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Inicio » Actividades I+D > Publicaciones 2001 > New Compact Design for an Ion Source
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"New Compact Design for an Ion Source"
H. Huck, D.E. Di Gregorio, J.O. Fernández Niello, E.B. Halac, M. Igarzábal, J. Orecchia and M.E. Reinoso
Nucl. Instrum. Meth. B 175-177 (2001) 772-776
The use of ion sources to generate beams of various species having different energies has been considered for a wide range of applications: production of new materials, particle accelerators, proton-therapy machines, ion-implantation systems, lithography, etc. In particular, we produce thin films of amorphous carbon with some properties of diamond by deposition of hydrocarbon ions. Materials coated with these diamond-like films have demonstrated properties of biocompatibility and osseointegration. Recently, multicusp ion sources have been developed in many laboratories around the world. In their design, a set of columns of permanent magnets are arranged with alternating polarity to generate longitudinal line-cusp magnetic fields that can efficiently confine the primary ionizing electrons and the plasma. Both filament-discharge and radiofrequency (rf) induction discharge are used in the multicusp ion sources. We have redesigned an existing filament-discharge ion source by adding a set of permanent magnets at the external wall of the discharge chamber. We have tested different geometrical configurations of the magnets including the multicusp ion source configuration. In our final design, the external surface of the ion chamber is surrounded by four bars (1.2 cm x 3 cm x 5 cm) of magnets which are arranged 90° apart each other, with the same polarity pointing to the axis of the chamber. The permanent magnets are made of a metallic neodymium alloy and have a field intensity of 0.34 T at contact. The plasma is contained in a thin-walled (3 mm-thick) stainless steel cylinder 3 cm diameter by 3 cm long. This new compact ion source can deliver a current of 2 mA with a minimum power in the filament-discharge stage. With a 1.5-mm diameter extraction aperture, a positive hydrogen beam current density of 100 mA/cm² can be obtained at a filament-discharge power of 100 W. Details of the design of this ion source and parameters of its operation will be presented and discussed. Tests of further improvements in the performance of the ion source are underway.
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