Date of Award
Doctor of Philosophy (PhD)
Physics and Astronomy
Highly charged ions (HCIs) exist in many hot astrophysical environments where they play an important role in plasma dynamics. Charge exchange involving highly charged ions has been shown to be responsible for many observed X-ray emissions from a variety of astrophysical sources. Proper modeling of these environments requires an understanding of this process, including the electronic structure of each ion species as well as their charge exchange cross sections. This dissertation investigates charge exchange processes with highly charged ions which are present in astrophysical environments via a laboratory-based study.
The Clemson University electron beam ion trap (CUEBIT) laboratory was utilized for the creation and extraction of charge state and energy selected highly charged ions. To create highly charged ions, very low pressures are required, and frequent de-icing of cryogenic stages in the CUEBIT source was required. The sublimation of various ices were studied to inform these de-icing procedures. Measurements of the sublimation temperatures at UHV pressures were performed, and these measurements support empirical formulas existing in the literature.
Techniques were developed to optimize the extraction yields of the desired ion species (i.e. the highest charge states). These ions were used in a crossed beam spectroscopy experiment to observe charge exchange. Optimizing the system for precision X-ray spectroscopy requires an accurate characterization of the ion beam at the target chamber. A new method for obtaining spatially resolved absolute current density profiles of ion beams was developed. The advantage of this method is that it requires only electrostatic deflectors and a fixed Faraday cup and is robust across a wide range of energies and fluxes.
Two separate estimates of the charge exchange rate, one computational and one experimental, were carried out and found to be in agreement with each other. Finally, the first measurements of X-ray emissions resulting from HCI charge exchange at Clemson were performed with a spectrometer. This combined experimental and theoretical effort provide a powerful benchmark for ions at collision energies of astrophysical interest and represent the first steps towards the planned triple coincidence measurements of HCI CX.
Mattish, Richard, "Study of Highly Charged Ion Charge Exchange with Applications to X-Ray Astrophysics" (2023). All Dissertations. 3441.
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