Patent ID: 6025590
Filing Date: 2000-02-15
Classification: H01J

Abstract:
An ion detector comprising:a) a conversion electrode disposed on a second axis intersecting substantially perpendicular to an incidence axis of object ions and displaced from the incidence axis, the conversion electrode having a voltage applied of opposite polarity to that of the object ions for emitting secondary electrons or positive ions through collisions with the object ions;b) a detection unit disposed on the second axis in opposition to the conversion electrode across the incidence axis, the detection unit detecting the secondary ions or the positive ions; andc) a shield electrode having a substantially cylindrical body with an axis of the cylindrical body on the second axis,where:the shield electrode comprises a sidewall enveloping a space between the conversion electrode and the detection unit and a bottom wall provided at a side where the detection unit is disposed;the side wall is provided with an entrance opening at the incidence axis for introducing the object ions into the shield electrode; andthe bottom wall is provided with an exit opening for introducing said secondary electrons or positive ions into the detection unit.