Development of a two-stage magnetic electron-guide

A fully operational electron-guide, constituted by the succession of a toroidal magnetic lens and a solenoid, is described and its properties are tested. An absolute efficiency between 1% and 2.2% is obtained in a large energy range, from 150 keV to more than 2 MeV, together with a large β+ rejection. It is shown that a substantial efficiency increase can be obtained by superposing an axial magnetic field on the toroidal one.