| 摘要 |
PURPOSE:To maintain a charged particle beam focused onto a sample or a material always to a desired diameter, by constituting a device such that an obtaining means of ratio of lead out voltage to accelerating voltage and a generating means of a control signal in accordance with the obtained ratio are equipped to control a power source of a lens by the control signal. CONSTITUTION:An ion beam is focused once to a point P in the drawing by lens action of a lead out electrode 5 and accelerating electrode 6. The accelerated ion beam is partially detected by an ion detector 9, and the detected signal, after being amplified, is compared with reference voltage from a variable power source 12 in a differential amplifier 11. Here if a quantity of the accelerated ion beam changes, a signal is generated from the amplifier 11. A difference signal is supplied to a lead out power source 8, and lead out voltage applied to the electrode 5 is controlled in such a manner that said difference signal becomes 0, that is, the ion beam quantity always becomes constant. |
