Abstract: A charge converter converts a positive ion into a negative ion. The charge converter is provided with a housing for containing a solid magnesium. A primary heater is also provided in the housing for heating up the solid magnesium to generate a sublimated evaporation of magnesium which fills within the housing. The housing is formed with a pair of beam passage holes through which a positive beam passes the housing. A secondary heater is further provided in the vicinity of the paired beam passage holes for heating the beam passage holes so as to prevent re-crystallization and adhesion of magnesium evaporation on an inner wall of each of the beam passage holes. A ternary heater may further optionally be provided entirely and uniformly around the housing for keeping a uniform distribution in temperature of the housing so as to keep a uniform temperature distribution of the solid magnesium to elongate a time during which the necessary magnesium evaporation is obtained.