Deducing the U237 ( n,f ) cross section using the surrogate ratio method

Abstract

We have deduced the cross section for $^{237}\mathrm{U}$($n,f$) over an equivalent neutron energy range from 0 to 20 MeV using the surrogate ratio method. A 55 MeV $^{4}\mathrm{He}$ beam from the 88 inch cyclotron at Lawrence Berkeley National Laboratory was used to induce fission in the following reactions: $^{238}\mathrm{U}$$(\ensuremath{\alpha},{\ensuremath{\alpha}}^{\ensuremath{'}}f)$ and $^{236}\mathrm{U}$$(\ensuremath{\alpha},{\ensuremath{\alpha}}^{\ensuremath{'}}f)$. The $^{238}\mathrm{U}$ reaction was a surrogate for $^{237}\mathrm{U}$$(n,f)$, and the $^{236}\mathrm{U}$ reaction was used as a surrogate for $^{235}\mathrm{U}$$(n,f)$. Scattered \ensuremath{\alpha} particles were detected in a fully depleted segmented silicon telescope array over an angle range of ${35}^{\ifmmode^\circ\else\textdegree\fi{}}$ to ${60}^{\ifmmode^\circ\else\textdegree\fi{}}$ with respect to the beam axis. The fission fragments were detected in a third independent silicon detector located at backward angles between ${106}^{\ifmmode^\circ\else\textdegree\fi{}}$ and ${131}^{\ifmmode^\circ\else\textdegree\fi{}}$.