| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply device for sweeping a charged particle beam that can accurately calculate and display the amplitude and offset of driving current such as triangular waves to be supplied to a sweeping coil irrespective of the frequency of the driving current.SOLUTION: ADC 61 samples a current waveform achieved by detecting current supplied to a sweeping coil with a current sensor, and converts the current waveform to a digital value. A maximum value detector 63 and a minimum value detector 64 detect a maximum value Dmax and a minimum value Dmin during a detection period of about two periods set based on frequency information of a reference signal such as a triangular wave, and an amplitude calculator 65 calculates an amplitude value P of the current waveform from Dmax-Dmin. An offset calculator 66 calculates an offset value Q of the current waveform from (P/2)+Dmin. These amplitude value P and offset value Q are displayed directly, or properly converted and displayed on a display unit. Accordingly, even when the frequency of the driving current is low (near to DC component), the accurate amplitude value and offset value can be displayed.SELECTED DRAWING: Figure 2 |
