1 - IAEA Nuclear Data Services

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elastic scattering processes to extract some information about
level scheme. Such a study is included iñá systematic research
done by nuclear physics group on the radiative widths for El
electromagnetic transition j_1j» ¡_ 2 i* ® nr previous results are
reported in references [ 3] ,• [ 4j and j_ 5] •
With respect to our preceding measurements, our experimental appartus
has been improved. The new tangential beam hole is used, which
allows a great reduction of gamma and neutron background.
Without source and with a borated paraffin filter (total thick­
ness -50 cm) we have no detectable gamma flux above ~3 MeV and
a neutron flux of a -few n/cm 2 sec. A goniometer was built for
directional correlation analysis between scattered and incident
gamma-rays and for cascade gamma-rays angular correlations. The
gamma-spectra are analysed with 5"x5" (Nal(Tl) and 30 cc Ge(Li)
detectors. For correlation measurements a Ge(Li) detector pair
spectrometer or an anti-Compton spectrometer can be used. All
detectors are shielded by lead and full external apparatus is
inclosed in a large borated paraffin and concrete bunker.
Gamma-ray spectroscopy and thermal neutron radiative capture
experiment
Two Ge(Li) gamma-ray detectors (a 30 cm3 sensitive volume Ge(Li)
coaxial detector and a 3 cm3 sensitive volume planar detector
from Princeton) are in use from the summer of 1967.
137
The best line,width obtained for the Cs 661 KeV gamma-rays
152
is less than 4 KeV. The gamma-rays. from the decay of Eu
(T¿ = 9.3h for the isomeric state decay and T-§-' = 12.5y for
the ground state decay) have been studied. New transitions and
new levels have been identified, y-y coincidences with
Nal(Tl)-Ge(Li) detectors and Ge(Li)-Ge(Li) detectors are in
progress, as well as y~Y angular correlations measurements.
The same detection chain.will be employed to study the thermal
neutron radiative capture. During 1967 since the reactor was