Abstract: We measure the density of an aluminum coating film with the relativistic effect experimental spectrometer based on β-ray attenuation and electron energy losses in materials. The systematic error in energy loss method is large due to the widely distributed electron energy spectrum leaving lots of room for improvement. The density of aluminum coating film sample measured in β-ray attenuation method is ( 2.6 ± 0.2) g /cm² .

Key words: β-ray, attenuation, energy loss, aluminum coating film, density