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Ion Beams In Multi-Species Plasma, Evan M. Aguirre, Earl E. Scime, Timothy N. Good 2018 West Virginia University

Ion Beams In Multi-Species Plasma, Evan M. Aguirre, Earl E. Scime, Timothy N. Good

Physics and Astronomy Faculty Publications

Argon and xenon ion velocity distribution functions are measured in Ar-He, Ar-Xe, and Xe-He expanding helicon plasmas to determine if ion beam velocity is enhanced by the presence of lighter ions. Contrary to observations in mixed gas sheath experiments, we find that adding a lighter ion does not increase the ion beam speed. The predominant effect is a reduction of ion beam velocity consistent with increased drag arising from increased gas pressure under all conditions: constant total gas pressure, equal plasma densities of different ions, and very different plasma densities of different ions. These results suggest that the physics responsible ...


Optimization Of Magnetic Chicane For Maximum Electron Beam Compression, Nathan W. Ray, Vida-Michelle Nixon, Matthias Fuchs 2018 University of Nebraska-Lincoln

Optimization Of Magnetic Chicane For Maximum Electron Beam Compression, Nathan W. Ray, Vida-Michelle Nixon, Matthias Fuchs

UCARE Research Products

Research concerned with optimizing a negatively chirped, relativistic, short electron beam using General Particle Tracer (GPT). The GPT simulations have the ability to include realistic beam effects such as space charge, fringe fields and emittance. A series of electron beam energy spreads were simulated through several different iterations of dipole magnets and, utilizing GPT's optimization ability, the most consistent set of parameters was selected and displayed on the poster. With our presented iteration of parameters we noted a 89.5% compression of the electron beam along the propagating axis.


Plasmonic Grating Geometrics And Wavelength-Dependent Focus Depth In Infrared Detectors, Patrick R. Kennedy 2018 Air Force Institute of Technology

Plasmonic Grating Geometrics And Wavelength-Dependent Focus Depth In Infrared Detectors, Patrick R. Kennedy

Theses and Dissertations

The objective for this research is to determine a relationship between plasmonic grating geometries and the wavelength-dependent focus depth. This research is focused on enhancing the signal collected by infrared detectors by using a metal grating as a planar lens to focus light in the detecting region of the substrate. This can be used to maintain a thinner absorbing region and possibly to create multi-color imaging in a single pixel. Simulations demonstrate that the plasmonic lens is capable of creating a wavelength dependent focus spot.


Electron Parallel Closures For The 3 + 1 Fluid Model, Jeong-Young Ji, Ilon Joseph 2018 Utah State University

Electron Parallel Closures For The 3 + 1 Fluid Model, Jeong-Young Ji, Ilon Joseph

All Physics Faculty Publications

Linear closures are obtained for arbitrary collisionality for the 3 þ 1 fluid model which includes the evolution of density, flow velocity, and pressure both parallel and perpendicular to a preferred direction, usually a magnetic field. A large set of 6400 moment equations is solved to provide closures that are accurate in the collisional regime and well into the collisionless regime. The closures in the collisionless limit are determined by solving the kinetic equation with a model collision operator. Simple fits for the kernel functions that define the closures are obtained for arbitrary collisionality in wave number space. The results ...


Excited Argon 1s5 Production In Microhollow Cathode Discharges, Richard D. Peterson 2018 Air Force Institute of Technology

Excited Argon 1s5 Production In Microhollow Cathode Discharges, Richard D. Peterson

Theses and Dissertations

Diode-pumped rare gas lasers (DPRGL) have been in development for their potential to become high energy lasers with excellent beam quality that is typical of gas lasers. DPRGL require metastable densities on the order of 1013 cm-3 at pressures around one atmosphere for efficient operation. Argon 1s5 number densities have been measured in microhollow cathode discharges (MHCD) using tunable diode laser absorption spectroscopy. The MHCD had copper electrodes with gaps of 127 and 254 µm and hole diameters from 100-400 µm. Absorbance was measured at pressures of 37 Torr up to 400 Torr, where absorbance could no longer ...


Optically Controlled Laser-Plasma Electron Acceleration For Compact Gamma-Ray Sources, Serge Y. Kalmykov, X. Davoine, Isaac Ghebregziabher, Bradley A. Shadwick 2018 CEA, DAM DIF

Optically Controlled Laser-Plasma Electron Acceleration For Compact Gamma-Ray Sources, Serge Y. Kalmykov, X. Davoine, Isaac Ghebregziabher, Bradley A. Shadwick

Serge Youri Kalmykov

Thomson scattering (TS) from electron beams produced in laser-plasma accelerators may generate femtosecond pulses of quasi-monochromatic, multi-MeV photons. Scaling laws suggest that reaching the necessary GeVelectron energy, with a percent-scale energy spread and five-dimensional brightness over 10^16 A/m^2, requires acceleration in centimeter-length, tenuous plasmas (n ~ 10^17 cm^-#3;3), with petawatt-class lasers. Ultrahigh per-pulse power mandates single-shot operation, frustrating applications dependent on dosage. To generate high-quality near-GeV beams at a manageable average power (thus affording kHz repetition rate), we propose acceleration in a cavity of electron density, driven with an incoherent stack of sub-Joule laser pulses ...


Numerical Studies Of Electrohydrodynamic Flow Induced By Corona And Dielectric Barrier Discharges, Chaoao Shi 2018 The University of Western Ontario

Numerical Studies Of Electrohydrodynamic Flow Induced By Corona And Dielectric Barrier Discharges, Chaoao Shi

Electronic Thesis and Dissertation Repository

Electrohyrodynamic (EHD) flow produced by gas discharges allows the control of airflow through electrostatic forces. Various promising applications of EHD can be considered, but this requires a deeper understanding of the physical mechanisms involved.

This thesis investigates the EHD flow generated by three forms of gas discharge. First, a multiple pin-plate EHD dryer associated with the positive corona discharge is studied using a stationary model. Second, the dynamics of a dielectric barrier discharge (DBD) plasma actuator is simulated with a time-dependent solver. Third, different configurations of the extended DBD are explored to enhance the EHD flow.

The results of the ...


Time-Resolved Electron (E,2E) Momentum Spectroscopy: Application To Laser-Driven Electron Population Transfer In Atoms, Hua-Chieh Shao, Anthony F. Starace 2018 University of Nebraska - Lincoln

Time-Resolved Electron (E,2E) Momentum Spectroscopy: Application To Laser-Driven Electron Population Transfer In Atoms, Hua-Chieh Shao, Anthony F. Starace

Anthony F. Starace Publications

Owing to its ability to provide unique information on electron dynamics, time-resolved electron momentum spectroscopy (EMS) is used to study theoretically a laser-driven electronic motion in atoms. Specifically, a chirped laser pulse is used to adiabatically transfer the populations of lithium atoms from the ground state to the first excited state. During this process, impact ionization near the Bethe ridge by time-delayed ultrashort, high-energy electron pulses is used to image the instantaneous momentum density of this electronic population transfer. Simulations with 100 fs and 1 fs pulse durations demonstrate the capability of EMS to image the time-varying momentum density, including ...


Optically Controlled Laser-Plasma Electron Accelerator For Compact Gamma-Ray Sources, Serge Y. Kalmykov, X. Davoine, Isaac Ghebregziabher, Bradley A. Shadwick 2018 CEA, DAM DIF

Optically Controlled Laser-Plasma Electron Accelerator For Compact Gamma-Ray Sources, Serge Y. Kalmykov, X. Davoine, Isaac Ghebregziabher, Bradley A. Shadwick

Serge Youri Kalmykov

Generating quasi-monochromatic, femtosecond gamma-ray pulses via Thomson scattering (TS) demands exceptional electron beam (e-beam) quality, such as percent scale energy spread and five-dimensional brightness over 10^16 A/m^2. We show that near-GeV e-beams with these metrics can be accelerated in a cavity of electron density, driven with an incoherent stack of Joule-scale laser pulses through a mm-size, dense plasma (n ~ 10^19 cm^-􀀀3). Changing the time delay, frequency difference, and energy ratio of the stack components controls the e-beam phase space on the femtosecond scale, while the modest energy of the optical driver helps afford kHz-scale repetition ...


Multi-Color, Femtosecond Gamma-Ray Pulse Trains Driven By Comb-Like Electron Beams, Serge Y. Kalmykov, X. Davoine, Isaac Ghebregziabher, Bradley A. Shadwick 2018 CEA, DAM DIF

Multi-Color, Femtosecond Gamma-Ray Pulse Trains Driven By Comb-Like Electron Beams, Serge Y. Kalmykov, X. Davoine, Isaac Ghebregziabher, Bradley A. Shadwick

Serge Youri Kalmykov

Photon engineering can be exploited to control the nonlinear evolution of the drive pulse in a laser–plasma accelerator (LPA), offering new avenues to tailor electron beam phase space on a femtosecond time scale. One promising option is to drive an LPA with an incoherent stack of two sub-Joule, multi-TW pulses of different colors. Slow self-compression of the bi-color optical driver delays electron dephasing, boosting electron beam energy without accumulation of a massive low-energy tail. The modest energy of the stack affords kHz-scale repetition rate at manageable laser average power. Propagating the stack in a pre-formed plasma channel induces periodic ...


Lanthanum-Mediated Dehydrogenation Of Butenes: Spectroscopy And Formation Of La(C4H6) Isomers, Wenjin Cao, Dilkrushi Hewage, Dong-Sheng Yang 2018 University of Kentucky

Lanthanum-Mediated Dehydrogenation Of Butenes: Spectroscopy And Formation Of La(C4H6) Isomers, Wenjin Cao, Dilkrushi Hewage, Dong-Sheng Yang

Chemistry Faculty Publications

La atom reactions with 1-butene, 2-butene, and isobutene are carried out in a laser-vaporization molecular beam source. The three reactions yield the same La-hydrocarbon products from the dehydrogenation and carbon-carbon bond cleavage and coupling of the butenes. The dehydrogenated species La(C4H6) is the major product, which is characterized with mass-analyzed threshold ionization (MATI) spectroscopy and quantum chemical computations. The MATI spectrum of La(C4H6) produced from the La+1-butene reaction exhibits two band systems, whereas the MATI spectra produced from the La+2-butene and isobutene reactions display only a single band system. Each ...


Numerical Solutions To Hall Magnetohydrodynamic Equations Near An X-Type Magnetic Neutral Line, Kyle Reger 2018 University of Central Florida

Numerical Solutions To Hall Magnetohydrodynamic Equations Near An X-Type Magnetic Neutral Line, Kyle Reger

The Pegasus Review: UCF Undergraduate Research Journal

The Hall Magnetohydrodynamic (MHD) model is a new paradigm for describing fast magnetic reconnection processes in space and laboratory plasmas. Current sheets form and store enormous amounts of magnetic energy at X-type magnetic neutral points, which is released as magnetic storms when the sheets break up. The fast magnetic reconnection process impacts solar flares and Earth's geomagnetic sub-storms, which affect global weather. The fast magnetic reconnection process also influences fusion reactors, which may be used as a future energy source. Numerical analysis of approximate solutions to the Hall MHD equations at X-type magnetic neutral points offer these solutions further ...


Xuv-Assisted High-Order-Harmonic-Generation Spectroscopy, T. S. Sarantseva, M. V. Frolov, N. L. Manakov, A. A. Silaev, N. V. Vvedenskii, Anthony F. Starace 2018 Voronezh State University

Xuv-Assisted High-Order-Harmonic-Generation Spectroscopy, T. S. Sarantseva, M. V. Frolov, N. L. Manakov, A. A. Silaev, N. V. Vvedenskii, Anthony F. Starace

Anthony F. Starace Publications

Using the analytic time-dependent effective range theory, we study two-color high-order harmonic generation (HHG) involving a weak extreme ultraviolet (XUV) pulse and an intense infrared laser field. Our analysis shows that XUV-assisted HHG spectra contain multiple additional plateau structures originating from absorption of one or more XUV photons at the photorecombination step of HHG. We show also that the HHG rate corresponding to the nth plateau can be presented in a factorized form involving the XUV-assisted (multiphoton) photorecombination cross section (PRCS) corresponding to absorption of n XUV photons of energy Ω and emission of a harmonic of energy Ωh ...


Developing Computational Models For Pulsed-Inductive Plasma Formation, Zachary Aaron Gill 2018 Missouri University of Science and Technology

Developing Computational Models For Pulsed-Inductive Plasma Formation, Zachary Aaron Gill

Masters Theses

"Pulsed-inductive discharges are a common method of producing a plasma. They provide a mechanism for quickly and efficiently generating a large volume of plasma for rapid use and are seen in applications including propulsion, fusion power, and high-power lasers. However, some common designs see a delayed response time due to the plasma forming when the magnitude of the magnetic field in the device is at a minimum. New designs are difficult to evaluate due to the amount of time needed to construct a new geometry and the high monetary cost of changing the power generation circuit. To more quickly evaluate ...


Plasma Medicine: A Brief Introduction, Mounir Laroussi 2018 Old Dominion University

Plasma Medicine: A Brief Introduction, Mounir Laroussi

Electrical & Computer Engineering Faculty Publications

This mini review is to introduce the readers of Plasma to the field of plasma medicine. This is a multidisciplinary field of research at the intersection of physics, engineering, biology and medicine. Plasma medicine is only about two decades old, but the research community active in this emerging field has grown tremendously in the last few years. Today, research is being conducted on a number of applications including wound healing and cancer treatment. Although a lot of knowledge has been created and our understanding of the fundamental mechanisms that play important roles in the interaction between low temperature plasma and ...


Production And Correlation Of Reactive Oxygen And Nitrogen Species In Gas- And Liquid-Phase Generated By Helium Plasma Jets Under Different Pulse Widths, Zhijie Liu, Chunxi Zhou, Dingxin Liu, Dehui Xu, Wenjie Xia, Qingjie Cui, Bingchuan Wang, Michael G. Kong 2018 Old Dominion University

Production And Correlation Of Reactive Oxygen And Nitrogen Species In Gas- And Liquid-Phase Generated By Helium Plasma Jets Under Different Pulse Widths, Zhijie Liu, Chunxi Zhou, Dingxin Liu, Dehui Xu, Wenjie Xia, Qingjie Cui, Bingchuan Wang, Michael G. Kong

Bioelectrics Publications

In this paper, we present the effects of the pulse width (PW) on the plasma jet's discharge characteristics, particularly focusing on the production and correlation of the reactive oxygen and nitrogen species (RONS) in gas- and liquid-phase. It is found that the length of plasma jet plume first increases before the PW of 10 μs, then gradually decreases and finally almost remains unchanged beyond 150 μs. The plasma bullet disappears after the falling edge of the voltage pulse at low PW, while it terminates far ahead of the falling edge of voltage pulse at high PW. This ...


Comparison Between The Water Activation Effects By Pulsed And Sinusoidal Helium Plasma Jets, Han Xu, Dingxin Liu, WEnjie Xia, Chen Chen, Weitao Wang, Zhijie Liu, Xiaohua Wang, Michael G. Kong 2018 Old Dominion University

Comparison Between The Water Activation Effects By Pulsed And Sinusoidal Helium Plasma Jets, Han Xu, Dingxin Liu, Wenjie Xia, Chen Chen, Weitao Wang, Zhijie Liu, Xiaohua Wang, Michael G. Kong

Bioelectrics Publications

Comparisons between pulsed and sinusoidal plasma jets have been extensively reported for the discharge characteristics and gaseous reactive species, but rarely for the aqueous reactive species in water solutions treated by the two types of plasma jets. This motivates us to compare the concentrations of aqueous reactive species induced by a pulsed and a sinusoidal plasma jet, since it is widely reported that these aqueous reactive species play a crucial role in various plasma biomedical applications. Experimental results show that the aqueous H2O2, OH/O2, and O2/ONOO induced by the pulsed plasma jet have ...


Exploration Of Equal Tune Transverse Coupling In The Spallation Neutron Source Accumulator Ring, Robert Edward Potts III 2017 University of Tennessee, Knoxville

Exploration Of Equal Tune Transverse Coupling In The Spallation Neutron Source Accumulator Ring, Robert Edward Potts Iii

Doctoral Dissertations

The development of hadron machines is one of the main areas of focus in accelerator technology and is specifically called out as a priority in the high energy physics 10-year plan[70]. The trend for future accelerators is to move towards very high-intensity high-power accelerators to be used as proton drivers for secondary particles, target stations, and high-energy accelerators. These accelerators require lower beam losses and more stringent beam controls to maintain typical loss levels and meet specific final beam distributions.

This study focuses on the recently documented coupling resonance in the Spallation Neutron Source (SNS) accumulator ring. It was ...


Spatial Structure Of Ion Beams In An Expanding Plasma, Evan M. Aguirre, Earl E. Scime, Derek S. Thompson, Timothy N. Good 2017 West Virginia University

Spatial Structure Of Ion Beams In An Expanding Plasma, Evan M. Aguirre, Earl E. Scime, Derek S. Thompson, Timothy N. Good

Physics and Astronomy Faculty Publications

We report spatially resolved perpendicular and parallel, to the magnetic field, ion velocity distribution function (IVDF) measurements in an expanding argon helicon plasma. The parallel IVDFs, obtained through laser induced fluorescence (LIF), show an ion beam with v ≈ 8000 m/s flowing downstream and confined to the center of the discharge. The ion beam is measurable for tens of centimeters along the expansion axis before the LIF signal fades, likely a result of metastable quenching of the beam ions. The parallel ion beam velocity slows in agreement with expectations for the measured parallel electric field. The perpendicular IVDFs show an ...


Compton Scattering From 4He At 61 Mev, M. H. Sikora, M. W. Ahmed, A. Banu, C. Bartram, B. Crowe, E. J. Downie, G. Feldman, H. Gao, H. W. Grießhammer, H. Hao, C. R. Howell, H. J. Karwowski, D. P. Kendellen, Michael A. Kovash, X. Li, D. M. Markoff, S. Mikhailov, V. Popov, R. E. Pywell, J. A. Silano, M. C. Spraker, P. Wallace, H. R. Weller, C. S. Whisnant, Y. K. Wu, W. Xiong, X. Yan, Z. W. Zhao 2017 Duke University

Compton Scattering From 4He At 61 Mev, M. H. Sikora, M. W. Ahmed, A. Banu, C. Bartram, B. Crowe, E. J. Downie, G. Feldman, H. Gao, H. W. Grießhammer, H. Hao, C. R. Howell, H. J. Karwowski, D. P. Kendellen, Michael A. Kovash, X. Li, D. M. Markoff, S. Mikhailov, V. Popov, R. E. Pywell, J. A. Silano, M. C. Spraker, P. Wallace, H. R. Weller, C. S. Whisnant, Y. K. Wu, W. Xiong, X. Yan, Z. W. Zhao

Physics and Astronomy Faculty Publications

The Compton scattering cross section from 4He has been measured with high statistical accuracy over a scattering angle range of 40−159 using a quasimonoenergetic 61-MeV photon beam at the High Intensity Gamma-Ray Source. The data are interpreted using a phenomenological model sensitive to the dipole isoscalar electromagnetic polarizabilities (αs and βs) of the nucleon. These data can be fit with the model using values of αs and βs that are consistent with the currently accepted values. These data will serve as benchmarks of future calculations from effective field theories and lattice quantum chromodynamics.


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