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  • Articles: DFG German National Licenses  (9)
  • 1995-1999  (5)
  • 1990-1994  (4)
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  • Articles: DFG German National Licenses  (9)
Material
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Nonequilibrium phonon detectors (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 1791-1804 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Many experiments in nuclear and particle physics would benefit from a device capable of detecting nonionizing events with a low energy threshold. We report on experimental tests of a low-temperature detector based on the registration of nonequilibrium phonons. The device is composed of a silicon single crystal with superconducting tunnel junctions (Al/Al2O3/Al) evaporated onto its surface. In first experiments a 20×10×3 mm3 crystal at an operating temperature of T = 0.37 K was tested with 5.5-MeV α particles. Pulse-height analysis and the timing of pulses in different junctions is shown to yield position and energy resolution. An energy threshold of 250 keV was estimated for absorption anywhere in the crystal. A position resolution of 0.6 mm was determined over a sensitive length of 10 mm. Though phonon focusing effects were registered in the vicinity of the [001] direction, scattered and reflected phonons dominate the signals in the general case. The experimental results are discussed in terms of ballistic and quasidiffuse phonon propagation. To improve the energy threshold, the operating temperature was lowered to 60 mK in order to increase junction sensitivity and a weak thermal coupling of the absorber to the heat bath was introduced to force phonons to leave the crystal via the detecting junctions. Si crystals of up to 20×20×10 mm3 size were used in these second experiments. With a 4 cm3 crystal a threshold of 270 keV was obtained. The performance in these experiments at 60 mK, however, was limited by exceptionally high values of the normal conducting junction resistances. With a reasonable value of this parameter it should be possible to realize an energy threshold of 1 keV with absorbers of a volume of several cm3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347233
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Determination of naturally occurring radionuclides in ultrapure organic liquids (1998)
    Springer
    Fresenius' journal of analytical chemistry 360 (1998), S. 664-668 
    Details
    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
    URL: http://dx.doi.org/10.1007/s002160050777
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Physics and performance of calorimetric particle detectors with dielectric absorbers and superconducting phase transition thermometers (1993)
    Springer
    Journal of low temperature physics 93 (1993), S. 213-218 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present results obtained with detectors consisting of dielectric absorber crystals and superconducting phase transition thermometers made of Ir/Au bilayers. With a 31 g sapphire crystal and an Ir/Au thermometer operated at 45 mK we have obtained an energy resolution of 220 eV (FWHM) for collimated 5.9 ke V X-rays. To explain the measured pulse shapes we have developed a model which includes the effect of non-thermal phonons. Results obtained previously with a 18 g Si absorber and an Ir/Au thermometer with broad transition allowed checking this model over a wide temperature range. A heater experiment performed with this calorimeter provides further support of our model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00693422
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Calorimeters with proximity-effect thermometers and lead and tin absorbers (1993)
    Springer
    Journal of low temperature physics 93 (1993), S. 219-224 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Taking advantage of the low critical temperatures of proximity-effect phase transition thermometers, superconductors with low Debye temperatures can be used as absorber materials for calorimetric detectors. We performed experiments with lead and tin absorbers of a mass of about 1 g. The energy resolutions for 6 keV X-rays are 1000 eV and 230 eV FWHM, respectively. A model which includes the effect of both thermal and non-thermal phonons explains the measured pulse shapes. The observed heat capacity of the absorbers agrees with that given by the Debye law. A comparison of heat pulses and of radiation induced pulses shows a thermalization efficiency close to 100%. No evidence for trapping of energy as quasiparticles is observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00693423
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Munich dark matter search (1993)
    Springer
    Journal of low temperature physics 93 (1993), S. 797-802 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We plan a dark matter search using cryogenic calorimetric detectors with superconducting phase transition thermometers. We discuss such an experiment, compare its estimated sensitivity range with other dark matter searches, and discuss its planned realization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00693515
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Search for the electron-positron decay of axions and axionlike particles at a nuclear power reactor at Bugey (1995)
    Springer
    The European physical journal 68 (1995), S. 221-227 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF01566670
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Ultra-sensitive determination of K, Th, U and other trace impurities in liquid organic scintillators by NAA (1998)
    Springer
    Journal of radioanalytical and nuclear chemistry 234 (1998), S. 43-49 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF02389745
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Neutron activation analysis of detector components for the solar neutrino experiment BOREXINO (1997)
    Springer
    Journal of radioanalytical and nuclear chemistry 216 (1997), S. 293-297 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF02033793
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Neutron activation analysis of ultrapure water in a 500 ml silicon single crystal irradiation flask (1998)
    Springer
    Journal of radioanalytical and nuclear chemistry 234 (1998), S. 37-41 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF02389744
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    Paper (German National Licenses)
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