PRODUCTION OF H- IN A NEW TYPE COMPACT ELECTRON-CYCLOTRON RESONANCE ION-SOURCE

A new type compact electron cyclotron resonance ion source is constituted by using permanent magnets and a 2.45-GHz microwave. A cylindrical vessel of Pyrex glass is mounted inside a TE11-mode waveguide. A cusp field is formed in the vessel by two water-cooled permanent magnets, the one being a SmCo cylinder and the other being a ferrite doughnut-shaped ring. The cusp field is modified from the conventional one in that the field at the upper part serves commonly as a wave radiator and a plasma confinement space. As a result, an overdense plasma can be realized with typical parameters N e=2.5×1011 cm-3 and Te=3.5 eV at 5×10-4 Torr. The field at the lower section is opened toward the bottom extraction part to allow a downward drift of the produced plasma. This facilitates the extraction of the H- beam from the bottom electrode system. The beam current density showed a maximum value of 0.5 mA cm-2 at 4×10 -4 Torr. The result is compared with the calculation by using rate equations.