46 Matching Results

Results open in a new window/tab.

Materials Science at the Extremes of Pressure and Strain Rate (open access)

Materials Science at the Extremes of Pressure and Strain Rate

Solid state experiments at very high pressures and strain rates are possible on high power laser facilities, albeit over brief intervals of time and spatial small scales. A new shockless drive has been developed on the Omega laser. VISAR measurements establish the high strain rates, 10{sup 7}-10{sup 8} s{sup -1}. Solid-state strength is inferred using the Rayleigh-Taylor instability as a ''diagnostic''. Temperature and compression in polycrystalline samples can be deduced from EXAFS measurements. Lattice response can be inferred from time-resolved x-ray diffraction. Deformation mechanisms can be identified by examining recovered samples. We will briefly review this new area of laser-based materials science research, then present a path forward for carrying these solid-state experiments to much higher pressures, P >> 1 Mbar, on the NIF laser facility.
Date: August 20, 2003
Creator: Remington, B. A.; Cavallo, R. M.; Edwards, M. J.; Lasinski, B. F.; Lorenz, K. T.; Lorenzana, H. E. et al.
System: The UNT Digital Library
A Neutron Source Facility for Neutron Cross-Section Measurements on Radioactive Targets at RIA (open access)

A Neutron Source Facility for Neutron Cross-Section Measurements on Radioactive Targets at RIA

The stockpile stewardship program is interested in neutron cross-section measurements on nuclei that are a few nucleons away from stability. Since neutron targets do not exist, radioactive targets are the only way to directly perform these measurements. This requires a facility that can provide high production rates for these short-lived nuclei as well as a source of neutrons. The Rare Isotope Accelerator (RIA) promises theses high production rates. Thus, adding a co-located neutron source facility to the RIA project baseline would allow these neutron cross-section measurements to be made. A conceptual design for such a neutron source has been developed, which would use two accelerators, a Dynamitron and a linac, to create the neutrons through a variety of reactions (d-d, d-t, deuteron break-up, p-Li). This range of reactions is needed in order to provide the desired energy range from 10's of keV to 20 MeV. The facility would also have hot cells to perform chemistry on the radioactive material both before and after neutron irradiation. The present status of this design and direction of future work will be discussed.
Date: May 20, 2003
Creator: Ahle, L. E.; Bernstein, L.; Rusnak, B. & Berio, R.
System: The UNT Digital Library
PLEIADES: A Picosecond Compton Scattering X-Ray Source for Advanced Backlighting and Time-Resolved Material Studies (open access)

PLEIADES: A Picosecond Compton Scattering X-Ray Source for Advanced Backlighting and Time-Resolved Material Studies

The PLEIADES (Picosecond Laser-Electron Inter-Action for the Dynamical Evaluation of Structures) facility has produced first light at 70 keV. This milestone offers a new opportunity to develop laser-driven, compact, tunable x-ray sources for critical applications such as diagnostics for the National Ignition Facility and time-resolved material studies. The electron beam was focused to 50 {micro}m rms, at 57 MeV, with 260 C of charge, a relative energy spread of 0.2%, and a normalized emittance of 5 mm mrad horizontally and 13 mm mrad vertically. The scattered 820-nm laser pulse had an energy of 180 mJ and a duration of 54 fs. Initial x-rays were captured with a cooled charge-coupled device using a Cesium Iodide scintillator; the peak photon energy was approximately 78 keV, with a total x-ray flux of 1.3 x 10{sup 6} photons/shot, and the observed angular distribution found to agree very well with three-dimensional codes. Simple K-edge radiography of a tantalum foil showed good agreement with the theoretical divergence-angle dependence of the x-ray energy. Optimization of the x-ray dose is currently underway, with the goal of reaching 10{sup 8} photons per shot and a peak brightness approaching 10{sup 20} photons/mm{sup 2}/mrad{sup 2}/s/0.1%bandwidth.
Date: October 20, 2003
Creator: Gibson, D J; Anderson, S G; Barty, C P; Betts, S M; Booth, R; Brown, W J et al.
System: The UNT Digital Library
Multi-scale Science: Supporting Emerging Practice with Semantically Derived Provenance (open access)

Multi-scale Science: Supporting Emerging Practice with Semantically Derived Provenance

Scientific progress is becoming increasingly dependent of our ability to study phenomena at multiple scales and from multiple perspectives. The ability to recontextualize third party data within the semantic and syntactic framework of a given research project is increasingly seen as a primary barrier in multi-scale science. Within the Collaboratory for Multiscale Chemical Science (CMCS) project, we are developing a general-purpose informatics-based approach that emphasizes ''on-demand'' metadata creation, configurable data translations, and semantic mapping to support the rapidly increasing and continually evolving requirements for managing data, metadata, and data relationships in such projects. A concrete example of this approach is the design of the CMCS provenance subsystem. The concept of provenance varies across communities, and multiple independent applications contribute to and use provenance. In CMCS, we have developed generic tools for viewing provenance relationships and for using them to, for example, scope notifications and searches. These tools rely on a configurable concept of provenance defined in terms of other relationships. The result is a very flexible mechanism capable of tracking data provenance across many disciplines and supporting multiple uses of provenance information.
Date: October 20, 2003
Creator: Myers, James D.; Pancerella, Carmen M.; Lansing, Carina S.; Schuchardt, Karen L.; Didier, Brett T. & Ashish, N., Goble, C
System: The UNT Digital Library
Characterization of Low Temperature Ferrite/Austenite Transformations in the Heat Affected Zone of 2205 Duplex Stainless Steel Arc Welds (open access)

Characterization of Low Temperature Ferrite/Austenite Transformations in the Heat Affected Zone of 2205 Duplex Stainless Steel Arc Welds

Spatially Resolved X-Ray Diffraction (SRXRD) has been used to identify a previously unobserved low temperature ferrite ({delta})/austenite({gamma}) phase transformation in the heat affected zone (HAZ) of 2205 Duplex Stainless Steel (DSS) welds. In this ''ferrite dip'' transformation, the ferrite transforms to austenite during heating to peak temperatures on the order of 750 C, and re-transforms to ferrite during cooling, resulting in a ferrite volume fraction equivalent to that in the base metal. Time Resolved X-Ray Diffraction (TRXRD) and laser dilatometry measurements during Gleeble{reg_sign} thermal simulations are performed in order to verify the existence of this low temperature phase transformation. Thermodynamic and kinetic models for phase transformations, including both local-equilibrium and para-equilibrium diffusion controlled growth, show that diffusion of substitutional alloying elements does not provide a reasonable explanation for the experimental observations. On the other hand, the diffusion of interstitial alloying elements may be rapid enough to explain this behavior. Based on both the experimental and modeling results, two mechanisms for the ''ferrite dip'' transformation, including the formation and decomposition of secondary austenite and an athermal martensitic-type transformation of ferrite to austenite, are considered.
Date: August 20, 2003
Creator: Palmer, T A; Elmer, J W; Babu, S S & Vitek, J M
System: The UNT Digital Library
Whole Genome Amplification of DNA from Residual Cells Left By Incidental Contact (open access)

Whole Genome Amplification of DNA from Residual Cells Left By Incidental Contact

Typically, the number of genetic analyses performed on a sample of DNA has been limited by the amount of starting material. For example, the small quantity of DNA obtained from the cells within a fingerprint meant that only a five to ten reactions could be performed off a single sample. We demonstrate a process wherein total genomic DNA is amplified before forensic typing analysis. The process requires as few as 8 cells and produces sufficient material for up to 20,000 subsequent PCR reactions. The technique is particularly useful to enhance current methods of latent print analysis and has been shown to be compatible with common forensic print visualization and removal techniques including dye staining and powders.
Date: November 20, 2003
Creator: Turteltaub, K; Sorensen, K; Christian, A; Williams, J & Vrankovich, G
System: The UNT Digital Library
Towards Perceptual Interface for Visualization Navigation of Large Data Sets Using Gesture Recognition with Bezier Curves and Registered 3-D Data (open access)

Towards Perceptual Interface for Visualization Navigation of Large Data Sets Using Gesture Recognition with Bezier Curves and Registered 3-D Data

This paper presents a gesture recognition system for visualization navigation. Scientists are interested in developing interactive settings for exploring large data sets in an intuitive environment. The input consists of registered 3-D data. A geometric method using Bezier curves is used for the trajectory analysis and classification of gestures. The hand gesture speed is incorporated into the algorithm to enable correct recognition from trajectories with variations in hand speed. The method is robust and reliable: correct hand identification rate is 99.9% (from 1641 frames), modes of hand movements are correct 95.6% of the time, recognition rate (given the right mode) is 97.9%. An application to gesture-controlled visualization of 3D bioinformatics data is also presented.
Date: March 20, 2003
Creator: Shin, M C; Tsap, L V & Goldgof, D B
System: The UNT Digital Library
UAV Cooperation Architectures for Persistent Sensing (open access)

UAV Cooperation Architectures for Persistent Sensing

With the number of small, inexpensive Unmanned Air Vehicles (UAVs) increasing, it is feasible to build multi-UAV sensing networks. In particular, by using UAVs in conjunction with unattended ground sensors, a degree of persistent sensing can be achieved. With proper UAV cooperation algorithms, sensing is maintained even though exceptional events, e.g., the loss of a UAV, have occurred. In this paper a cooperation technique that allows multiple UAVs to perform coordinated, persistent sensing with unattended ground sensors over a wide area is described. The technique automatically adapts the UAV paths so that on the average, the amount of time that any sensor has to wait for a UAV revisit is minimized. We also describe the Simulation, Tactical Operations and Mission Planning (STOMP) software architecture. This architecture is designed to help simulate and operate distributed sensor networks where multiple UAVs are used to collect data.
Date: March 20, 2003
Creator: Roberts, R. S.; Kent, C. A. & Jones, E. D.
System: The UNT Digital Library
SYMMETRIC TEXTURES IN SO(10) AND LMA SOLUTION FOR SOLAR NEUTRINOS. (open access)

SYMMETRIC TEXTURES IN SO(10) AND LMA SOLUTION FOR SOLAR NEUTRINOS.

A model based on SUSY SO(10) combined with SU(2) family symmetry is constructed. In contrast with the commonly used effective operator approach, 126-dimensional Higgs fields are utilized to construct the Yukawa sector. R-parity symmetry is thus preserved at low energies. The symmetric mass textures arising from the left-right symmetry breaking chain of SO(10) give rise to very good predictions for quark and lepton masses and mixings. The prediction for sin2{beta} agrees with the average of current bounds from BaBar and Belle. In the neutrino sector, our predictions are in good agreement with results from atmospheric neutrino experiments. Our model accommodates the LMA solution to the solar neutrino anomaly. The prediction of our model for the |U{sub ev{sub 3}}| element in the MNS matrix is close to the sensitivity of current experiments; thus the validity of our model can be tested in the near future. We also investigate the correlation between the |U{sub ev{sub 3}}| element and tan{sup 2} {theta}{sub {circle_dot}} in a general two-zero neutrino mass texture.
Date: July 20, 2003
Creator: CHEN,M. C. MAHANTHAPPA,K. T.
System: The UNT Digital Library
Laboratory Wavelengths of K-Shell Resonance Lines of O V and O VI (open access)

Laboratory Wavelengths of K-Shell Resonance Lines of O V and O VI

We present wavelength measurements of K-shell resonance lines of O V and O VI, using the University of California Lawrence Livermore National Laboratory EBIT-I electron beam ion trap. The wavelength accuracy of better than 140 ppm is sufficient to determine gas outflow velocities of warm absorbers associated with AGNs to within 40 km/s and better. Our measurements confirm that the outflow velocities associated with NGC 5548 and derived from O V and O VI lines are similar to those derived from the O VII lines. These kinematic measurements make for further evidence that the X-ray and UV absorbers in these systems are truly two manifestations of the same physical outflow.
Date: November 20, 2003
Creator: Beiersdorfer, Peter; Chen, Hui; Schmidt, Mike; Behar, Ehud; Trabert, Elmar & Thorn, Daniel B.
System: The UNT Digital Library
Initial Activation and Operation of the Power Conditioning System for the National Ignition Facility (open access)

Initial Activation and Operation of the Power Conditioning System for the National Ignition Facility

The NIF Power Conditioning System (PCS) resides in four Capacitor Bays, supplying energy to the Master and Power Amplifiers which reside in the two adjacent laser bays. Each capacitor bay will initially house 48 individual power conditioning modules, shown in Figure 2, with space reserved for expansion to 54 modules. The National Ignition Facility (NIF) Power Conditioning System (PCS) is a modular capacitive energy storage system that will be capable of storing nearly 400 MJ of electrical energy and delivering that energy to the nearly 8000 flashlamps in the NIF laser. The first sixteen modules of the power conditioning system have been built, tested and installed. Activation of the first nine power conditioning modules has been completed and commissioning of the first ''bundle'' of laser beamlines has begun. This paper will provide an overview of the power conditioning system design and describe the status and results of initial testing and activation of the first ''bundle'' of power conditioning modules.
Date: August 20, 2003
Creator: Newton, M A; Kamm, R E; Fulkerson, E S; Hulsey, S D; Lao, N; Parrish, G L et al.
System: The UNT Digital Library
A method for repairing amplitude defects in multilayer-coated EUV mask blanks (open access)

A method for repairing amplitude defects in multilayer-coated EUV mask blanks

EUV mask blanks are fabricated by depositing a reflective Mo/Si multilayer film onto super-polished substrates. Localized defects in this thin film coating can significantly perturb the reflected field and produce errors in the printed image. Ideally one would want to manufacture defect-free mask blanks; however, this may be very difficult to achieve in practice. One practical way to increase the yield of mask blanks is to be able to repair a significant number of the defects in the multilayer coating. In this paper we present a method for repairing defects that are near the top surface of the coating; we call these amplitude defects because they predominantly attenuate the amplitude of the reflected field. Although the discussion is targeted to the application of manufacturing masks for EUV lithography, the conclusions and results are also applicable to understanding the optical effects of multilayer erosion, including ion-induced multilayer erosion and condenser erosion in EUVL steppers.
Date: October 20, 2003
Creator: Barty, A.; Hau-Riege, S.; Stearns, D.; Clift, M.; Mirkarimi, P.; Gullikson, E. et al.
System: The UNT Digital Library
Deflagration Behavior of HMX-Based Explosives at High Temperatures and Pressures (open access)

Deflagration Behavior of HMX-Based Explosives at High Temperatures and Pressures

We report the deflagration behavior of several HMX-based explosives at pressure from 10-600 MPa and temperatures from 20-180 C. We have made laminar burn rate measurements with the LLNL High Pressure Strand Burner, in which burn wires are used to record the time-of-arrival of the burn front in the cylindrical sample as a function of pressure. The explosive samples are 6.4 mm in diameter and 63 mm long, with ten burn wires embedded at different positions in the sample. Burning on the cylindrical surface is inhibited with an epoxy layer. With this direct measurement we do not have to account for product gas equation of state or heat losses in the system, and the burn wires allow detection of irregular burning. We find that formulation details are very important to overall deflagration behavior - the presence of 10% or less by weight of binder leads to physical deconsolidation and rapid deflagration at high pressures, and a larger particle size distribution leads to slower deflagration. High temperatures have a relatively minor effect on the deflagration rate until the beta-to-delta phase transition temperature is reached, beyond which the deflagration rate increases approximately 40-fold.
Date: November 20, 2003
Creator: Maienschein, J L & Wardell, J F
System: The UNT Digital Library
Modeling of Stress Corrosion Cracking for High Level Radioactive-Waste Packages (open access)

Modeling of Stress Corrosion Cracking for High Level Radioactive-Waste Packages

A stress corrosion cracking (SCC) model has been adapted for performance prediction of high level radioactive-waste packages to be emplaced in the proposed Yucca Mountain radioactive-waste repository. SCC is one form of environmentally assisted cracking due to three factors, which must be present simultaneously: metallurgical susceptibility, critical environment, and static (or sustained) tensile stresses. For waste packages of the proposed Yucca Mountain repository, the outer barrier material is Alloy 22, a highly corrosion resistant alloy, the environment is represented by the water film present on the surface of the waste package from dripping or deliquescence of soluble salts present in any surface deposits, and the stress is principally the weld induced residual stress. SCC has historically been separated into ''initiation'' and ''propagation'' phases. Initiation of SCC will not occur on a smooth surface if the surface stress is below a threshold value defined as the threshold stress. Cracks can also initiate at and propagate from flaws (or defects) resulting from manufacturing processes (such as welding). To account for crack propagation, the slip dissolution/film rupture (SDFR) model is adopted to provide mathematical formulas for prediction of the crack growth rate. Once the crack growth rate at an initiated SCC is determined, …
Date: June 20, 2003
Creator: Lu, S C; Gordon, G M; Andresen, P L & Herrera, M L
System: The UNT Digital Library
On the transition rates of the Fe X and Fe XIV corona lines (open access)

On the transition rates of the Fe X and Fe XIV corona lines

Despite a considerable scatter of the theoretical predictions of the M1/E2 transition rate of the ''red iron line'' (FeX) in the solar corona, there is disagreement of all the results with the single measurement that used an electrostatic ion trap. Employing a heavy-ion storage ring for measuring the same transition in isoelectronic ions of Co, Ni, and Cu, the situation has been clarified, and a new data point for FeX can be determined by extrapolation. This result agrees with the basic atomic structure prediction for the line strength in combination with the experimental transition energy. For the ''green iron line'' (FeXIV), a recent measurement with an electron beam ion trap has resolved similar discrepancies.
Date: November 20, 2003
Creator: Trabert, E
System: The UNT Digital Library
Time-Domain Tools for the Investigation of Gain-Quenched Laser Logic (open access)

Time-Domain Tools for the Investigation of Gain-Quenched Laser Logic

Integrated all-optical logic gates that exploit the optical gain quenching effect in laterally optically pumped semiconductor multi-section edge-emitting lasers (SMEELs) are described. An accurate 2D time-domain (TD) model was implemented to investigate the gates' gain, modulation depth, and speed. Gain Quenched Laser Logic (GQLL) offer the potential of integrating several processing functions on the same chip and has many applications for all-optical high-speed switching. Lasers with optical gain control capable of routing and logic functions have been demonstrated via the gain quenching effect. In an inverter gate the laser output power is quenched when an optical input signal laterally coupled to the laser (control region) is high. NOR and NAND gates are achievable by adding other arms. The basic configuration of a GQLL device is schematically depicted in Fig. 1 . The Boolean completeness of this technology, the recent achievement in high laser modulation bandwidths, and the possibility of integrating lasers and passive waveguide interconnects progress using standard microelectronics fabrication techniques, makes GQLL the basis for a high-speed photonic logic family.
Date: August 20, 2003
Creator: Bond, T C & Kallman, J K
System: The UNT Digital Library
Stress-Strain Rate Relations in Ultra High Carbon Steels Deformed in the Ferrite Range of Temperature (open access)

Stress-Strain Rate Relations in Ultra High Carbon Steels Deformed in the Ferrite Range of Temperature

The stress-strain rate relations in ultrahigh carbon steels (UHCSs) have been analyzed at high temperatures in the ferrite range where dislocation slip is the principal deformation mechanism. Specifically, the present investigation centers on the factors influencing the strength of UHCS in the ferrite range of 500 to 700 C and in the strain rate range of 10{sup -3} to 10{sup 3} s{sup -1}. These steels contain iron carbide as a second phase either in the form of spheroidite or pearlite and vary in the grain size according to the processing history. The new variables that need to be taken into account are the effect of ferromagnetism and its change with temperature on the creep strength of the ferritic UHCSs. Recent studies have shown that ferromagnetism strongly influences the lattice and dislocation pipe diffusion coefficient and the elastic modulus of iron in the ferrite range of temperature. These variables are shown to influence the creep strength of ferrite-base steels and explain the high activation energies that are observed in many of the ferritic UHCSs.
Date: February 20, 2003
Creator: Syn, C K; Lesuer, D R; Sherby, O D & Taleff, E M
System: The UNT Digital Library
Photonuclear Benchmarks with a Comparison of COG and MCNPX Results (open access)

Photonuclear Benchmarks with a Comparison of COG and MCNPX Results

The Nuclear Data Section of the International Atomic Energy Agency (IAEA) has distributed an evaluated photonuclear data library in standard ENDF-6 format that is intended for use in transport codes. This ''IAEA Photonuclear Data Library'' consists of a number of individual ASCII text files for various elements that have been recently processed into the single binary (COG data library) file ''COGPNUC'' with corresponding changes to the COG code for use in transport calculations involving photonuclear reactions.
Date: October 20, 2003
Creator: Heinrichs, D P & Lent, E M
System: The UNT Digital Library
A Model and Controller Reduction Method for Robust Control Design (open access)

A Model and Controller Reduction Method for Robust Control Design

A bifurcation subsystem based model and controller reduction approach is presented. Using this approach a robust {micro}-synthesis SVC control is designed for interarea oscillation and voltage control based on a small reduced order bifurcation subsystem model of the full system. The control synthesis problem is posed by structured uncertainty modeling and control configuration formulation using the bifurcation subsystem knowledge of the nature of the interarea oscillation caused by a specific uncertainty parameter. Bifurcation subsystem method plays a key role in this paper because it provides (1) a bifurcation parameter for uncertainty modeling; (2) a criterion to reduce the order of the resulting MSVC control; and (3) a low order model for a bifurcation subsystem based SVC (BMSVC) design. The use of the model of the bifurcation subsystem to produce a low order controller simplifies the control design and reduces the computation efforts so significantly that the robust {micro}-synthesis control can be applied to large system where the computation makes robust control design impractical. The RGA analysis and time simulation show that the reduced BMSVC control design captures the center manifold dynamics and uncertainty structure of the full system model and is capable of stabilizing the full system and achieving satisfactory …
Date: October 20, 2003
Creator: Yue, M. & Schlueter, R.
System: The UNT Digital Library
Heavy Ion Fusion Sources (open access)

Heavy Ion Fusion Sources

None
Date: May 20, 2003
Creator: Grote, D P; Westenskow, G & Kwan, J
System: The UNT Digital Library
Tissue architecture: the ultimate regulator of breast epithelial function (open access)

Tissue architecture: the ultimate regulator of breast epithelial function

A problem in developmental biology that continues to take center stage is how higher organisms generate diverse tissues and organs given the same cellular genotype. In cell and tumor biology, the key question is not the production of form, but its preservation: how do tissues and organs maintain homeostasis, and how do cells within tissues lose or overcome these controls in cancer? Undoubtedly, mechanisms that maintain tissue specificity should share features with those employed to drive formation of the tissues. However, they are unlikely to be identical. At a simplistic level, developmental pathways may be thought of as a series of extremely rapid short-term events. Each new step depends on what came before, and the outcome is the organism itself at birth. All organs, with a few notable exceptions, such as the mammary gland and the brain, 'arrive' together and are complete when the organism is born. In mice and humans, these events occur in a mere 21 days and 9 months respectively. The stability of the differentiated state and the homeostasis of the organism, on the other hand, will last 40-110 times longer. How does the organism achieve this feat? How are tissues maintained? These questions also relate fundamentally …
Date: October 20, 2003
Creator: Bissell, Mina J; Rizki, Aylin & Mian, Saira
System: The UNT Digital Library
Supergravity Analysis of Hybrid Inflation Model from D3--D7 System (open access)

Supergravity Analysis of Hybrid Inflation Model from D3--D7 System

The slow-roll inflation is a beautiful paradigm, yet the inflaton potential can hardly be sufficiently flat when unknown gravitational effects are taken into account. However, the hybrid inflation models constructed in D = 4 N = 1 supergravity can be consistent with N = 2 supersymmetry, and can be naturally embedded into string theory. This article discusses the gravitational effects carefully in the string model, using D = 4 supergravity description. We adopt the D3--D7 system of Type IIB string theory compactified on K3 x T^2/Z_2 orientifold for definiteness. It turns out that the slow-roll parameter can be sufficiently small despite the non-minimal Kahler potential of the model. The conditions for this to happen are clarified in terms of string vacua. We also find that the geometry obtained by blowing up singularity, which is necessary for the positive vacuum energy, is stabilized by introducing certain 3-form fluxes.
Date: November 20, 2003
Creator: Koyama, Fumikazu; Tachikawa, Yuji & Watari, Taizan
System: The UNT Digital Library
Hard processes in hadron-nucleus and nucleus-nucleusinteractions (open access)

Hard processes in hadron-nucleus and nucleus-nucleusinteractions

None
Date: February 20, 2003
Creator: Satz (Ed.), H. & Wang (Ed.), X.-N.
System: The UNT Digital Library
Pulse shape and spectrum of coherent diffraction-limited transition radiation from electron beams (open access)

Pulse shape and spectrum of coherent diffraction-limited transition radiation from electron beams

The electric field in the temporal and spectral domain of coherent diffraction-limited transition radiation is studied. An electron bunch, with arbitrary longitudinal momentum distribution, propagating at normal incidence to a sharp metal-vacuum boundary with finite transverse dimension is considered. A general expression for the spatiotemporal electric field of the transition radiation is derived, and closed-form solutions for several special cases are given. The influence of parameters such as radial boundary size, electron momentum distribution, and angle of observation on the waveform (e.g., radiation pulse length and amplitude) are discussed. For a Gaussian electron bunch, the coherent radiation waveform is shown to have a single-cycle profile. Application to a novel THz source based on a laser-driven accelerator is discussed.
Date: December 20, 2003
Creator: van Tilborg, J.; Schroeder, C. B.; Esarey, E. & Leemans, W. P.
System: The UNT Digital Library