Electromagnet and charged particle accelerator

An electromagnet comprising:

• an iron core provided with at least one beam passing gap for travel of a separated charged particle beam, in addition to a main region for travel of the charged particle beam;
• an excitation coil wound around the iron core;
• a main vacuum duct, provided in the main region of the iron core, inside which the charged particle beam travels;
• and
• a sub-vacuum duct, provided in the at least one beam passing gap of the iron core, inside which the separated charged particle beam travels, wherein:
• the iron core is provided with a plurality of beam non-passing gaps through which the charged particle beam does not travel;
• each of the plurality of beam non-passing gaps is provided with a structure similar in configuration to the sub-vacuum duct provided in the at least one beam passing gap;
• a total number of the at least one beam passing gap and the plurality of beam non-passing gaps is four;
• and
• the at least one beam passing gap and the plurality of beam non-passing gaps are positioned at 90° angular intervals on a circumference centered on the main vacuum duct.