A study of the T(α,ɤ)Li⁷ reaction has been made at mean alpha particle energies of 1320, 560 and 350 Kev in a solid tritium-zirconium target. At the 1320 Kev energy the absolute 90° differential cross-section for transitions to the ground state has been found to be 1.89x10⁻³¹ cm² per steradian from analyses of spectra obtained in a 2¾"x4½” NaI crystal. At this energy the ratio of the differential cross-section for transitions to the first excited state to that for transitions to the ground state was found to be 0.446. This ratio was observed to remain the same at all detector angles. The excitation function roughly determined by additional runs at 560 and 350 Kev mean energy followed the form obtained by Riley of this laboratory in 1958. Angular distribution measurements at 1320 Kev gave the result that both the above mentioned gamma rays have the same angular dependence, this being 1-0.11 cos² θ + 0.39 cos⁴ θ. At 560 Kev mean energy their anisotropy was measured to be about 5%. A background from the target has been found to have an angular distribution at 1320 Kev mean alpha particle energy of 1+0.35 cos θ in laboratory co-ordinates. Both its excitation function, determined roughly from runs at 560 and 350 Kev, and its anisotropy followed a form in agreement with neutron counter measurements. It is suggested that this background is caused by neutrons from some still unknown reaction in the target. An investigation was also made of a standard thick-walled brass Geiger-Muller counter to determine its efficiency for photon energies from 0.5 to 20 Mev. A smooth curve was obtained showing efficiency increasing with gamma ray energy thus agreeing in form with previous experimental and theoretical results. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

No description available.

Experimental work was done to determine a satisfactory method of making counters to be used in future research work, to develop a means of testing them, and to find a counter circuit which could be used in connection with this work and for demonstration work. / Master of Science

In this work novel solid-state neutron detectors based on Gallium Nitride (GaN) have been produced and characterized. GaN is a radiation hard semiconductor which is commonly used in commercial optoelectronic devices. The important design consideration for producing GaN-based neutron detectors have been examined, and device simulations performed. Scintillators and p-i-n diode-type neutron detectors have been grown by metalorganic chemical vapor deposition (MOCVD) and characterized. GaN was found to be intrinsically neutron sensitive through the Nitrogen-14 (n, p) reaction. Neutron conversion layers which produce secondary ionizing radiation were also produced and evaluated. GaN scintillator response was found to scale highly linearly with nuclear reactor power, indicating that GaN-based detectors are suitable for use in the nuclear power industry. This work is the first demonstration of using GaN for neutron detection. This is a novel application for a mature semiconductor material. The results presented here provide a proof-of-concept for solid-state GaN-based neutron detectors which offer many potential advantages over the current state-of-the-art, including lower cost, lower power operation, and mechanical robustness. At present Helium-3 proportional counters are the preferred technology for neutron detection, however this isotope is extremely rare, and there is a global shortage. Meanwhile demand for neutron detectors from the nuclear power, particle physics, and homeland security sectors requires development of novel neutron detectors which are which are functional, cost-effective, and deployable.

Made available in DSpace on 2014-10-09T12:44:42Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:57:40Z (GMT). No. of bitstreams: 1 07178.pdf: 5559120 bytes, checksum: 99e8bb52573d489b59ca94f5400da04c (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-09-01T13:53:31Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação Biblioteca Central.pdf: 640355 bytes, checksum: ab7c428a444bd41995538edb1f138189 (MD5) / Made available in DSpace on 2016-09-01T13:53:32Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação Biblioteca Central.pdf: 640355 bytes, checksum: ab7c428a444bd41995538edb1f138189 (MD5) Previous issue date: 2016-02-25 / Considerando as mudanças que a literatura acadêmica tem apontado no que concerne à atuação do controller, a presente pesquisa teve por objetivo investigar o perfil deste profissional no contexto brasileiro. Partindo de dois perfis específicos (bean counters e business partners), o estudo se revestiu de uma tríplice missão: primeiro, relacionar quais as principais atividades desempenhadas por controllers atuantes no Brasil; segundo, discernir qual destes perfis destacados é predominante; e terceiro, entender como determinadas variáveis contingenciais (Tamanho da Organização, Desenvolvimento Regional e Descentralização) afetam este profissional no que diz respeito à sua autonomia e envolvimento com o negócio. O método empregado para a coleta de dados consistiu na aplicação de um questionário, disponível na plataforma Survey Monkey e respondido por controllers listados, principalmente, nas bases de dados da Associação Nacional dos Executivos de Finanças (Anefac) e da Universidade Federal de Pernambuco (UFPE). Os respondentes foram convidados por e-mail a participar da pesquisa e suas respostas sugerem a predominância de bean counters, sendo suas principais atividades: contabilizar, gerir, atender o fisco e cuidar das finanças. Tendo em conta as particularidades de cada variável, múltiplas ferramentas econométricas foram utilizadas para efetuar a análise: regressão linear, regressão logística binária, ANOVA e teste de Wald. Contudo, apenas a relação entre descentralização e envolvimento se mostrou positiva e significante. O fator idade – que, embora não previsto entre as hipóteses, emergiu dos dados – também se mostrou relevante: quanto mais idoso é o controller, maior a sua autonomia e mais inclinado a exercer o perfil business partner. / Considering the changes that academic literature has shown regarding the performance of the controller, the present study aimed to investigate the profile of this professional in the Brazilian context. Starting from two specific profiles (“bean counters” and “business partners"), the study was clothed in a threefold mission: first, to relate what the main activities performed by controllers operating in Brazil; second, to discern which of these outstanding profiles is predominant; and third, to understand how certain contingent variables (Organization Size, Regional Development and Decentralization) affect these professionals with regard to their autonomy and involvement with the business. The method used for data collection consisted of a questionnaire, available on the Survey Monkey platform and answered by listed controllers, mainly, in the National Association of Finance Executives and Federal University of Pernambuco databases. Respondents were invited via email to take the survey and their answers suggest the predominance of bean counters, being their main activities: accounting, management, attend the tax authorities and take care of the finances. Taking into account the particularities of each variable, multiple econometric tools were used to conduct the analysis: linear regression, binary logistic regression, ANOVA and Wald test. However, only the relationship between decentralization and involvement was positive and significant. The age factor – which, although not provided between the hypotheses emerged from the data – was also relevant: the oldestis the controller, the more autonomy and more inclined to exercise business partner profile.

Made available in DSpace on 2014-10-09T12:44:42Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:57:40Z (GMT). No. of bitstreams: 1 07178.pdf: 5559120 bytes, checksum: 99e8bb52573d489b59ca94f5400da04c (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:29:35Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:36Z (GMT). No. of bitstreams: 1 01292.pdf: 4197340 bytes, checksum: e065f97f212a4098373c6cd14232d7c2 (MD5) / Tese (Doutoramento) / IPEN/T / Universidade Estadual de Campinas - UNICAMP/SP

A microcomputer based hardware, the Time Interval Board, was designed and the software interface control program was developed. The board measures time intervals between consecutive pulses from a discriminator output. The data is stored in on-board 16K x 16 memory. The microcomputer empties and processes the data when the on-board memory is filled. Data collection continues until the preset collection period is finished or a forced end is initiated. During this period, control is passed between the hardware and the microcomputer via the interface circuit. The designed hardware is IBM PC compatible.

No description available.