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Articles 1 - 16 of 16
Full-Text Articles in Plasma and Beam Physics
Theoretical Study Of Localized Surface Plasmons Of Metal Nanoparticles, Clusters And Embedded Metal Nanoparticles In Matrices, Masoud Shabani Nezhad Navrood
Theoretical Study Of Localized Surface Plasmons Of Metal Nanoparticles, Clusters And Embedded Metal Nanoparticles In Matrices, Masoud Shabani Nezhad Navrood
Dissertations
Localized surface plasmons resonances (LSPRs) in metallic nanoparticles (NPs) arise from the interactions between incident light and conduction electrons and have attracted enormous research interest in recent years both for their fundamental nature as well as applications in interdisciplinary areas of sciences such as biological imaging, plasmonic photo-thermal therapy, photovoltaics, and plasmonic sensors. LSPRs are strongly localized and depend on the shape, size, the composition of the NPs, the polarization direction of the incident light, refractive index (RI) of the surrounding medium as well as on the chemical environment that surrounded NPs. Although significant research has progressed both theoretically and …
Coupled Ray-Tracing And Fokker-Planck Ebw Modeling For Spherical Tokamaks, Jakub Urban, Joan Decker, Y. Peysson, Josef Preinhaelter, Gary Taylor, Linda L. Vahala, George Vahala
Coupled Ray-Tracing And Fokker-Planck Ebw Modeling For Spherical Tokamaks, Jakub Urban, Joan Decker, Y. Peysson, Josef Preinhaelter, Gary Taylor, Linda L. Vahala, George Vahala
Electrical & Computer Engineering Faculty Publications
The AMR (Antenna—Mode-conversion—Ray-tracing) code [1, 2] has been recently coupled with the LUKE [3] Fokker-Planck code. This modeling suite is capable of complex simulations of electron Bernstein wave (EBW) emission, heating and current drive. We employ these codes to study EBW heating and current drive performance under spherical tokamak (ST) configurations—typical NSTX discharges are employed. EBW parameters, such as frequency, antenna position and direction, are varied and optimized for particular configurations and objectives. In this way, we show the versatility of EBWs.
Hydrodynamic Relaxation Of An Electron Plasma To A Near-Maximum Entropy State, D. J. Rodgers, S. Servidio, W. H. Matthaeus, D. C. Montgomery, T. B. Mitchell, T. Aziz
Hydrodynamic Relaxation Of An Electron Plasma To A Near-Maximum Entropy State, D. J. Rodgers, S. Servidio, W. H. Matthaeus, D. C. Montgomery, T. B. Mitchell, T. Aziz
Dartmouth Scholarship
Dynamical relaxation of a pure electron plasma in a Malmberg-Penning trap is studied, comparing experiments, numerical simulations and statistical theories of weakly dissipative two-dimensional (2D) turbulence. Simulations confirm that the dynamics are approximated well by a 2D hydrodynamic model. Statistical analysis favors a theoretical picture of relaxation to a near-maximum entropy state with constrained energy, circulation, and angular momentum. This provides evidence that 2D electron fluid relaxation in a turbulent regime is governed by principles of maximum entropy.
Generation Of Mie Size Microdroplet Aerosols With Applications In Laser-Driven Fusion Experiments, Andrew P. Higginbotham '09, O. Semonin '06, S. Bruce '08, C. Chan '08, M. Maindi '07, Thomas D. Donnelly, M. Maurer, W. Bang, I. Churina, J. Osterholz, I. Kim, A. C. Bernstein, T. Ditmire
Generation Of Mie Size Microdroplet Aerosols With Applications In Laser-Driven Fusion Experiments, Andrew P. Higginbotham '09, O. Semonin '06, S. Bruce '08, C. Chan '08, M. Maindi '07, Thomas D. Donnelly, M. Maurer, W. Bang, I. Churina, J. Osterholz, I. Kim, A. C. Bernstein, T. Ditmire
All HMC Faculty Publications and Research
We have developed a tunable source of Mie scale microdroplet aerosols that can be used for the generation of energetic ions. To demonstrate this potential, a terawatt Ti:Al2O3 laser focused to 2×1019 W/cm2 was used to irradiate heavy water (D2O) aerosols composed of micron-scale droplets. Energetic deuterium ions, which were generated in the laser-droplet interaction, produced deuterium-deuterium fusion with approximately 2×103 fusion neutrons measured per joule of incident laser energy.
Characterization Of Microwave Cavity Discharges In A Supersonic Flow, Dareth Janette Drake
Characterization Of Microwave Cavity Discharges In A Supersonic Flow, Dareth Janette Drake
Physics Theses & Dissertations
A partially ionized gas is referred to as either a plasma or a discharge depending on the degree of ionization. The term discharge is usually applied to a weakly ionized gas, i.e. mostly neutrals, where as a plasma usually has a larger degree of ionization. To characterize a discharge the plasma parameters, such as the rotational temperature, vibrational temperature, and electron density, must be determined. Detailed characterization of supersonic flowing discharges is important to many applications in aerospace and aerodynamics. One application is the use of plasma-assisted hydrogen combustion devices to aid in supersonic combustion. In conditions close to the …
Assessment Of Weather Sensitivities And Air Force Weather (Afw) Support To Tactical Lasers In The Lower Troposphere, Francesco J. Echeverria
Assessment Of Weather Sensitivities And Air Force Weather (Afw) Support To Tactical Lasers In The Lower Troposphere, Francesco J. Echeverria
Theses and Dissertations
ATL scientists need to develop a full understanding of the interaction effects between a high-energy laser beam and the atmosphere through which it propagates. Achieving this understanding is important for many reasons. In particular, the high cost of DE weapons systems makes each propagation event expensive. Having an understanding of the atmosphere in which a high-energy laser propagates will increase efficiency and effectiveness of the ATL weapon system, which in turn will decrease cost of operation. A tool that allows for the ATL war-fighter to determine the atmospheric effects on laser propagation currently does not exist. This study creates a …
Production And Characterization Of High Repetition Rate Terahertz Radiation In Femtosecond-Laser-Induced Air Plasma, Michael L. Dexter
Production And Characterization Of High Repetition Rate Terahertz Radiation In Femtosecond-Laser-Induced Air Plasma, Michael L. Dexter
Theses and Dissertations
The purpose of this research was to produce and characterize high repetition rate terahertz radiation in ionized air plasma. An 800 nanometer, 50 femtosecond, 0.35 Watt, 40 KHz, pulsed Ti:Sapphire laser system was used as the source infrared beam. This beam was focused onto a second harmonic generation crystal to produce a collinear, perpendicularly polarized secondary beam at 400 nm. After realigning the polarization of the fundamental to the second harmonic and compensating for group velocity dispersion introduced by the optics, both beams were recombined and focused by a 3.75 cm focal length mirror to form an air plasma. An …
Theoretical Model Analysis Of Absorption Of A Three Level Diode Pumped Alkali Laser, Charlton D. Lewis Ii
Theoretical Model Analysis Of Absorption Of A Three Level Diode Pumped Alkali Laser, Charlton D. Lewis Ii
Theses and Dissertations
This paper models the absorption phenomena of light in a three level diode pumped alkali laser system. Specifically this model calculates for a user defined set of system parameters the attenuation of the input pump beam and characteristics of the bleached wave. Using Wolfram's Mathematical 6.0 software all necessary physics for an accurate description of absorption was modeled from first principles: energy levels, cross sections, spin-orbit kinetic processes, saturation frequencies, pump attenuation, and differential transmittance, which is a representation of the bleached wave. A specific DPAL scenario was simulated, 455K system temperature, alkali concentration of 6.1 - 1013, …
Q-Switched And Mode Locked Short Pulses From A Diode Pumped, Yb-Doped Fiber Laser, Seth M. Swift
Q-Switched And Mode Locked Short Pulses From A Diode Pumped, Yb-Doped Fiber Laser, Seth M. Swift
Theses and Dissertations
A diode-pumped, ytterbium (Yb)-doped fiber laser system was designed and demonstrated to operate in continuous wave (cw), passively Q-switched and possibly passively mode locked operation. To our knowledge, this was the first fiber laser oscillator built at the Air Force Institute of Technology. A Cr4+:YAG (Chromium: Ytterbium Aluminum Garnett) crystal was used as a saturable absorber to generate Q-switched pulses. Attempts to mode lock the laser were performed using a semiconductor saturable absorber mirror (SESAM) and through nonlinear polarization rotation (NPR). The best output power result was 5 Watts (W) while pumping at 8.3 W, yielding 60% efficiency …
Thermal Inactivation Of Bacillus Anthracis Using Laser Irradiation Of Micro-Etched Platforms, Jeffrey B. Bacon
Thermal Inactivation Of Bacillus Anthracis Using Laser Irradiation Of Micro-Etched Platforms, Jeffrey B. Bacon
Theses and Dissertations
The purpose of this research was to determine the probability of kill for a thermal inactivation strategy for use against biological agents; specifically the resilient endospore of Bacillus anthracis (Ba). The effort focused on short durations (milliseconds to several seconds) and temperatures (300 to 1300 K) simulating the periphery effects after an explosion generated by conventional munitions. For an improved statistical counting, applied microlithography techniques were used to produce micro-etched glass platforms consisting of 532 circular sample wells, evenly spaced. Small carbon black radiators, which provide fast heating/cooling rate and confined temperature distribution, were produced by populating the etched wells …
Auroral Evidence For Multiple Reconnection In The Magnetospheric Tail Plasma Sheet, R. A. Treumann, C. H. Jaroschek, R. Pottelette
Auroral Evidence For Multiple Reconnection In The Magnetospheric Tail Plasma Sheet, R. A. Treumann, C. H. Jaroschek, R. Pottelette
Dartmouth Scholarship
We present auroral evidence for multiple and, most probably, small-scale reconnection in the near-Earth magnetospheric plasma sheet current layer during auroral activity. Hall currents as the source of upward and downward field-aligned currents require the generation of the corresponding electron fluxes. The auroral spatial ordering in a multiple sequence of these fluxes requires the assumption of the existence of several —and possibly— even many tailward reconnection sites.
Diagnostics For Ultracold Plasma Experiments, Lauren Rand
Diagnostics For Ultracold Plasma Experiments, Lauren Rand
Honors Theses
The goal of this experiment was to observe the effects of variations of experimental conditions on the ultracold plasma that formed as a result. The wavelength and power of the ionizing laser were varied to change the electron temperature and plasma density. The delay between the ionizing laser and the field ionization pulse was changed as well. In each case, plasma evolution and the resulting distribution of Rydberg states were observed. It was found that both electron temperature and plasma density directly affected the plasma lifetimes. However, neither electron temperature nor plasma density nor delay length had an effect on …
Beam-Energy And System-Size Dependence Of Dynamical Net Charge Fluctuations, B. I. Abelev, M. M. Aggarwal, Z. Ahammed, B. D. Anderson, D. Arkhipkin, G. S. Averichev, Y. Bai, J. Balewski, S. Bueltmann, Star Collaboration
Beam-Energy And System-Size Dependence Of Dynamical Net Charge Fluctuations, B. I. Abelev, M. M. Aggarwal, Z. Ahammed, B. D. Anderson, D. Arkhipkin, G. S. Averichev, Y. Bai, J. Balewski, S. Bueltmann, Star Collaboration
Physics Faculty Publications
We present measurements of net charge fluctuations in Au+Au collisions at √sNN=19.6, 62.4, 130, and 200 GeV, Cu+Cu collisions at √sNN=62.4 and 200 GeV, and p+p collisions at √s=200GeV using the dynamical net charge fluctuations measure ν+−,dyn. We observe that the dynamical fluctuations are nonzero at all energies and exhibit a modest dependence on beam energy. A weak system size dependence is also observed. We examine the collision centrality dependence of the net charge fluctuations and find that dynamical net charge fluctuations violate 1/Nch scaling but display approximate 1/Npart scaling. We also study the azimuthal and …
New Compact Tem-Type Deflecting And Crabbing Rf Structure, J. R. Delayen, H. Wang
New Compact Tem-Type Deflecting And Crabbing Rf Structure, J. R. Delayen, H. Wang
Physics Faculty Publications
A new type of rf structure for the deflection and crabbing of particle beams is presented. The structure is comprised of a number of parallel TEM resonant lines operating in opposing phase from each other. One of its advantages is its compactness compared to conventional crabbing cavities operating in the TM110 mode, thus allowing low frequency designs. This geometry would also be effective for the deflection of beams propagating at velocities substantially less than that of light.
Photodisintegration Of 4He Into P+T, Clas Collaboration, M. J. Amaryan, S. L. Careccia, G. E. Dodge, C. E. Hyde, S. E. Kuhn, M. Mayer, C. S. Nepali, M. R. Niroula, H. Seraydaryan, S. Tkachenko, L.B. Weinstein, J. Zhang
Photodisintegration Of 4He Into P+T, Clas Collaboration, M. J. Amaryan, S. L. Careccia, G. E. Dodge, C. E. Hyde, S. E. Kuhn, M. Mayer, C. S. Nepali, M. R. Niroula, H. Seraydaryan, S. Tkachenko, L.B. Weinstein, J. Zhang
Physics Faculty Publications
The two-body photodisintegration of 4He into a proton and a triton has been studied using the CEBAF Large-Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. Real photons produced with the Hall-B bremsstrahlung-tagging system in the energy range from 0.35 to 1.55 GeV were incident on a liquid 4He target. This is the first measurement of the photodisintegration of 4He above 0.4 GeV. The differential cross sections for the γ 4He →pt reaction were measured as a function of photon-beam energy and proton-scattering angle and are compared with the latest model calculations by J.-M. Laget. At …
Search For The Photoexcitation Of Exotic Mesons In The Π+Π+Π- System, Clas Collaboration, M. J. Amaryan, H. Bagdasaryan, S. Bektasoglu, S. Bültmann, G. E. Dodge, G. Gavalian, N. Guler, C. E. Hyde-Wright, N. Kalantarians, A. Klein, S. E. Kuhn, J. Lachniet, M. R. Niroula, L. M. Qin, S. Tkachenko, L. B. Weinstein, J. Zhang
Search For The Photoexcitation Of Exotic Mesons In The Π+Π+Π- System, Clas Collaboration, M. J. Amaryan, H. Bagdasaryan, S. Bektasoglu, S. Bültmann, G. E. Dodge, G. Gavalian, N. Guler, C. E. Hyde-Wright, N. Kalantarians, A. Klein, S. E. Kuhn, J. Lachniet, M. R. Niroula, L. M. Qin, S. Tkachenko, L. B. Weinstein, J. Zhang
Physics Faculty Publications
A search for exotic mesons in the π+π+π− system photoproduced by the charge exchange reaction γp→π+π+π−(n) was carried out by the CLAS Collaboration at Jefferson Lab. A tagged-photon beam with energies in the 4.8 to 5.4 GeV range, produced through bremsstrahlung from a 5.744 GeV electron beam, was incident on a liquid-hydrogen target. A partial wave analysis was performed on a sample of 83 000 events, the highest such statistics to date in this reaction at these energies. The main objective of this study was to look for the …