Targets for bulk hydrogen analysis using thermal neutrons

The reflection property of substances can be characterized by the reflection cross-section of thermal neutrons, σβ. A combination of the targets with thin polyethylene foils allowed an estimation of the flux depression of thermal neutrons caused by a bulk sample containing highly absorbing elements or compounds. Some new and more accurate σβ values were determined by using the combined target arrangement. For the ratio, R of the reflection and the elastic scattering cross-sections of thermal neutrons, R=σβ/σEL a value of 0.60±0.02 was found on the basis of the data obtained for a number of elements from H to Pb. Using this correlation factor, and the σEL values, the unknown σβ data can be deduced. The equivalent thicknesses, to polyethylene or hydrogen, of the different target materials were determined from the σβ values.