Physics Commons^™

Statistical Γ Rays In The Analysis Of Surrogate Nuclear Reactions, N. D. Scielzo, J. Escher, J. M. Allmond, M. S. Basunia, C. W. Beausang, L. A. Bernstein, D. L. Bleuel, J. T. Burke, R. M. Clark, F. S. Dietrich, P. Fallon, J. Gibelin, B. L. Goldblum, S. R. Lesher, M. A. Mcmahan, E. B. Norman, L. Phair, E. Rodriguez-Vieitez, S. A. Sheets, I. Thompson, M. Wiedeking

Physics Faculty Publications

The surrogate nuclear reaction method is being applied in many efforts to indirectly determine neutron-induced reaction cross sections on short-lived isotopes. This technique aims to extract accurate (n,γ) cross sections from measured decay properties of the compound nucleus of interest (created using a different reaction). The advantages and limitations of a method that identifies the γ-ray decay channel by detecting any high-energy (“statistical”) γ ray emitted during the relaxation of the compound nucleus were investigated. Data collected using the Silicon Telescope Array for Reaction Studies and Livermore-Berkeley Array for Collaborative Experiments silicon and germanium detector arrays were used …

Characterization Of An Axially Sampling Time-Of-Flight Mass Spectrometer For Upper Atmospheric Measurements, Addison E. Everett, Scott Schicker, Mike Watson, Wayne Sanderson, Dalon Work, Cameron Weston, James Dyer, Erik Syrstad

Graduate Student Posters

The mesosphere/lower thermosphere (MLT) lies between the turbulent mixing and diffusive layers of the earth’s upper atmosphere. Temperatures in this region are varied and include the coldest region of the earth’s atmosphere, the mesopause. Too high for aircraft and too low for satellites, the only method of direct access to the MLT is by sounding rocket for periods of at most a few minutes. Because of this, the MLT is the most difficult region of the earth’s atmosphere to access and is therefore the least understood region of the earth’s atmosphere. Accurate in-situ measurements of MLT species are important for …

Magnetic Vortices On Closely Packed Spherically Curved Surfaces, Robert Streubel, Denys Makarov, Florian Kronast, Volodymyr Kravchuk, Manfred Albrecht, Oliver G. Schmidt

Robert Streubel Papers

We investigate the change of magnetic vortex states driven by curvature. The equilibrium state and magnetization reversal of soft magnetic permalloy (Py, Ni ₈₀Fe ₂₀) caps on self-assembled spherical particles with diameters of 100, 330, and 800 nm are investigated, revealing the vortex ground state for individual caps and closely packed cap arrays. The magnetic coupling between vortices is substantially reduced due to the shape of the cap as apparent in a much weaker dependence of the magnetization reversal process on the separation distance. Interestingly, the remaining coupling is still sufficiently large to introduce chirality frustrated vortex states …

Cavity Modes And Their Excitations In Elliptical Plasmonic Patch Nanoantennas, Ayan Chakrabarty, Feng Wnag, Fred Minkowski, Kai Sun, Qi-Huo Wei

Qi-Huo Wei

We present experimental and theoretical studies of two dimensional periodic arrays of elliptical plasmonic patch nanoantennas. Experimental and simulation results demonstrate that the azimuthal symmetry breaking of the metal patches leads to the occurrence of even and odd resonant cavity modes and the excitation geometries dependent on their modal symmetries. We show that the cavity modes can be described by the product of radial and angular Mathieu functions with excellent agreements with both simulations and experiments. The effects of the patch periodicity on the excitation of the surface plasmon and its coupling with the cavity modes are also discussed.

Approaches To Control Nitrate Pollution In The San Joaquin Watershed, Misgana K. Muleta, Stephen Clayton

Physics

Modeling of the San Joaquin valley using SWAT can give a comprehensive overview of hydrologic traits of the San Joaquin River and its tributaries, specifically for nutrients like nitrate. The San Joaquin valley is a site of intense modeling interest and policy making, as the San Joaquin River joins the Sacramento River to feed into the Delta. The environmental impact of dissolved oxygen on aquatic life on the Delta is a particularly key concern (Quinn 2000). The San Joaquin watershed also represents considerable investment in agriculture on the valley floor and has been studied for nitrate, sediment, and salinity concerns …

Lhc One-Turn Delay Feedback Commissioning, T. Mastoridis, P. Baudrenghien, J. Molendijk

Physics

The LHC One-Turn delay FeedBack (OTFB) is an FPGA based feedback system part of the LHC cavity controller, which produces gain only around the revolution frequency (frev = 11.245 kHz) harmonics. As such, it helps reduce the transient beam loading and effective cavity impedance. Consequently, it increases the stability margin for Longitudinal Coupled Bunch Instabilities driven by the cavity impedance at the fundamental and allows reliable operation at higher beam currents. The OTFB was commissioned on all sixteen cavities in mid-October 2011 and has been used in operation since. The commissioning procedure and algorithms for setting-up are presented. The resulting …

Proposal For An Rf Roadmap Towards Ultimate Intensity In The Lhc, P. Baudrenghien, T. Mastoridis

Physics

The LHC currently operates with 1380 bunches at 50 ns spacing and 1.4 1011 p per bunch (0.35A DC). In this paper the RF operation with ultimate bunch intensity (1.7 1011 p per bunch) and 25 ns spacing (2808 bunches per beam) summing up to 0.86A DC is presented. With the higher beam current, the demanded klystron power will be increased and the longitudinal stability margin reduced. One must also consider the impact of a klystron trip (voltage and power transients in the three turns latency before the beam is actually dumped). In this work a scheme is proposed that …

Evaluating Alternative Hydraulic Solutions To Limit Nutrient Contamination Of An Aquifer In Southern California Read More: Http://Ascelibrary.Org/Doi/Abs/10.1061/9780784412312.009, Misgana K. Muleta, Jake M. Perry

Physics

Many small communities depend on groundwater sources for drinking water and they often use septic tanks for wastewater treatment and disposal. Nitrate and other pollutants leaking from poorly designed septic tank systems can percolate to the aquifers and alter quality of the groundwater. This study describes a groundwater model developed using Visual MODFLOW for an aquifer that is used as a water supply source for the communities of Beaumont and Cherry Valley, CA. The aquifer has been contaminated by nitrates leaking from septic tank systems. The model will assist in clarifying the extent of interactions between nitrate pollutants, percolation from …

Uncertainty Analysis And Calibration Of Swmm Using A Formal Bayesian Methodology Read More: Http://Ascelibrary.Org/Doi/Abs/10.1061/9780784412312.060, Misgana K. Muleta

Physics

Importance of uncertainty analysis (UA) to estimate the degree of reliability associated with model predictions is being understood. Consequently, literature that describes various Bayesian methods for the assessment of parameter and model predictive uncertainty has been steadily rising. Applications dealing with urban stormwater management are, however, very limited. This study demonstrates successful application of a formal Bayesian methodology for UA of the U.S. EPA Stormwater Management Model (SWMM), a widely used urban stormwater management model, and illustrates the methodology using a highly urbanized watershed in southern California. DREAM_(ZS), a recently developed effective and efficient sampling algorithm, and a …

A Formal, Bayesian Approach For Uncertainty Analysis Of A Watershed Model, Misgana K. Muleta

Physics

Uncertainty analysis (UA) has received substantial attention in water resources during the last decade. Bayesian approaches are often preferred for UA. This study describes a formal Bayesian approach for the assessment of parameter uncertainty and predictive uncertainty using a spatially distributed hydrologic model and will demonstrate its application using data from a well monitored experimental watershed. A Markov-Chain Monte Carlo (MCMC) scheme has been used to sample posterior parameter distributions. A formal, flexible likelihood function that explicitly accounts for heteroscedasticity, temporal correlation and non-normality of simulation residuals has been used to describe closeness of the simulated and observed streamflow. Performance …

Low Temperature Cathodoluminescence Of Space Observatory Materials, Amberly Evans Jensen, Gregory Wilson, Justin Dekany, Jr Dennison

Conference Proceedings

In recent charging studies, a discernable glow was detected emanating from sample surfaces undergoing electron beam bombardment that resulted from a luminescent effect termed cathodoluminescence. This suggests that some of the materials used as optical elements, structural components, and thermal control surfaces in the construction of space-based observatories might luminesce when exposed to sufficiently energetic charged particle fluxes from the space plasma environment. If these visible, infrared and ultraviolet emissions are intense enough, they can potentially produce optical contamination detrimental to the performance of the observatory optical elements and sensors, and act to limit their sensitivity and performance windows. As …

Design And Testing Of The Measuring System For The Characterization Of Magnetoelectric Composites, Thomas S. Ward Iv

University of New Orleans Theses and Dissertations

The goal of this thesis is to design, build and test a new measurement system for comprehensive studies of the magnetoelectric and the converse magnetoelectric effect. The research on multiferroic composites is an emerging field of research and there is no commercially available equipment. The method proposed here for testing magnetoelectric properties of the multiferroics is relatively inexpensive and versatile. The advantage of the new method described below is that the same set of instruments in different configurations enables multiple measurements of various parameters characterizing multiferroic composites.

The system was tested using two samples Fe₇₈Si₁₀B_{12 …}

Charging Effects Of Multilayered Dielectric Spacecraft Materials: Surface Voltage, Discharge And Arcing, Gregory Wilson, Amberly Evans Jensen, Justin Dekany, Jr Dennison

Conference Proceedings

Charging of thin-film, multilayer dielectric materials subject to electron bombardment was found to evolve with time. The charging behavior was also highly dependent on the incident energy of the monoenergetic electron beams; this is driven by energy dependant processes including the electron penetration depth, electron emission, and material conductivity. The electron penetration depth is the average range to which incident electrons at a given incident energy penetrate into the material, thus defining the mean depth of an embedded charge layer. The secondary electron yield is the ratio of electrons emitted from the surface to the number of incident electrons; this …

Electrohydrodynamic Enhancement Of Heat Transfer And Mass Transport In Gaseous Media, Bulk Dielectric Liquids And Dielectric Thin Liquid Films, Seyed Reza Mahmoudi

Electronic Thesis and Dissertation Repository

Controlling transport phenomena in liquid and gaseous media through electrostatic forces has brought new important scientific and industrial applications. Although numerous EHD applications have been explored and extensively studied so far, the fast-growing technologies, mainly in the semiconductor industry, introduce new challenges and demands. These challenges require enhancement of heat transfer and mass transport in small scales (sometimes in molecular scales) to remove highly concentrated heat fluxes from reduced size devices. Electric field induced flows, or electrohydrodynamics (EHD), have shown promise in both macro and micro-scale devices.

Several existing problems in EHD heat transfer enhancements were investigated in this thesis. …

High & Low Resolution Techniques To Solve Protein Structures, Nathan Wright

Science Enabled by Photon Sources: Local Research Interests in Virginia

Protein structure and dynamics form the platform on which almost all biomedical research is currently based, including hot topics like computer-aided drug design and established problems like creating a cure for cancer. Since most proteins are too small to visualize with even an electron microscope, biochemists must use either NMR spectroscopy or x-ray diffraction to determine what the structures look like. In my lab, we combine both techniques to describe fundamentally how normal and mutated proteins behave in muscle cells. We are specifically interested in the structural protein obscurin. This giant muscle protein helps to organize muscle cells, sense muscle …

Optical Techniques To Probe Internal Dynamics Of Soft Materials, Klebert Feitosa

Science Enabled by Photon Sources: Local Research Interests in Virginia

Like many other soft materials, foam displays complex fluid behavior. Under different circumstances it may behave like an elastic solid or a typical fluid depending on driving forces and the interactions between individual bubbles. To understand the inherent complexities of foam flow, an effective method to visualize its internal structure and dynamics is paramount. In this talk, I will introduce two techniques we have used in our lab to probe foam dynamics at the bubble level: optical tomography and confocal microscopy. The results show great promise to unveil the internal mechanisms that lead to the complex fluid behavior of foams.

X-Ray Fluorescence Microscopy: A Tool For Biology, Life Science & Nanomedicine, Stafan Vogt

Science Enabled by Photon Sources: Local Research Interests in Virginia

Trace elements, in particular metals, play a significant role in most known life forms. It is estimated that one-third of all known proteins contain metal cofactors, and the majority of these function as essential metalloenzymes catalyzing biochemical reactions. Trace metals are increasingly recognized as having a critical impact on human health both in their natural occurrence and via therapeutic drugs (e.g., environmental exposure to heavy metals, treatment with cisplatin-based drugs in chemotherapy, ...), and in diseases such as Alzheimer’s. Quantitative study of the distribution of trace elements on the cellular and subcellular level provide important information about functions and pathways …

Harvesting Heat Through Seebeck Spin Tunneling Effect, Costel Constantin

Science Enabled by Photon Sources: Local Research Interests in Virginia

Harvesting the wasted heat released in the atmosphere by electronic devices has become an important issue in microelectronics as devices shrink toward nanoscale dimensions while achieving an increase in operating speed. Spintronic devices that make use of electrons’ spin as an information carrier offer a promising path to create novel efficient devices thus reducing this wasted heat. Thermoelectronics, on the other hand, explores the possibility of converting heat into electrical power. Spin caloritronics is an exciting new research field that takes advantage of both spintronics and thermoelectronics. In this talk, I will present the design of a spin caloritronic device …

The Role Of Photon Sources In Materials Research: Past, Present, & Future, E. Ward Plummer

Science Enabled by Photon Sources: Local Research Interests in Virginia

In this lecture I will trace the development of Light Sources from the early days of parasitic operation to the new billion dollar dedicated facilities. Clearly, the mode of usage has changed, but so has the type of user. How have these facilities balanced the need for beyond the state-of-the art experiments and serving the needs for routine characterization of materials? How can and should these facilities address the needs for the development of a workforce needed for the next generation of machines and science? Have they produced the science and scientists anticipated? Where do we go next, what is …

Pmma Nanocomposites Composed Of Optically Active Doped Inorganic Nanocrystals, Kyle Gipson

Science Enabled by Photon Sources: Local Research Interests in Virginia

As technology advances, more efficient, cost-effective materials and processes are being developed to serve the duties of optical materials within networks. As light transfers data through polymer optical materials, the polymeric matrix absorbs the signal and this phenomenon is known as attenuation. Attenuation occurs via the higher vibrational energies with respect to fluoropolymers that are inherent with hydrocarbon amorphous polymers like polymethyl methacrylate (PMMA).

One solution to realize efficient light emission is to incorporate nanoparticles into the polymer matrix. In the research presented, aqueous solution-polymer precipitation was used to synthesize light harvesting ligand capped luminescent nanoparticles. Tb3+:LaF3 was the chromophore …