magnetic screens with {TAIL ~ 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 a discharge channel and at {HEAD ~ 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 { TAIL ~ 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 a discharge channel and at { HEAD ~ a distance } of about ½ of a discharge channels length its maximum values of magnetic field become Br≧0.6 Br , max
OTH OTH OTH 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 OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH