Date of Award

Spring 2005

Document Type

Restricted Thesis

Terms of Use

© 2005 Nathan C. Shupe. All rights reserved. Access to this work is restricted to users within the Swarthmore College network and may only be used for non-commercial, educational, and research purposes. Sharing with users outside of the Swarthmore College network is expressly prohibited. For all other uses, including reproduction and distribution, please contact the copyright holder.

Degree Name

Bachelor of Arts


Physics & Astronomy Department

First Advisor

David H. Cohen


We have conducted modeling studies of several gas cell shots on the Z accelerator at Sandia National Laboratories in order to study the effects of the irradiance of a low-density gas by a strong x-ray source. Thus far, we have successfully matched a synthesized neon absorption spectrum to an experimental spectrum obtained from one of the shots, with especially good agreement for many of the He-like neon absorption lines. We have also conducted a study scaling the density of the Ne in the gas cell, and have concluded that the minimum density for which there are still measurable spectral features is on the order of r-v 7.5 X 10¹⁶ cm⁻³, which implies an ionization parameter of r-v 70 erg cm s⁻¹. Lastly, we have synthesized new spectral diagnostics for future experiments in the form of time-resolved absorption and emission spectra, and predict that future experiments using such diagnostics will show the weakening of Li-like lines in both absorption and emission and the strengthening of the Lyman alpha line in emission as time progresses. These results have demonstrated we can successfully model the photoionization experiments being conducted at Sandia, and that our modeling procedure can be implemented to design new experiments for future shots at Sandia. Our analysis of the excitation/ionization kinematics and physical conditions of the photoionized plasma has also helped benchmark the atomic kinetics models for these plasmas, which should lead to better interpretation of measured spectra from plasmas photoionized by cosmic sources.