{HEAD ~ magnetic poles} placed at {TAIL ~ exit part} of ion source and a magnetic pole in a center of a discharge channel in a form of protrusion with a magnet or electromagnet placed in a central magnetic pole 
placed at
{ HEAD ~ magnetic poles } placed at { TAIL ~ exit part } of ion source and a magnetic pole in a center of a discharge channel in a form of protrusion with a magnet or electromagnet placed in a central magnetic pole
HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH