| 摘要 |
PURPOSE:To make it possible to display micro-impurities and a depth directional profile of a bulk element on a similar screen by applying a zero potential to a mesh on the stage ahead of a saturated value to which an electron multiplying tube attains and displaying an output of the electron multiplying tube as it is on a cathode-ray tube (CPT) and increasing the potential on a succeeding stage. CONSTITUTION:A secondary ion attenuator 6 is disposed on a pre-stage of an electron multiplying tube 7 on a route 5 of secondary ions which come from a mass spectrographic magnet 4 and connected with a minimal voltage generator 8 and a precision voltmeter 9. An output of the precision voltmeter 9 is introduced to a counting circuit 10 and converted into the fluctuated number of ion counting by the use of a calibration curved line so that the number is displayed on a CPT 11. Since the normal electron multiplying tube almost attains to its saturated output at up to 10<5>counts/sec or more, a counting region of majority ions is defined as 1X10<5>counts/ sec for example. Therefore, when the number of ions comes in excess of this defined counting number, the secondary ion attenuator 6 is operated and a mesh voltage is supplied so as to keep the counting number to be 1X10<5>counts/sec. Hence, a secondary ion mass spectrograph can be obtained so as to function improvably in a degree of up to 10 figures in a dynamic range. |
