| 摘要 |
PURPOSE:To make highly accurate mass spectrometry attainable, by interposing a set of quartered electrodes between a focusing lens and a beam limiting aperture, and regulating an ion beam optical system on the basis of an ion beam quantity to be irradiated to these quartered electrodes and another ion beam quantity to be reached to a smaple. CONSTITUTION:A beam monitor electrode 40 consists of a set of quartered electrodes 41-44, and an opening 45, where an ion beam is enough to pass through, is formed in the center. When the ion beam is irradiated to these equally divided electrodes 41-44, an electric current flows into each of these electrodes 41-44 in proportion to this irradiated quantity, and the current value at this time is detected by ammerters 71-74 for each electrode. With this constitution, ion beam quantities to be irradiated to each of these eqally divided electrodes are requlated so as to be equalized whereby optical axis alignment is carried out, and under this state, furthermore another ion beam quantity to be reached to a sample is regulated so as to become the maximum, thereby having a focal point of a focusing lens situated on an optical axis. |
