Abstract:
The neutron capture cross sections of 1 74Yb(n,γ)1 75Yb and 55Mn(n,γ)56Mn reactions at 0.0334
eV and 0.0536 eV energies were experimentally measured for the first time using
monochromatic neutrons from a neutron diffractometer and a neutron spectrometer at TRIGA
Mark II research reactor. The 197Au(𝑛𝛾198Au reaction was used as a monitor reaction to
determine the neutron beam intensity. High-resolution gamma-ray spectrometry system was
used to measure the radioactivity of the product nuclides. After considering all the correction
factors such as neutron self-shielding and gamma attenuation effects, the resultant cross
sections obtained for the reaction 1 74Yb(n,γ)1 75Yb at 0.0334 eV and 0.0536 eV energies are
56.8 ± 3.7 b and 44.2 ± 2.6 b, respectively. The determined experimental values for the reaction
at 0.0334 eV and 0.0536 eV are in agreement with the theoretically evaluated data libraries of
JENDL-4.0 and ENDF/B-VIII. However, experimentally determined data in this work are
around 45% less than the theoretically evaluated JEFF-3.3 data. Similarly, the resultant cross
sections obtained for the reaction 55Mn(n,γ)56Mn at 0.0334 eV and 0.0536 eV neutron energies
are 11.07±0.60 b and 9.03±0.49 b, respectively. The resultant data for the two reactions were
extrapolated to the 0.0253 eV energy by assuming 1/v dependence in the thermal energy
region. The extrapolated data at 0.0253 eV for 174Yb(n,γ)175Yb and 55Mn(n,γ)56Mn reactions
are 64.8±2.9 b and 12.93±0.99 b, respectively. The data obtained from this study at 0.0253 eV
for the reactions are compared with the integrally measured values reported in the literature
and different theoretically evaluated data libraries such as ENDF/B-VIII, JENDL-4.0,
ROSFOND-2010 and JEFF-3-3. The data obtained from this study at 0.0253 eV for
174Yb(n,γ)175Yb reaction validates the excitation functions of JENDL-4.0 and ENDF/B-VIII
data libraries. However, data obtained from this study do not support the JEFF-3-3 data library
ii
at thermal energy region for this reaction. On the other hand, the resultant cross sections for
55Mn(n,γ)56Mn reaction at 0.0253 eV, 0.0334 eV and 0.0536 eV are consistent with those data
libraries within the uncertainty limits. The new cross sectional data obtained from this study
are convenient to check the evaluated excitation functions at thermal energy region to resolve
discrepancies of the data for the studied reactions which can be used for the proper assessment
of the reactor criticality safety. Moreover, the obtained data from this study will also be useful
to measure activity distribution, therapeutic radioisotope production and studies related to the
interaction of neutrons with matter for the studied targets. This study will also encourage crosssection measurements for various reactions, at different energies in the thermal energy region,
at many places in the world where neutron diffractometer and spectrometer are installed.
