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11,028 Matching Results
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Absolute Intensities of the Vacuum Ultraviolet Spectra in a Metal-Etch Plasma Processing Discharge
In this paper we report absolute intensities of vacuum ultraviolet and near ultraviolet emission lines (4.8 eV to 18 eV ) for aluminum etching discharges in an inductively coupled plasma reactor. We report line intensities as a function of wafer type, pressure, gas mixture and rf excitation level. IrI a standard aluminum etching mixture containing C12 and BC13 almost all the light emitted at energies exceeding 8.8 eV was due to neutral atomic chlorine. Optical trapping of the WV radiation in the discharge complicates calculations of VUV fluxes to the wafer. However, we see total photon fluxes to the wailer at energies above 8.8 eV on the order of 4 x 1014 photons/cm2sec with anon- reactive wafer and 0.7 x 10 `4 photons/cm2sec with a reactive wtier. The maj ority of the radiation observed was between 8.9 and 9.3 eV. At these energies, the photons have enough energy to create electron-hole pairs in Si02, but may penetrate up to a micron into the Si02 before being absorbed. Relevance of these measurements to vacuum-W photon-induced darnage of Si02 during etching is discussed.
Date:
December 9, 1998
Creator:
Woodworth, J. R.; Blain, M. G.; Jarecki, R. L.; Hamilton, T. W. & Aragon, B. P.
System:
The UNT Digital Library
Absolute rate measurements of two-photon process of gases, liquids, and solids
Due to rapid improvements in high-power laser performance, two-photon absorption processes have become a very useful tool for studying the molecular structures of various gases, liquids and solids. However, measurements of absolute two-photon absorption cross sections were more or less ignored previously because of their small size. In this work, we obtained not only the two-photon absorption spectra, but also measurements of their absolute cross sections for various gases, liquids, and solids. 8 refs., 1 fig., 1 tab.
Date:
December 1, 1987
Creator:
Chen, C.H.; McCann, M.P. & Payne, M.G.
System:
The UNT Digital Library
Absolute total and one and two electron transfer cross sections for Ar{sup 8+} on Ar as a function of energy
The absolute total and one and two electron transfer cross sections for Ar{sup 8+} on Ar were measured as a function of projectile laboratory energy from 0.090 to 0.550 keV/amu. The effective one electron transfer cross section dominates above 0.32 keV/amu, while below this energy, the effective two electron transfer starts to become appreciable. The total cross section varies by a factor over the energy range explored. The overall error in the cross section measurement is estimated to be {plus_minus} 15%.
Date:
December 31, 1992
Creator:
Vancura, J. & Kostroun, V. O.
System:
The UNT Digital Library
Absorption and emission modulation in a MoS2–GaN (0001) heterostructure by interface phonon–exciton coupling
Article reporting the change in the transient absorption characteristics of monolayer MoS2 and the modified PL emission characteristics in a monolayer MoS2–GaN (0001) heterostructure due to the coupling of carriers with the phonon modes and the energy exchange at the interface. The results demonstrate the relevance of interface coupling between the semiconductors for the development of optical and electronic applications.
Date:
September 26, 2019
Creator:
Poudel, Yuba; Sławińska, Jagoda; Gopal, Priya; Seetharaman, Sairaman; Hennighausen, Zachariah; Kar, Swastik et al.
System:
The UNT Digital Library
An abstract-device interface for implementing portable parallel-I/O interfaces
Portable parallel programming has been hampered by the lack of a single, standard, portable application-programmer`s interface (API) for parallel I/O. Instead, the programmer must choose from several different APIs, many of which are not portable. To alleviate this problem, the authors have developed an abstract-device interface for parallel I/O, called ADIO. ADIO is not intended as a new API; rather, it is a strategy for implementing other APIs in a simple, portable, and efficient manner. ADIO facilitates the implementation of any existing or new API on any existing or new file system. ADIO thus enables users to experiment with different APIs, a feature that, they think, would help in the definition of a standard API. It also makes existing applications portable across a wide range of platforms. In this paper, they introduce the concept of ADIO. They describe the design of ADIO and its use in implementing APIs. They have currently implemented subsets of the Intel PFS, IBM PIOFS, and MPI-IO APIs on both the PFS and PIOFS file systems. As a result, they are able to run IBM PIOFS applications on the Intel Paragon, Intel PFS applications on the IBM SP, and MPI-IO applications on both systems. They report …
Date:
December 31, 1996
Creator:
Thakur, R.; Gropp, W. & Lusk, E.
System:
The UNT Digital Library
Abstracts of oral and poster sessions
The climate model of the Goddard Institute for Space Studies (GISS GCM) has been used to project the influence of increasing concentrations of greenhouse gases on the future global climate. New parameterizations for the GISS GCM are being developed to improve its depiction of current climate scenarios and to make it more sensitive to the variability of external forcing mechanisms such as sea-surface temperatures (SST), atmospheric aerosols and constituent trace gases. The new moist convection scheme makes cumulus fluxes proportional to vertical thermal instability and computes convective-scale downdrafts whose effect is to prevent excessive drying of the boundary layer by compensating subsidence. The physically-based ground hydrology component improves the land surface sensible and latent heat calculations by explicitly considering transpiration, evaporation from intercepted precipitation, evaporation from bare soil, infiltration, soil water flow and runoff. The revised planetary boundary layer uses a more valid physical model than previously to obtain more realistic near-surface winds and energy budgets. Preliminary results with newer versions of the GCM include a better seasonal migration of the ITCZ and more realistic tropical winds. One of our approaches to model validation is the evaluation of runs forced by globally observed sea-surface temperatures. The presentation will show how …
Date:
December 31, 1994
Creator:
Druyan, L. M.
System:
The UNT Digital Library
Abstracts of papers presented at the LVIII Cold Spring Harbor Symposium on quantitative Biology: DNA and chromosomes
This volume contains the abstracts of oral and poster presentations made at the LVIII Cold Spring Harbor Symposium on Quantitative Biology entitles DNA & Chromosomes. The meeting was held June 2--June 9, 1993 at Cold Spring Harbor, New York.
Date:
December 31, 1993
Creator:
unknown
System:
The UNT Digital Library
AC 95 - selected readings
Reports are presented on energy efficiency and conservation in residential buildings. Topics include housing and energy linkages; the people factor; low-income initiatives; green visions; utility programs; affordable comfort; housing as a system; and pressures and air flow in buildings.
Date:
December 31, 1995
Creator:
unknown
System:
The UNT Digital Library
Ac losses in YBa{sub 2}Cu{sub 3}O{sub 7} and Bi{sub 2}Sr{sub 2}Ca{sub 2}Ci{sub 3}O{sub 10} superconductors at power frequencies
Ac losses of sintered and melt-textured YBa{sub 2}Cu{sub 3}O{sub 7} bars and powder-in-a-tube processed Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} tapes were measured at 4.2, 65, 70 and 77 K and at 15--180 Hz. In general, the results are well described by the critical state model for the ac losses. However, the losses for the Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} tapes at 4.2 K exhibited significant contributions from the eddy currents in the Ag sheath.
Date:
December 31, 1991
Creator:
Orehotsky, J.; Reilly, K. M.; Suenaga, M.; Hikata, T.; Ueyama, M. & Sato, K.
System:
The UNT Digital Library
Accelerated Characterization of Metal Fuel Stored in the Hanford K Basins
Efforts are under way to gather data on the condition of the metal fuel and associated sludge stored in the water-filled Hanford K Basins. Most of the current data gathering activities are being performed in the basins without fuel movement. These techniques include a video survey of open storage canisters, determination of water/gas levels in sealed canisters, sampling of gas and water from sealed canisters (for chemical analysis) and measurement of sludge depth and sludge volume.
Date:
December 31, 1995
Creator:
Makenas, B. J.; Omberg, R. P.; Lawrence, L. A.; Marschman, S. C. & Abrefah, J.
System:
The UNT Digital Library
Accelerated Durability Testing of Electrochromic Windows
Prototype electrochromic windows made by several different U.S. companies have been tested in our laboratory for their long-term durability. Samples were subjected to alternate coloring and bleaching voltage cycles while exposed to simulated on 1-sun irradiance in a temperature-controlled environmental chamber with low relative humidity. The samples inside the chamber were tested under a matrix of different conditions. These conditions include: cycling at different temperatures (65 C, 85 C, and 107 C) under the irradiance, cycling versus no-cycling under the same irradiance and temperature, testing with different voltage waveforms and duty cycles with the same irradiance and temperature, cycling under various filtered irradiance intensities, and simple thermal exposure with no irradiance or cycling. The electro-optical characteristics of the samples were measured between 350 and 1,100 nm every 4,000 cycles for up to 20,000 cycles. Photographs of the samples were taken periodically wi th a digital camera to record cosmetic defects, the extent of residual coloration, and overall coloration and bleaching uniformity of the samples. Our results indicate that the most important cause of degradation is the combination of continuous cycling, elevated temperature, and irradiance. The relative importance of these variables, when considered synergistically or separately, depends on the particular device …
Date:
December 29, 1998
Creator:
Tracy, C. E.; Zhang, J. G.; Benson, D. K.; Czanderna, A. W. & Deb, S. K.
System:
The UNT Digital Library
Accelerated glass reaction under PCT conditions
Static leach tests similar to PCT (Product Consistency Test) were performed for up to 2 years to assess long-term reaction behavior of high-level nuclear waste glasses similar to those at Defense Waste Processing Facility. These tests show the reaction rate to decrease with the reaction time from an initially high rate to a low rate, but then to accelerate to a higher rate after reaction times of about 1 year, depending on glass surface area/leachant volume ratio used. Solution concentrations of soluble glass components increase as the reaction is accelerated, while release of other glass components into solution is controlled by secondary phases. Net result is that transformation of glass to stable phases is accelerated while the solution becomes enriched in soluble components not effectively contained in secondary phases. Rate becomes linear in time after the acceleration and may be similar to the initial forward rate. A current model of glass reaction predicts that the glass reaction will be accelerated upon the formation of secondary phases which lower the silicic acid solution concentration. These tests show total Si concentration to increase upon reaction acceleration, however, which may be due to the slightly higher pH attained with the acceleration. The sudden …
Date:
December 31, 1992
Creator:
Ebert, W. L.; Bates, J. K.; Buck, E. C. & Bradley, C. R.
System:
The UNT Digital Library
The accelerated testing of cements in brines
Cementitious materials may be employed in settings where they face prolonged exposure to Mg-rich brines. This study evaluated the possibility of using high temperatures to accelerate brine-cement reaction rates. Class-H cement coupons were tested in Mg-K-Na-C1- SO{sub 4} brines to 100{degrees}C. MgC1{sub 2}-NaC1 solutions were also employed in a test sequence that extended to 200{degrees}C. It was found that accelerated testing could be used successfully to evaluate the compatability of cementitious materials with such brines.
Date:
December 31, 1993
Creator:
Krumhansl, J. L.
System:
The UNT Digital Library
Accelerating polarized beams at the AGS
The acceleration of polarized beams in circular accelerators is complicated by the presence of numerous depolarizing resonances. During acceleration, a depolarizing resonance is crossed whenever the spin precession frequency equals the frequency with which spin-perturbing magnetic fields are encountered. There are two main types of depolarizing resonances corresponding to the possible sources of such fields: imperfection resonances, which are driven by magnet errors and misalignments, and intrinsic resonances, driven by the focusing fields. The resonance conditions are usually expressed in terms of the spin tune {nu}{sub s}, which is defined as the number of spin precessions per revolution. For an ideal planar accelerator, where orbiting particles experience only the vertical guide field, the spin tune is equal to G{gamma}, where G = 1.7928 is the anomalous magnetic moment of the proton and {gamma} is the relativistic Lorentz factor. The resonance condition for imperfection depolarizing resonances arise when {nu}{sub s} = G{gamma} = n, where n is an integer. Imperfection resonances are therefore separated by only 523 MeV energy steps. The condition for intrinsic resonances is {nu}{sub s} = G{gamma} = kP {+-} {nu}{sub y}, where k is an integer, {nu}{sub y} is the vertical betatron tune and P is the …
Date:
December 1, 1995
Creator:
Roser, T.
System:
The UNT Digital Library
Acceleration and storage of polarized proton beams
High energy polarized beam collisions will open up the unique physics opportunities of studying spin effects in hard processes. Proposals for polarized proton acceleration for several high energy colliders have been developed. A partial Siberian Snake in the AGS has recently been successfully tested and full Siberian Snakes, spin rotators, and polarimeters for RHIC are being developed to make the acceleration of polarized beams to 250 GeV possible. This allows for the unique possibility of colliding two 250 GeV polarized proton beams at luminosities of up to 2 x 10{sup 32} cm{sup -2} s{sup -1}.
Date:
December 31, 1995
Creator:
Roser, T.
System:
The UNT Digital Library
The acceleration and storage of radioactive ions for a neutrino factory
The term beta-beam has been coined for the production of a pure beam of electron neutrinos or their antiparticles through the decay of radioactive ions circulating in a storage ring. This concept requires radioactive ions to be accelerated to a Lorentz gamma of 150 for {sup 6}He and 60 for {sup 18}Ne. The neutrino source itself consists of a storage ring for this energy range, with long straight sections in line with the experiment(s). Such a decay ring does not exist at CERN today, nor does a high-intensity proton source for the production of the radioactive ions. Nevertheless, the existing CERN accelerator infrastructure could be used as this would still represent an important saving for a beta-beam facility. This paper outlines the first study, while some of the more speculative ideas will need further investigations.
Date:
December 23, 2003
Creator:
al., B. Autin et
System:
The UNT Digital Library
Acceleration in astrophysics
The origin of cosmic rays and applicable laboratory experiments are discussed. Some of the problems of shock acceleration for the production of cosmic rays are discussed in the context of astrophysical conditions. These are: The presumed unique explanation of the power law spectrum is shown instead to be a universal property of all lossy accelerators; the extraordinary isotropy of cosmic rays and the limited diffusion distances implied by supernova induced shock acceleration requires a more frequent and space-filling source than supernovae; the near perfect adiabaticity of strong hydromagnetic turbulence necessary for reflecting the accelerated particles each doubling in energy roughly 10{sup 5} to {sup 6} scatterings with negligible energy loss seems most unlikely; the evidence for acceleration due to quasi-parallel heliosphere shocks is weak. There is small evidence for the expected strong hydromagnetic turbulence, and instead, only a small number of particles accelerate after only a few shock traversals; the acceleration of electrons in the same collisionless shock that accelerates ions is difficult to reconcile with the theoretical picture of strong hydromagnetic turbulence that reflects the ions. The hydromagnetic turbulence will appear adiabatic to the electrons at their much higher Larmor frequency and so the electrons should not be scattered …
Date:
December 31, 1993
Creator:
Colgate, S. A.
System:
The UNT Digital Library
Acceleration of polarized proton beams
The acceleration of polarized beams in circular accelerators is complicated by the numerous depolarizing spin resonances. Using a partial Siberian snake and a rf dipole that ensure stable adiabatic spin motion during acceleration has made it possible to accelerate polarized protons to 25 GeV at the Brookhaven AGS. Full Siberian snakes are being developed for RHIC to make the acceleration of polarized protons to 250 GeV possible. A similar scheme is being studied for the 800 GeV HERA proton accelerator.
Date:
December 31, 1998
Creator:
Roser, T.
System:
The UNT Digital Library
Accelerator-based neutrino oscillation experiments
Neutrino oscillations were first discovered by experiments looking at neutrinos coming from extra-terrestrial sources, namely the sun and the atmosphere, but we will be depending on earth-based sources to take many of the next steps in this field. This article describes what has been learned so far from accelerator-based neutrino oscillation experiments, and then describe very generally what the next accelerator-based steps are. In section 2 the article discusses how one uses an accelerator to make a neutrino beam, in particular, one made from decays in flight of charged pions. There are several different neutrino detection methods currently in use, or under development. In section 3 these are presented, with a description of the general concept, an example of such a detector, and then a brief discussion of the outstanding issues associated with this detection technique. Finally, section 4 describes how the measurements of oscillation probabilities are made. This includes a description of the near detector technique and how it can be used to make the most precise measurements of neutrino oscillations.
Date:
December 1, 2007
Creator:
Harris, Deborah A.
System:
The UNT Digital Library
Accelerator-based systems for plutonium destruction and nuclear waste transmutation
Accelerator-base systems are described that can eliminate long-lived nuclear materials. The impact of these systems on global issues relating to plutonium minimization and nuclear waste disposal can be significant. An overview of the components that comprise these systems is given, along with discussion of technology development status and needs. A technology development plan is presented with emphasis on first steps that would demonstrate technical performance.
Date:
December 31, 1994
Creator:
Arthur, E. D.
System:
The UNT Digital Library
Accelerator break-out group summary
Interesting developments in accelerators have shown that they can be used as {open_quote}factory{close_quote}-type systems with the choice of technology dependent on the specific requirements of the application. The status and future possibilities for cyclotrons and linear accelerators are compared briefly, based on discussions at a break-out session on accelerators. Only high power systems with beam powers in excess of a MW average power were considered.
Date:
December 31, 1996
Creator:
Schriber, S.O. & Mandrillon, P.
System:
The UNT Digital Library
Accelerator Challenges and Opportunities for Future Neutrino Experiments
There are three types of future neutrino facilities currently under study, one based on decays of stored beta-unstable ion beams (?Beta Beams?), one based on decays of stored muon beams (?Neutrino Factory?), and one based on the decays of an intense pion beam (?Superbeam?). In this paper we discuss the challenges each design team must face and the R&D being carried out to turn those challenges into technical opportunities. A new program, the Muon Accelerator Program, has begun in the U.S. to carry out the R&D for muon-based facilities, including both the Neutrino Factory and, as its ultimate goal, a Muon Collider. The goals of this program will be briefly described.
Date:
December 24, 2010
Creator:
Zisman, Michael S
System:
The UNT Digital Library
An accelerator controls network designed for reliability and flexibility
The APS accelerator control system is a typical modern system based on the standard control system model, which consists of operator interfaces to a network and computer-controlled interfaces to hardware. The network provides a generalized communication path between the host computers, operator workstations, input/output crates, and other hardware that comprise the control system. The network is an integral part of all modern control systems and network performance will determine many characteristics of a control system. This paper describes the methods used to provide redundancy for various network system components as well as methods used to provide comprehensive monitoring of this network. The effect of archiving tens of thousands of data points on a regular basis and the effect on the controls network will be discussed. Metrics are provided on the performance of the system under various conditions.
Date:
December 2, 1997
Creator:
McDowell, W. P. & Sidorowicz, K. V.
System:
The UNT Digital Library
Accelerator design for the high-power industrial FEL
We have developed a conceptual design for an industrial-use kilowatt UV and IR FEL driven by a recirculating, energy-recovering 200 MeV, 1- 5 mA superconducting rf (SRF) electron accelerator. In this paper we describe the accelerator design of this FEL. The accelerator consists of a 10 MeV injector, a 96 MeV SRF linac with a two-pass transport which accelerates the beam to 200 MeV, followed by energy-recovery deceleration through two passes to the dump. Technical challenges include high-intensity injector development, multi-pass energy- recovery operation, SRF modifications and control for FEL operation, development of tuneable, nearly-isochronous, large-acceptance transports, and matching of the beam to the FEL wiggler. An overview of the accelerator design is presented. 9 refs., 1 fig., 1 tab.
Date:
December 31, 1995
Creator:
Neuffer, D. V.; Benson, S. & Bisognano, J.
System:
The UNT Digital Library