Detection efficiency of a heavy ion time-of-flight spectrometer with thin carbon foils in the start detector

We report measurements of the effect of heavy-ion scattering due to the passage through carbon foils with thicknesses of 4.5, 6.7, and 16.9 μg/cm2 in a wide energy range. For comparison of the results with theoretical predictions the actual foil thicknesses were determined by scaling energy loss measurements with tabulated stopping powers. Using these thicknesses the measurements in general agree well with theory. However, particularly for the 4.5 μg/cm2 foil, significant deviations from the specified thickness have been found very likely due to additional cover layers. The results are used to determine the loss in detection efficiency for low-energy heavy ions in instruments based on the time-of-flight method with thin carbon foils acting as converters for secondary electrons