Abstract and subjects
Fission cross sections have played a particularly important role in the history of fission and its applications. Much fundamental research has been done on this topic, and various phenomenological models devised to calculate fission barrier heights and energy-dependent cross sections. The problem remains daunting though, and the sensitivity of the calculated cross sections on estimates of fission barrier heights and level densities remains high. A fully quantitative and predictive model for fission cross sections, starting from ab initio calculations of the potential energy surface along the fission path, with dynamical and thermal properties accounted for, remains elusive. However, significant theoretical and experimental advances have been made, and are reported in this chapter. Section 1.1 starts with a brief review of the main historical milestones in our understanding of fission cross sections, some terminology and definitions, and an overview of fission cross section properties. Section 1.2 focuses on experimental techniques and detectors used in the measurement of fission cross sections. Section 1.3 introduces the formal R-matrix theory of fission cross sections, and its generalization to a double-humped fission barrier. Finally, Sect. 1.4 describes codes and techniques used in the evaluation of fission cross sections in modern libraries of nuclear data.