The CHNET TANDEM project (Cultural Heritage NETwork, Non-destructive Analysis Techniques for archEoMetry) of INFN aims to implement new non-invasive analysis techniques applicable in archeometry for the elemental characterization of archaeological samples. In particular, it would like to optimize two techniques: Muon Spectroscopy and Prompt Gamma-ray neutron Activation Analysis (PGAA). Both these techniques are based on the detection of prompt emissions of electromagnetic radiation: in the first case, of atomic type (muonic), in the second case, of nuclear type. PGAA involves the analysis of prompt photons emitted during nuclear disexcitation, the process that immediately follows the capture of a thermal neutron by a nucleus present in the sample (neutronic radiative capture process). By determining the energy of prompt photons, it is possible to trace back to what kind of nucleus is responsible for that emission, and therefore to the elemental composition of the sample in question. At LENA (Applied Nuclear Energy Laboratory) of the University of Pavia is under construction a facility to perform the PGAA: the archaeological samples are exposed to a beam of thermal neutrons produced by a research nuclear reactor (TRIGA Mark II) and with a dedicated HPGe detector (coaxial, of type n, 54x54 mm) are measured the prompt photons from the radiative capture processes occurred in the irradiated samples. The purpose of this thesis is to illustrate the characterization and optimization of the aforementioned HPGe detection apparatus, in order to perform PGAA at LENA. The characterization, performed both experimentally using standard calibration radioactive sources, both via Monte Carlo simulations with the MCNP code, involves the determination of the voltage and of the rise time which maximize the sensitive volume and the resolution of Ge crystal and the calibrations in energy, resolution and efficiency, necessary to determine the detector's response to the field of incident photons.
Il progetto INFN CHNET TANDEM (Cultural Heritage NETwork, Tecniche di Analisi Non Distruttive per l'archEoMetria) si propone di implementare nuove tecniche di analisi non invasive applicabili in archeometria per la caratterizzazione elementare di manufatti. In particolare, si vorrebbero ottimizzare due tecniche: la Spettroscopia Muonica e la Prompt Gamma-ray neutron Activation Analysis (PGAA). Entrambe le tecniche si basano sulla rivelazione di emissioni prompt di radiazione elettromagnetica: nel primo caso di tipo atomico (muonico), nel secondo di tipo nucleare. La PGAA prevede l’analisi dei fotoni prompt emessi durante la diseccitazione nucleare, processo immediatamente seguente la cattura di un neutrone termico da parte di un nucleo presente nel campione (processo di cattura neutronica radiativa). Determinando l’energia dei fotoni prompt, si può risalire a quale sia il tipo di nucleo responsabile dell’emissione, e quindi alla composizione elementare del campione in esame. Presso il LENA (Laboratorio Energia Nucleare Applicata) dell'Università degli Studi di Pavia è in fase di costruzione una facility in grado di eseguire la PGAA: i campioni archeologici vengono esposti a un fascio di neutroni termici in uscita da un reattore nucleare di ricerca (TRIGA Mark II) e con un detector HPGe dedicato (coassiale, di tipo n, 54x54 mm) vengono rivelati i fotoni prompt emessi dai processi di cattura radiativa avvenuti nei campioni irraggiati. Lo scopo di questa tesi è illustrare la caratterizzazione e l’ottimizzazione del suddetto apparato di rivelazione HPGe, al fine di eseguire la PGAA presso il LENA. La caratterizzazione, eseguita sia sperimentalmente con l’ausilio di sorgenti radioattive standard di calibrazione, sia tramite simulazioni Monte Carlo con il codice MCNP, prevede la determinazione della tensione e del rise time che massimizzano il volume sensibile e la risoluzione del cristallo di Ge e le calibrazioni in energia, in risoluzione e in efficienza, necessarie per determinare la risposta del rivelatore al campo di fotoni incidenti.
Caratterizzazione di un rivelatore HPGe per Prompt Gamma-ray neutron Activation Analysis (PGAA)
BARBESTA, CESARE
2017/2018
Abstract
The CHNET TANDEM project (Cultural Heritage NETwork, Non-destructive Analysis Techniques for archEoMetry) of INFN aims to implement new non-invasive analysis techniques applicable in archeometry for the elemental characterization of archaeological samples. In particular, it would like to optimize two techniques: Muon Spectroscopy and Prompt Gamma-ray neutron Activation Analysis (PGAA). Both these techniques are based on the detection of prompt emissions of electromagnetic radiation: in the first case, of atomic type (muonic), in the second case, of nuclear type. PGAA involves the analysis of prompt photons emitted during nuclear disexcitation, the process that immediately follows the capture of a thermal neutron by a nucleus present in the sample (neutronic radiative capture process). By determining the energy of prompt photons, it is possible to trace back to what kind of nucleus is responsible for that emission, and therefore to the elemental composition of the sample in question. At LENA (Applied Nuclear Energy Laboratory) of the University of Pavia is under construction a facility to perform the PGAA: the archaeological samples are exposed to a beam of thermal neutrons produced by a research nuclear reactor (TRIGA Mark II) and with a dedicated HPGe detector (coaxial, of type n, 54x54 mm) are measured the prompt photons from the radiative capture processes occurred in the irradiated samples. The purpose of this thesis is to illustrate the characterization and optimization of the aforementioned HPGe detection apparatus, in order to perform PGAA at LENA. The characterization, performed both experimentally using standard calibration radioactive sources, both via Monte Carlo simulations with the MCNP code, involves the determination of the voltage and of the rise time which maximize the sensitive volume and the resolution of Ge crystal and the calibrations in energy, resolution and efficiency, necessary to determine the detector's response to the field of incident photons.È consentito all'utente scaricare e condividere i documenti disponibili a testo pieno in UNITESI UNIPV nel rispetto della licenza Creative Commons del tipo CC BY NC ND.
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https://hdl.handle.net/20.500.14239/25448