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Item Ps2- in a magnetic field : structure and stability in the M=0 state.(Vanderbilt University. Dept. of Physics and Astronomy, 2016-05-02) Tregoning, Brett; Varga, Kálmán, 1963-The energy of the Ps2- (three electrons and two positrons or vice versa) system and all possible fragmentations are calculated in a magnetic field in their M=0 states using the stochastic variational method with a deformed correlated Gaussian basis set. The stability of the system at various field strengths is assessed through comparison of the system's energy to the threshold energy. Examination of the single particle and pairwise densities is also employed for assessment of stability. The structure of the system is examined through calculation of distances between the charged particles. The M=0 state of Ps2- is found to be stable in fields greater than 0.01 a.u.Item First observation of the direct detection of positive D-meson into anti-K-long + 3 pions and negative D-meson into K-long + 3 pions with the Fermilab FOCUS experiment(Vanderbilt University. Department of Physics and Astronomy, 2014-04) Stewart, Cameron; Johns, Will E.In this thesis the decays of positive D-mesons into neutral anti-K-mesons and three charged pions and of negative D-mesons into neutral K-mesons and three charged pions are reconstructed in both long and short neutral K-meson states. The data were taken with the Fermilab FOCUS spectrometer. This constitutes the first observation of these decays in the long K-meson mode. We detail the cuts necessary to find the branching ratio for the K-long to K-short modes for both positive and negative D-mesons, show that the ratio is 0.89, and detail further work that remains to be done. The K-long mode is reconstructed using the D-meson flight direction, the direction of the charged pions, and the energy deposited in the hadron calorimeter. The K-short decay is reconstructed directly using tracking information in the pi plus - pi minus decay mode.Item Thermal fabrication of gold nanocages(Vanderbilt University. Department of Physics and Astronomy, 2011-04-11) Remec, Miroslav; Dickerson, James H. (James Henry)The purpose of this research project was to test and characterize a new method for gold nanoparticle production. The main idea was based on the preliminary observations made in earlier work, which had suggested that small amounts of gold deposited onto a silicon substrate will spontaneously reshape into gold nanoparticles when treated to controlled high-temperature heating for a sufficient period of time. This idea for a fabrication process was extended to incorporate Electron Beam Lithography (EBL) gold patterning. The full fabrication method consisted of the following steps: (1) Preparation of clean silicon substrates, (2) Addition of a Poly(methyl methacrylate) (PMMA) Coat via spin coating, (3) Design of gold patterns for the EBL, (4) Gold patterning via EBL, (5) Gold deposition via electron beam evaporation, (6) PMMA mask removal via acetone wash, and (7) High-Temperature furnace heating, as well as plans for a final step (8) Isolation of the gold nanocages via HF etching. The project research required the use of the photolithographic facilities of the Vanderbilt Institute of Nanoscale Science and Engineering (VINSE), as well as the use of the high-temperature furnace and other basic needs supplied by the research group of Professor Dickerson. Some of the VINSE equipment required relatively extensive operational training. The research project has demonstrated that the described thermal fabrication method can uniformly and repeatedly produce Au nanoparticles of about 400 nm in diameter from Au deposits of 1 um2 area and 20 nm thickness. Larger areas displayed structural fragmentation into multiple nanoparticles, and this fragmentation effect increased proportionally with increasing area size. Due to time constraints, the many available parameters prevented a complete characterization of this fabrication method; however, useful insights were obtained for several of the parameters of the fabrication process. In particular, it can be expected that smaller nanoparticles may be fabricated in a straightforward manner by reducing the patterned area sizes of the gold deposits. Results suggested an intrinsic limitation to the method: for the requirement of product uniformity, each Au-area deposit had to produce only a single nanoparticle.Item High-energy attosecond-width electron diffraction simulations(Vanderbilt University. Department of Physics and Astronomy, 2013-04-22) Kidd, Daniel; Varga, KalmanElectron microscopy has been the recent subject of molecular imaging due to the strength of the electrons' interaction with the target molecule making for a detailed pattern at a small scale.[1] To achieve the best 4D image of the target, one needs sufficient spatial and temporal resolution, the prior being an issue of using electrons in the keV regime as to achieve an optimally small deBroglie wavelength, and the latter being improved by the temporal width of the electron wave packet itself.[2] In order to image the motion of the electronic structure of the target molecule, this width must be within the attosecond regime. In this paper, we use the computational method of time-dependent density functional theory (TDDFT) to model our targets of Beryllium and the Nitrogen molecule, N2 , and an incoming electron wave packet with an energy of 1500 eV.Item Data Logistics and the CMS Analysis Model(Vanderbilt University. Dept. of Physics and Astronomy, 2009-04-20) Managan, Julie E.The Compact Muon Solenoid Experiment (CMS) at the Large Hadron Collider (LHC) at CERN has brilliant prospects for uncovering new information about the physical structure of our universe. Soon physicists around the world will participate together in analyzing CMS data in search of new physics phenomena and the Higgs Boson. However, they face a significant problem: with 5 Petabytes of data needing distribution each year, how will physicists get the data they need? How and where will they be able to analyze it? Computing resources and scientists are scattered around the world, while CMS data exists in localized chunks. The CMS computing model only allows analysis of locally stored data, "tethering" analysis to storage. The Vanderbilt CMS team is actively working to solve this problem with the Research and Education Data Depot Network (REDDnet), a program run by Vanderbilt's Advanced Computing Center for Research and Education (ACCRE). I participated in this effort by testing data transfers into REDDnet via the gridFTP server, a File Transfer Protocol which incorporates an LHC Computing Grid security layer. I created a test suite which helped identify and solve a large number of problems with gridFTP. Once optimized, I achieved sustained throughputs of 700-800 Megabits per second (Mbps) over a 1 Gigabit per second (Gbps) connection, with remarkably few failures. GridFTP is the gateway between REDDnet and CMS, and my tests were designed to exercise and harden this important tool. My results support other indications that the REDDnet system will be a successful solution to the limitations of data-tethering in the CMS computing model.Item Progress towards a quantum dot photovoltaic : nanocrystal deposition on structured titanium dioxide nanotubes(Vanderbilt University. Dept. of Physics & Astronomy, 2008-04) Emmett, Kevin; Rosenthal, Sandra J.While this project did not successfully produce a working photovoltaic device, significant progress has been made in the individual components of the system. This thesis describes two of those components: fabrication of an ordered TiO2 thin film as electron conducting layer, and deposition of nanocrystals onto the TiO2surface. The anodized titanium nanotubes are a significant improvement over the earlier template technique. Additionally, electrophoretic deposition presents a novel approach to nanocrystal deposition techniques and is a promising alternative to the current chemical linking procedure. However, significant new approaches to imaging the deposited nanocrystals must be developed to verify surface coverage by these deposition techniques, particularly due to the highly ordered structure of the TiO2 thin films. Future work will be directed at completing the solar cell device by depositing a hole conducting layer on top of the nanotube array. Nanocrystal-sensitized solar cells may soon prove to be viable alternative to silicon photovoltaics.