Simon Schiffmann¶
Simulation of a neutron detector prototype
Abstract¶
The goal of this master thesis is to assess the application of a colorimetric energy-sensitive monitor to neutron spectrometry. This colorimetric analysis relies on the various luminescence colours radiated by the thin-film multilayer material that constitutes this monitor. It allows an energy determination of charged particle beams through the observation of the emitted light colour. To assess the application of this technology to a novel neutron spectrometry technique, simulations were conducted with the software BDSIM. Because of the novelty of this detection technique, various options were studied. However, an operation base was outlined: it consists of a variable moderation of the neutron beam and production of charged particles by a converter material. Firstly the moderating part was designed to modulate the distribution of the incident neutron beam. It aims to obtain output distributions dependent on the beam energy and as narrow as possible. For this part, the spatial correlation between the input and output neutron position was also investigated but it did not show conclusive results. Therefore the option kept was the modulation of the whole distribution of the incident beam. The composition and shape choices for this moderator were based on the simulation results and the literature presented in the state of the art of this work. The moderator was finally shaped as in prism with modified right-angled triangle bases and composed of paraffin. Secondly, the conversion part was modelled, it aims to generate charged particles that will be detected by the colorimetric monitor. Different materials were used for the simulations to assess their production rates of charged particles and their spectra. Finally, a boron carbide sheet of 8μm was chosen to be added to the moderator block. To conclude this work some representations were created with the colour parametrization proposed in the colorimetric monitor study. They illustrate what could be observed by a user or a usual camera that monitors a neutron beam. Overall the principles of this neutron spectrometry technique are quite conclusive, a variable moderation was achievable through a simple shape of moderator, and the generation of charged particles followed the same distribution as the one of neutrons that hit the converter. Nevertheless, major improvements in these two aspects of the device are still required for the fulfilment of this spectrometer.