Fall 2017 Physics Colloquium
Thursday, September 14th
New Physics Majors Induction Ceremony
Thursday, September 21st
Dr. David Schaffner, Bryn Mawr College
"Heliospheric-Relevant Plasma Turbulence in the Laboratory"
The heliosphere is an extremely rich laboratory for the study of plasma turbulence. However, its exploration is restricted by the limitations associated with remote observation and direct measurements through satellites. In this talk, I will discuss a different approach to the examination of heliospherically-relevant turbulence using a laboratory-based plasma experiment. With a specialized plasma source, magnetically dynamic plasma can be produced in a wind-tunnel-like environment which can mimic certain aspects of astrophysical magnetohydrodynamic (MHD) turbulence. I will explain the conditions through which this type of plasma can be created and then give an overview of the myriad of statistical techniques we use to understand this plasma’s turbulence characteristics. Using these metrics, we can compare the laboratory plasma to various regions of the heliosphere, including the solar wind and the magnetosheath. By utilizing the controlled conditions of the plasma in the laboratory, we can complement results from space physics and computer simulation analyses to generate a more comprehensive picture of heliospheric turbulence.
Thursday, November 2nd
Chris Johnson, STScI, Post Doctoral Research Fellow
"Crowded Field Photometry Using Image Subtraction and PSF Fitting: Frmo the Galactic Bulge to Massive Open Clusters"
Crowded field photometry is vital when analyzing dense stellar regions of space that contain thousands up to tens of millions of stars per square degree. Aperture photometry fails in these dense regions since stellar neighbors can be so close that they contribute unwanted light in to your aperture and give false magnitudes. Stars appear as point sources of light when imaged with a telescope and their light can be modeled as a Gaussian function. The light spreads out radially from the bright center (much like a bell curve) and we refer to this function as a "Point Spread Function" or PSF. We can then fit a basic PSF model to all the stars in the field, build up a better average PSF model by iterating through the image and rejecting bad pixels, variable stars, bad images, etc. and create a final master PSF. We then subtract this master from each individual star in each image again and the residuals left behind will tell us something about the source. I have extended the techniques that I used from graduate school to look at X-ray binaries in the Galactic Bulge to uncovering eclipsing binary populations in very young open clusters.
Tuesday, November 14th
Sigma Pi Sigma
Keynote Speaker - Olivia Lanes '14
"Quantum-Limited Measurement for Superconducting Qubits"
Quantum computing and quantum communication holds the promise of faster and more energy efficient computational processing because it relies on the superposition of quantum states. Several physical implementations, including trapped ions, isolated electron spins in semiconductors, and superconducting qubits are being pursued as potential physical platforms for realizing these quantum machines. All share a set of key requirements, including the ability to rapidly and repeatedly measure each quantum bit (or qubit) in the machine while minimally perturbing its state. She will present recent progress towards quantum-limited, quantum non-demolition measurement (that is, measurement that is as sensitive as allowed by quantum mechanics) of superconducting qubits. I will begin with an overview of the field of quantum information, explain the desire for a universal quantum computer, discuss measurement protocols, and end with recent data taken at the University of Pittsburgh on superconducting qubits.
4:30pm (Keynote Speaker & Induction Ceremony)
6:00 pm (Dinner) *you must sign up for dinner by November 8th in Tome 201
Social Hall West
Tuesday, November 28th
Physics Senior Research Presentations
Natalie G. Ferris & Ruth A. Strauss - "Ghost interference: a quantum phenomenon?"
“Ghost interference” refers to an interference pattern observed in a beam of light that does not actually pass through a diffracting mask such as a double slit. Ghost interference can be readily explored in the lab using a quantum source of light known as spontaneous parametric down conversion. However, to analyze double-slit interference with quantum light, we must first fully understand interference of classical light, including from partially-coherent sources. Results of double-slit interference for partially-coherent sources are presented. We show the effect of angular source size on the fringe visibility and discuss implications for ghost interference. In addition, a LabVIEW code was implemented to automate data collection. This will be essential for taking ghost interference data with single photons next semester.
Erin Wynne - "The Implementation of the Arduino Microcontroller to Aide in the Study of Coupled Logistic Map Circuits"
The logistic map is a simple non-linear dynamical system used to model the time-discrete growth of a population and is relied on heavily in undergraduate studies of chaos. Previously, Kevin Skowronski ’17 and Sean Jones ’17 built a circuit that successfully reproduces the behavior of a system of two coupled logistic maps. They were able to observe basic chaotic principals such as period doubling and the onset of chaos, in addition to more exotic behaviors such as “almost synchronized” and “anti-synchronized” chaos. However, the major limitation of this project was its data collection techniques, which tended to be time intensive and only feasible for a small subset of data points as all parameters had to be adjusted by hand. This semester, the Arduino Uno microcontroller was used to run the circuit and change its parameters, with the goal of eventually increasing the efficiency and sample size of data collection to produce logistic map and bifurcation plots similar to those you might see in a text book.
"Veronica Marie Rodriguez - "The Use of Automated Planetariums in Introductory Undergraduate Astronomy Education"
This presentation will discuss methods for developing effective planetarium shows on the Spitz ATM-4 Theater Automation System of Dickinson College's Kanev Planetarium; specifically centered on programs intended for use in introductory undergraduate astronomy courses. The presentation will also cover future work on dividing larger shows into smaller modules; with the intent to allow greater flexibility on the part of educators. The shows will then be tested on volunteer groups to analyze their usefulness in an educational setting. Once completed, the programs will be available for use by the Dickinson Department of Physics and Astronomy.
Stafford Lecture Room
Thursday, November 30th
Physics Senior Research Presentations
Ralph Hernandez and Zifan Lu - "Further Research on the RR Lyrae Variable Star: GM Orionis"
The pulsating nature of the RR Lyrae star allows us to apply the period-luminosity relationship which then allows us to determine the apparent and absolute magnitude of the star. The magnitudes can determine the distances of other astronomical objects therefore, RR Lyrae Stars can be considered as “standard candles” in astronomy. We will focus and explore the under-observed RR Lyrae star GM Orionis in the course of the research. Throughout the semester, we gained the knowledge on how to properly operate the Britton and NURO telescopes in order to gather data. The collected data includes GM Ori, standard fields, biases, flats, and darks. Once we have gained enough data, we begin the data reduction through the use of Image Reduction and Analysis Facility (IRAF). Through the reduction processes we are able to account for noise from the CCD, thermal energy, and the distortion due to optical effects. At the end of the semester, we hope to produce light curves which allow us to see the light intensity over a course of period. Our primary goal is to merge the result of our observation with the mechanism of RR Lyrae variables to understand the changes of GM Ori undergoes.
Ellis Johnson, Matt Persick and Isaac Ward - "Light Pollution in Carlisle, PA"
The production of light has served as a milestone in human technological advancement however, it also has demonstrated how light can impact the world we live in. Light pollution, or the brightening of the night sky due to wasted energy and inefficient lighting is one of these impacts. Using the town of Carlisle Pennsylvania as a case study, this presentation will address how light produced from various man made sources can impact sky brightness and how the levels of light pollution have changed over the past 2 years. To conduct this research, a sky brightness meter was used to collect data on the relative brightness of various areas in and around Carlisle and on Dickinson College campus. Through analysis of the sky brightness data, it can be shown that the change in type of light fixture used throughout Carlisle has led to the brightening of the sky over the past 2 years. Using these conclusions, it is possible to recommend policy changes to reduce light pollution and its associated negative effects.