Ion detector

An ion detector comprising:

• an ion incidence portion;
• a conversion dynode disposed at a position where ions taken up through the ion incidence portion reach, the conversion dynode emitting secondary electrons in response to incidence of the ions;
• a dynode unit for cascade-multiplying secondary electrons emitted from the conversion dynode, the dynode unit being constituted by multiple stages of dynodes from a first-stage dynode to a final-stage dynode disposed along a predetermined electron multiplication direction;
• a first electron detection portion disposed at a position where secondary electrons emitted from the final-stage dynode reach, the first electron detection portion including a semiconductor detector that has an electron multiplication function;
• a second electron detection portion that includes an electrode for capturing some of secondary electrons reaching any intermediate dynode located between the first-stage dynode and the final-stage dynode;
• and
• a gate part constituted by a plurality of dynodes including the final-stage dynode, the plurality of dynodes being located downstream of the intermediate dynode and arranged along a direction from the first-stage dynode toward the final-stage dynode, the gate part controlling switching between passage and interruption of secondary electrons which are directed from the intermediate dynode toward the semiconductor detector by adjusting set potentials of the plurality of dynodes,
• wherein during the interruption of secondary electrons,
• the gate part adjusts the set potentials of the plurality of dynodes so that all of the plurality of dynodes are set at a common potential.