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Full-Text Articles in Physics
Improving The Electrostatic Design Of The Jefferson Lab 300 Kv Dc Photogun, S.A.K. Wijethunga, M. A. Mamun, R. Suleiman, C. Hernandez-Garcia, B. Bullard, J. R. Delayen, J. Grames, G. A. Krafft, G. Palacios-Serrano, M. Poelker
Improving The Electrostatic Design Of The Jefferson Lab 300 Kv Dc Photogun, S.A.K. Wijethunga, M. A. Mamun, R. Suleiman, C. Hernandez-Garcia, B. Bullard, J. R. Delayen, J. Grames, G. A. Krafft, G. Palacios-Serrano, M. Poelker
Physics Faculty Publications
The 300 kV DC high voltage photogun at Jefferson Lab was redesigned to deliver electron beams with a much higher bunch charge and improved beam properties. The original design provided only a modest longitudinal electric field (Ez) at the photocathode, which limited the achievable extracted bunch charge. To reach the bunch charge goal of approximately few nC with 75 ps full-width at half-maximum Gaussian laser pulse width, the existing DC high voltage photogun electrodes and anode–cathode gap were modified to increase Ez at the photocathode. In addition, the anode aperture was spatially shifted with respect to the beamline longitudinal axis …
Studying The Interface Between Croconic Acid Thin Films And Substrates Using A Slow Positron Beam, Dean Peterson, Jiandang Liu, Jonas Etzweiler, Gabriel Sontoyo, Sara J. Callori, Kimberley R. Cousins, Timothy Usher, Renwu Zhang
Studying The Interface Between Croconic Acid Thin Films And Substrates Using A Slow Positron Beam, Dean Peterson, Jiandang Liu, Jonas Etzweiler, Gabriel Sontoyo, Sara J. Callori, Kimberley R. Cousins, Timothy Usher, Renwu Zhang
Physics Faculty Publications
Croconic acid (CA) is the first organic ferroelectric with a spontaneous polarity in bulk samples comparable to its inorganic counterparts. As a natural extension of study, ultrathin CA films (∼nm scale) were investigated to reveal ferroelectric effects in films on different substrates for their fundamental and industrial significance. However, the void defect at the interface between the film and substrate is presumed to interfere with surface effects. In this work, a non-invasive technique, a slow positron beam, coupled with Doppler broadening energy spectroscopy (DBES), is applied to study the void defects within the interfacial layer between CA films and Si …
Electrostatic Alignment Of Electrospun Peo Fibers By The Gap Method Increases Individual Fiber Modulus In Comparison To Non-Aligned Fibers Of Similar Diameter, Christopher Fryer, Meghan Scharnagl, Christine C. Helms
Electrostatic Alignment Of Electrospun Peo Fibers By The Gap Method Increases Individual Fiber Modulus In Comparison To Non-Aligned Fibers Of Similar Diameter, Christopher Fryer, Meghan Scharnagl, Christine C. Helms
Physics Faculty Publications
Studies on the alignment, physical and mechanical properties of individual electrospun fibers provide insight to their formation, production and optimization. Here we measure the alignment, diameter and modulus of individual fibers formed using the electrostatic gap method. We find electrostatic alignment produces fibers with a smaller diameter than their nonaligned counterparts have. Therefore, due to the dependence of fiber modulus on diameter aligned fibers have a higher modulus. Furthermore, we show that aligned and nonaligned fibers of the similar diameter have different moduli. Aligned fibers have a modulus 1.5 to 2 times larger than nonaligned fibers of the similar diameter.
Electrostatics At The Molecular Level, Ulrich Zurcher
Electrostatics At The Molecular Level, Ulrich Zurcher
Physics Faculty Publications
In molecular systems, positive and negative charges are separated, making them ideal systems to examine electrostatic interactions. The attractive force between positive and negative charges is balanced by repulsive ‘forces’ that are quantum-mechanical in origin. We introduce an ‘effective’ potential energy that captures the repulsion; it allows us to obtain fairly accurate estimates of the bonding properties of molecular systems. We use units (e.g., kcal mol–1 for energy) that emphasize the relevance of electrostatics to macroscopic behavior.
Low And Medium Β Superconducting Cavities And Accelerators, Jean R. Delayen
Low And Medium Β Superconducting Cavities And Accelerators, Jean R. Delayen
Physics Faculty Publications
No abstract provided.