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  • 2000-2004  (3)
  • 1995-1999  (5)
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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 1425-1429 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An energy resolution of ΔE=12 eV [full width at half maximum (FWHM)] has been measured for the 55Mn Kα1 line (E=5.9 keV) using a superconducting lead absorber (90×90×1.3 μm3) readout by a single aluminum superconducting tunnel junction (100×100 μm2). The total detector area has been illuminated, while a slit mask of 150 μm width was used to partially shadow the detector leads and substrate area from impinging x rays. The total electronic noise contribution was measured as ΔEelec=4 eV (FWHM). The superconducting tunnel junction is located on a Si3N4 membrane of thickness 0.3 μm, the lead absorber is separated from the superconducting tunnel junction's top layer by a thin layer of natural aluminum oxide. No deviations from linear energy response were observed in the energy range between E=1.74 keV and E=6.49 keV. The same resolution was obtained for a single aluminum superconducting tunnel junction, where the influence of substrate events was suppressed by a metallic buffer layer between tunnel junction and substrate. The escape of recombination phonons into the substrate causes small nonlinearities in the tunnel junction's energy response. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1063-7788
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We discuss the short-and long-term perspectives of the CRESST (Cryogenic Rare Event Search using Superconducting Thermometers) project and present the current status of the experiment and new results concerning detector development. In the search for elementary particle dark matter, CRESST is presently the most advanced deep underground, low-background, cryogenic facility. The basic technique involved is to search for WIMPs (Weakly Interacting Massive Particles) by the measurement of nonthermal phonons, as created by WIMP-induced nuclear recoils. Combined with our newly developed method for the simultaneous measurement of scintillation light, strong background discrimination is possible, resulting in a substantial increase in WIMP detection sensitivity. This will allow a test of the reported positive evidence for a WIMP signal by the DAMA Collaboration in the near future. In the long term, the present CRESST setup permits the installation of a detector mass up to 100 kg. In contrast to other projects, CRESST technology allows the employment of a large variety of detection materials. This offers a powerful tool in establishing a WIMP signal and in investigating WIMP properties in the event of a positive signal.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' journal of analytical chemistry 360 (1998), S. 664-668 
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract For the determination of trace elements in organic liquids radiochemical neutron activation analysis has been combined with counting methods geared to various decay modes of indicator radionuclides leading to a high sensitivity required for ultrapure samples. The activation parameters such as irradiation time, sample mass and neutron flux have been enlarged to the maximum possible in the available irradiation facility. Separation yields and adsorption losses have been studied in detail for a set of elements in order to rule out losses during the separation process. The attainable limits of detection are 2 · 10–16g/g for U and Lu, in the 5 · 10–15g/g range for Th and Sm, in the 1 · 10–14g/g region for La, 5 · 10–13g/g for Rb, Cd and 2 · 10–12g/g for K and In. Although the analysis focused on traces of naturally occurring radioisotopes, results for Cr, Fe, W and Zn are presented as well.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of radioanalytical and nuclear chemistry 216 (1997), S. 293-297 
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The proposed solar neutrino experiment BOREXINO requires detector components of high radiopurity. The acceptable levels for U and Th contaminations reach down to the sub-ppq region. To select suitable materials a very sensitive analysis method have to be applied. In this article a highly developed neutron activation analysis techniques are presented, which have been used to determine the K, Th and U content of detector components, namely nylon, water and liquid scintillator.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of radioanalytical and nuclear chemistry 234 (1998), S. 37-41 
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Trace element analysis of ultrapure liquids requires the avoidance of contamination not only during preparation but also during irradiation of the sample. Double subboiling distilled water activated within flasks made out of synthetic quartz shows a significant correlation between irradiation time, quality of the flasks and the determined trace element concentration. The resulting falsification of the analysis and limitation of sensitivity seems to be caused by diffusion-like processes during irradiation. Even though single crystal FZ-silicon is rather brittle, it has been possible to fabricate a 500 ml irradiation flask out of this extremely pure material. The flask as well as its application in the analysis of double subboiling distilled water are discussed in the article.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of radioanalytical and nuclear chemistry 234 (1998), S. 43-49 
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract We present a NAA method to determine ultratraces of K, Th, U and other trace impurities in liquid organic scintillators, which are known as ultrapure detector materials for neutrino or dark matter experiments. A combined optimization of relevant factors for sensitive NAA has been realized, leading to a sensitivity for U down to 10−16g/g. Samples of 250 ml have been irradiated up to 120 h at a thermal neutron flux of 5–8·1012·n·cm−2·s−1. Acidic extraction, wet ashing and TBP-extraction are used for radiochemical separations. Finally, coincidence techniques are applied for increased sensitivity.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The Pauli exclusion principle (PEP) has been tested for nucleons (n,p) in ${}^{12}{\rm C}$ and ${}^{16}{\rm O}$ nuclei, using the results of background measurements with the prototype of the Borexino detector, the Counting Test Facility (CTF). The approach consisted of a search for $\gamma$ , n, p and/or $\alpha$ ’s emitted in a non-Paulian transition of 1P- shell nucleons to the filled 1S 1/2 shell in nuclei. Similarly, the Pauli-forbidden $\beta^{\pm}$ decay processes were searched for. Due to the extremely low background and the large mass (4.2 tons) of the CTF detector, the following most stringent up-to-date experimental bounds on PEP violating transitions of nucleons have been established: $\tau({}^{12}{\rm C} \rightarrow {}^{12}{\rm\widetilde C} + \gamma) 〉 2.1\cdot10^{27} \mathrm y$ , $\tau({}^{12}{\rm C} \rightarrow {}^{11}{\rm\widetilde B} + p) 〉 5.0\cdot10^{26} {\mathrm{y}}$ , $\tau({}^{12}{\rm C} ({}^{16}{\rm O}) \rightarrow {}^{11}{\rm\widetilde C} ({}^{15}{\rm\widetilde O} ) + n) 〉 3.7 \cdot 10^{26} {\mathrm{y}}$ , $\tau({}^{12}{\rm C} \rightarrow {}^{8}{\rm\widetilde{Be}} + \alpha) 〉 6.1 \cdot 10^{23} \mathrm y$ , $\tau({}^{12}{\rm C} \rightarrow {}^{12}{\rm\widetilde N} + e^- + \widetilde{\nu_e}) 〉 7.6 \cdot 10^{27} \mathrm y$ and $\tau({}^{12}{\rm C} \rightarrow {}^{12}{\rm\widetilde B} + e^ + + \nu_e) 〉 7.7 \cdot 10^{27} \mathrm y$ , all at $90 \%$ C.L.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A search for the decay of isoscalar penetrating particles into ane + e-pair has been performed at the nuclear power reactor Bugey 5, situated close to Lyon (France). The detector set-up, consisting of an arrangement of large-area multiwire proportional chambers, and the data analysis are described. No excess of decay events over background has been observed. For standard axions, therefrom, stringent upper limits for the branching ratio 〈Γ a /Γ M γ , averaged over the entire reactor gamma spectrum of magnetic multipolarity, have been obtained. Analysis in terms of the decay χ→e ++e − of a more general axionlike boson χ yields new constraints for the decay constantf χ which enhance existing laboratory limits considerably.
    Type of Medium: Electronic Resource
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