Undergraduate Honors Theses

Thesis Defended

Spring 2019

Document Type


Type of Thesis

Departmental Honors



First Advisor

Mike Litos


The Plasma Wakefield Accelerator (PWFA) is a type of advanced particle accelerator that can generate high energy particle beams with a reduced footprint and cost compared to conventional accelerators. Recent experiments have shown that the PWFA is able to accelerate an electron beam by 9 GeV in just over a meter. However, to continue making progress the PWFA must be shown to also preserve the beam quality, as quantified by the beam emittance. This requires a carefully tailored plasma source, and therefore, a sufficiently reliable plasma density diagnostic. Stark broadening has been frequently used as a laboratory plasma diagnostic as it provides a fast and reliable approach to determine plasma density and temperature. As the recombined atoms in a plasma de-excite, they release photons and spectral lines are observed. However, when the de-excitation is perturbed by the local electric field of the plasma, the spectral lines are broadened. The full width at half maximum (FWHM) of the broadened spectral line is proportional to the strength of local electric field produced by nearby ions and electrons. The field strength, in turn, is proportional to local plasma density. Therefore, by measuring the FWHM of broadened spectral lines, we are able to indirectly measure the plasma density.