Heavy-ion induced secondary electron emission — A possible method for Z-identification

A system is described for the detection of secondary electrons which are emitted when ions pass through foils. The yield of secondary electrons from one and two carbon foils, each being about 6 μg/cm2thick, was measured for ions in the 1 MeV/ nucleon range as a function of the atomic number Zand the velocity of the ions. Due to the influence of high energy δ-rays, the yield from two foils is more than twice as high as that from one foil and it is highly Z-dependent. When using two foils instead of one, the relative half width of the frequency distribution of the number of secondary electrons is reduced because of the improved statistics. It should, therefore, be possible to apply a secondary electron detector with many foils for the Z-identification of heavy ions in a similar way as a dE/dx-detector.