Patent ID: 8492715

Claim:
Method of protecting a radiation detector in a charged particle beam apparatus, the apparatus including a source for producing a beam of charged particles, a condenser system including lenses for illuminating a sample, a projection system including lenses for forming a magnified image of the sample on a detector system, the detector system including a radiation detector, the method comprising: exposing the detector to radiation using a first set of parameters, the set of parameters including condenser lens settings, projection lens settings, charged particle beam energy and beam current, predicting the flux density to which the detector will be exposed at a changed parameters before implementing said change in parameters, the prediction based on an optical model and/or a look-up table with one or more input variables from the group of condenser lens settings, projection lens settings, charged particle beam energy, beam current as input, and comparing the predicted flux density with a predetermined value, and, depending on the comparison, either Implement said change of parameters when the predicted flux density is below the predetermined value, or Avoid exposure of the detector to the flux density associated with the requested change in parameters when the predicted flux density is above the predetermined value.