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Stochastic Kinetic Monte Carlo algorithms for long-range Hamiltonians (open access)

Stochastic Kinetic Monte Carlo algorithms for long-range Hamiltonians

We present a higher order kinetic Monte Carlo methodology suitable to model the evolution of systems in which the transition rates are non- trivial to calculate or in which Monte Carlo moves are likely to be non- productive flicker events. The second order residence time algorithm first introduced by Athenes et al.[1] is rederived from the n-fold way algorithm of Bortz et al.[2] as a fully stochastic algorithm. The second order algorithm can be dynamically called when necessary to eliminate unproductive flickering between a metastable state and its neighbors. An algorithm combining elements of the first order and second order methods is shown to be more efficient, in terms of the number of rate calculations, than the first order or second order methods alone while remaining statistically identical. This efficiency is of prime importance when dealing with computationally expensive rate functions such as those arising from long- range Hamiltonians. Our algorithm has been developed for use when considering simulations of vacancy diffusion under the influence of elastic stress fields. We demonstrate the improved efficiency of the method over that of the n-fold way in simulations of vacancy diffusion in alloys. Our algorithm is seen to be an order of magnitude …
Date: October 13, 2003
Creator: Mason, D R; Rudd, R E & Sutton, A P
System: The UNT Digital Library
The National Ignition Facility: The World's Largest Laser (open access)

The National Ignition Facility: The World's Largest Laser

The National Ignition Facility (NIF), currently under construction at the Lawrence Livermore National Laboratory, is a stadium-sized facility containing a 192-beam, 1.8-Megajoule, 500-Terawatt, ultraviolet laser system together with a 10-meter diameter target chamber with room for nearly 100 experimental diagnostics. When completed, NIF will be the world's largest and most energetic laser experimental system, providing an international center to study inertial confinement fusion and the physics of matter at extreme energy densities and pressures. NIF's 192 energetic laser beams will compress fusion targets to conditions required for thermonuclear burn, liberating more energy than required to initiate the fusion reactions. Other NIF experiments will allow the study of physical processes at temperatures approaching 10{sup 8} K and 10{sup 11} Bars, conditions that exist naturally only in the interior of stars, planets and in nuclear weapons. NIF has now completed the first phases of its laser commissioning program. The first four beams of NIF have generated 106 kilo-joules of infrared light, exceeding design requirements. Operation of single beams at the second harmonic (531 nm) and third harmonic (351 nm) at greater than 10 kilojoules have also exceeded the performance criteria. NIF's target experimental systems are being commissioned and experiments have begun. This …
Date: October 13, 2003
Creator: Moses, E I
System: The UNT Digital Library
Long baseline neutrino oscillations: Parameter degeneracies and JHF/NuMI complementarity (open access)

Long baseline neutrino oscillations: Parameter degeneracies and JHF/NuMI complementarity

A summary of the parameter degeneracy issue for long baseline neutrino oscillations is presented and how a sequence of measurements can be used to resolve all degeneracies. Next, a comparison of the JHF and NuMI Off-Axis proposals is made with emphasis on how both experiments running neutrinos can distinguish between the normal and inverted hierarchies provided the E/L of NuMI is less than or equal to the E/L of JHF. Due to the space limitations of this proceedings only an executive style summary can be presented here, but the references and transparencies of the talk contain the detailed arguments.
Date: October 13, 2003
Creator: Parke, Stephen; Minakata, Hisakazu & Nunokawa, Hiroshi
System: The UNT Digital Library
Underlying event studies at CDF (open access)

Underlying event studies at CDF

We present recent studies about the ''underlying event'' which originates mostly from soft spectator interactions. First Run II data results are compared to published Run I results and to QCD Monte Carlo models.
Date: October 13, 2003
Creator: Lami, S.
System: The UNT Digital Library
Charm and beauty at the Tevatron (open access)

Charm and beauty at the Tevatron

The large heavy quark production cross section in p{bar p} collisions makes the Tevatron an excellent place to study charm and bottom physics. This allows for a rich program of spectroscopy, CP parameter measurements, and searches for new physics.
Date: October 13, 2003
Creator: Cranshaw, J.
System: The UNT Digital Library
["The New Face of Gay Power" article, October 13, 2003] (open access)

["The New Face of Gay Power" article, October 13, 2003]

An article, written by John Cloud for Time Magazine, about Cody, Wyoming five years after the murder of a young gay man named Matthew Shepard. It is one of the more liberal cities in the state and is also home to one of the Republican Unity Coalition's chairmen, Alan Simpson.
Date: October 13, 2003
Creator: Cloud, John
System: The UNT Digital Library
ERHIC INTERACTION REGION DESIGN. (open access)

ERHIC INTERACTION REGION DESIGN.

This paper presents the current interaction region design status of the ring-ring version of the electron-ion collider eRHIC (release 2.0).
Date: October 13, 2003
Creator: MONTAG,C. PARKER,B. PTITSYN,V. TEPIKIAN,S. WANG,D. WANG,F.
System: The UNT Digital Library
Data Acquisition for Sns Beam Loss Monitor System (open access)

Data Acquisition for Sns Beam Loss Monitor System

The Spallation Neutron Source (SNS) beam loss monitor system uses VME based electronics to measure the radiation produced by lost beam. Beam loss signals from cylindrical argon-filled ion chambers and neutron detectors will be conditioned in analog front-end (AFE) circuitry. These signals will be digitized and further processed in a dedicated VME crate. Fast beam inhibit and low-level, long-term loss warnings will be generated to provide machine protection. The fast loss data will have a bandwidth of 35kHz. While the low level, long-term loss data will have much higher sensitivity. This is further complicated by the 3 decade range of intensity as the Ring accumulates beam. Therefore a bandwidth of 100kHz and dynamic range larger than 21 bits data acquisition system will be required for this purpose. Based on the evaluation of several commercial ADC modules in preliminary design phase, a 24 bits Sigma-Delta data acquisition VME bus card was chosen as the SNS BLM digitizer. An associated vxworks driver and EPICS device support module also have been developed at BNL. Simulating test results showed this system is fully qualified for both fast loss and low-level, long-term loss application. The first prototype including data acquisition hardware setup and EPICS software …
Date: October 13, 2003
Creator: Yeng, Y.; Gassner, D.; Hoff, L. & Witkover, R.
System: The UNT Digital Library
Testing and Quality Assurance of the Control System During NIF Commissioning (open access)

Testing and Quality Assurance of the Control System During NIF Commissioning

The strategy used to develop the National Ignition Facility Integrated Computer Control System (NIF ICCS) calls for incremental cycles of construction and formal test to deliver nearly one million lines of code. Software releases that implement specific functionality are approved for deployment when offline tests conducted in the ICCS Integration and Test Facility verify functional, performance and interface requirements using test procedures derived from system requirements. At this stage of the project the controls team has delivered approximately 3/4 of the planned software by performing dozens of development and test cycles within offline test facilities and followed by online tests to confirm integrated operation in the NIF. Test incidents are recorded and tracked from development to successful deployment by the verification team, with hardware and software changes approved by the appropriate change control board. Project metrics are generated by the Software Quality Assurance manager and monitored by ICCS management. Test results are summarized and reported to responsible individuals and Project managers under a work authorization and permit process that assesses risk and evaluates control system upgrade readiness. NIF is well into the first phases of its laser commissioning program to characterize and operate the first four laser beams and target …
Date: October 13, 2003
Creator: Casavant, D; Carey, R; Cline, B; Lagin, L; Ludwigsen, P; Reddi, U et al.
System: The UNT Digital Library
Status of the National Ignition Facility Integrated Computer Control System (open access)

Status of the National Ignition Facility Integrated Computer Control System

The National Ignition Facility (NIF), currently under construction at the Lawrence Livermore National Laboratory, is a stadium-sized facility containing a 192-beam, 1.8-Megajoule, 500-Terawatt, ultraviolet laser system together with a 10-meter diameter target chamber with room for nearly 100 experimental diagnostics. When completed, NIF will be the world's largest and most energetic laser experimental system, providing an international center to study inertial confinement fusion and the physics of matter at extreme energy densities and pressures. NIF's 192 energetic laser beams will compress fusion targets to conditions required for thermonuclear burn, liberating more energy than required to initiate the fusion reactions. Laser hardware is modularized into line replaceable units such as deformable mirrors, amplifiers, and multi-function sensor packages that are operated by the Integrated Computer Control System (ICCS). ICCS is a layered architecture of 300 front-end processors attached to nearly 60,000 control points and coordinated by supervisor subsystems in the main control room. The functional subsystems--beam control including automatic beam alignment and wavefront correction, laser pulse generation and pre-amplification, diagnostics, pulse power, and timing--implement automated shot control, archive data, and support the actions of fourteen operators at graphic consoles. Object-oriented software development uses a mixed language environment of Ada (for functional controls) …
Date: October 13, 2003
Creator: Lagin, L.; Bryant, R.; Carey, R.; Casavant, D.; Edwards, O.; Ferguson, W. et al.
System: The UNT Digital Library
ANALOG I/O MODULE TEST SYSTEM BASED ON EPICS CA PROTOCOL AND ACTIVEX CA INTERFACE (open access)

ANALOG I/O MODULE TEST SYSTEM BASED ON EPICS CA PROTOCOL AND ACTIVEX CA INTERFACE

Analog input (ADC) and output (DAC) modules play a substantial role in device level control of accelerator and large experiment physics control system. In order to get the best performance some features of analog modules including linearity, accuracy, crosstalk, thermal drift and so on have to be evaluated during the preliminary design phase. Gain and offset error calibration and thermal drift compensation (if needed) may have to be done in the implementation phase as well. A natural technique for performing these tasks is to interface the analog VO modules and GPIB interface programmable test instruments with a computer, which can complete measurements or calibration automatically. A difficulty is that drivers of analog modules and test instruments usually work on totally different platforms (vxworks VS Windows). Developing new test routines and drivers for testing instruments under VxWorks (or any other RTOS) platform is not a good solution because such systems have relatively poor user interface and developing such software requires substantial effort. EPICS CA protocol and ActiveX CA interface provide another choice, a PC and LabVIEW based test system. Analog 110 module can be interfaced from LabVIEW test routines via ActiveX CA interface. Test instruments can be controlled via LabVIEW drivers, …
Date: October 13, 2003
Creator: Yeng,Y.
System: The UNT Digital Library
The National Ignition Facility: Status of the Integrated Computer Control System (open access)

The National Ignition Facility: Status of the Integrated Computer Control System

The National Ignition Facility (NIF), currently under construction at the Lawrence Livermore National Laboratory, is a stadium-sized facility containing a 192-beam, 1.8-Megajoule, 500-Terawatt, ultraviolet laser system together with a 10-meter diameter target chamber with room for nearly 100 experimental diagnostics. When completed, NIF will be the world's largest and most energetic laser experimental system, providing an international center to study inertial confinement fusion and the physics of matter at extreme energy densities and pressures. NIF's 192 energetic laser beams will compress fusion targets to conditions required for thermonuclear burn, liberating more energy than required to initiate the fusion reactions. Laser hardware is modularized into line replaceable units such as deformable mirrors, amplifiers, and multi-function sensor packages that are operated by the Integrated Computer Control System (ICCS). ICCS is a layered architecture of 300 front-end processors attached to nearly 60,000 control points and coordinated by supervisor subsystems in the main control room. The functional subsystems--beam control including automatic beam alignment and wavefront correction, laser pulse generation and pre-amplification, diagnostics, pulse power, and timing--implement automated shot control, archive data, and support the actions of fourteen operators at graphic consoles. Object-oriented software development uses a mixed language environment of Ada (for functional controls) …
Date: October 13, 2003
Creator: Van Arsdall, P. J.; Bryant, R.; Carey, R.; Casavant, D.; Demaret, R.; Edwards, O. et al.
System: The UNT Digital Library
Nucleation of GaN/AlN quantum dots (open access)

Nucleation of GaN/AlN quantum dots

We study the nucleation of GaN islands grown by plasma-assisted molecular-beam epitaxy on AlN in a Stranski-Krastanov mode. In particular, we assess the variation of their height and density as a function of GaN coverage. We show that the GaN growth passes four stages: initially, the growth is layer-by-layer; subsequently, bidimensional precursor islands form, which transform into genuine three-dimensional islands. During the latter stage, the height and the density of the islands increase with GaN coverage until the density saturates. During further GaN growth, the density remains constant and a bimodal height distribution appears. The variation of island height and density as a function of substrate temperature is discussed in the framework of an equilibrium model for Stranski-Krastanov growth [R. E. Rudd et al., Phys. Rev. Lett. 90, 146101 (2003)].
Date: October 13, 2003
Creator: Adelmann, C.; Daudin, B.; Oliver, R. A.; Briggs, G. A. D. & Rudd, R. E.
System: The UNT Digital Library
Regiospecific hydroxylation of isoflavones by cytochrome P450 81E enzymes from Medicago truncatula (open access)

Regiospecific hydroxylation of isoflavones by cytochrome P450 81E enzymes from Medicago truncatula

Article on regiospecific hydroxylation of isoflavones by cytochrome P450 81E enzymes from Medicago truncatula.
Date: October 13, 2003
Creator: Liu, Chang-Jun; Huhman, David; Sumner, Lloyd W. & Dixon, R. A.
System: The UNT Digital Library
Adapting SAM for CDF (open access)

Adapting SAM for CDF

The CDF and D0 experiments probe the high-energy frontier and as they do so have accumulated hundreds of Terabytes of data on the way to petabytes of data over the next two years. The experiments have made a commitment to use the developing Grid based on the SAM system to handle these data. The D0 SAM has been extended for use in CDF as common patterns of design emerged to meet the similar requirements of these experiments. The process by which the merger was achieved is explained with particular emphasis on lessons learned concerning the database design patterns plus realization of the use cases.
Date: October 13, 2003
Creator: Bonham, D.; Garzoglio, G.; Herber, R.; Kowalkowski, J.; Litvintsev, D.; Lueking, L. et al.
System: The UNT Digital Library