Patent ID: 7060978

Claim:
A detector system for a particle beam apparatus having an optical axis defining a direction and a beam guiding tube, said detector system comprising: a target structure arranged within the beam path of said particle beam apparatus, said target structure having a near axis region adjacent to said optical axis and a region remote from said optical axis, said near axis region consisting of a material being strongly electron converting, said region remote from said optical axis being off-set in the direction of said optical axis from said near axis region, an electron detector system for detecting conversion electrons emitted from said near axis region, said electron detector system being arranged, measured in the direction of said optical axis, closer to said near axis region than to said region remote from said optical axis, said electron detector system having an electrode being at a positive electrostatic potential compared to said beam guiding tube, said electrostatic potential generating a strongly localized field within said beam guiding tube so that conversion electrons emitted from said near axis region are extracted by said localized field towards said electron detector system, whereby conversion electrons emitted in other regions than said near axis region are not extracted towards said electron detector system, and a deflecting system comprising at least an electrostatic deflection field and a magnetic deflecting field, said electrostatic and magnetic deflecting fields being aligned perpendicular to each other.