1. A helical permanent magnet structure, comprising:at least one magnet assembly, comprising:
a plurality of permanent magnets with a magnetization direction, the permanent magnets being formed as helical shape and arranged as a helical surface, and the center of the helical surface having a longitudinal passage for being passed through by a charged particle; and
a plurality of poles with the same amount of the permanent magnets, wherein the poles are magnetized by the permanent magnets and absorb on one side of the permanent magnets; and
an inner frame surrounding outside and limiting the magnet assembly,
wherein the magnet assembly further comprises a plurality of positioning members, and the permanent magnets and the poles are positioned in the inner frame.