Abstract: A cathode chamber (1) with a thermionic cathode (3) generates a low-voltage arc discharge in a vacuum treatment chamber (11). Arcing on wall portions of the treatment chamber (11) is prevented by providing a screen (20), operated so as to be electrically floating, in the region of a diaphragm (9), through which diaphragm (9) the discharge is drawn from the cathode chamber (1) into the treatment chamber (11). The discharge is ignited by impressing portions of the cathode chamber wall with the ignition potential, with respect to the potential of the cathode (3).

Abstract: In order to remove material from the surfaces in a vacuum chamber it is proposed to activate hydrogen gas in a plasma with the aid of a low voltage arc discharge which is supported by a hot emitting electrode in a cathode chamber. The removing method allows the cleaning of surfaces onto which subsequently safely adhering layers of a highest purity can be precipitated. The method can also be used for cleaning vacuum chambers. The small expenditures regarding apparatuses with the high rates of removal to be obtained produce a highly economical practicing of the method.