Patent ID: 9576768
Date: 2017-02-21
CPC Classifications: H01J

Claim:
1. A multipole lens comprising: first through twelfth polar elements disposed with rotational symmetry; first and second coils mounted on the first polar element; a third coil mounted on the second polar element; a fourth coil mounted on the third polar element; fifth and sixth coils mounted on the fourth polar element; a seventh coil mounted on the fifth polar element; an eighth coil mounted on the sixth polar element; ninth and tenth coils mounted on the seventh polar element; an eleventh coil mounted on the eighth polar element; a twelfth coil mounted on the ninth polar element; thirteenth and fourteenth coils mounted on the tenth polar element; a fifteenth coil mounted on the eleventh polar element; a sixteenth coil mounted on the twelfth polar element; a first power supply for supplying excitation currents to the first, fourth, ninth, and twelfth coils connected in series; a second power supply for supplying excitation currents to the third, fifth, eleventh, and thirteenth coils connected in series; a third power supply for supplying excitation currents to the sixth, eighth, fourteenth, and sixteenth coils connected in series; and a fourth power supply for supplying excitation currents to the second, seventh, tenth, and fifteenth coils connected in series, wherein the first, third, sixth, seventh, ninth, eleventh, fourteenth, and fifteenth coils produce magnetic fields in a first direction; and wherein the second, fourth, fifth, eighth, tenth, twelfth, thirteenth, and sixteenth coils produce magnetic fields in a direction opposite to the first direction.