Let us consider the parallel beam of charged particles with equal velocity entering into the perpendicular magnetic field B. Under the action of Lorentz force the particles of different masses will follow the paths bent on different radii. This principle is used in electromagnetic method of isotopes separation.

For electromagnetic isotopes separation we can use also a paraxial beam of particles of equal energy. If the aperture of the beam is rather small, then after a half of the circle the particles will meet in a point. Distance from the slot (source of particles) to the point of focusing depends upon the mass of a particle. Width of the focus for every type of isotopes depends on the angle aperture of the particles beam.

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