magnetic screens with magnetic means provide a magnetic field that has a minimum value, close to zero, at an anode area, in such away that a magnetic field increases along {HEAD ~ a discharge channel} and at {TAIL ~ a distance} of about ½ of a discharge channels length its maximum values of magnetic field become Br≧0.6 Br,max 
magnetic screens with magnetic means provide a magnetic field that has a minimum value , close to zero , at an anode area , in such away that a magnetic field increases along { HEAD ~ a discharge channel } and at { TAIL ~ a distance } of about ½ of a discharge channels length its maximum values of magnetic field become Br≧0.6 Br , max
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