The 13C(3He,α₀₁₂)12C reactions at sub-Coulomb energies present an opportunity to study the spectroscopy of the compound nucleus 16O at relatively high excitation energies thanks to their high -value. 16O is a self-conjugate nucleus meaning that a number of its excited states might be explained by the quartet model, which assumes the presence of quasi-single-particle structure of quartets, composed of 2 protons and 2 neutrons. The experimental data available in the literature regarding these reactions is particularly scarse at low bombarding energies, where only old and incomplete data has been published, involving a limited range of angles and energies. With the HELICA experiment, the absolute cross sections of the 13C(3He,α₀₁₂)12C reactions were measured, for the first time, at 1.4 - 2.2 MeV bombarding energies over a large angular domain. The experiment exploited high-quality 3He beams produced at the AN2000 accelerator of Legnaro National Laboratories (LNL), and a dedicated array of a new generation modular hodoscope: OSCAR. This thesis introduces the theory behind the 13C(3He,α₀₁₂)12C reactions and deals with the detailed derivation of experimental absolute cross sections. The energy calibration of the silicon detectors of OSCAR is discussed with examples concerning various techniques that were used to calibrate different detection stages. The identification method is laid out for the reaction ejectile of interest, namely the α-particles. Lastly, new results of the absolute cross section and the angular distributions at various energies are presented and future studies are proposed to reveal possible resonance structures in the compound nucleus and the competition with direct processes.
Le reazioni 13C(3He,α₀₁₂)12C a energie sub-coulombiane rappresentano una opportunità per studiare la spettroscopia del nucleo composto 16O a energie di eccitazione relativamente alte grazie al loro alto -value. 16O è un nucleo auto-coniugato, nel quale un certo numero degli stati eccitati può essere spiegato dal modello a quartetto, che presuppone la presenza di una struttura quasi-particella-singola di quartetti composti da 2 protoni e 2 neutroni. I dati sperimentali disponibili in letteratura su queste reazioni a basse energie di bombardamento sono vecchi e incompleti poiché coinvolgono un range limitato di angoli ed energie. Con l'esperimento HELICA, sono state misurate per la prima volta le sezioni d'urto assolute delle reazioni 13C(3He , α₀ ₁ ₂ )12C a energie di bombardamento di 1.4 - 2.2 MeV. L'esperimento ha fatto uso dei fasci accelerati di 3He prodotti dall'acceleratore AN2000 dei Laboratori Nazionali di Legnaro (LNL) e di un array dedicato di odoscopi modulare di nuova generazione: OSCAR. Questa tesi introduce la teoria alla base delle reazioni 13C(3He,α₀₁₂)12C e si occupa della derivazione delle sezioni d'urto in unità assolute. La calibrazione in energia dei rivelatori al silicio di OSCAR è discussa con esempi riguardanti varie tecniche, che sono state utilizzate per calibrare i diversi stadi di rivelazione. Il metodo di identificazione utilizzato permette di misurare in modo non ambiguo l’eiettile di reazione di interesse, ovvero le particelle α. Infine, vengono presentati i nuovi risultati della sezione d'urto in termini assoluti e delle distribuzioni angolari a varie energie, e vengono proposti possibili studi futuri per sondare strutture risonanti nel nucleo composto e il ruolo di effetti diretti.
Studio della reazione 3He+13C con l'apparato OSCAR.
AYTEKIN, MUALLA
2021/2022
Abstract
The 13C(3He,α₀₁₂)12C reactions at sub-Coulomb energies present an opportunity to study the spectroscopy of the compound nucleus 16O at relatively high excitation energies thanks to their high -value. 16O is a self-conjugate nucleus meaning that a number of its excited states might be explained by the quartet model, which assumes the presence of quasi-single-particle structure of quartets, composed of 2 protons and 2 neutrons. The experimental data available in the literature regarding these reactions is particularly scarse at low bombarding energies, where only old and incomplete data has been published, involving a limited range of angles and energies. With the HELICA experiment, the absolute cross sections of the 13C(3He,α₀₁₂)12C reactions were measured, for the first time, at 1.4 - 2.2 MeV bombarding energies over a large angular domain. The experiment exploited high-quality 3He beams produced at the AN2000 accelerator of Legnaro National Laboratories (LNL), and a dedicated array of a new generation modular hodoscope: OSCAR. This thesis introduces the theory behind the 13C(3He,α₀₁₂)12C reactions and deals with the detailed derivation of experimental absolute cross sections. The energy calibration of the silicon detectors of OSCAR is discussed with examples concerning various techniques that were used to calibrate different detection stages. The identification method is laid out for the reaction ejectile of interest, namely the α-particles. Lastly, new results of the absolute cross section and the angular distributions at various energies are presented and future studies are proposed to reveal possible resonance structures in the compound nucleus and the competition with direct processes.File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.12608/41576