Abstract: An essentially linear ion beam is derived from an ion emitting sample, inding a high-frequency mass filter of essentially linear ion beam path, the ion beam path extending towards an ion-electron converter of general rotation symmetrical shape with respect to an axis, the ion-electron converter having an axis aligned with the essentially linear ion beam path and including an electrode which has an aperture traversed by the beam from the source after having passed through the filter, the electrode having a secondary electron-emissive surface on a side thereof which is averted from the ion source and formed as a smoothly curved concave surface defining a converter chamber, the ions which have passed through the aperture being reflected back unto the secondary electron-emissive surface to then being detected by an electrode positioned within the converter chamber.

Abstract: The ion-electron converter is primarily intended for the measurement of small positive ion currents. The essential feature of the converter is its curved conversion electrode which generates an electrostatic field with favorable ion-optical properties; in addition, it avoids high field strength at the conversion electrode, thus reducing spurious field electron emission. Both properties result in an ion detector of high efficiency and sensitivity for positive ions.