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Sökning: WFRF:(Whitlow Harry J)

  • Resultat 1-10 av 37
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1.
  • Whitlow, Harry J, et al. (författare)
  • Measurements of Si ion stopping in amorphous silicon
  • 2002
  • Ingår i: Nuclear Instruments & Methods in Physics Research. Section B: Beam Interactions with Materials and Atoms. - 0168-583X. ; 190:1-4, s. 84-88
  • Tidskriftsartikel (refereegranskat)abstract
    • The stopping of Si-28 ions in polycrystalline Si foils has been measured over the energy range 0.1-3.3 MeV per nucleon. For the low energy interval (0.1-0.5 MeV per nucleon), time of flight-energy elastic recoil detection analysis method was used, whilst for the high energy region (1.2-3.3 MeV per nucleon) the energy loss in the same foil was measured using a Si p-i-n diode with the Si-28 ions directly incident on the foil following acceleration. Below the stopping maximum the results are in good agreement with literature data based on Doppler shift measurements of short nuclear lifetimes but are about 20%, smaller than the SRIM prediction. Above the stopping maximum the data are in agreement with SRIM within the limits of statistical uncertainty.
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3.
  • Timmers, H, et al. (författare)
  • Threshold stoichiometry for beam induced nitrogen depletion of SiN
  • 2002
  • Ingår i: Nuclear Instruments & Methods in Physics Research. Section B: Beam Interactions with Materials and Atoms. - 0168-583X. ; 190, s. 428-432
  • Tidskriftsartikel (refereegranskat)abstract
    • Measurements of the stoichiometry of silicon nitride films as a function of the number of incident ions using heavy ion elastic recoil detection (ERD) show that beam-induced nitrogen depletion depends on the projectile species. the beam energy, and the initial stoichiometry. A threshold stoichiometry exists in the range 1.3 > N/Si greater than or equal to 1, below which the films are stable against nitrogen depletion. Above this threshold, depletion is essentially linear with incident fluence. The depletion rate correlates non-linearly with the electronic energy loss of the projectile ion in the film. Sufficiently long exposure of nitrogen-rich films renders the mechanism, which prevents depletion of nitrogen-poor films, ineffective. Compromising depth-resolution. nitrogen depletion from SiN films during ERD analysis can be reduced significantly by using projectile beams with low atomic numbers. (C) 2002 Published by Elsevier Science B.V.
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4.
  • Weijers-Dall, T D M, et al. (författare)
  • Measurements of the stopping forces for heavy ions in Ge, Ag and Au using novel 'polka-dot' detectors
  • 2006
  • Ingår i: Nuclear Instruments & Methods in Physics Research. Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X. ; 251:2, s. 352-360
  • Tidskriftsartikel (refereegranskat)abstract
    • Measurements of the stopping forces for C-14, N-14 and O-16 ions in Ge and Au, for N-14 and F-19 ions in Ag, as well as for F-19 ions in Au have been made, respectively. A novel technique, reported recently, using PIN diodes coated directly with the stopping medium in a polka dot pattern was used. This provided a set of precise, self-consistent measurements on the same stopping medium. Results show small but significant deviations from SRIM stopping predictions and are also compared to a recently-developed empirical stopping force predictor.
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5.
  • Whitlow, Harry J., et al. (författare)
  • Dynamic Analysis of major elements in biological tissue validating quantification of trace life elements in MeV ion beam microscopy
  • 2024
  • Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier. - 0168-583X .- 1872-9584. ; 554
  • Tidskriftsartikel (refereegranskat)abstract
    • MeV ion microprobe measurements of the lesser and trace life element concentrations in biological tissues are challenging because of complex spatial inhomogeneities in these types of samples. Measurements on ex vivo tissue sections require determination of the matrix element composition and the tissue section thickness. For these reasons, in this work, we adapted the Dynamic Analysis approach known from literature, to interpret the MeV ion microscopy data to determine concentrations of H, C, O, and N as well as the thickness of different tissue regions in Non Human Primate (NHP) mesenteric lymph node section. The results showed no strong variations of the matrix element contents regardless of section thickness variations in the tissue. The matrix information was used to quantify total-Ca molarities and a significant ∼30 mM Ca concentration hotspot was observed at the edge of sinus structure in the mesenteric lymph node as compared to the 3-4 mM total-Ca levels in the surrounding tissues. Thus, MeV ion microprobe imaging combined with dynamic analysis comprise a novel chemometric approach paving a way for quantitative analysis of similarly complicated animal and plant biological tissue sections.
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6.
  • Zhang, Yanwen, et al. (författare)
  • Radiation detector resolution over a continuous energy range
  • 2007
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 91:9
  • Tidskriftsartikel (refereegranskat)abstract
    • An ion approach is demonstrated to determine energy resolution in both semiconductor detectors and scintillators over a continuous energy range. For semiconductors, the energy resolution of a silicon detector was measured as a function of helium ion energy, and the values from extrapolation to high energies are in good agreement with the literature data from alpha measurements. For scintillators, benchmark crystals subject to He+ irradiation were investigated, and the agreement of energy resolution between the ion and gamma measurements indicates that the ion approach can be used to predict the energy resolution of the candidate materials in thin-film form or small crystals when large crystals necessary for gamma-ray measurements are unavailable.
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7.
  • Banerjee, Sanjana, et al. (författare)
  • Invasive or Biomonitoring Species? Use of Pomacea maculata Operculum as a Tool to Determine Metal Pollutants : a Micro-PIXE Investigation
  • 2023
  • Ingår i: Water, Air and Soil Pollution. - : Springer Nature. - 0049-6979 .- 1573-2932. ; 234:6
  • Tidskriftsartikel (refereegranskat)abstract
    • Pomacea maculata is a widely distributed agricultural and environmental pest in Asia. It is also causing ecological damage and threatening human health in the Southeastern United States. However, its limited mobility and fast consumption of aquatic vegetation may make it an excellent biomonitor to evaluate the pollution status of freshwater coastal ecosystems. This work investigated the capability of the operculum of this snail to accumulate toxic metals in a laboratory environment. We measured the elemental composition of the nucleus and edge regions on the varnish layer of the operculum by employing a MeV ion microprobe instrument. Iron, copper, and zinc were present in the operculum at trace levels. Copper was present at elevated levels in the operculum of snails exposed to copper for 2 weeks. Additionally, heterogeneity in the distribution of major and trace elements within the gastropod's operculum was revealed by 2D elemental images obtained using microparticle-induced X-ray emission spectrometry. On average, the nucleus of the operculum showed a higher accumulation of copper than did the edge. These results demonstrate that micro-PIXE can be used to look at the within-tissue distribution of toxic metals in hard tissues like a snail's operculum. We propose that the operculum metal concentrations can be used as a bioindicator capable of providing information on the ecosystem's health and potentially reveal temporal changes in this health.
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8.
  • Carlén, Lars, et al. (författare)
  • CHICSi - a compact ultra-high vacuum compatible detector system for nuclear reaction experiments at storage rings. III. readout system
  • 2004
  • Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 516:2-3, s. 327-347
  • Tidskriftsartikel (refereegranskat)abstract
    • (CHICSi) Celsius Heavy Ion Collaboration Si detector system is a high granularity, modular detector telescope array for operation around the cluster-jet target/circulating beam intersection of the CELSIUS storage ring at the The. Svedberg Laboratory in Uppsala, Sweden. It is able to provide identity and momentum vector of up to 100 charged particles and fragments from proton-nucleus and nucleus-nucleus collisions at intermediate energies, 50-1000A MeV. All detector telescopes as well as the major part of electronic readout system are placed inside the target chamber in ultra-high vacuum (UHV, 10(-9)-10(-7) Pa). This requires Very Large Scale Integrated (VLSI) microchip for the spectroscopic signal processing and the generation and transport of digital control signals. Eighteen telescopes, read out with chip-on-board technique by ceramics Mother Boards (MB) and corresponding 18 microchips are mounted on a 450 x 45 mm(2) Grand Mother Board (GMB), processed on FR4 glass-fibre material. Each of these 28 GMB units contains a daisy-chain organisation of the VLSI chips and associated protection circuits. Analogue-to-digital conversion of the spectroscopic signals is performed on a board outside the chamber which is connected on one side to a power distribution board, directly attached to a UHV mounting flange, and on the other side to the VME-based data acquisition system (CHICSiDAQ). This in its turn is connected via a fibre-optic link to the general TSL acquisition system (SVEDAQ), and in this way data from auxiliary detector systems, read out in CAMAC mode, can be stored in coincidence with CHICSi data.
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9.
  • Ekman, Jörgen, et al. (författare)
  • Retention of Pb isotopes in glass surfaces for retrospective assessment of radon exposure
  • 2006
  • Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier. - 0168-583X .- 1872-9584. ; 249:1-2, s. 544-547
  • Tidskriftsartikel (refereegranskat)abstract
    • In recent years there has been increasing interest in radio-epidemiological techniques to retrospectively measure the radon dose exposure by determining the activity of 210Pb, the longest-lived 222Rn progeny, in glass surface layers. In this study the diffusion of 39 keV 209Pb+ ions implanted into glass using the IGISOL facility has been studied under conditions that mimic the recoil implantation of 210Pb from 222Rn. The resulting depth distributions of 209Pb were then measured after heat treatment in vacuum at different temperatures by a sputter erosion technique. The diffusion coefficient could be described by an Arrhenius equation D = D0exp(−H/kT) where and H = 2.81 ± 0.11 eV. No statistically significant loss of 209Pb from the sample was observed for annealing between 470 and 600 °C.
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  • Resultat 1-10 av 37

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