Areal-density measurement of 12C and 13C foils and layers using the (3He,p) nuclear reaction

A method of accurately measuring the areal densities of isotopic stable carbon layers and foils is presented. The method utilizes the (3He,p) nuclear reaction at incident energies near 3.5 MeV. A self-supporting foil whose areal density is accurately known from a Rutherford backscattering measurement is used as a standard. The particular advantage of the method presented here is that it can be used on 12C or 13C layers deposited on massive substrates. Accuracies of ±5% are obtained. Preparation and characterisation of 13C layers with areal densities near 20 μg/cm2 is described. The application of this method to 12C foils and layers is outlined.