Electromagnet for betatron

Betatron electroomagnet construction in which the ferromagnetic magnetoguide pole pieces have radial ribs on the cylindrical part is suggested. It is shown that such shape of the pole pieces increases the focusing forces and improves the conditions of magnet cooling. The above construction permits to create a field with sign-variable gradient the intensity of which changes by azimuth in the accelerators with a small radius. Such field possesses stiff focusing properties