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1,755 Matching Results

Start Over Year 1994

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Results: 1 - 24 of 1,755 next

(open access)

Crossing symmetry is incompatible with general relativity

None

Date: December 1, 1994

Creator: Noyes, H. P.

Object Type: Report

System: The UNT Digital Library

(open access)

Crab crossing in a gamma-gamma collider

The crabbing of an incident photon beam from a laser, and the electron beam with which it interacts at the conversion point, is shown to have the same efficiency as in head-on Compton scattering, but with the advantages of a crossing geometry. The resulting {gamma}-ray beam is also crabbed, which allows for a crossing collision point, while maintaining the luminosity at the same value it would have in a head-on collision.

Date: August 1, 1994

Creator: Xie, M.; Kim, K. J. & Sessler, A.

Object Type: Article

System: The UNT Digital Library

(open access)

Final report Task Order Number B239641 between the Regents of the University of California and Institute of Experimental Physics task 1: Conceptual design. Part 1

The current worldwide developmental status of high power lasers and pumping systems for laser ignition facilities is presented. Design philosophies of pulsed power systems for laser fusion (LF) research facilities are discussed. A conceptual design of the facility pulsed power systems is discussed in detail. In conclusion, a thorough analysis of current worldwide LF research is given.

Date: November 1, 1994

Creator: Galakhov, I. V.; Kirillov, G. A. & Murugov, V. M.

Object Type: Report

System: The UNT Digital Library

(open access)

Final joint environmental assessment for the construction and routine operation of a 12-kilovolt (KV) overhead powerline right-of-way, and formal authorization for a 10-inch and 8-inch fresh water pipeline right-of-way, Naval Petroleum Reserve No. 1, Kern County, California

The purpose and need of the proposed action, which is the installation of an overhead powerline extension from an Naval Petroleum Reserve No. 1 (NPR-1) power source to the WKWD Station A, is to significantly reduce NPR-1`s overall utility costs. While the proposed action is independently justified on its own merits and is not tied to the proposed NPR-1 Cogeneration Facility, the proposed action would enable DOE to tie the NPR-1 fresh water pumps at Station A into the existing NPR-1 electrical distribution system. With the completion of the cogeneration facility in late 1994 or early 1995, the proposed action would save additional utility costs. This report deals with the environmental impacts of the construction of the powerline and the water pipeline. In addition, information is given about property rights and attaining permission to cross the property of proposed affected owners.

Date: October 1, 1994

Creator: unknown

Object Type: Report

System: The UNT Digital Library

(open access)

Closed orbit distortion from parasitic collisions in PEP-II

The dipole force on the beams caused by the parasitic collisions (PCs) induces closed orbit distortions in the interaction region (IR): ``typical`` bunches (those far away from the ion-clearing gap), collide center-on-center with a small horizontal crossing angle; ``pacman`` bunches (those close to the gap) not only collide at an angle, but their centers are displaced as well; and the orbit separation between the beams at the PCs is different from nominal. We evaluate these effects as a function of horizontal tune in first-order approximation. This analysis yields one set of constraints that are absolutely necessary, although far from sufficient, for reliable operation. We conclude that the crossing angle and orbit displacements are small except for tune values very close to the integer (above or below), and that fractional tunes {approx_gt} 0.35 are favored.

Date: June 1, 1994

Creator: Furman, M. A.

Object Type: Article

System: The UNT Digital Library

(open access)

Spin polarization of {sup 23}Mg in {sup 24}Mg + Au, Cu and Al collisions at 91 A MeV

Spin polarization of beta-emitting fragment {sup 23}Mg(I{sup {pi}} = 3/2{sup +}, T{sub l/2} = 11.3 s) produced through the projectile fragmentation process in {sup 24}Mg + Au, Cu and Al collisions has been observed at 91 A MeV. General trend in the observed momentum dependence of polarization is reproduced well qualitatively by a simple fragmentation model based on the participant-spectator picture, for heavy and light targets. However the polarization behavior differs from this model in terms of zero crossing momentum, which become prominent in the case of Cu target, where the polarization is not monotone function of the fragment momentum.

Date: September 1, 1994

Creator: Matsuta, K.; Fukuda, S. & Izumikawa, T.

Object Type: Article

System: The UNT Digital Library

(open access)

Higher Order Mode Damping for a Detuned Structure

We report in this paper the current status of our investigation of the possibility of suppressing the wake reappearance by providing relatively weak damping via the vacuum manifolds. The four vacuum manifolds running the length of the structure also function as multimode waveguides which serve to drain power from the HOM`s through the large coupling slots located in each cell, except, as discussed later, for a few at each end of the manifolds.

Date: August 1, 1994

Creator: Kroll, N.; Thompson, K.; Bane, K.; Ko, K.; Miller, R.; Ruth, R. et al.

Object Type: Article

System: The UNT Digital Library

(open access)

Multipole contribution from an off-axis orbit in an IR quadrupole and the consequences on the dynamic aperture

The low-energy beam of the proposed PEP-II B factory enters the first quadrupole (Q1) after the interaction point off axis in order to separate the low-energy beam from the high-energy beam. The off-axis beam orbit in Q1 gives rise to significant feed-down terms from higher multipoles that originate from systematic effects and random fabrication errors. The authors study superconducting and permanent magnet designs of Q1, and look at the effect these different designs have on the dynamic aperture. Including a dipole field in a superconducting design allows one to offset the magnetic axis from the mechanical axis, thereby maintaining the separation of the beams while greatly reducing the feed-down effect. They illustrate relevant points of the discussion with tracking results for the PEP-II low-energy ring.

Date: June 1, 1994

Creator: Sullivan, M.; Caspi, S. & Forest, E.

Object Type: Article

System: The UNT Digital Library

(open access)

The PEP-II Asymmetric B Factory: Design details and R&D results

PEP-II, a 9 GeV {times} 3.1 GeV electron-positron collider with a design luminosity of 3 {times} 10{sup 33} cm{sup {minus}2}s{sup {minus}1} has now been approved for construction by SLAC, LBL and LLNL for the purpose of studying CP violation in the B{bar B} system. This upgrade project involves replacing the vacuum and RF systeum of PEP, which will serve as the high-energy ring (HER), along with the addition of a new low-energy ring (LER) mounted atop the HER. Designs for both rings are described, and the anticipated project construction schedule is indicated. Collider operation will begin at the end of 1998. An aggressive R&D program has been carried out to validate our design choices; key results in the areas of lattice design, vacuum, RF, and multibunch feedback are summarized.

Date: June 1, 1994

Creator: Bloom, E.; DeStaebler, H. & Dorfan, J.

Object Type: Article

System: The UNT Digital Library

(open access)

Tests for resistivity boundary changes at Ohaaki, New Zealand

Close-spaced resistivity measurements along ten traverse lines crossing the resistivity boundary of the Ohaaki Geothermal Field, New Zealand, were first measured in 1975 and remeasured in 1992. The 1992 resistivity profiles were similar in shape to the original ones. On both occasions very sharp resistivity boundaries were delineated along the southern and southwestern edges of the field where apparent resistivity rises sharply over a horizontal distance of a few hundred metres from 2-5 ohm m on the inside of the field to 20-50 ohm m on the outside. On two of the southern lines the resistivity boundary appears to have moved outwards by about 100 m, which may be caused by southward movement of reinjected waste water from nearby drillholes. On the other southern lines the outward movement appears to be less than about 25 m, which is the limit of resolution of the survey. Over the 17 year interval apparent resistivity values have dropped slightly at most measurement sites. The decrease is more pronounced on the inside of the field boundary where apparent resistivities have declined by up to about 40 percent. Some of this decrease is attributed to reinjection of conductive waste water near the field boundary causing …

Date: January 20, 1994

Creator: Risk, G.F.

Object Type: Article

System: The UNT Digital Library

(open access)

Bunch-by-bunch longitudinal feedback system for PEP-II

This paper describes the implementation of the bunch-by-bunch longitudinal feedback system for the PEP-II B Factory. Bunch spacing down to 2 ns is achieved using 500 Megasamples per second A/D and D/A converters, and AT&T 1610 Digital Signal Processors are integrated to run a downsampled feedback algorithm for each bunch in parallel. This general purpose programmable system, packaged in VXI and VME, is modular and scalable to offer portability to other accelerator rings. The control and monitoring hardware and software architecture have been developed to provide ease of operation as well as diagnostic tools for machine physics.

Date: June 1, 1994

Creator: Oxoby, G.; Claus, R. & Fox, J.

Object Type: Article

System: The UNT Digital Library

(open access)

First results from the final focus test beam

We have used the Final Focus Test Beam beamline and associated instrumentation to reduce the 46.6 GeV SLAC electron beam to a vertical size of 70 nm. This represents a reduction from the linac beam size by a factor of 320, comparable to the demagnification required by a TeV-scale linear collider, and addresses the same aberrations predicted in such an environment. The beam dimensions were measured by two novel beam size monitors at the focal point. Details of the optical and hardware design of the beam line, necessary tuning operations, beam size monitor principles, and future plans are discussed.

Date: July 1, 1994

Creator: Tenenbaum, P. & Collaboration, FFTB

Object Type: Article

System: The UNT Digital Library

(open access)

NEO-LISP: Deflecting near-earth objects using high average power, repetitively pulsed lasers

Several kinds of Near-Earth objects exist for which one would like to cause modest orbit perturbations, but which are inaccessible to normal means of interception because of their number, distance or the lack of early warning. For these objects, LISP (Laser Impulse Space Propulsion) is an appropriate technique for rapidly applying the required mechanical impulse from a ground-based station. In order of increasing laser energy required, examples are: (1) repositioning specially prepared geosynchronous satellites for an enhanced lifetime, (2) causing selected items of space junk to re-enter and burn up in the atmosphere on a computed trajectory, and (3) safely deflecting Earth-directed comet nuclei and earth-crossing asteroids (ECA`s) a few tens of meters in size (the most hazardous size). They will discuss each of these problems in turn and show that each application is best matched by its own matrix of LISP laser pulse width, pulse repetition rate, wavelength and average power. The latter ranges from 100W to 3GW for the cases considered. They will also discuss means of achieving the active beam phase error correction during passage through the atmosphere and very large exit pupil in the optical system which are required in each of these cases.

Date: October 1, 1994

Creator: Phipps, C. R. & Michaelis, M. M.

Object Type: Article

System: The UNT Digital Library

(open access)

Manifold damping of the NLC detuned accelerating structure

In order to investigate the reappearance of the HOM wakefield of a detuned accelerator structure and relax tolerance requirements, we propose to provide low level damping by coupling all cavities to several identical and symmetrically located waveguides (manifolds) which run parallel to each accelerator structure and are terminated at each end by matched loads. The waveguides are designed such that all modes which couple to the acceleration mode are non-propagating at the acceleration mode frequency. Hence the coupling irises can be designed to provide large coupling to higher frequency modes without damping the acceleration mode. Because the higher order modes are detuned, they are localized and have a broad spectrum of phase velocities of both signs. They are therefore capable of coupling effectively to all propagating modes in the waveguides. Methods of analyzing and results obtained for the very complex system of modes in the accelerating structure and manifolds are presented.

Date: September 1, 1994

Creator: Kroll, N.; Thompson, K.; Bane, K.; Ko, K.; Miller, R.; Ruth, R. et al.

Object Type: Article

System: The UNT Digital Library

(open access)

Operation and performance of a longitudinal damping system using parallel digital signal processing

A programmable longitudinal feedback system based on four AT&T 1610 digital signal processors has been developed as a component of the PEP-II R&D program. This Longitudinal Quick Prototype is a proof of concept for the PEP-II system and implements full speed bunch-by-bunch signal processing for storage rings with bunch spacings of 4 ns. The design implements, via software, a general purpose feedback controller which allows the system to be operated at several accelerator facilities. The system configuration used for tests at the LBL Advanced Light Source is described. Open and closed loop results showing the detection and calculation of feedback signals from bunch motion are presented, and the system is shown to damp coupled-bunch instabilities in the ALS. Use of the system for accelerator diagnostics is illustrated via measurement of injection transients and analysis of open loop bunch motion.

Date: June 1, 1994

Creator: Fox, J. D.; Hindi, H. & Linscott, I.

Object Type: Article

System: The UNT Digital Library

(open access)

Measurement of the left-right asymmetry in Z boson production by electron-positron collisions

None

Date: April 1, 1994

Creator: Elia, R. D.

Object Type: Thesis or Dissertation

System: The UNT Digital Library

(open access)

Current experiments in elementary particle physics. Revision

This report contains summaries of 568 current and recent experiments in elementary particle physics. Experiments that finished taking data before 1988 are excluded. Included are experiments at BEPC (Beijing), BNL, CEBAF, CERN, CESR, DESY, FNAL, INS (Tokyo), ITEP (Moscow), IUCF (Bloomington), KEK, LAMPF, Novosibirsk, PNPI (St. Petersburg), PSI, Saclay, Serpukhov, SLAC, and TRIUMF, and also several underground and underwater experiments. Instructions are given for remote searching of the computer database (maintained under the SLAC/SPIRES system) that contains the summaries.

Date: August 1, 1994

Creator: Galic, H.; Armstrong, F. E. & von Przewoski, B.

Object Type: Report

System: The UNT Digital Library

(open access)

Electronic structure of (La, Sr){sub 2}CuO{sub 4} and Ba{sub 0.6}K{sub 0.4}BiO{sub 3}

We have measured and calculated the electron-positron momentum distribution of La{sub 2-x}Sr{sub x}CuO{sub 4} samples for Sr concentration of 0, 0.1,0.13, and 0.2 and Ba{sub 0.6}K{sub 0.4}BiO{sub 3}. The momentum distribution of all samples contained features derived from the overlap of the positron distribution with the valence electrons. In addition, discontinuities typical of a Fermi surface are seen in the superconducting samples. The form and position of these features are in general agreement with band theory for both La{sub 2-x}Sr{sub x}CuO{sub 4} and Ba{sub 0.6}K{sub 0.4}BiO{sub 3}. However, the evolution of the Fermi surface with doping in La{sub 2-x}Sr{sub x}CuO{sub 4} differed significantly from expectations based on single electron band theories.

Date: May 1, 1994

Creator: Howell, R. H.; Fluss, M. J.; Sterne, P. A.; Kaiser, J. H.; Kitazawa, K.; Kojima, H. et al.

Object Type: Article

System: The UNT Digital Library

(open access)

Quantum theory of chemical reaction rates

If one wishes to describe a chemical reaction at the most detailed level possible, i.e., its state-to-state differential scattering cross section, then it is necessary to solve the Schroedinger equation to obtain the S-matrix as a function of total energy E and total angular momentum J, in terms of which the cross sections can be calculated as given by equation (1) in the paper. All other physically observable attributes of the reaction can be derived from the cross sections. Often, in fact, one is primarily interested in the least detailed quantity which characterizes the reaction, namely its thermal rate constant, which is obtained by integrating Eq. (1) over all scattering angles, summing over all product quantum states, and Boltzmann-averaging over all initial quantum states of reactants. With the proper weighting factors, all of these averages are conveniently contained in the cumulative reaction probability (CRP), which is defined by equation (2) and in terms of which the thermal rate constant is given by equation (3). Thus, having carried out a full state-to-state scattering calculation to obtain the S-matrix, one can obtain the CRP from Eq. (2), and then rate constant from Eq. (3), but this seems like ``overkill``; i.e., if one …

Date: October 1, 1994

Creator: Miller, W. H.

Object Type: Article

System: The UNT Digital Library

(open access)

Correlation function analysis of the COBE differential microwave radiometer sky maps

The Differential Microwave Radiometer (DMR) aboard the COBE satellite has detected anisotropies in the cosmic microwave background (CMB) radiation. A two-point correlation function analysis which helped lead to this discovery is presented in detail. The results of a correlation function analysis of the two year DMR data set is presented. The first and second year data sets are compared and found to be reasonably consistent. The positive correlation for separation angles less than {approximately}20{degree} is robust to Galactic latitude cuts and is very stable from year to year. The Galactic latitude cut independence of the correlation function is strong evidence that the signal is not Galactic in origin. The statistical significance of the structure seen in the correlation function of the first, second and two year maps is respectively > 9{sigma}, > 10{sigma} and > 18{sigma} above the noise. The noise in the DMR sky maps is correlated at a low level. The structure of the pixel temperature covariance matrix is given. The noise covariance matrix of a DMR sky map is diagonal to an accuracy of better than 1%. For a given sky pixel, the dominant noise covariance occurs with the ring of pixels at an angular separation of …

Date: August 1, 1994

Creator: Lineweaver, C. H.

Object Type: Thesis or Dissertation

System: The UNT Digital Library

(open access)

Detonation equation of state at LLNL, 1993

None

Date: March 1, 1994

Creator: Souers, P. C. & Haselman, L. C. Jr.

Object Type: Report

System: The UNT Digital Library

(open access)

A calorimetric measurement of the strong coupling constant in electron-positron annihilation at a center-of-mass energy of 91.6 GeV

In this work, a measurement of the strong coupling constant {alpha}{sub s} in e{sup +}e{sup {minus}} annihilation at a center-of-mass energy of 91.6 GeV is presented. The measurement was performed with the SLD at the Stanford Linear Collider facility located at the Stanford Linear Accelerator Center in California. The procedure used consisted of measuring the rate of hard gluon radiation from the primary quarks in a sample of 9,878 hadronic events. After defining the asymptotic manifestation of partons as `jets`, various phenomenological models were used to correct for the hadronization process. A value for the QCD scale parameter {Lambda}{sub bar MS}, defined in the {sub bar MS} renormalization convention with 5 active quark flavors, was then obtained by a direct fit to O({alpha}{sub s}{sup 2}) calculations. The value of {alpha}{sub s} obtained was {alpha}{sub s}(M{sub z0}) = 0.122 {plus_minus} 0.004 {sub {minus}0.007} {sup +0.008} where the uncertainties are experimental (combined statistical and systematic) and theoretical (systematic) respectively. Equivalently, {Lambda}{sub bar MS} = 0.28 {sub {minus}0.10}{sup +0.16} GeV where the experimental and theoretical uncertainties have been combined.

Date: April 1, 1994

Creator: Martirena, S. G.

Object Type: Thesis or Dissertation

System: The UNT Digital Library

(open access)

Energy states and energy flow near the transition states of unimolecular reactions

The use of lasers with jet-cooled samples has improved energy and angular momentum resolution for the reactant and time resolution for the rate constant by orders of magnitude. The resolution of product quantum states has added a new dimension to unimolecular dynamics. In the past, the geometry, barrier height and vibrational frequencies of the transition state in RRKM theory were adjusted to fit thermal unimolecular reaction rate data. There have been successful quantitative tests of the ability of ab initio theory to calculate transition state geometries accurately and barrier heights to a few kJ/mol for simple molecules. Predicted frequencies tend to be somewhat too high for the softest modes which are of most importance in determining rates; however, the basic normal modes and sequence of frequencies seem to be correctly predicted. RRKM theory can be used with ab initio results to predict rate constants to within a factor of two or three and may be used for quantitative extrapolation to conditions not accessible in the laboratory but important in practical situations. Experiments on single molecular eigenstates have revealed quantum statistical fluctuations in rates which are predicted quantitatively in the appropriate extension of RRKM theory. Many experiments seeking to demonstrate non-statistical …

Date: October 1, 1994

Creator: Moore, C. Bradley

Object Type: Report

System: The UNT Digital Library

(open access)

Study of b{anti b} production in e{sup +}e{sup {minus}} annihilation at {radical}s = 29 GeV with the aid of neural networks

The author presents a measurement of {sigma}(b{anti b})/{sigma}(q{anti q}) in the annihilation process e{sup +}e{sup {minus}} {yields} q{anti q} {yields} hadrons at {radical}s = 29 GeV. The analysis is based on 66 pb{sup {minus}1} of data collected between 1984 and 1986 with the TPC/2{gamma} detector at PEP. To identify bottom events, he uses a neural network with inputs that are computed from the 3-momenta of all of the observed charged hadrons in each event. He also presents a study of bias in techniques for measuring inclusive {pi}{sup {+-}}, K{sup {+-}}, and p/{anti p} production in the annihilation process e{sup +}e{sup {minus}} {yields} b{anti b} {yields} hadrons at {radical}s = 29 GeV, using a neural network to identify bottom-quark jets. In this study, charged particles are identified by a simultaneous measurement of momentum and ionization energy loss (dE/dx).

Date: November 1, 1994

Creator: Lambert, D. J.

Object Type: Thesis or Dissertation

System: The UNT Digital Library

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