Energy dependence of negative pion-induced fission in tin

Abstract

Microscopic fission cross-sections are calculated for negative pion-induced fission of tin. The target–detector assemblies were prepared by sandwichin thin layers of tin ( ∼ 1 mg / cm 2 ) between sheets of CR-39 plastic which are used as dielectric track detectors. Stacks of such sandwiches, having 4 π -geometric configuration, were irradiated at normal incidence with negative pion beams at the AGS of Brookhaven National Laboratory, USA at energies 500, 672, 1068 and 1665 MeV. After exposure, the detector sandwiches were etched for the tracks of the particles produced as a result of interactions of negative pions with the target atoms. The tracks produced by the pion-induced fission fragments of tin were separated from the total tracks observed using etching time and track length criteria. Using the track statistic of fission fragments, the experimental fission cross-sections induced by negative pions in tin have been calculated and compared with theoretical fission cross-sections computed for pions at 400–1800 MeV energies using the cascade-exciton model code CEM95. Experimental and theoretical values of fission cross-sections have been compared with the data available in literature. An increasing trend of cross-sections with the energy of the incident pion is observed in both data and calculations.