YT: A Multi-Code Analysis Toolkit for Astrophysical Simulation Data (open access)

YT: A Multi-Code Analysis Toolkit for Astrophysical Simulation Data

The analysis of complex multiphysics astrophysical simulations presents a unique and rapidly growing set of challenges: reproducibility, parallelization, and vast increases in data size and complexity chief among them. In order to meet these challenges, and in order to open up new avenues for collaboration between users of multiple simulation platforms, we present yt (available at http://yt.enzotools.org/) an open source, community-developed astrophysical analysis and visualization toolkit. Analysis and visualization with yt are oriented around physically relevant quantities rather than quantities native to astrophysical simulation codes. While originally designed for handling Enzo's structure adaptive mesh refinement data, yt has been extended to work with several different simulation methods and simulation codes including Orion, RAMSES, and FLASH. We report on its methods for reading, handling, and visualizing data, including projections, multivariate volume rendering, multi-dimensional histograms, halo finding, light cone generation, and topologically connected isocontour identification. Furthermore, we discuss the underlying algorithms yt uses for processing and visualizing data, and its mechanisms for parallelization of analysis tasks.
Date: June 23, 2011
Creator: Turk, Matthew J.; /San Diego, CASS; Smith, Britton D.; U., /Michigan State; Oishi, Jeffrey S.; /KIPAC, Menlo Park /Stanford U., Phys. Dept. et al.
Object Type: Article
System: The UNT Digital Library
ANNUAL RADIOACTIVE WASTE TANK INSPECTION PROGRAM 2010 (open access)

ANNUAL RADIOACTIVE WASTE TANK INSPECTION PROGRAM 2010

Aqueous radioactive wastes from Savannah River Site (SRS) separations and vitrification processes are contained in large underground carbon steel tanks. Inspections made during 2010 to evaluate these vessels and other waste handling facilities along with evaluations based on data from previous inspections are the subject of this report. The 2010 inspection program revealed that the structural integrity and waste confinement capability of the Savannah River Site waste tanks were maintained. All inspections scheduled per SRR-LWE-2009-00138, HLW Tank Farm Inspection Plan for 2010, were completed. Ultrasonic measurements (UT) performed in 2010 met the requirements of C-ESG-00006, In-Service Inspection Program for High Level Waste Tanks, Rev. 3, and WSRC-TR-2002-00061, Rev.6. UT inspections were performed on Tanks 30, 31 and 32 and the findings are documented in SRNL-STI-2010-00533, Tank Inspection NDE Results for Fiscal Year 2010, Waste Tanks 30, 31 and 32. A total of 5824 photographs were made and 1087 visual and video inspections were performed during 2010. Ten new leaksites at Tank 5 were identified in 2010. The locations of these leaksites are documented in C-ESR-G-00003, SRS High Level Waste Tank Leaksite Information, Rev.5. Ten leaksites at Tank 5 were documented during tank wall/annulus cleaning activities. None of these new leaksites …
Date: June 23, 2011
Creator: West, B. & Waltz, R.
Object Type: Report
System: The UNT Digital Library
Market and behavioral barriers to energy efficiency: A preliminary evaluation of the case for tariff financing in California (open access)

Market and behavioral barriers to energy efficiency: A preliminary evaluation of the case for tariff financing in California

Consumers regularly forgo purchases of high efficiency appliances that appear to be cost effective at a reasonable rate of return. While some argue that this is a true revelation of preferences for appliance features, this 'efficiency gap' can be largely explained by a combination of market and behavioral failures that reduce consumers ability to evaluate the relative value of appliances and skew preferences toward initial cost savings, undervaluing future reductions in operating costs. These failures and barriers include externalities of energy use, imperfect competition between manufacturers, asymmetric information, bounded rationality, split incentives, and transaction costs (Golove 1996). Recognizing the social benefit of energy conservation, several major methods are used by policymakers to ensure that efficient appliances are purchased: minimum efficiency standards, Energy Star labeling, and rebates and tax credits. There is no single market for energy services; there are hundreds of uses, thousands of intermediaries, and millions of users, and likewise, no single appropriate government intervention (Golove 1996). Complementary approaches must be implemented, considering policy and institutional limitations. In this paper, I first lay out the rationale for government intervention by addressing the market and behavioral failures and barriers that arise in the context of residential energy efficiency. I then …
Date: June 23, 2011
Creator: Fujita, K. Sydny
Object Type: Report
System: The UNT Digital Library
Fair Oaks Dairy Farms Cellulosic Ethanol Technology Review Summary (open access)

Fair Oaks Dairy Farms Cellulosic Ethanol Technology Review Summary

At Fair Oaks Dairy, dried manure solids (''DMS'') are currently used as a low value compost. United Power was engaged to evaluate the feasibility of processing these DMS into ethanol utilizing commercially available cellulosic biofuels conversion platforms. The Fair Oaks Dairy group is transitioning their traditional ''manure to methane'' mesophilic anaerobic digester platform to an integrated bio-refinery centered upon thermophilic digestion. Presently, the Digested Manure Solids (DMS) are used as a low value soil amendment (compost). United Power evaluated the feasibility of processing DMS into higher value ethanol utilizing commercially available cellulosic biofuels conversion platforms. DMS was analyzed and over 100 potential technology providers were reviewed and evaluated. DMS contains enough carbon to be suitable as a biomass feedstock for conversion into ethanol by gasification technology, or as part of a conversion process that would include combined heat and power. In the first process, 100% of the feedstock is converted into ethanol. In the second process, the feedstock is combusted to provide heat to generate electrical power supporting other processes. Of the 100 technology vendors evaluated, a short list of nine technology providers was developed. From this, two vendors were selected as finalists (one was an enzymatic platform and one …
Date: June 23, 2011
Creator: Wold, Andrew & Divers, Robert
Object Type: Report
System: The UNT Digital Library
Carboxysomal carbonic anhydrases: Structure and role in microbial CO2 fixation (open access)

Carboxysomal carbonic anhydrases: Structure and role in microbial CO2 fixation

Cyanobacteria and some chemoautotrophic bacteria are able to grow in environments with limiting CO2 concentrations by employing a CO2-concentrating mechanism (CCM) that allows them to accumulate inorganic carbon in their cytoplasm to concentrations several orders of magnitude higher than that on the outside. The final step of this process takes place in polyhedral protein microcompartments known as carboxysomes, which contain the majority of the CO2-fixing enzyme, RubisCO. The efficiency of CO2 fixation by the sequestered RubisCO is enhanced by co-localization with a specialized carbonic anhydrase that catalyzes dehydration of the cytoplasmic bicarbonate and ensures saturation of RubisCO with its substrate, CO2. There are two genetically distinct carboxysome types that differ in their protein composition and in the carbonic anhydrase(s) they employ. Here we review the existing information concerning the genomics, structure and enzymology of these uniquely adapted carbonic anhydrases, which are of fundamental importance in the global carbon cycle.
Date: June 23, 2010
Creator: Cannon, Gordon C.; Heinhorst, Sabine & Kerfeld, Cheryl A.
Object Type: Article
System: The UNT Digital Library
On the Importance of Symmetrizing RF Coupler Fields for Low Emittance Beams (open access)

On the Importance of Symmetrizing RF Coupler Fields for Low Emittance Beams

The input power of accelerator structure is normally fed through a coupling slot(s) on the outer wall of the accelerator structure via magnetic coupling. While providing perfect matching, the coupling slots may produce non-axial-symmetric fields in the coupler cell that can induce emittance growth as the beam is accelerated in such a field. This effect is especially important for low emittance beams at low energies such as in the injector accelerators for light sources. In this paper, we present studies of multipole fields of different rf coupler designs and their effect on beam emittance for an X-band photocathode gun being jointly designed with LLNL, and X-band accelerator structures. We will present symmetrized rf coupler designs for these components to preserve the beam emittance.
Date: June 23, 2011
Creator: Li, Zenghai.; Zhou, Feng.; Vlieks, Arnold. & Adolphsen, Chris.
Object Type: Article
System: The UNT Digital Library
ARPES Studies of Cuprate Fermiology: Superconductivity, Pseudogap and Quasiparticle Dynamics (open access)

ARPES Studies of Cuprate Fermiology: Superconductivity, Pseudogap and Quasiparticle Dynamics

We present angle-resolved photoemission spectroscopy (ARPES) studies of the cuprate high-temperature superconductors which elucidate the relation between superconductivity and the pseudogap and highlight low-energy quasiparticle dynamics in the superconducting state. Our experiments suggest that the pseudogap and superconducting gap represent distinct states, which coexist below T{sub c}. Studies on Bi-2212 demonstrate that the near-nodal and near-antinodal regions behave differently as a function of temperature and doping, implying that different orders dominate in different momentum-space regions. However, the ubiquity of sharp quasiparticles all around the Fermi surface in Bi-2212 indicates that superconductivity extends into the momentum-space region dominated by the pseudogap, revealing subtlety in this dichotomy. In Bi-2201, the temperature dependence of antinodal spectra reveals particle-hole asymmetry and anomalous spectral broadening, which may constrain the explanation for the pseudogap. Recognizing that electron-boson coupling is an important aspect of cuprate physics, we close with a discussion of the multiple 'kinks' in the nodal dispersion. Understanding these may be important to establishing which excitations are important to superconductivity.
Date: June 23, 2011
Creator: Vishik, Inna
Object Type: Article
System: The UNT Digital Library
STATUS REPORT FOR MOISTURE EFFECTS ON COMPACTION OF FIBERBOARD IN A 9975 SHIPPING PACKAGE (open access)

STATUS REPORT FOR MOISTURE EFFECTS ON COMPACTION OF FIBERBOARD IN A 9975 SHIPPING PACKAGE

Compaction of lower layers in the fiberboard overpack has been observed in 9975 packages that contain elevated moisture. Lab testing has resulted in a better understanding of the relationship between the fiberboard moisture level and compaction of the lower fiberboard assembly, and the behavior of the fiberboard during transport. In laboratory tests, higher moisture content has been shown to correspond to higher total compaction of fiberboard material, greater rate of compaction, and continued compaction over a longer period of time. In addition, laboratory tests have shown that the application of a dynamic load results in higher fiberboard compaction. The test conditions and sample geometric/loading configurations were chosen to simulate the regulatory requirements for 9975 package input dynamic loading. Dynamic testing was conducted over a period of six months to acquire immediate and cumulative changes in geometric data for various moisture levels. Currently, one sample set has undergone a complete dynamic test regimen, while testing of another set is still in-progress. The dynamic input, data acquisition, test effects on sample dynamic parameters, and interim results from this test program are summarized and compared to regulatory specifications for dynamic loading. This will provide a basis from which to evaluate the impact of …
Date: June 23, 2011
Creator: Stefek, T.; Daugherty, W. & Estochen, E.
Object Type: Report
System: The UNT Digital Library
Scoping Thermal Analysis of Alternative Dual-Purpose Canister Disposal Concepts (open access)

Scoping Thermal Analysis of Alternative Dual-Purpose Canister Disposal Concepts

None
Date: June 23, 2013
Creator: Greenberg, H R; Wen, J & Buscheck, T A
Object Type: Report
System: The UNT Digital Library
Ultraviolet Thomson scattering measurements of the electron feature with an energetic 263 nm probe (open access)

Ultraviolet Thomson scattering measurements of the electron feature with an energetic 263 nm probe

None
Date: June 23, 2011
Creator: Ross, J S; Divol, L; Sorce, C; Froula, D H & Glenzer, S H
Object Type: Article
System: The UNT Digital Library
Wind Energy Facilities and Residential Properties: The Effect of Proximity and View on Sales Prices (open access)

Wind Energy Facilities and Residential Properties: The Effect of Proximity and View on Sales Prices

With increasing numbers of communities considering wind power developments, empirical investigations regarding related community concerns are needed. One such concern is that proximate property values may be adversely affected, yet relatively little research exists on the subject. The present research investigates roughly 7,500 sales of single-family homes surrounding 24 existing U.S. wind facilities. Across four different hedonic models, and a variety of robustness tests, the results are consistent: neither the view of the wind facilities nor the distance of the home to those facilities is found to have a statistically significant effect on sales prices, yet further research is warranted.
Date: June 23, 2011
Creator: University, San Diego State; College, Bard Center for Environmental Policy at Bard; Hoen, Ben; Wiser, Ryan; Cappers, Peter; Thayer, Mark et al.
Object Type: Article
System: The UNT Digital Library
Results of the FY09 Enhanced DOE High Level Waste Melter Throughput Studies at SRNL (open access)

Results of the FY09 Enhanced DOE High Level Waste Melter Throughput Studies at SRNL

High-level waste (HLW) throughput (i.e., the amount of waste processed per unit time) is a function of two critical parameters: waste loading (WL) and melt rate. For the Waste Treatment and Immobilization Plant (WTP) at the Hanford Site and the Defense Waste Processing Facility (DWPF) at the Savannah River Site (SRS), increasing HLW throughput would significantly reduce the overall mission life cycle costs for the Department of Energy (DOE). The objective of this task is to develop data, assess property models, and refine or develop the necessary models to support increased WL of HLW at SRS. It is a continuation of the studies initiated in FY07, but is under the specific guidance of a Task Change Request (TCR)/Work Authorization received from DOE headquarters (Project Number RV071301). Using the data generated in FY07, FY08 and historical data, two test matrices (60 glasses total) were developed at the Savannah River National Laboratory (SRNL) in order to generate data in broader compositional regions. These glasses were fabricated and characterized using chemical composition analysis, X-ray Diffraction (XRD), viscosity, liquidus temperature (TL) measurement and durability as defined by the Product Consistency Test (PCT). The results of this study are summarized below: (1) In general, the …
Date: June 23, 2010
Creator: Johnson, F. & Edwards, T.
Object Type: Report
System: The UNT Digital Library
The Carboxysome and Other Bacterial Microcompartments (open access)

The Carboxysome and Other Bacterial Microcompartments

- Carboxysomes are part of the carbon concentrating mechanism in cyanobacteria and chemoautotrophs. - Carboxysomes are a subclass of bacterial microcompartments (BMCs); BMCs can encapsulate a range of metabolic processes. - Like some viral particles, the carboxysome can be modeled as an icosahedron-in its case, having 4,000-5,000 hexameric shell subunits and 12 surface pentamers to generate curvature. - The threefold axis of symmetry of the CsoS1D protein in carboxysomes forms a pore that can open and close, allowing for selective diffusion. - Genetic modules encoding BMC shell proteins and the enzymes that they encapsulate are horizontally transferable, suggesting they enable bacteria to adapt to diverse environments.
Date: June 23, 2010
Creator: Kerfeld, Cheryl A.; Greenleaf, William B. & Kinney, James N.
Object Type: Article
System: The UNT Digital Library
Meteorology-induced variations in the spatial behavior of summer ozone pollution in Central California (open access)

Meteorology-induced variations in the spatial behavior of summer ozone pollution in Central California

Cluster analysis was applied to daily 8 h ozone maxima modeled for a summer season to characterize meteorology-induced variations in the spatial distribution of ozone. Principal component analysis is employed to form a reduced dimension set to describe and interpret ozone spatial patterns. The first three principal components (PCs) capture {approx}85% of total variance, with PC1 describing a general spatial trend, and PC2 and PC3 each describing a spatial contrast. Six clusters were identified for California's San Joaquin Valley (SJV) with two low, three moderate, and one high-ozone cluster. The moderate ozone clusters are distinguished by elevated ozone levels in different parts of the valley: northern, western, and eastern, respectively. The SJV ozone clusters have stronger coupling with the San Francisco Bay area (SFB) than with the Sacramento Valley (SV). Variations in ozone spatial distributions induced by anthropogenic emission changes are small relative to the overall variations in ozone amomalies observed for the whole summer. Ozone regimes identified here are mostly determined by the direct and indirect meteorological effects. Existing measurement sites are sufficiently representative to capture ozone spatial patterns in the SFB and SV, but the western side of the SJV is under-sampled.
Date: June 23, 2010
Creator: Jin, Ling; Harley, Robert A. & Brown, Nancy J.
Object Type: Article
System: The UNT Digital Library
Ion Species and Charge States of Vacuum Arc Plasma with Gas Feed and Longitudinal Magnetic Field (open access)

Ion Species and Charge States of Vacuum Arc Plasma with Gas Feed and Longitudinal Magnetic Field

The evolution of copper ion species and charge state distributions is measured for a long vacuum arc discharge plasma operated in the presence of a longitudinal magnetic field of several 10 mT and working gas (Ar). It was found that changing the cathode-anode distance within 20 cm as well as increasing the gas pressure did not affect the arc burning voltage and power dissipation by much. In contrast, burning voltage and power dissipation were greatly increased as the magnetic field was increased. The longer the discharge gap the greater was the fraction of gaseous ions and the lower the fraction of metal ions, while the mean ion charge state was reduced. It is argued that the results are affected by charge exchange collisions and electron impact ionization.
Date: June 23, 2010
Creator: Oks, Efim & Anders, Andre
Object Type: Article
System: The UNT Digital Library
Nevada Test Site 2009 Waste Management Monitoring Report Area 3 and Area 5 Radioactive Waste Management Sites (open access)

Nevada Test Site 2009 Waste Management Monitoring Report Area 3 and Area 5 Radioactive Waste Management Sites

Environmental monitoring data were collected at and around the Area 3 and Area 5 Radioactive Waste Management Sites (RWMSs) at the Nevada Test Site (NTS). These data are associated with radiation exposure, air, groundwater, meteorology, vadose zone, subsidence, and biota. This report summarizes the 2009 environmental data to provide an overall evaluation of RWMS performance and to support environmental compliance and performance assessment (PA) activities. Some of these data (e.g., radiation exposure, air, and groundwater) are presented in other reports. Direct radiation monitoring data indicate exposure levels at the RWMSs are within the range of background levels measured at the NTS. Air monitoring data at the Area 3 and Area 5 RWMSs indicate that tritium concentrations are slightly above background levels. All gamma spectroscopy results for air particulates collected at the Area 3 and Area 5 RWMS were below the minimum detectable concentrations, and concentrations of americium and plutonium are only slightly above detection limits. The measured levels of radionuclides in air particulates and moisture are below derived concentration guides for these radionuclides. Radon flux from waste covers is well below regulatory limits. Groundwater monitoring data indicate that the groundwater in the uppermost aquifer beneath the Area 5 RWMS is …
Date: June 23, 2010
Creator: Waste, NSTec Radioactive
Object Type: Report
System: The UNT Digital Library
Assessing the Impacts of Reduced Noise Operations of Wind Turbines on Neighbor Annoyance: A Preliminary Analysis in Vinalhaven, Maine (open access)

Assessing the Impacts of Reduced Noise Operations of Wind Turbines on Neighbor Annoyance: A Preliminary Analysis in Vinalhaven, Maine

Neighbors living near the 3 turbine, 4.5 MW Vinalhaven, Maine wind power facility, which began operations in late 2009, have complained that the noise from the turbines is unwelcome and annoying. Fox Islands Wind, the owner of the facility, hypothesized that implementing a Noise Reduced Operation (NRO) for the turbines, which effectively limits the turbines maximum rpm and power output, would reduce the sound levels produced by the turbines, and therefore might also reduce the degree to which the neighbors report being annoyed by those sounds. To test this hypothesis in a preliminary fashion, a pilot study was conducted in early 2010, the results of which are the subject of this brief report. The study included asking near-by residents - those within roughly 3000 feet - to rate the sounds and the degree to which they were annoyed by them using logs which they filled out at multiple times during the day on as many days as were possible in the 35 day study period in February and March, 2010. Meanwhile, FIW adjusted the NRO settings of the turbines in a random fashion in the evenings during the same period, but in a pattern that the respondents were not made …
Date: June 23, 2010
Creator: Hoen, Ben; Wiser, Ryan & Eckholdt, Haftan
Object Type: Report
System: The UNT Digital Library
G-Band Vapor Radiometer Profiler (GVRP) Handbook (open access)

G-Band Vapor Radiometer Profiler (GVRP) Handbook

The G-Band Vapor Radiometer Profiler (GVRP) provides time-series measurements of brightness temperatures from 15 channels between 170 and 183.310 GHz. Atmospheric emission in this spectral region is primarily due to water vapor, with some influence from liquid water. Channels between 170.0 and 176.0 GHz are particularly sensitive to the presence of liquid water. The sensitivity to water vapor of the 183.31-GHz line is approximately 30 times higher than at the frequencies of the two-channel microwave radiometer (MWR) for a precipitable water vapor (PWV) amount of less than 2.5 mm. Measurements from the GVRP instrument are therefore especially useful during low-humidity conditions (PWV < 5 mm). In addition to integrated water vapor and liquid water, the GVRP can provide low-resolution vertical profiles of water vapor in very dry conditions.
Date: June 23, 2010
Creator: Caddeau, M. P.
Object Type: Report
System: The UNT Digital Library
Rapid Determination of 237 Np and Pu Isotopes in Water by Inductively Coupled Plasma Mass Spectrometry and Alpha Spectrometry (open access)

Rapid Determination of 237 Np and Pu Isotopes in Water by Inductively Coupled Plasma Mass Spectrometry and Alpha Spectrometry

A new method that allows rapid preconcentration and separation of plutonium and neptunium in water samples was developed for the measurement of {sup 237}Np and Pu isotopes by inductively-coupled plasma mass spectrometry (ICP-MS) and alpha spectrometry; a hybrid approach. {sup 238}U can interfere with {sup 239}Pu measurement by ICP-MS as {sup 238}UH{sup +} mass overlap and {sup 237}Np via peak tailing. The method provide enhanced removal of uranium by separating Pu and Np initially on TEVA Resin, then moving Pu to DGA resin for additional removal of uranium. The decontamination factor for uranium from Pu is almost 100,000 and the decontamination factor for U from Np is greater than 10,000. This method uses stacked extraction chromatography cartridges and vacuum box technology to facilitate rapid separations. Preconcentration is performed using a streamlined calcium phosphate precipitation method. Purified solutions are split between ICP-MS and alpha spectrometry so that long and short-lived Pu isotopes can be measured successfully. The method allows for simultaneous extraction of 20 samples (including QC samples) in 4 to 6 hours, and can also be used for emergency response. {sup 239}Pu, {sup 242}Pu and {sup 237}Np were measured by ICP-MS, while {sup 236}Pu, {sup 238}Pu, and {sup 239}Pu were …
Date: June 23, 2010
Creator: Maxwell, S.; Jones, V.; Culligan, B.; Nichols, S. & Noyes, G.
Object Type: Article
System: The UNT Digital Library
DOE Response to Japan (open access)

DOE Response to Japan

DOE/NNSA NA‐40 was requested to provide support with consequence management activities following the incident at the Fukushima Dai’ichi Nuclear Power Plant. The response involved the deployment of several DOE/NNSA NA‐40 assets to provide specialized capabilities analysts, scientists, doctors, nurses, specialized equipment and systems to characterize the deposition for the protection of the public and the environment. General response activities revolved around the concepts of: predictive modeling; monitoring and data collection from the air and on the ground; assessing the collected data and other relevant information; interpreting the data; and coordinating the communication of the interpreted data to the appropriate stakeholders.
Date: June 23, 2011
Creator: Mena, Wendy Pemberton and RaJah
Object Type: Article
System: The UNT Digital Library
Using Qualified Energy Conservation Bonds (QECBs) to Fund a Residential Energy Efficiency Loan Program: Case Study on Saint Louis County, MO (open access)

Using Qualified Energy Conservation Bonds (QECBs) to Fund a Residential Energy Efficiency Loan Program: Case Study on Saint Louis County, MO

Qualified Energy Conservation Bonds (QECBs) are federally-subsidized debt instruments that enable state, tribal, and local government issuers to borrow money to fund a range of qualified energy conservation projects. QECBs offer issuers very attractive borrowing rates and long terms, and can fund low-interest energy efficiency loans for home and commercial property owners. Saint Louis County, MO recently issued over $10 million of QECBs to finance the Saint Louis County SAVES residential energy efficiency loan program. The county's experience negotiating QECB regulations and restrictions can inform future issuers.
Date: June 23, 2011
Creator: Zimring, Mark
Object Type: Report
System: The UNT Digital Library
Top Quark Amplitudes with an Anomolous Magnetic Moment (open access)

Top Quark Amplitudes with an Anomolous Magnetic Moment

The anomalous magnetic moment of the top quark may be measured during the first run of the LHC at 7 TeV. For these measurements, it will be useful to have available tree amplitudes with t{bar t} and arbitrarily many photons and gluons, including both QED and color anomalous magnetic moments. In this paper, we present a method for computing these amplitudes using the Britto-Cachazo-Feng-Witten recursion formula. Because we deal with an effective theory with higher-dimension couplings, there are roadblocks to a direct computation with the Britto-Cachazo-Feng-Witten method. We evade these by using an auxiliary scalar theory to compute a subset of the amplitudes.
Date: June 23, 2011
Creator: Larkoski, Andrew J. & Peskin, Michael E.
Object Type: Article
System: The UNT Digital Library
Multipacting Analysis for the Half-Wave Spoke Resonator Crab Cavity for LHC (open access)

Multipacting Analysis for the Half-Wave Spoke Resonator Crab Cavity for LHC

A compact 400-MHz half-wave spoke resonator (HWSR) superconducting crab cavity is being developed for the LHC upgrade. The cavity shape and the LOM/HOM couplers for such a design have been optimized to meet the space and beam dynamics requirements, and satisfactory RF parameters have been obtained. As it is known that multipacting is an issue of concern in a superconducting cavity which may limit the achievable gradient. Thus it is important in the cavity RF design to eliminate the potential MP conditions to save time and cost of cavity development. In this paper, we present the multipacting analysis for the HWSR crab cavity using the Track3P code developed at SLAC, and to discuss means to mitigate potential multipacting barriers. Track3P was used to analyze potential MP in the cavity and the LOM, HOM and FPC couplers. No resonances were found in the LOM couplers and the coaxial beam pipe. Resonant trajectories were identified on various locations in cavity, HOM and FPC couplers. Most of the resonances are not at the peak SEY of Nb. Run-away resonances were identified in broader areas on the cavity end plate and in the HOM coupler. The enhancement counter for run-away resonances does not show …
Date: June 23, 2011
Creator: Ge, Lixin & Li, Zenghai
Object Type: Article
System: The UNT Digital Library
Mechanism of Synthesis of Ultra-Long Single Wall Carbon Nanotubes in Arc Discharge Plasma (open access)

Mechanism of Synthesis of Ultra-Long Single Wall Carbon Nanotubes in Arc Discharge Plasma

In this project fundamental issues related to synthesis of single wall carbon nanotubes (SWNTs), which is relationship between plasma parameters and SWNT characteristics were investigated. Given that among plasma-based techniques arc discharge stands out as very advantageous in several ways (fewer defects, high flexibility, longer lifetime) this techniques warrants attention from the plasma physics and plasma technology standpoint. Both experimental and theoretical investigations of the plasma and SWNTs synthesis were conducted. Experimental efforts focused on plasma diagnostics, measurements of nanostructures parameters, and nanoparticle characterization. Theoretical efforts focused to focus on multi-dimensional modeling of the arc discharge and single wall nanotube synthesis in arc plasmas. It was demonstrated in experiment and theoretically that controlling plasma parameters can affect nanostucture synthesis altering SWNT properties (length and diameter) and leading to synthesis of new structures such as a few-layer graphene. Among clearly identified parameters affecting synthesis are magnetic and electric fields. Knowledge of the plasma parameters and discharge characteristics is crucial for ability to control synthesis process by virtue of both magnetic and electric fields. New graduate course on plasma engineering was introduced into curriculum. 3 undergraduate students were attracted to the project and 3 graduate students (two are female) were involved in …
Date: June 23, 2013
Creator: Keidar, Michael
Object Type: Report
System: The UNT Digital Library