Mass spectrometer with main voltage generating unit and auxiliary power supply

A switch circuit is turned ON and switch circuits are turned OFF to apply a negative direct-current voltage from a negative voltage generating unit to a flight tube, and while a measurement is conducted, a switch circuit is turned ON, and a capacitor is charged by an auxiliary positive voltage generating unit. When the polarity of the applied voltage is switched from negative to positive, the switch circuit is turned OFF and the switch circuit is turned ON to supply a large current from the capacitor to the flight tube, thus the capacitance of the flight tube is charged to a positive potential quickly. After that, the switch circuit is turned OFF and the switch circuit is turned ON to apply a stable positive direct-current voltage from a positive voltage generating unit to the flight tube.