Session F6: P2: Poster Session II

A Student Experiment to Prove the Laws of Conservation of Energy and Momentum for Nuclear Reactions Using a 1.5 MeV Van de Graaff Accelerator

The year 1931 saw the first artificially induced nuclear reaction in the Cavendish Laboratory. The men behind this ground breaking experiment, J.D. Cockcroft and E.T.S. Walton, used a 150 kilovolt accelerator with a screen of zinc sulfide to detect the emitted alpha particles from the ${ }^7$Li (p,$\alpha )\alpha $ reaction. In 1951 the Nobel Prize was awarded in recognition of work that in effect started the nuclear age. The Q value for a nuclear reaction is defined as $\Delta $mc$^2$, where $\Delta $m is the mass converted to energy during the reaction. In order to study the kinematic equations the following reactions were performed: ${ }^7$Li (p,$\alpha )\alpha $, ${ }^6$Li (p,${ }^3$He)$\alpha $, ${ }^{19}$F (p,$\alpha ){ }^{16}$O and ${ }^{11}$B (p,$\alpha ){ }^8$Be. The experiments were carried out with a 1.5 MeV proton beam from a Van de Graaff accelerator. The experimental energies for the reaction products were compared to the theoretical values obtained using the kinematic equations.   

Deuterium Depth Profiling of Semiconductor Devices Using the $^{3}$He(d,p)$^{4}$He Reaction

The non-resonant reaction, $^{3}$He(d,p)$^{4}$He, is commonly used to determine the depth profile of deuterium in various materials such as group II-VI and III-V semiconductors. While deuterium can passivate electrically-active defects in materials, the `decoration' or tagging of defects by deuterium provides a simple method for defect profiling. This is important in many materials, such as HgCdTe, CdTe, and GaN, whose properties are substantially degraded by a high-density of as-grown defects. Thus, NRA of deuterated material was investigated to determine its efficacy in analysis of defect profiles, i.e. the concentration and location of the defects. We have demonstrated that the $^{3}$He-D reaction accurately predicts the total deuterium in samples. Results were obtained using a 640 keV $^{3}$He beam and a large solid-angle detector to count the reaction products, i.e. p, and $^{4}$He. Results will be presented, which were obtained using detectors of different thicknesses. Both standards and computer simulations were used to normalize our results.   

Save the Crew: A Superconducting Toroid Shield for Deep-Space Manned Missions

Without proper shielding, astronauts traveling beyond the Earth's magnetosphere would be exposed to lethal doses of radiation. Passive shielding is not adequate to protect astronauts from either high-energy galactic cosmic rays or the intense bursts of energetic protons from solar flares. A more effective way is to create a magnetosphere on the spacecraft using a superconducting toroid that surrounds the crew compartment. The optimal geometry of the toroid, computed mechanical stresses, and results of radiation dose calculations are presented and compared with the passive shielding scenario.   

Positron Emission Tomography: A Basic Analysis

Positron Emission Tomography is useful in detecting biological abnormalities. The technique involves attaching radiotracers to a material used inside the body, in many cases glucose. Glucose is absorbed most readily in areas of unusual cell growth or uptake of nutrients so through natural processes the treated glucose highlights regions of tumors and other degenerative disorders such as Alzheimer's disease. The higher the concentration of isotopes, the more dynamic the area. Isotopes commonly used as tracers are 11C, 18F, 13N, and 15O due to their easy production and short half-lives. Once the tracers have saturated an area of tissue they are detected using coincidence detectors collinear with individual isotopes. As the isotope decays it emits a positron which, upon annihilating an electron, produces two oppositely directioned gamma rays. The PET machine consists of several pairs of detectors, each 180 degrees from their partner detector. When the oppositely positioned detectors are collinear with the area of the isotope, a computer registers the location of the isotope and can compile an image of the activity of the highlighted area based on the position and strength of the isotopes.   

An Investigation of the Canis Major Overdensity

Using 2MASS colors Martin et al. (2004) uncovered evidence for a remnant dwarf galaxy in Canis Major, in the form of an overdensity of M-giant stars. The spatial distribution of the M-giants indicate an extended, and likely disrupted, group of stars extending over roughly 30 degrees of the sky. We present new photometry and color magnitude diagrams for various Canis fields obtained at McDonald Observatory and Cerro Tololo Inter-American Observatory. We also obtained spectra at McDonald Observatory of blue stars selected from the photometry. I present kinematic results.   

VLBI Imaging of Active Galactic Nuclei

We employ high-resolution, high-sensitivity, very-long baseline interferometry (VLBI) radio imaging of parsec-scale jets in radio sources to confirm a partial unification theory of active galactic nuclei (AGNs). Various types of AGN contain supermassive black-holes viewed with different orientation angles to the observer's line-of-sight. In the radio, most AGN can be divided into a very bright central core component and a fainter, elongated jet component. We have used a program called DIFMAP to construct high- resolution images of the quasar 3C207, and then modeled the structure of the core and inner jet components. Images of 3C207 were obtained over six epochs in 2005, to observe temporal changes in the core/jet structure. We find multiple components within the core, oriented in a manner that is consistent with their jet components. Some evidence of bending is seen as well. Bending can be interpreted both as evidence of jet interactions with the interstellar medium or as possible precession of the black hole's rotation axis.   

Determining the Viscous Potential from MHD Simulations and Comparing it to Observations

The viscous potential is produced by a mechanical interaction between the magnetosphere and the solar wind and is generally thought to have a value of about 20 kV. Preliminary investigations using the Lyon-Fedder-Mobarry global MHD simulation indicate that the viscous potential increases with increasing solar wind density. To determine if this is in fact the case, we have selected solar wind intervals where the ionospheric potential due to merging with the solar wind should be extremely small. During those periods, we use the DMSP satellites to determine the value of the transpolar potential, which we assume to be driven primarily by the viscous interaction. In this study we will compare those observations to the MHD results.   

Measures of Geo-effectiveness in Storms

Geomagnetic storms are produced by solar wind disturbances causing large currents to flow throughout the magnetosphere. These currents are the magnetosphere's response to the solar wind electric field and the rate of the interplanetary magnetic field's reconnection with the magnetosphere. To gauge the geo-effectiveness of a storm, or the magnetosphere's response to the storm, we consider the ratio of the ring current injection rate (RCIR) to measures of the solar wind input. {\it Burton et al.} [1975] called this parameter $\alpha$, using {\it VB$_{s}$} as the solar wind input. We calculate three versions of $\alpha$: $\alpha$$_{1}$ is the {\it Burton et al.} [1975] parameter, $\alpha$$_{2}$ is the ratio of the RCIR to the {\it Newell et al.} [2007] universal coupling function, $\alpha$$_{3}$ is the ratio of the RCIR to a measure of the dayside reconnection rate recently proposed by Borovsky. Using each of these values of $\alpha$, we rank 100 storms with Dst $<$ -75 nT, between 1995 and 2005. The top 10\% and lowest 10\% of storms are examined in detail to determine what characteristics they might have in common.   

Skill Scores for Ionospheric Modeling

This paper examines two ionospheric models, Themosphere Ionosphere Nested Grid (TING) and International Reference Ionosphere (IRI), and compares them to each other and to ionosonde data from the SPIDR data base for the time period of July 1995 from the 4th through the 17th. We make this comparison by calculating standard skills scores. TING had a much larger dynamic range than IRI and overall both weren't good fits to the data being at times as far off as 20\% or more.   

Correlation between precipitation, dust storms and Gulf of California moisture surges in the Paso del Norte region during the North American Monsoon

Previous statistical analyses performed by the authors have demonstrated an anti-correlation between dust storms and precipitation during the North American Monsoon. During monsoon season both precipitation and dust storms appear to be associated with a moisture inflow approaching from Gulf of California (GOC) labeled as a ``moisture surge.'' A series of meteorological observations are presented in an effort to establish a connection between dust storms and reduced precipitation amounts in El Paso, Texas and surrounding areas in the presence of GOC moisture surges. These data sets were utilized (1) to recognize GOC moisture surges, (2) to investigate whether increased aerosol mass and number densities were responsible for decreased precipitation amounts, and (3) to evaluate atmospheric conditions during a moisture surge in the Paso del Norte region.   

A One-Way Light Beam Experiment

A one-way light experiment has been recently designed and implemented to determine the displacement of a light beam after traveling a straight path of sixty meters as a function of time. The primary goal of this experiment is to determine the affect of the earth's motion on the propagation of light from a source to a sensor both of which are stationary in the laboratory frame of reference. Progressive improvements to the inital design over the past three months have resulted in angular measurements with nanoradian resolution. Beam position data and environmental data along the path are being collected over time periods of several days. Additional improvements to the apparatus are being considered. A detailed description of the experiment and its operation is given. Also presented are (1) the data collected during the development phase and (2) the results from a preliminary analysis of these data.   

Analitic Thermodynamic Calculations for an Immobilized Molecule under Poisson-Boltzmann Interactions using a Spheroidal Geometry

The change in some thermodynamic quantities such as Gibbs' free energy, entropy and enthalpy of the binding of a particle tethered to a surface or particle are analytically calculated. These particles are considered ellipsoids and submerged in a liquid. The ionic strength of the media allows the linearized version of the Poisson-Boltzmann equation (from the theory of the double layer interaction) to properly describe the interactions between an ion penetrable spheroid and a hard plate. We believe that this is an adequate model for a DNA chip and the predicted electrostatic effects suggest the feasibility of electronic control and detection of DNA hybridization and design of chips, avoiding the DNA folding problem.   

AC losses in conventional and block coil geometry superconducting dipoles

The upgrade of injection synchrotrons of LHC requires pulsed magnets reaching 5T with a ramp rate of the order of 1-2T/s. AC losses in the magnets are the major concern. A standard method of AC loss evaluations underestimates experimental results in the critical high field region A modified method used to estimate AC losses in GSI001 model magnet tested recently at BNL gave an excellent agreement with the experimental results. Both methods were applied to analyze recent designs of a cosine current distribution and block-coil geometry superconducting dipoles. We find that the simple and robust block-coil geometry dipole over performs conventional one in both: reduced AC losses and less amount of superconducting wire.   

The Use of Color as a Third Dimension on Maps

This study investigated student understanding of the use of to represent height and temperature. Fifty-four undergraduates were surveyed. Eight students were chosen interviewed to investigate in more detail the responses provided on the surveys. We found that students have an embedded color scheme for temperatures, with red representing hot and blue representing cold (as expected), but there was no embedded scheme when color was applied to height. We found that students did not have a preference when viewing a topographic map with different color schemes, but did prefer the color scheme of the figure that they viewed first. We observed that the students did have an prior notion of what the topographic figure was representing, and tried to fit the color scheme shown to match their idea. During the interviews we also found that even the slightest deviations from a specific color scheme gives rise to confusion. These results, therefore, show the importance of detail consistency when using visualizations in a lecture where the population is composed of novices.   

Designing Water Rockets as a Multi-disciplinary Project for Physics, Calculus, and Engineering Courses

We report the development of a cross-disciplinary activity for strengthening and relating student understanding of concepts from introductory physics, calculus, and engineering courses. Students, most simultaneously enrolled in all three classes, used material from physics and calculus to design rockets built from soda water bottles. They then constructed these rockets and a launcher in their engineering class and concluded the project with a public launch. Topics addressed include kinematics, dynamics, and fluid dynamics.