Electron multiplier for a multi-channel photomultiplier tube

A multi-channel electron multiplier of the type comprising a plurality of conductive sheets stacked parallel to each other, in which two adjacent sheets intended to convey the same voltage constitute, in accordance with the direction of displacement of the electrons, a focusing half-dynode and a multiplying half-dynode, respectively, jointly constituting a dynode which has different channels in common, each sheet comprising active zones in a number which is equal to the number of channels, which are perforated by a regular configuration of apertures, and comprising unapertured separation zones, characterized in that, for controlling the gain of a given channel, the multiplier comprises a control electrode in the form of a sheet which is situated between the sheets of a dynode, having a window provided with a grating which is highly transparent to the electrons and the area of which is situated opposite the active zone of said given channel, while said electrode has apertures opposite the active zones of the other channels, and in that the control electrode is provided with connection means for applying an adjustable voltage.