Abstract: A method and a device for determining the distance from the sample to be examined to at least one reference point which function independently of the type of sample. A signal is modulated to a first potential of a sample and a primary particle beam is directed at the sample, resulting in a secondary particle beam being formed by an interaction, the particles of this beam having the modulated signal. The particles of the secondary particle beam and the signal modulated to the potential of the particles of the secondary particle beam are detected. By comparing the detected modulated signal to a reference signal, the distance is determined from the relationship between the reference signal and the detected modulated signal. The device has the corresponding components for implementing the method.

Abstract: A process for the purification of gases loaded in particular with chemical residues, in particular of the exhaust air from printing equipment, in which process the gas to be purified is drawn off from the regions producing the impurities and led via piping to an arrangement of adsorber-filter cartridges that serve for the separation of the impurities from the gas and are periodically separated in a cyclical manner from the exhaust flow for the carrying out of a regeneration process.

Abstract: The invention is directed to a method for controlling the emission current of an electron source and to a correspondingly controlled electron source. For this purpose, a parallel circuit comprising resistors 6 and field-effect transistors 7 is connected in the high-voltage circuit between the cathode 1 and the control electrode 2. The supply voltage for the field-effect transistors 7 is generated by voltage dividing the voltage across the resistors 6. The measurement of the emission current takes place at low-voltage potential and a control signal obtained from the measuring signal is optically transmitted via a light-conducting fiber or a light waveguide to the control circuit in the high-voltage part. The emission current control at high-voltage potential is provided without additional voltage supplies. Additional insulating transformers are therefore not required.