Laminated channel plate electron multiplier

A laminated channel plate electron multiplier, comprising:

• a stack of electrically-conductive sheet dynodes, the dynodes being insulated and separated from one another by insulating separators, the stack having channels passing through the stack from an outer surface of an input dynode to an output dynode, the input dynode being separated and insulated from the immediately adjacent dynode by an insulating separator having a first substantially uniform thickness, each channel including aligned apertures formed by walls in the dynodes, the apertures having maximum cross-sectional dimensions which are substantially the same;
• exposed secondary electron emissive surfaces provided on the walls of the apertures, and
• means for enabling the provision of an electron repelling field in a vicinity of the outer surface of the input dynode;
• characterized in that the enabling means includes an apertured carrier sheet and an electrically-insulating spacing material, the spacing material having a second substantially uniform thickness, the spacing material and the apertured sheet being provided at the vicinity of the outer surface and being arranged such that the apertured sheet is insulated and spaced from the outer surface by the spacing material, the apertured sheet and the spacing material being further arranged such that the apertures in the carrier sheet are in register with the apertures in the input dynode, each aperture in the carrier sheet having a smallest diameter at least as large as the diameter of the respective opening at the outer surface of the input dynode, the second substantially uniform thickness of the spacing material being greater than the first substantially uniform thickness of the insulator separator which insulates the input dynode from the immediately adjacent dynode.