| 摘要 |
PURPOSE:To enable determination of a partial pressure of below 10<-11>Torr to be performed by placing a modulation electrode between an analyzing part and an electron-impact-type ion source, installing hot cathodes along the outer circumference of the anode of the ion source and installing a trumpet-like ion-drawing electrode facing the open end of the anode. CONSTITUTION:An ion source (a) is constituted of an anode 1, hot cathodes 2, an electron reflector 3 and a shield electrode 4. The reflector 3 is an ion-drawing electrode and has a gradually-expanding trumpet-like shape. The expanded open end of the reflector 3 faces the open end of the anode 1. The electrode 4 is attached in such a manner as to cover the anode 1 and the cathodes 2. Between the ion source (a) and the mass filter analyzer 5 of a mass spectrometer (A), a modulation electrode 7 is placed through a focus electrode 6. Ions discharged from the analyzer 5, after passing through an ion-collecting electrode 8 and a minute a.c. amplifier 9, are amplified by an a.c. amplifier 10. The thus amplified ions, and a signal sent through a phase apparatus 13 after being dividedly supplied from a modulator 11 are fed to the inputs of an analog multiplier 14. The output of the multiplier 14 is taken out through an LPF15 thereby enabling a partial pressure of below 10<-11>Torr to be measured. |
