As explained above the static or movable magnetic shield may be provided with at least one through hole 541, 661, 641 e.g. for allowing the propagation path of the e-beam to pass or for allowing a connecting structure that connects the object table to the stage to pass. In order to keep an effect of stray fields through the through hole low, a distance of the magnetic shield to a magnetic lens of the electron optics system 500, 600 along the optical axis of the electron optics system 500, 600 may be at least 5 times larger than a diameter of the through hole. A diameter of the through hole of 1/10^th or less of the distance of the magnetic shield to the magnetic lens of the electron optics system 500, 600 may further reduce an effect of stray fields through the through hole.

A further effect of the magnetic shielding may be to provide for thermal shielding. Accordingly, at least one of the magnetic shield and the local magnetic shield may further act as a thermal shield.

A further effect of the magnetic shielding may be to provide a barrier for particles, thereby e.g. forming a barrier for contamination. Accordingly, at least one of the magnetic shield and the local magnetic shield further acts as a particle barrier.