Crab Crossing Consideration For Meic,
2011
Old Dominion University
Crab Crossing Consideration For Meic, S. Ahmed, Y. Derbenev, Geoffrey A. Krafft, Y. Zhang, Subashini De Silva, Jean R. Delayen, A. Castilla
Physics Faculty Publications
Crab crossing of colliding electron and ion beams is essential for accommodating the high bunch repetition frequency in the conceptual design of MEIC – a high luminosity polarized electron-ion collider at Jefferson Lab. The scheme eliminates parasitic beam-beam interactions and avoids luminosity reduction by restoring head-on collisions at interaction points. In this paper, we report the possible crabbing schemes and requirements for both electron and proton beams.
Crab Crossing Schemes And Studies For Electron Ion Collider,
2011
Old Dominion University
Crab Crossing Schemes And Studies For Electron Ion Collider, S. Ahmed, Y. Derbenev, V. Morozov, A. Castilla, Geoffrey A. Krafft, B. Yunn, Subashini U. De Silva, Jean R. Delayen
Physics Faculty Publications
This report shows our progress in crab crossing consideration for future electron-ion collider envisioned at JLab. In this design phase, we are evaluating two crabbing schemes viz., the deflecting and dispersive. The mathematical formulations and lattice design for these schemes are discussed in this paper. Numerical simulations involving particle tracking through a realistic deflecting RF cavity and optics illustrate the desired crab tilt of 25 mrad for 1.35 MV. Evolution of beam propagation are shown which provides the physical insight of the crabbing phenomenon.
Beam Dynamics Studies Of Parallel-Bar Deflecting Cavities,
2011
Old Dominion University
Beam Dynamics Studies Of Parallel-Bar Deflecting Cavities, S. Ahmed, G. A. Krafft, K. Deitrick, Subashini U. De Silva, Jean R. Delayen, M. Spata, M. Tiefenback, A. Hofler, K. Beard
Physics Faculty Publications
We have performed three-dimensional simulations of beam dynamics for parallel-bar transverse electromagnetic mode (TEM) type RF separators: normal- and superconducting. The compact size of these cavities as compared to conventional TM110 type structures is more attractive particularly at low frequency. Highly concentrated electromagnetic fields between the parallel bars provide strong electrical stability to the beam for any mechanical disturbance. An array of eight 2-cell normal conducting cavities or a one- or two-cell superconducting structure are enough to produce the required vertical displacement at the Lambertson magnet. Both the normal and superconducting structures show very small emittance dilution due to the …
Multipacting Analysis Of The Superconducting Parallel-Bar Cavity,
2011
Old Dominion University
Multipacting Analysis Of The Superconducting Parallel-Bar Cavity, Subashini De Silva, Jean R. Delayen
Physics Faculty Publications
The superconducting parallel-bar cavity [1] is a deflecting/crabbing cavity with attractive properties, compared to other conventional designs, that is being considered for a number of applications. Multipacting can be a limiting factor to the performance of in any superconducting structure. In the parallel-bar cavity the main contribution to the deflection is due to the transverse deflecting voltage, between the parallel bars, making the design potentially prone to multipacting. This paper presents the results of analytical calculations and numerical simulations of multipacting in the parallel-bar cavity with resonant voltage, impact energies and corresponding particle trajectories.
Mechanical Study Of Superconducting Parallel-Bar Deflecting/Crabbing Cavities,
2011
Old Dominion University
Mechanical Study Of Superconducting Parallel-Bar Deflecting/Crabbing Cavities, Hyekyoung Park, Jean R. Delayen, Subashini De Silva
Physics Faculty Publications
The superconducting parallel-bar deflecting/crabbing cavities have improved properties compared to conventional cavity structures. It is currently being considered for number of applications. The mechanical design analysis is performed on two designs of the 499 MHz parallel-bar deflecting cavity for the Jefferson Lab 12 GeV upgrade. The main purpose of the mechanical study is to examine the structural stability of the cavities under the operating conditions in the accelerators. The study results will suggest the need for additional structural strengthening. Also the study results will help to develop a concept of the tuning method. If the cavity is to be installed …
Design Of Superconducting Multi-Spoke Cavities For High Velocity Applications,
2011
Old Dominion University
Design Of Superconducting Multi-Spoke Cavities For High Velocity Applications, C. S. Hopper, Jean R. Delayen
Physics Faculty Publications
Superconducting spoke cavities have been designed and tested for particle velocities up to β0 ~ 0.6 and are currently being designed for velocities up to β0 = 1. We present the electromagnetic designs for two-spoke cavities operating at 325 MHz for β0 = 0.82 and β0 = 1.
Magnetism Of Cluster-Deposited Y–Co Nanoparticles,
2011
University of Nebraska-Lincoln
Magnetism Of Cluster-Deposited Y–Co Nanoparticles, Balamuruga Balamurugan, Ralph Skomski, Xingzhong Li, V. R. Shah, George C. Hadjipanayis, Jeffrey E. Shield, David J. Sellmyer
Faculty Publications from Nebraska Center for Materials and Nanoscience
Nanoparticles of YCo2, YCo3, and YCo5 are produced by cluster-deposition and investigated both structurally and magnetically. The nanoparticles have sizes of less than 10 nm and are superparamagnetic at 300 K, irrespective of stoichiometry. As-produced nanoparticles exhibit disordered structures with magnetic properties differing from those of the bulk particles. The temperature-dependent magnetization curves of the nanoparticles reveal blocking temperatures from 110 to 250 K, depending on stoichiometry. The magnetic anisotropy constant K1 of disordered YCo5 nanoparticles of 7.8 nm in size is 3.5×106ergs/cm3, higher than those of the disordered YCo …
Resonant Photoemission Of Rare Earth Doped Gan Thin Films,
2011
Air Force Institute of Technology
Resonant Photoemission Of Rare Earth Doped Gan Thin Films, S. R. Mchale, J. W. Mcclory, J. C. Petrosky, J. Wu, R. Palai, Yaroslav B. Losovyj, Peter A. Dowben
Peter Dowben Publications
The 4d → 4f Fano resonances for various rare earth doped GaN thin films (RE = Gd, Er, Yb) were investigated using synchrotron photoemission spectroscopy. The resonant photoemission Fano profiles show that the major Gd and Er rare earth 4f weight is at about 5–6 eV below the valence band maximum, similar to the 4f weights in the valence band of many other rare earth doped semiconductors. For Yb, there is very little resonant enhancement of the valence band of Yb doped GaN, consistent with a largely 4f14 occupancy.
Measurement System For High Pressure Characterizations Of Materials,
2010
University of Nevada, Las Vegas
Measurement System For High Pressure Characterizations Of Materials, Matthew K. Jacobsen
UNLV Theses, Dissertations, Professional Papers, and Capstones
Thermoelectric materials have long been investigated for possible use as power sources. This application was recently put to use in the Voyager space program, powering the deep space probes. Despite the usefulness of these materials, the use of pressure to investigate the material properties has only recently become interesting. As such, the work in this document was to developing a system for concurrently measuring the necessary properties. This system is capable of measuring the electrical resistivity, thermal conductivity, and Seebeck coefficient in the pressure range from 0 - 10 GPa. The results for zinc, almandine garnet, and nickel are presented …
A Comprehensive Rocket And Radar Study Of Midlatitude Spread F,
2010
Embry-Riddle Aeronautical University
A Comprehensive Rocket And Radar Study Of Midlatitude Spread F, G.D. Earle, P. Bhanja, P.A. Roddy, C.M. Swenson, Aroh Barjatya, Et Al.
Publications
An instrumented sounding rocket launched from Wallops Island Virginia has flown through a midlatitude spread F (MSF) event in conjunction with simultaneous ionosonde, HF radar, and 244 MHz scintillation observations from the ground. The in situ measurements include the electric field, horizontal neutral wind, and plasma density within the spread F region. The ground‐based HF radar measurements of wave signatures in the bottomside F region ledge reveal the presence of waves propagating to the north and northwest prior to and during the spreading event. The periods of these bottomside waves range from 16 to 60 min, and they are shown …
Development Of Acrylamide Based Photopolymer For Full Colour Display Holography,
2010
Technological University Dublin
Development Of Acrylamide Based Photopolymer For Full Colour Display Holography, Chakrapani Meka
Doctoral
Holography is a firmly established discipline that can be used as a tool for scientific and engineering studies and as a display medium as well. Until now both silver halide photographic emulsions (SHPE) and dichromated gelatine (DCG) have been the most common materials used for high efficiency full colour reflection hologram recording. However, these materials require wet chemical processing for developing the holograms which is laborious and costly from the point of view of commercial applications. Self-developing photopolymers such as acrylamide based photopolymer (ABP) which do not require development are the ideal choice for real-time recording and reconstruction of holograms. …
Pulsed Laser Deposition Of Graphite Counter Electrodes For Dye-Sensitized Solar Cells,
2010
Old Dominion University
Pulsed Laser Deposition Of Graphite Counter Electrodes For Dye-Sensitized Solar Cells, Krishna P. Acharya, Himal Khatri, Sylvain Marsillac, Bruno Ullrich, Pavel Anzenbacher, Mikhail Zamkov
Electrical & Computer Engineering Faculty Publications
We report on pulsed laser deposition of graphite onto flexible plastic and conductive glass substrates for use as a counter electrode in dye-sensitized solar cells. The efficiency of as-prepared graphite electrodes was tested using CdS-sensitized solar cell architecture resulting in external quantum efficiency comparable to that of conventional platinum counter electrodes. This work highlights the possibility of using pulsed laser deposited graphite as a low-cost alternative to platinum, which could be fabricated both on flexible and rigid substrates.
Doping Dependence Of Electronic And Mechanical Properties Of Gase1−XTeX And Ga1−XInXSe From First Principles,
2010
University of South Carolina - Columbia
Doping Dependence Of Electronic And Mechanical Properties Of Gase1−XTeX And Ga1−XInXSe From First Principles, Zs. Rak, S. D. Mahanti, K. C. Mandal, N. C. Fernelius
Faculty Publications
No abstract provided.
Energetyka Niskoemisyjna,
2010
Wroclaw University of Technology
Energetyka Niskoemisyjna, Wojciech M. Budzianowski
Wojciech Budzianowski
No abstract provided.
Structural, Magnetic, And Defect Properties Of Co-Pt-Type Magnetic-Storage Alloys: Density-Functional Theory Study Of Thermal Processing Effects,
2010
University of Illinois at Urbana-Champaign
Structural, Magnetic, And Defect Properties Of Co-Pt-Type Magnetic-Storage Alloys: Density-Functional Theory Study Of Thermal Processing Effects, Aftab Alam, Brent Kraczek, Duane D. Johnson
Duane D. Johnson
Using an optimized-basis Korringa-Kohn-Rostoker-coherent-potential approximation method, we calculate formation enthalpies ΔEf, structural, and magnetic properties of paramagnetic (PM) and ferromagnetic, disordered A1 and ordered L10 CoPt, FePd, and FePt systems that are of interest for high-density magnetic-recording media. To address processing effects, we focus on the point defects that dictate thermal properties and planar defects (e.g., c domain and antiphase boundaries) which can serve as pinning centers for magnetic domains and affect storage properties. We determine bulk Curie (Tc) and order-disorder (To-d) transition temperatures within 4% of observed values, and estimates for nanoparticles. Planar-defect energies γhklx show that the favorable …
Nonlinear Observers For Human-In-The-Loop Control Systems,
2010
Embry-Riddle Aeronautical University - Daytona Beach
Nonlinear Observers For Human-In-The-Loop Control Systems, Samuel Kitchen Mckinley
Master's Theses - Daytona Beach
The development of models for a human-in-the-loop with hardware is an area of ongoing research. The ability to simulate a human-in-the-loop with hardware provides a platform for better understanding the dynamics of human and machine cognition. A human-in-the-loop model provides information that can be used to design more efficient human interfaces and smarter autonomous assistant controllers. This can make a complex task such as flying an aircraft safer and more accessible. This thesis explores different possibilities for human operator models to be modeled in the loop with a vehicle. A human is modeled as a linear state feedback controller in …
Boron Carbide Based Solid State Neutron Detectors: The Effects Of Bias And Time Constant On Detection Efficiency,
2010
University of Nebraska-Lincoln
Boron Carbide Based Solid State Neutron Detectors: The Effects Of Bias And Time Constant On Detection Efficiency, Nina Hong, John Mullins, Keith Foreman, Shireen Adenwalla
Shireen Adenwalla Papers
Neutron detection in thick boron carbide(BC)/n-type Si heterojunction diodes shows a threefold increase in efficiency with applied bias and longer time constants. The improved efficiencies resulting from long time constants have been conclusively linked to the much longer charge collection times in the BC layer. Neutron detection signals from both the p-type BC layer and the n-type Si side of the heterojunction diode are observed, with comparable efficiencies. Collectively, these provide strong evidence that the semiconducting BC layer plays an active role in neutron detection, both in neutron capture and in charge generation and collection.
Construction And Enhancement Of Stereo Vacuum Tube Amplifier With Precision Machined Enclosure,
2010
California Polytechnic State University - San Luis Obispo
Construction And Enhancement Of Stereo Vacuum Tube Amplifier With Precision Machined Enclosure, Nikolaus (Nik) Glazar
Physics
The purpose of this project was to build a high fidelity tube amplifier from a kit, and machine a beautiful enclosure to house the electronics. Improvements were made to the circuit, and the amplifier was then tested for audio performance.
An Investigation Of Gas Bubble Generation And Measurement In Water And Mercury,
2010
University of Tennessee, Knoxville
An Investigation Of Gas Bubble Generation And Measurement In Water And Mercury, Stuart A Walker
Masters Theses
The pressure increase attributed to the energy deposition in the liquid metal target of the Spallation Neutron Source results in cavitation and pitting erosion of the target pressure boundary. Introducing compressibility in the form of small gas bubbles will extend the lifetime of the target vessel. The pressure rise caused by the beam energy deposition occurs in one microsecond, which encourages use of bubbles of radius less than 20 microns, such that the bubble response to pressure change is adequately fast. Gas volume fraction near 0.5% is sufficient to accommodate the mercury volumetric expansion and reduce the pressure rise. Bubble …
Improving Low Order, Linear, Positive Spatial Quadratures For The Partial Current Neutron Transport Method,
2010
Air Force Institute of Technology
Improving Low Order, Linear, Positive Spatial Quadratures For The Partial Current Neutron Transport Method, John M. Snyder
Theses and Dissertations
AFIT researchers have developed a new approach to solving Discrete Ordinates equations, which approximate the linear Boltzmann Transport Equation (BTE). The usual approach is von Neumann iteration on the scattering source, which requires repeated sweeps through the spatial-angular grid. Acceptable convergence requires complicated and expensive acceleration schemes. The new approach, Partial-Current Transport (PCT) with Adaptive Distribution Iteration, eliminates scattering source iteration through matrix inversions and a reduced-size global linear algebra problem. It creates the needed matrices directly from the standard spatial quadratures used in the sweeping. Positivity, linearity, and (higher-than-first-order) accuracy are the key desirable qualities with all Discrete Ordinates …
