Masters Degrees (Physics)

Permanent URI for this collection

https://scholar.sun.ac.za/handle/10019.1/3639

Browse

Browsing Masters Degrees (Physics) by browse.metadata.advisor "Bark, R. A."

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    Resonance ionization spectroscopy with time of flight mass spectrometry
    (Stellenbosch : Stellenbosch University, 2019-04) Waso, Frederick John; Steenkamp, Christine M.; Du Plessis, Anton; Bark, R. A.; Stellenbosch University. Faculty of Science. Dept. of Physics.
    ENGLISH ABSTRACT : Resonance ionization using laser light is one of the most useful techniques for isolating radioactive isotopes and producing radioactive ion beams at accelerator facilities around the world. The aim of this study was to develop an offline experiment for resonance ionization spectroscopy (RIS) using the nonradioactive element tin. Tin was selected as a test element due to its unique nuclear properties and is an element of interest in various nuclear and astrophysical studies. Various properties of the nucleus can impact the atomic energy levels of the atom. Laser spectroscopy can be used to probe and determine these nuclear properties. RIS is one spectroscopic technique that can be used for this purpose. RIS will be used to produce ions of non-radioactive tin and a time-of-flight mass spectrometer (ToF-MS) will be used to detect these ions. Two separate atom sources have been designed and developed, namely a supersonic jet source and an effusive atomic beam source. Due to administrative delays the ToF-MS could not be implemented in the current study. Simulations using the IBSimu simulation library were performed to study and understand the influence of various experimental parameters in an effort to predict optimal parameters for the experimental setup. The impact of the initial volume and velocity distribution of the ions in the atom sources were studied. From the simulations it was observed that a fine margin exists between a too small or too big initial volume. The resolution decreases as the initial volume increases, but at too small volumes space charge effects start to reduce the resolution of the mass spectra as well. It was observed that ions with large transverse velocity components reduce the resolution of the ToF-MS. Proper beam collimation through the use of skimmers can help reduce the transverse velocity spread and improve the resolution of the instrument. The ToF-MS is fitted with an ion reflector called a reflectron. The reflectron greatly improves the resolution of the ToF-MS and is a crucial component to obtain high resolution spectra. From the results it was observed that a linear potential gradient in the reflectron would be optimal for the resolution of the ToF-MS. The two atom sources were compared, and depending on the aim both sources have distinct advantages. The effusive source will be easier to implement and will be ideal to test the sensitivity and resolution of the ToF-MS. The Doppler broadening of the spectral lines in the effusive beam, however, makes selective excitation and ionization impossible. The supersonic jet limits Doppler broadening and is therefore crucial for selective ionization of Sn. The simulations provided an insight into the influence of various experimental parameters that will facilitate the implementation of the ToF-MS at a later stage.