Patent ID: 6844548

Claim:
A Wien filter having an optical axis substantially parallel to a Z-axis, the Wien filter producing at least a dipole electric field in the direction of an X-axis and a dipole magnetic field in the direction of a Y-axis, said Wien filter comprising: 12 poles extending substantially parallel to the optical axis in the direction of the Z-axis, said 12 poles having front ends facing the optical axis within an XY-plane, said front ends having a 12-fold rotational symmetry about the optical axis, wherein two axes perpendicular to said optical axis are assumed to be the X- and Y-axes, wherein a first electric potential of positive or negative sign is applied to four ones of said 12 poles whose front ends are substantially parallel to the X-axis and also applied to four ones of said 12 poles whose front ends are at an angle of 45 to the X-axis to produce the dipole electric field, and wherein a first magnetic potential or magnetomotive force of positive or negative sign is applied to four ones of said 12 poles whose front ends substantially parallel to the Y-axis and also applied to four ones of said 12 poles whose front ends are at an angle of 45 to the Y-axis to produce the dipole magnetic field.