Collective focusing ion accelerator

Electrons can be confined in a “bumpy” torus so that they are effectively trapped by mirror magnetic fields and do not circulate around the torus. The electron space charge can be used to confine or focus a much smaller number of ions. Since the ion motion is non-adiabatic and only weakly dependent on the magnetic field, ions can be accelerated around the torus by a small toroidal electric field. A high current ion accelerator has been proposed that is based on these principles. Experiments on electron injection and confinement in mirror geometry have been completed earlier. We have built a toroidal experiment based on the same technology. The first experimental results on electron confinement are reported. The confinement time is 2 millisec. for an electron density at about 10¹²cm^-3.