Thickness measurement for thick actinide targets

We report the measurement of the thickness and composition of several films of actinide material used for measuring photofission cross sections in two experiments performed at the Saskatchewan Accelerator Laboratory (SAL) and at the Thomas Jefferson National Accelerator Facility (JLab). We characterized films of 237Np, 232Th, 238U, 235U, and 233U. The films had thicknesses of the order of 1 mg/cm2, and were deposited on aluminum foils 100 μm thick. By the activities and the energy losses of the α-particles emitted by the films we were able to determine the composition of each film and to measure its thickness with a precision of up to 2%.