Patent ID: 6624412
Filing Date: 2003-09-23
Classification: G21K

Abstract:
An energy filter having first, second, and third magnetic field regions through which a charged-particle beam successively passes, said energy filter comprising:said first magnetic field region that said beam first enters and exits, said beam exhibiting a radius of rotation of R1 in said first magnetic field region; said second magnetic field region that said beam going out of said first magnetic field region then enters and exits, said beam exhibiting a radius of rotation of R2 in said second magnetic field region; said third magnetic field region that said beam going out of said second magnetic field region finally enters and exits, said beam exhibiting a radius of rotation of R1 in said third magnetic field region; said first, second, and third magnetic field regions being so arranged that the optical axis of the beam incident on said first magnetic field region where the beam exhibits the radius of rotation of R1 and the optical axis of the beam emerging from said third magnetic field region where the beam exhibits the radius of rotation of R1 are in line; and wherein a nonuniform magnetic field that becomes continuously intenser toward the center of rotation of the beam is produced in each of said first, second, and third magnetic field regions.