An ion source has {HEAD ~ shorter central magnetic pole} than regular closed drift ion source with {TAIL ~ magnetic screens} that provide positive magnetic gradient in an ion sources discharge channel 
An ion source has { HEAD ~ shorter central magnetic pole } than regular closed drift ion source with { TAIL ~ magnetic screens } that provide positive magnetic gradient in an ion sources discharge channel
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH