A multi-beam apparatus for observing a sample with high resolution and high throughput and in flexibly varying observing conditions is proposed. The apparatus uses a movable collimating lens to flexibly vary the currents of the plural probe spots without influencing the intervals thereof, a new source-conversion unit to form the plural images of the single electron source and compensate off-axis aberrations of the plural probe spots with respect to observing conditions, and a pre-beamlet-forming means to reduce the strong Coulomb effect due to the primary-electron beam.

A charged particle beam system includes a source of charged particles and a charged particle beam column to focus the charged particles into a charged particle beam having a landing energy. A magnetic lens is formed in the charged particle beam column along an axis based on a magnetic lens excitation in the coils. The magnetic lens focuses the charged particle beam at a first crossover on the axis. An electrostatic lens is formed in the charged particle beam column along the axis based on a voltage applied to the booster tube. The electrostatic lens focuses the charged particle beam at a second crossover on the axis. The first crossover is based on the magnetic lens excitation. The introduction of an extra crossover overcomes previous limitations of the maximum working distance at very small landing energies and maximum field of view.

A multi-beam apparatus for observing a sample with high resolution and high throughput and in flexibly varying observing conditions is proposed. The apparatus uses a movable collimating lens to flexibly vary the currents of the plural probe spots without influencing the intervals thereof, a new source-conversion unit to form the plural images of the single electron source and compensate off-axis aberrations of the plural probe spots with respect to observing conditions, and a pre-beamlet-forming means to reduce the strong Coulomb effect due to the primary-electron beam.

A charged particle optics for a charged particle beam apparatus having a charged particle beam and a beam propagation direction of the charged particle beam apparatus is described. The charged particle optics includes a focusing lens. The focusing lens includes a first electrode with a first aperture; a second electrode with a second aperture, the second electrode being mechanically movable at least in a first direction perpendicular to the beam propagation direction; and an actuator coupled to the second electrode to move the second electrode in at least the first direction for displacement of the second aperture with respect to the first aperture. The charged particle optics further includes a deflection system positioned upstream of the second electrode to deflect the charged particle beam, based on the displacement, to guide the charged particle beam through the second aperture.