Multiparameter study of the long-range α-particles emitted in the thermal neutron induced fission of 235U

The correlations between the various parameters in the thermal neutron induced fission of 235U accompanied by long-range α-particles (LRA) have been measured employing a back-to-back gridded ionization chamber. Semiconductor detectors were placed symmetrically along the electric field direction of the chamber behind the thin windows of the collector plates for the measurement of the LRA energies. A distinguishing feature of the present method is that the angle between the fission fragments and the electric field direction (hence the direction of α-particle emission) is also determined electronically by the analysis of the coincident collector and grid pulses of the ionization chamber. About 5 x 105 LRA-accompanied fission events and about 2 x 106 binary fission events were recorded and analyzed to obtain a number of correlations of interest between the fragment mass, total kinetic energy, LRA energy and fragment-LRA angle. These experimental results are presented and discussed with regard to the emission mechanism of the LRA. (orig.)