System of electron irradiation

A system of electron irradiation, comprising an electron accelerator and an electron beam focusing device,

• wherein the electron accelerator is arranged for emitting and accelerating a beam of electrons,
• wherein the electron beam focusing device is located at a rear end of the electron irradiation and comprises a beam restraining rail and 2n+1 sets of magnetic poles,
• wherein the beam restraining rail forms a beam restraining channel through which the beam of electrons are to pass,
• wherein the 2n+1 sets of magnetic poles are installed on the beam restraining rail and are distributed at different locations of the beam restraining channel,
• wherein an nth set of magnetic poles of the 2n+1 sets of magnetic poles are arranged for performing, on the beam of electrons, focusing in a first direction,
• wherein an (n+1)th set of magnetic poles of the 2n+1 sets of magnetic poles are arranged for performing, on the beam of electrons, focusing in a second direction,
• wherein the second direction is perpendicular to the first direction,
• wherein the n is a positive integer.