Hybrid scheme of positron source at SPARC_LAB LNF facility

The hybrid scheme of the positron source for SPARC_LAB LNF facility (Frascati, Italy) is proposed. The comparison of the positron yield in a thin amorphous W converter of 0.1 mm thickness produced by bremsstrahlung, by axial 〈1 0 0〉 and planar (1 1 0) channeling radiations in a W crystal is performed for the positron energy range of 1 ÷ 3 MeV. It is shown that the radiation from 200 MeV electrons (parameters of SPARC_LAB LNF Frascati) in a 10 μm W crystal can produce positrons in the radiator of 0.1 mm thickness with the rate of 10-102 s−1 at planar channeling, of 102-103 s−1 at bremsstrahlung and of 103-104 s−1 at axial channeling.