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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Produção de feixes radioativos ricos em nêutrons na região de massa A=10 a 15 / Production of neutron-rich radioactive beams in region of mass A=10 to 15

George Abud Scotton 26 April 2017 (has links)
Investigação da estrutura de núcleos exóticos é uma área bastante ativa da Física Nuclear atual. O desenvolvimento dessa área foi acentuado com a possibilidade de uso de feixes radioativos. Inspirados nessa possibilidade, laboratórios espalhados pelo mundo estão se desenvolvendo para produzir feixes radioativos de núcleos cada vez mais ricos em prótons ou em nêutrons. O uso de elementos radioativos como feixes têm oferecido oportunidades novas e únicas para pesquisa em física nuclear. Questões fundamentais tais como qual a natureza da matéria nuclear e como elementos pesados são sintetizados em novas, supernovas e estrelas de nêutrons podem ser abordadas em investigações utilizando-se feixes radioativos. Neste trabalho abordamos a produção de alguns desses feixes na região de massa A=10 e 15, especificamente, 10Be, 12B, 14C e 15C. Descrevemos métodos de produção e aplicamos simulações para produção de feixes com esses núcleos. Abordamos as peculiaridades na produção de cada um deles com o intuito de produzir feixes o mais intenso e puros possíveis. Nas simulações utilizamos a plataforma Lise++ baseada em método de Monte Carlo e foi dada ênfase na utilização de um sistema de duplo-solenoides. As simulações foram comparadas com resultados experimentais obtidos com esse sistema para os feixes de 12B e 14C, onde um bom acordo foi obtido. / Nuclear Structure Investigations of exotic nuclei is currently a very active area of Nuclear Physics. Many laboratories around the world are developing their system to produce radioactive beams of nuclei rich in protons or neutrons. The use of these radioactive elements as beams has offered new and unique opportunities for research in nuclear physics. Fundamental questions such as what the nature of nuclear matter is and how heavy elements are synthesized in novae, supernovae and neutron stars can be addressed in investigations using radioactive beams. In this work we address the production of some of these beams in the region of mass A = 10 and 15, specifically 10Be, 12B e 14,15C. We describe production methods and apply simulations using the plataforma Lise++ with Monte Carlo method. We addressed the peculiarities related to the production of each of them, in the sense to get the most intense and pure secondary radioactive beams possible. In the simulations, emphasis was given to the use of a double-solenoid system. The simulations were compared with experimental results obtained with these systems for the 12B and 14C beams, where a good agreement was obtained.
12

High resolution β-decay study of neutron-rich (74-77)Zn into (74-77)Ga

Siwakoti, Durga P 09 August 2019 (has links)
Previously developed Zn decay schemes were limited by a number of factors including low production rates and detector efficiencies making it impossible to place weak transitions. Furthermore, most of the published results are from initial exploratory measurements while subsequent studies in this region either ignored the data obtained from the Zn decays or was not analyzed due to the focus on more exotic nuclei. In the current experiments, a nearly pure beam of the Cu isotope was provided by the Holifield Radioactive Ion Beam Facility (HRIBF) for the study of the Cu -> Zn -> Ga -> Ge β-decay chain using the Low-energy Radioactive Ion Beam Spectroscopy Station (LeRIBSS) setup. The high efficiency of the detector system along with the nearly pure primary beam allowed a detailed study of the γ-ray emission from the decay chain without any member of the decay chain being dominant. The γγ and βγ gamma coincidence data obtained from the experiment was used to develop revised decay schemes in which statistical significance for each observed coincidence peak was determined quantitatively. Presented in this work are updated and expanded decay schemes with new energy levels along with new βeeding intensities and logft values for the Zn -> Ga decays. In each of the Zn decays, a number of new energy levels and transitions have been proposed to the structure of respective Ga isotopes in addition to correcting discrepancies from previous works. The 74Zn β decay now has 29 new γ rays assigned to 74Ga in addition to previous 35 transitions (Winger et al., 1989} depopulating 19 energy states, including 7 new ones. The maximum level energy is increased from previous 1086- to 1555-keV. Similarly, the updated 75Zn decay scheme has its level energy increased from previous (Ekstrom et al., 1986) 3209- to 3924-keV, with addition of 37 new energy levels and 53 new γ rays. New decay scheme for 76Zn is established up to 2603 keV, similar to previous literature (Ekstrom et al.) with addition of 4 new energy levels and total of 5 new γ-ray transitions. In case of 77Zn decay, we proposed the decay scheme up to 3948 keV with addition of 8 new energy levels and 10 new γ-ray transitions.
13

A feasibility study of the (3He,8He) reaction with the K600 magnetic spectrometer

Swartz, Jacobus Andreas 03 1900 (has links)
Thesis (MSc (Physics))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Highly exotic nuclei can be studied in rare reactions using stable beams, with macroscopic intensities, and thick targets. Exotic nuclei are interesting for a number of reasons e.g. for testing nuclear models under conditions of high isospins. In the case of very neutron-deficient nuclei, two-proton decay is the most recently discovered nuclear decay mode and the subject of many theoretical investigations involving cluster and shell models. This thesis presents a feasibility study of investigating light exotic nuclei near the proton drip line with the K600 magnetic spectrometer. The 27Al(3He,8He)22Al five-neutron pick-up reaction was investigated at a spectrometer angle of θlab = 8◦ with a beam energy of Elab = 220 MeV. This reaction can be used to populate highly neutron-deficient nuclei. Should the study of this reaction prove to be feasible, then a number of nuclei on the proton drip line or beyond could be investigated. A new data acquisition system, with VME electronics and MIDAS software, was used along with one new drift chamber, which consists of both an X wire plane and a U wire plane. The particles 1,2,3H and 3,4He were all identified as outgoing particles from the collision of 3He with 27Al. Cross section calculations were performed for these observed reactions. Discrete spectra for the (3He,6He) and (3He,8He) reactions could not be identified. The mass calculation of A ∼ 20 nuclei on the proton drip line depends on the determination of the Coulomb energy, which differs a lot between mirror nuclei. Mass calculations were performed for known nuclei in the mass region A ≤ 50, using the Isobaric Multiplet Mass Equation. Agreement with experimental data was found to be far better in odd nuclei than in even nuclei. Hence mass predictions were performed for odd nuclei along the proton drip line. / AFRIKAANSE OPSOMMING: Hoogs eksotiese kerne kan bestudeer word in seldsame reaksies deur middel van stabiele bundels, met makroskopiese intensiteite, en dik teikens. Eksotiese kerne is interessant om verskeie redes, onder andere om kernfisiese modelle te toets onder omstandighede van ho¨e isospin. In die geval van baie neutron-arm kerne is twee-proton verval die nuutste ontdekte tipe van kernverval. Dit is ook die onderwerp van vele teoretiese studies met betrekking tot bondel en skilmodelle. Hierdie tesis beskryf ‘n uitvoerbaarheidstudie vir die ondersoek van ligte eksotiese kerne naby die proton drup lyn met behulp van die K600 magnetiese spektrometer. Die 27Al(3He,8He)22Al vyf-neutron kaapreaksie is ondersoek by ‘n spektrometer hoek van θlab = 8◦ met ‘n bundel energie van Elab = 220 MeV. Sou die uitvoerbaarheidstudie van hierdie reaksie slaag, dan kan verskeie kerne op of anderkant die proton drup lyn ondersoek word. ‘n Nuwe data verkrygingssisteem, met VME elektronika en MIDAS sagteware, is gebruik saam met een nuwe dryfkamer, wat bestaan uit beide ‘n X draadvlak en ‘n U draadvlak. Die partikels 1,2,3H en 3,4He is almal geidentifiseer as uitgaande partikels van die botsing van 3He met 27Al. Kansvlak-berekeninge is uitgevoer vir alle waargenome reaksies. Diskrete spektra kon nie gevind word vir die (3He,6He) of (3He,8He) reaksies nie. Die massa berekening van A ∼ 20 kerne op die proton drup lyn is afhanklik van die bepaling van die Coulomb energie, wat baie verskil tussen spie¨elkerne. Massa berekeninge is uitgevoer vir bekende kerne in die massa gebied A ≤ 50, deur die gebruik van die Isobariese Multiplet Massa Vergelyking. Die ooreenstemming met eksperimentele data was baie beter in die geval van onewe kerne as met ewe kerne. Daarom was die massa voorspellings uitgevoer vir slegs onewe kerne naby die proton drup lyn.
14

Coulomb breakup of halo nuclei by a time-dependent method

Capel, Pierre 29 January 2004 (has links)
Halo nuclei are among the strangest nuclear structures. They are viewed as a core containing most of the nucleons surrounded by one or two loosely bound nucleons. These have a high probability of presence at a large distance from the core. Therefore, they constitute a sort of halo surrounding the other nucleons. The core, remaining almost unperturbed by the presence of the halo is seen as a usual nucleus. <P> The Coulomb breakup reaction is one of the most useful tools to study these nuclei. It corresponds to the dissociation of the halo from the core during a collision with a heavy (high <I>Z</I>) target. In order to correctly extract information about the structure of these nuclei from experimental cross sections, an accurate theoretical description of this mechanism is necessary. <P> In this work, we present a theoretical method for studying the Coulomb breakup of one-nucleon halo nuclei. This method is based on a semiclassical approximation in which the projectile is assumed to follow a classical trajectory. In this approximation, the projectile is seen as evolving in a time-varying potential simulating its interaction with the target. This leads to the resolution of a time-dependent Schrödinger equation for the projectile wave function. <P> In our method, the halo nucleus is described with a two-body structure: a pointlike nucleon linked to a pointlike core. In the present state of our model, the interaction between the two clusters is modelled by a local potential. <P> The main idea of our method is to expand the projectile wave function on a three-dimensional spherical mesh. With this mesh, the representation of the time-dependent potential is fully diagonal. Furthermore, it leads to a simple representation of the Hamiltonian modelling the halo nucleus. This expansion is used to derive an accurate evolution algorithm. <P> With this method, we study the Coulomb breakup of three nuclei: <sup>11</sup>Be, <sup>15</sup>C and <sup>8</sup>B. <sup>11</sup>Be is the best known one-neutron halo nucleus. Its Coulomb breakup has been extensively studied both experimentally and theoretically. Nevertheless, some uncertainty remains about its structure. The good agreement between our calculations and recent experimental data suggests that it can be seen as a <I>s1/2</I> neutron loosely bound to a <sup>10</sup>Be core in its 0<sup>+</sup> ground state. However, the extraction of the corresponding spectroscopic factor have to wait for the publication of these data. <P> <sup>15</sup>C is a candidate one-neutron halo nucleus whose Coulomb breakup has just been studied experimentally. The results of our model are in good agreement with the preliminary experimental data. It seems therefore that <sup>15</sup>C can be seen as a <sup>14</sup>C core in its 0<sup>+</sup> ground state surrounded by a <I>s1/2</I> neutron. Our analysis suggests that the spectroscopic factor corresponding to this configuration should be slightly lower than unity. <P> We have also used our method to study the Coulomb breakup of the candidate one-proton halo nucleus <sup>8</sup>B. Unfortunately, no quantitative agreement could be obtained between our results and the experimental data. This is mainly due to an inaccuracy in the treatment of the results of our calculations. Accordingly, no conclusion can be drawn about the pertinence of the two-body model of <sup>8</sup>B before an accurate reanalysis of these results. <P> In the future, we plan to improve our method in two ways. The first concerns the modelling of the halo nuclei. It would be indeed of particular interest to test other models of halo nuclei than the simple two-body structure used up to now. The second is the extension of this semiclassical model to two-neutron halo nuclei. However, this cannot be achieved without improving significantly the time-evolution algorithm so as to reach affordable computational times.
15

Investigação do espalhamento elástico do núcleo radioativo 12B em um alvo de 58Ni / Investigation of elastic scattering of radioactive 12B nucleus on 58Ni target.

Zevallos, Erick Oscar Natividad 22 August 2018 (has links)
No presente trabalho medimos e analisamos distribuições angulares para o processo de espalhamento elástico do núcleo radioativo de 12B em alvo de 58Ni. As medidas foram realizadas nas energias de Elab=30.0 e 33.0 MeV no laboratório do acelerador Pelletron. Essas energias são próximas a barreira Coulombiana (VB=28.0 MeV) para esse sistema. Para a produção do feixe radioativo de 12B utilizamos o sistema RIBRAS instalado nesse laboratório. As distribuições angulares foram analisadas com o modelo ótico, utilizando potenciais de Woods-Saxon e Potencial de São Paulo. Para uma interpretação física mais consistente e um estudo da influência de outros canais de reação no espalhamento elástico analisamos também considerando o método de canais acoplados. Considerando o acoplamento dos canais de espalhamento inelásticos, reorientação e spin-órbita pudemos descrever a distribuição angular na energia de 30.0 MeV. No entanto esses canais não foram suficientes para descrever a distribuição angular na energia de 33.0 MeV, indicando que outros canais como de transferência e/ou break-up possam ser importes. A partir da análise das distribuições angulares com modelo ótico obtivemos também a seção de choque total de reação. Essas seções de choque foram comparadas com a de outros sistemas utilizando métodos de redução, indicando que o projétil 12B segue uma sistemática intermediária entre núcleos fortemente ligados e fracamente ligados. Finalmente, discutimos a sistemática dos resultados de canais acoplados para o espalhamento elásticos dos isótopos de Boro 8,10,11,12B no alvo 58Ni em termos da configuração de clusters dos projéteis. / In the present work we measure and analyzed angular distributions for the process of elastic scattering of the radioactive nucleus of 12B in a target of 58Ni. The measurements were performed in the energies of Elab = 30.0 and 33.0 MeV in the Pelletron accelerator laboratory. These energies are close to the Colombian barrier (VB = 28.0 MeV) for this system. For the production of the radioactive beam of 12B we used the RIBRAS system installed in this laboratory. The angular distributions were analyzed with the optical model, using potentials of Woods-Saxon and Potential of São Paulo. For a more consistent physical interpretation and a study of the influence of other reaction channels in the elastic scattering we also analyze the coupled channel method. Considering the coupling of the inelastic scattering channels, reorientation and spin-orbit we could describe the angular distribution in the energy of 30.0 MeV. However, these channels were not enough to describe the angular distribution in the energy of 33.0 MeV, indicating that other channels as transfer and / or break-up can be amounts. From the analysis of the angular distributions with optical model we also obtained the section of total reaction shock. These cross sections were compared with those of other systems using reduction methods, indicating that projectile 12B follows a systematic intermediate between tightly bound and weakly bonded cores. Finally, we discuss the systematics of the results of elastic scattering channels of the Boron isotopes 8,10,11,12B in the 58Ni target in terms of the cluster configuration of the projectiles.
16

Medidas de espalhamento ressonante 6He+p e da reação 3He(7Be,)6 Be / Measurements of the 6He+p ressonant scattering and the 3He(7Be,)6Be reaction

Condori, Ruben Pampa 18 December 2012 (has links)
A espectroscopia de núcleos leves como ANTPOT. 6,7 Li e outros no contínuo é ainda um campo relativamente pouco explorado, e a possibilidade de se produzir esses núcleos a partir de canais de entrada envolvendo núcleos exóticos é relativamente recente. Em particular, o estudo do ANTPOT. 7 Li em energias de excitação em torno do limiar ANTPOT. 6 He+p é interessante pois corresponde a uma região próxima ao estado fundamental do exótico análogo isobárico ANTPO. 7 He. Neste trabalho, apresentamos resultados de um estudo do espalhamento ressonante ANTPOT. 6 He+p utilizando feixe de ANTPOT. 6 He. As medidas da função de excitação ANTPOT. 6 He+p foram realizadas no sistema RIBRAS (\"Radioactive Ion Beams in Brasil\") do Instituto de Física da Universidade de São Paulo. O feixe secundário foi produzido mediante a reação primária ANTPOT. 9 Be(ANTPOT. 7 Li, ANTPOT. 6 He). Fez-se pela primeira vez, uso do conjunto de dois solenóides do sistema RIBRAS para purificar o feixe secundário de ANTPOT. 6 He, que incide em um alvo sólido de CH IND. 2, grosso o bastante para parar o feixe incidente de ANTPOT. 6 He. Assim, somente as partículas leves de recuo foram detectados, as quais levam a informação do sistema composto ANTPOT. 7 Li. Dessa forma foram analisados os espectros obtidos das reações p(ANTPOT. 6 He,p) e p(ANTPOT. 6 He,). Além disso realizamos um estudo da reação ANTPOT. 3 He(ANTPOT. 7 Be, )ANTPOT. 6 Be. A experiência foi realizada no CRIB-RIKEN fazendo uso de um feixe puro de ANTPOT. 7 Be e um alvo gasoso de ANTPOT. 3 He. O feixe de ANTPOT. 7 Be tem uma energia de laboratório de E IND. lab= 53.4 MeV e foi produzido pela reação primária de ANTPOT. 7 Li(p, n)ANTPOT. 7 Be usando um alvo criogênico H IND. 2. Existem na literatura estados excitados identificados nos núcleos ANTPOT. 6 Li e ANTPOT. 6 He, mas apenas poucos estados no ANTPOT 6 Be. Além do interesse na estrutura nuclear, a importância destes estados no ANTPOT. 6 Be próximos ao limiar de ANTPOT. 3 He ANTPOT. 3 He a 11.48MeV está principalmente na astrofísica. A possível existência de ressonâncias perto deste limiar poderia trazer fortes implicações na queima próton-próton em estrelas. / The spectroscopy in the continuum of light nuclei such as 6,7 Li and others still remains a relatively unexplored field, and the ability to produce these nuclei from entrance channels involving exotic nuclei is relatively recent. In particular, the study of 7Li at excitation energies around the 6He+p threshold is interesting since it corresponds to a region near to the ground state of the exotic analog isobaric 7He. In this work we present the results of the study of the resonant scattering p+6He. The measurements of the excitation function of the system p+6He have been performed in the RIBRAS system (\"Radioactive Ion Beams in Brasil\") of the Institute of Physics of the University of São Paulo. The secondary beam has been produced by the primary reaction 9Be(7Li,6 He). For the first time, the two solenoids of the RIBRAS system have been used to purify the secondary 6He beam, which collides into a solid CH2, thick enough to stop the incident 6He beam. Only the light recoil particles have been detected, which provide information of the compound system 7Li. We analyzed the spectrum obtained from the p(6He,p) and p(6He,) reactions. In addition, we performed a study of the 3He(7Be, )6Be reaction. The experiment has been performed at the CRIB-RIKEN laboratory (Japan), using a pure 7Be beam and a 3He gas target. The 7Be beam had an energy of Elab = 53.4MeV and has been produced by the 7Li(p, n)7Be primary reaction, using a H2 cryogenic target. There are in the literature, excited states identified in the nuclei 6Li and 6He but only a few states in 6Be. Besides the interest in nuclear structure, the importance of these states at 6Be near the threshold of 3He3He at 11.48MeV lies mainly in astrophysics. The possible existence of resonances near this threshold could bring strong implications for proton-proton burning in stars.
17

Estudo do espalhamento elástico de projetéis exóticos por alvo de massa intermediária / Study of elastic scattering between exotic projectiles and medium target

Almeida, Viviane Morcelle de 22 May 2007 (has links)
Radioactive beams of 8Li and 6He were produced using the double superconducting solenoid system of RIBRAS (Radioactive Ion Beams in Brasil) with a primary beam of 7Li of Elab = 30 MeV, at the São Paulo Pelletron Accelerator. The production reactions were 9Be(7Li, 8Li)8Be and 9Be(7Li, 6He)10B. The angular distributions of the elastic scattering of the 8Li radioactive beam of 26.0 MeV and 6He radioactive beam of 23.0 MeV were measured on 51V target of 1.9 mg/cm2.The elastic scattering angular distributions were analyzed using Optical Model, where the real and imaginary parts are described through a Non-Local Interaction Model called São Paulo Potential . The results were compared with the data present in the literature. The largest cross section, particularly for the halo 6He, shows evidence of the importance of the break up for these medium mass systems. [1]R. Lichtenthaler et al, Eur. Phys. J. A 25,s01,733 (2005); [2]L.C. Chamon et al, Phys. Rev. C66 (2002) 014610. / Radioactive beams of 8Li and 6He were produced using the double superconducting solenoid system of RIBRAS (Radioactive Ion Beams in Brasil) with a primary beam of 7Li of Elab = 30 MeV, at the São Paulo Pelletron Accelerator. The production reactions were 9Be(7Li, 8Li)8Be and 9Be(7Li, 6He)10B. The angular distributions of the elastic scattering of the 8Li radioactive beam of 26.0 MeV and 6He radioactive beam of 23.0 MeV were measured on 51V target of 1.9 mg/cm2.The elastic scattering angular distributions were analyzed using Optical Model, where the real and imaginary parts are described through a Non-Local Interaction Model called São Paulo Potential . The results were compared with the data present in the literature. The largest cross section, particularly for the halo 6He, shows evidence of the importance of the break up for these medium mass systems. [1]R. Lichtenthaler et al, Eur. Phys. J. A 25,s01,733 (2005); [2]L.C. Chamon et al, Phys. Rev. C66 (2002) 014610.
18

Investigação do espalhamento elástico do núcleo radioativo 12B em um alvo de 58Ni / Investigation of elastic scattering of radioactive 12B nucleus on 58Ni target.

Erick Oscar Natividad Zevallos 22 August 2018 (has links)
No presente trabalho medimos e analisamos distribuições angulares para o processo de espalhamento elástico do núcleo radioativo de 12B em alvo de 58Ni. As medidas foram realizadas nas energias de Elab=30.0 e 33.0 MeV no laboratório do acelerador Pelletron. Essas energias são próximas a barreira Coulombiana (VB=28.0 MeV) para esse sistema. Para a produção do feixe radioativo de 12B utilizamos o sistema RIBRAS instalado nesse laboratório. As distribuições angulares foram analisadas com o modelo ótico, utilizando potenciais de Woods-Saxon e Potencial de São Paulo. Para uma interpretação física mais consistente e um estudo da influência de outros canais de reação no espalhamento elástico analisamos também considerando o método de canais acoplados. Considerando o acoplamento dos canais de espalhamento inelásticos, reorientação e spin-órbita pudemos descrever a distribuição angular na energia de 30.0 MeV. No entanto esses canais não foram suficientes para descrever a distribuição angular na energia de 33.0 MeV, indicando que outros canais como de transferência e/ou break-up possam ser importes. A partir da análise das distribuições angulares com modelo ótico obtivemos também a seção de choque total de reação. Essas seções de choque foram comparadas com a de outros sistemas utilizando métodos de redução, indicando que o projétil 12B segue uma sistemática intermediária entre núcleos fortemente ligados e fracamente ligados. Finalmente, discutimos a sistemática dos resultados de canais acoplados para o espalhamento elásticos dos isótopos de Boro 8,10,11,12B no alvo 58Ni em termos da configuração de clusters dos projéteis. / In the present work we measure and analyzed angular distributions for the process of elastic scattering of the radioactive nucleus of 12B in a target of 58Ni. The measurements were performed in the energies of Elab = 30.0 and 33.0 MeV in the Pelletron accelerator laboratory. These energies are close to the Colombian barrier (VB = 28.0 MeV) for this system. For the production of the radioactive beam of 12B we used the RIBRAS system installed in this laboratory. The angular distributions were analyzed with the optical model, using potentials of Woods-Saxon and Potential of São Paulo. For a more consistent physical interpretation and a study of the influence of other reaction channels in the elastic scattering we also analyze the coupled channel method. Considering the coupling of the inelastic scattering channels, reorientation and spin-orbit we could describe the angular distribution in the energy of 30.0 MeV. However, these channels were not enough to describe the angular distribution in the energy of 33.0 MeV, indicating that other channels as transfer and / or break-up can be amounts. From the analysis of the angular distributions with optical model we also obtained the section of total reaction shock. These cross sections were compared with those of other systems using reduction methods, indicating that projectile 12B follows a systematic intermediate between tightly bound and weakly bonded cores. Finally, we discuss the systematics of the results of elastic scattering channels of the Boron isotopes 8,10,11,12B in the 58Ni target in terms of the cluster configuration of the projectiles.
19

Estudo do espalhamento elástico de projetéis exóticos por alvo de massa intermediária / Study of elastic scattering between exotic projectiles and medium target

Viviane Morcelle de Almeida 22 May 2007 (has links)
Radioactive beams of 8Li and 6He were produced using the double superconducting solenoid system of RIBRAS (Radioactive Ion Beams in Brasil) with a primary beam of 7Li of Elab = 30 MeV, at the São Paulo Pelletron Accelerator. The production reactions were 9Be(7Li, 8Li)8Be and 9Be(7Li, 6He)10B. The angular distributions of the elastic scattering of the 8Li radioactive beam of 26.0 MeV and 6He radioactive beam of 23.0 MeV were measured on 51V target of 1.9 mg/cm2.The elastic scattering angular distributions were analyzed using Optical Model, where the real and imaginary parts are described through a Non-Local Interaction Model called São Paulo Potential . The results were compared with the data present in the literature. The largest cross section, particularly for the halo 6He, shows evidence of the importance of the break up for these medium mass systems. [1]R. Lichtenthaler et al, Eur. Phys. J. A 25,s01,733 (2005); [2]L.C. Chamon et al, Phys. Rev. C66 (2002) 014610. / Radioactive beams of 8Li and 6He were produced using the double superconducting solenoid system of RIBRAS (Radioactive Ion Beams in Brasil) with a primary beam of 7Li of Elab = 30 MeV, at the São Paulo Pelletron Accelerator. The production reactions were 9Be(7Li, 8Li)8Be and 9Be(7Li, 6He)10B. The angular distributions of the elastic scattering of the 8Li radioactive beam of 26.0 MeV and 6He radioactive beam of 23.0 MeV were measured on 51V target of 1.9 mg/cm2.The elastic scattering angular distributions were analyzed using Optical Model, where the real and imaginary parts are described through a Non-Local Interaction Model called São Paulo Potential . The results were compared with the data present in the literature. The largest cross section, particularly for the halo 6He, shows evidence of the importance of the break up for these medium mass systems. [1]R. Lichtenthaler et al, Eur. Phys. J. A 25,s01,733 (2005); [2]L.C. Chamon et al, Phys. Rev. C66 (2002) 014610.
20

Medidas de espalhamento ressonante 6He+p e da reação 3He(7Be,)6 Be / Measurements of the 6He+p ressonant scattering and the 3He(7Be,)6Be reaction

Ruben Pampa Condori 18 December 2012 (has links)
A espectroscopia de núcleos leves como ANTPOT. 6,7 Li e outros no contínuo é ainda um campo relativamente pouco explorado, e a possibilidade de se produzir esses núcleos a partir de canais de entrada envolvendo núcleos exóticos é relativamente recente. Em particular, o estudo do ANTPOT. 7 Li em energias de excitação em torno do limiar ANTPOT. 6 He+p é interessante pois corresponde a uma região próxima ao estado fundamental do exótico análogo isobárico ANTPO. 7 He. Neste trabalho, apresentamos resultados de um estudo do espalhamento ressonante ANTPOT. 6 He+p utilizando feixe de ANTPOT. 6 He. As medidas da função de excitação ANTPOT. 6 He+p foram realizadas no sistema RIBRAS (\"Radioactive Ion Beams in Brasil\") do Instituto de Física da Universidade de São Paulo. O feixe secundário foi produzido mediante a reação primária ANTPOT. 9 Be(ANTPOT. 7 Li, ANTPOT. 6 He). Fez-se pela primeira vez, uso do conjunto de dois solenóides do sistema RIBRAS para purificar o feixe secundário de ANTPOT. 6 He, que incide em um alvo sólido de CH IND. 2, grosso o bastante para parar o feixe incidente de ANTPOT. 6 He. Assim, somente as partículas leves de recuo foram detectados, as quais levam a informação do sistema composto ANTPOT. 7 Li. Dessa forma foram analisados os espectros obtidos das reações p(ANTPOT. 6 He,p) e p(ANTPOT. 6 He,). Além disso realizamos um estudo da reação ANTPOT. 3 He(ANTPOT. 7 Be, )ANTPOT. 6 Be. A experiência foi realizada no CRIB-RIKEN fazendo uso de um feixe puro de ANTPOT. 7 Be e um alvo gasoso de ANTPOT. 3 He. O feixe de ANTPOT. 7 Be tem uma energia de laboratório de E IND. lab= 53.4 MeV e foi produzido pela reação primária de ANTPOT. 7 Li(p, n)ANTPOT. 7 Be usando um alvo criogênico H IND. 2. Existem na literatura estados excitados identificados nos núcleos ANTPOT. 6 Li e ANTPOT. 6 He, mas apenas poucos estados no ANTPOT 6 Be. Além do interesse na estrutura nuclear, a importância destes estados no ANTPOT. 6 Be próximos ao limiar de ANTPOT. 3 He ANTPOT. 3 He a 11.48MeV está principalmente na astrofísica. A possível existência de ressonâncias perto deste limiar poderia trazer fortes implicações na queima próton-próton em estrelas. / The spectroscopy in the continuum of light nuclei such as 6,7 Li and others still remains a relatively unexplored field, and the ability to produce these nuclei from entrance channels involving exotic nuclei is relatively recent. In particular, the study of 7Li at excitation energies around the 6He+p threshold is interesting since it corresponds to a region near to the ground state of the exotic analog isobaric 7He. In this work we present the results of the study of the resonant scattering p+6He. The measurements of the excitation function of the system p+6He have been performed in the RIBRAS system (\"Radioactive Ion Beams in Brasil\") of the Institute of Physics of the University of São Paulo. The secondary beam has been produced by the primary reaction 9Be(7Li,6 He). For the first time, the two solenoids of the RIBRAS system have been used to purify the secondary 6He beam, which collides into a solid CH2, thick enough to stop the incident 6He beam. Only the light recoil particles have been detected, which provide information of the compound system 7Li. We analyzed the spectrum obtained from the p(6He,p) and p(6He,) reactions. In addition, we performed a study of the 3He(7Be, )6Be reaction. The experiment has been performed at the CRIB-RIKEN laboratory (Japan), using a pure 7Be beam and a 3He gas target. The 7Be beam had an energy of Elab = 53.4MeV and has been produced by the 7Li(p, n)7Be primary reaction, using a H2 cryogenic target. There are in the literature, excited states identified in the nuclei 6Li and 6He but only a few states in 6Be. Besides the interest in nuclear structure, the importance of these states at 6Be near the threshold of 3He3He at 11.48MeV lies mainly in astrophysics. The possible existence of resonances near this threshold could bring strong implications for proton-proton burning in stars.

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