Abstract: An electron source particularly for a RHEED measurement system or a RHEED measurement system as such includes an electron emitter (5), a first deflection stage (6a, b) for radiating an electron beam onto a sample (1), and a second deflection stage between the first stage (6a, b) and the sample 1, preferably near the sample.

Abstract: An apparatus and method for imaging on a detector a particle beam of charged particles having a distinct energy distribution and a distinct angle distribution. The apparatus has deflectors which are provided to create in the particle beam essentially parallel particle paths spaced to correspond to their original angle distribution. The deflectors also direct the particle beam to semi-transmissive, aligned filter electrodes, which produce a potential difference to create a deceleration field to allow the particles to pass through by means of energy selectivity.