An ion implanter of cylindrical geometry is described suitable for uniform implantation at a few keV of inert gas ions of narrow energy distribution into conducting targets of axial symmetry. For helium implantation the ion current in the present device can easily be maintained at over 1 mA, allowing high dose implantation of large areas (several tens of cm2) in minutes. For temperature control of the target, a thermal shunt is incorporated. The sizes and the implantation energy of the device are scalable. Reactive gases can also be implanted with the device when operated at lower pressures and ion currents.