Patent ID: 7718979

Claim:
Particle-optical apparatus comprising: a vacuum chamber, a particle-optical column mounted on the vacuum chamber for producing a particle beam round a particle-optical axis, said particle-optical column comprising a particle source, a sample carrier located in the vacuum chamber for carrying a sample at a sample position, said sample position located on the particle-optical axis, a mirror for collecting light emitted from the sample position or focussing light on the sample position, said mirror showing a through-hole round the particle-optical axis, and evacuation means for evacuating the apparatus, characterized in that a diaphragm is placed between the sample position and the mirror, said diaphragm dividing a first volume within the vacuum chamber in which the sample position is located from a second volume, said diaphragm showing an aperture round the particle-optical axis for passing particles produced by the particle-optical column and for passing light between the mirror and the sample position, the aperture limiting the gas flow from the first volume to the second volume to such a value, that, when the pressure at the sample position is the equilibrium pressure of a fluid with an equilibrium pressure above 1 mbar, the evacuation means can evacuate the second vacuum to a pressure sufficiently low to cause negligible scattering of the particle beam in the second volume when compared to the scattering in the first volume, the distance between the aperture and the sample position can be adjusted to be, or is fixed at, less than four times the diameter of the aperture, and the mirror is located between the diaphragm and the particle source.