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Simulation and Optimization of the Neutron Velocity Selector

Moeini Roodbally, Hamed | 2019

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51838 (46)
  4. University: Sharif University of Technology
  5. Department: Energy Engineering
  6. Advisor(s): Hosseini, Abolfazl
  7. Abstract:
  8. To study the structure of materials, among materials containing hydrogen, an instrument called the "small-angle neutron scattering instrument" is used. Having a monochromatic neutron beam is the most basic component of this instrument. This beam is often produced using a device called the "neutron velocity selector". The neutron velocity selector is a rotating mechanical piece that allows for passage of neutrons at a certain speed, according to its rotational speed. In fact, this device produces a monochromatic neutron beam with continuous flux. Until now, it has been designed and manufactured in a variety of models, which are generally divided into two groups of multi-disc and multi-blade selector. Each selector device is characterized by two parameters of the transmission factor and resolution. The transmission factor is defined as the ratio of the intensity of the neutrons of the output from the selector to the intensity of the input neutrons, at a specific wavelength. This research conducted with the aim simulation of multi-blade model with the use of McStas software, due to the superiority of the transmission factor and its resolution to the multi-disc model. McStas is a software based on the Monte Carlo method, which has the great ability to simulate small neutron scattering instrument. To do the simulation, McStas software installed on Ubuntu operating system, and after learning it, the selector simulated with the assumption that the blades are completely absorbing and that the neutron beam does not interact with the input and output windows of the selector. Finally, in order to verify simulation, a instrument defined in McStas. Simulations showed that the selector transmission factor and resolution for the case where the neutron beam entered into the selector has a uniform angular distribution and with divergence of 6', is 94.29 ± 0.05% and 10.52 ± 0.05%, respectively. Comparison of these results with the reported experimental values showed that the error in measuring the transmission factor and resolution is 0.31% and 5.2% respectively
  9. Keywords:
  10. Small-Angle Neutron Scattering Instrument ; Neutron Velocity Selector ; Transmission Coefficient ; Resolution

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