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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 …
Cathodoluminescence Studies Of Defects In Coated Boron Nitride, Kévin Guerch, Justin Dekany, Jr Dennison, Thierry Paulmier, Sophie Guillemet-Fritsch, Pascal Lenormand
Cathodoluminescence Studies Of Defects In Coated Boron Nitride, Kévin Guerch, Justin Dekany, Jr Dennison, Thierry Paulmier, Sophie Guillemet-Fritsch, Pascal Lenormand
Journal Articles
Optical emission properties of Boron Nitride (BN) substrates, BN with alumina (Al2O3) coating, and thermally-annealed alumina-coated boron nitride (an-BN/Al2O3) were investigated under electron irradiation using cathodoluminescence (CL) measurements. Tests were performed temperatures ranging from ~100 K to ~300 K, with monoenergetic beams from 5 keV to 30 keV, and electron flux densities from 1 nA.cm-2 to 500 nA.cm-2. These experiments were conducted to identify the effects of coating and thermal annealing on the nature and occupation of defect states in different samples with BN substrates. Previous studies have shown that these treatments can limit the charging of BN substrates. Consequently, …
Investigation Of Electric Field–Induced Structural Changes At Fe-Doped Srtio3 Anode Interfaces By Second Harmonic Generation, David Ascienzo, Haochen Yuan, Steven Greenbaum, Thorsten J. Bayer, Russell A. Maier, Jian-Jun Wang, Clive A. Randall, Elizabeth C. Dickey, Haibin Zhao, Yuhang Ren
Investigation Of Electric Field–Induced Structural Changes At Fe-Doped Srtio3 Anode Interfaces By Second Harmonic Generation, David Ascienzo, Haochen Yuan, Steven Greenbaum, Thorsten J. Bayer, Russell A. Maier, Jian-Jun Wang, Clive A. Randall, Elizabeth C. Dickey, Haibin Zhao, Yuhang Ren
Publications and Research
We report on the detection of electric field–induced second harmonic generation (EFISHG) from the anode interfaces of reduced and oxidized Fe-doped SrTiO3 (Fe:STO) single crystals. For the reduced crystal, we observe steady enhancements of the susceptibility components as the imposed dc-voltage increases. The enhancements are attributed to a field-stabilized electrostriction, leading to Fe:Ti-O bond stretching and bending in Fe:Ti-O6 octahedra. For the oxidized crystal, no obvious structural changes are observed below 16 kV/cm. Above 16 kV/cm, a sharp enhancement of the susceptibilities occurs due to local electrostrictive deformations in response to oxygen vacancy migrations away from the anode. Differences between …
Electrical Properties Of Annealed And Coated Boron Nitride Under Electron Beam Irradiation, Kevin Guerch, Theirry Paulmier, Jr Dennison, Justin Dekany, Pascal Lenormand, Sophie Guillemet-Fritsch
Electrical Properties Of Annealed And Coated Boron Nitride Under Electron Beam Irradiation, Kevin Guerch, Theirry Paulmier, Jr Dennison, Justin Dekany, Pascal Lenormand, Sophie Guillemet-Fritsch
Journal Articles
The charging and relaxation kinetics of pyrolytic boron nitride (BN) substrates, BN with an aluminium oxide (BN/Al2O3) coating, and thermally-annealed alumina-coated boron nitride (an-BN/Al2O3) were investigated under low power electron irradiation (5 < E0 < 20 keV, Ji = 10 nA.cm-2 at room temperature) in the CEDRE facility at ONERA (Toulouse, France). Surface potentials of each ceramics configuration were measured over time using the Kelvin probe method. The influence of coating and annealing treatments to limit charging is discussed in this paper. A thorough study of a an–BN/Al2O3 sample was carried out …
Low-Fluence Electron Yields Of Highly Insulating Materials, Ryan Hoffman, John R. Dennison, Clint D. Thomson, Jennifer Albresten
Low-Fluence Electron Yields Of Highly Insulating Materials, Ryan Hoffman, John R. Dennison, Clint D. Thomson, Jennifer Albresten
All Physics Faculty Publications
Electron-induced electron yields of high-resistivity high-yield materials - ceramic polycrystalline aluminum oxide and polymer polyimide (Kapton HN) - were made by using a low-fluence pulsed incident electron beam and charge neutralization electron source to minimize charge accumulation. Large changes in the energy-dependent total yield curves and yield decay curves were observed, even for incident electron fluences of < 3 fC/mm2. The evolution of the electron yield as charge accumulates in the material is modeled in terms of electron recapture based on an extended Chung-Everhart model of the electron emission spectrum. This model is used to explain the anomalies measured in highly …
Dissolution, Reactor, And Environmental Behavior Of Zro2-Mgo Inert Fuel Matrix, Kenneth Czerwinski
Dissolution, Reactor, And Environmental Behavior Of Zro2-Mgo Inert Fuel Matrix, Kenneth Czerwinski
Fuels Campaign (TRP)
This project will examine inert fuels containing ZrO2 and MgO as the inert matrix. Ceramics with this inert matrix, Ce, U and eventually Pu will be synthesized and examined. While the Advanced Fuel Cycle Initiative focus is on inert fuels with Pu as the fissile component, this task will perform initial laboratory experiments with Ce and U. The initial work with Ce will be performed early in the project with results used as a basis for U studies. Reactor physics calculations will be used to examine suitable quantities of burnable poisons from the candidate elements Gd, Er, or Hf. …
Dissolution, Reactor, And Environmental Behavior Of Zro2-Mgo Inert Fuel Matrix, Kenneth Czerwinski
Dissolution, Reactor, And Environmental Behavior Of Zro2-Mgo Inert Fuel Matrix, Kenneth Czerwinski
Fuels Campaign (TRP)
This project will examine inert fuels containing ZrO2 and MgO as the inert matrix. Ceramics with this inert matrix, Ce, U and eventually Pu will be synthesized and examined. While the Advanced Fuel Cycle Initiative focus is on inert fuels with Pu as the fissile component, this task will perform initial laboratory experiments with Ce and U. The initial work with Ce will be performed early in the project with results used as a basis for U studies. Reactor physics calculations will be used to examine suitable quantities of burnable poisons from the candidate elements Gd, Er, or Hf. …
Dissolution, Reactor, And Environmental Behavior Of Zro2-Mgo Inert Fuel Matrix, Kenneth Czerwinski
Dissolution, Reactor, And Environmental Behavior Of Zro2-Mgo Inert Fuel Matrix, Kenneth Czerwinski
Fuels Campaign (TRP)
This project examines inert fuels containing ZrO2 and MgO as the inert matrix, with the relative amount of MgO varied from 30% to 70% in ZrO2. Reactor physics calculations are used to examine suitable quantities of burnable poisons from the candidate elements Gd, Er, or Hf with reactor grade Pu providing the fissile component, with up to 10% of 239Pu. Ceramics are synthesized and characterized based on the reactor physics results. The solubility of the fuel ceramics, in reactor conditions, reprocessing conditions, and repository conditions, are investigated in a manner to provide thermodynamic data necessary for …
Dissolution, Reactor, And Environmental Behavior Of Zro2-Mgo Inert Fuel Matrix, Kenneth Czerwinski
Dissolution, Reactor, And Environmental Behavior Of Zro2-Mgo Inert Fuel Matrix, Kenneth Czerwinski
Fuels Campaign (TRP)
This project examines inert fuels containing ZrO2 and MgO as the inert matrix, with the relative amount of MgO varied from 30% to 70% in ZrO2. Reactor physics calculations are used to examine suitable quantities of burnable poisons from the candidate elements Gd, Er, or Hf with reactor grade Pu providing the fissile component, with up to 10% of 239Pu. Ceramics are synthesized and characterized based on the reactor physics results. The solubility of the fuel ceramics, in reactor conditions, reprocessing conditions, and repository conditions, are investigated in a manner to provide thermodynamic data necessary for …