Sub-100Â keV ion beam generation with a Van De Graaff accelerator using an external DC voltage supply

We present a method to produce stable proton and helium ion beams with energies of 10-100 keV from a 30-year-old Van De Graaff accelerator using an external stabilized DC voltage supply instead of the belt charging system. Requiring no other modifications, this makes an ideal system for ion irradiation with fluences up to 1015 ions/cm2. Such ion energies and fluences are required in the emerging fields such as silicon micromachining using ion irradiation and we give examples of structures created with sizes as small as 200 nm.