Fission-in-flight technique and the slowing-down of recoil nuclei in gases

Abstract

The study of heavy nuclei recoil dynamics in gas is required by experiments of fission-fragment angular distributions measured with the fission-in-flight technique.

The dependence of the number of recoiling nuclei on the collection distance and the dependence of the number of recoiling nuclei on the gas pressure were measured for a given pressure value and for a given collection distance, respectively.

The experimental data are discussed in terms of two slowing-down processes, the pure electronic ($\text{d}\text{E}\text{d}\text{x}\text{∼kv}$) and the pure nuclear ($\text{d}\text{E}\text{d}\text{x}\text{∼}\text{const}$), which fit this intermediate recoil velocity range ($\text{v}\text{c}\text{⩾2×10}{}^{\mathrm{-3}}$).

In the case of the dependence of the number of recoiling nuclei on the collection distance the agreement is considerably improved when the angular distribution of the recoil products is taken into account.