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Hot-electron-ring physics (open access)

Hot-electron-ring physics

Separate abstracts were prepared for each of the 16 included papers. (MOW)
Date: June 1, 1982
Creator: Uckan, N.A. (ed.)
System: The UNT Digital Library
Recent US target-physics-related research in heavy-ion inertial fusion: simulations for tamped targets and for disk experiments in accelerator test facilities (open access)

Recent US target-physics-related research in heavy-ion inertial fusion: simulations for tamped targets and for disk experiments in accelerator test facilities

Within the last few years, there have also appeared in the Heavy-Ion Fusion literature several studies of targets which have outer tampers. One-dimensional simulations indicate higher target gains with a judicious amount of tamping. But for these targets, a full investigation has not been carried through in regards to conservative criteria for fluid instabilities as well as reasonable imperfections in target fabrication and illumination symmetry which all affect target ignition and burn. Comparisons of these results with the gain survey of Part I would have to be performed with care. These calculations suggest that experiments relating to high temperature disk heating, as well as beam deposition, focusing and transport can be performed within the context of current design proposals for accelerator test-facilities. Since the test-facilities have lower ion kinetic energy and beam pulse power as compared to reactor drivers, we achieve high-beam intensities at the focal spot by using short focal distance and properly designed beam optics.
Date: June 24, 1982
Creator: Mark, J.W.K.
System: The UNT Digital Library
Molecular ingredients of heterogeneous catalysis (open access)

Molecular ingredients of heterogeneous catalysis

The purpose of this paper is to present a review and status report to those in theoretical chemistry of the rapidly developing surface science of heterogeneous catalysis. The art of catalysis is developing into science. This profound change provides one with opportunities not only to understand the molecular ingredients of important catalytic systems but also to develop new and improved catalyst. The participation of theorists to find answers to important questions is sorely needed for the sound development of the field. It is the authors hope that some of the outstanding problems of heterogeneous catalysis that are identified in this paper will be investigated. For this purpose the paper is divided into several sections. The brief Introduction to the methodology and recent results of the surface science of heterogeneous catalysis is followed by a review of the concepts of heterogeneous catalysis. Then, the experimental results that identified the three molecular ingredients of catalysis, structure, carbonaceous deposit and the oxidation state of surface atoms are described. Each section is closed with a summary and a list of problems that require theoretical and experimental scrutiny. Finally attempts to build new catalyst systems and the theoretical and experimental problems that appeared in the …
Date: June 1, 1982
Creator: Somorjai, G.A.
System: The UNT Digital Library
Fractional charge search (open access)

Fractional charge search

A device to search for fractional charge in matter is described. The sample is coupled to a low-noise amplifier by a periodically varying capacitor and the resulting signal is synchronously detected. The varying capacitor is constructed as a rapidly spinning wheel. Samples of any material in volumes of up to 0.05 ml may be searched in less than an hour.
Date: June 1, 1982
Creator: Innes, W.; Klein, S.; Perl, M. & Price, J.C.
System: The UNT Digital Library
Design of neutron streak camera for fusion diagnostics (open access)

Design of neutron streak camera for fusion diagnostics

The D-T burn time for advanced laser-fusion targets is calculated to be very short, < 50 ps. We describe the design of a neutron streak camera of 16 ps resolving time that can be used to study the temporal history of fusion burn. The cathode of the neutron streak camera is sensitive to neutrons and is curved such that the difference in the neutron path lengths from a point source to various parts of the cathode is compensated by electron transit times within the streak tube. Thus the cathode can be made large for high sensitivity, without sacrificing time resolution. The cathode is coated with 1 ..mu..m UO/sub 2/. Each fission fragment leaving the cathode generates 400 secondary electrons that are all < 20 eV. These electrons are focussed to a point with an extractor and an anode, and are then purified with an electrostatic deflector. The electron beam is streaked and detected with the standard streak camera techniques. Careful shielding is needed for x-rays from the fusion target and general background. It appears that the neutron streak camera can be a viable and unique tool for studying temporal history of fusion burns in D-T plasmas of a few keV …
Date: June 1, 1982
Creator: Wang, C. L.; Kalibjian, R. & Singh, M. S.
System: The UNT Digital Library
Formation of a quark-gluon plasma in nuclear collisions (open access)

Formation of a quark-gluon plasma in nuclear collisions

The spatial dependence of the energy deposition in the fragmentation regions is estimated for nuclear collisions at ISR energies, ..sqrt..s/A >approx. 30 GeV/nucleon. Two models (the trailing cascade and sequential decay scenarios) are contrasted. The results are compared to the quark-gluon plasma energy density computed via QCD lattice methods.
Date: June 1, 1982
Creator: Gyulassy, M.
System: The UNT Digital Library
Hot-electron-ring physics (open access)

Hot-electron-ring physics

Separate abstracts were prepared for each of the 24 included papers. The remaining paper appeared previously in ERA. (MOW)
Date: June 1, 1982
Creator: Uckan, N.A. (ed.)
System: The UNT Digital Library
Electron energy distributions, vibrational population distributions, and negative-ion concentrations in hydrogen discharges (open access)

Electron energy distributions, vibrational population distributions, and negative-ion concentrations in hydrogen discharges

We consider the negative ion concentrations in hydrogen discharges caused by electron excitation and dissociative attachment processes. The principal formation and destruction processes are discussed for electron densities in the range 10/sup 8/ to 10/sup 13/ electrons cm/sup -3/. Expressions are developed for calculating the high energy portion of the electron energy distribution in the discharge; using these energy distributions the electron excitation rates are evaluated. At low densities, the vibrational distribution arises from singlet electronic excitations and triplet excitations through the /sup 3/..pi../sub u/ state, in equilibrium with wall de-excitation processes. At high densities singlet excitations predominate in equilibrium with atom-molecule de-excitation processes. Possibilities for negative ion generation in a two-chamber tandem system are discussed in which the vibrational excitation occurs in a high power, high electron temperature discharge, kT/sub e/ = 5 eV, and dissociative attachment occurs in a low temperature kT/sub e/ = 1 eV, plasma chamber.
Date: June 28, 1982
Creator: Hiskes, J.R. & Karo, A.M.
System: The UNT Digital Library
Preliminary results on nu/sub. mu. / + e/sup -/. -->. nu/sub. mu. / + e/sup -/ (open access)

Preliminary results on nu/sub. mu. / + e/sup -/. -->. nu/sub. mu. / + e/sup -/

We present here preliminary results on a recent experiment on nu/sub ..mu../ - e/sup -/ elastic scattering. A brief review of the Glashow-Salam-Weinberg theory is given, indicating how the measurement of the total cross section gives rise to an ambiguous solution for sin/sup 2/ THETA/sub w/, and showing how the differential cross section can be used to resolve the ambiguity. The experimental configuration and the extraction of the signal are described. The data are compared with those from our previous experiment, and relevant distributions from the combined data sample are presented. The differential cross section is examined in an attempt to resolve the ambiguity in sin/sup 2/ THETA/sub w/, the lower value of sin/sup 2/ THETA/sub w/ = 0.20 being favored.
Date: June 1, 1982
Creator: Baker, N.J.; Connolly, P.L. & Kahn, S.A.
System: The UNT Digital Library
R and D in the FY 1983 budget: impacts on the national laboratories (open access)

R and D in the FY 1983 budget: impacts on the national laboratories

A report on the impact upon LBL of the policy changes and budget actions in Department of Energy programs since early 1981 is given, and some views are given on more general problems that appear to underlie the interaction between the federal government, which supports research, and the scientific community, which performs it. (WHK)
Date: June 1, 1982
Creator: Shirley, D.A.
System: The UNT Digital Library
NTD germanium: a novel material for low-temperature bolometers (open access)

NTD germanium: a novel material for low-temperature bolometers

Six samples of ultra-pure (absolute value N/sub A/ - N/sub D/ absolute value less than or equal to 10/sup 11/cm/sup -3/), single-crystal germanium have been neutron transmutation doped with neutron doses between 7.5 x 10/sup 16/ and 1.88 x 10/sup 18/cm/sup -2/. After thermal annealing at 400/sup 0/C for six hours in a pure argon atmosphere, the samples have been characterized with Hall effect and resistivity measurements between 300 and 0.3 K. Our results show that the resistivity in the low temperature, hopping conduction regime can be approximated with rho = rho/sub 0/exp(..delta../T). The three more heavily doped samples show values for rho/sub 0/ and ..delta.. ranging from 430 to 3.3 ..cap omega.. cm and from 4.9 to 2.8 K, respectively. The excellent reproducibility of neutron transmutation doping and the values of rho/sub 0/ and ..delta.. make NTD Ge a prime candidate for the fabrication of low temperature, low noise bolometers. The large variation in the tabulated values of the thermal neutron cross sections for the different germanium isotopes makes it clear that accurate measurements of these cross-sections for well defined neutron energy spectra would be highly desirable.
Date: June 1, 1982
Creator: Haller, E. E.; Palaio, N. P.; Rodder, M.; Hansen, W. L. & Kreysa, E.
System: The UNT Digital Library
Non-rigid molecular group theory and its applications (open access)

Non-rigid molecular group theory and its applications

The use of generalized wreath product groups as representations of symmetry groups of nonrigid molecules is considered. Generating function techniques are outlined for nuclear spin statistics and character tables of the symmetry groups of nonrigid molecules. Several applications of nonrigid molecular group theory to NMR spectroscopy, rovibronic splitting and nuclear spin statistics of nonrigid molecules, molecular beam deflection and electric resonance experiments of weakly bound Van der Waal complexes, isomerization processes, configuration interaction calculations and the symmetry of crystals with structural distortions are described. 81 references.
Date: June 1, 1982
Creator: Balasubramanian, K.
System: The UNT Digital Library
Radiation enhancement with /sup 127/I-deoxyuridine (open access)

Radiation enhancement with /sup 127/I-deoxyuridine

A technique for radiation enhancement of photon radiotherapy is outlined. High LET radiations in the form of Auger electron distributions are generated by photoactivation of stable iodine incorporated as iodinated deoxyuridine (IdUrd). Of the several halogenated deoxyribonucleosides evaluated, IdUrd was found to be the only thymidine analog providing effective photoactivation. This mechanism is combined with radiation sensitization to produce an overall radiation enhancement. Calculations show that 5% replacement of Tyd in tumor DNA should multiply the biological effectiveness of low energy photons by a factor of approx. 2. Higher replacements would provide higher gains. Enhancement results from chemical sensitization by IdUrd, where it is known that effects of irradiation are multiplied by factors of from approx. 1.5 to 3 as replacement varies from 10 to 50%. Additional enhancement results from the stimulation of Auger cascades in DNA. Five percent replacement has been obtained in human tumor in vivo. Twice that has been obtained in murine tumors. Our data indicates that damage from photoactivation as well as chemical sensitization does not repair. Thus, it is anticipated that use of low dose rates associated with permanent implants of Sm-145 sources (38-45 KeV x-rays; T1/2 = 340 d) will yield an additional increase …
Date: June 1, 1982
Creator: Fairchild, R.G.
System: The UNT Digital Library
Application of Monte Carlo codes to neutron dosimetry (open access)

Application of Monte Carlo codes to neutron dosimetry

In neutron dosimetry, calculations enable one to predict the response of a proposed dosimeter before effort is expended to design and fabricate the neutron instrument or dosimeter. The nature of these calculations requires the use of computer programs that implement mathematical models representing the transport of radiation through attenuating media. Numerical, and in some cases analytical, solutions of these models can be obtained by one of several calculational techniques. All of these techniques are either approximate solutions to the well-known Boltzmann equation or are based on kernels obtained from solutions to the equation. The Boltzmann equation is a precise mathematical description of neutron behavior in terms of position, energy, direction, and time. The solution of the transport equation represents the average value of the particle flux density. Integral forms of the transport equation are generally regarded as the formal basis for the Monte Carlo method, the results of which can in principle be made to approach the exact solution. This paper focuses on the Monte Carlo technique.
Date: June 15, 1982
Creator: Prevo, C.T.
System: The UNT Digital Library
Optical pumping of hot phonons in GaAs (open access)

Optical pumping of hot phonons in GaAs

Optical pumping of hot LO phonons in GaAs has been studied as a function of the excitation photon frequency. The experimental results are in good agreement with a model calculation which includes both inter- and intra-valley electron-phonon scatterings. The GAMMA-L and GAMMA-X intervalley electron-phonon interactions in GaAs have been estimated.
Date: June 30, 1982
Creator: Collins, C.L. & Yu, P.Y.
System: The UNT Digital Library
Risk Analysis of Nuclear Safeguards Regulations. [Aggregated Systems Model (ASM)] (open access)

Risk Analysis of Nuclear Safeguards Regulations. [Aggregated Systems Model (ASM)]

The Aggregated Systems Model (ASM), a probabilisitic risk analysis tool for nuclear safeguards, was applied to determine benefits and costs of proposed amendments to NRC regulations governing nuclear material control and accounting systems. The objective of the amendments was to improve the ability to detect insiders attempting to steal large quantities of special nuclear material (SNM). Insider threats range from likely events with minor consequences to unlikely events with catastrophic consequences. Moreover, establishing safeguards regulations is complicated by uncertainties in threats, safeguards performance, and consequences, and by the subjective judgments and difficult trade-offs between risks and safeguards costs. The ASM systematically incorporates these factors in a comprehensive, analytical framework. The ASM was used to evaluate the effectiveness of current safeguards and to quantify the risk of SNM theft. Various modifications designed to meet the objectives of the proposed amendments to reduce that risk were analyzed. Safeguards effectiveness was judged in terms of the probability of detecting and preventing theft, the expected time to detection, and the expected quantity of SNM diverted in a year. Data were gathered in tours and interviews at NRC-licensed facilities. The assessment at each facility was begun by carefully selecting scenarios representing the range of potential …
Date: June 1, 1982
Creator: Al-Ayat, R. A.; Altman, W. D. & Judd, B. R.
System: The UNT Digital Library
Multizone infiltration monitoring system (open access)

Multizone infiltration monitoring system

A multizone infiltration monitoring system (MIMS) using a single tracer gas has been developed. MIMS measures zonal infiltration and exfiltration as well as interzonal air movement rates. The system has been used at the 4-zone test house at the SERI interim field site, and this paper presents preliminary results. The present system can determine zonal infiltration rates, and the results show significant differences in infiltration rates for the various zones.
Date: June 1, 1982
Creator: Wortman, D.N.; Burch, J. & Judkoff, R.
System: The UNT Digital Library
Power-conditioning system for the Advanced Test Accelerator (open access)

Power-conditioning system for the Advanced Test Accelerator

The Advanced Test Accelerator (ATA) is a pulsed, linear induction, electron accelerator currently under construction and nearing completion at Lawrence Livermore National Laboratory's Site 300 near Livermore, California. The ATA is a 50 MeV, 10 kA machine capable of generating electron beam pulses at a 1 kHz rate in a 10 pulse burst, 5 pps average, with a pulse width of 70 ns FWHM. Ten 18 kV power supplies are used to charge 25 capacitor banks with a total energy storage of 8 megajoules. Energy is transferred from the capacitor banks in 500 microsecond pulses through 25 Command Resonant Charge units (CRC) to 233 Thyratron Switch Chassis. Each Thyratron Switch Chassis contains a 2.5 microfarad capacitor and is charged to 25 kV (780 joules) with voltage regulation of +- .05%. These capacitors are switched into 10:1 step-up resonant transformers to charge 233 Blumleins to 250 kV in 20 microseconds. A magnetic modulator is used instead of a Blumlein to drive the grid of the injector.
Date: June 1, 1982
Creator: Newton, M. A.; Smith, M. E.; Birx, D. L.; Branum, D. R.; Cook, E. G.; Copp, R. L. et al.
System: The UNT Digital Library
Quantification of human performance through the use of nuclear-power-plant experience (open access)

Quantification of human performance through the use of nuclear-power-plant experience

There is wide agreement throughout the commercial nuclear industry that there is a severe shortage of data on man-machine success or failure rates. At the same time, the need to adequately integrate human performance and system's analysis in the evaluation of nuclear power plant availability and safety is recognized as a dominant need. Therefore, if we are to successfully address the industry's current requirements, we must optimize the use of all existing data. This paper discusses the problem and suggests useful ways of utilizing available nuclear data and presents a conceptual format to better collect actuarial data on the most critical, from a safety perspective, aspects of the man-machine interface in a nuclear power plant.
Date: June 1, 1982
Creator: Hall, R.E.
System: The UNT Digital Library
A-bomb survivor dosimetry update (open access)

A-bomb survivor dosimetry update

A-bomb survivor data have been generally accepted as applicable. Also, the initial radiations have tended to be accepted as the dominant radiation source for all survivors. There was general acceptance of the essential reliability of both the biological effects data and the causative radiation dose values. There are considerations casting doubt on these acceptances, but very little quantification of th implied uncertainties has been attempted. The exception was A-bomb survivor dosimetry, where free-field kerma values for initial radiations were thought to be accurate to about 30%, and doses to individual survivors were treated as effectively error-free. In 1980, a major challenge to the accepted A-bomb survivor dosimetry was announced, and was quickly followed by a succession of explanations and displays showing the soundness of that challenge. In fact, a complete replacement set of free-field kerma values was provided which was suitable for use in constructing an entire new dosimetry for Hiroshima and Nagasaki. The new values showed many changes greater than the accepted 30% uncertainty. An approximate new dosimetry was indeed constructed, and used to convert existing leukemia cause-and-effect data from the old to the new dose values, by way of assessing the impact. (ERB)
Date: June 1, 1982
Creator: Loewe, W.E.
System: The UNT Digital Library
Natural Poisson structures of nonlinear plasma dynamics (open access)

Natural Poisson structures of nonlinear plasma dynamics

Hamiltonian field theories, for models of nonlinear plasma dynamics, require a Poisson bracket structure for functionals of the field variables. These are presented, applied, and derived for several sets of field variables: coherent waves, incoherent waves, particle distributions, and multifluid electrodynamics. Parametric coupling of waves and plasma yields concise expressions for ponderomotive effects (in kinetic and fluid models) and for induced scattering.
Date: June 1, 1982
Creator: Kaufman, A. N.
System: The UNT Digital Library
Intrinsic-damage-threshold study. Final report for the period ending November 15, 1979 (open access)

Intrinsic-damage-threshold study. Final report for the period ending November 15, 1979

We have prepared bare fused silica surfaces by subjecting the mechanically polished surface to a rastered cw CO/sub 2/ laser beam. Analysis shows that this processing causes: (1) removal of a uniform layer of fused silica; and (2) a probable re-fusing or healing of existing subsurface fractures. The fused silica removal rate is found to be a function of the laser intensity and scan rate. These surfaces are seen to have very low scatter and to be very smooth. In addition, they have exhibited entrance surface damage thresholds at 1.06 ..mu..m and 1 nsec, which are substantially above those seen on the mechanically polished surface. When damage does occur, it tends to be at a few isolated points rather than the general uniform damage seen on the mechanically polished part. In addition to the damage results, we will discuss an observational technique used for viewing these surfaces which employs dark-field illumination.
Date: June 1, 1982
Creator: Temple, P. A.
System: The UNT Digital Library
Comparison of detector materials for time-of-flight positron tomography (open access)

Comparison of detector materials for time-of-flight positron tomography

Knowledge of detection efficiency and timing resolution is essential when comparing detector materials for time-of-flight positron tomography. We present results of Monte Carlo calculations of the detection efficiency of plastic, lead loaded plastic, NaI(T1), liquid xenon, bismuth germanate (BGO), CsF, BaF/sub 2/, Ge, and HgI/sub 2/ for 511 keV photons. We also use recently published values of timing resolution for these detector materials to tabulate the quantity (efficiency)/sup 2//(time resolution) which is a measure of the relative sensitivity for time of flight positron tomography.
Date: June 1, 1982
Creator: Derenzo, S.E.
System: The UNT Digital Library
Recent results from the Bevalac (open access)

Recent results from the Bevalac

In a collision between a 1.8 GeV/amu argon ion and a lead target, the overlapping regions of projectile and target undergo violent interaction while the non-overlapping regions either continue with beam velocity and break up into projectile fragments or remain at rest and break into target fragments. Projectile fragements are the easiest to study; the participants, in the mid-rapidity region, are the next easiest, while the target fragments have not been extensively studied, except by radiochemistry techniques. This talk concentrates (with the exception of a discussion of anomalous projectile fragments) on the participant region, where one would expect to find high densities and temperatures and where evidence of any phase transition might be found. The extensive evidence for a high degree of equilibration at Bevalac energies is omitted, even though the stopping power of nuclei is crucial for possible studies at higher energies.
Date: June 1, 1982
Creator: Pugh, H.G.
System: The UNT Digital Library