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August 9, 2013
On this page... TREND 2013 Presentations
- Probing anamalously high quantum efficiency of self-healing gold photocathodes
- Using frequency tuning to extend bandwidth in a Pasotron
- Dispersive waves and magnetic reconnection
- Effects of substrate topography on actin dynamics and B cell receptor clustering
- Control of intensity drive of a Cavity QED system
- Plum Pudding model for growing small-world networks
- Evolution of a non-linear system - route to chaos
- Behavior of shear-driven granular materials under applied loads
- Mirror MOT for coupling neutral atoms to a superconducting resonator
- Startle response changes collective behavior
- Suppressing SBS thorugh chaotic phase modulation
Winners of TREND Fair 2013
Best Overall Project:
"Plum Pudding model for growing small-world networks" by Alexander Gorowara (University of North Carolina) and Ari Zitin (Worcester Polytechnic Institute)
Two projects were equally deserving to receive the award for Runner-Up for Best Overall Project:
"Probing anamously high quantum efficiency of self-healing gold photocathodes," Alexandra Boldin, Macalester College
"Using frequency tuning to extend bandwidth in a Pasotron," Carleen Boyer, University of Michigan
Alexandra Boldin, Macalester College
Advisor: Dr. Eric Montogmery
We are examining cesium auride (CsAu) as a potential photocathode material. This summer, we will be building a new Ultra-High Vacuum test chamber, which will allow for both gold and cesium deposition on the cathode as well as measurements of quantum efficiency. All processes will occur without breaking vacuum, a change from the current system in which the cathode must be brought to atmosphere after gold deposition. We hope that this change will show improvement in the quantum efficiency levels of CsAu cathodes.
Carleen Boyer, University of Michigan
Advisors: Dr. John Rodgers and Prof. Daniel Lathrop
A plasma-assisted slow-wave oscillator, or Pasotron, utilizes a beam of electrons in order to generate microwaves. In traditional high-power microwave systems, a solenoid creates a magnetic field which focuses the beam. Rather than relying on an external magnetic field, the Pasotron uses the magnetic field from the electron beam itself to focus and transport this beam. This results in an apparatus that is more compact. We explore the spectrum of radiation of a particular Pasotron, and examine the results of tuning the device in order to extend the bandwidth while maintaining high output power and efficiency.
Alexander Flanagan, University of Wisconsin-Madison
Advisors: Prof. James Drake and Dr. Marc Swisdak
Magnetic reconnection in solar flares, the magnetosphere, and laboratory plasma experiments often occurs at a much quicker rate than slow Sweet-Parker reconnection would predict. Fast reconnection is associated with the presence of dispersive waves in the outflow of the reconnected magnetic field. These dispersive waves arise in parameter regimes that previous two-fluid simulations have mapped out. For our research we use full-particle kinetic simulations to further explore the transition from a regime which exhibits non-quadratic waves and slow reconnection, to a regime that exhibits dispersive waves and fast reconnection.
Jacob Fondreist, University of Alabama
Advisor: Prof. Arpitah Upadhyaya
Quantitative analysis of the immune system has long been an elusive problem, but recently scientists have been able to make significant progress in the field thanks to advances in biology. In this research, we focus on the mechanics of the actin cytoskeleton and movements of antibodies in B lymphocytes, particularly on how they behave with respect to their surroundings. By placing the B cells substrates of uniformly spaced ridges on the scale of micrometers, it is possible to make detailed measurements on the cell’s movements and attribute to them a meaning.
Jorge Oswaldo Gómez Muñoz, Universidad Nacional Autónoma de México
Advisor: Prof. Luis Orozco
Our experiments with low photon number in a two-mode optical cavity require having optimal control of our driving laser intensity. We use a fiber electro optical modulator (EOM) to shift the frequency of the laser beam, but it is sensitive to the temperature of the environment, which degrades the amplitude of the sideband modulation. We are designing an electronic circuit to implement a feedback system with proportional integral and derivative gain (PID) to monitor and correct drifts in sideband amplitude. To do this we sample the output beam measuring the size of the modulation with the help of a photodiode and a mixer. The circuit then corrects through small changes in the voltage bias of the EOM. Since this EOM works as a Mach-Zehnder interferometer the end result is a precise interference when two beams are recombined at the end. We expect the stability over one hour to be better than 1%.
(Work supported in part by NSF through the PFC@JQI)
Alexander Gorowara, University of North Carolina and Ari Zitin, Worcester Polytechnic Institute
Advisors: Profs. Thomas Antonsen, Michelle Girvan, and Ed Ott
Researchers have studied spatially embedded complex networks which are static in time, but networks in nature are inherently dynamical, gaining links and nodes as they develop over time. We explore the properties of growing networks, investigating the relationship between statistical network properties and the space in which they are embedded. In particular, we consider a class of models in which nodes are placed one by one in random locations in space and, after placement, form connections with nearby nodes. We find that the resulting networks are small world-networks, and we characterize how spatial embedding supports the emergence of small-world properties.
Haneih Nejadriahi, St. Olaf College
Advisor: Dr. John Rodgers
Phase locked loops (PLL) are widely important in modern electronic communication and control systems. They are used in systems where it is necessary to estimate the phase of a received (feedback) signal. The goal of this project was to investigate the stability of a second order PLL and observe the route to chaos in a third order PLL as well as a second order PLL with time delayed feedback by advanced usage of scientific instruments and exploring their new functionalities. To prove the validity, these experimental studies have been compared to the theories of chaos along with computer simulations.
Allyson Rice, University of Texas at Austin
Advisor: Associate Professor Wolfgang Losert
Granular materials, such as sand, are ubiquitous in natural and industrial settings, so understanding properties of grain dynamics remains important. While sheared granular materials have been studied extensively, little is known about how grains behave under both shear and external pressure. Using the Refractive Index Matched Scanning (RIMS) method, we performed three dimensional imaging experiments on piles of steady-sheared, monodisperse acrylic beads under various pressures. We tracked our grains and analyzed velocity profiles, mean square displacements, and contact networks. We find grains behave differently under pressure and shear than they behave under shear alone, and that these differences become more marked as pressure increases. Specifically, increasing pressure creates wider shear zones and suppresses vortex formation in flows.
Eslava del Rio Argüelles, Universidad Autónoma de San Luis Potosí
Advisor: Prof. Luis Orozco
The mirror magneto-optical trap (Mirror MOT) uses two beams and two gold mirrors to trap and cool gas of neutral atoms. We are designing and building this compact atom trap to work in a cryogenic environment. Alkali metal dispensers provide a source of rubidium vapor in the ultrahigh vacuum chamber. One wire in “U” shape produces a field gradient for a spatially-dependent force. Another pair of coils is used to produce a bias field that cancels a component of the field gradient. Two beams are collimated and aligned onto the gold mirrors, and the first-order of diffraction forms a cross of reflected beams, whose overlap volume defines the trapping region.
(Work supported in part by NSF through the PFC@JQI)
Tony Sang, Concordia College
Advisor: Associate Professor Derek Paley
The actions of autonomous agents in groups have been investigated to accurately represent group movements. Previous models have not taken into account changes within the group caused by responses to stimuli. Responses to external and internal stimuli can be represented by a dichotomous variable startle. A probabilistic method accounting for startling was integrated with spatially dependent governing equations that simulated vortical motion among a large body of agents. Using this synthesis, changes in kinetic behavior due to being startled and the effects of motion on startling were captured. These changes included dynamic transitions in the formation and varying startle propagation.
Rafael Setra, University of Maryland
Advisors: Profs. Thomas Murphy and Raj Roy
Stimulated Brillouin scattering (SBS) is a nonlinear interaction between optical and acoustical waves that can severely limit the power transmitted through fiber optic systems. Here, we explore both experimentally and theoretically the possibility of using chaotic phase modulation to suppress SBS, and we compare the results to conventional non-chaotic modulation. We also present a theoretical model to simulate the output of a fiber optic system in the presence of such phase modulation, and we compare the simulation results to experimental data. Finally, we explore ways to exploit chaotic synchronization to recover the un-modulated carrier at the receiver.