Periodic permanent magnet assembly for electron tubes

摘要

A periodic permanent magnet (PPM) assembly for producing a focusing field in a travelling wave tube 86 comprises two semi-cylindrical stacks produced by alternately stacking pole pieces 16, 18 and magnets 50, 52. Once formed the two stacks are joined around the travelling wave tube 86 and locked together as a result of the male locking flanges 20 on one stack engaging with the female receptacles 24 on the other stack.