Evaluation of two proposed improvements to the gradient B drift geometry

Recent work relating to various gradient transport schemes for electron pulse compression are discussed. First, the magnetic fields in the schemes are calculated. Infinite wire fields are found to be correct regardless of the entrance foil cone angle. The fields outside the transport volumes are zero. Next, the electron drift rates and injection criteria are extended and verified numerically. The injection criteria are valid for any entrance foil cone half angle between 0 and π/2 radians. Finally, two improvements to the basic transport scheme in the references are evaluated. The conical entrance foil idea seems to be the best way of increasing warm beam electron injection efficiencies. This idea would not work for a cold beam because the cold beam electrons' angles, α, would be less than the critical angle needed for injection. The cold beam injection efficiency, however, can be improved by the use of double entrance foils with a reversed current. The double entrance foil idea with a forward current appears to be unsatisfactory because beam radii increase greatly. The main disadvantage of these ideas is increased complexity. One should note, however, the conclusions in this report are all based on assumed electron beam distributions. Different results may be obtained when the actual distributions emitted from the candidate electron diodes become known