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  • 11
    Digitale Medien
    Digitale Medien
    Instrumental Neutron Activation Analysis for Certification of Ion-Implanted Arsenic in Silicon (2000)
    Springer
    Journal of radioanalytical and nuclear chemistry 245 (2000), S. 57-63 
    Details
    ISSN: 1588-2780
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Energietechnik
    Notizen: Abstract Standard reference material (SRM) 2134 Arsenic Implant in Silicon was produced at the National Institute of Standards and Technology (NIST) as a calibrant for secondary ion mass spectrometry. Instrumental neutron activation analysis was used as a primary method for certification of the arsenic implanted dose. A complete evaluation of all sources of uncertainty yielded an expanded relative uncertainty for the mean value of this SRM to be 0.38% at approximately the 95% level of confidence. No evidence indicating significant heterogeneity among samples was observed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006703131599
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  • 12
    Digitale Medien
    Digitale Medien
    Determination of boron in borosilicate glasses by neutron capture prompt gamma-ray activation analysis (1987)
    Springer
    Journal of radioanalytical and nuclear chemistry 109 (1987), S. 109-115 
    Details
    ISSN: 1588-2780
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Energietechnik
    Notizen: Abstract Major levels of boron in borosilicate glasses have been determined nondestructively by neutron activation analysis. In contrast to chemical methods for determining boron as a major component, the described nuclear method has few interferences and does not require chemical separation of boron prior to its quantitation. The effects of neutron self-shielding by boron (1 to 8% by weight) are examined, minimized by dilution of powdered samples with high purity graphite, and circumvented by comparative analyses. Results of the analysis of a series of glasses with increasing boron composition are 1.150±.005% and 7.766±.035% for the low and high members of the series. Accuracy of these results depends upon comparative analyses with the certified Standard Reference Material, SRM 93a (3.89±0.02% B). Once analyzed, the glasses are useful as secondary standards for alpha track counting, and also ion and electron microprobe analyses of glasses.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02117528
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  • 13
    Digitale Medien
    Digitale Medien
    A pulse generator simulating Ge-detector signals for dead-time and pile-up correction in gamma-ray spectrometry in INAA without distortion of the detector spectrum (1997)
    Springer
    Journal of radioanalytical and nuclear chemistry 215 (1997), S. 249-252 
    Details
    ISSN: 1588-2780
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Energietechnik
    Notizen: Abstract Commercially available pulse generators for use in γ-ray spectroscopy to correct for dead-time and pile-up losses share the problem that the fall-time of the output pulses does not match the fall-time of the detector pulse. Upon pulse shaping in the main amplifier the pulser's signals result in a considerable undershoot of the amplifier's output signal, which cannot be restored by theP/Z network. As a result, peaks in the γ-ray spectrum are broadened. Moreover, amplitude stability of the generators is often poorer than the overall gain stability of the spectrometer. To overcome these problems a special pulse generator has been developed at the Interfaculty Reactor Institute, which simulates Ge-detector signals. It generates pulses with a constant frequency of 25 Hz using a crystal oscillator controlled mercury relay. The stability of the generator's amplitude and frequency is extremely high and the peak-shapes in the γ-ray spectrum are not distorted.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02034473
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  • 14
    Digitale Medien
    Digitale Medien
    Prompt Gamma-Ray Activation Analysis: Fundamentals and Applications (2000)
    Springer
    Journal of radioanalytical and nuclear chemistry 243 (2000), S. 181-189 
    Details
    ISSN: 1588-2780
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Energietechnik
    Notizen: Abstract Prompt gamma-ray activation analysis (PGAA) is an important nuclear analytical technique that complements conventional neutron activation analysis (NAA). When a target is placed in a beam of neutrons, gamma-rays emitted upon neutron capture are measured by a shielded germanium detector, yielding quantitative elemental analysis. The radiation is penetrating and the analysis both nondestructive and independent of the chemical form of the element(s) being measured. The technique is most useful for measurement of light elements (H, B, C, N, Si, P, S, Cl) which can not be easily measured by other methods. Best sensitivity is achieved with neutron beams from research reactors. Although sample preparation is minimal, care must be taken to select proper standards and blanks, and numerous corrections must sometimes be applied to the data from the complex spectra. PGAA has proven useful for multielement analysis of a wide variety of different materials spanning a broad range of scientific disciplines. Of particular importance has been the measurement of hydrogen in materials.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006796003933
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  • 15
    Digitale Medien
    Digitale Medien
    Activation analysis opportunities using cold neutron beams (1987)
    Springer
    Journal of radioanalytical and nuclear chemistry 112 (1987), S. 321-330 
    Details
    ISSN: 1588-2780
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Energietechnik
    Notizen: Abstract Guided beams of cold neutrons being installed at a number of research reactors may become increasingly available for analytical research. A guided cold beam will provide higher neutron fluence rates and lower background interferences than in present facilities. In an optimized facility, fluence rates of 109 n·cm−2·s−1 are obtainable. Focusing a large area beam onto a small target will further increase the neutron intensity. In addition, the shift to lower neutron energy increases the effective cross sections. The absence of fast neutrons and gamma rays permits detectors to be placed near the sample without intolerable background, and thus the efficiency for counting prompt gamma rays can be much higher than in present systems. Measurements made at the hydrogen cold source of the FRJ-2 (DIDO) reactor at the KFA provide a numerical evaluation of the improvements in PGAA with respect to signal-to-background ratios of important elements and matrices.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02132364
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  • 16
    Digitale Medien
    Digitale Medien
    Precise determination of aluminum by instrumental neutron activation (1987)
    Springer
    Journal of radioanalytical and nuclear chemistry 113 (1987), S. 35-42 
    Details
    ISSN: 1588-2780
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Energietechnik
    Notizen: Abstract Because of the short half life of Al-28, the determination of aluminum by neutron activation is subject to many inaccuracies: variation of irradiation conditions between sample and standard, uncertainties in timing, and the effects of high and varying count rate, in addition to other sources of error that must be controlled even in work with long-lived nuclides. These errors can all be made smaller than the fundamental limit set by counting statistics, even when that limit is below 0.5 percent. The transfer function from the observed number of net counts to the counting rate at the end of irradiation is modeled as a product of three processes: radioactive decay and extending and nonextending dead time. The procedure has been applied to the analysis of NBS SRM 1633a Fly Ash. The mean concentration measured was 14.085% Al, with a standard deviation of the mean 0.023% Al for four determinations. The final results showed no significant imprecision beyond counting statistics. The accuracy of the method is shown by the analysis of high-purity single-crystal sapphire.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02036046
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  • 17
    Digitale Medien
    Digitale Medien
    Neutron captue prompt gamma-ray activation analysis at the NIST Cold Neutron Research Facility (1993)
    Springer
    Journal of radioanalytical and nuclear chemistry 167 (1993), S. 121-126 
    Details
    ISSN: 1588-2780
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Energietechnik
    Notizen: Abstract An instrument for neutron capture prompt gamma-ray activation analysis (PGAA) has been constructed as part of the Cold Neutron Research Facility at the 20 MW National Institute of Standards and Technology Research Reactor. The neutron fluence rate (thermal equivalent) is 1.5·108 n ·cm−2·s−1, with negligible fast neutrons and gamma-rays. With compact geometry and hydrogen-free construction, the sensitivity is sevenfold better than an existing thermal instrument. Hydrogen background is thirtyfold lower.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02035470
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  • 18
    Digitale Medien
    Digitale Medien
    Advanced detector systems: What do they have to offer for activation analysis? (1993)
    Springer
    Journal of radioanalytical and nuclear chemistry 167 (1993), S. 187-195 
    Details
    ISSN: 1588-2780
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Energietechnik
    Notizen: Abstract Neutron activated reference materials have been analyzed using a standard Ge(Li)-detector with 17% relative efficiency, a very large Ge-detector with 96% relative efficiency, and a well-type Ge detector. Sensitivities are presented, and usefulness of these systems for NAA is compared on the basis of performance, economics and complexity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02035479
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  • 19
    Digitale Medien
    Digitale Medien
    Local area networks in NAA: Advantages and pitfalls (1993)
    Springer
    Journal of radioanalytical and nuclear chemistry 169 (1993), S. 443-452 
    Details
    ISSN: 1588-2780
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Energietechnik
    Notizen: Abstract Both at IRI and at NIST, Local Area Networks (LANs) are being used to acquire and process data from multiple gamma-ray spectrometers. In this paper, differences and similarities between three systems are discussed, resulting in recommendations for new systems to be set up.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02043001
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  • 20
    Digitale Medien
    Digitale Medien
    Cold neutron prompt gamma activation analysis at NIST: A progress report (1994)
    Springer
    Journal of radioanalytical and nuclear chemistry 180 (1994), S. 263-269 
    Details
    ISSN: 1588-2780
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Energietechnik
    Notizen: Abstract An instrument for prompt gamma-ray activation analysis is now in operation at the NIST Cold Neutron Research Facility (CNRF). The cold neutron beam is relatively free of contamination by fast neutrons and reactor gamma rays, and the neutron fluence rate is 1.5·108 cm−2·s−1 (thermal equivalent). As a result of a compact target-detector geometry the sensitivity is better by a factor of as much as seven than that obtained with an existing thermal instrument, and hydrogen background is a factor of 50 lower. We have applied this instrument to multielement analysis of the Allende meteorite and other materials.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02035914
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