Crawford

X-ray Diffraction
 

Good

Plasmas

Plasmas, or ionized gases, constitute 95% of the matter in the universe, but are rare in terrestrial settings except in a variety of man-made applications ranging from fluorescent lightbulbs to arc welders, from material processing to thermonuclear fusion reactors.  In order to study behavior of plasmas, many diverse diagnostic methods have been employed.  Two methods to be investigated in the projects that I am offering this semester utilize electrostatic Langmuir probes, and laser optogalvanic spectroscopy.  The student may choose between these two projects. 

1.          An electrostatic Langmuir probe is simply a conductor inserted into a plasma that is biased at variable voltages in order to collect charged particles, i.e. electrons and ions.  An analysis of current/voltage (I/V) characteristic curves yields several fundamental plasma parameters including ion and electron densities, electron temperature, and the ionization energy of the gaseous atom.  The goal of this project is to gain experience with a Langmuir probe, gathering and analyzing several I/V characteristics under varying operating conditions of an argon plasma in a  transistor tube, and in the Pickets Charged Plasma Device.  Although close supervision is provided to help the student understand the plasma-probe model and perform the analysis, this project allows the student to work very independently, setting her own schedule for experimental work and analysis.

2.         Laser optogalvanic spectroscopy (LOGS) is a method to study atomic or ionic species found in a plasma discharge.  Resonant absorption of laser light results in a change in discharge current that is easily detected.  The topic to be investigated in this project will vary from one student to another, but will include analysis of the mechanism of the optogalvanic effect, the Zeeman effect in Sodium gas, and hyperfine splitting in Niobium.  In this project the student will work closely with the instructor, who will provide technical laser support.  Due to the collaborative nature, we must find suitable meeting times for the experiment, with both schedules restricting the choices.  Two full afternoons each week will be necessary for adequate progress.  In the last session the student will be working more on his own.  The goal of this project is to introduce the student to lasers and laser spectroscopy, while at the same time learning something about plasmas and atomic structure. 

Galactic chemical evolution is the study of the origin, evolution, and distribution of the nuclear species that exist in the gas, dust, and stars of galaxies. Although astronomers are quite interested in how elements are produced and distributed throughout galaxies consider this: the very oxygen you breathe was forged in massive stars and expelled into the interstellar medium to eventually become part of our solar system. The family tree of oxygen (like any nuclear species) is a complicated one. To constrain our ideas of how stars produce elements like O, Ne, S, Cl, and Ar, and how galaxies subsequently distribute these products of stellar evolution, we look to the observed abundances of these elements in our very own galaxy the Milky Way.

In our brief time together we will analyze abundance data for Milky Way planetary nebulae, HII regions, supernovae remnants, and stars. We will plot the abundances of aforementioned elements vs. radial distance from the center of the Galaxy (galactocentric distance). This type of plot should result in a gradient. We are interested in whether this gradient shows a true correlation between galactocentric distance and the rate at which stars convert hydrogen into heavier elements. Is it a linear relationship? How can we discern a true correlation in data when r² isn't close to 1? We'll apply simple statistical techniques to these data sets to understand their nature while looking more broadly into the context of galactic chemical evolution.

Pella

Neutron Activation

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Adventures in Mossbauer Spectroscopy 

Students will use the neutron howitzer to produce radioactive isotopes and determine their half-lives. In addition you will determine the ratio of the thermal neutron flux, to the fast neutron flux for the Pu-Be source.

Mossbauer

Students will continue Mossbauer adventures started in PH 310, measuring isomer shifts, hyperfine spectra, and the effects of quadrupole splitting for various unknown samples.