A Thermal Neutron Velocity Selector and Its Application to the Measurement of the Cross Section of Boron

Abstract

A mechanical velocity selector for the study of monochromatic neutrons in the range of energies below 0.3 ev is described.The instrument has been applied to the measurement of the cross section of boron, which is found to be 703\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}24}$ ${\mathrm{cm}}^{2}$ for neutrons of 2200 meters per second velocity.