diagrammatic side view section in fig2 of a high density plasma flood system is taken through a beamline and magnetic flood system according to the prior art in this case the beam 2 is surrounded by a wall 3 called a u2018 guide tube u2019 which is not a functionally descriptive name that serves to mount a set of linked magnets 10 the beam direction in fig2 would be into or out of the drawing plane in the present commercial product the guide tube magnets are equal size guide tube magnets are equal size and magnetically linked the two magnets nearest the arc chamber have the opposite polarity facing the source magnet this links magnetic flux to the source magnetic field and increases electron emission current the remaining guide tube magnets serve to distribute emission electrons around the beam cross section while minimizing the magnetic flux across the beam 2 the magnetic system includes the source magnet 7 and guide tube magnets 9 as well as a source magnetic yoke 8 the cold plasma magnetic filter effect described in u s pat no 5 545 257 is achieved by design of the source magnet and the primary electrons power source in this case a cathode filament my earlier u s pat no 5 545 257 describes additional detail and it is herewith incorporated by reference in its entirety fig2 illustrates a basic diagram of the distribution of a source magnet 7 a source magnetic yoke 8 and.