Physics Lecture Series | Spring 2013

As a Math major I loved the beauty of high level Mathematics but struggled to see the application. In Physics I found a relevant and tangible application to the beauty of Mathematics. However, I wanted to apply my new craft to a field that would affect people's day to day lives. When I stumbled across exploration seismology as an undergraduate student, it satisfied the 'relevant and tangible' criteria with an added bonus: the opportunity to blow stuff up. Now working as a professional Geophysicist, I sometimes miss the dusty days in the field. However, the science has become more challenging and the application of Physics more crucial. In some ways the Earth has itself become the ultimate non-linear problem, were fundamental wave theory is key to hydrocarbon exploration and drilling safety.

The American Petroleum Institute estimates that The Gulf of Mexico accounts for 30 percent of domestic oil production. However, this region also presents unique challenges for Geophysicists due to the pervasive presence of salt. Basic seismic reflection theory assumes a normal incidence ray path from source to receiver. However, salt, in addition to having a much higher acoustic velocity than sediment, deforms plastically into pillow-like structures in the subsurface. This combination of high acoustic velocity contrast and irregular deformation geometry causes seismic energy to be diffracted away from receivers, creating areas of poor seismic illumination called "shadow zones". The application of basic wave theory is crucial to understanding where shadow zones occur and in determining the robustness of a seismic reflection interpretation. A robust seismic reflection interpretation facilitates an accurate Earth model which becomes the basis for well design and planning. In the end, it's the understanding of fundamental Physics that makes it possible to find and safely extract the hydrocarbons we rely on every day.

Our objective is to create a unique environment consisting of a magnetized high energy density plasma (n ~ 1019 cm-3, T ~ 10 keV) produced by laser irradiation of atomic or molecular clusters in a megagauss magnetic field. With deuterium or CD4 clusters the DD fusion neutron yield can be up to 107 neutrons/shot. Requirements on the magnetic field source are: on-axis field strength of 1-2 megagauss in a cylindrical volume of 1 cm3 (reaching b ~ 1 for 10 keV plasma), portability so it can be installed at laser facilities e.g. Texas Petawatt Laser (TPW), operation in vacuum conditions, and constant field for ~100 ns. In a collaboration between the University of Texas at Austin (UT) and Sandia National Laboratories (SNL), we have designed, built, and tested a pulsed power source suitable for cluster fusion experiments at the TPW.

Various lines of evidence suggest that Mars may possess a planetary inventory of water equivalent to a 1-km deep global ocean averaged over the planet's surface. Currently, only a few percent of this amount is found in visible reservoirs such as the Martian atmosphere and polar caps. The remainder is thought to reside in the subsurface, as ground ice, groundwater and hydrated minerals. Four billion years ago, the geologic evidence suggests that the distribution and state of water on Mars were substantially different, including the existence of a northern ocean that may have covered up to a third of the planet and supported a dynamic hydrologic cycle — including episodic rainfall. This talk will address how the climatic and geothermal evolution of Mars is thought to have affected the distribution and state of water, and influenced the geomorphic evolution of the planet's surface. Insights provided by recent spacecraft missions, including the current Curiosity rover investigation of Gale crater, will also be discussed.

An abundance of data from an international fleet of robotic lunar spacecraft is revolutionizing our understanding of the processes and history of the Moon. One of the biggest surprises of recent exploration is that water and other volatile substances are present on the Moon in greater quantities than had been previously thought. Most - but not all -of these new occurrences are associated with the unique environment of the poles. We have found water on the Moon in at least five different occurrences:

1. Water is or was in the lunar interior as a minor component (250-700 ppm). Water from the deep mantle (> 400 km depth) was a component of volatiles driving pyroclastic (fire-fountain) eruptions;
2. Water and hydroxyl (OH) molecules are found on the surface at latitudes > 65 at both poles. These molecules are present as an adsorbed monolayer and/or bound in mineral structures and they show increasing concentration with increasing latitude (~800 ppm and greater). This water is also temporally variable and preferentially located in cooler locales (it's moving);
3. Exospheric water was observed in space above the south pole. The Chandrayaan-1 MIP mass spectrometer measured ~ 10-7 torr H2O, two orders of magnitude higher than normal exospheric abundance; 4) Water ice is admixed into regolith in the south polar region. The LCROSS impact site on the floor of Cabaeus is 5-10 wt.% water; both ice particles and water vapor was ejected during impact. Other cometary volatiles (e.g., carbon dioxide, methane, sulfur dioxide, methanol, ethanol) are also present. The volatiles vary in concentration laterally and vertically and their associated regolith has a "fluffy" physical nature; 5) Relatively thick (~2-3 m) deposits of "pure" water ice is found in some permanently shadowed craters near the poles. The high radio frequency CPR materials occur in over 40 craters (3-12 km dia.) near north pole and about half that amount near the south pole. Radar mapping suggests over 600 million metric tonnes of "pure" water ice in the north; these deposits are in addition to any ice mixed with dirt, such as found by LCROSS. The new data indicate a rich and complex history of volatile materials on the Moon.

Physics Education Research (PER) is a multi-disciplinary research field, which encompasses much more than Physics and Education (as one might expect). I'll discuss some surprising aspects of PER as well as their implications for instruction.

I will discuss to theories of the immune system and describe a theory of the immune response to vaccines. I will illustrate this theory by application to design of the annual influenza vaccine. I will use this theory to explain limitations in the vaccine for dengue fever and to suggest a transport-inspired amelioration of these limitations.

• Physical Theory of the Immune System

Exploration of outer space requires placing humans and their instrumentation at risk from ionizing radiation. Ground based experiments utilizing particle accelerators are often used to simulate the space radiation environment. This talk summarizes research at PVAMU related to radiation dosimetry, shielding, and materials and electronic device radiation tolerance for space applications.

Seismic Geophysics is the study of how sound travels through the earth. In the energy industry, it is used to create images of the stratigraphy of a reservoir. I will be overviewing the process of reservoir development, highlighting where seismic technologies play a role and how borehole seismic ties it all together. In addition, I will be presenting a cross section of roles that Physicists currently play in Schlumberger.

Single-walled carbon nanotubes are artificial nanostructures of great interest to basic and applied researchers because of their remarkable mechanical, thermal, electronic, and optical properties. This talk will describe the discovery and interpretation of near-infrared fluorescence from such nanotubes. In addition, selected recent projects will be summarized that illustrate how nanotube fluorescence can be used for novel studies in chemistry, biology, and engineering.

Lacking an atmosphere to erode the surface with wind and water, the Moon's surface ages through chemical and physical interactions with meteoroids and the solar wind. Over time, these interactions cause the surface to darken, especially at wavelengths short-ward of visible light.

Lunar swirls are bright, curvilinear surface features that are found in discrete locations across the Moon's surface. From the collection of measurements over the past 40 years, we know that every swirl 1) appears to be fresh, and 2) is associated with a local magnetic anomaly. The swirls impart no apparent topography - they appear to overprint the surface on which they lie - indicating that they are either a very thin layer material or the manifestation of a phenomenon that is influencing the surface aging process. New measurements from recent international lunar missions and the active collaboration of experts in the scientific fields from which these instruments derive have begun to shed new light on the lunar swirls. The wide range of scientific fields and instrument observations demonstrates that the study of lunar swirls is more than just a study of a lunar phenomenon. The swirls provide a laboratory to study the solar wind, space weathering, and complex electromagnetic interactions in the solar system.

Numerical simulations are becoming a more effective tool for conducting detailed investigations into the evolution of our universe. In this presentation, I show how the framework of numerical relativity can be used for studying cosmological models. To do this, I am working to develop large-scale simulations of the dynamical processes in the early universe. These take into account interactions of dark matter, scalar perturbations, gravitational waves, magnetic fields, gauge fields and a turbulent plasma. The codes described in this report utilize either the Chern-Simons field or a relativistic plasma and are based on the Cactus framework. They are being developed and tested on the Texas Learning and Computation Center's Xanadu cluster.

Magnetic nozzles, like Laval nozzles, are observed in several natural systems and have application in areas such as electric propulsion and plasma processing. Plasma flowing through these nozzles is inherently tied to the field lines and must separate for momentum redirection or particle transport to occur. Plasma detachment from a magnetic nozzle and the associated physical mechanisms have been investigated. Experimental results are presented from the plume of the VASIMR VX-200 device flowing along an axisymmetric magnetic nozzle and operated at two ion energies to explore momentum dependent detachment. The argon plume expanded into a 150m3 vacuum chamber where the background pressure was low enough that charge-exchange mean-free-paths were longer than experiment scale lengths. Plasma parameters were mapped over a large spatial range using measurements from multiple plasma diagnostics. The data show that the plume does not follow the magnetic field lines. The detachment process is best described as a two part process: First, ions detach by the loss of the magnetic moment when the quantity |v/fcLB| becomes of order unity. Second, plasma instabilities drive a turbulent electric field that creates anomalous electron transport up to a factor of 4 1 above collisional diffusion; electron cross-field velocities approximate that of the ions and depart on more centralized field lines. Electrons are believed to detach by breakdown of magnetic moment further downstream in the weaker magnetic field.