a corresponding plurality of pole piece concentrators attached to said inside pole surfaces of {HEAD ~ said magnets}, respectively, each pole piece concentrator having two radially opposite ends, one radially opposite end being {TAIL ~ an inside end} and the other radially opposite end being an outside end, each pole piece tapering radially inwardly from a relatively large cross sectional area at its outside end adjacent said inside pole surface of its respective magnet to a relatively small cross sectional area at its opposite and inside end, 
a corresponding plurality of pole piece concentrators attached to said inside pole surfaces of { HEAD ~ said magnets } , respectively , each pole piece concentrator having two radially opposite ends , one radially opposite end being { TAIL ~ an inside end } and the other radially opposite end being an outside end , each pole piece tapering radially inwardly from a relatively large cross sectional area at its outside end adjacent said inside pole surface of its respective magnet to a relatively small cross sectional area at its opposite and inside end ,
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