Duoplasmatron for carbon ion production

A solid carbon ion source of duoplasmatron type developed for producing poly - and monocrystalline carbon films with precipitation out of ion beams with minimum quantity of neutral atoms is described. In the duoplasmatron described electric arc burns not in a gas but in vapours of working medium-graphite, produced directly in a discharge chamber of the source. Graphite is heated to temperature providing 10-2 - 10-3 Torr pressure of its vapour necessary for arc burning in two stages. Before ignition of the arc graphite is heated with thermoemissive electron current from hot cathode to inner evaporator walls (0.4 A, 250 V). After the ignition of the arc which occurs at achievement of necessary vapour pressure, heating is performed with the same arc (5 A, 40 V). Tantalum has been choosen as a basic structural material for evaporator parts. The duoplasmatron described gives 15-20 mA steady total current of carbon ions. Mass spectrometric measurements of ion beam composition have shown that impurity ions are present in it in a quantity by 3-4 orders less than basic ones. Ionization coefficient constitutes 80-98%. Ion energy spread does not exceed 20 eV, beam divergence angle 4-5 deg, consumed power-500 W. Service life of the source is determined from cathode service life and amounts to 45-50 h