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Optimization of plastic scintillator thicknesses for online beta detection in mixed fieldsPourtangestani, Khadijeh 01 December 2010 (has links)
For efficient beta detection in a mixed beta gamma field, Monte Carlo simulation models have been built to optimize the thickness of a plastic scintillator, used in whole body monitor. The simulation has been performed using MCNP/X code and different thicknesses of plastic scintillators ranging from 150 to 600 um have been used. The relationship between the thickness of the scintillator and the efficiency of the detector has been analyzed. For 150 m thickness, an experimental investigation has been conducted with different beta sources at different positions on the scintillator and the counting efficiency of the unit has been measured. Evaluated data along with experimental ones have been discussed. A thickness of 300 um to 500 um has been found to be an optimum thickness for better beta detection efficiency in the presence of low energy gamma ray. / UOIT
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Estudo de um sistema de coincidência 4-pi-beta-gama para a medida absoluta de atividade de radionuclídeos empregando cintiladores plásticosPIUVEZAM FILHO, HELIO 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:52:39Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:02:17Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
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Otimizacao do metodo de polimerizacao para producao de detectores plasticos cintiladores de grandes dimensoesCOSTA, NELSON P. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:43:46Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:09:55Z (GMT). No. of bitstreams: 1
06650.pdf: 4804396 bytes, checksum: 4f29fb57f44398a132f7549c46a4c525 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Estudo de um sistema de coincidência 4-pi-beta-gama para a medida absoluta de atividade de radionuclídeos empregando cintiladores plásticosPIUVEZAM FILHO, HELIO 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:52:39Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:02:17Z (GMT). No. of bitstreams: 0 / O presente trabalho teve como objetivo o estudo de um sistema de coincidências 4?(PS)?-?, para a medida absoluta de atividade, empregando cintiladores plásticos, em geometria 4?. Além de experimentos no sistema de coincidências, foram feitas também simulações utilizando o Método de Monte Carlo, por meio dos programas PENELOPE e ESQUEMA. Estas simulações tiveram como objetivo estabelecer a curva de extrapolação do método de coincidência 4??-? e comparar com os dados experimentais. Uma nova geometria foi proposta para o sistema de coincidências, onde foi acrescentada uma segunda fotomultiplicadora ao sistema anterior. Este procedimento objetivou melhorar a coleção de luz do cintilador plástico, uma vez que este sistema apresentava limitações na energia mínima detectada, em razão da presença de ruído eletrônico e baixo ganho. Os resultados mostram que houve uma melhoria na relação sinal-ruído, com redução na energia mínima detectável. Além disso, observou-se um aumento na eficiência de detecção. Com estas modificações, tornou-se viável a padronização de radionuclídeos que emitem elétrons ou raios-X de baixa energia, ampliando o número de radionuclídeos padronizáveis com este tipo de sistema. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
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Otimizacao do metodo de polimerizacao para producao de detectores plasticos cintiladores de grandes dimensoesCOSTA, NELSON P. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:43:46Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:09:55Z (GMT). No. of bitstreams: 1
06650.pdf: 4804396 bytes, checksum: 4f29fb57f44398a132f7549c46a4c525 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Test of fast neutron detectors for spectroscopy with (3He,n) two proton stripping reactionsElbasher, Mohamed Elbasher Ahmed 03 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Nine 100x100x600 mm3 plastic scintillators, formerly built for the neutron time
of ight measurements at iThemba LABS, were refurbished. The position resolution
of these detectors was determined using muon cosmic rays and coincident
measurement techniques. Average position resolution of 4.28 cm (FWHM)
was found. In order to predict the time spectrum of the large-volume detector
Monte Carlo simulations have been performed. These simulations aimed at
anticipating the separation of statistical neutrons, prompt gamma rays and
uncorrelated gamma rays from the fast neutrons emitted in the reaction of
interest. One of the neutron detectors was tested using fast neutrons from
the 232Th( ,xn) reaction at 42 MeV. Statistical neutrons from fusion evaporation
reactions were produced in 152Sm(12C,xn) fusion evaporation reaction.
Coincidences between neutrons and gamma rays were successfully identi ed.
Prompt gamma rays and uncorrelated gamma rays were also identi ed. / AFRIKAANSE OPSOMMING: Nege 100x100x600 mm3 plastiese scintillators, wat aanvanklik gebou was vir
neutron vlugtyds meetings by iThemba LABS, was hernu. Die posisie resolusie
van die detektore was bepaal deurmiddel van muon kosmiese straling en koïnsidensie
meet tegnieke. Posisie resolusie van 4.28 cm (FWHM) was verkry.
Monte Carlo simulasies is gebruik om die posisie resolusie van'n groot volume
detektor te voorspel. Hierdie simulasies is daarop gemik om onderskeid te
maak tussen statistiese neutrone, gelyktydige gamma strale en ongekorreleerde
gamma strale vanaf vinnige neutrone in die reaksie van belang uitgestraal word.
Een neutron detektor was getoets deur gebruik te maak van vinnige neutrone
wat uit die reaksie 232Th( ,xn) by 42 MeV ontstaan. Statistiese neutrone vanaf
splitsings verdampingsreaksies, gelyktydige gamma strale en ongekorreleerde
gamma strale was geidenti seer. Statistiese neutrone van samesmelting verdamping
reaksies was geproduseer in die reaksie 152Sm(12C,xn). Toeval tussen
neutrone en gamma strale was suksesvol geïdenti seer, gevra gamma strale en
ongekorreleerd gamma strale was ook geïdenti seer.
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