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Slow electrons ejected from helium by electron impact

Description: In radiation research, electron-impact data are needed regardless of incident particles because the diffusion of energy from the initial track is accomplished by the secondary electrons generated in the target medium. Most experimental data on angular and energy distributions of secondary electrons are incomplete in their coverage of angles and energies, particularly for slow electrons, while energy deposition modeling calculations require full coverage of angles and energies of both secondary and incident electrons. We have used various theoretical and experimental consistency checks to select and revise available theoretical and experimental data to obtain recommended cross sections for the secondary electrons produced by electron-impact ionization of He.
Date: January 1, 1983
Creator: Kim, Y.K.
Partner: UNT Libraries Government Documents Department

Transition Probabilities for Atoms

Description: Current status of advanced theoretical methods for transition probabilities for atoms and ions is discussed. An experiment on the f values of the resonance transitions of the Kr and Xe isoelectronic sequences is suggested as a test for the theoretical methods.
Date: 1980-23~
Creator: Kim, Y. K.
Partner: UNT Libraries Government Documents Department

Sorption Characteristics of Aqueous Co(II) on Preformed Iron Ferrite Impregnated into Phenolsulphonic Formaldehyde Resin

Description: A series of stepwise procedures to prepare a new organic-inorganic composite magnetic resin with phenolsulphonicformaldehyde and freshly formed iron ferrite was established, based upon wet-and-neutralization method for synthesizing iron ferrite and pearl-polymerization method for synthesizing rigid bead-type composite resin. The composite resin prepared by the above method shows stably high removal efficiency (maximally over 3.1 meq./gresin) to Co(II) species from wastewater in a wide range of solution pH. The wide range of applicable solution pH (i.e. pH 4.09 to 10.32) implies that the composite resin overcomes the limitations of the conventional ferrite process that is practically applicable only to alkaline conditions. It has been found that both ion exchange (by the organic resin constituent) and surface adsorption (by the inorganic adsorbent constituent) are major reaction mechanisms for removing Co(II) from wastewater, but surface precipitation results in the high sorption capacity to Co(II) beyond normal ion exchange capacity of the phenolsulphonic-formaldehyde resin. Standard enthalpy change derived from van't Hoff equation is 32.0 kJ{center_dot}mol-1 conforming to the typical range for chemisorption or ion exchange. In a wide range of equilibrium Co(II) concentration, the overall isotherm is qualitatively explained by the generalized adsorption isotherm concept proposed by McKinley. At the experimental conditions where the composite resin shows equivalent selectivity to Co(II) and other competing reagents (i.e. EDTA and Na), the ratios of Co(II) to other chemicals turn out to be 2:1 and 1:221, respectively. In addition, the selectivity of the PSF-F to Co(II) species is very high (about 72% of Co(II)-removal efficiency) even when the molar ratio of Co(II) to Ca(II) is 1:30. It is anticipated that the composite resin can also be used for column-operation with process-control by applying external magnetic field, since the rigid bead-type composite resin shows magnetic-susceptibility due to its paramagnetic inorganic constituent (i.e. iron ferrite).
Date: February 26, 2002
Creator: Lee, K. J. & Kim, Y. K.
Partner: UNT Libraries Government Documents Department

Charge state of sputtered impurity ions near a limiter or divertor in a tokamak

Description: Many impurity atoms sputtered from a limiter or divertor plate are ionized in the scrapeoff zone and return to the sputtering surface bacause of friction with incoming plasma ions. The final charge state attained by such impurities has been calculated for a variety of plasma edge conditions. The surface materials considered are tungsten, beryllium, beryllium oxide, and carbon. Estimates of the successive ionization cross sections for tungsten are developed. In all cases examined, returning impurity ions are found to be multiply ionized. This implies a significant energy gain in the sheath region, with important implications for self-sputtering of redeposited surface material.
Date: March 1, 1983
Creator: Boley, C.D.; Brooks, J.N. & Kim, Y.K.
Partner: UNT Libraries Government Documents Department

NiO exchange bias layers grown by direct ion beam sputtering of a nickel oxide target

Description: A new process for fabricating NiO exchange bias layers has been developed. The process involves the direct ion beam sputtering (IBS) of a NiO target. The process is simpler than other deposition techniques for producing NiO buffer layers, and facilitates the deposition of an entire spin-valve layered structure using IBS without breaking vacuum. The layer thickness and temperature dependence of the exchange field for NiO/NiFe films produced using IBS are presented and are similar to those reported for similar films deposited using reactive magnetron sputtering. The magnetic properties of highly textured exchange couples deposited on single crystal substrates are compared to those of simultaneously deposited polycrystalline films, and both show comparable exchange fields. These results are compared to current theories describing the exchange coupling at the NiO/NiFe interface.
Date: March 1, 1996
Creator: Michel, R.P.; Chaiken, A.; Johnson, L.E. & Kim, Y.K.
Partner: UNT Libraries Government Documents Department

Report of the working group on precision measurements - measurements of the W boson mass and width.

Description: We discuss the prospects for measuring the W mass and width in Run II. The basic techniques used to measure M{sub W} are described and the statistical, theoretical and detector-related uncertainties are discussed in detail. Alternative methods of measuring the W mass at the Tevatron and the prospects for M{sub W} measurements at other colliders are also described.
Date: November 29, 2000
Creator: Brock, R.; Erler, J.; Kim, Y.-K.; Marciano, W.; Ashmanskas, W.; Baur, U. et al.
Partner: UNT Libraries Government Documents Department

Performance study of GPUs in real-time trigger applications for HEP experiments

Description: Graphical Processing Units (GPUs) have evolved into highly parallel, multi-threaded, multicore powerful processors with high memory bandwidth. GPUs are used in a variety of intensive computing applications. The combination of highly parallel architecture and high memory bandwidth makes GPUs a potentially promising technology for effective real-time processing for High Energy Physics (HEP) experiments. However, not much is known of their performance in real-time applications that require low latency, such as the trigger for HEP experiments. We describe an R and D project with the goal to study the performance of GPU technology for possible low latency applications, performing basic operations as well as some more advanced HEP lower-level trigger algorithms (such as fast tracking or jet finding). We present some preliminary results on timing measurements, comparing the performance of a CPU versus a GPU with NVIDIA's CUDA general-purpose parallel computing architecture, carried out at CDF's Level-2 trigger test stand. These studies will provide performance benchmarks for future studies to investigate the potential and limitations of GPUs for real-time applications in HEP experiments.
Date: June 1, 2011
Creator: Ketchum, W.; U., /Chicago; Amerio, S.; /INFN, Padua; Bastieri, D.; Bauce, M. et al.
Partner: UNT Libraries Government Documents Department

Measurement of the top quark mass using the template method in the lepton plus jets channel with in situ W ---> j j calibration at CDF-II

Description: We report an updated measurement of the top quark mass in the lepton plus jets channel of t{bar t} events from p{bar p} collisions at {radical}s = 1.96 TeV. This measurement uses a dataset with integrated luminosity of 680 pb{sup -1}, containing 360 t{bar t} candidates separated into four subsamples. A top quark mass is reconstructed for each event by using energy and momentum constraints on the top quark pair decay products. We also employ the reconstructed mass of hadronic W boson decays W {yields} jj to constrain in situ the largest systematic uncertainty of the top quark mass measurement: the jet energy scale. Monte Carlo templates of the reconstructed top quark and W boson mass are produced as a function of the true top quark mass and the jet energy scale. The distribution of reconstructed top quark and W boson mass in the data are compared to the Monte Carlo templates using a likelihood fit to obtain: M{sub top} = 173.4 {+-} 2.8 GeV/c{sup 2}.
Date: May 1, 2006
Creator: Adelman, Jahred A.; Arguin, J.F.; Bellettini, G.; Brubaker, E.; Budagov, J.; Chlachidze, G. et al.
Partner: UNT Libraries Government Documents Department

Exotic Physics: Search for New Physics Leading to High Mass Tau Pairs With ppbar Collisions at 1.96 TeV Using Cdf Ii

Description: Abstract: We present the results of a search for anomalous resonant production of tau lepton pairs with large invariant mass, the first such search using the CDF II Detector in Run II of the Tevatron p{bar p} collider. Such anomalous production could arise from various new physics processes. In a data sample corresponding to 195 pb{sup -1} of integrated luminosity we predict 2.8 {+-} 0.5 events from Standard Model background processes and observe 4. We use this result to set limits on the production of heavy scalar and vector particles decaying to tau lepton pairs.
Date: June 15, 2005
Creator: Academia Sinica Institute of Physics
Partner: UNT Libraries Government Documents Department