Analysis of the “dilemma effect” in fifth-order deflection aberration

In this paper, the coma of the fifth-order aberration at a large deflection angle has been analyzed by using multipole field theory. The dilemma effect exists in the comas of fifth-order aberration. The dilemma effect, whose value Dr is constant and independent of the 10-pole field, is the linear combination of coma aberrations. The coma of the fifth-order aberration is corrected by adjusting the 10-pole field distribution when Dr is zero or small. The factors that influence the dilemma effect have been calculated and analyzed.