Secondary radiation mitigation in electron-impact x-ray sources

Abstract

A transmission-type X-ray source is disclosed, comprising an electron source for providing an electron beam; a target configured to generate X-ray radiation by interaction with the electron beam; an X-ray transparent exit window; a plurality of electron beam limiting apertures, each configured to limit an angular distribution of the electron beam; a secondary radiation limiting aperture; a first deflector arranged to deflect the electron beam from the secondary radiation limiting aperture towards the target; a second optional deflector arranged to deflect the electron beam from a selected one of the electron beam limiting apertures towards the secondary radiation limiting aperture; and an aperture selector configured to make the selected one of the electron beam limiting apertures and the electron beam path coincide; wherein each of the electron beam limiting apertures and the secondary radiation limiting aperture are arranged so that there is no direct line of sight for secondary X-ray radiation from the electron beam limiting apertures to the exit window. The aperture selector may comprise a third deflector arranged to deflect the electron beam towards the selected one of the electron beam limiting apertures, or an actuator arranged to bring the selected one of the electron beam limiting apertures into the electron beam path.

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