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  • 1
    Electronic Resource
    Electronic Resource
    Parity nonconservation and Brosa modes in nuclear fission (1995)
    Springer
    The European physical journal 351 (1995), S. 281-288 
    Details
    ISSN: 1434-601X
    Keywords: 24.80.Dc ; 25.85.Ec
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The parity nonconserving (PNC) asymmetry coefficient α for the angular distribution of fragment emission from binary fission of233U irradiated by polarized thermal neutrons has been measured. Complementary fragments were detected by a double ionization chamber with high resolving power. The experiment was carried out at the high flux reactor of the ILL, Grenoble. Integrated over all masses and energies of light fragments from asymmetric fission of234Uh, the PNC asymmetry coefficient is found to be α=(3.29±0.31) × 10−4.The positive sign of α indicates a preferential emission of light fragments parallel to the spin of neutrons inducing fission. Theory claims that PNC effects are sensitive to the properties of the fission barrier. On the other hand, one may wonder whether characteristics of eventual fragments are already specified at the barrier. The measurement of PNC asymmetries for distinct mass-energy ranges of fragments has been utilized to answer this question. Mass-energy distributions of fragments were analyzed along the lines of the Brosa model of fission as a superposition of individual modes. Within experimental uncertainty no mode dependence of asymmetric fission could be disclosed. The result is in keeping with the Brosa model where asymmetric modes bifurcate only once the standard fission barrier has been passed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01290909
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  • 2
    Electronic Resource
    Electronic Resource
    Experimental check of the dispersion law for ultracold neutrons (1998)
    Springer
    JETP letters 67 (1998), S. 786-792 
    Details
    ISSN: 1090-6487
    Keywords: 28.20.Cz ; 11.55.Fv
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An experiment to check the standard dispersion law for ultracold neutrons is described. The experiment is based on searching for a shift of the resonance line of a neutron interference filter as the neutron velocity component parallel to the filter surface is varied. The first results attest to a statistically significant effect. No mimicking effects were found in a control experiment, but their possible existence cannot be completely ruled out at present.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.567749
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  • 3
    Electronic Resource
    Electronic Resource
    Search for anomalous transmission of ultracold neutrons through metal foils (1998)
    Springer
    JETP letters 67 (1998), S. 459-463 
    Details
    ISSN: 1090-6487
    Keywords: 25.40.Dn
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Results are presented on the search for anomalous transmission of ultracold neutrons (UCNs) through beryllium (thickness ∼0.14 mm), stainless steel (0.05 and 0.015 mm), and copper (0.01 and 0.018 mm) foils. This anomalous transmission is considered to be a possible reason for the disappearance of UCNs from beryllium bottles, an effect which was discovered in experiments at the St. Petersburg Nuclear Physics Institute and which was recently observed in the experiment of V. E. Varlamov et al., JETP Lett. 66, 336 (1997). No transmission was found in our measurements at the 10−7 level except in the case of copper foils, which we attribute to the presence in the UCN flux of an admixture of neutrons with energies higher than the boundary energy for copper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.567710
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  • 4
    Electronic Resource
    Electronic Resource
    Destruction of26Al in explosive nucleosynthesis (1986)
    Springer
    The European physical journal 323 (1986), S. 1-11 
    Details
    ISSN: 1434-601X
    Keywords: 25.90 ; 95.90
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The26Al(n, p)26Mg reaction has been studied using neutron spectra which closely resembled Maxwell-Boltzmann (M.-B.) distributions with thermal energies ofkT=40 ×10−6, 31 and 71 keV and also forE n =270–350 keV. These energies correspond to stellar temperaturesT 9=4.6×10−7, 0.36, 0.82 and 3.1–4.1, whereT 9 is in units of 109 K. The partial cross sections for thep 0-(p 1-)transition are found to equal 26±10(1,850 ±150), 13±6(124±17), 16±13(84±14) and 21±8(72±15) mb for the above neutron spectra, respectively. The astrophysical reaction rate is determined for the combinedp 0- andp 1-transitions to beN A 〈σν〉=(0.324±0.026, 20.5±2.7, 22.6±4.3 and 38.7±11.1) ×106 cm3 mole−1 s−1. The results are compared with previous investigations and with statistical model calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01294550
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    Paper (German National Licenses)
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