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Finite laser beam particle simulations of beat wave acceleration show that a coherent plasma wave excited by two colinear laser beams at a difference frequency equal to the plasma frequency can produce maximum electron energies as... more
Finite laser beam particle simulations of beat wave acceleration show that a coherent plasma wave excited by two colinear laser beams at a difference frequency equal to the plasma frequency can produce maximum electron energies as predicted by simple one dimensional theory. The time to saturation amplitude of the plasma wave electric field agrees with the Rosenbluth-Liu theory. Stimulated Raman
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Two-dimensional particle simulations with a finite laser beam show that beat wave acceleration can produce energetic electrons as seen in one-dimensional simulations. The competition and interplay between various nonlinear phenomena --... more
Two-dimensional particle simulations with a finite laser beam show that beat wave acceleration can produce energetic electrons as seen in one-dimensional simulations. The competition and interplay between various nonlinear phenomena -- backward Raman scattering, stimulated Compton scattering, self-focussing, filamentation, and harmonic generation -- were delineated through the two-dimensional simulations.
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Los Alamos National Laboratory has developed a virtual patient record system called TeleMed which is based on a distributed national radiographic and patient record repository located throughout the country. Without leaving their offices,... more
Los Alamos National Laboratory has developed a virtual patient record system called TeleMed which is based on a distributed national radiographic and patient record repository located throughout the country. Without leaving their offices, participating doctors can view clinical drug and radiographic data via a sophisticated multimedia interface. For example, a doctor can match a patient`s radiographic information with the data in the repository, review treatment history and success, and then determine the best treatment. Furthermore, the features of TeleMed that make it attractive to clinicians and diagnosticians make it valuable for teaching and presentation as well. Thus, a resident can use TeleMed for self-training in diagnostic techniques and a physician can use it to explain to a patient the course of their illness. In fact, the data can be viewed simultaneously by users at two or more distant locations for consultation with specialists in different fields. This capability is o...
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One of the most powerful tools available for telemedicine is a multimedia medical record accessible over a wide area and simultaneously editable by multiple physicians. The ability to do this through an intuitive interface linking... more
One of the most powerful tools available for telemedicine is a multimedia medical record accessible over a wide area and simultaneously editable by multiple physicians. The ability to do this through an intuitive interface linking multiple distributed data repositories while maintaining full data integrity is a fundamental enabling technology in healthcare. The author discusses the role of distributed object technology using CORBA in providing this capability including an example of such a system (TeleMed) which can be accessed through the World Wide Web. Issues of security, scalability, data integrity, and useability are emphasized.
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The interaction between an intense laser and an underdense plasma results in many different phenomena. In particular, the interaction may result in collective processes called parametric instabilities, some of which produce plasma... more
The interaction between an intense laser and an underdense plasma results in many different phenomena. In particular, the interaction may result in collective processes called parametric instabilities, some of which produce plasma waves1,2,3. The plasma waves can eventually produce energetic electrons as they damp away their energy. The generation of energetic electrons is detrimental for laser fusion4, essential for plasma particle accelerators5 and essential in current drive in tokamaks6, to name a few subject areas.
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Copious microwaves are emitted when sufficiently intense, pulsed radiation from the Antares COâ laser was impinged on a cylindrical polyethylene. The microwaves omitted were investigated as to pulse width and power spectrum in the... more
Copious microwaves are emitted when sufficiently intense, pulsed radiation from the Antares COâ laser was impinged on a cylindrical polyethylene. The microwaves omitted were investigated as to pulse width and power spectrum in the frequency range of 26 to 40 GHz. As the COâ laser excels in the production of hard x-rays, Helios and Antares data on high-Z targets are
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The absorption of intense laser light by a plasma is known to produce a high-energy component of electrons. Even though the hot-electron pressure may be larger than the cold-background pressure, the background temperature can control the... more
The absorption of intense laser light by a plasma is known to produce a high-energy component of electrons. Even though the hot-electron pressure may be larger than the cold-background pressure, the background temperature can control the self-consistent profile modification. Since temperatures in high-intensity experiments seem to be similar for CO2 and Nd glass lasers, the profile modification may be so
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The infinity of roots for real wave number and complex frequency of the dispersion relation for transverse electromagnetic waves propagating in a thermal plasma parallel to an applied magnetic field are studied theoretically and observed... more
The infinity of roots for real wave number and complex frequency of the dispersion relation for transverse electromagnetic waves propagating in a thermal plasma parallel to an applied magnetic field are studied theoretically and observed in numerical simulations. In addition to the usual weakly damped whistler and ion cyclotron roots, there are infinitely many more heavily damped electron (ion) roots characterized by real frequency near the gyrofrequency and damping rate proportional to the wave number. The electron modes have been observed in a thermal electromagnetic numerical simulation plasma, and their dispersion agrees well with finite-temperature linear theory. These modes may be observable experimentally.
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ABSTRACT A CO2 laser was used to irradiate hollow polystyrene cylinders along their axis. The laser-generated high-energy electrons appear to uniformly heat the cylinder throughout its volume and the cylinder explodes. The imploding and... more
ABSTRACT A CO2 laser was used to irradiate hollow polystyrene cylinders along their axis. The laser-generated high-energy electrons appear to uniformly heat the cylinder throughout its volume and the cylinder explodes. The imploding and stagnation character of the exploding cylinder gives rise to a long x-ray pulse, much longer than the laser pulse, and to a peak emission that occurs after the laser pulse. The fast ions that are generated appear not to interact with the thermal plasma. Two-dimensional calculations that reproduce much of the experimental x-ray signature and observed hydrodynamic flow are presented.
The Rapid Syndrome Validation Project (RSVP) is a collaboration of several institutions: Sandia and Los Alamos National Laboratories, the University of New Mexico Department of Emergency Medicine, and the NM Department of Health Office of... more
The Rapid Syndrome Validation Project (RSVP) is a collaboration of several institutions: Sandia and Los Alamos National Laboratories, the University of New Mexico Department of Emergency Medicine, and the NM Department of Health Office of Epidemiology. RSVP is a system that operates at the intersection of individual health care providers, public health and bioterrorism. Physicians quickly enter clinical and demographic information on patients exhibiting symptoms and signs of the syndromes of interest. It provides early warning and response to emerging biological threats, as well as emerging epidemics and diseases. RSVP provides real time clinical information to the provider and any other potential user such as the DOH, about current symptoms, disease prevalence and location. The system also serves as a mechanism for the Department of Health to inform health care providers of health alerts and to facilitate the process of collecting data on reportable diseases. We describe here the p...
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One of the most powerful tools available for telemedicine is a multimedia medical record accessible over a wide area and simultaneously editable by multiple physicians. The ability to do this through an intuitive interface linking... more
One of the most powerful tools available for telemedicine is a multimedia medical record accessible over a wide area and simultaneously editable by multiple physicians. The ability to do this through an intuitive interface linking multiple distributed data repositories while maintaining full data integrity is a fundamental enabling technology in healthcare. We discuss the role of distributed object technology using Java and CORBA in providing this capability including an example of such a system (TeleMed) which can be accessed through the World Wide Web. Issues of security, scalability, data integrity, and usability are emphasized.
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Although C++ has been successfully used in a variety of computer science applications, it has just recently begun to be used in scientific applications. We have found that the object-oriented properties of C++ lend themselves well to... more
Although C++ has been successfully used in a variety of computer science applications, it has just recently begun to be used in scientific applications. We have found that the object-oriented properties of C++ lend themselves well to scientific computations by making maintenance of the code easier, by making the code easier to understand, and by providing a better paradigm for
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In the rather general analysis presented, the pump wave is self-consistently calculated. The full electromagnetic wave equations are used in the study of the excited waves. It is pointed out that there is an exchange of energy between the... more
In the rather general analysis presented, the pump wave is self-consistently calculated. The full electromagnetic wave equations are used in the study of the excited waves. It is pointed out that there is an exchange of energy between the pump and the excited wave after the initial saturation due to pump depletion. The ion wave develops secondary maxima which propagate down the density gradient.
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It is pointed out that the set of languages used to program supercomputers has evolved from hand-coded assembler and partially vectorized Fortran to include such diverse possibilities as C++, Sisal, and even Ada. It is noted that... more
It is pointed out that the set of languages used to program supercomputers has evolved from hand-coded assembler and partially vectorized Fortran to include such diverse possibilities as C++, Sisal, and even Ada. It is noted that proponents of these languages are often fanatical in their support, attempting to share the obvious advantages of a particular language with their skeptical
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Electrons heated by absorption of laser energy are shown to generate intense magnetic fields which rapidly spread from the edge of the laser spot along the target surface. The fields convectively transport hot electrons and confine a... more
Electrons heated by absorption of laser energy are shown to generate intense magnetic fields which rapidly spread from the edge of the laser spot along the target surface. The fields convectively transport hot electrons and confine a major fraction of the deposited laser energy in the corona. Eventually, this energy is lost to fast-ion blowoff or deposited at large distances from the spot. This model qualitatively explains many experimental observations of thermal-transport inhibition and fast-ion loss.
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A simple model involving resonant absorption in a self-consistent sharp density gradient is found to be in quantitative agreement with the suprathermal-electron spectrum from recent laser-plasma--interaction experiments and to explain... more
A simple model involving resonant absorption in a self-consistent sharp density gradient is found to be in quantitative agreement with the suprathermal-electron spectrum from recent laser-plasma--interaction experiments and to explain qualitatively the scaling of that suprathermal-electron spectrum with laser power and wavelength.
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The long-term absorption and scattering of light obliquely incident on an inhomogeneous and self-consistent evolving plasma profile including differential ion flow is considered. In general, the plasma has a sharp rise in density from... more
The long-term absorption and scattering of light obliquely incident on an inhomogeneous and self-consistent evolving plasma profile including differential ion flow is considered. In general, the plasma has a sharp rise in density from subcritical to supercritical. The subcritical density decreases for increasing radiation pressure relative to the plasma pressure. In this profile an instability develops of the radiating decay type which modulates and generally enhances the absorption. The plasma density profile appears to evolve toward large light absorption.
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Electrons heated by absorption of laser energy are shown to generate intense magnetic fields which rapidly spread from the edge of the laser spot along the target surface. The fields convectively transport hot electrons and confine a... more
Electrons heated by absorption of laser energy are shown to generate intense magnetic fields which rapidly spread from the edge of the laser spot along the target surface. The fields convectively transport hot electrons and confine a major fraction of the deposited laser energy in the corona. Eventually, this energy is lost to fast-ion blowoff or deposited at large distances from the spot. This model qualitatively explains many experimental observations of thermal-transport inhibition and fast-ion loss.
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A simple model involving resonant absorption in a self-consistent sharp density gradient is found to be in quantitative agreement with the suprathermal-electron spectrum from recent laser-plasma--interaction experiments and to explain... more
A simple model involving resonant absorption in a self-consistent sharp density gradient is found to be in quantitative agreement with the suprathermal-electron spectrum from recent laser-plasma--interaction experiments and to explain qualitatively the scaling of that suprathermal-electron spectrum with laser power and wavelength.