopes was calculated in different regions of interest of the image, with a deviation of 5–9% (depending on the signal intensity) from theoretical values, even in single pixel areas. The EBCCDcamera has shown strong detection capabilities even for single beta particle interaction and the response of the system has found to be very fast, allowing us to achieve a real time distribution map of radioisotopes. In fact, it is possible to load in RAM and display on a monitor a single distribution image map in about 1 s. Better distribution uniformity was obtained by integrating a sequence of 16, 32 or 64 images. By analysing a single beta interaction (i.e. a point spread function (PSF) on the image) the modulation transfer function (MTF) of the system has been calculated leading to a global resolution of about 80 m at 10% MTF