Nucleon-induced fission cross-sections of tantalum and separated tungsten isotopes and 'compound nucleus' effect in intermediate energy region

摘要

Neutron- and proton-induced fission cross-sections of separated isotopes oftungsten (182W, 183W, 184W, and 186W) and 181Ta relative to 209Bi have beenmeasured in the incident nucleon energy region 50 - 200 MeV using fissionchambers based on thin-film breakdown counters (TFBC) using quasi-monoenergeticneutrons from the 7Li(p,n) reaction and at the proton beams of The SvedbergLaboratory (TSL), Uppsala University (Uppsala, Sweden). The results arecompared with predictions by the CEM03.01 event generator, as well as with therecent data for nuclei in the lead-bismuth region. The effect of "compoundnucleus" in the intermediate energy region is discussed, displaying inexponential dependence of nucleon-induced fission cross-sections on theparameter Z^2/A of the composite system (projectile+target nucleus), and inother characteristics of the fission process for which parameter Z^2/A plays arole similar to the one of the usual liquid-drop parameter Z^2/A of compoundnuclei.