1 - IAEA Nuclear Data Services

- 97•-,
XVI. GRUPPO DI RICERCA DEL CONTRATTO EURATOM-CNEN-IÑFN - ISTITUTO
DI FÍSICA DELL'UNIVERSITA', PAVIA (ITALY)
1.1. The Low Energy Group of the Nuclear Physics Institute of the
University of Pavia has begun the study of the emission of
long-range alpha-particles and light nuclei during nuclear
fission, in order to achieve more detailed and accurate inform­
ation about the fission problem and the nuclear matter in
general [1], [2], [3], [4], [ 5~]. In this year, it has been
measured the energy spectrum of the alpha-particles and identi­
fied the helium isotopes from thermal neutron induced fission
of 2 3%u, using a neutron beam extracted from the Triga Mark II
reactor of the University of Pavia.
In order to identify the various light charged particles, a
DE-E solid state telescope, allowing simultaneous determination
of- the total kinetic energy and energy loss of the incident.
particles, has been employed [6].
The energy spectrum of the 11.300 detected long-range alpha-
-particles above 13 MeVJ corrected for loss in the Nickel
absorber, is shown in fig. 1.
The gaussian curve has its maximum at 16 MeV and a 4,66 MeV
HVHM. The peak energy is slightly less than reported in the
only 2 3%>u experiment known to us which was performed by Perfi-
lov and coll. \_1~\ with very poor statistics.
The He isotopes recorded are the following [8J:
- 47 events of "He with energy above 17 MeV giving an intensity
of 0,4 relative to emission of 100 alpha-particles
- 42 events attributable to ^He above 12 MeV with a yield rela­
tive to emission of alpha-particles of 2.6.10~3
- 7 events attributable to 8He.