Resource Type

Language

Alignment validation (open access)

Alignment validation

The four experiments, ALICE, ATLAS, CMS and LHCb are currently under constructionat CERN. They will study the products of proton-proton collisions at the Large Hadron Collider. All experiments are equipped with sophisticated tracking systems, unprecedented in size and complexity. Full exploitation of both the inner detector andthe muon system requires an accurate alignment of all detector elements. Alignmentinformation is deduced from dedicated hardware alignment systems and the reconstruction of charged particles. However, the system is degenerate which means the data is insufficient to constrain all alignment degrees of freedom, so the techniques are prone to converging on wrong geometries. This deficiency necessitates validation and monitoring of the alignment. An exhaustive discussion of means to validate is subject to this document, including examples and plans from all four LHC experiments, as well as other high energy experiments.
Date: September 6, 2008
Creator: ALICE; ATLAS; CMS; LHCb & Golling, Tobias
System: The UNT Digital Library
Geometric metastability, quivers and holography (open access)

Geometric metastability, quivers and holography

We use large N duality to study brane/anti-brane configurations on a class of Calabi-Yau manifolds. With only branes present, the Calabi-Yau manifolds in question give rise to N=2 ADE quiver theories deformed by superpotential terms. We show that the large N duality conjecture of hep-th/0610249 reproduces correctly the known qualitative features of the brane/anti-brane physics. In the supersymmetric case, the gauge theories have Seiberg dualities which are represented as flops in the geometry. Moreover, the holographic dual geometry encodes the whole RG flow of the gauge theory. In the non-supersymmetric case, the large N duality predicts that the brane/anti-brane theories also enjoy such dualities, and allows one to pick out the good description at a given energy scale.
Date: September 6, 2007
Creator: Aganagic, Mina; Aganagic, Mina; Beem, Christopher & Freivogel, Ben
System: The UNT Digital Library
Measuring the impact of suspending Umrah, a global mass gathering in Saudi Arabia on the COVID‑19 pandemic (open access)

Measuring the impact of suspending Umrah, a global mass gathering in Saudi Arabia on the COVID‑19 pandemic

This article uses a stratified SEIR epidemic model to evaluate the impact of Umrah, a global Muslim pilgrimage to Mecca, on the spread of the COVID-19 pandemic during the month of Ramadan, the peak of the Umrah season. The analyses provide insights into the effects of global mass gatherings on the progression of the COVID-19 pandemic locally and globally.
Date: September 6, 2021
Creator: Alshammari, Sultanah M.; Almutiry, Waleed K.; Gwalani, Harsha; Algarni, Saeed M. & Saeedi, Kawther
System: The UNT Digital Library
An Update on the Status of the NIF Power Conditioning System (open access)

An Update on the Status of the NIF Power Conditioning System

The National Ignition Facility (NIF) Power Conditioning System provides the pulsed excitation required to drive flashlamps in the laser's optical amplifiers. Modular in design, each of the 192 Main Energy Storage Modules (MESMs) stores up to 2.2 MJ of electrical energy in its capacitor bank before delivering the energy to 20 pairs of flashlamps in a 400 {micro}s pulse (10% power points). The peak current of each MESM discharge is 0.5 MA. Production, installation, commissioning and operation of the NIF Power Conditioning continue to progress rapidly, with the goals of completing accelerated production and commissioning by early 2008, while maintaining an aggressive operation schedule. To date, more than 97% of the required modules have been assembled, shipped and installed in the facility, representing more that 380 MJ of stored energy available for driving NIF flashlamps. The MESMs have displayed outstanding reliability during daily, multiple-shift operations.
Date: September 6, 2007
Creator: Arnold, P. A.; Hulsey, S.; Ullery, G. T.; Petersen, D. E.; Pendleton, D. L.; Ollis, C. W. et al.
System: The UNT Digital Library
Increasing the Space Charge Limit and Other Effects of Cesium Seeding in Hydrogen Negative Ion Sources (open access)

Increasing the Space Charge Limit and Other Effects of Cesium Seeding in Hydrogen Negative Ion Sources

The role of cesium seeding in increasing the negative ion current in volume sources is described. By a reduction in the local plasma potential the current of extracted electrons is vastly reduced. As a result, cesium increases the fraction of the transverse space charge limit available to the ions by as much as a factor of three. In addition, cesium can increase the total space charge limit by injection of Cs+ into the presheath-a newly recognized phenomenon consistent with experimental measurements and determined from application of a Double-Vlasov model for negative ion extraction.
Date: September 6, 1999
Creator: Bacal, M.; Bruneteau, J.; Raridon, R.J. & Whealton, J.H.
System: The UNT Digital Library
Effect of Cesium and Xenon Seeding in Negative Hydrogen Ion Sources (open access)

Effect of Cesium and Xenon Seeding in Negative Hydrogen Ion Sources

It is well known that cesium seeding in volume hydrogen negative ion sources leads to a large reduction of the extracted electron current and in some cases to the enhancement of the negative ion current. The cooling of the electrons due to the addition of this heavy impurity was proposed as a possible cause of the mentioned observations. In order to verify this assumption, the authors seeded the hydrogen plasma with xenon, which has an atomic weight almost equal to that of cesium. The plasma properties were studied in the extraction region of the negative ion source Camembert III using a cylindrical electrostatic probe while the negative ion relative density was studied using laser photodetachment. It is shown that the xenon mixing does not enhance the negative ion density and leads to the increase of the electron density, while the cesium seeding reduces the electron density.
Date: September 6, 1999
Creator: Bacal, M.; Brunteau, A. M.; Deniset, C.; Elizarov, L. I.; Sube, F.; Tontegode, A. Y. et al.
System: The UNT Digital Library
Status of the BNL High Current EBIS Test Stand. (open access)

Status of the BNL High Current EBIS Test Stand.

As part of a new, compact heavy ion injector for AGS/RHIC complex at Brookhaven National Laboratory we are developing an Electron Beam Ion Source (EBIS) that would satisfy present and future requirements. Such a source should be capable of producing intensities of e.g. Al{sup 35+} ions of about 3 x 10{sup 9} particles/pulse or U{sup 45+} of about 2 x 10{sup 9} particles/pulse. To achieve this, the required e-beam intensity is 10A, at a pulse length of 100ms. An EBIS test stand has been constructed, designed for the full electron beam power and having close to 1/2 of the trap length of an EBIS for RHIC. Initial electron beam tests have resulted in a 50{micro}s, 13A electron beam. Ion production and extraction has been shown with a 3.1 A, 50 ms electron beam, achieving an ion yield of 19 nC/pulse (neutralization degree of 61%); fast extraction trials have yielded extracted ion pulses of 1mA peak current and 18{micro}s at FWHM. Details of the test stand construction, results of the electron beam studies, and properties of the extracted ion pulse are presented.
Date: September 6, 1999
Creator: Beebe, E.
System: The UNT Digital Library
Coherent synchrotron radiation and microbunching in bunch compressor. (open access)

Coherent synchrotron radiation and microbunching in bunch compressor.

Coherent synchrotron radiation (CSR) is of great interest to those designing accelerators as drivers for free-electron lasers (FELs) and energy recovery linacs (ERLs). A growing body of experimental evidence indicates the potentially serious impact of CSR on beam quality as we attempt to create high-brightness, high-current electron bunches using magnetic compression techniques. It is not an over-statement to say that the success of FEL and ERL projects could well depend on how well CSR is understood in the design phase. Simulation codes typically show qualitative or rough quantitative agreement with experiments, indicating that our understanding of the physics is improving but incomplete. For example, an unexpected microbunching instability was recently discovered with the code ''elegant'' and is now the subject of intense theoretical work. This paper presents an overview of CSR issues, including recent simulation results on the CSR instability. Experimental results and issues are also discussed.
Date: September 6, 2002
Creator: Borland, M.
System: The UNT Digital Library
Recovery of Minerals and Metals from Geothermal Fluids (open access)

Recovery of Minerals and Metals from Geothermal Fluids

None
Date: September 6, 2005
Creator: Bourcier, W L; Lin, M & Nix, G
System: The UNT Digital Library
Stretched Wire Mechanics (open access)

Stretched Wire Mechanics

Stretched wires are beginning to play an important role in the alignment of accelerators and synchrotron light sources. Stretched wires are proposed for the alignment of the 130 meter long LCLS undulator. Wire position technology has reached sub-micron resolution yet analyses of perturbations to wire straightness are hard to find. This paper considers possible deviations of stretched wire from the simple 2-dimensional catenary form.
Date: September 6, 2005
Creator: Bowden, Gordon
System: The UNT Digital Library
Advanced, Environmentally Friendly Hydroelectric Turbines for the Restoration of Fish and Water Quality (open access)

Advanced, Environmentally Friendly Hydroelectric Turbines for the Restoration of Fish and Water Quality

Hydroelectric power contributes about 10 percent of the electrical energy generated in the United States, and nearly 20 percent of the world�s electrical energy. The contribution of hydroelectric generation has declined in recent years, often as a consequence of environmental concerns centering around (1) restriction of upstream and downstream fish passage by the dam, and (2) alteration of water quality and river flows by the impoundment. The Advanced Hydropower Turbine System (AHTS) Program of the U.S. Department of Energy is developing turbine technology which would help to maximize global hydropower resources while minimizing adverse environmental effects. Major technical goals for the Program are (1) the reduction of mortality among turbine-passed fish to 2 percent or less, compared to current levels ranging up to 30 percent or greater; and (2) development of aerating turbines that would ensure that water discharged from reservoirs has a dissolved oxygen concentration of at least 6 mg/L. These advanced, �environmentally friendly� turbines would be suitable both for new hydropower installations and for retrofitting at existing dams. Several new turbine designs that have been he AHTS program are described.
Date: September 6, 1999
Creator: Brookshier, P. A.; Cada, G. F.; Flynn, J. V.; Rinehart, B. N.; Sale, M. J. & Sommers, G. L.
System: The UNT Digital Library
Exploring Lifetime Effects in Femtoscopy (open access)

Exploring Lifetime Effects in Femtoscopy

We investigate the role of lifetime effects from resonances and emission duration tails in femtoscopy at RHIC in two Blast-Wave models. We find the non-Gaussian components compare well with published source imaged data, but the value of R{sub out} obtained from Gaussian fits is not insensitive to the non-Gaussian contributions when realistic acceptance cuts are applied to models.
Date: September 6, 2005
Creator: Brown, D.; Soltz, R.; Newby, J. & Kisiel, A.
System: The UNT Digital Library
Inductively Heated Shape Memory Polymer for the Magnetic Actuation of Medical Devices (open access)

Inductively Heated Shape Memory Polymer for the Magnetic Actuation of Medical Devices

Presently there is interest in making medical devices such as expandable stents and intravascular microactuators from shape memory polymer (SMP). One of the key challenges in realizing SMP medical devices is the implementation of a safe and effective method of thermally actuating various device geometries in vivo. A novel scheme of actuation by Curie-thermoregulated inductive heating is presented. Prototype medical devices made from SMP loaded with Nickel Zinc ferrite ferromagnetic particles were actuated in air by applying an alternating magnetic field to induce heating. Dynamic mechanical thermal analysis was performed on both the particle-loaded and neat SMP materials to assess the impact of the ferrite particles on the mechanical properties of the samples. Calorimetry was used to quantify the rate of heat generation as a function of particle size and volumetric loading of ferrite particles in the SMP. These tests demonstrated the feasibility of SMP actuation by inductive heating. Rapid and uniform heating was achieved in complex device geometries and particle loading up to 10% volume content did not interfere with the shape recovery of the SMP.
Date: September 6, 2005
Creator: Buckley, Patrick R.; McKinley, Gareth H.; Wilson, Thomas S.; Small, Ward, IV; Benett, William J.; Bearinger, Jane P. et al.
System: The UNT Digital Library
Design of Long Induction Linacs (open access)

Design of Long Induction Linacs

A self-consistent design strategy for induction linacs is presented which addresses the issues of brightness preservation against space charge induced emittance growth, minimization of the beam breakup instability and the suppression of beam centroid motion due to chromatic effects (corkscrew) and misaligned focusing elements. A simple steering algorithm is described that widens the effective energy bandwidth of the transport system.
Date: September 6, 1990
Creator: Caporaso, G.J. & Cole, A.G.
System: The UNT Digital Library
Steady State Microbunching for High Brilliance and High Repetition Rate Storage Ring-Based Light Sources (open access)

Steady State Microbunching for High Brilliance and High Repetition Rate Storage Ring-Based Light Sources

Electron-based light sources have proven to be effective sources of high brilliance, high frequency radiation. Such sources are typically either linac-Free Electron Laser (FEL) or storage ring types. The linac-FEL type has high brilliance (because the beam is microbunched) but low repetition rate. The storage ring type has high repetition rate (rapid beam circulation) but comparatively low brilliance or coherence. We propose to explore the feasibility of a microbunched beam in a storage ring that promises high repetition rate and high brilliance. The steady-state-micro-bunch (SSMB) beam in storage ring could provide CW sources for THz, EUV, or soft X-rays. Several SSMB mechanisms have been suggested recently, and in this report, we review a number of these SSMB concepts as promising directions for high brilliance, high repetition rate light sources of the future. The trick of SSMB lies in the RF system, together with the associated synchrotron beam dynamics, of the storage ring. Considering various different RF arrangements, there could be considered a number of scenarios of the SSMB. In this report, we arrange these scenarios more or less in order of the envisioned degree of technical challenge to the RF system, and not in the chronological order of their original …
Date: September 6, 2012
Creator: Chao, Alex; Ratner, Daniel & Jiao, Yi
System: The UNT Digital Library
Experimental analysis of high-resolution soft x-ray microscopy (open access)

Experimental analysis of high-resolution soft x-ray microscopy

The soft x-ray, full-field microscope XM-1 at Lawrence Berkeley National Laboratory's (LBNL) Advanced Light Source has already demonstrated its capability to resolve 25-nm features. This was accomplished using a micro zone plate (MZP) with an outer zone width of 25 nm. Limited by the aspect ratio of the resist used in the fabrication, the gold-plating thickness of that zone plate is around 40 nm. However, some applications, in particular, biological imaging, prefer improved efficiency, which can be achieved by high-aspect-ratio zone plates. We accomplish this by using a bilayer-resist process in the zone plate fabrication. As our first attempt, a 40-nm-outer-zone-width MZP with a nickel-plating thickness of 150 nm (aspect ratio of 4:1) was successfully fabricated. Relative to the 25-nm MZP, this zone plate is ten times more efficient. Using this high-efficiency MZP, a line test pattern with half period of 30 nm is resolved by the microscope at photon energy of 500 eV. Furthermore, with a new multilayer mirror, the XM-1 can now perform imaging up to 1.8 keV. An image of a line test pattern with half period of 40 nm has a measured modulation of 90%. The image was taken at 1.77 keV with the high-efficiency MZP …
Date: September 6, 2001
Creator: Chao, Weilun; Anderson, Erik H.; Denbeaux, Gregory; Harteneck, Bruce; Pearson, Angelic L.; Olynick, Deirdre et al.
System: The UNT Digital Library
Improvement of Quality in Publication of Experimental Thermophysical Property Data: Challenges, Assessment Tools, Global Implementation, and Online Support (open access)

Improvement of Quality in Publication of Experimental Thermophysical Property Data: Challenges, Assessment Tools, Global Implementation, and Online Support

Article on the improvement of quality in the publication of experimental thermophysical property data.
Date: September 6, 2013
Creator: Chirico, Robert D.; Frenkel, Michael; Magee, Joseph W.; Diky, Vladimir; Muzny, Chris D.; Kazakov, Andrei F. et al.
System: The UNT Digital Library
Successes and Experiences of the WIPP Project (open access)

Successes and Experiences of the WIPP Project

In May 1998, the US Environmental Agency (EPA) certified the US Department of Energy's (DOE) Waste Isolation Pilot Plant (WIPP) as being in compliance with all of the applicable regulations governing the permanent disposal of spent nuclear fuel, high-level waste, and transuranic radioactive waste. The WIPP, a transuranic waste repository, is the first deep geologic repository in the US to have successfully demonstrated regulatory compliance with long-term radioactive waste disposal regulations and be certified to receive wastes. Many lessons were learned throughout the 25-year history of the WIPP--from site selection to the ultimate successful certification. The experiences and lessons learned from the WIPP may be of general interest to other repository programs in the world. The lessons learned include all facets of a repository program: programmatic, managerial, regulatory, technical, and social. This paper addresses critical issues that arose during the 25 years of WIPP history and how they influenced the program.
Date: September 6, 2000
Creator: Chu, Margaret S. Y. & Weart, Wendell D.
System: The UNT Digital Library
Project Management Actions Demolition of a Research Facility Building 431 (open access)

Project Management Actions Demolition of a Research Facility Building 431

The Demolition of B431 is required to achieve the mission of LLNL and the NNSA FIRP objectives by: (1) Supporting the NNSA Infrastructure Plan goal to ''demolish excess facilities as early as possible''; (2) Banking square footage that allows continued application of advanced science and nuclear technology to the Nation's defense; and (3) Helping maintain and enhance the safety, security, and reliability of the weapons stockpile. A significant effort has been put into the demolition concept in order to ensure that it is well thought out and represents best-value to the government for the money.
Date: September 6, 2005
Creator: Collins, W L
System: The UNT Digital Library
Angular distributions of electrons photoemitted from core levels of oriented diatomic molecules: Multiple scattering theory in non-spherical potentials (open access)

Angular distributions of electrons photoemitted from core levels of oriented diatomic molecules: Multiple scattering theory in non-spherical potentials

We use multiple scattering in non-spherical potentials (MSNSP) to calculate the angular distributions of electrons photoemitted from the 1s-shells of CO and N2 gas-phase molecules with fixed-in-space orientations. For low photoelectron kinetic energies (E<50 eV), as appropriate to certain shape-resonances, the electron scattering must be represented by non-spherical scattering potentials, which are naturally included in our formalism. Our calculations accurately reproduce the experimental angular patterns recently measured by several groups, including those at the shape-resonance energies. The MSNSP theory thus enhances the sensitivity to spatial electronic distribution and dynamics, paving the way toward their determination from experiment.
Date: September 6, 2001
Creator: Diez Muino, R.; Rolles, D.; Garcia de Abajo, F. J.; Fadley, C. S. & Van Hove, M. A.
System: The UNT Digital Library
An atomic force microcopy study of the mechanical and electricalproperties of monolayer films of molecules with aromatic end groups (open access)

An atomic force microcopy study of the mechanical and electricalproperties of monolayer films of molecules with aromatic end groups

The effect of intermolecular {pi}-{pi} stacking on the electrical and mechanical properties of monolayer films molecules containing aromatic groups was studied using atomic force microscopy. Two types of aromatic molecules, (4-mercaptophenyl) anthrylacetylene (MPAA) and (4-mercaptophenyl)-phenylacetylene (MPPA) were used as model systems with different {pi}-{pi} stacking strength. Monolayer films of these molecules on Au(111) surfaces exhibited conductivities differing by more than one order of magnitude, MPAA being the most conductive and MPPA the least conductive. The response to compressive loads by the AFM tip was also found to be very different for both molecules. In MPAA films distinct molecular conductivity changes are observed upon mechanical perturbation. This effect however was not observed on the MPPA film, where intermolecular {pi}-{pi} interactions are likely weaker.
Date: September 6, 2007
Creator: Fang, Liang; Park, J.Y.; Ma, H.; Jen, A.K.-Y. & Salmeron, M.
System: The UNT Digital Library
A Conceptual model of coupled biogeochemical and hydrogeologicalprocesses affected by in situ Cr(VI) bioreduction in groundwater atHanford 100H Site (open access)

A Conceptual model of coupled biogeochemical and hydrogeologicalprocesses affected by in situ Cr(VI) bioreduction in groundwater atHanford 100H Site

The overall objective of this presentation is to demonstratea conceptual multiscale, multidomain model of coupling of biogeochemicaland hydrogeological processes during bioremediation of Cr(VI)contaminated groundwater at Hanford 100H site. A slow releasepolylactate, Hydrogen Release Compound (HRCTM), was injected in Hanfordsediments to stimulate immobilization of Cr(VI). The HRC injectioninduced a 2-order-of-magnitude increase in biomass and the onset ofreducing biogeochemical conditions [e.g., redox potential decreased from+240 to -130 mV and dissolved oxygen (DO) was completely removed]. Athree-well system, comprised of an injection well and upgradient anddowngradient monitoring wells, was used for conducting the in situbiostimulation, one regional flow (no-pumping) tracer test, and fivepumping tests along with the Br-tracer injection. Field measurements wereconducted using a Br ion-selective electrode and a multiparameter flowcell to collect hourly data on temperature, pH, redox potential,electrical conductivity, and DO. Groundwater sampling was conducted bypumping through specially designed borehole water samplers.Cross-borehole radar tomography and seismic measurements were carried outto assess the site background lithological heterogeneity and themigration pathways of HRC byproducts through groundwater after the HRCinjection.
Date: September 6, 2006
Creator: Faybishenko, B.; Long, P. E.; Hazen, T. C.; Hubbard, S. S.; Williams, K. H.; Peterson, J. E. et al.
System: The UNT Digital Library
Enhanced and multiplexed detection via a novel RCA-aptamer based sensing system (open access)

Enhanced and multiplexed detection via a novel RCA-aptamer based sensing system

None
Date: September 6, 2006
Creator: Fischer, N O; Dolan, C E; Tarasow, T M & Tok, J H
System: The UNT Digital Library
Laser Scanner Demonstration (open access)

Laser Scanner Demonstration

In the Summer of 2004 a request for proposals went out to potential vendors to offer a three-dimensional laser scanner for a number of unique metrology tasks at the Stanford Linear Accelerator Center (SLAC). Specifications were established including range, accuracy, scan density, resolution and field of view in consideration of anticipated department requirements. Four vendors visited the site to present their system and they were asked to perform three unique tests with their system on a two day visit to SLAC. Two of the three tests were created to emulate real-world applications at SLAC while the third was an accuracy and resolution series of experiments. The scope of these tests is presented and some of the vendor's results are included.
Date: September 6, 2005
Creator: Fuss, B.
System: The UNT Digital Library