Beam divergence and ion density measurements for an induction coupled ion beam source

In this article the ion beam of H+ and Ar+ produced from the low‐pressure radio frequency ionized plasma is analyzed for beam divergence. The divergence measurement method adopted for a low‐energy beam is described. The divergence values for H+ and Ar+, respectively, are 0.4° and 1.1° for a beam energy of 2.5 kV. It is found that the beam divergence varies with the extraction voltage. In case of H+ beam, the divergence value varies from 2.8° to 0.4° for the extraction voltage of 500 V to 2.5 kV, and in the case of Ar+ beam this value is from 1.3° to 1.1° for the extraction voltage of 1000 V to 2.5 kV. The extraction electrode is concave outward as shown in the figure of the extraction system. The rf plasma is diagnosed using the double‐probe technique for ion density estimation. The axial variation of the electron density and the electron temperature are obtained for both hydrogen as well as argon plasmas. The electron density is maximum, near the end of the coil.