Measurements of gamma-ray production cross sections of proton beam at energies of 66 to 125 MeV with calcium target

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dc.contributor.authorKunyana, Ayanda
dc.date.accessioned2018-08-06T15:05:17Z
dc.date.available2018-08-06T15:05:17Z
dc.date.issued2018
dc.descriptionA dissertation submitted to the Faculty Of Science and Agriculture in fulfillment of the requirements for the Degree of Master Of Science in the Department of Physics at the University Of Zululand, 2018en_US
dc.description.abstractCosmic rays are highly energetic charged particles not produced on Earth. Primary cosmic rays are composed mainly of protons, alpha particles and nuclei of many heavier elements. Secondary cosmic rays including neutrons, pions, positrons, and muons are created following the interaction of primary cosmic rays with atmo- sphere. A lot of radioisotopes are formed by interactions with cosmic rays. Most cosmogenic isotopes are formed in the atmosphere, while some are formed in-situ in soil and rock exposed to cosmic rays. One of the most important isotopes pro- duced by interaction of secondary cosmic rays with 40Ca is 41Ca. It is formed by 40Ca(n; )41Ca nuclear reaction. Worthy to note that 40Ca is one of the most abundant element in the Earth's crust. However, what would happen if instead of a neutron a proton interacts with the calcium nucleus? This study investi- gates the excitations of 40Ca following interactions with high-energy protons in 40Ca(p; p0)40Ca reaction. We use the information carried out by the -rays dur- ing the de-excitation of the 40Ca nucleus to calculate the -ray production cross sections, which relate to the probability of the 40Ca(p; p0)40Ca reaction to occur. This helps to gain information about the processes that occur in the stars and in the interstellar space, see section 1.3.2.Similar reactions take place when a high-energy protons interact with calcium in human tissues. High-energy protons can destroy cancer cells. Hence, during proton therapy, a proton beam of speci_c radiation dose is delivered to the tumor while sparing the nearby healthy tissues. Without continuous monitoring of the delivered proton beam, this can turn into a disaster. To fully enjoy the benefits of proton therapy we need to monitor the dose deposition. During the treatment,the proton beam delivered is absorbed by the patient. The only way to get the in-vivo dose verification measurements is by using secondary radiation. Using the information from the detection of secondary prompt -rays helps to determine the location of the deposited dose since the two are mutually related.The aim of this research is to evaluate the prompt -ray production cross sections, measured for strong -ray lines excited in the proton bombardment of a calcium target. The _first part of this study was to experimentally measure the -ray production cross sections for proton-nucleus collisions in calcium. To achieve these cross section measurements, thin natural calcium targets were bombarded with a proton beam in the energy range of 66 MeV to 125 MeV delivered by the Separated Sector Cyclotron (SSC) at iThemba LABS.Three standard -ray emitting sources, 137Cs, 60Co and 152Eu, were used for energy and e_ciency calibrations of the detectors. Geant4 code was run for modeling the efficiency of the AFRODITE detector system for E > 1:4 MeV . The emitted -rays were detected with the high-purity Ge detectors of the AFRODITE array in the angular range of 90_ to 168_. The total cross sections for the 754.8 keV and the 3736.5 keV peaks were determined by fitting the angular distribution data with Legendre polynomials. We extracted for the first time the total cross section excitation functions for the 40Ca(p; p0)40Ca reaction for two -rays in 40Ca at five different energies (66, 80, 95, 110 and 125 MeV ). The results from these measurements can be used in a range of applications in radiation therapy, geology and astrophysics.en_US
dc.description.sponsorshipNational Research Foundationen_US
dc.identifier.urihttps://hdl.handle.net/10530/1701
dc.publisherUniversity of Zululanden_US
dc.subjectAFRODITE --cross section --beam energy --Gamma ray ( -ray)en_US
dc.titleMeasurements of gamma-ray production cross sections of proton beam at energies of 66 to 125 MeV with calcium targeten_US
dc.typeThesisen_US
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