1 - IAEA Nuclear Data Services

1.3. Fission Cross Sections
E. Pfletschinger
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239
Preliminary measurements of the fission cross section ratio of Pu
-535
to "" U were done in the energy range from 30 keV to 300 keV by time-
of-flight technique with Xenon scintillation fission detectors. Till
now no relevant results could be obtained due to the difficulties of
discriminating fission against background caused by response of the
multipliers to neutrons and by a-pile up.
New detectors were prepared which allow to observe both fission pro­
ducts in coincidence and in the very near future measurements will
be done with these detectors, trying also to enlarge the energy range
in both directions.
1.k. Operation of the Machine
H. Miessner
The pulsed 3 MeV Van de Graaff worked without any serious breakdowns
during the period covered by this report and only routine repairs
were necessary. The total weekly operation time of the machine was
about 130 hrs ; 83% of this tiï»e was effectively used as measuring
time.
A high vacuum test pumpstand including the whole terminal equipment
of the machine (ion source, deflection chamber, pulsing device and
power supply) was installed. Some improvements of the ion source
system let us hope that it will be possible to increase the beam
current by 30— 50$.