Theoretical study and systematic analysis of positive pion-induced fission cross-sections of heavy nuclei

The study of pion-induced nuclear reactions are important because pion not only plays the role of a projectile, but also serves as intermediate step particle as in the case of interaction of other projectiles like photon and antiproton. The studies of pion-induced nuclear reaction have important applications, such as in accelerator-driven system (ADS) and in basic nuclear research to probe the nuclear structure. The studies of pion-induced reaction, particularly fission, are as important as the studies of nucleon-induced nuclear reactions, because inter-nuclear cascades in spallation targets are partly propagated by pions. The pion-induced fission has not been as much studied as fission induced by nucleons. The reason is that there is a limited number of facilities available for production of pions, and beam time is scant. Previously, pion-induced fission has been studied using dielectric track-detectors; at present the work has not been carried out using this technique due to non-availability of exposure facilities. So there is a need of computer codes to study cross-section of pion-induced fission, and the proper documentation of existing experimental data. In the present work, fission cross-sections induced by positive pions, for targets 209Bi, 231Pa, 232Th, 238U and 239Pu are computed using the cascade-exciton model code CEM95 upto 2500 MeV energy. Also a systematics of positive pion-induced fission is performed on the basis of that performed cross-sections of proton-induced fission. The computed cross-sections of fission using CEM95 have been compared with the available experimental data and with the fission cross-sections obtained using the systematics analysis. A reasonable agreement has been observed.