Cyclotron for accelerating charged particles around an axis, comprising an electromagnet with an upper pole and a lower pole, producing a magnetic field in the direction of said axis; a Dee electrode assembly and a counter Dee electrode assembly separated from each other by a gap for accelerating said charged particles and a pair of ion sources (1, 2) located in a central region of the cyclotron. Said ion sources (1, 2) are located at a distance of said axis such that the particles emitted from the first ion source (1) pass between said first (1) and second (2) ion sources after a path of half a turn, and radially outwards of the second ion source (2) after a path of three half-turns, and reciprocally.