Effective Supergravity from the Weakly Coupled HeteroticString (open access)

Effective Supergravity from the Weakly Coupled HeteroticString

The motivation for Calabi-Yau-like compactifications of the weakly coupled E{sub 8} {circle_times} E{sub 8} heterotic string theory, its particle spectrum and the issue of dilaton stabilization are briefly reviewed. Modular invariant models for hidden sector condensation and supersymmetry breaking are described at the quantum level of the effective field theory. Their phenomenological and cosmological implications, including a possible origin for R-parity, are discussed.
Date: May 1, 2005
Creator: Gaillard, Mary K.
System: The UNT Digital Library
Development and Validation of High-Resolution State Wind Resource Maps for the United States (Poster) (open access)

Development and Validation of High-Resolution State Wind Resource Maps for the United States (Poster)

A poster presentation for AWEA's WindPower 2005 conference in Denver, Colorado, May 15 -18, 2005 that provides an outline of the approach and process used for validating U.S. wind resource maps.
Date: May 1, 2005
Creator: Elliott, D. & Schwartz, M.
System: The UNT Digital Library
Laser Guiding at Relativistic Intensities and Wakefield ParticleAcceleration in Plasma Channels (open access)

Laser Guiding at Relativistic Intensities and Wakefield ParticleAcceleration in Plasma Channels

High quality electron beams with hundreds of picoCoulombs ofcharge inpercent energy spread above 80 MeV were produced for the firsttime in high gradient laser wakefield accelerators by guiding the drivelaser pulse.
Date: May 1, 2005
Creator: Geddes, C. G. R.; Toth, Cs.; van Tilborg, J.; Esarey, E.; Schroeder, C. B.; Bruhwiler, D. et al.
System: The UNT Digital Library
Macro-System Model (Poster) (open access)

Macro-System Model (Poster)

Poster presentation on Macro-System Model for the 2005 Hydrogen, Fuel Cells & Infrastructure Technologies Program Annual Review held in Arlington, Virginia on May 23-26, 2005
Date: May 1, 2005
Creator: Ruth, M.
System: The UNT Digital Library
LIMITS OF Nb3Sn ACCELERATOR MAGNETS (open access)

LIMITS OF Nb3Sn ACCELERATOR MAGNETS

Pushing accelerator magnets beyond 10 T holds a promise of future upgrades to machines like the Tevatron at Fermilab and the LHC at CERN. Exceeding the current density limits of NbTi superconductor, Nb{sub 3}Sn is at present the only practical superconductor capable of generating fields beyond 10 T. Several Nb{sub 3}Sn pilot magnets, with fields as high as 16 T, have been built and tested, paving the way for future attempts at fields approaching 20 T. High current density conductor is required to generate high fields with reduced conductor volume. However this significantly increases the Lorentz force and stress. Future designs of coils and structures will require managing stresses of several 100's of MPa and forces of 10's of MN/m. The combined engineering requirements on size and cost of accelerator magnets will involve magnet technology that diverges from the one currently used with NbTi conductor. In this paper we shall address how far the engineering of high field magnets can be pushed, and what are the issues and limitations before such magnets can be used in particle accelerators.
Date: May 1, 2005
Creator: Caspi, Shlomo & Ferracin, Paolo
System: The UNT Digital Library
Fitting the luminosity decay in the Tevatron (open access)

Fitting the luminosity decay in the Tevatron

This paper explores how to fit the decay of the luminosity in the Tevatron. The standard assumptions of a fixed-lifetime exponential decay are only appropriate for very short time intervals. A ''1/time'' functional form fits well, and is supported by analytical derivations. A more complex form, assuming a time-varying lifetime-like term, also produces good results. Changes in the luminosity can be factored into two phenomena: The luminosity burn-off rate, and the burn-off rate from non-luminosity effects. This is particularly relevant for the antiprotons in the Tevatron. The luminous and the non-luminous burn rate of the antiprotons are shown for Tevatron stores.
Date: May 1, 2005
Creator: McCrory, E.; Shiltsev, V.; Slaughter, A. J. & Xiao, A.
System: The UNT Digital Library
Using star tracks to determine the absolute pointing of the Fluorescence Detector telescopes of the Pierre Auger Observatory (open access)

Using star tracks to determine the absolute pointing of the Fluorescence Detector telescopes of the Pierre Auger Observatory

To accurately reconstruct a shower axis from the Fluorescence Detector data it is essential to establish with high precision the absolute pointing of the telescopes. To d that they calculate the absolute pointing of a telescope using sky background data acquired during regular data taking periods. The method is based on the knowledge of bright star's coordinates that provide a reliable and stable coordinate system. it can be used to check the absolute telescope's pointing and its long-term stability during the whole life of the project, estimated in 20 years. They have analyzed background data taken from January to October 2004 to determine the absolute pointing of the 12 telescopes installed both in Los Leones and Coihueco. The method is based on the determination of the mean-time of the variance signal left by a star traversing a PMT's photocathode which is compared with the mean-time obtained by simulating the track of that star on the same pixel.
Date: May 1, 2005
Creator: De Donato, Cinzia; Sanchez, Federico; /Milan U. /INFN, Milan; Santander, Marcos; Natl.Tech.U., San Rafael; Camin, Daniel et al.
System: The UNT Digital Library
Advances in the understanding and operations of superconducting colliders (open access)

Advances in the understanding and operations of superconducting colliders

Chromaticity drift during injection is a well-known phenomenon in superconducting colliders, such as the Tevatron, HERA and RHIC. Imperfect compensation of the drift effects can contribute to beam loss and emittance growth. It is caused by the drift of the sextupole component in the dipole magnets due to current redistribution in its superconducting coils. Recently extensive studies of chromaticity drift were conducted at the Tevatron, aiming at the improvement of the luminosity performance in the ongoing run II. These studies included not only beam experiments, but also extensive off-line magnetic measurements on spare Tevatron dipoles. Less known, until recently, is that chromaticity drift is often accompanied by tune and coupling drift. This was recently discovered in the Tevatron. We believe that these effects are the product of systematic beam offset in conjunction with the sextupole drifts (and their compensation in the chromaticity correctors). These discoveries are most relevant to the upcoming LHC, where the drift effects will have even more dramatic consequences given the high beam current. It is therefore not a surprise that CERN has been the source of major advances in the understanding of dynamic effects during the LHC superconducting magnet development. The following will briefly review the …
Date: May 1, 2005
Creator: Annala, G.; Bauer, P.; Bottura, L.; Martens, M. A.; Sammut, N.; Velev, G. et al.
System: The UNT Digital Library
US accelerator contribution to the LHC (open access)

US accelerator contribution to the LHC

In 1998, the United States entered into an agreement with CERN to help build the Large Hadron Collider (LHC), with contributions to the accelerator and to the large HEP detectors. To accomplish this, the US LHC Accelerator Project was formed, encompassing expertise from Brookhaven National Laboratory (BNL), Fermi National Accelerator Laboratory (FNAL) and the Lawrence Berkeley National Laboratory (LBNL). This report is a summary of these contributions including the progress towards project completion, as well as a discussion of future plans for continued US participation in the LHC accelerator.
Date: May 1, 2005
Creator: Lamm, Michael J.
System: The UNT Digital Library
Field quality study in Nb(3)Sn accelerator magnets (open access)

Field quality study in Nb(3)Sn accelerator magnets

Four nearly identical Nb{sub 3}Sn dipole models of the same design were built and tested at Fermilab. It provided a unique opportunity of systematic study the field quality effects in Nb{sub 3}Sn accelerator magnets. The results of these studies are reported in the paper.
Date: May 1, 2005
Creator: Kashikhin, V. V.; Ambrosio, G.; Andreev, N.; Barzi, E.; Bossert, R.; DiMarco, J. et al.
System: The UNT Digital Library
Modeling the Market Potential of Hydrogen from Wind and Competing Sources (open access)

Modeling the Market Potential of Hydrogen from Wind and Competing Sources

Developed from the Wind Deployment Systems (WinDS) model, the Hydrogen Deployment Systems (HyDS) model is a computer model of U.S. market expansion of hydrogen production from wind and other sources over the next 50 years. The WinDS model was developed in 2003 to model the expansion of generation and transmission capacity in the U.S. electric sector spanning the next 50 years. It minimizes system-wide costs of meeting loads, reserve requirements, and emission constraints by building and operating new generators and transmission in 26 two-year periods from 2000 to 2050. While it includes all major types of conventional generators, the WinDS model focuses on addressing the market issues of greatest significance to wind-specifically issues of electricity transmission and intermittency.
Date: May 1, 2005
Creator: Short, Walter; Blair, Nate & Heimiller, Donna
System: The UNT Digital Library
Deterioration of the skew quadrupole moment in Tevatron dipoles over time (open access)

Deterioration of the skew quadrupole moment in Tevatron dipoles over time

During the 20 years since it was first commissioned, the Fermilab Tevatron has developed strong coupling between the two transverse degrees of freedom. A circuit of skew quadrupole magnets is used to correct for coupling and, though capable, its required strength has increased since 1983 by more than an order of magnitude. In more recent years changes to the Tevatron for colliding beams operation have altered the skew quadrupole corrector distribution and strong local coupling become evident, often encumbering routine operation during the present physics run. Detailed magnet measurements were performed on each individual magnet during construction, and in early 2003 it was realized that measurements could be performed on the magnets in situ which could determine coil movements within the iron yoke since the early 1980's. It was discovered that the superconducting coils had become vertically displaced relative to their yokes since their construction. The ensuing systematic skew quadrupole field introduced by this displacement accounts for the required corrector settings and observed beam behavior. An historical account of the events leading to this discovery and progress toward its remedy are presented.
Date: May 1, 2005
Creator: Syphers, M. J. & Harding, D. J.
System: The UNT Digital Library
Towards a Wind Energy Climatology at Advanced Turbine Hub-Heights: Preprint (open access)

Towards a Wind Energy Climatology at Advanced Turbine Hub-Heights: Preprint

Measurements of wind characteristics over a wide range of heights up to and above 100 m are useful to: (1) characterize the local and regional wind climate; (2) validate wind resource estimates derived from numerical models; and (3) evaluate changes in wind characteristics and wind shear over the area swept by the blades. Developing wind climatology at advanced turbine hub heights for the United States benefits wind energy development. Tall tower data from Kansas, Indiana, and Minnesota (which have the greatest number of tall towers with measurement data) will be the focus of this paper. Analyses of data from the tall towers will start the process of developing a comprehensive climatology.
Date: May 1, 2005
Creator: Schwartz, M. & Elliott, D.
System: The UNT Digital Library
Beauty production cross section measurements at E(cm) = 1.96-TeV (open access)

Beauty production cross section measurements at E(cm) = 1.96-TeV

The RunII physics program at the Tevatron started in spring 2001 with protons and antiprotons colliding at an energy of {radical}s = 1.96 TeV, and it is carrying on with more than 500 pb{sup -1} of data as collected by both the CDF and D0 experiments. Recent results on beauty production cross section measurements are here reported.
Date: May 1, 2005
Creator: D'Onofrio, Monica & U., /Geneva
System: The UNT Digital Library
First-principles simulation and comparison with beam tests for transverse instabilities and damper performance in the Fermilab Main Injector (open access)

First-principles simulation and comparison with beam tests for transverse instabilities and damper performance in the Fermilab Main Injector

An end-to-end performance calculation and comparison with beam tests was performed for the bunch-by-bunch digital transverse damper in the Fermilab Main Injector. Time dependent magnetic wakefields responsible for ''Resistive Wall'' transverse instabilities in the Main Injector were calculated with OPERA-2D using the actual beam pipe and dipole magnet lamination geometry. The leading order dipole component was parameterized and used as input to a bunch-by-bunch simulation which included the filling pattern and injection errors experienced in high-intensity operation of the Main Injector. The instability growth times, and the spreading of the disturbance due to newly misinjected batches was compared between simulations and beam data collected by the damper system. Further simulation models the effects of the damper system on the beam.
Date: May 1, 2005
Creator: Nicklaus, Dennis; Foster, G. William & Kashikhin, Vladimir
System: The UNT Digital Library
Progress on using NEA cathodes in an RF gun (open access)

Progress on using NEA cathodes in an RF gun

RF guns have proven useful in multiple accelerator applications, and are an attractive electron source for the ILC. Using a NEA GaAs photocathode in such a gun allows for the production of polarized electron beams. However the lifetime of a NEA cathode in this environment is reduced by ion and electron bombardment and residual gas oxidation. We report progress made with studies to produce a RF gun using a NEA GaAs photocathode to produce polarized electron beams. We discuss simulations of ion back bombardment and attempts to reduce the residual gas pressure in the gun are discussed. Future directions are also discussed.
Date: May 1, 2005
Creator: Anderson, T.; Edwards, H.; Bluem, H.; Schultheiss, T.; Sinclair, C. & Huening, M.
System: The UNT Digital Library
Searches for the standard model Higgs boson at the Tevatron (open access)

Searches for the standard model Higgs boson at the Tevatron

The CDF and D0 experiments at the Tevatron have searched for the Standard Model Higgs boson in data collected between 2001 and 2004. Upper limits have been placed on the production cross section times branching ratio to b{bar b} pairs or W{sup +}W{sup -} pairs as a function of the Higgs boson mass. projections indicate that the Tevatron experiments have a chance of discovering a M{sub H} = 115 GeV Higgs with the total dataset foreseen by 2009, or excluding it at 95% C.L. up to a mass of 135 GeV.
Date: May 1, 2005
Creator: Dorigo, Tommaso & U., /Padua
System: The UNT Digital Library
Status of slip stacking at Fermilab Main Injector (open access)

Status of slip stacking at Fermilab Main Injector

In order to achieve an increase in proton intensity, the Fermilab Main Injector (MI) will use a stacking process called ''slip stacking'' [1]. The intensity will be doubled by injecting one train of bunches at a slightly lower energy, another at a slightly higher energy, then bringing them together for the final capture. Beam studies have been performed for this process and we have already verified that, at least for low beam intensities, the stacking procedure works as expected [2]. For high intensity operation, development work of the feedback and feedforward systems was done during the last machine shut down, from August to November 2004 [3].
Date: May 1, 2005
Creator: Seiya, K.; Berenc, T.; Dey, J.; Chase, B.; Rivetta, C.; Kourbanis, I. et al.
System: The UNT Digital Library
Tevatron beam position monitor upgrade (open access)

Tevatron beam position monitor upgrade

The Tevatron Beam Position Monitor (BPM) readout electronics and software have been upgraded to improve measurement precision, functionality and reliability. The original system, designed and built in the early 1980's, became inadequate for current and future operations of the Tevatron. The upgraded system consists of 960 channels of new electronics to process analog signals from 240 BPMs, new front-end software, new online and controls software, and modified applications to take advantage of the improved measurements and support the new functionality. The new system reads signals from both ends of the existing directional stripline pickups to provide simultaneous proton and antiproton position measurements. Measurements using the new system are presented that demonstrate its improved resolution and overall performance.
Date: May 1, 2005
Creator: Wolbers, Stephen; Banerjee, B.; Barker, B.; Bledsoe, S.; Boes, T.; Bowden, M. et al.
System: The UNT Digital Library
Betatron tune spread generation and differential chromaticity control by octupole families at Tevatron (open access)

Betatron tune spread generation and differential chromaticity control by octupole families at Tevatron

Existing Tevatron octupoles have been rearranged into four functional families. Two of these families generate betatron tune spreads in the vertical and horizontal planes whereas the other two control the differential chromaticity between the proton and antiproton helices. The calculated effect on the tunes and chromaticity is compared with direct measurements. Analytical formulas for betatron tune distribution functions are presented.
Date: May 1, 2005
Creator: Ivanov, P. M.; Alexahin, Y.; Annala, J.; Lebedev, V. A. & /Fermilab
System: The UNT Digital Library
A Hardware transverse beam frequency response simulator (open access)

A Hardware transverse beam frequency response simulator

We built an electronic instrument that can mimic the transverse beam frequency response. The instrument consists of (1) a time delay circuit with an analog-to-digital converter (ADC) which contains a first-in-first-out random assess memory (FIFO RAM) and a digital-to-analog converter (DAC); (2) a variable phase shifter circuit which is based on an all pass filter with a bandwidth of 25kHz to 30kHz and (3) a commutating filter which is a nonlinear band pass filter. With this instrument, we can dynamically adjust the betatron tune, the synchrotron tune, and the chromaticity. Using this instrument, we are able to test other beam systems without using actual beam.
Date: May 1, 2005
Creator: Ning, J. & Tan, C. Y.
System: The UNT Digital Library
Studies of the chromaticity, tune and coupling drift in the Tevatron (open access)

Studies of the chromaticity, tune and coupling drift in the Tevatron

Chromaticity drift is a well-known and more or less well-understood phenomenon in superconducting colliders such as the Tevatron. Less known is the effect of tune and coupling drift, also observed in the Tevatron during injection. These effects are caused by field drifts in the superconducting magnets. Controlling the behavior of the tune, coupling, and chromaticity is an important part of reducing beam loss at injection and at the start of the Tevatron ramp. In this context we conducted several beam-studies during the period of April to August 2004 in which we measured the drift in the Tevatron chromaticity, tunes, and coupling during the injection porch. In some cases we also measured the snapback at the start of the ramp. We will present the results of these studies data and put them into context of the results of off-line magnetic measurements conducted in spare Tevatron dipoles.
Date: May 1, 2005
Creator: Martens, Michael A.; Annala, Jerry; Bauer, Pierre; Shiltsev, Vladimir & Velev, Gueorgui
System: The UNT Digital Library
Iso-adiabatic merging of pbar stacks in the Fermilab Recycler (open access)

Iso-adiabatic merging of pbar stacks in the Fermilab Recycler

Considerable longitudinal emittance (LE) dilution is seen during merging of two stacks of pbars in the Fermilab Recycler. The emittance dilution results from the sequence of RF manipulations used for merging. Here I present a new scheme for merging two stacks adiabatically. This involves energy matching of the two stacks before merging. An analytical expression is derived for energy matching condition. The scheme is illustrated with multi-particle beam dynamics simulations and beam measurements. The beam experiments have shown that one can preserve the emittance to better than 15%.
Date: May 1, 2005
Creator: Bhat, C. M.
System: The UNT Digital Library
B0(S) mixing, lifetime difference and rare decays at the Tevatron (open access)

B0(S) mixing, lifetime difference and rare decays at the Tevatron

Recent results on B{sub s}{sup 0} mixing, lifetime difference and rare decays obtained by the CDF and D0 collaborations using the data samples collected at the Tevatron Collider in the period 2002-2005 are presented.
Date: May 1, 2005
Creator: Burdin, Sergey
System: The UNT Digital Library