Moderator design for accelerator based neutron radiography and tomography systems /
MIT is in the initial phase of developing a small accelerator based neutron imaging system. The system includes a radiofrequency quadrupole (RFQ) accelerator--producing neutrons by the reaction 9Be(d,n) 1OB--a neutron moderator, an object rotation platform, a 6LiF-ZnS scintillator screen converter,...
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| Format: | Thesis Book |
| Language: | English |
| Published: |
c1994
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| Summary: | MIT is in the initial phase of developing a small accelerator based neutron imaging system. The system includes a radiofrequency quadrupole (RFQ) accelerator--producing neutrons by the reaction 9Be(d,n) 1OB--a neutron moderator, an object rotation platform, a 6LiF-ZnS scintillator screen converter, and an electro-optic cooled charged coupled device (CCD) detection system.The objective of this work was to design a neutron moderator which produces a high thermal neutron flux with a uniform flux distribution over a large area, using an accelerator based neutron source. Specifically, the objective was to produce a uniform thermal beam with an area greater than our scintillating converter screen, which has dimensions of 18 x 24 cm (432 cm 2). Moderator designs producing a cylindrical thermal beam with a cross-sectional area of 491 cm2 (12.5 cm radius) were analyzed theoretically using a Monte Carlo Neutron-Particle Transport simulation (MCNP) code from Los Alamos National Laboratory. A previously modeled neutron energy and angular distribution for 0.9 MeV 9Be(d,n)'B reaction was analyzed and used for all simulations. A moderator material was chosen after analyzing the moderating characteristics of several materials. The assessment of each moderator design was based on the magnitude and uniformity of the thermal beam flux. Geometric variables unique to each design were altered in an attempt to find the optimum configuration |
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| Physical Description: | 129 leaves : ill. ; 29 cm |
| Bibliography: | Includes bibliographical references (leaves 103-106) |