Two Dimensional Electron Dynamics in Magnetically Insulated Systems

The electron flow in multi-gap inductive accelerators, such as Hermes III operating in positive polarity, is studied by numerical simulation and modeling. The objective of this work is to determine the operating principles of the electron flow such that an optimally efficient design of the Hermes-type machine can be achieved for intense ion beam generation. A 2-D fully electromagnetic particle in cell code, MASK, is used to represent the electrons emitted in the accelerating gaps and their dynamics. Because the electrons emitted in different gaps have different energies and canonical momenta, the theory of single-component magnetic insulation has to be extended in order to describe such multi-component electron flows. MASK is used to simulate multi-component electron flow in multi-gap accelerators with two, three, and four gaps. Observations from these simulations are used to develop new one-dimensional, time -independent models for magnetically insulated, multi-component electron flows. These models incorporate the time-averaged effects of diamagnetic electron vortices which were observed in the flows. An analytic self-consistent description of a cylindrical vortex is found that compares favorably with vortices observed in simulation. The models are checked against the simulation data by constructing equivalent circuits for the simulated accelerators using the voltage -current relations predicted by the models. The circuit models are incorporated into a software package to aid in the design of multi-gap inductive accelerators.