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  • 1995-1999  (4)
  • 1990-1994
  • 1997  (4)
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  • 1995-1999  (4)
  • 1990-1994
Year
  • 1
    Electronic Resource
    Electronic Resource
    Performance and operation of a beam chopping system for a cyclotron with multiturn extraction (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1714-1719 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A beam chopping system for a cyclotron is in operation at the JAERI cyclotron facility. A combination of a pulse voltage chopper in the injection line and a sinusoidal voltage chopper after the exit of the cyclotron is adopted to produce beam pulses spaced at 1 μs–1 ms intervals from natural cyclotron beams. The chopping system was designed according to a simple formulation of the chopping process in which the multiturn extraction was taken into account. Performance of the chopping system was experimentally proved to satisfy requirements of the design. In actual operation to produce beam pulses at long intervals, however, the number of the multiturn extraction is usually larger than the assumed value in the design because of a large phase acceptance of the cyclotron. Careful tuning of the acceleration phase width or the base magnetic field of the cyclotron is necessary to reduce it. It is essential to strictly define the acceleration phase of injected beams in the central region of the cyclotron to improve this situation. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147980
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Resonant tunneling through a self-assembled Si quantum dot (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 2291-2293 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nanometer-scale Si quantum dots have been spontaneously fabricated on SiO2 by controlling the early stages of low-pressure chemical vapor deposition from pure silane. The tunneling current through Au/1 nm-SiO2/a single Si quantum dot/1 nm-SiO2/n+-Si(100) double-barrier structures has exhibited the clear current bump or negative conductance at 300 K with a peak current to valley ratio as high as 10. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118816
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Determination of traces of uranium and thorium in (Ba, Sr) TiO3 ferroelectrics by inductively coupled plasma mass spectrometry (1997)
    Springer
    Fresenius' journal of analytical chemistry 357 (1997), S. 647-651 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract  Traces of uranium and thorium in barium(II), strontium(II) titanate ((Ba, Sr)TiO3) ferroelectric materials were determined by inductively coupled plasma mass spectrometry (ICP-MS). Samples were completely dissolved by a mixture of 1.4% H2O2 and 1.0 mol⋅l-1 HNO3. For a complete separation of the analytes from the matrix elements, a two step separation technique involving leaching and anion-exchange was applied. By the leaching step with HNO3 more than 90% of the matrix can be removed whereas the analytes completely remained in the solution. The anion-exchange step was carried out on a BIO⋅RAD AG1-X8 column with a mixture of 1.0 mol⋅l-1 HF and 0.5 mol⋅l-1 HNO3 as eluent. The content of uranium and thorium was subsequently measured by ICP-MS. The detection limits (D.L.) obtained were 0.043 ng g-1 and 0.035 ng g-1 for U and Th, respectively. The reproducibility was satisfactory with a relative standard deviation of less than 3% (at the 1 ng g-1 level, n=5). The matrix concentrations in the final solution were reduced to the sub-μg ml-1 level which is in the range of the detection limits of USN-ICP-AES (ultrasonic nebulization-ICP-atomic emission spectroscopy). The method was successfully applied to the determination of uranium and thorium in three synthetic (Ba, Sr)TiO3 samples spiked with the analytes at levels of 1, 5 and 10 ng g-1 and three (Ba, Sr)TiO3 ferroelectric samples containing sub-ng g-1 levels of the analytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160050228
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  • 4
    Electronic Resource
    Electronic Resource
    Determination of fluorine in standard rocks by photon activation analysis (1997)
    Springer
    Journal of radioanalytical and nuclear chemistry 217 (1997), S. 267-271 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A highly sensitive determination of fluorine in standard rocks by photon activation using the19F(γ,n)18F reaction combined with pyrohydrolysis for the separation of18F has been reported. The irradiation energy was operated at 20 MeV to avoid the interference from Na, because Na is one of the major element in rocks and18F is also produced from Na via23Na(γ,αn)18F reaction above its threshold energy, 20.9 MeV. After irradiation, fluorine was extracted by pyrohydrolysis and separated as LaF3 precipitate. It was ascertained that the average recovery of fluorine in standard rocks was about 90% and the precipitate was of high radiochemical purity. This method was applied to the analysis of ten GSJ rock reference samples and two USGS standard rocks issued by the Geological Survey of Japan and the United States Geological Survey, respectively. The detection limit of this method was 0.02 μg/g, and the results obtained by this method were in good agreement with the recommended values. This method was easily applied to the determination of a few ppm level of fluorine in rock samples, such as ultrabasic rock and feldspar.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02034454
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    Paper (German National Licenses)
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