Apparatus for multiple charged-particle beams

A non-transitory computer readable medium storing a set of instructions that is executable by one or more processors of a multi-beam apparatus to cause the multi-beam apparatus to perform a method to observe a sample, the method comprising:

• forming a plurality of beamlets from a primary electron beam by a pre-current limiting aperture array, each of the plurality of beamlets having an associated beam current;
• modifying the associated beam current of each of the plurality of beamlets by a beam-limiting unit;
• directing the plurality of beamlets to form a crossover within or at least near an objective lens by a sector magnet unit, the objective lens configured to focus each of the plurality of beamlets onto a surface of the sample and form a plurality of probe spots thereon;
• and
• directing a plurality of secondary electron beams generated from the plurality of probe spots to an electron detection device by the sector magnet unit, the electron detection device comprising a plurality of detection elements configured to detect the plurality of secondary electron beams.