PURPOSE: To prevent the turbulence in a magnetic field after degaussing and initializing an electromagnet by degaussing and initializing an electromagnet having a small exciting quantity after degaussing and initializing an electromagnet having a large exciting quantity.
CONSTITUTION: A central processing unit 21 receives a degaussing and initializing command and outputs a start command signal to a ring deflecting quadrupole electromagnet power source control unit 24. The unit 24 sets a ring deflecting quadrupole electromagnet power source 25 ON according to the signal to supply a current to an electromagnet on the basis of the current pattern stored in a pattern memory 26. When the degaussing and initializing are ended, the unit 24 transmits an end state signal to the unit 21. Then, the unit 21 outputs the start command signal to a corrected electromagnet power source control unit 28 to supply the current based on the current pattern of a set pattern memory 30 to the corrected electromagnet. Thus, electromagnets are extinguished/initialized separately according to the magnitude of exciting quantity, whereby the turbulence in the magnetic field of electromagnets is prevented after the degaussing and initializing.