Development of a magnetic quadrupole lens for low energy heavy ion beam transport

A magnetic quadrupole lens system coupled to a 30° bending deflection magnet was designed and constructed to realize a beam focusing of Xe⁺ ions with the energy less than 200 eV. Compared to a triplet electrostatic quadrupole lens system, the quadrupole doublet magnetic lens system showed a larger beam transmission, indicating the mitigation of the space charge in the beam transport region free of the electrostatic field. The misalignment of the magnetic field axis was observed probably due to a slow change in magnetization of magnetic materials to construct the magnetic circuit of the quadrupole lens. A countermeasure to realign the beam axis by coupling the permanent magnets to trim coil electromagnets is proposed.