Patent ID: 8466413

Claim:
An ion detector for detecting positive ions and negative ions, comprising: a housing provided with an ion entrance to make the positive ions and the negative ions enter; a conversion dynode which is disposed in the housing and to which a negative potential is applied; a scintillator which is disposed in the housing and has an electron incident surface which is opposed to the conversion dynode and into which secondary electrons emitted from the conversion dynode are made incident; a conductive layer which is formed on the electron incident surface and to which a positive potential is applied; and a photodetector which detects light emitted by the scintillator in response to incidence of the secondary electrons, and further comprising a pair of electrode members which are made to have the same potential as that of the housing and which are disposed in the housing so as to be located closer to the ion entrance side than the conversion dynode and the conductive layer and so as to face each other across the ion entrance, when viewed from the ion entrance side, in a direction substantially perpendicular to a direction in which the conversion dynode and the conductive layer are opposed.