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Impulsive ion acceleration in earth's outer magnetosphere
Considerable observational evidence is found that ions are accelerated to high energies in the outer magnetosphere during geomagnetic disturbances. The acceleration often appears to be quite impulsive causing temporally brief (10's of seconds), very intense bursts of ions in the distant plasma sheet as well as in the near-tail region. These ion bursts extend in energy from 10's of keV to over 1 MeV and are closely associated with substorm expansive phase onsets. Although the very energetic ions are not of dominant importance for magnetotail plasma dynamics, they serve as an important tracer population. Their absolute intensity and brief temporal appearance bespeaks a strong and rapid acceleration process in the near-tail, very probably involving large induced electric fields substantially greater than those associated with cross-tail potential drops. Subsequent to their impulsive acceleration, these ions are injected into the outer trapping regions forming ion ''drift echo'' events, as well as streaming tailward away from their acceleration site in the near-earth plasma sheet. Most auroral ion acceleration processes occur (or are greatly enhanced) during the time that these global magnetospheric events are occurring in the magnetotail. A qualitative model relating energetic ion populations to near-tail magnetic reconnection at substorm onset followed by …
Date:
January 1, 1985
Creator:
Baker, D.N. & Belian, R.D.
System:
The UNT Digital Library
The limited streamer tubes system for the SLD warm iron calorimeter
The SLD detector at the Stanford Linear Accelerator Center is a general purpose device for studying e{sup +}{epsilon}{sup {minus}} interaction at the Z{sup 0}. The SLD calorimeter system consists of two parts: a lead Liquid Argon Calorimeter (LAC) with both electromagnetic (22 radiation lengths) and hadronic sections (2.8 absorption lengths) housed inside the coil, and the Warm Ion limited streamer tubes Calorimeter (WIC) outside the coil which uses as radiator the iron of the flux return for the magnetic field. The WIC completes the measurement of the hadronic shower energy ({approximately}85% on average is contained in the LAC) and it provides identification and tracking for muons over 99% of the solid angle. In this note we report on the construction, test and commissioning of such a large system.
Date:
January 1, 1992
Creator:
Benvenuti, A. C.; Camanzi, B.; Piemontese, L.; Zucchelli, P.; Calcaterra, A.; De Sangro, R. et al.
System:
The UNT Digital Library
Schemes for anti pp interactions at ISABELLE
Various schemes for obtaining anti pp interactions are outlined, and the luminosities obtainable for each case calculated. In the simplest realistic case, a luminosity of 1.3 x 10/sup 29/ is obtained with a 13 hour filling time. The addition of special rf systems in both the AGS and ISABELLE give a scheme with luminosity 8 x 10/sup 29/ in 6 hours. The use of stochastic cooling to stack raises the luminosity to as high as 10/sup 31/ but the filling time is then 68 hours. Finally a scheme is considered that uses a special 30 GeV capture ring. With this, a luminosity of 10/sup 31/ could be achieved after 20 hours, or higher if a larger filling time were acceptable. Further gains could be made if a smaller proton spot on the target is used but a simple calculation suggests that even the spot size assumed may explode the target too fast.
Date:
September 8, 1977
Creator:
Palmer, Robert B.
System:
The UNT Digital Library
Proceedings of the LAMPF workshop on physics with polarized nuclear targets
Topics of discussion included static and dynamic methods for polarizing nuclei, proton and pion nucleus scattering experiments, and possible future experiments at LAMPF. Separate abstracts were prepared for 11 papers in this report. (DWL)
Date:
August 1, 1986
Creator:
Burleson, G.; Gibbs, W.; Hoffmann, G.; Jarmer, J. J. & Tanaka, N. (eds.)
System:
The UNT Digital Library
Relativistic effects in the atomic and nuclear few-body problems
Relativistic effects in the atomic and nuclear few-body systems are classified and discussed with the emphasis on electromagnetic transitions. The size of relativistic corrections, calculational techniques and ambiguities, and comparison of theory and experiment are considered. 8 figures.
Date:
January 1, 1980
Creator:
Friar, J.L.
System:
The UNT Digital Library
Non-linear instability of DIII-D to error fields
Otherwise stable DIII-D discharges can become nonlinearly unstable to locked modes and disrupt when subjected to resonant m = 2, n = 1 error field caused by irregular poloidal field coils, i.e. intrinsic field errors. Instability is observed in DIII-D when the magnitude of the radial component of the m = 2, n = 1 error field with respect to the toroidal field is B{sub r21}/B{sub T} of about 1.7 {times} 10{sup {minus}4}. The locked modes triggered by an external error field are aligned with the static error field and the plasma fluid rotation ceases as a result of the growth of the mode. The triggered locked modes are the precursors of the subsequent plasma disruption. The use of an n = 1 coil'' to partially cancel intrinsic errors, or to increase them, results in a significantly expanded, or reduced, stable operating parameter space. Precise error field measurements have allowed the design of an improved correction coil for DIII-D, the C-coil'', which could further cancel error fields and help to avoid disruptive locked modes. 6 refs., 4 figs.
Date:
October 1, 1991
Creator:
La Haye, R. J. & Scoville, J. T.
System:
The UNT Digital Library
Comments on septa and other small production angle magnets
A discussion is given of possible septum magnet parameters for small production angle experiments in the ISABELLE storage rings. Superconducting septa and torroidal septa are also considered. (PMA)
Date:
August 25, 1977
Creator:
Allinger, J.; Danby, G. & Jackson, J.
System:
The UNT Digital Library
Measurements of Non-Leptonic Weak Decays of Lambda Hypernuclei
Aspects of recent measurements of the mesonic and non-mesonic partial decay rates of {sub {Lambda}}{sup 5}He, and {sub {Lambda}}{sup 12}C are discussed. We comment on what the experiments tell us about the spin-isospin structure of {Delta}S=1 weak interaction in the nuclear environment. 14 refs., 1 fig.
Date:
January 1, 1991
Creator:
Schumacher, Reinhard A.
System:
The UNT Digital Library
De-entrainment on vertical elements in air droplet cross flow. [PWR]
De-entrainment phenomena on vertical elements in air-water droplet cross flow are generated using a horizontal array of water spray nozzles and a draft-induced wind tunnel. These conditions are used to obtain experimental values of the de-entrainment efficiency of isolated elements (25.4-, 63.5-, and 101.6-mm-diam cylinders and a 76.2-mm-square tube), and of an array of 101.6-mm-diam cylinders. A flow model is developed that extrapolates the de-entrainment efficiency of isolated elements through the use of a correlation for the interference effect to predict the efficiency of large arrays of similar elements. This simple model is shown to provide a good prediction of the de-entrainment efficiency of arrays in terms of the efficiency of an isolated element.
Date:
January 1, 1980
Creator:
Dallman, J.C. & Kirchner, W.L.
System:
The UNT Digital Library
Fifth high-energy heavy-ion study
This was the fifth of a continuing series of summer studies held at LBL to discuss high energy heavy ion collisions. Recently, a similar meeting has been held on alternate years at GSI (Darmstadt); and, in 1979, we held a meeting at LBL exclusively devoted to ultra-relativistic nuclear collisions. Two new features distinguish this study from earlier meetings in the series. First, the energy range for discussion was broadened by including collisions from about 20 MeV/nucleon to the highest available in the cosmic radiation. The lower range, particularly below 100 MeV/nucleon, will be under intense study in the near future with machines such as the upgraded Bevalac, Michigan State University Superconducting Cyclotron, GANIL in France, and the SC at CERN. Recently, the high energy collision regime has been expanded by the successful operation of the CERN ISR with alpha particles. Second, in addition to an extensive program of invited talks, we decided for the first time to actively solicit contributions. Forty-seven individual items from the conference were prepared separately for the data base. (GHT)
Date:
October 1, 1981
Creator:
unknown
System:
The UNT Digital Library
Applications of induction linac technology to heavy ion fusion
Evaluation of the application of heavy ion accelerators to ignite d-t pellets in a thermonuclear reactor is discussed. Accelerator design requirements considered include transport-limited current, beam injection conditions, and pulse bunching and focusing characteristics. The desirability of resonant and non-resonant accelerating structures is comparatively examined. The required power system switch tubes are discussed. It is concluded that heavy ion accelerators could offer a promising solution to the pellet-igniter problem. The advantages pointed out for this approach include electric efficiency greater than 10 percent, the possibility of high repetition rates (1 to 10 Hz), and a mature technological base. (RME)
Date:
July 1, 1977
Creator:
Faltens, A. & Keefe, D.
System:
The UNT Digital Library
Laser-plasma interaction experiments at laser wavelengths of 1. 064. mu. m, 0. 532. mu. m, and 0. 355. mu. m
The effect of laser wavelength on laser-plasma coupling is one of the critical issues facing the laser driven inertial confinement community. The advantages of using lasers with output wavelength less than 1 ..mu..m, such as enhanced absorption and hydrodynamic efficiency, reduction in parametric instabilities and corresponding suprathermal electron generation, have long been predicted theoretically.
Date:
January 1, 1982
Creator:
Campbell, E. M.; Mead, W. C. & Turner, R. E.
System:
The UNT Digital Library
Stark broadening of isolated lines from high-Z emitters in dense plasmas
The joint distribution of the electric microfield and its longitudinal derivative is required for the calculation of line profiles for the He-like ions in very dense plasmas. We used a molecular dynamics code to compute exact distributions in single- and multi-component plasmas, and then we investigated various analytical approximations to these results. We found that a simplified, two-nearest-neighbor scheme leads to surprisingly accurate distribution functions. Our results are illustrated by sample profiles for Ne/sup +8/ and Ar/sup +16/ resonance lines.
Date:
September 1, 1980
Creator:
Weisheit, J.C. & Pollock, E.L.
System:
The UNT Digital Library
Growth regulation by macrophages
The evidence reviewed here indicates that macrophages, either acting alone or in concert with other cells, influence the proliferation of multiple types of cells. Most of the data indicate that these effects are mediated by soluble macrophage-elaborated products (probably proteins) although the role of direct cell-to-cell contacts cannot be ruled out in all cases. A degree of success has been achieved on the biochemical characterization of these factors, due mainly to their low specific activity in conditioned medium and the lack of rapid, specific assays. Understanding the growth-regulating potential of macrophages is an important and needed area of research.
Date:
January 1, 1982
Creator:
Wharton, W.; Walker, E. & Stewart, C.C.
System:
The UNT Digital Library
Diskless LSI-11 systems
Programs for dedicated LSI-11 based systems can easily be stored in ROM instead of floppy disks, yet execute the same as disk-stored programs. Two sample systems are described.
Date:
January 1, 1982
Creator:
Ford, W. & Shirk, D. G.
System:
The UNT Digital Library
Sintering of polycrystalline ionic conductors:. beta. ''-Al/sub 2/O/sub 3/ and NASICON
The densification kinetics for both ..beta..''-alumina and NASICON are dramatically different. ..beta..''-Alumina sinters by a reactive liquid process whereas NASICON densifies by a solid state method. More importantly, a qualitative examination of particle and agglomerate distributions, phase composition, linear shrinkage analysis, and heating rate effects can result in a concise determination of sintering processes without recourse to more quantitative techniques. Such a simple procedural method should be a basis for any beginning investigative study into the densification mechanism of new multicomponent ceramic materials.
Date:
January 1, 1979
Creator:
McEntire, B. J.; Miller, G. R. & Gordon, R. S.
System:
The UNT Digital Library
Severe accident core heatup transients in modular high temperature gas-cooled reactors without operating Reactor Cavity Cooling Systems
The ultimate decay heat removal system for the current Modular High Temperature Gas-Cooled reactors is a completely passive natural convection air cooling loop. This paper considers an extremely remote accident scenario, where even this passive system fails, and heat rejection is only via a layer of thermal insulation to the reactor silo structure and the surrounding soil. The results show that even in this case the peak fuel temperatures remain well within safe limits. However, vessel and concrete temperatures can - under extreme circumstances and after several weeks - reach temperature levels at which structural failure becomes possible.
Date:
January 1, 1988
Creator:
Kroeger, P. G.
System:
The UNT Digital Library
The microscopic world: A demonstration of electron microscopy for younger students
None
Date:
January 1, 1991
Creator:
Horton, L. L.
System:
The UNT Digital Library
Surprising patterns of CMOS susceptibility to ESD and implications on long-term reliability
CMOS electrostatic discharge (ESD) failures in a product where, by design, the device input terminals are not accessible to ESD led to this study of device susceptibility and an analysis of the long-term reliability of devices in assemblies from that production line. Some surprising patterns of device susceptibility are established and it is shown that the probability of long-term failure in devices whose electrical characteristics have been degraded by electrostatic discharge is small.
Date:
January 1, 1980
Creator:
Schwank, J.R.; Baker, R.P. & Armendariz, M.G.
System:
The UNT Digital Library
Alkali sorber (RABSAM), September 1, 1990--August 30, 1991
The objective of this work is to develop a regenerable activated-bauxite sorber alkali monitor that requires no high-temperature/high-pressure sampling line for the reliable in situ measurement of alkali-vapor concentration in the exhaust from the pressurized fluidized-bed combustion of coal. 11 refs., 2 figs., 1 tab.
Date:
January 1, 1991
Creator:
Lee, S. H. D. & Swift, M. W.
System:
The UNT Digital Library
Resource capture by single leaves
Leaves show a variety of strategies for maximizing CO{sub 2} and light capture. These are more meaningfully explained if they are considered in the context of maximizing capture relative to the utilization of water, nutrients and carbohydrates reserves. There is considerable variation between crops in their efficiency of CO{sub 2} and light capture at the leaf level. Understanding of these mechanisms indicate some ways in which efficiency of resource capture could be level cannot be meaningfully considered without simultaneous understanding of implications at the canopy level. 36 refs., 5 figs., 1 tab.
Date:
May 1, 1992
Creator:
Long, S.P.
System:
The UNT Digital Library
Damage nucleation in Si during ion irradiation
Damage nucleation in single crystals of silicon during ion irradiation is investigated. Experimental results and mechanisms for damage nucleation during both room and liquid nitrogen temperature irradiation with different mass ions are discussed. It is shown that the accumulation of damage during room temperature irradiation depends on the rate of implantation. These dose rate effects are found to decrease in magnitude as the mass of the ions is increased. The significance of dose rate effects and their mass dependence on nucleation mechanisms is discussed.
Date:
January 1, 1984
Creator:
Holland, O.W.; Fathy, D. & Narayan, J.
System:
The UNT Digital Library
Statistical magnetohydrodynamics and reversed-field-pinch quiescence
A statistical model of a bounded, incompressible, cylindrical magnetofluid is presented. This model predicts the presence of magnetic fluctuations about a cylindrically-symmetric, Bessel-function-model, mean magnetic field, which satisfies del x <B> = ..mu.. <B>. As theta ..-->.. 1.56, the model predicts that the significant region of the fluctuation spectrum narrows down to a single (coherent) m = 1 mode. An analogy between the Debye length of an electrostatic plasma and ..mu../sup -1/ suggests the physical validity o the model's prediction of <deltaB(r)deltaB(r')> when /r - r'/ greater than or equal to ..mu../sup -1/.
Date:
January 1, 1982
Creator:
Turner, L.
System:
The UNT Digital Library
Importance of the specific heat anomaly in the design of binary Rankine cycle power plants
The transposed critical temperature (TPCT) is shown to be an extremely important thermodynamic property in the selection of working fluids and turbine states for geothermal power plants operating on a closed organic (binary) Rankine cycle. When the optimum working fluid composition and process states are determined for specified source and sink conditions, turbine inlet states consistently lie adjacent to the working fluids' TPCT line for all resource temperatures, constraints, and cost and efficiency factors investigated.
Date:
May 1, 1980
Creator:
Pope, W.L.; Doyle, P.A.; Fulton, R.L. & Silvester, L.F.
System:
The UNT Digital Library