Patent ID: 6972412

Claim:
A particle-optical apparatus comprising a sample holder arranged for receiving a sample, a particle source arranged for producing a primary beam of first electrically charged particles along an optical axis for irradiating said sample, a first detector having an aperture and arranged for detecting electron signals originating from the sample due to said irradiation, a detection space formed by at least said sample holder and said first detector, and an immersion lens arranged for providing a magnetic field for focusing the primary beam in the vicinity of the sample holder, wherein said first detector is arranged for providing an electric field in the detection space, and wherein the detection space includes a gas, said first detector and said immersion lens arranged for providing the electric field and the magnetic field such that the detection space comprises a first portion in which the electric field includes a component (“E”) that is oriented transverse to the magnetic field (“B”) and in which 2*m*(E/B)^2/q is greater than the ionization energy of the gas, where “m” is the mass of an electron and “q” is the charge of an electron, the apparatus operating in an amplification domain that provides magnetron enhanced amplification of an electron signal from the sample.