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Abstract

The gridded twin ionization chamber developed at CBNM is used to measure the kinetic energy, mass and angular distributions of the fission fragments of the spontaneous fission of "252"Cf. Together with a neutron time-of-flight detector this experimental arrangement permits to measure the correlations between neutron emission, fragment angle, mass and energy of the fission fragments. Without neutron coincidences 40.106 fission events were recorded which are evaluated to give mass-, total kinetic energy- and the variance distributions in a broad mass range from mass 67 to 185. About 3.106 fission events were recorded in coincidence with a neutron detected in the time-of-flight detector. Angular distributions in the CM-system revealed isotropy in the whole fission neutron energy range. This permits the conclusion that fission neutrons are emitted from the fully accelerated fragments and that the hitherto assumed scission neutron component of 15 to 20% is much smaller, as can be determined from the uncertainty of the second Legendre polynomial coefficient. The average number of neutrons was determined as a function of fragment mass and TKE. The mass range for =v(A) was extended beyond that of earlier measurements and revealed two new sawteeth near masses 80 and 176. The slopes and end points of =v(TKE) were also determined for each fragment mass. The fragment centre-of-mass fission neutron spectra were determined as function of fragment mass and TKE. These spectra permitted the evaluation of the average neutron energy =eta(A,TKE) the nuclear temperature T(A,TKE) and the lambda-factor from the cascade evaporation model. These quantities permitted the evaluation of the level density parameter a(A) in the mass range from 90 to 169.

Additional information

Authors: BUDTZ JO RGENSEN C, JRC GEEL ESTAB. (BELGIUM);KNITTER H H JRC GEEL ESTAB. (BELGIUM), JRC GEEL ESTAB. (BELGIUM)
Bibliographic Reference: IAEA CONSULTANTS MEETING ON PHYSICS OF NEUTRON EMISSION IN FISSION, MITO (JAPAN), MAY, 24-27, 1988, AVAILABILITY: CEC-LUXEMBOURG, DG-XIII-C-3, POB 1907, MENTIONING PAPER EN 34058 ORA
Availability: Can be ordered online
Record Number: 1989126115800 / Last updated on: 1989-06-01
Category: PUBLICATION
Available languages: en