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Full-Text Articles in Physics
Diffractive Imaging Of Laser Induced Molecular Reactions With Kiloelectron-Volt Ultrafast Electron Diffraction, Yanwei Xiong
Diffractive Imaging Of Laser Induced Molecular Reactions With Kiloelectron-Volt Ultrafast Electron Diffraction, Yanwei Xiong
Department of Physics and Astronomy: Dissertations, Theses, and Student Research
Capturing the structural changes during a molecular reaction with ultrafast electron diffraction (UED) requires a high spatiotemporal resolution and sufficiently high signal-to-noise to record the signals with high fidelity. In this dissertation, I have focused on the development of a tabletop gas phase keV-UED setup with a femtosecond temporal resolution. A DC electron gun was employed to generate electron pulses with a high repetition rate of 5 kHz. The space charge effect in the electron pulse was ameliorated by compressing the 90 keV electron pulse longitudinally with a time varying electric field in an RF cavity. The velocity mismatch between …
Perturbative Generalization Of Nonparaxial Ultrashort Tightly-Focused Elegant Laguerre-Gaussian Beams, Andrew M. Vikartofsky
Perturbative Generalization Of Nonparaxial Ultrashort Tightly-Focused Elegant Laguerre-Gaussian Beams, Andrew M. Vikartofsky
Department of Physics and Astronomy: Dissertations, Theses, and Student Research
An analytical method for calculating the electromagnetic fields of a nonparaxial elegant Laguerre-Gaussian (eLG) vortex beam is presented for arbitrary pulse duration, spot size, and LG mode. This perturbative approach provides a numerically tractable model for the calculation of arbitrarily high radial and azimuthal LG modes in the nonparaxial regime, without requiring integral representations of the fields. A key feature of this perturbative model is its use of a Poisson-like frequency spectrum, which allows for the proper description of pulses of arbitrarily short duration. The time-domain representation of this model is presented as a non-recursive closed-form expression to any order …
Upgrade To The Pierre Auger Cosmic Ray Observatory's Lidar System, Emily B. Petermann
Upgrade To The Pierre Auger Cosmic Ray Observatory's Lidar System, Emily B. Petermann
Department of Physics and Astronomy: Dissertations, Theses, and Student Research
The Pierre Auger Cosmic Ray Observatory currently operates four elastic lidar systems in order to characterize the atmospheric aerosol content above the observatory. The atmospheric information gained by the lidar system is then used in the calibration of the observatory’s four fluorescence detectors. Currently the four lidars in operation are unable to accurately determine the aerosol content below a distance of 1 km. A project is currently underway to upgrade the current lidar system by adding an additional detector to each of the existing lidar systems. The considered designs for this upgrade and the initial results from the upgrade prototype …