Secondary Emission from Thin Metal Foils Bombarded with 70-MeV Electrons

The secondary electron emission coefficient from several elements in the form of thin foils has been measured using 70 MeV electrons as bombarding particles. Using foils with different atomic numbers, it was found that the secondary emission coefficient per target electron in the metal is noticeably larger for light elements, especially in cases of beryllium and aluminum. This indicates that metal oxide on the foil surface (Malter effect) is playing a dominant role in the secondary emission of these metals. For other metals, the experimental results seem to indicate a relatively small variation in the secondary emission coefficient per target electron, less than that predicted by V. J. Vanhuyse and R. E. Van de Vijver, but with the same general behavior. The lack of thickness dependence in the case of tantalum coils is in agreement with the extensive experimental work of B. Planskoy and with the theoretical treatment of the secondary emission by Aggson. The secondary electron emission coefficients will be given for the measured foils and the experimental values will be compared with the existing theories. Finally, the construction of a bakeable secondary emission current monitor will be described.