| 摘要 |
This invention provides a mass analyzer provided with an ion source comprising a filament. An electroconductive heat shielding plate (11) with a thermoelectron passage opening (12) bored therein is inserted into between a filament (3) and an ionization chamber (2). The heat shielding plate (11) is thermally connected through an aluminum block (10) to a heater for regulating the temperature of the ionization chamber (2) to about 200 to 300°C and is electrically set to a ground potential which is substantially the same potential as that of the ionization chamber (2). According to the above constitution, radiation heat generated during lighting of the filament is shielded by the heat shielding plate. This is advantageous in that abnormal heating of a part of the wall surface of the ionization chamber can be eliminated, the inside of the ionization chamber can be maintained at a substantially uniform temperature, and the generation of noise due to the production of metal decomposition products by the abnormal heating can be prevented. Further, since the heat shielding plate prevents the entry of thermoelectron acceleration electric fields into the ionization chamber through the electron incidence port, the take-out of ions produced within the ionization chamber is not inhibited, contributing to improved ion take-out efficiency. |
