27 Matching Results

Search Results

Advanced search parameters have been applied.

Understanding Modern Magnets through Conformal Mapping

Description: When I had to choose, within some narrow range, the topic of this paper, I received great help from a colleague in Berkeley and from Prof. Little when it was suggested that I should pick among the possible subjects of my talk the subject that Prof. Bloch would have enjoyed most. Since Prof. Bloch would prefer a scalpel over a sword every time, I hope and think that most people will approve my choice. When one intends to talk about a subject that is as old as conformal mapping and one does not want to lose the audience in a very short time, it is advisable to start by explaining both the motivation for the talk as well as the goals one has in mind when giving the talk. This particular talk has been motivated by the increasing frequency with which one hears, from people that ought to know better, statements like: 'Conformal mapping is really a thing of the past because of all the marvelous computer programs that we now have'. Even though, or more likely because, I have been intimately involved in the development of some large and widely used computer codes, I am deeply disturbed by such statements since they indicate a severe lack of understanding of the purpose of conformal mapping techniques, computers, and computer codes. In my view, conformal mapping can be an extremely powerful computational technique, and the easy availability of computers has made that aspect even more important now than it has been in the past. Additionally, and more importantly, conformal mapping can give very deep and unique insight into problems, giving often solutions to problems that can not be obtained with any other method, in particular not with computers. Wanting to demonstrate in particular the latter part, I set myself two goals ...
Date: October 27, 1989
Creator: Halbach, K.
Partner: UNT Libraries Government Documents Department

Adiabatic Focuser

Description: Theoretical analysis is made of an intense relativistic electron beam. such as would be available from a linear collider, moving through a plasma of increasing density, but density always less than that of the beam (underdense). In this situation. the plasma electrons are expelled from the beam channel and the electrons are subject to an ever-increasing focusing force provided by the channel ions. Analysis is made on the beam radiation energy loss in the classical, the transition, and the quantum regimes. It is shown that the focuser is insensitive to the beam energy spread due to radiation loss. Furthermore, because of the different scaling behaviors in the nonclassical regimes, the radiation limit on lenses (the Oide limit) can be exceeded. The sensitivity of the system to the optic mismatch and the nonlinearity is also analyzed. Examples are given with SLC-type and TLC-type parameters.
Date: August 1, 1989
Creator: Chen, P.; Oide, K.; Sessler, Andrew M. & Yu, S.S.
Partner: UNT Libraries Government Documents Department

EIGENMODE ANALYSIS OF OPTICAL GUIDING IN FREE ELECTRON LASERS

Description: The spatial properties of the optical field and hence the performance of a free electron laser depend on the fact that the electron beam, which acts as both an amplifying and a refractive medium, is transversely nonuniform. Under certain circumstances, optical guiding may be realized, where the optical field is stably confined near the electron beam and amplified along the beam over many Rayleigh ranges. We show that the three-dimensional evolution of the optical field through the interaction region can be determined by a guided mode expansion before saturation. Optical guiding occurs when the fundamental growing mode becomes dominant. The guided mode expansion is made possible by implementing the biorthogonality of the eigenmodes of the coupled electron-beam-optical-wave system. The eigenmodes are found to be of vectorial form with three components; one specifies the guided optical mode and the other two describe the density and the energy modulations of the electron beam.
Date: March 1, 1989
Creator: Xie, M.; Deacon, D.A.G. & Madey, J.M.J.
Partner: UNT Libraries Government Documents Department

Functional differentiation and alveolar morphogenesis of primary mammary cultures on reconstituted basement membrane

Description: An essential feature of mammary gland differentiation during pregnancy is the formation of alveoli composed of polarized epithelial cells, which, under the influence of lactogenic hormones, secrete vectorially and sequester milk proteins. Previous culture studies have described either organization of cells polarized towards lumina containing little or no demonstrable tissue-specific protein, or establishment of functional secretory cells exhibiting little or no glandular architecture. In this paper, we report that tissue-specific vectorial secretion coincides with the formation of functional alveoli-like structures by primary mammary epithelial cells cultured on a reconstituted basement membrane matrix (derived from Engelbreth-Holm-Swarm murine tumour). Morphogenesis of these unique three-dimensional structures was initiated by cell-directed remodelling of the exogenous matrix leading to reorganization of cells into matrixensheathed aggregates by 24 h after plating. The aggregates subsequently cavitated, so that by day 6 the cells were organized into hollow spheres in which apical cell surfaces faced lumina sealed by tight junctions and basal surfaces were surrounded by a distinct basal lamina. The profiles of proteins secreted into the apical (luminal) and basal (medium) compartments indicated that these alveoli-like structures were capable of an appreciable amount of vectorial secretion. Immunoprecipitation with a broad spectrum milk antiserum showed that more than 80% of caseins were secreted into the lumina, whereas iron-binding proteins (both lactoferrin and transferrin) were present in comparable amounts in each compartment. Thus, these mammary cells established protein targeting pathways directing milk-specific proteins to the luminal compartment. A time course monitoring secretory activity demonstrated that establishment of tissue-specific vectorial secretion and increased total and milk protein secretion coincided with functional alveolar-like multicellular architecture. This culture system is unique among models of epithelial cell polarity in that it demonstrates several aspects of epithelial cell polarization: vectorial secretion, apical junctions, a sequestered compartment and formation of a basal lamina. These lumina-containing ...
Date: February 1, 1989
Creator: BARCELLOS-HOFF, M. H; AGGELER, J.; RAM, T. G & BISSELL, M. J
Partner: UNT Libraries Government Documents Department

Development of Superconducting Strang and Cable with Improved Properties for Use in SSC Magnets

Description: The critical current requirement for the NbTi superconductor strand was set at 2750 A/mm{sup 2} (5 T, 4.2 K) in the SSC Conceptual Design, compared with a value of 1800 A/mm{sup 2} which was specified for the strand used in the Tevatron dipoles. In addition, a filament diameter of 5 {micro}m, instead of the 9 {micro}m diameter used in the Tevatron. was chosen to reduce field distonion at injection. In order to meet the requirements for field homogeneity, the dimensional requirements for both strand and cable were also tightened. The technical solutions employed to achieve these improved properties and the resulting specifications will be discussed.
Date: February 1, 1989
Creator: Scanlan, R. M.
Partner: UNT Libraries Government Documents Department

Removal of Singularities from Taylor Series

Description: A mathematical procedure is described whereby the radius of convergence of a Taylor series can be increased through the inclusion of complex poles in a rational approximation. Computer results show that this technique is quite independent of the asymptotic limit of the power series and only depends on the positions of the singularities. Aside from the applications in one variable, this method vastly improves perturbative solutions to symplectic, dynamical mappings in many dimensions by removing resonances in the complex plane.
Date: August 1, 1989
Creator: La Mon, K.
Partner: UNT Libraries Government Documents Department

Multibunch Instability Investigations for a Tau-Charm Factory

Description: In the design of high-luminosity colliders for high-energy physics, it has become clear that multibunch instabilities will be one of the primary effects that limit beam intensity, and hence luminosity. This paper reports on a series of calculations of multibunch growth rates, using the LBL accelerator physics code ZAP, that illustrate the seriousness of the effect for typical design parameters of a Tau-Charm Factory. A common feature of high-luminosity machines is the requirement of a small beta function at the interaction point. To maintain the advantages of a low beta function, however, requires that the rms bunch length, {sigma}{sub {ell}}, be smaller than {beta}*. This leads, in general, to several inconvenient aspects: (1) The requirement for short bunches leads to the need for a substantial amount of RF hardware-introducing just the narrow-band (high-Q) impedance that generates multibunch instabilities in the first place. (2) The need for short bunches means that bunch lengthening from the longitudinal microwave instability must be avoided. Since the longitudinal impedance Z{sub {parallel}}/n cannot be reduced indefinitely, there is a clear benefit to using many bunches, with lower current per bunch. (3) The short bunches have a Fourier spectrum extending up to very high frequencies, thus effectively sampling impedances in this regime that would be essentially invisible to longer bunches. This aspect can be seen in the exponential cutoff factor, proportional to ({sigma}{sub {ell}/R}){sup 2}, in the expressions for the effective impedance given. In practice, it is difficult to achieve a high luminosity without having a high average beam current in the rings. Because the multibunch growth rates scale linearly with average current, the resulting-rates tend to be very high. It might be imagined that, for sufficient bunch separation and low enough Q values for the higher-order cavity modes, the wake fields have time to die away ...
Date: May 1, 1989
Creator: Zisman, Michael S.
Partner: UNT Libraries Government Documents Department

Flip-Flop Modes in Symmetric and Asymmetric Colliding-Beam Storage Rings

Description: A model of self-consistent beam blow-up in a colliding beam storage ring is described which explains the appearance of flip-flop modes in both symmetric and asymmetric beam systems. It derives the strong-strong steady-states and their stabilities from the weak-strong behavior. This model agrees well with the observed flip-flop behavior in storage rings, including the hysteresis seen when the beams are flipped from one asymmetric steady state to the other. It can be used to predict the behavior of proposed facilities in which the two colliding beams are characterized by different parameters.
Date: August 1, 1989
Creator: Tennyson, J.L.
Partner: UNT Libraries Government Documents Department

GTO-DOE/Industry Cost Shared Research; Microseismic Characterization and Monitoring in Geothermal Systems

Description: The application of passive seismic studies in geothermal regions have undergone significant changes in the last 15 years. The primary application is now in the monitoring of subsurface processes, rather than exploration. A joint Geothermal Technology Organization (GTO) industry/DOE, monitoring project involving GEO, Unocal Geothermal, and LBL, was carried out at The Geysers geothermal field in northern California using a special high frequency monitoring system. This several-month-long experiment monitored the discrete and continuous seismic signals before, during, and after a fluid stimulation of a marginal production well. Almost 350,000 liters of water were pumped into the well over a four-hour, and a three-hour time period for two consecutive days in June of 1988. No significant changes in the background seismicity or the seismic noise were detected during the monitoring period. Analysis of the background seismicity did indicate that the earthquakes at The Geysers contain frequencies higher than 50 Hz. and possibly as high as 100 Hz.
Date: March 21, 1989
Creator: Majer, E.L.
Partner: UNT Libraries Government Documents Department

A Measurement of the Temperature of the Cosmic MicrowaveBackground at a Frequency of 7.5 GHz

Description: We have measured the intensity of the cosmic microwave background (CMB) at a frequency of 7.5 GHz (wavelength 4.0 cm) using a ground-based, total power radiometer calibrated at the horn aperture by an external cryogenic reference target. The radiometer measured the difference in antenna temperature between the reference target and the zenith sky from a dry, high-altitude site. Subtraction of foreground signals (primarily atmospheric and galactic emission) measured with the same instrument leaves the CMB as the residual. The radiometer measured the atmospheric antenna temperature by correlating the signal change with the airmass in the beam during tip scans. The small galactic signal was subtracted based on extrapolation from lower frequencies, and was checked by differential drift scans. The limiting uncertainty in the CMB measurement was the effect of ground radiation in the antenna sidelobes during atmospheric measurements. The thermodynamic temperature of the CMB at 7.5 GHz is 2.59 {+-} 0.07 K (68% confidence level).
Date: June 1, 1989
Creator: Kogut, A.; Bensadoun, M.; De Amici, Giovanni; Levin, S.; Smoot,George F. & Witebsky, C.
Partner: UNT Libraries Government Documents Department

Design and Testing of a Superfluid Liquid Helium CoolingLoop

Description: This paper describes the design and preliminary testing of a cryogenic cooling loop that uses a thermomechanical pump to circulate superfluid liquid helium. The cooling loop test apparatus is designed to prove forced liquid helium flow concepts that will be used on the Astromag superconducting magnet facility.
Date: July 24, 1989
Creator: Gavin, L.M.; Green, M.A.; Levin, S.M.; Smoot, George F. & Witebsky, C.
Partner: UNT Libraries Government Documents Department

Calorimetric Ionization Detector

Description: A new mode of operation for ionization detectors is described. The amount of ionization produced in a detector is determined by measuring the amount of heat generated during the carrier collection process. Very high detection sensitivities, including single carrier detection, may be achieved at cryogenic temperatures. Results from an experimental device operated at T = 0.3K is presented.
Date: July 1, 1989
Creator: Luke, P.N.; Beeman, J.; Goulding, F.S.; Labov, S.E. & Silver, E.H.
Partner: UNT Libraries Government Documents Department

A REVIEW OF ASSUMPTIONS AND ANALYSIS IN EPRI EA-3409,"HOUSEHOLD APPLIANCE CHOICE: REVISION OF REEPS BEHAVIORAL MODELS"

Description: This paper revises and extends EPRI report EA-3409, ''Household Appliance Choice: Revision of REEPS Behavioral Models.'' That paper reported the results of an econometric study of major appliance choice in new residential construction. Errors appeared in two tables of that report. We offer revised versions of those tables, and a brief analysis of the consequences and significance of the errors. The present paper also proposes several possible extensions and re-specifications of the models examined by EPRI. Some of these are judged to be highly successful; they both satisfy economic intuition more completely than the original specification and produce a better quality fit to the dependent variable. We feel that inclusion of these modifications produces a more useful set of coefficients for economic modeling than the original specification. This paper focuses on EPRI's models of residential space heating technology choice. That choice was modeled as a nested logit structure, with consumers choosing whether to have central air conditioning or not, and, given that choice, what kind of space heating system to have. The model included five space heating alternatives with central cooling (gas, oil, and electric forced-air; heat pumps; and electric baseboard) and eight alternatives without it (gas, oil, and electric forced-air; gas and oil boilers and non-central systems; and electric baseboard heat). The structure of the nested logit model is shown in Figure 1.
Date: May 1, 1989
Creator: Wood, D.J.; Ruderman, H. & McMahon, J. E.
Partner: UNT Libraries Government Documents Department

Low-Frequency Measurements of the CMB Spectrum

Description: As part of an extended program to characterize the spectrum of the cosmic microwave background (CMB) at low frequencies, we have performed multiple measurements from a high-altitude site in California. On average, these measurements suggest a CMB temperature slightly lower than measurements at higher frequencies. Atmospheric conditions and the encroachment of civilization are now significant limitations from our present observing site. In November 1989, we will make new measurements from the South Pole Amundsen-Scott Station at frequencies 0.82, 1.5, 2.5, 3.8, 7.5, and 90 GHz. We discuss recent measurements and indicate improvements possible from a polar observing site.
Date: October 1, 1989
Creator: Kogut, A.; Bensadoun, M.; De Amici, Giovanni; Levin, S.; Limon,M.; Smoot, George F. et al.
Partner: UNT Libraries Government Documents Department

On Two-Phase Relative Permeability and Capillary Pressure ofRough-Walled Rock Fractures

Description: This paper presents a conceptual and numerical model of multiphase flow in fractures. The void space of real rough-walled rock fractures is conceptualized as a two-dimensional heterogeneous porous medium, characterized by aperture as a function of position in the fracture plane. Portions of a fracture are occupied by wetting and nonwetting phase, respectively, according to local capillary pressure and accessibility criteria. Phase occupancy and permeability are derived by assuming a parallel-plate approximation for suitably small subregions in the fracture plane. For log-normal aperture distributions, a simple approximation to fracture capillary pressure is obtained in closed form; it is found to resemble the typical shape of Leverett's j-function. Wetting and non-wetting phase relative permeabilities are calculated by numerically simulating single phase flows separately in the wetted and non-wetted pore spaces. Illustrative examples indicate that relative permeabilities depend sensitively on the nature and range of spatial correlation between apertures. It is also observed that interference between fluid phases flowing in a fracture tends to be strong, with the sum of wetting and nonwetting phase relative permeabilities being considerably less than 1 at intermediate saturations.
Date: September 1989
Creator: Pruess, K. & Tsang, Y. W.
Partner: UNT Libraries Government Documents Department

Photoelectron Spectroscopy and Electronic Structure of Heavy GroupIV-VI Diatomics

Description: Vibrationally-resolved HeI (584{angstrom}) photoelectron spectra of the heavy group IV-VI diatomics SnSe, SnTe, PbSe, and PbTe were obtained with a new high temperature molecular beam source. Ionization potentials and spectroscopic constants are reported for all the ionic states observed. Relativistic complete active space MCSCF followed by multireference singles + doubles relativistic CI calculations which included up to 200,000 configurations were made on both the neutral diatomics and their positive ions. Ionization potentials and spectroscopic constants were calculated and were in good agreement with the experimentally-measured values. Relativistic CI potential energy curves were calculated for all the neutral ground states and the ionic states involved. Relativistic effects were shown to play an important role in these heavy diatomics. The {sup 2}{Sigma}{sub 1/2}{sup +} and {sup 2}{Pi}{sub 1/2} states for all four molecular ions showed avoided curve crossings, which resulted in pronounced shoulders in the {Omega} = 1/2 potential energy curves of PbTe{sup +}. Experimentally, autoionization transitions were also observed for the PbTe{sup +} spectrum. The importance of the relativistic effect and chemical bonding in the heavy diatomics are discussed.
Date: September 1, 1989
Creator: Wang, L.-S.; Niu, B.; Lee, Yuan T.; Shirley, D.A. & Balasubramanian, K.
Partner: UNT Libraries Government Documents Department

The Temperature of the Cosmic Background Radiation: Results fromthe 1987 and 1988 Measurements at 3.8 GHz

Description: We have measured the temperature of the cosmic background radiation (CBR) at a frequency of 3.8 GHz (7.9 cm wavelength), during two consecutive summers, obtaining a brightness temperature, T{sub CBR}, of 2.56 {+-} 0.08 K in 1987 and 2.71 {+-} 0.07 K in 1988 (68% confidence level). The new results are in agreement with our previous measurement at 3.7 GHz obtained in 1986, and have smaller error bars. Combining measurements from all three years we obtain T{sub CBR} = 2.64 {+-} 0.07 K.
Date: November 10, 1989
Creator: De Amici, Giovanni; Bensadoun, M.; Bersanelli, M.; Kogut, A.; Levine, S.; Smoot, George F. et al.
Partner: UNT Libraries Government Documents Department

Preclosure monitoring and performance confirmation at Yucca Mountain: Applicability of geophysical, geohydrological, and geochemical methods

Description: The present paper presents considerations on studies that would be required for preclosure monitoring and performance confirmation of a nuclear waste geologic repository in an unsaturated zone. The critical parameters that should be monitored are reviewed and two scales of measurement relevant to monitoring activities, room scale and repository scale, are taken as a framework for investigation. A number of monitoring methods based on geophysics, geohydrology, and geochemistry are briefly summarized for their potential usefulness for preclosure monitoring and performance confirmation of the geologic repository. Particular emphasis is given to measurement of the spatial distribution of parameters in contrast to single-point measurements of quantities. 12 refs., 1 fig., 1 tab.
Date: June 1, 1989
Creator: Tsang, C.F.
Partner: UNT Libraries Government Documents Department

Letter report (T-418): Progress report on solubility measurements, October 1, 1987--September 30, 1988

Description: This letter report describes the technical activities of the waste element solubility study during Fiscal Year (FY88, October 1, 1987 to September 30, 1988). This experimental waste element solubility study provides experimentally determined limits on radionuclide concentrations in groundwater from Yucca Mountain. Furthermore, the results of this study are essential for verifying the validity of radionuclide transport calculations, and for providing the maximum concentrations for the radionuclide sorption tests. Solubility is the source term for radionuclide transport calculations. The solubility in this study is controlled by fewer variables than are used in the multiparameter transport model. Therefore, modeling must be capable of predicting the results of this waste element solubility study. Agreement between the experimental result and the modeling predictions will validate the geochemical module of the transport model. 3 refs., 8 figs.
Date: March 21, 1989
Creator: Nitsche, H.
Partner: UNT Libraries Government Documents Department

VSP [Vertical Seismic Profiling] and cross hole tomographic imaging for fracture characterization

Description: For the past several years LBL has been carrying out experiments at various fractured rock sites to determine the fundamental nature of the propagation of seismic waves in fractured media. These experiments have been utilizing high frequency (1000 to 10000 Hz.) signals in a cross-hole configuration at scales of several tens of meters. Three component sources and receivers are used to map fracture density, and orientation. The goal of the experiments has been to relate the seismological parameters to the hydrological parameters, if possible, in order to provide a more accurate description of a starting model for hydrological characterization. The work is ultimately aimed at the characterization and monitoring of the Yucca Mountain site for the storage of nuclear waste. In addition to these controlled experiments multicomponent VSP work has been carried out at several sites to determine fracture characteristics. The results to date indicate that both P-wave and S-wave can be used to map the location of fractures. In addition, fractures that are open and conductive are much more visible to seismic waves that non-conductive fractures. The results of these tests indicate direct use in an unsaturated environment. 12 refs., 10 figs.
Date: September 1, 1989
Creator: Majer, E.L.; Peterson, J.E.; Myer, L.R.; Karasaki, K.; Daley, T.M. & Long, J.C.S.
Partner: UNT Libraries Government Documents Department

Waste package performance in unsaturated rock

Description: The unsaturated rock and near-atmospheric pressure of the potential nuclear waste repository at Yucca Mountain present new problems of predicting waste package performance. In this paper we present some illustrations of predictions of waste package performance and discuss important data needs. 11 refs., 9 figs., 1 tab.
Date: March 1, 1989
Creator: Pigford, T.H. & Lee, W.W.-L.
Partner: UNT Libraries Government Documents Department

Proceedings of the workshop on triggering and data acquisition for experiments at the Supercollider

Description: This meeting covered the following subjects: triggering requirements for SSC physics; CDF level 3 trigger; D0 trigger design; AMY trigger systems; Zeus calorimeter first level trigger; data acquisition for the Zeus Central Tracking Detector; trigger and data acquisition aspects for SSC tracking; data acquisition systems for the SSC; validating triggers in CDF level 3; optical data transmission at SSC; time measurement system at SSC; SSC/BCD data acquisition system; microprocessors and other processors for triggering and filtering at the SSC; data acquisition, event building, and on-line processing; LAA real-time benchmarks; object-oriented system building at SSC; and software and project management. Selected papers are indexed separately for inclusion in the Energy Science and Technology Database.
Date: April 1, 1989
Creator: Donaldson, R.
Partner: UNT Libraries Government Documents Department

CP violation at the Z peak

Description: Some possibilities for searches of CP-nonconservation in decays of the Z boson produced in e{sup +}e{sup {minus}} collisions are briefly reviewed. 18 refs.
Date: June 1, 1989
Creator: Bernreuther, W.
Partner: UNT Libraries Government Documents Department