A simple and compact method for measuring the hydrogen fraction of hybrid ion beams is introduced in this paper. The method is based on the difference of stopping powers for protons and other heavier ions. This method was used in a measurement of the hydrogen ion fraction of a beam produced by a vacuum arc ion source, and was also proposed to be used in quasi-mono-energetic laser accelerators. In the vacuum arc ion source case, results obtained by this method agree well with that measured by time-of-flight spectrometry and magnetic mass analysis methods.
