| 摘要 |
PROBLEM TO BE SOLVED: To provide a technology capable of measuring a pressure down to a low pressure level without enlarging the volume of an ion source and increasing a filament current. SOLUTION: A magnetic field 50 is generated by a magnetic field generator 20 and a larger number of gas elements can be ionized in comparison with the past by spirally moving thermions in the magnetic field. Thereby, a larger quantity of the gas elements can be ionized in comparison with the past only by sending an electric current of the same level as one in the past to a filament 31. Accordingly, even if there are not many gas elements under a low pressure, a large number of gas elements can be efficiently ionized by a small quantity of thermions, and a bigger ion current can be obtained in comparison with the one in the past, so that an ion current having a level capable of measuring a partial pressure and a total pressure even under a low pressure can be obtained. Since, even if the current supplied to the filament 31 is reduced, an ion current of almost the same level as one in the past can be obtained, a life of the filament 31 can be extended. |
