Installation and optimization of a gamma spectrometry system in anticoincidence.

The work covered by this thesis was carried out at the Brasimone ENEA Research Centre, the National Agency for New Technologies, Energy and Sustainable Economic Development, with the aim of optimising a gamma spectrometry system in anticoincidence for the detection of noble gases, in particular the radioactive isotopes of xenon 131mXe, 133Xe, 133mXe and 135Xe. The laboratory of the ENEA Research Center of Brasimone, where the experimental apparatus is found to carry out the measurements of 131mXe, 133Xe, 133mXe and 135Xe, collaborates constantly with the monitoring network and is able to provide, if necessary, data and analysis on noble gases. The signals produced by the interaction of cosmic rays that manage to pass the screen have been recognized as the main cause of the increase of the detector background because they give rise to the Compton continuum and, as a result, they increase the value of detectable MDA. For this reason, a system in anticoincidence has been developed through the use of two plastic scintillators, placed over the shielding of the Hpge detector, which sends pulses recording within a gate located in the germanium multichannel analyzer: at the time the signal arrives from the scintillator, the gate blocks data acquisition to avoid recording pulses generated by cosmic radiation. For both configurations of the system, therefore, both with the anti-coincidence apparatus inactive and in operation, energy, FWHM and efficiency calibrations had to be carried out using a certified multi-peak source. The solution proposed, in conclusion of the thesis, to eliminate any electronic interference with the efficiency of the detector provides for the replacement of the current electronic apparatus with a new fully digitized, made by the company CAEN, Nuclear Electronic Construction Equipment.