Corrector for correcting first-order chromatic aberrations of the first degree

A corrector for correcting energy-dependent first-order aberrations of the first degree and third-order spherical aberrations of an electron-optical lens system, the corrector comprising:

• a first quadrupole-septuplet including at least seven quadrupoles defining a center plane;
• said quadrupoles of said first quadrupole-septuplet being excitable symmetrically to said center plane along a linear axis;
• at least five octopoles excitable within said first quadrupole-septuplet;
• a second quadrupole-septuplet including at least seven quadrupoles defining a second center plane;
• said quadrupoles of said second quadrupole-septuplet being excitable symmetrically to said second center plane along said linear axis;
• at least five octopoles excitable within said second quadrupole-septuplet;
• and,
• said first and second quadrupole septuplets being geometrically equal and being arranged serially one behind the other along said linear axis.

An electron-optical imaging system comprising:

• a lens arrangement for imaging a first plane into a second plane along an optical axis;
• a corrector for correcting energy-dependent first-order aberrations of the first degree and third-order spherical aberrations of said lens arrangement;
• and,
• said corrector including:
• a quadrupole-septuplet including at least seven quadrupoles defining a center plane (ZS);
• said quadrupoles being excitable symmetrically to said center plane (ZS) along a linear axis;
• and, at least five octopoles excitable within said quadrupole-septuplet.