The Design of a Plasma Instrument: The Design of a Low Energy Ion Mass Spectrometer through Numerical Simulations
Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
The process of designing this instrument have been divided into periods of gathering information, applying this knowledge in the form of analytical design, simulating the behaviour, analysing it, evaluating it and optimizing it. The output of this process is an instrument capable of resolving low energy ions to a high degree of detail in mass and charge.The Earth constantly loses matter, mostly in the form of H+ and O+ ions by outflow processes from atmosphere and ionosphere. These ions are cold but simulation measurements have suggested that this low-energy plasma will travel far out through the magnetotail lobes and feed the plasma sheet or escape beyond and just a few measurements have ever been made in this region. The quantification and insight of the loss processes of the Earths low energy ions are important for understanding the evolution of atmospheres on other celestial bodies.The combination of a top hat electrostatic analyser and a high mas resolution system enables the instrument to resolve low energy ions with a high degree of detail in mass and charge. The top hat electrostatic analyser acts as a filter that lets through the low energy ions of desired energy within a certain energy limit with the help of a guiding voltage. These ions are then timed inside a time of flight system that works by utilizing a linear electric field. The nature of this field makes the ion move in a predictable pattern according to the motion of a harmonic oscillator. This movement is beneficial because it renders the flight path of the ion independent of energy degradation and angular scattering common to conventional time of flight systems. The end result is a high mass resolution only dependent upon the flight time of the ion.The final instrument is 8 to 10 cm long, depending on the thickness of the lower MCP, and 4 cm in diameter. The geometric factor is ~1.09∙10^-4 cm^2 str eV/eV for positive ions and ~1.11∙ 10^-3 cm^2 str eV/eV in total for both positive and negative ions. The mass resolution of thesystem is 50 m/dm for lighter positive ions and 180 m/dm for heavier ions such as oxygen.
Place, publisher, year, edition, pages
2013. , 75 p.
IdentifiersURN: urn:nbn:se:ltu:diva-43870Local ID: 1b1cce22-1586-4ee2-ba5e-250cbb181006OAI: oai:DiVA.org:ltu-43870DiVA: diva2:1017112
Subject / course
Student thesis, at least 30 credits
Space Engineering, master's level
Validerat; 20130922 (global_studentproject_submitter)2016-10-042016-10-04Bibliographically approved