Device for the achromatic magnetic deflection of a beam of charged particles and an irradiation apparatus using such a device

A device for the achromatic magnetic deflection of a beam of charged accelerated particles, comprising at least one electromagnet having pole pieces delimiting air gaps in which are created magnetic fields having the same direction and specific values so as to obtain paths of particles having the form of loops whose lengths are a function of the momentum of the particles, said pole pieces forming a first, a second and a third magnetic sector disposed one after the other and joined together, the whole of these magnetic sectors having a plane of symmetry perpendicular to the plane of the mean path of said beam of particles, and intersecting this plane along an axis XX, forming an axis of symmetry, and magnetic deflection device presenting successively to the beam of particles a flat input face E, a first curved face F.sub.1, a second curved face F.sub.2 and a flat output face S, said input E and output S faces forming therebetween an angle 2.alpha., said identical curved faces F.sub.1 and F.sub.2 as well as said axis of symmetry XX being substantially orthogonal to the different paths of said particles, the values of said magnetic inductions created in the first and third magnetic sectors being respectively equal to KB.sub.o, B.sub.o being the value of the magnetic induction in the second magnetic sector and K a numerical co-efficient less than 1.