Browsing by Author "Comrie, Angus"

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    A new compact neutron spectrometer
    (2016) Comrie, Angus; Buffler, Andrew; Smit, Ricky
    A new compact neutron spectrometer has been designed, developed and characterized. The detector is based on EJ299-33 plastic scintillator coupled to silicon photomultipliers, and a digital implementation of pulse shape discrimination is used to separate events associated with neutrons from those associated with gamma-rays. The spectrometer is suitable over the neutron energy range 1 – 100 MeV, and the development illustrated with measurements made using an Am-Be radioisotopic source, a D-T sealed tube neutron generator and quasi-monoenergetic neutron beams produced using the iThemba LABS cyclotron. A segmented variation of the spectrometer is capable of providing directional information through the comparison of count rates between scintillator cells.
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    The effect of δ [delta] rays on impact parameter resolution in pixel detectors
    (2011) Comrie, Angus
    A review of the ALICE detector in the context of heavy ion collisions is given, along with a discussion on the use of Monte Carlo simulations in high energy physics. An investigation of the accuracy of GEANT3 simulation of low energy electrons is detailed.
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    Study of Pt-Ge interaction using thin film and lateral diffusion couples
    (1997) Nemutudi, Rudzani; Comrie, Angus
    The formation of germanides of platinum has been investigated using both conventional thin films and lateral diffusion couples. The investigation was carried out using such established techniques as XRD, RBS and SEM. Using results from both thin film and lateral diffusion couples, a comparison has been made of the behaviour of Pt-Ge system in parameters such as phase formation sequence, growth kinetics and dominant diffusing species. In their sequential order of formation, three distinct phases, Pt₂Ge, PtGe and PtGe₂, have been identified in thin films in the temperature range 200 - 300°C. The first phase, Pt₂Ge, was found not to follow a layered mode of formation. Both PtGe and PtGe₂ phases were found to obey a (t)1/2 law, indicating a diffusion limited growth process. By employing Ti as an inert marker, platinum was observed as the dominant diffusing species during Pt₂Ge formation. On the dominant diffusing species during PtGe and PtGe₂ formation, the thin film results were but tentative. Upon annealing at 500°C/30,90,180min, lateral diffusion couples of Pt rich source (on Ge thin film) resulted in only a limited lateral growth, and multiple phases were not observed. However, when samples of Ge rich source (on Pt thin film) were annealed at the same temperature and times, lateral interaction was observed proceeding on a relatively large scale. Germanium atoms were found to have encroached into the surrounding Pt thin film as far as ±30μm away from the Ge source region, with multiple phases growing simultaneously, viz PtGe₂, PtGe and Pt₂Ge₃. Inside the source region, the composition of the innermost compound corresponded to PtGe₂ phase. Pt₂Ge₃ was located between PtGe₂ and the initial island/thin film interface line. The compound outside the source region was characterised as PtGe. Pt₂Ge₃ phase was observed to have resulted from PtGe₂ disintegration through the mechanism 2PtGe₂ -+ Pt₂Ge₃ + Ge. Plots obtained from μRBS and SEM lateral measurements indicate that the growth of observed phases (PtGe₂, Pt₂Ge₃ and PtGe) all follow a square-root-of-time law, a characteristic of diffusion limited growth process.
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    UCT Physics Course 1 Laboratory 2nd Semester 2011
    (2012) Fearon, Jeff; Comrie, Angus
    A series of pre-practical talks detailing the aims of each of five electrical experiments, and instructions on how to use the equipment. The UCT Physics Course 1 Laboratory is run in parallel with and is complimentary to the main stream, calculus-based physics course PHY1004W.
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    VRDAV is: remote visualisation of astronomy data with a standalone virtual reality device
    (2025) Van Zyl, Michaela; Simmonds, Robert; Comrie, Angus
    This dissertation explores the challenges of visualising vast astronomy data cubes using a virtual reality environment, addressing the ever-increasing volume of data collected by radio astronomy instruments. As the amount of data grows year after year—ranging from terabytes to petabytes—radio astronomy researchers face significant difficulties in processing, storing, and analysing this immense data. The visual analysis of the collected data is a crucial part of radio astronomy research. Traditional visualisation tools are often inadequate due to the size and complexity of the data. The Data far exceeds the computational capabilities of devices like laptops or home desktop computers. Researchers are often required to either access specialised systems or analyse small portions of the data at a time. Specialised systems are typically locked to specific locations and inaccessible to many, and segmenting the data can obscure the broader context of a dataset. These points highlight the need for a new approach to overcome the presented limitations. The objective of this research is to develop a prototype system that enables the visualization of large astronomy data cubes in a virtual reality environment using a standalone VR headset. The system is specifically designed to operate on devices with limited computational power, such as laptops and VR headsets. Making it accessible to a wider range of users. The research addresses key questions, including the feasibility of remote implementation, the scalability of the system for handling large datasets, and a performance comparison with existing astronomy visualisation systems. The VRDAVis system design follows a client-server architecture, where the client-side communicates with the server to visualise large astronomy data cubes. These client devices are either a computer or standalone VR headset. The system pre-processes the data into multiple resolution levels, these levels are referred to as mipmaps, to reduce the computational load on the client. The front-end, built as a web-based application, allows users to select data cubes and progressively visualise different levels of detail. The resolution levels start from a low-resolution overview to higher resolution as a user zooms in on areas of interest. The client and server communicate via WebSock-ets, and WebRTC is used for peer-to-peer connections when transferring the application's state between devices (e.g., from desktop to VR). The VRDAVis system was tested through an qualitative study, with participants who were astronomy researchers familiar with VR technology. The participants were asked to perform various actions using VRDAVis. The tasks involved selecting a file on the laptop, transferring the session to the VR head-set, and interacting with the data cube. Key findings were gathered from user feedback, focusing on their experience with the system's usability, interaction with the visualizations, and the overall workflow. Observations on task performance and any difficulties encountered were also collected, along with participants' impressions of working in the VR environment.