Mjerenje nuklearnih reakcija sa snopom 3^He na jezgrama 2^H, 9^Be i 12^C

master's thesis

• Title (english): Measurements of nuclear reactions with the 3^He beam on the 2^H, 9^Be and 12^C
• Author: Luka Palada
• Mentor: Neven Soić (mentor)
• Mentor: Matko Milin (mentor)
• Committee member: Matko Milin (predsjednik povjerenstva)
• Committee member: Neven Soić (član povjerenstva)
• Committee member: Nils Paar (član povjerenstva)
• Committee member: Mihael Makek (član povjerenstva)
• Committee member: Ivica Smolić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Physics); Zagreb
• Defense date and country: 2019-07-19, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics

Abstract

Nuklearna reakcija je proces interakcije dvije atomske jezgre u kojem dolazi do izmjene energije i nukleona između jezgara. Zbog vrlo kratkog dosega nuklearne sile i jakog kulonskog odbijanja između jezgara, do izmjene nukleona može doći ako je relativna brzina između reaktanata dovoljno velika da vodi na značajnu vjerojatnost tuneliranja kroz kulonsku barijeru. Dinamika nuklearne reakcije ovisi prvenstveno o dostupnoj ukupnoj energiji u procesu, ali i značajnim dijelom o gradi jezgara koje sudjeluju u reakciji. Istovremeno nuklearne reakcije su važan alat za proučavanje grade jezgara. Ogroman dio danas poznatih podataka o atomskim jezgrama nađen je proučavanjem reakcija. Porastom količine poznatih podataka o nuklearnim reakcijama i gradi jezgara razvijene su mnoge analitičke metode bazirane na nuklearnim reakcijama koje se danas standardno koriste u brojnim područjima istraživanja. Nuklearne reakcije se danas često koriste u kvantitativnim istraživanjima raznih uzoraka, a napredne metode omogućuju relativno brzo 2D i 3D mapiranje vrlo malih količina izotopa velikog broja kemijskih elemenata u širokom spektru uzoraka. Mjerenja nuklearnih reakcija obavljena u sklopu ovog rada dio su šire eksperimentalne kampanje mjerenja udarnih presjeka nuklearnih reakcija izazvanih snopom 3He na različitim metama u rasponu energija snopa od 1.2 do 5 MeV u širokom području kutova od 110° - 170°. U ovom radu je prikazan prvi set mjerenja u kojem je postavljen i testiran eksperimentalni postav za mjerenje nuklearnih reakcija na akceleratorskom postrojenju Instituta Ruđer Bošković. U ovoj eksperimentalnoj kampanji prikupit će se kvalitetni podaci udarnih presjeka za niz nuklearnih reakcija s 3^He snopom koji trenutno ili nisu dostupni ili su dostupni, ali s velikim pogreškama mjerenja i za ograničene skupove energija snopa i kutova. Ti udarni presjeci su ključni podaci potrebni za karakterizaciju širokog spektra uzoraka medu kojima su i uzorci potrebni za razvoj fuzijskih postrojenja u okviru međunarodnog projekta Eurofusion financiranog od strane Europske komisije. Konkretno u ovom radu izmjerene su reakcije na metama 9^Be, CD_2 i 12^C. Energije snopa iznosile su 2.4 i 4 MeV. Produkti reakcija detektirani su u dva dvostruko segmentirana silicijska vrpčasta detektora (DSSSD). Na svakoj od meta promatrani su sljedeći procesi: elastično raspršenje na podlozi od zlata, elastično raspršenje na meti, reakcija s 1^H kao jednim od produkata, te reakcija s 4^He kao jednim od produkata. Kalibracija detektora izvršena je izvorom koji emitira čestice na tri različite energije. Navedene reakcije, pobuđena stanja nedetektiranih jezgara i ispravnost kalibracije promatrani su 2D histogramima ovisnosti energije pobuđenja o kutu detekcije. Dobiveni rezultati diskutirani su u kontekstu mehanizma nuklearne reakcije i strukture jezgara uključenih u reakcije.

Abstract (english)

Nuclear reaction is a process of interaction of two nuclei in which energy and nucleons exchange between nuclei takes place. Because of the very short nuclear force range and the strong Coulomb repulsion between the nuclei, the nucleons exchange can occur if the relative velocity between the reactants is large enough to lead to a significant probability of tunneling through Coulomb barrier. The dynamics of the nuclear reaction depends primarily on the available total energy in the process, but also significantly on the nucleus structure of nuclei that take part in the reaction. At the same time, nuclear reactions are an important tool for studying nuclear structure. The vast part of today’s known atomic nuclei data was found by studying nuclear reactions. By the enlarge of known nuclear reaction and nuclear structure data, many analytical methods based on nuclear reactions have been developed, which are nowadays standardized tools in numerous researches. Nuclear reactions are often used in quantitative analysis of various material samples, and advanced methods allow for relatively fast 2D and 3D mapping of very small quantities of isotopes of a large number of chemical elements in a wide spectrum of material samples. Measurements of nuclear reactions carried out within the frame of this thesis are part of a wider experimental campaign of measuring cross-sections of nuclear reactions induced by the 3^He beams on different targets in energy range of 1.2 to 5 MeV on the wide-angle area of 110° - 170°. This thesis presents the first set of measurements in which an experimental setup was set and tested for measuring nuclear reactions at the accelerator facility of the Ruđer Bošković Institute. In this experimental campaign, high-quality data of the cross-sections for a number of nuclear reactions induced with the 3^He beam, which were not measured yet or existing results have large measurement errors and cover only small range of energies and angles, will be collected. Those cross sections represent key data required for the characterization of a wide spectrum of material samples, including samples required for the development of fusion plants within the framework of the Eurofusion international project funded by the European Commission, are listed. In this thesis reactions on the 9^Be, CD_2 and 12^C targets were measured. The beam energies were 4 and 2.4 MeV. The reaction products were detected with two double sided silicon strip detectors (DSSSD). The following processes were observed on each target: elastic scattering on a gold backing, elastic scattering on the target, reaction with 1^H as one of the products and reaction with 4^He as one of the products. The calibration of the detectors was performed by a source emitting particles of three different energies. Mentioned reactions, the excited states of the not detected nuclei and the calibration accuracy were observed by the 2D histograms of the excitation energy on the detection angle dependence. The obtained results are discussed in the context of the mechanism of nuclear reaction and the structure of nuclei involved in the reactions.

• Keywords: nuklearne reakcije; direktne reakcije; reakcije složenom jezgrom; lake jezgre; nuklearna struktura; tandem Van de Graaff ubrzivač; DSSSD detektori
• Keywords (english): nuclear reactions; direct reactions; compound nucleus reactions; light nuclei; nuclear structure; tandem Van de Graaff accelerator; DSSSD detectors
• Language: croatian
• URN:NBN: urn:nbn:hr:217:526811
• Study programme: Title: Physics; specializations in: Research; Course: Research; Study programme type: university; Study level: integrated undergraduate and graduate; Academic / professional title: magistar/magistra fizike (magistar/magistra fizike)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2020-01-07 10:00:25