You limited your search to:

  Partner: UNT Libraries Government Documents Department
 Decade: 1990-1999
1.2 MW klystron for Asymmetric Storage Ring B Factory

1.2 MW klystron for Asymmetric Storage Ring B Factory

Date: March 1, 1995
Creator: Fowkes, W.R.; Caryotakis, G. & Doyle, E.
Description: A cw klystron operating at 476 MHz has been developed jointly by SLAC and Varian Associates. The unique set of characteristics of this tube were strongly guided by requirements of the fast feedback necessary to prevent oscillations of the storage ring beams caused by the detuned accelerating cavity. This requires a combination of bandwidth and short group delay within the klystron. The RF feedback stabilization scheme also requires amplitude modulation making it necessary to operate the klystron about 10% below saturation. Performance specifications and initial operating results are presented.
Contributing Partner: UNT Libraries Government Documents Department
1-GeV Linac Upgrade Study at Fermilab

1-GeV Linac Upgrade Study at Fermilab

Date: September 1, 1998
Creator: Popovic, M., Moretti, A., Noble, R., Schmidt, C. W., FNAL
Description: A linac injector for a new proton source complex at Fermilab is assumed to have a kinetic energy of 1 GeV. This linac would be sized to accelerate 100 mA of H{sup -} beam in a 200 microsecond pulse at a 15 Hz repetition rate. This would be adequate to produce {approximately}10{sup 14} protons per pulse allowing for future improvements of the new proton source complex. An alternate proposal is to add 600 MeV of side coupled cavity linac at 805 MHz to the existing 400 MeV Linac. This addition may either be in a new location or use the present Booster tunnel. A discussion of these possibilities will be given.
Contributing Partner: UNT Libraries Government Documents Department
(02.2) Scoping experiments; (02.3) long-term corrosion testing and properties evaluation of candidate waste package basket material

(02.2) Scoping experiments; (02.3) long-term corrosion testing and properties evaluation of candidate waste package basket material

Date: December 20, 1996
Creator: VanKonynenburg, R. A.
Description: The work described in this activity plan addresses Information Need 2.7.3 of the Yucca Mountain Site Characterization Plan (l), which reads Determination that the design criteria in lOCFR60.130 through 60.133 and any appropriate additional design objectives pertaining to criticality control have been met. This work falls under section WBS 1.2.2.5 2 (Basket Materials) of WBS 1.2.2.5 (Waste Package Materials) in the Work Breakdown Structure of the Yucca Mountain Site Characterization Project.
Contributing Partner: UNT Libraries Government Documents Department
The 2.3 {angstrom} crystal structure of cholera toxin B subunit pentamer: Choleragenoid

The 2.3 {angstrom} crystal structure of cholera toxin B subunit pentamer: Choleragenoid

Date: February 1, 1996
Creator: Zhang, Rong-Guang; Westbrook, M.L.; Maulik, P.R.; Reed, R.A.; Shipley, G.; Westbrook, E.M. et al.
Description: Cholera toxin, a heterohexameric AB{sub 5} enterotoxin released by Vibrio cholera, induces a profuse secretory diarrhea in susceptible hosts. Choleragenoid, the B subunit pentamer of cholera toxin, directs the enzymatic A subunit to its target by binding to GM{sub 1} gangliosides exposed on the luminal surface of intestinal epithelial cells. We have solved the crystal structure of choleragenoid at 2.3 {Angstrom} resolution by combining single isomorphous replacement with non-crystallographic symmetry averaging. The structure of the B subunits, and their pentameric arrangement, closely resembles that reported for the intact holotoxin (choleragen), the heat-labile enterotoxin from E. coli, and for a choleragenoid-GM{sub 1} pentasaccharide complex. In the absence of the A subunit the central cavity of the B pentamer is a highly solvated channel. The binding of the A subunit or the receptor pentasaccharide to choleragenoid has only a modest effect on the local stereochemistry and does not perceptibly alter the subunit interface.
Contributing Partner: UNT Libraries Government Documents Department
2-D electric fields and drifts near the magnetic separatrix in divertor tokamaks

2-D electric fields and drifts near the magnetic separatrix in divertor tokamaks

Date: November 15, 1998
Creator: Mattor, N.; Porter, G. D.; Rognlien, T. D. & Ryutov, D. D.
Description: A 2-D calculation is presented for the transport of plasma in the edge region of a divertor tokamak solving continuity, momentum, and energy balance fluid equations. The model uses anomalous radial diffusion, including perpendicular ion momentum, and classical cross-field drifts transport. Parallel and perpendicular currents yield a self-consistent electrostatic potential on both sides of the magnetic separatrix. Outside the separatrix, the simulation extends to material divertor plates where the incident plasma is recycled as neutral gas and where the plate sheath and parallel currents dominate the potential structure. Inside the separatrix, various radial current terms - from viscosity, charge-exchange and poloidal damping, inertia, and {triangledown}B - contribute to the determining the potential. The model rigorously enforces cancellation of gyro-viscous and magnetization terms from the transport equations. The results emphasize the importance of E x B particle flow under the X-point which depends on the sign of the toroidal magnetic field. Radial electric field (E{sub y}) profiles at the outer midplane are small with weak shear when high L-mode diffusion coefficients are used and are large with strong shear when smaller H-mode diffusion coefficients are used. The magnitude and shear of the electric field (E{sub y}) is larger both when the ...
Contributing Partner: UNT Libraries Government Documents Department
2-D Finite Element Cable and Box IEMP Analysis

2-D Finite Element Cable and Box IEMP Analysis

Date: December 17, 1998
Creator: Scivner, G.J. & Turner, C.D.
Description: A 2-D finite element code has been developed for the solution of arbitrary geometry cable SGEMP and box IEMP problems. The quasi- static electric field equations with radiation- induced charge deposition and radiation-induced conductivity y are numerically solved on a triangular mesh. Multiple regions of different dielectric materials and multiple conductors are permitted.
Contributing Partner: UNT Libraries Government Documents Department
2-D image segmentation using minimum spanning trees

2-D image segmentation using minimum spanning trees

Date: September 1, 1995
Creator: Xu, Y. & Uberbacher, E.C.
Description: This paper presents a new algorithm for partitioning a gray-level image into connected homogeneous regions. The novelty of this algorithm lies in the fact that by constructing a minimum spanning tree representation of a gray-level image, it reduces a region partitioning problem to a minimum spanning tree partitioning problem, and hence reduces the computational complexity of the region partitioning problem. The tree-partitioning algorithm, in essence, partitions a minimum spanning tree into subtrees, representing different homogeneous regions, by minimizing the sum of variations of gray levels over all subtrees under the constraints that each subtree should have at least a specified number of nodes, and two adjacent subtrees should have significantly different average gray-levels. Two (faster) heuristic implementations are also given for large-scale region partitioning problems. Test results have shown that the segmentation results are satisfactory and insensitive to noise.
Contributing Partner: UNT Libraries Government Documents Department
N = 2 string amplitudes

N = 2 string amplitudes

Date: August 1, 1995
Creator: Ooguri, H.
Description: In physics, solvable models have played very important roles. Understanding a simple model in detail teaches us a lot about more complicated models in generic situations. Five years ago, C. Vafa and I found that the closed N = 2 string theory, that is a string theory with the N = 2 local supersymmetry on the worldsheet, is classically equivalent to the self-dual Einstein gravity in four spacetime dimensions. Thus this string theory is solvable at the classical level. More recently, we have examined the N = 2 string partition function for spacial compactifications, and computed it to all order in the string perturbation expansion. The fact that such computation is possible at all suggests that the N = 2 string theory is solvable even quantum mechanically.
Contributing Partner: UNT Libraries Government Documents Department
A 2 to 4 nm high power FEL on the SLAC linac

A 2 to 4 nm high power FEL on the SLAC linac

Date: September 1, 1992
Creator: Pellegrini, C.; Rosenzweig, J.; Nuhn, H.D.; Pianetta, P.; Tatchyn, R.; Winick, H. et al.
Description: We report the results of preliminary studies of a 2 to 4 nm SASE FEL, using a photoinjector to produce the electron beam, and the SLAC linac to accelerate it to an energy up to 10 GeV. Longitudinal bunch compression is used to increases ten fold the peak current to 2.5 kA, while reducing the bunch length to the subpicosecond range. The saturated output power is in the multi-gigawatt range, producing about 10{sup 14} coherent photons within a bandwidth of about 0.2% rms, in a pulse of several millijoules. At 120Hz repetition rate the average power is about 1 W. The system is optimized for x-ray microscopy in the water window around 2 to 4 nm, and will permit imaging a biological sample in a single subpicosecond pulse.
Contributing Partner: UNT Libraries Government Documents Department
3-D computer simulations of EM fields in the APS vacuum chamber: Part 1, Frequency-domain analysis

3-D computer simulations of EM fields in the APS vacuum chamber: Part 1, Frequency-domain analysis

Date: September 4, 1990
Creator: Chou, W. & Bridges, J.
Description: The vacuum chamber proposed for the storage ring of the 7-GeV Advanced Photon Source (APS) basically consists of two parts: the beam chamber and the antechamber, connected to each other by a narrow gap. A sector of 1-meter-long chamber with dosed end plates, to which are attached the 1-inch-diameter beampipes centered at the beam chamber, has been built for experimental purposes. The 3-D code MAFIA has been used to simulate the frequency-domain behaviors of EM fields in this setup. The results are summarized in this note and are compared with that previously obtained from 2-D simulations and that from network analyzer measurements. They are in general agreement. A parallel analysis in the time-domain is reported in a separate note. The method of our simulations can be briefly described as follows. The 1-inch diameter beampipes are terminated by conducting walls at a length of 2 cm. The whole geometry can thus be considered as a cavity. The lowest RF modes of this geometry are computed using MAFIA. The eigenfrequencies of these modes are a direct output of the eigenvalue solver E3, whereas the type of each mode is determined by employing the postprocessor P3. The mesh sizes are chosen such that ...
Contributing Partner: UNT Libraries Government Documents Department
FIRST PREV 1 2 3 4 5 NEXT LAST