A design software suite for periodic permanent magnet stacks

We report on an advanced analysis tool that facilitates the design and development of periodic permanent magnet (PPM) focusing systems used in traveling wave tubes (TWTs). The tool consists of three modules that share design data through a graphical user interface. One module, called mPPM, analyzes an infinitely long periodic stack using an application of magnetic circuit theory. The second module analyzes beam stability by computing the focusing properties of the stack as a user-specified electron beam propagates through it. The third module is the LesPPM code of R. Jackson, which computes the B-field of a finite length PPM stack, i.e. a magnet stack with open ends, using an equivalent coil approach.