Numerical Simulation of the Acceleration of Ion-Loaded Electron Rings

Numerical studies were performed to simulate the acceleration of ion-loaded electron rings by the magnetic expansion method. A finite-sized multiparticle code is used that computes particle-particle interaction forces directly and approximates conductive boundaries. Initial conditions are electron-ion rings in equilibrium, trapped in a magnetic mirror. On one side, the magnetic field is reduced in time, allowing the ion-loaded ring to move into a region of expansion acceleration. The calculations show that the use of a "squirrel-cage" type conductor inside the beam, which suppresses azimuthal magnetic image currents, assures sufficient axial focusing to retain the integrity of the ring.