Ion detectors

An ion detector 400 for a mass and/or ion mobility spectrometer, comprising: a dynode 402 arranged such that primary ions 412 to be detected by the ion detector impact upon the dynode and generate first electrons 414 and secondary positive ions 416; an electron detector 404 arranged to attract and detect said first electrons; and an apertured electrode 410, comprising a plurality of apertures, that is arranged such that at least some of said secondary positive ions pass through the apertures of the electrode. The apertured electrode (e.g. grid or mesh) may be at ground potential or at a negative potential. A positive potential may be applied to the dynode. A potential may be applied to the electron detector that is greater than the potential applied to the dynode. The apertured electrode may filter the secondary positive ions from the electrons. A method of detecting ions is also disclosed.