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Performance Verification of the Astro-E2 X-ray spectrometer in the flight configuration (open access)

Performance Verification of the Astro-E2 X-ray spectrometer in the flight configuration

The X-ray Spectrometer (XRS) is a high resolution, non-dispersive cryogenic detector on board the X-ray satellite, Astro-E2 (Suzaku), which was successfully launched on July 10, 2005. The XRS achieves an energy resolution of 6 eV at 6 keV (FWHM) and covers a broad energy range of {approx} 0.07-10 keV. The XRS will enable powerful plasma diagnostics of a variety of astrophysical objects such as the dynamics of gas in clusters of galaxies. The XRS was integrated to the spacecraft in September 2004, and took a series of spacecraft tests until April 2005. We describe results of the XRS performance verification in the spacecraft configuration. First, the noise level was extremely low on the spacecraft, and most of the pixels achieved an energy resolution of 5-6 eV at 5.9 keV. Microphonics from the mechanical cooler was one of the concerns, but they did not interfere with the detector, when the dewar was integrated to the spacecraft and filled with solid neon. To attain the best energy resolution, however, correction of gain drift is mandatory. The XRS has a dedicated calibration pixel for that purpose, and drift correction using the calibration pixel is very effective when the gain variation is due to …
Date: September 12, 2005
Creator: Ota, N.; Boyce, K. R.; Brown, G. V.; Cottam, J.; Fujimoto, R.; Furusho, T. et al.
System: The UNT Digital Library
Dust-Particle Transport in Tokamak Edge Plasmas (open access)

Dust-Particle Transport in Tokamak Edge Plasmas

Dust particulates in the size range of 10nm-100{micro}m are found in all fusion devices. Such dust can be generated during tokamak operation due to strong plasma/material-surface interactions. Some recent experiments and theoretical estimates indicate that dust particles can provide an important source of impurities in the tokamak plasma. Moreover, dust can be a serious threat to the safety of next-step fusion devices. In this paper, recent experimental observations on dust in fusion devices are reviewed. A physical model for dust transport simulation, and a newly developed code DUSTT, are discussed. The DUSTT code incorporates both dust dynamics due to comprehensive dust-plasma interactions as well as the effects of dust heating, charging, and evaporation. The code tracks test dust particles in realistic plasma backgrounds as provided by edge-plasma transport codes. Results are presented for dust transport in current and next-step tokamaks. The effect of dust on divertor plasma profiles and core plasma contamination is examined.
Date: September 12, 2005
Creator: Pigarov, A Y; Krasheninnikov, S I; Soboleva, T K & Rognlien, T D
System: The UNT Digital Library
Molecular dynamics simulation of liquid water: Hybrid density functionals (open access)

Molecular dynamics simulation of liquid water: Hybrid density functionals

The structure, dynamical and electronic properties of liquid water utilizing different hybrid density functionals were tested within the plane wave framework of first principles molecular dynamics simulations. The computational approach, which employs modified functionals with short-ranged Hartree-Fock exchange, was first tested in calculations of the structural and bonding properties of the water dimer and cyclic water trimer. Liquid water simulations were performed at the state point of 350 K at the experimental density. Simulations included three different hybrid functionals, a meta functional, four gradient corrected functionals, the local density and Hartree-Fock approximation. It is found that hybrid functionals are superior in reproducing the experimental structure and dynamical properties as measured by the radial distribution function and self diffusion constant when compared to the pure density functionals. The local density and Hartree-Fock approximations show strongly over- and under-structured liquids, respectively. Hydrogen bond analysis shows that the hybrid functionals give slightly smaller averaged numbers of hydrogen bonds and similar hydrogen bond populations as pure density functionals. The average molecular dipole moments in the liquid from the three hybrid functionals are lower than from the corresponding pure density functionals.
Date: September 12, 2005
Creator: Todorova, T.; Seitsonen, A.; Hutter, J.; Kuo, W. & Mundy, C.
System: The UNT Digital Library
Registration and Fusion of X-Ray and Ultrasound Images for As-Built Modeling (open access)

Registration and Fusion of X-Ray and Ultrasound Images for As-Built Modeling

None
Date: September 12, 2005
Creator: Clark, G A & Jackson, J A
System: The UNT Digital Library
DETERMINATION OF INVENTORIES AND POWER DISTRIBUTIONS FOR THE NSBR. (open access)

DETERMINATION OF INVENTORIES AND POWER DISTRIBUTIONS FOR THE NSBR.

This memo presents the details of the methodology for developing fuel inventories for the NBSR along with power distributions predicted with this set of inventories. Several improvements have been made to the MCNP model of the NBSR since a set of calculations was performed in 2002 in support of the NBSR relicensing and SAR update. One of the most significant changes in the model was to divide the fuel elements into upper and lower halves so the effects of uneven burn between the two halves (due to the shim arms) can be determined. The present set of power distributions are provided for comparison with the previous safety analyses.
Date: September 12, 2005
Creator: Hanson, A. L. & DIAMOND, D. J.
System: The UNT Digital Library
Localized functionalization of single nanopores (open access)

Localized functionalization of single nanopores

We demonstrate the localization of chemical functionality at the entrance of single nanopores for the first time by using the controlled growth of an oxide ring. Nanopores were fabricated by Focused Ion Beam machining on silicon platforms, locally derivatized by ion beam assisted oxide deposition, and further functionalized with DNA probes via silane chemistry. Ionic current recorded through single nanopores at various stages of the fabrication process demonstrated that the apertures can be locally functionalized with DNA probes. Future applications for this functional platform include the selective detection of biological organisms and molecules by ionic current blockade measurements.
Date: September 12, 2005
Creator: Nilsson, J; Lee, J I; Ratto, T V & Letant, S E
System: The UNT Digital Library
THE FLUORBOARD A STATISTICALLY BASED DASHBOARD METHOD FOR IMPROVING SAFETY (open access)

THE FLUORBOARD A STATISTICALLY BASED DASHBOARD METHOD FOR IMPROVING SAFETY

None
Date: September 12, 2005
Creator: PREVETTE, S.S.
System: The UNT Digital Library
Spectroscopy and New Particles in BaBar (open access)

Spectroscopy and New Particles in BaBar

Results on charmonium states and searches for pentaquark states at the BABAR experiment are presented.
Date: September 12, 2005
Creator: Petersen, B.Aa.
System: The UNT Digital Library
Measurements of Radiation Near An Atomic Spectral Line From the Interaction of a 30-GeV Electron Beam And a Long Plasma (open access)

Measurements of Radiation Near An Atomic Spectral Line From the Interaction of a 30-GeV Electron Beam And a Long Plasma

Emissions produced or initiated by a 30 GeV electron beam propagating through a {approx}1 m long heat pipe oven containing neutral and partially ionized vapor have been measured near atomic spectral lines in a beam-plasma wakefield experiment. The Cerenkov spatial profile has been studied as a function of oven temperature and pressure, observation wavelength, and ionizing laser intensity and delay. The Cerenkov peak angle is affected by the creation of plasma; estimates of plasma and neutral density have been extracted. Increases in visible background radiation consistent with increased plasma recombination emissions due to dissipation of wakefields were simultaneously measured.
Date: September 12, 2005
Creator: Catravas, P.; Chattopadhyay, S.; Esarey, E.; Leemans, W. P.; Assmann, R.; Decker, F. J. et al.
System: The UNT Digital Library
W-Band Sheet Beam Klystron Simulation (open access)

W-Band Sheet Beam Klystron Simulation

With the development of ever higher energy particle accelerators comes the need for compactness and high gradient, which in turn require very high frequency high power rf sources. Recent development work in W-band accelerating techniques has spurred the development of a high-power W-band source. Axisymmetric sources suffer from fundamental power output limitations (P{sub sat} {approx} {lambda}{sup 2}) brought on by the conflicting requirements of small beam sizes and high beam current. The sheet beam klystron allows for an increase in beam current without substantial increase in the beam current density, allowing for reduced cathode current densities and focusing field strengths. Initial simulations of a 20:1 aspect ratio sheet beam/cavity interaction using the 3 dimensional particle-in-cell code Magic3D have demonstrated a 35% beam-power to RF power extraction efficiency. Calculational work and numerical simulations leading to a prototype W-band sheet beam klystron will be presented, together with preliminary cold test structure studies of a proposed RF cavity geometry.
Date: September 12, 2005
Creator: Colby, E. R.; Caryotakis, G.; Fowkes, W. R. & Smithe, D. N.
System: The UNT Digital Library
High Frequency Laser-Based Ultrasound (open access)

High Frequency Laser-Based Ultrasound

To obtain micrometer resolution of materials using acoustics requires frequencies around 1 GHz. Attenuation of such frequencies is high, limiting the thickness of the parts that can be characterized. Although acoustic microscopes can operate up to several GHz in frequency, they are used primarily as a surface characterization tool. The use of a pulsed laser for acoustic generation allows generation directly in the part, eliminating the loss of energy associated with coupling the energy from a piezoelectric transducer to the part of interest. The use of pulsed laser acoustic generation in combination with optical detection is investigated for the non-contact characterization of materials with features that must be characterized to micrometer resolution.
Date: September 12, 2005
Creator: Huber, R; Chinn, D; Balogun, O & Murray, T
System: The UNT Digital Library
Single Bunch Monopole Instability (open access)

Single Bunch Monopole Instability

We study single bunch stability with respect to monopole longitudinal oscillations in electron storage rings. Our analysis is different from the standard approach based on the linearized Vlasov equation. Rather, we reduce the full nonlinear Fokker-Planck equation to a Schroedinger-like equation which is subsequently analyzed by perturbation theory. We show that the Haissinski solution [3] may become unstable with respect to monopole oscillations and derive a stability criterion in terms of the ring impedance.
Date: September 12, 2005
Creator: Podobedov, B. & Heifets, S.
System: The UNT Digital Library
X-ray Emission from Megamaser Galaxy IC 2560 (open access)

X-ray Emission from Megamaser Galaxy IC 2560

Observation of the H{sub 2}O megamaser galaxy IC 2560 with the Chandra Observatory reveals a complex spectrum composed of soft X-ray emission due to multi-temperature thermal plasma, and a hard continuum with strong emission lines. The continuum is most likely a Compton reflection (reprocessing) of primary emission that is completely absorbed at least up to 7 keV. The lines can be identified with fluorescence from Si, S and Fe in the lowest ionization stages. The equivalent widths of the Si and S lines are broadly compatible with those anticipated for reprocessing by optically thick cold plasma of Solar abundances, while the large equivalent width of the Fe line requires some overabundance of iron. A contribution to the line from a transmitted component cannot be ruled out, but the limits on the strength of the Compton shoulder make it less likely. From the bolometric luminosity of the nuclear region, we infer that the source radiates at 1-10% of its Eddington luminosity, for an adopted central mass of 3 x 10{sup 6} M{sub {circle_dot}}. The overall spectrum is consistent with the hypotheses that the central engines powering the detected megamsers in accretion disks are obscured from direct view by the associated accretion …
Date: September 12, 2005
Creator: Madejski, Greg; /SLAC /KIPAC, Menlo Park; Done, Chris; U., /Durham; Zycki, Piotr; /Warsaw, Copernicus Astron. Ctr. et al.
System: The UNT Digital Library
A 90-GHz Photoinjector (open access)

A 90-GHz Photoinjector

Photocathode rf guns depend on mode locked laser systems to produce an electron beam at a given phase of the rf. In general, the laser pulse is less than {sigma}{sub z} = 10{sup o} of rf phase in length and the required stability is on the order of {Delta}{phi} = 1{sup o}. At 90 GHz (W-band), these requirements correspond to {sigma}{sub z} = 333 fsec and {Delta}{phi} = 33 fsec. Laser system with pulse lengths in the fsec regime are commercially available, the timing stability is a major concern. We propose a multi-cell W-band photoinjector that does not require a mode locked laser system. Thereby eliminating the stability requirements at W-band. The laser pulse is allowed to be many rf periods long. In principle, the photoinjector can now be considered as a thermionic rf gun. Instead of using an alpha magnet to compress the electron bunch, which would have a detrimental effect on the transverse phase space quality due to longitudinal phase space mixing, we propose to use long pulse laser system and a pair of undulators to produce a low emittance, high current, ultra-short electron bunch for beam dynamics experiments in the 90 GHz regime.
Date: September 12, 2005
Creator: Palmer, D. T.; Hogan, M. J.; Ferrario, M. & Serafini, L.
System: The UNT Digital Library
MIP Reconstruction Techniques and Minimum Spanning Tree Clustering (open access)

MIP Reconstruction Techniques and Minimum Spanning Tree Clustering

The development of a tracking algorithm for minimum ionizing particles in the calorimeter and of a clustering algorithm based on the Minimum Spanning Tree approach are described. They do not depend on information from the central tracking system. Both are important components of a particle flow algorithm currently under development.
Date: September 12, 2005
Creator: Mader, Wolfgang F.
System: The UNT Digital Library
NUMERICAL METHODS FOR THE SIMULATION OF HIGH INTENSITY HADRON SYNCHROTRONS. (open access)

NUMERICAL METHODS FOR THE SIMULATION OF HIGH INTENSITY HADRON SYNCHROTRONS.

Numerical algorithms for PIC simulation of beam dynamics in a high intensity synchrotron on a parallel computer are presented. We introduce numerical solvers of the Laplace-Poisson equation in the presence of walls, and algorithms to compute tunes and twiss functions in the presence of space charge forces. The working code for the simulation here presented is SIMBAD, that can be run as stand alone or as part of the UAL (Unified Accelerator Libraries) package.
Date: September 12, 2005
Creator: LUCCIO, A.; D'IMPERIO, N. & MALITSKY, N.
System: The UNT Digital Library
STATISTICAL CHALLENGES FOR SEARCHES FOR NEW PHYSICS AT THE LHC. (open access)

STATISTICAL CHALLENGES FOR SEARCHES FOR NEW PHYSICS AT THE LHC.

Because the emphasis of the LHC is on 5{sigma} discoveries and the LHC environment induces high systematic errors, many of the common statistical procedures used in High Energy Physics are not adequate. I review the basic ingredients of LHC searches, the sources of systematics, and the performance of several methods. Finally, I indicate the methods that seem most promising for the LHC and areas that are in need of further study.
Date: September 12, 2005
Creator: Cranmer, Kyle
System: The UNT Digital Library
As-Built Modeling of Ojbects for Performance Assessment (open access)

As-Built Modeling of Ojbects for Performance Assessment

The goal of ''as-built'' computational modeling is to incorporate the most representative geometry and material information for an (fabricated or legacy) object into simulations. While most engineering finite element simulations are based on an object's idealized ''as-designed'' configuration with information obtained from technical drawings or computer-aided design models, ''as-built'' modeling uses nondestructive characterization and metrology techniques to provide the feature information. By incorporating more representative geometry and material features as initial conditions, the uncertainty in the simulation results can be reduced, providing a more realistic understanding of the event and object being modeled. In this paper, key steps and technology areas in the as-built modeling framework are: (1) inspection using non-destructive characterization (NDC) and metrology techniques; (2) data reduction (signal and image processing including artifact removal, data sensor fusion, and geometric feature extraction); and (3) engineering and physics analysis using finite element codes. We illustrate the process with a cylindrical phantom and include a discussion of the key concepts and areas that need improvement. Our results show that reasonable as-built initial conditions based on a volume overlap criteria can be achieved and that notable differences between simulations of the as-built and as-designed configurations can be observed for a given load …
Date: September 12, 2005
Creator: Kokko, E J; Martz, H E; Chinn, D J; Childs, H. R.; Jackson, J A; Chambers, D H et al.
System: The UNT Digital Library