Bulletin of the American Physical Society
APS Ohio Section Fall 2020
Volume 65, Number 15
Friday–Saturday, October 16–17, 2020; VIRTUAL
Session D01: Poster Session (6:00-7:30pm) |
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D01.00001: Cooling without warming: New Materials for Environmentally Friendly Refrigeration Babajide Akintunde, Arjun Pathak, Prayushi Bhorania, Mahmud Khan Improving energy efficiency and mitigating climate change are current topics of significant global interest. Magnetic refrigeration can help in the realization of these goals. Unlike the conventional refrigerators, which use greenhouse effect related gases, thereby contributing to global warming, magnetic refrigeration is environmentally friendly. In addition, this technology is about 20-30{\%} more energy efficient than the current cooling technology. Magnetic refrigeration technology utilizes the phenomenon of magnetocaloric effect (MCE), the process of heating and cooling of magnetic material when exposed to an external magnetic field. Magnetic materials exhibiting large MCE near room temperature are desired for application in this technology. In this study, we prepare a series of Mn0.5Fe0.5$+$xNi1-xSi0.94Al0.06 materials with potential application in magnetic refrigeration, using a conventional arc-melting technique. These materials are composed of cheap and non-toxic elements that address some drawbacks associated with several previously developed materials. The structural, magnetic, and magnetocaloric properties of these materials will be presented. [Preview Abstract] |
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D01.00002: The effect of stoichiometric variation on the magnetocaloric properties of Mn0.5$+$xFe0.5Ni1-x Si0.95 Al0.05 alloys. Ranjit Chandra Das, Arjun K. Pathak, Prayushi Bhorania, Mahmud Khan Magnetocaloric effect (MCE) signifies the thermodynamic phenomenon in which the application of an external magnetic field alters the temperature of a special class of materials. These materials are known as Magnetocaloric materials (MCMs). In recent years a wide variety of materials have been designed and discovered that exhibit giant magnetocaloric effects. However, most of these materials are often prepared either by rare earth, expensive, or toxic elements. Therefore, the discovery of new MCMs remains an active field of research. Keeping this discussion in mind, we are investigating the magnetocaloric properties of a series of Mn0.5$+$xFe0.5Ni1-xSi0.95Al0.05. The constituent elements of the system are cheap and abundant, which makes them a promising candidate for magnetic refrigeration. The crystalline and magnetic properties of the samples will be presented and discussed. [Preview Abstract] |
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D01.00003: Optimization of the CuInSe$_{\mathrm{2}}$ Absorber for the Bottom Cell of a Polycrystalline Thin Film Tandem Solar Cell. Dhurba Raj Sapkota, Puja Pradhan, Prakash Koirala, Balaji Ramanujam, Corey Grice, Randy j. Ellingson, Richard Irving, Michael J. Heben, Robert W. Collins Thin film CuIn$_{\mathrm{1-x}}$Ga$_{\mathrm{x}}$Se$_{\mathrm{2}}$ (CIGS) is an important absorber material for single junction solar cells. CIGS with Ga content x \textasciitilde 0.3, having a bandgap near 1.2 eV, is well known to provide the highest efficiencies. CuInSe$_{\mathrm{2}}$ (x $=$ 0) has recently attracted interest as a possible bottom cell absorber of a tandem solar cell due to its narrow bandgap of 1.0 eV and suitable p-type electronic properties. The CIGS materials yielding the highest efficiency solar cells are deposited by multisource evaporation which requires accurate calibration of Cu, In, and Ga atomic fluxes in the deposition process. In this research, a CIS calibration has been developed by utilizing real time spectroscopic ellipsometry analysis for thin film depositions of copper (Cu), copper selenide (Cu$_{\mathrm{2}}$Se) and indium selenide (In$_{\mathrm{2}}$Se$_{\mathrm{3}})$ to determine the atomic fluxes at different Cu and In evaporation source temperatures. Using this calibration, CIS can be deposited at different rates while maintaining the desired p-type stoichiometry of [Cu]/[In] $=$ 0.9. Guided by the calibration, optimization of CuInSe$_{\mathrm{2}}$ solar cells has been demonstrated by incorporation of one-stage CIS absorbers fabricated over a range of deposition rates . [Preview Abstract] |
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D01.00004: Quantum Mechanics and Density Functional Theory of the Rosen-Morse Potential Eric Hinojosa, Antonio Cancio Density Functional Theory (DFT) is an electronic structure method widely used to calculate the electronic, optical and magnetic properties of materials in terms of atoms and the electrons that glue them together. One way to test and improve DFT theories is to apply them to simple, one-dimensional potentials. Such potentials allow easy testing of new theories, as calculations can be made quickly and analytic answers are sometimes known. We study the Rosen-Morse potential, a quantum potential used to model vibrations and predict energy spectra of molecules. It is also used in nanoscience to model an electron trapped in a thin layer between two materials. We adapt previously written code to study this potential, using Python along with the numpy and matplotlib library. We calculate eigen-orbitals and bound state energies and then study "pseudo-atom" systems consisting of RM potentials with all bound states completely occupied, simulating the electronic shell structure of the atom. We use these systems to test the predictions of density functionals of the kinetic energy, including the Thomas-Fermi, Von Weizsacker, and local gradient-expansion. Our data indicates that kinetic energy models that are typically poor in three-dimensions are nearly exact for this model. [Preview Abstract] |
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D01.00005: Percolation through Voids around Impenetrating Toroidal Inclusions Payton Linton, Alexandra Ballow, Donald Priour Porous materials made up of impermeable grains constrain fluid flow to voids around the impenetrable inclusions. A percolation transition marks the boundary between densities of grains permitting bulk transport and concentrations blocking traversal on macroscopic scales. With dynamical infiltration of void spaces using virtual tracer particles, we treat inclusion geometries exactly. We calculate the critical number density per volume $\rho $c for toroidal inclusions. The critical number is well-known for axially symmetric shapes and faceted solids, but has yet to be calculated for any non-convex particles. We consider aligned and randomly oriented inclusions, for torii with both circular and square cross-sections. The excluded volumes tend to finite values for both randomly oriented and aligned torii. In a definitive difference from convex solids, aligned tori are less permeable than their randomly oriented counterparts in certain situations such as when torii are narrow. [Preview Abstract] |
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D01.00006: Imaging of the Soft Matter Particulate Systems by Scanning Electron Microscopy Richard Sent, Samantha Tietjen, Petru Fodor, Kiril Streletzky Polymeric microgels suspended in water exhibit a reversible volume transition phase upon heating which leads to nanoparticles deswelling by as much as a factor of 15 in volume. Microgels are typically characterized by noninvasive techniques of dynamic light scattering (DLS), which probe particle structure/dynamics. More direct methods such as scanning electron microscopy (SEM) are useful for visualizing polydisperse microgel samples. As SEM typically uses high vacuum to characterize dried samples it is problematic as the dehydrated microgels collapse under vacuum. This project explores wet particle imaging in an ionic liquid stable under high vacuum. Particles were suspended in a thin ionic liquid film on a copper grid and were studied for both size distribution and dynamics. The experiment was tried on separate suspensions of silica particles and polymeric microgels. The silica particles exhibited Brownian motion proving the concept of the approach. While the average SEM sizes of microgels generally agreed with sizes obtained by DLS in ionic liquid at room temperature, the initial attempts at diffusion analysis using SEM particle tracking yielded mixed results. The microgels were often observed to drift significantly, clustering with nearby particles and drifting towards the grid edges. [Preview Abstract] |
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D01.00007: Performance Evaluation of Calorimeter Clustering Algorithms for Particle Tracking Alexandra Ballow, Alina Lazar, Brian Isbell, Kesung Wu, Alexander Sim The challenge of reconstructing tracks of particles produced in high energy collisions is mainly computational. With the ever-growing data from scientific experiments, it is imperative to have automatic ways to analyze that data. Combinatorics approaches currently used to track particles will become inadequate as the number of simultaneous collisions will increase in the next phase of the High Luminosity Large Hadron Collider (HLLHC). To reduce the complexity of combinatorial approaches we evaluate several iterative algorithms based on clustering algorithms to reconstruct particle trajectories. Specifically, we analyze clustering algorithms based on sparse binning and DBSCAN. The sparse binning algorithm separates the detector space into bins before performing the grouping step. This idea speeds up the algorithm but affects the accuracy. We ran a high-performance computing implementation of the proposed clustering approaches on a public dataset containing a large set of simulated collision events. The performance evaluation is done for three different clustering implementations in terms of average accuracy and computational speed. [Preview Abstract] |
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D01.00008: Lifetime measurements of the rovibrational levels of the $6^{1}\Sigma_{g}^{+}$ state of sodium dimer Lok Raj Pant, Dinesh Wagle, Michael Saaranen, Burcin Bayram We measured the lifetime on the $6^{1}\Sigma_{g}^{+} (\nu = 6,7,8, J= 31)$ state of sodium molecule. The molecules of sodium were formed inside the heat-pipe at around $300^{\circ}$C in the presence of the argon gas as a buffer medium. The ground state of sodium molecules were populated thermally and excited from the ground state to the $6^{1}\Sigma_{g}^{+} (\nu = 6,7,8, J= 31)$ states through a double resonance, with $A^{1}\Sigma_{u}^{+} (8,30)$ as an intermediate state. Two pulsed dye lasers, pumped by 532 nm Nd:YAG laser, were used for two-step excitation to the final state. The disperse fluorescence spectrum was collected and sent to the photon counter which measured the lifetime of the selected state. The radiative lifetime was extracted from the Stern-Volmer plot. [Preview Abstract] |
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D01.00009: Qubit switching using STIRAP in trapped-ion quantum states Zach Manson, Chitra Rangan Trapped-ion quantum states are well-known to be good candidates for qubits in quantum computing. We study the application of an adiabatic method known as STIRAP to achieve qubit switching. Stimulated Raman Adiabatic Passage (STIRAP) is method of quantum control that utilizes a specific atomic structure known as a 3-Level Lambda System (3LLS). The system consists of two ground states that are coupled to an intermediate excited state via two counter-intuitively ordered pulses known as the Stokes and pump pulses. STIRAP is a notable method of population transfer because not only is it robust against small experimental variations, but it also has the unique property to allow the complete transfer of population between the two ground states without loss of population due to spontaneous emission from the excited state. STIRAP can be extended to other chain-wise connected multi-level systems such as those that are present in the trapped-ion. In this study, we numerically determine the optimal pump and Stokes pulses that will maximize qubit switching in 3, 5, and 7-quantum states of the trapped-ion. We find that the overlap between the two pulses increases as the number of chainwise-connected states increase. We discuss the potential applicability of this method in quantum computing. [Preview Abstract] |
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D01.00010: Measurement of photoionization cross sections from 6s5d $^{\mathrm{1}}$D$_{\mathrm{2}}^{\mathrm{\thinspace }}$excited state of ytterbium at and above the first ionization threshold Bilal Shafique, Raheel Ali, Sami ulHaq, Muhammad Rafique, Muhammad Aslam Baig Experimental investigations of the photoionization cross sections from the 6s5d $^{\mathrm{1}}$D$_{\mathrm{2\thinspace }}$excited state are reported for atomic Ytterbium. A heat pipe-cum-linear thermionic diode ion detector employing saturation technique and working in space charge limited mode has been used for generating the atomic vapors of Yb. A Nd:YAG pumped narrow bandwidth (\textasciitilde 0.2 cm$^{\mathrm{-1}})$ Hanna-type dye laser charged with LDS-698 dye and tuned at 722.6 nm is used for the two-photon resonance transition 6s$^{\mathrm{2}} \quad^{\mathrm{1}}$S$_{\mathrm{0}} \quad \to $ 6s5d $^{\mathrm{1}}$D$_{\mathrm{2}}$. The excited state population is then promoted to the ionization threshold at 439.2 nm and above threshold at 355 nm and 300 nm. The intensity of exciting laser (722.6 nm) is kept fixed while the ionizing laser energies are varied using neutral density filters. The data is plotted between ionizing laser energy and photo-ion signal. The experimental data points are fitted using the least square fit algorithm which yield photoionization cross sections at ionization threshold and in the continuum. [Preview Abstract] |
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D01.00011: Power Narrowing via Optical Pumping Aaron Weiser, Matthew Commons, Jonathan Feigert, John George, Michael Crescimanno Ancillary phase-independent optical fields can be used as probes of lineshape changes due to optical pumping in saturated absorption spectroscopy (SAS). We test a strictly population-based theoretical model of power-driven resonance narrowing by comparing it with experimental results of Rubidium SAS in D1-D1 (pump-probe) and D2-D1 $+$ ancillary optical fields [Preview Abstract] |
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D01.00012: Fast Quantum Control of Bose-Einstein Condensates for Inertial Sensing Applications Skyler Wright, Chris Larson, E. Carlo Samson We report on our numerical simulations of high-fidelity, fast quantum control of Bose-Einstein condensates (BECs), as we extend them to full 3D simulations, while performing a new set of 2D simulations. We simulate a painted potential that provides transverse confinement to the atoms, in unison with a harmonic potential for vertical confinement. This combination results to arbitrary and dynamic 3D traps, which control the spatial transport of the BEC. To maintain high fidelity after transport, we implement shortcuts-to-adiabaticity (STAs) to design the BEC trajectory in our simulations. STAs allow fast movement while suppressing excitations that can result due to the rapid transitions of the quantum state. In our 3D simulations, quantum fidelities resulting from different, experimentally viable transport times and trap-depths are compared. In our 2D simulations, we further our study of the directionality of the quantum control by commuting the BEC at a 45-degree angle as well as reflecting the movement halfway through the transport time. This new set of 2D simulations is in preparation for the analysis of STA implementation during the operation of a BEC Mach-Zehnder interferometer. [Preview Abstract] |
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D01.00013: The Design, Validation, and Future Plans for a New Neutron Detector at Ohio University Kristyn Brandenburg, Zachary Meisel, Carl Brune, Shiv Subedi, Doug Soltesz, Thomas Massey Though ($\alpha$,n) reaction cross sections play a key role in nuclear astrophysics and applications, many are poorly constrained by nuclear experiments and have significant uncertainties in theoretical predictions. Improving this situation will be done in part using a newly developed neutron long counter, HeBGB, at the Ohio University Edwards Accelerator Lab. The detector was designed using the MCNP6 software to have near constant efficiency in the neutron energy range relevant for core-collapse supernovae and special nuclear materials. Efficiency validation measurements have been performed with HeBGB, which utilize well-characterized reactions with constrained cross sections and known neutron energies. The first measurement conducted with HeBGB is $^{27}{\rm Al}$($\alpha$,n) near threshold, which dominates the astrophysical rate, has disagreement between theoretical predictions and has only one prior measurement in this energy regime. [Preview Abstract] |
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D01.00014: Energy Densities of Simulated Nuclei and collisions Ian Freeman Traditional methods of simulating nuclear fragmentations require considerable amounts of computational resources. To combat this, we have utilized a new classical nuclear model to both reduce computational load and maintain a high level of accuracy. We have successfully produced simulated nuclei of lead-208 and will report on the energy densities of simulated collisions. We will also report on the stable configurations of the nuclei, and qualitatively analyze the implications of the resulting energy heatmaps. This work provides a complete proof of concept for studying nuclear collisions and multifragmentation, which will be developed in future work with parallelized code to survey the distributions of the fragmentations and compare them to results from real collisions. [Preview Abstract] |
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D01.00015: Simulated Multifragmentation of $^{\mathrm{40}}$Ca with $^{\mathrm{40}}$Ca Collisions Brighton Coe Nuclear collision simulations are a valuable tool for studying the distribution of fragmentation products but require significant processor time to simulate. Using a simple two-body interaction model that treats each nucleon as a point particle significantly reduces this time while maintaining a high level of accuracy. With this model, we report on collisions of $^{\mathrm{40}}$Ca with $^{\mathrm{40}}$Ca and present their resulting fragmentation distributions.~ [Preview Abstract] |
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D01.00016: Real-Time Integrated Weld Analyzer Shubham Kukreja Resistance spot welding is a process in which metal plates at contact are joined by the heat obtained from resistance to electric current. As the stack thickness of metal plates increase, it is very difficult to evaluate the quality of a spot weld using destructive testing. Therefore, ultrasonic imaging is an excellent non-destructive testing solution. Real-Time Integrated Weld Analyzer (RIWA) is a combination of an advanced non-destructive ultrasonic system which provides a solution to evaluate resistance spot welds in real-time. The hardware of the system consists of a high frequency ultrasonic transducer that is integrated into the welding electrode, which generates ultrasonic waves that pass through the electrode cap into the welded plates. The key feature of the technology is that inspection of the weld is conducted during the real time monitoring of the welding process. The software of the system uses machine learning algorithms to detect key events such as melting onset, steel-steel interface disappearance, saturation and expulsion as the weld nugget grows. In this study, we will be presenting the process of preparing and labeling the ultrasonic B scans of spot welds as it is an important step for the implementation of machine learning algorithms. [Preview Abstract] |
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