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30 years of high-intensity negative ion sources for accelerators (open access)

30 years of high-intensity negative ion sources for accelerators

Thirty years ago, July 1, 1971, significant enhancement of negative ion emission from a gas discharge following an admixture of cesium was observed for the first time. This observation became the basis for the development of Surface Plasma Sources (SPS) for efficient production of negative ions from the interaction of plasma particles with electrodes on which adsorbed cesium reduced the surface work-function. The emission current density of negative ions increased rapidly from j {approximately} 10 mA/cm{sup 2} to 3.7 A/cm{sup 2} with a flat cathode and up to 8 A/cm{sup 2} with an optimized geometrical focusing in the long pulse SPS, and to 0.3 A/cm{sup 2} for DC SPS, recently increased up to 0.7 A/cm{sup 2}. Discovery of charge-exchange cooling helped decrease the negative ion temperature T below 1 eV, and increase brightness by many orders to a level compatible with the best proton sources, B = j/T> 1 A/cm{sup 2} eV. The combination of the SPS with charge-exchange injection improved large accelerators operation and has permitted beam accumulation up to space-charge limit and overcome this limit several times. The early SPS for accelerators have been in operation without modification for {approximately} 25 years. Advanced version of the SPS for …
Date: July 25, 2001
Creator: Dudnikov, Vadim
System: The UNT Digital Library
A 75-keV, 145-mA PROTON INJECTOR (open access)

A 75-keV, 145-mA PROTON INJECTOR

None
Date: July 1, 2001
Creator: Sherman, J. D.; Figueroa, T. L. & Al, Et
System: The UNT Digital Library
2001 Gordon Research Conference on Laser Diagnostics in Combustion. Final Progress Report (open access)

2001 Gordon Research Conference on Laser Diagnostics in Combustion. Final Progress Report

None
Date: July 6, 2001
Creator: unknown
System: The UNT Digital Library
ABSOLUTE PARTIAL GAMMA-RAY CROSS SECTIONS IN 238U(n,xngamma) REACTIONS (open access)

ABSOLUTE PARTIAL GAMMA-RAY CROSS SECTIONS IN 238U(n,xngamma) REACTIONS

None
Date: July 1, 2001
Creator: Fotiadis, N.; Johns, G. & Al, Et
System: The UNT Digital Library
Accurate Hydrogen Depth Profiling by Reflection Elastic Recoil Detection Analysis (open access)

Accurate Hydrogen Depth Profiling by Reflection Elastic Recoil Detection Analysis

None
Date: July 1, 2001
Creator: Verda, R. D.; Tesmer, J. R. & Al, Et
System: The UNT Digital Library
Adaptive Optics Control Strategies for Extremely Large Telescopes (open access)

Adaptive Optics Control Strategies for Extremely Large Telescopes

Adaptive optics for the 30-100 meter class telescopes now being considered will require an extension in almost every area of AO system component technology. In this paper, we present scaling laws and strawman error budgets for AO systems on extremely large telescopes (ELTs) and discuss the implications for component technology and computational architecture. In the component technology area, we discuss the advanced efforts being pursued at the NSF Center for Adaptive Optics (CfAO) in the development of large number of degrees of freedom deformable mirrors, wavefront sensors, and guidestar lasers. It is important to note that the scaling of present wavefront reconstructor algorithms will become computationally intractable for ELTs and will require the development of new algorithms and advanced numerical mathematics techniques. We present the computational issues and discuss the characteristics of new algorithmic approaches that show promise in scaling to ELT AO systems.
Date: July 26, 2001
Creator: Gavel, D T
System: The UNT Digital Library
Advances in ANL reactor physics methods inspired by A. F. Henry. (open access)

Advances in ANL reactor physics methods inspired by A. F. Henry.

None
Date: July 6, 2001
Creator: Khalil, H. S.; Taiwo, T. A.; Yang, W. S. & Finck, P. J.
System: The UNT Digital Library
Alignment of the Fermilab D0 Detector (open access)

Alignment of the Fermilab D0 Detector

The Fermilab D0 detector was used for the discovery of the top quark during Run I in 1996. It is currently being upgraded to exploit the physics potential to be presented by the Main Injector and the Tevatron Collider during Run II in the Fall of 2000. Some of the essential elements of this upgrade is the upgrade of the Solenoid Magnet, the Central Fiber Tracker, the Preshower Detectors, the Calorimeter System, and the Muon System. This paper discusses the survey and alignment of the these detectors with emphasis on the Muon detector system. The alignment accuracy is specified as better than 0.5mm. A combination of the Laser Tracker, BETS, and V-STARS systems are used for the survey.
Date: July 20, 2001
Creator: Oshinowo, Babatunde O'Sheg
System: The UNT Digital Library
American Nuclear Society nuclear criticality safety division. (open access)

American Nuclear Society nuclear criticality safety division.

Development of an ANSI/ANS Standard for the training and qualification of criticality safety engineers has been underway for nearly one year. The working group for this Standard is comprised of criticality safety experts from regulatory, licensee and contractor organizations. Its goal is to develop a standard that can be uniformly adopted, that covers all criticality safety engineer qualification levels, and that includes all required competencies such that most of the qualifications can be easily transferred between sites. This status report is presented to let the general criticality safety community know of progress on the Standard, and to solicit feedback to the working group as it continues work on ANSI/ANS-8.26.
Date: July 26, 2001
Creator: Morman, J. A. & McKamy, J.
System: The UNT Digital Library
Analysis of Dyes Extracted from Millimeter-Size Nylon Fibers by Micellar Electrokinetic Chromatography (open access)

Analysis of Dyes Extracted from Millimeter-Size Nylon Fibers by Micellar Electrokinetic Chromatography

The Learning Objective is to present to the forensic community a potential qualitative/quantitative method for trace-fiber color comparisons using micellar electrokinetic chromatography (MEKC). Developing a means of analyzing extracted dye constituents from millimeter-size nylon fiber samples was the objective of this research initiative. Aside from ascertaining fiber type, color evaluation and source comparison of trace-fiber evidence plays a critical role in forensic-fiber examinations. Literally thousands of dyes exist to date, including both natural and synthetic compounds. Typically a three-color-dye combination is employed to affect a given color on fiber material. The result of this practice leads to a significant number of potential dye combinations capable of producing a similar color and shade. Since a typical forensic fiber sample is 2 mm or less in length, an ideal forensic dye analysis would qualitatively and quantitatively identify the extracted dye constituents from a sample size of 1 mm or smaller. The goal of this research was to develop an analytical method for comparing individual dye constituents from trace-fiber evidence with dyes extracted from a suspected source, while preserving as much of the original evidence as possible.
Date: July 30, 2001
Creator: Lewis, L. A.
System: The UNT Digital Library
Analytical study and tracking simulations of the beam-beam compensation at Tevatron (open access)

Analytical study and tracking simulations of the beam-beam compensation at Tevatron

Head-on and long-range induced tunespread of about 0.025 in the Tevatron collider at Run II (together with the increased strength of the resonances) can significantly deteriorate the {bar p} lifetime and the collider luminosity. It was proposed to employ the so-called Tevatron Electron Lenses (TEL) to compress the beam-beam footprint and eliminate completely the bunch-to-bunch tunespread (PACMAN effect) for small amplitude particles. The first lens has been recently installed and tested [1]. This report presents results of analytical studies and tracking simulations of the linear beam-beam compensation (elimination of the bunch-to-bunch tune variation). Compression of the beam-beam footprint (nonlinear compensation) is discussed in [2].
Date: July 2, 2001
Creator: Shatilov, Dmitry; Alexahin, Yuri & Shiltsev, Vladimir
System: The UNT Digital Library
Antenna-coupled arrays of voltage-biased superconducting bolometers (open access)

Antenna-coupled arrays of voltage-biased superconducting bolometers

We report on the development of antenna-coupled Voltage-biased Superconducting Bolometers (VSBs) which use Transition-edge Sensors (TES). Antenna coupling can greatly simplify the fabrication of large multi-frequency bolometer arrays compared to horn-coupled techniques. This simplification can make it practical to implement 1000+ element arrays that fill the focal plane of mm/sub-mm wave telescopes. We have designed a prototype device with a double-slot dipole antenna, integrated band-defining filters, and a membrane-suspended bolometer. A test chip has been constructed and will be tested shortly.
Date: July 23, 2001
Creator: Myers, Michael J.; Lee, Adrian T.; Richards, P. L.; Schwan, D.; Skidmore, J. T.; Smith, A. D. et al.
System: The UNT Digital Library
Application of scaling properties of the Vlasov and the Fokker-Planck equations to improved macroparticle models (open access)

Application of scaling properties of the Vlasov and the Fokker-Planck equations to improved macroparticle models

Numerical simulations of cooling processes over minutes or hours of real time are usually carried out using direct solution of the Fokker-Planck equation. However, by using scaling rules derived from that equation, it is possible to use macroparticle representations of the beam distribution. Besides having applications for cooling alone, the macroparticle approach allows combining the cooling process with other dynamical processes which are represented by area-preserving maps. A time-scaling rule derived from the Vlasov equation can be used to adjust the time step of a map-based dynamics calculation to one more suitable for combining with a macroparticle Fokker-Planck calculation. The time scaling for the Vlasov equation is also useful for substantially more rapid calculations when a macroparticle model of a conservative multiparticle system requires a large number of macroparticles to faithfully produce the collective potential or when the model must simulate a long time period.
Date: July 12, 2001
Creator: MacLachlan, James A.
System: The UNT Digital Library
Application of Sensitivity and Uncertainty Analysis Methods to a Validation Study for Weapons-Grade Mixed-Oxide Fuel (open access)

Application of Sensitivity and Uncertainty Analysis Methods to a Validation Study for Weapons-Grade Mixed-Oxide Fuel

At the Oak Ridge National Laboratory (ORNL), sensitivity and uncertainty (S/U) analysis methods and a Generalized Linear Least-Squares Methodology (GLLSM) have been developed to quantitatively determine the similarity or lack thereof between critical benchmark experiments and an application of interest. The S/U and GLLSM methods provide a mathematical approach, which is less judgment based relative to traditional validation procedures, to assess system similarity and estimate the calculational bias and uncertainty for an application of interest. The objective of this paper is to gain experience with the S/U and GLLSM methods by revisiting a criticality safety evaluation and associated traditional validation for the shipment of weapons-grade (WG) MOX fuel in the MO-1 transportation package. In the original validation, critical experiments were selected based on a qualitative assessment of the MO-1 and MOX contents relative to the available experiments. Subsequently, traditional trending analyses were used to estimate the {Delta}k bias and associated uncertainty. In this paper, the S/U and GLLSM procedures are used to re-evaluate the suite of critical experiments associated with the original MO-1 evaluation. Using the S/U procedures developed at ORNL, critical experiments that are similar to the undamaged and damaged MO-1 package are identified based on sensitivity and uncertainty …
Date: July 20, 2001
Creator: Dunn, M.E.
System: The UNT Digital Library
AN APPROACH TO EXTREME-SCALE SIMULATION OF NOVEL ARCHITECTURES (open access)

AN APPROACH TO EXTREME-SCALE SIMULATION OF NOVEL ARCHITECTURES

None
Date: July 1, 2001
Creator: ALEXANDER, F. J.; BERKBIGLER, K. & AL, ET
System: The UNT Digital Library
Architecture of a software quench management system (open access)

Architecture of a software quench management system

Testing superconducting accelerator magnets is inherently coupled with the proper handling of quenches; i.e., protecting the magnet and characterizing the quench process. Therefore, software implementations must include elements of both data acquisition and real-time controls. The architecture of the quench management software developed at Fermilab's Magnet Test Facility is described. This system consists of quench detection, quench protection, and quench characterization components that execute concurrently in a distributed system. Collaboration between the elements of quench detection, quench characterization and current control are discussed, together with a schema of distributed saving of various quench-related data. Solutions to synchronization and reliability in such a distributed quench system are also presented.
Date: July 30, 2001
Creator: al., Jerzy M. Nogiec et
System: The UNT Digital Library
Argonne Wakefield Accelerator facility upgrade. (open access)

Argonne Wakefield Accelerator facility upgrade.

The Argonne Wakefield Accelerator has been successfully used for conducting wakefield experiments in dielectric loaded structures and plasmas. Although the initial wakefield experiments were successful, higher drive beam quality would substantially improve the wakefield accelerating gradients. For this reason they have built a new 1-1/2 cell L-band photocathode RF gun. This gun is expected to produce 10-100 nC bunches with 2-5 ps rms pulse length and normalized emittance less than 100 mm mrad. The gun will initially have a copper photocathode, which will soon be replaced by a high quantum efficiency cesium telluride one, allowing the generation of a train of high charge bunches. the beam energy at the exit of the gun cavity will be in the range 7.5-10 MeV. A standing-wave linac structure operating at the same frequency (1.3 GHz) will increase the beam energy to about 15 MeV. This beam will be used in high-gradient wakefield acceleration experiments and other high intensity electron beam applications. Traveling-wave dielectric loaded structures, operating at 7.8 and 15.6 GHz, will be excited by the propagation of single bunches or by trains of up to 32 electron bunches, reaching gradients in excess of 100 MV/m over distances of the order of 1 …
Date: July 11, 2001
Creator: Conde, M. E.; Gai, W.; Konecny, R.; Power, J. G.; Schoessow, P. & Sun, X.
System: The UNT Digital Library
Arpes Evidence for a Quasiparticle Liquid in Overdoped Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+delta}. (open access)

Arpes Evidence for a Quasiparticle Liquid in Overdoped Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+delta}.

High resolution angle-resolved photoemission spectroscopy of highly overdoped Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} with a T{sub c} = 51K indicates that the basic transport processes in this material are fundamentally different from both the lesser doped cuprates as well as model metallic compounds. The overdoped sample has sharp ARPES peaks at the Fermi energy throughout the Brillouin zone even in the normal state, unlike the lesser-doped compounds. In particular, the spectra near ({pi},0) point show the presence of a sharp peak well above T{sub c}. The ARPES lineshapes, and thus the self energy, at a given energy are almost independent of k. Further, the quasiparticle scattering rate at the Fermi energy seems to be closely tied to direct resistivity measurements. This leads us to the conclusion that overdoped Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} is best described as a quasiparticle liquid. However, the energy dependence of the scattering rates is quite similar to that found in the lesser-doped compounds and quite different from that seen in a typical metal.
Date: July 23, 2001
Creator: Wells, B. O.; Yusof, Z.; Valla, T.; Fedorov, A. V.; Johnson, P.; Kendziora, C. et al.
System: The UNT Digital Library
Assessing the Efficiency of US Electricity Markets (open access)

Assessing the Efficiency of US Electricity Markets

None
Date: July 1, 2001
Creator: Arciniegas, Ismael E.; Barrett, Chris & Marathe, Achla
System: The UNT Digital Library
Asymptotics, streamlines, and reservoir modeling: a pathway to production tomography (open access)

Asymptotics, streamlines, and reservoir modeling: a pathway to production tomography

None
Date: July 30, 2001
Creator: Vasco, D. W. & Datta-Gupta, Akhil
System: The UNT Digital Library
Band gap variation of size- and shape-controlled colloidal CdSe quantum rods (open access)

Band gap variation of size- and shape-controlled colloidal CdSe quantum rods

None
Date: July 8, 2001
Creator: Li, Liang-shi; Hu, Jiangtao; Yang, Weidong & Alivisatos, A. Paul
System: The UNT Digital Library
Baryon Resonances from a Novel Fat-Link Fermion Action (open access)

Baryon Resonances from a Novel Fat-Link Fermion Action

We present first results for masses of positive and negative parity excited baryons in lattice QCD using an O(a{sup 2}) improved gluon action and a Fat Link Irrelevant Clover (FLIC) fermion action in which only the irrelevant operators are constructed with fat links. The results are in agreement with earlier calculations of N* resonances using improved actions and exhibit a clear mass splitting between the nucleon and its chiral partner, even for the Wilson fermion action. The results also indicate a splitting between the lowest J{sup P}=1/2{sup -} states for the standard nucleon interpolating fields.
Date: July 1, 2001
Creator: Melnitchouk, W.; Bilson-Thompson, S.; Bonnet, F. D. R.; Coddington, P. D.; Lee, F. X.; Leinweber, D. B. et al.
System: The UNT Digital Library
Bayesian Separation of Lamb Wave Signatures (open access)

Bayesian Separation of Lamb Wave Signatures

A persistent problem in the analysis of Lamb wave signatures in experimental data is the fact that several different modes appear simultaneously in the signal. The modes overlap in both the frequency and time domains. Attempts to separate the overlapping Lamb wave signatures by conventional signal processing methods have been unsatisfactory. This paper reports an exciting alternative to conventional methods. Severely overlapping Lamb waves are found to be readily separable by Bayesian parameter estimation. The authors have used linear-chirped Gaussian-windowed sinusoids as models of each Lamb wave mode. The separation algorithm allows each mode to be examined individually.
Date: July 19, 2001
Creator: Kercel, Stephen W.; Klein, Marvin B. & Pouet, Bruno
System: The UNT Digital Library
Beam-Beam Compensation in Tevatron: Status Report (open access)

Beam-Beam Compensation in Tevatron: Status Report

The project of beam-beam compensation (BBC) in the Tevatron using electron beams [1] has passed a successful first step in experimental studies. The first Tevatron electron lens (TEL) has been installed in the Tevatron, commissioned, and demonstrated the theoretically predicted shift of betatron frequencies of a high energy proton beam due to a high current low energy electron beam. After the first series of studies in March-April 2001 (total of 7 shifts), we achieved tuneshifts of 980 GeV protons of about dQ=+0.007 with some 3 A of the electron beam current while the proton lifetime was in the range of 10 hours (some 24 hours at the best). Future work will include diagnostics improvement, beam studies with antiprotons, and fabrication of the 2nd TEL.
Date: July 12, 2001
Creator: Shiltsev, Vladimir D.; Kuznetsov, G.; Solyak, N.; Wildman, D.; Zhang, X. L.; Alexahin, Yu. et al.
System: The UNT Digital Library