| 摘要 |
PROBLEM TO BE SOLVED: To prevent partial missing in mass spectrum by a dead time following saturation by controlling the gain of a final ion detector before an ion pulse reaches this detector to avoid saturation. SOLUTION: An intermediate ion detector 14 whose central part is rectangularly cut using time convergence of each ion pulse is provided at a space convergence point 13 of the ion pulse existing in the ion pulse track from an ion band 3 to a mirror portion 9. A gain control circuit 30 of a final ion detector 10 is provided which sets the final ion detector 10 to the optimal gain based on each ion pulse current measured in the detector 14. Therefore, the intermediate ion detector 14 detects a small part of each ion pulse coming to the space convergence point 13. Ions passing here disperse again over time, but after reflection by the mirror portion 9, converge again with time in the final ion detector 10. This ion pulse is measured as a mass spectrum, and gain of the final ion detector 10 is set so that the pulse does not saturate before reaching here. |
