| 摘要 |
PURPOSE:To prevent contamination of a surface of an emitter chip and to stabilize an ion-source activity by cooling a surface which has cryopump function in an ionization chamber to reduce temperature to about 20 deg.K and raising purity of an inlet gas arrived to the emitter chip. CONSTITUTION:An ion source 3 is provided to the cooling surface 2 of refregerating machine 1 and it is cooled. An ionization chamber 4 is produced with silver wall 10 having a high thermal conductivity and a gas supply port 5 is provided with a cooling trap 6. Since a high voltage is applied to the ion source emitter chip 3, it is fixed using a sapphire 7 as the insulator having high thermal conductivity and is kept at a low temperature. Temperature of silver wall 10 of ionization chamber is controlled with a heater 8 and a thermocouple thermometer 9 provided around the ionization chamber 4. Since a liquidization temperature of hydrogen is 20K when the hydrogen gas is used, when temperature is set to about 30K, impurities except for helium, for example, H2O, CO, CO2, N2, etc. are absorbed by the cooling trap 6 and internal wall of ionization chamber and a very high purity hydrogen is supplied to the emitter chip 3. |
