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Performance Limitations in High-Energy Ion Colliders (open access)

Performance Limitations in High-Energy Ion Colliders

High-energy ion colliders (hadron colliders operating with ions other than protons) are premier research tools for nuclear physics. The collision energy and high luminosity are important design and operations considerations. The experiments also expect flexibility with frequent changes in the collision energy, detector fields, and ion species, including asymmetric collisions. For the creation, acceleration, and storage of bright intense ion beams limits are set by space charge, charge exchange, and intrabeam scattering effects. The latter leads to luminosity lifetimes of only a few hours for intense heavy ions beams. Currently, the Relativistic Heavy Ion Collider (RHIC) at BNL is the only operating high-energy ion collider. Later this decade the Large Hadron Collider (LHC), under construction at CERN, will also run with heavy ions.
Date: May 16, 2005
Creator: Fischer, W.
System: The UNT Digital Library
BEAM-BEAM SIMULATIONS FOR THE ERHIC ELECTRON RING. (open access)

BEAM-BEAM SIMULATIONS FOR THE ERHIC ELECTRON RING.

To study collisions between polarized electrons and heavy ions or polarized protons at high energy, adding a 10 GeV electron storage ring to the existing RHIC facility is currently under consideration. To achieve high luminosities of several 10{sup 33} cm{sup -2} sec{sup -1} range, a vertical beam-beam tuneshift parameter of {zeta}{sub y} = 0.08 is required for the electron beam. Simulation studies are being performed to study the feasibility of this high tuneshift parameter and explore the potential for even higher tuneshifts. Recent results of these studies are presented.
Date: May 16, 2005
Creator: Montag, C.
System: The UNT Digital Library
Status of The General Atomics Low Speed Urban Maglev Technology Development Program (open access)

Status of The General Atomics Low Speed Urban Maglev Technology Development Program

This paper presents the status of General Atomics Urban Maglev Program. The development provides an innovative approach for low speed transportation suitable for very challenging urban environments. Permanent magnets arranged in a 'Halbach' array configuration produce a relatively stiff magnetic suspension operating with an air gap of 25 mm. The project has progressed from design and prototype hardware testing, to the construction of a 120-meter full-scale test track, located in San Diego, California. Dynamic testing of the levitation, propulsion and guidance systems is being performed.
Date: June 16, 2004
Creator: Gurol, S; Baldi, R; Bever, D & Post, R
System: The UNT Digital Library
Beam Loss Estimates and Control for the BNL Neutrino Facility. (open access)

Beam Loss Estimates and Control for the BNL Neutrino Facility.

The requirement for low beam loss is very important both to protect the beam component, and to make the hands-on maintenance possible. In this report, the design considerations to achieving high intensity and low loss will be presented. We start by specifying the beam loss limit at every physical process followed by the proper design and parameters for realizing the required goals. The process considered in this paper include the emittance growth in the linac, the H{sup -} injection, the transition crossing, the coherent instabilities and the extraction losses.
Date: May 16, 2005
Creator: Weng, W. T.; Lee, Y. Y.; Raparia, D.; Tsoupas, N.; Beebe-Wang, J.; Wei, J. et al.
System: The UNT Digital Library
Jet-Induced Star Formation (open access)

Jet-Induced Star Formation

Jets from radio galaxies can have dramatic effects on the medium through which they propagate. We review observational evidence for jet-induced star formation in low ('FR-I') and high ('FR-II') luminosity radio galaxies, at low and high redshifts respectively. We then discuss numerical simulations which are aimed to explain a jet-induced starburst ('Minkowski's Object') in the nearby FR-I type radio galaxy NGC 541. We conclude that jets can induce star formation in moderately dense (10 cm{sup -3}), warm (10{sup 4} K) gas; that this may be more common in the dense environments of forming, active galaxies; and that this may provide a mechanism for 'positive' feedback from AGN in the galaxy formation process.
Date: December 16, 2003
Creator: van Breugel, W.; Fragile, C.; Anninos, P. & Murray, S.
System: The UNT Digital Library
Statistical techniques to find similar objects in images (open access)

Statistical techniques to find similar objects in images

One problem in similarity-based object retrieval (SBOR) is how to define and estimate the similarity between two objects. In this paper we present a shape similarity measure based on thin-plate splines, and compare its performance with several other measures used in SBOR. We evaluate the methods on both artificial and real images.
Date: October 16, 2003
Creator: Fodor, I K
System: The UNT Digital Library
The Astro-E2 XRS/EBIT Microcalorimeter XC-ray Spectrometer (open access)

The Astro-E2 XRS/EBIT Microcalorimeter XC-ray Spectrometer

The X-ray Spectrometer (XRS) instrument is a revolutionary non-dispersive spectrometer that will form the basis for the Astro-E2 observatory to be launched in 2005. We have recently installed a flight spare XRS microcalorimeter spectrometer at the EBIT-I and SuperEBIT facility at LLNL replacing the XRS from the earlier Astro-E mission and providing twice the resolving power. The XRS microcalorimeter is an x-ray detector that senses the heat deposited by the incident photon. It achieves a high energy resolution by operating at 0.06K and by carefully engineering the heat capacity and thermal conductance. The XRS/EBIT instrument has 32 pixels in a square geometry and achieves an energy resolution of 6 eV at 6 keV, with a bandpass from 0.1 to 12 keV (or more at higher operating temperature). The instrument allows detailed studies of the x-ray line emission of laboratory plasmas. The XRS/EBIT also provides an extensive calibration 'library' for the Astro-E2 observatory.
Date: April 16, 2004
Creator: Porter, F S; Brown, G V; Boyce, K R; Kelley, R L; Kilbourne, C A; Beiersdorfer, P et al.
System: The UNT Digital Library
Pulsed Power Applications in High Intensity Proton Rings. (open access)

Pulsed Power Applications in High Intensity Proton Rings.

Pulsed power technology has been applied in particle accelerators and storage rings for over four decades. It is most commonly used in injection, extraction, beam manipulation, source, and focusing systems. These systems belong to the class of repetitive pulsed power. In this presentation, we review and discuss the history, present status, and future challenge of pulsed power applications in high intensity proton accelerators and storage rings.
Date: May 16, 2005
Creator: Zhang, S. Y.; Sandberg, J. & Al., Et
System: The UNT Digital Library
Massive Data Pre-Processing with a Cluster Based Approach (open access)

Massive Data Pre-Processing with a Cluster Based Approach

Data coming from complex simulation models reach easily dimensions much greater than available computational resources. Visualization of such data still represents the most intuitive and effective tool for scientific inspection of simulated phenomena. To ease this process several techniques have been adopted mainly concerning the use of hierarchical multi-resolution representations. In this paper we present the implementation of a hierarchical indexing schema for multiresolution data tailored to overwork the computational power of distributed environments.
Date: December 16, 2004
Creator: Borgo, R.; Cignoni, P.; Pascucci, V. & Scopigno, R.
System: The UNT Digital Library
Positron Annihilation Spectroscopy of Nanostructural Features in Model Reactor Pressure Vessel Steels (open access)

Positron Annihilation Spectroscopy of Nanostructural Features in Model Reactor Pressure Vessel Steels

Irradiation embrittlement in nuclear reactor pressure vessel steels results from the formation of a high number density of nanometer sized copper rich precipitates and sub-nanometer defect-solute clusters. We present positron annihilation spectroscopy (PAS) results to characterize the compositions and magnetic character of these defects in model A533B reactor pressure vessel steels. The results confirm the presence of copper-rich precipitates after irradiation. The measured orbital electron momentum spectra indicate the precipitates are alloyed with Mn and Ni. The copper precipitates larger than R {approx} 1.2 nm (from SANS measurements) are non-magnetic, which limits the possible Fe content of the precipitates to at most a few %. Notably, large vacancy clusters observed in neutron irradiated Fe-Cu alloys were not observed in the steels after irradiation.
Date: July 16, 2003
Creator: Glade, S C; Wirth, B D; Asoka-Kumar, P; Sterne, P A & Odette, G R
System: The UNT Digital Library
Micromechanics of Transformation Superplasticity in Ti-6Al-4V/TiBw Composites (open access)

Micromechanics of Transformation Superplasticity in Ti-6Al-4V/TiBw Composites

Transformation superplasticity is a deformation mechanism induced by thermally-cycling a polymorphic material through the phase transformation range while simultaneously applying an external biasing stress. Unlike microstructural superplasticity, which requires a fine, equiaxed grain structure, this mechanism can be applied to coarse-grained alloys and composites. In this article, we review our research on transformation superplasticity of Ti-6Al-4V/TiB-whisker reinforced composites, during thermal cycling through the titanium {alpha}/{beta} transformation range. The composites exhibit Newtonian flow and superplastic extension under these conditions. We describe the constitutive behavior of composites containing 0, 5 and 10 vol% reinforcing whiskers, and consider the effects of load transfer from matrix to whisker on superplastic deformation using existing rheological models. Additionally, strain hardening due to gradual whisker alignment is observed, and rationalized in terms of increased load transfer for aligned whiskers.
Date: October 16, 2001
Creator: Schuh, C & Dunand, D C
System: The UNT Digital Library
In-situ Studies of Highly Charged Ions at the LLNL EBIT (open access)

In-situ Studies of Highly Charged Ions at the LLNL EBIT

The properties of highly charged ions and their interaction with electrons and atoms is being studied in-situ at the LLNL electron beam ion traps, EBIT-II and SuperEBIT. Spectroscopic measurements provide data on electron-ion and ion-atom interactions as well as accurate transition energies of lines relevant for understanding QED, nuclear magnetization, and the effects of relativity on complex, state-of-the-art atomic calculations.
Date: August 16, 2001
Creator: Beiersdorfer, P
System: The UNT Digital Library
Optimization of the Phase Advance Between Rhic Interaction Points. (open access)

Optimization of the Phase Advance Between Rhic Interaction Points.

The authors consider a scenario of having two identical Interaction Points (IPs) in the Relativistic Heavy Ion Collider (RHIC). The strengths of beam-beam resonances strongly depend on the phase advance between these two IPs and therefore certain phase advances could improve beam life-time and luminosity. The authors compute the dynamic aperture (DA) as function of the phase advance between these IPs to find the optimum settings.The beam-beam interaction is treated in the weak-strong approximation and a non-linear model of the lattice is used. For the current RHIC proton working point (0.69.0.685) [1] the design lattice is found to have the optimum phase advance. However this is not the case for other working points.
Date: May 16, 2005
Creator: Tomas, R. & Fischer, W.
System: The UNT Digital Library
Electron Cloud at Collimator and Injection Region of the Spallation Neutron Source Accumulator Ring. (open access)

Electron Cloud at Collimator and Injection Region of the Spallation Neutron Source Accumulator Ring.

The beam loss along the Spallation Neutron Source's accumulator ring is mainly located at the collimator region and injection region. This paper studied the electron cloud build-up at these two regions with the three-dimension program CLOUDLAND.
Date: May 16, 2005
Creator: Wang, L.; Hseuh, H. C.; Lee, Y. Y.; Raparia, D.; Wei, J. & Cousineau, S.
System: The UNT Digital Library
HELIUM FLOW INDUCED ORBIT JITTER AT RHIC. (open access)

HELIUM FLOW INDUCED ORBIT JITTER AT RHIC.

Horizontal beam orbit jitter at frequencies around 10 Hz has been observed in RHIC for several years. The distinct frequencies of this jitter have been found at superconducting low-beta quadrupole triplets around the ring, where they coincide with mechanical modes of the cold masses. Recently, we have identified liquid helium flow as the driving force of these oscillations.
Date: May 16, 2005
Creator: Montag, C.; He, P.; Jia, L.; Nicoletti, A.; Satogata, T. & AL., ET
System: The UNT Digital Library
Precision surveying system for PEP (open access)

Precision surveying system for PEP

A semi-automatic precision surveying system is being developed for PEP. Reference elevations for vertical alignment will be provided by a liquid level. The short range surveying will be accomplished using a Laser Surveying System featuring automatic data acquisition and analysis.
Date: March 16, 1977
Creator: Gunn, J.; Lauritzen, T.; Sah, R. & Pellisier, P. F.
System: The UNT Digital Library
Synchrotron Radiation in Erhic Interaction Region. (open access)

Synchrotron Radiation in Erhic Interaction Region.

The electron-ion collider eRHIC [1] currently under study at BNL consists of an electron storage ring added to the existing RHIC complex. The interaction region of this facility has to provide the required low-beta focusing while accommodating the synchrotron radiation generated by beam separation close to the interaction point. In the current design, the synchrotron radiation caused by 10GeV electrons bent by separator dipole magnets will be guided through the interaction region and dumped 5m downstream. However, it is unavoidable to stop a fraction of the photons at the septum where the electron and ion vacuum systems are separated. In order to protect the septum and minimize the backward synchrotron radiation, an absorber and collimation system will be employed. In this paper, we fist present the overview of the current design of the eRHIC interaction region with special emphasis on the synchrotron radiation. Then the initial design of the absorber, including its geometrical and physical property, will be described. Finally, our initial investigation of synchrotron radiation in the eRHIC interaction region, especially a simulation of the backward scattering from the absorber, will be presented.
Date: May 16, 2005
Creator: Beebe-Wang, J. J.; Montag, C. & AL., ET
System: The UNT Digital Library
COMPARISON OF OFF-LINE IR BUMP AND ACTION-ANGLE KICK MINIMIZATION. (open access)

COMPARISON OF OFF-LINE IR BUMP AND ACTION-ANGLE KICK MINIMIZATION.

The interaction region bump (IR bump) nonlinear correction method has been used for the sextupole and octupole field error on-line corrections in the Relativistic Heavy Ion Collider (RHIC) . Some differences were found for the sextupole and octupole corrector strengths between the on-line IR bump correction and the predictions from the action-angle kick minimization. In this article, we compare the corrector strengths from these two methods based on the RHIC Blue ring lattice with the IR nonlinear modeling. The comparison confirms the differences between resulting corrector strengths. And the reason for the differences is found and discussed.
Date: May 16, 2005
Creator: Luo, Y.; Pilat, F.; Ptitsyn, V.; Trbojevic, D. & Wei, J.
System: The UNT Digital Library
Upgrade of Rhic Vacuum Systems for High Luminosity Operation. (open access)

Upgrade of Rhic Vacuum Systems for High Luminosity Operation.

With increasing ion beam intensity during recent RHIC operations, rapid pressure rises of several decades were observed at most warm sections and at a few cold sections. The pressure rises are associated with electron multi-pacting, electron stimulated desorption and beam ion induced desorption and have been one of the major intensity and luminosity limiting factors for RHIC. Improvement of the warm sections has been carried out in the last few years. Extensive in-situ bakes, additional UHV pumping and anti-grazing ridges have been implemented. Several hundred meters of NEG coated beam pipes have been installed and activated. Vacuum monitoring and logging were enhanced. Preventive measures, such as pumping before cool down to reduce monolayer condensates, were also taken to suppress the pressure rises in the cold sections. The effectiveness of these measures in reducing the pressure rises during machine studies and during physics runs are discussed and summarized.
Date: May 16, 2005
Creator: Hseuh, H. C.; Mapes, M.; Smart, L. A.; Todd, R. & Weiss, D.
System: The UNT Digital Library
Software Quality Assurance for Nuclear Safety Systems (open access)

Software Quality Assurance for Nuclear Safety Systems

The US Department of Energy has undertaken an initiative to improve the quality of software used to design and operate their nuclear facilities across the United States. One aspect of this initiative is to revise or create new directives and guides associated with quality practices for the safety software in its nuclear facilities. Safety software includes the safety structures, systems, and components software and firmware, support software and design and analysis software used to ensure the safety of the facility. DOE nuclear facilities are unique when compared to commercial nuclear or other industrial activities in terms of the types and quantities of hazards that must be controlled to protect workers, public and the environment. Because of these differences, DOE must develop an approach to software quality assurance that ensures appropriate risk mitigation by developing a framework of requirements that accomplishes the following goals: {sm_bullet} Ensures the software processes developed to address nuclear safety in design, operation, construction and maintenance of its facilities are safe {sm_bullet} Considers the larger system that uses the software and its impacts {sm_bullet} Ensures that the software failures do not create unsafe conditions Software designers for nuclear systems and processes must reduce risks in software applications …
Date: May 16, 2004
Creator: Sparkman, D R & Lagdon, R
System: The UNT Digital Library
K-Alpha Emission Spectra From Non-Equilibrium Ionizing Plasmas (open access)

K-Alpha Emission Spectra From Non-Equilibrium Ionizing Plasmas

K{alpha} X-ray emission spectra from highly charged Fe ions have been theoretically predicted using a detailed and systematic spectral model. Account has been taken of the fundamental atomic radiative-emission processes associated with inner-shell electron collisional excitation and ionization, as well as dielectronic recombination. Particular emphasis has been directed at extreme non-equilibrium or transient-ionization conditions, which can occur in astrophysical and tokamak plasmas. Good agreement has been found in comparisons with spectral observations on the EBIT-II electron beam ion trap at the Lawrence Livermore National Laboratory. We have identified spectral features that can serve as diagnostics of the electron density, the line-formation mechanism, and the charge-state distribution.
Date: December 16, 2004
Creator: Jacobs, V L; Decaux, V & Beiersdorfer, P
System: The UNT Digital Library
Injector Linac for the Bnl Super Neutrino Beam Project. (open access)

Injector Linac for the Bnl Super Neutrino Beam Project.

BNL plans to upgrade the AGS proton beam power from the present 0.14 MW to higher than 1.0 MW and beyond for a neutrino facility. We have examined possible upgrade to the AGS accelerator complex that would meet the requirements of the proton beam of 1.0 MW for neutrino superbeam facility. The major contribution for the higher power is from the increase of the repetition rate of the AGS from 0.3 Hz to 2.5 Hz, with moderate increase from the intensity. To increase the AGS repetition rate we are proposing to replace booster with a 1.5 GeV linac. We will replace part of existing 200 MeV linac with coupled cavity structure from 116 MeV to 400 MeV and then add an additional 1.1 GeV superconducting linac to reach a final energy of 1.5 GeV for direct H{sup -} injection into the AGS. We will present possible choices for the upgrade and our choice and its design.
Date: May 16, 2005
Creator: Raparia, D.; Alessi, J.; Ruggiero, A. & Weng, W. T.
System: The UNT Digital Library
Parallel Computation of the Topology of Level Sets (open access)

Parallel Computation of the Topology of Level Sets

This paper introduces two efficient algorithms that compute the Contour Tree of a 3D scalar field F and its augmented version with the Betti numbers of each isosurface. The Contour Tree is a fundamental data structure in scientific visualization that is used to preprocess the domain mesh to allow optimal computation of isosurfaces with minimal overhead storage. The Contour Tree can also be used to build user interfaces reporting the complete topological characterization of a scalar field, as shown in Figure 1. Data exploration time is reduced since the user understands the evolution of level set components with changing isovalue. The Augmented Contour Tree provides even more accurate information segmenting the range space of the scalar field in portion of invariant topology. The exploration time for a single isosurface is also improved since its genus is known in advance. Our first new algorithm augments any given Contour Tree with the Betti numbers of all possible corresponding isocontours in linear time with the size of the tree. Moreover we show how to extend the scheme introduced in [3] with the Betti number computation without increasing its complexity. Thus, we improve on the time complexity from our previous approach [10] from O(m …
Date: December 16, 2004
Creator: Pascucci, V & Cole-McLaughlin, K
System: The UNT Digital Library
The Extraction Lambertson Septum Magnet of the Sns. (open access)

The Extraction Lambertson Septum Magnet of the Sns.

In the Spallation Neutron Source, after multiple injections to an accumulator ring, a final extraction delivers the full proton beam to the target, achieved by a series of kickers and a thin septum magnet. Here we discuss the lattice geometry, beam dynamics and optics, and the vacuum, electromagnetic and mechanical design aspects of the Extraction Lambertson Septum Magnet (ELS). Relevant data are established. Vector calculus is solved for pitch and roll angles, which are shown schematically in magnet sections.
Date: May 16, 2005
Creator: J., Rank; Miglionico, G.; Raparia, D.; Tsoupas, N.; Tuozzolo, J. & Lee, Y. Y.
System: The UNT Digital Library