Aspects of charge distribution measurement for Cf252 (sf)

Abstract

Measurements of charge distributions of fragments in the spontaneous fission of $^{252}\mathrm{Cf}$ have been performed using a unique detector setup consisting of a typical grid-ionization chamber coupled with a $\mathrm{\ensuremath{\Delta}}E\ensuremath{-}E$ charged particle telescope. We find that the fragment mass dependency of the kinetic-energy-averaged width of the charge distribution shows a systematically decreasing trend with obvious fluctuations. The variation of the widths of the charge distribution with kinetic energy shows a pan-like shape. This is due to the large number of neutrons emitted at the high excitation energies and cold fragmentation at the low excitation energies. Deviation of the kinetic-energy-averaged most probable charge ${Z}_{p}$ from the unchanged charge distribution (UCD), $\mathrm{\ensuremath{\Delta}}Z$, as a function of the mass number of primary fragments, ${A}^{*}$, changes from negative for mass asymmetric fission to positive near the symmetric fissions. Concerning the kinetic energy dependence of ${Z}_{p}$ given primary mass number ${A}^{*}$, obvious increasing tendencies of ${Z}_{p}$ with increasing kinetic energy are observed.