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    Accurate Characterisation of Refractive Components for Future CMB Missions

    Tynan, Niall (2016) Accurate Characterisation of Refractive Components for Future CMB Missions. Masters thesis, National University of Ireland Maynooth.

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    The focus of this thesis is on the experimental verification and computational modelling of refractive components for operation in the terahertz frequency band for future missions to measure the Cosmic Microwave Background (CMB) radiation. The specific components that were characterised were a set of dielectric lenses. These were made as part of a European Space Agency contract to further the refractive technology in the terahertz band of the frequency spectrum. Two different types of prototype lens were made for this project in Cardiff University and testing performed at Maynooth University (MU) and Cardiff University. An antireflection coating was applied to the prototype lenses and measured to test its effectiveness. During the manufacturing process some issues were detected, including a difference in refractive index between the finished lens and the sample batch material. In addition the lenses were found to have become warped during the application of the antireflection coating. This was due to the material not undergoing an annealing process before manufacture of the lenses. The measurements carried out helped to identify and resolve the discrepancy between the refractive index of the test batch supplied, used to measure refractive index, and the actual lens, through comparison with the model developed and the simulations carried out by the TICRA company in Denmark. The measurements also tested the coating that was applied to the lens surface and confirmed good performance at 100 GHz and fall off at a lower frequency of 75 GHz, as expected. After an initial set of measurements of the lenses, improvements were made to the alignment system and the lenses were retested. This resulted in measurements with reduced offsets of the components in the system. A computer simulation of the measurement setup was performed using an in house software package called Maynooth Optical Design and Analysis Laboratory (MODAL) to assess the accuracy of the measurements and test the model. The model showed good agreement between the feed horn measurements and simulations for all horns. The offsets in the physical system had to be included in the model in order to obtain agreement between the real and modelled systems. Computational simulations were performed for the uncoated lenses and showed good overall agreement but discrepancy in the comparison with high resolution measurements.

    Item Type: Thesis (Masters)
    Additional Information: M.Sc.
    Keywords: Accurate Characterisation; Refractive Components; Future CMB Missions;
    Academic Unit: Faculty of Science and Engineering > Experimental Physics
    Item ID: 7536
    Depositing User: IR eTheses
    Date Deposited: 19 Oct 2016 11:10
      Use Licence: This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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