True Ternary Fission, Collinear Cluster Tri (CCT) Partition of ^{<span class="cmr-7">252</span>}Cf

Abstract

Ternary fission" has been studied previously as a process, where a lighter fragment with A < 30 amu is emitted perpendicular to the fission axis. We use the term "true ternary fission" for a fission process with three masses of comparable size, A > 35. Theoretical considerations repeatedly predicted that true ternary fission must occur in a collinear (prolate) geometry. Over the last decade (see Pyatkov et al. in Eur. Phys. J. A45 29 (2010) and refs. therein), the true ternary fission decay in neutron induced fission 235 U (n,fff) and in spontaneous fission of 252 Cf (sf) has been studied. The name used for this process is (CCT), with three cluster-fragments of similar size in a collinear decay. The measurements are based on binary coincidences containing TOF and energy determinations, in two detector telescopes placed at 180 • . The masses and energies of the registered two fragments give complete kinematic solutions. The missing mass events in binary coincidences can be determined, these events are obtained by blocking one of the lighter fragments (after multiple scattering in the backing) on a structure in front of the detectors. The relatively high total yield of CCT (more than 10 −3 per binary fission) is explained. It is due to the favorable Q-values (more positive than for binary) and the large phase space of the CCT-decay, dominated by three (magic) clusters: e.g. isotopes of Sn, Ca and Ni. The kinetic energies of the fragments have been calculated. The fragments placed in between the other two have very low kinetic energies (below 20 MeV) and have thus escaped their detection in previous work on "ternary fission", where in addition an oblate shape and a triangle for the momentum vectors had been assumed.

34Si accompanied ternary fission of 242Cm in equatorial and collinear configuration

“…It is also to be noted that, these theoretical predictions using the proximity potential on the relative yield of ternary fragmentation, is in agreement with those theoretical predictions reported by Manimaran et al, 52 using the Three cluster model with Yukawa+Exponential potential. We would also like to mention that, Oertzen et al, 53 have experimentally observed that, the ternary fragmentation of heavy nuclei with heavy third particle (heavier than 4 He, 10 Be, etc. ), is only possible in a collinear configuration.…”

Nuclear shell effect and collinear tripartition of nuclei

“…Theoretical interpretation of the collinear tri-partition of 252 Cf and 236 U [6][7][8] needs the knowledge about the mechanism of fission of the residual super-deformed system. The sequential mechanism of the true ternary fission without correlation between two ruptures of the two necks connecting three fragments in collinear configuration was assumed in Ref.…”

α-accompanied cold ternary fission ofPu238–244isotopes in equatorial and collinear configuration

“…Later, Vijayaraghavan et al [27] studied the ternary fission of 252 Cf isotope for different positioning of the fragments starting from collinear configuration to the triangular configuration. Various theoretical groups [28][29][30] have developed several theoretical models to study the collinear cluster tri-partition, a new decay mode of heavy nuclei, for the spontaneous ternary fission of 252 Cf and 236 U nuclei.…”