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- All Physics Faculty Publications (5)
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- All Graduate Theses and Dissertations, Spring 1920 to Summer 2023 (1)
- Biology, Chemistry, and Environmental Sciences Faculty Articles and Research (1)
- Dartmouth Scholarship (1)
- Electrical & Computer Engineering Faculty Publications (1)
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Articles 1 - 26 of 26
Full-Text Articles in Physics
Electron Emission And Transport Properties Database For Spacecraft Charging Models, Phil Lundgreen
Electron Emission And Transport Properties Database For Spacecraft Charging Models, Phil Lundgreen
Theses and Dissertations
Modeling the rate and likelihood of spacecraft charging during spacecraft mission is critical to determine mission length, proposed spacecraft attitude, and spacecraft design. The focus of this work is the creation and utilization of a database of secondary electron yield (SEY) measurements for a host of materials to increase accuracy in spacecraft modeling. Traditional methods of SEY data selection for input into spacecraft charging codes typically include the use of compiled materials databases incorporated in charging codes or selecting values from a specific scientific study. The SEY database allows users to select data inputs based upon the details associated with …
Studies On Secondary Electron Emission Induced Charging In Dielectric Materials: Novel Methods And Applications For Space And Plasma Technologies, Leandro Olano Garcia
Studies On Secondary Electron Emission Induced Charging In Dielectric Materials: Novel Methods And Applications For Space And Plasma Technologies, Leandro Olano Garcia
Theses and Dissertations
The interaction of ionizing radiation with matter is of critical importance in many areas of science and technology such as space and plasma technology. Secondary electron emission is a direct consequence of electron irradiation on materials. To characterize materials in terms of secondary electron emission, the secondary emission yield (SEY) and the energy spectra of the secondary electrons are key physical properties. Secondary emission yields of materials are usually too high to avoid Multipactor effect or other related phenomena in applications for space. In addition, the measurement of electron energy spectra of secondary electrons in dielectric materials is a challenge …
Secondary Electron Yield Measurements Of Carbon Nanotube Forests: Dependence On Morphology And Substrate, Brian Wood, Jordan Lee, Gregory Wilson, T. -C. Shen, Jr Dennison
Secondary Electron Yield Measurements Of Carbon Nanotube Forests: Dependence On Morphology And Substrate, Brian Wood, Jordan Lee, Gregory Wilson, T. -C. Shen, Jr Dennison
Journal Articles
Total, secondary, and backscatter electron yield data were taken with beam energies between 15 eV and 30 keV, in conjunction with energy emission data, to determine the extent of suppression of yield caused by carbon nanotube (CNT) forest coatings on substrates. CNT forests can potentially lower substrate yield due to both its inherently low-yield, low-atomic number (Z) carbon composition, and its bundled, high-aspect ratio structure. Rough surfaces, and in particular, surfaces with deep high-aspect-ratio voids, can suppress yields, as the electrons emitted from lower lying surfaces are recaptured by surface protrusions rather than escaping the near-surface region. Yields of multilayered …
Few-Body Dynamics Underlying Postcollision Effects In The Ionization Of H₂ By 75-Kev Proton Impact, M. Dhital, S. Bastola, A. Silvus, Don H. Madison, Michael Schulz
Few-Body Dynamics Underlying Postcollision Effects In The Ionization Of H₂ By 75-Kev Proton Impact, M. Dhital, S. Bastola, A. Silvus, Don H. Madison, Michael Schulz
Physics Faculty Research & Creative Works
We have measured fully differential cross sections (FDCS) for ionization in 75-keVp+H2 collisions for ejected electron speeds close to the projectile speed. The data were analyzed in dependence on both the electron emission angle and the projectile scattering angle. Pronounced postcollisional effects between the projectile and the ejected electrons were observed. Significant differences between experiment and theory and between two conceptually very similar theoretical models were found. This shows that in the region of electron-projectile velocity-matching the FDCS is very sensitive to the details of the underlying few-body dynamics.
Suppresion Of Electron Yield With Carbon Nanotube Forests: A Case Study, Brian Wood, Jordan Lee, Gregory Wilson, T.-C. Shen, Jr Dennison
Suppresion Of Electron Yield With Carbon Nanotube Forests: A Case Study, Brian Wood, Jordan Lee, Gregory Wilson, T.-C. Shen, Jr Dennison
Conference Proceedings
Electron emission of carbon nanotube (CNT) forests grown on silicon substrates was measured to investigate possible electron yield suppression due to the composition and morphology of CNT forests. CNT forests are vertically-oriented tubular formations of graphitic carbon grown on a substrate; these have been widely investigated for their extreme properties in optical, electrical, and mechanical aspects of physics and material sciences. CNT coatings are good candidates for yield reduction, in analogy with the near-ideal blackbody optical properties of CNT forests. Carbon with its low atomic number has an inherent low yield due to its low density of bulk electrons. Furthermore, …
Hemispherical Grid Retarding Field Analyzer Redesign For Secondary Electron Emission Studies, Greg Wilson, Jr Dennison
Hemispherical Grid Retarding Field Analyzer Redesign For Secondary Electron Emission Studies, Greg Wilson, Jr Dennison
Presentations
A redesign of the Hemispherical Grid Retarding Field Analyzer is discussed in relationship to multilayer charging models. In order to accurately extend single layer charging models to dynamic multilayer scenarios, precise measurements of electron emission as well as the net surface potential must be made. By learning from the previous design and thinking of future applications, the new instrument will greatly enhance our ability to precisely measure materials undergoing energetic electron bombardment.
Hemispherical Grid Retarding Field Analyzer Redesign For Secondary Electron Emission Studies, Greg Wilson, Jr Dennison
Hemispherical Grid Retarding Field Analyzer Redesign For Secondary Electron Emission Studies, Greg Wilson, Jr Dennison
Conference Proceedings
A redesign of the Hemispherical Grid Retarding Field Analyzer is discussed in relationship to multilayer charging models. In order to accurately extend single layer charging models to dynamic multilayer scenarios, precise measurements of electron emission as well as the net surface potential must be made. By learning from the previous design and thinking of future applications, the new instrument will greatly enhance our ability to precisely measure materials undergoing energetic electron bombardment.
Electron-Impact Ionization Of H₂O At Low Projectile Energy: Internormalized Triple-Differential Cross Sections In Three-Dimensional Kinematics, Xueguang Ren, Sadek Amami, Khokon Hossen, Esam Ali, Chuangang Ning, James Colgan, Don H. Madison, Andrew Dorn
Electron-Impact Ionization Of H₂O At Low Projectile Energy: Internormalized Triple-Differential Cross Sections In Three-Dimensional Kinematics, Xueguang Ren, Sadek Amami, Khokon Hossen, Esam Ali, Chuangang Ning, James Colgan, Don H. Madison, Andrew Dorn
Physics Faculty Research & Creative Works
We report a combined experimental and theoretical study of the electron-impact ionization of water (H2O) at the relatively low incident energy of E0=81eV in which either the 1b1 or 3a1 orbitals are ionized leading to the stable H2O cation. The experimental data were measured by using a reaction microscope, which can cover nearly the entire 4π solid angle for the secondary electron emission over a range of ejection energies. We present experimental data for the scattering angles of 6⁰ and 10⁰ for the faster of the two outgoing electrons as a function …
Cryostat System For Spacecraft Materials Testing, Justin Dekany
Cryostat System For Spacecraft Materials Testing, Justin Dekany
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
An existing space environment simulation test chamber used in the study of electron emission, sample charging and discharge, electrostatic discharge and arcing, electron transport, and luminescence of spacecraft materials now has extended temperature control capabilities. By incorporating a two-stage, closed-cycle helium cryostat, it is now possible to simulate the temperature typical spacecraft will experience when in orbit, ranging from < 40 K to > 450 K. The system was designed to maintain compatibility with an existing ultrahigh vacuum chamber that can simulate diverse space environments. This vacuum chamber can simulate space environment conditions by producing the same pressure, amount of electrons, electromagnetic radiation and temperature …
Positional Control Of Plasmonic Fields And Electron Emission, Robert Campbell Word, Joseph P. Fitzgerald, Rolf Könenkamp
Positional Control Of Plasmonic Fields And Electron Emission, Robert Campbell Word, Joseph P. Fitzgerald, Rolf Könenkamp
Physics Faculty Publications and Presentations
We report the positional control of plasmonic fields and electron emission in a continuous gap antenna structure of sub-micron size. We show experimentally that a nanoscale area of plasmon-enhanced electron emission can be motioned by changing the polarization of an exciting optical beam of 800 nm wavelength. Finite-difference calculations are presented to support the experiments and to show that the plasmon-enhanced electric field distribution of the antenna can be motioned precisely and predictively.
Ultrahigh Vacuum Cryostat System For Extended Low Temperature Space Environment Testing, Justin Dekany, Robert H. Johnson, Gregory Wilson, Amberly Evans Jensen, Jr Dennison
Ultrahigh Vacuum Cryostat System For Extended Low Temperature Space Environment Testing, Justin Dekany, Robert H. Johnson, Gregory Wilson, Amberly Evans Jensen, Jr Dennison
Graduate Student Publications
The range of temperature measurements have been significantly extended for an existing space environment simulation test chamber used in the study of electron emission, sample charging and discharge, electrostatic discharge and arcing, electron transport, and luminescence of spacecraft materials. This was accomplished by incorporating a new two- stage, closed-cycle helium cryostat which has an extended sample temperature range from450 K, with long-term controlled stability of
Femtosecond Photoelectron Point Projection Microscope, Erik Quinonez, Jonathan Handali, Brett Barwick
Femtosecond Photoelectron Point Projection Microscope, Erik Quinonez, Jonathan Handali, Brett Barwick
Faculty Scholarship
By utilizing a nanometer ultrafast electron source in a point projection microscope we demonstrate that images of nanoparticles with spatial resolutions of the order of 100 nanometers can be obtained. The duration of the emission process of the photoemitted electrons used to make images is shown to be of the order of 100 fs using an autocorrelation technique. The compact geometry of this photoelectron point projection microscope does not preclude its use as a simple ultrafast electron microscope, and we use simple analytic models to estimate temporal resolutions that can be expected when using it as a pump-probe ultrafast electron …
The Effects Of Surface Modification On Spacecraft Charging Parameters, Amberly Evans Jensen, Jr Dennison
The Effects Of Surface Modification On Spacecraft Charging Parameters, Amberly Evans Jensen, Jr Dennison
Graduate Student Publications
Charging of materials by incident radiation is affected by both environmental and physical conditions. Modifying a material’s physical surface will change its reflection, transmission and absorption of the incident radiation which are integrally related to the accumulation of charge and energy deposition in the material. General arguments for incident and emitted photons, electrons and ions are considered. An optical analysis of the effects of surface modification on spacecraft charging parameters on prototypical polyimide Kapton HNTM and Cu samples is presented. Samples were roughened with abrasive compounds ranging from 0.5 to 10 μm in size, comparable to the range of incident …
A Model Of So-Called "Zebra" Emissions In Solar Flare Radio Burst Continua, R. A. Treumann, R. Nakamura, W. Baumjohann
A Model Of So-Called "Zebra" Emissions In Solar Flare Radio Burst Continua, R. A. Treumann, R. Nakamura, W. Baumjohann
Dartmouth Scholarship
A simple mechanism for the generation of elec- tromagnetic “Zebra” pattern emissions is proposed. “Zebra” bursts are regularly spaced narrow-band radio emissions on the otherwise broadband radio continuum emitted by the ac- tive solar corona. The mechanism is based on the generation of an ion-ring distribution in a magnetic mirror geometry in the presence of a properly directed field-aligned electric po- tential field. Such ion-rings or ion-conics are well known from magnetospheric observations. Under coronal condi- tions they may become weakly relativistic. In this case the ion-cyclotron maser generates a number of electromagnetic ion-cyclotron harmonics which modulate the electron maser …
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 …
Inverse Velocity Dependence Of Vibrationally Promoted Electron Emission From A Metal Surface, N. H. Nahler, J. D. White, Jerry L. Larue, Daniel J. Auerbach, Alec M. Wodtke
Inverse Velocity Dependence Of Vibrationally Promoted Electron Emission From A Metal Surface, N. H. Nahler, J. D. White, Jerry L. Larue, Daniel J. Auerbach, Alec M. Wodtke
Biology, Chemistry, and Environmental Sciences Faculty Articles and Research
All previous experimental and theoretical studies of molecular interactions at metal surfaces show that electronically nonadiabatic influences increase with molecular velocity. We report the observation of a nonadiabatic electronic effect that follows the opposite trend: The probability of electron emission from a low–work function surface—Au(111) capped by half a monolayer of Cs—increases as the velocity of the incident NO molecule decreases during collisions with highly vibrationally excited NO(X2π½, V = 18; V is the vibrational quantum number of NO), reaching 0.1 at the lowest velocity studied. We show that these results are consistent with a vibrational …
Studies Of Breakdown In A Pressurized Rf Cavity, M. Bastaninejad, A. A. Elmustafa, C. M. Ankenbrandt, A. Moretti, M. Popovic, K. Yonehara, D. M. Kaplan, M. Alsharo'a, P. M. Hanlet, R. P. Johnson, M. Kuchnir, D. Newsham, D. V. Rose, C. Thoma, D. R. Welch
Studies Of Breakdown In A Pressurized Rf Cavity, M. Bastaninejad, A. A. Elmustafa, C. M. Ankenbrandt, A. Moretti, M. Popovic, K. Yonehara, D. M. Kaplan, M. Alsharo'a, P. M. Hanlet, R. P. Johnson, M. Kuchnir, D. Newsham, D. V. Rose, C. Thoma, D. R. Welch
Mechanical & Aerospace Engineering Faculty Publications
Microscopic images of the surfaces of metallic electrodes used in high-pressure gas-filled 805 MHz RF cavity experiments [1] have been used to investigate the mechanism of RF breakdown [2]. The images show evidence for melting and boiling in small regions of ∼10 micron diameter on tungsten, molybdenum, and beryllium electrode surfaces. In these experiments, the dense hydrogen gas in the cavity prevents electrons or ions from being accelerated to high enough energy to participate in the breakdown process so that the only important variables are the fields and the metallic surfaces. The distributions of breakdown remnants on the electrode surfaces …
Evolution Of The Electron Yield Curves Of Insulators As A Function Of Impinging Electron Fluence And Energy, John R. Dennison, Alec Sim, Clint Thomson
Evolution Of The Electron Yield Curves Of Insulators As A Function Of Impinging Electron Fluence And Energy, John R. Dennison, Alec Sim, Clint Thomson
All Physics Faculty Publications
Electron emission and concomitant charge accumulation near the surface of insulators is central to understanding spacecraft charging. A study of changes in electron emission yields as a result of internal charge buildup due to electron dose is presented. Evolution of total, backscattered, and secondary yield results over a broad range of incident energies are presented for two representative insulators, Kapton and Al2O3. Reliable yield curves for uncharged insulators are measured, and quantifiable changes in yields are observed due to <100-fC/mm2 fluences. Excellent agreement with a phenomenological argument based on insulator charging predicted by the yield curve …
The Effect Of Low Energy Electron And Uv/Vis Radiation Aging On The Electron Emission Properties And Breakdown Of Thin-Film Dielectrics, John R. Dennison, C. D. Thomson, Alec Sim
The Effect Of Low Energy Electron And Uv/Vis Radiation Aging On The Electron Emission Properties And Breakdown Of Thin-Film Dielectrics, John R. Dennison, C. D. Thomson, Alec Sim
All Physics Faculty Publications
Studies of secondary and backscattered electron yield curves of thin-film dielectrics have recently been made using pulsed, low current electron beam methods to minimize insulator charging. These capabilities have allowed us to investigate the evolution of surface and internal charge profiles as a function of low energy electron (keV) pulsed-electron fluence to determine how quickly insulators charge, and how this can affect subsequent electron emission properties. We have also studied critical incident electron energies that result in electrical breakdown of insulator materials and the effect of breakdown on subsequent emission, charging and conduction. The qualitative physics of such processes in …
Measurement Of Conductivity And Charge Storage In Insulators Related To Spacecraft Charging, A. R. Frederickson, John R. Dennison
Measurement Of Conductivity And Charge Storage In Insulators Related To Spacecraft Charging, A. R. Frederickson, John R. Dennison
All Physics Faculty Publications
Improved experimental methods are discussed for laboratory measurement of conductivity and electric field in insulating spacecraft material intended for space radiation and plasma environments. These measurement techniques investigate the following features: 1) measurements of conductivity are up to four orders of magnitude smaller than those determined by existing standard methods. 2) Conductivity is altered as radiation accumulates and trapping states fill with electrons. 3) With intense kiloelectronvolt electron irradiation, electrons are continually emitted for hours from the irradiated surface after the irradiation ceases. 4) Charging induced by electron irradiation is strongly modified by the electron-hole pairs that the irradiation generates …
Electron Bernstein Wave-X-O Mode Conversion And Electron Cyclotron Emission In Mast, Josef Preinhaelter, Pavol Pavlo, Vladimir Shevchenko, Martin Valovic, Linda L. Vahala, George Vahala
Electron Bernstein Wave-X-O Mode Conversion And Electron Cyclotron Emission In Mast, Josef Preinhaelter, Pavol Pavlo, Vladimir Shevchenko, Martin Valovic, Linda L. Vahala, George Vahala
Electrical & Computer Engineering Faculty Publications
Electron cyclotron emission (ECE) from overdense plasmas can only occur due to electron Bernstein waves (EBW) mode converting near the upper hybrid region to an electromagnetic wave. Experimental data of ECE observations on MAST are studied and compared with EBW-X-O mode conversion modeling results.
Three-Body Coulomb Problem Probed By Mapping The Bethe Surface In Ionizing Ion-Atom Collisions, Robert Moshammer, Appathurai N. Perumal, Michael Schulz, V. D. Rodriguez, Holger Kollmus, Rido Mann, Siegbert Hagmann, Joachim Hermann Ullrich
Three-Body Coulomb Problem Probed By Mapping The Bethe Surface In Ionizing Ion-Atom Collisions, Robert Moshammer, Appathurai N. Perumal, Michael Schulz, V. D. Rodriguez, Holger Kollmus, Rido Mann, Siegbert Hagmann, Joachim Hermann Ullrich
Physics Faculty Research & Creative Works
The three-body Coulomb problem has been explored in kinematically complete experiments on single ionization of helium by 100 MeV / u C 6 + and 3.6 MeV / u u 5 3 + impact. Low-energy electron emission (E e < 150 eV ) as a function of the projectile deflection ϑ p (momentum transfer), i.e., the Bethe surface [[15]], has been mapped with Δ ϑ p ± 25 nanoradian resolution at extremely large perturbations (3.6 MeV / uAu53+ ) where single ionization occurs at impact parameters of typically 10 times the He K -shell radius. The experimental data are not in agreement with state-of-the-art continuum distorted wave-eikonal initial state theory.
Fully Differential Cusp Electron Production Cross Sections For 75-Kev H₂⁺ + He Collisions, L. An, Kh Khayvat, Michael Schulz
Fully Differential Cusp Electron Production Cross Sections For 75-Kev H₂⁺ + He Collisions, L. An, Kh Khayvat, Michael Schulz
Physics Faculty Research & Creative Works
A kinematically complete experiment on single ionization for 75-keV H2+ + H e collisions was performed by measuring the fully momentum analyzed projectiles and recoil ions in coincidence. The electron momentum was deduced from momentum conservation. Clear signatures of the postcollision interaction between the outgoing projectiles and the electrons were observed in the momentum spectra of all collision products simultaneously.
Short-Pulse Laser-Induced Stabilization Of Autoionizing States, Heider N. Ereifej, J. Greg Story
Short-Pulse Laser-Induced Stabilization Of Autoionizing States, Heider N. Ereifej, J. Greg Story
Physics Faculty Research & Creative Works
Atoms in doubly excited states above the first ionization limit can decay via autoionization in which an electron is emitted leaving an ion, or by photoemission which leaves the atom in a singly excited state. In this paper, it is demonstrated that interaction between the atoms and a laser pulse that is short compared to the autoionization lifetime can lead to large enhancement of the photoemission process by stimulating the atoms to emit a photon. Since the resultant singly excited atoms do not autoionize, this process can be viewed as an enhancement of the stabilization of the doubly excited atoms …
Effects Of The Evolution Of Spacecraft Surfaces On Secondary Electron Emission Andspacecraft Charging, R. E. Davies, John R. Dennison
Effects Of The Evolution Of Spacecraft Surfaces On Secondary Electron Emission Andspacecraft Charging, R. E. Davies, John R. Dennison
All Physics Faculty Publications
Spacecraft charging due to the natural plasma environment found in all orbits is known to produce many of the observed spacecraft anomalies and failures. A primary factor in adverse spacecraft charging is the secondary electron emission of differing materials on the spacecraft. Precipitating electrons and ions from the plasma to spacecraft surfaces can result in varying amounts of charge being released, depending on the secondary electron yield of the materials; this can lead to arcing between surfaces. NASA's Space and Environments Effects (SEE) program has recognized the need to improve their current materials database for modeling spacecraft charging and have …
Spontaneous Emission In Microcavity Lasers, Dustin Philip Ziegler
Spontaneous Emission In Microcavity Lasers, Dustin Philip Ziegler
Theses and Dissertations
An understanding of spontaneous emission processes within microcavities is crucial in addressing the need to make tomorrow's microlasers more efficient. One approach to improving the device efficiency is to reduce the threshold input energy at which lasing begins to occur. It has been suggested that the threshold in a microcavity laser can be decreased by increasing the fraction of spontaneous emission into the lasing mode, this can be accomplished by preferentially coupling the gain medium of the laser to the electromagnetic cavity mode of interest. It therefore becomes necessary to understand the mechanism by which this coupling takes place. This …