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The “SF” System of Sextupoles for the JLAB 10 KW Free Electron Laser Upgrade (open access)

The “SF” System of Sextupoles for the JLAB 10 KW Free Electron Laser Upgrade

The characteristics of the system of “SF” Sextupoles for the infrared Free Electron Laser Upgrade1 at the Thomas Jefferson National Accelerator Facility (JLab) are described. These eleven sextupoles possess a large field integral (2.15 T/m) with +/- 0.2%
Date: May 1, 2009
Creator: George Biallas, Mark Augustine, Kenneth Baggett, David Douglas, Robin Wines
Object Type: Article
System: The UNT Digital Library
High Power Co-Axial SRF Coupler (open access)

High Power Co-Axial SRF Coupler

There are over 35 coupler designs for SRF cavities ranging in frequency from 325 to 1500 MHz. Two-thirds of these designs are coaxial couplers using disk or cylindrical ceramics in various combinations and configurations. While it is well known that dielectric losses go down by several orders of magnitude at cryogenic temperatures, it not well known that the thermal conductivity also goes down, and it is the ratio of thermal conductivity to loss tangent (SRF ceramic Quality Factor) and ceramic volume which will determine the heat load of any given design. We describe a novel robust co-axial SRF coupler design which uses compressed window technology. This technology will allow the use of highly thermally conductive materials for cryogenic windows. The mechanical designs will fit into standard-sized ConFlat® flanges for ease of assembly. Two windows will be used in a coaxial line. The distance between the windows is adjusted to cancel their reflections so that the same window can be used in many different applications at various frequencies.
Date: May 1, 2009
Creator: M.L. Neubauer, R.A. Rimmer
Object Type: Article
System: The UNT Digital Library
Buffered Electropolishing – A New Way for Achieving Extremely Smooth Surface Finish on Nb SRF Cavities to be Used in Particle Accelerators (open access)

Buffered Electropolishing – A New Way for Achieving Extremely Smooth Surface Finish on Nb SRF Cavities to be Used in Particle Accelerators

Future accelerators require unprecedented cavity performance, which is strongly influenced by interior surface nano-smoothness. Electropolishing (EP) is the technique of choice to be developed for high-field superconducting radio frequency (SRF) cavities. Electrochemical impedance spectroscopy (EIS) and related techniques point to the electropolishing mechanism of Nb in a sulphuric and hydrofluoric acid electrolyte controlled by a compact surface salt film under F- diffusion-limited mass transport control. These and other findings are guiding a systematic characterization to form the basis for cavities process optimization.
Date: May 1, 2009
Creator: Hui Tian, Charles Reece, Michael Kelley
Object Type: Article
System: The UNT Digital Library
Oxidation in Environments with Elevated CO2 Levels (open access)

Oxidation in Environments with Elevated CO2 Levels

Efforts to reduce greenhouse gas emissions from fossil energy power productions focus primarily on either pre- or post-combustion removal of CO2. The research presented here examines corrosion and oxidation issues associated with two types of post-combustion CO2 removal processes—oxyfuel combustion in refit boilers and oxyfuel turbines.
Date: May 1, 2009
Creator: Holcomb, Gordon H.
Object Type: Article
System: The UNT Digital Library
Superconducting Multi-Cell Deflecting Cavity for Short-Pulse X-Ray Generation at the Advanced Photon Source (open access)

Superconducting Multi-Cell Deflecting Cavity for Short-Pulse X-Ray Generation at the Advanced Photon Source

A superconducting multi-cell cavity for the production of short x-ray pulses at the Advanced Photon Source (APS) has been explored as an alternative to a single-cell cavity design in order to improve the packing factor and potentially reduce the number of high-power RF systems and low-level RF controls required. The cavity will operate at 2815 MHz in the APS storage ring and will require heavy damping of parasitic modes to maintain stable beam operation. Novel on-cell dampers, attached directly to the cavity body, have been utilized by taking advantage of the magnetic field null on the equatorial plane in order to enhance damping. Design issues and simulation results will be discussed.
Date: May 1, 2009
Creator: G.J. Waldschmidt, L.H. Morrison, R. Nassiri, R.A. Rimmer, K. Tian, H. Wang
Object Type: Article
System: The UNT Digital Library
CSR Interaction for a 2D Energy-Chirped Bunch on a General Orbit (open access)

CSR Interaction for a 2D Energy-Chirped Bunch on a General Orbit

When an electron bunch with initial linear energy chirp traverses a bunch compression chicane, the bunch interacts with itself via coherent synchrotron radiation (CSR) and space charge force. The effective longitudinal CSR force for such kind of 2D bunch on a circular orbit has been analyzed earlier [1]. In this paper, we present the analytical results of the effective longitudinal CSR force for a 2D energy-chirped bunch going through a general orbit, which includes the entrance and exit of a circular orbit. In particular, we will show the behavior of the force in the last bend of a chicane when the bunch is under extreme compression. This is the condition when bifurcation of bunch phase space occurs in many CSR measurements. [1] R. Li, Phys. Rev. ST Accel. Beams 11, 024401 (2008)
Date: May 1, 2009
Creator: Li, Rui
Object Type: Article
System: The UNT Digital Library
Recent Progress on Design Studies of High-Luminosity Ring-Ring Electron-Ion Collider at CEBAF (open access)

Recent Progress on Design Studies of High-Luminosity Ring-Ring Electron-Ion Collider at CEBAF

The conceptual design of a ring-ring electron-ion collider based on CEBAF has been continuously optimized to cover a wide center-of-mass energy region and to achieve high luminosity and polarization to support next generation nuclear science programs. Here, we summarize the recent design improvements and R&D progress on interaction region optics with chromatic aberration compensation, matching and tracking of electron polarization in the Figure-8 ring, beam-beam simulations and ion beam cooling studies.
Date: May 1, 2009
Creator: Zhang, Y.; Bruell, A.; Chevtsov, P.; Derbenev, Y. S.; Ent, R.; Krafft, G. A. et al.
Object Type: Article
System: The UNT Digital Library
[Letters from members] (open access)

[Letters from members]

Letter from Jo Terrell to WCSD Board on May 1, 2009, discussing her resignation of President of Stonewall Democrats of Williamson County. Also, emails from Daniel Graney to Erin Moore, Kaye Gooch, and Al Daniels on May, 1 2009, discussing Jo Terrell's resignations as President of Stonewall Democrats of Williamson County.
Date: May 1, 2009
Creator: unknown
Object Type: Letter
System: The UNT Digital Library
Design of Superconducting Parallel Bar Deflecting and Crabbing rf Structures (open access)

Design of Superconducting Parallel Bar Deflecting and Crabbing rf Structures

A new concept for a deflecting and crabbing rf structure based on half-wave resonant lines was introduced recently*. It offers significant advantages to existing designs and, because of it compactness, allows low frequency operation. This concept has been further refined and optimized for superconducting implementation. Results of this optimization and application to a 400 MHz crabbing cavity and a 499 MHz deflecting cavity are presented.
Date: May 1, 2009
Creator: Jean Delayen, Haipeng Wang
Object Type: Article
System: The UNT Digital Library
Surface Topography of 'Hotspot' Regions from a Single Cell SRF Cavity (open access)

Surface Topography of 'Hotspot' Regions from a Single Cell SRF Cavity

Performance of SRF cavities are limited by non-linear localized effects. The variation of local material characters between "hot" and "cold" spots is thus of intense interest. Such locations were identified in a BCP-etched large-grain single-cell cavity and removed for examination by high resolution electron microscopy (SEM), electron-back scattering diffraction microscopy (EBSD), optical microscopy, and 3D profilometry. Pits with clearly discernable crystal facets were observed in both "hotspot" and "coldspot" specimens. The pits were found in-grain, at bi-crystal boundaries, and on tri-crystal junctions. They are interpreted as etch pits induced by surface crystal defects (e.g. dislocations). All "coldspots" examined had qualitatively low density of etching pits or very shallow tri-crystal boundary junction. EBSD revealed the crystal structure surrounding the pits via crystal phase orientation mapping, while 3D profilometry gave information on the depth and size of the pits. In addition, a survey of the samples by energy dispersive X-ray analysis (EDX) did not show any significant contamination of the samples surface.
Date: May 1, 2009
Creator: Xin Zhao, Gianluigi Ciovati, Charles Reece, Andy Wu
Object Type: Article
System: The UNT Digital Library
Ultrafast X-Ray Coherent Control (open access)

Ultrafast X-Ray Coherent Control

This main purpose of this grant was to develop the nascent #12;eld of ultrafast x-ray science using accelerator-based sources, and originally developed from an idea that a laser could modulate the di#11;racting properties of a x-ray di#11;racting crystal on a fast enough time scale to switch out in time a shorter slice from the already short x-ray pulses from a synchrotron. The research was carried out primarily at the Advanced Photon Source (APS) sector 7 at Argonne National Laboratory and the Sub-Picosecond Pulse Source (SPPS) at SLAC; in anticipation of the Linac Coherent Light Source (LCLS) x-ray free electron laser that became operational in 2009 at SLAC (all National User Facilities operated by BES). The research centered on the generation, control and measurement of atomic-scale dynamics in atomic, molecular optical and condensed matter systems with temporal and spatial resolution . It helped develop the ultrafast physics, techniques and scienti#12;c case for using the unprecedented characteristics of the LCLS. The project has been very successful with results have been disseminated widely and in top journals, have been well cited in the #12;eld, and have laid the foundation for many experiments being performed on the LCLS, the world's #12;rst hard x-ray free …
Date: May 1, 2009
Creator: Reis, David
Object Type: Report
System: The UNT Digital Library
Task 2: Materials for Advanced Boiler and Oxy-combustion Systems (open access)

Task 2: Materials for Advanced Boiler and Oxy-combustion Systems

Characterize advanced boiler (oxy-fuel combustion, biomass cofired) gas compositions and ash deposits Generate critical data on the effects of environmental conditions; develop a unified test method with a view to future standardisation
Date: May 1, 2009
Creator: Holcomb, G. R. & McGhee, B.
Object Type: Article
System: The UNT Digital Library
Greensheet (Houston, Tex.), Vol. 40, No. 155, Ed. 1 Friday, May 1, 2009 (open access)

Greensheet (Houston, Tex.), Vol. 40, No. 155, Ed. 1 Friday, May 1, 2009

Free weekly newspaper that includes business and classified advertising.
Date: May 1, 2009
Creator: unknown
Object Type: Newspaper
System: The Portal to Texas History
Stability Issues of the Mu2e Proton Beam (open access)

Stability Issues of the Mu2e Proton Beam

Stability issues of the mu2e proton beam are discussed. These include space-charge distortion of bunch shape, microwave instabilities, mode-coupling instabilities, head-tail instabilities, as well as electron-cloud effects. We have studied several beam stability issues of the proton beam heading to the target for the mu2e experiment. We find bunch-shape distortions driven by the space charge force is reasonably small, and longitudinal microwave instability will unlikely to occur. Electron-cloud buildup, with density up to {rho}{sub e} {approx} 2 x 10{sup 12} m{sup -3} in the Accumulator, can probably drive head-tail instabilities. However, these, together with the instabilities driven by the resistive-wall impedance can be avoided by restricting the chromaticity to larger than {approx} 0.2. TMCI will not occur even when the electron-cloud wake is included.
Date: May 1, 2009
Creator: Ng, King-Yuen
Object Type: Article
System: The UNT Digital Library
Unclassified Source Term and Radionuclide Data for Corrective Action Unit 97: Yucca Flat/Climax Mine, Nevada Test Site, Nevada, Revision 1 (open access)

Unclassified Source Term and Radionuclide Data for Corrective Action Unit 97: Yucca Flat/Climax Mine, Nevada Test Site, Nevada, Revision 1

This report documents the evaluation of the information and data available on the unclassified source term and radionuclide contamination for CAU 97: Yucca Flat/Climax Mine. The total residual inventory of radionuclides associated with one or more tests is known as the radiologic source term (RST). The RST is comprised of radionuclides in water, glass, or other phases or mineralogic forms. The hydrologic source term (HST) of an underground nuclear test is the portion of the total RST that is released into the groundwater over time following the test. In this report, the HST represents radionuclide release some time after the explosion and does not include the rapidly evolving mechanical, thermal, and chemical processes during the explosion. The CAU 97: Yucca Flat/Climax Mine has many more detonations and a wider variety of settings to consider compared to other CAUs. For instance, the source term analysis and evaluation performed for CAUs 101 and 102: Central and Western Pahute Mesa and CAU 98: Frenchman Flat did not consider vadose zone attenuation because many detonations were located near or below the water table. However, the large number of Yucca Flat/Climax Mine tests and the location of many tests above the water table warrant a …
Date: May 1, 2009
Creator: Martian, Peter
Object Type: Report
System: The UNT Digital Library
Performance Evaluation for Modular, Scalable Overhead Cooling Systems In Data Centers (open access)

Performance Evaluation for Modular, Scalable Overhead Cooling Systems In Data Centers

Scientific and enterprise data centers, IT equipment product development, and research data center laboratories typically require continuous cooling to control inlet air temperatures within recommended operating levels for the IT equipment. The consolidation and higher density aggregation of slim computing, storage and networking hardware has resulted in higher power density than what the raised-floor system design, coupled with commonly used computer rack air conditioning (CRAC) units, was originally conceived to handle. Many existing data centers and newly constructed data centers adopt CRAC units, which inherently handle heat transfer within data centers via air as the heat transfer media. This results in energy performance of the ventilation and cooling systems being less than optimal. Understanding the current trends toward higher power density in IT computing, more and more IT equipment manufacturers are designing their equipment to operate in 'conventional' data center environments, while considering provisions of alternative cooling solutions to either their equipment or supplemental cooling in rack or row systems. Naturally, the trend toward higher power density resulting from current and future generations of servers has, in the meanwhile, created significant opportunities for precision cooling suppliers to engineer and manufacture packaged modular and scalable systems. The modular and scalable cooling …
Date: May 1, 2009
Creator: Xu, TengFang T.
Object Type: Report
System: The UNT Digital Library
Connecticut Transit (CTTRANSIT) Fuel Cell Transit Bus: Second Evaluation Report and Appendices (open access)

Connecticut Transit (CTTRANSIT) Fuel Cell Transit Bus: Second Evaluation Report and Appendices

This report describes operations at Connecticut Transit (CTTRANSIT) in Hartford for one prototype fuel cell bus and three new diesel buses operating from the same location. The evaluation period in this report (January 2008 through February 2009) has been chosen to coincide with a UTC Power propulsion system changeout that occurred on January 15, 2008.
Date: May 1, 2009
Creator: Chandler, K. & Eudy, L.
Object Type: Report
System: The UNT Digital Library
Measurement of electron neutrino appearance with the MINOS experiment (open access)

Measurement of electron neutrino appearance with the MINOS experiment

MINOS is a long-baseline two-detector neutrino oscillation experiment that uses a high intensity muon neutrino beam to investigate the phenomena of neutrino oscillations. By measuring the neutrino interactions in a detector near the neutrino source and again 735 km away from the production site, it is possible to probe the parameters governing neutrino oscillation. The majority of the {nu}{sub {mu}} oscillate to {nu}{sub {tau}} but a small fraction may oscillate instead to {nu}{sub e}. This thesis presents a measurement of the {nu}{sub e} appearance rate in the MINOS far detector using the first two years of exposure. Methods for constraining the far detector backgrounds using the near detector measurements is discussed and a technique for estimating the uncertainty on the background and signal selection are developed. A 1.6{sigma} excess over the expected background rate is found providing a hint of {nu}{sub e} appearance.
Date: May 1, 2009
Creator: Boehm, Joshua Adam Alpern & U., /Harvard
Object Type: Thesis or Dissertation
System: The UNT Digital Library
NREL Gearbox Reliability Collaborative Analysis Round Robin: Preprint (open access)

NREL Gearbox Reliability Collaborative Analysis Round Robin: Preprint

The Gearbox Reliability Collaborative is working to determine the causes and loading conditions that result in the premature failure of wind turbine gearboxes.
Date: May 1, 2009
Creator: Oyague, F.; Butterfield, C. P. & Sheng, S.
Object Type: Article
System: The UNT Digital Library
The K- pi+ S-wave from the D+ --> k- pi+ pi+ Decay (open access)

The K- pi+ S-wave from the D+ --> k- pi+ pi+ Decay

Using data from FOCUS (E831) experiment at Fermilab, we present a model independent partial-wave analysis of the K{sup -}{pi}{sup +} S-wave amplitude from the decay D{sup +} {yields} K{sup -}{pi}{sup +}{pi}{sup +}. The S-wave is a generic complex function to be determined directly from the data fit. The P- and D-waves are parameterized by a sum of Breit-Wigner amplitudes. The measurement of the S-wave amplitude covers the whole elastic range of the K{sup -}{pi}{sup +} system.
Date: May 1, 2009
Creator: Link, J. M.; Yager, P. M.; /UC, Davis; Anjos, J. C.; Bediaga, I.; Castromonte, C. et al.
Object Type: Article
System: The UNT Digital Library
Human Factors and Data Fusion as Part of Control Systems Resilience (open access)

Human Factors and Data Fusion as Part of Control Systems Resilience

Human performance and human decision making is counted upon as a crucial aspect of overall system resilience. Advanced control systems have the potential to provide operators and asset owners a wide range of data, deployed at different levels that can be used to support operator situation awareness. However, the sheer amount of data available can make it challenging for operators to assimilate information and respond appropriately. This paper reviews some of the challenges and issues associated with providing operators with actionable state awareness and argues for the over arching importance of integrating human factors as part of intelligent control systems design and implementation. It is argued that system resilience is improved by implementing human factors in operations and maintenance. This paper also introduces issues associated with resilience and data fusion and highlights areas in which human factors including field studies hold promise.
Date: May 1, 2009
Creator: Gertman, David I.
Object Type: Article
System: The UNT Digital Library
A Neutronic Analysis of TRU Recycling in PWRs Loaded with MOX-UE Fuel (MOX with U-235 Enriched U Support) (open access)

A Neutronic Analysis of TRU Recycling in PWRs Loaded with MOX-UE Fuel (MOX with U-235 Enriched U Support)

This report presents the results of a study dealing with the homogeneous recycling of either Pu or Pu+Np or Pu+Np+Am or Pu+Np+Am+Cm in PWRs using MOX-UE fuel, i.e. standard MOX fuel with a U235 enriched uranium support instead of the standard tail uranium (0.25%) for standard MOX fuel. This approach allows to multirecycle Pu or TRU (Pu+MA) as long as U235 is available, by keeping the Pu or TRU content in the fuel constant and at a value ensuring a negative moderator void coefficient (i.e. the loss of the coolant brings imperatively the reactor to a subcritical state). Once this value is determined, the U235 enrichment of the MOX-UE fuel is adjusted in order to reach the target burnup (51 GWd/t in this study).
Date: May 1, 2009
Creator: Youinou, G. & Bays, S.
Object Type: Report
System: The UNT Digital Library
A Dual Triangle Timing Circuit for Improved Performance of 4-Quadrant H-Bridge Switches (open access)

A Dual Triangle Timing Circuit for Improved Performance of 4-Quadrant H-Bridge Switches

Fermilab is in the process of upgrading its Booster Correction Element System to include full field correction element magnets to correct position and chromaticity throughout the booster cycle. This upgrade requires power supplies with maximum outputs of {+-}180V/{+-}65A, with current bandwidths of 5k Hz and with slew rates of min to max current in 1ms. For seamless operation around zero current and voltage, we use continuous switching on both sides of the bridge. Although the straightforward way of coordinating the switching on both sides of the bridge can be accomplished with one triangle timing wave and one voltage reference, we have found that using two triangle waves yields a switching coordination that effectively doubles the frequency of the differential ripple on the load and allows for better filtering of the output ripple.
Date: May 1, 2009
Creator: Krafczyk, G.; Jensen, C.; Pfeffer, H.; Warchol, G. & /Fermilab
Object Type: Article
System: The UNT Digital Library
MODIFIED CHOKE FLOW CRITERION FOR THE TWO-PHASE TWO-FLUID MODEL (open access)

MODIFIED CHOKE FLOW CRITERION FOR THE TWO-PHASE TWO-FLUID MODEL

A choked condition exists when mass flow rate becomes independent of the downstream conditions. In other words, no information can propagate in the upstream direction under this condition. The real part of the solution of the characteristic equation for the model represents velocity of the signal propagation and the imaginary part is the growth (or decay) rate of that signal. Therefore, if the real part of these eigenvalues is positive then no signal propagates in the upstream direction (choosing downstream direction to be the positive direction) resulting in the choke flow. In order to develop the choke criterion, a non-dimensional form of the characteristic equation is derived for the standard two-phase two-fluid model. The equation is in the terms of a slip Mach number Ms. It can be shown that the slip Mach number is small for many applications including nuclear reactor safety simulations. The eigenvalues of the characteristic equation are obtained as a power series expansion about the point Ms = 0. These eigenvalues are used to develop a choking criterion for the compressible two-phase flows.
Date: May 1, 2009
Creator: Singh, Suneet & Mousseau, Vincent A.
Object Type: Article
System: The UNT Digital Library