title: Effect of source tuning parameters on the plasma potential of heavy ions in the 18 GHz high temperature superconducting electron cyclotron resonance ion source.
abstract: Plasma potentials for various heavy ions have been measured using the retarding field technique in the 18 GHz high temperature superconducting ECR ion source, PKDELIS [C. Bieth, S. Kantas, P. Sortais, D. Kanjilal, G. Rodrigues, S. Milward, S. Harrison, and R. McMahon, Nucl. Instrum. Methods B 235, 498 (2005); D. Kanjilal, G. Rodrigues, P. Kumar, A. Mandal, A. Roy, C. Bieth, S. Kantas, and P. Sortais, Rev. Sci. Instrum. 77, 03A317 (2006)]. The ion beam extracted from the source is decelerated close to the location of a mesh which is polarized to the source potential and beams having different plasma potentials are measured on a Faraday cup located downstream of the mesh. The influence of various source parameters, viz., RF power, gas pressure, magnetic field, negative dc bias, and gas mixing on the plasma potential is studied. The study helped to find an upper limit of the energy spread of the heavy ions, which can influence the design of the longitudinal optics of the high current injector being developed at the Inter University Accelerator Centre. It is observed that the plasma potentials are decreasing for increasing charge states and a mass effect is clearly observed for the ions with similar operating gas pressures. In the case of gas mixing, it is observed that the plasma potential minimizes at an optimum value of the gas pressure of the mixing gas and the mean charge state maximizes at this value. Details of the measurements carried out as a function of various source parameters and its impact on the longitudinal optics are presented.
authors.affiliation: Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi, India. gerosro@gmail.com
authors.forename: G
authors.initials: G
authors.lastname: Rodrigues
authors.forename: R
authors.initials: R
authors.lastname: Baskaran
authors.forename: S
authors.initials: S
authors.lastname: Kukrety
authors.forename: Y
authors.initials: Y
authors.lastname: Mathur
authors.forename: Sarvesh
authors.initials: S
authors.lastname: Kumar
authors.forename: A
authors.initials: A
authors.lastname: Mandal
authors.forename: D
authors.initials: D
authors.lastname: Kanjilal
authors.forename: A
authors.initials: A
authors.lastname: Roy