To correct in real time the variation of temperature dependency for varying the performance of a charged particle optical member by installing a pole piece for controlling charged particle beams in an electromagnetic member, arranging a temperature sensor in close vicinity to the polo piece, finding a correction value of exciting current of the electromagnetic member, and supplying correcting exciting current to the electromagnetic member.
A focus coil 100, a lense 100 with a pole piece 40, and a deflector 50 are concentrically arranged in close vicinity around a beam cylinder 10, the deflector 50 is positioned on the inner side of the lense 25 and arranged in close vicinity to the pole piece 40. Heat is transmitted from the deflector 50 to the pole piece 40, and heat transmission rate varies by the heat difference between the deflector 50 and the pole piece 40. A thermal resistance device (RTD) or a thermistor 60 is installed in very close vicinity to the pole piece 40 to measure temperature of the pole piece 40, analog output of the thermistor 60 is converted into a digital signal with an A/D converter 70, and a correcting exciting current value is calculated with a calculating machine 80.
SCOTT MESHIKKU
CHRIS ROBINSON
JAMES ROCKLOWER
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