ساخت داينودهاي چند برابركننده الكترون و تعيين ضريب جذب و تكثير آن

Fabrication of the dynodes of the electron multiplier and measurement of their absorption and multiplication factors

In this work the shape and arrangement of dynodes were studied in an electron multiplier tube using the focusing role of electrostatic fields. Since the kind and particularly the work ftinction of the emitting surface of dynode is effective in the number of out coming electrons, therefore dynodes made from curved pieces of hard aluminum were coated with a thin layer of MgO for its low work function in pressure of 10~6 torr .As it will be explained later vacuum coating was performed in several methods. In the absence of applied voltage the ratio of out coming electron current to incident electron current of each dynode was obtained, then one minus each ratio number was plotted against the extractor voltage . Using this diagram the absorption coefficient was found to be equal to 0.134. The ratio of out coming electron current to incident electron current of each dynode was plotted, from these diagrams the multiplication factor of dynodes coated with MgO was found to be equal to 3.7.