1 - IAEA Nuclear Data Services
1 - IAEA Nuclear Data Services
1 - IAEA Nuclear Data Services
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Neutron Capture Cross Sections<br />
H. Weigmann, J. Winter<br />
Capture Cross Sections<br />
The detector [12] for neutron capture cross section<br />
measurements which was described in the last Annual<br />
Progress Report has been used for measurements on<br />
240<br />
natural Mo, Pu, natural Cu, and natural Nd.<br />
Measurements__on_Natural_Mo<br />
<strong>Data</strong> for natural Mo have been obtained in the neutron<br />
energy range, from 10 eV to 25 keV [13]. An area analysis<br />
which contains a Monte-Carlo subroutine to calculate<br />
the multiple scattering contribution to the<br />
capture areas, has been applied to resonances with<br />
known isotopic assignment; it yields gr for small<br />
resonances and IV for large ones. Above 1 keV neutron<br />
energy, the observed capture rate has been averaged<br />
to give the mean capture cross section which is in<br />
good agreement with earlier measurements. Por the<br />
final attribution and analysis of some resonances to<br />
specific isotopes of Mo, measurements on separated<br />
isotopes are planned.<br />
240<br />
Measurements_on Pu<br />
Neutron radiative capture in<br />
240<br />
Pu has been studied<br />
in the neutron energy range from 38 eV to 820 eV [14].<br />
The resonance area analysis of the capture data has<br />
been combined with the transmission area analysis<br />
(see above) to obtain the resonance parameters.<br />
The radiative widths of 32 resonances have been determined<br />
yielding a mean value of = (23.2 _+ 2.0)<br />
meV. The observation of unusual large radiative widths<br />
for some resonances at the upper limit of the analysed<br />
energy range has been interpreted as being due to the<br />
presence of subthreshold fission in these resonances.<br />
This interpretation has been confirmed in a measure-