ABSTRACT
In the framework of the PREDIS EU project, a wireless battery-operated gamma-ray detection system was developed in order to provide a medium-to-long-term monitoring system for radioactive waste drums. It was initially proposed to monitor the gamma radioactivity outcoming from steel drums containing cemented radwaste, even though it could be usefully employed in a wider range of applications. Gamma rays are penetrating and convey information from the drum's internal structure, as the count rate measured on the surface depends on the thickness and density of the crossed materials. A number of sensors arranged around a drum, typically four units, provide indications of the emission anisotropy, and any sensitive change in the measured count rate would hint at some anomaly, thus triggering a suitable inspection by operators.
ABSTRACT
The photosensitivity, responsivity, and signal-to-noise ratio of organic phototransistors depend on the timing characteristics of light pulses. However, in the literature, such figures of merit (FoM) are typically extracted in stationary conditions, very often from IV curves taken under constant light exposure. In this work, we studied the most relevant FoM of a DNTT-based organic phototransistor as a function of the timing parameters of light pulses, to assess the device suitability for real-time applications. The dynamic response to light pulse bursts at ~470 nm (close to the DNTT absorption peak) was characterized at different irradiances under various working conditions, such as pulse width and duty cycle. Several bias voltages were explored to allow for a trade-off to be made between operating points. Amplitude distortion in response to light pulse bursts was also addressed.