| 摘要 |
PURPOSE:To prevent any damage due to heat from occurring, by forming the form of a fine hole of an anode electrode into a slit-form fine hole, and installing it as being approximated to the ion drawing out port formed in the side of a main discharge chamber. CONSTITUTION:In order to generate sub-discharge, most of the thermoelectrons fed out of a filament 16 rush in an inner surface of a fine hole 13 of an anode electrode 6, but this fine hole 13 is of a slit type and its inner area is large enough, heating value with the inrush of these thermoelectrons transmits the anode electrode 6 and spreads out in succession, so that this anode electrode 6 in and around the fine hole 13 is in no case subjected to thermal expansion abnormally. Accordingly, it is approximated to an ion drawing out port 11 at the side of a main discharge chamber 3 and the slit-form fine hole 13 is formed whereby sheet like plasma can be jetted to a spot just in front of the ion drawing out port from a sub-discharge chamber 4. With this constitution, any damage to an insulator due to heat is prevented from occurring and its durability is improved, thus a large ion current can be obtained.
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