Improvements in electron multipliers

The present invention provides an apparatus for amplifying an electron signal caused by the impact of a particle with an electron emissive surface, the apparatus comprising: a first electron emissive surface configured to receive an input particle and thereby emit one or more secondary electrons, a series of second and subsequent electron emissive surfaces configured to form an amplified electron signal from the one or more secondary electrons emitted by the first electron emissive surface, and one or more power supplies configured to apply bias voltage(s) to one or more of the emissive surfaces, the bias voltage(s) being sufficient to form the amplified electron signal, wherein the apparatus is configured such that the terminal electron emissive surface(s) of the series of second and subsequent electron emissive surfaces draw a higher electrical current than that of the remainder electron emissive surface(s). The present apparatus may be used as part of detector in a mass spectrometer, for example.