| 摘要 |
PURPOSE:To stabilize the discharge current by detecting the discharge current from an electron gun while feeding back the variation produced by comparing said output with the setting to an electron gun. CONSTITUTION:An electron gun 30 is constructed with a LaB6 cathode 31, a heater 32, a wenelt electrode 33 and an anode 34. A bias resistor circuit 36 is connected between the cathode 31 and the wenelt electrode 33, while a rectifier circuit 38 is connected between the wenelt electrode 33 and the anode 34 through a discharge current detecting resistor 37 then the high voltage where the anode side 34 is positive is applied. Here said resistor 37 will detect the discharge current of the electron gun 30 as the voltage drop. Said detected voltage is compared by the referential voltage 39 corresponding to the predetermined discharge current and the error amplifier 40, then the resistance of a bias resistance circuit 36 is controlled on the basis of the differential voltage thus to control the discharge current. Consequently the discharge current can be controlled to the predetermined level. |
