Thickness dependence of positron induced secondary electron emission in forward geometry from thin carbon foils

Secondary electron (SE) emission from thin carbon foils induced by 1–20 keV positrons has been investigated over a range of nominal foil thicknesses from 1.0to5.0μg/cm2. The measurement of SEs was carried out in forward geometry using a microchannel plate as a detector. The SE yield γ   has been measured as a function of beam energy and compared with our Monte Carlo simulation results. We also present in this paper the material parameter Λ=γ/(dE/dx)Λ=γ/(dE/dx) and the emitted SE energy spectra. For incident positron energy of 5 keV or higher, the distribution is found to be characterized by the Sickafus form, AE-mAE-m and m   is close to 1. For low energy incident positrons, however, another form, Bexp(-E/t)Bexp(-E/t), is proposed for describing the SE distribution.