Session E14: Undergraduate Research III

Live

Classical physics has been viewed as incapable of dealing with atomic phenomena. We will give an overview of the numerous models created by well-known people like J.J. Thompson and more obscure individuals like Gryzinski. The phenomena correctly described are far greater than known in the literature. We will see stability, spectra, and chemical properties can be explained by classical mechanics. In addition to atomic models, classical ideas are adequate for molecular phenomena and chemical bonds   

Live

One of the reasons that the concept of fields was introduced by Faraday and Maxwell was to envision momentum and energy being propagated from point to point. In \underline {A Treatise on Electricity and Magnetism}, Maxwell gives the analogy of information being transmitted to a passenger on a ship with the use of ocean waves or messages attached to projectiles. In static situations, it is harder for beginning students to see how the electromagnetic field can carry momentum. In the early 1960's, Feynman gave students a paradox that helped undergraduates envision the need of momentum flow in a charged disk that begins to turn when an attached solenoid has its current terminated. In the literature, it appears that many physicists are confused by this apparent paradox. We will show that fields are unnecessary for the resolution of this thought experiment.   

Live

The \textit{anode heel effect} refers to a decrease of the intensity of an x-ray beam from the cathode side to the anode side. This variation is measured along the longitudinal axis of the x-ray tube and is a result of the geometry of the anode head. This experiment, conducted at the Tri-State Regional Cancer Center in Ashland, KY, used a quality assurance, detector array called an ArcCHECK. The array is a cylindrical imaging phantom containing 1386 n-type silicon diodes arranged in a helix over the apparatus. Using ArcCHECK, beam profiles and dose distribution plots for x-ray beam energies of 75kV and 140kV were produced. This talk will focus on the plots and the noticeable effects at both 75kV and 140kV.   

Live

Under the right set of conditions, a rotating saddle potential can be used to confine the movement of a particle moving on its surface. A time varying hyperbolic potential of this type is generally considered the go-to mechanical analog to the RF Paul trap. The work done so far has concentrated on symmetric saddles, which are characterized by equal curvatures along the trapping and anti-trapping directions. However, the vast majority of applications using the RF Paul trap, ranging from atomic clocks to quantum computing and simulations, require an asymmetry in the saddle-like electric potential. This asymmetry (or break in the degeneracy) is required for laser cooling and various quantum manipulations. Therefore, an asymmetric rotating saddle may be a more appropriate mechanical analog to the RF Paul trap. In this paper, we investigate the motion of trapped particles in asymmetric saddles. We find that the motion is highly sensitive to the degree of asymmetry in the saddle potential. Notably, we find that asymmetry in curvature between the trapping and anti-trapping directions arising from manufacturing defects can lead to significant changes in the particle\^{a}\texteuro \texttrademark s trajectory. We explore the impact of asymmetry on precession and discuss similarities and differences in the stability of motion for the rotating saddle and RF Paul trap. Lifetime measurements in rotating saddles with varying degree of symmetry are used to trace out key aspects of the a-q stability diagram, which include counterintuitive demonstrations of stability for saddles with negative symmetry.   

Not Participating

An efficient procedure for the dispersion and quantification of a network of multi-walled carbon nanotubes (MWCNTs) was developed. The dispersion technique is scalable to wafer-size samples, making the process useful in industrial applications. Using image processing, the fractal dimension factor (D) of the MWCNT network that represents its geometric complexity was determined and correlated to the areal concentration of the CNTs in the network. The less complex network that has a lower density of CNTs had the highest D factor, tending towards 2, which is the characteristic value for a two- dimensional network. The electrical resistance of the thin MWCNT network was found to scale with the areal mass density of MWCNTs by a power law, with a percolation exponent of 1.42 and a percolation threshold of 0.12 micrograms per cm$^{\mathrm{2}}$. The sheet resistance of the highly dense MWCNT networks was about six orders of magnitude lower than that of less dense networks; attributed to a higher number of wire contacts. The dependence of the resistance on the areal density of CNTs in the network and on CNT network complexity was analyzed to validate a two-dimensional percolation behavior.   

Live

Eikonal approximation, which uses the intuition of geometrical optics, has been used in high energy scattering theories for more than a hundred years. More recently, eikonal approximation has been used in quantum mechanics in the form of WKB approximation, although it originated in the field of electromagnetism and optics. In this work, we revisit eikonal approximation in the context of electromagnetic scattering. We study the scattering of a monochromatic electromagnetic wave off a weak dielectric sphere in the eikonal approximation. Scattering of a monochromatic electromagnetic wave off a weak dielectric sphere can also be solved exactly. We use the Green function formalism to exactly solve the scattering cross section for our electromagnetic configuration using partial wave method. We numerically solve and compare the scattering cross section obtained using eikonal approximation with the partial wave method. We expect our work to shed some light on the regime of validity of eikonal approximation.   

Live

Heisenberg's uncertainty principle is often presented as a ``purely quantum'' relation with no analogue in the classical $\hbar \to 0$ limit. However, this formulation of the classical limit is problematic for many reasons, one of which stems from dimensional analysis. Since $\hbar$ is a dimensionful constant, we may always work in natural units in which $\hbar = 1$. Dimensional analysis prescribes that all physical laws can be expressed purely in terms of dimensionless quantities. It follows that the existence of a dimensionally consistent constraint on $\Delta x \Delta p$ requires the existence of a dimensionful parameter with units of action. In this talk, I will argue that any definition of the classical uncertainty, if it is to be meaningful, must be formulated in terms of dimensionless quantities. I will compare the uncertainty of certain coupled classical systems and their quantum counterparts and show that they converge in the classical limit. Most notably, since these systems feature additional dimensionful scales, the uncertainty bounds are dependent on multiple dimensionless parameters, in accordance with dimensional considerations.   

Live

Humimic Medical offers six different density grades of medical gel. Gelatin {\#}5 medical gel, density of 898.4 kg/m$^{\mathrm{3}}$ and a Young's Modulus of 1.09 x 10$^{\mathrm{5}}$ Pa, is commonly used to simulate blood clots and brain tissue. Its texture makes it useful for medical imaging and surgical training procedures. The goal for this study is to measure the mass attenuation coefficient for a beam of beta particles and gamma rays. Sources used for this experiment were Cesium-137, Sr-90, TI-204, and CO-60. We will discuss our data collection method using a ST-360 Radiation Counter with a GM-35 probe and the coefficient values obtain for each type of source.   

Live

One prevailing source of natural radioactivity in Eastern Kentucky is Ohio Shale, a member of the black organic shale family. Our goal for this study is to measure the amount of radioactivity in an outcrop of Ohio Shale as a means to better understand its radioactive nature and the shielding effects of the nonradioactive Three Lick Bed rock that covers half the shale. We used eight commercially purchased Gamma Scout radiation monitors that employ a halogen filled Geiger-Muller tube to detect the ionizing radiation particles. Using these detectors, we found significant fluctuations in the data in spite of their factory calibration. This led to a relative calibration of the detectors in the laboratory with a 5.0 $\mu $Ci CS-137 source that did not successfully smooth out the fluctuations in the outcrop data. Taking the lessons learned during the first pass and calibration, we developed a new data collection method for a second pass of the outcrop. This talk will focus on the data collection methods and calibration and conclude with a discussion of future opportunities.