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PROGRESS IN BEAM FOCUSING AND COMPRESSION FOR WARM-DENSE MATTER EXPERIMENTS (open access)

PROGRESS IN BEAM FOCUSING AND COMPRESSION FOR WARM-DENSE MATTER EXPERIMENTS

The Heavy-Ion Fusion Sciences Virtual National Laboratory is pursuing an approach to target heating experiments in the Warm Dense Matter regime, using spacecharge-dominated ion beams that are simultaneously longitudinally bunched and transversely focused. Longitudinal beam compression by large factors has beendemonstrated in the Neutralized Drift Compression Experiment (NDCX) with controlledramps and forced neutralization. Using an injected 30-mA K+ ion beam with initialkinetic energy 0.3 MeV, axial compression leading to ~;;50-fold current amplification andsimultaneous radial focusing to beam radii of a few mm have led to encouraging energy deposition approaching the intensities required for eV-range target heating experiments. We discuss the status of several improvements to our Neutralized Drift Compression Experiment and associated beam diagnostics that are under development to reach the necessary higher beam intensities, including: (1) greater axial compression via a longer velocity ramp using a new bunching module with approximately twice the available voltseconds; (2) improved centroid control via beam steering dipoles to mitigate aberrations in the bunching module; (3) time-dependent focusing elements to correct considerable chromatic aberrations; and (4) plasma injection improvements to establish a plasma density always greater than the beam density, expected to be>1013 cm-3.
Date: September 25, 2008
Creator: Seidl, P. A.; Anders, A.; Bieniosek, F. M.; Barnard, J. J.; Calanog, J.; Chen, A. X. et al.
System: The UNT Digital Library
A method for obtaining three-dimensional computation equilibrium of non-neutral plasmas using WARP (open access)

A method for obtaining three-dimensional computation equilibrium of non-neutral plasmas using WARP

Computer simulation studies of the stability and transport properties of trapped non-neutral plasmas require the numerical realization of a three-dimensional plasma distribution. This paper presents a new numerical method for obtaining, without an explicit model for physical collisions in the code, a low noise three-dimensional computational equilibrium distribution. This requires both the loading of particles into an idealized distribution and the relaxation from that distribution toward an approximate numerical equilibrium. The equilibrium can then be modified through a slow change of system parameters, to generate other equilibria. In the present work we apply this method to a UC Berkeley experiment on electron confinement in magnetic geometries appropriate for the ALPHA anti-hydrogen experiment, using the three-dimensional Particle-In-Cell code WARP. WARP's guiding center mover and its option to switch between different solvers during a simulation are highly valuable because they speed up the simulations; they enable the practical use of the new technique for generating numerical equilibrium states of trapped nonneutral plasmas.
Date: March 25, 2006
Creator: Wurtele, J.; Wurtele, J.; Friedman, A.; Grote, D. P.; Vay, J. L. & Gomberoff, K.
System: The UNT Digital Library
Physicochemical properties and toxicities of hydrophobicpiperidinium and pyrrolidinium ionic liquids (open access)

Physicochemical properties and toxicities of hydrophobicpiperidinium and pyrrolidinium ionic liquids

Some properties are reported for hydrophobic ionic liquids (IL) containing 1-methyl-1-propyl pyrrolidinium [MPPyrro]{sup +}, 1-methyl-1-butyl pyrrolidinium [MBPyrro]{sup +}, 1-methyl-1-propyl piperidinium [MPPip]{sup +}, 1-methyl-1-butyl piperidinium [MBPip]{sup +}, 1-methyl-1-octylpyrrolidinium [MOPyrro]{sup +} and 1-methyl-1-octylpiperidinium [MOPip]{sup +} cations. These liquids provide new alternatives to pyridinium and imidazolium ILs. High thermal stability of an ionic liquid increases safety in applications like rechargeable lithium-ion batteries and other electrochemical devices. Thermal properties, ionic conductivities, viscosities, and mutual solubilities with water are reported. In addition, toxicities of selected ionic liquids have been measured using a human cancer cell-line. The ILs studied here are sparingly soluble in water but hygroscopic. We show some structure-property relationships that may help to design green solvents for specific applications. While ionic liquids are claimed to be environmentally-benign solvents, as yet few data have been published to support these claims.
Date: June 25, 2007
Creator: Salminen, Justin; Papaiconomou, Nicolas; Kumar, R. Anand; Lee,Jong-Min; Kerr, John; Newman, John et al.
System: The UNT Digital Library
TOWARDS 100% POLARIZATION IN THE OPTICALLY-PUMPED POLARIZED ION SOURCE. (open access)

TOWARDS 100% POLARIZATION IN THE OPTICALLY-PUMPED POLARIZED ION SOURCE.

The depolarization factors in the multi-step spin-transfer polarization technique and basic limitations on maximum polarization in the OPPIS (Optically-Pumped Polarized H{sup -} Ion Source) are discussed. Detailed studies of polarization losses in the RHIC OPPIS and the source parameters optimization resulted in the OPPIS polarization increase to 86-90%. This contributed to increasing polarization in the AGS and RHIC to 65-70%.
Date: June 25, 2007
Creator: ZELENSKI,A.; ALESSI, J.; KOKHANOVSKI, S.; KPONOU, A.; RITTER, B.J. & ZUBETS, V.
System: The UNT Digital Library
A Detailed Chemical Kinetic Reaction Mechanism for n-Alkane Hydrocarbons from n-Octane to n-Hexadecane (open access)

A Detailed Chemical Kinetic Reaction Mechanism for n-Alkane Hydrocarbons from n-Octane to n-Hexadecane

Detailed chemical kinetic reaction mechanisms have been developed to describe the pyrolysis and oxidation of the n-alkanes, including n-octane (n-C{sub 8}H{sub 18}), n-nonane (n-C{sub 9}H{sub 20}), n-decane (n-C{sub 10}H{sub 22}), n-undecane (n-C{sub 11}H{sub 24}), n-dodecane (n-C{sub 12}H{sub 26}), n-tridecane (n-C{sub 13}H{sub 28}), n-tetradecane (n-C{sub 14}H{sub 30}), n-pentadecane (n-C{sub 15}H{sub 32}), and n-hexadecane (n-C{sub 16}H{sub 34}). These mechanisms include both high temperature and low temperature reaction pathways. The mechanisms are based on previous mechanisms for n-heptane, using the same reaction class mechanism construction developed initially for n-heptane. Individual reaction class rules are as simple as possible in order to focus on the parallelism between all of the n-alkane fuels included in the mechanisms, and there is an intent to develop these mechanisms further in the future to incorporate greater levels of accuracy and predictive capability. Several of these areas for improvement are identified and explained in detail. These mechanisms are validated through comparisons between computed and experimental data from as many different sources as possible. In addition, numerical experiments are carried out to examine features of n-alkane combustion in which the detailed mechanisms can be used to compare processes in all of the n-alkane fuels. The mechanisms for all of these …
Date: September 25, 2007
Creator: Westbrook, C K; Pitz, W J; Herbinet, O; Silke, E J & Curran, H J
System: The UNT Digital Library
Particulate matter chemistry and dynamics in the Twilight Zone at VERTIGO ALOHA and K2 Sites (open access)

Particulate matter chemistry and dynamics in the Twilight Zone at VERTIGO ALOHA and K2 Sites

Understanding particle dynamics in the 'Twilight Zone' is critical to prediction of the ocean's carbon cycle. As part of the VERTIGO (VERtical Transformations In the Global Ocean) project, this rarely sampled regime extending from the base of the euphotic layer to 1000 m, was characterized by double-paired day/night Multiple Unit Large Volume in-situ Filtration System (MULVFS) deployments and by {approx}100 high-frequency CTD/transmissometer/turbidity sensor profiles. VERTIGO studies lasting three weeks, contrasted oligotrophic station ALOHA (22.75{sup o}N 158{sup o}W), sampled in June-July 2004, with a biologically productive location (47{sup o}N 161{sup o}E) near station K2 in the Oyashio, occupied July-August 2005. Profiles of major and minor particulate components (C{sub org}, N, P, Ca, Si, Sr, Ba, Mn) in <1, 1-51, and >51 {micro}m size fractions, in-water optics, neutrally buoyant sediment trap (NBST) fluxes, and zooplankton data were intercompared. MULVFS total C{sub org} and C-Star particle beam attenuation coefficient (C{sub P}) were consistently related at both sites with a 27 {micro}M m{sup -1} conversion factor. 26 At K2, C{sub P} profiles further showed a multitude of transient spikes throughout the water column and spike abundance profiles closely paralleled the double peaked abundance profiles of zooplankton. Also at K2, copepods contributed {approx}40% and 10%, …
Date: March 25, 2008
Creator: Bishop, James K.B. & Wood, T.J.
System: The UNT Digital Library
Thermal Emittance Measurement Design for Diamond Secondary Emission (open access)

Thermal Emittance Measurement Design for Diamond Secondary Emission

Thermal emittance is a very important characteristic of cathodes. A carefully designed method of measuring the thermal emittance of secondary emission from diamond is presented. Comparison of possible schemes is carried out by simulation, and the most accessible and accurate method and values are chosen. Systematic errors can be controlled and maintained at small values, and are carefully evaluated. Aberration and limitations of all equipment are taken into account.
Date: June 25, 2007
Creator: Wu, Q.; Ben-Zvi, Ilan; Burrill, A.; Chang, X.; Kayran, D.; Rao, T. et al.
System: The UNT Digital Library
A Flight Simulator for ATF2 - A Mechanism for International Collaboration in the Writing and Deployment of Online Beam Dynamics Algorithms (open access)

A Flight Simulator for ATF2 - A Mechanism for International Collaboration in the Writing and Deployment of Online Beam Dynamics Algorithms

The goals of ATF2 are to test a novel compact final focus optics design with local chromaticity correction intended for use in future linear colliders. The newly designed extraction line and final focus system will be used to produce a 37nm vertical waist from an extracted beam from the ATF ring of {approx}30nm vertical normalized emittance, and to stabilize it at the IP-waist to the {approx}2nm level. Static and dynamic tolerances on all accelerator components are very tight; the achievement of the ATF2 goals is reliant on the application of multiple high-level beam dynamics control algorithms to align and tune the electron beam in the extraction line and final focus system. Much algorithmic development work has been done in Japan and by colleagues in collaborating nations in North America and Europe. We describe here development work towards realizing a 'flight simulator' environment for the shared development and implementation of beam dynamics code. This software exists as a 'middle-layer' between the lower-level control systems (EPICS and V-SYSTEM) and the multiple higher-level beam dynamics modeling tools in use by the three regions (SAD, Lucretia, PLACET, MAD...).
Date: July 25, 2008
Creator: White, Glen; Molloy, Stephen; Seryi, Andrei; Schulte, Daniel; Tomas, Rogelio; Kuroda, Shigeru et al.
System: The UNT Digital Library
SUPERCONDUCTING MAGNET NEEDS FOR THE ILC. (open access)

SUPERCONDUCTING MAGNET NEEDS FOR THE ILC.

The ILC Reference Design Report was completed early in February 2007. The Magnet Systems Group was formed to translate magnetic field requirements into magnet designs and cost estimates for the Reference Design. As presently configured, the lLC will have more than 13,000 magnetic elements of which more than 2300 will be based on superconducting technology. This paper will describe the major superconducting magnet needs for the ILC as presently determined by the Area Systems Groups, responsible for beam line design, working with the Magnet Systems Group. The superconducting magnet components include Main Linac quadrupoles, Positron Source undulators, Damping Ring wigglers, a complex array of Final Focus superconducting elements in the Beam Delivery System, and large superconducting solenoids in the e{sup +} and e{sup -} Sources, and the Ring to Main Linac lines.
Date: June 25, 2007
Creator: PARKER, B.; TOMPKINS, J. C.; KASHIKHIN, V. I.; PALMER, M. A. & CLARKE, J. A.
System: The UNT Digital Library
Billion particle linac simulations for future light sources (open access)

Billion particle linac simulations for future light sources

In this paper we report on multi-physics, multi-billion macroparticle simulation of beam transport in a free electron laser (FEL) linac for future light source applications. The simulation includes a self-consistent calculation of 3D space-charge effects, short-range geometry wakefields, longitudinal coherent synchrotron radiation (CSR) wakefields, and detailed modeling of RF acceleration and focusing. We discuss the need for and the challenges associated with such large-scale simulation. Applications to the study of the microbunching instability in an FEL linac are also presented.
Date: September 25, 2008
Creator: Ryne, R. D.; Venturini, M.; Zholents, A. A. & Qiang, J.
System: The UNT Digital Library
Gluon scattering in N=4 super-Yang-Mills theory fromweak to strong coupling (open access)

Gluon scattering in N=4 super-Yang-Mills theory fromweak to strong coupling

I describe some recent developments in the understanding of gluon scattering amplitudes in N = 4 super-Yang-Mills theory in the large-N{sub c} limit. These amplitudes can be computed to high orders in the weak coupling expansion, and also now at strong coupling using the AdS/CFT correspondence. They hold the promise of being solvable to all orders in the gauge coupling, with the help of techniques based on integrability. They are intimately related to expectation values for polygonal Wilson loops composed of light-like segments.
Date: March 25, 2008
Creator: Dixon, Lance J.
System: The UNT Digital Library
High resolution 17 keV to 75 keV backlighters for High Energy Density experiments (open access)

High resolution 17 keV to 75 keV backlighters for High Energy Density experiments

We have developed 17 keV to 75 keV 1-dimensional and 2-dimensional high-resolution (< 10 {micro}m) radiography using high-intensity short pulse lasers. High energy K-{alpha} sources are created by fluorescence from hot electrons interacting in the target material after irradiation by lasers with intensity I{sub L} > 10{sup 17} W/cm{sup 2}. We have achieved high resolution point projection 1-dimensional and 2-dimensional radiography using micro-foil and micro-wire targets attached to low-Z substrate materials. The micro-wire size was 10 {micro}m x 10 {micro}m x 300 {micro}m on a 300 {micro}m x 300 {micro}m x 5 {micro}m CH substrate. The radiography performance was demonstrated using the Titan laser at LLNL. We observed that the resolution is dominated by the micro-wire target size and there is very little degradation from the plasma plume, implying that the high energy x-ray photons are generated mostly within the micro-wire volume. We also observe that there are enough K{alpha} photons created with a 300 J, 1-{omega}, 40 ps pulse laser from these small volume targets, and that the signal-to-noise ratio is sufficiently high, for single shot radiography experiments. This unique technique will be used on future high energy density (HED) experiments at the new Omega-EP, ZR and NIF facilities.
Date: February 25, 2008
Creator: Park, H.; Maddox, B. R.; Giraldez, E.; Hatchett, S. P.; Hudson, L.; Izumi, N. et al.
System: The UNT Digital Library
On-site Analysis of Explosives in Various Matrices (open access)

On-site Analysis of Explosives in Various Matrices

Lawrence Livermore National Laboratory (LLNL) has developed several different strategies and technologies for the on-site detection of explosives. These on-site detection techniques include a colorimetric test, thin layer chromatography (TLC) kit and portable gas chromatography mass spectrometer (GC/MS). The screening of suspicious containers on-site and the search for trace explosive residue in a post-blast forensic investigation are of great importance. For these reasons, LLNL's Forensic Science Center has developed a variety of fieldable detection technologies to screen for a wide range of explosives in various matrices and scenarios. Ideally, what is needed is a fast, accurate, easy-to-use, pocket-size and inexpensive field screening test for explosives.
Date: January 25, 2006
Creator: Reynolds, J. G.; Nunes, P.; Whipple, R. E. & Alcaraz, A.
System: The UNT Digital Library
The energy coupling efficiency of multi-wavelength laser pulses to damage initiating defects in DKDP nonlinear crystals (open access)

The energy coupling efficiency of multi-wavelength laser pulses to damage initiating defects in DKDP nonlinear crystals

The bulk damage performance of potassium dihydrogen phosphate crystals under simultaneous exposure to 1064-, 532-, and 355-nm nanosecond-laser pulses is investigated in order to probe the laser-induced defect reactions leading to damage initiation during frequency conversion. The results provide insight into the mechanisms governing the behavior of the damage initiating defects under exposure to high power laser light. In addition, it is suggested that the damage performance can be directly related to and predicted from the damage behavior of the crystal at each wavelength separately.
Date: September 25, 2007
Creator: DeMange, P; Negres, R A; Rubenchik, A M; Radousky, H B; Feit, M D & Demos, S G
System: The UNT Digital Library
Colliding pulse injection experiments in non-collinear geometryfor controlled laser plasma wakefield acceleration of electrons (open access)

Colliding pulse injection experiments in non-collinear geometryfor controlled laser plasma wakefield acceleration of electrons

An optical injection scheme for a laser-plasma basedaccelerator which employs a non-collinear counter-propagating laser beamto push background electrons in the focusing and acceleration phase viaponderomotive beat with the trailing part of the wakefield driver pulseis discussed. Preliminary experiments were performed using a drive beamof a_0 = 2.6 and colliding beam of a_1 = 0.8 both focused on the middleof a 200 mu m slit jet backed with 20 bar, which provided ~; 260 mu mlong gas plume. The enhancement in the total charge by the collidingpulse was observed with sharp dependence on the delay time of thecolliding beam. Enhancement of the neutron yield was also measured, whichsuggests a generation of electrons above 10 MeV.
Date: June 25, 2007
Creator: Toth, Carl B.; Esarey, Eric H.; Geddes, Cameron G.R.; Leemans,Wim P.; Nakamura, Kei; Panasenko, Dmitriy et al.
System: The UNT Digital Library
THE SUPERCONDUCTION MAGNETS OF THE ILC BEAM DELIVERY SYSTEM. (open access)

THE SUPERCONDUCTION MAGNETS OF THE ILC BEAM DELIVERY SYSTEM.

The ILC Reference Design Report was completed early in February 2007. The Magnet Systems Group was formed to translate magnetic field requirements into magnet designs and cost estimates for the Reference Design. As presently configured, the ILC will have more than 13,000 magnetic elements of which more than 2300 will be based on superconducting technology. This paper will describe the major superconducting magnet needs for the ILC as presently determined by the Area Systems Groups, responsible for beam line design, working with the Magnet Systems Group. The superconducting magnet components include Main Linac quadrupoles, Positron Source undulators, Damping Ring wigglers, a complex array of Final Focus superconducting elements in the Beam Delivery System, and large superconducting solenoids in the e{sup +} and e{sup -} Sources, and the Ring to Main Linac lines.
Date: June 25, 2007
Creator: PARKER,B.; ANEREELA, M.; ESCALLIE, J.; HE, P.; JAIN, A.; MARONE, A. et al.
System: The UNT Digital Library
Discovery of Radio Emission From Transient Anomalous X-Ray Pulsar XTE J1810-197 (open access)

Discovery of Radio Emission From Transient Anomalous X-Ray Pulsar XTE J1810-197

We report the first detection of radio emission from any anomalous X-ray pulsar (AXP). Data from the Very Large Array (VLA) MAGPIS survey with angular resolution 6'' reveals a point-source of flux density 4.5 {+-} 0.5 mJy at 1.4 GHz at the precise location of the 5.54 s pulsar XTE J1810-197. This is greater than upper limits from all other AXPs and from quiescent states of soft gamma-ray repeaters (SGRs). The detection was made in 2004 January, 1 year after the discovery of XTE J1810-197 during its only known outburst. Additional VLA observations both before and after the outburst yield only upper limits that are comparable to or larger than the single detection, neither supporting nor ruling out a decaying radio afterglow related to the X-ray turn-on. Another hypothesis is that, unlike the other AXPs and SGRs, XTE J1810-197 may power a radio synchrotron nebula by the interaction of its particle wind with a moderately dense environment that was not evacuated by previous activity from this least luminous, in X-rays, of the known magnetars.
Date: October 25, 2005
Creator: Halpern, J P; Gotthelf, E V; Becker, R H; Helfand, D J & White, R L
System: The UNT Digital Library
Workshop on ENU Mutagenesis: Planning for Saturation, July 25-28, 2002 (open access)

Workshop on ENU Mutagenesis: Planning for Saturation, July 25-28, 2002

The goal of the conference is to enhance the development of improved technologies and new approaches to the identification of genes underlying chemically-induced mutant phenotypes. The conference brings together ENU mutagenesis experts from the United States and aborad for a small, intensive workshop to consider these issues.
Date: July 25, 2002
Creator: Nadeau, Joseph H
System: The UNT Digital Library
A simple and realistic model of supersymmetry breaking (open access)

A simple and realistic model of supersymmetry breaking

We present a simple and realistic model of supersymmetry breaking. In addition to the minimal supersymmetric standard model, we only introduce a hidden sector gauge group SU(5) and three fields X, F and \bar{F}. Supersymmetry is broken at a local minimum of the potential, and its effects are transmitted to the supersymmetric standard model sector through both standard model gauge loops and local operators suppressed by the cutoff scale, which is taken to be the unification scale. The form of the local operators is controlled by a U(1) symmetry. The generated supersymmetry breaking and mu parameters are comparable in size, and no flavor or CP violating terms arise. The spectrum of the first two generation superparticles is that of minimal gauge mediation with the number of messengers N_mess = 5 and the messenger scale 1011 GeV< M_mess< 1013 GeV. The spectrum of the Higgs bosons and third generation superparticles, however, can deviate from it. The lightest supersymmetric particle is the gravitino with a mass of order (1-10) GeV.
Date: September 25, 2007
Creator: Nomura, Yasunori & Papucci, Michele
System: The UNT Digital Library
Standard Practice for Dosimetry of Proton Beams for use in Radiation Effects Testing of Electronics (open access)

Standard Practice for Dosimetry of Proton Beams for use in Radiation Effects Testing of Electronics

Representatives of facilities that routinely deliver protons for radiation effect testing are collaborating to establish a set of standard best practices for proton dosimetry. These best practices will be submitted to the ASTM International for adoption.
Date: July 25, 2008
Creator: McMahan, Margaret A.; Blackmore, Ewart; Cascio, Ethan W.; Castaneda, Carlos; von Przewoski, Barbara & Eisen, Harvey
System: The UNT Digital Library
Simulation of lean premixed turbulent combustion (open access)

Simulation of lean premixed turbulent combustion

There is considerable technological interest in developingnew fuel-flexible combustion systems that can burn fuels such ashydrogenor syngas. Lean premixed systems have the potential to burn thesetypes of fuels with high efficiency and low NOx emissions due to reducedburnt gas temperatures. Although traditional scientific approaches basedon theory and laboratory experiment have played essential roles indeveloping our current understanding of premixed combustion, they areunable to meet the challenges of designing fuel-flexible lean premixedcombustion devices. Computation, with itsability to deal with complexityand its unlimited access to data, hasthe potential for addressing thesechallenges. Realizing this potential requires the ability to perform highfidelity simulations of turbulent lean premixed flames under realisticconditions. In this paper, we examine the specialized mathematicalstructure of these combustion problems and discuss simulation approachesthat exploit this structure. Using these ideas we can dramatically reducecomputational cost, making it possible to perform high-fidelitysimulations of realistic flames. We illustrate this methodology byconsidering ultra-lean hydrogen flames and discuss how this type ofsimulation is changing the way researchers study combustion.
Date: June 25, 2006
Creator: Bell, John B.; Day, Marcus S.; Almgren, Ann S.; Lijewski, MichaelJ.; Rendleman, Charles A.; Cheng, Robert K. et al.
System: The UNT Digital Library
Volume-selective magnetic resonance imaging using an adjustable, single-sided, portable sensor (open access)

Volume-selective magnetic resonance imaging using an adjustable, single-sided, portable sensor

Portable, single-sided NMR sensors can operate under conditions inaccessible to conventional NMR while featuring lower cost, portability, and the ability to analyze arbitrary-sized objects. Such sensors can nondestructively probe the interior of samples by collecting images and measuring relaxation and diffusion constants,and, given careful shimming schemes, even perform chemical analysis. The inherently strong magnetic-field gradients of single-sided sensors developed so far has prevented imaging of materials with high water content, such as biological tissues, over large volumes whereas designs with more homogeneous fields suffer from low field strength and typically cannot probe volumes larger than 10 cm3. We present a design with a continuously adjustable sensitive volume, enabling the effective volume to be enlarged several fold. This process allows for imaging in reasonable times of much bigger objects and opens the door to the possibility of clinical imaging with portable sensors. We demonstrate MRI in axial and saggital planes, at different depths of the sensitive volume and T1-weighted contrast in a tissue sample.
Date: November 25, 2008
Creator: Paulsen, Jeffrey L.; Bouchard, Louis S.; Graziani, Dominic; Blümich, Bernhard & Pines, Alexander
System: The UNT Digital Library
Verification (mostly) for High Energy Density Radiation Transport: 5 Case Studies (open access)

Verification (mostly) for High Energy Density Radiation Transport: 5 Case Studies

None
Date: August 25, 2006
Creator: Castor, J I
System: The UNT Digital Library
An analytical solution for transient gas flow in a multi-wellsystem (open access)

An analytical solution for transient gas flow in a multi-wellsystem

Soil vapor extraction (SVE) combined with air injectionprovides an efficient way for the cleanup of vadose zone contaminated byvolatile organic chemicals (VOCs). A successful design of an SVE system,however, relies on a good knowledge of the induced gas flow field in thevadose zone. Analytical solutions are available to help understand thegas flow field at steady-state. However, most SVE systems must pass atransient period before reaching steady (or quasi-steady) state and thelength of the period should be system-specific. This paper presents ananalytical solution for transient gas flow in a vadose zone withextraction and injection wells. The transient solution approaches thesteady-state solution as time increases. Calculations have shown that fora shallow well (screened in a depth of less than 10 m) in a vadose zonewith an air permeability of 1 darcy (10-12 m2) or larger, the systemreaches steady-state in just several hours. Decreasing the airpermeability or increasing the screen depth increases the time to reachsteady-state. In practical applications the transient solution may berelatively insignificant in an SVE design. However, the solution can beimportant in site characterization through pneumatic tests. A procedureis provided for applying the dimensionless solution in estimating airpermeability and air-filled porosity. An example is also given to use thetransient solution …
Date: May 25, 2006
Creator: Shan, Chao
System: The UNT Digital Library