1 - IAEA Nuclear Data Services

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1.2. Measurement of Radiative Capture Cross Sections
D. Korape, W. Poenitz and K. Menlove
In 1967 three measurements were performed for the accurate deter­
mination of the energy dependence of the capture cross section of
gold which is frequently used as cross section standard. Each of
these measured cross section shapes was normalized to an absolute
value o^ U (30 KeV) - .596 barn /*1/.
n, v
One of these shape measurements• ¿~1J uses an energy independent
"grey neutron detector" /Z^-J as flux monitor for monoenergetic neutron
pulses and a large liquid scintillator /_ 3 _/ for the detection of
capture events in the gold sample. Two other shape measurements
with the large liquid scintillator referred to the ' B (n^y) £'^J
and Li (n,a) /~5_7 cross.sections using a Li-glass detector and
a ' B -slab viewed by h Nal-cristalls. Fig. 5. shows the results of
these three measurements. The full line represents an average curve
through the experimental points of the "grey neutron detector"
measurement.
The new standard cross section for Au (n,y) (Fig. 17) was used to
renormalize our preliminary capture cross section data for Nb, Mo,
Pd, Ag, Cd, In, Co, Hf, Ta, W and Re £ J> J. Fig. 6-17 show the re­
sults of this revaluation and the data of other authors. Fitted
curves and the contributions from the single partial waves 1 = 0,1,2
are represented by full lines; inelastic scattering effects were
not taken into account in the calculated curves. The p- and d-wave
strength functions derived from these least square fits are shown
in the following table I. •