Curious zig–zag in modulation characteristic curves of a Bayard–Alpert gauge in the extrahigh-vacuum region and its analysis by computer simulation

Abstract

The modulation characteristic curves of a three-grid modulation Bayard–Alpert gauge were studied. This modulation gauge had operated satisfactorily in rather high-pressure regions. But, in very low-pressure regions, curious zig–zags appeared in the modulation characteristic curves, and it was difficult to determine optimum working conditions of this gauge. By experimental studies and computer simulation, it was clarified that these zig–zags were caused by the change of x-ray flux irradiating on the ion collector and that the flux change was induced by the change in trajectories of electrons emitted from the filament depending on a special geometrical construction of the gauge.