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Technology for large tandem mirror experiments (open access)

Technology for large tandem mirror experiments

Construction of a large tandem mirror (MFTF-B) will soon begin at Lawrence Livermore National Laboratory (LLNL). Designed to reach break-even plasma conditions, the facility will significantly advance the physics and technology of magnetic-mirror-based fusion reactors. This paper describes the objectives and the design of the facility.
Date: September 4, 1980
Creator: Thomassen, K.I.
System: The UNT Digital Library
Development of an Immersed Boundary Method to Resolve Complex Terrain in the Weather Research and Forecasting Model (open access)

Development of an Immersed Boundary Method to Resolve Complex Terrain in the Weather Research and Forecasting Model

Flow and dispersion processes in urban areas are profoundly influenced by the presence of buildings which divert mean flow, affect surface heating and cooling, and alter the structure of turbulence in the lower atmosphere. Accurate prediction of velocity, temperature, and turbulent kinetic energy fields are necessary for determining the transport and dispersion of scalars. Correct predictions of scalar concentrations are vital in densely populated urban areas where they are used to aid in emergency response planning for accidental or intentional releases of hazardous substances. Traditionally, urban flow simulations have been performed by computational fluid dynamics (CFD) codes which can accommodate the geometric complexity inherent to urban landscapes. In these types of models the grid is aligned with the solid boundaries, and the boundary conditions are applied to the computational nodes coincident with the surface. If the CFD code uses a structured curvilinear mesh, then time-consuming manual manipulation is needed to ensure that the mesh conforms to the solid boundaries while minimizing skewness. If the CFD code uses an unstructured grid, then the solver cannot be optimized for the underlying data structure which takes an irregular form. Unstructured solvers are therefore often slower and more memory intensive than their structured counterparts. …
Date: September 4, 2007
Creator: Lunquist, K A; Chow, F K; Lundquist, J K & Mirocha, J D
System: The UNT Digital Library
Integrated Optical Probes (open access)

Integrated Optical Probes

Optical probes used in velocimetry measurements have typically been individual probes that collect data for a single diagnostic at a single point. These probes have been used in diagnostics such as VISAR, PDV, and radiometry, which measure surface velocity, temperature, and other characteristics. When separate probes are used for these measurements, the different diagnostic points measured must be significantly separated. We have developed integrated probes that collect data for multiple optical diagnostics; these probes measure points in close proximity.
Date: September 4, 2008
Creator: Brent Frogget, Douglas DeVore, Vincent Romero, David Esquibel, and David Holtkamp
System: The UNT Digital Library
An Improved WRF for Urban-Scale and Complex-Terrain Applications (open access)

An Improved WRF for Urban-Scale and Complex-Terrain Applications

Simulations of atmospheric flow through urban areas must account for a wide range of physical phenomena including both mesoscale and urban processes. Numerical weather prediction models, such as the Weather and Research Forecasting model (WRF), excel at predicting synoptic and mesoscale phenomena. With grid spacings of less than 1 km (as is required for complex heterogeneous urban areas), however, the limits of WRF's terrain capabilities and subfilter scale (SFS) turbulence parameterizations are exposed. Observations of turbulence in urban areas frequently illustrate a local imbalance of turbulent kinetic energy (TKE), which cannot be captured by current turbulence models. Furthermore, WRF's terrain-following coordinate system is inappropriate for high-resolution simulations that include buildings. To address these issues, we are implementing significant modifications to the ARW core of the Weather Research and Forecasting model. First, we are implementing an improved turbulence model, the Dynamic Reconstruction Model (DRM), following Chow et al. (2005). Second, we are modifying WRF's terrain-following coordinate system by implementing an immersed boundary method (IBM) approach to account for the effects of urban geometries and complex terrain. Companion papers detailing the improvements enabled by the DRM and the IBM approaches are also presented (by Mirocha et al., paper 13.1, and K.A. Lundquist …
Date: September 4, 2007
Creator: Lundquist, J K; Chow, F K; Mirocha, J D & Lundquist, K A
System: The UNT Digital Library
Debris and Shrapnel Mitigation Procedure for NIF Experiments (open access)

Debris and Shrapnel Mitigation Procedure for NIF Experiments

All experiments at the National Ignition Facility (NIF) will produce debris and shrapnel from vaporized, melted, or fragmented target/diagnostics components. For some experiments mitigation is needed to reduce the impact of debris and shrapnel on optics and diagnostics. The final optics, e.g., wedge focus lens, are protected by two layers of debris shields. There are 192 relatively thin (1-3 mm) disposable debris shields (DDS's) located in front of an equal number of thicker (10 mm) main debris shields (MDS's). The rate of deposition of debris on DDS's affects their replacement rate and hence has an impact on operations. Shrapnel (molten and solid) can have an impact on both types of debris shields. There is a benefit to better understanding these impacts and appropriate mitigation. Our experiments on the Omega laser showed that shrapnel from Ta pinhole foils could be redirected by tilting the foils. Other mitigation steps include changing location or material of the component identified as the shrapnel source. Decisions on the best method to reduce the impact of debris and shrapnel are based on results from a number of advanced simulation codes. These codes are validated by a series of dedicated experiments. One of the 3D codes, NIF's …
Date: September 4, 2007
Creator: Eder, D.; Koniges, A.; Landen, O.; Masters, N.; Fisher, A.; Jones, O. et al.
System: The UNT Digital Library
Neutron response characteristics of CR-39 polymer for reactor and dosimetry applications (open access)

Neutron response characteristics of CR-39 polymer for reactor and dosimetry applications

A desensitized etching technique has been developed which has resulted in an excellent differential energy response for alpha particles in the energy range 3 to 14 MeV. This response complements the previously reported differential proton and integral alpha energy responses obtained with different etching techniques. Proton recoil track yields and diameter distributions have been measured for CR-39 polymer solid state track recorders which were exposed to monoenergetic neutron sources in the energy range 0.57 to 15.1 MeV using various thicknesses and types of proton radiator materials.
Date: September 4, 1981
Creator: Ruddy, F. H.; Gold, R.; Preston, C. C.; Roberts, J. H.; Benton, E. V. & Schraube, H.
System: The UNT Digital Library
Buffon needle method of track counting (open access)

Buffon needle method of track counting

A new technique of quantitative track counting, the Buffon needle method, is advanced. It is based on random sampling of the solid state track recorder (SSTR) surface. This new method extends quantitative track scanning to track densities well up into the track pile-up regime. It is shown that the Buffon needle method possesses a reduced dependence upon both track density nonuniformity and track size distribution. Sources of experimental error arising in the Buffon needle method are assessed. The validity of the Buffon needle method is demonstrated down to at least the 10% uncertainty level (1sigma) by manual sampling of high fission track density mica SSTR observed with scanning electron microscopy.
Date: September 4, 1981
Creator: Gold, R.; Roberts, J.H. & Ruddy, F.H.
System: The UNT Digital Library
Wake potentials and impedances for the ATA (Advanced Test Accelerator) induction cell (open access)

Wake potentials and impedances for the ATA (Advanced Test Accelerator) induction cell

The AMOS Wakefield Code is used to calculate the impedances of the induction cell used in the Advanced Test Accelerator (ATA) at Livermore. We present the wakefields and impedances for multipoles m = 0, 1 and 2. The ATA cell is calculated to have a maximum transverse impedance of approximately 1000 {Omega}/m at 875 MHz with a quality factor Q = 5. The sensitivity of the impedance spectra to modeling variations is discussed.
Date: September 4, 1990
Creator: Craig, George D.
System: The UNT Digital Library
Reduction of Beam Corkscrew Motion on the ETAII Linear Induction Accelerator (open access)

Reduction of Beam Corkscrew Motion on the ETAII Linear Induction Accelerator

The ETAII linear induction accelerator (6MeV, 3kA, 70ns) is designed to drive a microwave free electron laser (FEL) and demonstrate the front end accelerator technology for a shorter wavelength FEL. Performance to date has been limited by beam corkscrew motion that is driven by energy sweep and misalignment of the solenoidal focusing magnets. Modifications to the pulse power distribution system and magnetic alignment are expected to reduce the radius of corkscrew motion from its present value of 1 cm to less than 1 mm. The modifications have so far been carried out on the first 2.7 MeV (injector plus 20 accelerator cells) and experiments are beginning. In this paper we will present calculations of central flux line alignment, beam corkscrew motion and beam brightness that are anticipated with the modified ETAII. 10 refs., 4 figs., 1 tab.
Date: September 4, 1990
Creator: Turner, W. C.; Allen, S. L.; Brand, H. R.; Caporaso, G. J.; Chambers, F. W.; Chen, Y. J. et al.
System: The UNT Digital Library
Status Report on Fermilab Experiment E-760: A Study of Charmonium Produced by Proton-Antiproton Annihilation (open access)

Status Report on Fermilab Experiment E-760: A Study of Charmonium Produced by Proton-Antiproton Annihilation

This was a status report on Fermilab experiment E-760 -- an experiment to study charmonium states by resonant formation in proton-antiproton annihilation. The experiment uses antiprotons circulating in the Fermilab antiproton-accumulator as the beam and an internal hydrogen gas-jet as the target. Data taking with the full complement of apparatus started in early July 1990.
Date: September 4, 1990
Creator: Pordes, Stephen
System: The UNT Digital Library
Ground State Properties and Energy Parameters of the Anderson Lattice System, CeAl{sub2} (open access)

Ground State Properties and Energy Parameters of the Anderson Lattice System, CeAl{sub2}

None
Date: September 4, 1978
Creator: Parks, R. D.; Kupferberg, L. C.; Croft, M. C.; Shapiro, S. M. & Gorewitz, E.
System: The UNT Digital Library
RF Gas Plasma Source Development for Heavy Ion Fusion (open access)

RF Gas Plasma Source Development for Heavy Ion Fusion

Presently the Heavy Ion Fusion Virtual National Laboratory is researching ion sources and injector concepts to understand how to optimize beam brightness over a range of currents (50-2000 mA argon equivalent). One concept initially accelerates millimeter size, milliamp beamlets to 1 MeV before merging them into centimeter size, ampere beams. Computer simulations have shown the final brightness of the merged beams is dominated by the emittance growth of the merging process, as long as the beamlets ion temperature is below a few eV. Thus, a RF multicusp source capable of high current density can produce beams with better brightness compared to ones extracted from a colder source with a large aperture and lower current density. As such, experiments have begun to develop a RF multicusp source capable of delivering one amp of extracted beam current. It is expected that it will require 10 kW of 13 MHz RF power delivered via a quartz shielded, one and half turn, four inch diameter antenna. Important considerations in the development of the source include the dependence of current density and beam ion temperature on consumed RF power and gas pressure. A fast rise time ({approx} 100 ns) for the extracted beam pulse must …
Date: September 4, 2001
Creator: Ahle, L.; Hall, R. P.; Molvik, A. W.; Kwan, J. W. & Leung, K. N.
System: The UNT Digital Library
High Current Ion Source Development for Heavy Ion Fusion (open access)

High Current Ion Source Development for Heavy Ion Fusion

We are developing high-current-density high-brightness sources for Heavy Ion Fusion applications. Heavy ion driven inertial fusion requires beams of high brightness in order to achieve high power density at the target for high target gain. At present, there are no existing ion source types that can readily meet all the driver HIF requirements, though sources exist which are adequate for present experiments and which with further development may achieve driver requirements. Our two major efforts have been on alumino-silicate sources and RF plasma sources. Experiments being performed on a 10-cm alumino-silicate source are described. To obtain a compact system for a HIF driver we are studying RF plasma sources where low current beamlets are combined to produce a high current beam. A 80-kV 20-{micro}s source has produced up to 5 mA of Ar{sup +} in a single beamlet. The extraction current density was 100 mA/cm{sup 2}. We present measurements of the extracted current density as a function of RF power and gas pressure, current density uniformity, emittance, and energy dispersion (due to charge exchange).
Date: September 4, 2003
Creator: Westenskow, G A; Grote, D P & Kwan, J W
System: The UNT Digital Library
Coherent electron cooling demonstration experiment (open access)

Coherent electron cooling demonstration experiment

Coherent electron cooling (CEC) has a potential to significantly boost luminosity of high-energy, high-intensity hadron-hadron and electron-hadron colliders. In a CEC system, a hadron beam interacts with a cooling electron beam. A perturbation of the electron density caused by ions is amplified and fed back to the ions to reduce the energy spread and the emittance of the ion beam. To demonstrate the feasibility of CEC we propose a proof-of-principle experiment at RHIC using SRF linac. In this paper, we describe the setup for CeC installed into one of RHIC's interaction regions. We present results of analytical estimates and results of initial simulations of cooling a gold-ion beam at 40 GeV/u energy via CeC. We plan to complete the program in five years. During first two years we will build coherent electron cooler in IP2 of RHIC. In parallel we will develop complete package of computer simulation tools for the start-to-end simulation predicting exact performance of a CeC. The later activity will be the core of Tech X involvement into the project. We will use these tools to predict the performance of our CeC device. The experimental demonstration of the CeC will be undertaken in years three to five of …
Date: September 4, 2011
Creator: Litvinenko, V. N.; Belomestnykh, S.; Ben-Zvi, Ilan; Brutus, J. C.; Fedotov, A.; Hao, Y. et al.
System: The UNT Digital Library
Electronic structure of the iron-based superconductor LaOFeP (open access)

Electronic structure of the iron-based superconductor LaOFeP

The recent discovery of superconductivity in the iron oxypnictide family of compounds1?9 has generated intense interest. The layeredcrystal structure with transition-metal ions in planar square-lattice form and the discovery of spin-density-wave order near 130 K seem to hint at a strong similarity with the copper oxide superconductors. An important current issue is the nature ofthe ground state of the parent compounds. Two distinct classes of theories, distinguished by the underlying band structure, havebeen put forward: a local-moment antiferromagnetic ground state in the strong-coupling approach, and an itinerant ground statein the weak-coupling approach. The first approach stresses onsite correlations, proximity to a Mott-insulating state and, thus, the resemblance to the high-transition-temperature copper oxides, whereas the second approach emphasizes the itinerant-electronphysics and the interplay between the competing ferromagnetic and antiferromagnetic fluctuations. The debate over the two approaches is partly due to the lack of conclusive experimental information on the electronic structures. Here wereport angle-resolved photoemission spectroscopy (ARPES) of LaOFeP (superconducting transition temperature, Tc55.9 K),the first-reported iron-based superconductor. Our results favour the itinerant ground state, albeit with band renormalization. In addition, our data reveal important differences between these and copper-based superconductors.
Date: September 4, 2008
Creator: Lu, D. H.; Yi, M.; Mo, S. K.; Erickson, A. S.; Analytis, J.; Chu, J. H. et al.
System: The UNT Digital Library
Recommendation for Mitigations of the Electron Cloud Instability in the ILC (open access)

Recommendation for Mitigations of the Electron Cloud Instability in the ILC

Electron cloud has been identified as one of the highest priority issues for the international Linear Collider (ILC) Damping Rings (DR). An electron cloud Working Group (WG) has evaluated the electron cloud effect and instability, and mitigation solutions for the electron cloud formation. Working group deliverables include recommendations for the baseline and alternate solutions to the electron cloud formation in various regions of the ILC Positron DR, which is presently assumed to be the 3.2 km design. Detailed studies of a range of mitigation options including coatings, clearing electrodes, grooves and novel concepts, were carried out over the previous several years by nearly 50 researchers, and the results of the studies form the basis for the recommendation. The recommendations are the result of the working group discussions held at numerous meetings and during a dedicated workshop. In addition, a number of items requiring further investigation were identified during the discussions at the Cornell meeting and studies will be carried out at CesrTA, a test accelerator dedicated to electron cloud studies, and other institutions.
Date: September 4, 2011
Creator: Pivi, M. T. F.; Wang, L.; Demma, T.; Guiducci, S.; Suetsugu, Y.; Shibata, K. et al.
System: The UNT Digital Library
A Novel Neutron Imaging Calibration System Using a Neutron Generating Accelerator Tube (open access)

A Novel Neutron Imaging Calibration System Using a Neutron Generating Accelerator Tube

Neutron Imaging is a key diagnostic for use in inertial confinement fusion (ICF) experiments, and has been fielded on experiments at Omega and Z. It will also be a key diagnostics at the National Ignition Facility (NIF) located at Lawrence Livermore National Laboratory (LLNL) and eventually at the Laser Megajoule in France. Most systems are based on a neutron pinhole array placed at the target chamber while it is imaged by a scintillating fiber block. The light output of this scintillator is coupled via a reducer to a fiber bundle which transports the image to a CCD camera. Alternatively some systems use optical lens assemblies to focus the light onto a camera.For ICF applications the neutron imaging systems will primarily look at 14.2 MeV neutrons. However, 2.2 MeV and 20+ MeV neutrons will also be present and will potentially provide key information.
Date: September 4, 2009
Creator: Ali, Z., Davis, B., Tinsley, J. R., Miller, E. K.
System: The UNT Digital Library
Supersymmetric Defect Models and Mirror Symmetry (open access)

Supersymmetric Defect Models and Mirror Symmetry

None
Date: September 4, 2013
Creator: Hook, Anson; Kachru, Shamit & Torroba, Gonzalo
System: The UNT Digital Library
Engineering-scale destruction of organics at Savannah River Site using the silver(II) ion (open access)

Engineering-scale destruction of organics at Savannah River Site using the silver(II) ion

Electrochemical destruction of organics to carbon dioxide, water, and inorganic salts using the silver(II) ion as an oxidizer has been demonstrated at the Savannah River Site (SRS) on a laboratory scale. An engineering-scale facility has been constructed at SRS for a process demonstration of the technology using benzene. Organic destruction rates, cell efficiencies and off gas generation will be related to key process variables. Electrocell design, peripheral support equipment, engineering considerations, safety issues, and operating parameters will be discussed. Future test plans and the impact of early results on the direction of the organics destruction program at SRS will also be addressed.
Date: September 4, 1991
Creator: Fleischman, S. D. & Pierce, R. A.
System: The UNT Digital Library
Airborne spread of foot-and-mouth disease - model intercomparison (open access)

Airborne spread of foot-and-mouth disease - model intercomparison

Foot-and-mouth disease is a highly infectious vesicular disease of cloven-hoofed animals caused by foot-and-mouth disease virus. It spreads by direct contact between animals, by animal products (milk, meat and semen), by mechanical transfer on people or fomites and by the airborne route - with the relative importance of each mechanism depending on the particular outbreak characteristics. Over the years a number of workers have developed or adapted atmospheric dispersion models to assess the risk of foot-and-mouth disease virus spread through the air. Six of these models were compared at a workshop hosted by the Institute for Animal Health/Met Office during 2008. A number of key issues emerged from the workshop and subsequent modelling work: (1) in general all of the models predicted similar directions for 'at risk' livestock with much of the remaining differences strongly related to differences in the meteorological data used; (2) determination of an accurate sequence of events is highly important, especially if the meteorological conditions vary substantially during the virus emission period; and (3) differences in assumptions made about virus release, environmental fate, and subsequent infection can substantially modify the size and location of the downwind risk area. Close relationships have now been established between participants, …
Date: September 4, 2008
Creator: Gloster, J; Jones, A; Redington, A; Burgin, L; Sorensen, J H; Turner, R et al.
System: The UNT Digital Library
Measurement of cathodeluminescence efficiency of phosphors for micro-channel plate based x-ray framing cameras (open access)

Measurement of cathodeluminescence efficiency of phosphors for micro-channel plate based x-ray framing cameras

None
Date: September 4, 2012
Creator: Izumi, N.; Emig, J.; Moody, J.; Middleton, C.; Holder, J.; Glenn, S. et al.
System: The UNT Digital Library
A Non-scaling Fixed Field Alternating Gradient Accelerator for the Final Acceleration Stage of the International Design Study of the Neutrino Factory. (open access)

A Non-scaling Fixed Field Alternating Gradient Accelerator for the Final Acceleration Stage of the International Design Study of the Neutrino Factory.

The International Design Study of the Neutrino Factory (IDS-NF) has recently completed its Interim Design Report (IDR), which presents our current baseline design of the neutrino factory. To increase the efficiency and reduce the cost of acceleration, the IDR design uses a linear non-scaling fixed field alternating gradient accelerator (FFAG) for its final acceleration stage. We present the current lattice design of that FFAG, including the main ring plus its injection and extraction systems. We describe parameters for the main ring magnets, kickers, and septa, as well as the power supplies for the kickers. We present a first pass at an engineering layout for the ring and its subsystems.
Date: September 4, 2011
Creator: Berg, J. S.; Aslaninejad, M.; Pasternak, J.; Witte, H.; Bliss, N.; Cordwell M. et al.
System: The UNT Digital Library
Scintillating Fiber Array Characterization and Alignment for Neutron Imaging using the High Energy X-ray (HEX) Facility (open access)

Scintillating Fiber Array Characterization and Alignment for Neutron Imaging using the High Energy X-ray (HEX) Facility

The Neutron Imager diagnostic at the National Ignition Facility (NIF) located at Lawrence Livermore National Laboratory (LLNL) will produce high-resolution, gated images of neutron-generating implosions. A similar pinhole imaging experiment (PINEX) diagnostic was recently deployed at the Z facility at Sandia National Laboratories (SNL). Both the SNL and LLNL neutron imagers use similar fiber array scintillators (BCF-99-555). Despite diverse resolution and magnification requirements, both diagnostics put significant onus on the scintillator spatial quality and alignment precision to maintain optimal point spread. Characterization and alignment of the Z-PINEX scintillator and imaging system were done at NSTec/Livermore Operations in 2009, and is currently underway for the NIF Neutron Imager.
Date: September 4, 2009
Creator: Buckles, R. A., Ali, Z. A., Cradick, J. R., Traille, A. J., Warthan, W. A.
System: The UNT Digital Library
The Heavy Photon Search Experiment (open access)

The Heavy Photon Search Experiment

None
Date: September 4, 2013
Creator: Hansson Adrian, Per
System: The UNT Digital Library