Radiofrequency hydrogen ion source with permanent magnets providing axial magnetic field^a)

Uniform axial magnetic field of about 70 G is applied to a radiofrequency (rf) hydrogen ion source by arrays of permanent magnets. The plasma density and electron temperature downstream of the source and near the magnetic filter are compared with those in the previously described ion source, where the axial field has been applied by two solenoids. The source is operated at ∼350 kHz and above 10 kW rf power with a field-effect-transistor-based invertor power supply in 1.5 Pa hydrogen. The results show that the plasma density of ∼10¹⁹ m⁻³ near the source exit and ∼10¹⁸ m⁻³ near the magnetic filter can be obtained, which are higher than those with the solenoids.