Abstract
Transformation by life test of secondary-electron emitting surfaces of 2.5% Mg-Ag and 1.5% Be-Cu alloys are studied by means of electron diffraction. Oxidation products MgO and BeO which covered the activated surfaces are found to have been removed considerably from the surfaces after the test which reduced the secondary emission yield from initial values 4_??_7 to 2_??_4. It is also found that the oxide removed from the surfaces is deposited on the surfaces of nickel plates placed to face the emitting surfaces; the nickel plates produce diffraction pattern corresponding to MgO and Mg-metal in the case of 2.5% Mg-Ag and that composed of two halos coinciding with the strong Debye rings appropriate for BeO in the case of 1.5% Be-Cu. The substantial changes of the surfaces are considered to be the main cause of the damage of the secondary emission surfaces.
